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Overview
Comment:Only the bare basics work. But we might as well go ahead and call this the trunk since we are unlikely to ever need to bisect back into this massive rewrite effort.
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: a101b3e1c470f1f2a0dd6ef6768ce8ca596f3a22
User & Date: drh 2012-02-21 20:03:27
Context
2012-02-22
00:11
Remove the OP_CreateTable and OP_CreateIndex opcodes, which are not required with the key/value backend. check-in: 31b1faa995 user: drh tags: trunk
2012-02-21
20:03
Only the bare basics work. But we might as well go ahead and call this the trunk since we are unlikely to ever need to bisect back into this massive rewrite effort. check-in: a101b3e1c4 user: drh tags: trunk
20:01
Inserting multiple rows into a table and querying via full-table scan is now working. Leaf check-in: 6838c8a3a7 user: drh tags: remove-btree
2012-01-26
22:11
Always call OP_MakeKey before OP_MakeRecord prior to adding content to an index. check-in: 29c1ec8e6b user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to ext/fts3/fts3.c.

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#include <stdlib.h>
#include <stddef.h>
#include <stdio.h>
#include <string.h>
#include <stdarg.h>

#include "fts3.h"
#ifndef SQLITE_CORE 
# include "sqlite4ext.h"
  SQLITE_EXTENSION_INIT1
#endif

static int fts3EvalNext(Fts3Cursor *pCsr);
static int fts3EvalStart(Fts3Cursor *pCsr);
static int fts3TermSegReaderCursor(
    Fts3Cursor *, const char *, int, int, Fts3MultiSegReader **);

/* 







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#include <stdlib.h>
#include <stddef.h>
#include <stdio.h>
#include <string.h>
#include <stdarg.h>

#include "fts3.h"





static int fts3EvalNext(Fts3Cursor *pCsr);
static int fts3EvalStart(Fts3Cursor *pCsr);
static int fts3TermSegReaderCursor(
    Fts3Cursor *, const char *, int, int, Fts3MultiSegReader **);

/* 

Changes to ext/fts3/fts3Int.h.

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*/
#if defined(SQLITE_ENABLE_FTS4) && !defined(SQLITE_ENABLE_FTS3)
# define SQLITE_ENABLE_FTS3
#endif

#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)

/* If not building as part of the core, include sqlite4ext.h. */
#ifndef SQLITE_CORE
# include "sqlite4ext.h" 
extern const sqlite4_api_routines *sqlite4_api;
#endif

#include "sqlite4.h"
#include "fts3_tokenizer.h"
#include "fts3_hash.h"

/*
** This constant controls how often segments are merged. Once there are
** FTS3_MERGE_COUNT segments of level N, they are merged into a single







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*/
#if defined(SQLITE_ENABLE_FTS4) && !defined(SQLITE_ENABLE_FTS3)
# define SQLITE_ENABLE_FTS3
#endif

#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)







#include "sqlite4.h"
#include "fts3_tokenizer.h"
#include "fts3_hash.h"

/*
** This constant controls how often segments are merged. Once there are
** FTS3_MERGE_COUNT segments of level N, they are merged into a single

Changes to main.mk.

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TCCX =  $(TCC) $(OPTS) -I. -I$(TOP)/src -I$(TOP) 
TCCX += -I$(TOP)/ext/rtree -I$(TOP)/ext/icu -I$(TOP)/ext/fts3
TCCX += -I$(TOP)/ext/async

# Object files for the SQLite library.
#
LIBOBJ+= alter.o analyze.o attach.o auth.o \
         backup.o bitvec.o btmutex.o btree.o build.o \
         callback.o complete.o ctime.o date.o delete.o expr.o fault.o fkey.o \
         fts3.o fts3_aux.o fts3_expr.o fts3_hash.o fts3_icu.o fts3_porter.o \
         fts3_snippet.o fts3_tokenizer.o fts3_tokenizer1.o \
         fts3_write.o func.o global.o hash.o \
         icu.o insert.o journal.o kvmem.o legacy.o loadext.o \
         main.o malloc.o math.o mem0.o mem1.o mem2.o mem3.o mem5.o \
         memjournal.o \
         mutex.o mutex_noop.o mutex_os2.o mutex_unix.o mutex_w32.o \
         notify.o opcodes.o os.o os_os2.o os_unix.o os_win.o \
         pager.o parse.o pcache.o pcache1.o pragma.o prepare.o printf.o \
         random.o resolve.o rowset.o rtree.o select.o status.o storage.o \
         table.o tokenize.o trigger.o \
         update.o util.o varint.o \
         vdbe.o vdbeapi.o vdbeaux.o vdbeblob.o vdbecodec.o \
         vdbemem.o vdbesort.o vdbetrace.o \
         walker.o where.o utf.o vtab.o



# All of the source code files.
#
SRC = \
  $(TOP)/src/alter.c \
  $(TOP)/src/analyze.c \
  $(TOP)/src/attach.c \
  $(TOP)/src/auth.c \
  $(TOP)/src/backup.c \
  $(TOP)/src/bitvec.c \
  $(TOP)/src/btmutex.c \
  $(TOP)/src/btree.c \
  $(TOP)/src/btree.h \
  $(TOP)/src/btreeInt.h \
  $(TOP)/src/build.c \
  $(TOP)/src/callback.c \
  $(TOP)/src/complete.c \
  $(TOP)/src/ctime.c \
  $(TOP)/src/date.c \
  $(TOP)/src/delete.c \
  $(TOP)/src/expr.c \
................................................................................
  $(TOP)/src/fkey.c \
  $(TOP)/src/func.c \
  $(TOP)/src/global.c \
  $(TOP)/src/hash.c \
  $(TOP)/src/hash.h \
  $(TOP)/src/hwtime.h \
  $(TOP)/src/insert.c \
  $(TOP)/src/journal.c \
  $(TOP)/src/kvmem.c \
  $(TOP)/src/legacy.c \
  $(TOP)/src/loadext.c \
  $(TOP)/src/main.c \
  $(TOP)/src/malloc.c \
  $(TOP)/src/math.c \
  $(TOP)/src/mem0.c \
  $(TOP)/src/mem1.c \
  $(TOP)/src/mem2.c \
  $(TOP)/src/mem3.c \
  $(TOP)/src/mem5.c \
  $(TOP)/src/memjournal.c \
  $(TOP)/src/mutex.c \
  $(TOP)/src/mutex.h \
  $(TOP)/src/mutex_noop.c \
  $(TOP)/src/mutex_os2.c \
  $(TOP)/src/mutex_unix.c \
  $(TOP)/src/mutex_w32.c \
  $(TOP)/src/notify.c \
  $(TOP)/src/os.c \
  $(TOP)/src/os.h \
  $(TOP)/src/os_common.h \
  $(TOP)/src/os_os2.c \
  $(TOP)/src/os_unix.c \
  $(TOP)/src/os_win.c \
  $(TOP)/src/pager.c \
  $(TOP)/src/pager.h \
  $(TOP)/src/parse.y \
  $(TOP)/src/pcache.c \
  $(TOP)/src/pcache.h \
  $(TOP)/src/pcache1.c \
  $(TOP)/src/pragma.c \
  $(TOP)/src/prepare.c \
  $(TOP)/src/printf.c \
  $(TOP)/src/random.c \
  $(TOP)/src/resolve.c \
  $(TOP)/src/rowset.c \
  $(TOP)/src/select.c \
  $(TOP)/src/shell.c \
  $(TOP)/src/sqlite.h.in \
  $(TOP)/src/sqlite4ext.h \
  $(TOP)/src/sqliteInt.h \
  $(TOP)/src/sqliteLimit.h \
  $(TOP)/src/status.c \
  $(TOP)/src/storage.c \
  $(TOP)/src/storage.h \
  $(TOP)/src/table.c \
  $(TOP)/src/tclsqlite.c \
................................................................................
  $(TOP)/src/update.c \
  $(TOP)/src/util.c \
  $(TOP)/src/varint.c \
  $(TOP)/src/vdbe.c \
  $(TOP)/src/vdbe.h \
  $(TOP)/src/vdbeapi.c \
  $(TOP)/src/vdbeaux.c \
  $(TOP)/src/vdbeblob.c \
  $(TOP)/src/vdbemem.c \
  $(TOP)/src/vdbesort.c \
  $(TOP)/src/vdbetrace.c \
  $(TOP)/src/vdbeInt.h \
  $(TOP)/src/vtab.c \
  $(TOP)/src/walker.c \
  $(TOP)/src/where.c

# Source code for extensions
#
SRC += \
  $(TOP)/ext/fts1/fts1.c \
  $(TOP)/ext/fts1/fts1.h \
  $(TOP)/ext/fts1/fts1_hash.c \
  $(TOP)/ext/fts1/fts1_hash.h \
  $(TOP)/ext/fts1/fts1_porter.c \
  $(TOP)/ext/fts1/fts1_tokenizer.h \
  $(TOP)/ext/fts1/fts1_tokenizer1.c
SRC += \
  $(TOP)/ext/fts2/fts2.c \
  $(TOP)/ext/fts2/fts2.h \
  $(TOP)/ext/fts2/fts2_hash.c \
  $(TOP)/ext/fts2/fts2_hash.h \
  $(TOP)/ext/fts2/fts2_icu.c \
  $(TOP)/ext/fts2/fts2_porter.c \
  $(TOP)/ext/fts2/fts2_tokenizer.h \
  $(TOP)/ext/fts2/fts2_tokenizer.c \
  $(TOP)/ext/fts2/fts2_tokenizer1.c
SRC += \
  $(TOP)/ext/fts3/fts3.c \
  $(TOP)/ext/fts3/fts3.h \
  $(TOP)/ext/fts3/fts3Int.h \
  $(TOP)/ext/fts3/fts3_aux.c \
  $(TOP)/ext/fts3/fts3_expr.c \
  $(TOP)/ext/fts3/fts3_hash.c \
  $(TOP)/ext/fts3/fts3_hash.h \
................................................................................

# Source code to the test files.
#
TESTSRC = \
  $(TOP)/ext/fts3/fts3_term.c \
  $(TOP)/ext/fts3/fts3_test.c \
  $(TOP)/src/test1.c \
  $(TOP)/src/test2.c \
  $(TOP)/src/test3.c \
  $(TOP)/src/test4.c \
  $(TOP)/src/test5.c \
  $(TOP)/src/test6.c \
  $(TOP)/src/test7.c \
  $(TOP)/src/test8.c \
  $(TOP)/src/test9.c \
  $(TOP)/src/test_autoext.c \
  $(TOP)/src/test_backup.c \
  $(TOP)/src/test_btree.c \
  $(TOP)/src/test_config.c \
  $(TOP)/src/test_demovfs.c \
  $(TOP)/src/test_devsym.c \
  $(TOP)/src/test_func.c \
  $(TOP)/src/test_fuzzer.c \
  $(TOP)/src/test_hexio.c \
  $(TOP)/src/test_init.c \
  $(TOP)/src/test_intarray.c \
  $(TOP)/src/test_journal.c \
  $(TOP)/src/test_malloc.c \
  $(TOP)/src/test_mutex.c \
  $(TOP)/src/test_onefile.c \
  $(TOP)/src/test_osinst.c \
  $(TOP)/src/test_pcache.c \
  $(TOP)/src/test_quota.c \
  $(TOP)/src/test_rtree.c \
  $(TOP)/src/test_schema.c \
  $(TOP)/src/test_server.c \
  $(TOP)/src/test_storage.c \
  $(TOP)/src/test_superlock.c \
  $(TOP)/src/test_syscall.c \
  $(TOP)/src/test_tclvar.c \
  $(TOP)/src/test_thread.c \
  $(TOP)/src/test_vfs.c \
  $(TOP)/src/test_wholenumber.c \
  $(TOP)/src/test_wsd.c

#TESTSRC += $(TOP)/ext/fts2/fts2_tokenizer.c
#TESTSRC += $(TOP)/ext/fts3/fts3_tokenizer.c

TESTSRC2 = \
  $(TOP)/src/attach.c \
  $(TOP)/src/backup.c \
  $(TOP)/src/btree.c \
  $(TOP)/src/build.c \
  $(TOP)/src/date.c \
  $(TOP)/src/expr.c \
  $(TOP)/src/func.c \
  $(TOP)/src/insert.c \
  $(TOP)/src/mem5.c \
  $(TOP)/src/os.c \
  $(TOP)/src/os_os2.c \
  $(TOP)/src/os_unix.c \
  $(TOP)/src/os_win.c \
  $(TOP)/src/pager.c \
  $(TOP)/src/pragma.c \
  $(TOP)/src/prepare.c \
  $(TOP)/src/printf.c \
  $(TOP)/src/random.c \
  $(TOP)/src/pcache.c \
  $(TOP)/src/pcache1.c \
  $(TOP)/src/select.c \
  $(TOP)/src/tokenize.c \
  $(TOP)/src/utf.c \
  $(TOP)/src/util.c \
  $(TOP)/src/vdbeapi.c \
  $(TOP)/src/vdbeaux.c \
  $(TOP)/src/vdbe.c \
................................................................................
  $(TOP)/ext/fts3/fts3_expr.c \
  $(TOP)/ext/fts3/fts3_tokenizer.c \
  $(TOP)/ext/fts3/fts3_write.c

# Header files used by all library source files.
#
HDR = \
   $(TOP)/src/btree.h \
   $(TOP)/src/btreeInt.h \
   $(TOP)/src/hash.h \
   $(TOP)/src/hwtime.h \
   keywordhash.h \
   $(TOP)/src/mutex.h \
   opcodes.h \
   $(TOP)/src/os.h \
   $(TOP)/src/os_common.h \
   $(TOP)/src/pager.h \
   $(TOP)/src/pcache.h \
   parse.h  \
   sqlite4.h  \
   $(TOP)/src/sqlite4ext.h \
   $(TOP)/src/sqliteInt.h  \
   $(TOP)/src/sqliteLimit.h \
   $(TOP)/src/storage.h \
   $(TOP)/src/vdbe.h \
   $(TOP)/src/vdbeInt.h

# Header files used by extensions
#
EXTHDR += \
  $(TOP)/ext/fts1/fts1.h \
  $(TOP)/ext/fts1/fts1_hash.h \
  $(TOP)/ext/fts1/fts1_tokenizer.h
EXTHDR += \
  $(TOP)/ext/fts2/fts2.h \
  $(TOP)/ext/fts2/fts2_hash.h \
  $(TOP)/ext/fts2/fts2_tokenizer.h
EXTHDR += \
  $(TOP)/ext/fts3/fts3.h \
  $(TOP)/ext/fts3/fts3Int.h \
  $(TOP)/ext/fts3/fts3_hash.h \
  $(TOP)/ext/fts3/fts3_tokenizer.h
EXTHDR += \
  $(TOP)/ext/rtree/rtree.h
EXTHDR += \







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TCCX =  $(TCC) $(OPTS) -I. -I$(TOP)/src -I$(TOP) 
TCCX += -I$(TOP)/ext/rtree -I$(TOP)/ext/icu -I$(TOP)/ext/fts3
TCCX += -I$(TOP)/ext/async

# Object files for the SQLite library.
#
LIBOBJ+= alter.o analyze.o attach.o auth.o \
         bitvec.o build.o \
         callback.o complete.o ctime.o date.o delete.o expr.o fault.o fkey.o \
         fts3.o fts3_aux.o fts3_expr.o fts3_hash.o fts3_icu.o fts3_porter.o \
         fts3_snippet.o fts3_tokenizer.o fts3_tokenizer1.o \
         fts3_write.o func.o global.o hash.o \
         icu.o insert.o kvmem.o legacy.o \
         main.o malloc.o math.o mem0.o mem1.o mem2.o mem3.o mem5.o \

         mutex.o mutex_noop.o mutex_os2.o mutex_unix.o mutex_w32.o \
         opcodes.o os.o os_os2.o os_unix.o os_win.o \
         parse.o pragma.o prepare.o printf.o \
         random.o resolve.o rowset.o rtree.o select.o status.o storage.o \
         table.o tokenize.o trigger.o \
         update.o util.o varint.o \
         vdbe.o vdbeapi.o vdbeaux.o vdbecodec.o vdbecursor.o \
         vdbemem.o vdbesort.o vdbetrace.o \
         walker.o where.o utf.o vtab.o



# All of the source code files.
#
SRC = \
  $(TOP)/src/alter.c \
  $(TOP)/src/analyze.c \
  $(TOP)/src/attach.c \
  $(TOP)/src/auth.c \

  $(TOP)/src/bitvec.c \




  $(TOP)/src/build.c \
  $(TOP)/src/callback.c \
  $(TOP)/src/complete.c \
  $(TOP)/src/ctime.c \
  $(TOP)/src/date.c \
  $(TOP)/src/delete.c \
  $(TOP)/src/expr.c \
................................................................................
  $(TOP)/src/fkey.c \
  $(TOP)/src/func.c \
  $(TOP)/src/global.c \
  $(TOP)/src/hash.c \
  $(TOP)/src/hash.h \
  $(TOP)/src/hwtime.h \
  $(TOP)/src/insert.c \

  $(TOP)/src/kvmem.c \
  $(TOP)/src/legacy.c \

  $(TOP)/src/main.c \
  $(TOP)/src/malloc.c \
  $(TOP)/src/math.c \
  $(TOP)/src/mem0.c \
  $(TOP)/src/mem1.c \
  $(TOP)/src/mem2.c \
  $(TOP)/src/mem3.c \
  $(TOP)/src/mem5.c \

  $(TOP)/src/mutex.c \
  $(TOP)/src/mutex.h \
  $(TOP)/src/mutex_noop.c \
  $(TOP)/src/mutex_os2.c \
  $(TOP)/src/mutex_unix.c \
  $(TOP)/src/mutex_w32.c \

  $(TOP)/src/os.c \
  $(TOP)/src/os.h \
  $(TOP)/src/os_common.h \
  $(TOP)/src/os_os2.c \
  $(TOP)/src/os_unix.c \
  $(TOP)/src/os_win.c \


  $(TOP)/src/parse.y \



  $(TOP)/src/pragma.c \
  $(TOP)/src/prepare.c \
  $(TOP)/src/printf.c \
  $(TOP)/src/random.c \
  $(TOP)/src/resolve.c \
  $(TOP)/src/rowset.c \
  $(TOP)/src/select.c \
  $(TOP)/src/shell.c \
  $(TOP)/src/sqlite.h.in \

  $(TOP)/src/sqliteInt.h \
  $(TOP)/src/sqliteLimit.h \
  $(TOP)/src/status.c \
  $(TOP)/src/storage.c \
  $(TOP)/src/storage.h \
  $(TOP)/src/table.c \
  $(TOP)/src/tclsqlite.c \
................................................................................
  $(TOP)/src/update.c \
  $(TOP)/src/util.c \
  $(TOP)/src/varint.c \
  $(TOP)/src/vdbe.c \
  $(TOP)/src/vdbe.h \
  $(TOP)/src/vdbeapi.c \
  $(TOP)/src/vdbeaux.c \

  $(TOP)/src/vdbemem.c \
  $(TOP)/src/vdbesort.c \
  $(TOP)/src/vdbetrace.c \
  $(TOP)/src/vdbeInt.h \
  $(TOP)/src/vtab.c \
  $(TOP)/src/walker.c \
  $(TOP)/src/where.c

# Source code for extensions
#
SRC += \


















  $(TOP)/ext/fts3/fts3.c \
  $(TOP)/ext/fts3/fts3.h \
  $(TOP)/ext/fts3/fts3Int.h \
  $(TOP)/ext/fts3/fts3_aux.c \
  $(TOP)/ext/fts3/fts3_expr.c \
  $(TOP)/ext/fts3/fts3_hash.c \
  $(TOP)/ext/fts3/fts3_hash.h \
................................................................................

# Source code to the test files.
#
TESTSRC = \
  $(TOP)/ext/fts3/fts3_term.c \
  $(TOP)/ext/fts3/fts3_test.c \
  $(TOP)/src/test1.c \


  $(TOP)/src/test4.c \
  $(TOP)/src/test5.c \
  $(TOP)/src/test6.c \
  $(TOP)/src/test7.c \
  $(TOP)/src/test8.c \
  $(TOP)/src/test9.c \



  $(TOP)/src/test_config.c \
  $(TOP)/src/test_demovfs.c \
  $(TOP)/src/test_devsym.c \

  $(TOP)/src/test_fuzzer.c \
  $(TOP)/src/test_hexio.c \
  $(TOP)/src/test_init.c \
  $(TOP)/src/test_intarray.c \
  $(TOP)/src/test_journal.c \
  $(TOP)/src/test_malloc.c \
  $(TOP)/src/test_mutex.c \
  $(TOP)/src/test_onefile.c \
  $(TOP)/src/test_osinst.c \


  $(TOP)/src/test_rtree.c \
  $(TOP)/src/test_schema.c \

  $(TOP)/src/test_storage.c \


  $(TOP)/src/test_tclvar.c \
  $(TOP)/src/test_thread.c \
  $(TOP)/src/test_vfs.c \
  $(TOP)/src/test_wholenumber.c \
  $(TOP)/src/test_wsd.c

#TESTSRC += $(TOP)/ext/fts2/fts2_tokenizer.c
#TESTSRC += $(TOP)/ext/fts3/fts3_tokenizer.c

TESTSRC2 = \
  $(TOP)/src/attach.c \


  $(TOP)/src/build.c \
  $(TOP)/src/date.c \
  $(TOP)/src/expr.c \
  $(TOP)/src/func.c \
  $(TOP)/src/insert.c \
  $(TOP)/src/mem5.c \
  $(TOP)/src/os.c \
  $(TOP)/src/os_os2.c \
  $(TOP)/src/os_unix.c \
  $(TOP)/src/os_win.c \

  $(TOP)/src/pragma.c \
  $(TOP)/src/prepare.c \
  $(TOP)/src/printf.c \
  $(TOP)/src/random.c \


  $(TOP)/src/select.c \
  $(TOP)/src/tokenize.c \
  $(TOP)/src/utf.c \
  $(TOP)/src/util.c \
  $(TOP)/src/vdbeapi.c \
  $(TOP)/src/vdbeaux.c \
  $(TOP)/src/vdbe.c \
................................................................................
  $(TOP)/ext/fts3/fts3_expr.c \
  $(TOP)/ext/fts3/fts3_tokenizer.c \
  $(TOP)/ext/fts3/fts3_write.c

# Header files used by all library source files.
#
HDR = \


   $(TOP)/src/hash.h \
   $(TOP)/src/hwtime.h \
   keywordhash.h \
   $(TOP)/src/mutex.h \
   opcodes.h \
   $(TOP)/src/os.h \
   $(TOP)/src/os_common.h \


   parse.h  \
   sqlite4.h  \

   $(TOP)/src/sqliteInt.h  \
   $(TOP)/src/sqliteLimit.h \
   $(TOP)/src/storage.h \
   $(TOP)/src/vdbe.h \
   $(TOP)/src/vdbeInt.h



EXTHDR = \








  $(TOP)/ext/fts3/fts3.h \
  $(TOP)/ext/fts3/fts3Int.h \
  $(TOP)/ext/fts3/fts3_hash.h \
  $(TOP)/ext/fts3/fts3_tokenizer.h
EXTHDR += \
  $(TOP)/ext/rtree/rtree.h
EXTHDR += \

Changes to notes/key_encoding.txt.

88
89
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97
98
99
100
101
102
103
104
105
106
107
108
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111

112
113
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115





116
117
118












119


120

121
122



123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141

142
143
144
145
146
147
148
149
150
151
152
153
and 0x0c.

Finite non-zero values are classified as either large, or small.
Small values have an absolute value less than 1.  Large values have an
absolute value of 1 or more.  The value 1.0 is considered large.

For both large and small values, we compute a mantissa M and an
exponent E.  The mantissa is a base-10 representation of the
value.  The exponent E determines where to put the decimal point.

Each decimal digit of the mantissa is stored in a half-byte.  There
are two decimal digits per byte.  Digit 0 has a value of 1.  Digit 9
has a value of A (binary 1010).  The other digits have values in 
between.  A value of 0 is the end-of-content marker.  The mantissa 
is composed  of one or more bytes, ending with a single byte where
the lower four bits at least are the end-of-content mark.  The upper
four bits of the last byte may or may not be zero too, depending on
how many other digits exist in the mantissa.

If we assume all digits of the mantissa occur to the right of the
decimal point, then the exponent E is one less than the power of ten 
by which one must multiply the mantissa to recover the original value. 
Or, E is one less than the number of digits that occur to the left of 
the decimal point.


Examples:

   Value          Exponent E      Significand M (in hex)





  --------        ----------      ----------------------
    1.0              0              20
    100.0            2              20












    1234             3              23 45 00


    12345            4              23 45 60

    12.345           1              23 45 60
    0.123            -1             23 40




The E value is stored in the encoding as an unsigned varint.  And 
since E can be negative, that means we need separate cases for positive
and negative E value.  That is why large and small numbers are treated
differently.  Large numbers have a positive or zero E and small numbers
have a negative E.

Large negative numbers have an initial byte of 0x08 followed by the
ones-complement of the varint of E followed by the ones-complement of
M.  Small negative numbers have an initial byte of 0x09 followed by
the varint of -E followed by the ones-complement of M.  Small positive
numbers have an initial byte of 0x0b followed by the ones-complement of
the varint of -E followed by M.  Finally, large positive nubmers have
an initial byte of 0x0c followed by the varint of E followed by M.

SUMMARY

Each SQL value is encoded as one or more bytes.  The first byte of
the encoding is as follows:


  0x05 NULL
  0x06 NaN
  0x07 negative infinity
  0x08 negative-large ~E ~M
  0x09 negative-small -E ~M
  0x0a zero
  0x0b positive-small ~-E M
  0x0c positive-large E M
  0x0d positive infinity
  0x0e text T
  0x0f binary B







|


|
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<
<
<


|
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<
<
>



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>
>
>
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>
>
>
>
>
>
>
>
>
>
>
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>
|
>
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>
>
>




|
|












|
>












88
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91
92
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95
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100
101




102
103
104
105


106
107
108
109
110
111
112
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114
115
116
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118
119
120
121
122
123
124
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127
128
129
130
131
132
133
134
135
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137
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139
140
141
142
143
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146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
and 0x0c.

Finite non-zero values are classified as either large, or small.
Small values have an absolute value less than 1.  Large values have an
absolute value of 1 or more.  The value 1.0 is considered large.

For both large and small values, we compute a mantissa M and an
exponent E.  The mantissa is a base-100 representation of the
value.  The exponent E determines where to put the decimal point.

Each centimal digit of the mantissa is stored in a byte.  If the
value of the centimal digit is X (hence X>=0 and X<=99) then the
byte value will be 2*X+1 for every byte of the mantissa, except
for the last byte which will be 2*X+0.





If we assume all digits of the mantissa occur to the right of the
decimal point, then the exponent E is the power of one hundred
by which one must multiply the mantissa to recover the original 


value.

Examples:

   Value               Exponent E    Significand M (in hex)
  --------             ----------    ----------------------
    1.0                    1          02
    10.0                   1          14
    99.0                   1          b4
    99.01                  1          b5 02
    99.0001                1          b5 01 02
    100.0                  2          03 00
    100.1                  2          03 02
    100.01                 2          03 01 02
    1234                   2          19 44
    9999                   2          c7 c6
    9999.000001            2          c7 c7 01 01 02
    9999.000009            2          c7 c7 01 01 12
    9999.00001             2          c7 c7 01 01 14
    9999.00009             2          c7 c7 01 01 b4
    9999.000099            2          c7 c7 01 01 c6
    9999.0001              2          c7 c7 01 02
    9999.001               2          c7 c7 01 14
    9999.01                2          c7 c7 02
    9999.1                 2          c7 c7 14
    10000                  3          02
    10001                  3          03 00 02
    12345                  3          03 2f 5a
    123450                 4          19 45 64
    1234.5                 3          19 45 64 
    12.345                 2          19 45 64
    0.123                  0          19 3c
    0.0123                 0          03 2e
    0.00123               -1          19 3c
    9223372036854775807   10          13 2d 43 91 07 89 6d 9b 75 0e

The E value is stored in the encoding as an unsigned varint.  And 
since E can be negative, that means we need separate cases for positive
and negative E value.  That is why large and small numbers are treated
differently.  Large numbers have a positive E and small numbers
have a zero or negative E.

Large negative numbers have an initial byte of 0x08 followed by the
ones-complement of the varint of E followed by the ones-complement of
M.  Small negative numbers have an initial byte of 0x09 followed by
the varint of -E followed by the ones-complement of M.  Small positive
numbers have an initial byte of 0x0b followed by the ones-complement of
the varint of -E followed by M.  Finally, large positive nubmers have
an initial byte of 0x0c followed by the varint of E followed by M.

SUMMARY

Each SQL value is encoded as one or more bytes.  The first byte of
the encoding, its meaning, and a terse description of the bytes that
follow is given by the following table:

  0x05 NULL
  0x06 NaN
  0x07 negative infinity
  0x08 negative-large ~E ~M
  0x09 negative-small -E ~M
  0x0a zero
  0x0b positive-small ~-E M
  0x0c positive-large E M
  0x0d positive infinity
  0x0e text T
  0x0f binary B

Changes to src/alter.c.

335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
...
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
...
583
584
585
586
587
588
589
590
591
592
593
594
595
596
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599
600
601
602
603
604
605
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607
608
609
610
611
612
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614
615
616
617
618
619
620
621
...
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
...
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
...
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
  int iDb;                   /* Index of database containing pTab */
#ifndef SQLITE_OMIT_TRIGGER
  Trigger *pTrig;
#endif

  v = sqlite4GetVdbe(pParse);
  if( NEVER(v==0) ) return;
  assert( sqlite4BtreeHoldsAllMutexes(pParse->db) );
  iDb = sqlite4SchemaToIndex(pParse->db, pTab->pSchema);
  assert( iDb>=0 );

#ifndef SQLITE_OMIT_TRIGGER
  /* Drop any table triggers from the internal schema. */
  for(pTrig=sqlite4TriggerList(pParse, pTab); pTrig; pTrig=pTrig->pNext){
    int iTrigDb = sqlite4SchemaToIndex(pParse->db, pTrig->pSchema);
................................................................................
#endif
  VTable *pVTab = 0;        /* Non-zero if this is a v-tab with an xRename() */
  int savedDbFlags;         /* Saved value of db->flags */

  savedDbFlags = db->flags;  
  if( NEVER(db->mallocFailed) ) goto exit_rename_table;
  assert( pSrc->nSrc==1 );
  assert( sqlite4BtreeHoldsAllMutexes(pParse->db) );

  pTab = sqlite4LocateTable(pParse, 0, pSrc->a[0].zName, pSrc->a[0].zDatabase);
  if( !pTab ) goto exit_rename_table;
  iDb = sqlite4SchemaToIndex(pParse->db, pTab->pSchema);
  zDb = db->aDb[iDb].zName;
  db->flags |= SQLITE_PreferBuiltin;

................................................................................
exit_rename_table:
  sqlite4SrcListDelete(db, pSrc);
  sqlite4DbFree(db, zName);
  db->flags = savedDbFlags;
}


/*
** Generate code to make sure the file format number is at least minFormat.
** The generated code will increase the file format number if necessary.
*/
void sqlite4MinimumFileFormat(Parse *pParse, int iDb, int minFormat){
  Vdbe *v;
  v = sqlite4GetVdbe(pParse);
  /* The VDBE should have been allocated before this routine is called.
  ** If that allocation failed, we would have quit before reaching this
  ** point */
  if( ALWAYS(v) ){
    int r1 = sqlite4GetTempReg(pParse);
    int r2 = sqlite4GetTempReg(pParse);
    int j1;
    sqlite4VdbeAddOp3(v, OP_ReadCookie, iDb, r1, BTREE_FILE_FORMAT);
    sqlite4VdbeUsesBtree(v, iDb);
    sqlite4VdbeAddOp2(v, OP_Integer, minFormat, r2);
    j1 = sqlite4VdbeAddOp3(v, OP_Ge, r2, 0, r1);
    sqlite4VdbeAddOp3(v, OP_SetCookie, iDb, BTREE_FILE_FORMAT, r2);
    sqlite4VdbeJumpHere(v, j1);
    sqlite4ReleaseTempReg(pParse, r1);
    sqlite4ReleaseTempReg(pParse, r2);
  }
}

/*
** This function is called after an "ALTER TABLE ... ADD" statement
** has been parsed. Argument pColDef contains the text of the new
** column definition.
**
** The Table structure pParse->pNewTable was extended to include
** the new column during parsing.
................................................................................
  sqlite4 *db;              /* The database connection; */

  db = pParse->db;
  if( pParse->nErr || db->mallocFailed ) return;
  pNew = pParse->pNewTable;
  assert( pNew );

  assert( sqlite4BtreeHoldsAllMutexes(db) );
  iDb = sqlite4SchemaToIndex(db, pNew->pSchema);
  zDb = db->aDb[iDb].zName;
  zTab = &pNew->zName[16];  /* Skip the "sqlite_altertab_" prefix on the name */
  pCol = &pNew->aCol[pNew->nCol-1];
  pDflt = pCol->pDflt;
  pTab = sqlite4FindTable(db, zTab, zDb);
  assert( pTab );
................................................................................
      zDb, SCHEMA_TABLE(iDb), pNew->addColOffset, zCol, pNew->addColOffset+1,
      zTab
    );
    sqlite4DbFree(db, zCol);
    db->flags = savedDbFlags;
  }

  /* If the default value of the new column is NULL, then set the file
  ** format to 2. If the default value of the new column is not NULL,
  ** the file format becomes 3.
  */
  sqlite4MinimumFileFormat(pParse, iDb, pDflt ? 3 : 2);

  /* Reload the schema of the modified table. */
  reloadTableSchema(pParse, pTab, pTab->zName);
}

/*
** This function is called by the parser after the table-name in
** an "ALTER TABLE <table-name> ADD" statement is parsed. Argument 
................................................................................
  int iDb;
  int i;
  int nAlloc;
  sqlite4 *db = pParse->db;

  /* Look up the table being altered. */
  assert( pParse->pNewTable==0 );
  assert( sqlite4BtreeHoldsAllMutexes(db) );
  if( db->mallocFailed ) goto exit_begin_add_column;
  pTab = sqlite4LocateTable(pParse, 0, pSrc->a[0].zName, pSrc->a[0].zDatabase);
  if( !pTab ) goto exit_begin_add_column;

#ifndef SQLITE_OMIT_VIRTUALTABLE
  if( IsVirtual(pTab) ){
    sqlite4ErrorMsg(pParse, "virtual tables may not be altered");







<







 







<







 







<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<







 







<







 







<
<
<
<
<
<







 







<







335
336
337
338
339
340
341

342
343
344
345
346
347
348
...
407
408
409
410
411
412
413

414
415
416
417
418
419
420
...
581
582
583
584
585
586
587

























588
589
590
591
592
593
594
...
605
606
607
608
609
610
611

612
613
614
615
616
617
618
...
687
688
689
690
691
692
693






694
695
696
697
698
699
700
...
717
718
719
720
721
722
723

724
725
726
727
728
729
730
  int iDb;                   /* Index of database containing pTab */
#ifndef SQLITE_OMIT_TRIGGER
  Trigger *pTrig;
#endif

  v = sqlite4GetVdbe(pParse);
  if( NEVER(v==0) ) return;

  iDb = sqlite4SchemaToIndex(pParse->db, pTab->pSchema);
  assert( iDb>=0 );

#ifndef SQLITE_OMIT_TRIGGER
  /* Drop any table triggers from the internal schema. */
  for(pTrig=sqlite4TriggerList(pParse, pTab); pTrig; pTrig=pTrig->pNext){
    int iTrigDb = sqlite4SchemaToIndex(pParse->db, pTrig->pSchema);
................................................................................
#endif
  VTable *pVTab = 0;        /* Non-zero if this is a v-tab with an xRename() */
  int savedDbFlags;         /* Saved value of db->flags */

  savedDbFlags = db->flags;  
  if( NEVER(db->mallocFailed) ) goto exit_rename_table;
  assert( pSrc->nSrc==1 );


  pTab = sqlite4LocateTable(pParse, 0, pSrc->a[0].zName, pSrc->a[0].zDatabase);
  if( !pTab ) goto exit_rename_table;
  iDb = sqlite4SchemaToIndex(pParse->db, pTab->pSchema);
  zDb = db->aDb[iDb].zName;
  db->flags |= SQLITE_PreferBuiltin;

................................................................................
exit_rename_table:
  sqlite4SrcListDelete(db, pSrc);
  sqlite4DbFree(db, zName);
  db->flags = savedDbFlags;
}



























/*
** This function is called after an "ALTER TABLE ... ADD" statement
** has been parsed. Argument pColDef contains the text of the new
** column definition.
**
** The Table structure pParse->pNewTable was extended to include
** the new column during parsing.
................................................................................
  sqlite4 *db;              /* The database connection; */

  db = pParse->db;
  if( pParse->nErr || db->mallocFailed ) return;
  pNew = pParse->pNewTable;
  assert( pNew );


  iDb = sqlite4SchemaToIndex(db, pNew->pSchema);
  zDb = db->aDb[iDb].zName;
  zTab = &pNew->zName[16];  /* Skip the "sqlite_altertab_" prefix on the name */
  pCol = &pNew->aCol[pNew->nCol-1];
  pDflt = pCol->pDflt;
  pTab = sqlite4FindTable(db, zTab, zDb);
  assert( pTab );
................................................................................
      zDb, SCHEMA_TABLE(iDb), pNew->addColOffset, zCol, pNew->addColOffset+1,
      zTab
    );
    sqlite4DbFree(db, zCol);
    db->flags = savedDbFlags;
  }







  /* Reload the schema of the modified table. */
  reloadTableSchema(pParse, pTab, pTab->zName);
}

/*
** This function is called by the parser after the table-name in
** an "ALTER TABLE <table-name> ADD" statement is parsed. Argument 
................................................................................
  int iDb;
  int i;
  int nAlloc;
  sqlite4 *db = pParse->db;

  /* Look up the table being altered. */
  assert( pParse->pNewTable==0 );

  if( db->mallocFailed ) goto exit_begin_add_column;
  pTab = sqlite4LocateTable(pParse, 0, pSrc->a[0].zName, pSrc->a[0].zDatabase);
  if( !pTab ) goto exit_begin_add_column;

#ifndef SQLITE_OMIT_VIRTUALTABLE
  if( IsVirtual(pTab) ){
    sqlite4ErrorMsg(pParse, "virtual tables may not be altered");

Changes to src/analyze.c.

153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
...
474
475
476
477
478
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486
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491
...
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
...
741
742
743
744
745
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748
749
750
751
752
753
754
755
...
778
779
780
781
782
783
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786
787
788
789
790
791
792
....
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
  u8 aCreateTbl[] = {0, 0};

  int i;
  sqlite4 *db = pParse->db;
  Db *pDb;
  Vdbe *v = sqlite4GetVdbe(pParse);
  if( v==0 ) return;
  assert( sqlite4BtreeHoldsAllMutexes(db) );
  assert( sqlite4VdbeDb(v)==db );
  pDb = &db->aDb[iDb];

  /* Create new statistic tables if they do not exist, or clear them
  ** if they do already exist.
  */
  for(i=0; i<ArraySize(aTable); i++){
................................................................................
    /* Do not gather statistics on views or virtual tables */
    return;
  }
  if( memcmp(pTab->zName, "sqlite_", 7)==0 ){
    /* Do not gather statistics on system tables */
    return;
  }
  assert( sqlite4BtreeHoldsAllMutexes(db) );
  iDb = sqlite4SchemaToIndex(db, pTab->pSchema);
  assert( iDb>=0 );
  assert( sqlite4SchemaMutexHeld(db, iDb, 0) );
#ifndef SQLITE_OMIT_AUTHORIZATION
  if( sqlite4AuthCheck(pParse, SQLITE_ANALYZE, pTab->zName, 0,
      db->aDb[iDb].zName ) ){
    return;
  }
#endif

................................................................................
  int iMem;

  sqlite4BeginWriteOperation(pParse, 0, iDb);
  iStatCur = pParse->nTab;
  pParse->nTab += 3;
  openStatTable(pParse, iDb, iStatCur, 0, 0);
  iMem = pParse->nMem+1;
  assert( sqlite4SchemaMutexHeld(db, iDb, 0) );
  for(k=sqliteHashFirst(&pSchema->tblHash); k; k=sqliteHashNext(k)){
    Table *pTab = (Table*)sqliteHashData(k);
    analyzeOneTable(pParse, pTab, 0, iStatCur, iMem);
  }
  loadAnalysis(pParse, iDb);
}

................................................................................
** in pTab that should be analyzed.
*/
static void analyzeTable(Parse *pParse, Table *pTab, Index *pOnlyIdx){
  int iDb;
  int iStatCur;

  assert( pTab!=0 );
  assert( sqlite4BtreeHoldsAllMutexes(pParse->db) );
  iDb = sqlite4SchemaToIndex(pParse->db, pTab->pSchema);
  sqlite4BeginWriteOperation(pParse, 0, iDb);
  iStatCur = pParse->nTab;
  pParse->nTab += 3;
  if( pOnlyIdx ){
    openStatTable(pParse, iDb, iStatCur, pOnlyIdx->zName, "idx");
  }else{
................................................................................
  char *z, *zDb;
  Table *pTab;
  Index *pIdx;
  Token *pTableName;

  /* Read the database schema. If an error occurs, leave an error message
  ** and code in pParse and return NULL. */
  assert( sqlite4BtreeHoldsAllMutexes(pParse->db) );
  if( SQLITE_OK!=sqlite4ReadSchema(pParse) ){
    return;
  }

  assert( pName2!=0 || pName1==0 );
  if( pName1==0 ){
    /* Form 1:  Analyze everything */
................................................................................
int sqlite4AnalysisLoad(sqlite4 *db, int iDb){
  analysisInfo sInfo;
  HashElem *i;
  char *zSql;
  int rc;

  assert( iDb>=0 && iDb<db->nDb );
  assert( db->aDb[iDb].pBt!=0 );

  /* Clear any prior statistics */
  assert( sqlite4SchemaMutexHeld(db, iDb, 0) );
  for(i=sqliteHashFirst(&db->aDb[iDb].pSchema->idxHash);i;i=sqliteHashNext(i)){
    Index *pIdx = sqliteHashData(i);
    sqlite4DefaultRowEst(pIdx);
#ifdef SQLITE_ENABLE_STAT3
    sqlite4DeleteIndexSamples(db, pIdx);
    pIdx->aSample = 0;
#endif







<







 







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<







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  u8 aCreateTbl[] = {0, 0};

  int i;
  sqlite4 *db = pParse->db;
  Db *pDb;
  Vdbe *v = sqlite4GetVdbe(pParse);
  if( v==0 ) return;

  assert( sqlite4VdbeDb(v)==db );
  pDb = &db->aDb[iDb];

  /* Create new statistic tables if they do not exist, or clear them
  ** if they do already exist.
  */
  for(i=0; i<ArraySize(aTable); i++){
................................................................................
    /* Do not gather statistics on views or virtual tables */
    return;
  }
  if( memcmp(pTab->zName, "sqlite_", 7)==0 ){
    /* Do not gather statistics on system tables */
    return;
  }

  iDb = sqlite4SchemaToIndex(db, pTab->pSchema);
  assert( iDb>=0 );

#ifndef SQLITE_OMIT_AUTHORIZATION
  if( sqlite4AuthCheck(pParse, SQLITE_ANALYZE, pTab->zName, 0,
      db->aDb[iDb].zName ) ){
    return;
  }
#endif

................................................................................
  int iMem;

  sqlite4BeginWriteOperation(pParse, 0, iDb);
  iStatCur = pParse->nTab;
  pParse->nTab += 3;
  openStatTable(pParse, iDb, iStatCur, 0, 0);
  iMem = pParse->nMem+1;

  for(k=sqliteHashFirst(&pSchema->tblHash); k; k=sqliteHashNext(k)){
    Table *pTab = (Table*)sqliteHashData(k);
    analyzeOneTable(pParse, pTab, 0, iStatCur, iMem);
  }
  loadAnalysis(pParse, iDb);
}

................................................................................
** in pTab that should be analyzed.
*/
static void analyzeTable(Parse *pParse, Table *pTab, Index *pOnlyIdx){
  int iDb;
  int iStatCur;

  assert( pTab!=0 );

  iDb = sqlite4SchemaToIndex(pParse->db, pTab->pSchema);
  sqlite4BeginWriteOperation(pParse, 0, iDb);
  iStatCur = pParse->nTab;
  pParse->nTab += 3;
  if( pOnlyIdx ){
    openStatTable(pParse, iDb, iStatCur, pOnlyIdx->zName, "idx");
  }else{
................................................................................
  char *z, *zDb;
  Table *pTab;
  Index *pIdx;
  Token *pTableName;

  /* Read the database schema. If an error occurs, leave an error message
  ** and code in pParse and return NULL. */

  if( SQLITE_OK!=sqlite4ReadSchema(pParse) ){
    return;
  }

  assert( pName2!=0 || pName1==0 );
  if( pName1==0 ){
    /* Form 1:  Analyze everything */
................................................................................
int sqlite4AnalysisLoad(sqlite4 *db, int iDb){
  analysisInfo sInfo;
  HashElem *i;
  char *zSql;
  int rc;

  assert( iDb>=0 && iDb<db->nDb );
  assert( db->aDb[iDb].pKV!=0 );

  /* Clear any prior statistics */

  for(i=sqliteHashFirst(&db->aDb[iDb].pSchema->idxHash);i;i=sqliteHashNext(i)){
    Index *pIdx = sqliteHashData(i);
    sqlite4DefaultRowEst(pIdx);
#ifdef SQLITE_ENABLE_STAT3
    sqlite4DeleteIndexSamples(db, pIdx);
    pIdx->aSample = 0;
#endif

Changes to src/attach.c.

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    if( rc==SQLITE_NOMEM ) db->mallocFailed = 1;
    sqlite4_result_error(context, zErr, -1);
    sqlite4_free(zErr);
    return;
  }
  assert( pVfs );
  flags |= SQLITE_OPEN_MAIN_DB;
  rc = sqlite4BtreeOpen(pVfs, zPath, db, &aNew->pBt, 0, flags);
  if( rc==SQLITE_OK ) sqlite4KVStoreOpen(zPath, &aNew->pKV);
  sqlite4_free( zPath );
  db->nDb++;
  if( rc==SQLITE_CONSTRAINT ){
    rc = SQLITE_ERROR;
    zErrDyn = sqlite4MPrintf(db, "database is already attached");
  }else if( rc==SQLITE_OK ){
    Pager *pPager;
    aNew->pSchema = sqlite4SchemaGet(db, aNew->pBt);
    if( !aNew->pSchema ){
      rc = SQLITE_NOMEM;
    }else if( aNew->pSchema->file_format && aNew->pSchema->enc!=ENC(db) ){
      zErrDyn = sqlite4MPrintf(db, 
        "attached databases must use the same text encoding as main database");
      rc = SQLITE_ERROR;
    }
    pPager = sqlite4BtreePager(aNew->pBt);
    sqlite4PagerLockingMode(pPager, db->dfltLockMode);
    /*sqlite4BtreeSecureDelete(aNew->pBt,
                             sqlite4BtreeSecureDelete(db->aDb[0].pBt,-1) );*/
  }
  aNew->safety_level = 3;
  aNew->zName = sqlite4DbStrDup(db, zName);
  if( rc==SQLITE_OK && aNew->zName==0 ){
    rc = SQLITE_NOMEM;
  }


#ifdef SQLITE_HAS_CODEC
  if( rc==SQLITE_OK ){
    extern int sqlite4CodecAttach(sqlite4*, int, const void*, int);
    extern void sqlite4CodecGetKey(sqlite4*, int, void**, int*);
    int nKey;
    char *zKey;
    int t = sqlite4_value_type(argv[2]);
    switch( t ){
      case SQLITE_INTEGER:
      case SQLITE_FLOAT:
        zErrDyn = sqlite4DbStrDup(db, "Invalid key value");
        rc = SQLITE_ERROR;
        break;
        
      case SQLITE_TEXT:
      case SQLITE_BLOB:
        nKey = sqlite4_value_bytes(argv[2]);
        zKey = (char *)sqlite4_value_blob(argv[2]);
        rc = sqlite4CodecAttach(db, db->nDb-1, zKey, nKey);
        break;

      case SQLITE_NULL:
        /* No key specified.  Use the key from the main database */
        sqlite4CodecGetKey(db, 0, (void**)&zKey, &nKey);
        if( nKey>0 || sqlite4BtreeGetReserve(db->aDb[0].pBt)>0 ){
          rc = sqlite4CodecAttach(db, db->nDb-1, zKey, nKey);
        }
        break;
    }
  }
#endif

  /* If the file was opened successfully, read the schema for the new database.
  ** If this fails, or if opening the file failed, then close the file and 
  ** remove the entry from the db->aDb[] array. i.e. put everything back the way
  ** we found it.
  */
  if( rc==SQLITE_OK ){
    sqlite4BtreeEnterAll(db);
    rc = sqlite4Init(db, &zErrDyn);
    sqlite4BtreeLeaveAll(db);
  }
  if( rc ){
    int iDb = db->nDb - 1;
    assert( iDb>=2 );
    if( db->aDb[iDb].pBt ){
      sqlite4BtreeClose(db->aDb[iDb].pBt);
      db->aDb[iDb].pBt = 0;
      sqlite4KVStoreClose(db->aDb[iDb].pKV);
      db->aDb[iDb].pKV = 0;
      db->aDb[iDb].pSchema = 0;
    }
    sqlite4ResetInternalSchema(db, -1);
    db->nDb = iDb;
    if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ){
................................................................................
  char zErr[128];

  UNUSED_PARAMETER(NotUsed);

  if( zName==0 ) zName = "";
  for(i=0; i<db->nDb; i++){
    pDb = &db->aDb[i];
    if( pDb->pBt==0 ) continue;
    if( sqlite4StrICmp(pDb->zName, zName)==0 ) break;
  }

  if( i>=db->nDb ){
    sqlite4_snprintf(sizeof(zErr),zErr, "no such database: %s", zName);
    goto detach_error;
  }
................................................................................
    goto detach_error;
  }
  if( !db->autoCommit ){
    sqlite4_snprintf(sizeof(zErr), zErr,
                     "cannot DETACH database within transaction");
    goto detach_error;
  }
  if( sqlite4BtreeIsInReadTrans(pDb->pBt) || sqlite4BtreeIsInBackup(pDb->pBt) ){
    sqlite4_snprintf(sizeof(zErr),zErr, "database %s is locked", zName);
    goto detach_error;
  }

  sqlite4BtreeClose(pDb->pBt);
  pDb->pBt = 0;
  sqlite4KVStoreClose(pDb->pKV);
  pDb->pKV = 0;
  pDb->pSchema = 0;
  sqlite4ResetInternalSchema(db, -1);
  return;

detach_error:







|
<






<
|







<
<
<
<

<





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<

<




|
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<







 







|







 







|




<
<







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    if( rc==SQLITE_NOMEM ) db->mallocFailed = 1;
    sqlite4_result_error(context, zErr, -1);
    sqlite4_free(zErr);
    return;
  }
  assert( pVfs );
  flags |= SQLITE_OPEN_MAIN_DB;
  rc = sqlite4KVStoreOpen(db, zName, zPath, &aNew->pKV, 0);

  sqlite4_free( zPath );
  db->nDb++;
  if( rc==SQLITE_CONSTRAINT ){
    rc = SQLITE_ERROR;
    zErrDyn = sqlite4MPrintf(db, "database is already attached");
  }else if( rc==SQLITE_OK ){

    aNew->pSchema = sqlite4SchemaGet(db);
    if( !aNew->pSchema ){
      rc = SQLITE_NOMEM;
    }else if( aNew->pSchema->file_format && aNew->pSchema->enc!=ENC(db) ){
      zErrDyn = sqlite4MPrintf(db, 
        "attached databases must use the same text encoding as main database");
      rc = SQLITE_ERROR;
    }




  }

  aNew->zName = sqlite4DbStrDup(db, zName);
  if( rc==SQLITE_OK && aNew->zName==0 ){
    rc = SQLITE_NOMEM;
  }


































  /* If the file was opened successfully, read the schema for the new database.
  ** If this fails, or if opening the file failed, then close the file and 
  ** remove the entry from the db->aDb[] array. i.e. put everything back the way
  ** we found it.
  */
  if( rc==SQLITE_OK ){

    rc = sqlite4Init(db, &zErrDyn);

  }
  if( rc ){
    int iDb = db->nDb - 1;
    assert( iDb>=2 );
    if( db->aDb[iDb].pKV ){


      sqlite4KVStoreClose(db->aDb[iDb].pKV);
      db->aDb[iDb].pKV = 0;
      db->aDb[iDb].pSchema = 0;
    }
    sqlite4ResetInternalSchema(db, -1);
    db->nDb = iDb;
    if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ){
................................................................................
  char zErr[128];

  UNUSED_PARAMETER(NotUsed);

  if( zName==0 ) zName = "";
  for(i=0; i<db->nDb; i++){
    pDb = &db->aDb[i];
    if( pDb->pKV==0 ) continue;
    if( sqlite4StrICmp(pDb->zName, zName)==0 ) break;
  }

  if( i>=db->nDb ){
    sqlite4_snprintf(sizeof(zErr),zErr, "no such database: %s", zName);
    goto detach_error;
  }
................................................................................
    goto detach_error;
  }
  if( !db->autoCommit ){
    sqlite4_snprintf(sizeof(zErr), zErr,
                     "cannot DETACH database within transaction");
    goto detach_error;
  }
  if( pDb->pKV->iTransLevel ){
    sqlite4_snprintf(sizeof(zErr),zErr, "database %s is locked", zName);
    goto detach_error;
  }



  sqlite4KVStoreClose(pDb->pKV);
  pDb->pKV = 0;
  pDb->pSchema = 0;
  sqlite4ResetInternalSchema(db, -1);
  return;

detach_error:

Deleted src/backup.c.

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/*
** 2009 January 28
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains the implementation of the sqlite4_backup_XXX() 
** API functions and the related features.
*/
#include "sqliteInt.h"
#include "btreeInt.h"

/* Macro to find the minimum of two numeric values.
*/
#ifndef MIN
# define MIN(x,y) ((x)<(y)?(x):(y))
#endif

/*
** Structure allocated for each backup operation.
*/
struct sqlite4_backup {
  sqlite4* pDestDb;        /* Destination database handle */
  Btree *pDest;            /* Destination b-tree file */
  u32 iDestSchema;         /* Original schema cookie in destination */
  int bDestLocked;         /* True once a write-transaction is open on pDest */

  Pgno iNext;              /* Page number of the next source page to copy */
  sqlite4* pSrcDb;         /* Source database handle */
  Btree *pSrc;             /* Source b-tree file */

  int rc;                  /* Backup process error code */

  /* These two variables are set by every call to backup_step(). They are
  ** read by calls to backup_remaining() and backup_pagecount().
  */
  Pgno nRemaining;         /* Number of pages left to copy */
  Pgno nPagecount;         /* Total number of pages to copy */

  int isAttached;          /* True once backup has been registered with pager */
  sqlite4_backup *pNext;   /* Next backup associated with source pager */
};

/*
** THREAD SAFETY NOTES:
**
**   Once it has been created using backup_init(), a single sqlite4_backup
**   structure may be accessed via two groups of thread-safe entry points:
**
**     * Via the sqlite4_backup_XXX() API function backup_step() and 
**       backup_finish(). Both these functions obtain the source database
**       handle mutex and the mutex associated with the source BtShared 
**       structure, in that order.
**
**     * Via the BackupUpdate() and BackupRestart() functions, which are
**       invoked by the pager layer to report various state changes in
**       the page cache associated with the source database. The mutex
**       associated with the source database BtShared structure will always 
**       be held when either of these functions are invoked.
**
**   The other sqlite4_backup_XXX() API functions, backup_remaining() and
**   backup_pagecount() are not thread-safe functions. If they are called
**   while some other thread is calling backup_step() or backup_finish(),
**   the values returned may be invalid. There is no way for a call to
**   BackupUpdate() or BackupRestart() to interfere with backup_remaining()
**   or backup_pagecount().
**
**   Depending on the SQLite configuration, the database handles and/or
**   the Btree objects may have their own mutexes that require locking.
**   Non-sharable Btrees (in-memory databases for example), do not have
**   associated mutexes.
*/

/*
** Return a pointer corresponding to database zDb (i.e. "main", "temp")
** in connection handle pDb. If such a database cannot be found, return
** a NULL pointer and write an error message to pErrorDb.
**
** If the "temp" database is requested, it may need to be opened by this 
** function. If an error occurs while doing so, return 0 and write an 
** error message to pErrorDb.
*/
static Btree *findBtree(sqlite4 *pErrorDb, sqlite4 *pDb, const char *zDb){
  int i = sqlite4FindDbName(pDb, zDb);

  if( i==1 ){
    Parse *pParse;
    int rc = 0;
    pParse = sqlite4StackAllocZero(pErrorDb, sizeof(*pParse));
    if( pParse==0 ){
      sqlite4Error(pErrorDb, SQLITE_NOMEM, "out of memory");
      rc = SQLITE_NOMEM;
    }else{
      pParse->db = pDb;
      if( sqlite4OpenTempDatabase(pParse) ){
        sqlite4Error(pErrorDb, pParse->rc, "%s", pParse->zErrMsg);
        rc = SQLITE_ERROR;
      }
      sqlite4DbFree(pErrorDb, pParse->zErrMsg);
      sqlite4StackFree(pErrorDb, pParse);
    }
    if( rc ){
      return 0;
    }
  }

  if( i<0 ){
    sqlite4Error(pErrorDb, SQLITE_ERROR, "unknown database %s", zDb);
    return 0;
  }

  return pDb->aDb[i].pBt;
}

/*
** Attempt to set the page size of the destination to match the page size
** of the source.
*/
static int setDestPgsz(sqlite4_backup *p){
  int rc;
  rc = sqlite4BtreeSetPageSize(p->pDest,sqlite4BtreeGetPageSize(p->pSrc),-1,0);
  return rc;
}

/*
** Create an sqlite4_backup process to copy the contents of zSrcDb from
** connection handle pSrcDb to zDestDb in pDestDb. If successful, return
** a pointer to the new sqlite4_backup object.
**
** If an error occurs, NULL is returned and an error code and error message
** stored in database handle pDestDb.
*/
sqlite4_backup *sqlite4_backup_init(
  sqlite4* pDestDb,                     /* Database to write to */
  const char *zDestDb,                  /* Name of database within pDestDb */
  sqlite4* pSrcDb,                      /* Database connection to read from */
  const char *zSrcDb                    /* Name of database within pSrcDb */
){
  sqlite4_backup *p;                    /* Value to return */

  /* Lock the source database handle. The destination database
  ** handle is not locked in this routine, but it is locked in
  ** sqlite4_backup_step(). The user is required to ensure that no
  ** other thread accesses the destination handle for the duration
  ** of the backup operation.  Any attempt to use the destination
  ** database connection while a backup is in progress may cause
  ** a malfunction or a deadlock.
  */
  sqlite4_mutex_enter(pSrcDb->mutex);
  sqlite4_mutex_enter(pDestDb->mutex);

  if( pSrcDb==pDestDb ){
    sqlite4Error(
        pDestDb, SQLITE_ERROR, "source and destination must be distinct"
    );
    p = 0;
  }else {
    /* Allocate space for a new sqlite4_backup object...
    ** EVIDENCE-OF: R-64852-21591 The sqlite4_backup object is created by a
    ** call to sqlite4_backup_init() and is destroyed by a call to
    ** sqlite4_backup_finish(). */
    p = (sqlite4_backup *)sqlite4_malloc(sizeof(sqlite4_backup));
    if( !p ){
      sqlite4Error(pDestDb, SQLITE_NOMEM, 0);
    }
  }

  /* If the allocation succeeded, populate the new object. */
  if( p ){
    memset(p, 0, sizeof(sqlite4_backup));
    p->pSrc = findBtree(pDestDb, pSrcDb, zSrcDb);
    p->pDest = findBtree(pDestDb, pDestDb, zDestDb);
    p->pDestDb = pDestDb;
    p->pSrcDb = pSrcDb;
    p->iNext = 1;
    p->isAttached = 0;

    if( 0==p->pSrc || 0==p->pDest || setDestPgsz(p)==SQLITE_NOMEM ){
      /* One (or both) of the named databases did not exist or an OOM
      ** error was hit.  The error has already been written into the
      ** pDestDb handle.  All that is left to do here is free the
      ** sqlite4_backup structure.
      */
      sqlite4_free(p);
      p = 0;
    }
  }
  if( p ){
    p->pSrc->nBackup++;
  }

  sqlite4_mutex_leave(pDestDb->mutex);
  sqlite4_mutex_leave(pSrcDb->mutex);
  return p;
}

/*
** Argument rc is an SQLite error code. Return true if this error is 
** considered fatal if encountered during a backup operation. All errors
** are considered fatal except for SQLITE_BUSY and SQLITE_LOCKED.
*/
static int isFatalError(int rc){
  return (rc!=SQLITE_OK && rc!=SQLITE_BUSY && ALWAYS(rc!=SQLITE_LOCKED));
}

/*
** Parameter zSrcData points to a buffer containing the data for 
** page iSrcPg from the source database. Copy this data into the 
** destination database.
*/
static int backupOnePage(sqlite4_backup *p, Pgno iSrcPg, const u8 *zSrcData){
  Pager * const pDestPager = sqlite4BtreePager(p->pDest);
  const int nSrcPgsz = sqlite4BtreeGetPageSize(p->pSrc);
  int nDestPgsz = sqlite4BtreeGetPageSize(p->pDest);
  const int nCopy = MIN(nSrcPgsz, nDestPgsz);
  const i64 iEnd = (i64)iSrcPg*(i64)nSrcPgsz;
#ifdef SQLITE_HAS_CODEC
  int nSrcReserve = sqlite4BtreeGetReserve(p->pSrc);
  int nDestReserve = sqlite4BtreeGetReserve(p->pDest);
#endif

  int rc = SQLITE_OK;
  i64 iOff;

  assert( p->bDestLocked );
  assert( !isFatalError(p->rc) );
  assert( iSrcPg!=PENDING_BYTE_PAGE(p->pSrc->pBt) );
  assert( zSrcData );

  /* Catch the case where the destination is an in-memory database and the
  ** page sizes of the source and destination differ. 
  */
  if( nSrcPgsz!=nDestPgsz && sqlite4PagerIsMemdb(pDestPager) ){
    rc = SQLITE_READONLY;
  }

#ifdef SQLITE_HAS_CODEC
  /* Backup is not possible if the page size of the destination is changing
  ** and a codec is in use.
  */
  if( nSrcPgsz!=nDestPgsz && sqlite4PagerGetCodec(pDestPager)!=0 ){
    rc = SQLITE_READONLY;
  }

  /* Backup is not possible if the number of bytes of reserve space differ
  ** between source and destination.  If there is a difference, try to
  ** fix the destination to agree with the source.  If that is not possible,
  ** then the backup cannot proceed.
  */
  if( nSrcReserve!=nDestReserve ){
    u32 newPgsz = nSrcPgsz;
    rc = sqlite4PagerSetPagesize(pDestPager, &newPgsz, nSrcReserve);
    if( rc==SQLITE_OK && newPgsz!=nSrcPgsz ) rc = SQLITE_READONLY;
  }
#endif

  /* This loop runs once for each destination page spanned by the source 
  ** page. For each iteration, variable iOff is set to the byte offset
  ** of the destination page.
  */
  for(iOff=iEnd-(i64)nSrcPgsz; rc==SQLITE_OK && iOff<iEnd; iOff+=nDestPgsz){
    DbPage *pDestPg = 0;
    Pgno iDest = (Pgno)(iOff/nDestPgsz)+1;
    if( iDest==PENDING_BYTE_PAGE(p->pDest->pBt) ) continue;
    if( SQLITE_OK==(rc = sqlite4PagerGet(pDestPager, iDest, &pDestPg))
     && SQLITE_OK==(rc = sqlite4PagerWrite(pDestPg))
    ){
      const u8 *zIn = &zSrcData[iOff%nSrcPgsz];
      u8 *zDestData = sqlite4PagerGetData(pDestPg);
      u8 *zOut = &zDestData[iOff%nDestPgsz];

      /* Copy the data from the source page into the destination page.
      ** Then clear the Btree layer MemPage.isInit flag. Both this module
      ** and the pager code use this trick (clearing the first byte
      ** of the page 'extra' space to invalidate the Btree layers
      ** cached parse of the page). MemPage.isInit is marked 
      ** "MUST BE FIRST" for this purpose.
      */
      memcpy(zOut, zIn, nCopy);
      ((u8 *)sqlite4PagerGetExtra(pDestPg))[0] = 0;
    }
    sqlite4PagerUnref(pDestPg);
  }

  return rc;
}

/*
** If pFile is currently larger than iSize bytes, then truncate it to
** exactly iSize bytes. If pFile is not larger than iSize bytes, then
** this function is a no-op.
**
** Return SQLITE_OK if everything is successful, or an SQLite error 
** code if an error occurs.
*/
static int backupTruncateFile(sqlite4_file *pFile, i64 iSize){
  i64 iCurrent;
  int rc = sqlite4OsFileSize(pFile, &iCurrent);
  if( rc==SQLITE_OK && iCurrent>iSize ){
    rc = sqlite4OsTruncate(pFile, iSize);
  }
  return rc;
}

/*
** Register this backup object with the associated source pager for
** callbacks when pages are changed or the cache invalidated.
*/
static void attachBackupObject(sqlite4_backup *p){
  sqlite4_backup **pp;
  assert( sqlite4BtreeHoldsMutex(p->pSrc) );
  pp = sqlite4PagerBackupPtr(sqlite4BtreePager(p->pSrc));
  p->pNext = *pp;
  *pp = p;
  p->isAttached = 1;
}

/*
** Copy nPage pages from the source b-tree to the destination.
*/
int sqlite4_backup_step(sqlite4_backup *p, int nPage){
  int rc;
  int destMode;       /* Destination journal mode */
  int pgszSrc = 0;    /* Source page size */
  int pgszDest = 0;   /* Destination page size */

  sqlite4_mutex_enter(p->pSrcDb->mutex);
  sqlite4BtreeEnter(p->pSrc);
  if( p->pDestDb ){
    sqlite4_mutex_enter(p->pDestDb->mutex);
  }

  rc = p->rc;
  if( !isFatalError(rc) ){
    Pager * const pSrcPager = sqlite4BtreePager(p->pSrc);     /* Source pager */
    Pager * const pDestPager = sqlite4BtreePager(p->pDest);   /* Dest pager */
    int ii;                            /* Iterator variable */
    int nSrcPage = -1;                 /* Size of source db in pages */
    int bCloseTrans = 0;               /* True if src db requires unlocking */

    /* If the source pager is currently in a write-transaction, return
    ** SQLITE_BUSY immediately.
    */
    if( p->pDestDb && p->pSrc->pBt->inTransaction==TRANS_WRITE ){
      rc = SQLITE_BUSY;
    }else{
      rc = SQLITE_OK;
    }

    /* Lock the destination database, if it is not locked already. */
    if( SQLITE_OK==rc && p->bDestLocked==0
     && SQLITE_OK==(rc = sqlite4BtreeBeginTrans(p->pDest, 2)) 
    ){
      p->bDestLocked = 1;
      sqlite4BtreeGetMeta(p->pDest, BTREE_SCHEMA_VERSION, &p->iDestSchema);
    }

    /* If there is no open read-transaction on the source database, open
    ** one now. If a transaction is opened here, then it will be closed
    ** before this function exits.
    */
    if( rc==SQLITE_OK && 0==sqlite4BtreeIsInReadTrans(p->pSrc) ){
      rc = sqlite4BtreeBeginTrans(p->pSrc, 0);
      bCloseTrans = 1;
    }

    /* Do not allow backup if the destination database is in WAL mode
    ** and the page sizes are different between source and destination */
    pgszSrc = sqlite4BtreeGetPageSize(p->pSrc);
    pgszDest = sqlite4BtreeGetPageSize(p->pDest);
    destMode = sqlite4PagerGetJournalMode(sqlite4BtreePager(p->pDest));
    if( SQLITE_OK==rc && destMode==PAGER_JOURNALMODE_WAL && pgszSrc!=pgszDest ){
      rc = SQLITE_READONLY;
    }
  
    /* Now that there is a read-lock on the source database, query the
    ** source pager for the number of pages in the database.
    */
    nSrcPage = (int)sqlite4BtreeLastPage(p->pSrc);
    assert( nSrcPage>=0 );
    for(ii=0; (nPage<0 || ii<nPage) && p->iNext<=(Pgno)nSrcPage && !rc; ii++){
      const Pgno iSrcPg = p->iNext;                 /* Source page number */
      if( iSrcPg!=PENDING_BYTE_PAGE(p->pSrc->pBt) ){
        DbPage *pSrcPg;                             /* Source page object */
        rc = sqlite4PagerGet(pSrcPager, iSrcPg, &pSrcPg);
        if( rc==SQLITE_OK ){
          rc = backupOnePage(p, iSrcPg, sqlite4PagerGetData(pSrcPg));
          sqlite4PagerUnref(pSrcPg);
        }
      }
      p->iNext++;
    }
    if( rc==SQLITE_OK ){
      p->nPagecount = nSrcPage;
      p->nRemaining = nSrcPage+1-p->iNext;
      if( p->iNext>(Pgno)nSrcPage ){
        rc = SQLITE_DONE;
      }else if( !p->isAttached ){
        attachBackupObject(p);
      }
    }
  
    /* Update the schema version field in the destination database. This
    ** is to make sure that the schema-version really does change in
    ** the case where the source and destination databases have the
    ** same schema version.
    */
    if( rc==SQLITE_DONE ){
      rc = sqlite4BtreeUpdateMeta(p->pDest,1,p->iDestSchema+1);
      if( rc==SQLITE_OK ){
        if( p->pDestDb ){
          sqlite4ResetInternalSchema(p->pDestDb, -1);
        }
        if( destMode==PAGER_JOURNALMODE_WAL ){
          rc = sqlite4BtreeSetVersion(p->pDest, 2);
        }
      }
      if( rc==SQLITE_OK ){
        int nDestTruncate;
        /* Set nDestTruncate to the final number of pages in the destination
        ** database. The complication here is that the destination page
        ** size may be different to the source page size. 
        **
        ** If the source page size is smaller than the destination page size, 
        ** round up. In this case the call to sqlite4OsTruncate() below will
        ** fix the size of the file. However it is important to call
        ** sqlite4PagerTruncateImage() here so that any pages in the 
        ** destination file that lie beyond the nDestTruncate page mark are
        ** journalled by PagerCommitPhaseOne() before they are destroyed
        ** by the file truncation.
        */
        assert( pgszSrc==sqlite4BtreeGetPageSize(p->pSrc) );
        assert( pgszDest==sqlite4BtreeGetPageSize(p->pDest) );
        if( pgszSrc<pgszDest ){
          int ratio = pgszDest/pgszSrc;
          nDestTruncate = (nSrcPage+ratio-1)/ratio;
          if( nDestTruncate==(int)PENDING_BYTE_PAGE(p->pDest->pBt) ){
            nDestTruncate--;
          }
        }else{
          nDestTruncate = nSrcPage * (pgszSrc/pgszDest);
        }
        sqlite4PagerTruncateImage(pDestPager, nDestTruncate);

        if( pgszSrc<pgszDest ){
          /* If the source page-size is smaller than the destination page-size,
          ** two extra things may need to happen:
          **
          **   * The destination may need to be truncated, and
          **
          **   * Data stored on the pages immediately following the 
          **     pending-byte page in the source database may need to be
          **     copied into the destination database.
          */
          const i64 iSize = (i64)pgszSrc * (i64)nSrcPage;
          sqlite4_file * const pFile = sqlite4PagerFile(pDestPager);
          i64 iOff;
          i64 iEnd;

          assert( pFile );
          assert( (i64)nDestTruncate*(i64)pgszDest >= iSize || (
                nDestTruncate==(int)(PENDING_BYTE_PAGE(p->pDest->pBt)-1)
             && iSize>=PENDING_BYTE && iSize<=PENDING_BYTE+pgszDest
          ));

          /* This call ensures that all data required to recreate the original
          ** database has been stored in the journal for pDestPager and the
          ** journal synced to disk. So at this point we may safely modify
          ** the database file in any way, knowing that if a power failure
          ** occurs, the original database will be reconstructed from the 
          ** journal file.  */
          rc = sqlite4PagerCommitPhaseOne(pDestPager, 0, 1);

          /* Write the extra pages and truncate the database file as required */
          iEnd = MIN(PENDING_BYTE + pgszDest, iSize);
          for(
            iOff=PENDING_BYTE+pgszSrc; 
            rc==SQLITE_OK && iOff<iEnd; 
            iOff+=pgszSrc
          ){
            PgHdr *pSrcPg = 0;
            const Pgno iSrcPg = (Pgno)((iOff/pgszSrc)+1);
            rc = sqlite4PagerGet(pSrcPager, iSrcPg, &pSrcPg);
            if( rc==SQLITE_OK ){
              u8 *zData = sqlite4PagerGetData(pSrcPg);
              rc = sqlite4OsWrite(pFile, zData, pgszSrc, iOff);
            }
            sqlite4PagerUnref(pSrcPg);
          }
          if( rc==SQLITE_OK ){
            rc = backupTruncateFile(pFile, iSize);
          }

          /* Sync the database file to disk. */
          if( rc==SQLITE_OK ){
            rc = sqlite4PagerSync(pDestPager);
          }
        }else{
          rc = sqlite4PagerCommitPhaseOne(pDestPager, 0, 0);
        }
    
        /* Finish committing the transaction to the destination database. */
        if( SQLITE_OK==rc
         && SQLITE_OK==(rc = sqlite4BtreeCommitPhaseTwo(p->pDest, 0))
        ){
          rc = SQLITE_DONE;
        }
      }
    }
  
    /* If bCloseTrans is true, then this function opened a read transaction
    ** on the source database. Close the read transaction here. There is
    ** no need to check the return values of the btree methods here, as
    ** "committing" a read-only transaction cannot fail.
    */
    if( bCloseTrans ){
      TESTONLY( int rc2 );
      TESTONLY( rc2  = ) sqlite4BtreeCommitPhaseOne(p->pSrc, 0);
      TESTONLY( rc2 |= ) sqlite4BtreeCommitPhaseTwo(p->pSrc, 0);
      assert( rc2==SQLITE_OK );
    }
  
    if( rc==SQLITE_IOERR_NOMEM ){
      rc = SQLITE_NOMEM;
    }
    p->rc = rc;
  }
  if( p->pDestDb ){
    sqlite4_mutex_leave(p->pDestDb->mutex);
  }
  sqlite4BtreeLeave(p->pSrc);
  sqlite4_mutex_leave(p->pSrcDb->mutex);
  return rc;
}

/*
** Release all resources associated with an sqlite4_backup* handle.
*/
int sqlite4_backup_finish(sqlite4_backup *p){
  sqlite4_backup **pp;                 /* Ptr to head of pagers backup list */
  MUTEX_LOGIC( sqlite4_mutex *mutex; ) /* Mutex to protect source database */
  int rc;                              /* Value to return */

  /* Enter the mutexes */
  if( p==0 ) return SQLITE_OK;
  sqlite4_mutex_enter(p->pSrcDb->mutex);
  sqlite4BtreeEnter(p->pSrc);
  MUTEX_LOGIC( mutex = p->pSrcDb->mutex; )
  if( p->pDestDb ){
    sqlite4_mutex_enter(p->pDestDb->mutex);
  }

  /* Detach this backup from the source pager. */
  if( p->pDestDb ){
    p->pSrc->nBackup--;
  }
  if( p->isAttached ){
    pp = sqlite4PagerBackupPtr(sqlite4BtreePager(p->pSrc));
    while( *pp!=p ){
      pp = &(*pp)->pNext;
    }
    *pp = p->pNext;
  }

  /* If a transaction is still open on the Btree, roll it back. */
  sqlite4BtreeRollback(p->pDest);

  /* Set the error code of the destination database handle. */
  rc = (p->rc==SQLITE_DONE) ? SQLITE_OK : p->rc;
  sqlite4Error(p->pDestDb, rc, 0);

  /* Exit the mutexes and free the backup context structure. */
  if( p->pDestDb ){
    sqlite4_mutex_leave(p->pDestDb->mutex);
  }
  sqlite4BtreeLeave(p->pSrc);
  if( p->pDestDb ){
    /* EVIDENCE-OF: R-64852-21591 The sqlite4_backup object is created by a
    ** call to sqlite4_backup_init() and is destroyed by a call to
    ** sqlite4_backup_finish(). */
    sqlite4_free(p);
  }
  sqlite4_mutex_leave(mutex);
  return rc;
}

/*
** Return the number of pages still to be backed up as of the most recent
** call to sqlite4_backup_step().
*/
int sqlite4_backup_remaining(sqlite4_backup *p){
  return p->nRemaining;
}

/*
** Return the total number of pages in the source database as of the most 
** recent call to sqlite4_backup_step().
*/
int sqlite4_backup_pagecount(sqlite4_backup *p){
  return p->nPagecount;
}

/*
** This function is called after the contents of page iPage of the
** source database have been modified. If page iPage has already been 
** copied into the destination database, then the data written to the
** destination is now invalidated. The destination copy of iPage needs
** to be updated with the new data before the backup operation is
** complete.
**
** It is assumed that the mutex associated with the BtShared object
** corresponding to the source database is held when this function is
** called.
*/
void sqlite4BackupUpdate(sqlite4_backup *pBackup, Pgno iPage, const u8 *aData){
  sqlite4_backup *p;                   /* Iterator variable */
  for(p=pBackup; p; p=p->pNext){
    assert( sqlite4_mutex_held(p->pSrc->pBt->mutex) );
    if( !isFatalError(p->rc) && iPage<p->iNext ){
      /* The backup process p has already copied page iPage. But now it
      ** has been modified by a transaction on the source pager. Copy
      ** the new data into the backup.
      */
      int rc;
      assert( p->pDestDb );
      sqlite4_mutex_enter(p->pDestDb->mutex);
      rc = backupOnePage(p, iPage, aData);
      sqlite4_mutex_leave(p->pDestDb->mutex);
      assert( rc!=SQLITE_BUSY && rc!=SQLITE_LOCKED );
      if( rc!=SQLITE_OK ){
        p->rc = rc;
      }
    }
  }
}

/*
** Restart the backup process. This is called when the pager layer
** detects that the database has been modified by an external database
** connection. In this case there is no way of knowing which of the
** pages that have been copied into the destination database are still 
** valid and which are not, so the entire process needs to be restarted.
**
** It is assumed that the mutex associated with the BtShared object
** corresponding to the source database is held when this function is
** called.
*/
void sqlite4BackupRestart(sqlite4_backup *pBackup){
  sqlite4_backup *p;                   /* Iterator variable */
  for(p=pBackup; p; p=p->pNext){
    assert( sqlite4_mutex_held(p->pSrc->pBt->mutex) );
    p->iNext = 1;
  }
}

#ifndef SQLITE_OMIT_VACUUM
/*
** Copy the complete content of pBtFrom into pBtTo.  A transaction
** must be active for both files.
**
** The size of file pTo may be reduced by this operation. If anything 
** goes wrong, the transaction on pTo is rolled back. If successful, the 
** transaction is committed before returning.
*/
int sqlite4BtreeCopyFile(Btree *pTo, Btree *pFrom){
  int rc;
  sqlite4_file *pFd;              /* File descriptor for database pTo */
  sqlite4_backup b;
  sqlite4BtreeEnter(pTo);
  sqlite4BtreeEnter(pFrom);

  assert( sqlite4BtreeIsInTrans(pTo) );
  pFd = sqlite4PagerFile(sqlite4BtreePager(pTo));
  if( pFd->pMethods ){
    i64 nByte = sqlite4BtreeGetPageSize(pFrom)*(i64)sqlite4BtreeLastPage(pFrom);
    rc = sqlite4OsFileControl(pFd, SQLITE_FCNTL_OVERWRITE, &nByte);
    if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
    if( rc ) goto copy_finished;
  }

  /* Set up an sqlite4_backup object. sqlite4_backup.pDestDb must be set
  ** to 0. This is used by the implementations of sqlite4_backup_step()
  ** and sqlite4_backup_finish() to detect that they are being called
  ** from this function, not directly by the user.
  */
  memset(&b, 0, sizeof(b));
  b.pSrcDb = pFrom->db;
  b.pSrc = pFrom;
  b.pDest = pTo;
  b.iNext = 1;

  /* 0x7FFFFFFF is the hard limit for the number of pages in a database
  ** file. By passing this as the number of pages to copy to
  ** sqlite4_backup_step(), we can guarantee that the copy finishes 
  ** within a single call (unless an error occurs). The assert() statement
  ** checks this assumption - (p->rc) should be set to either SQLITE_DONE 
  ** or an error code.
  */
  sqlite4_backup_step(&b, 0x7FFFFFFF);
  assert( b.rc!=SQLITE_OK );
  rc = sqlite4_backup_finish(&b);
  if( rc==SQLITE_OK ){
    pTo->pBt->btsFlags &= ~BTS_PAGESIZE_FIXED;
  }else{
    sqlite4PagerClearCache(sqlite4BtreePager(b.pDest));
  }

  assert( sqlite4BtreeIsInTrans(pTo)==0 );
copy_finished:
  sqlite4BtreeLeave(pFrom);
  sqlite4BtreeLeave(pTo);
  return rc;
}
#endif /* SQLITE_OMIT_VACUUM */
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Deleted src/btmutex.c.

