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Overview
Comment:Pager tests working. (CVS 1308)
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1:910067a200c4b25b5d813a84146673d3d1c80952
User & Date: drh 2004-04-26 14:10:21
Context
2004-04-29
14:42
Sync all version 3 changes. (CVS 1309) check-in: 51892d6c user: drh tags: trunk
2004-04-26
14:10
Pager tests working. (CVS 1308) check-in: 910067a2 user: drh tags: trunk
2004-04-23
23:43
Begin modifying the BTree code for the new version-3 file format. This is a work-in-progress. As of this check-in, SQLite will not build. (CVS 1306) check-in: ce0bbd3a user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to main.mk.

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# This is how we compile
#
TCCX = $(TCC) $(OPTS) $(THREADSAFE) $(USLEEP) -I. -I$(TOP)/src

# Object files for the SQLite library.
#



LIBOBJ = attach.o auth.o btree.o btree_rb.o build.o copy.o date.o delete.o \
         expr.o func.o hash.o insert.o \
         main.o opcodes.o os.o pager.o parse.o pragma.o printf.o random.o \
         select.o table.o tokenize.o trigger.o update.o util.o \
         vacuum.o vdbe.o vdbeaux.o where.o tclsqlite.o

# All of the source code files.
#
SRC = \









  $(TOP)/src/attach.c \
  $(TOP)/src/auth.c \
  $(TOP)/src/btree.c \
  $(TOP)/src/btree.h \
  $(TOP)/src/btree_rb.c \
  $(TOP)/src/build.c \
  $(TOP)/src/copy.c \
................................................................................
  $(TOP)/src/vdbeaux.c \
  $(TOP)/src/vdbeInt.h \
  $(TOP)/src/where.c

# Source code to the test files.
#
TESTSRC = \






  $(TOP)/src/btree.c \
  $(TOP)/src/func.c \
  $(TOP)/src/os.c \
  $(TOP)/src/pager.c \
  $(TOP)/src/test1.c \
  $(TOP)/src/test2.c \
  $(TOP)/src/test3.c \







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# This is how we compile
#
TCCX = $(TCC) $(OPTS) $(THREADSAFE) $(USLEEP) -I. -I$(TOP)/src

# Object files for the SQLite library.
#
LIBOBJ = hash.o os.o pager.o random.o \
         util.o tclsqlite.o

LIBOBJ_ORIG = attach.o auth.o btree.o btree_rb.o build.o copy.o date.o delete.o \
         expr.o func.o hash.o insert.o \
         main.o opcodes.o os.o pager.o parse.o pragma.o printf.o random.o \
         select.o table.o tokenize.o trigger.o update.o util.o \
         vacuum.o vdbe.o vdbeaux.o where.o tclsqlite.o

# All of the source code files.
#
SRC = \
  $(TOP)/src/hash.c \
  $(TOP)/src/hash.h \
  $(TOP)/src/os.c \
  $(TOP)/src/pager.c \
  $(TOP)/src/pager.h \
  $(TOP)/src/random.c \
  $(TOP)/src/util.c 

SRC_ORIG = \
  $(TOP)/src/attach.c \
  $(TOP)/src/auth.c \
  $(TOP)/src/btree.c \
  $(TOP)/src/btree.h \
  $(TOP)/src/btree_rb.c \
  $(TOP)/src/build.c \
  $(TOP)/src/copy.c \
................................................................................
  $(TOP)/src/vdbeaux.c \
  $(TOP)/src/vdbeInt.h \
  $(TOP)/src/where.c

# Source code to the test files.
#
TESTSRC = \
  $(TOP)/src/os.c \
  $(TOP)/src/pager.c \
  $(TOP)/src/test2.c \
  $(TOP)/src/md5.c

TESTSRC_ORIG = \
  $(TOP)/src/btree.c \
  $(TOP)/src/func.c \
  $(TOP)/src/os.c \
  $(TOP)/src/pager.c \
  $(TOP)/src/test1.c \
  $(TOP)/src/test2.c \
  $(TOP)/src/test3.c \

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** 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.
**
*************************************************************************
** $Id: btree.c,v 1.104 2004/04/23 23:43:10 drh Exp $
**
** 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.
................................................................................
**
** Cells are of variable length.  The first cell begins on the byte defined
** in the page header.  Cells do not necessarily occur in order - they can
** skip around on the page.
**
**    SIZE    DESCRIPTION
**      2     Byte offset of the next cell.  0 if this is the last cell
**      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.  Omitted if the 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.
**
................................................................................
*/
#include "sqliteInt.h"
#include "pager.h"
#include "btree.h"
#include <assert.h>

/* Forward declarations */
static BtOps sqliteBtreeOps;
static BtCursorOps sqliteBtreeCursorOps;

/*
** This is a magic string that appears at the beginning of every
** SQLite database in order to identify the file as a real database.
**                                  0123456789 123456 */
static const char zMagicHeader[] = "SQLite version 3";

................................................................................
**
** 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.
*/
struct MemPage {
  struct BTree *pBt;             /* Pointer back to BTree structure */
  unsigned char *aData;          /* Pointer back to the start of the page */

  u8 idxShift;                   /* True if Cell indices have changed */
  u8 isOverfull;                 /* Some aCell[] points outside u.aDisk[] */
  u8 intKey;                     /* True if intkey flag is set */
  u8 leaf;                       /* True if leaf flag is set */
  u8 zeroData;                   /* True if zero data flag is set */
  u8 hdrOffset;                  /* 100 for page 1.  0 otherwise */
  Pgno pgno;                     /* Page number for this page */
  MemPage *pParent;              /* The parent of this page.  NULL for root */
  int idxParent;                 /* Index in pParent->apCell[] of this node */
  int nFree;                     /* Number of free bytes on the page */
  int nCell;                     /* Number of entries on this page */
  unsigned char **aCell;         /* Pointer to start of each cell */
};

/*
** 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)

/*
** Everything we need to know about an open database
*/
struct Btree {
  BtOps *pOps;          /* Function table */
  Pager *pPager;        /* The page cache */
  BtCursor *pCursor;    /* A list of all open cursors */
  MemPage *page1;       /* First page of the database */
  u8 inTrans;           /* True if a transaction is in progress */
  u8 inCkpt;            /* True if there is a checkpoint on the transaction */
  u8 readOnly;          /* True if the underlying file is readonly */
  int pageSize;         /* Number of usable bytes on each page */
  int maxLocal;         /* Maximum local payload */
};
typedef Btree Bt;

/*
** A cursor is a pointer to a particular entry in the BTree.
** The entry is identified by its MemPage and the index in
** MemPage.apCell[] of the entry.
*/
struct BtCursor {
  BtCursorOps *pOps;        /* Function table */
  Btree *pBt;               /* The Btree to which this cursor belongs */
  BtCursor *pNext, *pPrev;  /* Forms a linked list of all cursors */
  BtCursor *pShared;        /* Loop of cursors with the same root page */


  Pgno pgnoRoot;            /* The root page of this tree */
  MemPage *pPage;           /* Page that contains the entry */
  int idx;                  /* Index of the entry in pPage->apCell[] */
  u8 wrFlag;                /* True if writable */
  u8 eSkip;                 /* Determines if next step operation is a no-op */
  u8 iMatch;                /* compare result from last sqliteBtreeMoveto() */
};

/*
** Legal values for BtCursor.eSkip.
*/
#define SKIP_NONE     0   /* Always step the cursor */
#define SKIP_NEXT     1   /* The next sqliteBtreeNext() is a no-op */
#define SKIP_PREV     2   /* The next sqliteBtreePrevious() is a no-op */
#define SKIP_INVALID  3   /* Calls to Next() and Previous() are invalid */

/* Forward declarations */
static int fileBtreeCloseCursor(BtCursor *pCur);

/*
** Read or write a two-, four-, and eight-byte integer values
*/
static u32 get2byte(unsigned char *p){
  return (p[0]<<8) | p[1];
}
static u32 get4byte(unsigned char *p){
  return (p[0]<<24) | (p[1]<<16) | (p[2]<<8) | p[3];
}
static u64 get4byte(unsigned char *p){
  u64 v = get4byte(p);
  return (v<<32) | get4byte(&p[4]);
}
static void put2byte(unsigned char *p, u32 v){
  p[0] = v>>8;
  p[1] = v;
}
................................................................................
  do{
    p[i++] = v & 0x7f;
    v >>= 7;
  }while( v!=0 );
  p[i-1] |= 0x80;
  return i;
}


























/*
** Compute the total number of bytes that a Cell needs on the main
** database page.  The number returned includes the Cell header,
** local payload storage, and the pointer to overflow pages (if
** applicable).  Additional space allocated on overflow pages
** is NOT included in the value returned from this routine.
*/
static int cellSize(MemPage *pPage, unsigned char *pCell){

  int n, nPayload;
  u64 nData, nKey;
  int maxPayload;
  if( pPage->leaf ){
    n = 2;
  }else{
    n = 6;
  }
  if( pPage->zeroData ){
    nData = 0;
  }else{
    n += getVarint(&pCell[n], &nData);
  }


  if( pPage->intKey ){
    u64 dummy;
    nKey = getVarint(&pCell[n], &dummy);
  }else{
    n += getVarint(pCell, &nKey);

  }
  nPayload = nKey + nData;
  maxPayload = pPage->pBt->maxPayload;
  if( nPayload>maxPayload ){
    nPayload = maxPayload + 4;
  }
  return n + nPayload;
}

/*
** Defragment the page given.  All Cells are moved to the
** beginning of the page and all free space is collected 
** into one big FreeBlk at the end of the page.
*/
static void defragmentPage(MemPage *pPage){
  int pc, i, n;
  int start, hdr;
  int leftover;
  unsigned char *oldPage;
  unsigned char newPage[SQLITE_PAGE_SIZE];

  assert( sqlitepager_iswriteable(pPage->aData) );
  assert( pPage->pBt!=0 );
  assert( pPage->pageSize <= SQLITE_PAGE_SIZE );
  oldPage = pPage->aData;
  hdr = pPage->hdrOffset;
  ptr = 3+hdr;
  n = 6+hdr;
  if( !pPage->leaf ){
    n += 4;
  }
  start = n;
  pc = get2byte(&oldPage[ptr]);
  i = 0;
  while( pc>0 ){
    assert( n<pPage->pageSize );
    size = cellSize(pPage, &oldPage[pc]);
    memcpy(&newPage[n], &oldPage[pc], size);
    put2byte(&newPage[ptr],n);
    pPage->aCell[i] = &oldPage[n];
    n += size;
    ptr = pc;
    pc = get2byte(&oldPage[pc]);
  }
  leftover = pPage->pageSize - n;
  assert( leftover>=0 );
  assert( pPage->nFree==leftover );
  if( leftover<4 ){
    oldPage[hdr+5] = leftover;
    leftover = 0;
    n = pPage->pageSize;
  }
  memcpy(&oldPage[start], &newPage[start], n-start);
  if( leftover==0 ){
    put2byte(&oldPage[hdr+3], 0);
  }else if( leftover>=4 ){
    put2byte(&oldPage[hdr+3], n);
    put2byte(&oldPage[n], 0);
................................................................................
** calls defragementPage() to consolidate all free space before 
** allocating the new chunk.
**
** Algorithm:  Carve a piece off of the first freeblock that is
** nByte in size or that larger.
*/
static int allocateSpace(MemPage *pPage, int nByte){
  int ptr, pc, hdr;
  int size;
  unsigned char *data;
#ifndef NDEBUG
  int cnt = 0;
#endif

  data = pPage->aData;
................................................................................
  assert( pPage->pBt );
  if( nByte<4 ) nByte = 4;
  if( pPage->nFree<nByte || pPage->isOverfull ) return 0;
  hdr = pPage->hdrOffset;
  if( data[hdr+5]>=252 ){
    defragmentPage(pPage);
  }
  ptr = hdr+1;
  pc = get2byte(&data[ptr]);
  assert( ptr<pc );
  assert( pc<=pPage->pageSize-4 );
  while( (size = get2byte(&data[pc+2])<nByte ){
    ptr = pc;
    pc = get2byte(&data[ptr]);
    assert( pc<=pPage->pageSize-4 );
    assert( pc>=ptr+size+4 || pc==0 );
    if( pc==0 ){
      assert( (cnt++)==0 );
      defragmentPage(pPage);
      assert( data[hdr+5]==0 );
      ptr = pPage->hdrOffset+1;
      pc = get2byte(&data[ptr]);
    }
  }
  assert( pc>0 && size>=nByte );
  assert( pc+size<=pPage->pageSize );
  if( size>nByte+4 ){
    put2byte(&data[ptr], pc+nByte);
    put2byte(&data[pc+size], get2byte(&data[pc]));
    put2byte(&data[pc+size+2], size-nByte);
  }else{
    put2byte(&data[ptr], get2byte(&data[pc]));
    data[hdr+5] += size-nByte;
  }
  pPage->nFree -= nByte;
  assert( pPage->nFree>=0 );
  return pc;
}

................................................................................
** 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 void freeSpace(MemPage *pPage, int start, int size){
  int end = start + size;  /* End of the segment being freed */
  int ptr, pbegin, pend;
#ifndef NDEBUG
  int tsize = 0;          /* Total size of all freeblocks */
#endif
  unsigned char *data = pPage->aData;

  assert( pPage->pBt!=0 );
  assert( sqlitepager_iswriteable(data) );
  assert( start>=pPage->hdrOffset+6+(pPage->leaf?0:4) );
  assert( end<=pPage->pBt->pageSize );
  if( size<4 ) size = 4;

  /* Add the space back into the linked list of freeblocks */
  ptr = pPage->hdrOffset + 1;
  while( (pbegin = get2byte(&data[ptr]))<start && pbegin>0 ){
    assert( pbegin<=pPage->pBt->pageSize-4 );
    assert( pbegin>ptr );
    ptr = pbegin;
  }
  assert( pbegin<=pPage->pBt->pageSize-4 );
  assert( pbegin>ptr || pbegin==0 );
  put2bytes(&data[ptr], start);
  put2bytes(&data[start], pbegin);
  put2bytes(&data[start+2], size);
  pPage->nFree += size;

  /* Coalesce adjacent free blocks */
  ptr = pPage->hdrOffset + 1;
  while( (pbegin = get2byte(&data[ptr]))>0 ){
    int pnext, psize;
    assert( pbegin>ptr );
    assert( pbegin<pPage->pBt->pageSize-4 );
    pnext = get2byte(&data[pbegin]);
    psize = get2byte(&data[pbegin+2]);
    if( pbegin + psize + 3 >= pnext && pnext>0 ){
      int frag = pnext - (pbegin+psize);
      assert( frag<=data[pPage->hdrOffset+5] );
      data[pPage->hdrOffset+5] -= frag;
      put2byte(&data[pbegin], get2byte(&data[pnext]));
      put2byte(&data[pbegin+2], pnext+get2byte(&data[pnext+2])-pbegin);
    }else{
      assert( (tsize += psize)>0 );
      ptr = pbegin;
    }
  }
  assert( tsize+data[pPage->hdrOffset+5]==pPage->nFree );
}


/*
** The following is the default comparison function for (non-integer)
** keys in the btrees.  This function returns negative, zero, or
** positive if the first key is less than, equal to, or greater than
** the second.
**
*/
................................................................................
    } 
  }
  return 0;

bad_key:
  return 1;
}
  

/*
** Initialize the auxiliary information for a disk block.
**
** The pParent parameter must be a pointer to the MemPage which
** is the parent of the page being initialized.  The root of a
** BTree has no parent and so for that page, pParent==NULL.
................................................................................
** 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 initPage(
  Bt *pBt,               /* The Btree */
  unsigned char *data,   /* Start of the data for the page */
  Pgno pgnoThis,         /* The page number */
  MemPage *pParent       /* The parent.  Might be NULL */
){
  MemPage *pPage;
  int c, pc, i;
  int sumCell = 0;       /* Total size of all cells */
  unsigned char *data;

  pPage = (MemPage*)&aData[pBt->pageSize];


  if( pPage->pParent ){
    assert( pPage->pParent==pParent );
    return SQLITE_OK;
  }
  if( pParent ){
    pPage->pParent = pParent;
    sqlitepager_ref(pParent->aData);
  }
  if( pPage->pBt!=0 ) return SQLITE_OK;
  pPage->pBt = pBt;
  pPage->nCell = 0;
  pPage->pgno = pgnoThis;

  pPage->hdrOffset = hdr = pgnoThis==1 ? 100 : 0;
  c = data[pPage->hdrOffset];
  pPage->intKey = (c & PTF_INTKEY)!=0;
  pPage->zeroData = (c & PTF_ZERODATA)!=0;
  pPage->leaf = (c & PTF_INTKEY)!=0;

  /* Initialize the cell count and cell pointers */
  pc = get2byte(&data[hdr+3]);
  while( pc>0 ){
................................................................................
  pPage->nFree = data[hdr+5];
  pc = get2byte(&data[hdr+1]);
  while( pc>0 ){
    int next, size;
    if( pc>=pBt->pageSize ) return SQLITE_CORRUPT;
    next = get2byte(&data[pc]);
    size = get2byte(&data[pc+2]);
    if( next>0 && next<=pc+size+3 ) return SQLITE_CURRUPT;
    pPage->nFree += size;
    pc = next;
  }
  if( pPage->nFree>=pBt->pageSize ) return SQLITE_CORRUPT;

  /* Sanity check:  Cells and freespace and header must sum to the size
  ** a page. */
................................................................................
/*
** 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;
  Btree *pBt = pPage->pBt;
  int hdr = pPage->pgno==1 ? 100 : 0;
  int first;

  assert( sqlitepager_iswriteable(data) );
  memset(&data[hdr], 0, pBt->pageSize - hdr);
  data[hdr] = flags;
  first = hdr + 6 + 4*((flags&0x01)!=0);
  put2byte(&data[hdr+1], first);
................................................................................
  pPage->nCell = 0;
  pPage->nFree = pBt->pageSize - first;
  pPage->intKey = (flags & PTF_INTKEY)!=0;
  pPage->leaf = (flags & PTF_LEAF)!=0;
  pPage->zeroData = (flags & PTF_ZERODATA)!=0;
  pPage->hdrOffset = hdr;
}
































/*
** This routine is called when the reference count for a page
** reaches zero.  We need to unref the pParent pointer when that
** happens.
*/
static void pageDestructor(void *pData){
  MemPage *pPage = (MemPage*)&((char*)pData)[SQLITE_PAGE_SIZE];
  if( pPage->pParent ){
    MemPage *pParent = pPage->pParent;
    pPage->pParent = 0;
    sqlitepager_unref(pParent->aData);
  }
  sqliteFree(pPage->aCell);
  pPage->aCell = 0;

}

/*
** Open a new database.
**
** Actually, this routine just sets up the internal data structures
** for accessing the database.  We do not open the database file 
................................................................................
** until the first page is loaded.
**
** zFilename is the name of the database file.  If zFilename is NULL
** a new database with a random name is created.  This randomly named
** database file will be deleted when sqliteBtreeClose() is called.
*/
int sqliteBtreeOpen(
  const char *zFilename,    /* Name of the file containing the BTree database */
  int omitJournal,          /* if TRUE then do not journal this file */
  int nCache,               /* How many pages in the page cache */
  Btree **ppBtree           /* Pointer to new Btree object written here */


