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Overview
Comment:Add the experimental mem5.c memory allocator. Allocate the content part of cache pages separately from the header. (See check-ins (4495) and (4409)). (CVS 4789)
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1:669ece8c82bfa69add852589dd1211751cb26fb2
User & Date: drh 2008-02-14 23:26:56
Context
2008-02-14
23:44
Fix a bug in EXPLAIN growing out of the new Mem implementation. (CVS 4790) check-in: 4df62a55 user: drh tags: trunk
23:26
Add the experimental mem5.c memory allocator. Allocate the content part of cache pages separately from the header. (See check-ins (4495) and (4409)). (CVS 4789) check-in: 669ece8c user: drh tags: trunk
23:24
Fix a typo in a comment used to generate documentation. (CVS 4788) check-in: 65e66dd8 user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to main.mk.

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TCCX = $(TCC) $(OPTS) -I. -I$(TOP)/src

# Object files for the SQLite library.
#
LIBOBJ+= alter.o analyze.o attach.o auth.o btmutex.o btree.o build.o \
         callback.o complete.o date.o delete.o \
         expr.o fault.o func.o hash.o insert.o journal.o loadext.o \
         main.o malloc.o mem1.o mem2.o mem3.o mem4.o mutex.o mutex_os2.o \
         mutex_unix.o mutex_w32.o \
         opcodes.o os.o os_os2.o os_unix.o os_win.o \
         pager.o parse.o pragma.o prepare.o printf.o random.o \
         select.o table.o $(TCLOBJ) tokenize.o trigger.o \
         update.o util.o vacuum.o \
         vdbe.o vdbeapi.o vdbeaux.o vdbeblob.o vdbefifo.o vdbemem.o \
         where.o utf.o legacy.o vtab.o

................................................................................
  $(TOP)/src/loadext.c \
  $(TOP)/src/main.c \
  $(TOP)/src/malloc.c \
  $(TOP)/src/mem1.c \
  $(TOP)/src/mem2.c \
  $(TOP)/src/mem3.c \
  $(TOP)/src/mem4.c \

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







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TCCX = $(TCC) $(OPTS) -I. -I$(TOP)/src

# Object files for the SQLite library.
#
LIBOBJ+= alter.o analyze.o attach.o auth.o btmutex.o btree.o build.o \
         callback.o complete.o date.o delete.o \
         expr.o fault.o func.o hash.o insert.o journal.o loadext.o \
         main.o malloc.o mem1.o mem2.o mem3.o mem4.o mem5.o \
         mutex.o mutex_os2.o mutex_unix.o mutex_w32.o \
         opcodes.o os.o os_os2.o os_unix.o os_win.o \
         pager.o parse.o pragma.o prepare.o printf.o random.o \
         select.o table.o $(TCLOBJ) tokenize.o trigger.o \
         update.o util.o vacuum.o \
         vdbe.o vdbeapi.o vdbeaux.o vdbeblob.o vdbefifo.o vdbemem.o \
         where.o utf.o legacy.o vtab.o

................................................................................
  $(TOP)/src/loadext.c \
  $(TOP)/src/main.c \
  $(TOP)/src/malloc.c \
  $(TOP)/src/mem1.c \
  $(TOP)/src/mem2.c \
  $(TOP)/src/mem3.c \
  $(TOP)/src/mem4.c \
  $(TOP)/src/mem5.c \
  $(TOP)/src/mutex.c \
  $(TOP)/src/mutex.h \
  $(TOP)/src/mutex_os2.c \
  $(TOP)/src/mutex_unix.c \
  $(TOP)/src/mutex_w32.c \
  $(TOP)/src/os.c \
  $(TOP)/src/os.h \

Changes to src/mem1.c.

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**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains the C functions that implement a memory
** allocation subsystem for use by SQLite.  
**
** $Id: mem1.c,v 1.15 2008/02/13 18:25:27 danielk1977 Exp $
*/


/*
** This version of the memory allocator is the default.  It is
** used when no other memory allocator is specified using compile-time
** macros.
*/
#if !defined(SQLITE_MEMDEBUG) && !defined(SQLITE_MEMORY_SIZE) \
     && !defined(SQLITE_MMAP_HEAP_SIZE)

/*
** We will eventually construct multiple memory allocation subsystems
** suitable for use in various contexts:
**
**    *  Normal multi-threaded builds
**    *  Normal single-threaded builds
**    *  Debugging builds
**
** This initial version is suitable for use in normal multi-threaded
** builds.  We envision that alternative versions will be stored in
** separate source files.  #ifdefs will be used to select the code from
** one of the various memN.c source files for use in any given build.
*/
#include "sqliteInt.h"

/*
** All of the static variables used by this module are collected
** into a single structure named "mem".  This is to keep the
** static variables organized and to reduce namespace pollution
** when this module is combined with other in the amalgamation.
*/
................................................................................
      mem.mxUsed = mem.nowUsed;
    }
  }
  sqlite3_mutex_leave(mem.mutex);
  return (void*)p;
}

#endif /* !SQLITE_MEMDEBUG && !SQLITE_OMIT_MEMORY_ALLOCATION */







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**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains the C functions that implement a memory
** allocation subsystem for use by SQLite.  
**
** $Id: mem1.c,v 1.16 2008/02/14 23:26:56 drh Exp $
*/
#include "sqliteInt.h"

/*
** This version of the memory allocator is the default.  It is
** used when no other memory allocator is specified using compile-time
** macros.
*/
#ifdef SQLITE_SYSTEM_MALLOC

















/*
** All of the static variables used by this module are collected
** into a single structure named "mem".  This is to keep the
** static variables organized and to reduce namespace pollution
** when this module is combined with other in the amalgamation.
*/
................................................................................
      mem.mxUsed = mem.nowUsed;
    }
  }
  sqlite3_mutex_leave(mem.mutex);
  return (void*)p;
}

#endif /* SQLITE_SYSTEM_MALLOC */

Changes to src/mem2.c.