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/*
** 2007 August 27
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file contains code used to implement mutexes on Btree objects.
** This code really belongs in btree.c.  But btree.c is getting too
** big and we want to break it down some.  This packaged seemed like
** a good breakout.
*/
#include "btreeInt.h"
#ifndef SQLITE_OMIT_SHARED_CACHE
#if SQLITE_THREADSAFE

/*
** Obtain the BtShared mutex associated with B-Tree handle p. Also,
** set BtShared.db to the database handle associated with p and the
** p->locked boolean to true.
*/
static void lockBtreeMutex(Btree *p){
  assert( p->locked==0 );
  assert( sqlite4_mutex_notheld(p->pBt->mutex) );
  assert( sqlite4_mutex_held(p->db->mutex) );

  sqlite4_mutex_enter(p->pBt->mutex);
  p->pBt->db = p->db;
  p->locked = 1;
}

/*
** Release the BtShared mutex associated with B-Tree handle p and
** clear the p->locked boolean.
*/
static void unlockBtreeMutex(Btree *p){
  BtShared *pBt = p->pBt;
  assert( p->locked==1 );
  assert( sqlite4_mutex_held(pBt->mutex) );
  assert( sqlite4_mutex_held(p->db->mutex) );
  assert( p->db==pBt->db );

  sqlite4_mutex_leave(pBt->mutex);
  p->locked = 0;
}

/*
** Enter a mutex on the given BTree object.
**
** If the object is not sharable, then no mutex is ever required
** and this routine is a no-op.  The underlying mutex is non-recursive.
** But we keep a reference count in Btree.wantToLock so the behavior
** of this interface is recursive.
**
** To avoid deadlocks, multiple Btrees are locked in the same order
** by all database connections.  The p->pNext is a list of other
** Btrees belonging to the same database connection as the p Btree
** which need to be locked after p.  If we cannot get a lock on
** p, then first unlock all of the others on p->pNext, then wait
** for the lock to become available on p, then relock all of the
** subsequent Btrees that desire a lock.
*/
void sqlite4BtreeEnter(Btree *p){
  Btree *pLater;

  /* Some basic sanity checking on the Btree.  The list of Btrees
  ** connected by pNext and pPrev should be in sorted order by
  ** Btree.pBt value. All elements of the list should belong to
  ** the same connection. Only shared Btrees are on the list. */
  assert( p->pNext==0 || p->pNext->pBt>p->pBt );
  assert( p->pPrev==0 || p->pPrev->pBt<p->pBt );
  assert( p->pNext==0 || p->pNext->db==p->db );
  assert( p->pPrev==0 || p->pPrev->db==p->db );
  assert( p->sharable || (p->pNext==0 && p->pPrev==0) );

  /* Check for locking consistency */
  assert( !p->locked || p->wantToLock>0 );
  assert( p->sharable || p->wantToLock==0 );

  /* We should already hold a lock on the database connection */
  assert( sqlite4_mutex_held(p->db->mutex) );

  /* Unless the database is sharable and unlocked, then BtShared.db
  ** should already be set correctly. */
  assert( (p->locked==0 && p->sharable) || p->pBt->db==p->db );

  if( !p->sharable ) return;
  p->wantToLock++;
  if( p->locked ) return;

  /* In most cases, we should be able to acquire the lock we
  ** want without having to go throught the ascending lock
  ** procedure that follows.  Just be sure not to block.
  */
  if( sqlite4_mutex_try(p->pBt->mutex)==SQLITE_OK ){
    p->pBt->db = p->db;
    p->locked = 1;
    return;
  }

  /* To avoid deadlock, first release all locks with a larger
  ** BtShared address.  Then acquire our lock.  Then reacquire
  ** the other BtShared locks that we used to hold in ascending
  ** order.
  */
  for(pLater=p->pNext; pLater; pLater=pLater->pNext){
    assert( pLater->sharable );
    assert( pLater->pNext==0 || pLater->pNext->pBt>pLater->pBt );
    assert( !pLater->locked || pLater->wantToLock>0 );
    if( pLater->locked ){
      unlockBtreeMutex(pLater);
    }
  }
  lockBtreeMutex(p);
  for(pLater=p->pNext; pLater; pLater=pLater->pNext){
    if( pLater->wantToLock ){
      lockBtreeMutex(pLater);
    }
  }
}

/*
** Exit the recursive mutex on a Btree.
*/
void sqlite4BtreeLeave(Btree *p){
  if( p->sharable ){
    assert( p->wantToLock>0 );
    p->wantToLock--;
    if( p->wantToLock==0 ){
      unlockBtreeMutex(p);
    }
  }
}

#ifndef NDEBUG
/*
** Return true if the BtShared mutex is held on the btree, or if the
** B-Tree is not marked as sharable.
**
** This routine is used only from within assert() statements.
*/
int sqlite4BtreeHoldsMutex(Btree *p){
  assert( p->sharable==0 || p->locked==0 || p->wantToLock>0 );
  assert( p->sharable==0 || p->locked==0 || p->db==p->pBt->db );
  assert( p->sharable==0 || p->locked==0 || sqlite4_mutex_held(p->pBt->mutex) );
  assert( p->sharable==0 || p->locked==0 || sqlite4_mutex_held(p->db->mutex) );

  return (p->sharable==0 || p->locked);
}
#endif


#ifndef SQLITE_OMIT_INCRBLOB
/*
** Enter and leave a mutex on a Btree given a cursor owned by that
** Btree.  These entry points are used by incremental I/O and can be
** omitted if that module is not used.
*/
void sqlite4BtreeEnterCursor(BtCursor *pCur){
  sqlite4BtreeEnter(pCur->pBtree);
}
void sqlite4BtreeLeaveCursor(BtCursor *pCur){
  sqlite4BtreeLeave(pCur->pBtree);
}
#endif /* SQLITE_OMIT_INCRBLOB */


/*
** Enter the mutex on every Btree associated with a database
** connection.  This is needed (for example) prior to parsing
** a statement since we will be comparing table and column names
** against all schemas and we do not want those schemas being
** reset out from under us.
**
** There is a corresponding leave-all procedures.
**
** Enter the mutexes in accending order by BtShared pointer address
** to avoid the possibility of deadlock when two threads with
** two or more btrees in common both try to lock all their btrees
** at the same instant.
*/
void sqlite4BtreeEnterAll(sqlite4 *db){
  int i;
  Btree *p;
  assert( sqlite4_mutex_held(db->mutex) );
  for(i=0; i<db->nDb; i++){
    p = db->aDb[i].pBt;
    if( p ) sqlite4BtreeEnter(p);
  }
}
void sqlite4BtreeLeaveAll(sqlite4 *db){
  int i;
  Btree *p;
  assert( sqlite4_mutex_held(db->mutex) );
  for(i=0; i<db->nDb; i++){
    p = db->aDb[i].pBt;
    if( p ) sqlite4BtreeLeave(p);
  }
}

/*
** Return true if a particular Btree requires a lock.  Return FALSE if
** no lock is ever required since it is not sharable.
*/
int sqlite4BtreeSharable(Btree *p){
  return p->sharable;
}

#ifndef NDEBUG
/*
** Return true if the current thread holds the database connection
** mutex and all required BtShared mutexes.
**
** This routine is used inside assert() statements only.
*/
int sqlite4BtreeHoldsAllMutexes(sqlite4 *db){
  int i;
  if( !sqlite4_mutex_held(db->mutex) ){
    return 0;
  }
  for(i=0; i<db->nDb; i++){
    Btree *p;
    p = db->aDb[i].pBt;
    if( p && p->sharable &&
         (p->wantToLock==0 || !sqlite4_mutex_held(p->pBt->mutex)) ){
      return 0;
    }
  }
  return 1;
}
#endif /* NDEBUG */

#ifndef NDEBUG
/*
** Return true if the correct mutexes are held for accessing the
** db->aDb[iDb].pSchema structure.  The mutexes required for schema
** access are:
**
**   (1) The mutex on db
**   (2) if iDb!=1, then the mutex on db->aDb[iDb].pBt.
**
** If pSchema is not NULL, then iDb is computed from pSchema and
** db using sqlite4SchemaToIndex().
*/
int sqlite4SchemaMutexHeld(sqlite4 *db, int iDb, Schema *pSchema){
  Btree *p;
  assert( db!=0 );
  if( pSchema ) iDb = sqlite4SchemaToIndex(db, pSchema);
  assert( iDb>=0 && iDb<db->nDb );
  if( !sqlite4_mutex_held(db->mutex) ) return 0;
  if( iDb==1 ) return 1;
  p = db->aDb[iDb].pBt;
  assert( p!=0 );
  return p->sharable==0 || p->locked==1;
}
#endif /* NDEBUG */

#else /* SQLITE_THREADSAFE>0 above.  SQLITE_THREADSAFE==0 below */
/*
** The following are special cases for mutex enter routines for use
** in single threaded applications that use shared cache.  Except for
** these two routines, all mutex operations are no-ops in that case and
** are null #defines in btree.h.
**
** If shared cache is disabled, then all btree mutex routines, including
** the ones below, are no-ops and are null #defines in btree.h.
*/

void sqlite4BtreeEnter(Btree *p){
  p->pBt->db = p->db;
}
void sqlite4BtreeEnterAll(sqlite4 *db){
  int i;
  for(i=0; i<db->nDb; i++){
    Btree *p = db->aDb[i].pBt;
    if( p ){
      p->pBt->db = p->db;
    }
  }
}
#endif /* if SQLITE_THREADSAFE */
#endif /* ifndef SQLITE_OMIT_SHARED_CACHE */
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Deleted src/btree.c.

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/*
** 2004 April 6
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "btreeInt.h"

/*
** The header string that appears at the beginning of every
** SQLite database.
*/
static const char zMagicHeader[] = SQLITE_FILE_HEADER;

/*
** Set this global variable to 1 to enable tracing using the TRACE
** macro.
*/
#if 0
int sqlite4BtreeTrace=1;  /* True to enable tracing */
# define TRACE(X)  if(sqlite4BtreeTrace){printf X;fflush(stdout);}
#else
# define TRACE(X)
#endif

/*
** Extract a 2-byte big-endian integer from an array of unsigned bytes.
** But if the value is zero, make it 65536.
**
** This routine is used to extract the "offset to cell content area" value
** from the header of a btree page.  If the page size is 65536 and the page
** is empty, the offset should be 65536, but the 2-byte value stores zero.
** This routine makes the necessary adjustment to 65536.
*/
#define get2byteNotZero(X)  (((((int)get2byte(X))-1)&0xffff)+1)

#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** A list of BtShared objects that are eligible for participation
** in shared cache.  This variable has file scope during normal builds,
** but the test harness needs to access it so we make it global for 
** test builds.
**
** Access to this variable is protected by SQLITE_MUTEX_STATIC_MASTER.
*/
#ifdef SQLITE_TEST
BtShared *SQLITE_WSD sqlite4SharedCacheList = 0;
#else
static BtShared *SQLITE_WSD sqlite4SharedCacheList = 0;
#endif
#endif /* SQLITE_OMIT_SHARED_CACHE */

#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Enable or disable the shared pager and schema features.
**
** This routine has no effect on existing database connections.
** The shared cache setting effects only future calls to
** sqlite4_open(), sqlite4_open16(), or sqlite4_open_v2().
*/
int sqlite4_enable_shared_cache(int enable){
  sqlite4GlobalConfig.sharedCacheEnabled = enable;
  return SQLITE_OK;
}
#endif



#ifdef SQLITE_OMIT_SHARED_CACHE
  /*
  ** The functions querySharedCacheTableLock(), setSharedCacheTableLock(),
  ** and clearAllSharedCacheTableLocks()
  ** manipulate entries in the BtShared.pLock linked list used to store
  ** shared-cache table level locks. If the library is compiled with the
  ** shared-cache feature disabled, then there is only ever one user
  ** of each BtShared structure and so this locking is not necessary. 
  ** So define the lock related functions as no-ops.
  */
  #define querySharedCacheTableLock(a,b,c) SQLITE_OK
  #define setSharedCacheTableLock(a,b,c) SQLITE_OK
  #define clearAllSharedCacheTableLocks(a)
  #define downgradeAllSharedCacheTableLocks(a)
  #define hasSharedCacheTableLock(a,b,c,d) 1
  #define hasReadConflicts(a, b) 0
#endif

#ifndef SQLITE_OMIT_SHARED_CACHE

#ifdef SQLITE_DEBUG
/*
**** This function is only used as part of an assert() statement. ***
**
** Check to see if pBtree holds the required locks to read or write to the 
** table with root page iRoot.   Return 1 if it does and 0 if not.
**
** For example, when writing to a table with root-page iRoot via 
** Btree connection pBtree:
**
**    assert( hasSharedCacheTableLock(pBtree, iRoot, 0, WRITE_LOCK) );
**
** When writing to an index that resides in a sharable database, the 
** caller should have first obtained a lock specifying the root page of
** the corresponding table. This makes things a bit more complicated,
** as this module treats each table as a separate structure. To determine
** the table corresponding to the index being written, this
** function has to search through the database schema.
**
** Instead of a lock on the table/index rooted at page iRoot, the caller may
** hold a write-lock on the schema table (root page 1). This is also
** acceptable.
*/
static int hasSharedCacheTableLock(
  Btree *pBtree,         /* Handle that must hold lock */
  Pgno iRoot,            /* Root page of b-tree */
  int isIndex,           /* True if iRoot is the root of an index b-tree */
  int eLockType          /* Required lock type (READ_LOCK or WRITE_LOCK) */
){
  Schema *pSchema = (Schema *)pBtree->pBt->pSchema;
  Pgno iTab = 0;
  BtLock *pLock;

  /* If this database is not shareable, or if the client is reading
  ** and has the read-uncommitted flag set, then no lock is required. 
  ** Return true immediately.
  */
  if( (pBtree->sharable==0)
   || (eLockType==READ_LOCK && (pBtree->db->flags & SQLITE_ReadUncommitted))
  ){
    return 1;
  }

  /* If the client is reading  or writing an index and the schema is
  ** not loaded, then it is too difficult to actually check to see if
  ** the correct locks are held.  So do not bother - just return true.
  ** This case does not come up very often anyhow.
  */
  if( isIndex && (!pSchema || (pSchema->flags&DB_SchemaLoaded)==0) ){
    return 1;
  }

  /* Figure out the root-page that the lock should be held on. For table
  ** b-trees, this is just the root page of the b-tree being read or
  ** written. For index b-trees, it is the root page of the associated
  ** table.  */
  if( isIndex ){
    HashElem *p;
    for(p=sqliteHashFirst(&pSchema->idxHash); p; p=sqliteHashNext(p)){
      Index *pIdx = (Index *)sqliteHashData(p);
      if( pIdx->tnum==(int)iRoot ){
        iTab = pIdx->pTable->tnum;
      }
    }
  }else{
    iTab = iRoot;
  }

  /* Search for the required lock. Either a write-lock on root-page iTab, a 
  ** write-lock on the schema table, or (if the client is reading) a
  ** read-lock on iTab will suffice. Return 1 if any of these are found.  */
  for(pLock=pBtree->pBt->pLock; pLock; pLock=pLock->pNext){
    if( pLock->pBtree==pBtree 
     && (pLock->iTable==iTab || (pLock->eLock==WRITE_LOCK && pLock->iTable==1))
     && pLock->eLock>=eLockType 
    ){
      return 1;
    }
  }

  /* Failed to find the required lock. */
  return 0;
}
#endif /* SQLITE_DEBUG */

#ifdef SQLITE_DEBUG
/*
**** This function may be used as part of assert() statements only. ****
**
** Return true if it would be illegal for pBtree to write into the
** table or index rooted at iRoot because other shared connections are
** simultaneously reading that same table or index.
**
** It is illegal for pBtree to write if some other Btree object that
** shares the same BtShared object is currently reading or writing
** the iRoot table.  Except, if the other Btree object has the
** read-uncommitted flag set, then it is OK for the other object to
** have a read cursor.
**
** For example, before writing to any part of the table or index
** rooted at page iRoot, one should call:
**
**    assert( !hasReadConflicts(pBtree, iRoot) );
*/
static int hasReadConflicts(Btree *pBtree, Pgno iRoot){
  BtCursor *p;
  for(p=pBtree->pBt->pCursor; p; p=p->pNext){
    if( p->pgnoRoot==iRoot 
     && p->pBtree!=pBtree
     && 0==(p->pBtree->db->flags & SQLITE_ReadUncommitted)
    ){
      return 1;
    }
  }
  return 0;
}
#endif    /* #ifdef SQLITE_DEBUG */

/*
** Query to see if Btree handle p may obtain a lock of type eLock 
** (READ_LOCK or WRITE_LOCK) on the table with root-page iTab. Return
** SQLITE_OK if the lock may be obtained (by calling
** setSharedCacheTableLock()), or SQLITE_LOCKED if not.
*/
static int querySharedCacheTableLock(Btree *p, Pgno iTab, u8 eLock){
  BtShared *pBt = p->pBt;
  BtLock *pIter;

  assert( sqlite4BtreeHoldsMutex(p) );
  assert( eLock==READ_LOCK || eLock==WRITE_LOCK );
  assert( p->db!=0 );
  assert( !(p->db->flags&SQLITE_ReadUncommitted)||eLock==WRITE_LOCK||iTab==1 );
  
  /* If requesting a write-lock, then the Btree must have an open write
  ** transaction on this file. And, obviously, for this to be so there 
  ** must be an open write transaction on the file itself.
  */
  assert( eLock==READ_LOCK || (p==pBt->pWriter && p->inTrans==TRANS_WRITE) );
  assert( eLock==READ_LOCK || pBt->inTransaction==TRANS_WRITE );
  
  /* This routine is a no-op if the shared-cache is not enabled */
  if( !p->sharable ){
    return SQLITE_OK;
  }

  /* If some other connection is holding an exclusive lock, the
  ** requested lock may not be obtained.
  */
  if( pBt->pWriter!=p && (pBt->btsFlags & BTS_EXCLUSIVE)!=0 ){
    sqlite4ConnectionBlocked(p->db, pBt->pWriter->db);
    return SQLITE_LOCKED_SHAREDCACHE;
  }

  for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
    /* The condition (pIter->eLock!=eLock) in the following if(...) 
    ** statement is a simplification of:
    **
    **   (eLock==WRITE_LOCK || pIter->eLock==WRITE_LOCK)
    **
    ** since we know that if eLock==WRITE_LOCK, then no other connection
    ** may hold a WRITE_LOCK on any table in this file (since there can
    ** only be a single writer).
    */
    assert( pIter->eLock==READ_LOCK || pIter->eLock==WRITE_LOCK );
    assert( eLock==READ_LOCK || pIter->pBtree==p || pIter->eLock==READ_LOCK);
    if( pIter->pBtree!=p && pIter->iTable==iTab && pIter->eLock!=eLock ){
      sqlite4ConnectionBlocked(p->db, pIter->pBtree->db);
      if( eLock==WRITE_LOCK ){
        assert( p==pBt->pWriter );
        pBt->btsFlags |= BTS_PENDING;
      }
      return SQLITE_LOCKED_SHAREDCACHE;
    }
  }
  return SQLITE_OK;
}
#endif /* !SQLITE_OMIT_SHARED_CACHE */

#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Add a lock on the table with root-page iTable to the shared-btree used
** by Btree handle p. Parameter eLock must be either READ_LOCK or 
** WRITE_LOCK.
**
** This function assumes the following:
**
**   (a) The specified Btree object p is connected to a sharable
**       database (one with the BtShared.sharable flag set), and
**
**   (b) No other Btree objects hold a lock that conflicts
**       with the requested lock (i.e. querySharedCacheTableLock() has
**       already been called and returned SQLITE_OK).
**
** SQLITE_OK is returned if the lock is added successfully. SQLITE_NOMEM 
** is returned if a malloc attempt fails.
*/
static int setSharedCacheTableLock(Btree *p, Pgno iTable, u8 eLock){
  BtShared *pBt = p->pBt;
  BtLock *pLock = 0;
  BtLock *pIter;

  assert( sqlite4BtreeHoldsMutex(p) );
  assert( eLock==READ_LOCK || eLock==WRITE_LOCK );
  assert( p->db!=0 );

  /* A connection with the read-uncommitted flag set will never try to
  ** obtain a read-lock using this function. The only read-lock obtained
  ** by a connection in read-uncommitted mode is on the sqlite_master 
  ** table, and that lock is obtained in BtreeBeginTrans().  */
  assert( 0==(p->db->flags&SQLITE_ReadUncommitted) || eLock==WRITE_LOCK );

  /* This function should only be called on a sharable b-tree after it 
  ** has been determined that no other b-tree holds a conflicting lock.  */
  assert( p->sharable );
  assert( SQLITE_OK==querySharedCacheTableLock(p, iTable, eLock) );

  /* First search the list for an existing lock on this table. */
  for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
    if( pIter->iTable==iTable && pIter->pBtree==p ){
      pLock = pIter;
      break;
    }
  }

  /* If the above search did not find a BtLock struct associating Btree p
  ** with table iTable, allocate one and link it into the list.
  */
  if( !pLock ){
    pLock = (BtLock *)sqlite4MallocZero(sizeof(BtLock));
    if( !pLock ){
      return SQLITE_NOMEM;
    }
    pLock->iTable = iTable;
    pLock->pBtree = p;
    pLock->pNext = pBt->pLock;
    pBt->pLock = pLock;
  }

  /* Set the BtLock.eLock variable to the maximum of the current lock
  ** and the requested lock. This means if a write-lock was already held
  ** and a read-lock requested, we don't incorrectly downgrade the lock.
  */
  assert( WRITE_LOCK>READ_LOCK );
  if( eLock>pLock->eLock ){
    pLock->eLock = eLock;
  }

  return SQLITE_OK;
}
#endif /* !SQLITE_OMIT_SHARED_CACHE */

#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Release all the table locks (locks obtained via calls to
** the setSharedCacheTableLock() procedure) held by Btree object p.
**
** This function assumes that Btree p has an open read or write 
** transaction. If it does not, then the BTS_PENDING flag
** may be incorrectly cleared.
*/
static void clearAllSharedCacheTableLocks(Btree *p){
  BtShared *pBt = p->pBt;
  BtLock **ppIter = &pBt->pLock;

  assert( sqlite4BtreeHoldsMutex(p) );
  assert( p->sharable || 0==*ppIter );
  assert( p->inTrans>0 );

  while( *ppIter ){
    BtLock *pLock = *ppIter;
    assert( (pBt->btsFlags & BTS_EXCLUSIVE)==0 || pBt->pWriter==pLock->pBtree );
    assert( pLock->pBtree->inTrans>=pLock->eLock );
    if( pLock->pBtree==p ){
      *ppIter = pLock->pNext;
      assert( pLock->iTable!=1 || pLock==&p->lock );
      if( pLock->iTable!=1 ){
        sqlite4_free(pLock);
      }
    }else{
      ppIter = &pLock->pNext;
    }
  }

  assert( (pBt->btsFlags & BTS_PENDING)==0 || pBt->pWriter );
  if( pBt->pWriter==p ){
    pBt->pWriter = 0;
    pBt->btsFlags &= ~(BTS_EXCLUSIVE|BTS_PENDING);
  }else if( pBt->nTransaction==2 ){
    /* This function is called when Btree p is concluding its 
    ** transaction. If there currently exists a writer, and p is not
    ** that writer, then the number of locks held by connections other
    ** than the writer must be about to drop to zero. In this case
    ** set the BTS_PENDING flag to 0.
    **
    ** If there is not currently a writer, then BTS_PENDING must
    ** be zero already. So this next line is harmless in that case.
    */
    pBt->btsFlags &= ~BTS_PENDING;
  }
}

/*
** This function changes all write-locks held by Btree p into read-locks.
*/
static void downgradeAllSharedCacheTableLocks(Btree *p){
  BtShared *pBt = p->pBt;
  if( pBt->pWriter==p ){
    BtLock *pLock;
    pBt->pWriter = 0;
    pBt->btsFlags &= ~(BTS_EXCLUSIVE|BTS_PENDING);
    for(pLock=pBt->pLock; pLock; pLock=pLock->pNext){
      assert( pLock->eLock==READ_LOCK || pLock->pBtree==p );
      pLock->eLock = READ_LOCK;
    }
  }
}

#endif /* SQLITE_OMIT_SHARED_CACHE */

static void releasePage(MemPage *pPage);  /* Forward reference */

/*
***** This routine is used inside of assert() only ****
**
** Verify that the cursor holds the mutex on its BtShared
*/
#ifdef SQLITE_DEBUG
static int cursorHoldsMutex(BtCursor *p){
  return sqlite4_mutex_held(p->pBt->mutex);
}
#endif


#ifndef SQLITE_OMIT_INCRBLOB
/*
** Invalidate the overflow page-list cache for cursor pCur, if any.
*/
static void invalidateOverflowCache(BtCursor *pCur){
  assert( cursorHoldsMutex(pCur) );
  sqlite4_free(pCur->aOverflow);
  pCur->aOverflow = 0;
}

/*
** Invalidate the overflow page-list cache for all cursors opened
** on the shared btree structure pBt.
*/
static void invalidateAllOverflowCache(BtShared *pBt){
  BtCursor *p;
  assert( sqlite4_mutex_held(pBt->mutex) );
  for(p=pBt->pCursor; p; p=p->pNext){
    invalidateOverflowCache(p);
  }
}

/*
** This function is called before modifying the contents of a table
** to invalidate any incrblob cursors that are open on the
** row or one of the rows being modified.
**
** If argument isClearTable is true, then the entire contents of the
** table is about to be deleted. In this case invalidate all incrblob
** cursors open on any row within the table with root-page pgnoRoot.
**
** Otherwise, if argument isClearTable is false, then the row with
** rowid iRow is being replaced or deleted. In this case invalidate
** only those incrblob cursors open on that specific row.
*/
static void invalidateIncrblobCursors(
  Btree *pBtree,          /* The database file to check */
  i64 iRow,               /* The rowid that might be changing */
  int isClearTable        /* True if all rows are being deleted */
){
  BtCursor *p;
  BtShared *pBt = pBtree->pBt;
  assert( sqlite4BtreeHoldsMutex(pBtree) );
  for(p=pBt->pCursor; p; p=p->pNext){
    if( p->isIncrblobHandle && (isClearTable || p->info.nKey==iRow) ){
      p->eState = CURSOR_INVALID;
    }
  }
}

#else
  /* Stub functions when INCRBLOB is omitted */
  #define invalidateOverflowCache(x)
  #define invalidateAllOverflowCache(x)
  #define invalidateIncrblobCursors(x,y,z)
#endif /* SQLITE_OMIT_INCRBLOB */

/*
** Set bit pgno of the BtShared.pHasContent bitvec. This is called 
** when a page that previously contained data becomes a free-list leaf 
** page.
**
** The BtShared.pHasContent bitvec exists to work around an obscure
** bug caused by the interaction of two useful IO optimizations surrounding
** free-list leaf pages:
**
**   1) When all data is deleted from a page and the page becomes
**      a free-list leaf page, the page is not written to the database
**      (as free-list leaf pages contain no meaningful data). Sometimes
**      such a page is not even journalled (as it will not be modified,
**      why bother journalling it?).
**
**   2) When a free-list leaf page is reused, its content is not read
**      from the database or written to the journal file (why should it
**      be, if it is not at all meaningful?).
**
** By themselves, these optimizations work fine and provide a handy
** performance boost to bulk delete or insert operations. However, if
** a page is moved to the free-list and then reused within the same
** transaction, a problem comes up. If the page is not journalled when
** it is moved to the free-list and it is also not journalled when it
** is extracted from the free-list and reused, then the original data
** may be lost. In the event of a rollback, it may not be possible
** to restore the database to its original configuration.
**
** The solution is the BtShared.pHasContent bitvec. Whenever a page is 
** moved to become a free-list leaf page, the corresponding bit is
** set in the bitvec. Whenever a leaf page is extracted from the free-list,
** optimization 2 above is omitted if the corresponding bit is already
** set in BtShared.pHasContent. The contents of the bitvec are cleared
** at the end of every transaction.
*/
static int btreeSetHasContent(BtShared *pBt, Pgno pgno){
  int rc = SQLITE_OK;
  if( !pBt->pHasContent ){
    assert( pgno<=pBt->nPage );
    pBt->pHasContent = sqlite4BitvecCreate(pBt->nPage);
    if( !pBt->pHasContent ){
      rc = SQLITE_NOMEM;
    }
  }
  if( rc==SQLITE_OK && pgno<=sqlite4BitvecSize(pBt->pHasContent) ){
    rc = sqlite4BitvecSet(pBt->pHasContent, pgno);
  }
  return rc;
}

/*
** Query the BtShared.pHasContent vector.
**
** This function is called when a free-list leaf page is removed from the
** free-list for reuse. It returns false if it is safe to retrieve the
** page from the pager layer with the 'no-content' flag set. True otherwise.
*/
static int btreeGetHasContent(BtShared *pBt, Pgno pgno){
  Bitvec *p = pBt->pHasContent;
  return (p && (pgno>sqlite4BitvecSize(p) || sqlite4BitvecTest(p, pgno)));
}

/*
** Clear (destroy) the BtShared.pHasContent bitvec. This should be
** invoked at the conclusion of each write-transaction.
*/
static void btreeClearHasContent(BtShared *pBt){
  sqlite4BitvecDestroy(pBt->pHasContent);
  pBt->pHasContent = 0;
}

/*
** Save the current cursor position in the variables BtCursor.nKey 
** and BtCursor.pKey. The cursor's state is set to CURSOR_REQUIRESEEK.
**
** The caller must ensure that the cursor is valid (has eState==CURSOR_VALID)
** prior to calling this routine.  
*/
static int saveCursorPosition(BtCursor *pCur){
  int rc;

  assert( CURSOR_VALID==pCur->eState );
  assert( 0==pCur->pKey );
  assert( cursorHoldsMutex(pCur) );

  rc = sqlite4BtreeKeySize(pCur, &pCur->nKey);
  assert( rc==SQLITE_OK );  /* KeySize() cannot fail */

  /* If this is an intKey table, then the above call to BtreeKeySize()
  ** stores the integer key in pCur->nKey. In this case this value is
  ** all that is required. Otherwise, if pCur is not open on an intKey
  ** table, then malloc space for and store the pCur->nKey bytes of key 
  ** data.
  */
  if( 0==pCur->apPage[0]->intKey ){
    void *pKey = sqlite4Malloc( (int)pCur->nKey );
    if( pKey ){
      rc = sqlite4BtreeKey(pCur, 0, (int)pCur->nKey, pKey);
      if( rc==SQLITE_OK ){
        pCur->pKey = pKey;
      }else{
        sqlite4_free(pKey);
      }
    }else{
      rc = SQLITE_NOMEM;
    }
  }
  assert( !pCur->apPage[0]->intKey || !pCur->pKey );

  if( rc==SQLITE_OK ){
    int i;
    for(i=0; i<=pCur->iPage; i++){
      releasePage(pCur->apPage[i]);
      pCur->apPage[i] = 0;
    }
    pCur->iPage = -1;
    pCur->eState = CURSOR_REQUIRESEEK;
  }

  invalidateOverflowCache(pCur);
  return rc;
}

/*
** Save the positions of all cursors (except pExcept) that are open on
** the table  with root-page iRoot. Usually, this is called just before cursor
** pExcept is used to modify the table (BtreeDelete() or BtreeInsert()).
*/
static int saveAllCursors(BtShared *pBt, Pgno iRoot, BtCursor *pExcept){
  BtCursor *p;
  assert( sqlite4_mutex_held(pBt->mutex) );
  assert( pExcept==0 || pExcept->pBt==pBt );
  for(p=pBt->pCursor; p; p=p->pNext){
    if( p!=pExcept && (0==iRoot || p->pgnoRoot==iRoot) && 
        p->eState==CURSOR_VALID ){
      int rc = saveCursorPosition(p);
      if( SQLITE_OK!=rc ){
        return rc;
      }
    }
  }
  return SQLITE_OK;
}

/*
** Clear the current cursor position.
*/
void sqlite4BtreeClearCursor(BtCursor *pCur){
  assert( cursorHoldsMutex(pCur) );
  sqlite4_free(pCur->pKey);
  pCur->pKey = 0;
  pCur->eState = CURSOR_INVALID;
}

/*
** In this version of BtreeMoveto, pKey is a packed index record
** such as is generated by the OP_MakeRecord opcode.  Unpack the
** record and then call BtreeMovetoUnpacked() to do the work.
*/
static int btreeMoveto(
  BtCursor *pCur,     /* Cursor open on the btree to be searched */
  const void *pKey,   /* Packed key if the btree is an index */
  i64 nKey,           /* Integer key for tables.  Size of pKey for indices */
  int bias,           /* Bias search to the high end */
  int *pRes           /* Write search results here */
){
  int rc;                    /* Status code */
  UnpackedRecord *pIdxKey;   /* Unpacked index key */
  char aSpace[150];          /* Temp space for pIdxKey - to avoid a malloc */
  char *pFree = 0;

  if( pKey ){
    assert( nKey==(i64)(int)nKey );
    pIdxKey = sqlite4VdbeAllocUnpackedRecord(
        pCur->pKeyInfo, aSpace, sizeof(aSpace), &pFree
    );
    if( pIdxKey==0 ) return SQLITE_NOMEM;
    sqlite4VdbeRecordUnpack(pCur->pKeyInfo, (int)nKey, pKey, pIdxKey);
  }else{
    pIdxKey = 0;
  }
  rc = sqlite4BtreeMovetoUnpacked(pCur, pIdxKey, nKey, bias, pRes);
  if( pFree ){
    sqlite4DbFree(pCur->pKeyInfo->db, pFree);
  }
  return rc;
}

/*
** Restore the cursor to the position it was in (or as close to as possible)
** when saveCursorPosition() was called. Note that this call deletes the 
** saved position info stored by saveCursorPosition(), so there can be
** at most one effective restoreCursorPosition() call after each 
** saveCursorPosition().
*/
static int btreeRestoreCursorPosition(BtCursor *pCur){
  int rc;
  assert( cursorHoldsMutex(pCur) );
  assert( pCur->eState>=CURSOR_REQUIRESEEK );
  if( pCur->eState==CURSOR_FAULT ){
    return pCur->skipNext;
  }
  pCur->eState = CURSOR_INVALID;
  rc = btreeMoveto(pCur, pCur->pKey, pCur->nKey, 0, &pCur->skipNext);
  if( rc==SQLITE_OK ){
    sqlite4_free(pCur->pKey);
    pCur->pKey = 0;
    assert( pCur->eState==CURSOR_VALID || pCur->eState==CURSOR_INVALID );
  }
  return rc;
}

#define restoreCursorPosition(p) \
  (p->eState>=CURSOR_REQUIRESEEK ? \
         btreeRestoreCursorPosition(p) : \
         SQLITE_OK)

/*
** Determine whether or not a cursor has moved from the position it
** was last placed at.  Cursors can move when the row they are pointing
** at is deleted out from under them.
**
** This routine returns an error code if something goes wrong.  The
** integer *pHasMoved is set to one if the cursor has moved and 0 if not.
*/
int sqlite4BtreeCursorHasMoved(BtCursor *pCur, int *pHasMoved){
  int rc;

  rc = restoreCursorPosition(pCur);
  if( rc ){
    *pHasMoved = 1;
    return rc;
  }
  if( pCur->eState!=CURSOR_VALID || pCur->skipNext!=0 ){
    *pHasMoved = 1;
  }else{
    *pHasMoved = 0;
  }
  return SQLITE_OK;
}

#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** Given a page number of a regular database page, return the page
** number for the pointer-map page that contains the entry for the
** input page number.
**
** Return 0 (not a valid page) for pgno==1 since there is
** no pointer map associated with page 1.  The integrity_check logic
** requires that ptrmapPageno(*,1)!=1.
*/
static Pgno ptrmapPageno(BtShared *pBt, Pgno pgno){
  int nPagesPerMapPage;
  Pgno iPtrMap, ret;
  assert( sqlite4_mutex_held(pBt->mutex) );
  if( pgno<2 ) return 0;
  nPagesPerMapPage = (pBt->usableSize/5)+1;
  iPtrMap = (pgno-2)/nPagesPerMapPage;
  ret = (iPtrMap*nPagesPerMapPage) + 2; 
  if( ret==PENDING_BYTE_PAGE(pBt) ){
    ret++;
  }
  return ret;
}

/*
** Write an entry into the pointer map.
**
** This routine updates the pointer map entry for page number 'key'
** so that it maps to type 'eType' and parent page number 'pgno'.
**
** If *pRC is initially non-zero (non-SQLITE_OK) then this routine is
** a no-op.  If an error occurs, the appropriate error code is written
** into *pRC.
*/
static void ptrmapPut(BtShared *pBt, Pgno key, u8 eType, Pgno parent, int *pRC){
  DbPage *pDbPage;  /* The pointer map page */
  u8 *pPtrmap;      /* The pointer map data */
  Pgno iPtrmap;     /* The pointer map page number */
  int offset;       /* Offset in pointer map page */
  int rc;           /* Return code from subfunctions */

  if( *pRC ) return;

  assert( sqlite4_mutex_held(pBt->mutex) );
  /* The master-journal page number must never be used as a pointer map page */
  assert( 0==PTRMAP_ISPAGE(pBt, PENDING_BYTE_PAGE(pBt)) );

  assert( pBt->autoVacuum );
  if( key==0 ){
    *pRC = SQLITE_CORRUPT_BKPT;
    return;
  }
  iPtrmap = PTRMAP_PAGENO(pBt, key);
  rc = sqlite4PagerGet(pBt->pPager, iPtrmap, &pDbPage);
  if( rc!=SQLITE_OK ){
    *pRC = rc;
    return;
  }
  offset = PTRMAP_PTROFFSET(iPtrmap, key);
  if( offset<0 ){
    *pRC = SQLITE_CORRUPT_BKPT;
    goto ptrmap_exit;
  }
  assert( offset <= (int)pBt->usableSize-5 );
  pPtrmap = (u8 *)sqlite4PagerGetData(pDbPage);

  if( eType!=pPtrmap[offset] || get4byte(&pPtrmap[offset+1])!=parent ){
    TRACE(("PTRMAP_UPDATE: %d->(%d,%d)\n", key, eType, parent));
    *pRC= rc = sqlite4PagerWrite(pDbPage);
    if( rc==SQLITE_OK ){
      pPtrmap[offset] = eType;
      put4byte(&pPtrmap[offset+1], parent);
    }
  }

ptrmap_exit:
  sqlite4PagerUnref(pDbPage);
}

/*
** Read an entry from the pointer map.
**
** This routine retrieves the pointer map entry for page 'key', writing
** the type and parent page number to *pEType and *pPgno respectively.
** An error code is returned if something goes wrong, otherwise SQLITE_OK.
*/
static int ptrmapGet(BtShared *pBt, Pgno key, u8 *pEType, Pgno *pPgno){
  DbPage *pDbPage;   /* The pointer map page */
  int iPtrmap;       /* Pointer map page index */
  u8 *pPtrmap;       /* Pointer map page data */
  int offset;        /* Offset of entry in pointer map */
  int rc;

  assert( sqlite4_mutex_held(pBt->mutex) );

  iPtrmap = PTRMAP_PAGENO(pBt, key);
  rc = sqlite4PagerGet(pBt->pPager, iPtrmap, &pDbPage);
  if( rc!=0 ){
    return rc;
  }
  pPtrmap = (u8 *)sqlite4PagerGetData(pDbPage);

  offset = PTRMAP_PTROFFSET(iPtrmap, key);
  if( offset<0 ){
    sqlite4PagerUnref(pDbPage);
    return SQLITE_CORRUPT_BKPT;
  }
  assert( offset <= (int)pBt->usableSize-5 );
  assert( pEType!=0 );
  *pEType = pPtrmap[offset];
  if( pPgno ) *pPgno = get4byte(&pPtrmap[offset+1]);

  sqlite4PagerUnref(pDbPage);
  if( *pEType<1 || *pEType>5 ) return SQLITE_CORRUPT_BKPT;
  return SQLITE_OK;
}

#else /* if defined SQLITE_OMIT_AUTOVACUUM */
  #define ptrmapPut(w,x,y,z,rc)
  #define ptrmapGet(w,x,y,z) SQLITE_OK
  #define ptrmapPutOvflPtr(x, y, rc)
#endif

/*
** Given a btree page and a cell index (0 means the first cell on
** the page, 1 means the second cell, and so forth) return a pointer
** to the cell content.
**
** This routine works only for pages that do not contain overflow cells.
*/
#define findCell(P,I) \
  ((P)->aData + ((P)->maskPage & get2byte(&(P)->aCellIdx[2*(I)])))
#define findCellv2(D,M,O,I) (D+(M&get2byte(D+(O+2*(I)))))


/*
** This a more complex version of findCell() that works for
** pages that do contain overflow cells.
*/
static u8 *findOverflowCell(MemPage *pPage, int iCell){
  int i;
  assert( sqlite4_mutex_held(pPage->pBt->mutex) );
  for(i=pPage->nOverflow-1; i>=0; i--){
    int k;
    struct _OvflCell *pOvfl;
    pOvfl = &pPage->aOvfl[i];
    k = pOvfl->idx;
    if( k<=iCell ){
      if( k==iCell ){
        return pOvfl->pCell;
      }
      iCell--;
    }
  }
  return findCell(pPage, iCell);
}

/*
** Parse a cell content block and fill in the CellInfo structure.  There
** are two versions of this function.  btreeParseCell() takes a 
** cell index as the second argument and btreeParseCellPtr() 
** takes a pointer to the body of the cell as its second argument.
**
** Within this file, the parseCell() macro can be called instead of
** btreeParseCellPtr(). Using some compilers, this will be faster.
*/
static void btreeParseCellPtr(
  MemPage *pPage,         /* Page containing the cell */
  u8 *pCell,              /* Pointer to the cell text. */
  CellInfo *pInfo         /* Fill in this structure */
){
  u16 n;                  /* Number bytes in cell content header */
  u32 nPayload;           /* Number of bytes of cell payload */

  assert( sqlite4_mutex_held(pPage->pBt->mutex) );

  pInfo->pCell = pCell;
  assert( pPage->leaf==0 || pPage->leaf==1 );
  n = pPage->childPtrSize;
  assert( n==4-4*pPage->leaf );
  if( pPage->intKey ){
    if( pPage->hasData ){
      n += getVarint32(&pCell[n], nPayload);
    }else{
      nPayload = 0;
    }
    n += getVarint(&pCell[n], (u64*)&pInfo->nKey);
    pInfo->nData = nPayload;
  }else{
    pInfo->nData = 0;
    n += getVarint32(&pCell[n], nPayload);
    pInfo->nKey = nPayload;
  }
  pInfo->nPayload = nPayload;
  pInfo->nHeader = n;
  testcase( nPayload==pPage->maxLocal );
  testcase( nPayload==pPage->maxLocal+1 );
  if( likely(nPayload<=pPage->maxLocal) ){
    /* This is the (easy) common case where the entire payload fits
    ** on the local page.  No overflow is required.
    */
    if( (pInfo->nSize = (u16)(n+nPayload))<4 ) pInfo->nSize = 4;
    pInfo->nLocal = (u16)nPayload;
    pInfo->iOverflow = 0;
  }else{
    /* If the payload will not fit completely on the local page, we have
    ** to decide how much to store locally and how much to spill onto
    ** overflow pages.  The strategy is to minimize the amount of unused
    ** space on overflow pages while keeping the amount of local storage
    ** in between minLocal and maxLocal.
    **
    ** Warning:  changing the way overflow payload is distributed in any
    ** way will result in an incompatible file format.
    */
    int minLocal;  /* Minimum amount of payload held locally */
    int maxLocal;  /* Maximum amount of payload held locally */
    int surplus;   /* Overflow payload available for local storage */

    minLocal = pPage->minLocal;
    maxLocal = pPage->maxLocal;
    surplus = minLocal + (nPayload - minLocal)%(pPage->pBt->usableSize - 4);
    testcase( surplus==maxLocal );
    testcase( surplus==maxLocal+1 );
    if( surplus <= maxLocal ){
      pInfo->nLocal = (u16)surplus;
    }else{
      pInfo->nLocal = (u16)minLocal;
    }
    pInfo->iOverflow = (u16)(pInfo->nLocal + n);
    pInfo->nSize = pInfo->iOverflow + 4;
  }
}
#define parseCell(pPage, iCell, pInfo) \
  btreeParseCellPtr((pPage), findCell((pPage), (iCell)), (pInfo))
static void btreeParseCell(
  MemPage *pPage,         /* Page containing the cell */
  int iCell,              /* The cell index.  First cell is 0 */
  CellInfo *pInfo         /* Fill in this structure */
){
  parseCell(pPage, iCell, pInfo);
}

/*
** Compute the total number of bytes that a Cell needs in the cell
** data area of the btree-page.  The return number includes the cell
** data header and the local payload, but not any overflow page or
** the space used by the cell pointer.
*/
static u16 cellSizePtr(MemPage *pPage, u8 *pCell){
  u8 *pIter = &pCell[pPage->childPtrSize];
  u32 nSize;

#ifdef SQLITE_DEBUG
  /* The value returned by this function should always be the same as
  ** the (CellInfo.nSize) value found by doing a full parse of the
  ** cell. If SQLITE_DEBUG is defined, an assert() at the bottom of
  ** this function verifies that this invariant is not violated. */
  CellInfo debuginfo;
  btreeParseCellPtr(pPage, pCell, &debuginfo);
#endif

  if( pPage->intKey ){
    u8 *pEnd;
    if( pPage->hasData ){
      pIter += getVarint32(pIter, nSize);
    }else{
      nSize = 0;
    }

    /* pIter now points at the 64-bit integer key value, a variable length 
    ** integer. The following block moves pIter to point at the first byte
    ** past the end of the key value. */
    pEnd = &pIter[9];
    while( (*pIter++)&0x80 && pIter<pEnd );
  }else{
    pIter += getVarint32(pIter, nSize);
  }

  testcase( nSize==pPage->maxLocal );
  testcase( nSize==pPage->maxLocal+1 );
  if( nSize>pPage->maxLocal ){
    int minLocal = pPage->minLocal;
    nSize = minLocal + (nSize - minLocal) % (pPage->pBt->usableSize - 4);
    testcase( nSize==pPage->maxLocal );
    testcase( nSize==pPage->maxLocal+1 );
    if( nSize>pPage->maxLocal ){
      nSize = minLocal;
    }
    nSize += 4;
  }
  nSize += (u32)(pIter - pCell);

  /* The minimum size of any cell is 4 bytes. */
  if( nSize<4 ){
    nSize = 4;
  }

  assert( nSize==debuginfo.nSize );
  return (u16)nSize;
}

#ifdef SQLITE_DEBUG
/* This variation on cellSizePtr() is used inside of assert() statements
** only. */
static u16 cellSize(MemPage *pPage, int iCell){
  return cellSizePtr(pPage, findCell(pPage, iCell));
}
#endif

#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** If the cell pCell, part of page pPage contains a pointer
** to an overflow page, insert an entry into the pointer-map
** for the overflow page.
*/
static void ptrmapPutOvflPtr(MemPage *pPage, u8 *pCell, int *pRC){
  CellInfo info;
  if( *pRC ) return;
  assert( pCell!=0 );
  btreeParseCellPtr(pPage, pCell, &info);
  assert( (info.nData+(pPage->intKey?0:info.nKey))==info.nPayload );
  if( info.iOverflow ){
    Pgno ovfl = get4byte(&pCell[info.iOverflow]);
    ptrmapPut(pPage->pBt, ovfl, PTRMAP_OVERFLOW1, pPage->pgno, pRC);
  }
}
#endif


/*
** Defragment the page given.  All Cells are moved to the
** end of the page and all free space is collected into one
** big FreeBlk that occurs in between the header and cell
** pointer array and the cell content area.
*/
static int defragmentPage(MemPage *pPage){
  int i;                     /* Loop counter */
  int pc;                    /* Address of a i-th cell */
  int hdr;                   /* Offset to the page header */
  int size;                  /* Size of a cell */
  int usableSize;            /* Number of usable bytes on a page */
  int cellOffset;            /* Offset to the cell pointer array */
  int cbrk;                  /* Offset to the cell content area */
  int nCell;                 /* Number of cells on the page */
  unsigned char *data;       /* The page data */
  unsigned char *temp;       /* Temp area for cell content */
  int iCellFirst;            /* First allowable cell index */
  int iCellLast;             /* Last possible cell index */


  assert( sqlite4PagerIswriteable(pPage->pDbPage) );
  assert( pPage->pBt!=0 );
  assert( pPage->pBt->usableSize <= SQLITE_MAX_PAGE_SIZE );
  assert( pPage->nOverflow==0 );
  assert( sqlite4_mutex_held(pPage->pBt->mutex) );
  temp = sqlite4PagerTempSpace(pPage->pBt->pPager);
  data = pPage->aData;
  hdr = pPage->hdrOffset;
  cellOffset = pPage->cellOffset;
  nCell = pPage->nCell;
  assert( nCell==get2byte(&data[hdr+3]) );
  usableSize = pPage->pBt->usableSize;
  cbrk = get2byte(&data[hdr+5]);
  memcpy(&temp[cbrk], &data[cbrk], usableSize - cbrk);
  cbrk = usableSize;
  iCellFirst = cellOffset + 2*nCell;
  iCellLast = usableSize - 4;
  for(i=0; i<nCell; i++){
    u8 *pAddr;     /* The i-th cell pointer */
    pAddr = &data[cellOffset + i*2];
    pc = get2byte(pAddr);
    testcase( pc==iCellFirst );
    testcase( pc==iCellLast );
#if !defined(SQLITE_ENABLE_OVERSIZE_CELL_CHECK)
    /* These conditions have already been verified in btreeInitPage()
    ** if SQLITE_ENABLE_OVERSIZE_CELL_CHECK is defined 
    */
    if( pc<iCellFirst || pc>iCellLast ){
      return SQLITE_CORRUPT_BKPT;
    }
#endif
    assert( pc>=iCellFirst && pc<=iCellLast );
    size = cellSizePtr(pPage, &temp[pc]);
    cbrk -= size;
#if defined(SQLITE_ENABLE_OVERSIZE_CELL_CHECK)
    if( cbrk<iCellFirst ){
      return SQLITE_CORRUPT_BKPT;
    }
#else
    if( cbrk<iCellFirst || pc+size>usableSize ){
      return SQLITE_CORRUPT_BKPT;
    }
#endif
    assert( cbrk+size<=usableSize && cbrk>=iCellFirst );
    testcase( cbrk+size==usableSize );
    testcase( pc+size==usableSize );
    memcpy(&data[cbrk], &temp[pc], size);
    put2byte(pAddr, cbrk);
  }
  assert( cbrk>=iCellFirst );
  put2byte(&data[hdr+5], cbrk);
  data[hdr+1] = 0;
  data[hdr+2] = 0;
  data[hdr+7] = 0;
  memset(&data[iCellFirst], 0, cbrk-iCellFirst);
  assert( sqlite4PagerIswriteable(pPage->pDbPage) );
  if( cbrk-iCellFirst!=pPage->nFree ){
    return SQLITE_CORRUPT_BKPT;
  }
  return SQLITE_OK;
}

/*
** Allocate nByte bytes of space from within the B-Tree page passed
** as the first argument. Write into *pIdx the index into pPage->aData[]
** of the first byte of allocated space. Return either SQLITE_OK or
** an error code (usually SQLITE_CORRUPT).
**
** The caller guarantees that there is sufficient space to make the
** allocation.  This routine might need to defragment in order to bring
** all the space together, however.  This routine will avoid using
** the first two bytes past the cell pointer area since presumably this
** allocation is being made in order to insert a new cell, so we will
** also end up needing a new cell pointer.
*/
static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
  const int hdr = pPage->hdrOffset;    /* Local cache of pPage->hdrOffset */
  u8 * const data = pPage->aData;      /* Local cache of pPage->aData */
  int nFrag;                           /* Number of fragmented bytes on pPage */
  int top;                             /* First byte of cell content area */
  int gap;        /* First byte of gap between cell pointers and cell content */
  int rc;         /* Integer return code */
  int usableSize; /* Usable size of the page */
  
  assert( sqlite4PagerIswriteable(pPage->pDbPage) );
  assert( pPage->pBt );
  assert( sqlite4_mutex_held(pPage->pBt->mutex) );
  assert( nByte>=0 );  /* Minimum cell size is 4 */
  assert( pPage->nFree>=nByte );
  assert( pPage->nOverflow==0 );
  usableSize = pPage->pBt->usableSize;
  assert( nByte < usableSize-8 );

  nFrag = data[hdr+7];
  assert( pPage->cellOffset == hdr + 12 - 4*pPage->leaf );
  gap = pPage->cellOffset + 2*pPage->nCell;
  top = get2byteNotZero(&data[hdr+5]);
  if( gap>top ) return SQLITE_CORRUPT_BKPT;
  testcase( gap+2==top );
  testcase( gap+1==top );
  testcase( gap==top );

  if( nFrag>=60 ){
    /* Always defragment highly fragmented pages */
    rc = defragmentPage(pPage);
    if( rc ) return rc;
    top = get2byteNotZero(&data[hdr+5]);
  }else if( gap+2<=top ){
    /* Search the freelist looking for a free slot big enough to satisfy 
    ** the request. The allocation is made from the first free slot in 
    ** the list that is large enough to accomadate it.
    */
    int pc, addr;
    for(addr=hdr+1; (pc = get2byte(&data[addr]))>0; addr=pc){
      int size;            /* Size of the free slot */
      if( pc>usableSize-4 || pc<addr+4 ){
        return SQLITE_CORRUPT_BKPT;
      }
      size = get2byte(&data[pc+2]);
      if( size>=nByte ){
        int x = size - nByte;
        testcase( x==4 );
        testcase( x==3 );
        if( x<4 ){
          /* Remove the slot from the free-list. Update the number of
          ** fragmented bytes within the page. */
          memcpy(&data[addr], &data[pc], 2);
          data[hdr+7] = (u8)(nFrag + x);
        }else if( size+pc > usableSize ){
          return SQLITE_CORRUPT_BKPT;
        }else{
          /* The slot remains on the free-list. Reduce its size to account
          ** for the portion used by the new allocation. */
          put2byte(&data[pc+2], x);
        }
        *pIdx = pc + x;
        return SQLITE_OK;
      }
    }
  }

  /* Check to make sure there is enough space in the gap to satisfy
  ** the allocation.  If not, defragment.
  */
  testcase( gap+2+nByte==top );
  if( gap+2+nByte>top ){
    rc = defragmentPage(pPage);
    if( rc ) return rc;
    top = get2byteNotZero(&data[hdr+5]);
    assert( gap+nByte<=top );
  }


  /* Allocate memory from the gap in between the cell pointer array
  ** and the cell content area.  The btreeInitPage() call has already
  ** validated the freelist.  Given that the freelist is valid, there
  ** is no way that the allocation can extend off the end of the page.
  ** The assert() below verifies the previous sentence.
  */
  top -= nByte;
  put2byte(&data[hdr+5], top);
  assert( top+nByte <= (int)pPage->pBt->usableSize );
  *pIdx = top;
  return SQLITE_OK;
}

/*
** Return a section of the pPage->aData to the freelist.
** The first byte of the new free block is pPage->aDisk[start]
** and the size of the block is "size" bytes.
**
** Most of the effort here is involved in coalesing adjacent
** free blocks into a single big free block.
*/
static int freeSpace(MemPage *pPage, int start, int size){
  int addr, pbegin, hdr;
  int iLast;                        /* Largest possible freeblock offset */
  unsigned char *data = pPage->aData;

  assert( pPage->pBt!=0 );
  assert( sqlite4PagerIswriteable(pPage->pDbPage) );
  assert( start>=pPage->hdrOffset+6+pPage->childPtrSize );
  assert( (start + size) <= (int)pPage->pBt->usableSize );
  assert( sqlite4_mutex_held(pPage->pBt->mutex) );
  assert( size>=0 );   /* Minimum cell size is 4 */

  if( pPage->pBt->btsFlags & BTS_SECURE_DELETE ){
    /* Overwrite deleted information with zeros when the secure_delete
    ** option is enabled */
    memset(&data[start], 0, size);
  }

  /* Add the space back into the linked list of freeblocks.  Note that
  ** even though the freeblock list was checked by btreeInitPage(),
  ** btreeInitPage() did not detect overlapping cells or
  ** freeblocks that overlapped cells.   Nor does it detect when the
  ** cell content area exceeds the value in the page header.  If these
  ** situations arise, then subsequent insert operations might corrupt
  ** the freelist.  So we do need to check for corruption while scanning
  ** the freelist.
  */
  hdr = pPage->hdrOffset;
  addr = hdr + 1;
  iLast = pPage->pBt->usableSize - 4;
  assert( start<=iLast );
  while( (pbegin = get2byte(&data[addr]))<start && pbegin>0 ){
    if( pbegin<addr+4 ){
      return SQLITE_CORRUPT_BKPT;
    }
    addr = pbegin;
  }
  if( pbegin>iLast ){
    return SQLITE_CORRUPT_BKPT;
  }
  assert( pbegin>addr || pbegin==0 );
  put2byte(&data[addr], start);
  put2byte(&data[start], pbegin);
  put2byte(&data[start+2], size);
  pPage->nFree = pPage->nFree + (u16)size;

  /* Coalesce adjacent free blocks */
  addr = hdr + 1;
  while( (pbegin = get2byte(&data[addr]))>0 ){
    int pnext, psize, x;
    assert( pbegin>addr );
    assert( pbegin <= (int)pPage->pBt->usableSize-4 );
    pnext = get2byte(&data[pbegin]);
    psize = get2byte(&data[pbegin+2]);
    if( pbegin + psize + 3 >= pnext && pnext>0 ){
      int frag = pnext - (pbegin+psize);
      if( (frag<0) || (frag>(int)data[hdr+7]) ){
        return SQLITE_CORRUPT_BKPT;
      }
      data[hdr+7] -= (u8)frag;
      x = get2byte(&data[pnext]);
      put2byte(&data[pbegin], x);
      x = pnext + get2byte(&data[pnext+2]) - pbegin;
      put2byte(&data[pbegin+2], x);
    }else{
      addr = pbegin;
    }
  }

  /* If the cell content area begins with a freeblock, remove it. */
  if( data[hdr+1]==data[hdr+5] && data[hdr+2]==data[hdr+6] ){
    int top;
    pbegin = get2byte(&data[hdr+1]);
    memcpy(&data[hdr+1], &data[pbegin], 2);
    top = get2byte(&data[hdr+5]) + get2byte(&data[pbegin+2]);
    put2byte(&data[hdr+5], top);
  }
  assert( sqlite4PagerIswriteable(pPage->pDbPage) );
  return SQLITE_OK;
}

/*
** Decode the flags byte (the first byte of the header) for a page
** and initialize fields of the MemPage structure accordingly.
**
** Only the following combinations are supported.  Anything different
** indicates a corrupt database files:
**
**         PTF_ZERODATA
**         PTF_ZERODATA | PTF_LEAF
**         PTF_LEAFDATA | PTF_INTKEY
**         PTF_LEAFDATA | PTF_INTKEY | PTF_LEAF
*/
static int decodeFlags(MemPage *pPage, int flagByte){
  BtShared *pBt;     /* A copy of pPage->pBt */

  assert( pPage->hdrOffset==(pPage->pgno==1 ? 100 : 0) );
  assert( sqlite4_mutex_held(pPage->pBt->mutex) );
  pPage->leaf = (u8)(flagByte>>3);  assert( PTF_LEAF == 1<<3 );
  flagByte &= ~PTF_LEAF;
  pPage->childPtrSize = 4-4*pPage->leaf;
  pBt = pPage->pBt;
  if( flagByte==(PTF_LEAFDATA | PTF_INTKEY) ){
    pPage->intKey = 1;
    pPage->hasData = pPage->leaf;
    pPage->maxLocal = pBt->maxLeaf;
    pPage->minLocal = pBt->minLeaf;
  }else if( flagByte==PTF_ZERODATA ){
    pPage->intKey = 0;
    pPage->hasData = 0;
    pPage->maxLocal = pBt->maxLocal;
    pPage->minLocal = pBt->minLocal;
  }else{
    return SQLITE_CORRUPT_BKPT;
  }
  pPage->max1bytePayload = pBt->max1bytePayload;
  return SQLITE_OK;
}

/*
** Initialize the auxiliary information for a disk block.
**
** Return SQLITE_OK on success.  If we see that the page does
** not contain a well-formed database page, then return 
** SQLITE_CORRUPT.  Note that a return of SQLITE_OK does not
** guarantee that the page is well-formed.  It only shows that
** we failed to detect any corruption.
*/
static int btreeInitPage(MemPage *pPage){

  assert( pPage->pBt!=0 );
  assert( sqlite4_mutex_held(pPage->pBt->mutex) );
  assert( pPage->pgno==sqlite4PagerPagenumber(pPage->pDbPage) );
  assert( pPage == sqlite4PagerGetExtra(pPage->pDbPage) );
  assert( pPage->aData == sqlite4PagerGetData(pPage->pDbPage) );

  if( !pPage->isInit ){
    u16 pc;            /* Address of a freeblock within pPage->aData[] */
    u8 hdr;            /* Offset to beginning of page header */
    u8 *data;          /* Equal to pPage->aData */
    BtShared *pBt;        /* The main btree structure */
    int usableSize;    /* Amount of usable space on each page */
    u16 cellOffset;    /* Offset from start of page to first cell pointer */
    int nFree;         /* Number of unused bytes on the page */
    int top;           /* First byte of the cell content area */
    int iCellFirst;    /* First allowable cell or freeblock offset */
    int iCellLast;     /* Last possible cell or freeblock offset */

    pBt = pPage->pBt;

    hdr = pPage->hdrOffset;
    data = pPage->aData;
    if( decodeFlags(pPage, data[hdr]) ) return SQLITE_CORRUPT_BKPT;
    assert( pBt->pageSize>=512 && pBt->pageSize<=65536 );
    pPage->maskPage = (u16)(pBt->pageSize - 1);
    pPage->nOverflow = 0;
    usableSize = pBt->usableSize;
    pPage->cellOffset = cellOffset = hdr + 12 - 4*pPage->leaf;
    pPage->aDataEnd = &data[usableSize];
    pPage->aCellIdx = &data[cellOffset];
    top = get2byteNotZero(&data[hdr+5]);
    pPage->nCell = get2byte(&data[hdr+3]);
    if( pPage->nCell>MX_CELL(pBt) ){
      /* To many cells for a single page.  The page must be corrupt */
      return SQLITE_CORRUPT_BKPT;
    }
    testcase( pPage->nCell==MX_CELL(pBt) );

    /* A malformed database page might cause us to read past the end
    ** of page when parsing a cell.  
    **
    ** The following block of code checks early to see if a cell extends
    ** past the end of a page boundary and causes SQLITE_CORRUPT to be 
    ** returned if it does.
    */
    iCellFirst = cellOffset + 2*pPage->nCell;
    iCellLast = usableSize - 4;
#if defined(SQLITE_ENABLE_OVERSIZE_CELL_CHECK)
    {
      int i;            /* Index into the cell pointer array */
      int sz;           /* Size of a cell */

      if( !pPage->leaf ) iCellLast--;
      for(i=0; i<pPage->nCell; i++){
        pc = get2byte(&data[cellOffset+i*2]);
        testcase( pc==iCellFirst );
        testcase( pc==iCellLast );
        if( pc<iCellFirst || pc>iCellLast ){
          return SQLITE_CORRUPT_BKPT;
        }
        sz = cellSizePtr(pPage, &data[pc]);
        testcase( pc+sz==usableSize );
        if( pc+sz>usableSize ){
          return SQLITE_CORRUPT_BKPT;
        }
      }
      if( !pPage->leaf ) iCellLast++;
    }  
#endif

    /* Compute the total free space on the page */
    pc = get2byte(&data[hdr+1]);
    nFree = data[hdr+7] + top;
    while( pc>0 ){
      u16 next, size;
      if( pc<iCellFirst || pc>iCellLast ){
        /* Start of free block is off the page */
        return SQLITE_CORRUPT_BKPT; 
      }
      next = get2byte(&data[pc]);
      size = get2byte(&data[pc+2]);
      if( (next>0 && next<=pc+size+3) || pc+size>usableSize ){
        /* Free blocks must be in ascending order. And the last byte of
	** the free-block must lie on the database page.  */
        return SQLITE_CORRUPT_BKPT; 
      }
      nFree = nFree + size;
      pc = next;
    }

    /* At this point, nFree contains the sum of the offset to the start
    ** of the cell-content area plus the number of free bytes within
    ** the cell-content area. If this is greater than the usable-size
    ** of the page, then the page must be corrupted. This check also
    ** serves to verify that the offset to the start of the cell-content
    ** area, according to the page header, lies within the page.
    */
    if( nFree>usableSize ){
      return SQLITE_CORRUPT_BKPT; 
    }
    pPage->nFree = (u16)(nFree - iCellFirst);
    pPage->isInit = 1;
  }
  return SQLITE_OK;
}

/*
** Set up a raw page so that it looks like a database page holding
** no entries.
*/
static void zeroPage(MemPage *pPage, int flags){
  unsigned char *data = pPage->aData;
  BtShared *pBt = pPage->pBt;
  u8 hdr = pPage->hdrOffset;
  u16 first;

  assert( sqlite4PagerPagenumber(pPage->pDbPage)==pPage->pgno );
  assert( sqlite4PagerGetExtra(pPage->pDbPage) == (void*)pPage );
  assert( sqlite4PagerGetData(pPage->pDbPage) == data );
  assert( sqlite4PagerIswriteable(pPage->pDbPage) );
  assert( sqlite4_mutex_held(pBt->mutex) );
  if( pBt->btsFlags & BTS_SECURE_DELETE ){
    memset(&data[hdr], 0, pBt->usableSize - hdr);
  }
  data[hdr] = (char)flags;
  first = hdr + 8 + 4*((flags&PTF_LEAF)==0 ?1:0);
  memset(&data[hdr+1], 0, 4);
  data[hdr+7] = 0;
  put2byte(&data[hdr+5], pBt->usableSize);
  pPage->nFree = (u16)(pBt->usableSize - first);
  decodeFlags(pPage, flags);
  pPage->hdrOffset = hdr;
  pPage->cellOffset = first;
  pPage->aDataEnd = &data[pBt->usableSize];
  pPage->aCellIdx = &data[first];
  pPage->nOverflow = 0;
  assert( pBt->pageSize>=512 && pBt->pageSize<=65536 );
  pPage->maskPage = (u16)(pBt->pageSize - 1);
  pPage->nCell = 0;
  pPage->isInit = 1;
}


/*
** Convert a DbPage obtained from the pager into a MemPage used by
** the btree layer.
*/
static MemPage *btreePageFromDbPage(DbPage *pDbPage, Pgno pgno, BtShared *pBt){
  MemPage *pPage = (MemPage*)sqlite4PagerGetExtra(pDbPage);
  pPage->aData = sqlite4PagerGetData(pDbPage);
  pPage->pDbPage = pDbPage;
  pPage->pBt = pBt;
  pPage->pgno = pgno;
  pPage->hdrOffset = pPage->pgno==1 ? 100 : 0;
  return pPage; 
}