){
  Btree *pBt;
  int rc;



  /*
  ** 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(u64)==8 );
................................................................................
  pBt = sqliteMalloc( sizeof(*pBt) );
  if( pBt==0 ){
    *ppBtree = 0;
    return SQLITE_NOMEM;
  }
  if( nCache<10 ) nCache = 10;
  rc = sqlitepager_open(&pBt->pPager, zFilename, nCache, EXTRA_SIZE,
                        !omitJournal);
  if( rc!=SQLITE_OK ){
    if( pBt->pPager ) sqlitepager_close(pBt->pPager);
    sqliteFree(pBt);
    *ppBtree = 0;
    return rc;
  }
  sqlitepager_set_destructor(pBt->pPager, pageDestructor);
  pBt->pCursor = 0;
  pBt->page1 = 0;
  pBt->readOnly = sqlitepager_isreadonly(pBt->pPager);
  pBt->pOps = &sqliteBtreeOps;
  pBt->pageSize = SQLITE_PAGE_SIZE;
  pBt->maxLocal = (SQLITE_PAGE_SIZE-10)/4-12;
  *ppBtree = pBt;
  return SQLITE_OK;
}

/*
** Close an open database and invalidate all cursors.
*/
static int fileBtreeClose(Btree *pBt){
  while( pBt->pCursor ){
    fileBtreeCloseCursor(pBt->pCursor);
  }
  sqlitepager_close(pBt->pPager);
  sqliteFree(pBt);
  return SQLITE_OK;
}

/*
................................................................................
** 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.
*/
static int fileBtreeSetCacheSize(Btree *pBt, int mxPage){
  sqlitepager_set_cachesize(pBt->pPager, mxPage);
  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.
*/
static int fileBtreeSetSafetyLevel(Btree *pBt, int level){
  sqlitepager_set_safety_level(pBt->pPager, level);
  return SQLITE_OK;
}

/*
** Get a reference to page1 of the database file.  This will
** also acquire a readlock on that file.
................................................................................
** 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.  SQLITE_PROTOCOL is returned
** if there is a locking protocol violation.
*/
static int lockBtree(Btree *pBt){
  int rc;
  unsigned char *data;
  if( pBt->page1 ) return SQLITE_OK;
  rc = sqlitepager_get(pBt->pPager, 1, (void**)&data);
  if( rc!=SQLITE_OK ) return rc;


  /* Do some checking to help insure the file we opened really is
  ** a valid database file. 
  */
  if( sqlitepager_pagecount(pBt->pPager)>0 ){
    if( memcmp(data, zMagicHeader, 16)!=0 ){
      rc = SQLITE_NOTADB;
      goto page1_init_failed;
    }
    /*** TBD:  Other header checks such as page size ****/
  }
  pBt->page1 = (MemPage*)&data[SQLITE_PAGE_SIZE];
  return rc;

page1_init_failed:
  sqlitepager_unref(pBt->data);
  pBt->page1 = 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 are any outstanding cursors, this routine is a no-op.
**
** If there is a transaction in progress, this routine is a no-op.
*/
static void unlockBtreeIfUnused(Btree *pBt){
  if( pBt->inTrans==0 && pBt->pCursor==0 && pBt->page1!=0 ){
    sqlitepager_unref(pBt->page1->aData);
    pBt->page1 = 0;
    pBt->inTrans = 0;
    pBt->inCkpt = 0;
  }
}

/*
** Create a new database by initializing the first page of the
** file.
*/
static int newDatabase(Btree *pBt){
  MemPage *pP1;
  unsigned char *data;
  int rc;
  if( sqlitepager_pagecount(pBt->pPager)>1 ) return SQLITE_OK;
  pP1 = pBt->page1;
  assert( pP1!=0 );
  data = pP1->aData;
  rc = sqlitepager_write(data);
  if( rc ) return rc;
  memcpy(data, zMagicHeader, sizeof(zMagicHeader));
  assert( sizeof(zMagicHeader)==16 );
  put2byte(&data[16], SQLITE_PAGE_SIZE);
................................................................................
**      sqliteBtreeCreateIndex()
**      sqliteBtreeClearTable()
**      sqliteBtreeDropTable()
**      sqliteBtreeInsert()
**      sqliteBtreeDelete()
**      sqliteBtreeUpdateMeta()
*/
static int fileBtreeBeginTrans(Btree *pBt){
  int rc;
  if( pBt->inTrans ) return SQLITE_ERROR;
  if( pBt->readOnly ) return SQLITE_READONLY;
  if( pBt->page1==0 ){
    rc = lockBtree(pBt);
    if( rc!=SQLITE_OK ){
      return rc;
    }
  }
  rc = sqlitepager_begin(pBt->page1);
  if( rc==SQLITE_OK ){
    rc = newDatabase(pBt);
  }
  if( rc==SQLITE_OK ){
    pBt->inTrans = 1;
    pBt->inCkpt = 0;
  }else{
    unlockBtreeIfUnused(pBt);
  }
  return rc;
}

/*
** Commit the transaction currently in progress.
**
** This will release the write lock on the database file.  If there
** are no active cursors, it also releases the read lock.
*/
static int fileBtreeCommit(Btree *pBt){
  int rc;
  rc = pBt->readOnly ? SQLITE_OK : sqlitepager_commit(pBt->pPager);
  pBt->inTrans = 0;
  pBt->inCkpt = 0;
  unlockBtreeIfUnused(pBt);
  return rc;
}

/*
** 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.
*/
static int fileBtreeRollback(Btree *pBt){
  int rc;
  BtCursor *pCur;
  if( pBt->inTrans==0 ) return SQLITE_OK;
  pBt->inTrans = 0;
  pBt->inCkpt = 0;
  rc = pBt->readOnly ? SQLITE_OK : sqlitepager_rollback(pBt->pPager);
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    if( pCur->pPage && pCur->pPage->pBt==0 ){
      sqlitepager_unref(pCur->pPage);

      pCur->pPage = 0;
    }
  }
  unlockBtreeIfUnused(pBt);
  return rc;
}

................................................................................
** main transaction.  You must start a transaction before starting a
** checkpoint.  The checkpoint is ended automatically if the transaction
** commits or rolls back.
**
** Only one checkpoint may be active at a time.  It is an error to try
** to start a new checkpoint if another checkpoint is already active.
*/
static int fileBtreeBeginCkpt(Btree *pBt){
  int rc;
  if( !pBt->inTrans || pBt->inCkpt ){
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  rc = pBt->readOnly ? SQLITE_OK : sqlitepager_ckpt_begin(pBt->pPager);
  pBt->inCkpt = 1;
  return rc;
}


/*
** Commit a checkpoint to transaction currently in progress.  If no
** checkpoint is active, this is a no-op.
*/
static int fileBtreeCommitCkpt(Btree *pBt){
  int rc;
  if( pBt->inCkpt && !pBt->readOnly ){
    rc = sqlitepager_ckpt_commit(pBt->pPager);
  }else{
    rc = SQLITE_OK;
  }
  pBt->inCkpt = 0;
  return rc;
}

/*
** Rollback the checkpoint to the current transaction.  If there
** is no active checkpoint or transaction, this routine is a no-op.
**
** 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.
*/
static int fileBtreeRollbackCkpt(Btree *pBt){
  int rc;
  BtCursor *pCur;
  if( pBt->inCkpt==0 || pBt->readOnly ) return SQLITE_OK;
  rc = sqlitepager_ckpt_rollback(pBt->pPager);
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    if( pCur->pPage && pCur->pPage->isInit==0 ){
      sqlitepager_unref(pCur->pPage);

      pCur->pPage = 0;
    }
  }
  pBt->inCkpt = 0;
  return rc;
}


















/*
** Create a new cursor for the BTree whose root is on the page
** iTable.  The act of acquiring a cursor gets a read lock on 
** the database file.
**
** If wrFlag==0, then the cursor can only be used for reading.
................................................................................
** intend to use the sqliteBtreeNext() system call.  All other cursors
** should be opened with wrFlag==1 even if they never really intend
** to write.
** 
** 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.






*/
static 
int fileBtreeCursor(Btree *pBt, int iTable, int wrFlag, BtCursor **ppCur){








  int rc;
  BtCursor *pCur, *pRing;

  if( pBt->readOnly && wrFlag ){
    *ppCur = 0;
    return SQLITE_READONLY;
  }
................................................................................
  }
  pCur = sqliteMalloc( sizeof(*pCur) );
  if( pCur==0 ){
    rc = SQLITE_NOMEM;
    goto create_cursor_exception;
  }
  pCur->pgnoRoot = (Pgno)iTable;
  rc = sqlitepager_get(pBt->pPager, pCur->pgnoRoot, (void**)&pCur->pPage);
  if( rc!=SQLITE_OK ){
    goto create_cursor_exception;
  }
  rc = initPage(pBt, pCur->pPage, pCur->pgnoRoot, 0);
  if( rc!=SQLITE_OK ){
    goto create_cursor_exception;
  }
  pCur->pOps = &sqliteBtreeCursorOps;

  pCur->pBt = pBt;
  pCur->wrFlag = wrFlag;
  pCur->idx = 0;
  pCur->eSkip = SKIP_INVALID;
  pCur->pNext = pBt->pCursor;
  if( pCur->pNext ){
    pCur->pNext->pPrev = pCur;
................................................................................
  pBt->pCursor = pCur;
  *ppCur = pCur;
  return SQLITE_OK;

create_cursor_exception:
  *ppCur = 0;
  if( pCur ){
    if( pCur->pPage ) sqlitepager_unref(pCur->pPage);
    sqliteFree(pCur);
  }
  unlockBtreeIfUnused(pBt);
  return rc;
}

/*
** Close a cursor.  The read lock on the database file is released
** when the last cursor is closed.
*/
static int fileBtreeCloseCursor(BtCursor *pCur){
  Btree *pBt = pCur->pBt;
  if( pCur->pPrev ){
    pCur->pPrev->pNext = pCur->pNext;
  }else{
    pBt->pCursor = pCur->pNext;
  }
  if( pCur->pNext ){
    pCur->pNext->pPrev = pCur->pPrev;
  }
  if( pCur->pPage ){
    sqlitepager_unref(pCur->pPage);
  }
  if( pCur->pShared!=pCur ){
    BtCursor *pRing = pCur->pShared;
    while( pRing->pShared!=pCur ){ pRing = pRing->pShared; }
    pRing->pShared = pCur->pShared;
  }
  unlockBtreeIfUnused(pBt);
  sqliteFree(pCur);
................................................................................
** The temporary cursor is not on the cursor list for the Btree.
*/
static void getTempCursor(BtCursor *pCur, BtCursor *pTempCur){
  memcpy(pTempCur, pCur, sizeof(*pCur));
  pTempCur->pNext = 0;
  pTempCur->pPrev = 0;
  if( pTempCur->pPage ){
    sqlitepager_ref(pTempCur->pPage);
  }
}

/*
** Delete a temporary cursor such as was made by the CreateTemporaryCursor()
** function above.
*/
static void releaseTempCursor(BtCursor *pCur){
  if( pCur->pPage ){
    sqlitepager_unref(pCur->pPage);
  }
}

/*
** Set *pSize to the number of bytes of key in the entry the
** cursor currently points to.  Always return SQLITE_OK.
** Failure is not possible.  If the cursor is not currently
** pointing to an entry (which can happen, for example, if
** the database is empty) then *pSize is set to 0.
*/
static int fileBtreeKeySize(BtCursor *pCur, int *pSize){
  Cell *pCell;
  MemPage *pPage;

  pPage = pCur->pPage;
  assert( pPage!=0 );
  if( pCur->idx >= pPage->nCell ){
    *pSize = 0;
  }else{
    pCell = pPage->apCell[pCur->idx];
    *pSize = NKEY(pCur->pBt, pCell->h);







  }
  return SQLITE_OK;
}

/*
** Read payload information from the entry that the pCur cursor is
** pointing to.  Begin reading the payload at "offset" and read
** a total of "amt" bytes.  Put the result in zBuf.
**
** This routine does not make a distinction between key and data.
** It just reads bytes from the payload area.
*/
static int getPayload(BtCursor *pCur, int offset, int amt, char *zBuf){






  char *aPayload;
  Pgno nextPage;
  int rc;

  Btree *pBt = pCur->pBt;



  assert( pCur!=0 && pCur->pPage!=0 );


  assert( pCur->idx>=0 && pCur->idx<pCur->pPage->nCell );
  aPayload = pCur->pPage->apCell[pCur->idx]->aPayload;






















  if( offset<MX_LOCAL_PAYLOAD ){
    int a = amt;
    if( a+offset>MX_LOCAL_PAYLOAD ){
      a = MX_LOCAL_PAYLOAD - offset;

    }
    memcpy(zBuf, &aPayload[offset], a);
    if( a==amt ){
      return SQLITE_OK;
    }
    offset = 0;
    zBuf += a;
    amt -= a;
  }else{
    offset -= MX_LOCAL_PAYLOAD;
  }
  if( amt>0 ){
    nextPage = SWAB32(pBt, pCur->pPage->apCell[pCur->idx]->ovfl);
  }

  while( amt>0 && nextPage ){
    OverflowPage *pOvfl;
    rc = sqlitepager_get(pBt->pPager, nextPage, (void**)&pOvfl);
    if( rc!=0 ){
      return rc;
    }
    nextPage = SWAB32(pBt, pOvfl->iNext);
    if( offset<OVERFLOW_SIZE ){
      int a = amt;
      if( a + offset > OVERFLOW_SIZE ){
        a = OVERFLOW_SIZE - offset;
      }
      memcpy(zBuf, &pOvfl->aPayload[offset], a);
      offset = 0;
      amt -= a;
      zBuf += a;
    }else{
      offset -= OVERFLOW_SIZE;
    }
    sqlitepager_unref(pOvfl);
  }
  if( amt>0 ){
    return SQLITE_CORRUPT;
  }
  return SQLITE_OK;
}

/*
** Read part of the key associated with cursor pCur.  A maximum
** of "amt" bytes will be transfered into zBuf[].  The transfer
** begins at "offset".  The number of bytes actually read is
** returned. 
**

** Change:  It used to be that the amount returned will be smaller
** than the amount requested if there are not enough bytes in the key
** to satisfy the request.  But now, it must be the case that there
** is enough data available to satisfy the request.  If not, an exception
** is raised.  The change was made in an effort to boost performance
** by eliminating unneeded tests.
*/
static int fileBtreeKey(BtCursor *pCur, int offset, int amt, char *zBuf){
  MemPage *pPage;

  assert( amt>=0 );
  assert( offset>=0 );
  assert( pCur->pPage!=0 );
  pPage = pCur->pPage;
  if( pCur->idx >= pPage->nCell ){

    return 0;
  }
  assert( amt+offset <= NKEY(pCur->pBt, pPage->apCell[pCur->idx]->h) );
  getPayload(pCur, offset, amt, zBuf);



































  return amt;
}




/*
** Set *pSize to the number of bytes of data in the entry the
** cursor currently points to.  Always return SQLITE_OK.
** Failure is not possible.  If the cursor is not currently
** pointing to an entry (which can happen, for example, if
** the database is empty) then *pSize is set to 0.
*/
static int fileBtreeDataSize(BtCursor *pCur, int *pSize){
  Cell *pCell;
  MemPage *pPage;

  pPage = pCur->pPage;
  assert( pPage!=0 );
  if( pCur->idx >= pPage->nCell ){
    *pSize = 0;
  }else{


    pCell = pPage->apCell[pCur->idx];
    *pSize = NDATA(pCur->pBt, pCell->h);







  }
  return SQLITE_OK;
}

/*
** Read part of the data associated with cursor pCur.  A maximum
** of "amt" bytes will be transfered into zBuf[].  The transfer
** begins at "offset".  The number of bytes actually read is
** returned.  The amount returned will be smaller than the
** amount requested if there are not enough bytes in the data
** to satisfy the request.

*/
static int fileBtreeData(BtCursor *pCur, int offset, int amt, char *zBuf){
  Cell *pCell;
  MemPage *pPage;

  assert( amt>=0 );
  assert( offset>=0 );
  assert( pCur->pPage!=0 );
  pPage = pCur->pPage;
  if( pCur->idx >= pPage->nCell ){
    return 0;
  }
  pCell = pPage->apCell[pCur->idx];
  assert( amt+offset <= NDATA(pCur->pBt, pCell->h) );
  getPayload(pCur, offset + NKEY(pCur->pBt, pCell->h), amt, zBuf);
  return amt;
}

/*
** Compare an external key against the key on the entry that pCur points to.
**
** The external key is pKey and is nKey bytes long.  The last nIgnore bytes
** of the key associated with pCur are ignored, as if they do not exist.
** (The normal case is for nIgnore to be zero in which case the entire
** internal key is used in the comparison.)
**
** The comparison result is written to *pRes as follows:
**
**    *pRes<0    This means pCur<pKey
**
**    *pRes==0   This means pCur==pKey for all nKey bytes
**
**    *pRes>0    This means pCur>pKey
**
** When one key is an exact prefix of the other, the shorter key is
** considered less than the longer one.  In order to be equal the
** keys must be exactly the same length. (The length of the pCur key
** is the actual key length minus nIgnore bytes.)
*/
static int fileBtreeKeyCompare(
  BtCursor *pCur,       /* Pointer to entry to compare against */
  const void *pKey,     /* Key to compare against entry that pCur points to */
  int nKey,             /* Number of bytes in pKey */
  int nIgnore,          /* Ignore this many bytes at the end of pCur */
  int *pResult          /* Write the result here */
){
  Pgno nextPage;
  int n, c, rc, nLocal;
  Cell *pCell;
  Btree *pBt = pCur->pBt;
  const char *zKey  = (const char*)pKey;

  assert( pCur->pPage );
  assert( pCur->idx>=0 && pCur->idx<pCur->pPage->nCell );
  pCell = pCur->pPage->apCell[pCur->idx];
  nLocal = NKEY(pBt, pCell->h) - nIgnore;
  if( nLocal<0 ) nLocal = 0;
  n = nKey<nLocal ? nKey : nLocal;
  if( n>MX_LOCAL_PAYLOAD ){
    n = MX_LOCAL_PAYLOAD;
  }
  c = memcmp(pCell->aPayload, zKey, n);
  if( c!=0 ){
    *pResult = c;
    return SQLITE_OK;
  }
  zKey += n;
  nKey -= n;
  nLocal -= n;
  nextPage = SWAB32(pBt, pCell->ovfl);
  while( nKey>0 && nLocal>0 ){
    OverflowPage *pOvfl;
    if( nextPage==0 ){
      return SQLITE_CORRUPT;
    }
    rc = sqlitepager_get(pBt->pPager, nextPage, (void**)&pOvfl);
    if( rc ){
      return rc;
    }
    nextPage = SWAB32(pBt, pOvfl->iNext);
    n = nKey<nLocal ? nKey : nLocal;
    if( n>OVERFLOW_SIZE ){
      n = OVERFLOW_SIZE;
    }
    c = memcmp(pOvfl->aPayload, zKey, n);
    sqlitepager_unref(pOvfl);
    if( c!=0 ){
      *pResult = c;
      return SQLITE_OK;
    }
    nKey -= n;
    nLocal -= n;
    zKey += n;
  }
  if( c==0 ){
    c = nLocal - nKey;
  }
  *pResult = c;
  return SQLITE_OK;
}