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**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains the C functions that implement a memory
** allocation subsystem for use by SQLite.  
**
** $Id: mem2.c,v 1.20 2008/02/13 18:25:27 danielk1977 Exp $
*/


/*
** This version of the memory allocator is used only if the
** SQLITE_MEMDEBUG macro is defined and SQLITE_OMIT_MEMORY_ALLOCATION
** is not defined.
*/
#if defined(SQLITE_MEMDEBUG)

/*
** We will eventually construct multiple memory allocation subsystems
** suitable for use in various contexts:
**
**    *  Normal multi-threaded builds
**    *  Normal single-threaded builds
**    *  Debugging builds
**
** This version is suitable for use in debugging builds.
**
** Features:
**
**    * Every allocate has guards at both ends.
**    * New allocations are initialized with randomness
**    * Allocations are overwritten with randomness when freed
**    * Optional logs of malloc activity generated
**    * Summary of outstanding allocations with backtraces to the
**      point of allocation.
**    * The ability to simulate memory allocation failure
*/
#include "sqliteInt.h"
#include <stdio.h>

/*
** The backtrace functionality is only available with GLIBC
*/
#ifdef __GLIBC__
  extern int backtrace(void**,int);
  extern void backtrace_symbols_fd(void*const*,int,int);
#else
# define backtrace(A,B) 0
# define backtrace_symbols_fd(A,B,C)
#endif


/*
** Each memory allocation looks like this:
**
**  ------------------------------------------------------------------------
**  | Title |  backtrace pointers |  MemBlockHdr |  allocation |  EndGuard |
**  ------------------------------------------------------------------------
................................................................................
  for(i=0; i<NCSIZE; i++){
    nTotal += mem.sizeCnt[i];
  }
  return nTotal;
}


#endif /* SQLITE_MEMDEBUG && !SQLITE_OMIT_MEMORY_ALLOCATION */







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**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains the C functions that implement a memory
** allocation subsystem for use by SQLite.  
**
** $Id: mem2.c,v 1.21 2008/02/14 23:26:56 drh Exp $
*/
#include "sqliteInt.h"

/*
** This version of the memory allocator is used only if the
** SQLITE_MEMDEBUG macro is defined

*/
#ifdef SQLITE_MEMDEBUG
























/*
** The backtrace functionality is only available with GLIBC
*/
#ifdef __GLIBC__
  extern int backtrace(void**,int);
  extern void backtrace_symbols_fd(void*const*,int,int);
#else
# define backtrace(A,B) 0
# define backtrace_symbols_fd(A,B,C)
#endif
#include <stdio.h>

/*
** Each memory allocation looks like this:
**
**  ------------------------------------------------------------------------
**  | Title |  backtrace pointers |  MemBlockHdr |  allocation |  EndGuard |
**  ------------------------------------------------------------------------
................................................................................
  for(i=0; i<NCSIZE; i++){
    nTotal += mem.sizeCnt[i];
  }
  return nTotal;
}


#endif /* SQLITE_MEMDEBUG */

Changes to src/mem3.c.

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** use of malloc().  All dynamically allocatable memory is
** contained in a static array, mem.aPool[].  The size of this
** fixed memory pool is SQLITE_MEMORY_SIZE bytes.
**
** This version of the memory allocation subsystem is used if
** and only if SQLITE_MEMORY_SIZE is defined.
**
** $Id: mem3.c,v 1.10 2008/02/14 15:31:52 danielk1977 Exp $
*/


/*
** This version of the memory allocator is used only when 
** SQLITE_MEMORY_SIZE is defined.
*/
#if defined(SQLITE_MEMORY_SIZE)
#include "sqliteInt.h"

#ifdef SQLITE_MEMDEBUG
# error  cannot define both SQLITE_MEMDEBUG and SQLITE_MEMORY_SIZE
#endif

/*
** Maximum size (in Mem3Blocks) of a "small" chunk.
*/
#define MX_SMALL 10









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** use of malloc().  All dynamically allocatable memory is
** contained in a static array, mem.aPool[].  The size of this
** fixed memory pool is SQLITE_MEMORY_SIZE bytes.
**
** This version of the memory allocation subsystem is used if
** and only if SQLITE_MEMORY_SIZE is defined.
**
** $Id: mem3.c,v 1.11 2008/02/14 23:26:56 drh Exp $
*/
#include "sqliteInt.h"

/*
** This version of the memory allocator is used only when 
** SQLITE_MEMORY_SIZE is defined.
*/



#ifdef SQLITE_MEMORY_SIZE



/*
** Maximum size (in Mem3Blocks) of a "small" chunk.
*/
#define MX_SMALL 10


Changes to src/mem4.c.

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**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains the C functions that implement a memory
** allocation subsystem for use by SQLite.  
**
** $Id: mem4.c,v 1.1 2007/11/29 18:36:49 drh Exp $
*/


/*
** This version of the memory allocator attempts to obtain memory
** from mmap() if the size of the allocation is close to the size
** of a virtual memory page.  If the size of the allocation is different
** from the virtual memory page size, then ordinary malloc() is used.
** Ordinary malloc is also used if space allocated to mmap() is
................................................................................
** exhausted.
**
** Enable this memory allocation by compiling with -DSQLITE_MMAP_HEAP_SIZE=nnn
** where nnn is the maximum number of bytes of mmap-ed memory you want 
** to support.   This module may choose to use less memory than requested.
**
*/
#if defined(SQLITE_MMAP_HEAP_SIZE)

#if defined(SQLITE_MEMDEBUG) || defined(SQLITE_MEMORY_SIZE)
# error cannot use SQLITE_MMAP_HEAP_SIZE with either SQLITE_MEMDEBUG \
        or SQLITE_MEMORY_SIZE
#endif

/*
** This is a test version of the memory allocator that attempts to
** use mmap() and madvise() for allocations and frees of approximately
** the virtual memory page size.
*/
#include <sys/types.h>
#include <sys/mman.h>
#include <errno.h>
#include "sqliteInt.h"
#include <unistd.h>


/*
** All of the static variables used by this module are collected
** into a single structure named "mem".  This is to keep the
** static variables organized and to reduce namespace pollution
................................................................................
    memsys4Free(pPrior);
  }
  assert( mem.mutex!=0 );
  sqlite3_mutex_leave(mem.mutex);
  return (void*)p;
}