/*
** Get a page from the pager.  Initialize the MemPage.pBt and
** MemPage.aData elements if needed.
**
** If the noContent flag is set, it means that we do not care about
** the content of the page at this time.  So do not go to the disk
** to fetch the content.  Just fill in the content with zeros for now.
** If in the future we call sqlite4PagerWrite() on this page, that
** means we have started to be concerned about content and the disk
** read should occur at that point.
*/
static int btreeGetPage(
  BtShared *pBt,       /* The btree */
  Pgno pgno,           /* Number of the page to fetch */
  MemPage **ppPage,    /* Return the page in this parameter */
  int noContent        /* Do not load page content if true */
){
  int rc;
  DbPage *pDbPage;

  assert( sqlite4_mutex_held(pBt->mutex) );
  rc = sqlite4PagerAcquire(pBt->pPager, pgno, (DbPage**)&pDbPage, noContent);
  if( rc ) return rc;
  *ppPage = btreePageFromDbPage(pDbPage, pgno, pBt);
  return SQLITE_OK;
}

/*
** Retrieve a page from the pager cache. If the requested page is not
** already in the pager cache return NULL. Initialize the MemPage.pBt and
** MemPage.aData elements if needed.
*/
static MemPage *btreePageLookup(BtShared *pBt, Pgno pgno){
  DbPage *pDbPage;
  assert( sqlite4_mutex_held(pBt->mutex) );
  pDbPage = sqlite4PagerLookup(pBt->pPager, pgno);
  if( pDbPage ){
    return btreePageFromDbPage(pDbPage, pgno, pBt);
  }
  return 0;
}

/*
** Return the size of the database file in pages. If there is any kind of
** error, return ((unsigned int)-1).
*/
static Pgno btreePagecount(BtShared *pBt){
  return pBt->nPage;
}
u32 sqlite4BtreeLastPage(Btree *p){
  assert( sqlite4BtreeHoldsMutex(p) );
  assert( ((p->pBt->nPage)&0x8000000)==0 );
  return (int)btreePagecount(p->pBt);
}

/*
** Get a page from the pager and initialize it.  This routine is just a
** convenience wrapper around separate calls to btreeGetPage() and 
** btreeInitPage().
**
** If an error occurs, then the value *ppPage is set to is undefined. It
** may remain unchanged, or it may be set to an invalid value.
*/
static int getAndInitPage(
  BtShared *pBt,          /* The database file */
  Pgno pgno,           /* Number of the page to get */
  MemPage **ppPage     /* Write the page pointer here */
){
  int rc;
  assert( sqlite4_mutex_held(pBt->mutex) );

  if( pgno>btreePagecount(pBt) ){
    rc = SQLITE_CORRUPT_BKPT;
  }else{
    rc = btreeGetPage(pBt, pgno, ppPage, 0);
    if( rc==SQLITE_OK ){
      rc = btreeInitPage(*ppPage);
      if( rc!=SQLITE_OK ){
        releasePage(*ppPage);
      }
    }
  }

  testcase( pgno==0 );
  assert( pgno!=0 || rc==SQLITE_CORRUPT );
  return rc;
}

/*
** Release a MemPage.  This should be called once for each prior
** call to btreeGetPage.
*/
static void releasePage(MemPage *pPage){
  if( pPage ){
    assert( pPage->aData );
    assert( pPage->pBt );
    assert( sqlite4PagerGetExtra(pPage->pDbPage) == (void*)pPage );
    assert( sqlite4PagerGetData(pPage->pDbPage)==pPage->aData );
    assert( sqlite4_mutex_held(pPage->pBt->mutex) );
    sqlite4PagerUnref(pPage->pDbPage);
  }
}

/*
** During a rollback, when the pager reloads information into the cache
** so that the cache is restored to its original state at the start of
** the transaction, for each page restored this routine is called.
**
** This routine needs to reset the extra data section at the end of the
** page to agree with the restored data.
*/
static void pageReinit(DbPage *pData){
  MemPage *pPage;
  pPage = (MemPage *)sqlite4PagerGetExtra(pData);
  assert( sqlite4PagerPageRefcount(pData)>0 );
  if( pPage->isInit ){
    assert( sqlite4_mutex_held(pPage->pBt->mutex) );
    pPage->isInit = 0;
    if( sqlite4PagerPageRefcount(pData)>1 ){
      /* pPage might not be a btree page;  it might be an overflow page
      ** or ptrmap page or a free page.  In those cases, the following
      ** call to btreeInitPage() will likely return SQLITE_CORRUPT.
      ** But no harm is done by this.  And it is very important that
      ** btreeInitPage() be called on every btree page so we make
      ** the call for every page that comes in for re-initing. */
      btreeInitPage(pPage);
    }
  }
}

/*
** Invoke the busy handler for a btree.
*/
static int btreeInvokeBusyHandler(void *pArg){
  BtShared *pBt = (BtShared*)pArg;
  assert( pBt->db );
  assert( sqlite4_mutex_held(pBt->db->mutex) );
  return sqlite4InvokeBusyHandler(&pBt->db->busyHandler);
}

/*
** Open a database file.
** 
** zFilename is the name of the database file.  If zFilename is NULL
** then an ephemeral database is created.  The ephemeral database might
** be exclusively in memory, or it might use a disk-based memory cache.
** Either way, the ephemeral database will be automatically deleted 
** when sqlite4BtreeClose() is called.
**
** If zFilename is ":memory:" then an in-memory database is created
** that is automatically destroyed when it is closed.
**
** The "flags" parameter is a bitmask that might contain bits like
** BTREE_OMIT_JOURNAL and/or BTREE_MEMORY.
**
** If the database is already opened in the same database connection
** and we are in shared cache mode, then the open will fail with an
** SQLITE_CONSTRAINT error.  We cannot allow two or more BtShared
** objects in the same database connection since doing so will lead
** to problems with locking.
*/
int sqlite4BtreeOpen(
  sqlite4_vfs *pVfs,      /* VFS to use for this b-tree */
  const char *zFilename,  /* Name of the file containing the BTree database */
  sqlite4 *db,            /* Associated database handle */
  Btree **ppBtree,        /* Pointer to new Btree object written here */
  int flags,              /* Options */
  int vfsFlags            /* Flags passed through to sqlite4_vfs.xOpen() */
){
  BtShared *pBt = 0;             /* Shared part of btree structure */
  Btree *p;                      /* Handle to return */
  sqlite4_mutex *mutexOpen = 0;  /* Prevents a race condition. Ticket #3537 */
  int rc = SQLITE_OK;            /* Result code from this function */
  u8 nReserve;                   /* Byte of unused space on each page */
  unsigned char zDbHeader[100];  /* Database header content */

  /* True if opening an ephemeral, temporary database */
  const int isTempDb = zFilename==0 || zFilename[0]==0;

  /* Set the variable isMemdb to true for an in-memory database, or 
  ** false for a file-based database.
  */
#ifdef SQLITE_OMIT_MEMORYDB
  const int isMemdb = 0;
#else
  const int isMemdb = (zFilename && strcmp(zFilename, ":memory:")==0)
                       || (isTempDb && sqlite4TempInMemory(db));
#endif

  assert( db!=0 );
  assert( pVfs!=0 );
  assert( sqlite4_mutex_held(db->mutex) );
  assert( (flags&0xff)==flags );   /* flags fit in 8 bits */

  /* Only a BTREE_SINGLE database can be BTREE_UNORDERED */
  assert( (flags & BTREE_UNORDERED)==0 || (flags & BTREE_SINGLE)!=0 );

  /* A BTREE_SINGLE database is always a temporary and/or ephemeral */
  assert( (flags & BTREE_SINGLE)==0 || isTempDb );

  if( isMemdb ){
    flags |= BTREE_MEMORY;
  }
  if( (vfsFlags & SQLITE_OPEN_MAIN_DB)!=0 && (isMemdb || isTempDb) ){
    vfsFlags = (vfsFlags & ~SQLITE_OPEN_MAIN_DB) | SQLITE_OPEN_TEMP_DB;
  }
  p = sqlite4MallocZero(sizeof(Btree));
  if( !p ){
    return SQLITE_NOMEM;
  }
  p->inTrans = TRANS_NONE;
  p->db = db;
#ifndef SQLITE_OMIT_SHARED_CACHE
  p->lock.pBtree = p;
  p->lock.iTable = 1;
#endif

#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
  /*
  ** If this Btree is a candidate for shared cache, try to find an
  ** existing BtShared object that we can share with
  */
  if( isMemdb==0 && isTempDb==0 ){
    if( vfsFlags & SQLITE_OPEN_SHAREDCACHE ){
      int nFullPathname = pVfs->mxPathname+1;
      char *zFullPathname = sqlite4Malloc(nFullPathname);
      MUTEX_LOGIC( sqlite4_mutex *mutexShared; )
      p->sharable = 1;
      if( !zFullPathname ){
        sqlite4_free(p);
        return SQLITE_NOMEM;
      }
      rc = sqlite4OsFullPathname(pVfs, zFilename, nFullPathname, zFullPathname);
      if( rc ){
        sqlite4_free(zFullPathname);
        sqlite4_free(p);
        return rc;
      }
#if SQLITE_THREADSAFE
      mutexOpen = sqlite4MutexAlloc(SQLITE_MUTEX_STATIC_OPEN);
      sqlite4_mutex_enter(mutexOpen);
      mutexShared = sqlite4MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
      sqlite4_mutex_enter(mutexShared);
#endif
      for(pBt=GLOBAL(BtShared*,sqlite4SharedCacheList); pBt; pBt=pBt->pNext){
        assert( pBt->nRef>0 );
        if( 0==strcmp(zFullPathname, sqlite4PagerFilename(pBt->pPager))
                 && sqlite4PagerVfs(pBt->pPager)==pVfs ){
          int iDb;
          for(iDb=db->nDb-1; iDb>=0; iDb--){
            Btree *pExisting = db->aDb[iDb].pBt;
            if( pExisting && pExisting->pBt==pBt ){
              sqlite4_mutex_leave(mutexShared);
              sqlite4_mutex_leave(mutexOpen);
              sqlite4_free(zFullPathname);
              sqlite4_free(p);
              return SQLITE_CONSTRAINT;
            }
          }
          p->pBt = pBt;
          pBt->nRef++;
          break;
        }
      }
      sqlite4_mutex_leave(mutexShared);
      sqlite4_free(zFullPathname);
    }
#ifdef SQLITE_DEBUG
    else{
      /* In debug mode, we mark all persistent databases as sharable
      ** even when they are not.  This exercises the locking code and
      ** gives more opportunity for asserts(sqlite4_mutex_held())
      ** statements to find locking problems.
      */
      p->sharable = 1;
    }
#endif
  }
#endif
  if( pBt==0 ){
    /*
    ** The following asserts make sure that structures used by the btree are
    ** the right size.  This is to guard against size changes that result
    ** when compiling on a different architecture.
    */
    assert( sizeof(i64)==8 || sizeof(i64)==4 );
    assert( sizeof(u64)==8 || sizeof(u64)==4 );
    assert( sizeof(u32)==4 );
    assert( sizeof(u16)==2 );
    assert( sizeof(Pgno)==4 );
  
    pBt = sqlite4MallocZero( sizeof(*pBt) );
    if( pBt==0 ){
      rc = SQLITE_NOMEM;
      goto btree_open_out;
    }
    rc = sqlite4PagerOpen(pVfs, &pBt->pPager, zFilename,
                          EXTRA_SIZE, flags, vfsFlags, pageReinit);
    if( rc==SQLITE_OK ){
      rc = sqlite4PagerReadFileheader(pBt->pPager,sizeof(zDbHeader),zDbHeader);
    }
    if( rc!=SQLITE_OK ){
      goto btree_open_out;
    }
    pBt->openFlags = (u8)flags;
    pBt->db = db;
    sqlite4PagerSetBusyhandler(pBt->pPager, btreeInvokeBusyHandler, pBt);
    p->pBt = pBt;
  
    pBt->pCursor = 0;
    pBt->pPage1 = 0;
    if( sqlite4PagerIsreadonly(pBt->pPager) ) pBt->btsFlags |= BTS_READ_ONLY;
#ifdef SQLITE_SECURE_DELETE
    pBt->btsFlags |= BTS_SECURE_DELETE;
#endif
    pBt->pageSize = (zDbHeader[16]<<8) | (zDbHeader[17]<<16);
    if( pBt->pageSize<512 || pBt->pageSize>SQLITE_MAX_PAGE_SIZE
         || ((pBt->pageSize-1)&pBt->pageSize)!=0 ){
      pBt->pageSize = 0;
#ifndef SQLITE_OMIT_AUTOVACUUM
      /* If the magic name ":memory:" will create an in-memory database, then
      ** leave the autoVacuum mode at 0 (do not auto-vacuum), even if
      ** SQLITE_DEFAULT_AUTOVACUUM is true. On the other hand, if
      ** SQLITE_OMIT_MEMORYDB has been defined, then ":memory:" is just a
      ** regular file-name. In this case the auto-vacuum applies as per normal.
      */
      if( zFilename && !isMemdb ){
        pBt->autoVacuum = (SQLITE_DEFAULT_AUTOVACUUM ? 1 : 0);
        pBt->incrVacuum = (SQLITE_DEFAULT_AUTOVACUUM==2 ? 1 : 0);
      }
#endif
      nReserve = 0;
    }else{
      nReserve = zDbHeader[20];
      pBt->btsFlags |= BTS_PAGESIZE_FIXED;
#ifndef SQLITE_OMIT_AUTOVACUUM
      pBt->autoVacuum = (get4byte(&zDbHeader[36 + 4*4])?1:0);
      pBt->incrVacuum = (get4byte(&zDbHeader[36 + 7*4])?1:0);
#endif
    }
    rc = sqlite4PagerSetPagesize(pBt->pPager, &pBt->pageSize, nReserve);
    if( rc ) goto btree_open_out;
    pBt->usableSize = pBt->pageSize - nReserve;
    assert( (pBt->pageSize & 7)==0 );  /* 8-byte alignment of pageSize */
   
#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
    /* Add the new BtShared object to the linked list sharable BtShareds.
    */
    if( p->sharable ){
      MUTEX_LOGIC( sqlite4_mutex *mutexShared; )
      pBt->nRef = 1;
      MUTEX_LOGIC( mutexShared = sqlite4MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);)
      if( SQLITE_THREADSAFE && sqlite4GlobalConfig.bCoreMutex ){
        pBt->mutex = sqlite4MutexAlloc(SQLITE_MUTEX_FAST);
        if( pBt->mutex==0 ){
          rc = SQLITE_NOMEM;
          db->mallocFailed = 0;
          goto btree_open_out;
        }
      }
      sqlite4_mutex_enter(mutexShared);
      pBt->pNext = GLOBAL(BtShared*,sqlite4SharedCacheList);
      GLOBAL(BtShared*,sqlite4SharedCacheList) = pBt;
      sqlite4_mutex_leave(mutexShared);
    }
#endif
  }

#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
  /* If the new Btree uses a sharable pBtShared, then link the new
  ** Btree into the list of all sharable Btrees for the same connection.
  ** The list is kept in ascending order by pBt address.
  */
  if( p->sharable ){
    int i;
    Btree *pSib;
    for(i=0; i<db->nDb; i++){
      if( (pSib = db->aDb[i].pBt)!=0 && pSib->sharable ){
        while( pSib->pPrev ){ pSib = pSib->pPrev; }
        if( p->pBt<pSib->pBt ){
          p->pNext = pSib;
          p->pPrev = 0;
          pSib->pPrev = p;
        }else{
          while( pSib->pNext && pSib->pNext->pBt<p->pBt ){
            pSib = pSib->pNext;
          }
          p->pNext = pSib->pNext;
          p->pPrev = pSib;
          if( p->pNext ){
            p->pNext->pPrev = p;
          }
          pSib->pNext = p;
        }
        break;
      }
    }
  }
#endif
  *ppBtree = p;

btree_open_out:
  if( rc!=SQLITE_OK ){
    if( pBt && pBt->pPager ){
      sqlite4PagerClose(pBt->pPager);
    }
    sqlite4_free(pBt);
    sqlite4_free(p);
    *ppBtree = 0;
  }else{
    /* If the B-Tree was successfully opened, set the pager-cache size to the
    ** default value. Except, when opening on an existing shared pager-cache,
    ** do not change the pager-cache size.
    */
    if( sqlite4BtreeSchema(p, 0, 0)==0 ){
      sqlite4PagerSetCachesize(p->pBt->pPager, SQLITE_DEFAULT_CACHE_SIZE);
    }
  }
  if( mutexOpen ){
    assert( sqlite4_mutex_held(mutexOpen) );
    sqlite4_mutex_leave(mutexOpen);
  }
  return rc;
}

/*
** Decrement the BtShared.nRef counter.  When it reaches zero,
** remove the BtShared structure from the sharing list.  Return
** true if the BtShared.nRef counter reaches zero and return
** false if it is still positive.
*/
static int removeFromSharingList(BtShared *pBt){
#ifndef SQLITE_OMIT_SHARED_CACHE
  MUTEX_LOGIC( sqlite4_mutex *pMaster; )
  BtShared *pList;
  int removed = 0;

  assert( sqlite4_mutex_notheld(pBt->mutex) );
  MUTEX_LOGIC( pMaster = sqlite4MutexAlloc(SQLITE_MUTEX_STATIC_MASTER); )
  sqlite4_mutex_enter(pMaster);
  pBt->nRef--;
  if( pBt->nRef<=0 ){
    if( GLOBAL(BtShared*,sqlite4SharedCacheList)==pBt ){
      GLOBAL(BtShared*,sqlite4SharedCacheList) = pBt->pNext;
    }else{
      pList = GLOBAL(BtShared*,sqlite4SharedCacheList);
      while( ALWAYS(pList) && pList->pNext!=pBt ){
        pList=pList->pNext;
      }
      if( ALWAYS(pList) ){
        pList->pNext = pBt->pNext;
      }
    }
    if( SQLITE_THREADSAFE ){
      sqlite4_mutex_free(pBt->mutex);
    }
    removed = 1;
  }
  sqlite4_mutex_leave(pMaster);
  return removed;
#else
  return 1;
#endif
}

/*
** Make sure pBt->pTmpSpace points to an allocation of 
** MX_CELL_SIZE(pBt) bytes.
*/
static void allocateTempSpace(BtShared *pBt){
  if( !pBt->pTmpSpace ){
    pBt->pTmpSpace = sqlite4PageMalloc( pBt->pageSize );
  }
}

/*
** Free the pBt->pTmpSpace allocation
*/
static void freeTempSpace(BtShared *pBt){
  sqlite4PageFree( pBt->pTmpSpace);
  pBt->pTmpSpace = 0;
}

/*
** Close an open database and invalidate all cursors.
*/
int sqlite4BtreeClose(Btree *p){
  BtShared *pBt = p->pBt;
  BtCursor *pCur;

  /* Close all cursors opened via this handle.  */
  assert( sqlite4_mutex_held(p->db->mutex) );
  sqlite4BtreeEnter(p);
  pCur = pBt->pCursor;
  while( pCur ){
    BtCursor *pTmp = pCur;
    pCur = pCur->pNext;
    if( pTmp->pBtree==p ){
      sqlite4BtreeCloseCursor(pTmp);
    }
  }

  /* Rollback any active transaction and free the handle structure.
  ** The call to sqlite4BtreeRollback() drops any table-locks held by
  ** this handle.
  */
  sqlite4BtreeRollback(p);
  sqlite4BtreeLeave(p);

  /* If there are still other outstanding references to the shared-btree
  ** structure, return now. The remainder of this procedure cleans 
  ** up the shared-btree.
  */
  assert( p->wantToLock==0 && p->locked==0 );
  if( !p->sharable || removeFromSharingList(pBt) ){
    /* The pBt is no longer on the sharing list, so we can access
    ** it without having to hold the mutex.
    **
    ** Clean out and delete the BtShared object.
    */
    assert( !pBt->pCursor );
    sqlite4PagerClose(pBt->pPager);
    if( pBt->xFreeSchema && pBt->pSchema ){
      pBt->xFreeSchema(pBt->pSchema);
    }
    sqlite4DbFree(0, pBt->pSchema);
    freeTempSpace(pBt);
    sqlite4_free(pBt);
  }

#ifndef SQLITE_OMIT_SHARED_CACHE
  assert( p->wantToLock==0 );
  assert( p->locked==0 );
  if( p->pPrev ) p->pPrev->pNext = p->pNext;
  if( p->pNext ) p->pNext->pPrev = p->pPrev;
#endif

  sqlite4_free(p);
  return SQLITE_OK;
}

/*
** Change the limit on the number of pages allowed in the cache.
**
** The maximum number of cache pages is set to the absolute
** value of mxPage.  If mxPage is negative, the pager will
** operate asynchronously - it will not stop to do fsync()s
** to insure data is written to the disk surface before
** continuing.  Transactions still work if synchronous is off,
** and the database cannot be corrupted if this program
** crashes.  But if the operating system crashes or there is
** an abrupt power failure when synchronous is off, the database
** could be left in an inconsistent and unrecoverable state.
** Synchronous is on by default so database corruption is not
** normally a worry.
*/
int sqlite4BtreeSetCacheSize(Btree *p, int mxPage){
  BtShared *pBt = p->pBt;
  assert( sqlite4_mutex_held(p->db->mutex) );
  sqlite4BtreeEnter(p);
  sqlite4PagerSetCachesize(pBt->pPager, mxPage);
  sqlite4BtreeLeave(p);
  return SQLITE_OK;
}

/*
** Change the way data is synced to disk in order to increase or decrease
** how well the database resists damage due to OS crashes and power
** failures.  Level 1 is the same as asynchronous (no syncs() occur and
** there is a high probability of damage)  Level 2 is the default.  There
** is a very low but non-zero probability of damage.  Level 3 reduces the
** probability of damage to near zero but with a write performance reduction.
*/
#ifndef SQLITE_OMIT_PAGER_PRAGMAS
int sqlite4BtreeSetSafetyLevel(
  Btree *p,              /* The btree to set the safety level on */
  int level,             /* PRAGMA synchronous.  1=OFF, 2=NORMAL, 3=FULL */
  int fullSync,          /* PRAGMA fullfsync. */
  int ckptFullSync       /* PRAGMA checkpoint_fullfync */
){
  BtShared *pBt = p->pBt;
  assert( sqlite4_mutex_held(p->db->mutex) );
  assert( level>=1 && level<=3 );
  sqlite4BtreeEnter(p);
  sqlite4PagerSetSafetyLevel(pBt->pPager, level, fullSync, ckptFullSync);
  sqlite4BtreeLeave(p);
  return SQLITE_OK;
}
#endif

/*
** Return TRUE if the given btree is set to safety level 1.  In other
** words, return TRUE if no sync() occurs on the disk files.
*/
int sqlite4BtreeSyncDisabled(Btree *p){
  BtShared *pBt = p->pBt;
  int rc;
  assert( sqlite4_mutex_held(p->db->mutex) );  
  sqlite4BtreeEnter(p);
  assert( pBt && pBt->pPager );
  rc = sqlite4PagerNosync(pBt->pPager);
  sqlite4BtreeLeave(p);
  return rc;
}

/*
** Change the default pages size and the number of reserved bytes per page.
** Or, if the page size has already been fixed, return SQLITE_READONLY 
** without changing anything.
**
** The page size must be a power of 2 between 512 and 65536.  If the page
** size supplied does not meet this constraint then the page size is not
** changed.
**
** Page sizes are constrained to be a power of two so that the region
** of the database file used for locking (beginning at PENDING_BYTE,
** the first byte past the 1GB boundary, 0x40000000) needs to occur
** at the beginning of a page.
**
** If parameter nReserve is less than zero, then the number of reserved
** bytes per page is left unchanged.
**
** If the iFix!=0 then the BTS_PAGESIZE_FIXED flag is set so that the page size
** and autovacuum mode can no longer be changed.
*/
int sqlite4BtreeSetPageSize(Btree *p, int pageSize, int nReserve, int iFix){
  int rc = SQLITE_OK;
  BtShared *pBt = p->pBt;
  assert( nReserve>=-1 && nReserve<=255 );
  sqlite4BtreeEnter(p);
  if( pBt->btsFlags & BTS_PAGESIZE_FIXED ){
    sqlite4BtreeLeave(p);
    return SQLITE_READONLY;
  }
  if( nReserve<0 ){
    nReserve = pBt->pageSize - pBt->usableSize;
  }
  assert( nReserve>=0 && nReserve<=255 );
  if( pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE &&
        ((pageSize-1)&pageSize)==0 ){
    assert( (pageSize & 7)==0 );
    assert( !pBt->pPage1 && !pBt->pCursor );
    pBt->pageSize = (u32)pageSize;
    freeTempSpace(pBt);
  }
  rc = sqlite4PagerSetPagesize(pBt->pPager, &pBt->pageSize, nReserve);
  pBt->usableSize = pBt->pageSize - (u16)nReserve;
  if( iFix ) pBt->btsFlags |= BTS_PAGESIZE_FIXED;
  sqlite4BtreeLeave(p);
  return rc;
}

/*
** Return the currently defined page size
*/
int sqlite4BtreeGetPageSize(Btree *p){
  return p->pBt->pageSize;
}

#if !defined(SQLITE_OMIT_PAGER_PRAGMAS) || !defined(SQLITE_OMIT_VACUUM)
/*
** Return the number of bytes of space at the end of every page that
** are intentually left unused.  This is the "reserved" space that is
** sometimes used by extensions.
*/
int sqlite4BtreeGetReserve(Btree *p){
  int n;
  sqlite4BtreeEnter(p);
  n = p->pBt->pageSize - p->pBt->usableSize;
  sqlite4BtreeLeave(p);
  return n;
}

/*
** Set the maximum page count for a database if mxPage is positive.
** No changes are made if mxPage is 0 or negative.
** Regardless of the value of mxPage, return the maximum page count.
*/
int sqlite4BtreeMaxPageCount(Btree *p, int mxPage){
  int n;
  sqlite4BtreeEnter(p);
  n = sqlite4PagerMaxPageCount(p->pBt->pPager, mxPage);
  sqlite4BtreeLeave(p);
  return n;
}

/*
** Set the BTS_SECURE_DELETE flag if newFlag is 0 or 1.  If newFlag is -1,
** then make no changes.  Always return the value of the BTS_SECURE_DELETE
** setting after the change.
*/
int sqlite4BtreeSecureDelete(Btree *p, int newFlag){
  int b;
  if( p==0 ) return 0;
  sqlite4BtreeEnter(p);
  if( newFlag>=0 ){
    p->pBt->btsFlags &= ~BTS_SECURE_DELETE;
    if( newFlag ) p->pBt->btsFlags |= BTS_SECURE_DELETE;
  } 
  b = (p->pBt->btsFlags & BTS_SECURE_DELETE)!=0;
  sqlite4BtreeLeave(p);
  return b;
}
#endif /* !defined(SQLITE_OMIT_PAGER_PRAGMAS) || !defined(SQLITE_OMIT_VACUUM) */

/*
** Change the 'auto-vacuum' property of the database. If the 'autoVacuum'
** parameter is non-zero, then auto-vacuum mode is enabled. If zero, it
** is disabled. The default value for the auto-vacuum property is 
** determined by the SQLITE_DEFAULT_AUTOVACUUM macro.
*/
int sqlite4BtreeSetAutoVacuum(Btree *p, int autoVacuum){
#ifdef SQLITE_OMIT_AUTOVACUUM
  return SQLITE_READONLY;
#else
  BtShared *pBt = p->pBt;
  int rc = SQLITE_OK;
  u8 av = (u8)autoVacuum;

  sqlite4BtreeEnter(p);
  if( (pBt->btsFlags & BTS_PAGESIZE_FIXED)!=0 && (av ?1:0)!=pBt->autoVacuum ){
    rc = SQLITE_READONLY;
  }else{
    pBt->autoVacuum = av ?1:0;
    pBt->incrVacuum = av==2 ?1:0;
  }
  sqlite4BtreeLeave(p);
  return rc;
#endif
}

/*
** Return the value of the 'auto-vacuum' property. If auto-vacuum is 
** enabled 1 is returned. Otherwise 0.
*/
int sqlite4BtreeGetAutoVacuum(Btree *p){
#ifdef SQLITE_OMIT_AUTOVACUUM
  return BTREE_AUTOVACUUM_NONE;
#else
  int rc;
  sqlite4BtreeEnter(p);
  rc = (
    (!p->pBt->autoVacuum)?BTREE_AUTOVACUUM_NONE:
    (!p->pBt->incrVacuum)?BTREE_AUTOVACUUM_FULL:
    BTREE_AUTOVACUUM_INCR
  );
  sqlite4BtreeLeave(p);
  return rc;
#endif
}


/*
** Get a reference to pPage1 of the database file.  This will
** also acquire a readlock on that file.
**
** SQLITE_OK is returned on success.  If the file is not a
** well-formed database file, then SQLITE_CORRUPT is returned.
** SQLITE_BUSY is returned if the database is locked.  SQLITE_NOMEM
** is returned if we run out of memory. 
*/
static int lockBtree(BtShared *pBt){
  int rc;              /* Result code from subfunctions */
  MemPage *pPage1;     /* Page 1 of the database file */
  int nPage;           /* Number of pages in the database */
  int nPageFile = 0;   /* Number of pages in the database file */
  int nPageHeader;     /* Number of pages in the database according to hdr */

  assert( sqlite4_mutex_held(pBt->mutex) );
  assert( pBt->pPage1==0 );
  rc = sqlite4PagerSharedLock(pBt->pPager);
  if( rc!=SQLITE_OK ) return rc;
  rc = btreeGetPage(pBt, 1, &pPage1, 0);
  if( rc!=SQLITE_OK ) return rc;

  /* Do some checking to help insure the file we opened really is
  ** a valid database file. 
  */
  nPage = nPageHeader = get4byte(28+(u8*)pPage1->aData);
  sqlite4PagerPagecount(pBt->pPager, &nPageFile);
  if( nPage==0 || memcmp(24+(u8*)pPage1->aData, 92+(u8*)pPage1->aData,4)!=0 ){
    nPage = nPageFile;
  }
  if( nPage>0 ){
    u32 pageSize;
    u32 usableSize;
    u8 *page1 = pPage1->aData;
    rc = SQLITE_NOTADB;
    if( memcmp(page1, zMagicHeader, 16)!=0 ){
      goto page1_init_failed;
    }

#ifdef SQLITE_OMIT_WAL
    if( page1[18]>1 ){
      pBt->btsFlags |= BTS_READ_ONLY;
    }
    if( page1[19]>1 ){
      goto page1_init_failed;
    }
#else
    if( page1[18]>2 ){
      pBt->btsFlags |= BTS_READ_ONLY;
    }
    if( page1[19]>2 ){
      goto page1_init_failed;
    }

    /* If the write version is set to 2, this database should be accessed
    ** in WAL mode. If the log is not already open, open it now. Then 
    ** return SQLITE_OK and return without populating BtShared.pPage1.
    ** The caller detects this and calls this function again. This is
    ** required as the version of page 1 currently in the page1 buffer
    ** may not be the latest version - there may be a newer one in the log
    ** file.
    */
    if( page1[19]==2 && (pBt->btsFlags & BTS_NO_WAL)==0 ){
      int isOpen = 0;
      rc = sqlite4PagerOpenWal(pBt->pPager, &isOpen);
      if( rc!=SQLITE_OK ){
        goto page1_init_failed;
      }else if( isOpen==0 ){
        releasePage(pPage1);
        return SQLITE_OK;
      }
      rc = SQLITE_NOTADB;
    }
#endif

    /* The maximum embedded fraction must be exactly 25%.  And the minimum
    ** embedded fraction must be 12.5% for both leaf-data and non-leaf-data.
    ** The original design allowed these amounts to vary, but as of
    ** version 3.6.0, we require them to be fixed.
    */
    if( memcmp(&page1[21], "\100\040\040",3)!=0 ){
      goto page1_init_failed;
    }
    pageSize = (page1[16]<<8) | (page1[17]<<16);
    if( ((pageSize-1)&pageSize)!=0
     || pageSize>SQLITE_MAX_PAGE_SIZE 
     || pageSize<=256 
    ){
      goto page1_init_failed;
    }
    assert( (pageSize & 7)==0 );
    usableSize = pageSize - page1[20];
    if( (u32)pageSize!=pBt->pageSize ){
      /* After reading the first page of the database assuming a page size
      ** of BtShared.pageSize, we have discovered that the page-size is
      ** actually pageSize. Unlock the database, leave pBt->pPage1 at
      ** zero and return SQLITE_OK. The caller will call this function
      ** again with the correct page-size.
      */
      releasePage(pPage1);
      pBt->usableSize = usableSize;
      pBt->pageSize = pageSize;
      freeTempSpace(pBt);
      rc = sqlite4PagerSetPagesize(pBt->pPager, &pBt->pageSize,
                                   pageSize-usableSize);
      return rc;
    }
    if( (pBt->db->flags & SQLITE_RecoveryMode)==0 && nPage>nPageFile ){
      rc = SQLITE_CORRUPT_BKPT;
      goto page1_init_failed;
    }
    if( usableSize<480 ){
      goto page1_init_failed;
    }
    pBt->pageSize = pageSize;
    pBt->usableSize = usableSize;
#ifndef SQLITE_OMIT_AUTOVACUUM
    pBt->autoVacuum = (get4byte(&page1[36 + 4*4])?1:0);
    pBt->incrVacuum = (get4byte(&page1[36 + 7*4])?1:0);
#endif
  }

  /* maxLocal is the maximum amount of payload to store locally for
  ** a cell.  Make sure it is small enough so that at least minFanout
  ** cells can will fit on one page.  We assume a 10-byte page header.
  ** Besides the payload, the cell must store:
  **     2-byte pointer to the cell
  **     4-byte child pointer
  **     9-byte nKey value
  **     4-byte nData value
  **     4-byte overflow page pointer
  ** So a cell consists of a 2-byte pointer, a header which is as much as
  ** 17 bytes long, 0 to N bytes of payload, and an optional 4 byte overflow
  ** page pointer.
  */
  pBt->maxLocal = (u16)((pBt->usableSize-12)*64/255 - 23);
  pBt->minLocal = (u16)((pBt->usableSize-12)*32/255 - 23);
  pBt->maxLeaf = (u16)(pBt->usableSize - 35);
  pBt->minLeaf = (u16)((pBt->usableSize-12)*32/255 - 23);
  if( pBt->maxLocal>127 ){
    pBt->max1bytePayload = 127;
  }else{
    pBt->max1bytePayload = (u8)pBt->maxLocal;
  }
  assert( pBt->maxLeaf + 23 <= MX_CELL_SIZE(pBt) );
  pBt->pPage1 = pPage1;
  pBt->nPage = nPage;
  return SQLITE_OK;

page1_init_failed:
  releasePage(pPage1);
  pBt->pPage1 = 0;
  return rc;
}

/*
** If there are no outstanding cursors and we are not in the middle
** of a transaction but there is a read lock on the database, then
** this routine unrefs the first page of the database file which 
** has the effect of releasing the read lock.
**
** If there is a transaction in progress, this routine is a no-op.
*/
static void unlockBtreeIfUnused(BtShared *pBt){
  assert( sqlite4_mutex_held(pBt->mutex) );
  assert( pBt->pCursor==0 || pBt->inTransaction>TRANS_NONE );
  if( pBt->inTransaction==TRANS_NONE && pBt->pPage1!=0 ){
    assert( pBt->pPage1->aData );
    assert( sqlite4PagerRefcount(pBt->pPager)==1 );
    assert( pBt->pPage1->aData );
    releasePage(pBt->pPage1);
    pBt->pPage1 = 0;
  }
}

/*
** If pBt points to an empty file then convert that empty file
** into a new empty database by initializing the first page of
** the database.
*/
static int newDatabase(BtShared *pBt){
  MemPage *pP1;
  unsigned char *data;
  int rc;

  assert( sqlite4_mutex_held(pBt->mutex) );
  if( pBt->nPage>0 ){
    return SQLITE_OK;
  }
  pP1 = pBt->pPage1;
  assert( pP1!=0 );
  data = pP1->aData;
  rc = sqlite4PagerWrite(pP1->pDbPage);
  if( rc ) return rc;
  memcpy(data, zMagicHeader, sizeof(zMagicHeader));
  assert( sizeof(zMagicHeader)==16 );
  data[16] = (u8)((pBt->pageSize>>8)&0xff);
  data[17] = (u8)((pBt->pageSize>>16)&0xff);
  data[18] = 1;
  data[19] = 1;
  assert( pBt->usableSize<=pBt->pageSize && pBt->usableSize+255>=pBt->pageSize);
  data[20] = (u8)(pBt->pageSize - pBt->usableSize);
  data[21] = 64;
  data[22] = 32;
  data[23] = 32;
  memset(&data[24], 0, 100-24);
  zeroPage(pP1, PTF_INTKEY|PTF_LEAF|PTF_LEAFDATA );
  pBt->btsFlags |= BTS_PAGESIZE_FIXED;
#ifndef SQLITE_OMIT_AUTOVACUUM
  assert( pBt->autoVacuum==1 || pBt->autoVacuum==0 );
  assert( pBt->incrVacuum==1 || pBt->incrVacuum==0 );
  put4byte(&data[36 + 4*4], pBt->autoVacuum);
  put4byte(&data[36 + 7*4], pBt->incrVacuum);
#endif
  pBt->nPage = 1;
  data[31] = 1;
  return SQLITE_OK;
}

/*
** Attempt to start a new transaction. A write-transaction
** is started if the second argument is nonzero, otherwise a read-
** transaction.  If the second argument is 2 or more and exclusive
** transaction is started, meaning that no other process is allowed
** to access the database.  A preexisting transaction may not be
** upgraded to exclusive by calling this routine a second time - the
** exclusivity flag only works for a new transaction.
**
** A write-transaction must be started before attempting any 
** changes to the database.  None of the following routines 
** will work unless a transaction is started first:
**
**      sqlite4BtreeCreateTable()
**      sqlite4BtreeCreateIndex()
**      sqlite4BtreeClearTable()
**      sqlite4BtreeDropTable()
**      sqlite4BtreeInsert()
**      sqlite4BtreeDelete()
**      sqlite4BtreeUpdateMeta()
**
** If an initial attempt to acquire the lock fails because of lock contention
** and the database was previously unlocked, then invoke the busy handler
** if there is one.  But if there was previously a read-lock, do not
** invoke the busy handler - just return SQLITE_BUSY.  SQLITE_BUSY is 
** returned when there is already a read-lock in order to avoid a deadlock.
**
** Suppose there are two processes A and B.  A has a read lock and B has
** a reserved lock.  B tries to promote to exclusive but is blocked because
** of A's read lock.  A tries to promote to reserved but is blocked by B.
** One or the other of the two processes must give way or there can be
** no progress.  By returning SQLITE_BUSY and not invoking the busy callback
** when A already has a read lock, we encourage A to give up and let B
** proceed.
*/
int sqlite4BtreeBeginTrans(Btree *p, int wrflag){
  sqlite4 *pBlock = 0;
  BtShared *pBt = p->pBt;
  int rc = SQLITE_OK;

  sqlite4BtreeEnter(p);
  btreeIntegrity(p);

  /* If the btree is already in a write-transaction, or it
  ** is already in a read-transaction and a read-transaction
  ** is requested, this is a no-op.
  */
  if( p->inTrans==TRANS_WRITE || (p->inTrans==TRANS_READ && !wrflag) ){
    goto trans_begun;
  }

  /* Write transactions are not possible on a read-only database */
  if( (pBt->btsFlags & BTS_READ_ONLY)!=0 && wrflag ){
    rc = SQLITE_READONLY;
    goto trans_begun;
  }

#ifndef SQLITE_OMIT_SHARED_CACHE
  /* If another database handle has already opened a write transaction 
  ** on this shared-btree structure and a second write transaction is
  ** requested, return SQLITE_LOCKED.
  */
  if( (wrflag && pBt->inTransaction==TRANS_WRITE)
   || (pBt->btsFlags & BTS_PENDING)!=0
  ){
    pBlock = pBt->pWriter->db;
  }else if( wrflag>1 ){
    BtLock *pIter;
    for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
      if( pIter->pBtree!=p ){
        pBlock = pIter->pBtree->db;
        break;
      }
    }
  }
  if( pBlock ){
    sqlite4ConnectionBlocked(p->db, pBlock);
    rc = SQLITE_LOCKED_SHAREDCACHE;
    goto trans_begun;
  }
#endif

  /* Any read-only or read-write transaction implies a read-lock on 
  ** page 1. So if some other shared-cache client already has a write-lock 
  ** on page 1, the transaction cannot be opened. */
  rc = querySharedCacheTableLock(p, MASTER_ROOT, READ_LOCK);
  if( SQLITE_OK!=rc ) goto trans_begun;

  pBt->btsFlags &= ~BTS_INITIALLY_EMPTY;
  if( pBt->nPage==0 ) pBt->btsFlags |= BTS_INITIALLY_EMPTY;
  do {
    /* Call lockBtree() until either pBt->pPage1 is populated or
    ** lockBtree() returns something other than SQLITE_OK. lockBtree()
    ** may return SQLITE_OK but leave pBt->pPage1 set to 0 if after
    ** reading page 1 it discovers that the page-size of the database 
    ** file is not pBt->pageSize. In this case lockBtree() will update
    ** pBt->pageSize to the page-size of the file on disk.
    */
    while( pBt->pPage1==0 && SQLITE_OK==(rc = lockBtree(pBt)) );

    if( rc==SQLITE_OK && wrflag ){
      if( (pBt->btsFlags & BTS_READ_ONLY)!=0 ){
        rc = SQLITE_READONLY;
      }else{
        rc = sqlite4PagerBegin(pBt->pPager,wrflag>1,sqlite4TempInMemory(p->db));
        if( rc==SQLITE_OK ){
          rc = newDatabase(pBt);
        }
      }
    }
  
    if( rc!=SQLITE_OK ){
      unlockBtreeIfUnused(pBt);
    }
  }while( (rc&0xFF)==SQLITE_BUSY && pBt->inTransaction==TRANS_NONE &&
          btreeInvokeBusyHandler(pBt) );

  if( rc==SQLITE_OK ){
    if( p->inTrans==TRANS_NONE ){
      pBt->nTransaction++;
#ifndef SQLITE_OMIT_SHARED_CACHE
      if( p->sharable ){
	assert( p->lock.pBtree==p && p->lock.iTable==1 );
        p->lock.eLock = READ_LOCK;
        p->lock.pNext = pBt->pLock;
        pBt->pLock = &p->lock;
      }
#endif
    }
    p->inTrans = (wrflag?TRANS_WRITE:TRANS_READ);
    if( p->inTrans>pBt->inTransaction ){
      pBt->inTransaction = p->inTrans;
    }
    if( wrflag ){
      MemPage *pPage1 = pBt->pPage1;
#ifndef SQLITE_OMIT_SHARED_CACHE
      assert( !pBt->pWriter );
      pBt->pWriter = p;
      pBt->btsFlags &= ~BTS_EXCLUSIVE;
      if( wrflag>1 ) pBt->btsFlags |= BTS_EXCLUSIVE;
#endif

      /* If the db-size header field is incorrect (as it may be if an old
      ** client has been writing the database file), update it now. Doing
      ** this sooner rather than later means the database size can safely 
      ** re-read the database size from page 1 if a savepoint or transaction
      ** rollback occurs within the transaction.
      */
      if( pBt->nPage!=get4byte(&pPage1->aData[28]) ){
        rc = sqlite4PagerWrite(pPage1->pDbPage);
        if( rc==SQLITE_OK ){
          put4byte(&pPage1->aData[28], pBt->nPage);
        }
      }
    }
  }


trans_begun:
  if( rc==SQLITE_OK && wrflag ){
    /* This call makes sure that the pager has the correct number of
    ** open savepoints. If the second parameter is greater than 0 and
    ** the sub-journal is not already open, then it will be opened here.
    */
    rc = sqlite4PagerOpenSavepoint(pBt->pPager, p->db->nSavepoint);
  }

  btreeIntegrity(p);
  sqlite4BtreeLeave(p);
  return rc;
}

#ifndef SQLITE_OMIT_AUTOVACUUM

/*
** Set the pointer-map entries for all children of page pPage. Also, if
** pPage contains cells that point to overflow pages, set the pointer
** map entries for the overflow pages as well.
*/
static int setChildPtrmaps(MemPage *pPage){
  int i;                             /* Counter variable */
  int nCell;                         /* Number of cells in page pPage */
  int rc;                            /* Return code */
  BtShared *pBt = pPage->pBt;
  u8 isInitOrig = pPage->isInit;
  Pgno pgno = pPage->pgno;

  assert( sqlite4_mutex_held(pPage->pBt->mutex) );
  rc = btreeInitPage(pPage);
  if( rc!=SQLITE_OK ){
    goto set_child_ptrmaps_out;
  }
  nCell = pPage->nCell;

  for(i=0; i<nCell; i++){
    u8 *pCell = findCell(pPage, i);

    ptrmapPutOvflPtr(pPage, pCell, &rc);

    if( !pPage->leaf ){
      Pgno childPgno = get4byte(pCell);
      ptrmapPut(pBt, childPgno, PTRMAP_BTREE, pgno, &rc);
    }
  }

  if( !pPage->leaf ){
    Pgno childPgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
    ptrmapPut(pBt, childPgno, PTRMAP_BTREE, pgno, &rc);
  }

set_child_ptrmaps_out:
  pPage->isInit = isInitOrig;
  return rc;
}

/*
** Somewhere on pPage is a pointer to page iFrom.  Modify this pointer so
** that it points to iTo. Parameter eType describes the type of pointer to
** be modified, as  follows:
**
** PTRMAP_BTREE:     pPage is a btree-page. The pointer points at a child 
**                   page of pPage.
**
** PTRMAP_OVERFLOW1: pPage is a btree-page. The pointer points at an overflow
**                   page pointed to by one of the cells on pPage.
**
** PTRMAP_OVERFLOW2: pPage is an overflow-page. The pointer points at the next
**                   overflow page in the list.
*/
static int modifyPagePointer(MemPage *pPage, Pgno iFrom, Pgno iTo, u8 eType){
  assert( sqlite4_mutex_held(pPage->pBt->mutex) );
  assert( sqlite4PagerIswriteable(pPage->pDbPage) );
  if( eType==PTRMAP_OVERFLOW2 ){
    /* The pointer is always the first 4 bytes of the page in this case.  */
    if( get4byte(pPage->aData)!=iFrom ){
      return SQLITE_CORRUPT_BKPT;
    }
    put4byte(pPage->aData, iTo);
  }else{
    u8 isInitOrig = pPage->isInit;
    int i;
    int nCell;

    btreeInitPage(pPage);
    nCell = pPage->nCell;

    for(i=0; i<nCell; i++){
      u8 *pCell = findCell(pPage, i);
      if( eType==PTRMAP_OVERFLOW1 ){
        CellInfo info;
        btreeParseCellPtr(pPage, pCell, &info);
        if( info.iOverflow
         && pCell+info.iOverflow+3<=pPage->aData+pPage->maskPage
         && iFrom==get4byte(&pCell[info.iOverflow])
        ){
          put4byte(&pCell[info.iOverflow], iTo);
          break;
        }
      }else{
        if( get4byte(pCell)==iFrom ){
          put4byte(pCell, iTo);
          break;
        }
      }
    }
  
    if( i==nCell ){
      if( eType!=PTRMAP_BTREE || 
          get4byte(&pPage->aData[pPage->hdrOffset+8])!=iFrom ){
        return SQLITE_CORRUPT_BKPT;
      }
      put4byte(&pPage->aData[pPage->hdrOffset+8], iTo);
    }

    pPage->isInit = isInitOrig;
  }
  return SQLITE_OK;
}


/*
** Move the open database page pDbPage to location iFreePage in the 
** database. The pDbPage reference remains valid.
**
** The isCommit flag indicates that there is no need to remember that
** the journal needs to be sync()ed before database page pDbPage->pgno 
** can be written to. The caller has already promised not to write to that
** page.
*/
static int relocatePage(
  BtShared *pBt,           /* Btree */
  MemPage *pDbPage,        /* Open page to move */
  u8 eType,                /* Pointer map 'type' entry for pDbPage */
  Pgno iPtrPage,           /* Pointer map 'page-no' entry for pDbPage */
  Pgno iFreePage,          /* The location to move pDbPage to */
  int isCommit             /* isCommit flag passed to sqlite4PagerMovepage */
){
  MemPage *pPtrPage;   /* The page that contains a pointer to pDbPage */
  Pgno iDbPage = pDbPage->pgno;
  Pager *pPager = pBt->pPager;
  int rc;

  assert( eType==PTRMAP_OVERFLOW2 || eType==PTRMAP_OVERFLOW1 || 
      eType==PTRMAP_BTREE || eType==PTRMAP_ROOTPAGE );
  assert( sqlite4_mutex_held(pBt->mutex) );
  assert( pDbPage->pBt==pBt );

  /* Move page iDbPage from its current location to page number iFreePage */
  TRACE(("AUTOVACUUM: Moving %d to free page %d (ptr page %d type %d)\n", 
      iDbPage, iFreePage, iPtrPage, eType));
  rc = sqlite4PagerMovepage(pPager, pDbPage->pDbPage, iFreePage, isCommit);
  if( rc!=SQLITE_OK ){
    return rc;
  }
  pDbPage->pgno = iFreePage;

  /* If pDbPage was a btree-page, then it may have child pages and/or cells
  ** that point to overflow pages. The pointer map entries for all these
  ** pages need to be changed.
  **
  ** If pDbPage is an overflow page, then the first 4 bytes may store a
  ** pointer to a subsequent overflow page. If this is the case, then
  ** the pointer map needs to be updated for the subsequent overflow page.
  */
  if( eType==PTRMAP_BTREE || eType==PTRMAP_ROOTPAGE ){
    rc = setChildPtrmaps(pDbPage);
    if( rc!=SQLITE_OK ){
      return rc;
    }
  }else{
    Pgno nextOvfl = get4byte(pDbPage->aData);
    if( nextOvfl!=0 ){
      ptrmapPut(pBt, nextOvfl, PTRMAP_OVERFLOW2, iFreePage, &rc);
      if( rc!=SQLITE_OK ){
        return rc;
      }
    }
  }

  /* Fix the database pointer on page iPtrPage that pointed at iDbPage so
  ** that it points at iFreePage. Also fix the pointer map entry for
  ** iPtrPage.
  */
  if( eType!=PTRMAP_ROOTPAGE ){
    rc = btreeGetPage(pBt, iPtrPage, &pPtrPage, 0);
    if( rc!=SQLITE_OK ){
      return rc;
    }
    rc = sqlite4PagerWrite(pPtrPage->pDbPage);
    if( rc!=SQLITE_OK ){
      releasePage(pPtrPage);
      return rc;
    }
    rc = modifyPagePointer(pPtrPage, iDbPage, iFreePage, eType);
    releasePage(pPtrPage);
    if( rc==SQLITE_OK ){
      ptrmapPut(pBt, iFreePage, eType, iPtrPage, &rc);
    }
  }
  return rc;
}

/* Forward declaration required by incrVacuumStep(). */
static int allocateBtreePage(BtShared *, MemPage **, Pgno *, Pgno, u8);

/*
** Perform a single step of an incremental-vacuum. If successful,
** return SQLITE_OK. If there is no work to do (and therefore no
** point in calling this function again), return SQLITE_DONE.
**
** More specificly, this function attempts to re-organize the 
** database so that the last page of the file currently in use
** is no longer in use.
**
** If the nFin parameter is non-zero, this function assumes
** that the caller will keep calling incrVacuumStep() until
** it returns SQLITE_DONE or an error, and that nFin is the
** number of pages the database file will contain after this 
** process is complete.  If nFin is zero, it is assumed that
** incrVacuumStep() will be called a finite amount of times
** which may or may not empty the freelist.  A full autovacuum
** has nFin>0.  A "PRAGMA incremental_vacuum" has nFin==0.
*/
static int incrVacuumStep(BtShared *pBt, Pgno nFin, Pgno iLastPg){
  Pgno nFreeList;           /* Number of pages still on the free-list */
  int rc;

  assert( sqlite4_mutex_held(pBt->mutex) );
  assert( iLastPg>nFin );

  if( !PTRMAP_ISPAGE(pBt, iLastPg) && iLastPg!=PENDING_BYTE_PAGE(pBt) ){
    u8 eType;
    Pgno iPtrPage;

    nFreeList = get4byte(&pBt->pPage1->aData[36]);
    if( nFreeList==0 ){
      return SQLITE_DONE;
    }

    rc = ptrmapGet(pBt, iLastPg, &eType, &iPtrPage);
    if( rc!=SQLITE_OK ){
      return rc;
    }
    if( eType==PTRMAP_ROOTPAGE ){
      return SQLITE_CORRUPT_BKPT;
    }

    if( eType==PTRMAP_FREEPAGE ){
      if( nFin==0 ){
        /* Remove the page from the files free-list. This is not required
        ** if nFin is non-zero. In that case, the free-list will be
        ** truncated to zero after this function returns, so it doesn't 
        ** matter if it still contains some garbage entries.
        */
        Pgno iFreePg;
        MemPage *pFreePg;
        rc = allocateBtreePage(pBt, &pFreePg, &iFreePg, iLastPg, 1);
        if( rc!=SQLITE_OK ){
          return rc;
        }
        assert( iFreePg==iLastPg );
        releasePage(pFreePg);
      }
    } else {
      Pgno iFreePg;             /* Index of free page to move pLastPg to */
      MemPage *pLastPg;

      rc = btreeGetPage(pBt, iLastPg, &pLastPg, 0);
      if( rc!=SQLITE_OK ){
        return rc;
      }

      /* If nFin is zero, this loop runs exactly once and page pLastPg
      ** is swapped with the first free page pulled off the free list.
      **
      ** On the other hand, if nFin is greater than zero, then keep
      ** looping until a free-page located within the first nFin pages
      ** of the file is found.
      */
      do {
        MemPage *pFreePg;
        rc = allocateBtreePage(pBt, &pFreePg, &iFreePg, 0, 0);
        if( rc!=SQLITE_OK ){
          releasePage(pLastPg);
          return rc;
        }
        releasePage(pFreePg);
      }while( nFin!=0 && iFreePg>nFin );
      assert( iFreePg<iLastPg );
      
      rc = sqlite4PagerWrite(pLastPg->pDbPage);
      if( rc==SQLITE_OK ){
        rc = relocatePage(pBt, pLastPg, eType, iPtrPage, iFreePg, nFin!=0);
      }
      releasePage(pLastPg);
      if( rc!=SQLITE_OK ){
        return rc;
      }
    }
  }

  if( nFin==0 ){
    iLastPg--;
    while( iLastPg==PENDING_BYTE_PAGE(pBt)||PTRMAP_ISPAGE(pBt, iLastPg) ){
      if( PTRMAP_ISPAGE(pBt, iLastPg) ){
        MemPage *pPg;
        rc = btreeGetPage(pBt, iLastPg, &pPg, 0);
        if( rc!=SQLITE_OK ){
          return rc;
        }
        rc = sqlite4PagerWrite(pPg->pDbPage);
        releasePage(pPg);
        if( rc!=SQLITE_OK ){
          return rc;
        }
      }
      iLastPg--;
    }
    sqlite4PagerTruncateImage(pBt->pPager, iLastPg);
    pBt->nPage = iLastPg;
  }
  return SQLITE_OK;
}

/*
** A write-transaction must be opened before calling this function.
** It performs a single unit of work towards an incremental vacuum.
**
** If the incremental vacuum is finished after this function has run,
** SQLITE_DONE is returned. If it is not finished, but no error occurred,
** SQLITE_OK is returned. Otherwise an SQLite error code. 
*/
int sqlite4BtreeIncrVacuum(Btree *p){
  int rc;
  BtShared *pBt = p->pBt;

  sqlite4BtreeEnter(p);
  assert( pBt->inTransaction==TRANS_WRITE && p->inTrans==TRANS_WRITE );
  if( !pBt->autoVacuum ){
    rc = SQLITE_DONE;
  }else{
    invalidateAllOverflowCache(pBt);
    rc = incrVacuumStep(pBt, 0, btreePagecount(pBt));
    if( rc==SQLITE_OK ){
      rc = sqlite4PagerWrite(pBt->pPage1->pDbPage);
      put4byte(&pBt->pPage1->aData[28], pBt->nPage);
    }
  }
  sqlite4BtreeLeave(p);
  return rc;
}

/*
** This routine is called prior to sqlite4PagerCommit when a transaction
** is commited for an auto-vacuum database.
**
** If SQLITE_OK is returned, then *pnTrunc is set to the number of pages
** the database file should be truncated to during the commit process. 
** i.e. the database has been reorganized so that only the first *pnTrunc
** pages are in use.
*/
static int autoVacuumCommit(BtShared *pBt){
  int rc = SQLITE_OK;
  Pager *pPager = pBt->pPager;
  VVA_ONLY( int nRef = sqlite4PagerRefcount(pPager) );

  assert( sqlite4_mutex_held(pBt->mutex) );
  invalidateAllOverflowCache(pBt);
  assert(pBt->autoVacuum);
  if( !pBt->incrVacuum ){
    Pgno nFin;         /* Number of pages in database after autovacuuming */
    Pgno nFree;        /* Number of pages on the freelist initially */
    Pgno nPtrmap;      /* Number of PtrMap pages to be freed */
    Pgno iFree;        /* The next page to be freed */
    int nEntry;        /* Number of entries on one ptrmap page */
    Pgno nOrig;        /* Database size before freeing */

    nOrig = btreePagecount(pBt);
    if( PTRMAP_ISPAGE(pBt, nOrig) || nOrig==PENDING_BYTE_PAGE(pBt) ){
      /* It is not possible to create a database for which the final page
      ** is either a pointer-map page or the pending-byte page. If one
      ** is encountered, this indicates corruption.
      */
      return SQLITE_CORRUPT_BKPT;
    }

    nFree = get4byte(&pBt->pPage1->aData[36]);
    nEntry = pBt->usableSize/5;
    nPtrmap = (nFree-nOrig+PTRMAP_PAGENO(pBt, nOrig)+nEntry)/nEntry;
    nFin = nOrig - nFree - nPtrmap;
    if( nOrig>PENDING_BYTE_PAGE(pBt) && nFin<PENDING_BYTE_PAGE(pBt) ){
      nFin--;
    }
    while( PTRMAP_ISPAGE(pBt, nFin) || nFin==PENDING_BYTE_PAGE(pBt) ){
      nFin--;
    }
    if( nFin>nOrig ) return SQLITE_CORRUPT_BKPT;

    for(iFree=nOrig; iFree>nFin && rc==SQLITE_OK; iFree--){
      rc = incrVacuumStep(pBt, nFin, iFree);
    }
    if( (rc==SQLITE_DONE || rc==SQLITE_OK) && nFree>0 ){
      rc = sqlite4PagerWrite(pBt->pPage1->pDbPage);
      put4byte(&pBt->pPage1->aData[32], 0);
      put4byte(&pBt->pPage1->aData[36], 0);
      put4byte(&pBt->pPage1->aData[28], nFin);
      sqlite4PagerTruncateImage(pBt->pPager, nFin);
      pBt->nPage = nFin;
    }
    if( rc!=SQLITE_OK ){
      sqlite4PagerRollback(pPager);
    }
  }

  assert( nRef==sqlite4PagerRefcount(pPager) );
  return rc;
}

#else /* ifndef SQLITE_OMIT_AUTOVACUUM */
# define setChildPtrmaps(x) SQLITE_OK
#endif

/*
** This routine does the first phase of a two-phase commit.  This routine
** causes a rollback journal to be created (if it does not already exist)
** and populated with enough information so that if a power loss occurs
** the database can be restored to its original state by playing back
** the journal.  Then the contents of the journal are flushed out to
** the disk.  After the journal is safely on oxide, the changes to the
** database are written into the database file and flushed to oxide.
** At the end of this call, the rollback journal still exists on the
** disk and we are still holding all locks, so the transaction has not
** committed.  See sqlite4BtreeCommitPhaseTwo() for the second phase of the
** commit process.
**
** This call is a no-op if no write-transaction is currently active on pBt.
**
** Otherwise, sync the database file for the btree pBt. zMaster points to
** the name of a master journal file that should be written into the
** individual journal file, or is NULL, indicating no master journal file 
** (single database transaction).
**
** When this is called, the master journal should already have been
** created, populated with this journal pointer and synced to disk.
**
** Once this is routine has returned, the only thing required to commit
** the write-transaction for this database file is to delete the journal.
*/
int sqlite4BtreeCommitPhaseOne(Btree *p, const char *zMaster){
  int rc = SQLITE_OK;
  if( p->inTrans==TRANS_WRITE ){
    BtShared *pBt = p->pBt;
    sqlite4BtreeEnter(p);
#ifndef SQLITE_OMIT_AUTOVACUUM
    if( pBt->autoVacuum ){
      rc = autoVacuumCommit(pBt);
      if( rc!=SQLITE_OK ){
        sqlite4BtreeLeave(p);
        return rc;
      }
    }
#endif
    rc = sqlite4PagerCommitPhaseOne(pBt->pPager, zMaster, 0);
    sqlite4BtreeLeave(p);
  }
  return rc;
}

/*
** This function is called from both BtreeCommitPhaseTwo() and BtreeRollback()
** at the conclusion of a transaction.
*/
static void btreeEndTransaction(Btree *p){
  BtShared *pBt = p->pBt;
  assert( sqlite4BtreeHoldsMutex(p) );

  btreeClearHasContent(pBt);
  if( p->inTrans>TRANS_NONE && p->db->activeVdbeCnt>1 ){
    /* If there are other active statements that belong to this database
    ** handle, downgrade to a read-only transaction. The other statements
    ** may still be reading from the database.  */
    downgradeAllSharedCacheTableLocks(p);
    p->inTrans = TRANS_READ;
  }else{
    /* If the handle had any kind of transaction open, decrement the 
    ** transaction count of the shared btree. If the transaction count 
    ** reaches 0, set the shared state to TRANS_NONE. The unlockBtreeIfUnused()
    ** call below will unlock the pager.  */
    if( p->inTrans!=TRANS_NONE ){
      clearAllSharedCacheTableLocks(p);
      pBt->nTransaction--;
      if( 0==pBt->nTransaction ){
        pBt->inTransaction = TRANS_NONE;
      }
    }

    /* Set the current transaction state to TRANS_NONE and unlock the 
    ** pager if this call closed the only read or write transaction.  */
    p->inTrans = TRANS_NONE;
    unlockBtreeIfUnused(pBt);
  }

  btreeIntegrity(p);
}

/*
** Commit the transaction currently in progress.
**
** This routine implements the second phase of a 2-phase commit.  The
** sqlite4BtreeCommitPhaseOne() routine does the first phase and should
** be invoked prior to calling this routine.  The sqlite4BtreeCommitPhaseOne()
** routine did all the work of writing information out to disk and flushing the
** contents so that they are written onto the disk platter.  All this
** routine has to do is delete or truncate or zero the header in the
** the rollback journal (which causes the transaction to commit) and
** drop locks.
**
** Normally, if an error occurs while the pager layer is attempting to 
** finalize the underlying journal file, this function returns an error and
** the upper layer will attempt a rollback. However, if the second argument
** is non-zero then this b-tree transaction is part of a multi-file 
** transaction. In this case, the transaction has already been committed 
** (by deleting a master journal file) and the caller will ignore this 
** functions return code. So, even if an error occurs in the pager layer,
** reset the b-tree objects internal state to indicate that the write
** transaction has been closed. This is quite safe, as the pager will have
** transitioned to the error state.
**
** This will release the write lock on the database file.  If there
** are no active cursors, it also releases the read lock.
*/
int sqlite4BtreeCommitPhaseTwo(Btree *p, int bCleanup){

  if( p->inTrans==TRANS_NONE ) return SQLITE_OK;
  sqlite4BtreeEnter(p);
  btreeIntegrity(p);

  /* If the handle has a write-transaction open, commit the shared-btrees 
  ** transaction and set the shared state to TRANS_READ.
  */
  if( p->inTrans==TRANS_WRITE ){
    int rc;
    BtShared *pBt = p->pBt;
    assert( pBt->inTransaction==TRANS_WRITE );
    assert( pBt->nTransaction>0 );
    rc = sqlite4PagerCommitPhaseTwo(pBt->pPager);
    if( rc!=SQLITE_OK && bCleanup==0 ){
      sqlite4BtreeLeave(p);
      return rc;
    }
    pBt->inTransaction = TRANS_READ;
  }

  btreeEndTransaction(p);
  sqlite4BtreeLeave(p);
  return SQLITE_OK;
}

/*
** Do both phases of a commit.
*/
int sqlite4BtreeCommit(Btree *p){
  int rc;
  sqlite4BtreeEnter(p);
  rc = sqlite4BtreeCommitPhaseOne(p, 0);
  if( rc==SQLITE_OK ){
    rc = sqlite4BtreeCommitPhaseTwo(p, 0);
  }
  sqlite4BtreeLeave(p);
  return rc;
}

#ifndef NDEBUG
/*
** Return the number of write-cursors open on this handle. This is for use
** in assert() expressions, so it is only compiled if NDEBUG is not
** defined.
**
** For the purposes of this routine, a write-cursor is any cursor that
** is capable of writing to the databse.  That means the cursor was
** originally opened for writing and the cursor has not be disabled
** by having its state changed to CURSOR_FAULT.
*/
static int countWriteCursors(BtShared *pBt){
  BtCursor *pCur;
  int r = 0;
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    if( pCur->wrFlag && pCur->eState!=CURSOR_FAULT ) r++; 
  }
  return r;
}
#endif

/*
** This routine sets the state to CURSOR_FAULT and the error
** code to errCode for every cursor on BtShared that pBtree
** references.
**
** Every cursor is tripped, including cursors that belong
** to other database connections that happen to be sharing
** the cache with pBtree.
**
** This routine gets called when a rollback occurs.
** All cursors using the same cache must be tripped
** to prevent them from trying to use the btree after
** the rollback.  The rollback may have deleted tables
** or moved root pages, so it is not sufficient to
** save the state of the cursor.  The cursor must be
** invalidated.
*/
void sqlite4BtreeTripAllCursors(Btree *pBtree, int errCode){
  BtCursor *p;
  sqlite4BtreeEnter(pBtree);
  for(p=pBtree->pBt->pCursor; p; p=p->pNext){
    int i;
    sqlite4BtreeClearCursor(p);
    p->eState = CURSOR_FAULT;
    p->skipNext = errCode;
    for(i=0; i<=p->iPage; i++){
      releasePage(p->apPage[i]);
      p->apPage[i] = 0;
    }
  }
  sqlite4BtreeLeave(pBtree);
}

/*
** Rollback the transaction in progress.  All cursors will be
** invalided by this operation.  Any attempt to use a cursor
** that was open at the beginning of this operation will result
** in an error.
**
** This will release the write lock on the database file.  If there
** are no active cursors, it also releases the read lock.
*/
int sqlite4BtreeRollback(Btree *p){
  int rc;
  BtShared *pBt = p->pBt;
  MemPage *pPage1;

  sqlite4BtreeEnter(p);
  rc = saveAllCursors(pBt, 0, 0);
#ifndef SQLITE_OMIT_SHARED_CACHE
  if( rc!=SQLITE_OK ){
    /* This is a horrible situation. An IO or malloc() error occurred whilst
    ** trying to save cursor positions. If this is an automatic rollback (as
    ** the result of a constraint, malloc() failure or IO error) then 
    ** the cache may be internally inconsistent (not contain valid trees) so
    ** we cannot simply return the error to the caller. Instead, abort 
    ** all queries that may be using any of the cursors that failed to save.
    */
    sqlite4BtreeTripAllCursors(p, rc);
  }
#endif
  btreeIntegrity(p);

  if( p->inTrans==TRANS_WRITE ){
    int rc2;

    assert( TRANS_WRITE==pBt->inTransaction );
    rc2 = sqlite4PagerRollback(pBt->pPager);
    if( rc2!=SQLITE_OK ){
      rc = rc2;
    }

    /* The rollback may have destroyed the pPage1->aData value.  So
    ** call btreeGetPage() on page 1 again to make
    ** sure pPage1->aData is set correctly. */
    if( btreeGetPage(pBt, 1, &pPage1, 0)==SQLITE_OK ){
      int nPage = get4byte(28+(u8*)pPage1->aData);
      testcase( nPage==0 );
      if( nPage==0 ) sqlite4PagerPagecount(pBt->pPager, &nPage);
      testcase( pBt->nPage!=nPage );
      pBt->nPage = nPage;
      releasePage(pPage1);
    }
    assert( countWriteCursors(pBt)==0 );
    pBt->inTransaction = TRANS_READ;
  }

  btreeEndTransaction(p);
  sqlite4BtreeLeave(p);
  return rc;
}

/*
** Start a statement subtransaction. The subtransaction can can be rolled
** back independently of the main transaction. You must start a transaction 
** before starting a subtransaction. The subtransaction is ended automatically 
** if the main transaction commits or rolls back.
**
** Statement subtransactions are used around individual SQL statements
** that are contained within a BEGIN...COMMIT block.  If a constraint
** error occurs within the statement, the effect of that one statement
** can be rolled back without having to rollback the entire transaction.
**
** A statement sub-transaction is implemented as an anonymous savepoint. The
** value passed as the second parameter is the total number of savepoints,
** including the new anonymous savepoint, open on the B-Tree. i.e. if there
** are no active savepoints and no other statement-transactions open,
** iStatement is 1. This anonymous savepoint can be released or rolled back
** using the sqlite4BtreeSavepoint() function.
*/
int sqlite4BtreeBeginStmt(Btree *p, int iStatement){
  int rc;
  BtShared *pBt = p->pBt;
  sqlite4BtreeEnter(p);
  assert( p->inTrans==TRANS_WRITE );
  assert( (pBt->btsFlags & BTS_READ_ONLY)==0 );
  assert( iStatement>0 );
  assert( iStatement>p->db->nSavepoint );
  assert( pBt->inTransaction==TRANS_WRITE );
  /* At the pager level, a statement transaction is a savepoint with
  ** an index greater than all savepoints created explicitly using
  ** SQL statements. It is illegal to open, release or rollback any
  ** such savepoints while the statement transaction savepoint is active.
  */
  rc = sqlite4PagerOpenSavepoint(pBt->pPager, iStatement);
  sqlite4BtreeLeave(p);
  return rc;
}

/*
** The second argument to this function, op, is always SAVEPOINT_ROLLBACK
** or SAVEPOINT_RELEASE. This function either releases or rolls back the
** savepoint identified by parameter iSavepoint, depending on the value 
** of op.
**
** Normally, iSavepoint is greater than or equal to zero. However, if op is
** SAVEPOINT_ROLLBACK, then iSavepoint may also be -1. In this case the 
** contents of the entire transaction are rolled back. This is different
** from a normal transaction rollback, as no locks are released and the
** transaction remains open.
*/
int sqlite4BtreeSavepoint(Btree *p, int op, int iSavepoint){
  int rc = SQLITE_OK;
  if( p && p->inTrans==TRANS_WRITE ){
    BtShared *pBt = p->pBt;
    assert( op==SAVEPOINT_RELEASE || op==SAVEPOINT_ROLLBACK );
    assert( iSavepoint>=0 || (iSavepoint==-1 && op==SAVEPOINT_ROLLBACK) );
    sqlite4BtreeEnter(p);
    rc = sqlite4PagerSavepoint(pBt->pPager, op, iSavepoint);
    if( rc==SQLITE_OK ){
      if( iSavepoint<0 && (pBt->btsFlags & BTS_INITIALLY_EMPTY)!=0 ){
        pBt->nPage = 0;
      }
      rc = newDatabase(pBt);
      pBt->nPage = get4byte(28 + pBt->pPage1->aData);

      /* The database size was written into the offset 28 of the header
      ** when the transaction started, so we know that the value at offset
      ** 28 is nonzero. */
      assert( pBt->nPage>0 );
    }
    sqlite4BtreeLeave(p);
  }
  return rc;
}

/*
** Create a new cursor for the BTree whose root is on the page
** iTable. If a read-only cursor is requested, it is assumed that
** the caller already has at least a read-only transaction open
** on the database already. If a write-cursor is requested, then
** the caller is assumed to have an open write transaction.
**
** If wrFlag==0, then the cursor can only be used for reading.
** If wrFlag==1, then the cursor can be used for reading or for
** writing if other conditions for writing are also met.  These
** are the conditions that must be met in order for writing to
** be allowed:
**
** 1:  The cursor must have been opened with wrFlag==1
**
** 2:  Other database connections that share the same pager cache
**     but which are not in the READ_UNCOMMITTED state may not have
**     cursors open with wrFlag==0 on the same table.  Otherwise
**     the changes made by this write cursor would be visible to
**     the read cursors in the other database connection.
**
** 3:  The database must be writable (not on read-only media)
**
** 4:  There must be an active transaction.
**
** No checking is done to make sure that page iTable really is the
** root page of a b-tree.  If it is not, then the cursor acquired
** will not work correctly.
**
** It is assumed that the sqlite4BtreeCursorZero() has been called
** on pCur to initialize the memory space prior to invoking this routine.
*/
static int btreeCursor(
  Btree *p,                              /* The btree */
  int iTable,                            /* Root page of table to open */
  int wrFlag,                            /* 1 to write. 0 read-only */
  struct KeyInfo *pKeyInfo,              /* First arg to comparison function */
  BtCursor *pCur                         /* Space for new cursor */
){
  BtShared *pBt = p->pBt;                /* Shared b-tree handle */

  assert( sqlite4BtreeHoldsMutex(p) );
  assert( wrFlag==0 || wrFlag==1 );

  /* The following assert statements verify that if this is a sharable 
  ** b-tree database, the connection is holding the required table locks, 
  ** and that no other connection has any open cursor that conflicts with 
  ** this lock.  */
  assert( hasSharedCacheTableLock(p, iTable, pKeyInfo!=0, wrFlag+1) );
  assert( wrFlag==0 || !hasReadConflicts(p, iTable) );

  /* Assert that the caller has opened the required transaction. */
  assert( p->inTrans>TRANS_NONE );
  assert( wrFlag==0 || p->inTrans==TRANS_WRITE );
  assert( pBt->pPage1 && pBt->pPage1->aData );

  if( NEVER(wrFlag && (pBt->btsFlags & BTS_READ_ONLY)!=0) ){
    return SQLITE_READONLY;
  }
  if( iTable==1 && btreePagecount(pBt)==0 ){
    assert( wrFlag==0 );
    iTable = 0;
  }