/*
** Move the cursor down to a new child page.  The newPgno argument is the
** page number of the child page in the byte order of the disk image.
*/
static int moveToChild(BtCursor *pCur, int newPgno){
  int rc;
  MemPage *pNewPage;


  Btree *pBt = pCur->pBt;

  newPgno = SWAB32(pBt, newPgno);
  rc = sqlitepager_get(pBt->pPager, newPgno, (void**)&pNewPage);
  if( rc ) return rc;
  rc = initPage(pBt, pNewPage, newPgno, pCur->pPage);

  if( rc ) return rc;
  assert( pCur->idx>=pCur->pPage->nCell
          || pCur->pPage->apCell[pCur->idx]->h.leftChild==SWAB32(pBt,newPgno) );
  assert( pCur->idx<pCur->pPage->nCell
          || pCur->pPage->u.hdr.rightChild==SWAB32(pBt,newPgno) );
  pNewPage->idxParent = pCur->idx;

  pCur->pPage->idxShift = 0;
  sqlitepager_unref(pCur->pPage);

  pCur->pPage = pNewPage;
  pCur->idx = 0;
  if( pNewPage->nCell<1 ){
    return SQLITE_CORRUPT;
  }
  return SQLITE_OK;
}
................................................................................
** the largest cell index.
*/
static void moveToParent(BtCursor *pCur){
  Pgno oldPgno;
  MemPage *pParent;
  MemPage *pPage;
  int idxParent;

  pPage = pCur->pPage;
  assert( pPage!=0 );
  pParent = pPage->pParent;
  assert( pParent!=0 );
  idxParent = pPage->idxParent;
  sqlitepager_ref(pParent);

  sqlitepager_unref(pPage);
  pCur->pPage = pParent;
  assert( pParent->idxShift==0 );
  if( pParent->idxShift==0 ){
    pCur->idx = idxParent;
#ifndef NDEBUG  
    /* Verify that pCur->idx is the correct index to point back to the child
    ** page we just came from 
    */
    oldPgno = SWAB32(pCur->pBt, sqlitepager_pagenumber(pPage));
    if( pCur->idx<pParent->nCell ){
      assert( pParent->apCell[idxParent]->h.leftChild==oldPgno );

    }else{
      assert( pParent->u.hdr.rightChild==oldPgno );

    }
#endif
  }else{
    /* The MemPage.idxShift flag indicates that cell indices might have 
    ** changed since idxParent was set and hence idxParent might be out
    ** of date.  So recompute the parent cell index by scanning all cells
    ** and locating the one that points to the child we just came from.
    */
    int i;
    pCur->idx = pParent->nCell;
    oldPgno = SWAB32(pCur->pBt, sqlitepager_pagenumber(pPage));
    for(i=0; i<pParent->nCell; i++){
      if( pParent->apCell[i]->h.leftChild==oldPgno ){

        pCur->idx = i;
        break;
      }
    }
  }
}

/*
** Move the cursor to the root page
*/
static int moveToRoot(BtCursor *pCur){
  MemPage *pNew;
  int rc;
  Btree *pBt = pCur->pBt;

  rc = sqlitepager_get(pBt->pPager, pCur->pgnoRoot, (void**)&pNew);
  if( rc ) return rc;
  rc = initPage(pBt, pNew, pCur->pgnoRoot, 0);
  if( rc ) return rc;
  sqlitepager_unref(pCur->pPage);
  pCur->pPage = pNew;
  pCur->idx = 0;
  return SQLITE_OK;
}

/*
** Move the cursor down to the left-most leaf entry beneath the
** entry to which it is currently pointing.
*/
static int moveToLeftmost(BtCursor *pCur){
  Pgno pgno;
  int rc;


  while( (pgno = pCur->pPage->apCell[pCur->idx]->h.leftChild)!=0 ){



    rc = moveToChild(pCur, pgno);
    if( rc ) return rc;
  }
  return SQLITE_OK;
}

/*
................................................................................
** between moveToLeftmost() and moveToRightmost().  moveToLeftmost()
** finds the left-most entry beneath the *entry* whereas moveToRightmost()
** finds the right-most entry beneath the *page*.
*/
static int moveToRightmost(BtCursor *pCur){
  Pgno pgno;
  int rc;


  while( (pgno = pCur->pPage->u.hdr.rightChild)!=0 ){


    pCur->idx = pCur->pPage->nCell;
    rc = moveToChild(pCur, pgno);
    if( rc ) return rc;
  }
  pCur->idx = pCur->pPage->nCell - 1;
  return SQLITE_OK;
}

/* 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.
*/
static int fileBtreeFirst(BtCursor *pCur, int *pRes){
  int rc;
  if( pCur->pPage==0 ) return SQLITE_ABORT;
  rc = moveToRoot(pCur);
  if( rc ) return rc;
  if( pCur->pPage->nCell==0 ){
    *pRes = 1;
    return SQLITE_OK;
................................................................................
  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.
*/
static int fileBtreeLast(BtCursor *pCur, int *pRes){
  int rc;
  if( pCur->pPage==0 ) return SQLITE_ABORT;
  rc = moveToRoot(pCur);
  if( rc ) return rc;
  assert( pCur->pPage->isInit );
  if( pCur->pPage->nCell==0 ){
    *pRes = 1;
................................................................................
  }
  *pRes = 0;
  rc = moveToRightmost(pCur);
  pCur->eSkip = SKIP_NONE;
  return rc;
}

/* Move the cursor so that it points to an entry near pKey.
** Return a success code.





**
** 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.
**
** The result of comparing the key with the entry to which the
................................................................................
**
**     *pRes==0     The cursor is left pointing at an entry that
**                  exactly matches pKey.
**
**     *pRes>0      The cursor is left pointing at an entry that
**                  is larger than pKey.
*/
static
int fileBtreeMoveto(BtCursor *pCur, const void *pKey, int nKey, int *pRes){
  int rc;
  if( pCur->pPage==0 ) return SQLITE_ABORT;
  pCur->eSkip = SKIP_NONE;
  rc = moveToRoot(pCur);
  if( rc ) return rc;
  for(;;){
    int lwr, upr;
    Pgno chldPg;
    MemPage *pPage = pCur->pPage;
    int c = -1;  /* pRes return if table is empty must be -1 */
    lwr = 0;
    upr = pPage->nCell-1;
    while( lwr<=upr ){


      pCur->idx = (lwr+upr)/2;
      rc = fileBtreeKeyCompare(pCur, pKey, nKey, 0, &c);

















      if( rc ) return rc;

      if( c==0 ){
        pCur->iMatch = c;
        if( pRes ) *pRes = 0;
        return SQLITE_OK;
      }
      if( c<0 ){
        lwr = pCur->idx+1;
      }else{
        upr = pCur->idx-1;
      }
    }
    assert( lwr==upr+1 );
    assert( pPage->isInit );


    if( lwr>=pPage->nCell ){
      chldPg = pPage->u.hdr.rightChild;

    }else{
      chldPg = pPage->apCell[lwr]->h.leftChild;

    }
    if( chldPg==0 ){
      pCur->iMatch = c;
      if( pRes ) *pRes = c;
      return SQLITE_OK;
    }
    pCur->idx = lwr;
................................................................................

/*
** 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.
*/
static int fileBtreeNext(BtCursor *pCur, int *pRes){
  int rc;
  MemPage *pPage = pCur->pPage;
  assert( pRes!=0 );
  if( pPage==0 ){
    *pRes = 1;
    return SQLITE_ABORT;
  }
................................................................................
    pCur->eSkip = SKIP_NONE;
    *pRes = 0;
    return SQLITE_OK;
  }
  pCur->eSkip = SKIP_NONE;
  pCur->idx++;
  if( pCur->idx>=pPage->nCell ){
    if( pPage->u.hdr.rightChild ){
      rc = moveToChild(pCur, pPage->u.hdr.rightChild);
      if( rc ) return rc;
      rc = moveToLeftmost(pCur);
      *pRes = 0;
      return rc;
    }
    do{
      if( pPage->pParent==0 ){
................................................................................
      moveToParent(pCur);
      pPage = pCur->pPage;
    }while( pCur->idx>=pPage->nCell );
    *pRes = 0;
    return SQLITE_OK;
  }
  *pRes = 0;
  if( pPage->u.hdr.rightChild==0 ){
    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.
*/
static int fileBtreePrevious(BtCursor *pCur, int *pRes){
  int rc;
  Pgno pgno;
  MemPage *pPage;
  pPage = pCur->pPage;
  if( pPage==0 ){
    *pRes = 1;
    return SQLITE_ABORT;
................................................................................
  if( pCur->eSkip==SKIP_PREV ){
    pCur->eSkip = SKIP_NONE;
    *pRes = 0;
    return SQLITE_OK;
  }
  pCur->eSkip = SKIP_NONE;
  assert( pCur->idx>=0 );
  if( (pgno = pPage->apCell[pCur->idx]->h.leftChild)!=0 ){

    rc = moveToChild(pCur, pgno);
    if( rc ) return rc;
    rc = moveToRightmost(pCur);
  }else{
    while( pCur->idx==0 ){
      if( pPage->pParent==0 ){
        if( pRes ) *pRes = 1;
................................................................................
**
** 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.
*/
static int allocatePage(Btree *pBt, MemPage **ppPage, Pgno *pPgno, Pgno nearby){

  PageOne *pPage1 = pBt->page1;

  int rc;
  if( pPage1->freeList ){
    OverflowPage *pOvfl;
    FreelistInfo *pInfo;







    rc = sqlitepager_write(pPage1);
    if( rc ) return rc;
    SWAB_ADD(pBt, pPage1->nFree, -1);
    rc = sqlitepager_get(pBt->pPager, SWAB32(pBt, pPage1->freeList),
                        (void**)&pOvfl);


    if( rc ) return rc;
    rc = sqlitepager_write(pOvfl);
    if( rc ){
      sqlitepager_unref(pOvfl);

      return rc;
    }
    pInfo = (FreelistInfo*)pOvfl->aPayload;

    if( pInfo->nFree==0 ){
      *pPgno = SWAB32(pBt, pPage1->freeList);
      pPage1->freeList = pOvfl->iNext;




      *ppPage = (MemPage*)pOvfl;
    }else{

      int closest, n;
      n = SWAB32(pBt, pInfo->nFree);

      if( n>1 && nearby>0 ){
        int i, dist;
        closest = 0;
        dist = SWAB32(pBt, pInfo->aFree[0]) - nearby;

        if( dist<0 ) dist = -dist;
        for(i=1; i<n; i++){
          int d2 = SWAB32(pBt, pInfo->aFree[i]) - nearby;

          if( d2<0 ) d2 = -d2;
          if( d2<dist ) closest = i;
        }
      }else{
        closest = 0;
      }
      SWAB_ADD(pBt, pInfo->nFree, -1);
      *pPgno = SWAB32(pBt, pInfo->aFree[closest]);
      pInfo->aFree[closest] = pInfo->aFree[n-1];
      rc = sqlitepager_get(pBt->pPager, *pPgno, (void**)ppPage);
      sqlitepager_unref(pOvfl);
      if( rc==SQLITE_OK ){
        sqlitepager_dont_rollback(*ppPage);
        rc = sqlitepager_write(*ppPage);
      }
    }
  }else{
    *pPgno = sqlitepager_pagecount(pBt->pPager) + 1;
    rc = sqlitepager_get(pBt->pPager, *pPgno, (void**)ppPage);
    if( rc ) return rc;
    rc = sqlitepager_write(*ppPage);
  }
  return rc;
}

/*
** Add a page of the database file to the freelist.  Either pgno or
** pPage but not both may be 0. 
**
** sqlitepager_unref() is NOT called for pPage.
*/
static int freePage(Btree *pBt, void *pPage, Pgno pgno){
  PageOne *pPage1 = pBt->page1;
  OverflowPage *pOvfl = (OverflowPage*)pPage;
  int rc;
  int needUnref = 0;
  MemPage *pMemPage;

  if( pgno==0 ){
    assert( pOvfl!=0 );
    pgno = sqlitepager_pagenumber(pOvfl);
  }
  assert( pgno>2 );
  assert( sqlitepager_pagenumber(pOvfl)==pgno );
  pMemPage = (MemPage*)pPage;
  pMemPage->isInit = 0;
  if( pMemPage->pParent ){
    sqlitepager_unref(pMemPage->pParent);
    pMemPage->pParent = 0;
  }
  rc = sqlitepager_write(pPage1);
  if( rc ){
    return rc;
  }
  SWAB_ADD(pBt, pPage1->nFree, 1);
  if( pPage1->nFree!=0 && pPage1->freeList!=0 ){
    OverflowPage *pFreeIdx;
    rc = sqlitepager_get(pBt->pPager, SWAB32(pBt, pPage1->freeList),
                        (void**)&pFreeIdx);
    if( rc==SQLITE_OK ){
      FreelistInfo *pInfo = (FreelistInfo*)pFreeIdx->aPayload;
      int n = SWAB32(pBt, pInfo->nFree);
      if( n<(sizeof(pInfo->aFree)/sizeof(pInfo->aFree[0])) ){
        rc = sqlitepager_write(pFreeIdx);
        if( rc==SQLITE_OK ){
          pInfo->aFree[n] = SWAB32(pBt, pgno);
          SWAB_ADD(pBt, pInfo->nFree, 1);
          sqlitepager_unref(pFreeIdx);
          sqlitepager_dont_write(pBt->pPager, pgno);
          return rc;
        }
      }
      sqlitepager_unref(pFreeIdx);
    }
  }
  if( pOvfl==0 ){
    assert( pgno>0 );
    rc = sqlitepager_get(pBt->pPager, pgno, (void**)&pOvfl);
    if( rc ) return rc;
    needUnref = 1;
  }
  rc = sqlitepager_write(pOvfl);
  if( rc ){
    if( needUnref ) sqlitepager_unref(pOvfl);
    return rc;
  }
  pOvfl->iNext = pPage1->freeList;
  pPage1->freeList = SWAB32(pBt, pgno);
  memset(pOvfl->aPayload, 0, OVERFLOW_SIZE);
  if( needUnref ) rc = sqlitepager_unref(pOvfl);
  return rc;
}

/*
** Erase all the data out of a cell.  This involves returning overflow
** pages back the freelist.
*/
static int clearCell(Btree *pBt, Cell *pCell){
  Pager *pPager = pBt->pPager;
  OverflowPage *pOvfl;
  Pgno ovfl, nextOvfl;
  int rc;

  if( NKEY(pBt, pCell->h) + NDATA(pBt, pCell->h) <= MX_LOCAL_PAYLOAD ){
    return SQLITE_OK;
  }
  ovfl = SWAB32(pBt, pCell->ovfl);
  pCell->ovfl = 0;
  while( ovfl ){
    rc = sqlitepager_get(pPager, ovfl, (void**)&pOvfl);
    if( rc ) return rc;
    nextOvfl = SWAB32(pBt, pOvfl->iNext);
    rc = freePage(pBt, pOvfl, ovfl);
    if( rc ) return rc;
    sqlitepager_unref(pOvfl);
    ovfl = nextOvfl;
  }
  return SQLITE_OK;
}

/*
** Create a new cell from key and data.  Overflow pages are allocated as
** necessary and linked to this cell.  
*/
static int fillInCell(
  Btree *pBt,              /* The whole Btree.  Needed to allocate pages */
  Cell *pCell,             /* Populate this Cell structure */
  const void *pKey, int nKey,    /* The key */
  const void *pData,int nData    /* The data */
){
  OverflowPage *pOvfl, *pPrior;
  Pgno *pNext;
  int spaceLeft;
  int n, rc;
  int nPayload;
  const char *pPayload;
  char *pSpace;
  Pgno nearby = 0;

  pCell->h.leftChild = 0;
  pCell->h.nKey = SWAB16(pBt, nKey & 0xffff);
  pCell->h.nKeyHi = nKey >> 16;
  pCell->h.nData = SWAB16(pBt, nData & 0xffff);
  pCell->h.nDataHi = nData >> 16;
  pCell->h.iNext = 0;

  pNext = &pCell->ovfl;
  pSpace = pCell->aPayload;
  spaceLeft = MX_LOCAL_PAYLOAD;
  pPayload = pKey;
  pKey = 0;
  nPayload = nKey;
  pPrior = 0;
  while( nPayload>0 ){
    if( spaceLeft==0 ){
      rc = allocatePage(pBt, (MemPage**)&pOvfl, pNext, nearby);
      if( rc ){
        *pNext = 0;
      }else{
        nearby = *pNext;
      }
      if( pPrior ) sqlitepager_unref(pPrior);
      if( rc ){
        clearCell(pBt, pCell);
        return rc;
      }
      if( pBt->needSwab ) *pNext = swab32(*pNext);
      pPrior = pOvfl;
      spaceLeft = OVERFLOW_SIZE;
      pSpace = pOvfl->aPayload;
      pNext = &pOvfl->iNext;
















    }
    n = nPayload;
    if( n>spaceLeft ) n = spaceLeft;
    memcpy(pSpace, pPayload, n);

    nPayload -= n;
    if( nPayload==0 && pData ){
      pPayload = pData;


      nPayload = nData;
      pData = 0;
    }else{
      pPayload += n;
    }
    spaceLeft -= n;
    pSpace += n;
  }
  *pNext = 0;
  if( pPrior ){
    sqlitepager_unref(pPrior);
  }
  return SQLITE_OK;
}

/*
** Change the MemPage.pParent pointer on the page whose number is
** given in the second argument so that MemPage.pParent holds the
................................................................................