#endif /* !SQLITE_MEMDEBUG && !SQLITE_OMIT_MEMORY_ALLOCATION */







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**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains the C functions that implement a memory
** allocation subsystem for use by SQLite.  
**
** $Id: mem4.c,v 1.2 2008/02/14 23:26:56 drh Exp $
*/
#include "sqliteInt.h"

/*
** This version of the memory allocator attempts to obtain memory
** from mmap() if the size of the allocation is close to the size
** of a virtual memory page.  If the size of the allocation is different
** from the virtual memory page size, then ordinary malloc() is used.
** Ordinary malloc is also used if space allocated to mmap() is
................................................................................
** exhausted.
**
** Enable this memory allocation by compiling with -DSQLITE_MMAP_HEAP_SIZE=nnn
** where nnn is the maximum number of bytes of mmap-ed memory you want 
** to support.   This module may choose to use less memory than requested.
**
*/
#ifdef SQLITE_MMAP_HEAP_SIZE






/*
** This is a test version of the memory allocator that attempts to
** use mmap() and madvise() for allocations and frees of approximately
** the virtual memory page size.
*/
#include <sys/types.h>
#include <sys/mman.h>
#include <errno.h>

#include <unistd.h>


/*
** All of the static variables used by this module are collected
** into a single structure named "mem".  This is to keep the
** static variables organized and to reduce namespace pollution
................................................................................
    memsys4Free(pPrior);
  }
  assert( mem.mutex!=0 );
  sqlite3_mutex_leave(mem.mutex);
  return (void*)p;
}

#endif /* SQLITE_MMAP_HEAP_SIZE */

Added src/mem5.c.













































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































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/*
** 2007 October 14
**
** 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 C functions that implement a memory
** allocation subsystem for use by SQLite. 
**
** This version of the memory allocation subsystem omits all
** use of malloc().  All dynamically allocatable memory is
** contained in a static array, mem.aPool[].  The size of this
** fixed memory pool is SQLITE_POW2_MEMORY_SIZE bytes.
**
** This version of the memory allocation subsystem is used if
** and only if SQLITE_POW2_MEMORY_SIZE is defined.
**
** $Id: mem5.c,v 1.1 2008/02/14 23:26:56 drh Exp $
*/
#include "sqliteInt.h"

/*
** This version of the memory allocator is used only when 
** SQLITE_POW2_MEMORY_SIZE is defined.
*/
#ifdef SQLITE_POW2_MEMORY_SIZE

/*
** Maximum size (in Mem3Blocks) of a "small" chunk.
*/
#define MX_SMALL 10


/*
** Number of freelist hash slots
*/
#define N_HASH  61

/*
** A memory allocation (also called a "chunk") consists of two or 
** more blocks where each block is 8 bytes.  The first 8 bytes are 
** a header that is not returned to the user.
**
** A chunk is two or more blocks that is either checked out or
** free.  The first block has format u.hdr.  u.hdr.size4x is 4 times the
** size of the allocation in blocks if the allocation is free.
** The u.hdr.size4x&1 bit is true if the chunk is checked out and
** false if the chunk is on the freelist.  The u.hdr.size4x&2 bit
** is true if the previous chunk is checked out and false if the
** previous chunk is free.  The u.hdr.prevSize field is the size of
** the previous chunk in blocks if the previous chunk is on the
** freelist. If the previous chunk is checked out, then
** u.hdr.prevSize can be part of the data for that chunk and should
** not be read or written.
**
** We often identify a chunk by its index in mem.aPool[].  When
** this is done, the chunk index refers to the second block of
** the chunk.  In this way, the first chunk has an index of 1.
** A chunk index of 0 means "no such chunk" and is the equivalent
** of a NULL pointer.
**
** The second block of free chunks is of the form u.list.  The
** two fields form a double-linked list of chunks of related sizes.
** Pointers to the head of the list are stored in mem.aiSmall[] 
** for smaller chunks and mem.aiHash[] for larger chunks.
**
** The second block of a chunk is user data if the chunk is checked 
** out.  If a chunk is checked out, the user data may extend into
** the u.hdr.prevSize value of the following chunk.
*/
typedef struct Mem3Block Mem3Block;
struct Mem3Block {
  union {
    struct {
      u32 prevSize;   /* Size of previous chunk in Mem3Block elements */
      u32 size4x;     /* 4x the size of current chunk in Mem3Block elements */
    } hdr;
    struct {
      u32 next;       /* Index in mem.aPool[] of next free chunk */
      u32 prev;       /* Index in mem.aPool[] of previous free chunk */
    } list;
  } u;
};

/*
** All of the static variables used by this module are collected
** into a single structure named "mem".  This is to keep the
** static variables organized and to reduce namespace pollution
** when this module is combined with other in the amalgamation.
*/
static struct {
  /*
  ** True if we are evaluating an out-of-memory callback.
  */
  int alarmBusy;
  
  /*
  ** Mutex to control access to the memory allocation subsystem.
  */
  sqlite3_mutex *mutex;
  
  /*
  ** The minimum amount of free space that we have seen.
  */
  u32 mnMaster;

  /*
  ** iMaster is the index of the master chunk.  Most new allocations
  ** occur off of this chunk.  szMaster is the size (in Mem3Blocks)
  ** of the current master.  iMaster is 0 if there is not master chunk.
  ** The master chunk is not in either the aiHash[] or aiSmall[].
  */
  u32 iMaster;
  u32 szMaster;


u64 totalAlloc;
u64 totalExcess;
int nAlloc;

  /*
  ** Array of lists of free blocks according to the block size 
  ** for smaller chunks, or a hash on the block size for larger
  ** chunks.
  */
  u32 aiSmall[MX_SMALL-1];   /* For sizes 2 through MX_SMALL, inclusive */
  u32 aiHash[N_HASH];        /* For sizes MX_SMALL+1 and larger */

  /*
  ** Memory available for allocation
  */
  Mem3Block aPool[SQLITE_POW2_MEMORY_SIZE/sizeof(Mem3Block)+2];
} mem;