  /* Now that no other errors can occur, finish filling in the BtCursor
  ** variables and link the cursor into the BtShared list.  */
  pCur->pgnoRoot = (Pgno)iTable;
  pCur->iPage = -1;
  pCur->pKeyInfo = pKeyInfo;
  pCur->pBtree = p;
  pCur->pBt = pBt;
  pCur->wrFlag = (u8)wrFlag;
  pCur->pNext = pBt->pCursor;
  if( pCur->pNext ){
    pCur->pNext->pPrev = pCur;
  }
  pBt->pCursor = pCur;
  pCur->eState = CURSOR_INVALID;
  pCur->cachedRowid = 0;
  return SQLITE_OK;
}
int sqlite4BtreeCursor(
  Btree *p,                                   /* The btree */
  int iTable,                                 /* Root page of table to open */
  int wrFlag,                                 /* 1 to write. 0 read-only */
  struct KeyInfo *pKeyInfo,                   /* First arg to xCompare() */
  BtCursor *pCur                              /* Write new cursor here */
){
  int rc;
  sqlite4BtreeEnter(p);
  rc = btreeCursor(p, iTable, wrFlag, pKeyInfo, pCur);
  sqlite4BtreeLeave(p);
  return rc;
}

/*
** Return the size of a BtCursor object in bytes.
**
** This interfaces is needed so that users of cursors can preallocate
** sufficient storage to hold a cursor.  The BtCursor object is opaque
** to users so they cannot do the sizeof() themselves - they must call
** this routine.
*/
int sqlite4BtreeCursorSize(void){
  return ROUND8(sizeof(BtCursor));
}

/*
** Initialize memory that will be converted into a BtCursor object.
**
** The simple approach here would be to memset() the entire object
** to zero.  But it turns out that the apPage[] and aiIdx[] arrays
** do not need to be zeroed and they are large, so we can save a lot
** of run-time by skipping the initialization of those elements.
*/
void sqlite4BtreeCursorZero(BtCursor *p){
  memset(p, 0, offsetof(BtCursor, iPage));
}

/*
** Set the cached rowid value of every cursor in the same database file
** as pCur and having the same root page number as pCur.  The value is
** set to iRowid.
**
** Only positive rowid values are considered valid for this cache.
** The cache is initialized to zero, indicating an invalid cache.
** A btree will work fine with zero or negative rowids.  We just cannot
** cache zero or negative rowids, which means tables that use zero or
** negative rowids might run a little slower.  But in practice, zero
** or negative rowids are very uncommon so this should not be a problem.
*/
void sqlite4BtreeSetCachedRowid(BtCursor *pCur, sqlite4_int64 iRowid){
  BtCursor *p;
  for(p=pCur->pBt->pCursor; p; p=p->pNext){
    if( p->pgnoRoot==pCur->pgnoRoot ) p->cachedRowid = iRowid;
  }
  assert( pCur->cachedRowid==iRowid );
}

/*
** Return the cached rowid for the given cursor.  A negative or zero
** return value indicates that the rowid cache is invalid and should be
** ignored.  If the rowid cache has never before been set, then a
** zero is returned.
*/
sqlite4_int64 sqlite4BtreeGetCachedRowid(BtCursor *pCur){
  return pCur->cachedRowid;
}

/*
** Close a cursor.  The read lock on the database file is released
** when the last cursor is closed.
*/
int sqlite4BtreeCloseCursor(BtCursor *pCur){
  Btree *pBtree = pCur->pBtree;
  if( pBtree ){
    int i;
    BtShared *pBt = pCur->pBt;
    sqlite4BtreeEnter(pBtree);
    sqlite4BtreeClearCursor(pCur);
    if( pCur->pPrev ){
      pCur->pPrev->pNext = pCur->pNext;
    }else{
      pBt->pCursor = pCur->pNext;
    }
    if( pCur->pNext ){
      pCur->pNext->pPrev = pCur->pPrev;
    }
    for(i=0; i<=pCur->iPage; i++){
      releasePage(pCur->apPage[i]);
    }
    unlockBtreeIfUnused(pBt);
    invalidateOverflowCache(pCur);
    /* sqlite4_free(pCur); */
    sqlite4BtreeLeave(pBtree);
  }
  return SQLITE_OK;
}

/*
** Make sure the BtCursor* given in the argument has a valid
** BtCursor.info structure.  If it is not already valid, call
** btreeParseCell() to fill it in.
**
** BtCursor.info is a cache of the information in the current cell.
** Using this cache reduces the number of calls to btreeParseCell().
**
** 2007-06-25:  There is a bug in some versions of MSVC that cause the
** compiler to crash when getCellInfo() is implemented as a macro.
** But there is a measureable speed advantage to using the macro on gcc
** (when less compiler optimizations like -Os or -O0 are used and the
** compiler is not doing agressive inlining.)  So we use a real function
** for MSVC and a macro for everything else.  Ticket #2457.
*/
#ifndef NDEBUG
  static void assertCellInfo(BtCursor *pCur){
    CellInfo info;
    int iPage = pCur->iPage;
    memset(&info, 0, sizeof(info));
    btreeParseCell(pCur->apPage[iPage], pCur->aiIdx[iPage], &info);
    assert( memcmp(&info, &pCur->info, sizeof(info))==0 );
  }
#else
  #define assertCellInfo(x)
#endif
#ifdef _MSC_VER
  /* Use a real function in MSVC to work around bugs in that compiler. */
  static void getCellInfo(BtCursor *pCur){
    if( pCur->info.nSize==0 ){
      int iPage = pCur->iPage;
      btreeParseCell(pCur->apPage[iPage],pCur->aiIdx[iPage],&pCur->info);
      pCur->validNKey = 1;
    }else{
      assertCellInfo(pCur);
    }
  }
#else /* if not _MSC_VER */
  /* Use a macro in all other compilers so that the function is inlined */
#define getCellInfo(pCur)                                                      \
  if( pCur->info.nSize==0 ){                                                   \
    int iPage = pCur->iPage;                                                   \
    btreeParseCell(pCur->apPage[iPage],pCur->aiIdx[iPage],&pCur->info); \
    pCur->validNKey = 1;                                                       \
  }else{                                                                       \
    assertCellInfo(pCur);                                                      \
  }
#endif /* _MSC_VER */

#ifndef NDEBUG  /* The next routine used only within assert() statements */
/*
** Return true if the given BtCursor is valid.  A valid cursor is one
** that is currently pointing to a row in a (non-empty) table.
** This is a verification routine is used only within assert() statements.
*/
int sqlite4BtreeCursorIsValid(BtCursor *pCur){
  return pCur && pCur->eState==CURSOR_VALID;
}
#endif /* NDEBUG */

/*
** Set *pSize to the size of the buffer needed to hold the value of
** the key for the current entry.  If the cursor is not pointing
** to a valid entry, *pSize is set to 0. 
**
** For a table with the INTKEY flag set, this routine returns the key
** itself, not the number of bytes in the key.
**
** The caller must position the cursor prior to invoking this routine.
** 
** This routine cannot fail.  It always returns SQLITE_OK.  
*/
int sqlite4BtreeKeySize(BtCursor *pCur, i64 *pSize){
  assert( cursorHoldsMutex(pCur) );
  assert( pCur->eState==CURSOR_INVALID || pCur->eState==CURSOR_VALID );
  if( pCur->eState!=CURSOR_VALID ){
    *pSize = 0;
  }else{
    getCellInfo(pCur);
    *pSize = pCur->info.nKey;
  }
  return SQLITE_OK;
}

/*
** Set *pSize to the number of bytes of data in the entry the
** cursor currently points to.
**
** The caller must guarantee that the cursor is pointing to a non-NULL
** valid entry.  In other words, the calling procedure must guarantee
** that the cursor has Cursor.eState==CURSOR_VALID.
**
** Failure is not possible.  This function always returns SQLITE_OK.
** It might just as well be a procedure (returning void) but we continue
** to return an integer result code for historical reasons.
*/
int sqlite4BtreeDataSize(BtCursor *pCur, u32 *pSize){
  assert( cursorHoldsMutex(pCur) );
  assert( pCur->eState==CURSOR_VALID );
  getCellInfo(pCur);
  *pSize = pCur->info.nData;
  return SQLITE_OK;
}

/*
** Given the page number of an overflow page in the database (parameter
** ovfl), this function finds the page number of the next page in the 
** linked list of overflow pages. If possible, it uses the auto-vacuum
** pointer-map data instead of reading the content of page ovfl to do so. 
**
** If an error occurs an SQLite error code is returned. Otherwise:
**
** The page number of the next overflow page in the linked list is 
** written to *pPgnoNext. If page ovfl is the last page in its linked 
** list, *pPgnoNext is set to zero. 
**
** If ppPage is not NULL, and a reference to the MemPage object corresponding
** to page number pOvfl was obtained, then *ppPage is set to point to that
** reference. It is the responsibility of the caller to call releasePage()
** on *ppPage to free the reference. In no reference was obtained (because
** the pointer-map was used to obtain the value for *pPgnoNext), then
** *ppPage is set to zero.
*/
static int getOverflowPage(
  BtShared *pBt,               /* The database file */
  Pgno ovfl,                   /* Current overflow page number */
  MemPage **ppPage,            /* OUT: MemPage handle (may be NULL) */
  Pgno *pPgnoNext              /* OUT: Next overflow page number */
){
  Pgno next = 0;
  MemPage *pPage = 0;
  int rc = SQLITE_OK;

  assert( sqlite4_mutex_held(pBt->mutex) );
  assert(pPgnoNext);

#ifndef SQLITE_OMIT_AUTOVACUUM
  /* Try to find the next page in the overflow list using the
  ** autovacuum pointer-map pages. Guess that the next page in 
  ** the overflow list is page number (ovfl+1). If that guess turns 
  ** out to be wrong, fall back to loading the data of page 
  ** number ovfl to determine the next page number.
  */
  if( pBt->autoVacuum ){
    Pgno pgno;
    Pgno iGuess = ovfl+1;
    u8 eType;

    while( PTRMAP_ISPAGE(pBt, iGuess) || iGuess==PENDING_BYTE_PAGE(pBt) ){
      iGuess++;
    }

    if( iGuess<=btreePagecount(pBt) ){
      rc = ptrmapGet(pBt, iGuess, &eType, &pgno);
      if( rc==SQLITE_OK && eType==PTRMAP_OVERFLOW2 && pgno==ovfl ){
        next = iGuess;
        rc = SQLITE_DONE;
      }
    }
  }
#endif

  assert( next==0 || rc==SQLITE_DONE );
  if( rc==SQLITE_OK ){
    rc = btreeGetPage(pBt, ovfl, &pPage, 0);
    assert( rc==SQLITE_OK || pPage==0 );
    if( rc==SQLITE_OK ){
      next = get4byte(pPage->aData);
    }
  }

  *pPgnoNext = next;
  if( ppPage ){
    *ppPage = pPage;
  }else{
    releasePage(pPage);
  }
  return (rc==SQLITE_DONE ? SQLITE_OK : rc);
}

/*
** Copy data from a buffer to a page, or from a page to a buffer.
**
** pPayload is a pointer to data stored on database page pDbPage.
** If argument eOp is false, then nByte bytes of data are copied
** from pPayload to the buffer pointed at by pBuf. If eOp is true,
** then sqlite4PagerWrite() is called on pDbPage and nByte bytes
** of data are copied from the buffer pBuf to pPayload.
**
** SQLITE_OK is returned on success, otherwise an error code.
*/
static int copyPayload(
  void *pPayload,           /* Pointer to page data */
  void *pBuf,               /* Pointer to buffer */
  int nByte,                /* Number of bytes to copy */
  int eOp,                  /* 0 -> copy from page, 1 -> copy to page */
  DbPage *pDbPage           /* Page containing pPayload */
){
  if( eOp ){
    /* Copy data from buffer to page (a write operation) */
    int rc = sqlite4PagerWrite(pDbPage);
    if( rc!=SQLITE_OK ){
      return rc;
    }
    memcpy(pPayload, pBuf, nByte);
  }else{
    /* Copy data from page to buffer (a read operation) */
    memcpy(pBuf, pPayload, nByte);
  }
  return SQLITE_OK;
}

/*
** This function is used to read or overwrite payload information
** for the entry that the pCur cursor is pointing to. If the eOp
** parameter is 0, this is a read operation (data copied into
** buffer pBuf). If it is non-zero, a write (data copied from
** buffer pBuf).
**
** A total of "amt" bytes are read or written beginning at "offset".
** Data is read to or from the buffer pBuf.
**
** The content being read or written might appear on the main page
** or be scattered out on multiple overflow pages.
**
** If the BtCursor.isIncrblobHandle flag is set, and the current
** cursor entry uses one or more overflow pages, this function
** allocates space for and lazily popluates the overflow page-list 
** cache array (BtCursor.aOverflow). Subsequent calls use this
** cache to make seeking to the supplied offset more efficient.
**
** Once an overflow page-list cache has been allocated, it may be
** invalidated if some other cursor writes to the same table, or if
** the cursor is moved to a different row. Additionally, in auto-vacuum
** mode, the following events may invalidate an overflow page-list cache.
**
**   * An incremental vacuum,
**   * A commit in auto_vacuum="full" mode,
**   * Creating a table (may require moving an overflow page).
*/
static int accessPayload(
  BtCursor *pCur,      /* Cursor pointing to entry to read from */
  u32 offset,          /* Begin reading this far into payload */
  u32 amt,             /* Read this many bytes */
  unsigned char *pBuf, /* Write the bytes into this buffer */ 
  int eOp              /* zero to read. non-zero to write. */
){
  unsigned char *aPayload;
  int rc = SQLITE_OK;
  u32 nKey;
  int iIdx = 0;
  MemPage *pPage = pCur->apPage[pCur->iPage]; /* Btree page of current entry */
  BtShared *pBt = pCur->pBt;                  /* Btree this cursor belongs to */

  assert( pPage );
  assert( pCur->eState==CURSOR_VALID );
  assert( pCur->aiIdx[pCur->iPage]<pPage->nCell );
  assert( cursorHoldsMutex(pCur) );

  getCellInfo(pCur);
  aPayload = pCur->info.pCell + pCur->info.nHeader;
  nKey = (pPage->intKey ? 0 : (int)pCur->info.nKey);

  if( NEVER(offset+amt > nKey+pCur->info.nData) 
   || &aPayload[pCur->info.nLocal] > &pPage->aData[pBt->usableSize]
  ){
    /* Trying to read or write past the end of the data is an error */
    return SQLITE_CORRUPT_BKPT;
  }

  /* Check if data must be read/written to/from the btree page itself. */
  if( offset<pCur->info.nLocal ){
    int a = amt;
    if( a+offset>pCur->info.nLocal ){
      a = pCur->info.nLocal - offset;
    }
    rc = copyPayload(&aPayload[offset], pBuf, a, eOp, pPage->pDbPage);
    offset = 0;
    pBuf += a;
    amt -= a;
  }else{
    offset -= pCur->info.nLocal;
  }

  if( rc==SQLITE_OK && amt>0 ){
    const u32 ovflSize = pBt->usableSize - 4;  /* Bytes content per ovfl page */
    Pgno nextPage;

    nextPage = get4byte(&aPayload[pCur->info.nLocal]);

#ifndef SQLITE_OMIT_INCRBLOB
    /* If the isIncrblobHandle flag is set and the BtCursor.aOverflow[]
    ** has not been allocated, allocate it now. The array is sized at
    ** one entry for each overflow page in the overflow chain. The
    ** page number of the first overflow page is stored in aOverflow[0],
    ** etc. A value of 0 in the aOverflow[] array means "not yet known"
    ** (the cache is lazily populated).
    */
    if( pCur->isIncrblobHandle && !pCur->aOverflow ){
      int nOvfl = (pCur->info.nPayload-pCur->info.nLocal+ovflSize-1)/ovflSize;
      pCur->aOverflow = (Pgno *)sqlite4MallocZero(sizeof(Pgno)*nOvfl);
      /* nOvfl is always positive.  If it were zero, fetchPayload would have
      ** been used instead of this routine. */
      if( ALWAYS(nOvfl) && !pCur->aOverflow ){
        rc = SQLITE_NOMEM;
      }
    }

    /* If the overflow page-list cache has been allocated and the
    ** entry for the first required overflow page is valid, skip
    ** directly to it.
    */
    if( pCur->aOverflow && pCur->aOverflow[offset/ovflSize] ){
      iIdx = (offset/ovflSize);
      nextPage = pCur->aOverflow[iIdx];
      offset = (offset%ovflSize);
    }
#endif

    for( ; rc==SQLITE_OK && amt>0 && nextPage; iIdx++){

#ifndef SQLITE_OMIT_INCRBLOB
      /* If required, populate the overflow page-list cache. */
      if( pCur->aOverflow ){
        assert(!pCur->aOverflow[iIdx] || pCur->aOverflow[iIdx]==nextPage);
        pCur->aOverflow[iIdx] = nextPage;
      }
#endif

      if( offset>=ovflSize ){
        /* The only reason to read this page is to obtain the page
        ** number for the next page in the overflow chain. The page
        ** data is not required. So first try to lookup the overflow
        ** page-list cache, if any, then fall back to the getOverflowPage()
        ** function.
        */
#ifndef SQLITE_OMIT_INCRBLOB
        if( pCur->aOverflow && pCur->aOverflow[iIdx+1] ){
          nextPage = pCur->aOverflow[iIdx+1];
        } else 
#endif
          rc = getOverflowPage(pBt, nextPage, 0, &nextPage);
        offset -= ovflSize;
      }else{
        /* Need to read this page properly. It contains some of the
        ** range of data that is being read (eOp==0) or written (eOp!=0).
        */
#ifdef SQLITE_DIRECT_OVERFLOW_READ
        sqlite4_file *fd;
#endif
        int a = amt;
        if( a + offset > ovflSize ){
          a = ovflSize - offset;
        }

#ifdef SQLITE_DIRECT_OVERFLOW_READ
        /* If all the following are true:
        **
        **   1) this is a read operation, and 
        **   2) data is required from the start of this overflow page, and
        **   3) the database is file-backed, and
        **   4) there is no open write-transaction, and
        **   5) the database is not a WAL database,
        **
        ** then data can be read directly from the database file into the
        ** output buffer, bypassing the page-cache altogether. This speeds
        ** up loading large records that span many overflow pages.
        */
        if( eOp==0                                             /* (1) */
         && offset==0                                          /* (2) */
         && pBt->inTransaction==TRANS_READ                     /* (4) */
         && (fd = sqlite4PagerFile(pBt->pPager))->pMethods     /* (3) */
         && pBt->pPage1->aData[19]==0x01                       /* (5) */
        ){
          u8 aSave[4];
          u8 *aWrite = &pBuf[-4];
          memcpy(aSave, aWrite, 4);
          rc = sqlite4OsRead(fd, aWrite, a+4, (i64)pBt->pageSize*(nextPage-1));
          nextPage = get4byte(aWrite);
          memcpy(aWrite, aSave, 4);
        }else
#endif

        {
          DbPage *pDbPage;
          rc = sqlite4PagerGet(pBt->pPager, nextPage, &pDbPage);
          if( rc==SQLITE_OK ){
            aPayload = sqlite4PagerGetData(pDbPage);
            nextPage = get4byte(aPayload);
            rc = copyPayload(&aPayload[offset+4], pBuf, a, eOp, pDbPage);
            sqlite4PagerUnref(pDbPage);
            offset = 0;
          }
        }
        amt -= a;
        pBuf += a;
      }
    }
  }

  if( rc==SQLITE_OK && amt>0 ){
    return SQLITE_CORRUPT_BKPT;
  }
  return rc;
}

/*
** Read part of the key associated with cursor pCur.  Exactly
** "amt" bytes will be transfered into pBuf[].  The transfer
** begins at "offset".
**
** The caller must ensure that pCur is pointing to a valid row
** in the table.
**
** Return SQLITE_OK on success or an error code if anything goes
** wrong.  An error is returned if "offset+amt" is larger than
** the available payload.
*/
int sqlite4BtreeKey(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
  assert( cursorHoldsMutex(pCur) );
  assert( pCur->eState==CURSOR_VALID );
  assert( pCur->iPage>=0 && pCur->apPage[pCur->iPage] );
  assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
  return accessPayload(pCur, offset, amt, (unsigned char*)pBuf, 0);
}

/*
** Read part of the data associated with cursor pCur.  Exactly
** "amt" bytes will be transfered into pBuf[].  The transfer
** begins at "offset".
**
** Return SQLITE_OK on success or an error code if anything goes
** wrong.  An error is returned if "offset+amt" is larger than
** the available payload.
*/
int sqlite4BtreeData(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
  int rc;

#ifndef SQLITE_OMIT_INCRBLOB
  if ( pCur->eState==CURSOR_INVALID ){
    return SQLITE_ABORT;
  }
#endif

  assert( cursorHoldsMutex(pCur) );
  rc = restoreCursorPosition(pCur);
  if( rc==SQLITE_OK ){
    assert( pCur->eState==CURSOR_VALID );
    assert( pCur->iPage>=0 && pCur->apPage[pCur->iPage] );
    assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
    rc = accessPayload(pCur, offset, amt, pBuf, 0);
  }
  return rc;
}

/*
** Return a pointer to payload information from the entry that the 
** pCur cursor is pointing to.  The pointer is to the beginning of
** the key if skipKey==0 and it points to the beginning of data if
** skipKey==1.  The number of bytes of available key/data is written
** into *pAmt.  If *pAmt==0, then the value returned will not be
** a valid pointer.
**
** This routine is an optimization.  It is common for the entire key
** and data to fit on the local page and for there to be no overflow
** pages.  When that is so, this routine can be used to access the
** key and data without making a copy.  If the key and/or data spills
** onto overflow pages, then accessPayload() must be used to reassemble
** the key/data and copy it into a preallocated buffer.
**
** The pointer returned by this routine looks directly into the cached
** page of the database.  The data might change or move the next time
** any btree routine is called.
*/
static const unsigned char *fetchPayload(
  BtCursor *pCur,      /* Cursor pointing to entry to read from */
  int *pAmt,           /* Write the number of available bytes here */
  int skipKey          /* read beginning at data if this is true */
){
  unsigned char *aPayload;
  MemPage *pPage;
  u32 nKey;
  u32 nLocal;

  assert( pCur!=0 && pCur->iPage>=0 && pCur->apPage[pCur->iPage]);
  assert( pCur->eState==CURSOR_VALID );
  assert( cursorHoldsMutex(pCur) );
  pPage = pCur->apPage[pCur->iPage];
  assert( pCur->aiIdx[pCur->iPage]<pPage->nCell );
  if( NEVER(pCur->info.nSize==0) ){
    btreeParseCell(pCur->apPage[pCur->iPage], pCur->aiIdx[pCur->iPage],
                   &pCur->info);
  }
  aPayload = pCur->info.pCell;
  aPayload += pCur->info.nHeader;
  if( pPage->intKey ){
    nKey = 0;
  }else{
    nKey = (int)pCur->info.nKey;
  }
  if( skipKey ){
    aPayload += nKey;
    nLocal = pCur->info.nLocal - nKey;
  }else{
    nLocal = pCur->info.nLocal;
    assert( nLocal<=nKey );
  }
  *pAmt = nLocal;
  return aPayload;
}


/*
** For the entry that cursor pCur is point to, return as
** many bytes of the key or data as are available on the local
** b-tree page.  Write the number of available bytes into *pAmt.
**
** The pointer returned is ephemeral.  The key/data may move
** or be destroyed on the next call to any Btree routine,
** including calls from other threads against the same cache.
** Hence, a mutex on the BtShared should be held prior to calling
** this routine.
**
** These routines is used to get quick access to key and data
** in the common case where no overflow pages are used.
*/
const void *sqlite4BtreeKeyFetch(BtCursor *pCur, int *pAmt){
  const void *p = 0;
  assert( sqlite4_mutex_held(pCur->pBtree->db->mutex) );
  assert( cursorHoldsMutex(pCur) );
  if( ALWAYS(pCur->eState==CURSOR_VALID) ){
    p = (const void*)fetchPayload(pCur, pAmt, 0);
  }
  return p;
}
const void *sqlite4BtreeDataFetch(BtCursor *pCur, int *pAmt){
  const void *p = 0;
  assert( sqlite4_mutex_held(pCur->pBtree->db->mutex) );
  assert( cursorHoldsMutex(pCur) );
  if( ALWAYS(pCur->eState==CURSOR_VALID) ){
    p = (const void*)fetchPayload(pCur, pAmt, 1);
  }
  return p;
}


/*
** Move the cursor down to a new child page.  The newPgno argument is the
** page number of the child page to move to.
**
** This function returns SQLITE_CORRUPT if the page-header flags field of
** the new child page does not match the flags field of the parent (i.e.
** if an intkey page appears to be the parent of a non-intkey page, or
** vice-versa).
*/
static int moveToChild(BtCursor *pCur, u32 newPgno){
  int rc;
  int i = pCur->iPage;
  MemPage *pNewPage;
  BtShared *pBt = pCur->pBt;

  assert( cursorHoldsMutex(pCur) );
  assert( pCur->eState==CURSOR_VALID );
  assert( pCur->iPage<BTCURSOR_MAX_DEPTH );
  if( pCur->iPage>=(BTCURSOR_MAX_DEPTH-1) ){
    return SQLITE_CORRUPT_BKPT;
  }
  rc = getAndInitPage(pBt, newPgno, &pNewPage);
  if( rc ) return rc;
  pCur->apPage[i+1] = pNewPage;
  pCur->aiIdx[i+1] = 0;
  pCur->iPage++;

  pCur->info.nSize = 0;
  pCur->validNKey = 0;
  if( pNewPage->nCell<1 || pNewPage->intKey!=pCur->apPage[i]->intKey ){
    return SQLITE_CORRUPT_BKPT;
  }
  return SQLITE_OK;
}

#if 0
/*
** Page pParent is an internal (non-leaf) tree page. This function 
** asserts that page number iChild is the left-child if the iIdx'th
** cell in page pParent. Or, if iIdx is equal to the total number of
** cells in pParent, that page number iChild is the right-child of
** the page.
*/
static void assertParentIndex(MemPage *pParent, int iIdx, Pgno iChild){
  assert( iIdx<=pParent->nCell );
  if( iIdx==pParent->nCell ){
    assert( get4byte(&pParent->aData[pParent->hdrOffset+8])==iChild );
  }else{
    assert( get4byte(findCell(pParent, iIdx))==iChild );
  }
}
#else
#  define assertParentIndex(x,y,z) 
#endif

/*
** Move the cursor up to the parent page.
**
** pCur->idx is set to the cell index that contains the pointer
** to the page we are coming from.  If we are coming from the
** right-most child page then pCur->idx is set to one more than
** the largest cell index.
*/
static void moveToParent(BtCursor *pCur){
  assert( cursorHoldsMutex(pCur) );
  assert( pCur->eState==CURSOR_VALID );
  assert( pCur->iPage>0 );
  assert( pCur->apPage[pCur->iPage] );

  /* UPDATE: It is actually possible for the condition tested by the assert
  ** below to be untrue if the database file is corrupt. This can occur if
  ** one cursor has modified page pParent while a reference to it is held 
  ** by a second cursor. Which can only happen if a single page is linked
  ** into more than one b-tree structure in a corrupt database.  */
#if 0
  assertParentIndex(
    pCur->apPage[pCur->iPage-1], 
    pCur->aiIdx[pCur->iPage-1], 
    pCur->apPage[pCur->iPage]->pgno
  );
#endif
  testcase( pCur->aiIdx[pCur->iPage-1] > pCur->apPage[pCur->iPage-1]->nCell );

  releasePage(pCur->apPage[pCur->iPage]);
  pCur->iPage--;
  pCur->info.nSize = 0;
  pCur->validNKey = 0;
}

/*
** Move the cursor to point to the root page of its b-tree structure.
**
** If the table has a virtual root page, then the cursor is moved to point
** to the virtual root page instead of the actual root page. A table has a
** virtual root page when the actual root page contains no cells and a 
** single child page. This can only happen with the table rooted at page 1.
**
** If the b-tree structure is empty, the cursor state is set to 
** CURSOR_INVALID. Otherwise, the cursor is set to point to the first
** cell located on the root (or virtual root) page and the cursor state
** is set to CURSOR_VALID.
**
** If this function returns successfully, it may be assumed that the
** page-header flags indicate that the [virtual] root-page is the expected 
** kind of b-tree page (i.e. if when opening the cursor the caller did not
** specify a KeyInfo structure the flags byte is set to 0x05 or 0x0D,
** indicating a table b-tree, or if the caller did specify a KeyInfo 
** structure the flags byte is set to 0x02 or 0x0A, indicating an index
** b-tree).
*/
static int moveToRoot(BtCursor *pCur){
  MemPage *pRoot;
  int rc = SQLITE_OK;
  Btree *p = pCur->pBtree;
  BtShared *pBt = p->pBt;

  assert( cursorHoldsMutex(pCur) );
  assert( CURSOR_INVALID < CURSOR_REQUIRESEEK );
  assert( CURSOR_VALID   < CURSOR_REQUIRESEEK );
  assert( CURSOR_FAULT   > CURSOR_REQUIRESEEK );
  if( pCur->eState>=CURSOR_REQUIRESEEK ){
    if( pCur->eState==CURSOR_FAULT ){
      assert( pCur->skipNext!=SQLITE_OK );
      return pCur->skipNext;
    }
    sqlite4BtreeClearCursor(pCur);
  }

  if( pCur->iPage>=0 ){
    int i;
    for(i=1; i<=pCur->iPage; i++){
      releasePage(pCur->apPage[i]);
    }
    pCur->iPage = 0;
  }else if( pCur->pgnoRoot==0 ){
    pCur->eState = CURSOR_INVALID;
    return SQLITE_OK;
  }else{
    rc = getAndInitPage(pBt, pCur->pgnoRoot, &pCur->apPage[0]);
    if( rc!=SQLITE_OK ){
      pCur->eState = CURSOR_INVALID;
      return rc;
    }
    pCur->iPage = 0;

    /* If pCur->pKeyInfo is not NULL, then the caller that opened this cursor
    ** expected to open it on an index b-tree. Otherwise, if pKeyInfo is
    ** NULL, the caller expects a table b-tree. If this is not the case,
    ** return an SQLITE_CORRUPT error.  */
    assert( pCur->apPage[0]->intKey==1 || pCur->apPage[0]->intKey==0 );
    if( (pCur->pKeyInfo==0)!=pCur->apPage[0]->intKey ){
      return SQLITE_CORRUPT_BKPT;
    }
  }

  /* Assert that the root page is of the correct type. This must be the
  ** case as the call to this function that loaded the root-page (either
  ** this call or a previous invocation) would have detected corruption 
  ** if the assumption were not true, and it is not possible for the flags 
  ** byte to have been modified while this cursor is holding a reference
  ** to the page.  */
  pRoot = pCur->apPage[0];
  assert( pRoot->pgno==pCur->pgnoRoot );
  assert( pRoot->isInit && (pCur->pKeyInfo==0)==pRoot->intKey );

  pCur->aiIdx[0] = 0;
  pCur->info.nSize = 0;
  pCur->atLast = 0;
  pCur->validNKey = 0;

  if( pRoot->nCell==0 && !pRoot->leaf ){
    Pgno subpage;
    if( pRoot->pgno!=1 ) return SQLITE_CORRUPT_BKPT;
    subpage = get4byte(&pRoot->aData[pRoot->hdrOffset+8]);
    pCur->eState = CURSOR_VALID;
    rc = moveToChild(pCur, subpage);
  }else{
    pCur->eState = ((pRoot->nCell>0)?CURSOR_VALID:CURSOR_INVALID);
  }
  return rc;
}

/*
** Move the cursor down to the left-most leaf entry beneath the
** entry to which it is currently pointing.
**
** The left-most leaf is the one with the smallest key - the first
** in ascending order.
*/
static int moveToLeftmost(BtCursor *pCur){
  Pgno pgno;
  int rc = SQLITE_OK;
  MemPage *pPage;

  assert( cursorHoldsMutex(pCur) );
  assert( pCur->eState==CURSOR_VALID );
  while( rc==SQLITE_OK && !(pPage = pCur->apPage[pCur->iPage])->leaf ){
    assert( pCur->aiIdx[pCur->iPage]<pPage->nCell );
    pgno = get4byte(findCell(pPage, pCur->aiIdx[pCur->iPage]));
    rc = moveToChild(pCur, pgno);
  }
  return rc;
}

/*
** Move the cursor down to the right-most leaf entry beneath the
** page to which it is currently pointing.  Notice the difference
** between moveToLeftmost() and moveToRightmost().  moveToLeftmost()
** finds the left-most entry beneath the *entry* whereas moveToRightmost()
** finds the right-most entry beneath the *page*.
**
** The right-most entry is the one with the largest key - the last
** key in ascending order.
*/
static int moveToRightmost(BtCursor *pCur){
  Pgno pgno;
  int rc = SQLITE_OK;
  MemPage *pPage = 0;

  assert( cursorHoldsMutex(pCur) );
  assert( pCur->eState==CURSOR_VALID );
  while( rc==SQLITE_OK && !(pPage = pCur->apPage[pCur->iPage])->leaf ){
    pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
    pCur->aiIdx[pCur->iPage] = pPage->nCell;
    rc = moveToChild(pCur, pgno);
  }
  if( rc==SQLITE_OK ){
    pCur->aiIdx[pCur->iPage] = pPage->nCell-1;
    pCur->info.nSize = 0;
    pCur->validNKey = 0;
  }
  return rc;
}

/* Move the cursor to the first entry in the table.  Return SQLITE_OK
** on success.  Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
int sqlite4BtreeFirst(BtCursor *pCur, int *pRes){
  int rc;

  assert( cursorHoldsMutex(pCur) );
  assert( sqlite4_mutex_held(pCur->pBtree->db->mutex) );
  rc = moveToRoot(pCur);
  if( rc==SQLITE_OK ){
    if( pCur->eState==CURSOR_INVALID ){
      assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 );
      *pRes = 1;
    }else{
      assert( pCur->apPage[pCur->iPage]->nCell>0 );
      *pRes = 0;
      rc = moveToLeftmost(pCur);
    }
  }
  return rc;
}

/* Move the cursor to the last entry in the table.  Return SQLITE_OK
** on success.  Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
int sqlite4BtreeLast(BtCursor *pCur, int *pRes){
  int rc;
 
  assert( cursorHoldsMutex(pCur) );
  assert( sqlite4_mutex_held(pCur->pBtree->db->mutex) );

  /* If the cursor already points to the last entry, this is a no-op. */
  if( CURSOR_VALID==pCur->eState && pCur->atLast ){
#ifdef SQLITE_DEBUG
    /* This block serves to assert() that the cursor really does point 
    ** to the last entry in the b-tree. */
    int ii;
    for(ii=0; ii<pCur->iPage; ii++){
      assert( pCur->aiIdx[ii]==pCur->apPage[ii]->nCell );
    }
    assert( pCur->aiIdx[pCur->iPage]==pCur->apPage[pCur->iPage]->nCell-1 );
    assert( pCur->apPage[pCur->iPage]->leaf );
#endif
    return SQLITE_OK;
  }

  rc = moveToRoot(pCur);
  if( rc==SQLITE_OK ){
    if( CURSOR_INVALID==pCur->eState ){
      assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 );
      *pRes = 1;
    }else{
      assert( pCur->eState==CURSOR_VALID );
      *pRes = 0;
      rc = moveToRightmost(pCur);
      pCur->atLast = rc==SQLITE_OK ?1:0;
    }
  }
  return rc;
}

/* Move the cursor so that it points to an entry near the key 
** specified by pIdxKey or intKey.   Return a success code.
**
** For INTKEY tables, the intKey parameter is used.  pIdxKey 
** must be NULL.  For index tables, pIdxKey is used and intKey
** is ignored.
**
** If an exact match is not found, then the cursor is always
** left pointing at a leaf page which would hold the entry if it
** were present.  The cursor might point to an entry that comes
** before or after the key.
**
** An integer is written into *pRes which is the result of
** comparing the key with the entry to which the cursor is 
** pointing.  The meaning of the integer written into
** *pRes is as follows:
**
**     *pRes<0      The cursor is left pointing at an entry that
**                  is smaller than intKey/pIdxKey or if the table is empty
**                  and the cursor is therefore left point to nothing.
**
**     *pRes==0     The cursor is left pointing at an entry that
**                  exactly matches intKey/pIdxKey.
**
**     *pRes>0      The cursor is left pointing at an entry that
**                  is larger than intKey/pIdxKey.
**
*/
int sqlite4BtreeMovetoUnpacked(
  BtCursor *pCur,          /* The cursor to be moved */
  UnpackedRecord *pIdxKey, /* Unpacked index key */
  i64 intKey,              /* The table key */
  int biasRight,           /* If true, bias the search to the high end */
  int *pRes                /* Write search results here */
){
  int rc;

  assert( cursorHoldsMutex(pCur) );
  assert( sqlite4_mutex_held(pCur->pBtree->db->mutex) );
  assert( pRes );
  assert( (pIdxKey==0)==(pCur->pKeyInfo==0) );

  /* If the cursor is already positioned at the point we are trying
  ** to move to, then just return without doing any work */
  if( pCur->eState==CURSOR_VALID && pCur->validNKey 
   && pCur->apPage[0]->intKey 
  ){
    if( pCur->info.nKey==intKey ){
      *pRes = 0;
      return SQLITE_OK;
    }
    if( pCur->atLast && pCur->info.nKey<intKey ){
      *pRes = -1;
      return SQLITE_OK;
    }
  }

  rc = moveToRoot(pCur);
  if( rc ){
    return rc;
  }
  assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage] );
  assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->isInit );
  assert( pCur->eState==CURSOR_INVALID || pCur->apPage[pCur->iPage]->nCell>0 );
  if( pCur->eState==CURSOR_INVALID ){
    *pRes = -1;
    assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 );
    return SQLITE_OK;
  }
  assert( pCur->apPage[0]->intKey || pIdxKey );
  for(;;){
    int lwr, upr, idx;
    Pgno chldPg;
    MemPage *pPage = pCur->apPage[pCur->iPage];
    int c;

    /* pPage->nCell must be greater than zero. If this is the root-page
    ** the cursor would have been INVALID above and this for(;;) loop
    ** not run. If this is not the root-page, then the moveToChild() routine
    ** would have already detected db corruption. Similarly, pPage must
    ** be the right kind (index or table) of b-tree page. Otherwise
    ** a moveToChild() or moveToRoot() call would have detected corruption.  */
    assert( pPage->nCell>0 );
    assert( pPage->intKey==(pIdxKey==0) );
    lwr = 0;
    upr = pPage->nCell-1;
    if( biasRight ){
      pCur->aiIdx[pCur->iPage] = (u16)(idx = upr);
    }else{
      pCur->aiIdx[pCur->iPage] = (u16)(idx = (upr+lwr)/2);
    }
    for(;;){
      u8 *pCell;                          /* Pointer to current cell in pPage */

      assert( idx==pCur->aiIdx[pCur->iPage] );
      pCur->info.nSize = 0;
      pCell = findCell(pPage, idx) + pPage->childPtrSize;
      if( pPage->intKey ){
        i64 nCellKey;
        if( pPage->hasData ){
          u32 dummy;
          pCell += getVarint32(pCell, dummy);
        }
        getVarint(pCell, (u64*)&nCellKey);
        if( nCellKey==intKey ){
          c = 0;
        }else if( nCellKey<intKey ){
          c = -1;
        }else{
          assert( nCellKey>intKey );
          c = +1;
        }
        pCur->validNKey = 1;
        pCur->info.nKey = nCellKey;
      }else{
        /* The maximum supported page-size is 65536 bytes. This means that
        ** the maximum number of record bytes stored on an index B-Tree
        ** page is less than 16384 bytes and may be stored as a 2-byte
        ** varint. This information is used to attempt to avoid parsing 
        ** the entire cell by checking for the cases where the record is 
        ** stored entirely within the b-tree page by inspecting the first 
        ** 2 bytes of the cell.
        */
        int nCell = pCell[0];
        if( nCell<=pPage->max1bytePayload
         /* && (pCell+nCell)<pPage->aDataEnd */
        ){
          /* This branch runs if the record-size field of the cell is a
          ** single byte varint and the record fits entirely on the main
          ** b-tree page.  */
          testcase( pCell+nCell+1==pPage->aDataEnd );
          c = sqlite4VdbeRecordCompare(nCell, (void*)&pCell[1], pIdxKey);
        }else if( !(pCell[1] & 0x80) 
          && (nCell = ((nCell&0x7f)<<7) + pCell[1])<=pPage->maxLocal
          /* && (pCell+nCell+2)<=pPage->aDataEnd */
        ){
          /* The record-size field is a 2 byte varint and the record 
          ** fits entirely on the main b-tree page.  */
          testcase( pCell+nCell+2==pPage->aDataEnd );
          c = sqlite4VdbeRecordCompare(nCell, (void*)&pCell[2], pIdxKey);
        }else{
          /* The record flows over onto one or more overflow pages. In
          ** this case the whole cell needs to be parsed, a buffer allocated
          ** and accessPayload() used to retrieve the record into the
          ** buffer before VdbeRecordCompare() can be called. */
          void *pCellKey;
          u8 * const pCellBody = pCell - pPage->childPtrSize;
          btreeParseCellPtr(pPage, pCellBody, &pCur->info);
          nCell = (int)pCur->info.nKey;
          pCellKey = sqlite4Malloc( nCell );
          if( pCellKey==0 ){
            rc = SQLITE_NOMEM;
            goto moveto_finish;
          }
          rc = accessPayload(pCur, 0, nCell, (unsigned char*)pCellKey, 0);
          if( rc ){
            sqlite4_free(pCellKey);
            goto moveto_finish;
          }
          c = sqlite4VdbeRecordCompare(nCell, pCellKey, pIdxKey);
          sqlite4_free(pCellKey);
        }
      }
      if( c==0 ){
        if( pPage->intKey && !pPage->leaf ){
          lwr = idx;
          break;
        }else{
          *pRes = 0;
          rc = SQLITE_OK;
          goto moveto_finish;
        }
      }
      if( c<0 ){
        lwr = idx+1;
      }else{
        upr = idx-1;
      }
      if( lwr>upr ){
        break;
      }
      pCur->aiIdx[pCur->iPage] = (u16)(idx = (lwr+upr)/2);
    }
    assert( lwr==upr+1 || (pPage->intKey && !pPage->leaf) );
    assert( pPage->isInit );
    if( pPage->leaf ){
      chldPg = 0;
    }else if( lwr>=pPage->nCell ){
      chldPg = get4byte(&pPage->aData[pPage->hdrOffset+8]);
    }else{
      chldPg = get4byte(findCell(pPage, lwr));
    }
    if( chldPg==0 ){
      assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
      *pRes = c;
      rc = SQLITE_OK;
      goto moveto_finish;
    }
    pCur->aiIdx[pCur->iPage] = (u16)lwr;
    pCur->info.nSize = 0;
    pCur->validNKey = 0;
    rc = moveToChild(pCur, chldPg);
    if( rc ) goto moveto_finish;
  }
moveto_finish:
  return rc;
}


/*
** Return TRUE if the cursor is not pointing at an entry of the table.
**
** TRUE will be returned after a call to sqlite4BtreeNext() moves
** past the last entry in the table or sqlite4BtreePrev() moves past
** the first entry.  TRUE is also returned if the table is empty.
*/
int sqlite4BtreeEof(BtCursor *pCur){
  /* TODO: What if the cursor is in CURSOR_REQUIRESEEK but all table entries
  ** have been deleted? This API will need to change to return an error code
  ** as well as the boolean result value.
  */
  return (CURSOR_VALID!=pCur->eState);
}

/*
** Advance the cursor to the next entry in the database.  If
** successful then set *pRes=0.  If the cursor
** was already pointing to the last entry in the database before
** this routine was called, then set *pRes=1.
*/
int sqlite4BtreeNext(BtCursor *pCur, int *pRes){
  int rc;
  int idx;
  MemPage *pPage;

  assert( cursorHoldsMutex(pCur) );
  rc = restoreCursorPosition(pCur);
  if( rc!=SQLITE_OK ){
    return rc;
  }
  assert( pRes!=0 );
  if( CURSOR_INVALID==pCur->eState ){
    *pRes = 1;
    return SQLITE_OK;
  }
  if( pCur->skipNext>0 ){
    pCur->skipNext = 0;
    *pRes = 0;
    return SQLITE_OK;
  }
  pCur->skipNext = 0;

  pPage = pCur->apPage[pCur->iPage];
  idx = ++pCur->aiIdx[pCur->iPage];
  assert( pPage->isInit );

  /* If the database file is corrupt, it is possible for the value of idx 
  ** to be invalid here. This can only occur if a second cursor modifies
  ** the page while cursor pCur is holding a reference to it. Which can
  ** only happen if the database is corrupt in such a way as to link the
  ** page into more than one b-tree structure. */
  testcase( idx>pPage->nCell );

  pCur->info.nSize = 0;
  pCur->validNKey = 0;
  if( idx>=pPage->nCell ){
    if( !pPage->leaf ){
      rc = moveToChild(pCur, get4byte(&pPage->aData[pPage->hdrOffset+8]));
      if( rc ) return rc;
      rc = moveToLeftmost(pCur);
      *pRes = 0;
      return rc;
    }
    do{
      if( pCur->iPage==0 ){
        *pRes = 1;
        pCur->eState = CURSOR_INVALID;
        return SQLITE_OK;
      }
      moveToParent(pCur);
      pPage = pCur->apPage[pCur->iPage];
    }while( pCur->aiIdx[pCur->iPage]>=pPage->nCell );
    *pRes = 0;
    if( pPage->intKey ){
      rc = sqlite4BtreeNext(pCur, pRes);
    }else{
      rc = SQLITE_OK;
    }
    return rc;
  }
  *pRes = 0;
  if( pPage->leaf ){
    return SQLITE_OK;
  }
  rc = moveToLeftmost(pCur);
  return rc;
}


/*
** Step the cursor to the back to the previous entry in the database.  If
** successful then set *pRes=0.  If the cursor
** was already pointing to the first entry in the database before
** this routine was called, then set *pRes=1.
*/
int sqlite4BtreePrevious(BtCursor *pCur, int *pRes){
  int rc;
  MemPage *pPage;

  assert( cursorHoldsMutex(pCur) );
  rc = restoreCursorPosition(pCur);
  if( rc!=SQLITE_OK ){
    return rc;
  }
  pCur->atLast = 0;
  if( CURSOR_INVALID==pCur->eState ){
    *pRes = 1;
    return SQLITE_OK;
  }
  if( pCur->skipNext<0 ){
    pCur->skipNext = 0;
    *pRes = 0;
    return SQLITE_OK;
  }
  pCur->skipNext = 0;

  pPage = pCur->apPage[pCur->iPage];
  assert( pPage->isInit );
  if( !pPage->leaf ){
    int idx = pCur->aiIdx[pCur->iPage];
    rc = moveToChild(pCur, get4byte(findCell(pPage, idx)));
    if( rc ){
      return rc;
    }
    rc = moveToRightmost(pCur);
  }else{
    while( pCur->aiIdx[pCur->iPage]==0 ){
      if( pCur->iPage==0 ){
        pCur->eState = CURSOR_INVALID;
        *pRes = 1;
        return SQLITE_OK;
      }
      moveToParent(pCur);
    }
    pCur->info.nSize = 0;
    pCur->validNKey = 0;

    pCur->aiIdx[pCur->iPage]--;
    pPage = pCur->apPage[pCur->iPage];
    if( pPage->intKey && !pPage->leaf ){
      rc = sqlite4BtreePrevious(pCur, pRes);
    }else{
      rc = SQLITE_OK;
    }
  }
  *pRes = 0;
  return rc;
}

/*
** Allocate a new page from the database file.
**
** The new page is marked as dirty.  (In other words, sqlite4PagerWrite()
** has already been called on the new page.)  The new page has also
** been referenced and the calling routine is responsible for calling
** sqlite4PagerUnref() on the new page when it is done.
**
** SQLITE_OK is returned on success.  Any other return value indicates
** an error.  *ppPage and *pPgno are undefined in the event of an error.
** Do not invoke sqlite4PagerUnref() on *ppPage if an error is returned.
**
** If the "nearby" parameter is not 0, then a (feeble) effort is made to 
** locate a page close to the page number "nearby".  This can be used in an
** attempt to keep related pages close to each other in the database file,
** which in turn can make database access faster.
**
** If the "exact" parameter is not 0, and the page-number nearby exists 
** anywhere on the free-list, then it is guarenteed to be returned. This
** is only used by auto-vacuum databases when allocating a new table.
*/
static int allocateBtreePage(
  BtShared *pBt, 
  MemPage **ppPage, 
  Pgno *pPgno, 
  Pgno nearby,
  u8 exact
){
  MemPage *pPage1;
  int rc;
  u32 n;     /* Number of pages on the freelist */
  u32 k;     /* Number of leaves on the trunk of the freelist */
  MemPage *pTrunk = 0;
  MemPage *pPrevTrunk = 0;
  Pgno mxPage;     /* Total size of the database file */

  assert( sqlite4_mutex_held(pBt->mutex) );
  pPage1 = pBt->pPage1;
  mxPage = btreePagecount(pBt);
  n = get4byte(&pPage1->aData[36]);
  testcase( n==mxPage-1 );
  if( n>=mxPage ){
    return SQLITE_CORRUPT_BKPT;
  }
  if( n>0 ){
    /* There are pages on the freelist.  Reuse one of those pages. */
    Pgno iTrunk;
    u8 searchList = 0; /* If the free-list must be searched for 'nearby' */
    
    /* If the 'exact' parameter was true and a query of the pointer-map
    ** shows that the page 'nearby' is somewhere on the free-list, then
    ** the entire-list will be searched for that page.
    */
#ifndef SQLITE_OMIT_AUTOVACUUM
    if( exact && nearby<=mxPage ){
      u8 eType;
      assert( nearby>0 );
      assert( pBt->autoVacuum );
      rc = ptrmapGet(pBt, nearby, &eType, 0);
      if( rc ) return rc;
      if( eType==PTRMAP_FREEPAGE ){
        searchList = 1;
      }
      *pPgno = nearby;
    }
#endif

    /* Decrement the free-list count by 1. Set iTrunk to the index of the
    ** first free-list trunk page. iPrevTrunk is initially 1.
    */
    rc = sqlite4PagerWrite(pPage1->pDbPage);
    if( rc ) return rc;
    put4byte(&pPage1->aData[36], n-1);

    /* The code within this loop is run only once if the 'searchList' variable
    ** is not true. Otherwise, it runs once for each trunk-page on the
    ** free-list until the page 'nearby' is located.
    */
    do {
      pPrevTrunk = pTrunk;
      if( pPrevTrunk ){
        iTrunk = get4byte(&pPrevTrunk->aData[0]);
      }else{
        iTrunk = get4byte(&pPage1->aData[32]);
      }
      testcase( iTrunk==mxPage );
      if( iTrunk>mxPage ){
        rc = SQLITE_CORRUPT_BKPT;
      }else{
        rc = btreeGetPage(pBt, iTrunk, &pTrunk, 0);
      }
      if( rc ){
        pTrunk = 0;
        goto end_allocate_page;
      }
      assert( pTrunk!=0 );
      assert( pTrunk->aData!=0 );

      k = get4byte(&pTrunk->aData[4]); /* # of leaves on this trunk page */
      if( k==0 && !searchList ){
        /* The trunk has no leaves and the list is not being searched. 
        ** So extract the trunk page itself and use it as the newly 
        ** allocated page */
        assert( pPrevTrunk==0 );
        rc = sqlite4PagerWrite(pTrunk->pDbPage);
        if( rc ){
          goto end_allocate_page;
        }
        *pPgno = iTrunk;
        memcpy(&pPage1->aData[32], &pTrunk->aData[0], 4);
        *ppPage = pTrunk;
        pTrunk = 0;
        TRACE(("ALLOCATE: %d trunk - %d free pages left\n", *pPgno, n-1));
      }else if( k>(u32)(pBt->usableSize/4 - 2) ){
        /* Value of k is out of range.  Database corruption */
        rc = SQLITE_CORRUPT_BKPT;
        goto end_allocate_page;
#ifndef SQLITE_OMIT_AUTOVACUUM
      }else if( searchList && nearby==iTrunk ){
        /* The list is being searched and this trunk page is the page
        ** to allocate, regardless of whether it has leaves.
        */
        assert( *pPgno==iTrunk );
        *ppPage = pTrunk;
        searchList = 0;
        rc = sqlite4PagerWrite(pTrunk->pDbPage);
        if( rc ){
          goto end_allocate_page;
        }
        if( k==0 ){
          if( !pPrevTrunk ){
            memcpy(&pPage1->aData[32], &pTrunk->aData[0], 4);
          }else{
            rc = sqlite4PagerWrite(pPrevTrunk->pDbPage);
            if( rc!=SQLITE_OK ){
              goto end_allocate_page;
            }
            memcpy(&pPrevTrunk->aData[0], &pTrunk->aData[0], 4);
          }
        }else{
          /* The trunk page is required by the caller but it contains 
          ** pointers to free-list leaves. The first leaf becomes a trunk
          ** page in this case.
          */
          MemPage *pNewTrunk;
          Pgno iNewTrunk = get4byte(&pTrunk->aData[8]);
          if( iNewTrunk>mxPage ){ 
            rc = SQLITE_CORRUPT_BKPT;
            goto end_allocate_page;
          }
          testcase( iNewTrunk==mxPage );
          rc = btreeGetPage(pBt, iNewTrunk, &pNewTrunk, 0);
          if( rc!=SQLITE_OK ){
            goto end_allocate_page;
          }
          rc = sqlite4PagerWrite(pNewTrunk->pDbPage);
          if( rc!=SQLITE_OK ){
            releasePage(pNewTrunk);
            goto end_allocate_page;
          }
          memcpy(&pNewTrunk->aData[0], &pTrunk->aData[0], 4);
          put4byte(&pNewTrunk->aData[4], k-1);
          memcpy(&pNewTrunk->aData[8], &pTrunk->aData[12], (k-1)*4);
          releasePage(pNewTrunk);
          if( !pPrevTrunk ){
            assert( sqlite4PagerIswriteable(pPage1->pDbPage) );
            put4byte(&pPage1->aData[32], iNewTrunk);
          }else{
            rc = sqlite4PagerWrite(pPrevTrunk->pDbPage);
            if( rc ){
              goto end_allocate_page;
            }
            put4byte(&pPrevTrunk->aData[0], iNewTrunk);
          }
        }
        pTrunk = 0;
        TRACE(("ALLOCATE: %d trunk - %d free pages left\n", *pPgno, n-1));
#endif
      }else if( k>0 ){
        /* Extract a leaf from the trunk */
        u32 closest;
        Pgno iPage;
        unsigned char *aData = pTrunk->aData;
        if( nearby>0 ){
          u32 i;
          int dist;
          closest = 0;
          dist = sqlite4AbsInt32(get4byte(&aData[8]) - nearby);
          for(i=1; i<k; i++){
            int d2 = sqlite4AbsInt32(get4byte(&aData[8+i*4]) - nearby);
            if( d2<dist ){
              closest = i;
              dist = d2;
            }
          }
        }else{
          closest = 0;
        }

        iPage = get4byte(&aData[8+closest*4]);
        testcase( iPage==mxPage );
        if( iPage>mxPage ){
          rc = SQLITE_CORRUPT_BKPT;
          goto end_allocate_page;
        }
        testcase( iPage==mxPage );
        if( !searchList || iPage==nearby ){
          int noContent;
          *pPgno = iPage;
          TRACE(("ALLOCATE: %d was leaf %d of %d on trunk %d"
                 ": %d more free pages\n",
                 *pPgno, closest+1, k, pTrunk->pgno, n-1));
          rc = sqlite4PagerWrite(pTrunk->pDbPage);
          if( rc ) goto end_allocate_page;
          if( closest<k-1 ){
            memcpy(&aData[8+closest*4], &aData[4+k*4], 4);
          }
          put4byte(&aData[4], k-1);
          noContent = !btreeGetHasContent(pBt, *pPgno);
          rc = btreeGetPage(pBt, *pPgno, ppPage, noContent);
          if( rc==SQLITE_OK ){
            rc = sqlite4PagerWrite((*ppPage)->pDbPage);
            if( rc!=SQLITE_OK ){
              releasePage(*ppPage);
            }
          }
          searchList = 0;
        }
      }
      releasePage(pPrevTrunk);
      pPrevTrunk = 0;
    }while( searchList );
  }else{
    /* There are no pages on the freelist, so create a new page at the
    ** end of the file */
    rc = sqlite4PagerWrite(pBt->pPage1->pDbPage);
    if( rc ) return rc;
    pBt->nPage++;
    if( pBt->nPage==PENDING_BYTE_PAGE(pBt) ) pBt->nPage++;

#ifndef SQLITE_OMIT_AUTOVACUUM
    if( pBt->autoVacuum && PTRMAP_ISPAGE(pBt, pBt->nPage) ){
      /* If *pPgno refers to a pointer-map page, allocate two new pages
      ** at the end of the file instead of one. The first allocated page
      ** becomes a new pointer-map page, the second is used by the caller.
      */
      MemPage *pPg = 0;
      TRACE(("ALLOCATE: %d from end of file (pointer-map page)\n", pBt->nPage));
      assert( pBt->nPage!=PENDING_BYTE_PAGE(pBt) );
      rc = btreeGetPage(pBt, pBt->nPage, &pPg, 1);
      if( rc==SQLITE_OK ){
        rc = sqlite4PagerWrite(pPg->pDbPage);
        releasePage(pPg);
      }
      if( rc ) return rc;
      pBt->nPage++;
      if( pBt->nPage==PENDING_BYTE_PAGE(pBt) ){ pBt->nPage++; }
    }
#endif
    put4byte(28 + (u8*)pBt->pPage1->aData, pBt->nPage);
    *pPgno = pBt->nPage;

    assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
    rc = btreeGetPage(pBt, *pPgno, ppPage, 1);
    if( rc ) return rc;
    rc = sqlite4PagerWrite((*ppPage)->pDbPage);
    if( rc!=SQLITE_OK ){
      releasePage(*ppPage);
    }
    TRACE(("ALLOCATE: %d from end of file\n", *pPgno));
  }

  assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );

end_allocate_page:
  releasePage(pTrunk);
  releasePage(pPrevTrunk);
  if( rc==SQLITE_OK ){
    if( sqlite4PagerPageRefcount((*ppPage)->pDbPage)>1 ){
      releasePage(*ppPage);
      return SQLITE_CORRUPT_BKPT;
    }
    (*ppPage)->isInit = 0;
  }else{
    *ppPage = 0;
  }
  assert( rc!=SQLITE_OK || sqlite4PagerIswriteable((*ppPage)->pDbPage) );
  return rc;
}

/*
** This function is used to add page iPage to the database file free-list. 
** It is assumed that the page is not already a part of the free-list.
**
** The value passed as the second argument to this function is optional.
** If the caller happens to have a pointer to the MemPage object 
** corresponding to page iPage handy, it may pass it as the second value. 
** Otherwise, it may pass NULL.
**
** If a pointer to a MemPage object is passed as the second argument,
** its reference count is not altered by this function.
*/
static int freePage2(BtShared *pBt, MemPage *pMemPage, Pgno iPage){
  MemPage *pTrunk = 0;                /* Free-list trunk page */
  Pgno iTrunk = 0;                    /* Page number of free-list trunk page */ 
  MemPage *pPage1 = pBt->pPage1;      /* Local reference to page 1 */
  MemPage *pPage;                     /* Page being freed. May be NULL. */
  int rc;                             /* Return Code */
  int nFree;                          /* Initial number of pages on free-list */

  assert( sqlite4_mutex_held(pBt->mutex) );
  assert( iPage>1 );
  assert( !pMemPage || pMemPage->pgno==iPage );

  if( pMemPage ){
    pPage = pMemPage;
    sqlite4PagerRef(pPage->pDbPage);
  }else{
    pPage = btreePageLookup(pBt, iPage);
  }

  /* Increment the free page count on pPage1 */
  rc = sqlite4PagerWrite(pPage1->pDbPage);
  if( rc ) goto freepage_out;
  nFree = get4byte(&pPage1->aData[36]);
  put4byte(&pPage1->aData[36], nFree+1);

  if( pBt->btsFlags & BTS_SECURE_DELETE ){
    /* If the secure_delete option is enabled, then
    ** always fully overwrite deleted information with zeros.
    */
    if( (!pPage && ((rc = btreeGetPage(pBt, iPage, &pPage, 0))!=0) )
     ||            ((rc = sqlite4PagerWrite(pPage->pDbPage))!=0)
    ){
      goto freepage_out;
    }
    memset(pPage->aData, 0, pPage->pBt->pageSize);
  }

  /* If the database supports auto-vacuum, write an entry in the pointer-map
  ** to indicate that the page is free.
  */
  if( ISAUTOVACUUM ){
    ptrmapPut(pBt, iPage, PTRMAP_FREEPAGE, 0, &rc);
    if( rc ) goto freepage_out;
  }

  /* Now manipulate the actual database free-list structure. There are two
  ** possibilities. If the free-list is currently empty, or if the first
  ** trunk page in the free-list is full, then this page will become a
  ** new free-list trunk page. Otherwise, it will become a leaf of the
  ** first trunk page in the current free-list. This block tests if it
  ** is possible to add the page as a new free-list leaf.
  */
  if( nFree!=0 ){
    u32 nLeaf;                /* Initial number of leaf cells on trunk page */

    iTrunk = get4byte(&pPage1->aData[32]);
    rc = btreeGetPage(pBt, iTrunk, &pTrunk, 0);
    if( rc!=SQLITE_OK ){
      goto freepage_out;
    }

    nLeaf = get4byte(&pTrunk->aData[4]);
    assert( pBt->usableSize>32 );
    if( nLeaf > (u32)pBt->usableSize/4 - 2 ){
      rc = SQLITE_CORRUPT_BKPT;
      goto freepage_out;
    }
    if( nLeaf < (u32)pBt->usableSize/4 - 8 ){
      /* In this case there is room on the trunk page to insert the page
      ** being freed as a new leaf.
      **
      ** Note that the trunk page is not really full until it contains
      ** usableSize/4 - 2 entries, not usableSize/4 - 8 entries as we have
      ** coded.  But due to a coding error in versions of SQLite prior to
      ** 3.6.0, databases with freelist trunk pages holding more than
      ** usableSize/4 - 8 entries will be reported as corrupt.  In order
      ** to maintain backwards compatibility with older versions of SQLite,
      ** we will continue to restrict the number of entries to usableSize/4 - 8
      ** for now.  At some point in the future (once everyone has upgraded
      ** to 3.6.0 or later) we should consider fixing the conditional above
      ** to read "usableSize/4-2" instead of "usableSize/4-8".
      */
      rc = sqlite4PagerWrite(pTrunk->pDbPage);
      if( rc==SQLITE_OK ){
        put4byte(&pTrunk->aData[4], nLeaf+1);
        put4byte(&pTrunk->aData[8+nLeaf*4], iPage);
        if( pPage && (pBt->btsFlags & BTS_SECURE_DELETE)==0 ){
          sqlite4PagerDontWrite(pPage->pDbPage);
        }
        rc = btreeSetHasContent(pBt, iPage);
      }
      TRACE(("FREE-PAGE: %d leaf on trunk page %d\n",pPage->pgno,pTrunk->pgno));
      goto freepage_out;
    }
  }

  /* If control flows to this point, then it was not possible to add the
  ** the page being freed as a leaf page of the first trunk in the free-list.
  ** Possibly because the free-list is empty, or possibly because the 
  ** first trunk in the free-list is full. Either way, the page being freed
  ** will become the new first trunk page in the free-list.
  */
  if( pPage==0 && SQLITE_OK!=(rc = btreeGetPage(pBt, iPage, &pPage, 0)) ){
    goto freepage_out;
  }
  rc = sqlite4PagerWrite(pPage->pDbPage);
  if( rc!=SQLITE_OK ){
    goto freepage_out;
  }
  put4byte(pPage->aData, iTrunk);
  put4byte(&pPage->aData[4], 0);
  put4byte(&pPage1->aData[32], iPage);
  TRACE(("FREE-PAGE: %d new trunk page replacing %d\n", pPage->pgno, iTrunk));

freepage_out:
  if( pPage ){
    pPage->isInit = 0;
  }
  releasePage(pPage);
  releasePage(pTrunk);
  return rc;
}
static void freePage(MemPage *pPage, int *pRC){
  if( (*pRC)==SQLITE_OK ){
    *pRC = freePage2(pPage->pBt, pPage, pPage->pgno);
  }
}

/*
** Free any overflow pages associated with the given Cell.
*/
static int clearCell(MemPage *pPage, unsigned char *pCell){
  BtShared *pBt = pPage->pBt;
  CellInfo info;
  Pgno ovflPgno;
  int rc;
  int nOvfl;
  u32 ovflPageSize;

  assert( sqlite4_mutex_held(pPage->pBt->mutex) );
  btreeParseCellPtr(pPage, pCell, &info);
  if( info.iOverflow==0 ){
    return SQLITE_OK;  /* No overflow pages. Return without doing anything */
  }
  if( pCell+info.iOverflow+3 > pPage->aData+pPage->maskPage ){
    return SQLITE_CORRUPT;  /* Cell extends past end of page */
  }
  ovflPgno = get4byte(&pCell[info.iOverflow]);
  assert( pBt->usableSize > 4 );
  ovflPageSize = pBt->usableSize - 4;
  nOvfl = (info.nPayload - info.nLocal + ovflPageSize - 1)/ovflPageSize;
  assert( ovflPgno==0 || nOvfl>0 );
  while( nOvfl-- ){
    Pgno iNext = 0;
    MemPage *pOvfl = 0;
    if( ovflPgno<2 || ovflPgno>btreePagecount(pBt) ){
      /* 0 is not a legal page number and page 1 cannot be an 
      ** overflow page. Therefore if ovflPgno<2 or past the end of the 
      ** file the database must be corrupt. */
      return SQLITE_CORRUPT_BKPT;
    }
    if( nOvfl ){
      rc = getOverflowPage(pBt, ovflPgno, &pOvfl, &iNext);
      if( rc ) return rc;
    }

    if( ( pOvfl || ((pOvfl = btreePageLookup(pBt, ovflPgno))!=0) )
     && sqlite4PagerPageRefcount(pOvfl->pDbPage)!=1
    ){
      /* There is no reason any cursor should have an outstanding reference 
      ** to an overflow page belonging to a cell that is being deleted/updated.
      ** So if there exists more than one reference to this page, then it 
      ** must not really be an overflow page and the database must be corrupt. 
      ** It is helpful to detect this before calling freePage2(), as 
      ** freePage2() may zero the page contents if secure-delete mode is
      ** enabled. If this 'overflow' page happens to be a page that the
      ** caller is iterating through or using in some other way, this
      ** can be problematic.
      */
      rc = SQLITE_CORRUPT_BKPT;
    }else{
      rc = freePage2(pBt, pOvfl, ovflPgno);
    }

    if( pOvfl ){
      sqlite4PagerUnref(pOvfl->pDbPage);
    }
    if( rc ) return rc;
    ovflPgno = iNext;
  }
  return SQLITE_OK;
}

/*
** Create the byte sequence used to represent a cell on page pPage
** and write that byte sequence into pCell[].  Overflow pages are
** allocated and filled in as necessary.  The calling procedure
** is responsible for making sure sufficient space has been allocated
** for pCell[].
**
** Note that pCell does not necessary need to point to the pPage->aData
** area.  pCell might point to some temporary storage.  The cell will
** be constructed in this temporary area then copied into pPage->aData
** later.
*/
static int fillInCell(
  MemPage *pPage,                /* The page that contains the cell */
  unsigned char *pCell,          /* Complete text of the cell */
  const void *pKey, i64 nKey,    /* The key */
  const void *pData,int nData,   /* The data */
  int nZero,                     /* Extra zero bytes to append to pData */
  int *pnSize                    /* Write cell size here */
){
  int nPayload;
  const u8 *pSrc;
  int nSrc, n, rc;
  int spaceLeft;
  MemPage *pOvfl = 0;
  MemPage *pToRelease = 0;
  unsigned char *pPrior;
  unsigned char *pPayload;
  BtShared *pBt = pPage->pBt;
  Pgno pgnoOvfl = 0;
  int nHeader;
  CellInfo info;

  assert( sqlite4_mutex_held(pPage->pBt->mutex) );

  /* pPage is not necessarily writeable since pCell might be auxiliary
  ** buffer space that is separate from the pPage buffer area */
  assert( pCell<pPage->aData || pCell>=&pPage->aData[pBt->pageSize]
            || sqlite4PagerIswriteable(pPage->pDbPage) );

  /* Fill in the header. */
  nHeader = 0;
  if( !pPage->leaf ){
    nHeader += 4;
  }
  if( pPage->hasData ){
    nHeader += putVarint(&pCell[nHeader], nData+nZero);
  }else{
    nData = nZero = 0;
  }
  nHeader += putVarint(&pCell[nHeader], *(u64*)&nKey);
  btreeParseCellPtr(pPage, pCell, &info);
  assert( info.nHeader==nHeader );
  assert( info.nKey==nKey );
  assert( info.nData==(u32)(nData+nZero) );
  
  /* Fill in the payload */
  nPayload = nData + nZero;
  if( pPage->intKey ){
    pSrc = pData;
    nSrc = nData;
    nData = 0;
  }else{ 
    if( NEVER(nKey>0x7fffffff || pKey==0) ){
      return SQLITE_CORRUPT_BKPT;
    }
    nPayload += (int)nKey;
    pSrc = pKey;
    nSrc = (int)nKey;
  }
  *pnSize = info.nSize;
  spaceLeft = info.nLocal;
  pPayload = &pCell[nHeader];
  pPrior = &pCell[info.iOverflow];

  while( nPayload>0 ){
    if( spaceLeft==0 ){
#ifndef SQLITE_OMIT_AUTOVACUUM
      Pgno pgnoPtrmap = pgnoOvfl; /* Overflow page pointer-map entry page */
      if( pBt->autoVacuum ){
        do{
          pgnoOvfl++;
        } while( 
          PTRMAP_ISPAGE(pBt, pgnoOvfl) || pgnoOvfl==PENDING_BYTE_PAGE(pBt) 
        );
      }
#endif
      rc = allocateBtreePage(pBt, &pOvfl, &pgnoOvfl, pgnoOvfl, 0);
#ifndef SQLITE_OMIT_AUTOVACUUM
      /* If the database supports auto-vacuum, and the second or subsequent
      ** overflow page is being allocated, add an entry to the pointer-map
      ** for that page now. 
      **
      ** If this is the first overflow page, then write a partial entry 
      ** to the pointer-map. If we write nothing to this pointer-map slot,
      ** then the optimistic overflow chain processing in clearCell()
      ** may misinterpret the uninitialised values and delete the
      ** wrong pages from the database.
      */
      if( pBt->autoVacuum && rc==SQLITE_OK ){
        u8 eType = (pgnoPtrmap?PTRMAP_OVERFLOW2:PTRMAP_OVERFLOW1);
        ptrmapPut(pBt, pgnoOvfl, eType, pgnoPtrmap, &rc);
        if( rc ){
          releasePage(pOvfl);
        }
      }
#endif
      if( rc ){
        releasePage(pToRelease);
        return rc;
      }

      /* If pToRelease is not zero than pPrior points into the data area
      ** of pToRelease.  Make sure pToRelease is still writeable. */
      assert( pToRelease==0 || sqlite4PagerIswriteable(pToRelease->pDbPage) );

      /* If pPrior is part of the data area of pPage, then make sure pPage
      ** is still writeable */
      assert( pPrior<pPage->aData || pPrior>=&pPage->aData[pBt->pageSize]
            || sqlite4PagerIswriteable(pPage->pDbPage) );

      put4byte(pPrior, pgnoOvfl);
      releasePage(pToRelease);
      pToRelease = pOvfl;
      pPrior = pOvfl->aData;
      put4byte(pPrior, 0);
      pPayload = &pOvfl->aData[4];
      spaceLeft = pBt->usableSize - 4;
    }
    n = nPayload;
    if( n>spaceLeft ) n = spaceLeft;

    /* If pToRelease is not zero than pPayload points into the data area
    ** of pToRelease.  Make sure pToRelease is still writeable. */
    assert( pToRelease==0 || sqlite4PagerIswriteable(pToRelease->pDbPage) );

    /* If pPayload is part of the data area of pPage, then make sure pPage
    ** is still writeable */
    assert( pPayload<pPage->aData || pPayload>=&pPage->aData[pBt->pageSize]
            || sqlite4PagerIswriteable(pPage->pDbPage) );

    if( nSrc>0 ){
      if( n>nSrc ) n = nSrc;
      assert( pSrc );
      memcpy(pPayload, pSrc, n);
    }else{
      memset(pPayload, 0, n);
    }
    nPayload -= n;
    pPayload += n;
    pSrc += n;
    nSrc -= n;
    spaceLeft -= n;
    if( nSrc==0 ){
      nSrc = nData;
      pSrc = pData;
    }
  }
  releasePage(pToRelease);
  return SQLITE_OK;
}

/*
** Remove the i-th cell from pPage.  This routine effects pPage only.
** The cell content is not freed or deallocated.  It is assumed that
** the cell content has been copied someplace else.  This routine just
** removes the reference to the cell from pPage.
**
** "sz" must be the number of bytes in the cell.
*/
static void dropCell(MemPage *pPage, int idx, int sz, int *pRC){
  u32 pc;         /* Offset to cell content of cell being deleted */
  u8 *data;       /* pPage->aData */
  u8 *ptr;        /* Used to move bytes around within data[] */
  u8 *endPtr;     /* End of loop */
  int rc;         /* The return code */
  int hdr;        /* Beginning of the header.  0 most pages.  100 page 1 */

  if( *pRC ) return;

  assert( idx>=0 && idx<pPage->nCell );
  assert( sz==cellSize(pPage, idx) );
  assert( sqlite4PagerIswriteable(pPage->pDbPage) );
  assert( sqlite4_mutex_held(pPage->pBt->mutex) );
  data = pPage->aData;
  ptr = &pPage->aCellIdx[2*idx];
  pc = get2byte(ptr);
  hdr = pPage->hdrOffset;
  testcase( pc==get2byte(&data[hdr+5]) );
  testcase( pc+sz==pPage->pBt->usableSize );
  if( pc < (u32)get2byte(&data[hdr+5]) || pc+sz > pPage->pBt->usableSize ){
    *pRC = SQLITE_CORRUPT_BKPT;
    return;
  }
  rc = freeSpace(pPage, pc, sz);
  if( rc ){
    *pRC = rc;
    return;
  }
  endPtr = &pPage->aCellIdx[2*pPage->nCell - 2];
  assert( (SQLITE_PTR_TO_INT(ptr)&1)==0 );  /* ptr is always 2-byte aligned */
  while( ptr<endPtr ){
    *(u16*)ptr = *(u16*)&ptr[2];
    ptr += 2;
  }
  pPage->nCell--;
  put2byte(&data[hdr+3], pPage->nCell);
  pPage->nFree += 2;
}