/*
** 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 database the record should be inserted into.  The cursor
** is left pointing at the new record.
*/
static int fileBtreeInsert(
  BtCursor *pCur,                /* Insert data into the table of this cursor */
  const void *pKey, int nKey,    /* The key of the new record */
  const void *pData, int nData   /* The data of the new record */
){
  Cell newCell;
  int rc;
  int loc;
................................................................................
  assert( !pBt->readOnly );
  if( !pCur->wrFlag ){
    return SQLITE_PERM;   /* Cursor not open for writing */
  }
  if( checkReadLocks(pCur) ){
    return SQLITE_LOCKED; /* The table pCur points to has a read lock */
  }
  rc = fileBtreeMoveto(pCur, pKey, nKey, &loc);
  if( rc ) return rc;
  pPage = pCur->pPage;
  assert( pPage->isInit );
  rc = sqlitepager_write(pPage);
  if( rc ) return rc;
  rc = fillInCell(pBt, &newCell, pKey, nKey, pData, nData);
  if( rc ) return rc;
................................................................................
** sqliteBtreeNext() after a delete and the cursor will be left
** pointing to the first entry after the deleted entry.  Similarly,
** pCur->eSkip is set to SKIP_PREV is the cursor is left pointing to
** the entry prior to the deleted entry so that a subsequent call to
** sqliteBtreePrevious() will always leave the cursor pointing at the
** entry immediately before the one that was deleted.
*/
static int fileBtreeDelete(BtCursor *pCur){
  MemPage *pPage = pCur->pPage;
  Cell *pCell;
  int rc;
  Pgno pgnoChild;
  Btree *pBt = pCur->pBt;

  assert( pPage->isInit );
................................................................................
    ** to be a leaf so we can use it.
    */
    BtCursor leafCur;
    Cell *pNext;
    int szNext;
    int notUsed;
    getTempCursor(pCur, &leafCur);
    rc = fileBtreeNext(&leafCur, &notUsed);
    if( rc!=SQLITE_OK ){
      if( rc!=SQLITE_NOMEM ) rc = SQLITE_CORRUPT;
      return rc;
    }
    rc = sqlitepager_write(leafCur.pPage);
    if( rc ) return rc;
    dropCell(pBt, pPage, pCur->idx, cellSize(pBt, pCell));
................................................................................
**
** In the current implementation, BTree tables and BTree indices are the 
** the same.  In the future, we may change this so that BTree tables
** are restricted to having a 4-byte integer key and arbitrary data and
** BTree indices are restricted to having an arbitrary key and no data.
** But for now, this routine also serves to create indices.
*/
static int fileBtreeCreateTable(Btree *pBt, int *piTable){
  MemPage *pRoot;
  Pgno pgnoRoot;
  int rc;
  if( !pBt->inTrans ){
    /* Must start a transaction first */
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
................................................................................
  sqlitepager_unref(pPage);
  return rc;
}

/*
** Delete all information from a single table in the database.
*/
static int fileBtreeClearTable(Btree *pBt, int iTable){
  int rc;
  BtCursor *pCur;
  if( !pBt->inTrans ){
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    if( pCur->pgnoRoot==(Pgno)iTable ){
      if( pCur->wrFlag==0 ) return SQLITE_LOCKED;
      moveToRoot(pCur);
    }
  }
  rc = clearDatabasePage(pBt, (Pgno)iTable, 0);
  if( rc ){
    fileBtreeRollback(pBt);
  }
  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 2) is never added to the freelist.
*/
static int fileBtreeDropTable(Btree *pBt, int iTable){
  int rc;
  MemPage *pPage;
  BtCursor *pCur;
  if( !pBt->inTrans ){
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    if( pCur->pgnoRoot==(Pgno)iTable ){
      return SQLITE_LOCKED;  /* Cannot drop a table that has a cursor */
    }
  }
  rc = sqlitepager_get(pBt->pPager, (Pgno)iTable, (void**)&pPage);
  if( rc ) return rc;
  rc = fileBtreeClearTable(pBt, iTable);
  if( rc ) return rc;
  if( iTable>2 ){
    rc = freePage(pBt, pPage, iTable);
  }else{
    zeroPage(pBt, pPage);
  }
  sqlitepager_unref(pPage);
................................................................................
  return rc;
}
#endif

/*
** Read the meta-information out of a database file.
*/
static int fileBtreeGetMeta(Btree *pBt, int *aMeta){
  PageOne *pP1;
  int rc;
  int i;

  rc = sqlitepager_get(pBt->pPager, 1, (void**)&pP1);
  if( rc ) return rc;
  aMeta[0] = SWAB32(pBt, pP1->nFree);
  for(i=0; i<sizeof(pP1->aMeta)/sizeof(pP1->aMeta[0]); i++){
................................................................................
  sqlitepager_unref(pP1);
  return SQLITE_OK;
}

/*
** Write meta-information back into the database.
*/
static int fileBtreeUpdateMeta(Btree *pBt, int *aMeta){
  PageOne *pP1;
  int rc, i;
  if( !pBt->inTrans ){
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  pP1 = pBt->page1;
  rc = sqlitepager_write(pP1);
................................................................................
}
#endif

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

/*
** This structure is passed around through all the sanity checking routines
** in order to keep track of some global state information.
*/
................................................................................
** a table.  nRoot is the number of entries in aRoot.
**
** If everything checks out, this routine returns NULL.  If something is
** amiss, an error message is written into memory obtained from malloc()
** and a pointer to that error message is returned.  The calling function
** is responsible for freeing the error message when it is done.
*/
char *fileBtreeIntegrityCheck(Btree *pBt, int *aRoot, int nRoot){
  int i;
  int nRef;
  IntegrityCk sCheck;

  nRef = *sqlitepager_stats(pBt->pPager);
  if( lockBtree(pBt)!=SQLITE_OK ){
    return sqliteStrDup("Unable to acquire a read lock on the database");
................................................................................
  sqliteFree(sCheck.anRef);
  return sCheck.zErrMsg;
}

/*
** Return the full pathname of the underlying database file.
*/
static const char *fileBtreeGetFilename(Btree *pBt){
  assert( pBt->pPager!=0 );
  return sqlitepager_filename(pBt->pPager);
}

/*
** Copy the complete content of pBtFrom into pBtTo.  A transaction
** must be active for both files.
**
** The size of file pBtFrom may be reduced by this operation.
** If anything goes wrong, the transaction on pBtFrom is rolled back.
*/
static int fileBtreeCopyFile(Btree *pBtTo, Btree *pBtFrom){
  int rc = SQLITE_OK;
  Pgno i, nPage, nToPage;

  if( !pBtTo->inTrans || !pBtFrom->inTrans ) return SQLITE_ERROR;
  if( pBtTo->needSwab!=pBtFrom->needSwab ) return SQLITE_ERROR;
  if( pBtTo->pCursor ) return SQLITE_BUSY;
  memcpy(pBtTo->page1, pBtFrom->page1, SQLITE_USABLE_SIZE);
................................................................................
    sqlitepager_unref(pPage);
    sqlitepager_dont_write(pBtTo->pPager, i);
  }
  if( !rc && nPage<nToPage ){
    rc = sqlitepager_truncate(pBtTo->pPager, nPage);
  }
  if( rc ){
    fileBtreeRollback(pBtTo);
  }
  return rc;  
}

/*
** The following tables contain pointers to all of the interface
** routines for this implementation of the B*Tree backend.  To
** substitute a different implemention of the backend, one has merely
** to provide pointers to alternative functions in similar tables.
*/
static BtOps sqliteBtreeOps = {
    fileBtreeClose,
    fileBtreeSetCacheSize,
    fileBtreeSetSafetyLevel,
    fileBtreeBeginTrans,
    fileBtreeCommit,
    fileBtreeRollback,
    fileBtreeBeginCkpt,
    fileBtreeCommitCkpt,
    fileBtreeRollbackCkpt,
    fileBtreeCreateTable,
    fileBtreeCreateTable,  /* Really sqliteBtreeCreateIndex() */
    fileBtreeDropTable,
    fileBtreeClearTable,
    fileBtreeCursor,
    fileBtreeGetMeta,
    fileBtreeUpdateMeta,
    fileBtreeIntegrityCheck,
    fileBtreeGetFilename,
    fileBtreeCopyFile,
    fileBtreePager,
#ifdef SQLITE_TEST
    fileBtreePageDump,
#endif
};
static BtCursorOps sqliteBtreeCursorOps = {
    fileBtreeMoveto,
    fileBtreeDelete,
    fileBtreeInsert,
    fileBtreeFirst,
    fileBtreeLast,
    fileBtreeNext,
    fileBtreePrevious,
    fileBtreeKeySize,
    fileBtreeKey,
    fileBtreeKeyCompare,
    fileBtreeDataSize,
    fileBtreeData,
    fileBtreeCloseCursor,
#ifdef SQLITE_TEST
    fileBtreeCursorDump,
#endif
};







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<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
...
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
...
149
150
151
152
153
154
155
156

157
158
159
160
161
162
163
...
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210

211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227

228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248



249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
...
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341




342





343
344
345




346
347

348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
...
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
...
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
...
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
...
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
...
611
612
613
614
615
616
617
618


619
620

621
622

623

624
625
626
627
628
629
630
631
632
633
634

635

636
637
638
639
640
641
642
643
644
645
...
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
...
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
...
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
...
764
765
766
767
768
769
770
771


772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
...
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810

811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
...
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
...
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
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
...
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
....
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
....
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140


1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
....
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
....
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224


1225
1226
1227
1228
1229
1230
1231
....
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313

1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338

1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355

1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384

1385
1386
1387
1388




1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400

1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450

1451
1452
1453
1454
1455
1456
1457
1458
1459
1460

1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481

1482
1483
1484
1485
1486
1487
1488
1489
1490
1491

1492

1493
1494
1495



















































































1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506

1507

1508
1509




1510
1511
1512

1513
1514
1515
1516
1517
1518
1519
1520
....
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551

1552

1553
1554

1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565

1566

1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601

1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
....
1614
1615
1616
1617
1618
1619
1620
1621
1622

1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
....
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
....
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
....
1693
1694
1695
1696
1697
1698
1699

1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716

1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751

1752
1753

1754
1755
1756
1757
1758
1759
1760
1761
....
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
....
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
....
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
....
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
....
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893


1894
1895
1896
1897
1898
1899
1900
1901
1902
1903



1904
1905
1906
1907
1908

1909
1910
1911

1912
1913


1914
1915
1916
1917
1918
1919
1920
1921

1922
1923
1924
1925

1926
1927
1928

1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036









2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113

2114
2115
2116
2117
2118


2119
2120
2121
2122



2123
2124
2125
2126
2127
2128
2129
....
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
....
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
....
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
....
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
....
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
....
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
....
3132
3133
3134
3135
3136
3137
3138
3139

3140
3141
3142
3143
3144
3145
3146
....
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
....
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
3307
....
3565
3566
3567
3568
3569
3570
3571
3572
3573
3574
3575
3576
3577
3578
3579
....
3629
3630
3631
3632
3633
3634
3635
3636
3637
3638
3639
3640
3641
3642
3643
3644
3645
3646
3647
3648
3649
3650
3651
3652
3653
3654
3655
....
3672
3673
3674
3675
3676
3677
3678
3679
3680
3681
3682


















































** 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.
**
*************************************************************************
** $Id: btree.c,v 1.105 2004/04/26 14:10:21 drh Exp $
**
** 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.
................................................................................
**
** Cells are of variable length.  The first cell begins on the byte defined
** in the page header.  Cells do not necessarily occur in order - they can
** skip around on the page.
**
**    SIZE    DESCRIPTION
**      2     Byte offset of the next cell.  0 if this is the last cell
**      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.
**
................................................................................
*/
#include "sqliteInt.h"
#include "pager.h"
#include "btree.h"
#include <assert.h>

/* Forward declarations */
typedef struct MemPage MemPage;


/*
** This is a magic string that appears at the beginning of every
** SQLite database in order to identify the file as a real database.
**                                  0123456789 123456 */
static const char zMagicHeader[] = "SQLite version 3";

................................................................................
**
** 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.
*/
struct MemPage {
  struct Btree *pBt;             /* Pointer back to BTree structure */
  unsigned char *aData;          /* Pointer back to the start of the page */
  u8 isInit;                     /* True if previously initialized */
  u8 idxShift;                   /* True if Cell indices have changed */
  u8 isOverfull;                 /* Some aCell[] do not fit on page */
  u8 intKey;                     /* True if intkey flag is set */
  u8 leaf;                       /* True if leaf flag is set */
  u8 zeroData;                   /* True if zero data flag is set */
  u8 hdrOffset;                  /* 100 for page 1.  0 otherwise */
  Pgno pgno;                     /* Page number for this page */
  MemPage *pParent;              /* The parent of this page.  NULL for root */
  int idxParent;                 /* Index in pParent->aCell[] of this node */
  int nFree;                     /* Number of free bytes on the page */
  int nCell;                     /* Number of entries on this page */
  unsigned char **aCell;         /* Pointer to start of each cell */
};

/*
** 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)

/*
** Everything we need to know about an open database
*/
struct Btree {

  Pager *pPager;        /* The page cache */
  BtCursor *pCursor;    /* A list of all open cursors */
  MemPage *pPage1;      /* First page of the database */
  u8 inTrans;           /* True if a transaction is in progress */
  u8 inStmt;            /* True if there is a checkpoint on the transaction */
  u8 readOnly;          /* True if the underlying file is readonly */
  int pageSize;         /* Number of usable bytes on each page */
  int maxLocal;         /* Maximum local payload */
};
typedef Btree Bt;

/*
** A cursor is a pointer to a particular entry in the BTree.
** The entry is identified by its MemPage and the index in
** MemPage.apCell[] of the entry.
*/
struct BtCursor {

  Btree *pBt;               /* The Btree to which this cursor belongs */
  BtCursor *pNext, *pPrev;  /* Forms a linked list of all cursors */
  BtCursor *pShared;        /* Loop of cursors with the same root page */
  int (*xCompare)(void*,int,const void*,int,const void*); /* Key comp func */
  void *pArg;               /* First arg to xCompare() */
  Pgno pgnoRoot;            /* The root page of this tree */
  MemPage *pPage;           /* Page that contains the entry */
  int idx;                  /* Index of the entry in pPage->aCell[] */
  u8 wrFlag;                /* True if writable */
  u8 eSkip;                 /* Determines if next step operation is a no-op */
  u8 iMatch;                /* compare result from last sqliteBtreeMoveto() */
};

/*
** Legal values for BtCursor.eSkip.
*/
#define SKIP_NONE     0   /* Always step the cursor */
#define SKIP_NEXT     1   /* The next sqliteBtreeNext() is a no-op */
#define SKIP_PREV     2   /* The next sqliteBtreePrevious() is a no-op */
#define SKIP_INVALID  3   /* Calls to Next() and Previous() are invalid */




/*
** Read or write a two-, four-, and eight-byte big-endian integer values.
*/
static u32 get2byte(unsigned char *p){
  return (p[0]<<8) | p[1];
}
static u32 get4byte(unsigned char *p){
  return (p[0]<<24) | (p[1]<<16) | (p[2]<<8) | p[3];
}
static u64 get8byte(unsigned char *p){
  u64 v = get4byte(p);
  return (v<<32) | get4byte(&p[4]);
}
static void put2byte(unsigned char *p, u32 v){
  p[0] = v>>8;
  p[1] = v;
}
................................................................................
  do{
    p[i++] = v & 0x7f;
    v >>= 7;
  }while( v!=0 );
  p[i-1] |= 0x80;
  return i;
}

/*
** Parse a cell header and fill in the CellInfo structure.
*/
static void parseCellHeader(
  MemPage *pPage,         /* Page containing the cell */
  unsigned char *pCell,   /* The cell */
  u64 *pnData,            /* Number of bytes of data in payload */
  u64 *pnKey,             /* Number of bytes of key, or key value for intKey */
  int *pnHeader           /* Size of header in bytes.  Offset to payload */
){
  int n;
  if( pPage->leaf ){
    n = 2;
  }else{
    n = 6;
  }
  if( pPage->zeroData ){
    *pnData = 0;
  }else{
    n += getVarint(&pCell[n], pnData);
  }
  n += getVarint(pCell, pnKey);
  *pnHeader = n;
}

/*
** Compute the total number of bytes that a Cell needs on the main
** database page.  The number returned includes the Cell header,
** local payload storage, and the pointer to overflow pages (if
** applicable).  Additional space allocated on overflow pages
** is NOT included in the value returned from this routine.
*/
static int cellSize(MemPage *pPage, unsigned char *pCell){
  CellInfo info;
  int n;
  u64 nData, nKey;
  int nPayload, maxPayload;










  parseCellHeader(pPage, pCell, &nData, &nKey, &n);
  nPayload = (int)nData;
  if( !pPage->intKey ){




    nPayload += (int)nKey;
  }

  maxPayload = pPage->pBt->maxLocal;
  if( nPayload>maxPayload ){
    nPayload = maxPayload + 4;
  }
  return n + nPayload;
}

/*
** Defragment the page given.  All Cells are moved to the
** beginning of the page and all free space is collected 
** into one big FreeBlk at the end of the page.
*/
static void defragmentPage(MemPage *pPage){
  int pc, i, n, addr;
  int start, hdr, size;
  int leftover;
  unsigned char *oldPage;
  unsigned char newPage[SQLITE_PAGE_SIZE];

  assert( sqlitepager_iswriteable(pPage->aData) );
  assert( pPage->pBt!=0 );
  assert( pPage->pageSize <= SQLITE_PAGE_SIZE );
  oldPage = pPage->aData;
  hdr = pPage->hdrOffset;
  addr = 3+hdr;
  n = 6+hdr;
  if( !pPage->leaf ){
    n += 4;
  }
  start = n;
  pc = get2byte(&oldPage[addr]);
  i = 0;
  while( pc>0 ){
    assert( n<pPage->pBt->pageSize );
    size = cellSize(pPage, &oldPage[pc]);
    memcpy(&newPage[n], &oldPage[pc], size);
    put2byte(&newPage[addr],n);
    pPage->aCell[i] = &oldPage[n];
    n += size;
    addr = pc;
    pc = get2byte(&oldPage[pc]);
  }
  leftover = pPage->pBt->pageSize - n;
  assert( leftover>=0 );
  assert( pPage->nFree==leftover );
  if( leftover<4 ){
    oldPage[hdr+5] = leftover;
    leftover = 0;
    n = pPage->pBt->pageSize;
  }
  memcpy(&oldPage[start], &newPage[start], n-start);
  if( leftover==0 ){
    put2byte(&oldPage[hdr+3], 0);
  }else if( leftover>=4 ){
    put2byte(&oldPage[hdr+3], n);
    put2byte(&oldPage[n], 0);
................................................................................
** calls defragementPage() to consolidate all free space before 
** allocating the new chunk.
**
** Algorithm:  Carve a piece off of the first freeblock that is
** nByte in size or that larger.
*/
static int allocateSpace(MemPage *pPage, int nByte){
  int addr, pc, hdr;
  int size;
  unsigned char *data;
#ifndef NDEBUG
  int cnt = 0;
#endif

  data = pPage->aData;
................................................................................
  assert( pPage->pBt );
  if( nByte<4 ) nByte = 4;
  if( pPage->nFree<nByte || pPage->isOverfull ) return 0;
  hdr = pPage->hdrOffset;
  if( data[hdr+5]>=252 ){
    defragmentPage(pPage);
  }
  addr = hdr+1;
  pc = get2byte(&data[addr]);
  assert( addr<pc );
  assert( pc<=pPage->pageSize-4 );
  while( (size = get2byte(&data[pc+2]))<nByte ){
    addr = pc;
    pc = get2byte(&data[addr]);
    assert( pc<=pPage->pageSize-4 );
    assert( pc>=addr+size+4 || pc==0 );
    if( pc==0 ){
      assert( (cnt++)==0 );
      defragmentPage(pPage);
      assert( data[hdr+5]==0 );
      addr = pPage->hdrOffset+1;
      pc = get2byte(&data[addr]);
    }
  }
  assert( pc>0 && size>=nByte );
  assert( pc+size<=pPage->pageSize );
  if( size>nByte+4 ){
    put2byte(&data[addr], pc+nByte);
    put2byte(&data[pc+size], get2byte(&data[pc]));
    put2byte(&data[pc+size+2], size-nByte);
  }else{
    put2byte(&data[addr], get2byte(&data[pc]));
    data[hdr+5] += size-nByte;
  }
  pPage->nFree -= nByte;
  assert( pPage->nFree>=0 );
  return pc;
}