/*
** Unlink the chunk at mem.aPool[i] from list it is currently
** on.  *pRoot is the list that i is a member of.
*/
static void memsys3UnlinkFromList(u32 i, u32 *pRoot){
  u32 next = mem.aPool[i].u.list.next;
  u32 prev = mem.aPool[i].u.list.prev;
  assert( sqlite3_mutex_held(mem.mutex) );
  if( prev==0 ){
    *pRoot = next;
  }else{
    mem.aPool[prev].u.list.next = next;
  }
  if( next ){
    mem.aPool[next].u.list.prev = prev;
  }
  mem.aPool[i].u.list.next = 0;
  mem.aPool[i].u.list.prev = 0;
}

/*
** Unlink the chunk at index i from 
** whatever list is currently a member of.
*/
static void memsys3Unlink(u32 i){
  u32 size, hash;
  assert( sqlite3_mutex_held(mem.mutex) );
  assert( (mem.aPool[i-1].u.hdr.size4x & 1)==0 );
  assert( i>=1 );
  size = mem.aPool[i-1].u.hdr.size4x/4;
  assert( size==mem.aPool[i+size-1].u.hdr.prevSize );
  assert( size>=2 );
  if( size <= MX_SMALL ){
    memsys3UnlinkFromList(i, &mem.aiSmall[size-2]);
  }else{
    hash = size % N_HASH;
    memsys3UnlinkFromList(i, &mem.aiHash[hash]);
  }
}

/*
** Link the chunk at mem.aPool[i] so that is on the list rooted
** at *pRoot.
*/
static void memsys3LinkIntoList(u32 i, u32 *pRoot){
  assert( sqlite3_mutex_held(mem.mutex) );
  mem.aPool[i].u.list.next = *pRoot;
  mem.aPool[i].u.list.prev = 0;
  if( *pRoot ){
    mem.aPool[*pRoot].u.list.prev = i;
  }
  *pRoot = i;
}

/*
** Link the chunk at index i into either the appropriate
** small chunk list, or into the large chunk hash table.
*/
static void memsys3Link(u32 i){
  u32 size, hash;
  assert( sqlite3_mutex_held(mem.mutex) );
  assert( i>=1 );
  assert( (mem.aPool[i-1].u.hdr.size4x & 1)==0 );
  size = mem.aPool[i-1].u.hdr.size4x/4;
  assert( size==mem.aPool[i+size-1].u.hdr.prevSize );
  assert( size>=2 );
  if( size <= MX_SMALL ){
    memsys3LinkIntoList(i, &mem.aiSmall[size-2]);
  }else{
    hash = size % N_HASH;
    memsys3LinkIntoList(i, &mem.aiHash[hash]);
  }
}

/*
** Enter the mutex mem.mutex. Allocate it if it is not already allocated.
**
** Also:  Initialize the memory allocation subsystem the first time
** this routine is called.
*/
static void memsys3Enter(void){
  if( mem.mutex==0 ){
    mem.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MEM);
    mem.aPool[0].u.hdr.size4x = SQLITE_POW2_MEMORY_SIZE/2 + 2;
    mem.aPool[SQLITE_POW2_MEMORY_SIZE/8].u.hdr.prevSize = SQLITE_POW2_MEMORY_SIZE/8;
    mem.aPool[SQLITE_POW2_MEMORY_SIZE/8].u.hdr.size4x = 1;
    mem.iMaster = 1;
    mem.szMaster = SQLITE_POW2_MEMORY_SIZE/8;
    mem.mnMaster = mem.szMaster;
  }
  sqlite3_mutex_enter(mem.mutex);
}

/*
** Return the amount of memory currently checked out.
*/
sqlite3_int64 sqlite3_memory_used(void){
  sqlite3_int64 n;
  memsys3Enter();
  n = SQLITE_POW2_MEMORY_SIZE - mem.szMaster*8;
  sqlite3_mutex_leave(mem.mutex);  
  return n;
}

/*
** Return the maximum amount of memory that has ever been
** checked out since either the beginning of this process
** or since the most recent reset.
*/
sqlite3_int64 sqlite3_memory_highwater(int resetFlag){
  sqlite3_int64 n;
  memsys3Enter();
  n = SQLITE_POW2_MEMORY_SIZE - mem.mnMaster*8;
  if( resetFlag ){
    mem.mnMaster = mem.szMaster;
  }
printf("alloc-cnt=%d avg-size=%lld avg-excess=%lld\n",
mem.nAlloc, mem.totalAlloc/mem.nAlloc, mem.totalExcess/mem.nAlloc);
  sqlite3_mutex_leave(mem.mutex);  
  return n;
}

/*
** Change the alarm callback.
**
** This is a no-op for the static memory allocator.  The purpose
** of the memory alarm is to support sqlite3_soft_heap_limit().
** But with this memory allocator, the soft_heap_limit is really
** a hard limit that is fixed at SQLITE_POW2_MEMORY_SIZE.
*/
int sqlite3_memory_alarm(
  void(*xCallback)(void *pArg, sqlite3_int64 used,int N),
  void *pArg,
  sqlite3_int64 iThreshold
){
  return SQLITE_OK;
}

/*
** Called when we are unable to satisfy an allocation of nBytes.
*/
static void memsys3OutOfMemory(int nByte){
  if( !mem.alarmBusy ){
    mem.alarmBusy = 1;
    assert( sqlite3_mutex_held(mem.mutex) );
    sqlite3_mutex_leave(mem.mutex);
    sqlite3_release_memory(nByte);
    sqlite3_mutex_enter(mem.mutex);
    mem.alarmBusy = 0;
  }
}

/*
** Return the size of an outstanding allocation, in bytes.  The
** size returned omits the 8-byte header overhead.  This only
** works for chunks that are currently checked out.
*/
int sqlite3MallocSize(void *p){
  int iSize = 0;
  if( p ){
    Mem3Block *pBlock = (Mem3Block*)p;
    assert( (pBlock[-1].u.hdr.size4x&1)!=0 );
    iSize = (pBlock[-1].u.hdr.size4x&~3)*2 - 4;
  }
  return iSize;
}