/*
** Insert a new cell on pPage at cell index "i".  pCell points to the
** content of the cell.
**
** If the cell content will fit on the page, then put it there.  If it
** will not fit, then make a copy of the cell content into pTemp if
** pTemp is not null.  Regardless of pTemp, allocate a new entry
** in pPage->aOvfl[] and make it point to the cell content (either
** in pTemp or the original pCell) and also record its index. 
** Allocating a new entry in pPage->aCell[] implies that 
** pPage->nOverflow is incremented.
**
** If nSkip is non-zero, then do not copy the first nSkip bytes of the
** cell. The caller will overwrite them after this function returns. If
** nSkip is non-zero, then pCell may not point to an invalid memory location 
** (but pCell+nSkip is always valid).
*/
static void insertCell(
  MemPage *pPage,   /* Page into which we are copying */
  int i,            /* New cell becomes the i-th cell of the page */
  u8 *pCell,        /* Content of the new cell */
  int sz,           /* Bytes of content in pCell */
  u8 *pTemp,        /* Temp storage space for pCell, if needed */
  Pgno iChild,      /* If non-zero, replace first 4 bytes with this value */
  int *pRC          /* Read and write return code from here */
){
  int idx = 0;      /* Where to write new cell content in data[] */
  int j;            /* Loop counter */
  int end;          /* First byte past the last cell pointer in data[] */
  int ins;          /* Index in data[] where new cell pointer is inserted */
  int cellOffset;   /* Address of first cell pointer in data[] */
  u8 *data;         /* The content of the whole page */
  u8 *ptr;          /* Used for moving information around in data[] */
  u8 *endPtr;       /* End of the loop */

  int nSkip = (iChild ? 4 : 0);

  if( *pRC ) return;

  assert( i>=0 && i<=pPage->nCell+pPage->nOverflow );
  assert( pPage->nCell<=MX_CELL(pPage->pBt) && MX_CELL(pPage->pBt)<=10921 );
  assert( pPage->nOverflow<=ArraySize(pPage->aOvfl) );
  assert( sqlite4_mutex_held(pPage->pBt->mutex) );
  /* The cell should normally be sized correctly.  However, when moving a
  ** malformed cell from a leaf page to an interior page, if the cell size
  ** wanted to be less than 4 but got rounded up to 4 on the leaf, then size
  ** might be less than 8 (leaf-size + pointer) on the interior node.  Hence
  ** the term after the || in the following assert(). */
  assert( sz==cellSizePtr(pPage, pCell) || (sz==8 && iChild>0) );
  if( pPage->nOverflow || sz+2>pPage->nFree ){
    if( pTemp ){
      memcpy(pTemp+nSkip, pCell+nSkip, sz-nSkip);
      pCell = pTemp;
    }
    if( iChild ){
      put4byte(pCell, iChild);
    }
    j = pPage->nOverflow++;
    assert( j<(int)(sizeof(pPage->aOvfl)/sizeof(pPage->aOvfl[0])) );
    pPage->aOvfl[j].pCell = pCell;
    pPage->aOvfl[j].idx = (u16)i;
  }else{
    int rc = sqlite4PagerWrite(pPage->pDbPage);
    if( rc!=SQLITE_OK ){
      *pRC = rc;
      return;
    }
    assert( sqlite4PagerIswriteable(pPage->pDbPage) );
    data = pPage->aData;
    cellOffset = pPage->cellOffset;
    end = cellOffset + 2*pPage->nCell;
    ins = cellOffset + 2*i;
    rc = allocateSpace(pPage, sz, &idx);
    if( rc ){ *pRC = rc; return; }
    /* The allocateSpace() routine guarantees the following two properties
    ** if it returns success */
    assert( idx >= end+2 );
    assert( idx+sz <= (int)pPage->pBt->usableSize );
    pPage->nCell++;
    pPage->nFree -= (u16)(2 + sz);
    memcpy(&data[idx+nSkip], pCell+nSkip, sz-nSkip);
    if( iChild ){
      put4byte(&data[idx], iChild);
    }
    ptr = &data[end];
    endPtr = &data[ins];
    assert( (SQLITE_PTR_TO_INT(ptr)&1)==0 );  /* ptr is always 2-byte aligned */
    while( ptr>endPtr ){
      *(u16*)ptr = *(u16*)&ptr[-2];
      ptr -= 2;
    }
    put2byte(&data[ins], idx);
    put2byte(&data[pPage->hdrOffset+3], pPage->nCell);
#ifndef SQLITE_OMIT_AUTOVACUUM
    if( pPage->pBt->autoVacuum ){
      /* The cell may contain a pointer to an overflow page. If so, write
      ** the entry for the overflow page into the pointer map.
      */
      ptrmapPutOvflPtr(pPage, pCell, pRC);
    }
#endif
  }
}

/*
** Add a list of cells to a page.  The page should be initially empty.
** The cells are guaranteed to fit on the page.
*/
static void assemblePage(
  MemPage *pPage,   /* The page to be assemblied */
  int nCell,        /* The number of cells to add to this page */
  u8 **apCell,      /* Pointers to cell bodies */
  u16 *aSize        /* Sizes of the cells */
){
  int i;            /* Loop counter */
  u8 *pCellptr;     /* Address of next cell pointer */
  int cellbody;     /* Address of next cell body */
  u8 * const data = pPage->aData;             /* Pointer to data for pPage */
  const int hdr = pPage->hdrOffset;           /* Offset of header on pPage */
  const int nUsable = pPage->pBt->usableSize; /* Usable size of page */

  assert( pPage->nOverflow==0 );
  assert( sqlite4_mutex_held(pPage->pBt->mutex) );
  assert( nCell>=0 && nCell<=(int)MX_CELL(pPage->pBt)
            && (int)MX_CELL(pPage->pBt)<=10921);
  assert( sqlite4PagerIswriteable(pPage->pDbPage) );

  /* Check that the page has just been zeroed by zeroPage() */
  assert( pPage->nCell==0 );
  assert( get2byteNotZero(&data[hdr+5])==nUsable );

  pCellptr = &pPage->aCellIdx[nCell*2];
  cellbody = nUsable;
  for(i=nCell-1; i>=0; i--){
    u16 sz = aSize[i];
    pCellptr -= 2;
    cellbody -= sz;
    put2byte(pCellptr, cellbody);
    memcpy(&data[cellbody], apCell[i], sz);
  }
  put2byte(&data[hdr+3], nCell);
  put2byte(&data[hdr+5], cellbody);
  pPage->nFree -= (nCell*2 + nUsable - cellbody);
  pPage->nCell = (u16)nCell;
}

/*
** The following parameters determine how many adjacent pages get involved
** in a balancing operation.  NN is the number of neighbors on either side
** of the page that participate in the balancing operation.  NB is the
** total number of pages that participate, including the target page and
** NN neighbors on either side.
**
** The minimum value of NN is 1 (of course).  Increasing NN above 1
** (to 2 or 3) gives a modest improvement in SELECT and DELETE performance
** in exchange for a larger degradation in INSERT and UPDATE performance.
** The value of NN appears to give the best results overall.
*/
#define NN 1             /* Number of neighbors on either side of pPage */
#define NB (NN*2+1)      /* Total pages involved in the balance */


#ifndef SQLITE_OMIT_QUICKBALANCE
/*
** This version of balance() handles the common special case where
** a new entry is being inserted on the extreme right-end of the
** tree, in other words, when the new entry will become the largest
** entry in the tree.
**
** Instead of trying to balance the 3 right-most leaf pages, just add
** a new page to the right-hand side and put the one new entry in
** that page.  This leaves the right side of the tree somewhat
** unbalanced.  But odds are that we will be inserting new entries
** at the end soon afterwards so the nearly empty page will quickly
** fill up.  On average.
**
** pPage is the leaf page which is the right-most page in the tree.
** pParent is its parent.  pPage must have a single overflow entry
** which is also the right-most entry on the page.
**
** The pSpace buffer is used to store a temporary copy of the divider
** cell that will be inserted into pParent. Such a cell consists of a 4
** byte page number followed by a variable length integer. In other
** words, at most 13 bytes. Hence the pSpace buffer must be at
** least 13 bytes in size.
*/
static int balance_quick(MemPage *pParent, MemPage *pPage, u8 *pSpace){
  BtShared *const pBt = pPage->pBt;    /* B-Tree Database */
  MemPage *pNew;                       /* Newly allocated page */
  int rc;                              /* Return Code */
  Pgno pgnoNew;                        /* Page number of pNew */

  assert( sqlite4_mutex_held(pPage->pBt->mutex) );
  assert( sqlite4PagerIswriteable(pParent->pDbPage) );
  assert( pPage->nOverflow==1 );

  /* This error condition is now caught prior to reaching this function */
  if( pPage->nCell<=0 ) return SQLITE_CORRUPT_BKPT;

  /* Allocate a new page. This page will become the right-sibling of 
  ** pPage. Make the parent page writable, so that the new divider cell
  ** may be inserted. If both these operations are successful, proceed.
  */
  rc = allocateBtreePage(pBt, &pNew, &pgnoNew, 0, 0);

  if( rc==SQLITE_OK ){

    u8 *pOut = &pSpace[4];
    u8 *pCell = pPage->aOvfl[0].pCell;
    u16 szCell = cellSizePtr(pPage, pCell);
    u8 *pStop;

    assert( sqlite4PagerIswriteable(pNew->pDbPage) );
    assert( pPage->aData[0]==(PTF_INTKEY|PTF_LEAFDATA|PTF_LEAF) );
    zeroPage(pNew, PTF_INTKEY|PTF_LEAFDATA|PTF_LEAF);
    assemblePage(pNew, 1, &pCell, &szCell);

    /* If this is an auto-vacuum database, update the pointer map
    ** with entries for the new page, and any pointer from the 
    ** cell on the page to an overflow page. If either of these
    ** operations fails, the return code is set, but the contents
    ** of the parent page are still manipulated by thh code below.
    ** That is Ok, at this point the parent page is guaranteed to
    ** be marked as dirty. Returning an error code will cause a
    ** rollback, undoing any changes made to the parent page.
    */
    if( ISAUTOVACUUM ){
      ptrmapPut(pBt, pgnoNew, PTRMAP_BTREE, pParent->pgno, &rc);
      if( szCell>pNew->minLocal ){
        ptrmapPutOvflPtr(pNew, pCell, &rc);
      }
    }
  
    /* Create a divider cell to insert into pParent. The divider cell
    ** consists of a 4-byte page number (the page number of pPage) and
    ** a variable length key value (which must be the same value as the
    ** largest key on pPage).
    **
    ** To find the largest key value on pPage, first find the right-most 
    ** cell on pPage. The first two fields of this cell are the 
    ** record-length (a variable length integer at most 32-bits in size)
    ** and the key value (a variable length integer, may have any value).
    ** The first of the while(...) loops below skips over the record-length
    ** field. The second while(...) loop copies the key value from the
    ** cell on pPage into the pSpace buffer.
    */
    pCell = findCell(pPage, pPage->nCell-1);
    pStop = &pCell[9];
    while( (*(pCell++)&0x80) && pCell<pStop );
    pStop = &pCell[9];
    while( ((*(pOut++) = *(pCell++))&0x80) && pCell<pStop );

    /* Insert the new divider cell into pParent. */
    insertCell(pParent, pParent->nCell, pSpace, (int)(pOut-pSpace),
               0, pPage->pgno, &rc);

    /* Set the right-child pointer of pParent to point to the new page. */
    put4byte(&pParent->aData[pParent->hdrOffset+8], pgnoNew);
  
    /* Release the reference to the new page. */
    releasePage(pNew);
  }

  return rc;
}
#endif /* SQLITE_OMIT_QUICKBALANCE */

#if 0
/*
** This function does not contribute anything to the operation of SQLite.
** it is sometimes activated temporarily while debugging code responsible 
** for setting pointer-map entries.
*/
static int ptrmapCheckPages(MemPage **apPage, int nPage){
  int i, j;
  for(i=0; i<nPage; i++){
    Pgno n;
    u8 e;
    MemPage *pPage = apPage[i];
    BtShared *pBt = pPage->pBt;
    assert( pPage->isInit );

    for(j=0; j<pPage->nCell; j++){
      CellInfo info;
      u8 *z;
     
      z = findCell(pPage, j);
      btreeParseCellPtr(pPage, z, &info);
      if( info.iOverflow ){
        Pgno ovfl = get4byte(&z[info.iOverflow]);
        ptrmapGet(pBt, ovfl, &e, &n);
        assert( n==pPage->pgno && e==PTRMAP_OVERFLOW1 );
      }
      if( !pPage->leaf ){
        Pgno child = get4byte(z);
        ptrmapGet(pBt, child, &e, &n);
        assert( n==pPage->pgno && e==PTRMAP_BTREE );
      }
    }
    if( !pPage->leaf ){
      Pgno child = get4byte(&pPage->aData[pPage->hdrOffset+8]);
      ptrmapGet(pBt, child, &e, &n);
      assert( n==pPage->pgno && e==PTRMAP_BTREE );
    }
  }
  return 1;
}
#endif

/*
** This function is used to copy the contents of the b-tree node stored 
** on page pFrom to page pTo. If page pFrom was not a leaf page, then
** the pointer-map entries for each child page are updated so that the
** parent page stored in the pointer map is page pTo. If pFrom contained
** any cells with overflow page pointers, then the corresponding pointer
** map entries are also updated so that the parent page is page pTo.
**
** If pFrom is currently carrying any overflow cells (entries in the
** MemPage.aOvfl[] array), they are not copied to pTo. 
**
** Before returning, page pTo is reinitialized using btreeInitPage().
**
** The performance of this function is not critical. It is only used by 
** the balance_shallower() and balance_deeper() procedures, neither of
** which are called often under normal circumstances.
*/
static void copyNodeContent(MemPage *pFrom, MemPage *pTo, int *pRC){
  if( (*pRC)==SQLITE_OK ){
    BtShared * const pBt = pFrom->pBt;
    u8 * const aFrom = pFrom->aData;
    u8 * const aTo = pTo->aData;
    int const iFromHdr = pFrom->hdrOffset;
    int const iToHdr = ((pTo->pgno==1) ? 100 : 0);
    int rc;
    int iData;
  
  
    assert( pFrom->isInit );
    assert( pFrom->nFree>=iToHdr );
    assert( get2byte(&aFrom[iFromHdr+5]) <= (int)pBt->usableSize );
  
    /* Copy the b-tree node content from page pFrom to page pTo. */
    iData = get2byte(&aFrom[iFromHdr+5]);
    memcpy(&aTo[iData], &aFrom[iData], pBt->usableSize-iData);
    memcpy(&aTo[iToHdr], &aFrom[iFromHdr], pFrom->cellOffset + 2*pFrom->nCell);
  
    /* Reinitialize page pTo so that the contents of the MemPage structure
    ** match the new data. The initialization of pTo can actually fail under
    ** fairly obscure circumstances, even though it is a copy of initialized 
    ** page pFrom.
    */
    pTo->isInit = 0;
    rc = btreeInitPage(pTo);
    if( rc!=SQLITE_OK ){
      *pRC = rc;
      return;
    }
  
    /* If this is an auto-vacuum database, update the pointer-map entries
    ** for any b-tree or overflow pages that pTo now contains the pointers to.
    */
    if( ISAUTOVACUUM ){
      *pRC = setChildPtrmaps(pTo);
    }
  }
}

/*
** This routine redistributes cells on the iParentIdx'th child of pParent
** (hereafter "the page") and up to 2 siblings so that all pages have about the
** same amount of free space. Usually a single sibling on either side of the
** page are used in the balancing, though both siblings might come from one
** side if the page is the first or last child of its parent. If the page 
** has fewer than 2 siblings (something which can only happen if the page
** is a root page or a child of a root page) then all available siblings
** participate in the balancing.
**
** The number of siblings of the page might be increased or decreased by 
** one or two in an effort to keep pages nearly full but not over full. 
**
** Note that when this routine is called, some of the cells on the page
** might not actually be stored in MemPage.aData[]. This can happen
** if the page is overfull. This routine ensures that all cells allocated
** to the page and its siblings fit into MemPage.aData[] before returning.
**
** In the course of balancing the page and its siblings, cells may be
** inserted into or removed from the parent page (pParent). Doing so
** may cause the parent page to become overfull or underfull. If this
** happens, it is the responsibility of the caller to invoke the correct
** balancing routine to fix this problem (see the balance() routine). 
**
** If this routine fails for any reason, it might leave the database
** in a corrupted state. So if this routine fails, the database should
** be rolled back.
**
** The third argument to this function, aOvflSpace, is a pointer to a
** buffer big enough to hold one page. If while inserting cells into the parent
** page (pParent) the parent page becomes overfull, this buffer is
** used to store the parent's overflow cells. Because this function inserts
** a maximum of four divider cells into the parent page, and the maximum
** size of a cell stored within an internal node is always less than 1/4
** of the page-size, the aOvflSpace[] buffer is guaranteed to be large
** enough for all overflow cells.
**
** If aOvflSpace is set to a null pointer, this function returns 
** SQLITE_NOMEM.
*/
static int balance_nonroot(
  MemPage *pParent,               /* Parent page of siblings being balanced */
  int iParentIdx,                 /* Index of "the page" in pParent */
  u8 *aOvflSpace,                 /* page-size bytes of space for parent ovfl */
  int isRoot                      /* True if pParent is a root-page */
){
  BtShared *pBt;               /* The whole database */
  int nCell = 0;               /* Number of cells in apCell[] */
  int nMaxCells = 0;           /* Allocated size of apCell, szCell, aFrom. */
  int nNew = 0;                /* Number of pages in apNew[] */
  int nOld;                    /* Number of pages in apOld[] */
  int i, j, k;                 /* Loop counters */
  int nxDiv;                   /* Next divider slot in pParent->aCell[] */
  int rc = SQLITE_OK;          /* The return code */
  u16 leafCorrection;          /* 4 if pPage is a leaf.  0 if not */
  int leafData;                /* True if pPage is a leaf of a LEAFDATA tree */
  int usableSpace;             /* Bytes in pPage beyond the header */
  int pageFlags;               /* Value of pPage->aData[0] */
  int subtotal;                /* Subtotal of bytes in cells on one page */
  int iSpace1 = 0;             /* First unused byte of aSpace1[] */
  int iOvflSpace = 0;          /* First unused byte of aOvflSpace[] */
  int szScratch;               /* Size of scratch memory requested */
  MemPage *apOld[NB];          /* pPage and up to two siblings */
  MemPage *apCopy[NB];         /* Private copies of apOld[] pages */
  MemPage *apNew[NB+2];        /* pPage and up to NB siblings after balancing */
  u8 *pRight;                  /* Location in parent of right-sibling pointer */
  u8 *apDiv[NB-1];             /* Divider cells in pParent */
  int cntNew[NB+2];            /* Index in aCell[] of cell after i-th page */
  int szNew[NB+2];             /* Combined size of cells place on i-th page */
  u8 **apCell = 0;             /* All cells begin balanced */
  u16 *szCell;                 /* Local size of all cells in apCell[] */
  u8 *aSpace1;                 /* Space for copies of dividers cells */
  Pgno pgno;                   /* Temp var to store a page number in */

  pBt = pParent->pBt;
  assert( sqlite4_mutex_held(pBt->mutex) );
  assert( sqlite4PagerIswriteable(pParent->pDbPage) );

#if 0
  TRACE(("BALANCE: begin page %d child of %d\n", pPage->pgno, pParent->pgno));
#endif

  /* At this point pParent may have at most one overflow cell. And if
  ** this overflow cell is present, it must be the cell with 
  ** index iParentIdx. This scenario comes about when this function
  ** is called (indirectly) from sqlite4BtreeDelete().
  */
  assert( pParent->nOverflow==0 || pParent->nOverflow==1 );
  assert( pParent->nOverflow==0 || pParent->aOvfl[0].idx==iParentIdx );

  if( !aOvflSpace ){
    return SQLITE_NOMEM;
  }

  /* Find the sibling pages to balance. Also locate the cells in pParent 
  ** that divide the siblings. An attempt is made to find NN siblings on 
  ** either side of pPage. More siblings are taken from one side, however, 
  ** if there are fewer than NN siblings on the other side. If pParent
  ** has NB or fewer children then all children of pParent are taken.  
  **
  ** This loop also drops the divider cells from the parent page. This
  ** way, the remainder of the function does not have to deal with any
  ** overflow cells in the parent page, since if any existed they will
  ** have already been removed.
  */
  i = pParent->nOverflow + pParent->nCell;
  if( i<2 ){
    nxDiv = 0;
    nOld = i+1;
  }else{
    nOld = 3;
    if( iParentIdx==0 ){                 
      nxDiv = 0;
    }else if( iParentIdx==i ){
      nxDiv = i-2;
    }else{
      nxDiv = iParentIdx-1;
    }
    i = 2;
  }
  if( (i+nxDiv-pParent->nOverflow)==pParent->nCell ){
    pRight = &pParent->aData[pParent->hdrOffset+8];
  }else{
    pRight = findCell(pParent, i+nxDiv-pParent->nOverflow);
  }
  pgno = get4byte(pRight);
  while( 1 ){
    rc = getAndInitPage(pBt, pgno, &apOld[i]);
    if( rc ){
      memset(apOld, 0, (i+1)*sizeof(MemPage*));
      goto balance_cleanup;
    }
    nMaxCells += 1+apOld[i]->nCell+apOld[i]->nOverflow;
    if( (i--)==0 ) break;

    if( i+nxDiv==pParent->aOvfl[0].idx && pParent->nOverflow ){
      apDiv[i] = pParent->aOvfl[0].pCell;
      pgno = get4byte(apDiv[i]);
      szNew[i] = cellSizePtr(pParent, apDiv[i]);
      pParent->nOverflow = 0;
    }else{
      apDiv[i] = findCell(pParent, i+nxDiv-pParent->nOverflow);
      pgno = get4byte(apDiv[i]);
      szNew[i] = cellSizePtr(pParent, apDiv[i]);

      /* Drop the cell from the parent page. apDiv[i] still points to
      ** the cell within the parent, even though it has been dropped.
      ** This is safe because dropping a cell only overwrites the first
      ** four bytes of it, and this function does not need the first
      ** four bytes of the divider cell. So the pointer is safe to use
      ** later on.  
      **
      ** But not if we are in secure-delete mode. In secure-delete mode,
      ** the dropCell() routine will overwrite the entire cell with zeroes.
      ** In this case, temporarily copy the cell into the aOvflSpace[]
      ** buffer. It will be copied out again as soon as the aSpace[] buffer
      ** is allocated.  */
      if( pBt->btsFlags & BTS_SECURE_DELETE ){
        int iOff;

        iOff = SQLITE_PTR_TO_INT(apDiv[i]) - SQLITE_PTR_TO_INT(pParent->aData);
        if( (iOff+szNew[i])>(int)pBt->usableSize ){
          rc = SQLITE_CORRUPT_BKPT;
          memset(apOld, 0, (i+1)*sizeof(MemPage*));
          goto balance_cleanup;
        }else{
          memcpy(&aOvflSpace[iOff], apDiv[i], szNew[i]);
          apDiv[i] = &aOvflSpace[apDiv[i]-pParent->aData];
        }
      }
      dropCell(pParent, i+nxDiv-pParent->nOverflow, szNew[i], &rc);
    }
  }

  /* Make nMaxCells a multiple of 4 in order to preserve 8-byte
  ** alignment */
  nMaxCells = (nMaxCells + 3)&~3;

  /*
  ** Allocate space for memory structures
  */
  k = pBt->pageSize + ROUND8(sizeof(MemPage));
  szScratch =
       nMaxCells*sizeof(u8*)                       /* apCell */
     + nMaxCells*sizeof(u16)                       /* szCell */
     + pBt->pageSize                               /* aSpace1 */
     + k*nOld;                                     /* Page copies (apCopy) */
  apCell = sqlite4ScratchMalloc( szScratch ); 
  if( apCell==0 ){
    rc = SQLITE_NOMEM;
    goto balance_cleanup;
  }
  szCell = (u16*)&apCell[nMaxCells];
  aSpace1 = (u8*)&szCell[nMaxCells];
  assert( EIGHT_BYTE_ALIGNMENT(aSpace1) );

  /*
  ** Load pointers to all cells on sibling pages and the divider cells
  ** into the local apCell[] array.  Make copies of the divider cells
  ** into space obtained from aSpace1[] and remove the the divider Cells
  ** from pParent.
  **
  ** If the siblings are on leaf pages, then the child pointers of the
  ** divider cells are stripped from the cells before they are copied
  ** into aSpace1[].  In this way, all cells in apCell[] are without
  ** child pointers.  If siblings are not leaves, then all cell in
  ** apCell[] include child pointers.  Either way, all cells in apCell[]
  ** are alike.
  **
  ** leafCorrection:  4 if pPage is a leaf.  0 if pPage is not a leaf.
  **       leafData:  1 if pPage holds key+data and pParent holds only keys.
  */
  leafCorrection = apOld[0]->leaf*4;
  leafData = apOld[0]->hasData;
  for(i=0; i<nOld; i++){
    int limit;
    
    /* Before doing anything else, take a copy of the i'th original sibling
    ** The rest of this function will use data from the copies rather
    ** that the original pages since the original pages will be in the
    ** process of being overwritten.  */
    MemPage *pOld = apCopy[i] = (MemPage*)&aSpace1[pBt->pageSize + k*i];
    memcpy(pOld, apOld[i], sizeof(MemPage));
    pOld->aData = (void*)&pOld[1];
    memcpy(pOld->aData, apOld[i]->aData, pBt->pageSize);

    limit = pOld->nCell+pOld->nOverflow;
    if( pOld->nOverflow>0 ){
      for(j=0; j<limit; j++){
        assert( nCell<nMaxCells );
        apCell[nCell] = findOverflowCell(pOld, j);
        szCell[nCell] = cellSizePtr(pOld, apCell[nCell]);
        nCell++;
      }
    }else{
      u8 *aData = pOld->aData;
      u16 maskPage = pOld->maskPage;
      u16 cellOffset = pOld->cellOffset;
      for(j=0; j<limit; j++){
        assert( nCell<nMaxCells );
        apCell[nCell] = findCellv2(aData, maskPage, cellOffset, j);
        szCell[nCell] = cellSizePtr(pOld, apCell[nCell]);
        nCell++;
      }
    }       
    if( i<nOld-1 && !leafData){
      u16 sz = (u16)szNew[i];
      u8 *pTemp;
      assert( nCell<nMaxCells );
      szCell[nCell] = sz;
      pTemp = &aSpace1[iSpace1];
      iSpace1 += sz;
      assert( sz<=pBt->maxLocal+23 );
      assert( iSpace1 <= (int)pBt->pageSize );
      memcpy(pTemp, apDiv[i], sz);
      apCell[nCell] = pTemp+leafCorrection;
      assert( leafCorrection==0 || leafCorrection==4 );
      szCell[nCell] = szCell[nCell] - leafCorrection;
      if( !pOld->leaf ){
        assert( leafCorrection==0 );
        assert( pOld->hdrOffset==0 );
        /* The right pointer of the child page pOld becomes the left
        ** pointer of the divider cell */
        memcpy(apCell[nCell], &pOld->aData[8], 4);
      }else{
        assert( leafCorrection==4 );
        if( szCell[nCell]<4 ){
          /* Do not allow any cells smaller than 4 bytes. */
          szCell[nCell] = 4;
        }
      }
      nCell++;
    }
  }

  /*
  ** Figure out the number of pages needed to hold all nCell cells.
  ** Store this number in "k".  Also compute szNew[] which is the total
  ** size of all cells on the i-th page and cntNew[] which is the index
  ** in apCell[] of the cell that divides page i from page i+1.  
  ** cntNew[k] should equal nCell.
  **
  ** Values computed by this block:
  **
  **           k: The total number of sibling pages
  **    szNew[i]: Spaced used on the i-th sibling page.
  **   cntNew[i]: Index in apCell[] and szCell[] for the first cell to
  **              the right of the i-th sibling page.
  ** usableSpace: Number of bytes of space available on each sibling.
  ** 
  */
  usableSpace = pBt->usableSize - 12 + leafCorrection;
  for(subtotal=k=i=0; i<nCell; i++){
    assert( i<nMaxCells );
    subtotal += szCell[i] + 2;
    if( subtotal > usableSpace ){
      szNew[k] = subtotal - szCell[i];
      cntNew[k] = i;
      if( leafData ){ i--; }
      subtotal = 0;
      k++;
      if( k>NB+1 ){ rc = SQLITE_CORRUPT_BKPT; goto balance_cleanup; }
    }
  }
  szNew[k] = subtotal;
  cntNew[k] = nCell;
  k++;

  /*
  ** The packing computed by the previous block is biased toward the siblings
  ** on the left side.  The left siblings are always nearly full, while the
  ** right-most sibling might be nearly empty.  This block of code attempts
  ** to adjust the packing of siblings to get a better balance.
  **
  ** This adjustment is more than an optimization.  The packing above might
  ** be so out of balance as to be illegal.  For example, the right-most
  ** sibling might be completely empty.  This adjustment is not optional.
  */
  for(i=k-1; i>0; i--){
    int szRight = szNew[i];  /* Size of sibling on the right */
    int szLeft = szNew[i-1]; /* Size of sibling on the left */
    int r;              /* Index of right-most cell in left sibling */
    int d;              /* Index of first cell to the left of right sibling */

    r = cntNew[i-1] - 1;
    d = r + 1 - leafData;
    assert( d<nMaxCells );
    assert( r<nMaxCells );
    while( szRight==0 || szRight+szCell[d]+2<=szLeft-(szCell[r]+2) ){
      szRight += szCell[d] + 2;
      szLeft -= szCell[r] + 2;
      cntNew[i-1]--;
      r = cntNew[i-1] - 1;
      d = r + 1 - leafData;
    }
    szNew[i] = szRight;
    szNew[i-1] = szLeft;
  }

  /* Either we found one or more cells (cntnew[0])>0) or pPage is
  ** a virtual root page.  A virtual root page is when the real root
  ** page is page 1 and we are the only child of that page.
  **
  ** UPDATE:  The assert() below is not necessarily true if the database
  ** file is corrupt.  The corruption will be detected and reported later
  ** in this procedure so there is no need to act upon it now.
  */
#if 0
  assert( cntNew[0]>0 || (pParent->pgno==1 && pParent->nCell==0) );
#endif

  TRACE(("BALANCE: old: %d %d %d  ",
    apOld[0]->pgno, 
    nOld>=2 ? apOld[1]->pgno : 0,
    nOld>=3 ? apOld[2]->pgno : 0
  ));

  /*
  ** Allocate k new pages.  Reuse old pages where possible.
  */
  if( apOld[0]->pgno<=1 ){
    rc = SQLITE_CORRUPT_BKPT;
    goto balance_cleanup;
  }
  pageFlags = apOld[0]->aData[0];
  for(i=0; i<k; i++){
    MemPage *pNew;
    if( i<nOld ){
      pNew = apNew[i] = apOld[i];
      apOld[i] = 0;
      rc = sqlite4PagerWrite(pNew->pDbPage);
      nNew++;
      if( rc ) goto balance_cleanup;
    }else{
      assert( i>0 );
      rc = allocateBtreePage(pBt, &pNew, &pgno, pgno, 0);
      if( rc ) goto balance_cleanup;
      apNew[i] = pNew;
      nNew++;

      /* Set the pointer-map entry for the new sibling page. */
      if( ISAUTOVACUUM ){
        ptrmapPut(pBt, pNew->pgno, PTRMAP_BTREE, pParent->pgno, &rc);
        if( rc!=SQLITE_OK ){
          goto balance_cleanup;
        }
      }
    }
  }

  /* Free any old pages that were not reused as new pages.
  */
  while( i<nOld ){
    freePage(apOld[i], &rc);
    if( rc ) goto balance_cleanup;
    releasePage(apOld[i]);
    apOld[i] = 0;
    i++;
  }

  /*
  ** Put the new pages in accending order.  This helps to
  ** keep entries in the disk file in order so that a scan
  ** of the table is a linear scan through the file.  That
  ** in turn helps the operating system to deliver pages
  ** from the disk more rapidly.
  **
  ** An O(n^2) insertion sort algorithm is used, but since
  ** n is never more than NB (a small constant), that should
  ** not be a problem.
  **
  ** When NB==3, this one optimization makes the database
  ** about 25% faster for large insertions and deletions.
  */
  for(i=0; i<k-1; i++){
    int minV = apNew[i]->pgno;
    int minI = i;
    for(j=i+1; j<k; j++){
      if( apNew[j]->pgno<(unsigned)minV ){
        minI = j;
        minV = apNew[j]->pgno;
      }
    }
    if( minI>i ){
      MemPage *pT;
      pT = apNew[i];
      apNew[i] = apNew[minI];
      apNew[minI] = pT;
    }
  }
  TRACE(("new: %d(%d) %d(%d) %d(%d) %d(%d) %d(%d)\n",
    apNew[0]->pgno, szNew[0],
    nNew>=2 ? apNew[1]->pgno : 0, nNew>=2 ? szNew[1] : 0,
    nNew>=3 ? apNew[2]->pgno : 0, nNew>=3 ? szNew[2] : 0,
    nNew>=4 ? apNew[3]->pgno : 0, nNew>=4 ? szNew[3] : 0,
    nNew>=5 ? apNew[4]->pgno : 0, nNew>=5 ? szNew[4] : 0));

  assert( sqlite4PagerIswriteable(pParent->pDbPage) );
  put4byte(pRight, apNew[nNew-1]->pgno);

  /*
  ** Evenly distribute the data in apCell[] across the new pages.
  ** Insert divider cells into pParent as necessary.
  */
  j = 0;
  for(i=0; i<nNew; i++){
    /* Assemble the new sibling page. */
    MemPage *pNew = apNew[i];
    assert( j<nMaxCells );
    zeroPage(pNew, pageFlags);
    assemblePage(pNew, cntNew[i]-j, &apCell[j], &szCell[j]);
    assert( pNew->nCell>0 || (nNew==1 && cntNew[0]==0) );
    assert( pNew->nOverflow==0 );

    j = cntNew[i];

    /* If the sibling page assembled above was not the right-most sibling,
    ** insert a divider cell into the parent page.
    */
    assert( i<nNew-1 || j==nCell );
    if( j<nCell ){
      u8 *pCell;
      u8 *pTemp;
      int sz;

      assert( j<nMaxCells );
      pCell = apCell[j];
      sz = szCell[j] + leafCorrection;
      pTemp = &aOvflSpace[iOvflSpace];
      if( !pNew->leaf ){
        memcpy(&pNew->aData[8], pCell, 4);
      }else if( leafData ){
        /* If the tree is a leaf-data tree, and the siblings are leaves, 
        ** then there is no divider cell in apCell[]. Instead, the divider 
        ** cell consists of the integer key for the right-most cell of 
        ** the sibling-page assembled above only.
        */
        CellInfo info;
        j--;
        btreeParseCellPtr(pNew, apCell[j], &info);
        pCell = pTemp;
        sz = 4 + putVarint(&pCell[4], info.nKey);
        pTemp = 0;
      }else{
        pCell -= 4;
        /* Obscure case for non-leaf-data trees: If the cell at pCell was
        ** previously stored on a leaf node, and its reported size was 4
        ** bytes, then it may actually be smaller than this 
        ** (see btreeParseCellPtr(), 4 bytes is the minimum size of
        ** any cell). But it is important to pass the correct size to 
        ** insertCell(), so reparse the cell now.
        **
        ** Note that this can never happen in an SQLite data file, as all
        ** cells are at least 4 bytes. It only happens in b-trees used
        ** to evaluate "IN (SELECT ...)" and similar clauses.
        */
        if( szCell[j]==4 ){
          assert(leafCorrection==4);
          sz = cellSizePtr(pParent, pCell);
        }
      }
      iOvflSpace += sz;
      assert( sz<=pBt->maxLocal+23 );
      assert( iOvflSpace <= (int)pBt->pageSize );
      insertCell(pParent, nxDiv, pCell, sz, pTemp, pNew->pgno, &rc);
      if( rc!=SQLITE_OK ) goto balance_cleanup;
      assert( sqlite4PagerIswriteable(pParent->pDbPage) );

      j++;
      nxDiv++;
    }
  }
  assert( j==nCell );
  assert( nOld>0 );
  assert( nNew>0 );
  if( (pageFlags & PTF_LEAF)==0 ){
    u8 *zChild = &apCopy[nOld-1]->aData[8];
    memcpy(&apNew[nNew-1]->aData[8], zChild, 4);
  }

  if( isRoot && pParent->nCell==0 && pParent->hdrOffset<=apNew[0]->nFree ){
    /* The root page of the b-tree now contains no cells. The only sibling
    ** page is the right-child of the parent. Copy the contents of the
    ** child page into the parent, decreasing the overall height of the
    ** b-tree structure by one. This is described as the "balance-shallower"
    ** sub-algorithm in some documentation.
    **
    ** If this is an auto-vacuum database, the call to copyNodeContent() 
    ** sets all pointer-map entries corresponding to database image pages 
    ** for which the pointer is stored within the content being copied.
    **
    ** The second assert below verifies that the child page is defragmented
    ** (it must be, as it was just reconstructed using assemblePage()). This
    ** is important if the parent page happens to be page 1 of the database
    ** image.  */
    assert( nNew==1 );
    assert( apNew[0]->nFree == 
        (get2byte(&apNew[0]->aData[5])-apNew[0]->cellOffset-apNew[0]->nCell*2) 
    );
    copyNodeContent(apNew[0], pParent, &rc);
    freePage(apNew[0], &rc);
  }else if( ISAUTOVACUUM ){
    /* Fix the pointer-map entries for all the cells that were shifted around. 
    ** There are several different types of pointer-map entries that need to
    ** be dealt with by this routine. Some of these have been set already, but
    ** many have not. The following is a summary:
    **
    **   1) The entries associated with new sibling pages that were not
    **      siblings when this function was called. These have already
    **      been set. We don't need to worry about old siblings that were
    **      moved to the free-list - the freePage() code has taken care
    **      of those.
    **
    **   2) The pointer-map entries associated with the first overflow
    **      page in any overflow chains used by new divider cells. These 
    **      have also already been taken care of by the insertCell() code.
    **
    **   3) If the sibling pages are not leaves, then the child pages of
    **      cells stored on the sibling pages may need to be updated.
    **
    **   4) If the sibling pages are not internal intkey nodes, then any
    **      overflow pages used by these cells may need to be updated
    **      (internal intkey nodes never contain pointers to overflow pages).
    **
    **   5) If the sibling pages are not leaves, then the pointer-map
    **      entries for the right-child pages of each sibling may need
    **      to be updated.
    **
    ** Cases 1 and 2 are dealt with above by other code. The next
    ** block deals with cases 3 and 4 and the one after that, case 5. Since
    ** setting a pointer map entry is a relatively expensive operation, this
    ** code only sets pointer map entries for child or overflow pages that have
    ** actually moved between pages.  */
    MemPage *pNew = apNew[0];
    MemPage *pOld = apCopy[0];
    int nOverflow = pOld->nOverflow;
    int iNextOld = pOld->nCell + nOverflow;
    int iOverflow = (nOverflow ? pOld->aOvfl[0].idx : -1);
    j = 0;                             /* Current 'old' sibling page */
    k = 0;                             /* Current 'new' sibling page */
    for(i=0; i<nCell; i++){
      int isDivider = 0;
      while( i==iNextOld ){
        /* Cell i is the cell immediately following the last cell on old
        ** sibling page j. If the siblings are not leaf pages of an
        ** intkey b-tree, then cell i was a divider cell. */
        assert( j+1 < ArraySize(apCopy) );
        pOld = apCopy[++j];
        iNextOld = i + !leafData + pOld->nCell + pOld->nOverflow;
        if( pOld->nOverflow ){
          nOverflow = pOld->nOverflow;
          iOverflow = i + !leafData + pOld->aOvfl[0].idx;
        }
        isDivider = !leafData;  
      }

      assert(nOverflow>0 || iOverflow<i );
      assert(nOverflow<2 || pOld->aOvfl[0].idx==pOld->aOvfl[1].idx-1);
      assert(nOverflow<3 || pOld->aOvfl[1].idx==pOld->aOvfl[2].idx-1);
      if( i==iOverflow ){
        isDivider = 1;
        if( (--nOverflow)>0 ){
          iOverflow++;
        }
      }

      if( i==cntNew[k] ){
        /* Cell i is the cell immediately following the last cell on new
        ** sibling page k. If the siblings are not leaf pages of an
        ** intkey b-tree, then cell i is a divider cell.  */
        pNew = apNew[++k];
        if( !leafData ) continue;
      }
      assert( j<nOld );
      assert( k<nNew );

      /* If the cell was originally divider cell (and is not now) or
      ** an overflow cell, or if the cell was located on a different sibling
      ** page before the balancing, then the pointer map entries associated
      ** with any child or overflow pages need to be updated.  */
      if( isDivider || pOld->pgno!=pNew->pgno ){
        if( !leafCorrection ){
          ptrmapPut(pBt, get4byte(apCell[i]), PTRMAP_BTREE, pNew->pgno, &rc);
        }
        if( szCell[i]>pNew->minLocal ){
          ptrmapPutOvflPtr(pNew, apCell[i], &rc);
        }
      }
    }

    if( !leafCorrection ){
      for(i=0; i<nNew; i++){
        u32 key = get4byte(&apNew[i]->aData[8]);
        ptrmapPut(pBt, key, PTRMAP_BTREE, apNew[i]->pgno, &rc);
      }
    }

#if 0
    /* The ptrmapCheckPages() contains assert() statements that verify that
    ** all pointer map pages are set correctly. This is helpful while 
    ** debugging. This is usually disabled because a corrupt database may
    ** cause an assert() statement to fail.  */
    ptrmapCheckPages(apNew, nNew);
    ptrmapCheckPages(&pParent, 1);
#endif
  }

  assert( pParent->isInit );
  TRACE(("BALANCE: finished: old=%d new=%d cells=%d\n",
          nOld, nNew, nCell));

  /*
  ** Cleanup before returning.
  */
balance_cleanup:
  sqlite4ScratchFree(apCell);
  for(i=0; i<nOld; i++){
    releasePage(apOld[i]);
  }
  for(i=0; i<nNew; i++){
    releasePage(apNew[i]);
  }

  return rc;
}


/*
** This function is called when the root page of a b-tree structure is
** overfull (has one or more overflow pages).
**
** A new child page is allocated and the contents of the current root
** page, including overflow cells, are copied into the child. The root
** page is then overwritten to make it an empty page with the right-child 
** pointer pointing to the new page.
**
** Before returning, all pointer-map entries corresponding to pages 
** that the new child-page now contains pointers to are updated. The
** entry corresponding to the new right-child pointer of the root
** page is also updated.
**
** If successful, *ppChild is set to contain a reference to the child 
** page and SQLITE_OK is returned. In this case the caller is required
** to call releasePage() on *ppChild exactly once. If an error occurs,
** an error code is returned and *ppChild is set to 0.
*/
static int balance_deeper(MemPage *pRoot, MemPage **ppChild){
  int rc;                        /* Return value from subprocedures */
  MemPage *pChild = 0;           /* Pointer to a new child page */
  Pgno pgnoChild = 0;            /* Page number of the new child page */
  BtShared *pBt = pRoot->pBt;    /* The BTree */

  assert( pRoot->nOverflow>0 );
  assert( sqlite4_mutex_held(pBt->mutex) );

  /* Make pRoot, the root page of the b-tree, writable. Allocate a new 
  ** page that will become the new right-child of pPage. Copy the contents
  ** of the node stored on pRoot into the new child page.
  */
  rc = sqlite4PagerWrite(pRoot->pDbPage);
  if( rc==SQLITE_OK ){
    rc = allocateBtreePage(pBt,&pChild,&pgnoChild,pRoot->pgno,0);
    copyNodeContent(pRoot, pChild, &rc);
    if( ISAUTOVACUUM ){
      ptrmapPut(pBt, pgnoChild, PTRMAP_BTREE, pRoot->pgno, &rc);
    }
  }
  if( rc ){
    *ppChild = 0;
    releasePage(pChild);
    return rc;
  }
  assert( sqlite4PagerIswriteable(pChild->pDbPage) );
  assert( sqlite4PagerIswriteable(pRoot->pDbPage) );
  assert( pChild->nCell==pRoot->nCell );

  TRACE(("BALANCE: copy root %d into %d\n", pRoot->pgno, pChild->pgno));

  /* Copy the overflow cells from pRoot to pChild */
  memcpy(pChild->aOvfl, pRoot->aOvfl, pRoot->nOverflow*sizeof(pRoot->aOvfl[0]));
  pChild->nOverflow = pRoot->nOverflow;

  /* Zero the contents of pRoot. Then install pChild as the right-child. */
  zeroPage(pRoot, pChild->aData[0] & ~PTF_LEAF);
  put4byte(&pRoot->aData[pRoot->hdrOffset+8], pgnoChild);

  *ppChild = pChild;
  return SQLITE_OK;
}

/*
** The page that pCur currently points to has just been modified in
** some way. This function figures out if this modification means the
** tree needs to be balanced, and if so calls the appropriate balancing 
** routine. Balancing routines are:
**
**   balance_quick()
**   balance_deeper()
**   balance_nonroot()
*/
static int balance(BtCursor *pCur){
  int rc = SQLITE_OK;
  const int nMin = pCur->pBt->usableSize * 2 / 3;
  u8 aBalanceQuickSpace[13];
  u8 *pFree = 0;

  TESTONLY( int balance_quick_called = 0 );
  TESTONLY( int balance_deeper_called = 0 );

  do {
    int iPage = pCur->iPage;
    MemPage *pPage = pCur->apPage[iPage];

    if( iPage==0 ){
      if( pPage->nOverflow ){
        /* The root page of the b-tree is overfull. In this case call the
        ** balance_deeper() function to create a new child for the root-page
        ** and copy the current contents of the root-page to it. The
        ** next iteration of the do-loop will balance the child page.
        */ 
        assert( (balance_deeper_called++)==0 );
        rc = balance_deeper(pPage, &pCur->apPage[1]);
        if( rc==SQLITE_OK ){
          pCur->iPage = 1;
          pCur->aiIdx[0] = 0;
          pCur->aiIdx[1] = 0;
          assert( pCur->apPage[1]->nOverflow );
        }
      }else{
        break;
      }
    }else if( pPage->nOverflow==0 && pPage->nFree<=nMin ){
      break;
    }else{
      MemPage * const pParent = pCur->apPage[iPage-1];
      int const iIdx = pCur->aiIdx[iPage-1];

      rc = sqlite4PagerWrite(pParent->pDbPage);
      if( rc==SQLITE_OK ){
#ifndef SQLITE_OMIT_QUICKBALANCE
        if( pPage->hasData
         && pPage->nOverflow==1
         && pPage->aOvfl[0].idx==pPage->nCell
         && pParent->pgno!=1
         && pParent->nCell==iIdx
        ){
          /* Call balance_quick() to create a new sibling of pPage on which
          ** to store the overflow cell. balance_quick() inserts a new cell
          ** into pParent, which may cause pParent overflow. If this
          ** happens, the next interation of the do-loop will balance pParent 
          ** use either balance_nonroot() or balance_deeper(). Until this
          ** happens, the overflow cell is stored in the aBalanceQuickSpace[]
          ** buffer. 
          **
          ** The purpose of the following assert() is to check that only a
          ** single call to balance_quick() is made for each call to this
          ** function. If this were not verified, a subtle bug involving reuse
          ** of the aBalanceQuickSpace[] might sneak in.
          */
          assert( (balance_quick_called++)==0 );
          rc = balance_quick(pParent, pPage, aBalanceQuickSpace);
        }else
#endif
        {
          /* In this case, call balance_nonroot() to redistribute cells
          ** between pPage and up to 2 of its sibling pages. This involves
          ** modifying the contents of pParent, which may cause pParent to
          ** become overfull or underfull. The next iteration of the do-loop
          ** will balance the parent page to correct this.
          ** 
          ** If the parent page becomes overfull, the overflow cell or cells
          ** are stored in the pSpace buffer allocated immediately below. 
          ** A subsequent iteration of the do-loop will deal with this by
          ** calling balance_nonroot() (balance_deeper() may be called first,
          ** but it doesn't deal with overflow cells - just moves them to a
          ** different page). Once this subsequent call to balance_nonroot() 
          ** has completed, it is safe to release the pSpace buffer used by
          ** the previous call, as the overflow cell data will have been 
          ** copied either into the body of a database page or into the new
          ** pSpace buffer passed to the latter call to balance_nonroot().
          */
          u8 *pSpace = sqlite4PageMalloc(pCur->pBt->pageSize);
          rc = balance_nonroot(pParent, iIdx, pSpace, iPage==1);
          if( pFree ){
            /* If pFree is not NULL, it points to the pSpace buffer used 
            ** by a previous call to balance_nonroot(). Its contents are
            ** now stored either on real database pages or within the 
            ** new pSpace buffer, so it may be safely freed here. */
            sqlite4PageFree(pFree);
          }

          /* The pSpace buffer will be freed after the next call to
          ** balance_nonroot(), or just before this function returns, whichever
          ** comes first. */
          pFree = pSpace;
        }
      }

      pPage->nOverflow = 0;

      /* The next iteration of the do-loop balances the parent page. */
      releasePage(pPage);
      pCur->iPage--;
    }
  }while( rc==SQLITE_OK );

  if( pFree ){
    sqlite4PageFree(pFree);
  }
  return rc;
}


/*
** Insert a new record into the BTree.  The key is given by (pKey,nKey)
** and the data is given by (pData,nData).  The cursor is used only to
** define what table the record should be inserted into.  The cursor
** is left pointing at a random location.
**
** For an INTKEY table, only the nKey value of the key is used.  pKey is
** ignored.  For a ZERODATA table, the pData and nData are both ignored.
**
** If the seekResult parameter is non-zero, then a successful call to
** MovetoUnpacked() to seek cursor pCur to (pKey, nKey) has already
** been performed. seekResult is the search result returned (a negative
** number if pCur points at an entry that is smaller than (pKey, nKey), or
** a positive value if pCur points at an etry that is larger than 
** (pKey, nKey)). 
**
** If the seekResult parameter is non-zero, then the caller guarantees that
** cursor pCur is pointing at the existing copy of a row that is to be
** overwritten.  If the seekResult parameter is 0, then cursor pCur may
** point to any entry or to no entry at all and so this function has to seek
** the cursor before the new key can be inserted.
*/
int sqlite4BtreeInsert(
  BtCursor *pCur,                /* Insert data into the table of this cursor */
  const void *pKey, i64 nKey,    /* The key of the new record */
  const void *pData, int nData,  /* The data of the new record */
  int nZero,                     /* Number of extra 0 bytes to append to data */
  int appendBias,                /* True if this is likely an append */
  int seekResult                 /* Result of prior MovetoUnpacked() call */
){
  int rc;
  int loc = seekResult;          /* -1: before desired location  +1: after */
  int szNew = 0;
  int idx;
  MemPage *pPage;
  Btree *p = pCur->pBtree;
  BtShared *pBt = p->pBt;
  unsigned char *oldCell;
  unsigned char *newCell = 0;

  if( pCur->eState==CURSOR_FAULT ){
    assert( pCur->skipNext!=SQLITE_OK );
    return pCur->skipNext;
  }

  assert( cursorHoldsMutex(pCur) );
  assert( pCur->wrFlag && pBt->inTransaction==TRANS_WRITE
              && (pBt->btsFlags & BTS_READ_ONLY)==0 );
  assert( hasSharedCacheTableLock(p, pCur->pgnoRoot, pCur->pKeyInfo!=0, 2) );

  /* Assert that the caller has been consistent. If this cursor was opened
  ** expecting an index b-tree, then the caller should be inserting blob
  ** keys with no associated data. If the cursor was opened expecting an
  ** intkey table, the caller should be inserting integer keys with a
  ** blob of associated data.  */
  assert( (pKey==0)==(pCur->pKeyInfo==0) );

  /* If this is an insert into a table b-tree, invalidate any incrblob 
  ** cursors open on the row being replaced (assuming this is a replace
  ** operation - if it is not, the following is a no-op).  */
  if( pCur->pKeyInfo==0 ){
    invalidateIncrblobCursors(p, nKey, 0);
  }

  /* Save the positions of any other cursors open on this table.
  **
  ** In some cases, the call to btreeMoveto() below is a no-op. For
  ** example, when inserting data into a table with auto-generated integer
  ** keys, the VDBE layer invokes sqlite4BtreeLast() to figure out the 
  ** integer key to use. It then calls this function to actually insert the 
  ** data into the intkey B-Tree. In this case btreeMoveto() recognizes
  ** that the cursor is already where it needs to be and returns without
  ** doing any work. To avoid thwarting these optimizations, it is important
  ** not to clear the cursor here.
  */
  rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur);
  if( rc ) return rc;
  if( !loc ){
    rc = btreeMoveto(pCur, pKey, nKey, appendBias, &loc);
    if( rc ) return rc;
  }
  assert( pCur->eState==CURSOR_VALID || (pCur->eState==CURSOR_INVALID && loc) );

  pPage = pCur->apPage[pCur->iPage];
  assert( pPage->intKey || nKey>=0 );
  assert( pPage->leaf || !pPage->intKey );

  TRACE(("INSERT: table=%d nkey=%lld ndata=%d page=%d %s\n",
          pCur->pgnoRoot, nKey, nData, pPage->pgno,
          loc==0 ? "overwrite" : "new entry"));
  assert( pPage->isInit );
  allocateTempSpace(pBt);
  newCell = pBt->pTmpSpace;
  if( newCell==0 ) return SQLITE_NOMEM;
  rc = fillInCell(pPage, newCell, pKey, nKey, pData, nData, nZero, &szNew);
  if( rc ) goto end_insert;
  assert( szNew==cellSizePtr(pPage, newCell) );
  assert( szNew <= MX_CELL_SIZE(pBt) );
  idx = pCur->aiIdx[pCur->iPage];
  if( loc==0 ){
    u16 szOld;
    assert( idx<pPage->nCell );
    rc = sqlite4PagerWrite(pPage->pDbPage);
    if( rc ){
      goto end_insert;
    }
    oldCell = findCell(pPage, idx);
    if( !pPage->leaf ){
      memcpy(newCell, oldCell, 4);
    }
    szOld = cellSizePtr(pPage, oldCell);
    rc = clearCell(pPage, oldCell);
    dropCell(pPage, idx, szOld, &rc);
    if( rc ) goto end_insert;
  }else if( loc<0 && pPage->nCell>0 ){
    assert( pPage->leaf );
    idx = ++pCur->aiIdx[pCur->iPage];
  }else{
    assert( pPage->leaf );
  }
  insertCell(pPage, idx, newCell, szNew, 0, 0, &rc);
  assert( rc!=SQLITE_OK || pPage->nCell>0 || pPage->nOverflow>0 );

  /* If no error has occured and pPage has an overflow cell, call balance() 
  ** to redistribute the cells within the tree. Since balance() may move
  ** the cursor, zero the BtCursor.info.nSize and BtCursor.validNKey
  ** variables.
  **
  ** Previous versions of SQLite called moveToRoot() to move the cursor
  ** back to the root page as balance() used to invalidate the contents
  ** of BtCursor.apPage[] and BtCursor.aiIdx[]. Instead of doing that,
  ** set the cursor state to "invalid". This makes common insert operations
  ** slightly faster.
  **
  ** There is a subtle but important optimization here too. When inserting
  ** multiple records into an intkey b-tree using a single cursor (as can
  ** happen while processing an "INSERT INTO ... SELECT" statement), it
  ** is advantageous to leave the cursor pointing to the last entry in
  ** the b-tree if possible. If the cursor is left pointing to the last
  ** entry in the table, and the next row inserted has an integer key
  ** larger than the largest existing key, it is possible to insert the
  ** row without seeking the cursor. This can be a big performance boost.
  */
  pCur->info.nSize = 0;
  pCur->validNKey = 0;
  if( rc==SQLITE_OK && pPage->nOverflow ){
    rc = balance(pCur);

    /* Must make sure nOverflow is reset to zero even if the balance()
    ** fails. Internal data structure corruption will result otherwise. 
    ** Also, set the cursor state to invalid. This stops saveCursorPosition()
    ** from trying to save the current position of the cursor.  */
    pCur->apPage[pCur->iPage]->nOverflow = 0;
    pCur->eState = CURSOR_INVALID;
  }
  assert( pCur->apPage[pCur->iPage]->nOverflow==0 );

end_insert:
  return rc;
}

/*
** Delete the entry that the cursor is pointing to.  The cursor
** is left pointing at a arbitrary location.
*/
int sqlite4BtreeDelete(BtCursor *pCur){
  Btree *p = pCur->pBtree;
  BtShared *pBt = p->pBt;              
  int rc;                              /* Return code */
  MemPage *pPage;                      /* Page to delete cell from */
  unsigned char *pCell;                /* Pointer to cell to delete */
  int iCellIdx;                        /* Index of cell to delete */
  int iCellDepth;                      /* Depth of node containing pCell */ 

  assert( cursorHoldsMutex(pCur) );
  assert( pBt->inTransaction==TRANS_WRITE );
  assert( (pBt->btsFlags & BTS_READ_ONLY)==0 );
  assert( pCur->wrFlag );
  assert( hasSharedCacheTableLock(p, pCur->pgnoRoot, pCur->pKeyInfo!=0, 2) );
  assert( !hasReadConflicts(p, pCur->pgnoRoot) );

  if( NEVER(pCur->aiIdx[pCur->iPage]>=pCur->apPage[pCur->iPage]->nCell) 
   || NEVER(pCur->eState!=CURSOR_VALID)
  ){
    return SQLITE_ERROR;  /* Something has gone awry. */
  }

  /* If this is a delete operation to remove a row from a table b-tree,
  ** invalidate any incrblob cursors open on the row being deleted.  */
  if( pCur->pKeyInfo==0 ){
    invalidateIncrblobCursors(p, pCur->info.nKey, 0);
  }

  iCellDepth = pCur->iPage;
  iCellIdx = pCur->aiIdx[iCellDepth];
  pPage = pCur->apPage[iCellDepth];
  pCell = findCell(pPage, iCellIdx);

  /* If the page containing the entry to delete is not a leaf page, move
  ** the cursor to the largest entry in the tree that is smaller than
  ** the entry being deleted. This cell will replace the cell being deleted
  ** from the internal node. The 'previous' entry is used for this instead
  ** of the 'next' entry, as the previous entry is always a part of the
  ** sub-tree headed by the child page of the cell being deleted. This makes
  ** balancing the tree following the delete operation easier.  */
  if( !pPage->leaf ){
    int notUsed;
    rc = sqlite4BtreePrevious(pCur, &notUsed);
    if( rc ) return rc;
  }

  /* Save the positions of any other cursors open on this table before
  ** making any modifications. Make the page containing the entry to be 
  ** deleted writable. Then free any overflow pages associated with the 
  ** entry and finally remove the cell itself from within the page.  
  */
  rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur);
  if( rc ) return rc;
  rc = sqlite4PagerWrite(pPage->pDbPage);
  if( rc ) return rc;
  rc = clearCell(pPage, pCell);
  dropCell(pPage, iCellIdx, cellSizePtr(pPage, pCell), &rc);
  if( rc ) return rc;

  /* If the cell deleted was not located on a leaf page, then the cursor
  ** is currently pointing to the largest entry in the sub-tree headed
  ** by the child-page of the cell that was just deleted from an internal
  ** node. The cell from the leaf node needs to be moved to the internal
  ** node to replace the deleted cell.  */
  if( !pPage->leaf ){
    MemPage *pLeaf = pCur->apPage[pCur->iPage];
    int nCell;
    Pgno n = pCur->apPage[iCellDepth+1]->pgno;
    unsigned char *pTmp;

    pCell = findCell(pLeaf, pLeaf->nCell-1);
    nCell = cellSizePtr(pLeaf, pCell);
    assert( MX_CELL_SIZE(pBt) >= nCell );

    allocateTempSpace(pBt);
    pTmp = pBt->pTmpSpace;

    rc = sqlite4PagerWrite(pLeaf->pDbPage);
    insertCell(pPage, iCellIdx, pCell-4, nCell+4, pTmp, n, &rc);
    dropCell(pLeaf, pLeaf->nCell-1, nCell, &rc);
    if( rc ) return rc;
  }

  /* Balance the tree. If the entry deleted was located on a leaf page,
  ** then the cursor still points to that page. In this case the first
  ** call to balance() repairs the tree, and the if(...) condition is
  ** never true.
  **
  ** Otherwise, if the entry deleted was on an internal node page, then
  ** pCur is pointing to the leaf page from which a cell was removed to
  ** replace the cell deleted from the internal node. This is slightly
  ** tricky as the leaf node may be underfull, and the internal node may
  ** be either under or overfull. In this case run the balancing algorithm
  ** on the leaf node first. If the balance proceeds far enough up the
  ** tree that we can be sure that any problem in the internal node has
  ** been corrected, so be it. Otherwise, after balancing the leaf node,
  ** walk the cursor up the tree to the internal node and balance it as 
  ** well.  */
  rc = balance(pCur);
  if( rc==SQLITE_OK && pCur->iPage>iCellDepth ){
    while( pCur->iPage>iCellDepth ){
      releasePage(pCur->apPage[pCur->iPage--]);
    }
    rc = balance(pCur);
  }

  if( rc==SQLITE_OK ){
    moveToRoot(pCur);
  }
  return rc;
}

/*
** Create a new BTree table.  Write into *piTable the page
** number for the root page of the new table.
**
** The type of type is determined by the flags parameter.  Only the
** following values of flags are currently in use.  Other values for
** flags might not work:
**
**     BTREE_INTKEY|BTREE_LEAFDATA     Used for SQL tables with rowid keys
**     BTREE_ZERODATA                  Used for SQL indices
*/
static int btreeCreateTable(Btree *p, int *piTable, int createTabFlags){
  BtShared *pBt = p->pBt;
  MemPage *pRoot;
  Pgno pgnoRoot;
  int rc;
  int ptfFlags;          /* Page-type flage for the root page of new table */

  assert( sqlite4BtreeHoldsMutex(p) );
  assert( pBt->inTransaction==TRANS_WRITE );
  assert( (pBt->btsFlags & BTS_READ_ONLY)==0 );

#ifdef SQLITE_OMIT_AUTOVACUUM
  rc = allocateBtreePage(pBt, &pRoot, &pgnoRoot, 1, 0);
  if( rc ){
    return rc;
  }
#else
  if( pBt->autoVacuum ){
    Pgno pgnoMove;      /* Move a page here to make room for the root-page */
    MemPage *pPageMove; /* The page to move to. */

    /* Creating a new table may probably require moving an existing database
    ** to make room for the new tables root page. In case this page turns
    ** out to be an overflow page, delete all overflow page-map caches
    ** held by open cursors.
    */
    invalidateAllOverflowCache(pBt);

    /* Read the value of meta[3] from the database to determine where the
    ** root page of the new table should go. meta[3] is the largest root-page
    ** created so far, so the new root-page is (meta[3]+1).
    */
    sqlite4BtreeGetMeta(p, BTREE_LARGEST_ROOT_PAGE, &pgnoRoot);
    pgnoRoot++;

    /* The new root-page may not be allocated on a pointer-map page, or the
    ** PENDING_BYTE page.
    */
    while( pgnoRoot==PTRMAP_PAGENO(pBt, pgnoRoot) ||
        pgnoRoot==PENDING_BYTE_PAGE(pBt) ){
      pgnoRoot++;
    }
    assert( pgnoRoot>=3 );

    /* Allocate a page. The page that currently resides at pgnoRoot will
    ** be moved to the allocated page (unless the allocated page happens
    ** to reside at pgnoRoot).
    */
    rc = allocateBtreePage(pBt, &pPageMove, &pgnoMove, pgnoRoot, 1);
    if( rc!=SQLITE_OK ){
      return rc;
    }

    if( pgnoMove!=pgnoRoot ){
      /* pgnoRoot is the page that will be used for the root-page of
      ** the new table (assuming an error did not occur). But we were
      ** allocated pgnoMove. If required (i.e. if it was not allocated
      ** by extending the file), the current page at position pgnoMove
      ** is already journaled.
      */
      u8 eType = 0;
      Pgno iPtrPage = 0;

      releasePage(pPageMove);

      /* Move the page currently at pgnoRoot to pgnoMove. */
      rc = btreeGetPage(pBt, pgnoRoot, &pRoot, 0);
      if( rc!=SQLITE_OK ){
        return rc;
      }
      rc = ptrmapGet(pBt, pgnoRoot, &eType, &iPtrPage);
      if( eType==PTRMAP_ROOTPAGE || eType==PTRMAP_FREEPAGE ){
        rc = SQLITE_CORRUPT_BKPT;
      }
      if( rc!=SQLITE_OK ){
        releasePage(pRoot);
        return rc;
      }
      assert( eType!=PTRMAP_ROOTPAGE );
      assert( eType!=PTRMAP_FREEPAGE );
      rc = relocatePage(pBt, pRoot, eType, iPtrPage, pgnoMove, 0);
      releasePage(pRoot);

      /* Obtain the page at pgnoRoot */
      if( rc!=SQLITE_OK ){
        return rc;
      }
      rc = btreeGetPage(pBt, pgnoRoot, &pRoot, 0);
      if( rc!=SQLITE_OK ){
        return rc;
      }
      rc = sqlite4PagerWrite(pRoot->pDbPage);
      if( rc!=SQLITE_OK ){
        releasePage(pRoot);
        return rc;
      }
    }else{
      pRoot = pPageMove;
    } 

    /* Update the pointer-map and meta-data with the new root-page number. */
    ptrmapPut(pBt, pgnoRoot, PTRMAP_ROOTPAGE, 0, &rc);
    if( rc ){
      releasePage(pRoot);
      return rc;
    }

    /* When the new root page was allocated, page 1 was made writable in
    ** order either to increase the database filesize, or to decrement the
    ** freelist count.  Hence, the sqlite4BtreeUpdateMeta() call cannot fail.
    */
    assert( sqlite4PagerIswriteable(pBt->pPage1->pDbPage) );
    rc = sqlite4BtreeUpdateMeta(p, 4, pgnoRoot);
    if( NEVER(rc) ){
      releasePage(pRoot);
      return rc;
    }

  }else{
    rc = allocateBtreePage(pBt, &pRoot, &pgnoRoot, 1, 0);
    if( rc ) return rc;
  }
#endif
  assert( sqlite4PagerIswriteable(pRoot->pDbPage) );
  if( createTabFlags & BTREE_INTKEY ){
    ptfFlags = PTF_INTKEY | PTF_LEAFDATA | PTF_LEAF;
  }else{
    ptfFlags = PTF_ZERODATA | PTF_LEAF;
  }
  zeroPage(pRoot, ptfFlags);
  sqlite4PagerUnref(pRoot->pDbPage);
  assert( (pBt->openFlags & BTREE_SINGLE)==0 || pgnoRoot==2 );
  *piTable = (int)pgnoRoot;
  return SQLITE_OK;
}
int sqlite4BtreeCreateTable(Btree *p, int *piTable, int flags){
  int rc;
  sqlite4BtreeEnter(p);
  rc = btreeCreateTable(p, piTable, flags);
  sqlite4BtreeLeave(p);
  return rc;
}

/*
** Erase the given database page and all its children.  Return
** the page to the freelist.
*/
static int clearDatabasePage(
  BtShared *pBt,           /* The BTree that contains the table */
  Pgno pgno,               /* Page number to clear */
  int freePageFlag,        /* Deallocate page if true */
  int *pnChange            /* Add number of Cells freed to this counter */
){
  MemPage *pPage;
  int rc;
  unsigned char *pCell;
  int i;

  assert( sqlite4_mutex_held(pBt->mutex) );
  if( pgno>btreePagecount(pBt) ){
    return SQLITE_CORRUPT_BKPT;
  }

  rc = getAndInitPage(pBt, pgno, &pPage);
  if( rc ) return rc;
  for(i=0; i<pPage->nCell; i++){
    pCell = findCell(pPage, i);
    if( !pPage->leaf ){
      rc = clearDatabasePage(pBt, get4byte(pCell), 1, pnChange);
      if( rc ) goto cleardatabasepage_out;
    }
    rc = clearCell(pPage, pCell);
    if( rc ) goto cleardatabasepage_out;
  }
  if( !pPage->leaf ){
    rc = clearDatabasePage(pBt, get4byte(&pPage->aData[8]), 1, pnChange);
    if( rc ) goto cleardatabasepage_out;
  }else if( pnChange ){
    assert( pPage->intKey );
    *pnChange += pPage->nCell;
  }
  if( freePageFlag ){
    freePage(pPage, &rc);
  }else if( (rc = sqlite4PagerWrite(pPage->pDbPage))==0 ){
    zeroPage(pPage, pPage->aData[0] | PTF_LEAF);
  }

cleardatabasepage_out:
  releasePage(pPage);
  return rc;
}

/*
** Delete all information from a single table in the database.  iTable is
** the page number of the root of the table.  After this routine returns,
** the root page is empty, but still exists.
**
** This routine will fail with SQLITE_LOCKED if there are any open
** read cursors on the table.  Open write cursors are moved to the
** root of the table.
**
** If pnChange is not NULL, then table iTable must be an intkey table. The
** integer value pointed to by pnChange is incremented by the number of
** entries in the table.
*/
int sqlite4BtreeClearTable(Btree *p, int iTable, int *pnChange){
  int rc;
  BtShared *pBt = p->pBt;
  sqlite4BtreeEnter(p);
  assert( p->inTrans==TRANS_WRITE );

  /* Invalidate all incrblob cursors open on table iTable (assuming iTable
  ** is the root of a table b-tree - if it is not, the following call is
  ** a no-op).  */
  invalidateIncrblobCursors(p, 0, 1);

  rc = saveAllCursors(pBt, (Pgno)iTable, 0);
  if( SQLITE_OK==rc ){
    rc = clearDatabasePage(pBt, (Pgno)iTable, 0, pnChange);
  }
  sqlite4BtreeLeave(p);
  return rc;
}

/*
** Erase all information in a table and add the root of the table to
** the freelist.  Except, the root of the principle table (the one on
** page 1) is never added to the freelist.
**
** This routine will fail with SQLITE_LOCKED if there are any open
** cursors on the table.
**
** If AUTOVACUUM is enabled and the page at iTable is not the last
** root page in the database file, then the last root page 
** in the database file is moved into the slot formerly occupied by
** iTable and that last slot formerly occupied by the last root page
** is added to the freelist instead of iTable.  In this say, all
** root pages are kept at the beginning of the database file, which
** is necessary for AUTOVACUUM to work right.  *piMoved is set to the 
** page number that used to be the last root page in the file before
** the move.  If no page gets moved, *piMoved is set to 0.
** The last root page is recorded in meta[3] and the value of
** meta[3] is updated by this procedure.
*/
static int btreeDropTable(Btree *p, Pgno iTable, int *piMoved){
  int rc;
  MemPage *pPage = 0;
  BtShared *pBt = p->pBt;

  assert( sqlite4BtreeHoldsMutex(p) );
  assert( p->inTrans==TRANS_WRITE );

  /* It is illegal to drop a table if any cursors are open on the
  ** database. This is because in auto-vacuum mode the backend may
  ** need to move another root-page to fill a gap left by the deleted
  ** root page. If an open cursor was using this page a problem would 
  ** occur.
  **
  ** This error is caught long before control reaches this point.
  */
  if( NEVER(pBt->pCursor) ){
    sqlite4ConnectionBlocked(p->db, pBt->pCursor->pBtree->db);
    return SQLITE_LOCKED_SHAREDCACHE;
  }

  rc = btreeGetPage(pBt, (Pgno)iTable, &pPage, 0);
  if( rc ) return rc;
  rc = sqlite4BtreeClearTable(p, iTable, 0);
  if( rc ){
    releasePage(pPage);
    return rc;
  }

  *piMoved = 0;

  if( iTable>1 ){
#ifdef SQLITE_OMIT_AUTOVACUUM
    freePage(pPage, &rc);
    releasePage(pPage);
#else
    if( pBt->autoVacuum ){
      Pgno maxRootPgno;
      sqlite4BtreeGetMeta(p, BTREE_LARGEST_ROOT_PAGE, &maxRootPgno);

      if( iTable==maxRootPgno ){
        /* If the table being dropped is the table with the largest root-page
        ** number in the database, put the root page on the free list. 
        */
        freePage(pPage, &rc);
        releasePage(pPage);
        if( rc!=SQLITE_OK ){
          return rc;
        }
      }else{
        /* The table being dropped does not have the largest root-page
        ** number in the database. So move the page that does into the 
        ** gap left by the deleted root-page.
        */
        MemPage *pMove;
        releasePage(pPage);
        rc = btreeGetPage(pBt, maxRootPgno, &pMove, 0);
        if( rc!=SQLITE_OK ){
          return rc;
        }
        rc = relocatePage(pBt, pMove, PTRMAP_ROOTPAGE, 0, iTable, 0);
        releasePage(pMove);
        if( rc!=SQLITE_OK ){
          return rc;
        }
        pMove = 0;
        rc = btreeGetPage(pBt, maxRootPgno, &pMove, 0);
        freePage(pMove, &rc);
        releasePage(pMove);
        if( rc!=SQLITE_OK ){
          return rc;
        }
        *piMoved = maxRootPgno;
      }