................................................................................
** 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 void freeSpace(MemPage *pPage, int start, int size){
  int end = start + size;  /* End of the segment being freed */
  int addr, pbegin, pend;
#ifndef NDEBUG
  int tsize = 0;          /* Total size of all freeblocks */
#endif
  unsigned char *data = pPage->aData;

  assert( pPage->pBt!=0 );
  assert( sqlitepager_iswriteable(data) );
  assert( start>=pPage->hdrOffset+6+(pPage->leaf?0:4) );
  assert( end<=pPage->pBt->pageSize );
  if( size<4 ) size = 4;

  /* Add the space back into the linked list of freeblocks */
  addr = pPage->hdrOffset + 1;
  while( (pbegin = get2byte(&data[addr]))<start && pbegin>0 ){
    assert( pbegin<=pPage->pBt->pageSize-4 );
    assert( pbegin>addr );
    addr = pbegin;
  }
  assert( pbegin<=pPage->pBt->pageSize-4 );
  assert( pbegin>addr || pbegin==0 );
  put2bytes(&data[addr], start);
  put2bytes(&data[start], pbegin);
  put2bytes(&data[start+2], size);
  pPage->nFree += size;

  /* Coalesce adjacent free blocks */
  addr = pPage->hdrOffset + 1;
  while( (pbegin = get2byte(&data[addr]))>0 ){
    int pnext, psize;
    assert( pbegin>addr );
    assert( pbegin<pPage->pBt->pageSize-4 );
    pnext = get2byte(&data[pbegin]);
    psize = get2byte(&data[pbegin+2]);
    if( pbegin + psize + 3 >= pnext && pnext>0 ){
      int frag = pnext - (pbegin+psize);
      assert( frag<=data[pPage->hdrOffset+5] );
      data[pPage->hdrOffset+5] -= frag;
      put2byte(&data[pbegin], get2byte(&data[pnext]));
      put2byte(&data[pbegin+2], pnext+get2byte(&data[pnext+2])-pbegin);
    }else{
      assert( (tsize += psize)>0 );
      addr = pbegin;
    }
  }
  assert( tsize+data[pPage->hdrOffset+5]==pPage->nFree );
}

#if 0
/*
** The following is the default comparison function for (non-integer)
** keys in the btrees.  This function returns negative, zero, or
** positive if the first key is less than, equal to, or greater than
** the second.
**
*/
................................................................................
    } 
  }
  return 0;

bad_key:
  return 1;
}
#endif

/*
** Initialize the auxiliary information for a disk block.
**
** The pParent parameter must be a pointer to the MemPage which
** is the parent of the page being initialized.  The root of a
** BTree has no parent and so for that page, pParent==NULL.
................................................................................
** 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 initPage(
  MemPage *pPage,        /* The page to be initialized */


  MemPage *pParent       /* The parent.  Might be NULL */
){

  int c, pc, i, hdr;
  int sumCell = 0;       /* Total size of all cells */



  assert( pPage->pBt!=0 );
  assert( pPage->aData == &((unsigned char*)pPage)[pPage->pBt->pageSize] );
  if( pPage->pParent ){
    assert( pPage->pParent==pParent );
    return SQLITE_OK;
  }
  if( pParent ){
    pPage->pParent = pParent;
    sqlitepager_ref(pParent->aData);
  }
  if( pPage->isInit ) return SQLITE_OK;

  pPage->nCell = 0;

  assert( sqlitepager_pagenumber(pPage->aData)==pPage->pgno );
  pPage->hdrOffset = hdr = pgnoThis==1 ? 100 : 0;
  c = pPage->aData[pPage->hdrOffset];
  pPage->intKey = (c & PTF_INTKEY)!=0;
  pPage->zeroData = (c & PTF_ZERODATA)!=0;
  pPage->leaf = (c & PTF_INTKEY)!=0;

  /* Initialize the cell count and cell pointers */
  pc = get2byte(&data[hdr+3]);
  while( pc>0 ){
................................................................................
  pPage->nFree = data[hdr+5];
  pc = get2byte(&data[hdr+1]);
  while( pc>0 ){
    int next, size;
    if( pc>=pBt->pageSize ) return SQLITE_CORRUPT;
    next = get2byte(&data[pc]);
    size = get2byte(&data[pc+2]);
    if( next>0 && next<=pc+size+3 ) return SQLITE_CORRUPT;
    pPage->nFree += size;
    pc = next;
  }
  if( pPage->nFree>=pBt->pageSize ) return SQLITE_CORRUPT;

  /* Sanity check:  Cells and freespace and header must sum to the size
  ** a page. */
................................................................................
/*
** 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;
  Btree *pBt = pPage->pBt;
  int hdr = pPage->hdrOffset;
  int first;

  assert( sqlitepager_iswriteable(data) );
  memset(&data[hdr], 0, pBt->pageSize - hdr);
  data[hdr] = flags;
  first = hdr + 6 + 4*((flags&0x01)!=0);
  put2byte(&data[hdr+1], first);
................................................................................
  pPage->nCell = 0;
  pPage->nFree = pBt->pageSize - first;
  pPage->intKey = (flags & PTF_INTKEY)!=0;
  pPage->leaf = (flags & PTF_LEAF)!=0;
  pPage->zeroData = (flags & PTF_ZERODATA)!=0;
  pPage->hdrOffset = hdr;
}

/*
** Get a page from the pager.  Initialize the MemPage.pBt and
** MemPage.aData elements if needed.
*/
static int getPage(Btree *pBt, Pgno pgno, MemPage **ppPage){
  int rc;
  unsigned char *aData;
  MemPage *pPage;
  rc = sqlitepager_get(pBt->pPager, pgno, &aData);
  if( rc ) return rc;
  pPage = (MemPage*)aData[pBt->pageSize];
  pPage->aData = aData;
  pPage->pBt = pBt;
  pPage->pgno = pgno;
  *ppPage = pPage;
  return SQLITE_OK;
}

/*
** Release a MemPage.  This should be called once for each prior
** call to getPage.
*/
static int releasePage(MemPage *pPage){
  if( pPage ){
    assert( pPage->aData );
    assert( pPage->pBt );
    assert( &pPage->aData[pPage->pBt->pageSize]==(unsigned char*)pPage );
    sqlitepager_unref(pPage->aData);
  }
}

/*
** This routine is called when the reference count for a page
** reaches zero.  We need to unref the pParent pointer when that
** happens.
*/
static void pageDestructor(void *pData){
  MemPage *pPage = (MemPage*)&((char*)pData)[SQLITE_PAGE_SIZE];
  if( pPage->pParent ){
    MemPage *pParent = pPage->pParent;
    pPage->pParent = 0;
    releasepage(pParent);
  }
  sqliteFree(pPage->aCell);
  pPage->aCell = 0;
  pPage->isInit = 0;
}

/*
** Open a new database.
**
** Actually, this routine just sets up the internal data structures
** for accessing the database.  We do not open the database file 
................................................................................
** until the first page is loaded.
**
** zFilename is the name of the database file.  If zFilename is NULL
** a new database with a random name is created.  This randomly named
** database file will be deleted when sqliteBtreeClose() is called.
*/
int sqliteBtreeOpen(
  const char *zFilename,  /* Name of the file containing the BTree database */


  Btree **ppBtree,        /* Pointer to new Btree object written here */
  int nCache,             /* Number of cache pages */
  int flags               /* Options */
){
  Btree *pBt;
  int rc, i;
  int nCache = 2000;
  int omitJournal = 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(u64)==8 );
................................................................................
  pBt = sqliteMalloc( sizeof(*pBt) );
  if( pBt==0 ){
    *ppBtree = 0;
    return SQLITE_NOMEM;
  }
  if( nCache<10 ) nCache = 10;
  rc = sqlitepager_open(&pBt->pPager, zFilename, nCache, EXTRA_SIZE,
                        (flags & BTREE_OMIT_JOURNAL)==0);
  if( rc!=SQLITE_OK ){
    if( pBt->pPager ) sqlitepager_close(pBt->pPager);
    sqliteFree(pBt);
    *ppBtree = 0;
    return rc;
  }
  sqlitepager_set_destructor(pBt->pPager, pageDestructor);
  pBt->pCursor = 0;
  pBt->page1 = 0;
  pBt->readOnly = sqlitepager_isreadonly(pBt->pPager);

  pBt->pageSize = SQLITE_PAGE_SIZE;
  pBt->maxLocal = (SQLITE_PAGE_SIZE-10)/4-12;
  *ppBtree = pBt;
  return SQLITE_OK;
}

/*
** Close an open database and invalidate all cursors.
*/
int sqlite3BtreeClose(Btree *pBt){
  while( pBt->pCursor ){
    sqlite3BtreeCloseCursor(pBt->pCursor);
  }
  sqlitepager_close(pBt->pPager);
  sqliteFree(pBt);
  return SQLITE_OK;
}

/*
................................................................................
** 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 sqilte3BtreeSetCacheSize(Btree *pBt, int mxPage){
  sqlitepager_set_cachesize(pBt->pPager, mxPage);
  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.
*/
int sqlite3BtreeSetSafetyLevel(Btree *pBt, int level){
  sqlitepager_set_safety_level(pBt->pPager, level);
  return SQLITE_OK;
}

/*
** Get a reference to page1 of the database file.  This will
** also acquire a readlock on that file.
................................................................................
** 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.  SQLITE_PROTOCOL is returned
** if there is a locking protocol violation.
*/
static int lockBtree(Btree *pBt){
  int rc;
  MemPage *pPage1;
  if( pBt->page1 ) return SQLITE_OK;
  rc = getPage(pBt, 1, &pPage1);
  if( rc!=SQLITE_OK ) return rc;
  

  /* Do some checking to help insure the file we opened really is
  ** a valid database file. 
  */
  if( sqlitepager_pagecount(pBt->pPager)>0 ){
    if( memcmp(pPage1->aData, zMagicHeader, 16)!=0 ){
      rc = SQLITE_NOTADB;
      goto page1_init_failed;
    }
    /*** TBD:  Other header checks such as page size ****/
  }
  pBt->pPage1 = pPage1;
  return rc;

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 are any outstanding cursors, this routine is a no-op.
**
** If there is a transaction in progress, this routine is a no-op.
*/
static void unlockBtreeIfUnused(Btree *pBt){
  if( pBt->inTrans==0 && pBt->pCursor==0 && pBt->pPage1!=0 ){
    releasePage(pBt->pPage1);
    pBt->pPage1 = 0;
    pBt->inTrans = 0;
    pBt->inStmt = 0;
  }
}

/*
** Create a new database by initializing the first page of the
** file.
*/
static int newDatabase(Btree *pBt){
  MemPage *pP1;
  unsigned char *data;
  int rc;
  if( sqlitepager_pagecount(pBt->pPager)>1 ) return SQLITE_OK;
  pP1 = pBt->pPage1;
  assert( pP1!=0 );
  data = pP1->aData;
  rc = sqlitepager_write(data);
  if( rc ) return rc;
  memcpy(data, zMagicHeader, sizeof(zMagicHeader));
  assert( sizeof(zMagicHeader)==16 );
  put2byte(&data[16], SQLITE_PAGE_SIZE);
................................................................................
**      sqliteBtreeCreateIndex()
**      sqliteBtreeClearTable()
**      sqliteBtreeDropTable()
**      sqliteBtreeInsert()
**      sqliteBtreeDelete()
**      sqliteBtreeUpdateMeta()
*/
int sqlite3BtreeBeginTrans(Btree *pBt){
  int rc;
  if( pBt->inTrans ) return SQLITE_ERROR;
  if( pBt->readOnly ) return SQLITE_READONLY;
  if( pBt->pPage1==0 ){
    rc = lockBtree(pBt);
    if( rc!=SQLITE_OK ){
      return rc;
    }
  }
  rc = sqlitepager_begin(pBt->pPage1->aData);
  if( rc==SQLITE_OK ){
    rc = newDatabase(pBt);
  }
  if( rc==SQLITE_OK ){
    pBt->inTrans = 1;
    pBt->inStmt = 0;
  }else{
    unlockBtreeIfUnused(pBt);
  }
  return rc;
}

/*
** Commit the transaction currently in progress.
**
** This will release the write lock on the database file.  If there
** are no active cursors, it also releases the read lock.
*/
int sqlite3BtreeCommit(Btree *pBt){
  int rc;
  rc = pBt->readOnly ? SQLITE_OK : sqlitepager_commit(pBt->pPager);
  pBt->inTrans = 0;
  pBt->inStmt = 0;
  unlockBtreeIfUnused(pBt);
  return rc;
}

/*
** 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 sqlite3BtreeRollback(Btree *pBt){
  int rc;
  BtCursor *pCur;
  if( pBt->inTrans==0 ) return SQLITE_OK;
  pBt->inTrans = 0;
  pBt->inStmt = 0;
  rc = pBt->readOnly ? SQLITE_OK : sqlitepager_rollback(pBt->pPager);
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    MemPage *pPage = pCur->pPage;
    if( pPage && !pPage->isInit ){
      releasePage(pPage);
      pCur->pPage = 0;
    }
  }
  unlockBtreeIfUnused(pBt);
  return rc;
}

................................................................................
** main transaction.  You must start a transaction before starting a
** checkpoint.  The checkpoint is ended automatically if the transaction
** commits or rolls back.
**
** Only one checkpoint may be active at a time.  It is an error to try
** to start a new checkpoint if another checkpoint is already active.
*/
int sqlite3BtreeBeginStmt(Btree *pBt){
  int rc;
  if( !pBt->inTrans || pBt->inStmt ){
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  rc = pBt->readOnly ? SQLITE_OK : sqlitepager_ckpt_begin(pBt->pPager);
  pBt->inStmt = 1;
  return rc;
}


/*
** Commit a checkpoint to transaction currently in progress.  If no
** checkpoint is active, this is a no-op.
*/
int sqlite3BtreeCommitStmt(Btree *pBt){
  int rc;
  if( pBt->inStmt && !pBt->readOnly ){
    rc = sqlitepager_ckpt_commit(pBt->pPager);
  }else{
    rc = SQLITE_OK;
  }
  pBt->inStmt = 0;
  return rc;
}

/*
** Rollback the checkpoint to the current transaction.  If there
** is no active checkpoint or transaction, this routine is a no-op.
**
** 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.
*/
int sqlite3BtreeRollbackStmt(Btree *pBt){
  int rc;
  BtCursor *pCur;
  if( pBt->inStmt==0 || pBt->readOnly ) return SQLITE_OK;
  rc = sqlitepager_ckpt_rollback(pBt->pPager);
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    MemPage *pPage = pCur->pPage;
    if( pPage && !pPage->isInit ){
      releasePage(pPage);
      pCur->pPage = 0;
    }
  }
  pBt->inStmt = 0;
  return rc;
}

/*
** Default key comparison function to be used if no comparison function
** is specified on the sqlite3BtreeCursor() call.
*/
static int dfltCompare(
  void *NotUsed,             /* User data is not used */
  int n1, const void *p1,    /* First key to compare */
  int n2, const void *p2     /* Second key to compare */
){
  int c;
  c = memcmp(p1, p2, n1<n2 ? n1 : n2);
  if( c==0 ){
    c = n1 - n2;
  }
  return c;
}

/*
** Create a new cursor for the BTree whose root is on the page
** iTable.  The act of acquiring a cursor gets a read lock on 
** the database file.
**
** If wrFlag==0, then the cursor can only be used for reading.
................................................................................
** intend to use the sqliteBtreeNext() system call.  All other cursors
** should be opened with wrFlag==1 even if they never really intend
** to write.
** 
** 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.
**
** The comparison function must be logically the same for every cursor
** on a particular table.  Changing the comparison function will result
** in incorrect operations.  If the comparison function is NULL, a
** default comparison function is used.  The comparison function is
** always ignored for INTKEY tables.
*/


int sqlite3BtreeCursor(
  Btree *pBt,                                 /* The btree */
  int iTable,                                 /* Root page of table to open */
  int wrFlag,                                 /* 1 to write. 0 read-only */
  int (*xCmp)(void*,int,const void*,int,const void*), /* Key Comparison func */
  void *pArg,                                 /* First arg to xCompare() */
  BtCursor **ppCur                            /* Write new cursor here */
){
  int rc;
  BtCursor *pCur, *pRing;

  if( pBt->readOnly && wrFlag ){
    *ppCur = 0;
    return SQLITE_READONLY;
  }
................................................................................
  }
  pCur = sqliteMalloc( sizeof(*pCur) );
  if( pCur==0 ){
    rc = SQLITE_NOMEM;
    goto create_cursor_exception;
  }
  pCur->pgnoRoot = (Pgno)iTable;
  rc = getPage(pBt, pCur->pgnoRoot, (void**)&pCur->pPage);
  if( rc!=SQLITE_OK ){
    goto create_cursor_exception;
  }
  rc = initPage(pCur->pPage, 0);
  if( rc!=SQLITE_OK ){
    goto create_cursor_exception;
  }
  pCur->xCompare = xCmp ? xCmp : dfltCompare;
  pCur->pArg = pArg;
  pCur->pBt = pBt;
  pCur->wrFlag = wrFlag;
  pCur->idx = 0;
  pCur->eSkip = SKIP_INVALID;
  pCur->pNext = pBt->pCursor;
  if( pCur->pNext ){
    pCur->pNext->pPrev = pCur;
................................................................................
  pBt->pCursor = pCur;
  *ppCur = pCur;
  return SQLITE_OK;

create_cursor_exception:
  *ppCur = 0;
  if( pCur ){
    releasePage(pCur->pPage);
    sqliteFree(pCur);
  }
  unlockBtreeIfUnused(pBt);
  return rc;
}

/*
** Close a cursor.  The read lock on the database file is released
** when the last cursor is closed.
*/
int sqlite3BtreeCloseCursor(BtCursor *pCur){
  Btree *pBt = pCur->pBt;
  if( pCur->pPrev ){
    pCur->pPrev->pNext = pCur->pNext;
  }else{
    pBt->pCursor = pCur->pNext;
  }
  if( pCur->pNext ){
    pCur->pNext->pPrev = pCur->pPrev;
  }
  releasePage(pCur->pPage);


  if( pCur->pShared!=pCur ){
    BtCursor *pRing = pCur->pShared;
    while( pRing->pShared!=pCur ){ pRing = pRing->pShared; }
    pRing->pShared = pCur->pShared;
  }
  unlockBtreeIfUnused(pBt);
  sqliteFree(pCur);
................................................................................
** The temporary cursor is not on the cursor list for the Btree.
*/
static void getTempCursor(BtCursor *pCur, BtCursor *pTempCur){
  memcpy(pTempCur, pCur, sizeof(*pCur));
  pTempCur->pNext = 0;
  pTempCur->pPrev = 0;
  if( pTempCur->pPage ){
    sqlitepager_ref(pTempCur->pPage->aData);
  }
}