/*
** Chunk i is a free chunk that has been unlinked.  Adjust its 
** size parameters for check-out and return a pointer to the 
** user portion of the chunk.
*/
static void *memsys3Checkout(u32 i, int nBlock){
  u32 x;
  assert( sqlite3_mutex_held(mem.mutex) );
  assert( i>=1 );
  assert( mem.aPool[i-1].u.hdr.size4x/4==nBlock );
  assert( mem.aPool[i+nBlock-1].u.hdr.prevSize==nBlock );
  x = mem.aPool[i-1].u.hdr.size4x;
  mem.aPool[i-1].u.hdr.size4x = nBlock*4 | 1 | (x&2);
  mem.aPool[i+nBlock-1].u.hdr.prevSize = nBlock;
  mem.aPool[i+nBlock-1].u.hdr.size4x |= 2;
  return &mem.aPool[i];
}

/*
** Carve a piece off of the end of the mem.iMaster free chunk.
** Return a pointer to the new allocation.  Or, if the master chunk
** is not large enough, return 0.
*/
static void *memsys3FromMaster(int nBlock){
  assert( sqlite3_mutex_held(mem.mutex) );
  assert( mem.szMaster>=nBlock );
  if( nBlock>=mem.szMaster-1 ){
    /* Use the entire master */
    void *p = memsys3Checkout(mem.iMaster, mem.szMaster);
    mem.iMaster = 0;
    mem.szMaster = 0;
    mem.mnMaster = 0;
    return p;
  }else{
    /* Split the master block.  Return the tail. */
    u32 newi, x;
    newi = mem.iMaster + mem.szMaster - nBlock;
    assert( newi > mem.iMaster+1 );
    mem.aPool[mem.iMaster+mem.szMaster-1].u.hdr.prevSize = nBlock;
    mem.aPool[mem.iMaster+mem.szMaster-1].u.hdr.size4x |= 2;
    mem.aPool[newi-1].u.hdr.size4x = nBlock*4 + 1;
    mem.szMaster -= nBlock;
    mem.aPool[newi-1].u.hdr.prevSize = mem.szMaster;
    x = mem.aPool[mem.iMaster-1].u.hdr.size4x & 2;
    mem.aPool[mem.iMaster-1].u.hdr.size4x = mem.szMaster*4 | x;
    if( mem.szMaster < mem.mnMaster ){
      mem.mnMaster = mem.szMaster;
    }
    return (void*)&mem.aPool[newi];
  }
}

/*
** *pRoot is the head of a list of free chunks of the same size
** or same size hash.  In other words, *pRoot is an entry in either
** mem.aiSmall[] or mem.aiHash[].  
**
** This routine examines all entries on the given list and tries
** to coalesce each entries with adjacent free chunks.  
**
** If it sees a chunk that is larger than mem.iMaster, it replaces 
** the current mem.iMaster with the new larger chunk.  In order for
** this mem.iMaster replacement to work, the master chunk must be
** linked into the hash tables.  That is not the normal state of
** affairs, of course.  The calling routine must link the master
** chunk before invoking this routine, then must unlink the (possibly
** changed) master chunk once this routine has finished.
*/
static void memsys3Merge(u32 *pRoot){
  u32 iNext, prev, size, i, x;

  assert( sqlite3_mutex_held(mem.mutex) );
  for(i=*pRoot; i>0; i=iNext){
    iNext = mem.aPool[i].u.list.next;
    size = mem.aPool[i-1].u.hdr.size4x;
    assert( (size&1)==0 );
    if( (size&2)==0 ){
      memsys3UnlinkFromList(i, pRoot);
      assert( i > mem.aPool[i-1].u.hdr.prevSize );
      prev = i - mem.aPool[i-1].u.hdr.prevSize;
      if( prev==iNext ){
        iNext = mem.aPool[prev].u.list.next;
      }
      memsys3Unlink(prev);
      size = i + size/4 - prev;
      x = mem.aPool[prev-1].u.hdr.size4x & 2;
      mem.aPool[prev-1].u.hdr.size4x = size*4 | x;
      mem.aPool[prev+size-1].u.hdr.prevSize = size;
      memsys3Link(prev);
      i = prev;
    }else{
      size /= 4;
    }
    if( size>mem.szMaster ){
      mem.iMaster = i;
      mem.szMaster = size;
    }
  }
}

/*
** Return a block of memory of at least nBytes in size.
** Return NULL if unable.
*/
static void *memsys3Malloc(int nByte){
  u32 i;
  int nBlock;
  int toFree;
  int x;

  assert( sqlite3_mutex_held(mem.mutex) );
  assert( sizeof(Mem3Block)==8 );
  for(x=256; x<nByte; x *= 2){}
mem.nAlloc++;
mem.totalAlloc += x;
mem.totalExcess += x - nByte;
  nByte = x;
  nBlock = (nByte + 11)/8;
  assert( nBlock >= 2 );

  /* STEP 1:
  ** Look for an entry of the correct size in either the small
  ** chunk table or in the large chunk hash table.  This is
  ** successful most of the time (about 9 times out of 10).
  */
  if( nBlock <= MX_SMALL ){
    i = mem.aiSmall[nBlock-2];
    if( i>0 ){
      memsys3UnlinkFromList(i, &mem.aiSmall[nBlock-2]);
      return memsys3Checkout(i, nBlock);
    }
  }else{
    int hash = nBlock % N_HASH;
    for(i=mem.aiHash[hash]; i>0; i=mem.aPool[i].u.list.next){
      if( mem.aPool[i-1].u.hdr.size4x/4==nBlock ){
        memsys3UnlinkFromList(i, &mem.aiHash[hash]);
        return memsys3Checkout(i, nBlock);
      }
    }
  }

  /* STEP 2:
  ** Try to satisfy the allocation by carving a piece off of the end
  ** of the master chunk.  This step usually works if step 1 fails.
  */
  if( mem.szMaster>=nBlock ){
    return memsys3FromMaster(nBlock);
  }


  /* STEP 3:  
  ** Loop through the entire memory pool.  Coalesce adjacent free
  ** chunks.  Recompute the master chunk as the largest free chunk.
  ** Then try again to satisfy the allocation by carving a piece off
  ** of the end of the master chunk.  This step happens very
  ** rarely (we hope!)
  */
  for(toFree=nBlock*16; toFree<SQLITE_POW2_MEMORY_SIZE*2; toFree *= 2){
    memsys3OutOfMemory(toFree);
    if( mem.iMaster ){
      memsys3Link(mem.iMaster);
      mem.iMaster = 0;
      mem.szMaster = 0;
    }
    for(i=0; i<N_HASH; i++){
      memsys3Merge(&mem.aiHash[i]);
    }
    for(i=0; i<MX_SMALL-1; i++){
      memsys3Merge(&mem.aiSmall[i]);
    }
    if( mem.szMaster ){
      memsys3Unlink(mem.iMaster);
      if( mem.szMaster>=nBlock ){
        return memsys3FromMaster(nBlock);
      }
    }
  }