      /* Set the new 'max-root-page' value in the database header. This
      ** is the old value less one, less one more if that happens to
      ** be a root-page number, less one again if that is the
      ** PENDING_BYTE_PAGE.
      */
      maxRootPgno--;
      while( maxRootPgno==PENDING_BYTE_PAGE(pBt)
             || PTRMAP_ISPAGE(pBt, maxRootPgno) ){
        maxRootPgno--;
      }
      assert( maxRootPgno!=PENDING_BYTE_PAGE(pBt) );

      rc = sqlite4BtreeUpdateMeta(p, 4, maxRootPgno);
    }else{
      freePage(pPage, &rc);
      releasePage(pPage);
    }
#endif
  }else{
    /* If sqlite4BtreeDropTable was called on page 1.
    ** This really never should happen except in a corrupt
    ** database. 
    */
    zeroPage(pPage, PTF_INTKEY|PTF_LEAF );
    releasePage(pPage);
  }
  return rc;  
}
int sqlite4BtreeDropTable(Btree *p, int iTable, int *piMoved){
  int rc;
  sqlite4BtreeEnter(p);
  rc = btreeDropTable(p, iTable, piMoved);
  sqlite4BtreeLeave(p);
  return rc;
}


/*
** This function may only be called if the b-tree connection already
** has a read or write transaction open on the database.
**
** Read the meta-information out of a database file.  Meta[0]
** is the number of free pages currently in the database.  Meta[1]
** through meta[15] are available for use by higher layers.  Meta[0]
** is read-only, the others are read/write.
** 
** The schema layer numbers meta values differently.  At the schema
** layer (and the SetCookie and ReadCookie opcodes) the number of
** free pages is not visible.  So Cookie[0] is the same as Meta[1].
*/
void sqlite4BtreeGetMeta(Btree *p, int idx, u32 *pMeta){
  BtShared *pBt = p->pBt;

  sqlite4BtreeEnter(p);
  assert( p->inTrans>TRANS_NONE );
  assert( SQLITE_OK==querySharedCacheTableLock(p, MASTER_ROOT, READ_LOCK) );
  assert( pBt->pPage1 );
  assert( idx>=0 && idx<=15 );

  *pMeta = get4byte(&pBt->pPage1->aData[36 + idx*4]);

  /* If auto-vacuum is disabled in this build and this is an auto-vacuum
  ** database, mark the database as read-only.  */
#ifdef SQLITE_OMIT_AUTOVACUUM
  if( idx==BTREE_LARGEST_ROOT_PAGE && *pMeta>0 ){
    pBt->btsFlags |= BTS_READ_ONLY;
  }
#endif

  sqlite4BtreeLeave(p);
}

/*
** Write meta-information back into the database.  Meta[0] is
** read-only and may not be written.
*/
int sqlite4BtreeUpdateMeta(Btree *p, int idx, u32 iMeta){
  BtShared *pBt = p->pBt;
  unsigned char *pP1;
  int rc;
  assert( idx>=1 && idx<=15 );
  sqlite4BtreeEnter(p);
  assert( p->inTrans==TRANS_WRITE );
  assert( pBt->pPage1!=0 );
  pP1 = pBt->pPage1->aData;
  rc = sqlite4PagerWrite(pBt->pPage1->pDbPage);
  if( rc==SQLITE_OK ){
    put4byte(&pP1[36 + idx*4], iMeta);
#ifndef SQLITE_OMIT_AUTOVACUUM
    if( idx==BTREE_INCR_VACUUM ){
      assert( pBt->autoVacuum || iMeta==0 );
      assert( iMeta==0 || iMeta==1 );
      pBt->incrVacuum = (u8)iMeta;
    }
#endif
  }
  sqlite4BtreeLeave(p);
  return rc;
}

#ifndef SQLITE_OMIT_BTREECOUNT
/*
** The first argument, pCur, is a cursor opened on some b-tree. Count the
** number of entries in the b-tree and write the result to *pnEntry.
**
** SQLITE_OK is returned if the operation is successfully executed. 
** Otherwise, if an error is encountered (i.e. an IO error or database
** corruption) an SQLite error code is returned.
*/
int sqlite4BtreeCount(BtCursor *pCur, i64 *pnEntry){
  i64 nEntry = 0;                      /* Value to return in *pnEntry */
  int rc;                              /* Return code */

  if( pCur->pgnoRoot==0 ){
    *pnEntry = 0;
    return SQLITE_OK;
  }
  rc = moveToRoot(pCur);

  /* Unless an error occurs, the following loop runs one iteration for each
  ** page in the B-Tree structure (not including overflow pages). 
  */
  while( rc==SQLITE_OK ){
    int iIdx;                          /* Index of child node in parent */
    MemPage *pPage;                    /* Current page of the b-tree */

    /* If this is a leaf page or the tree is not an int-key tree, then 
    ** this page contains countable entries. Increment the entry counter
    ** accordingly.
    */
    pPage = pCur->apPage[pCur->iPage];
    if( pPage->leaf || !pPage->intKey ){
      nEntry += pPage->nCell;
    }

    /* pPage is a leaf node. This loop navigates the cursor so that it 
    ** points to the first interior cell that it points to the parent of
    ** the next page in the tree that has not yet been visited. The
    ** pCur->aiIdx[pCur->iPage] value is set to the index of the parent cell
    ** of the page, or to the number of cells in the page if the next page
    ** to visit is the right-child of its parent.
    **
    ** If all pages in the tree have been visited, return SQLITE_OK to the
    ** caller.
    */
    if( pPage->leaf ){
      do {
        if( pCur->iPage==0 ){
          /* All pages of the b-tree have been visited. Return successfully. */
          *pnEntry = nEntry;
          return SQLITE_OK;
        }
        moveToParent(pCur);
      }while ( pCur->aiIdx[pCur->iPage]>=pCur->apPage[pCur->iPage]->nCell );

      pCur->aiIdx[pCur->iPage]++;
      pPage = pCur->apPage[pCur->iPage];
    }

    /* Descend to the child node of the cell that the cursor currently 
    ** points at. This is the right-child if (iIdx==pPage->nCell).
    */
    iIdx = pCur->aiIdx[pCur->iPage];
    if( iIdx==pPage->nCell ){
      rc = moveToChild(pCur, get4byte(&pPage->aData[pPage->hdrOffset+8]));
    }else{
      rc = moveToChild(pCur, get4byte(findCell(pPage, iIdx)));
    }
  }

  /* An error has occurred. Return an error code. */
  return rc;
}
#endif

/*
** Return the pager associated with a BTree.  This routine is used for
** testing and debugging only.
*/
Pager *sqlite4BtreePager(Btree *p){
  return p->pBt->pPager;
}

#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** Append a message to the error message string.
*/
static void checkAppendMsg(
  IntegrityCk *pCheck,
  char *zMsg1,
  const char *zFormat,
  ...
){
  va_list ap;
  if( !pCheck->mxErr ) return;
  pCheck->mxErr--;
  pCheck->nErr++;
  va_start(ap, zFormat);
  if( pCheck->errMsg.nChar ){
    sqlite4StrAccumAppend(&pCheck->errMsg, "\n", 1);
  }
  if( zMsg1 ){
    sqlite4StrAccumAppend(&pCheck->errMsg, zMsg1, -1);
  }
  sqlite4VXPrintf(&pCheck->errMsg, 1, zFormat, ap);
  va_end(ap);
  if( pCheck->errMsg.mallocFailed ){
    pCheck->mallocFailed = 1;
  }
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */

#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** Add 1 to the reference count for page iPage.  If this is the second
** reference to the page, add an error message to pCheck->zErrMsg.
** Return 1 if there are 2 ore more references to the page and 0 if
** if this is the first reference to the page.
**
** Also check that the page number is in bounds.
*/
static int checkRef(IntegrityCk *pCheck, Pgno iPage, char *zContext){
  if( iPage==0 ) return 1;
  if( iPage>pCheck->nPage ){
    checkAppendMsg(pCheck, zContext, "invalid page number %d", iPage);
    return 1;
  }
  if( pCheck->anRef[iPage]==1 ){
    checkAppendMsg(pCheck, zContext, "2nd reference to page %d", iPage);
    return 1;
  }
  return  (pCheck->anRef[iPage]++)>1;
}

#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** Check that the entry in the pointer-map for page iChild maps to 
** page iParent, pointer type ptrType. If not, append an error message
** to pCheck.
*/
static void checkPtrmap(
  IntegrityCk *pCheck,   /* Integrity check context */
  Pgno iChild,           /* Child page number */
  u8 eType,              /* Expected pointer map type */
  Pgno iParent,          /* Expected pointer map parent page number */
  char *zContext         /* Context description (used for error msg) */
){
  int rc;
  u8 ePtrmapType;
  Pgno iPtrmapParent;

  rc = ptrmapGet(pCheck->pBt, iChild, &ePtrmapType, &iPtrmapParent);
  if( rc!=SQLITE_OK ){
    if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ) pCheck->mallocFailed = 1;
    checkAppendMsg(pCheck, zContext, "Failed to read ptrmap key=%d", iChild);
    return;
  }

  if( ePtrmapType!=eType || iPtrmapParent!=iParent ){
    checkAppendMsg(pCheck, zContext, 
      "Bad ptr map entry key=%d expected=(%d,%d) got=(%d,%d)", 
      iChild, eType, iParent, ePtrmapType, iPtrmapParent);
  }
}
#endif

/*
** Check the integrity of the freelist or of an overflow page list.
** Verify that the number of pages on the list is N.
*/
static void checkList(
  IntegrityCk *pCheck,  /* Integrity checking context */
  int isFreeList,       /* True for a freelist.  False for overflow page list */
  int iPage,            /* Page number for first page in the list */
  int N,                /* Expected number of pages in the list */
  char *zContext        /* Context for error messages */
){
  int i;
  int expected = N;
  int iFirst = iPage;
  while( N-- > 0 && pCheck->mxErr ){
    DbPage *pOvflPage;
    unsigned char *pOvflData;
    if( iPage<1 ){
      checkAppendMsg(pCheck, zContext,
         "%d of %d pages missing from overflow list starting at %d",
          N+1, expected, iFirst);
      break;
    }
    if( checkRef(pCheck, iPage, zContext) ) break;
    if( sqlite4PagerGet(pCheck->pPager, (Pgno)iPage, &pOvflPage) ){
      checkAppendMsg(pCheck, zContext, "failed to get page %d", iPage);
      break;
    }
    pOvflData = (unsigned char *)sqlite4PagerGetData(pOvflPage);
    if( isFreeList ){
      int n = get4byte(&pOvflData[4]);
#ifndef SQLITE_OMIT_AUTOVACUUM
      if( pCheck->pBt->autoVacuum ){
        checkPtrmap(pCheck, iPage, PTRMAP_FREEPAGE, 0, zContext);
      }
#endif
      if( n>(int)pCheck->pBt->usableSize/4-2 ){
        checkAppendMsg(pCheck, zContext,
           "freelist leaf count too big on page %d", iPage);
        N--;
      }else{
        for(i=0; i<n; i++){
          Pgno iFreePage = get4byte(&pOvflData[8+i*4]);
#ifndef SQLITE_OMIT_AUTOVACUUM
          if( pCheck->pBt->autoVacuum ){
            checkPtrmap(pCheck, iFreePage, PTRMAP_FREEPAGE, 0, zContext);
          }
#endif
          checkRef(pCheck, iFreePage, zContext);
        }
        N -= n;
      }
    }
#ifndef SQLITE_OMIT_AUTOVACUUM
    else{
      /* If this database supports auto-vacuum and iPage is not the last
      ** page in this overflow list, check that the pointer-map entry for
      ** the following page matches iPage.
      */
      if( pCheck->pBt->autoVacuum && N>0 ){
        i = get4byte(pOvflData);
        checkPtrmap(pCheck, i, PTRMAP_OVERFLOW2, iPage, zContext);
      }
    }
#endif
    iPage = get4byte(pOvflData);
    sqlite4PagerUnref(pOvflPage);
  }
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */

#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** Do various sanity checks on a single page of a tree.  Return
** the tree depth.  Root pages return 0.  Parents of root pages
** return 1, and so forth.
** 
** These checks are done:
**
**      1.  Make sure that cells and freeblocks do not overlap
**          but combine to completely cover the page.
**  NO  2.  Make sure cell keys are in order.
**  NO  3.  Make sure no key is less than or equal to zLowerBound.
**  NO  4.  Make sure no key is greater than or equal to zUpperBound.
**      5.  Check the integrity of overflow pages.
**      6.  Recursively call checkTreePage on all children.
**      7.  Verify that the depth of all children is the same.
**      8.  Make sure this page is at least 33% full or else it is
**          the root of the tree.
*/
static int checkTreePage(
  IntegrityCk *pCheck,  /* Context for the sanity check */
  int iPage,            /* Page number of the page to check */
  char *zParentContext, /* Parent context */
  i64 *pnParentMinKey, 
  i64 *pnParentMaxKey
){
  MemPage *pPage;
  int i, rc, depth, d2, pgno, cnt;
  int hdr, cellStart;
  int nCell;
  u8 *data;
  BtShared *pBt;
  int usableSize;
  char zContext[100];
  char *hit = 0;
  i64 nMinKey = 0;
  i64 nMaxKey = 0;

  sqlite4_snprintf(sizeof(zContext), zContext, "Page %d: ", iPage);

  /* Check that the page exists
  */
  pBt = pCheck->pBt;
  usableSize = pBt->usableSize;
  if( iPage==0 ) return 0;
  if( checkRef(pCheck, iPage, zParentContext) ) return 0;
  if( (rc = btreeGetPage(pBt, (Pgno)iPage, &pPage, 0))!=0 ){
    checkAppendMsg(pCheck, zContext,
       "unable to get the page. error code=%d", rc);
    return 0;
  }

  /* Clear MemPage.isInit to make sure the corruption detection code in
  ** btreeInitPage() is executed.  */
  pPage->isInit = 0;
  if( (rc = btreeInitPage(pPage))!=0 ){
    assert( rc==SQLITE_CORRUPT );  /* The only possible error from InitPage */
    checkAppendMsg(pCheck, zContext, 
                   "btreeInitPage() returns error code %d", rc);
    releasePage(pPage);
    return 0;
  }

  /* Check out all the cells.
  */
  depth = 0;
  for(i=0; i<pPage->nCell && pCheck->mxErr; i++){
    u8 *pCell;
    u32 sz;
    CellInfo info;

    /* Check payload overflow pages
    */
    sqlite4_snprintf(sizeof(zContext), zContext,
             "On tree page %d cell %d: ", iPage, i);
    pCell = findCell(pPage,i);
    btreeParseCellPtr(pPage, pCell, &info);
    sz = info.nData;
    if( !pPage->intKey ) sz += (int)info.nKey;
    /* For intKey pages, check that the keys are in order.
    */
    else if( i==0 ) nMinKey = nMaxKey = info.nKey;
    else{
      if( info.nKey <= nMaxKey ){
        checkAppendMsg(pCheck, zContext, 
            "Rowid %lld out of order (previous was %lld)", info.nKey, nMaxKey);
      }
      nMaxKey = info.nKey;
    }
    assert( sz==info.nPayload );
    if( (sz>info.nLocal) 
     && (&pCell[info.iOverflow]<=&pPage->aData[pBt->usableSize])
    ){
      int nPage = (sz - info.nLocal + usableSize - 5)/(usableSize - 4);
      Pgno pgnoOvfl = get4byte(&pCell[info.iOverflow]);
#ifndef SQLITE_OMIT_AUTOVACUUM
      if( pBt->autoVacuum ){
        checkPtrmap(pCheck, pgnoOvfl, PTRMAP_OVERFLOW1, iPage, zContext);
      }
#endif
      checkList(pCheck, 0, pgnoOvfl, nPage, zContext);
    }

    /* Check sanity of left child page.
    */
    if( !pPage->leaf ){
      pgno = get4byte(pCell);
#ifndef SQLITE_OMIT_AUTOVACUUM
      if( pBt->autoVacuum ){
        checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage, zContext);
      }
#endif
      d2 = checkTreePage(pCheck, pgno, zContext, &nMinKey, i==0 ? NULL : &nMaxKey);
      if( i>0 && d2!=depth ){
        checkAppendMsg(pCheck, zContext, "Child page depth differs");
      }
      depth = d2;
    }
  }

  if( !pPage->leaf ){
    pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
    sqlite4_snprintf(sizeof(zContext), zContext, 
                     "On page %d at right child: ", iPage);
#ifndef SQLITE_OMIT_AUTOVACUUM
    if( pBt->autoVacuum ){
      checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage, zContext);
    }
#endif
    checkTreePage(pCheck, pgno, zContext, NULL, !pPage->nCell ? NULL : &nMaxKey);
  }
 
  /* For intKey leaf pages, check that the min/max keys are in order
  ** with any left/parent/right pages.
  */
  if( pPage->leaf && pPage->intKey ){
    /* if we are a left child page */
    if( pnParentMinKey ){
      /* if we are the left most child page */
      if( !pnParentMaxKey ){
        if( nMaxKey > *pnParentMinKey ){
          checkAppendMsg(pCheck, zContext, 
              "Rowid %lld out of order (max larger than parent min of %lld)",
              nMaxKey, *pnParentMinKey);
        }
      }else{
        if( nMinKey <= *pnParentMinKey ){
          checkAppendMsg(pCheck, zContext, 
              "Rowid %lld out of order (min less than parent min of %lld)",
              nMinKey, *pnParentMinKey);
        }
        if( nMaxKey > *pnParentMaxKey ){
          checkAppendMsg(pCheck, zContext, 
              "Rowid %lld out of order (max larger than parent max of %lld)",
              nMaxKey, *pnParentMaxKey);
        }
        *pnParentMinKey = nMaxKey;
      }
    /* else if we're a right child page */
    } else if( pnParentMaxKey ){
      if( nMinKey <= *pnParentMaxKey ){
        checkAppendMsg(pCheck, zContext, 
            "Rowid %lld out of order (min less than parent max of %lld)",
            nMinKey, *pnParentMaxKey);
      }
    }
  }

  /* Check for complete coverage of the page
  */
  data = pPage->aData;
  hdr = pPage->hdrOffset;
  hit = sqlite4PageMalloc( pBt->pageSize );
  if( hit==0 ){
    pCheck->mallocFailed = 1;
  }else{
    int contentOffset = get2byteNotZero(&data[hdr+5]);
    assert( contentOffset<=usableSize );  /* Enforced by btreeInitPage() */
    memset(hit+contentOffset, 0, usableSize-contentOffset);
    memset(hit, 1, contentOffset);
    nCell = get2byte(&data[hdr+3]);
    cellStart = hdr + 12 - 4*pPage->leaf;
    for(i=0; i<nCell; i++){
      int pc = get2byte(&data[cellStart+i*2]);
      u32 size = 65536;
      int j;
      if( pc<=usableSize-4 ){
        size = cellSizePtr(pPage, &data[pc]);
      }
      if( (int)(pc+size-1)>=usableSize ){
        checkAppendMsg(pCheck, 0, 
            "Corruption detected in cell %d on page %d",i,iPage);
      }else{
        for(j=pc+size-1; j>=pc; j--) hit[j]++;
      }
    }
    i = get2byte(&data[hdr+1]);
    while( i>0 ){
      int size, j;
      assert( i<=usableSize-4 );     /* Enforced by btreeInitPage() */
      size = get2byte(&data[i+2]);
      assert( i+size<=usableSize );  /* Enforced by btreeInitPage() */
      for(j=i+size-1; j>=i; j--) hit[j]++;
      j = get2byte(&data[i]);
      assert( j==0 || j>i+size );  /* Enforced by btreeInitPage() */
      assert( j<=usableSize-4 );   /* Enforced by btreeInitPage() */
      i = j;
    }
    for(i=cnt=0; i<usableSize; i++){
      if( hit[i]==0 ){
        cnt++;
      }else if( hit[i]>1 ){
        checkAppendMsg(pCheck, 0,
          "Multiple uses for byte %d of page %d", i, iPage);
        break;
      }
    }
    if( cnt!=data[hdr+7] ){
      checkAppendMsg(pCheck, 0, 
          "Fragmentation of %d bytes reported as %d on page %d",
          cnt, data[hdr+7], iPage);
    }
  }
  sqlite4PageFree(hit);
  releasePage(pPage);
  return depth+1;
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */

#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** This routine does a complete check of the given BTree file.  aRoot[] is
** an array of pages numbers were each page number is the root page of
** a table.  nRoot is the number of entries in aRoot.
**
** A read-only or read-write transaction must be opened before calling
** this function.
**
** Write the number of error seen in *pnErr.  Except for some memory
** allocation errors,  an error message held in memory obtained from
** malloc is returned if *pnErr is non-zero.  If *pnErr==0 then NULL is
** returned.  If a memory allocation error occurs, NULL is returned.
*/
char *sqlite4BtreeIntegrityCheck(
  Btree *p,     /* The btree to be checked */
  int *aRoot,   /* An array of root pages numbers for individual trees */
  int nRoot,    /* Number of entries in aRoot[] */
  int mxErr,    /* Stop reporting errors after this many */
  int *pnErr    /* Write number of errors seen to this variable */
){
  Pgno i;
  int nRef;
  IntegrityCk sCheck;
  BtShared *pBt = p->pBt;
  char zErr[100];

  sqlite4BtreeEnter(p);
  assert( p->inTrans>TRANS_NONE && pBt->inTransaction>TRANS_NONE );
  nRef = sqlite4PagerRefcount(pBt->pPager);
  sCheck.pBt = pBt;
  sCheck.pPager = pBt->pPager;
  sCheck.nPage = btreePagecount(sCheck.pBt);
  sCheck.mxErr = mxErr;
  sCheck.nErr = 0;
  sCheck.mallocFailed = 0;
  *pnErr = 0;
  if( sCheck.nPage==0 ){
    sqlite4BtreeLeave(p);
    return 0;
  }
  sCheck.anRef = sqlite4Malloc( (sCheck.nPage+1)*sizeof(sCheck.anRef[0]) );
  if( !sCheck.anRef ){
    *pnErr = 1;
    sqlite4BtreeLeave(p);
    return 0;
  }
  for(i=0; i<=sCheck.nPage; i++){ sCheck.anRef[i] = 0; }
  i = PENDING_BYTE_PAGE(pBt);
  if( i<=sCheck.nPage ){
    sCheck.anRef[i] = 1;
  }
  sqlite4StrAccumInit(&sCheck.errMsg, zErr, sizeof(zErr), 20000);
  sCheck.errMsg.useMalloc = 2;

  /* Check the integrity of the freelist
  */
  checkList(&sCheck, 1, get4byte(&pBt->pPage1->aData[32]),
            get4byte(&pBt->pPage1->aData[36]), "Main freelist: ");

  /* Check all the tables.
  */
  for(i=0; (int)i<nRoot && sCheck.mxErr; i++){
    if( aRoot[i]==0 ) continue;
#ifndef SQLITE_OMIT_AUTOVACUUM
    if( pBt->autoVacuum && aRoot[i]>1 ){
      checkPtrmap(&sCheck, aRoot[i], PTRMAP_ROOTPAGE, 0, 0);
    }
#endif
    checkTreePage(&sCheck, aRoot[i], "List of tree roots: ", NULL, NULL);
  }

  /* Make sure every page in the file is referenced
  */
  for(i=1; i<=sCheck.nPage && sCheck.mxErr; i++){
#ifdef SQLITE_OMIT_AUTOVACUUM
    if( sCheck.anRef[i]==0 ){
      checkAppendMsg(&sCheck, 0, "Page %d is never used", i);
    }
#else
    /* If the database supports auto-vacuum, make sure no tables contain
    ** references to pointer-map pages.
    */
    if( sCheck.anRef[i]==0 && 
       (PTRMAP_PAGENO(pBt, i)!=i || !pBt->autoVacuum) ){
      checkAppendMsg(&sCheck, 0, "Page %d is never used", i);
    }
    if( sCheck.anRef[i]!=0 && 
       (PTRMAP_PAGENO(pBt, i)==i && pBt->autoVacuum) ){
      checkAppendMsg(&sCheck, 0, "Pointer map page %d is referenced", i);
    }
#endif
  }

  /* Make sure this analysis did not leave any unref() pages.
  ** This is an internal consistency check; an integrity check
  ** of the integrity check.
  */
  if( NEVER(nRef != sqlite4PagerRefcount(pBt->pPager)) ){
    checkAppendMsg(&sCheck, 0, 
      "Outstanding page count goes from %d to %d during this analysis",
      nRef, sqlite4PagerRefcount(pBt->pPager)
    );
  }

  /* Clean  up and report errors.
  */
  sqlite4BtreeLeave(p);
  sqlite4_free(sCheck.anRef);
  if( sCheck.mallocFailed ){
    sqlite4StrAccumReset(&sCheck.errMsg);
    *pnErr = sCheck.nErr+1;
    return 0;
  }
  *pnErr = sCheck.nErr;
  if( sCheck.nErr==0 ) sqlite4StrAccumReset(&sCheck.errMsg);
  return sqlite4StrAccumFinish(&sCheck.errMsg);
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */

/*
** Return the full pathname of the underlying database file.
**
** The pager filename is invariant as long as the pager is
** open so it is safe to access without the BtShared mutex.
*/
const char *sqlite4BtreeGetFilename(Btree *p){
  assert( p->pBt->pPager!=0 );
  return sqlite4PagerFilename(p->pBt->pPager);
}

/*
** Return the pathname of the journal file for this database. The return
** value of this routine is the same regardless of whether the journal file
** has been created or not.
**
** The pager journal filename is invariant as long as the pager is
** open so it is safe to access without the BtShared mutex.
*/
const char *sqlite4BtreeGetJournalname(Btree *p){
  assert( p->pBt->pPager!=0 );
  return sqlite4PagerJournalname(p->pBt->pPager);
}

/*
** Return non-zero if a transaction is active.
*/
int sqlite4BtreeIsInTrans(Btree *p){
  assert( p==0 || sqlite4_mutex_held(p->db->mutex) );
  return (p && (p->inTrans==TRANS_WRITE));
}

#ifndef SQLITE_OMIT_WAL
/*
** Run a checkpoint on the Btree passed as the first argument.
**
** Return SQLITE_LOCKED if this or any other connection has an open 
** transaction on the shared-cache the argument Btree is connected to.
**
** Parameter eMode is one of SQLITE_CHECKPOINT_PASSIVE, FULL or RESTART.
*/
int sqlite4BtreeCheckpoint(Btree *p, int eMode, int *pnLog, int *pnCkpt){
  int rc = SQLITE_OK;
  if( p ){
    BtShared *pBt = p->pBt;
    sqlite4BtreeEnter(p);
    if( pBt->inTransaction!=TRANS_NONE ){
      rc = SQLITE_LOCKED;
    }else{
      rc = sqlite4PagerCheckpoint(pBt->pPager, eMode, pnLog, pnCkpt);
    }
    sqlite4BtreeLeave(p);
  }
  return rc;
}
#endif

/*
** Return non-zero if a read (or write) transaction is active.
*/
int sqlite4BtreeIsInReadTrans(Btree *p){
  assert( p );
  assert( sqlite4_mutex_held(p->db->mutex) );
  return p->inTrans!=TRANS_NONE;
}

int sqlite4BtreeIsInBackup(Btree *p){
  assert( p );
  assert( sqlite4_mutex_held(p->db->mutex) );
  return p->nBackup!=0;
}

/*
** This function returns a pointer to a blob of memory associated with
** a single shared-btree. The memory is used by client code for its own
** purposes (for example, to store a high-level schema associated with 
** the shared-btree). The btree layer manages reference counting issues.
**
** The first time this is called on a shared-btree, nBytes bytes of memory
** are allocated, zeroed, and returned to the caller. For each subsequent 
** call the nBytes parameter is ignored and a pointer to the same blob
** of memory returned. 
**
** If the nBytes parameter is 0 and the blob of memory has not yet been
** allocated, a null pointer is returned. If the blob has already been
** allocated, it is returned as normal.
**
** Just before the shared-btree is closed, the function passed as the 
** xFree argument when the memory allocation was made is invoked on the 
** blob of allocated memory. The xFree function should not call sqlite4_free()
** on the memory, the btree layer does that.
*/
void *sqlite4BtreeSchema(Btree *p, int nBytes, void(*xFree)(void *)){
  BtShared *pBt = p->pBt;
  sqlite4BtreeEnter(p);
  if( !pBt->pSchema && nBytes ){
    pBt->pSchema = sqlite4DbMallocZero(0, nBytes);
    pBt->xFreeSchema = xFree;
  }
  sqlite4BtreeLeave(p);
  return pBt->pSchema;
}

/*
** Return SQLITE_LOCKED_SHAREDCACHE if another user of the same shared 
** btree as the argument handle holds an exclusive lock on the 
** sqlite_master table. Otherwise SQLITE_OK.
*/
int sqlite4BtreeSchemaLocked(Btree *p){
  int rc;
  assert( sqlite4_mutex_held(p->db->mutex) );
  sqlite4BtreeEnter(p);
  rc = querySharedCacheTableLock(p, MASTER_ROOT, READ_LOCK);
  assert( rc==SQLITE_OK || rc==SQLITE_LOCKED_SHAREDCACHE );
  sqlite4BtreeLeave(p);
  return rc;
}


#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Obtain a lock on the table whose root page is iTab.  The
** lock is a write lock if isWritelock is true or a read lock
** if it is false.
*/
int sqlite4BtreeLockTable(Btree *p, int iTab, u8 isWriteLock){
  int rc = SQLITE_OK;
  assert( p->inTrans!=TRANS_NONE );
  if( p->sharable ){
    u8 lockType = READ_LOCK + isWriteLock;
    assert( READ_LOCK+1==WRITE_LOCK );
    assert( isWriteLock==0 || isWriteLock==1 );

    sqlite4BtreeEnter(p);
    rc = querySharedCacheTableLock(p, iTab, lockType);
    if( rc==SQLITE_OK ){
      rc = setSharedCacheTableLock(p, iTab, lockType);
    }
    sqlite4BtreeLeave(p);
  }
  return rc;
}
#endif

#ifndef SQLITE_OMIT_INCRBLOB
/*
** Argument pCsr must be a cursor opened for writing on an 
** INTKEY table currently pointing at a valid table entry. 
** This function modifies the data stored as part of that entry.
**
** Only the data content may only be modified, it is not possible to 
** change the length of the data stored. If this function is called with
** parameters that attempt to write past the end of the existing data,
** no modifications are made and SQLITE_CORRUPT is returned.
*/
int sqlite4BtreePutData(BtCursor *pCsr, u32 offset, u32 amt, void *z){
  int rc;
  assert( cursorHoldsMutex(pCsr) );
  assert( sqlite4_mutex_held(pCsr->pBtree->db->mutex) );
  assert( pCsr->isIncrblobHandle );

  rc = restoreCursorPosition(pCsr);
  if( rc!=SQLITE_OK ){
    return rc;
  }
  assert( pCsr->eState!=CURSOR_REQUIRESEEK );
  if( pCsr->eState!=CURSOR_VALID ){
    return SQLITE_ABORT;
  }

  /* Check some assumptions: 
  **   (a) the cursor is open for writing,
  **   (b) there is a read/write transaction open,
  **   (c) the connection holds a write-lock on the table (if required),
  **   (d) there are no conflicting read-locks, and
  **   (e) the cursor points at a valid row of an intKey table.
  */
  if( !pCsr->wrFlag ){
    return SQLITE_READONLY;
  }
  assert( (pCsr->pBt->btsFlags & BTS_READ_ONLY)==0
              && pCsr->pBt->inTransaction==TRANS_WRITE );
  assert( hasSharedCacheTableLock(pCsr->pBtree, pCsr->pgnoRoot, 0, 2) );
  assert( !hasReadConflicts(pCsr->pBtree, pCsr->pgnoRoot) );
  assert( pCsr->apPage[pCsr->iPage]->intKey );

  return accessPayload(pCsr, offset, amt, (unsigned char *)z, 1);
}

/* 
** Set a flag on this cursor to cache the locations of pages from the 
** overflow list for the current row. This is used by cursors opened
** for incremental blob IO only.
**
** This function sets a flag only. The actual page location cache
** (stored in BtCursor.aOverflow[]) is allocated and used by function
** accessPayload() (the worker function for sqlite4BtreeData() and
** sqlite4BtreePutData()).
*/
void sqlite4BtreeCacheOverflow(BtCursor *pCur){
  assert( cursorHoldsMutex(pCur) );
  assert( sqlite4_mutex_held(pCur->pBtree->db->mutex) );
  invalidateOverflowCache(pCur);
  pCur->isIncrblobHandle = 1;
}
#endif

/*
** Set both the "read version" (single byte at byte offset 18) and 
** "write version" (single byte at byte offset 19) fields in the database
** header to iVersion.
*/
int sqlite4BtreeSetVersion(Btree *pBtree, int iVersion){
  BtShared *pBt = pBtree->pBt;
  int rc;                         /* Return code */
 
  assert( iVersion==1 || iVersion==2 );

  /* If setting the version fields to 1, do not automatically open the
  ** WAL connection, even if the version fields are currently set to 2.
  */
  pBt->btsFlags &= ~BTS_NO_WAL;
  if( iVersion==1 ) pBt->btsFlags |= BTS_NO_WAL;

  rc = sqlite4BtreeBeginTrans(pBtree, 0);
  if( rc==SQLITE_OK ){
    u8 *aData = pBt->pPage1->aData;
    if( aData[18]!=(u8)iVersion || aData[19]!=(u8)iVersion ){
      rc = sqlite4BtreeBeginTrans(pBtree, 2);
      if( rc==SQLITE_OK ){
        rc = sqlite4PagerWrite(pBt->pPage1->pDbPage);
        if( rc==SQLITE_OK ){
          aData[18] = (u8)iVersion;
          aData[19] = (u8)iVersion;
        }
      }
    }
  }

  pBt->btsFlags &= ~BTS_NO_WAL;
  return rc;
}
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Deleted src/btree.h.

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/*
** 2001 September 15
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite B-Tree file
** subsystem.  See comments in the source code for a detailed description
** of what each interface routine does.
*/
#ifndef _BTREE_H_
#define _BTREE_H_

/* TODO: This definition is just included so other modules compile. It
** needs to be revisited.
*/
#define SQLITE_N_BTREE_META 10

/*
** If defined as non-zero, auto-vacuum is enabled by default. Otherwise
** it must be turned on for each database using "PRAGMA auto_vacuum = 1".
*/
#ifndef SQLITE_DEFAULT_AUTOVACUUM
  #define SQLITE_DEFAULT_AUTOVACUUM 0
#endif

#define BTREE_AUTOVACUUM_NONE 0        /* Do not do auto-vacuum */
#define BTREE_AUTOVACUUM_FULL 1        /* Do full auto-vacuum */
#define BTREE_AUTOVACUUM_INCR 2        /* Incremental vacuum */

/*
** Forward declarations of structure
*/
typedef struct Btree Btree;
typedef struct BtCursor BtCursor;
typedef struct BtShared BtShared;


int sqlite4BtreeOpen(
  sqlite4_vfs *pVfs,       /* VFS to use with this b-tree */
  const char *zFilename,   /* Name of database file to open */
  sqlite4 *db,             /* Associated database connection */
  Btree **ppBtree,         /* Return open Btree* here */
  int flags,               /* Flags */
  int vfsFlags             /* Flags passed through to VFS open */
);

/* The flags parameter to sqlite4BtreeOpen can be the bitwise or of the
** following values.
**
** NOTE:  These values must match the corresponding PAGER_ values in
** pager.h.
*/
#define BTREE_OMIT_JOURNAL  1  /* Do not create or use a rollback journal */
#define BTREE_MEMORY        2  /* This is an in-memory DB */
#define BTREE_SINGLE        4  /* The file contains at most 1 b-tree */
#define BTREE_UNORDERED     8  /* Use of a hash implementation is OK */

int sqlite4BtreeClose(Btree*);
int sqlite4BtreeSetCacheSize(Btree*,int);
int sqlite4BtreeSetSafetyLevel(Btree*,int,int,int);
int sqlite4BtreeSyncDisabled(Btree*);
int sqlite4BtreeSetPageSize(Btree *p, int nPagesize, int nReserve, int eFix);
int sqlite4BtreeGetPageSize(Btree*);
int sqlite4BtreeMaxPageCount(Btree*,int);
u32 sqlite4BtreeLastPage(Btree*);
int sqlite4BtreeSecureDelete(Btree*,int);
int sqlite4BtreeGetReserve(Btree*);
int sqlite4BtreeSetAutoVacuum(Btree *, int);
int sqlite4BtreeGetAutoVacuum(Btree *);
int sqlite4BtreeBeginTrans(Btree*,int);
int sqlite4BtreeCommitPhaseOne(Btree*, const char *zMaster);
int sqlite4BtreeCommitPhaseTwo(Btree*, int);
int sqlite4BtreeCommit(Btree*);
int sqlite4BtreeRollback(Btree*);
int sqlite4BtreeBeginStmt(Btree*,int);
int sqlite4BtreeCreateTable(Btree*, int*, int flags);
int sqlite4BtreeIsInTrans(Btree*);
int sqlite4BtreeIsInReadTrans(Btree*);
int sqlite4BtreeIsInBackup(Btree*);
void *sqlite4BtreeSchema(Btree *, int, void(*)(void *));
int sqlite4BtreeSchemaLocked(Btree *pBtree);
int sqlite4BtreeLockTable(Btree *pBtree, int iTab, u8 isWriteLock);
int sqlite4BtreeSavepoint(Btree *, int, int);

const char *sqlite4BtreeGetFilename(Btree *);
const char *sqlite4BtreeGetJournalname(Btree *);
int sqlite4BtreeCopyFile(Btree *, Btree *);

int sqlite4BtreeIncrVacuum(Btree *);

/* The flags parameter to sqlite4BtreeCreateTable can be the bitwise OR
** of the flags shown below.
**
** Every SQLite table must have either BTREE_INTKEY or BTREE_BLOBKEY set.
** With BTREE_INTKEY, the table key is a 64-bit integer and arbitrary data
** is stored in the leaves.  (BTREE_INTKEY is used for SQL tables.)  With
** BTREE_BLOBKEY, the key is an arbitrary BLOB and no content is stored
** anywhere - the key is the content.  (BTREE_BLOBKEY is used for SQL
** indices.)
*/
#define BTREE_INTKEY     1    /* Table has only 64-bit signed integer keys */
#define BTREE_BLOBKEY    2    /* Table has keys only - no data */

int sqlite4BtreeDropTable(Btree*, int, int*);
int sqlite4BtreeClearTable(Btree*, int, int*);
void sqlite4BtreeTripAllCursors(Btree*, int);

void sqlite4BtreeGetMeta(Btree *pBtree, int idx, u32 *pValue);
int sqlite4BtreeUpdateMeta(Btree*, int idx, u32 value);

/*
** The second parameter to sqlite4BtreeGetMeta or sqlite4BtreeUpdateMeta
** should be one of the following values. The integer values are assigned 
** to constants so that the offset of the corresponding field in an
** SQLite database header may be found using the following formula:
**
**   offset = 36 + (idx * 4)
**
** For example, the free-page-count field is located at byte offset 36 of
** the database file header. The incr-vacuum-flag field is located at
** byte offset 64 (== 36+4*7).
*/
#define BTREE_FREE_PAGE_COUNT     0
#define BTREE_SCHEMA_VERSION      1
#define BTREE_FILE_FORMAT         2
#define BTREE_DEFAULT_CACHE_SIZE  3
#define BTREE_LARGEST_ROOT_PAGE   4
#define BTREE_TEXT_ENCODING       5
#define BTREE_USER_VERSION        6
#define BTREE_INCR_VACUUM         7

int sqlite4BtreeCursor(
  Btree*,                              /* BTree containing table to open */
  int iTable,                          /* Index of root page */
  int wrFlag,                          /* 1 for writing.  0 for read-only */
  struct KeyInfo*,                     /* First argument to compare function */
  BtCursor *pCursor                    /* Space to write cursor structure */
);
int sqlite4BtreeCursorSize(void);
void sqlite4BtreeCursorZero(BtCursor*);

int sqlite4BtreeCloseCursor(BtCursor*);
int sqlite4BtreeMovetoUnpacked(
  BtCursor*,
  UnpackedRecord *pUnKey,
  i64 intKey,
  int bias,
  int *pRes
);
int sqlite4BtreeCursorHasMoved(BtCursor*, int*);
int sqlite4BtreeDelete(BtCursor*);
int sqlite4BtreeInsert(BtCursor*, const void *pKey, i64 nKey,
                                  const void *pData, int nData,
                                  int nZero, int bias, int seekResult);
int sqlite4BtreeFirst(BtCursor*, int *pRes);
int sqlite4BtreeLast(BtCursor*, int *pRes);
int sqlite4BtreeNext(BtCursor*, int *pRes);
int sqlite4BtreeEof(BtCursor*);
int sqlite4BtreePrevious(BtCursor*, int *pRes);
int sqlite4BtreeKeySize(BtCursor*, i64 *pSize);
int sqlite4BtreeKey(BtCursor*, u32 offset, u32 amt, void*);
const void *sqlite4BtreeKeyFetch(BtCursor*, int *pAmt);
const void *sqlite4BtreeDataFetch(BtCursor*, int *pAmt);
int sqlite4BtreeDataSize(BtCursor*, u32 *pSize);
int sqlite4BtreeData(BtCursor*, u32 offset, u32 amt, void*);
void sqlite4BtreeSetCachedRowid(BtCursor*, sqlite4_int64);
sqlite4_int64 sqlite4BtreeGetCachedRowid(BtCursor*);

char *sqlite4BtreeIntegrityCheck(Btree*, int *aRoot, int nRoot, int, int*);
struct Pager *sqlite4BtreePager(Btree*);

int sqlite4BtreePutData(BtCursor*, u32 offset, u32 amt, void*);
void sqlite4BtreeCacheOverflow(BtCursor *);
void sqlite4BtreeClearCursor(BtCursor *);

int sqlite4BtreeSetVersion(Btree *pBt, int iVersion);

#ifndef NDEBUG
int sqlite4BtreeCursorIsValid(BtCursor*);
#endif

#ifndef SQLITE_OMIT_BTREECOUNT
int sqlite4BtreeCount(BtCursor *, i64 *);
#endif

#ifdef SQLITE_TEST
int sqlite4BtreeCursorInfo(BtCursor*, int*, int);
void sqlite4BtreeCursorList(Btree*);
#endif

#ifndef SQLITE_OMIT_WAL
  int sqlite4BtreeCheckpoint(Btree*, int, int *, int *);
#endif

/*
** If we are not using shared cache, then there is no need to
** use mutexes to access the BtShared structures.  So make the
** Enter and Leave procedures no-ops.
*/
#ifndef SQLITE_OMIT_SHARED_CACHE
  void sqlite4BtreeEnter(Btree*);
  void sqlite4BtreeEnterAll(sqlite4*);
#else
# define sqlite4BtreeEnter(X) 
# define sqlite4BtreeEnterAll(X)
#endif

#if !defined(SQLITE_OMIT_SHARED_CACHE) && SQLITE_THREADSAFE
  int sqlite4BtreeSharable(Btree*);
  void sqlite4BtreeLeave(Btree*);
  void sqlite4BtreeEnterCursor(BtCursor*);
  void sqlite4BtreeLeaveCursor(BtCursor*);
  void sqlite4BtreeLeaveAll(sqlite4*);
#ifndef NDEBUG
  /* These routines are used inside assert() statements only. */
  int sqlite4BtreeHoldsMutex(Btree*);
  int sqlite4BtreeHoldsAllMutexes(sqlite4*);
  int sqlite4SchemaMutexHeld(sqlite4*,int,Schema*);
#endif
#else

# define sqlite4BtreeSharable(X) 0
# define sqlite4BtreeLeave(X)
# define sqlite4BtreeEnterCursor(X)
# define sqlite4BtreeLeaveCursor(X)
# define sqlite4BtreeLeaveAll(X)

# define sqlite4BtreeHoldsMutex(X) 1
# define sqlite4BtreeHoldsAllMutexes(X) 1
# define sqlite4SchemaMutexHeld(X,Y,Z) 1
#endif


#endif /* _BTREE_H_ */
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/*
** 2004 April 6
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
**
**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
**     "Sorting And Searching", pages 473-480. Addison-Wesley
**     Publishing Company, Reading, Massachusetts.
**
** The basic idea is that each page of the file contains N database
** entries and N+1 pointers to subpages.
**
**   ----------------------------------------------------------------
**   |  Ptr(0) | Key(0) | Ptr(1) | Key(1) | ... | Key(N-1) | Ptr(N) |
**   ----------------------------------------------------------------
**
** All of the keys on the page that Ptr(0) points to have values less
** than Key(0).  All of the keys on page Ptr(1) and its subpages have
** values greater than Key(0) and less than Key(1).  All of the keys
** on Ptr(N) and its subpages have values greater than Key(N-1).  And
** so forth.
**
** Finding a particular key requires reading O(log(M)) pages from the 
** disk where M is the number of entries in the tree.
**
** In this implementation, a single file can hold one or more separate 
** BTrees.  Each BTree is identified by the index of its root page.  The
** key and data for any entry are combined to form the "payload".  A
** fixed amount of payload can be carried directly on the database
** page.  If the payload is larger than the preset amount then surplus
** bytes are stored on overflow pages.  The payload for an entry
** and the preceding pointer are combined to form a "Cell".  Each 
** page has a small header which contains the Ptr(N) pointer and other
** information such as the size of key and data.
**
** FORMAT DETAILS
**
** The file is divided into pages.  The first page is called page 1,
** the second is page 2, and so forth.  A page number of zero indicates
** "no such page".  The page size can be any power of 2 between 512 and 65536.
** Each page can be either a btree page, a freelist page, an overflow
** page, or a pointer-map page.
**
** The first page is always a btree page.  The first 100 bytes of the first
** page contain a special header (the "file header") that describes the file.
** The format of the file header is as follows:
**
**   OFFSET   SIZE    DESCRIPTION
**      0      16     Header string: "SQLite format 4\000"
**     16       2     Page size in bytes.  
**     18       1     File format write version
**     19       1     File format read version
**     20       1     Bytes of unused space at the end of each page
**     21       1     Max embedded payload fraction
**     22       1     Min embedded payload fraction
**     23       1     Min leaf payload fraction
**     24       4     File change counter
**     28       4     Reserved for future use
**     32       4     First freelist page
**     36       4     Number of freelist pages in the file
**     40      60     15 4-byte meta values passed to higher layers
**
**     40       4     Schema cookie
**     44       4     File format of schema layer
**     48       4     Size of page cache
**     52       4     Largest root-page (auto/incr_vacuum)
**     56       4     1=UTF-8 2=UTF16le 3=UTF16be
**     60       4     User version
**     64       4     Incremental vacuum mode
**     68       4     unused
**     72       4     unused
**     76       4     unused
**
** All of the integer values are big-endian (most significant byte first).
**
** The file change counter is incremented when the database is changed
** This counter allows other processes to know when the file has changed
** and thus when they need to flush their cache.
**
** The max embedded payload fraction is the amount of the total usable
** space in a page that can be consumed by a single cell for standard
** B-tree (non-LEAFDATA) tables.  A value of 255 means 100%.  The default
** is to limit the maximum cell size so that at least 4 cells will fit
** on one page.  Thus the default max embedded payload fraction is 64.
**
** If the payload for a cell is larger than the max payload, then extra
** payload is spilled to overflow pages.  Once an overflow page is allocated,
** as many bytes as possible are moved into the overflow pages without letting
** the cell size drop below the min embedded payload fraction.
**
** The min leaf payload fraction is like the min embedded payload fraction
** except that it applies to leaf nodes in a LEAFDATA tree.  The maximum
** payload fraction for a LEAFDATA tree is always 100% (or 255) and it
** not specified in the header.
**
** Each btree pages is divided into three sections:  The header, the
** cell pointer array, and the cell content area.  Page 1 also has a 100-byte
** file header that occurs before the page header.
**
**      |----------------|
**      | file header    |   100 bytes.  Page 1 only.
**      |----------------|
**      | page header    |   8 bytes for leaves.  12 bytes for interior nodes
**      |----------------|
**      | cell pointer   |   |  2 bytes per cell.  Sorted order.
**      | array          |   |  Grows downward
**      |                |   v
**      |----------------|
**      | unallocated    |
**      | space          |
**      |----------------|   ^  Grows upwards
**      | cell content   |   |  Arbitrary order interspersed with freeblocks.
**      | area           |   |  and free space fragments.
**      |----------------|
**
** The page headers looks like this:
**
**   OFFSET   SIZE     DESCRIPTION
**      0       1      Flags. 1: intkey, 2: zerodata, 4: leafdata, 8: leaf
**      1       2      byte offset to the first freeblock
**      3       2      number of cells on this page
**      5       2      first byte of the cell content area
**      7       1      number of fragmented free bytes
**      8       4      Right child (the Ptr(N) value).  Omitted on leaves.
**
** The flags define the format of this btree page.  The leaf flag means that
** this page has no children.  The zerodata flag means that this page carries
** only keys and no data.  The intkey flag means that the key is a integer
** which is stored in the key size entry of the cell header rather than in
** the payload area.
**
** The cell pointer array begins on the first byte after the page header.
** The cell pointer array contains zero or more 2-byte numbers which are
** offsets from the beginning of the page to the cell content in the cell
** content area.  The cell pointers occur in sorted order.  The system strives
** to keep free space after the last cell pointer so that new cells can
** be easily added without having to defragment the page.
**
** Cell content is stored at the very end of the page and grows toward the
** beginning of the page.
**
** Unused space within the cell content area is collected into a linked list of
** freeblocks.  Each freeblock is at least 4 bytes in size.  The byte offset
** to the first freeblock is given in the header.  Freeblocks occur in
** increasing order.  Because a freeblock must be at least 4 bytes in size,
** any group of 3 or fewer unused bytes in the cell content area cannot
** exist on the freeblock chain.  A group of 3 or fewer free bytes is called
** a fragment.  The total number of bytes in all fragments is recorded.
** in the page header at offset 7.
**
**    SIZE    DESCRIPTION
**      2     Byte offset of the next freeblock
**      2     Bytes in this freeblock
**
** Cells are of variable length.  Cells are stored in the cell content area at
** the end of the page.  Pointers to the cells are in the cell pointer array
** that immediately follows the page header.  Cells is not necessarily
** contiguous or in order, but cell pointers are contiguous and in order.
**
** Cell content makes use of variable length integers.  A variable
** length integer is 1 to 9 bytes where the lower 7 bits of each 
** byte are used.  The integer consists of all bytes that have bit 8 set and
** the first byte with bit 8 clear.  The most significant byte of the integer
** appears first.  A variable-length integer may not be more than 9 bytes long.
** As a special case, all 8 bytes of the 9th byte are used as data.  This
** allows a 64-bit integer to be encoded in 9 bytes.
**
**    0x00                      becomes  0x00000000
**    0x7f                      becomes  0x0000007f
**    0x81 0x00                 becomes  0x00000080
**    0x82 0x00                 becomes  0x00000100
**    0x80 0x7f                 becomes  0x0000007f
**    0x8a 0x91 0xd1 0xac 0x78  becomes  0x12345678
**    0x81 0x81 0x81 0x81 0x01  becomes  0x10204081
**
** Variable length integers are used for rowids and to hold the number of
** bytes of key and data in a btree cell.
**
** The content of a cell looks like this:
**
**    SIZE    DESCRIPTION
**      4     Page number of the left child. Omitted if leaf flag is set.
**     var    Number of bytes of data. Omitted if the zerodata flag is set.
**     var    Number of bytes of key. Or the key itself if intkey flag is set.
**      *     Payload
**      4     First page of the overflow chain.  Omitted if no overflow
**
** Overflow pages form a linked list.  Each page except the last is completely
** filled with data (pagesize - 4 bytes).  The last page can have as little
** as 1 byte of data.
**
**    SIZE    DESCRIPTION
**      4     Page number of next overflow page
**      *     Data
**
** Freelist pages come in two subtypes: trunk pages and leaf pages.  The
** file header points to the first in a linked list of trunk page.  Each trunk
** page points to multiple leaf pages.  The content of a leaf page is
** unspecified.  A trunk page looks like this:
**
**    SIZE    DESCRIPTION
**      4     Page number of next trunk page
**      4     Number of leaf pointers on this page
**      *     zero or more pages numbers of leaves
*/
#include "sqliteInt.h"


/* The following value is the maximum cell size assuming a maximum page
** size give above.
*/
#define MX_CELL_SIZE(pBt)  ((int)(pBt->pageSize-8))

/* The maximum number of cells on a single page of the database.  This
** assumes a minimum cell size of 6 bytes  (4 bytes for the cell itself
** plus 2 bytes for the index to the cell in the page header).  Such
** small cells will be rare, but they are possible.
*/
#define MX_CELL(pBt) ((pBt->pageSize-8)/6)

/* Forward declarations */
typedef struct MemPage MemPage;
typedef struct BtLock BtLock;

/*
** This is a magic string that appears at the beginning of every
** SQLite database in order to identify the file as a real database.
**
** You can change this value at compile-time by specifying a
** -DSQLITE_FILE_HEADER="..." on the compiler command-line.  The
** header must be exactly 16 bytes including the zero-terminator so
** the string itself should be 15 characters long.  If you change
** the header, then your custom library will not be able to read 
** databases generated by the standard tools and the standard tools
** will not be able to read databases created by your custom library.
*/
#ifndef SQLITE_FILE_HEADER /* 123456789 123456 */
#  define SQLITE_FILE_HEADER "SQLite format 4"
#endif

/*
** Page type flags.  An ORed combination of these flags appear as the
** first byte of on-disk image of every BTree page.
*/
#define PTF_INTKEY    0x01
#define PTF_ZERODATA  0x02
#define PTF_LEAFDATA  0x04
#define PTF_LEAF      0x08

/*
** As each page of the file is loaded into memory, an instance of the following
** structure is appended and initialized to zero.  This structure stores
** information about the page that is decoded from the raw file page.
**
** The pParent field points back to the parent page.  This allows us to
** walk up the BTree from any leaf to the root.  Care must be taken to
** unref() the parent page pointer when this page is no longer referenced.
** The pageDestructor() routine handles that chore.
**
** Access to all fields of this structure is controlled by the mutex
** stored in MemPage.pBt->mutex.
*/
struct MemPage {
  u8 isInit;           /* True if previously initialized. MUST BE FIRST! */
  u8 nOverflow;        /* Number of overflow cell bodies in aCell[] */
  u8 intKey;           /* True if intkey flag is set */
  u8 leaf;             /* True if leaf flag is set */
  u8 hasData;          /* True if this page stores data */
  u8 hdrOffset;        /* 100 for page 1.  0 otherwise */
  u8 childPtrSize;     /* 0 if leaf==1.  4 if leaf==0 */
  u8 max1bytePayload;  /* min(maxLocal,127) */
  u16 maxLocal;        /* Copy of BtShared.maxLocal or BtShared.maxLeaf */
  u16 minLocal;        /* Copy of BtShared.minLocal or BtShared.minLeaf */
  u16 cellOffset;      /* Index in aData of first cell pointer */
  u16 nFree;           /* Number of free bytes on the page */
  u16 nCell;           /* Number of cells on this page, local and ovfl */
  u16 maskPage;        /* Mask for page offset */
  struct _OvflCell {   /* Cells that will not fit on aData[] */
    u8 *pCell;          /* Pointers to the body of the overflow cell */
    u16 idx;            /* Insert this cell before idx-th non-overflow cell */
  } aOvfl[5];
  BtShared *pBt;       /* Pointer to BtShared that this page is part of */
  u8 *aData;           /* Pointer to disk image of the page data */
  u8 *aDataEnd;        /* One byte past the end of usable data */
  u8 *aCellIdx;        /* The cell index area */
  DbPage *pDbPage;     /* Pager page handle */
  Pgno pgno;           /* Page number for this page */
};

/*
** The in-memory image of a disk page has the auxiliary information appended
** to the end.  EXTRA_SIZE is the number of bytes of space needed to hold
** that extra information.
*/
#define EXTRA_SIZE sizeof(MemPage)

/*
** A linked list of the following structures is stored at BtShared.pLock.
** Locks are added (or upgraded from READ_LOCK to WRITE_LOCK) when a cursor 
** is opened on the table with root page BtShared.iTable. Locks are removed
** from this list when a transaction is committed or rolled back, or when
** a btree handle is closed.
*/
struct BtLock {
  Btree *pBtree;        /* Btree handle holding this lock */
  Pgno iTable;          /* Root page of table */
  u8 eLock;             /* READ_LOCK or WRITE_LOCK */
  BtLock *pNext;        /* Next in BtShared.pLock list */
};

/* Candidate values for BtLock.eLock */
#define READ_LOCK     1
#define WRITE_LOCK    2

/* A Btree handle
**
** A database connection contains a pointer to an instance of
** this object for every database file that it has open.  This structure
** is opaque to the database connection.  The database connection cannot
** see the internals of this structure and only deals with pointers to
** this structure.
**
** For some database files, the same underlying database cache might be 
** shared between multiple connections.  In that case, each connection
** has it own instance of this object.  But each instance of this object
** points to the same BtShared object.  The database cache and the
** schema associated with the database file are all contained within
** the BtShared object.
**
** All fields in this structure are accessed under sqlite4.mutex.
** The pBt pointer itself may not be changed while there exists cursors 
** in the referenced BtShared that point back to this Btree since those
** cursors have to go through this Btree to find their BtShared and
** they often do so without holding sqlite4.mutex.
*/
struct Btree {
  sqlite4 *db;       /* The database connection holding this btree */
  BtShared *pBt;     /* Sharable content of this btree */
  u8 inTrans;        /* TRANS_NONE, TRANS_READ or TRANS_WRITE */
  u8 sharable;       /* True if we can share pBt with another db */
  u8 locked;         /* True if db currently has pBt locked */
  int wantToLock;    /* Number of nested calls to sqlite4BtreeEnter() */
  int nBackup;       /* Number of backup operations reading this btree */
  Btree *pNext;      /* List of other sharable Btrees from the same db */
  Btree *pPrev;      /* Back pointer of the same list */
#ifndef SQLITE_OMIT_SHARED_CACHE
  BtLock lock;       /* Object used to lock page 1 */
#endif
};

/*
** Btree.inTrans may take one of the following values.
**
** If the shared-data extension is enabled, there may be multiple users
** of the Btree structure. At most one of these may open a write transaction,
** but any number may have active read transactions.
*/
#define TRANS_NONE  0
#define TRANS_READ  1
#define TRANS_WRITE 2

/*
** An instance of this object represents a single database file.
** 
** A single database file can be in use at the same time by two
** or more database connections.  When two or more connections are
** sharing the same database file, each connection has it own
** private Btree object for the file and each of those Btrees points
** to this one BtShared object.  BtShared.nRef is the number of
** connections currently sharing this database file.
**
** Fields in this structure are accessed under the BtShared.mutex
** mutex, except for nRef and pNext which are accessed under the
** global SQLITE_MUTEX_STATIC_MASTER mutex.  The pPager field
** may not be modified once it is initially set as long as nRef>0.
** The pSchema field may be set once under BtShared.mutex and
** thereafter is unchanged as long as nRef>0.
**
** isPending:
**
**   If a BtShared client fails to obtain a write-lock on a database
**   table (because there exists one or more read-locks on the table),
**   the shared-cache enters 'pending-lock' state and isPending is
**   set to true.
**
**   The shared-cache leaves the 'pending lock' state when either of
**   the following occur:
**
**     1) The current writer (BtShared.pWriter) concludes its transaction, OR
**     2) The number of locks held by other connections drops to zero.
**
**   while in the 'pending-lock' state, no connection may start a new
**   transaction.
**
**   This feature is included to help prevent writer-starvation.
*/
struct BtShared {
  Pager *pPager;        /* The page cache */
  sqlite4 *db;          /* Database connection currently using this Btree */
  BtCursor *pCursor;    /* A list of all open cursors */
  MemPage *pPage1;      /* First page of the database */
  u8 openFlags;         /* Flags to sqlite4BtreeOpen() */
#ifndef SQLITE_OMIT_AUTOVACUUM
  u8 autoVacuum;        /* True if auto-vacuum is enabled */
  u8 incrVacuum;        /* True if incr-vacuum is enabled */
#endif
  u8 inTransaction;     /* Transaction state */
  u8 max1bytePayload;   /* Maximum first byte of cell for a 1-byte payload */
  u16 btsFlags;         /* Boolean parameters.  See BTS_* macros below */
  u16 maxLocal;         /* Maximum local payload in non-LEAFDATA tables */
  u16 minLocal;         /* Minimum local payload in non-LEAFDATA tables */
  u16 maxLeaf;          /* Maximum local payload in a LEAFDATA table */
  u16 minLeaf;          /* Minimum local payload in a LEAFDATA table */
  u32 pageSize;         /* Total number of bytes on a page */
  u32 usableSize;       /* Number of usable bytes on each page */
  int nTransaction;     /* Number of open transactions (read + write) */
  u32 nPage;            /* Number of pages in the database */
  void *pSchema;        /* Pointer to space allocated by sqlite4BtreeSchema() */
  void (*xFreeSchema)(void*);  /* Destructor for BtShared.pSchema */
  sqlite4_mutex *mutex; /* Non-recursive mutex required to access this object */
  Bitvec *pHasContent;  /* Set of pages moved to free-list this transaction */
#ifndef SQLITE_OMIT_SHARED_CACHE
  int nRef;             /* Number of references to this structure */
  BtShared *pNext;      /* Next on a list of sharable BtShared structs */
  BtLock *pLock;        /* List of locks held on this shared-btree struct */
  Btree *pWriter;       /* Btree with currently open write transaction */
#endif
  u8 *pTmpSpace;        /* BtShared.pageSize bytes of space for tmp use */
};

/*
** Allowed values for BtShared.btsFlags
*/
#define BTS_READ_ONLY        0x0001   /* Underlying file is readonly */
#define BTS_PAGESIZE_FIXED   0x0002   /* Page size can no longer be changed */
#define BTS_SECURE_DELETE    0x0004   /* PRAGMA secure_delete is enabled */
#define BTS_INITIALLY_EMPTY  0x0008   /* Database was empty at trans start */
#define BTS_NO_WAL           0x0010   /* Do not open write-ahead-log files */
#define BTS_EXCLUSIVE        0x0020   /* pWriter has an exclusive lock */
#define BTS_PENDING          0x0040   /* Waiting for read-locks to clear */

/*
** An instance of the following structure is used to hold information
** about a cell.  The parseCellPtr() function fills in this structure
** based on information extract from the raw disk page.
*/
typedef struct CellInfo CellInfo;
struct CellInfo {
  i64 nKey;      /* The key for INTKEY tables, or number of bytes in key */
  u8 *pCell;     /* Pointer to the start of cell content */
  u32 nData;     /* Number of bytes of data */
  u32 nPayload;  /* Total amount of payload */
  u16 nHeader;   /* Size of the cell content header in bytes */
  u16 nLocal;    /* Amount of payload held locally */
  u16 iOverflow; /* Offset to overflow page number.  Zero if no overflow */
  u16 nSize;     /* Size of the cell content on the main b-tree page */
};

/*
** Maximum depth of an SQLite B-Tree structure. Any B-Tree deeper than
** this will be declared corrupt. This value is calculated based on a
** maximum database size of 2^31 pages a minimum fanout of 2 for a
** root-node and 3 for all other internal nodes.
**
** If a tree that appears to be taller than this is encountered, it is
** assumed that the database is corrupt.
*/
#define BTCURSOR_MAX_DEPTH 20

/*
** A cursor is a pointer to a particular entry within a particular
** b-tree within a database file.
**
** The entry is identified by its MemPage and the index in
** MemPage.aCell[] of the entry.
**
** A single database file can be shared by two more database connections,
** but cursors cannot be shared.  Each cursor is associated with a
** particular database connection identified BtCursor.pBtree.db.
**
** Fields in this structure are accessed under the BtShared.mutex
** found at self->pBt->mutex. 
*/
struct BtCursor {
  Btree *pBtree;            /* The Btree to which this cursor belongs */
  BtShared *pBt;            /* The BtShared this cursor points to */
  BtCursor *pNext, *pPrev;  /* Forms a linked list of all cursors */
  struct KeyInfo *pKeyInfo; /* Argument passed to comparison function */
  Pgno pgnoRoot;            /* The root page of this tree */
  sqlite4_int64 cachedRowid; /* Next rowid cache.  0 means not valid */
  CellInfo info;            /* A parse of the cell we are pointing at */
  i64 nKey;        /* Size of pKey, or last integer key */
  void *pKey;      /* Saved key that was cursor's last known position */
  int skipNext;    /* Prev() is noop if negative. Next() is noop if positive */
  u8 wrFlag;                /* True if writable */
  u8 atLast;                /* Cursor pointing to the last entry */
  u8 validNKey;             /* True if info.nKey is valid */
  u8 eState;                /* One of the CURSOR_XXX constants (see below) */
#ifndef SQLITE_OMIT_INCRBLOB
  Pgno *aOverflow;          /* Cache of overflow page locations */
  u8 isIncrblobHandle;      /* True if this cursor is an incr. io handle */
#endif
  i16 iPage;                            /* Index of current page in apPage */
  u16 aiIdx[BTCURSOR_MAX_DEPTH];        /* Current index in apPage[i] */
  MemPage *apPage[BTCURSOR_MAX_DEPTH];  /* Pages from root to current page */
};

/*
** Potential values for BtCursor.eState.
**
** CURSOR_VALID:
**   Cursor points to a valid entry. getPayload() etc. may be called.
**
** CURSOR_INVALID:
**   Cursor does not point to a valid entry. This can happen (for example) 
**   because the table is empty or because BtreeCursorFirst() has not been
**   called.
**
** CURSOR_REQUIRESEEK:
**   The table that this cursor was opened on still exists, but has been 
**   modified since the cursor was last used. The cursor position is saved
**   in variables BtCursor.pKey and BtCursor.nKey. When a cursor is in 
**   this state, restoreCursorPosition() can be called to attempt to
**   seek the cursor to the saved position.
**
** CURSOR_FAULT:
**   A unrecoverable error (an I/O error or a malloc failure) has occurred
**   on a different connection that shares the BtShared cache with this
**   cursor.  The error has left the cache in an inconsistent state.
**   Do nothing else with this cursor.  Any attempt to use the cursor
**   should return the error code stored in BtCursor.skip
*/
#define CURSOR_INVALID           0
#define CURSOR_VALID             1
#define CURSOR_REQUIRESEEK       2
#define CURSOR_FAULT             3

/* 
** The database page the PENDING_BYTE occupies. This page is never used.
*/
# define PENDING_BYTE_PAGE(pBt) PAGER_MJ_PGNO(pBt)

/*
** These macros define the location of the pointer-map entry for a 
** database page. The first argument to each is the number of usable
** bytes on each page of the database (often 1024). The second is the
** page number to look up in the pointer map.
**
** PTRMAP_PAGENO returns the database page number of the pointer-map
** page that stores the required pointer. PTRMAP_PTROFFSET returns
** the offset of the requested map entry.
**
** If the pgno argument passed to PTRMAP_PAGENO is a pointer-map page,
** then pgno is returned. So (pgno==PTRMAP_PAGENO(pgsz, pgno)) can be
** used to test if pgno is a pointer-map page. PTRMAP_ISPAGE implements
** this test.
*/
#define PTRMAP_PAGENO(pBt, pgno) ptrmapPageno(pBt, pgno)
#define PTRMAP_PTROFFSET(pgptrmap, pgno) (5*(pgno-pgptrmap-1))
#define PTRMAP_ISPAGE(pBt, pgno) (PTRMAP_PAGENO((pBt),(pgno))==(pgno))

/*
** The pointer map is a lookup table that identifies the parent page for
** each child page in the database file.  The parent page is the page that
** contains a pointer to the child.  Every page in the database contains
** 0 or 1 parent pages.  (In this context 'database page' refers
** to any page that is not part of the pointer map itself.)  Each pointer map
** entry consists of a single byte 'type' and a 4 byte parent page number.
** The PTRMAP_XXX identifiers below are the valid types.
**
** The purpose of the pointer map is to facility moving pages from one
** position in the file to another as part of autovacuum.  When a page
** is moved, the pointer in its parent must be updated to point to the
** new location.  The pointer map is used to locate the parent page quickly.
**
** PTRMAP_ROOTPAGE: The database page is a root-page. The page-number is not
**                  used in this case.
**
** PTRMAP_FREEPAGE: The database page is an unused (free) page. The page-number 
**                  is not used in this case.
**
** PTRMAP_OVERFLOW1: The database page is the first page in a list of 
**                   overflow pages. The page number identifies the page that
**                   contains the cell with a pointer to this overflow page.
**
** PTRMAP_OVERFLOW2: The database page is the second or later page in a list of
**                   overflow pages. The page-number identifies the previous
**                   page in the overflow page list.
**
** PTRMAP_BTREE: The database page is a non-root btree page. The page number
**               identifies the parent page in the btree.
*/
#define PTRMAP_ROOTPAGE 1
#define PTRMAP_FREEPAGE 2
#define PTRMAP_OVERFLOW1 3
#define PTRMAP_OVERFLOW2 4
#define PTRMAP_BTREE 5

/* A bunch of assert() statements to check the transaction state variables
** of handle p (type Btree*) are internally consistent.
*/
#define btreeIntegrity(p) \
  assert( p->pBt->inTransaction!=TRANS_NONE || p->pBt->nTransaction==0 ); \
  assert( p->pBt->inTransaction>=p->inTrans ); 


/*
** The ISAUTOVACUUM macro is used within balance_nonroot() to determine
** if the database supports auto-vacuum or not. Because it is used
** within an expression that is an argument to another macro 
** (sqliteMallocRaw), it is not possible to use conditional compilation.
** So, this macro is defined instead.
*/
#ifndef SQLITE_OMIT_AUTOVACUUM
#define ISAUTOVACUUM (pBt->autoVacuum)
#else
#define ISAUTOVACUUM 0
#endif


/*
** This structure is passed around through all the sanity checking routines
** in order to keep track of some global state information.
*/
typedef struct IntegrityCk IntegrityCk;
struct IntegrityCk {
  BtShared *pBt;    /* The tree being checked out */
  Pager *pPager;    /* The associated pager.  Also accessible by pBt->pPager */
  Pgno nPage;       /* Number of pages in the database */
  int *anRef;       /* Number of times each page is referenced */
  int mxErr;        /* Stop accumulating errors when this reaches zero */
  int nErr;         /* Number of messages written to zErrMsg so far */
  int mallocFailed; /* A memory allocation error has occurred */
  StrAccum errMsg;  /* Accumulate the error message text here */
};

/*
** Routines to read or write a two- and four-byte big-endian integer values.
*/
#define get2byte(x)   ((x)[0]<<8 | (x)[1])
#define put2byte(p,v) ((p)[0] = (u8)((v)>>8), (p)[1] = (u8)(v))
#define get4byte sqlite4Get4byte
#define put4byte sqlite4Put4byte
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554
555
556
557
558
559
560
561
562
563
564
565
566
...
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897



898
899
900
901
902
903
904
....
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
....
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
....
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
....
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
....
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
....
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
....
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
....
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
....
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
....
3320
3321
3322
3323
3324
3325
3326
3327
3328
3329
3330
3331
3332
3333
3334
3335
3336
3337
3338
3339
3340
3341
3342
3343
....
3395
3396
3397
3398
3399
3400
3401
3402
3403
3404
3405
3406
3407
3408
3409
3410

3411
3412


3413
3414
3415
3416
3417
3418
3419
3420
3421
3422
3423
3424
3425
3426
3427
3428
3429
3430
3431
3432
....
3458
3459
3460
3461
3462
3463
3464
3465
3466
3467
3468
3469
3470
3471
3472
3473
3474
....
3481
3482
3483
3484
3485
3486
3487
3488
3489
3490
3491
3492
3493
3494
3495
....
3603
3604
3605
3606
3607
3608
3609
3610
3611
3612
3613
3614
3615
3616
3617
    */
    if( pParse->cookieGoto>0 ){
      yDbMask mask;
      int iDb;
      sqlite4VdbeJumpHere(v, pParse->cookieGoto-1);
      for(iDb=0, mask=1; iDb<db->nDb; mask<<=1, iDb++){
        if( (mask & pParse->cookieMask)==0 ) continue;
        sqlite4VdbeUsesBtree(v, iDb);
        sqlite4VdbeAddOp2(v,OP_Transaction, iDb, (mask & pParse->writeMask)!=0);
        if( db->init.busy==0 ){
          assert( sqlite4SchemaMutexHeld(db, iDb, 0) );
          sqlite4VdbeAddOp3(v, OP_VerifyCookie,
                            iDb, pParse->cookieValue[iDb],
                            db->aDb[iDb].pSchema->iGeneration);
        }
      }
#ifndef SQLITE_OMIT_VIRTUALTABLE
      {
................................................................................
Table *sqlite4FindTable(sqlite4 *db, const char *zName, const char *zDatabase){
  Table *p = 0;
  int i;
  int nName;
  assert( zName!=0 );
  nName = sqlite4Strlen30(zName);
  /* All mutexes are required for schema access.  Make sure we hold them. */
  assert( zDatabase!=0 || sqlite4BtreeHoldsAllMutexes(db) );
  for(i=OMIT_TEMPDB; i<db->nDb; i++){
    int j = (i<2) ? i^1 : i;   /* Search TEMP before MAIN */
    if( zDatabase!=0 && sqlite4StrICmp(zDatabase, db->aDb[j].zName) ) continue;
    assert( sqlite4SchemaMutexHeld(db, j, 0) );
    p = sqlite4HashFind(&db->aDb[j].pSchema->tblHash, zName, nName);
    if( p ) break;
  }
  return p;
}

/*
................................................................................
** using the ATTACH command.
*/
Index *sqlite4FindIndex(sqlite4 *db, const char *zName, const char *zDb){
  Index *p = 0;
  int i;
  int nName = sqlite4Strlen30(zName);
  /* All mutexes are required for schema access.  Make sure we hold them. */
  assert( zDb!=0 || sqlite4BtreeHoldsAllMutexes(db) );
  for(i=OMIT_TEMPDB; i<db->nDb; i++){
    int j = (i<2) ? i^1 : i;  /* Search TEMP before MAIN */
    Schema *pSchema = db->aDb[j].pSchema;
    assert( pSchema );
    if( zDb && sqlite4StrICmp(zDb, db->aDb[j].zName) ) continue;
    assert( sqlite4SchemaMutexHeld(db, j, 0) );
    p = sqlite4HashFind(&pSchema->idxHash, zName, nName);
    if( p ) break;
  }
  return p;
}

/*
................................................................................
** with the index.
*/
void sqlite4UnlinkAndDeleteIndex(sqlite4 *db, int iDb, const char *zIdxName){
  Index *pIndex;
  int len;
  Hash *pHash;

  assert( sqlite4SchemaMutexHeld(db, iDb, 0) );
  pHash = &db->aDb[iDb].pSchema->idxHash;
  len = sqlite4Strlen30(zIdxName);
  pIndex = sqlite4HashInsert(pHash, zIdxName, len, 0);
  if( ALWAYS(pIndex) ){
    if( pIndex->pTable->pIndex==pIndex ){
      pIndex->pTable->pIndex = pIndex->pNext;
    }else{
................................................................................
void sqlite4ResetInternalSchema(sqlite4 *db, int iDb){
  int i, j;
  assert( iDb<db->nDb );

  if( iDb>=0 ){
    /* Case 1:  Reset the single schema identified by iDb */
    Db *pDb = &db->aDb[iDb];
    assert( sqlite4SchemaMutexHeld(db, iDb, 0) );
    assert( pDb->pSchema!=0 );
    sqlite4SchemaClear(pDb->pSchema);

    /* If any database other than TEMP is reset, then also reset TEMP
    ** since TEMP might be holding triggers that reference tables in the
    ** other database.
    */
................................................................................
      sqlite4SchemaClear(pDb->pSchema);
    }
    return;
  }
  /* Case 2 (from here to the end): Reset all schemas for all attached
  ** databases. */
  assert( iDb<0 );
  sqlite4BtreeEnterAll(db);
  for(i=0; i<db->nDb; i++){
    Db *pDb = &db->aDb[i];
    if( pDb->pSchema ){
      sqlite4SchemaClear(pDb->pSchema);
    }
  }
  db->flags &= ~SQLITE_InternChanges;
  sqlite4VtabUnlockList(db);
  sqlite4BtreeLeaveAll(db);

  /* If one or more of the auxiliary database files has been closed,
  ** then remove them from the auxiliary database list.  We take the
  ** opportunity to do this here since we have just deleted all of the
  ** schema hash tables and therefore do not have to make any changes
  ** to any of those tables.
  */
  for(i=j=2; i<db->nDb; i++){
    struct Db *pDb = &db->aDb[i];
    if( pDb->pBt==0 ){
      sqlite4DbFree(db, pDb->zName);
      pDb->zName = 0;
      continue;
    }
    if( j<i ){
      db->aDb[j] = db->aDb[i];
    }
................................................................................
    pNext = pIndex->pNext;
    assert( pIndex->pSchema==pTable->pSchema );
    if( !db || db->pnBytesFreed==0 ){
      char *zName = pIndex->zName; 
      TESTONLY ( Index *pOld = ) sqlite4HashInsert(
	  &pIndex->pSchema->idxHash, zName, sqlite4Strlen30(zName), 0
      );
      assert( db==0 || sqlite4SchemaMutexHeld(db, 0, pIndex->pSchema) );
      assert( pOld==pIndex || pOld==0 );
    }
    freeIndex(db, pIndex);
  }

  /* Delete any foreign keys attached to this table. */
  sqlite4FkDelete(db, pTable);
................................................................................
void sqlite4UnlinkAndDeleteTable(sqlite4 *db, int iDb, const char *zTabName){
  Table *p;
  Db *pDb;

  assert( db!=0 );
  assert( iDb>=0 && iDb<db->nDb );
  assert( zTabName );
  assert( sqlite4SchemaMutexHeld(db, iDb, 0) );
  testcase( zTabName[0]==0 );  /* Zero-length table names are allowed */
  pDb = &db->aDb[iDb];
  p = sqlite4HashInsert(&pDb->pSchema->tblHash, zTabName,
                        sqlite4Strlen30(zTabName),0);
  sqlite4DeleteTable(db, p);
  db->flags |= SQLITE_InternChanges;
}
................................................................................