/*
** Delete a temporary cursor such as was made by the CreateTemporaryCursor()
** function above.
*/
static void releaseTempCursor(BtCursor *pCur){
  if( pCur->pPage ){
    sqlitepager_unref(pCur->pPage->aData);
  }
}

/*
** 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.
*/
int sqlite3BtreeKeySize(BtCursor *pCur, u64 *pSize){
  MemPage *pPage;

  pPage = pCur->pPage;
  assert( pPage!=0 );
  if( pCur->idx >= pPage->nCell ){
    *pSize = 0;
  }else{
    unsigned char *cell = pPage->aCell[pCur->idx];
    cell += 2;   /* Skip the offset to the next cell */
    if( pPage->leaf ){
      cell += 4;  /* Skip the child pointer */
    }
    if( !pPage->zeroData ){
      while( (0x80&*(data++))!=0 ){}  /* Skip the data size number */
    }
    getVarint(data, pSize);
  }
  return SQLITE_OK;
}

/*
** Read payload information from the entry that the pCur cursor is
** pointing to.  Begin reading the payload at "offset" and read
** a total of "amt" bytes.  Put the result in zBuf.
**
** This routine does not make a distinction between key and data.
** It just reads bytes from the payload area.
*/
static int getPayload(
  BtCursor *pCur,      /* Cursor pointing to entry to read from */
  int offset,          /* Begin reading this far into payload */
  int amt,             /* Read this many bytes */
  unsigned char *pBuf, /* Write the bytes into this buffer */ 
  int skipKey          /* offset begins at data if this is true */
){
  unsigned char *aPayload;
  Pgno nextPage;
  int rc;
  MemPage *pPage;
  Btree *pBt;
  u64 nData, nKey;
  int maxLocal, ovflSize;

  assert( pCur!=0 && pCur->pPage!=0 );
  pBt = pCur->pBt;
  pPage = pCur->pPage;
  assert( pCur->idx>=0 && pCur->idx<pPage->nCell );

  aPayload = pPage->aCell[pCur->idx];
  aPayload += 2;  /* Skip the next cell index */
  if( pPage->leaf ){
    aPayload += 4;  /* Skip the child pointer */
  }
  if( pPage->zeroData ){
    nData = 0;
  }else{
    aPayload += getVarint(aPayload, &nData);
  }
  aPayload += getVarInt(aPayload, &nKey);
  if( pPage->intKey ){
    nKey = 0;
  }
  assert( offset>=0 );
  if( skipKey ){
    offset += nKey;
  }
  if( offset+amt > nKey+nData ){
    sqlite SQLITE_ERROR;
  }
  maxLocal = pBt->maxLocal
  if( offset<maxLocal ){
    int a = amt;
    if( a+offset>maxLocal ){

      a = maxLocal - offset;
    }
    memcpy(zBuf, &aPayload[offset], a);
    if( a==amt ){
      return SQLITE_OK;
    }
    offset = 0;
    zBuf += a;
    amt -= a;
  }else{
    offset -= maxLocal;
  }
  if( amt>0 ){
    nextPage = get4bytes(&aPayload[maxLocal]);
  }
  ovflSize = pBt->pageSize - 4;
  while( amt>0 && nextPage ){

    rc = sqlitepager_get(pBt->pPager, nextPage, (void**)&aPayload);
    if( rc!=0 ){
      return rc;
    }
    nextPage = get4bytes(aPayload);
    if( offset<ovflSize ){
      int a = amt;
      if( a + offset > ovflSize ){
        a = ovflSize - offset;
      }
      memcpy(zBuf, &aPayload[offset], a);
      offset = 0;
      amt -= a;
      zBuf += a;
    }else{
      offset -= ovflSize;
    }
    sqlitepager_unref(aPayload);
  }
  if( amt>0 ){
    return SQLITE_CORRUPT;
  }
  return SQLITE_OK;
}

/*
** Read part of the key associated with cursor pCur.  Exactly
** "amt" bytes will be transfered into zBuf[].  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 sqlite3BtreeKey(BtCursor *pCur, int offset, int amt, void *pBuf){
  MemPage *pPage;

  assert( amt>=0 );
  assert( offset>=0 );
  assert( pCur->pPage!=0 );
  pPage = pCur->pPage;
  if( pCur->idx >= pPage->nCell || pPage->intKey ){
    assert( amt==0 );
    return SQLITE_OK;
  }

  return getPayload(pCur, offset, amt, (unsigned char*)pBuf, 0);
}

/*
** Return a pointer to the key of record that cursor pCur
** is point to if the entire key is in contiguous memory.
** If the key is split up among multiple tables, return 0.
** If pCur is not pointing to a valid entry return 0.
**
** The pointer returned is ephemeral.  The key may move
** or be destroyed on the next call to any Btree routine.
**
** This routine is used to do quick key comparisons in the
** common case where the entire key fits in the payload area
** of a cell and does not overflow onto secondary pages.
*/
void *sqlite3BtreeKeyFetch(BtCursor *pCur){
  unsigned char *aPayload;
  MemPage *pPage;
  Btree *pBt;
  u64 nData, nKey;

  assert( pCur!=0 && pCur->pPage!=0 );
  pBt = pCur->pBt;
  pPage = pCur->pPage;
  assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
  aPayload = pPage->aCell[pCur->idx];
  aPayload += 2;  /* Skip the next cell index */
  if( pPage->leaf ){
    aPayload += 4;  /* Skip the child pointer */
  }
  if( !pPage->zeroData ){
    aPayload += getVarint(aPayload, &nData);
  }
  aPayload += getVarInt(aPayload, &nKey);
  if( pPage->intKey || nKey>pBt->maxLocal ){
    return 0;
  }
  return aPayload;
}


/*
** Set *pSize to the number of bytes of data in the entry the
** cursor currently points to.  Always return SQLITE_OK.
** Failure is not possible.  If the cursor is not currently
** pointing to an entry (which can happen, for example, if
** the database is empty) then *pSize is set to 0.
*/
int sqlite3BtreeDataSize(BtCursor *pCur, u32 *pSize){

  MemPage *pPage;

  pPage = pCur->pPage;
  assert( pPage!=0 );
  if( pCur->idx >= pPage->nCell || pPage->zeroData ){
    *pSize = 0;
  }else{
    unsigned char *cell;
    u64 size;
    cell = pPage->aCell[pCur->idx];

    cell += 2;   /* Skip the offset to the next cell */
    if( pPage->leaf ){
      cell += 4;  /* Skip the child pointer */
    }
    getVarint(data, size);
    assert( (size & 0x00000000ffffffff)==size );
    *pSize = size;
  }
  return SQLITE_OK;
}

/*
** Read part of the data associated with cursor pCur.  Exactly
** "amt" bytes will be transfered into zBuf[].  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 sqlite3BtreeData(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){

  MemPage *pPage;

  assert( amt>=0 );
  assert( offset>=0 );
  assert( pCur->pPage!=0 );
  pPage = pCur->pPage;
  if( pCur->idx >= pPage->nCell ){
    return 0;
  }
  pCell = pPage->apCell[pCur->idx];

  return getPayload(pCur, offset, amt, pBuf, 1);

}

/*



















































































** Move the cursor down to a new child page.  The newPgno argument is the
** page number of the child page in the byte order of the disk image.
*/
static int moveToChild(BtCursor *pCur, u32 newPgno){
  int rc;
  MemPage *pNewPage;
  MemPage *pOldPage;
  unsigned char *aData;
  Btree *pBt = pCur->pBt;

  rc = getPage(pBt, newPgno, &pNewPage);

  if( rc ) return rc;

  rc = initPage(pNewPage, pCur->pPage);
  if( rc ) return rc;




  pNewPage->idxParent = pCur->idx;
  pOldPage = pCur->pPage;
  pOldPage->idxShift = 0;

  releasePage(pOldPage);
  pCur->pPage = pNewPage;
  pCur->idx = 0;
  if( pNewPage->nCell<1 ){
    return SQLITE_CORRUPT;
  }
  return SQLITE_OK;
}
................................................................................
** the largest cell index.
*/
static void moveToParent(BtCursor *pCur){
  Pgno oldPgno;
  MemPage *pParent;
  MemPage *pPage;
  int idxParent;

  pPage = pCur->pPage;
  assert( pPage!=0 );
  pParent = pPage->pParent;
  assert( pParent!=0 );
  idxParent = pPage->idxParent;
  sqlitepager_ref(pParent->aData);
  oldPgno = pPage->pgno;
  releasePage(pPage);
  pCur->pPage = pParent;
  assert( pParent->idxShift==0 );
  if( pParent->idxShift==0 ){
    pCur->idx = idxParent;
#ifndef NDEBUG  
    /* Verify that pCur->idx is the correct index to point back to the child
    ** page we just came from 
    */

    if( pCur->idx<pParent->nCell ){

      assert( get4Byte(&pParent->aCell[idxParent][2])==oldPgno );
    }else{

      assert( get4Byte(&pParent->aData[pParent->hdrOffset+6])==oldPgno );
    }
#endif
  }else{
    /* The MemPage.idxShift flag indicates that cell indices might have 
    ** changed since idxParent was set and hence idxParent might be out
    ** of date.  So recompute the parent cell index by scanning all cells
    ** and locating the one that points to the child we just came from.
    */
    int i;
    pCur->idx = pParent->nCell;

    for(i=0; i<pParent->nCell; i++){

      if( get4byte(&pParent->aCell[i][2])==oldPgno ){
        pCur->idx = i;
        break;
      }
    }
  }
}

/*
** Move the cursor to the root page
*/
static int moveToRoot(BtCursor *pCur){
  MemPage *pRoot;
  int rc;
  Btree *pBt = pCur->pBt;

  rc = sqlitepager_get(pBt->pPager, pCur->pgnoRoot, &pRoot);
  if( rc ) return rc;
  rc = initPage(pRoot, 0);
  if( rc ) return rc;
  releasePage(pCur->pPage);
  pCur->pPage = pRoot;
  pCur->idx = 0;
  return SQLITE_OK;
}

/*
** Move the cursor down to the left-most leaf entry beneath the
** entry to which it is currently pointing.
*/
static int moveToLeftmost(BtCursor *pCur){
  Pgno pgno;
  int rc;
  MemPage *pPage;


  while( !(pPage = pCur->pPage)->leaf ){
    assert( pCur->idx>=0 && pCur->idx<pPage->nPage );
    pgno = get4byte(pPage->aCell[pCur->idx][2]);
    rc = moveToChild(pCur, pgno);
    if( rc ) return rc;
  }
  return SQLITE_OK;
}

/*
................................................................................
** between moveToLeftmost() and moveToRightmost().  moveToLeftmost()
** finds the left-most entry beneath the *entry* whereas moveToRightmost()
** finds the right-most entry beneath the *page*.
*/
static int moveToRightmost(BtCursor *pCur){
  Pgno pgno;
  int rc;
  MemPage *pPage;


  while( !(pPage = pCur->pPage)->leaf ){
    pgno = get4byte(&pPage->aData[pPage->hdrOffset+6]);
    pCur->idx = pPage->nCell;
    rc = moveToChild(pCur, pgno);
    if( rc ) return rc;
  }
  pCur->idx = pPage->nCell - 1;
  return SQLITE_OK;
}

/* 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 sqlite3BtreeFirst(BtCursor *pCur, int *pRes){
  int rc;
  if( pCur->pPage==0 ) return SQLITE_ABORT;
  rc = moveToRoot(pCur);
  if( rc ) return rc;
  if( pCur->pPage->nCell==0 ){
    *pRes = 1;
    return SQLITE_OK;
................................................................................
  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 sqlite3BtreeLast(BtCursor *pCur, int *pRes){
  int rc;
  if( pCur->pPage==0 ) return SQLITE_ABORT;
  rc = moveToRoot(pCur);
  if( rc ) return rc;
  assert( pCur->pPage->isInit );
  if( pCur->pPage->nCell==0 ){
    *pRes = 1;
................................................................................
  }
  *pRes = 0;
  rc = moveToRightmost(pCur);
  pCur->eSkip = SKIP_NONE;
  return rc;
}

/* Move the cursor so that it points to an entry near pKey/nKey.
** Return a success code.
**
** For INTKEY tables, only the nKey parameter is used.  pKey is
** ignored.  For other tables, nKey is the number of bytes of data
** in nKey.  The comparison function specified when the cursor was
** created is used to compare keys.
**
** 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.
**
** The result of comparing the key with the entry to which the
................................................................................
**
**     *pRes==0     The cursor is left pointing at an entry that
**                  exactly matches pKey.
**
**     *pRes>0      The cursor is left pointing at an entry that
**                  is larger than pKey.
*/

int sqlite3BtreeMoveto(BtCursor *pCur, const void *pKey, u64 nKey, int *pRes){
  int rc;
  if( pCur->pPage==0 ) return SQLITE_ABORT;
  pCur->eSkip = SKIP_NONE;
  rc = moveToRoot(pCur);
  if( rc ) return rc;
  for(;;){
    int lwr, upr;
    Pgno chldPg;
    MemPage *pPage = pCur->pPage;
    int c = -1;  /* pRes return if table is empty must be -1 */
    lwr = 0;
    upr = pPage->nCell-1;
    while( lwr<=upr ){
      void *pCellKey;
      u64 nCellKey;
      pCur->idx = (lwr+upr)/2;

      nCellKey = sqlite3BtreeKeySize(pCur, &nCellKey);
      if( pPage->intKey ){
        if( nCellKey<nKey ){
          c = -1;
        }else if( nCellKey>nKey ){
          c = +1;
        }else{
          c = 0;
        }
      }else if( (pCellKey = sqlite3BtreeKeyFetch(pCur))!=0 ){
        c = pCur->xCompare(pCur->pArg, nCellKey, pCellKey, nKey, pKey);
      }else{
        pCellKey = sqliteMalloc( nCellKey );
        if( pCellKey==0 ) return SQLITE_NOMEM;
        rc = sqlite3BtreeKey(pCur, 0, nCellKey, pCellKey);
        c = pCur->xCompare(pCur->pArg, nCellKey, pCellKey, nKey, pKey);
        sqliteFree(pCellKey);
        if( rc ) return rc;
      }
      if( c==0 ){
        pCur->iMatch = c;
        if( pRes ) *pRes = 0;
        return SQLITE_OK;
      }
      if( c<0 ){
        lwr = pCur->idx+1;
      }else{
        upr = pCur->idx-1;
      }
    }
    assert( lwr==upr+1 );
    assert( pPage->isInit );
    if( pPage->leaf ){
      chldpg = 0;
    }else if( lwr>=pPage->nCell ){

      chldPg = get4byte(&pPage->aData[pPage->hdrOffset+6]);
    }else{

      chldPg = get4byte(&pPage->aCell[lwr][2]);
    }
    if( chldPg==0 ){
      pCur->iMatch = c;
      if( pRes ) *pRes = c;
      return SQLITE_OK;
    }
    pCur->idx = lwr;
................................................................................

/*
** 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 sqlite3BtreeNext(BtCursor *pCur, int *pRes){
  int rc;
  MemPage *pPage = pCur->pPage;
  assert( pRes!=0 );
  if( pPage==0 ){
    *pRes = 1;
    return SQLITE_ABORT;
  }
................................................................................
    pCur->eSkip = SKIP_NONE;
    *pRes = 0;
    return SQLITE_OK;
  }
  pCur->eSkip = SKIP_NONE;
  pCur->idx++;
  if( pCur->idx>=pPage->nCell ){
    if( !pPage->left ){
      rc = moveToChild(pCur, get4byte(&pPage->aData[pPage->hdrOffset+6]);
      if( rc ) return rc;
      rc = moveToLeftmost(pCur);
      *pRes = 0;
      return rc;
    }
    do{
      if( pPage->pParent==0 ){
................................................................................
      moveToParent(pCur);
      pPage = pCur->pPage;
    }while( pCur->idx>=pPage->nCell );
    *pRes = 0;
    return SQLITE_OK;
  }
  *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 sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
  int rc;
  Pgno pgno;
  MemPage *pPage;
  pPage = pCur->pPage;
  if( pPage==0 ){
    *pRes = 1;
    return SQLITE_ABORT;
................................................................................
  if( pCur->eSkip==SKIP_PREV ){
    pCur->eSkip = SKIP_NONE;
    *pRes = 0;
    return SQLITE_OK;
  }
  pCur->eSkip = SKIP_NONE;
  assert( pCur->idx>=0 );
  if( !pPage->left ){
    pgno = get4byte(&pPage->aCell[pCur->idx][2]);
    rc = moveToChild(pCur, pgno);
    if( rc ) return rc;
    rc = moveToRightmost(pCur);
  }else{
    while( pCur->idx==0 ){
      if( pPage->pParent==0 ){
        if( pRes ) *pRes = 1;
................................................................................
**
** 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.
*/
static int allocatePage(Btree *pBt, MemPage **ppPage, Pgno *pPgno, Pgno nearby){
  u32 pn;
  MemPage *pPage1;
  MemPage *pPage;
  int rc;


  int n;     /* Number of pages on the freelist */
  int k;     /* Number of leaves on the trunk of the freelist */

  pPage1 = pBt->pPage1;
  n = get4byte(&pPage1->aData[36]);
  if( n>0 ){
    /* There exists pages on the freelist.  Reuse one of those pages. */
    MemPage *pTrunk;
    rc = sqlitepager_write(pPage1->aData);
    if( rc ) return rc;



    put4byte(&pPage1->aData[36], n-1);
    rc = getPage(pBt, get4byte(&pPage1->aData[32]), &pTrunk);
    if( rc ) return rc;
    rc = sqlitepager_write(pTrunk->aData);
    if( rc ){

      releasePage(pTrunk);
      return rc;
    }

    k = get4byte(&pTrunk->aData[4]);
    if( k==0 ){


      /* The trunk has no leaves.  So extract the trunk page itself and
      ** use it as the newly allocated page */
      *pPgno = get4byte(pPage1->aData[32]);
      memcpy(&pPage1->aData[32], &pTrunk->aData[0], 4);
      *ppPage = pTrunk;
    }else{
      /* Extract a leaf from the trunk */
      int closest;

      unsigned char *aData = pTrunk->aData;
      if( nearby>0 ){
        int i, dist;
        closest = 0;

        dist = get4byte(&aData[8]) - nearby;
        if( dist<0 ) dist = -dist;
        for(i=1; i<n; i++){

          int d2 = get4byte(&aData[8+i*4]) - nearby;
          if( d2<0 ) d2 = -d2;
          if( d2<dist ) closest = i;
        }
      }else{
        closest = 0;
      }
      put4byte(&aData[4], n-1);
      *pPgno = get4data(&aData[8+closest*4]);
      memcpy(&aData[8+closest*4], &aData[4+closest*n], 4);
      rc = getPage(pBt, *pPgno, ppPage);
      releasePage(pTrunk);
      if( rc==SQLITE_OK ){
        sqlitepager_dont_rollback(*ppPage);
        rc = sqlitepager_write((*ppPage)->aData);
      }
    }
  }else{
    /* There are no pages on the freelist, so create a new page at the
    ** end of the file */
    *pPgno = sqlitepager_pagecount(pBt->pPager) + 1;
    rc = getPage(pBt, *pPgno, ppPage);
    if( rc ) return rc;
    rc = sqlitepager_write((*ppPage)->aData);
  }
  return rc;
}