  /* If none of the above worked, then we fail. */
  return 0;
}

/*
** Free an outstanding memory allocation.
*/
void memsys3Free(void *pOld){
  Mem3Block *p = (Mem3Block*)pOld;
  int i;
  u32 size, x;
  assert( sqlite3_mutex_held(mem.mutex) );
  assert( p>mem.aPool && p<&mem.aPool[SQLITE_POW2_MEMORY_SIZE/8] );
  i = p - mem.aPool;
  assert( (mem.aPool[i-1].u.hdr.size4x&1)==1 );
  size = mem.aPool[i-1].u.hdr.size4x/4;
  assert( i+size<=SQLITE_POW2_MEMORY_SIZE/8+1 );
  mem.aPool[i-1].u.hdr.size4x &= ~1;
  mem.aPool[i+size-1].u.hdr.prevSize = size;
  mem.aPool[i+size-1].u.hdr.size4x &= ~2;
  memsys3Link(i);

  /* Try to expand the master using the newly freed chunk */
  if( mem.iMaster ){
    while( (mem.aPool[mem.iMaster-1].u.hdr.size4x&2)==0 ){
      size = mem.aPool[mem.iMaster-1].u.hdr.prevSize;
      mem.iMaster -= size;
      mem.szMaster += size;
      memsys3Unlink(mem.iMaster);
      x = mem.aPool[mem.iMaster-1].u.hdr.size4x & 2;
      mem.aPool[mem.iMaster-1].u.hdr.size4x = mem.szMaster*4 | x;
      mem.aPool[mem.iMaster+mem.szMaster-1].u.hdr.prevSize = mem.szMaster;
    }
    x = mem.aPool[mem.iMaster-1].u.hdr.size4x & 2;
    while( (mem.aPool[mem.iMaster+mem.szMaster-1].u.hdr.size4x&1)==0 ){
      memsys3Unlink(mem.iMaster+mem.szMaster);
      mem.szMaster += mem.aPool[mem.iMaster+mem.szMaster-1].u.hdr.size4x/4;
      mem.aPool[mem.iMaster-1].u.hdr.size4x = mem.szMaster*4 | x;
      mem.aPool[mem.iMaster+mem.szMaster-1].u.hdr.prevSize = mem.szMaster;
    }
  }
}

/*
** Allocate nBytes of memory
*/
void *sqlite3_malloc(int nBytes){
  sqlite3_int64 *p = 0;
  if( nBytes>0 ){
    memsys3Enter();
    p = memsys3Malloc(nBytes);
    sqlite3_mutex_leave(mem.mutex);
  }
  return (void*)p; 
}

/*
** Free memory.
*/
void sqlite3_free(void *pPrior){
  if( pPrior==0 ){
    return;
  }
  assert( mem.mutex!=0 );
  sqlite3_mutex_enter(mem.mutex);
  memsys3Free(pPrior);
  sqlite3_mutex_leave(mem.mutex);  
}

/*
** Change the size of an existing memory allocation
*/
void *sqlite3_realloc(void *pPrior, int nBytes){
  int nOld;
  void *p;
  if( pPrior==0 ){
    return sqlite3_malloc(nBytes);
  }
  if( nBytes<=0 ){
    sqlite3_free(pPrior);
    return 0;
  }
  assert( mem.mutex!=0 );
  nOld = sqlite3MallocSize(pPrior);
  if( nBytes<=nOld && nBytes>=nOld-128 ){
    return pPrior;
  }
  sqlite3_mutex_enter(mem.mutex);
  p = memsys3Malloc(nBytes);
  if( p ){
    if( nOld<nBytes ){
      memcpy(p, pPrior, nOld);
    }else{
      memcpy(p, pPrior, nBytes);
    }
    memsys3Free(pPrior);
  }
  sqlite3_mutex_leave(mem.mutex);
  return p;
}

/*
** Open the file indicated and write a log of all unfreed memory 
** allocations into that log.
*/
void sqlite3_memdebug_dump(const char *zFilename){
#ifdef SQLITE_DEBUG
  FILE *out;
  int i, j;
  u32 size;
  if( zFilename==0 || zFilename[0]==0 ){
    out = stdout;
  }else{
    out = fopen(zFilename, "w");
    if( out==0 ){
      fprintf(stderr, "** Unable to output memory debug output log: %s **\n",
                      zFilename);
      return;
    }
  }
  memsys3Enter();
  fprintf(out, "CHUNKS:\n");
  for(i=1; i<=SQLITE_POW2_MEMORY_SIZE/8; i+=size/4){
    size = mem.aPool[i-1].u.hdr.size4x;
    if( size/4<=1 ){
      fprintf(out, "%p size error\n", &mem.aPool[i]);
      assert( 0 );
      break;
    }
    if( (size&1)==0 && mem.aPool[i+size/4-1].u.hdr.prevSize!=size/4 ){
      fprintf(out, "%p tail size does not match\n", &mem.aPool[i]);
      assert( 0 );
      break;
    }
    if( ((mem.aPool[i+size/4-1].u.hdr.size4x&2)>>1)!=(size&1) ){
      fprintf(out, "%p tail checkout bit is incorrect\n", &mem.aPool[i]);
      assert( 0 );
      break;
    }
    if( size&1 ){
      fprintf(out, "%p %6d bytes checked out\n", &mem.aPool[i], (size/4)*8-8);
    }else{
      fprintf(out, "%p %6d bytes free%s\n", &mem.aPool[i], (size/4)*8-8,
                  i==mem.iMaster ? " **master**" : "");
    }
  }
  for(i=0; i<MX_SMALL-1; i++){
    if( mem.aiSmall[i]==0 ) continue;
    fprintf(out, "small(%2d):", i);
    for(j = mem.aiSmall[i]; j>0; j=mem.aPool[j].u.list.next){
      fprintf(out, " %p(%d)", &mem.aPool[j],
              (mem.aPool[j-1].u.hdr.size4x/4)*8-8);
    }
    fprintf(out, "\n"); 
  }
  for(i=0; i<N_HASH; i++){
    if( mem.aiHash[i]==0 ) continue;
    fprintf(out, "hash(%2d):", i);
    for(j = mem.aiHash[i]; j>0; j=mem.aPool[j].u.list.next){
      fprintf(out, " %p(%d)", &mem.aPool[j],
              (mem.aPool[j-1].u.hdr.size4x/4)*8-8);
    }
    fprintf(out, "\n"); 
  }
  fprintf(out, "master=%d\n", mem.iMaster);
  fprintf(out, "nowUsed=%d\n", SQLITE_POW2_MEMORY_SIZE - mem.szMaster*8);
  fprintf(out, "mxUsed=%d\n", SQLITE_POW2_MEMORY_SIZE - mem.mnMaster*8);
  sqlite3_mutex_leave(mem.mutex);
  if( out==stdout ){
    fflush(stdout);
  }else{
    fclose(out);
  }
#endif
}