  /* If this is the magic sqlite_sequence table used by autoincrement,
  ** then record a pointer to this table in the main database structure
  ** so that INSERT can find the table easily.
  */
#ifndef SQLITE_OMIT_AUTOINCREMENT
  if( !pParse->nested && strcmp(zName, "sqlite_sequence")==0 ){
    assert( sqlite4SchemaMutexHeld(db, iDb, 0) );
    pTable->pSchema->pSeqTab = pTable;
  }
#endif

  /* Begin generating the code that will insert the table record into
  ** the SQLITE_MASTER table.  Note in particular that we must go ahead
  ** and allocate the record number for the table entry now.  Before any
  ** PRIMARY KEY or UNIQUE keywords are parsed.  Those keywords will cause
  ** indices to be created and the table record must come before the 
  ** indices.  Hence, the record number for the table must be allocated
  ** now.
  */
  if( !db->init.busy && (v = sqlite4GetVdbe(pParse))!=0 ){
    int j1;
    int fileFormat;
    int reg1, reg2, reg3;
    sqlite4BeginWriteOperation(pParse, 0, iDb);

#ifndef SQLITE_OMIT_VIRTUALTABLE
    if( isVirtual ){
      sqlite4VdbeAddOp0(v, OP_VBegin);
    }
#endif

    /* If the file format and encoding in the database have not been set, 
    ** set them now.
    */
    reg1 = pParse->regRowid = ++pParse->nMem;
    reg2 = pParse->regRoot = ++pParse->nMem;
    reg3 = ++pParse->nMem;
    sqlite4VdbeAddOp3(v, OP_ReadCookie, iDb, reg3, BTREE_FILE_FORMAT);
    sqlite4VdbeUsesBtree(v, iDb);
    j1 = sqlite4VdbeAddOp1(v, OP_If, reg3);
    fileFormat = (db->flags & SQLITE_LegacyFileFmt)!=0 ?
                  1 : SQLITE_MAX_FILE_FORMAT;
    sqlite4VdbeAddOp2(v, OP_Integer, fileFormat, reg3);
    sqlite4VdbeAddOp3(v, OP_SetCookie, iDb, BTREE_FILE_FORMAT, reg3);
    sqlite4VdbeAddOp2(v, OP_Integer, ENC(db), reg3);
    sqlite4VdbeAddOp3(v, OP_SetCookie, iDb, BTREE_TEXT_ENCODING, reg3);
    sqlite4VdbeJumpHere(v, j1);

    /* This just creates a place-holder record in the sqlite_master table.
    ** The record created does not contain anything yet.  It will be replaced
    ** by the real entry in code generated at sqlite4EndTable().
    **
    ** The rowid for the new entry is left in register pParse->regRowid.
    ** The root page number of the new table is left in reg pParse->regRoot.
    ** The rowid and root page number values are needed by the code that
    ** sqlite4EndTable will generate.
    */



#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE)
    if( isView || isVirtual ){
      sqlite4VdbeAddOp2(v, OP_Integer, 0, reg2);
    }else
#endif
    {
      sqlite4VdbeAddOp2(v, OP_CreateTable, iDb, reg2);
................................................................................
** and the probability of hitting the same cookie value is only
** 1 chance in 2^32.  So we're safe enough.
*/
void sqlite4ChangeCookie(Parse *pParse, int iDb){
  int r1 = sqlite4GetTempReg(pParse);
  sqlite4 *db = pParse->db;
  Vdbe *v = pParse->pVdbe;
  assert( sqlite4SchemaMutexHeld(db, iDb, 0) );
  sqlite4VdbeAddOp2(v, OP_Integer, db->aDb[iDb].pSchema->schema_cookie+1, r1);
  sqlite4VdbeAddOp3(v, OP_SetCookie, iDb, BTREE_SCHEMA_VERSION, r1);
  sqlite4ReleaseTempReg(pParse, r1);
}

/*
** Measure the number of characters needed to output the given
** identifier.  The number returned includes any quotes used
** but does not include the null terminator.
................................................................................

#ifndef SQLITE_OMIT_AUTOINCREMENT
    /* Check to see if we need to create an sqlite_sequence table for
    ** keeping track of autoincrement keys.
    */
    if( p->tabFlags & TF_Autoincrement ){
      Db *pDb = &db->aDb[iDb];
      assert( sqlite4SchemaMutexHeld(db, iDb, 0) );
      if( pDb->pSchema->pSeqTab==0 ){
        sqlite4NestedParse(pParse,
          "CREATE TABLE %Q.sqlite_sequence(name,seq)",
          pDb->zName
        );
      }
    }
................................................................................


  /* Add the table to the in-memory representation of the database.
  */
  if( db->init.busy ){
    Table *pOld;
    Schema *pSchema = p->pSchema;
    assert( sqlite4SchemaMutexHeld(db, iDb, 0) );
    pOld = sqlite4HashInsert(&pSchema->tblHash, p->zName,
                             sqlite4Strlen30(p->zName),p);
    if( pOld ){
      assert( p==pOld );  /* Malloc must have failed inside HashInsert() */
      db->mallocFailed = 1;
      return;
    }
................................................................................
    if( pSelTab ){
      assert( pTable->aCol==0 );
      pTable->nCol = pSelTab->nCol;
      pTable->aCol = pSelTab->aCol;
      pSelTab->nCol = 0;
      pSelTab->aCol = 0;
      sqlite4DeleteTable(db, pSelTab);
      assert( sqlite4SchemaMutexHeld(db, 0, pTable->pSchema) );
      pTable->pSchema->flags |= DB_UnresetViews;
    }else{
      pTable->nCol = 0;
      nErr++;
    }
    sqlite4SelectDelete(db, pSel);
  } else {
................................................................................

#ifndef SQLITE_OMIT_VIEW
/*
** Clear the column names from every VIEW in database idx.
*/
static void sqliteViewResetAll(sqlite4 *db, int idx){
  HashElem *i;
  assert( sqlite4SchemaMutexHeld(db, idx, 0) );
  if( !DbHasProperty(db, idx, DB_UnresetViews) ) return;
  for(i=sqliteHashFirst(&db->aDb[idx].pSchema->tblHash); i;i=sqliteHashNext(i)){
    Table *pTab = sqliteHashData(i);
    if( pTab->pSelect ){
      sqliteDeleteColumnNames(db, pTab);
      pTab->aCol = 0;
      pTab->nCol = 0;
................................................................................
      z += n+1;
    }
  }
  pFKey->isDeferred = 0;
  pFKey->aAction[0] = (u8)(flags & 0xff);            /* ON DELETE action */
  pFKey->aAction[1] = (u8)((flags >> 8 ) & 0xff);    /* ON UPDATE action */

  assert( sqlite4SchemaMutexHeld(db, 0, p->pSchema) );
  pNextTo = (FKey *)sqlite4HashInsert(&p->pSchema->fkeyHash, 
      pFKey->zTo, sqlite4Strlen30(pFKey->zTo), (void *)pFKey
  );
  if( pNextTo==pFKey ){
    db->mallocFailed = 1;
    goto fk_end;
  }
................................................................................
** created.  The register specified by memRootPage contains the
** root page number of the index.  If memRootPage is negative, then
** the index already exists and must be cleared before being refilled and
** the root page number of the index is taken from pIndex->tnum.
*/
static void sqlite4RefillIndex(Parse *pParse, Index *pIndex, int memRootPage){
  Table *pTab = pIndex->pTable;  /* The table that is indexed */
  int iTab = pParse->nTab++;     /* Btree cursor used for pTab */
  int iIdx = pParse->nTab++;     /* Btree cursor used for pIndex */
  int iSorter;                   /* Cursor opened by OpenSorter (if in use) */
  int addr1;                     /* Address of top of loop */
  int addr2;                     /* Address to jump to for next iteration */
  int tnum;                      /* Root page of index */
  Vdbe *v;                       /* Generate code into this virtual machine */
  KeyInfo *pKey;                 /* KeyInfo for index */
#ifdef SQLITE_OMIT_MERGE_SORT
................................................................................
  zExtra = (char *)(&pIndex->zName[nName+1]);
  memcpy(pIndex->zName, zName, nName+1);
  pIndex->pTable = pTab;
  pIndex->nColumn = pList->nExpr;
  pIndex->onError = (u8)onError;
  pIndex->autoIndex = (u8)(pName==0);
  pIndex->pSchema = db->aDb[iDb].pSchema;
  assert( sqlite4SchemaMutexHeld(db, iDb, 0) );

  /* Check to see if we should honor DESC requests on index columns
  */
  if( pDb->pSchema->file_format>=4 ){
    sortOrderMask = -1;   /* Honor DESC */
  }else{
    sortOrderMask = 0;    /* Ignore DESC */
................................................................................
  }

  /* Link the new Index structure to its table and to the other
  ** in-memory database structures. 
  */
  if( db->init.busy ){
    Index *p;
    assert( sqlite4SchemaMutexHeld(db, 0, pIndex->pSchema) );
    p = sqlite4HashInsert(&pIndex->pSchema->idxHash, 
                          pIndex->zName, sqlite4Strlen30(pIndex->zName),
                          pIndex);
    if( p ){
      assert( p==pIndex );  /* Malloc must have failed */
      db->mallocFailed = 1;
      goto exit_create_index;
................................................................................
  sqlite4 *db;
  Vdbe *v;
  int i;

  assert( pParse!=0 );
  db = pParse->db;
  assert( db!=0 );
/*  if( db->aDb[0].pBt==0 ) return; */
  if( sqlite4AuthCheck(pParse, SQLITE_TRANSACTION, "BEGIN", 0, 0) ){
    return;
  }
  v = sqlite4GetVdbe(pParse);
  if( !v ) return;
  if( type!=TK_DEFERRED ){
    for(i=0; i<db->nDb; i++){
      sqlite4VdbeAddOp2(v, OP_Transaction, i, (type==TK_EXCLUSIVE)+1);
      sqlite4VdbeUsesBtree(v, i);
    }
  }
  sqlite4VdbeAddOp2(v, OP_AutoCommit, 0, 0);
}

/*
** Commit a transaction
................................................................................

/*
** Make sure the TEMP database is open and available for use.  Return
** the number of errors.  Leave any error messages in the pParse structure.
*/
int sqlite4OpenTempDatabase(Parse *pParse){
  sqlite4 *db = pParse->db;
  if( db->aDb[1].pBt==0 && !pParse->explain ){
    int rc;
    Btree *pBt;
    static const int flags = 
          SQLITE_OPEN_READWRITE |
          SQLITE_OPEN_CREATE |
          SQLITE_OPEN_EXCLUSIVE |
          SQLITE_OPEN_DELETEONCLOSE |
          SQLITE_OPEN_TEMP_DB;


    rc = sqlite4BtreeOpen(db->pVfs, 0, db, &pBt, 0, flags);


    if( rc!=SQLITE_OK ){
      sqlite4ErrorMsg(pParse, "unable to open a temporary database "
        "file for storing temporary tables");
      pParse->rc = rc;
      return 1;
    }
    sqlite4KVStoreOpen(":memory", &db->aDb[1].pKV);
    db->aDb[1].pBt = pBt;
    assert( db->aDb[1].pSchema );
    if( SQLITE_NOMEM==sqlite4BtreeSetPageSize(pBt, db->nextPagesize, -1, 0) ){
      db->mallocFailed = 1;
      return 1;
    }
  }
  return 0;
}

/*
** Generate VDBE code that will verify the schema cookie and start
** a read-transaction for all named database files.
................................................................................
    pToplevel->cookieGoto = sqlite4VdbeAddOp2(v, OP_Goto, 0, 0)+1;
  }
  if( iDb>=0 ){
    sqlite4 *db = pToplevel->db;
    yDbMask mask;

    assert( iDb<db->nDb );
    assert( db->aDb[iDb].pBt!=0 || iDb==1 );
    assert( iDb<SQLITE_MAX_ATTACHED+2 );
    assert( sqlite4SchemaMutexHeld(db, iDb, 0) );
    mask = ((yDbMask)1)<<iDb;
    if( (pToplevel->cookieMask & mask)==0 ){
      pToplevel->cookieMask |= mask;
      pToplevel->cookieValue[iDb] = db->aDb[iDb].pSchema->schema_cookie;
      if( !OMIT_TEMPDB && iDb==1 ){
        sqlite4OpenTempDatabase(pToplevel);
      }
................................................................................
** attached database. Otherwise, invoke it for the database named zDb only.
*/
void sqlite4CodeVerifyNamedSchema(Parse *pParse, const char *zDb){
  sqlite4 *db = pParse->db;
  int i;
  for(i=0; i<db->nDb; i++){
    Db *pDb = &db->aDb[i];
    if( pDb->pBt && (!zDb || 0==sqlite4StrICmp(zDb, pDb->zName)) ){
      sqlite4CodeVerifySchema(pParse, i);
    }
  }
}

/*
** Generate VDBE code that prepares for doing an operation that
................................................................................
static void reindexDatabases(Parse *pParse, char const *zColl){
  Db *pDb;                    /* A single database */
  int iDb;                    /* The database index number */
  sqlite4 *db = pParse->db;   /* The database connection */
  HashElem *k;                /* For looping over tables in pDb */
  Table *pTab;                /* A table in the database */

  assert( sqlite4BtreeHoldsAllMutexes(db) );  /* Needed for schema access */
  for(iDb=0, pDb=db->aDb; iDb<db->nDb; iDb++, pDb++){
    assert( pDb!=0 );
    for(k=sqliteHashFirst(&pDb->pSchema->tblHash);  k; k=sqliteHashNext(k)){
      pTab = (Table*)sqliteHashData(k);
      reindexTable(pParse, pTab, zColl);
    }
  }







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446
447
448
...
507
508
509
510
511
512
513

514
515
516
517
518
519
520
...
541
542
543
544
545
546
547

548
549
550
551
552
553
554
...
828
829
830
831
832
833
834

835
836
837
838
839
840
841
842
843
844
845
846
847


848
849
850
851
852
853
854
855
856
















857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
....
1273
1274
1275
1276
1277
1278
1279

1280
1281
1282
1283
1284
1285
1286
1287
1288
....
1575
1576
1577
1578
1579
1580
1581

1582
1583
1584
1585
1586
1587
1588
....
1595
1596
1597
1598
1599
1600
1601

1602
1603
1604
1605
1606
1607
1608
....
1779
1780
1781
1782
1783
1784
1785

1786
1787
1788
1789
1790
1791
1792
....
1799
1800
1801
1802
1803
1804
1805

1806
1807
1808
1809
1810
1811
1812
....
2145
2146
2147
2148
2149
2150
2151

2152
2153
2154
2155
2156
2157
2158
....
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
....
2551
2552
2553
2554
2555
2556
2557

2558
2559
2560
2561
2562
2563
2564
....
2680
2681
2682
2683
2684
2685
2686

2687
2688
2689
2690
2691
2692
2693
....
3284
3285
3286
3287
3288
3289
3290

3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
....
3358
3359
3360
3361
3362
3363
3364
3365
3366
3367
3368
3369
3370
3371
3372
3373
3374
3375

3376
3377
3378
3379
3380
3381
3382
3383


3384




3385
3386
3387
3388
3389
3390
3391
....
3417
3418
3419
3420
3421
3422
3423
3424
3425

3426
3427
3428
3429
3430
3431
3432
....
3439
3440
3441
3442
3443
3444
3445
3446
3447
3448
3449
3450
3451
3452
3453
....
3561
3562
3563
3564
3565
3566
3567

3568
3569
3570
3571
3572
3573
3574
    */
    if( pParse->cookieGoto>0 ){
      yDbMask mask;
      int iDb;
      sqlite4VdbeJumpHere(v, pParse->cookieGoto-1);
      for(iDb=0, mask=1; iDb<db->nDb; mask<<=1, iDb++){
        if( (mask & pParse->cookieMask)==0 ) continue;

        sqlite4VdbeAddOp2(v,OP_Transaction, iDb, (mask & pParse->writeMask)!=0);
        if( db->init.busy==0 ){

          sqlite4VdbeAddOp3(v, OP_VerifyCookie,
                            iDb, pParse->cookieValue[iDb],
                            db->aDb[iDb].pSchema->iGeneration);
        }
      }
#ifndef SQLITE_OMIT_VIRTUALTABLE
      {
................................................................................
Table *sqlite4FindTable(sqlite4 *db, const char *zName, const char *zDatabase){
  Table *p = 0;
  int i;
  int nName;
  assert( zName!=0 );
  nName = sqlite4Strlen30(zName);
  /* All mutexes are required for schema access.  Make sure we hold them. */

  for(i=OMIT_TEMPDB; i<db->nDb; i++){
    int j = (i<2) ? i^1 : i;   /* Search TEMP before MAIN */
    if( zDatabase!=0 && sqlite4StrICmp(zDatabase, db->aDb[j].zName) ) continue;

    p = sqlite4HashFind(&db->aDb[j].pSchema->tblHash, zName, nName);
    if( p ) break;
  }
  return p;
}

/*
................................................................................
** using the ATTACH command.
*/
Index *sqlite4FindIndex(sqlite4 *db, const char *zName, const char *zDb){
  Index *p = 0;
  int i;
  int nName = sqlite4Strlen30(zName);
  /* All mutexes are required for schema access.  Make sure we hold them. */

  for(i=OMIT_TEMPDB; i<db->nDb; i++){
    int j = (i<2) ? i^1 : i;  /* Search TEMP before MAIN */
    Schema *pSchema = db->aDb[j].pSchema;
    assert( pSchema );
    if( zDb && sqlite4StrICmp(zDb, db->aDb[j].zName) ) continue;

    p = sqlite4HashFind(&pSchema->idxHash, zName, nName);
    if( p ) break;
  }
  return p;
}

/*
................................................................................
** with the index.
*/
void sqlite4UnlinkAndDeleteIndex(sqlite4 *db, int iDb, const char *zIdxName){
  Index *pIndex;
  int len;
  Hash *pHash;


  pHash = &db->aDb[iDb].pSchema->idxHash;
  len = sqlite4Strlen30(zIdxName);
  pIndex = sqlite4HashInsert(pHash, zIdxName, len, 0);
  if( ALWAYS(pIndex) ){
    if( pIndex->pTable->pIndex==pIndex ){
      pIndex->pTable->pIndex = pIndex->pNext;
    }else{
................................................................................
void sqlite4ResetInternalSchema(sqlite4 *db, int iDb){
  int i, j;
  assert( iDb<db->nDb );

  if( iDb>=0 ){
    /* Case 1:  Reset the single schema identified by iDb */
    Db *pDb = &db->aDb[iDb];

    assert( pDb->pSchema!=0 );
    sqlite4SchemaClear(pDb->pSchema);

    /* If any database other than TEMP is reset, then also reset TEMP
    ** since TEMP might be holding triggers that reference tables in the
    ** other database.
    */
................................................................................
      sqlite4SchemaClear(pDb->pSchema);
    }
    return;
  }
  /* Case 2 (from here to the end): Reset all schemas for all attached
  ** databases. */
  assert( iDb<0 );

  for(i=0; i<db->nDb; i++){
    Db *pDb = &db->aDb[i];
    if( pDb->pSchema ){
      sqlite4SchemaClear(pDb->pSchema);
    }
  }
  db->flags &= ~SQLITE_InternChanges;
  sqlite4VtabUnlockList(db);


  /* If one or more of the auxiliary database files has been closed,
  ** then remove them from the auxiliary database list.  We take the
  ** opportunity to do this here since we have just deleted all of the
  ** schema hash tables and therefore do not have to make any changes
  ** to any of those tables.
  */
  for(i=j=2; i<db->nDb; i++){
    struct Db *pDb = &db->aDb[i];
    if( pDb->pKV==0 ){
      sqlite4DbFree(db, pDb->zName);
      pDb->zName = 0;
      continue;
    }
    if( j<i ){
      db->aDb[j] = db->aDb[i];
    }
................................................................................
    pNext = pIndex->pNext;
    assert( pIndex->pSchema==pTable->pSchema );
    if( !db || db->pnBytesFreed==0 ){
      char *zName = pIndex->zName; 
      TESTONLY ( Index *pOld = ) sqlite4HashInsert(
	  &pIndex->pSchema->idxHash, zName, sqlite4Strlen30(zName), 0
      );

      assert( pOld==pIndex || pOld==0 );
    }
    freeIndex(db, pIndex);
  }

  /* Delete any foreign keys attached to this table. */
  sqlite4FkDelete(db, pTable);
................................................................................
void sqlite4UnlinkAndDeleteTable(sqlite4 *db, int iDb, const char *zTabName){
  Table *p;
  Db *pDb;

  assert( db!=0 );
  assert( iDb>=0 && iDb<db->nDb );
  assert( zTabName );

  testcase( zTabName[0]==0 );  /* Zero-length table names are allowed */
  pDb = &db->aDb[iDb];
  p = sqlite4HashInsert(&pDb->pSchema->tblHash, zTabName,
                        sqlite4Strlen30(zTabName),0);
  sqlite4DeleteTable(db, p);
  db->flags |= SQLITE_InternChanges;
}
................................................................................

  /* If this is the magic sqlite_sequence table used by autoincrement,
  ** then record a pointer to this table in the main database structure
  ** so that INSERT can find the table easily.
  */
#ifndef SQLITE_OMIT_AUTOINCREMENT
  if( !pParse->nested && strcmp(zName, "sqlite_sequence")==0 ){

    pTable->pSchema->pSeqTab = pTable;
  }
#endif

  /* Begin generating the code that will insert the table record into
  ** the SQLITE_MASTER table.  Note in particular that we must go ahead
  ** and allocate the record number for the table entry now.  Before any
  ** PRIMARY KEY or UNIQUE keywords are parsed.  Those keywords will cause
  ** indices to be created and the table record must come before the 
  ** indices.  Hence, the record number for the table must be allocated
  ** now.
  */
  if( !db->init.busy && (v = sqlite4GetVdbe(pParse))!=0 ){


    int reg1, reg2, reg3;
    sqlite4BeginWriteOperation(pParse, 0, iDb);

#ifndef SQLITE_OMIT_VIRTUALTABLE
    if( isVirtual ){
      sqlite4VdbeAddOp0(v, OP_VBegin);
    }
#endif


















    /* This just creates a place-holder record in the sqlite_master table.
    ** The record created does not contain anything yet.  It will be replaced
    ** by the real entry in code generated at sqlite4EndTable().
    **
    ** The rowid for the new entry is left in register pParse->regRowid.
    ** The root page number of the new table is left in reg pParse->regRoot.
    ** The rowid and root page number values are needed by the code that
    ** sqlite4EndTable will generate.
    */
    reg1 = pParse->regRowid = ++pParse->nMem;
    reg2 = pParse->regRoot = ++pParse->nMem;
    reg3 = ++pParse->nMem;
#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE)
    if( isView || isVirtual ){
      sqlite4VdbeAddOp2(v, OP_Integer, 0, reg2);
    }else
#endif
    {
      sqlite4VdbeAddOp2(v, OP_CreateTable, iDb, reg2);
................................................................................
** and the probability of hitting the same cookie value is only
** 1 chance in 2^32.  So we're safe enough.
*/
void sqlite4ChangeCookie(Parse *pParse, int iDb){
  int r1 = sqlite4GetTempReg(pParse);
  sqlite4 *db = pParse->db;
  Vdbe *v = pParse->pVdbe;

  sqlite4VdbeAddOp2(v, OP_Integer, db->aDb[iDb].pSchema->schema_cookie+1, r1);
  sqlite4VdbeAddOp3(v, OP_SetCookie, iDb, 0, r1);
  sqlite4ReleaseTempReg(pParse, r1);
}

/*
** Measure the number of characters needed to output the given
** identifier.  The number returned includes any quotes used
** but does not include the null terminator.
................................................................................

#ifndef SQLITE_OMIT_AUTOINCREMENT
    /* Check to see if we need to create an sqlite_sequence table for
    ** keeping track of autoincrement keys.
    */
    if( p->tabFlags & TF_Autoincrement ){
      Db *pDb = &db->aDb[iDb];

      if( pDb->pSchema->pSeqTab==0 ){
        sqlite4NestedParse(pParse,
          "CREATE TABLE %Q.sqlite_sequence(name,seq)",
          pDb->zName
        );
      }
    }
................................................................................


  /* Add the table to the in-memory representation of the database.
  */
  if( db->init.busy ){
    Table *pOld;
    Schema *pSchema = p->pSchema;

    pOld = sqlite4HashInsert(&pSchema->tblHash, p->zName,
                             sqlite4Strlen30(p->zName),p);
    if( pOld ){
      assert( p==pOld );  /* Malloc must have failed inside HashInsert() */
      db->mallocFailed = 1;
      return;
    }
................................................................................
    if( pSelTab ){
      assert( pTable->aCol==0 );
      pTable->nCol = pSelTab->nCol;
      pTable->aCol = pSelTab->aCol;
      pSelTab->nCol = 0;
      pSelTab->aCol = 0;
      sqlite4DeleteTable(db, pSelTab);

      pTable->pSchema->flags |= DB_UnresetViews;
    }else{
      pTable->nCol = 0;
      nErr++;
    }
    sqlite4SelectDelete(db, pSel);
  } else {
................................................................................

#ifndef SQLITE_OMIT_VIEW
/*
** Clear the column names from every VIEW in database idx.
*/
static void sqliteViewResetAll(sqlite4 *db, int idx){
  HashElem *i;

  if( !DbHasProperty(db, idx, DB_UnresetViews) ) return;
  for(i=sqliteHashFirst(&db->aDb[idx].pSchema->tblHash); i;i=sqliteHashNext(i)){
    Table *pTab = sqliteHashData(i);
    if( pTab->pSelect ){
      sqliteDeleteColumnNames(db, pTab);
      pTab->aCol = 0;
      pTab->nCol = 0;
................................................................................
      z += n+1;
    }
  }
  pFKey->isDeferred = 0;
  pFKey->aAction[0] = (u8)(flags & 0xff);            /* ON DELETE action */
  pFKey->aAction[1] = (u8)((flags >> 8 ) & 0xff);    /* ON UPDATE action */


  pNextTo = (FKey *)sqlite4HashInsert(&p->pSchema->fkeyHash, 
      pFKey->zTo, sqlite4Strlen30(pFKey->zTo), (void *)pFKey
  );
  if( pNextTo==pFKey ){
    db->mallocFailed = 1;
    goto fk_end;
  }
................................................................................
** created.  The register specified by memRootPage contains the
** root page number of the index.  If memRootPage is negative, then
** the index already exists and must be cleared before being refilled and
** the root page number of the index is taken from pIndex->tnum.
*/
static void sqlite4RefillIndex(Parse *pParse, Index *pIndex, int memRootPage){
  Table *pTab = pIndex->pTable;  /* The table that is indexed */
  int iTab = pParse->nTab++;     /* Cursor used for pTab */
  int iIdx = pParse->nTab++;     /* Cursor used for pIndex */
  int iSorter;                   /* Cursor opened by OpenSorter (if in use) */
  int addr1;                     /* Address of top of loop */
  int addr2;                     /* Address to jump to for next iteration */
  int tnum;                      /* Root page of index */
  Vdbe *v;                       /* Generate code into this virtual machine */
  KeyInfo *pKey;                 /* KeyInfo for index */
#ifdef SQLITE_OMIT_MERGE_SORT
................................................................................
  zExtra = (char *)(&pIndex->zName[nName+1]);
  memcpy(pIndex->zName, zName, nName+1);
  pIndex->pTable = pTab;
  pIndex->nColumn = pList->nExpr;
  pIndex->onError = (u8)onError;
  pIndex->autoIndex = (u8)(pName==0);
  pIndex->pSchema = db->aDb[iDb].pSchema;


  /* Check to see if we should honor DESC requests on index columns
  */
  if( pDb->pSchema->file_format>=4 ){
    sortOrderMask = -1;   /* Honor DESC */
  }else{
    sortOrderMask = 0;    /* Ignore DESC */
................................................................................
  }

  /* Link the new Index structure to its table and to the other
  ** in-memory database structures. 
  */
  if( db->init.busy ){
    Index *p;

    p = sqlite4HashInsert(&pIndex->pSchema->idxHash, 
                          pIndex->zName, sqlite4Strlen30(pIndex->zName),
                          pIndex);
    if( p ){
      assert( p==pIndex );  /* Malloc must have failed */
      db->mallocFailed = 1;
      goto exit_create_index;
................................................................................
  sqlite4 *db;
  Vdbe *v;
  int i;

  assert( pParse!=0 );
  db = pParse->db;
  assert( db!=0 );

  if( sqlite4AuthCheck(pParse, SQLITE_TRANSACTION, "BEGIN", 0, 0) ){
    return;
  }
  v = sqlite4GetVdbe(pParse);
  if( !v ) return;
  if( type!=TK_DEFERRED ){
    for(i=0; i<db->nDb; i++){
      sqlite4VdbeAddOp2(v, OP_Transaction, i, (type==TK_EXCLUSIVE)+1);
      sqlite4VdbeUsesStorage(v, i);
    }
  }
  sqlite4VdbeAddOp2(v, OP_AutoCommit, 0, 0);
}

/*
** Commit a transaction
................................................................................

/*
** Make sure the TEMP database is open and available for use.  Return
** the number of errors.  Leave any error messages in the pParse structure.
*/
int sqlite4OpenTempDatabase(Parse *pParse){
  sqlite4 *db = pParse->db;
  if( db->aDb[1].pKV==0 && !pParse->explain ){
    int rc;
#if 0
    static const int flags = 
          SQLITE_OPEN_READWRITE |
          SQLITE_OPEN_CREATE |
          SQLITE_OPEN_EXCLUSIVE |
          SQLITE_OPEN_DELETEONCLOSE |
          SQLITE_OPEN_TEMP_DB;
#endif


    rc = sqlite4KVStoreOpen(db, "temp", ":memory:", &db->aDb[1].pKV,
                            SQLITE_KVOPEN_TEMPORARY);
    if( rc!=SQLITE_OK ){
      sqlite4ErrorMsg(pParse, "unable to open a temporary database "
        "file for storing temporary tables");
      pParse->rc = rc;
      return 1;
    }


    assert( db->aDb[1].pSchema );




  }
  return 0;
}

/*
** Generate VDBE code that will verify the schema cookie and start
** a read-transaction for all named database files.
................................................................................
    pToplevel->cookieGoto = sqlite4VdbeAddOp2(v, OP_Goto, 0, 0)+1;
  }
  if( iDb>=0 ){
    sqlite4 *db = pToplevel->db;
    yDbMask mask;

    assert( iDb<db->nDb );
    assert( db->aDb[iDb].pKV!=0 || iDb==1 );
    assert( iDb<SQLITE_MAX_ATTACHED+2 );

    mask = ((yDbMask)1)<<iDb;
    if( (pToplevel->cookieMask & mask)==0 ){
      pToplevel->cookieMask |= mask;
      pToplevel->cookieValue[iDb] = db->aDb[iDb].pSchema->schema_cookie;
      if( !OMIT_TEMPDB && iDb==1 ){
        sqlite4OpenTempDatabase(pToplevel);
      }
................................................................................
** attached database. Otherwise, invoke it for the database named zDb only.
*/
void sqlite4CodeVerifyNamedSchema(Parse *pParse, const char *zDb){
  sqlite4 *db = pParse->db;
  int i;
  for(i=0; i<db->nDb; i++){
    Db *pDb = &db->aDb[i];
    if( pDb->pKV && (!zDb || 0==sqlite4StrICmp(zDb, pDb->zName)) ){
      sqlite4CodeVerifySchema(pParse, i);
    }
  }
}

/*
** Generate VDBE code that prepares for doing an operation that
................................................................................
static void reindexDatabases(Parse *pParse, char const *zColl){
  Db *pDb;                    /* A single database */
  int iDb;                    /* The database index number */
  sqlite4 *db = pParse->db;   /* The database connection */
  HashElem *k;                /* For looping over tables in pDb */
  Table *pTab;                /* A table in the database */


  for(iDb=0, pDb=db->aDb; iDb<db->nDb; iDb++, pDb++){
    assert( pDb!=0 );
    for(k=sqliteHashFirst(&pDb->pSchema->tblHash);  k; k=sqliteHashNext(k)){
      pTab = (Table*)sqliteHashData(k);
      reindexTable(pParse, pTab, zColl);
    }
  }

Changes to src/callback.c.

401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
...
433
434
435
436
437
438
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440
441
442
443
444
445
446
447
448
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450
451
452
453
454
455
456
457
** Free all resources held by the schema structure. The void* argument points
** at a Schema struct. This function does not call sqlite4DbFree(db, ) on the 
** pointer itself, it just cleans up subsidiary resources (i.e. the contents
** of the schema hash tables).
**
** The Schema.cache_size variable is not cleared.
*/
void sqlite4SchemaClear(void *p){
  Hash temp1;
  Hash temp2;
  HashElem *pElem;
  Schema *pSchema = (Schema *)p;

  temp1 = pSchema->tblHash;
  temp2 = pSchema->trigHash;
  sqlite4HashInit(&pSchema->trigHash);
  sqlite4HashClear(&pSchema->idxHash);
  for(pElem=sqliteHashFirst(&temp2); pElem; pElem=sqliteHashNext(pElem)){
    sqlite4DeleteTrigger(0, (Trigger*)sqliteHashData(pElem));
................................................................................
  }
}

/*
** Find and return the schema associated with a BTree.  Create
** a new one if necessary.
*/
Schema *sqlite4SchemaGet(sqlite4 *db, Btree *pBt){
  Schema * p;
  if( pBt ){
    p = (Schema *)sqlite4BtreeSchema(pBt, sizeof(Schema), sqlite4SchemaClear);
  }else{
    p = (Schema *)sqlite4DbMallocZero(0, sizeof(Schema));
  }
  if( !p ){
    db->mallocFailed = 1;
  }else if ( 0==p->file_format ){
    sqlite4HashInit(&p->tblHash);
    sqlite4HashInit(&p->idxHash);
    sqlite4HashInit(&p->trigHash);
    sqlite4HashInit(&p->fkeyHash);
    p->enc = SQLITE_UTF8;
  }
  return p;
}







|



<







 







|

<
<
<
|
<











401
402
403
404
405
406
407
408
409
410
411

412
413
414
415
416
417
418
...
432
433
434
435
436
437
438
439
440



441

442
443
444
445
446
447
448
449
450
451
452
** Free all resources held by the schema structure. The void* argument points
** at a Schema struct. This function does not call sqlite4DbFree(db, ) on the 
** pointer itself, it just cleans up subsidiary resources (i.e. the contents
** of the schema hash tables).
**
** The Schema.cache_size variable is not cleared.
*/
void sqlite4SchemaClear(Schema *pSchema){
  Hash temp1;
  Hash temp2;
  HashElem *pElem;


  temp1 = pSchema->tblHash;
  temp2 = pSchema->trigHash;
  sqlite4HashInit(&pSchema->trigHash);
  sqlite4HashClear(&pSchema->idxHash);
  for(pElem=sqliteHashFirst(&temp2); pElem; pElem=sqliteHashNext(pElem)){
    sqlite4DeleteTrigger(0, (Trigger*)sqliteHashData(pElem));
................................................................................
  }
}

/*
** Find and return the schema associated with a BTree.  Create
** a new one if necessary.
*/
Schema *sqlite4SchemaGet(sqlite4 *db){
  Schema * p;



  p = (Schema *)sqlite4DbMallocZero(0, sizeof(Schema));

  if( !p ){
    db->mallocFailed = 1;
  }else if ( 0==p->file_format ){
    sqlite4HashInit(&p->tblHash);
    sqlite4HashInit(&p->idxHash);
    sqlite4HashInit(&p->trigHash);
    sqlite4HashInit(&p->fkeyHash);
    p->enc = SQLITE_UTF8;
  }
  return p;
}

Changes to src/ctime.c.

235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
#endif
#ifdef SQLITE_OMIT_FOREIGN_KEY
  "OMIT_FOREIGN_KEY",
#endif
#ifdef SQLITE_OMIT_GET_TABLE
  "OMIT_GET_TABLE",
#endif
#ifdef SQLITE_OMIT_INCRBLOB
  "OMIT_INCRBLOB",
#endif
#ifdef SQLITE_OMIT_INTEGRITY_CHECK
  "OMIT_INTEGRITY_CHECK",
#endif
#ifdef SQLITE_OMIT_LIKE_OPTIMIZATION
  "OMIT_LIKE_OPTIMIZATION",
#endif
#ifdef SQLITE_OMIT_LOAD_EXTENSION







<
<
<







235
236
237
238
239
240
241



242
243
244
245
246
247
248
#endif
#ifdef SQLITE_OMIT_FOREIGN_KEY
  "OMIT_FOREIGN_KEY",
#endif
#ifdef SQLITE_OMIT_GET_TABLE
  "OMIT_GET_TABLE",
#endif



#ifdef SQLITE_OMIT_INTEGRITY_CHECK
  "OMIT_INTEGRITY_CHECK",
#endif
#ifdef SQLITE_OMIT_LIKE_OPTIMIZATION
  "OMIT_LIKE_OPTIMIZATION",
#endif
#ifdef SQLITE_OMIT_LOAD_EXTENSION

Changes to src/expr.c.

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      ** SELECT... statement are columns, then numeric affinity is used
      ** if either column has NUMERIC or INTEGER affinity. If neither
      ** 'x' nor the SELECT... statement are columns, then numeric affinity
      ** is used.
      */
      pExpr->iTable = pParse->nTab++;
      addr = sqlite4VdbeAddOp2(v, OP_OpenEphemeral, pExpr->iTable, !isRowid);
      if( rMayHaveNull==0 ) sqlite4VdbeChangeP5(v, BTREE_UNORDERED);
      memset(&keyInfo, 0, sizeof(keyInfo));
      keyInfo.nField = 1;

      if( ExprHasProperty(pExpr, EP_xIsSelect) ){
        /* Case 1:     expr IN (SELECT ...)
        **
        ** Generate code to write the results of the select into the temporary







<







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      ** SELECT... statement are columns, then numeric affinity is used
      ** if either column has NUMERIC or INTEGER affinity. If neither
      ** 'x' nor the SELECT... statement are columns, then numeric affinity
      ** is used.
      */
      pExpr->iTable = pParse->nTab++;
      addr = sqlite4VdbeAddOp2(v, OP_OpenEphemeral, pExpr->iTable, !isRowid);

      memset(&keyInfo, 0, sizeof(keyInfo));
      keyInfo.nField = 1;

      if( ExprHasProperty(pExpr, EP_xIsSelect) ){
        /* Case 1:     expr IN (SELECT ...)
        **
        ** Generate code to write the results of the select into the temporary

Changes to src/fkey.c.

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** table pTab. Remove the deleted foreign keys from the Schema.fkeyHash
** hash table.
*/
void sqlite4FkDelete(sqlite4 *db, Table *pTab){
  FKey *pFKey;                    /* Iterator variable */
  FKey *pNext;                    /* Copy of pFKey->pNextFrom */

  assert( db==0 || sqlite4SchemaMutexHeld(db, 0, pTab->pSchema) );
  for(pFKey=pTab->pFKey; pFKey; pFKey=pNext){

    /* Remove the FK from the fkeyHash hash table. */
    if( !db || db->pnBytesFreed==0 ){
      if( pFKey->pPrevTo ){
        pFKey->pPrevTo->pNextTo = pFKey->pNextTo;
      }else{







<







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** table pTab. Remove the deleted foreign keys from the Schema.fkeyHash
** hash table.
*/
void sqlite4FkDelete(sqlite4 *db, Table *pTab){
  FKey *pFKey;                    /* Iterator variable */
  FKey *pNext;                    /* Copy of pFKey->pNextFrom */


  for(pFKey=pTab->pFKey; pFKey; pFKey=pNext){

    /* Remove the FK from the fkeyHash hash table. */
    if( !db || db->pnBytesFreed==0 ){
      if( pFKey->pPrevTo ){
        pFKey->pPrevTo->pNextTo = pFKey->pNextTo;
      }else{

Changes to src/func.c.

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    /* IMP: R-64894-50321 The string "?000" is returned if the argument
    ** is NULL or contains no ASCII alphabetic characters. */
    sqlite4_result_text(context, "?000", 4, SQLITE_STATIC);
  }
}
#endif /* SQLITE_SOUNDEX */

#ifndef SQLITE_OMIT_LOAD_EXTENSION
/*
** A function that loads a shared-library extension then returns NULL.
*/
static void loadExt(sqlite4_context *context, int argc, sqlite4_value **argv){
  const char *zFile = (const char *)sqlite4_value_text(argv[0]);
  const char *zProc;
  sqlite4 *db = sqlite4_context_db_handle(context);
................................................................................
    FUNCTION(changes,            0, 0, 0, changes          ),
    FUNCTION(total_changes,      0, 0, 0, total_changes    ),
    FUNCTION(replace,            3, 0, 0, replaceFunc      ),
    FUNCTION(zeroblob,           1, 0, 0, zeroblobFunc     ),
  #ifdef SQLITE_SOUNDEX
    FUNCTION(soundex,            1, 0, 0, soundexFunc      ),
  #endif
  #ifndef SQLITE_OMIT_LOAD_EXTENSION
    FUNCTION(load_extension,     1, 0, 0, loadExt          ),
    FUNCTION(load_extension,     2, 0, 0, loadExt          ),
  #endif
    AGGREGATE(sum,               1, 0, 0, sumStep,         sumFinalize    ),
    AGGREGATE(total,             1, 0, 0, sumStep,         totalFinalize    ),
    AGGREGATE(avg,               1, 0, 0, sumStep,         avgFinalize    ),
 /* AGGREGATE(count,             0, 0, 0, countStep,       countFinalize  ), */







|







 







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    /* IMP: R-64894-50321 The string "?000" is returned if the argument
    ** is NULL or contains no ASCII alphabetic characters. */
    sqlite4_result_text(context, "?000", 4, SQLITE_STATIC);
  }
}
#endif /* SQLITE_SOUNDEX */

#if 0 /*ndef SQLITE_OMIT_LOAD_EXTENSION*/
/*
** A function that loads a shared-library extension then returns NULL.
*/
static void loadExt(sqlite4_context *context, int argc, sqlite4_value **argv){
  const char *zFile = (const char *)sqlite4_value_text(argv[0]);
  const char *zProc;
  sqlite4 *db = sqlite4_context_db_handle(context);
................................................................................
    FUNCTION(changes,            0, 0, 0, changes          ),
    FUNCTION(total_changes,      0, 0, 0, total_changes    ),
    FUNCTION(replace,            3, 0, 0, replaceFunc      ),
    FUNCTION(zeroblob,           1, 0, 0, zeroblobFunc     ),
  #ifdef SQLITE_SOUNDEX
    FUNCTION(soundex,            1, 0, 0, soundexFunc      ),
  #endif
  #if 0 /*ndef SQLITE_OMIT_LOAD_EXTENSION*/
    FUNCTION(load_extension,     1, 0, 0, loadExt          ),
    FUNCTION(load_extension,     2, 0, 0, loadExt          ),
  #endif
    AGGREGATE(sum,               1, 0, 0, sumStep,         sumFinalize    ),
    AGGREGATE(total,             1, 0, 0, sumStep,         totalFinalize    ),
    AGGREGATE(avg,               1, 0, 0, sumStep,         avgFinalize    ),
 /* AGGREGATE(count,             0, 0, 0, countStep,       countFinalize  ), */

Changes to src/insert.c.

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  assert( pParse->pTriggerTab==0 );
  assert( pParse==sqlite4ParseToplevel(pParse) );

  assert( v );   /* We failed long ago if this is not so */
  for(p = pParse->pAinc; p; p = p->pNext){
    pDb = &db->aDb[p->iDb];
    memId = p->regCtr;
    assert( sqlite4SchemaMutexHeld(db, 0, pDb->pSchema) );
    sqlite4OpenTable(pParse, 0, p->iDb, pDb->pSchema->pSeqTab, OP_OpenRead);
    sqlite4VdbeAddOp3(v, OP_Null, 0, memId, memId+1);
    addr = sqlite4VdbeCurrentAddr(v);
    sqlite4VdbeAddOp4(v, OP_String8, 0, memId-1, 0, p->pTab->zName, 0);
    sqlite4VdbeAddOp2(v, OP_Rewind, 0, addr+9);
    sqlite4VdbeAddOp3(v, OP_Column, 0, 0, memId);
    sqlite4VdbeAddOp3(v, OP_Ne, memId-1, addr+7, memId);
................................................................................
  for(p = pParse->pAinc; p; p = p->pNext){
    Db *pDb = &db->aDb[p->iDb];
    int j1, j2, j3, j4, j5;
    int iRec;
    int memId = p->regCtr;

    iRec = sqlite4GetTempReg(pParse);
    assert( sqlite4SchemaMutexHeld(db, 0, pDb->pSchema) );
    sqlite4OpenTable(pParse, 0, p->iDb, pDb->pSchema->pSeqTab, OP_OpenWrite);
    j1 = sqlite4VdbeAddOp1(v, OP_NotNull, memId+1);
    j2 = sqlite4VdbeAddOp0(v, OP_Rewind);
    j3 = sqlite4VdbeAddOp3(v, OP_Column, 0, 0, iRec);
    j4 = sqlite4VdbeAddOp3(v, OP_Eq, memId-1, 0, iRec);
    sqlite4VdbeAddOp2(v, OP_Next, 0, j3);
    sqlite4VdbeJumpHere(v, j2);







<







 







<







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  assert( pParse->pTriggerTab==0 );
  assert( pParse==sqlite4ParseToplevel(pParse) );

  assert( v );   /* We failed long ago if this is not so */
  for(p = pParse->pAinc; p; p = p->pNext){
    pDb = &db->aDb[p->iDb];
    memId = p->regCtr;

    sqlite4OpenTable(pParse, 0, p->iDb, pDb->pSchema->pSeqTab, OP_OpenRead);
    sqlite4VdbeAddOp3(v, OP_Null, 0, memId, memId+1);
    addr = sqlite4VdbeCurrentAddr(v);
    sqlite4VdbeAddOp4(v, OP_String8, 0, memId-1, 0, p->pTab->zName, 0);
    sqlite4VdbeAddOp2(v, OP_Rewind, 0, addr+9);
    sqlite4VdbeAddOp3(v, OP_Column, 0, 0, memId);
    sqlite4VdbeAddOp3(v, OP_Ne, memId-1, addr+7, memId);
................................................................................
  for(p = pParse->pAinc; p; p = p->pNext){
    Db *pDb = &db->aDb[p->iDb];
    int j1, j2, j3, j4, j5;
    int iRec;
    int memId = p->regCtr;

    iRec = sqlite4GetTempReg(pParse);

    sqlite4OpenTable(pParse, 0, p->iDb, pDb->pSchema->pSeqTab, OP_OpenWrite);
    j1 = sqlite4VdbeAddOp1(v, OP_NotNull, memId+1);
    j2 = sqlite4VdbeAddOp0(v, OP_Rewind);
    j3 = sqlite4VdbeAddOp3(v, OP_Column, 0, 0, iRec);
    j4 = sqlite4VdbeAddOp3(v, OP_Eq, memId-1, 0, iRec);
    sqlite4VdbeAddOp2(v, OP_Next, 0, j3);
    sqlite4VdbeJumpHere(v, j2);

Deleted src/journal.c.

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/*
** 2007 August 22
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file implements a special kind of sqlite4_file object used
** by SQLite to create journal files if the atomic-write optimization
** is enabled.
**
** The distinctive characteristic of this sqlite4_file is that the
** actual on disk file is created lazily. When the file is created,
** the caller specifies a buffer size for an in-memory buffer to
** be used to service read() and write() requests. The actual file
** on disk is not created or populated until either:
**
**   1) The in-memory representation grows too large for the allocated 
**      buffer, or
**   2) The sqlite4JournalCreate() function is called.
*/
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
#include "sqliteInt.h"


/*
** A JournalFile object is a subclass of sqlite4_file used by
** as an open file handle for journal files.
*/
struct JournalFile {
  sqlite4_io_methods *pMethod;    /* I/O methods on journal files */
  int nBuf;                       /* Size of zBuf[] in bytes */
  char *zBuf;                     /* Space to buffer journal writes */
  int iSize;                      /* Amount of zBuf[] currently used */
  int flags;                      /* xOpen flags */
  sqlite4_vfs *pVfs;              /* The "real" underlying VFS */
  sqlite4_file *pReal;            /* The "real" underlying file descriptor */
  const char *zJournal;           /* Name of the journal file */
};
typedef struct JournalFile JournalFile;

/*
** If it does not already exists, create and populate the on-disk file 
** for JournalFile p.
*/
static int createFile(JournalFile *p){
  int rc = SQLITE_OK;
  if( !p->pReal ){
    sqlite4_file *pReal = (sqlite4_file *)&p[1];
    rc = sqlite4OsOpen(p->pVfs, p->zJournal, pReal, p->flags, 0);
    if( rc==SQLITE_OK ){
      p->pReal = pReal;
      if( p->iSize>0 ){
        assert(p->iSize<=p->nBuf);
        rc = sqlite4OsWrite(p->pReal, p->zBuf, p->iSize, 0);
      }
    }
  }
  return rc;
}

/*
** Close the file.
*/
static int jrnlClose(sqlite4_file *pJfd){
  JournalFile *p = (JournalFile *)pJfd;
  if( p->pReal ){
    sqlite4OsClose(p->pReal);
  }
  sqlite4_free(p->zBuf);
  return SQLITE_OK;
}

/*
** Read data from the file.
*/
static int jrnlRead(
  sqlite4_file *pJfd,    /* The journal file from which to read */
  void *zBuf,            /* Put the results here */
  int iAmt,              /* Number of bytes to read */
  sqlite_int64 iOfst     /* Begin reading at this offset */
){
  int rc = SQLITE_OK;
  JournalFile *p = (JournalFile *)pJfd;
  if( p->pReal ){
    rc = sqlite4OsRead(p->pReal, zBuf, iAmt, iOfst);
  }else if( (iAmt+iOfst)>p->iSize ){
    rc = SQLITE_IOERR_SHORT_READ;
  }else{
    memcpy(zBuf, &p->zBuf[iOfst], iAmt);
  }
  return rc;
}

/*
** Write data to the file.
*/
static int jrnlWrite(
  sqlite4_file *pJfd,    /* The journal file into which to write */
  const void *zBuf,      /* Take data to be written from here */
  int iAmt,              /* Number of bytes to write */
  sqlite_int64 iOfst     /* Begin writing at this offset into the file */
){
  int rc = SQLITE_OK;
  JournalFile *p = (JournalFile *)pJfd;
  if( !p->pReal && (iOfst+iAmt)>p->nBuf ){
    rc = createFile(p);
  }
  if( rc==SQLITE_OK ){
    if( p->pReal ){
      rc = sqlite4OsWrite(p->pReal, zBuf, iAmt, iOfst);
    }else{
      memcpy(&p->zBuf[iOfst], zBuf, iAmt);
      if( p->iSize<(iOfst+iAmt) ){
        p->iSize = (iOfst+iAmt);
      }
    }
  }
  return rc;
}

/*
** Truncate the file.
*/
static int jrnlTruncate(sqlite4_file *pJfd, sqlite_int64 size){
  int rc = SQLITE_OK;
  JournalFile *p = (JournalFile *)pJfd;
  if( p->pReal ){
    rc = sqlite4OsTruncate(p->pReal, size);
  }else if( size<p->iSize ){
    p->iSize = size;
  }
  return rc;
}

/*
** Sync the file.
*/
static int jrnlSync(sqlite4_file *pJfd, int flags){
  int rc;
  JournalFile *p = (JournalFile *)pJfd;
  if( p->pReal ){
    rc = sqlite4OsSync(p->pReal, flags);
  }else{
    rc = SQLITE_OK;
  }
  return rc;
}

/*
** Query the size of the file in bytes.
*/
static int jrnlFileSize(sqlite4_file *pJfd, sqlite_int64 *pSize){
  int rc = SQLITE_OK;
  JournalFile *p = (JournalFile *)pJfd;
  if( p->pReal ){
    rc = sqlite4OsFileSize(p->pReal, pSize);
  }else{
    *pSize = (sqlite_int64) p->iSize;
  }
  return rc;
}

/*
** Table of methods for JournalFile sqlite4_file object.
*/
static struct sqlite4_io_methods JournalFileMethods = {
  1,             /* iVersion */
  jrnlClose,     /* xClose */
  jrnlRead,      /* xRead */
  jrnlWrite,     /* xWrite */
  jrnlTruncate,  /* xTruncate */
  jrnlSync,      /* xSync */
  jrnlFileSize,  /* xFileSize */
  0,             /* xLock */
  0,             /* xUnlock */
  0,             /* xCheckReservedLock */
  0,             /* xFileControl */
  0,             /* xSectorSize */
  0,             /* xDeviceCharacteristics */
  0,             /* xShmMap */
  0,             /* xShmLock */
  0,             /* xShmBarrier */
  0              /* xShmUnmap */
};

/* 
** Open a journal file.
*/
int sqlite4JournalOpen(
  sqlite4_vfs *pVfs,         /* The VFS to use for actual file I/O */
  const char *zName,         /* Name of the journal file */
  sqlite4_file *pJfd,        /* Preallocated, blank file handle */
  int flags,                 /* Opening flags */
  int nBuf                   /* Bytes buffered before opening the file */
){
  JournalFile *p = (JournalFile *)pJfd;
  memset(p, 0, sqlite4JournalSize(pVfs));
  if( nBuf>0 ){
    p->zBuf = sqlite4MallocZero(nBuf);
    if( !p->zBuf ){
      return SQLITE_NOMEM;
    }
  }else{
    return sqlite4OsOpen(pVfs, zName, pJfd, flags, 0);
  }
  p->pMethod = &JournalFileMethods;
  p->nBuf = nBuf;
  p->flags = flags;
  p->zJournal = zName;
  p->pVfs = pVfs;
  return SQLITE_OK;
}

/*
** If the argument p points to a JournalFile structure, and the underlying
** file has not yet been created, create it now.
*/
int sqlite4JournalCreate(sqlite4_file *p){
  if( p->pMethods!=&JournalFileMethods ){
    return SQLITE_OK;
  }
  return createFile((JournalFile *)p);
}

/* 
** Return the number of bytes required to store a JournalFile that uses vfs
** pVfs to create the underlying on-disk files.
*/
int sqlite4JournalSize(sqlite4_vfs *pVfs){
  return (pVfs->szOsFile+sizeof(JournalFile));
}
#endif
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Changes to src/kvmem.c.

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/*
** A complete in-memory Key/Value tree together with its
** transaction logs is an instance of the following object.
*/
struct KVMem {
  KVStore base;         /* Base class, must be first */
  KVMemNode *pRoot;     /* Root of the tree of content */
  int nTrans;           /* Number of nested option transactions */
  KVMemChng **apLog;    /* Array of transaction logs */
  int nCursor;          /* Number of outstanding cursors */
  int iMagicKVMemBase;  /* Magic number of sanity */
};
#define SQLITE_KVMEMBASE_MAGIC  0xbfcd47d0

/*
................................................................................
}

/*
** Create a new change record
*/
static KVMemChng *kvmemNewChng(KVMem *p, KVMemNode *pNode){
  KVMemChng *pChng;
  assert( p->nTrans>=2 );
  pChng = sqlite4_malloc( sizeof(*pChng) );
  if( pChng ){
    pChng->pNext = p->apLog[p->nTrans-2];
    p->apLog[p->nTrans-2] = pChng;
    pChng->pNode = pNode;
    pChng->oldTrans = pNode->mxTrans;
    pNode->mxTrans = p->nTrans;
    pChng->pData = pNode->pData;
    pNode->pData = 0;
  }
  return pChng;
}

/* Create a new node.
................................................................................
static KVMemNode *kvmemNewNode(
  KVMem *p,
  const KVByteArray *aKey,
  KVSize nKey
){
  KVMemNode *pNode;
  KVMemChng *pChng;
  assert( p->nTrans>=2 );
  pNode = sqlite4_malloc( sizeof(*pNode)+nKey-2 );
  if( pNode ){
    memset(pNode, 0, sizeof(*p));
    memcpy(pNode->aKey, aKey, nKey);
    pNode->nKey = nKey;
    pNode->nRef = 1;
    pChng = kvmemNewChng(p, pNode);
    if( pChng==0 ){
      sqlite4_free(pNode);
      pNode = 0;
................................................................................
** the transaction level will be equal to iLevel.  The transaction level
** must be at least 1 to read and at least 2 to write.
*/
static int kvmemBegin(KVStore *pKVStore, int iLevel){
  KVMem *p = (KVMem*)pKVStore;
  assert( p->iMagicKVMemBase==SQLITE_KVMEMBASE_MAGIC );
  assert( iLevel>0 );
  assert( iLevel==2 || iLevel==p->nTrans+1 );
  if( iLevel>=2 ){
    KVMemChng **apNewLog;
    apNewLog = sqlite4_realloc(p->apLog, sizeof(apNewLog[0])*(iLevel-1) );
    if( apNewLog==0 ) return SQLITE_NOMEM;
    p->apLog = apNewLog;
    p->apLog[iLevel-2] = 0;
  }
  p->nTrans = iLevel;
  return SQLITE_OK;
}

/*
** Commit a transaction or subtransaction.
**
** Make permanent all changes back through the most recent xBegin 
** with the iLevel+1.  If iLevel==0 then make all changes permanent.
** The argument iLevel will always be less than the current transaction
** level when this routine is called.




**
** After this routine returns successfully, the transaction level will be 
** equal to iLevel.
*/
static int kvmemCommit(KVStore *pKVStore, int iLevel){



  KVMem *p = (KVMem*)pKVStore;
  assert( p->iMagicKVMemBase==SQLITE_KVMEMBASE_MAGIC );
  assert( iLevel>=0 );
  assert( iLevel<p->nTrans );
  while( p->nTrans>iLevel && p->nTrans>1 ){
    KVMemChng *pChng, *pNext;
    for(pChng=p->apLog[p->nTrans-2]; pChng; pChng=pNext){
      KVMemNode *pNode = pChng->pNode;
      if( pNode->pData ){
        pNode->mxTrans = pChng->oldTrans;
      }else{
        kvmemRemoveNode(p, pNode);
      }
      kvmemDataUnref(pChng->pData);
      pNext = pChng->pNext;
      sqlite4_free(pChng);
    }
    p->apLog[p->nTrans-2] = 0;
    p->nTrans--;
  }
  p->nTrans = iLevel;
  return SQLITE_OK;
}

/*
** Rollback a transaction or subtransaction.
**
** Revert all uncommitted changes back through the most recent xBegin or 
................................................................................
** After this routine returns successfully, the transaction level will be
** equal to iLevel.
*/
static int kvmemRollback(KVStore *pKVStore, int iLevel){
  KVMem *p = (KVMem*)pKVStore;
  assert( p->iMagicKVMemBase==SQLITE_KVMEMBASE_MAGIC );
  assert( iLevel>=0 );
  assert( iLevel<p->nTrans );
  while( p->nTrans>iLevel && p->nTrans>1 ){
    KVMemChng *pChng, *pNext;
    for(pChng=p->apLog[p->nTrans-2]; pChng; pChng=pNext){
      KVMemNode *pNode = pChng->pNode;
      if( pChng->pData ){
        kvmemDataUnref(pNode->pData);
        pNode->pData = pChng->pData;
        pNode->mxTrans = pChng->oldTrans;
      }else{
        kvmemRemoveNode(p, pNode);
      }
      pNext = pChng->pNext;
      sqlite4_free(pChng);
    }
    p->apLog[p->nTrans-2] = 0;
    p->nTrans--;
  }
  p->nTrans = iLevel;
  return SQLITE_OK;
}












/*
** Implementation of the xReplace(X, aKey, nKey, aData, nData) method.
**
** Insert or replace the entry with the key aKey[0..nKey-1].  The data for
** the new entry is aData[0..nData-1].  Return SQLITE_OK on success or an
** error code if the insert fails.
................................................................................
  const KVByteArray *aData, KVSize nData
){
  KVMem *p = (KVMem*)pKVStore;
  KVMemNode *pNew, *pNode;
  KVMemData *pData;
  KVMemChng *pChng;
  assert( p->iMagicKVMemBase==SQLITE_KVMEMBASE_MAGIC );
  assert( p->nTrans>=2 );
  pData = kvmemDataNew(aData, nData);
  if( pData==0 ) return SQLITE_NOMEM;
  if( p->pRoot==0 ){
    pNode = pNew = kvmemNewNode(p, aKey, nKey);
    if( pNew==0 ) goto KVMemReplace_nomem;
    pNew->pUp = 0;
  }else{
................................................................................
        }else{
          pNode->pAfter = pNew = kvmemNewNode(p, aKey, nKey);
          if( pNew==0 ) goto KVMemReplace_nomem;
          pNew->pUp = pNode;
          break;
        }
      }else{
        if( pNode->mxTrans==p->nTrans ){
          kvmemDataUnref(pNode->pData);
        }else{
          pChng = kvmemNewChng(p, pNode);
          if( pChng==0 ) goto KVMemReplace_nomem;
        }
        pNode->pData = pData;
        return SQLITE_OK;
................................................................................
  KVCursor *pKVCursor, 
  const KVByteArray *aKey,
  KVSize nKey,
  int direction
){
  KVMemCursor *pCur;
  KVMemNode *pNode;

  int c;


  kvmemReset(pKVCursor);
  pCur = (KVMemCursor*)pKVCursor;
  assert( pCur->iMagicKVMemCur==SQLITE_KVMEMCUR_MAGIC );

  pNode = pCur->pOwner->pRoot;
  while( pNode ){
    c = kvmemKeyCompare(aKey, nKey, pNode->aKey, pNode->nKey);
    if( c==0
     || (c<0 && pNode->pBefore==0 && direction>0)
     || (c>0 && pNode->pAfter==0 && direction<0)
    ){
      pCur->pNode = kvmemNodeRef(pNode);

      pCur->pData = kvmemDataRef(pNode->pData);

      return c==0 ? SQLITE_OK : SQLITE_INEXACT;
    }
    pNode = (c<0) ? pNode->pBefore : pNode->pAfter;





  }












  return SQLITE_NOTFOUND;
}

/*
** Delete the entry that the cursor is pointing to.
**
** Though the entry is "deleted", it still continues to exist as a
** phantom.  Subsequent xNext or xPrev calls will work, as will
................................................................................
  KVMemChng *pChng;
  KVMem *p;

  pCur = (KVMemCursor*)pKVCursor;
  assert( pCur->iMagicKVMemCur==SQLITE_KVMEMCUR_MAGIC );
  p = pCur->pOwner;
  assert( p->iMagicKVMemBase==SQLITE_KVMEMBASE_MAGIC );
  assert( p->nTrans>=2 );
  pNode = pCur->pNode;
  if( pNode==0 ) return SQLITE_OK;
  if( pNode->pData==0 ) return SQLITE_OK;
  if( pNode->mxTrans<p->nTrans ){
    pChng = kvmemNewChng(p, pNode);
    if( pChng==0 ) return SQLITE_NOMEM;
  }else{
    kvmemDataUnref(pNode->pData);
    pNode->pData = 0;
  }
  return SQLITE_OK;
................................................................................
  do{
    pNode = kvmemNext(pNode);
  }while( pNode && pNode->pData==0 );
  if( pNode ){
    pCur->pNode = kvmemNodeRef(pNode);
    pCur->pData = kvmemDataRef(pNode->pData);
  }
  return pNode ? SQLITE_OK : SQLITE_DONE;
}

/*
** Move a cursor to the previous non-deleted node.
*/
static int kvmemPrevEntry(KVCursor *pKVCursor){
  KVMemCursor *pCur;
................................................................................
  do{
    pNode = kvmemPrev(pNode);
  }while( pNode && pNode->pData==0 );
  if( pNode ){
    pCur->pNode = kvmemNodeRef(pNode);
    pCur->pData = kvmemDataRef(pNode->pData);
  }
  return pNode ? SQLITE_OK : SQLITE_DONE;
}

/*
** Return the key of the node the cursor is pointing to.
*/
static int kvmemKey(
  KVCursor *pKVCursor,         /* The cursor whose key is desired */
................................................................................
** Destructor for the entire in-memory storage tree.
*/
static int kvmemClose(KVStore *pKVStore){
  KVMem *p = (KVMem*)pKVStore;
  if( p==0 ) return SQLITE_OK;
  assert( p->iMagicKVMemBase==SQLITE_KVMEMBASE_MAGIC );
  assert( p->nCursor==0 );

  if( p->nTrans ) kvmemCommit(pKVStore, 0);


  sqlite4_free(p->apLog);
  kvmemClearTree(p->pRoot);
  memset(p, 0, sizeof(*p));
  sqlite4_free(p);
  return SQLITE_OK;
}

................................................................................
  kvmemPrevEntry,
  kvmemDelete,
  kvmemKey,
  kvmemData,
  kvmemReset,
  kvmemCloseCursor,
  kvmemBegin,
  kvmemCommit,

  kvmemRollback,

  kvmemClose
};

/*
** Create a new in-memory storage engine and return a pointer to it.
*/
int sqlite4KVStoreOpenMem(KVStore **ppKVStore){
  KVMem *pNew = sqlite4_malloc( sizeof(*pNew) );
  if( pNew==0 ) return SQLITE_NOMEM;
  memset(pNew, 0, sizeof(*pNew));
  pNew->base.pStoreVfunc = &kvmemMethods;
  pNew->iMagicKVMemBase = SQLITE_KVMEMBASE_MAGIC;

  *ppKVStore = (KVStore*)pNew;
  return SQLITE_OK;
}







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/*
** A complete in-memory Key/Value tree together with its
** transaction logs is an instance of the following object.
*/
struct KVMem {
  KVStore base;         /* Base class, must be first */
  KVMemNode *pRoot;     /* Root of the tree of content */
  unsigned openFlags;   /* Flags used at open */
  KVMemChng **apLog;    /* Array of transaction logs */
  int nCursor;          /* Number of outstanding cursors */
  int iMagicKVMemBase;  /* Magic number of sanity */
};
#define SQLITE_KVMEMBASE_MAGIC  0xbfcd47d0

/*
................................................................................
}

/*
** Create a new change record
*/
static KVMemChng *kvmemNewChng(KVMem *p, KVMemNode *pNode){
  KVMemChng *pChng;
  assert( p->base.iTransLevel>=2 );
  pChng = sqlite4_malloc( sizeof(*pChng) );
  if( pChng ){
    pChng->pNext = p->apLog[p->base.iTransLevel-2];
    p->apLog[p->base.iTransLevel-2] = pChng;
    pChng->pNode = pNode;
    pChng->oldTrans = pNode->mxTrans;
    pNode->mxTrans = p->base.iTransLevel;
    pChng->pData = pNode->pData;
    pNode->pData = 0;
  }
  return pChng;
}

/* Create a new node.
................................................................................
static KVMemNode *kvmemNewNode(
  KVMem *p,
  const KVByteArray *aKey,
  KVSize nKey
){
  KVMemNode *pNode;
  KVMemChng *pChng;
  assert( p->base.iTransLevel>=2 );
  pNode = sqlite4_malloc( sizeof(*pNode)+nKey-2 );
  if( pNode ){
    memset(pNode, 0, sizeof(*pNode));
    memcpy(pNode->aKey, aKey, nKey);
    pNode->nKey = nKey;
    pNode->nRef = 1;
    pChng = kvmemNewChng(p, pNode);
    if( pChng==0 ){
      sqlite4_free(pNode);
      pNode = 0;
................................................................................
** the transaction level will be equal to iLevel.  The transaction level
** must be at least 1 to read and at least 2 to write.
*/
static int kvmemBegin(KVStore *pKVStore, int iLevel){
  KVMem *p = (KVMem*)pKVStore;
  assert( p->iMagicKVMemBase==SQLITE_KVMEMBASE_MAGIC );
  assert( iLevel>0 );
  assert( iLevel==2 || iLevel==p->base.iTransLevel+1 );
  if( iLevel>=2 ){
    KVMemChng **apNewLog;
    apNewLog = sqlite4_realloc(p->apLog, sizeof(apNewLog[0])*(iLevel-1) );
    if( apNewLog==0 ) return SQLITE_NOMEM;
    p->apLog = apNewLog;
    p->apLog[iLevel-2] = 0;
  }
  p->base.iTransLevel = iLevel;
  return SQLITE_OK;
}

/*
** Commit a transaction or subtransaction.
**
** Make permanent all changes back through the most recent xBegin 
** with the iLevel+1.  If iLevel==0 then make all changes permanent.
** The argument iLevel will always be less than the current transaction
** level when this routine is called.
**
** Commit is divided into two phases.  A rollback is still possible after
** phase one completes.  In this implementation, phase one is a no-op since
** phase two cannot fail.
**
** After this routine returns successfully, the transaction level will be 
** equal to iLevel.
*/
static int kvmemCommitPhaseOne(KVStore *pKVStore, int iLevel){
  return SQLITE_OK;
}
static int kvmemCommitPhaseTwo(KVStore *pKVStore, int iLevel){
  KVMem *p = (KVMem*)pKVStore;
  assert( p->iMagicKVMemBase==SQLITE_KVMEMBASE_MAGIC );
  assert( iLevel>=0 );
  assert( iLevel<p->base.iTransLevel );
  while( p->base.iTransLevel>iLevel && p->base.iTransLevel>1 ){
    KVMemChng *pChng, *pNext;
    for(pChng=p->apLog[p->base.iTransLevel-2]; pChng; pChng=pNext){
      KVMemNode *pNode = pChng->pNode;
      if( pNode->pData ){
        pNode->mxTrans = pChng->oldTrans;
      }else{
        kvmemRemoveNode(p, pNode);
      }
      kvmemDataUnref(pChng->pData);
      pNext = pChng->pNext;
      sqlite4_free(pChng);
    }
    p->apLog[p->base.iTransLevel-2] = 0;
    p->base.iTransLevel--;
  }
  p->base.iTransLevel = iLevel;
  return SQLITE_OK;
}

/*
** Rollback a transaction or subtransaction.
**
** Revert all uncommitted changes back through the most recent xBegin or 
................................................................................
** After this routine returns successfully, the transaction level will be
** equal to iLevel.
*/
static int kvmemRollback(KVStore *pKVStore, int iLevel){
  KVMem *p = (KVMem*)pKVStore;
  assert( p->iMagicKVMemBase==SQLITE_KVMEMBASE_MAGIC );
  assert( iLevel>=0 );
  assert( iLevel<p->base.iTransLevel );
  while( p->base.iTransLevel>iLevel && p->base.iTransLevel>1 ){
    KVMemChng *pChng, *pNext;
    for(pChng=p->apLog[p->base.iTransLevel-2]; pChng; pChng=pNext){
      KVMemNode *pNode = pChng->pNode;
      if( pChng->pData ){
        kvmemDataUnref(pNode->pData);
        pNode->pData = pChng->pData;
        pNode->mxTrans = pChng->oldTrans;
      }else{
        kvmemRemoveNode(p, pNode);
      }
      pNext = pChng->pNext;
      sqlite4_free(pChng);
    }
    p->apLog[p->base.iTransLevel-2] = 0;
    p->base.iTransLevel--;
  }
  p->base.iTransLevel = iLevel;
  return SQLITE_OK;
}

/*
** Revert a transaction back to what it was when it started.
*/
static int kvmemRevert(KVStore *pKVStore, int iLevel){
  int rc = kvmemRollback(pKVStore, iLevel-1);
  if( rc==SQLITE_OK ){
    rc = kvmemBegin(pKVStore, iLevel);
  }
  return rc;
}

/*
** Implementation of the xReplace(X, aKey, nKey, aData, nData) method.
**
** Insert or replace the entry with the key aKey[0..nKey-1].  The data for
** the new entry is aData[0..nData-1].  Return SQLITE_OK on success or an
** error code if the insert fails.
................................................................................
  const KVByteArray *aData, KVSize nData
){
  KVMem *p = (KVMem*)pKVStore;
  KVMemNode *pNew, *pNode;
  KVMemData *pData;
  KVMemChng *pChng;
  assert( p->iMagicKVMemBase==SQLITE_KVMEMBASE_MAGIC );
  assert( p->base.iTransLevel>=2 );
  pData = kvmemDataNew(aData, nData);
  if( pData==0 ) return SQLITE_NOMEM;
  if( p->pRoot==0 ){
    pNode = pNew = kvmemNewNode(p, aKey, nKey);
    if( pNew==0 ) goto KVMemReplace_nomem;
    pNew->pUp = 0;
  }else{
................................................................................
        }else{
          pNode->pAfter = pNew = kvmemNewNode(p, aKey, nKey);
          if( pNew==0 ) goto KVMemReplace_nomem;
          pNew->pUp = pNode;
          break;
        }
      }else{
        if( pNode->mxTrans==p->base.iTransLevel ){
          kvmemDataUnref(pNode->pData);
        }else{
          pChng = kvmemNewChng(p, pNode);
          if( pChng==0 ) goto KVMemReplace_nomem;
        }
        pNode->pData = pData;
        return SQLITE_OK;
................................................................................
  KVCursor *pKVCursor, 
  const KVByteArray *aKey,
  KVSize nKey,
  int direction
){
  KVMemCursor *pCur;
  KVMemNode *pNode;
  KVMemNode *pBest = 0;
  int c;
  int rc = SQLITE_NOTFOUND;

  kvmemReset(pKVCursor);
  pCur = (KVMemCursor*)pKVCursor;
  assert( pCur->iMagicKVMemCur==SQLITE_KVMEMCUR_MAGIC );

  pNode = pCur->pOwner->pRoot;
  while( pNode ){
    c = kvmemKeyCompare(aKey, nKey, pNode->aKey, pNode->nKey);
    if( c==0 ){
      pBest = pNode;
      rc = SQLITE_OK;

      pNode = 0;
    }else if( c>0 ){
      if( direction<0 ){
        pBest = pNode;
        rc = SQLITE_INEXACT;
      }

      pNode = pNode->pAfter;
    }else{
      if( direction>0 ){
        pBest = pNode;
        rc = SQLITE_INEXACT;
      }
      pNode = pNode->pBefore;
    }
  }
  kvmemNodeUnref(pCur->pNode);
  kvmemDataUnref(pCur->pData);
  if( pBest ){
    pCur->pNode = kvmemNodeRef(pBest);
    pCur->pData = kvmemDataRef(pBest->pData);
  }else{
    pCur->pNode = 0;
    pCur->pData = 0;
  }
  return rc;
}

/*
** Delete the entry that the cursor is pointing to.
**
** Though the entry is "deleted", it still continues to exist as a
** phantom.  Subsequent xNext or xPrev calls will work, as will
................................................................................
  KVMemChng *pChng;
  KVMem *p;

  pCur = (KVMemCursor*)pKVCursor;
  assert( pCur->iMagicKVMemCur==SQLITE_KVMEMCUR_MAGIC );
  p = pCur->pOwner;
  assert( p->iMagicKVMemBase==SQLITE_KVMEMBASE_MAGIC );
  assert( p->base.iTransLevel>=2 );
  pNode = pCur->pNode;
  if( pNode==0 ) return SQLITE_OK;
  if( pNode->pData==0 ) return SQLITE_OK;
  if( pNode->mxTrans<p->base.iTransLevel ){
    pChng = kvmemNewChng(p, pNode);
    if( pChng==0 ) return SQLITE_NOMEM;
  }else{
    kvmemDataUnref(pNode->pData);
    pNode->pData = 0;
  }
  return SQLITE_OK;
................................................................................
  do{
    pNode = kvmemNext(pNode);
  }while( pNode && pNode->pData==0 );
  if( pNode ){
    pCur->pNode = kvmemNodeRef(pNode);
    pCur->pData = kvmemDataRef(pNode->pData);
  }
  return pNode ? SQLITE_OK : SQLITE_NOTFOUND;
}

/*
** Move a cursor to the previous non-deleted node.
*/
static int kvmemPrevEntry(KVCursor *pKVCursor){
  KVMemCursor *pCur;
................................................................................
  do{
    pNode = kvmemPrev(pNode);
  }while( pNode && pNode->pData==0 );
  if( pNode ){
    pCur->pNode = kvmemNodeRef(pNode);
    pCur->pData = kvmemDataRef(pNode->pData);
  }
  return pNode ? SQLITE_OK : SQLITE_NOTFOUND;
}

/*
** Return the key of the node the cursor is pointing to.
*/
static int kvmemKey(
  KVCursor *pKVCursor,         /* The cursor whose key is desired */
................................................................................
** Destructor for the entire in-memory storage tree.
*/
static int kvmemClose(KVStore *pKVStore){
  KVMem *p = (KVMem*)pKVStore;
  if( p==0 ) return SQLITE_OK;
  assert( p->iMagicKVMemBase==SQLITE_KVMEMBASE_MAGIC );
  assert( p->nCursor==0 );
  if( p->base.iTransLevel ){
    kvmemCommitPhaseOne(pKVStore, 0);
    kvmemCommitPhaseTwo(pKVStore, 0);
  }
  sqlite4_free(p->apLog);
  kvmemClearTree(p->pRoot);
  memset(p, 0, sizeof(*p));
  sqlite4_free(p);
  return SQLITE_OK;
}

................................................................................
  kvmemPrevEntry,
  kvmemDelete,
  kvmemKey,
  kvmemData,
  kvmemReset,
  kvmemCloseCursor,
  kvmemBegin,
  kvmemCommitPhaseOne,
  kvmemCommitPhaseTwo,
  kvmemRollback,
  kvmemRevert,
  kvmemClose
};

/*
** Create a new in-memory storage engine and return a pointer to it.
*/
int sqlite4KVStoreOpenMem(KVStore **ppKVStore, unsigned openFlags){
  KVMem *pNew = sqlite4_malloc( sizeof(*pNew) );
  if( pNew==0 ) return SQLITE_NOMEM;
  memset(pNew, 0, sizeof(*pNew));
  pNew->base.pStoreVfunc = &kvmemMethods;
  pNew->iMagicKVMemBase = SQLITE_KVMEMBASE_MAGIC;
  pNew->openFlags = openFlags;
  *ppKVStore = (KVStore*)pNew;
  return SQLITE_OK;
}

Changes to src/legacy.c.