/*
** Add a page of the database file to the freelist.
**
** sqlitepager_unref() is NOT called for pPage.
*/
static int freePage(MemPage *pPage){
  Btree *pBt = pPage->pBt;
  MemPage *pPage1 = pBt->pPage1;
  int rc, n, k;

  /* Prepare the page for freeing */
  assert( pPage->pgno>1 );
  pPage->isInit = 0;
  releasePage(pPage->pParent);
  pPage->pParent = 0;

  /* Increment the free page count on page1 */
  rc = sqlitepager_write(pPage1->aData);
  if( rc ) return rc;
  n = get4byte(&pPage1->aData[36]);
  put4byte(&pPage1->aData[36], n+1);

  if( n==0 ){
    /* This is the first free page */
    memset(pPage->aData, 0, 8);
    put4byte(pPage1->aData[32], pPage->pgno);
  }else{
    /* Other free pages already exist.  Retrive the first trunk page
    ** of the freelist and find out how many leaves it has. */
    MemPage *pTrunk
    rc = getPage(pBt, get4byte(pPage1->aData[32], &pTrunk);
    if( rc ) return rc;
    k = get4byte(&pTrunk->aData[4]);
    if( k==pBt->pageSize/4 - 8 ){
      /* The trunk is full.  Turn the page being freed into a new
      ** trunk page with no leaves. */
      rc = sqlitepager_write(pPage->aData);
      if( rc ) return rc;
      put4byte(pPage->aData, pTrunk->pgno);
      put4byte(&pPage->aData[4], 0);
      put4byte(&pPage1->aData[32], pPage->pgno);
    }else{
      /* Add the newly freed page as a leaf on the current trunk */
      rc = sqlitepager_write(pTrunk->aData);
      if( rc ) return rc;
      put4byte(&pTrunk->aData[4], k+1);
      put4byte(&pTrunk->aData[8+k*4], pPage->pgno);
      sqlitepager_dont_write(pBt->pPager, pPage->pgno);
    }
    releasePage(pTrunk);
  }
  return rc;
}

/*
** Free any overflow pages associated with the given Cell.
*/
static int clearCell(MemPage *pPage, unsigned char *pCell){
  Btree *pBt = pPage->pBt;
  int rc, n;
  u64 nData, nKey;
  Pgno ovflPgno;

  parseCellHeader(pPage, pCell, &nData, &nKey, &n);
  nPayload = nData;
  if( !pPage->intKey ){
    nPayload += nKey;
  }
  if( nPayload<=pBt->maxLocal ){
    return;  /* There are no overflow pages.  Return without doing anything */
  }
  ovflPgno = get4byte(&pCell[n+pBt->maxLocal]);
  while( ovflPgno!=0 ){
    MemPage *pOvfl;
    rc = getPage(pBt, ovflPgno, &pOvfl);
    if( rc ) return rc;
    ovflPgno = get4byte(pOvfl->aData);
    rc = freePage(pBt, pOvfl, ovfl);
    if( rc ) return rc;
    sqlitepager_unref(pOvfl->aData);









  }
  return SQLITE_OK;
}

/*
** Compute the number of bytes required by a cell header.  If the *pHeader
** argument is not NULL, fill it in with the bytes of the header.
*/
static int makeCellHeader(
  MemPage *pPage,          /* The page that will contain the cell */
  u64 nKey,                /* Size of key, or the key value if intKey */
  int nData,               /* Size of data.  Ignored for zerodata */
  unsigned char *pHeader   /* Write header bytes here */
){
  int n = 2;
  if( !pPage->leaf ) n += 4;
  if( !pPage->zeroData ){
    n += putVarint(&pHeader[n], nData);
  }
  n += putVarint(&pHeader[n], nKey);
  return n;
}

/*
** Fill in the payload section of a cell into the space provided.  If
** the payload will not completely fit in the cell, allocate additional
** overflow pages and fill them in.
*/
static int fillInCell(
  MemPage *pPage,                /* The page that contains the cell */
  unsigned char *pCell,          /* Pointer to start of payload area */
  int nHeader,                   /* Number of bytes in the cell header */
  const void *pKey, u64 nKey,    /* The key */
  const void *pData,int nData    /* The data */
){
  int nPayload;
  const void *pSrc;
  int nSrc, nSrc2;
  int spaceLeft;
  MemPage *pOvfl = 0;
  unsigned char *pPrior;
  unsigned char *pPayload;
  Btree *pBt = pPage->pBt;
  Pgno pgnoOvfl = 0;

  nPayload = nData;
  if( pPage->intKey ){
    pSrc = pData;
    nSrc = nData;
    nSrc2 = 0;
  }else{
    nPayload += nKey;
    pSrc = pKey;
    nSrc = nKey;
  }
  spaceLeft = pBt->maxLocal;
  pPayload = &pCell[nHeader];
  pPrior = &pPayload[pBt->maxLocal];

  while( nPayload>0 ){
    if( spaceLeft==0 ){
      rc =  allocatePage(pBt, &pOvfl, &pgnoOvfl, pgnoOvfl);
      if( rc ){
        clearCell(pPage, pCell);
        return rc;
      }
      put4byte(pPrior, pgnoOvfl);
      pPrior = pOvfl->aData;
      put4byte(pPrior, 0);
      pPayload = &pOvfl->aData[4];
      spaceLeft = pBt->pageSize - 4;
    }
    n = nPayload;
    if( n>spaceLeft ) n = spaceLeft;
    if( n>nSrc ) n = nSrc;
    memcpy(pPayload, pSrc, n);
    nPayload -= n;

    nSrc -= n;
    spaceLeft -= n;
    if( nSrc==0 ){
      nSrc = nData;
      pSrc = pData;


    }
    if( pOvfl && (spaceLeft==0 || nPayload==0) ){
      releasePage(pOvfl);
    }



  }
  return SQLITE_OK;
}

/*
** Change the MemPage.pParent pointer on the page whose number is
** given in the second argument so that MemPage.pParent holds the
................................................................................

/*
** 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 database the record should be inserted into.  The cursor
** is left pointing at the new record.
*/
int sqlite3BtreeInsert(
  BtCursor *pCur,                /* Insert data into the table of this cursor */
  const void *pKey, int nKey,    /* The key of the new record */
  const void *pData, int nData   /* The data of the new record */
){
  Cell newCell;
  int rc;
  int loc;
................................................................................
  assert( !pBt->readOnly );
  if( !pCur->wrFlag ){
    return SQLITE_PERM;   /* Cursor not open for writing */
  }
  if( checkReadLocks(pCur) ){
    return SQLITE_LOCKED; /* The table pCur points to has a read lock */
  }
  rc = sqlite3BtreeMoveto(pCur, pKey, nKey, &loc);
  if( rc ) return rc;
  pPage = pCur->pPage;
  assert( pPage->isInit );
  rc = sqlitepager_write(pPage);
  if( rc ) return rc;
  rc = fillInCell(pBt, &newCell, pKey, nKey, pData, nData);
  if( rc ) return rc;
................................................................................
** sqliteBtreeNext() after a delete and the cursor will be left
** pointing to the first entry after the deleted entry.  Similarly,
** pCur->eSkip is set to SKIP_PREV is the cursor is left pointing to
** the entry prior to the deleted entry so that a subsequent call to
** sqliteBtreePrevious() will always leave the cursor pointing at the
** entry immediately before the one that was deleted.
*/
int sqlite3BtreeDelete(BtCursor *pCur){
  MemPage *pPage = pCur->pPage;
  Cell *pCell;
  int rc;
  Pgno pgnoChild;
  Btree *pBt = pCur->pBt;

  assert( pPage->isInit );
................................................................................
    ** to be a leaf so we can use it.
    */
    BtCursor leafCur;
    Cell *pNext;
    int szNext;
    int notUsed;
    getTempCursor(pCur, &leafCur);
    rc = sqlite3BtreeNext(&leafCur, &notUsed);
    if( rc!=SQLITE_OK ){
      if( rc!=SQLITE_NOMEM ) rc = SQLITE_CORRUPT;
      return rc;
    }
    rc = sqlitepager_write(leafCur.pPage);
    if( rc ) return rc;
    dropCell(pBt, pPage, pCur->idx, cellSize(pBt, pCell));
................................................................................
**
** In the current implementation, BTree tables and BTree indices are the 
** the same.  In the future, we may change this so that BTree tables
** are restricted to having a 4-byte integer key and arbitrary data and
** BTree indices are restricted to having an arbitrary key and no data.
** But for now, this routine also serves to create indices.
*/
int sqlite3BtreeCreateTable(Btree *pBt, int *piTable, int flags){
  MemPage *pRoot;
  Pgno pgnoRoot;
  int rc;
  if( !pBt->inTrans ){
    /* Must start a transaction first */
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
................................................................................
  sqlitepager_unref(pPage);
  return rc;
}

/*
** Delete all information from a single table in the database.
*/
int sqlite3BtreeClearTable(Btree *pBt, int iTable){
  int rc;
  BtCursor *pCur;
  if( !pBt->inTrans ){
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    if( pCur->pgnoRoot==(Pgno)iTable ){
      if( pCur->wrFlag==0 ) return SQLITE_LOCKED;
      moveToRoot(pCur);
    }
  }
  rc = clearDatabasePage(pBt, (Pgno)iTable, 0);
  if( rc ){
    sqlite3BtreeRollback(pBt);
  }
  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 2) is never added to the freelist.
*/
int sqlite3BtreeDropTable(Btree *pBt, int iTable){
  int rc;
  MemPage *pPage;
  BtCursor *pCur;
  if( !pBt->inTrans ){
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    if( pCur->pgnoRoot==(Pgno)iTable ){
      return SQLITE_LOCKED;  /* Cannot drop a table that has a cursor */
    }
  }
  rc = sqlitepager_get(pBt->pPager, (Pgno)iTable, (void**)&pPage);
  if( rc ) return rc;
  rc = sqlite3BtreeClearTable(pBt, iTable);
  if( rc ) return rc;
  if( iTable>2 ){
    rc = freePage(pBt, pPage, iTable);
  }else{
    zeroPage(pBt, pPage);
  }
  sqlitepager_unref(pPage);
................................................................................
  return rc;
}
#endif

/*
** Read the meta-information out of a database file.
*/
int sqlite3BtreeGetMeta(Btree *pBt, int idx, u32 *pMeta){

  int rc;
  int i;

  rc = sqlitepager_get(pBt->pPager, 1, (void**)&pP1);
  if( rc ) return rc;
  aMeta[0] = SWAB32(pBt, pP1->nFree);
  for(i=0; i<sizeof(pP1->aMeta)/sizeof(pP1->aMeta[0]); i++){
................................................................................
  sqlitepager_unref(pP1);
  return SQLITE_OK;
}

/*
** Write meta-information back into the database.
*/
int sqlite3BtreeUpdateMeta(Btree *pBt, int idx, u32 iMeta){
  PageOne *pP1;
  int rc, i;
  if( !pBt->inTrans ){
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  pP1 = pBt->page1;
  rc = sqlitepager_write(pP1);
................................................................................
}
#endif

/*
** Return the pager associated with a BTree.  This routine is used for
** testing and debugging only.
*/
Pager *sqlite3BtreePager(Btree *pBt){
  return pBt->pPager;
}

/*
** This structure is passed around through all the sanity checking routines
** in order to keep track of some global state information.
*/
................................................................................
** a table.  nRoot is the number of entries in aRoot.
**
** If everything checks out, this routine returns NULL.  If something is
** amiss, an error message is written into memory obtained from malloc()
** and a pointer to that error message is returned.  The calling function
** is responsible for freeing the error message when it is done.
*/
char *sqlite3BtreeIntegrityCheck(Btree *pBt, int *aRoot, int nRoot){
  int i;
  int nRef;
  IntegrityCk sCheck;

  nRef = *sqlitepager_stats(pBt->pPager);
  if( lockBtree(pBt)!=SQLITE_OK ){
    return sqliteStrDup("Unable to acquire a read lock on the database");
................................................................................
  sqliteFree(sCheck.anRef);
  return sCheck.zErrMsg;
}

/*
** Return the full pathname of the underlying database file.
*/
const char *sqlite3BtreeGetFilename(Btree *pBt){
  assert( pBt->pPager!=0 );
  return sqlitepager_filename(pBt->pPager);
}

/*
** Copy the complete content of pBtFrom into pBtTo.  A transaction
** must be active for both files.
**
** The size of file pBtFrom may be reduced by this operation.
** If anything goes wrong, the transaction on pBtFrom is rolled back.
*/
int sqlite3BtreeCopyFile(Btree *pBtTo, Btree *pBtFrom){
  int rc = SQLITE_OK;
  Pgno i, nPage, nToPage;

  if( !pBtTo->inTrans || !pBtFrom->inTrans ) return SQLITE_ERROR;
  if( pBtTo->needSwab!=pBtFrom->needSwab ) return SQLITE_ERROR;
  if( pBtTo->pCursor ) return SQLITE_BUSY;
  memcpy(pBtTo->page1, pBtFrom->page1, SQLITE_USABLE_SIZE);
................................................................................
    sqlitepager_unref(pPage);
    sqlitepager_dont_write(pBtTo->pPager, i);
  }
  if( !rc && nPage<nToPage ){
    rc = sqlitepager_truncate(pBtTo->pPager, nPage);
  }
  if( rc ){
    sqlite3BtreeRollback(pBtTo);
  }
  return rc;  
}


















































Changes to src/btree.h.

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**    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.
**
** @(#) $Id: btree.h,v 1.36 2004/02/10 02:57:59 drh Exp $
*/
#ifndef _BTREE_H_
#define _BTREE_H_

/*
** Forward declarations of structure
*/
typedef struct Btree Btree;
typedef struct BtCursor BtCursor;
typedef struct BtOps BtOps;
typedef struct BtCursorOps BtCursorOps;




/*
** An instance of the following structure contains pointers to all
** methods against an open BTree.  Alternative BTree implementations
** (examples: file based versus in-memory) can be created by substituting
** different methods.  Users of the BTree cannot tell the difference.
**
** In C++ we could do this by defining a virtual base class and then
** creating subclasses for each different implementation.  But this is
** C not C++ so we have to be a little more explicit.
*/







struct BtOps {
    int (*Close)(Btree*);
    int (*SetCacheSize)(Btree*, int);
    int (*SetSafetyLevel)(Btree*, int);
    int (*BeginTrans)(Btree*);
    int (*Commit)(Btree*);
    int (*Rollback)(Btree*);

    int (*BeginCkpt)(Btree*);
    int (*CommitCkpt)(Btree*);
    int (*RollbackCkpt)(Btree*);
    int (*CreateTable)(Btree*, int*);
    int (*CreateIndex)(Btree*, int*);

    int (*DropTable)(Btree*, int);
    int (*ClearTable)(Btree*, int);
    int (*Cursor)(Btree*, int iTable, int wrFlag, BtCursor **ppCur);
    int (*GetMeta)(Btree*, int*);
    int (*UpdateMeta)(Btree*, int*);
    char *(*IntegrityCheck)(Btree*, int*, int);

    const char *(*GetFilename)(Btree*);
    int (*Copyfile)(Btree*,Btree*);
    struct Pager *(*Pager)(Btree*);
#ifdef SQLITE_TEST
    int (*PageDump)(Btree*, int, int);
#endif
};



/*
** An instance of this structure defines all of the methods that can
** be executed against a cursor.
*/
struct BtCursorOps {
    int (*Moveto)(BtCursor*, const void *pKey, int nKey, int *pRes);
    int (*Delete)(BtCursor*);
    int (*Insert)(BtCursor*, const void *pKey, int nKey,
                             const void *pData, int nData);
    int (*First)(BtCursor*, int *pRes);
    int (*Last)(BtCursor*, int *pRes);
    int (*Next)(BtCursor*, int *pRes);
    int (*Previous)(BtCursor*, int *pRes);



    int (*KeySize)(BtCursor*, int *pSize);
    int (*Key)(BtCursor*, int offset, int amt, char *zBuf);
    int (*KeyCompare)(BtCursor*, const void *pKey, int nKey,
                                 int nIgnore, int *pRes);
    int (*DataSize)(BtCursor*, int *pSize);
    int (*Data)(BtCursor*, int offset, int amt, char *zBuf);
    int (*CloseCursor)(BtCursor*);
#ifdef SQLITE_TEST
    int (*CursorDump)(BtCursor*, int*);
#endif
};

/*
** The number of 4-byte "meta" values contained on the first page of each
** database file.
*/
#define SQLITE_N_BTREE_META 10

int sqliteBtreeOpen(const char *zFilename, int mode, int nPg, Btree **ppBtree);
int sqliteRbtreeOpen(const char *zFilename, int mode, int nPg, Btree **ppBtree);

#define btOps(pBt) (*((BtOps **)(pBt)))
#define btCOps(pCur) (*((BtCursorOps **)(pCur)))