#endif /* !SQLITE_POW2_MEMORY_SIZE */

Changes to src/pager.c.

14
15
16
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18
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20
21
22
23
24
25
26
27
28
....
1205
1206
1207
1208
1209
1210
1211

1212
1213
1214
1215
1216
1217
1218
....
2535
2536
2537
2538
2539
2540
2541

2542
2543
2544
2545
2546
2547
2548
....
3201
3202
3203
3204
3205
3206
3207

3208
3209
3210
3211
3212
3213
3214
....
3472
3473
3474
3475
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3477
3478

3479
3480
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3489
3490







3491
3492
3493
3494
3495
3496
3497
3498
3499
3500
3501
3502
3503
3504
** The pager is used to access a database disk file.  It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file.  The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.405 2008/02/02 20:47:38 drh Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include <assert.h>
#include <string.h>

/*
................................................................................
  PgHdr *pPg, *pNext;
  if( pPager->errCode ) return;
  for(pPg=pPager->pAll; pPg; pPg=pNext){
    IOTRACE(("PGFREE %p %d\n", pPager, pPg->pgno));
    PAGER_INCR(sqlite3_pager_pgfree_count);
    pNext = pPg->pNextAll;
    lruListRemove(pPg);

    sqlite3_free(pPg);
  }
  assert(pPager->lru.pFirst==0);
  assert(pPager->lru.pFirstSynced==0);
  assert(pPager->lru.pLast==0);
  pPager->pStmt = 0;
  pPager->pAll = 0;
................................................................................
      ppPg = &pPg->pNextAll;
    }else{
      *ppPg = pPg->pNextAll;
      IOTRACE(("PGFREE %p %d\n", pPager, pPg->pgno));
      PAGER_INCR(sqlite3_pager_pgfree_count);
      unlinkPage(pPg);
      makeClean(pPg);

      sqlite3_free(pPg);
      pPager->nPage--;
    }
  }
}

/*
................................................................................
      nReleased += (
          sizeof(*pPg) + pPager->pageSize
          + sizeof(u32) + pPager->nExtra
          + MEMDB*sizeof(PgHistory) 
      );
      IOTRACE(("PGFREE %p %d *\n", pPager, pPg->pgno));
      PAGER_INCR(sqlite3_pager_pgfree_count);

      sqlite3_free(pPg);
      pPager->nPage--;
    }else{
      /* An error occured whilst writing to the database file or 
      ** journal in pager_recycle(). The error is not returned to the 
      ** caller of this function. Instead, set the Pager.errCode variable.
      ** The error will be returned to the user (or users, in the case 
................................................................................
  /* Create a new PgHdr if any of the four conditions defined 
  ** above are met: */
  if( pPager->nPage<pPager->mxPage
   || pPager->lru.pFirst==0 
   || MEMDB
   || (pPager->lru.pFirstSynced==0 && pPager->doNotSync)
  ){

    if( pPager->nPage>=pPager->nHash ){
      pager_resize_hash_table(pPager,
         pPager->nHash<256 ? 256 : pPager->nHash*2);
      if( pPager->nHash==0 ){
        rc = SQLITE_NOMEM;
        goto pager_allocate_out;
      }
    }
    pagerLeave(pPager);
    nByteHdr = sizeof(*pPg) + sizeof(u32) + pPager->nExtra
              + MEMDB*sizeof(PgHistory);
    pPg = sqlite3_malloc( nByteHdr + pPager->pageSize );







    pagerEnter(pPager);
    if( pPg==0 ){
      rc = SQLITE_NOMEM;
      goto pager_allocate_out;
    }
    memset(pPg, 0, nByteHdr);
    pPg->pData = (void*)(nByteHdr + (char*)pPg);
    pPg->pPager = pPager;
    pPg->pNextAll = pPager->pAll;
    pPager->pAll = pPg;
    pPager->nPage++;
  }else{
    /* Recycle an existing page with a zero ref-count. */
    rc = pager_recycle(pPager, &pPg);







|







 







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>







 







>











|
>
>
>
>
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>






|







14
15
16
17
18
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20
21
22
23
24
25
26
27
28
....
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
....
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
....
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
....
3475
3476
3477
3478
3479
3480
3481
3482
3483
3484
3485
3486
3487
3488
3489
3490
3491
3492
3493
3494
3495
3496
3497
3498
3499
3500
3501
3502
3503
3504
3505
3506
3507
3508
3509
3510
3511
3512
3513
3514
3515
** The pager is used to access a database disk file.  It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file.  The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.406 2008/02/14 23:26:56 drh Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include <assert.h>
#include <string.h>