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    nCol = sqlite4_column_count(pStmt);

    while( 1 ){
      int i;
      rc = sqlite4_step(pStmt);

      /* Invoke the callback function if required */
      if( xCallback && (SQLITE_ROW==rc || 
          (SQLITE_DONE==rc && !callbackIsInit
                           && db->flags&SQLITE_NullCallback)) ){
        if( !callbackIsInit ){
          azCols = sqlite4DbMallocZero(db, 2*nCol*sizeof(const char*) + 1);
          if( azCols==0 ){
            goto exec_out;
          }
          for(i=0; i<nCol; i++){
            azCols[i] = (char *)sqlite4_column_name(pStmt, i);







|
<
<







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    nCol = sqlite4_column_count(pStmt);

    while( 1 ){
      int i;
      rc = sqlite4_step(pStmt);

      /* Invoke the callback function if required */
      if( xCallback && SQLITE_ROW==rc ){


        if( !callbackIsInit ){
          azCols = sqlite4DbMallocZero(db, 2*nCol*sizeof(const char*) + 1);
          if( azCols==0 ){
            goto exec_out;
          }
          for(i=0; i<nCol; i++){
            azCols[i] = (char *)sqlite4_column_name(pStmt, i);

Deleted src/loadext.c.

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/*
** 2006 June 7
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains code used to dynamically load extensions into
** the SQLite library.
*/

#ifndef SQLITE_CORE
  #define SQLITE_CORE 1  /* Disable the API redefinition in sqlite4ext.h */
#endif
#include "sqlite4ext.h"
#include "sqliteInt.h"
#include <string.h>

#ifndef SQLITE_OMIT_LOAD_EXTENSION

/*
** Some API routines are omitted when various features are
** excluded from a build of SQLite.  Substitute a NULL pointer
** for any missing APIs.
*/
#ifndef SQLITE_ENABLE_COLUMN_METADATA
# define sqlite4_column_database_name   0
# define sqlite4_column_database_name16 0
# define sqlite4_column_table_name      0
# define sqlite4_column_table_name16    0
# define sqlite4_column_origin_name     0
# define sqlite4_column_origin_name16   0
# define sqlite4_table_column_metadata  0
#endif

#ifdef SQLITE_OMIT_AUTHORIZATION
# define sqlite4_set_authorizer         0
#endif

#ifdef SQLITE_OMIT_UTF16
# define sqlite4_bind_text16            0
# define sqlite4_collation_needed16     0
# define sqlite4_column_decltype16      0
# define sqlite4_column_name16          0
# define sqlite4_column_text16          0
# define sqlite4_complete16             0
# define sqlite4_create_function16      0
# define sqlite4_errmsg16               0
# define sqlite4_open16                 0
# define sqlite4_prepare16              0
# define sqlite4_prepare16_v2           0
# define sqlite4_result_error16         0
# define sqlite4_result_text16          0
# define sqlite4_result_text16be        0
# define sqlite4_result_text16le        0
# define sqlite4_value_text16           0
# define sqlite4_value_text16be         0
# define sqlite4_value_text16le         0
# define sqlite4_column_database_name16 0
# define sqlite4_column_table_name16    0
# define sqlite4_column_origin_name16   0
#endif

#ifdef SQLITE_OMIT_COMPLETE
# define sqlite4_complete 0
# define sqlite4_complete16 0
#endif

#ifdef SQLITE_OMIT_DECLTYPE
# define sqlite4_column_decltype16      0
# define sqlite4_column_decltype        0
#endif

#ifdef SQLITE_OMIT_PROGRESS_CALLBACK
# define sqlite4_progress_handler 0
#endif

#ifdef SQLITE_OMIT_VIRTUALTABLE
# define sqlite4_create_module 0
# define sqlite4_create_module_v2 0
# define sqlite4_declare_vtab 0
# define sqlite4_vtab_config 0
# define sqlite4_vtab_on_conflict 0
#endif

#ifdef SQLITE_OMIT_SHARED_CACHE
# define sqlite4_enable_shared_cache 0
#endif

#ifdef SQLITE_OMIT_TRACE
# define sqlite4_profile       0
# define sqlite4_trace         0
#endif

#ifdef SQLITE_OMIT_GET_TABLE
# define sqlite4_free_table    0
# define sqlite4_get_table     0
#endif

#ifdef SQLITE_OMIT_INCRBLOB
#define sqlite4_bind_zeroblob  0
#define sqlite4_blob_bytes     0
#define sqlite4_blob_close     0
#define sqlite4_blob_open      0
#define sqlite4_blob_read      0
#define sqlite4_blob_write     0
#define sqlite4_blob_reopen    0
#endif

/*
** The following structure contains pointers to all SQLite API routines.
** A pointer to this structure is passed into extensions when they are
** loaded so that the extension can make calls back into the SQLite
** library.
**
** When adding new APIs, add them to the bottom of this structure
** in order to preserve backwards compatibility.
**
** Extensions that use newer APIs should first call the
** sqlite4_libversion_number() to make sure that the API they
** intend to use is supported by the library.  Extensions should
** also check to make sure that the pointer to the function is
** not NULL before calling it.
*/
static const sqlite4_api_routines sqlite4Apis = {
  sqlite4_aggregate_context,
#ifndef SQLITE_OMIT_DEPRECATED
  sqlite4_aggregate_count,
#else
  0,
#endif
  sqlite4_bind_blob,
  sqlite4_bind_double,
  sqlite4_bind_int,
  sqlite4_bind_int64,
  sqlite4_bind_null,
  sqlite4_bind_parameter_count,
  sqlite4_bind_parameter_index,
  sqlite4_bind_parameter_name,
  sqlite4_bind_text,
  sqlite4_bind_text16,
  sqlite4_bind_value,
  sqlite4_busy_handler,
  sqlite4_busy_timeout,
  sqlite4_changes,
  sqlite4_close,
  sqlite4_collation_needed,
  sqlite4_collation_needed16,
  sqlite4_column_blob,
  sqlite4_column_bytes,
  sqlite4_column_bytes16,
  sqlite4_column_count,
  sqlite4_column_database_name,
  sqlite4_column_database_name16,
  sqlite4_column_decltype,
  sqlite4_column_decltype16,
  sqlite4_column_double,
  sqlite4_column_int,
  sqlite4_column_int64,
  sqlite4_column_name,
  sqlite4_column_name16,
  sqlite4_column_origin_name,
  sqlite4_column_origin_name16,
  sqlite4_column_table_name,
  sqlite4_column_table_name16,
  sqlite4_column_text,
  sqlite4_column_text16,
  sqlite4_column_type,
  sqlite4_column_value,
  sqlite4_commit_hook,
  sqlite4_complete,
  sqlite4_complete16,
  sqlite4_create_collation,
  sqlite4_create_function,
  sqlite4_create_function16,
  sqlite4_create_module,
  sqlite4_data_count,
  sqlite4_db_handle,
  sqlite4_declare_vtab,
  sqlite4_enable_shared_cache,
  sqlite4_errcode,
  sqlite4_errmsg,
  sqlite4_errmsg16,
  sqlite4_exec,
#ifndef SQLITE_OMIT_DEPRECATED
  sqlite4_expired,
#else
  0,
#endif
  sqlite4_finalize,
  sqlite4_free,
  sqlite4_free_table,
  sqlite4_get_autocommit,
  sqlite4_get_auxdata,
  sqlite4_get_table,
  0,     /* Was sqlite4_global_recover(), but that function is deprecated */
  sqlite4_interrupt,
  sqlite4_last_insert_rowid,
  sqlite4_libversion,
  sqlite4_libversion_number,
  sqlite4_malloc,
  sqlite4_mprintf,
  sqlite4_open,
  sqlite4_open16,
  sqlite4_prepare,
  sqlite4_prepare16,
  sqlite4_profile,
  sqlite4_progress_handler,
  sqlite4_realloc,
  sqlite4_reset,
  sqlite4_result_blob,
  sqlite4_result_double,
  sqlite4_result_error,
  sqlite4_result_error16,
  sqlite4_result_int,
  sqlite4_result_int64,
  sqlite4_result_null,
  sqlite4_result_text,
  sqlite4_result_text16,
  sqlite4_result_text16be,
  sqlite4_result_text16le,
  sqlite4_result_value,
  sqlite4_rollback_hook,
  sqlite4_set_authorizer,
  sqlite4_set_auxdata,
  sqlite4_snprintf,
  sqlite4_step,
  sqlite4_table_column_metadata,
#ifndef SQLITE_OMIT_DEPRECATED
  sqlite4_thread_cleanup,
#else
  0,
#endif
  sqlite4_total_changes,
  sqlite4_trace,
#ifndef SQLITE_OMIT_DEPRECATED
  sqlite4_transfer_bindings,
#else
  0,
#endif
  sqlite4_update_hook,
  sqlite4_user_data,
  sqlite4_value_blob,
  sqlite4_value_bytes,
  sqlite4_value_bytes16,
  sqlite4_value_double,
  sqlite4_value_int,
  sqlite4_value_int64,
  sqlite4_value_numeric_type,
  sqlite4_value_text,
  sqlite4_value_text16,
  sqlite4_value_text16be,
  sqlite4_value_text16le,
  sqlite4_value_type,
  sqlite4_vmprintf,
  /*
  ** The original API set ends here.  All extensions can call any
  ** of the APIs above provided that the pointer is not NULL.  But
  ** before calling APIs that follow, extension should check the
  ** sqlite4_libversion_number() to make sure they are dealing with
  ** a library that is new enough to support that API.
  *************************************************************************
  */
  sqlite4_overload_function,

  /*
  ** Added after 3.3.13
  */
  sqlite4_prepare_v2,
  sqlite4_prepare16_v2,
  sqlite4_clear_bindings,

  /*
  ** Added for 3.4.1
  */
  sqlite4_create_module_v2,

  /*
  ** Added for 3.5.0
  */
  sqlite4_bind_zeroblob,
  sqlite4_blob_bytes,
  sqlite4_blob_close,
  sqlite4_blob_open,
  sqlite4_blob_read,
  sqlite4_blob_write,
  sqlite4_file_control,
  sqlite4_memory_highwater,
  sqlite4_memory_used,
#ifdef SQLITE_MUTEX_OMIT
  0, 
  0, 
  0,
  0,
  0,
#else
  sqlite4_mutex_alloc,
  sqlite4_mutex_enter,
  sqlite4_mutex_free,
  sqlite4_mutex_leave,
  sqlite4_mutex_try,
#endif
  sqlite4_open_v2,
  sqlite4_release_memory,
  sqlite4_result_error_nomem,
  sqlite4_result_error_toobig,
  sqlite4_sleep,
  sqlite4_soft_heap_limit,
  sqlite4_vfs_find,
  sqlite4_vfs_register,
  sqlite4_vfs_unregister,

  /*
  ** Added for 3.5.8
  */
  sqlite4_threadsafe,
  sqlite4_result_zeroblob,
  sqlite4_result_error_code,
  sqlite4_test_control,
  sqlite4_randomness,
  sqlite4_context_db_handle,

  /*
  ** Added for 3.6.0
  */
  sqlite4_extended_result_codes,
  sqlite4_limit,
  sqlite4_next_stmt,
  sqlite4_sql,
  sqlite4_status,

  /*
  ** Added for 3.7.4
  */
  sqlite4_backup_finish,
  sqlite4_backup_init,
  sqlite4_backup_pagecount,
  sqlite4_backup_remaining,
  sqlite4_backup_step,
#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
  sqlite4_compileoption_get,
  sqlite4_compileoption_used,
#else
  0,
  0,
#endif
  sqlite4_create_function_v2,
  sqlite4_db_config,
  sqlite4_db_mutex,
  sqlite4_db_status,
  sqlite4_extended_errcode,
  sqlite4_log,
  sqlite4_soft_heap_limit64,
  sqlite4_sourceid,
  sqlite4_stmt_status,
  sqlite4_strnicmp,
#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
  sqlite4_unlock_notify,
#else
  0,
#endif
#ifndef SQLITE_OMIT_WAL
  sqlite4_wal_autocheckpoint,
  sqlite4_wal_checkpoint,
  sqlite4_wal_hook,
#else
  0,
  0,
  0,
#endif
  sqlite4_blob_reopen,
  sqlite4_vtab_config,
  sqlite4_vtab_on_conflict,
};

/*
** Attempt to load an SQLite extension library contained in the file
** zFile.  The entry point is zProc.  zProc may be 0 in which case a
** default entry point name (sqlite4_extension_init) is used.  Use
** of the default name is recommended.
**
** Return SQLITE_OK on success and SQLITE_ERROR if something goes wrong.
**
** If an error occurs and pzErrMsg is not 0, then fill *pzErrMsg with 
** error message text.  The calling function should free this memory
** by calling sqlite4DbFree(db, ).
*/
static int sqlite4LoadExtension(
  sqlite4 *db,          /* Load the extension into this database connection */
  const char *zFile,    /* Name of the shared library containing extension */
  const char *zProc,    /* Entry point.  Use "sqlite4_extension_init" if 0 */
  char **pzErrMsg       /* Put error message here if not 0 */
){
  sqlite4_vfs *pVfs = db->pVfs;
  void *handle;
  int (*xInit)(sqlite4*,char**,const sqlite4_api_routines*);
  char *zErrmsg = 0;
  void **aHandle;
  int nMsg = 300 + sqlite4Strlen30(zFile);

  if( pzErrMsg ) *pzErrMsg = 0;

  /* Ticket #1863.  To avoid a creating security problems for older
  ** applications that relink against newer versions of SQLite, the
  ** ability to run load_extension is turned off by default.  One
  ** must call sqlite4_enable_load_extension() to turn on extension
  ** loading.  Otherwise you get the following error.
  */
  if( (db->flags & SQLITE_LoadExtension)==0 ){
    if( pzErrMsg ){
      *pzErrMsg = sqlite4_mprintf("not authorized");
    }
    return SQLITE_ERROR;
  }

  if( zProc==0 ){
    zProc = "sqlite4_extension_init";
  }

  handle = sqlite4OsDlOpen(pVfs, zFile);
  if( handle==0 ){
    if( pzErrMsg ){
      *pzErrMsg = zErrmsg = sqlite4_malloc(nMsg);
      if( zErrmsg ){
        sqlite4_snprintf(nMsg, zErrmsg, 
            "unable to open shared library [%s]", zFile);
        sqlite4OsDlError(pVfs, nMsg-1, zErrmsg);
      }
    }
    return SQLITE_ERROR;
  }
  xInit = (int(*)(sqlite4*,char**,const sqlite4_api_routines*))
                   sqlite4OsDlSym(pVfs, handle, zProc);
  if( xInit==0 ){
    if( pzErrMsg ){
      nMsg += sqlite4Strlen30(zProc);
      *pzErrMsg = zErrmsg = sqlite4_malloc(nMsg);
      if( zErrmsg ){
        sqlite4_snprintf(nMsg, zErrmsg,
            "no entry point [%s] in shared library [%s]", zProc,zFile);
        sqlite4OsDlError(pVfs, nMsg-1, zErrmsg);
      }
      sqlite4OsDlClose(pVfs, handle);
    }
    return SQLITE_ERROR;
  }else if( xInit(db, &zErrmsg, &sqlite4Apis) ){
    if( pzErrMsg ){
      *pzErrMsg = sqlite4_mprintf("error during initialization: %s", zErrmsg);
    }
    sqlite4_free(zErrmsg);
    sqlite4OsDlClose(pVfs, handle);
    return SQLITE_ERROR;
  }

  /* Append the new shared library handle to the db->aExtension array. */
  aHandle = sqlite4DbMallocZero(db, sizeof(handle)*(db->nExtension+1));
  if( aHandle==0 ){
    return SQLITE_NOMEM;
  }
  if( db->nExtension>0 ){
    memcpy(aHandle, db->aExtension, sizeof(handle)*db->nExtension);
  }
  sqlite4DbFree(db, db->aExtension);
  db->aExtension = aHandle;

  db->aExtension[db->nExtension++] = handle;
  return SQLITE_OK;
}
int sqlite4_load_extension(
  sqlite4 *db,          /* Load the extension into this database connection */
  const char *zFile,    /* Name of the shared library containing extension */
  const char *zProc,    /* Entry point.  Use "sqlite4_extension_init" if 0 */
  char **pzErrMsg       /* Put error message here if not 0 */
){
  int rc;
  sqlite4_mutex_enter(db->mutex);
  rc = sqlite4LoadExtension(db, zFile, zProc, pzErrMsg);
  rc = sqlite4ApiExit(db, rc);
  sqlite4_mutex_leave(db->mutex);
  return rc;
}

/*
** Call this routine when the database connection is closing in order
** to clean up loaded extensions
*/
void sqlite4CloseExtensions(sqlite4 *db){
  int i;
  assert( sqlite4_mutex_held(db->mutex) );
  for(i=0; i<db->nExtension; i++){
    sqlite4OsDlClose(db->pVfs, db->aExtension[i]);
  }
  sqlite4DbFree(db, db->aExtension);
}

/*
** Enable or disable extension loading.  Extension loading is disabled by
** default so as not to open security holes in older applications.
*/
int sqlite4_enable_load_extension(sqlite4 *db, int onoff){
  sqlite4_mutex_enter(db->mutex);
  if( onoff ){
    db->flags |= SQLITE_LoadExtension;
  }else{
    db->flags &= ~SQLITE_LoadExtension;
  }
  sqlite4_mutex_leave(db->mutex);
  return SQLITE_OK;
}

#endif /* SQLITE_OMIT_LOAD_EXTENSION */

/*
** The auto-extension code added regardless of whether or not extension
** loading is supported.  We need a dummy sqlite4Apis pointer for that
** code if regular extension loading is not available.  This is that
** dummy pointer.
*/
#ifdef SQLITE_OMIT_LOAD_EXTENSION
static const sqlite4_api_routines sqlite4Apis = { 0 };
#endif


/*
** The following object holds the list of automatically loaded
** extensions.
**
** This list is shared across threads.  The SQLITE_MUTEX_STATIC_MASTER
** mutex must be held while accessing this list.
*/
typedef struct sqlite4AutoExtList sqlite4AutoExtList;
static SQLITE_WSD struct sqlite4AutoExtList {
  int nExt;              /* Number of entries in aExt[] */          
  void (**aExt)(void);   /* Pointers to the extension init functions */
} sqlite4Autoext = { 0, 0 };

/* The "wsdAutoext" macro will resolve to the autoextension
** state vector.  If writable static data is unsupported on the target,
** we have to locate the state vector at run-time.  In the more common
** case where writable static data is supported, wsdStat can refer directly
** to the "sqlite4Autoext" state vector declared above.
*/
#ifdef SQLITE_OMIT_WSD
# define wsdAutoextInit \
  sqlite4AutoExtList *x = &GLOBAL(sqlite4AutoExtList,sqlite4Autoext)
# define wsdAutoext x[0]
#else
# define wsdAutoextInit
# define wsdAutoext sqlite4Autoext
#endif


/*
** Register a statically linked extension that is automatically
** loaded by every new database connection.
*/
int sqlite4_auto_extension(void (*xInit)(void)){
  int rc = SQLITE_OK;
#ifndef SQLITE_OMIT_AUTOINIT
  rc = sqlite4_initialize();
  if( rc ){
    return rc;
  }else
#endif
  {
    int i;
#if SQLITE_THREADSAFE
    sqlite4_mutex *mutex = sqlite4MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
#endif
    wsdAutoextInit;
    sqlite4_mutex_enter(mutex);
    for(i=0; i<wsdAutoext.nExt; i++){
      if( wsdAutoext.aExt[i]==xInit ) break;
    }
    if( i==wsdAutoext.nExt ){
      int nByte = (wsdAutoext.nExt+1)*sizeof(wsdAutoext.aExt[0]);
      void (**aNew)(void);
      aNew = sqlite4_realloc(wsdAutoext.aExt, nByte);
      if( aNew==0 ){
        rc = SQLITE_NOMEM;
      }else{
        wsdAutoext.aExt = aNew;
        wsdAutoext.aExt[wsdAutoext.nExt] = xInit;
        wsdAutoext.nExt++;
      }
    }
    sqlite4_mutex_leave(mutex);
    assert( (rc&0xff)==rc );
    return rc;
  }
}

/*
** Reset the automatic extension loading mechanism.
*/
void sqlite4_reset_auto_extension(void){
#ifndef SQLITE_OMIT_AUTOINIT
  if( sqlite4_initialize()==SQLITE_OK )
#endif
  {
#if SQLITE_THREADSAFE
    sqlite4_mutex *mutex = sqlite4MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
#endif
    wsdAutoextInit;
    sqlite4_mutex_enter(mutex);
    sqlite4_free(wsdAutoext.aExt);
    wsdAutoext.aExt = 0;
    wsdAutoext.nExt = 0;
    sqlite4_mutex_leave(mutex);
  }
}

/*
** Load all automatic extensions.
**
** If anything goes wrong, set an error in the database connection.
*/
void sqlite4AutoLoadExtensions(sqlite4 *db){
  int i;
  int go = 1;
  int rc;
  int (*xInit)(sqlite4*,char**,const sqlite4_api_routines*);

  wsdAutoextInit;
  if( wsdAutoext.nExt==0 ){
    /* Common case: early out without every having to acquire a mutex */
    return;
  }
  for(i=0; go; i++){
    char *zErrmsg;
#if SQLITE_THREADSAFE
    sqlite4_mutex *mutex = sqlite4MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
#endif
    sqlite4_mutex_enter(mutex);
    if( i>=wsdAutoext.nExt ){
      xInit = 0;
      go = 0;
    }else{
      xInit = (int(*)(sqlite4*,char**,const sqlite4_api_routines*))
              wsdAutoext.aExt[i];
    }
    sqlite4_mutex_leave(mutex);
    zErrmsg = 0;
    if( xInit && (rc = xInit(db, &zErrmsg, &sqlite4Apis))!=0 ){
      sqlite4Error(db, rc,
            "automatic extension loading failed: %s", zErrmsg);
      go = 0;
    }
    sqlite4_free(zErrmsg);
  }
}
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  }

  /* Do the rest of the initialization under the recursive mutex so
  ** that we will be able to handle recursive calls into
  ** sqlite4_initialize().  The recursive calls normally come through
  ** sqlite4_os_init() when it invokes sqlite4_vfs_register(), but other
  ** recursive calls might also be possible.
  **
  ** IMPLEMENTATION-OF: R-00140-37445 SQLite automatically serializes calls
  ** to the xInit method, so the xInit method need not be threadsafe.
  **
  ** The following mutex is what serializes access to the appdef pcache xInit
  ** methods.  The sqlite4_pcache_methods.xInit() all is embedded in the
  ** call to sqlite4PcacheInitialize().
  */
  sqlite4_mutex_enter(sqlite4GlobalConfig.pInitMutex);
  if( sqlite4GlobalConfig.isInit==0 && sqlite4GlobalConfig.inProgress==0 ){
    FuncDefHash *pHash = &GLOBAL(FuncDefHash, sqlite4GlobalFunctions);
    sqlite4GlobalConfig.inProgress = 1;
    memset(pHash, 0, sizeof(sqlite4GlobalFunctions));
    sqlite4RegisterGlobalFunctions();
    if( sqlite4GlobalConfig.isPCacheInit==0 ){
      rc = sqlite4PcacheInitialize();
    }
    if( rc==SQLITE_OK ){
      sqlite4GlobalConfig.isPCacheInit = 1;
      rc = sqlite4OsInit();
    }
    if( rc==SQLITE_OK ){
      sqlite4PCacheBufferSetup( sqlite4GlobalConfig.pPage, 
          sqlite4GlobalConfig.szPage, sqlite4GlobalConfig.nPage);
      sqlite4GlobalConfig.isInit = 1;
    }
    sqlite4GlobalConfig.inProgress = 0;
  }
  sqlite4_mutex_leave(sqlite4GlobalConfig.pInitMutex);

  /* Go back under the static mutex and clean up the recursive
  ** mutex to prevent a resource leak.
  */
................................................................................
int sqlite4_shutdown(void){
  if( sqlite4GlobalConfig.isInit ){
#ifdef SQLITE_EXTRA_SHUTDOWN
    void SQLITE_EXTRA_SHUTDOWN(void);
    SQLITE_EXTRA_SHUTDOWN();
#endif
    sqlite4_os_end();
    sqlite4_reset_auto_extension();
    sqlite4GlobalConfig.isInit = 0;
  }
  if( sqlite4GlobalConfig.isPCacheInit ){
    sqlite4PcacheShutdown();
    sqlite4GlobalConfig.isPCacheInit = 0;
  }
  if( sqlite4GlobalConfig.isMallocInit ){
    sqlite4MallocEnd();
    sqlite4GlobalConfig.isMallocInit = 0;
  }
  if( sqlite4GlobalConfig.isMutexInit ){
    sqlite4MutexEnd();
    sqlite4GlobalConfig.isMutexInit = 0;
................................................................................
    case SQLITE_CONFIG_SCRATCH: {
      /* Designate a buffer for scratch memory space */
      sqlite4GlobalConfig.pScratch = va_arg(ap, void*);
      sqlite4GlobalConfig.szScratch = va_arg(ap, int);
      sqlite4GlobalConfig.nScratch = va_arg(ap, int);
      break;
    }
    case SQLITE_CONFIG_PAGECACHE: {
      /* Designate a buffer for page cache memory space */
      sqlite4GlobalConfig.pPage = va_arg(ap, void*);
      sqlite4GlobalConfig.szPage = va_arg(ap, int);
      sqlite4GlobalConfig.nPage = va_arg(ap, int);
      break;
    }

    case SQLITE_CONFIG_PCACHE: {
      /* no-op */
      break;
    }
    case SQLITE_CONFIG_GETPCACHE: {
      /* now an error */
      rc = SQLITE_ERROR;
      break;
    }

    case SQLITE_CONFIG_PCACHE2: {
      /* Specify an alternative page cache implementation */
      sqlite4GlobalConfig.pcache2 = *va_arg(ap, sqlite4_pcache_methods2*);
      break;
    }
    case SQLITE_CONFIG_GETPCACHE2: {
      if( sqlite4GlobalConfig.pcache2.xInit==0 ){
        sqlite4PCacheSetDefault();
      }
      *va_arg(ap, sqlite4_pcache_methods2*) = sqlite4GlobalConfig.pcache2;
      break;
    }

#if defined(SQLITE_ENABLE_MEMSYS3) || defined(SQLITE_ENABLE_MEMSYS5)
    case SQLITE_CONFIG_HEAP: {
      /* Designate a buffer for heap memory space */
      sqlite4GlobalConfig.pHeap = va_arg(ap, void*);
      sqlite4GlobalConfig.nHeap = va_arg(ap, int);
      sqlite4GlobalConfig.mnReq = va_arg(ap, int);
................................................................................
}

/*
** Free up as much memory as we can from the given database
** connection.
*/
int sqlite4_db_release_memory(sqlite4 *db){
  int i;
  sqlite4_mutex_enter(db->mutex);
  sqlite4BtreeEnterAll(db);
  for(i=0; i<db->nDb; i++){
    Btree *pBt = db->aDb[i].pBt;
    if( pBt ){
      Pager *pPager = sqlite4BtreePager(pBt);
      sqlite4PagerShrink(pPager);
    }
  }
  sqlite4BtreeLeaveAll(db);
  sqlite4_mutex_leave(db->mutex);
  return SQLITE_OK;
}

/*
** Configuration settings for an individual database connection
*/
................................................................................
    sqlite4Error(db, SQLITE_BUSY, 
        "unable to close due to unfinalised statements");
    sqlite4_mutex_leave(db->mutex);
    return SQLITE_BUSY;
  }
  assert( sqlite4SafetyCheckSickOrOk(db) );

  for(j=0; j<db->nDb; j++){
    Btree *pBt = db->aDb[j].pBt;
    if( pBt && sqlite4BtreeIsInBackup(pBt) ){
      sqlite4Error(db, SQLITE_BUSY, 
          "unable to close due to unfinished backup operation");
      sqlite4_mutex_leave(db->mutex);
      return SQLITE_BUSY;
    }
  }

  /* Free any outstanding Savepoint structures. */
  sqlite4CloseSavepoints(db);

  for(j=0; j<db->nDb; j++){
    struct Db *pDb = &db->aDb[j];
    if( pDb->pBt ){
      sqlite4BtreeClose(pDb->pBt);
      pDb->pBt = 0;
      sqlite4KVStoreClose(pDb->pKV);
      pDb->pKV = 0;
      if( j!=1 ){
        pDb->pSchema = 0;
      }
    }
  }
................................................................................
  sqlite4HashClear(&db->aModule);
#endif

  sqlite4Error(db, SQLITE_OK, 0); /* Deallocates any cached error strings. */
  if( db->pErr ){
    sqlite4ValueFree(db->pErr);
  }
  sqlite4CloseExtensions(db);

  db->magic = SQLITE_MAGIC_ERROR;

  /* The temp-database schema is allocated differently from the other schema
  ** objects (using sqliteMalloc() directly, instead of sqlite4BtreeSchema()).
  ** So it needs to be freed here. Todo: Why not roll the temp schema into
  ** the same sqliteMalloc() as the one that allocates the database 
  ** structure?
  */
  sqlite4DbFree(db, db->aDb[1].pSchema);
  sqlite4_mutex_leave(db->mutex);
  db->magic = SQLITE_MAGIC_CLOSED;
................................................................................
*/
void sqlite4RollbackAll(sqlite4 *db){
  int i;
  int inTrans = 0;
  assert( sqlite4_mutex_held(db->mutex) );
  sqlite4BeginBenignMalloc();
  for(i=0; i<db->nDb; i++){
    if( db->aDb[i].pBt ){
      if( sqlite4BtreeIsInTrans(db->aDb[i].pBt) ){
        inTrans = 1;
      }
      sqlite4BtreeRollback(db->aDb[i].pBt);
      db->aDb[i].inTrans = 0;
    }
  }
  sqlite4VtabRollback(db);
  sqlite4EndBenignMalloc();

  if( db->flags&SQLITE_InternChanges ){
................................................................................
** to contains a zero-length string, all attached databases are 
** checkpointed.
*/
int sqlite4_wal_checkpoint(sqlite4 *db, const char *zDb){
  return sqlite4_wal_checkpoint_v2(db, zDb, SQLITE_CHECKPOINT_PASSIVE, 0, 0);
}

#ifndef SQLITE_OMIT_WAL
/*
** Run a checkpoint on database iDb. This is a no-op if database iDb is
** not currently open in WAL mode.
**
** If a transaction is open on the database being checkpointed, this 
** function returns SQLITE_LOCKED and a checkpoint is not attempted. If 
** an error occurs while running the checkpoint, an SQLite error code is 
** returned (i.e. SQLITE_IOERR). Otherwise, SQLITE_OK.
**
** The mutex on database handle db should be held by the caller. The mutex
** associated with the specific b-tree being checkpointed is taken by
** this function while the checkpoint is running.
**
** If iDb is passed SQLITE_MAX_ATTACHED, then all attached databases are
** checkpointed. If an error is encountered it is returned immediately -
** no attempt is made to checkpoint any remaining databases.
**
** Parameter eMode is one of SQLITE_CHECKPOINT_PASSIVE, FULL or RESTART.
*/
int sqlite4Checkpoint(sqlite4 *db, int iDb, int eMode, int *pnLog, int *pnCkpt){
  int rc = SQLITE_OK;             /* Return code */
  int i;                          /* Used to iterate through attached dbs */
  int bBusy = 0;                  /* True if SQLITE_BUSY has been encountered */

  assert( sqlite4_mutex_held(db->mutex) );
  assert( !pnLog || *pnLog==-1 );
  assert( !pnCkpt || *pnCkpt==-1 );

  for(i=0; i<db->nDb && rc==SQLITE_OK; i++){
    if( i==iDb || iDb==SQLITE_MAX_ATTACHED ){
      rc = sqlite4BtreeCheckpoint(db->aDb[i].pBt, eMode, pnLog, pnCkpt);
      pnLog = 0;
      pnCkpt = 0;
      if( rc==SQLITE_BUSY ){
        bBusy = 1;
        rc = SQLITE_OK;
      }
    }
  }

  return (rc==SQLITE_OK && bBusy) ? SQLITE_BUSY : rc;
}
#endif /* SQLITE_OMIT_WAL */

/*
** This function returns true if main-memory should be used instead of
** a temporary file for transient pager files and statement journals.
** The value returned depends on the value of db->temp_store (runtime
** parameter) and the compile time value of SQLITE_TEMP_STORE. The
** following table describes the relationship between these two values
** and this functions return value.
................................................................................
*/
static int createCollation(
  sqlite4* db,
  const char *zName, 
  u8 enc,
  void* pCtx,
  int(*xCompare)(void*,int,const void*,int,const void*),
  int(*xMakeKey)(void*,int,const void*,int,const void*),
  void(*xDel)(void*)
){
  CollSeq *pColl;
  int enc2;
  int nName = sqlite4Strlen30(zName);
  
  assert( sqlite4_mutex_held(db->mutex) );
................................................................................
  sqlite4 **ppDb,        /* OUT: Returned database handle */
  unsigned int flags,    /* Operational flags */
  const char *zVfs       /* Name of the VFS to use */
){
  sqlite4 *db;                    /* Store allocated handle here */
  int rc;                         /* Return code */
  int isThreadsafe;               /* True for threadsafe connections */
  char *zOpen = 0;                /* Filename argument to pass to BtreeOpen() */
  char *zErrMsg = 0;              /* Error message from sqlite4ParseUri() */

  *ppDb = 0;
#ifndef SQLITE_OMIT_AUTOINIT
  rc = sqlite4_initialize();
  if( rc ) return rc;
#endif
................................................................................
  db->aDb = db->aDbStatic;

  assert( sizeof(db->aLimit)==sizeof(aHardLimit) );
  memcpy(db->aLimit, aHardLimit, sizeof(db->aLimit));
  db->autoCommit = 1;
  db->nextAutovac = -1;
  db->nextPagesize = 0;
  db->flags |= SQLITE_ShortColNames | SQLITE_AutoIndex | SQLITE_EnableTrigger
#if SQLITE_DEFAULT_FILE_FORMAT<4
                 | SQLITE_LegacyFileFmt
#endif
#ifdef SQLITE_ENABLE_LOAD_EXTENSION
                 | SQLITE_LoadExtension
#endif
#if SQLITE_DEFAULT_RECURSIVE_TRIGGERS
................................................................................
    if( rc==SQLITE_NOMEM ) db->mallocFailed = 1;
    sqlite4Error(db, rc, zErrMsg ? "%s" : 0, zErrMsg);
    sqlite4_free(zErrMsg);
    goto opendb_out;
  }

  /* Open the backend database driver */
  rc = sqlite4BtreeOpen(db->pVfs, zOpen, db, &db->aDb[0].pBt, 0,
                        flags | SQLITE_OPEN_MAIN_DB);
  if( rc!=SQLITE_OK ){
    if( rc==SQLITE_IOERR_NOMEM ){
      rc = SQLITE_NOMEM;
    }
    sqlite4Error(db, rc, 0);
    goto opendb_out;
  }
  db->aDb[0].pSchema = sqlite4SchemaGet(db, db->aDb[0].pBt);
  db->aDb[1].pSchema = sqlite4SchemaGet(db, 0);
  sqlite4KVStoreOpen(zOpen, &db->aDb[0].pKV);

  /* The default safety_level for the main database is 'full'; for the temp
  ** database it is 'NONE'. This matches the pager layer defaults.  
  */
  db->aDb[0].zName = "main";
  db->aDb[0].safety_level = 3;
  db->aDb[1].zName = "temp";
  db->aDb[1].safety_level = 1;

  db->magic = SQLITE_MAGIC_OPEN;
  if( db->mallocFailed ){
    goto opendb_out;
  }

  /* Register all built-in functions, but do not attempt to read the
................................................................................
  sqlite4RegisterBuiltinFunctions(db);

  /* Load automatic extensions - extensions that have been registered
  ** using the sqlite4_automatic_extension() API.
  */
  rc = sqlite4_errcode(db);
  if( rc==SQLITE_OK ){
    sqlite4AutoLoadExtensions(db);
    rc = sqlite4_errcode(db);
    if( rc!=SQLITE_OK ){
      goto opendb_out;
    }
  }

#ifdef SQLITE_ENABLE_FTS1
................................................................................
  if( !db->mallocFailed && rc==SQLITE_OK){
    rc = sqlite4RtreeInit(db);
  }
#endif

  sqlite4Error(db, rc, 0);

  /* -DSQLITE_DEFAULT_LOCKING_MODE=1 makes EXCLUSIVE the default locking
  ** mode.  -DSQLITE_DEFAULT_LOCKING_MODE=0 make NORMAL the default locking
  ** mode.  Doing nothing at all also makes NORMAL the default.
  */
#ifdef SQLITE_DEFAULT_LOCKING_MODE
  db->dfltLockMode = SQLITE_DEFAULT_LOCKING_MODE;
  sqlite4PagerLockingMode(sqlite4BtreePager(db->aDb[0].pBt),
                          SQLITE_DEFAULT_LOCKING_MODE);
#endif

  /* Enable the lookaside-malloc subsystem */
  setupLookaside(db, 0, sqlite4GlobalConfig.szLookaside,
                        sqlite4GlobalConfig.nLookaside);

  sqlite4_wal_autocheckpoint(db, SQLITE_DEFAULT_WAL_AUTOCHECKPOINT);

opendb_out:
................................................................................
  sqlite4_log(SQLITE_CANTOPEN, 
              "cannot open file at line %d of [%.10s]",
              lineno, 20+sqlite4_sourceid());
  return SQLITE_CANTOPEN;
}


#ifndef SQLITE_OMIT_DEPRECATED
/*
** This is a convenience routine that makes sure that all thread-specific
** data for this thread has been deallocated.
**
** SQLite no longer uses thread-specific data so this routine is now a
** no-op.  It is retained for historical compatibility.
*/
void sqlite4_thread_cleanup(void){
}
#endif

/*
** Return meta information about a specific column of a database table.
** See comment in sqlite4.h (sqlite.h.in) for details.
*/
#ifdef SQLITE_ENABLE_COLUMN_METADATA
int sqlite4_table_column_metadata(
  sqlite4 *db,                /* Connection handle */
  const char *zDbName,        /* Database name or NULL */
  const char *zTableName,     /* Table name */
  const char *zColumnName,    /* Column name */
  char const **pzDataType,    /* OUTPUT: Declared data type */
  char const **pzCollSeq,     /* OUTPUT: Collation sequence name */
  int *pNotNull,              /* OUTPUT: True if NOT NULL constraint exists */
  int *pPrimaryKey,           /* OUTPUT: True if column part of PK */
  int *pAutoinc               /* OUTPUT: True if column is auto-increment */
){
  int rc;
  char *zErrMsg = 0;
  Table *pTab = 0;
  Column *pCol = 0;
  int iCol;

  char const *zDataType = 0;
  char const *zCollSeq = 0;
  int notnull = 0;
  int primarykey = 0;
  int autoinc = 0;

  /* Ensure the database schema has been loaded */
  sqlite4_mutex_enter(db->mutex);
  sqlite4BtreeEnterAll(db);
  rc = sqlite4Init(db, &zErrMsg);
  if( SQLITE_OK!=rc ){
    goto error_out;
  }

  /* Locate the table in question */
  pTab = sqlite4FindTable(db, zTableName, zDbName);
  if( !pTab || pTab->pSelect ){
    pTab = 0;
    goto error_out;
  }

  /* Find the column for which info is requested */
  if( sqlite4IsRowid(zColumnName) ){
    iCol = pTab->iPKey;
    if( iCol>=0 ){
      pCol = &pTab->aCol[iCol];
    }
  }else{
    for(iCol=0; iCol<pTab->nCol; iCol++){
      pCol = &pTab->aCol[iCol];
      if( 0==sqlite4StrICmp(pCol->zName, zColumnName) ){
        break;
      }
    }
    if( iCol==pTab->nCol ){
      pTab = 0;
      goto error_out;
    }
  }

  /* The following block stores the meta information that will be returned
  ** to the caller in local variables zDataType, zCollSeq, notnull, primarykey
  ** and autoinc. At this point there are two possibilities:
  ** 
  **     1. The specified column name was rowid", "oid" or "_rowid_" 
  **        and there is no explicitly declared IPK column. 
  **
  **     2. The table is not a view and the column name identified an 
  **        explicitly declared column. Copy meta information from *pCol.
  */ 
  if( pCol ){
    zDataType = pCol->zType;
    zCollSeq = pCol->zColl;
    notnull = pCol->notNull!=0;
    primarykey  = pCol->isPrimKey!=0;
    autoinc = pTab->iPKey==iCol && (pTab->tabFlags & TF_Autoincrement)!=0;
  }else{
    zDataType = "INTEGER";
    primarykey = 1;
  }
  if( !zCollSeq ){
    zCollSeq = "BINARY";
  }

error_out:
  sqlite4BtreeLeaveAll(db);

  /* Whether the function call succeeded or failed, set the output parameters
  ** to whatever their local counterparts contain. If an error did occur,
  ** this has the effect of zeroing all output parameters.
  */
  if( pzDataType ) *pzDataType = zDataType;
  if( pzCollSeq ) *pzCollSeq = zCollSeq;
  if( pNotNull ) *pNotNull = notnull;
  if( pPrimaryKey ) *pPrimaryKey = primarykey;
  if( pAutoinc ) *pAutoinc = autoinc;

  if( SQLITE_OK==rc && !pTab ){
    sqlite4DbFree(db, zErrMsg);
    zErrMsg = sqlite4MPrintf(db, "no such table column: %s.%s", zTableName,
        zColumnName);
    rc = SQLITE_ERROR;
  }
  sqlite4Error(db, rc, (zErrMsg?"%s":0), zErrMsg);
  sqlite4DbFree(db, zErrMsg);
  rc = sqlite4ApiExit(db, rc);
  sqlite4_mutex_leave(db->mutex);
  return rc;
}
#endif

/*
** Sleep for a little while.  Return the amount of time slept.
*/
int sqlite4_sleep(int ms){
  sqlite4_vfs *pVfs;
  int rc;
  pVfs = sqlite4_vfs_find(0);
................................................................................
int sqlite4_extended_result_codes(sqlite4 *db, int onoff){
  sqlite4_mutex_enter(db->mutex);
  db->errMask = onoff ? 0xffffffff : 0xff;
  sqlite4_mutex_leave(db->mutex);
  return SQLITE_OK;
}

/*
** Invoke the xFileControl method on a particular database.
*/
int sqlite4_file_control(sqlite4 *db, const char *zDbName, int op, void *pArg){
  int rc = SQLITE_ERROR;
  int iDb;
  sqlite4_mutex_enter(db->mutex);
  if( zDbName==0 ){
    iDb = 0;
  }else{
    for(iDb=0; iDb<db->nDb; iDb++){
      if( strcmp(db->aDb[iDb].zName, zDbName)==0 ) break;
    }
  }
  if( iDb<db->nDb ){
    Btree *pBtree = db->aDb[iDb].pBt;
    if( pBtree ){
      Pager *pPager;
      sqlite4_file *fd;
      sqlite4BtreeEnter(pBtree);
      pPager = sqlite4BtreePager(pBtree);
      assert( pPager!=0 );
      fd = sqlite4PagerFile(pPager);
      assert( fd!=0 );
      if( op==SQLITE_FCNTL_FILE_POINTER ){
        *(sqlite4_file**)pArg = fd;
        rc = SQLITE_OK;
      }else if( fd->pMethods ){
        rc = sqlite4OsFileControl(fd, op, pArg);
      }else{
        rc = SQLITE_NOTFOUND;
      }
      sqlite4BtreeLeave(pBtree);
    }
  }
  sqlite4_mutex_leave(db->mutex);
  return rc;   
}

/*
** Interface to the testing logic.
*/
int sqlite4_test_control(int op, ...){
  int rc = 0;
#ifndef SQLITE_OMIT_BUILTIN_TEST
................................................................................
    */
    case SQLITE_TESTCTRL_ALWAYS: {
      int x = va_arg(ap,int);
      rc = ALWAYS(x);
      break;
    }

    /*   sqlite4_test_control(SQLITE_TESTCTRL_RESERVE, sqlite4 *db, int N)
    **
    ** Set the nReserve size to N for the main database on the database
    ** connection db.
    */
    case SQLITE_TESTCTRL_RESERVE: {
      sqlite4 *db = va_arg(ap, sqlite4*);
      int x = va_arg(ap,int);
      sqlite4_mutex_enter(db->mutex);
      sqlite4BtreeSetPageSize(db->aDb[0].pBt, 0, x, 0);
      sqlite4_mutex_leave(db->mutex);
      break;
    }

    /*  sqlite4_test_control(SQLITE_TESTCTRL_OPTIMIZATIONS, sqlite4 *db, int N)
    **
    ** Enable or disable various optimizations for testing purposes.  The 
    ** argument N is a bitmask of optimizations to be disabled.  For normal
    ** operation N should be 0.  The idea is that a test program (like the
    ** SQL Logic Test or SLT test module) can run the same SQL multiple times
    ** with various optimizations disabled to verify that the same answer
................................................................................
  const char *z = sqlite4_uri_parameter(zFilename, zParam);
  sqlite4_int64 v;
  if( z && sqlite4Atoi64(z, &v, sqlite4Strlen30(z), SQLITE_UTF8)==SQLITE_OK ){
    bDflt = v;
  }
  return bDflt;
}

/*
** Return the filename of the database associated with a database
** connection.
*/
const char *sqlite4_db_filename(sqlite4 *db, const char *zDbName){
  int i;
  for(i=0; i<db->nDb; i++){
    if( db->aDb[i].pBt && sqlite4StrICmp(zDbName, db->aDb[i].zName)==0 ){
      return sqlite4BtreeGetFilename(db->aDb[i].pBt);
    }
  }
  return 0;
}







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  }

  /* Do the rest of the initialization under the recursive mutex so
  ** that we will be able to handle recursive calls into
  ** sqlite4_initialize().  The recursive calls normally come through
  ** sqlite4_os_init() when it invokes sqlite4_vfs_register(), but other
  ** recursive calls might also be possible.







  */
  sqlite4_mutex_enter(sqlite4GlobalConfig.pInitMutex);
  if( sqlite4GlobalConfig.isInit==0 && sqlite4GlobalConfig.inProgress==0 ){
    FuncDefHash *pHash = &GLOBAL(FuncDefHash, sqlite4GlobalFunctions);
    sqlite4GlobalConfig.inProgress = 1;
    memset(pHash, 0, sizeof(sqlite4GlobalFunctions));
    sqlite4RegisterGlobalFunctions();





    rc = sqlite4OsInit();






    sqlite4GlobalConfig.inProgress = 0;
  }
  sqlite4_mutex_leave(sqlite4GlobalConfig.pInitMutex);

  /* Go back under the static mutex and clean up the recursive
  ** mutex to prevent a resource leak.
  */
................................................................................
int sqlite4_shutdown(void){
  if( sqlite4GlobalConfig.isInit ){
#ifdef SQLITE_EXTRA_SHUTDOWN
    void SQLITE_EXTRA_SHUTDOWN(void);
    SQLITE_EXTRA_SHUTDOWN();
#endif
    sqlite4_os_end();
    /* sqlite4_reset_auto_extension(); */
    sqlite4GlobalConfig.isInit = 0;
  }




  if( sqlite4GlobalConfig.isMallocInit ){
    sqlite4MallocEnd();
    sqlite4GlobalConfig.isMallocInit = 0;
  }
  if( sqlite4GlobalConfig.isMutexInit ){
    sqlite4MutexEnd();
    sqlite4GlobalConfig.isMutexInit = 0;
................................................................................
    case SQLITE_CONFIG_SCRATCH: {
      /* Designate a buffer for scratch memory space */
      sqlite4GlobalConfig.pScratch = va_arg(ap, void*);
      sqlite4GlobalConfig.szScratch = va_arg(ap, int);
      sqlite4GlobalConfig.nScratch = va_arg(ap, int);
      break;
    }































#if defined(SQLITE_ENABLE_MEMSYS3) || defined(SQLITE_ENABLE_MEMSYS5)
    case SQLITE_CONFIG_HEAP: {
      /* Designate a buffer for heap memory space */
      sqlite4GlobalConfig.pHeap = va_arg(ap, void*);
      sqlite4GlobalConfig.nHeap = va_arg(ap, int);
      sqlite4GlobalConfig.mnReq = va_arg(ap, int);
................................................................................
}

/*
** Free up as much memory as we can from the given database
** connection.
*/
int sqlite4_db_release_memory(sqlite4 *db){

  sqlite4_mutex_enter(db->mutex);









  sqlite4_mutex_leave(db->mutex);
  return SQLITE_OK;
}

/*
** Configuration settings for an individual database connection
*/
................................................................................
    sqlite4Error(db, SQLITE_BUSY, 
        "unable to close due to unfinalised statements");
    sqlite4_mutex_leave(db->mutex);
    return SQLITE_BUSY;
  }
  assert( sqlite4SafetyCheckSickOrOk(db) );











  /* Free any outstanding Savepoint structures. */
  sqlite4CloseSavepoints(db);

  for(j=0; j<db->nDb; j++){
    struct Db *pDb = &db->aDb[j];
    if( pDb->pKV ){


      sqlite4KVStoreClose(pDb->pKV);
      pDb->pKV = 0;
      if( j!=1 ){
        pDb->pSchema = 0;
      }
    }
  }
................................................................................
  sqlite4HashClear(&db->aModule);
#endif

  sqlite4Error(db, SQLITE_OK, 0); /* Deallocates any cached error strings. */
  if( db->pErr ){
    sqlite4ValueFree(db->pErr);
  }


  db->magic = SQLITE_MAGIC_ERROR;

  /* The temp-database schema is allocated differently from the other schema
  ** objects (using sqliteMalloc() directly, instead of sqlite4BTreeSchema()).
  ** So it needs to be freed here. Todo: Why not roll the temp schema into
  ** the same sqliteMalloc() as the one that allocates the database 
  ** structure?
  */
  sqlite4DbFree(db, db->aDb[1].pSchema);
  sqlite4_mutex_leave(db->mutex);
  db->magic = SQLITE_MAGIC_CLOSED;
................................................................................
*/
void sqlite4RollbackAll(sqlite4 *db){
  int i;
  int inTrans = 0;
  assert( sqlite4_mutex_held(db->mutex) );
  sqlite4BeginBenignMalloc();
  for(i=0; i<db->nDb; i++){
    if( db->aDb[i].pKV ){
      if( db->aDb[i].pKV->iTransLevel ){
        inTrans = 1;
      }
      sqlite4KVStoreRollback(db->aDb[i].pKV, 0);
      db->aDb[i].inTrans = 0;
    }
  }
  sqlite4VtabRollback(db);
  sqlite4EndBenignMalloc();

  if( db->flags&SQLITE_InternChanges ){
................................................................................
** to contains a zero-length string, all attached databases are 
** checkpointed.
*/
int sqlite4_wal_checkpoint(sqlite4 *db, const char *zDb){
  return sqlite4_wal_checkpoint_v2(db, zDb, SQLITE_CHECKPOINT_PASSIVE, 0, 0);
}














































/*
** This function returns true if main-memory should be used instead of
** a temporary file for transient pager files and statement journals.
** The value returned depends on the value of db->temp_store (runtime
** parameter) and the compile time value of SQLITE_TEMP_STORE. The
** following table describes the relationship between these two values
** and this functions return value.
................................................................................
*/
static int createCollation(
  sqlite4* db,
  const char *zName, 
  u8 enc,
  void* pCtx,
  int(*xCompare)(void*,int,const void*,int,const void*),
  int(*xMakeKey)(void*,const void*,int,const void*,int),
  void(*xDel)(void*)
){
  CollSeq *pColl;
  int enc2;
  int nName = sqlite4Strlen30(zName);
  
  assert( sqlite4_mutex_held(db->mutex) );
................................................................................
  sqlite4 **ppDb,        /* OUT: Returned database handle */
  unsigned int flags,    /* Operational flags */
  const char *zVfs       /* Name of the VFS to use */
){
  sqlite4 *db;                    /* Store allocated handle here */
  int rc;                         /* Return code */
  int isThreadsafe;               /* True for threadsafe connections */
  char *zOpen = 0;                /* Filename passed to StorageOpen() */
  char *zErrMsg = 0;              /* Error message from sqlite4ParseUri() */

  *ppDb = 0;
#ifndef SQLITE_OMIT_AUTOINIT
  rc = sqlite4_initialize();
  if( rc ) return rc;
#endif
................................................................................
  db->aDb = db->aDbStatic;

  assert( sizeof(db->aLimit)==sizeof(aHardLimit) );
  memcpy(db->aLimit, aHardLimit, sizeof(db->aLimit));
  db->autoCommit = 1;
  db->nextAutovac = -1;
  db->nextPagesize = 0;
  db->flags |=  SQLITE_AutoIndex | SQLITE_EnableTrigger
#if SQLITE_DEFAULT_FILE_FORMAT<4
                 | SQLITE_LegacyFileFmt
#endif
#ifdef SQLITE_ENABLE_LOAD_EXTENSION
                 | SQLITE_LoadExtension
#endif
#if SQLITE_DEFAULT_RECURSIVE_TRIGGERS
................................................................................
    if( rc==SQLITE_NOMEM ) db->mallocFailed = 1;
    sqlite4Error(db, rc, zErrMsg ? "%s" : 0, zErrMsg);
    sqlite4_free(zErrMsg);
    goto opendb_out;
  }

  /* Open the backend database driver */
  rc = sqlite4KVStoreOpen(db, "main", zOpen, &db->aDb[0].pKV, 0);

  if( rc!=SQLITE_OK ){
    if( rc==SQLITE_IOERR_NOMEM ){
      rc = SQLITE_NOMEM;
    }
    sqlite4Error(db, rc, 0);
    goto opendb_out;
  }
  db->aDb[0].pSchema = sqlite4SchemaGet(db);
  db->aDb[1].pSchema = sqlite4SchemaGet(db);


  /* The default safety_level for the main database is 'full'; for the temp
  ** database it is 'NONE'. This matches the pager layer defaults.  
  */
  db->aDb[0].zName = "main";

  db->aDb[1].zName = "temp";


  db->magic = SQLITE_MAGIC_OPEN;
  if( db->mallocFailed ){
    goto opendb_out;
  }

  /* Register all built-in functions, but do not attempt to read the
................................................................................
  sqlite4RegisterBuiltinFunctions(db);

  /* Load automatic extensions - extensions that have been registered
  ** using the sqlite4_automatic_extension() API.
  */
  rc = sqlite4_errcode(db);
  if( rc==SQLITE_OK ){
    /* sqlite4AutoLoadExtensions(db); */
    rc = sqlite4_errcode(db);
    if( rc!=SQLITE_OK ){
      goto opendb_out;
    }
  }

#ifdef SQLITE_ENABLE_FTS1
................................................................................
  if( !db->mallocFailed && rc==SQLITE_OK){
    rc = sqlite4RtreeInit(db);
  }
#endif

  sqlite4Error(db, rc, 0);











  /* Enable the lookaside-malloc subsystem */
  setupLookaside(db, 0, sqlite4GlobalConfig.szLookaside,
                        sqlite4GlobalConfig.nLookaside);

  sqlite4_wal_autocheckpoint(db, SQLITE_DEFAULT_WAL_AUTOCHECKPOINT);

opendb_out:
................................................................................
  sqlite4_log(SQLITE_CANTOPEN, 
              "cannot open file at line %d of [%.10s]",
              lineno, 20+sqlite4_sourceid());
  return SQLITE_CANTOPEN;
}































































































































/*
** Sleep for a little while.  Return the amount of time slept.
*/
int sqlite4_sleep(int ms){
  sqlite4_vfs *pVfs;
  int rc;
  pVfs = sqlite4_vfs_find(0);
................................................................................
int sqlite4_extended_result_codes(sqlite4 *db, int onoff){
  sqlite4_mutex_enter(db->mutex);
  db->errMask = onoff ? 0xffffffff : 0xff;
  sqlite4_mutex_leave(db->mutex);
  return SQLITE_OK;
}








































/*
** Interface to the testing logic.
*/
int sqlite4_test_control(int op, ...){
  int rc = 0;
#ifndef SQLITE_OMIT_BUILTIN_TEST
................................................................................
    */
    case SQLITE_TESTCTRL_ALWAYS: {
      int x = va_arg(ap,int);
      rc = ALWAYS(x);
      break;
    }















    /*  sqlite4_test_control(SQLITE_TESTCTRL_OPTIMIZATIONS, sqlite4 *db, int N)
    **
    ** Enable or disable various optimizations for testing purposes.  The 
    ** argument N is a bitmask of optimizations to be disabled.  For normal
    ** operation N should be 0.  The idea is that a test program (like the
    ** SQL Logic Test or SLT test module) can run the same SQL multiple times
    ** with various optimizations disabled to verify that the same answer
................................................................................
  const char *z = sqlite4_uri_parameter(zFilename, zParam);
  sqlite4_int64 v;
  if( z && sqlite4Atoi64(z, &v, sqlite4Strlen30(z), SQLITE_UTF8)==SQLITE_OK ){
    bDflt = v;
  }
  return bDflt;
}














Deleted src/memjournal.c.

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/*
** 2008 October 7
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file contains code use to implement an in-memory rollback journal.
** The in-memory rollback journal is used to journal transactions for
** ":memory:" databases and when the journal_mode=MEMORY pragma is used.
*/
#include "sqliteInt.h"

/* Forward references to internal structures */
typedef struct MemJournal MemJournal;
typedef struct FilePoint FilePoint;
typedef struct FileChunk FileChunk;

/* Space to hold the rollback journal is allocated in increments of
** this many bytes.
**
** The size chosen is a little less than a power of two.  That way,
** the FileChunk object will have a size that almost exactly fills
** a power-of-two allocation.  This mimimizes wasted space in power-of-two
** memory allocators.
*/
#define JOURNAL_CHUNKSIZE ((int)(1024-sizeof(FileChunk*)))

/* Macro to find the minimum of two numeric values.
*/
#ifndef MIN
# define MIN(x,y) ((x)<(y)?(x):(y))
#endif

/*
** The rollback journal is composed of a linked list of these structures.
*/
struct FileChunk {
  FileChunk *pNext;               /* Next chunk in the journal */
  u8 zChunk[JOURNAL_CHUNKSIZE];   /* Content of this chunk */
};

/*
** An instance of this object serves as a cursor into the rollback journal.
** The cursor can be either for reading or writing.
*/
struct FilePoint {
  sqlite4_int64 iOffset;          /* Offset from the beginning of the file */
  FileChunk *pChunk;              /* Specific chunk into which cursor points */
};

/*
** This subclass is a subclass of sqlite4_file.  Each open memory-journal
** is an instance of this class.
*/
struct MemJournal {
  sqlite4_io_methods *pMethod;    /* Parent class. MUST BE FIRST */
  FileChunk *pFirst;              /* Head of in-memory chunk-list */
  FilePoint endpoint;             /* Pointer to the end of the file */
  FilePoint readpoint;            /* Pointer to the end of the last xRead() */
};

/*
** Read data from the in-memory journal file.  This is the implementation
** of the sqlite4_vfs.xRead method.
*/
static int memjrnlRead(
  sqlite4_file *pJfd,    /* The journal file from which to read */
  void *zBuf,            /* Put the results here */
  int iAmt,              /* Number of bytes to read */
  sqlite_int64 iOfst     /* Begin reading at this offset */
){
  MemJournal *p = (MemJournal *)pJfd;
  u8 *zOut = zBuf;
  int nRead = iAmt;
  int iChunkOffset;
  FileChunk *pChunk;

  /* SQLite never tries to read past the end of a rollback journal file */
  assert( iOfst+iAmt<=p->endpoint.iOffset );

  if( p->readpoint.iOffset!=iOfst || iOfst==0 ){
    sqlite4_int64 iOff = 0;
    for(pChunk=p->pFirst; 
        ALWAYS(pChunk) && (iOff+JOURNAL_CHUNKSIZE)<=iOfst;
        pChunk=pChunk->pNext
    ){
      iOff += JOURNAL_CHUNKSIZE;
    }
  }else{
    pChunk = p->readpoint.pChunk;
  }

  iChunkOffset = (int)(iOfst%JOURNAL_CHUNKSIZE);
  do {
    int iSpace = JOURNAL_CHUNKSIZE - iChunkOffset;
    int nCopy = MIN(nRead, (JOURNAL_CHUNKSIZE - iChunkOffset));
    memcpy(zOut, &pChunk->zChunk[iChunkOffset], nCopy);
    zOut += nCopy;
    nRead -= iSpace;
    iChunkOffset = 0;
  } while( nRead>=0 && (pChunk=pChunk->pNext)!=0 && nRead>0 );
  p->readpoint.iOffset = iOfst+iAmt;
  p->readpoint.pChunk = pChunk;

  return SQLITE_OK;
}

/*
** Write data to the file.
*/
static int memjrnlWrite(
  sqlite4_file *pJfd,    /* The journal file into which to write */
  const void *zBuf,      /* Take data to be written from here */
  int iAmt,              /* Number of bytes to write */
  sqlite_int64 iOfst     /* Begin writing at this offset into the file */
){
  MemJournal *p = (MemJournal *)pJfd;
  int nWrite = iAmt;
  u8 *zWrite = (u8 *)zBuf;

  /* An in-memory journal file should only ever be appended to. Random
  ** access writes are not required by sqlite.
  */
  assert( iOfst==p->endpoint.iOffset );
  UNUSED_PARAMETER(iOfst);

  while( nWrite>0 ){
    FileChunk *pChunk = p->endpoint.pChunk;
    int iChunkOffset = (int)(p->endpoint.iOffset%JOURNAL_CHUNKSIZE);
    int iSpace = MIN(nWrite, JOURNAL_CHUNKSIZE - iChunkOffset);

    if( iChunkOffset==0 ){
      /* New chunk is required to extend the file. */
      FileChunk *pNew = sqlite4_malloc(sizeof(FileChunk));
      if( !pNew ){
        return SQLITE_IOERR_NOMEM;
      }
      pNew->pNext = 0;
      if( pChunk ){
        assert( p->pFirst );
        pChunk->pNext = pNew;
      }else{
        assert( !p->pFirst );
        p->pFirst = pNew;
      }
      p->endpoint.pChunk = pNew;
    }

    memcpy(&p->endpoint.pChunk->zChunk[iChunkOffset], zWrite, iSpace);
    zWrite += iSpace;
    nWrite -= iSpace;
    p->endpoint.iOffset += iSpace;
  }

  return SQLITE_OK;
}

/*
** Truncate the file.
*/
static int memjrnlTruncate(sqlite4_file *pJfd, sqlite_int64 size){
  MemJournal *p = (MemJournal *)pJfd;
  FileChunk *pChunk;
  assert(size==0);
  UNUSED_PARAMETER(size);
  pChunk = p->pFirst;
  while( pChunk ){
    FileChunk *pTmp = pChunk;
    pChunk = pChunk->pNext;
    sqlite4_free(pTmp);
  }
  sqlite4MemJournalOpen(pJfd);
  return SQLITE_OK;
}

/*
** Close the file.
*/
static int memjrnlClose(sqlite4_file *pJfd){
  memjrnlTruncate(pJfd, 0);
  return SQLITE_OK;
}


/*
** Sync the file.
**
** Syncing an in-memory journal is a no-op.  And, in fact, this routine
** is never called in a working implementation.  This implementation
** exists purely as a contingency, in case some malfunction in some other
** part of SQLite causes Sync to be called by mistake.
*/
static int memjrnlSync(sqlite4_file *NotUsed, int NotUsed2){
  UNUSED_PARAMETER2(NotUsed, NotUsed2);
  return SQLITE_OK;
}

/*
** Query the size of the file in bytes.
*/
static int memjrnlFileSize(sqlite4_file *pJfd, sqlite_int64 *pSize){
  MemJournal *p = (MemJournal *)pJfd;
  *pSize = (sqlite_int64) p->endpoint.iOffset;
  return SQLITE_OK;
}

/*
** Table of methods for MemJournal sqlite4_file object.
*/
static const struct sqlite4_io_methods MemJournalMethods = {
  1,                /* iVersion */
  memjrnlClose,     /* xClose */
  memjrnlRead,      /* xRead */
  memjrnlWrite,     /* xWrite */
  memjrnlTruncate,  /* xTruncate */
  memjrnlSync,      /* xSync */
  memjrnlFileSize,  /* xFileSize */
  0,                /* xLock */
  0,                /* xUnlock */
  0,                /* xCheckReservedLock */
  0,                /* xFileControl */
  0,                /* xSectorSize */
  0,                /* xDeviceCharacteristics */
  0,                /* xShmMap */
  0,                /* xShmLock */
  0,                /* xShmBarrier */
  0                 /* xShmUnlock */
};

/* 
** Open a journal file.
*/
void sqlite4MemJournalOpen(sqlite4_file *pJfd){
  MemJournal *p = (MemJournal *)pJfd;
  assert( EIGHT_BYTE_ALIGNMENT(p) );
  memset(p, 0, sqlite4MemJournalSize());
  p->pMethod = (sqlite4_io_methods*)&MemJournalMethods;
}

/*
** Return true if the file-handle passed as an argument is 
** an in-memory journal 
*/
int sqlite4IsMemJournal(sqlite4_file *pJfd){
  return pJfd->pMethods==&MemJournalMethods;
}

/* 
** Return the number of bytes required to store a MemJournal file descriptor.
*/
int sqlite4MemJournalSize(void){
  return sizeof(MemJournal);
}
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Deleted src/notify.c.

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/*
** 2009 March 3
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file contains the implementation of the sqlite4_unlock_notify()
** API method and its associated functionality.
*/
#include "sqliteInt.h"
#include "btreeInt.h"

/* Omit this entire file if SQLITE_ENABLE_UNLOCK_NOTIFY is not defined. */
#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY

/*
** Public interfaces:
**
**   sqlite4ConnectionBlocked()
**   sqlite4ConnectionUnlocked()
**   sqlite4ConnectionClosed()
**   sqlite4_unlock_notify()
*/

#define assertMutexHeld() \
  assert( sqlite4_mutex_held(sqlite4MutexAlloc(SQLITE_MUTEX_STATIC_MASTER)) )

/*
** Head of a linked list of all sqlite4 objects created by this process
** for which either sqlite4.pBlockingConnection or sqlite4.pUnlockConnection
** is not NULL. This variable may only accessed while the STATIC_MASTER
** mutex is held.
*/
static sqlite4 *SQLITE_WSD sqlite4BlockedList = 0;

#ifndef NDEBUG
/*
** This function is a complex assert() that verifies the following 
** properties of the blocked connections list:
**
**   1) Each entry in the list has a non-NULL value for either 
**      pUnlockConnection or pBlockingConnection, or both.
**
**   2) All entries in the list that share a common value for 
**      xUnlockNotify are grouped together.
**
**   3) If the argument db is not NULL, then none of the entries in the
**      blocked connections list have pUnlockConnection or pBlockingConnection
**      set to db. This is used when closing connection db.
*/
static void checkListProperties(sqlite4 *db){
  sqlite4 *p;
  for(p=sqlite4BlockedList; p; p=p->pNextBlocked){
    int seen = 0;
    sqlite4 *p2;

    /* Verify property (1) */
    assert( p->pUnlockConnection || p->pBlockingConnection );

    /* Verify property (2) */