/*
................................................................................
  PgHdr *pPg, *pNext;
  if( pPager->errCode ) return;
  for(pPg=pPager->pAll; pPg; pPg=pNext){
    IOTRACE(("PGFREE %p %d\n", pPager, pPg->pgno));
    PAGER_INCR(sqlite3_pager_pgfree_count);
    pNext = pPg->pNextAll;
    lruListRemove(pPg);
    sqlite3_free(pPg->pData);
    sqlite3_free(pPg);
  }
  assert(pPager->lru.pFirst==0);
  assert(pPager->lru.pFirstSynced==0);
  assert(pPager->lru.pLast==0);
  pPager->pStmt = 0;
  pPager->pAll = 0;
................................................................................
      ppPg = &pPg->pNextAll;
    }else{
      *ppPg = pPg->pNextAll;
      IOTRACE(("PGFREE %p %d\n", pPager, pPg->pgno));
      PAGER_INCR(sqlite3_pager_pgfree_count);
      unlinkPage(pPg);
      makeClean(pPg);
      sqlite3_free(pPg->pData);
      sqlite3_free(pPg);
      pPager->nPage--;
    }
  }
}

/*
................................................................................
      nReleased += (
          sizeof(*pPg) + pPager->pageSize
          + sizeof(u32) + pPager->nExtra
          + MEMDB*sizeof(PgHistory) 
      );
      IOTRACE(("PGFREE %p %d *\n", pPager, pPg->pgno));
      PAGER_INCR(sqlite3_pager_pgfree_count);
      sqlite3_free(pPg->pData);
      sqlite3_free(pPg);
      pPager->nPage--;
    }else{
      /* An error occured whilst writing to the database file or 
      ** journal in pager_recycle(). The error is not returned to the 
      ** caller of this function. Instead, set the Pager.errCode variable.
      ** The error will be returned to the user (or users, in the case 
................................................................................
  /* Create a new PgHdr if any of the four conditions defined 
  ** above are met: */
  if( pPager->nPage<pPager->mxPage
   || pPager->lru.pFirst==0 
   || MEMDB
   || (pPager->lru.pFirstSynced==0 && pPager->doNotSync)
  ){
    void *pData;
    if( pPager->nPage>=pPager->nHash ){
      pager_resize_hash_table(pPager,
         pPager->nHash<256 ? 256 : pPager->nHash*2);
      if( pPager->nHash==0 ){
        rc = SQLITE_NOMEM;
        goto pager_allocate_out;
      }
    }
    pagerLeave(pPager);
    nByteHdr = sizeof(*pPg) + sizeof(u32) + pPager->nExtra
              + MEMDB*sizeof(PgHistory);
    pPg = sqlite3_malloc( nByteHdr );
    if( pPg ){
      pData = sqlite3_malloc( pPager->pageSize );
      if( pData==0 ){
        sqlite3_free(pPg);
        pPg = 0;
      }
    }
    pagerEnter(pPager);
    if( pPg==0 ){
      rc = SQLITE_NOMEM;
      goto pager_allocate_out;
    }
    memset(pPg, 0, nByteHdr);
    pPg->pData = pData;
    pPg->pPager = pPager;
    pPg->pNextAll = pPager->pAll;
    pPager->pAll = pPg;
    pPager->nPage++;
  }else{
    /* Recycle an existing page with a zero ref-count. */
    rc = pager_recycle(pPager, &pPg);

Changes to src/sqliteInt.h.

7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
...
113
114
115
116
117
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119


























120
121
122
123
124
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126
**    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.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.661 2008/02/13 18:25:27 danielk1977 Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_

/*
** The macro unlikely() is a hint that surrounds a boolean
** expression that is usually false.  Macro likely() surrounds
................................................................................
#if defined(THREADSAFE)
# define SQLITE_THREADSAFE THREADSAFE
#else
# define SQLITE_THREADSAFE 1
#endif
#endif



























/*
** We need to define _XOPEN_SOURCE as follows in order to enable
** recursive mutexes on most unix systems.  But Mac OS X is different.
** The _XOPEN_SOURCE define causes problems for Mac OS X we are told,
** so it is omitted there.  See ticket #2673.
**
** Later we learn that _XOPEN_SOURCE is poorly or incorrectly







|







 







>
>
>
>
>
>
>
>
>
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>
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7
8
9
10
11
12
13
14
15
16
17
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19
20
21
...
113
114
115
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118
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140
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146
147
148
149
150
151
152
**    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.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.662 2008/02/14 23:26:56 drh Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_

/*
** The macro unlikely() is a hint that surrounds a boolean
** expression that is usually false.  Macro likely() surrounds
................................................................................
#if defined(THREADSAFE)
# define SQLITE_THREADSAFE THREADSAFE
#else
# define SQLITE_THREADSAFE 1
#endif
#endif

/*
** Exactly one of the following macros must be defined in order to
** specify which memory allocation subsystem to use.
**
**     SQLITE_SYSTEM_MALLOC          // Use normal system malloc()
**     SQLITE_MEMDEBUG               // Debugging version of system malloc()
**     SQLITE_MEMORY_SIZE            // internal allocator #1
**     SQLITE_MMAP_HEAP_SIZE         // internal mmap() allocator
**     SQLITE_POW2_MEMORY_SIZE       // internal power-of-two allocator
**
** If none of the above are defined, then set SQLITE_SYSTEM_MALLOC as
** the default.
*/
#if defined(SQLITE_SYSTEM_MALLOC)+defined(SQLITE_MEMDEBUG)+\
    defined(SQLITE_MEMORY_SIZE)+defined(SQLITE_MMAP_HEAP_SIZE)+\
    defined(SQLITE_POW2_MEMORY_SIZE)>1
# error "At most one of the following compile-time configuration options\
 is allows: SQLITE_SYSTEM_MALLOC, SQLITE_MEMDEBUG, SQLITE_MEMORY_SIZE,\
 SQLITE_MMAP_HEAP_SIZE, SQLITE_POW2_MEMORY_SIZE"
#endif
#if defined(SQLITE_SYSTEM_MALLOC)+defined(SQLITE_MEMDEBUG)+\
    defined(SQLITE_MEMORY_SIZE)+defined(SQLITE_MMAP_HEAP_SIZE)+\
    defined(SQLITE_POW2_MEMORY_SIZE)==0
# define SQLITE_SYSTEM_MALLOC 1
#endif

/*
** We need to define _XOPEN_SOURCE as follows in order to enable
** recursive mutexes on most unix systems.  But Mac OS X is different.
** The _XOPEN_SOURCE define causes problems for Mac OS X we are told,
** so it is omitted there.  See ticket #2673.
**
** Later we learn that _XOPEN_SOURCE is poorly or incorrectly