#define sqliteBtreeClose(pBt)              (btOps(pBt)->Close(pBt))
#define sqliteBtreeSetCacheSize(pBt, sz)   (btOps(pBt)->SetCacheSize(pBt, sz))
#define sqliteBtreeSetSafetyLevel(pBt, sl) (btOps(pBt)->SetSafetyLevel(pBt, sl))
#define sqliteBtreeBeginTrans(pBt)         (btOps(pBt)->BeginTrans(pBt))
#define sqliteBtreeCommit(pBt)             (btOps(pBt)->Commit(pBt))
#define sqliteBtreeRollback(pBt)           (btOps(pBt)->Rollback(pBt))
#define sqliteBtreeBeginCkpt(pBt)          (btOps(pBt)->BeginCkpt(pBt))
#define sqliteBtreeCommitCkpt(pBt)         (btOps(pBt)->CommitCkpt(pBt))
#define sqliteBtreeRollbackCkpt(pBt)       (btOps(pBt)->RollbackCkpt(pBt))
#define sqliteBtreeCreateTable(pBt,piTable)\
                (btOps(pBt)->CreateTable(pBt,piTable))
#define sqliteBtreeCreateIndex(pBt, piIndex)\
                (btOps(pBt)->CreateIndex(pBt, piIndex))
#define sqliteBtreeDropTable(pBt, iTable) (btOps(pBt)->DropTable(pBt, iTable))
#define sqliteBtreeClearTable(pBt, iTable)\
                (btOps(pBt)->ClearTable(pBt, iTable))
#define sqliteBtreeCursor(pBt, iTable, wrFlag, ppCur)\
                (btOps(pBt)->Cursor(pBt, iTable, wrFlag, ppCur))
#define sqliteBtreeMoveto(pCur, pKey, nKey, pRes)\
                (btCOps(pCur)->Moveto(pCur, pKey, nKey, pRes))
#define sqliteBtreeDelete(pCur)           (btCOps(pCur)->Delete(pCur))
#define sqliteBtreeInsert(pCur, pKey, nKey, pData, nData) \
                (btCOps(pCur)->Insert(pCur, pKey, nKey, pData, nData))
#define sqliteBtreeFirst(pCur, pRes)      (btCOps(pCur)->First(pCur, pRes))
#define sqliteBtreeLast(pCur, pRes)       (btCOps(pCur)->Last(pCur, pRes))
#define sqliteBtreeNext(pCur, pRes)       (btCOps(pCur)->Next(pCur, pRes))
#define sqliteBtreePrevious(pCur, pRes)   (btCOps(pCur)->Previous(pCur, pRes))
#define sqliteBtreeKeySize(pCur, pSize)   (btCOps(pCur)->KeySize(pCur, pSize) )
#define sqliteBtreeKey(pCur, offset, amt, zBuf)\
                (btCOps(pCur)->Key(pCur, offset, amt, zBuf))
#define sqliteBtreeKeyCompare(pCur, pKey, nKey, nIgnore, pRes)\
                (btCOps(pCur)->KeyCompare(pCur, pKey, nKey, nIgnore, pRes))
#define sqliteBtreeDataSize(pCur, pSize)  (btCOps(pCur)->DataSize(pCur, pSize))
#define sqliteBtreeData(pCur, offset, amt, zBuf)\
                (btCOps(pCur)->Data(pCur, offset, amt, zBuf))
#define sqliteBtreeCloseCursor(pCur)      (btCOps(pCur)->CloseCursor(pCur))
#define sqliteBtreeGetMeta(pBt, aMeta)    (btOps(pBt)->GetMeta(pBt, aMeta))
#define sqliteBtreeUpdateMeta(pBt, aMeta) (btOps(pBt)->UpdateMeta(pBt, aMeta))
#define sqliteBtreeIntegrityCheck(pBt, aRoot, nRoot)\
                (btOps(pBt)->IntegrityCheck(pBt, aRoot, nRoot))
#define sqliteBtreeGetFilename(pBt)       (btOps(pBt)->GetFilename(pBt))
#define sqliteBtreeCopyFile(pBt1, pBt2)   (btOps(pBt1)->Copyfile(pBt1, pBt2))
#define sqliteBtreePager(pBt)             (btOps(pBt)->Pager(pBt))

#ifdef SQLITE_TEST
#define sqliteBtreePageDump(pBt, pgno, recursive)\
                (btOps(pBt)->PageDump(pBt, pgno, recursive))
#define sqliteBtreeCursorDump(pCur, aResult)\
                (btCOps(pCur)->CursorDump(pCur, aResult))
int btree_native_byte_order;
#endif /* SQLITE_TEST */


#endif /* _BTREE_H_ */







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**    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.
**
** @(#) $Id: btree.h,v 1.37 2004/04/26 14:10:21 drh Exp $
*/
#ifndef _BTREE_H_
#define _BTREE_H_

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




int sqlite3BtreeOpen(const char *zFilename, Btree **, int nCache, int flags);

/* The flags parameter to sqlite3BtreeOpen can be the bitwise or of the
** following values.







*/
#define BTREE_OMIT_JOURNAL  1  /* Do not use journal.  No argument */
#define BTREE_MEMORY        2  /* In-memory DB.  No argument */

int sqlite3BtreeClose(Btree*);
int sqlite3BtreeSetCacheSize(Btree*,int);
int sqlite3BtreeSetSafetyLevel(Btree*,int);
int sqlite3BtreeBeginTrans(Btree*);
int sqlite3BtreeCommit(Btree*);
int sqlite3BtreeRollback(Btree*);
int sqlite3BtreeBeginStmt(Btree*);
int sqlite3BtreeCommitStmt(Btree*);
int sqlite3BtreeRollbackStmt(Btree*);
int sqlite3BtreeCreateTable(Btree*, int*, int flags);


/* The flags parameter to sqlite3BtreeCreateTable can be the bitwise OR
** of the following flags:
*/
#define BTREE_INTKEY     1      /* Table has only 64-bit integer keys */
#define BTREE_ZERODATA   2      /* Table has keys only - no data */

int sqlite3BtreeDropTable(Btree*, int);
int sqlite3BtreeClearTable(Btree*, int);

int sqlite3BtreeGetMeta(Btree*, int idx, u32 *pValue);
int sqlite3BtreeUpdateMeta(Btree*, int idx, u32 value);


int sqlite3BtreeCursor(
  Btree*,                              /* BTree containing table to open */
  int iTable,                          /* Index of root page */
  int wrFlag,                          /* 1 for writing.  0 for read-only */
  int(*)(void*,int,const void*,int,const void*),  /* Key comparison function */
  void*,                               /* First argument to compare function */

  BtCursor **ppCursor                  /* Returned cursor */
);


int sqlite3BtreeCursorClose(BtCursor*);



int sqlite3BtreeMoveto(BtCursor*, const void *pKey, u64 nKey, int *pRes);
int sqlite3BtreeDelete(BtCursor*);
int sqlite3BtreeInsert(BtCursor*, const void *pKey, u64 nKey,
                                  const void *pData, int nData);
int sqlite3BtreeFirst(BtCursor*, int *pRes);
int sqlite3BtreeLast(BtCursor*, int *pRes);
int sqlite3BtreeNext(BtCursor*, int *pRes);
int sqlite3BtreePrevious(BtCursor*, int *pRes);
int sqlite3BtreeKeySize(BtCursor*, u64 *pSize);
int sqlite3BtreeKey(BtCursor*, u32 offset, u32 amt, void*);
void *sqlite3BtreeKeyFetch(BtCursor*);
int sqlite3BtreeDataSize(BtCursor*, u32 *pSize);
int sqlite3BtreeData(BtCursor*, u32 offset, u32 amt, void*);











































































#endif /* _BTREE_H_ */

Changes to src/md5.c.

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*/
int Md5_Init(Tcl_Interp *interp){
  Tcl_CreateCommand(interp, "md5", (Tcl_CmdProc*)md5_cmd, 0, 0);
  Tcl_CreateCommand(interp, "md5file", (Tcl_CmdProc*)md5file_cmd, 0, 0);
  return TCL_OK;
}


/*
** During testing, the special md5sum() aggregate function is available.
** inside SQLite.  The following routines implement that function.
*/
static void md5step(sqlite_func *context, int argc, const char **argv){
  MD5Context *p;
  int i;
................................................................................
  MD5Final(digest,p);
  DigestToBase16(digest, zBuf);
  sqlite_set_result_string(context, zBuf, strlen(zBuf));
}
void Md5_Register(sqlite *db){
  sqlite_create_aggregate(db, "md5sum", -1, md5step, md5finalize, 0);
}








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int Md5_Init(Tcl_Interp *interp){
  Tcl_CreateCommand(interp, "md5", (Tcl_CmdProc*)md5_cmd, 0, 0);
  Tcl_CreateCommand(interp, "md5file", (Tcl_CmdProc*)md5file_cmd, 0, 0);
  return TCL_OK;
}

#if 0
/*
** During testing, the special md5sum() aggregate function is available.
** inside SQLite.  The following routines implement that function.
*/
static void md5step(sqlite_func *context, int argc, const char **argv){
  MD5Context *p;
  int i;
................................................................................
  MD5Final(digest,p);
  DigestToBase16(digest, zBuf);
  sqlite_set_result_string(context, zBuf, strlen(zBuf));
}
void Md5_Register(sqlite *db){
  sqlite_create_aggregate(db, "md5sum", -1, md5step, md5finalize, 0);
}
#endif

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** 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 1.101 2004/02/25 02:20:41 drh Exp $
*/
#include "os.h"         /* Must be first to enable large file support */
#include "sqliteInt.h"
#include "pager.h"
#include <assert.h>
#include <string.h>

................................................................................


/*
** Each in-memory image of a page begins with the following header.
** This header is only visible to this pager module.  The client
** code that calls pager sees only the data that follows the header.
**
** Client code should call sqlitepager_write() on a page prior to making
** any modifications to that page.  The first time sqlitepager_write()
** is called, the original page contents are written into the rollback
** journal and PgHdr.inJournal and PgHdr.needSync are set.  Later, once
** the journal page has made it onto the disk surface, PgHdr.needSync
** is cleared.  The modified page cannot be written back into the original
** database file until the journal pages has been synced to disk and the
** PgHdr.needSync has been cleared.
**
** The PgHdr.dirty flag is set when sqlitepager_write() is called and
** is cleared again when the page content is written back to the original
** database file.
*/
typedef struct PgHdr PgHdr;
struct PgHdr {
  Pager *pPager;                 /* The pager to which this page belongs */
  Pgno pgno;                     /* The page number for this page */
................................................................................
#define JOURNAL_PG_SZ(X) \
   (SQLITE_PAGE_SIZE + sizeof(Pgno) + ((X)>=3)*sizeof(u32))

/*
** Enable reference count tracking here:
*/
#ifdef SQLITE_TEST
  int pager_refinfo_enable = 0;
  static void pager_refinfo(PgHdr *p){
    static int cnt = 0;
    if( !pager_refinfo_enable ) return;
    printf(
       "REFCNT: %4d addr=0x%08x nRef=%d\n",
       p->pgno, (int)PGHDR_TO_DATA(p), p->nRef
    );
    cnt++;   /* Something to set a breakpoint on */
  }
# define REFINFO(X)  pager_refinfo(X)
................................................................................
}

/*
** Add or remove a page from the list of all pages that are in the
** checkpoint journal.
**
** The Pager keeps a separate list of pages that are currently in
** the checkpoint journal.  This helps the sqlitepager_ckpt_commit()
** routine run MUCH faster for the common case where there are many
** pages in memory but only a few are in the checkpoint journal.
*/
static void page_add_to_ckpt_list(PgHdr *pPg){
  Pager *pPager = pPg->pPager;
  if( pPg->inCkpt ) return;
  assert( pPg->pPrevCkpt==0 && pPg->pNextCkpt==0 );
  pPg->pPrevCkpt = 0;
  if( pPager->pCkpt ){
    pPager->pCkpt->pPrevCkpt = pPg;
  }
  pPg->pNextCkpt = pPager->pCkpt;
  pPager->pCkpt = pPg;
  pPg->inCkpt = 1;
}
static void page_remove_from_ckpt_list(PgHdr *pPg){
  if( !pPg->inCkpt ) return;
  if( pPg->pPrevCkpt ){
    assert( pPg->pPrevCkpt->pNextCkpt==pPg );
    pPg->pPrevCkpt->pNextCkpt = pPg->pNextCkpt;
  }else{
    assert( pPg->pPager->pCkpt==pPg );
    pPg->pPager->pCkpt = pPg->pNextCkpt;
................................................................................
  pPager->pFirst = 0;
  pPager->pFirstSynced = 0;
  pPager->pLast = 0;
  pPager->pAll = 0;
  memset(pPager->aHash, 0, sizeof(pPager->aHash));
  pPager->nPage = 0;
  if( pPager->state>=SQLITE_WRITELOCK ){
    sqlitepager_rollback(pPager);
  }
  sqliteOsUnlock(&pPager->fd);
  pPager->state = SQLITE_UNLOCK;
  pPager->dbSize = -1;
  pPager->nRef = 0;
  assert( pPager->journalOpen==0 );
}
................................................................................
** This might give a performance improvement on windows where opening
** a file is an expensive operation.
*/
static int pager_unwritelock(Pager *pPager){
  int rc;
  PgHdr *pPg;
  if( pPager->state<SQLITE_WRITELOCK ) return SQLITE_OK;
  sqlitepager_ckpt_commit(pPager);
  if( pPager->ckptOpen ){
    sqliteOsClose(&pPager->cpfd);
    pPager->ckptOpen = 0;
  }
  if( pPager->journalOpen ){
    sqliteOsClose(&pPager->jfd);
    pPager->journalOpen = 0;
................................................................................
**         the checkpoint is stored in pPager->ckptSize, not in the
**         journal file itself.
**
**    (2)  In addition to playing back the checkpoint journal, also
**         playback all pages of the transaction journal beginning
**         at offset pPager->ckptJSize.
*/
static int pager_ckpt_playback(Pager *pPager){
  off_t szJ;               /* Size of the full journal */
  int nRec;                /* Number of Records */
  int i;                   /* Loop counter */
  int rc;

  /* Truncate the database back to its original size.
  */
................................................................................
  ** database file.  Note that the checkpoint journal always uses format
  ** 2 instead of format 3 since it does not need to be concerned with
  ** power failures corrupting the journal and can thus omit the checksums.
  */
  for(i=nRec-1; i>=0; i--){
    rc = pager_playback_one_page(pPager, &pPager->cpfd, 2);
    assert( rc!=SQLITE_DONE );
    if( rc!=SQLITE_OK ) goto end_ckpt_playback;
  }

  /* Figure out how many pages need to be copied out of the transaction
  ** journal.
  */
  rc = sqliteOsSeek(&pPager->jfd, pPager->ckptJSize);
  if( rc!=SQLITE_OK ){
    goto end_ckpt_playback;
  }
  rc = sqliteOsFileSize(&pPager->jfd, &szJ);
  if( rc!=SQLITE_OK ){
    goto end_ckpt_playback;
  }
  nRec = (szJ - pPager->ckptJSize)/JOURNAL_PG_SZ(journal_format);
  for(i=nRec-1; i>=0; i--){
    rc = pager_playback_one_page(pPager, &pPager->jfd, journal_format);
    if( rc!=SQLITE_OK ){
      assert( rc!=SQLITE_DONE );
      goto end_ckpt_playback;
    }
  }
  
end_ckpt_playback:
  if( rc!=SQLITE_OK ){
    pPager->errMask |= PAGER_ERR_CORRUPT;
    rc = SQLITE_CORRUPT;
  }
  return rc;
}

................................................................................
** The maximum number is the absolute value of the mxPage parameter.
** If mxPage is negative, the noSync flag is also set.  noSync bypasses
** calls to sqliteOsSync().  The pager runs much faster with noSync on,
** but if the operating system crashes or there is an abrupt power 
** failure, the database file might be left in an inconsistent and
** unrepairable state.  
*/
void sqlitepager_set_cachesize(Pager *pPager, int mxPage){
  if( mxPage>=0 ){
    pPager->noSync = pPager->tempFile;
    if( pPager->noSync==0 ) pPager->needSync = 0;
  }else{
    pPager->noSync = 1;
    mxPage = -mxPage;
  }
................................................................................
**              single disk sector is atomic, then this mode provides
**              assurance that the journal will not be corrupted to the
**              point of causing damage to the database during rollback.
**
** Numeric values associated with these states are OFF==1, NORMAL=2,
** and FULL=3.
*/
void sqlitepager_set_safety_level(Pager *pPager, int level){
  pPager->noSync =  level==1 || pPager->tempFile;
  pPager->fullSync = level==3 && !pPager->tempFile;
  if( pPager->noSync==0 ) pPager->needSync = 0;
}

/*
** Open a temporary file.  Write the name of the file into zName
................................................................................
** (zName must be at least SQLITE_TEMPNAME_SIZE bytes long.)  Write
** the file descriptor into *fd.  Return SQLITE_OK on success or some
** other error code if we fail.
**
** The OS will automatically delete the temporary file when it is
** closed.
*/
static int sqlitepager_opentemp(char *zFile, OsFile *fd){
  int cnt = 8;
  int rc;
  do{
    cnt--;
    sqliteOsTempFileName(zFile);
    rc = sqliteOsOpenExclusive(zFile, fd, 1);
  }while( cnt>0 && rc!=SQLITE_OK );
  return rc;
}

/*
** Create a new page cache and put a pointer to the page cache in *ppPager.
** The file to be cached need not exist.  The file is not locked until
** the first call to sqlitepager_get() and is only held open until the
** last page is released using sqlitepager_unref().
**
** If zFilename is NULL then a randomly-named temporary file is created
** and used as the file to be cached.  The file will be deleted
** automatically when it is closed.
*/
int sqlitepager_open(
  Pager **ppPager,         /* Return the Pager structure here */
  const char *zFilename,   /* Name of the database file to open */
  int mxPage,              /* Max number of in-memory cache pages */
  int nExtra,              /* Extra bytes append to each in-memory page */
  int useJournal           /* TRUE to use a rollback journal on this file */
){
  Pager *pPager;
................................................................................
    return SQLITE_NOMEM;
  }
  if( zFilename && zFilename[0] ){
    zFullPathname = sqliteOsFullPathname(zFilename);
    rc = sqliteOsOpenReadWrite(zFullPathname, &fd, &readOnly);
    tempFile = 0;
  }else{
    rc = sqlitepager_opentemp(zTemp, &fd);
    zFilename = zTemp;
    zFullPathname = sqliteOsFullPathname(zFilename);
    tempFile = 1;
  }
  if( sqlite_malloc_failed ){
    return SQLITE_NOMEM;
  }
................................................................................
}

/*
** Set the destructor for this pager.  If not NULL, the destructor is called
** when the reference count on each page reaches zero.  The destructor can
** be used to clean up information in the extra segment appended to each page.
**
** The destructor is not called as a result sqlitepager_close().  
** Destructors are only called by sqlitepager_unref().
*/
void sqlitepager_set_destructor(Pager *pPager, void (*xDesc)(void*)){
  pPager->xDestructor = xDesc;
}

/*
** Return the total number of pages in the disk file associated with
** pPager.
*/
int sqlitepager_pagecount(Pager *pPager){
  off_t n;
  assert( pPager!=0 );
  if( pPager->dbSize>=0 ){
    return pPager->dbSize;
  }
  if( sqliteOsFileSize(&pPager->fd, &n)!=SQLITE_OK ){
    pPager->errMask |= PAGER_ERR_DISK;
................................................................................
** Forward declaration
*/
static int syncJournal(Pager*);

/*
** Truncate the file to the number of pages specified.
*/
int sqlitepager_truncate(Pager *pPager, Pgno nPage){
  int rc;
  if( pPager->dbSize<0 ){
    sqlitepager_pagecount(pPager);
  }
  if( pPager->errMask!=0 ){
    rc = pager_errcode(pPager);
    return rc;
  }
  if( nPage>=(unsigned)pPager->dbSize ){
    return SQLITE_OK;
................................................................................
**
** If a transaction was in progress when this routine is called, that
** transaction is rolled back.  All outstanding pages are invalidated
** and their memory is freed.  Any attempt to use a page associated
** with this page cache after this function returns will likely
** result in a coredump.
*/
int sqlitepager_close(Pager *pPager){
  PgHdr *pPg, *pNext;
  switch( pPager->state ){
    case SQLITE_WRITELOCK: {
      sqlitepager_rollback(pPager);
      sqliteOsUnlock(&pPager->fd);
      assert( pPager->journalOpen==0 );
      break;
    }
    case SQLITE_READLOCK: {
      sqliteOsUnlock(&pPager->fd);
      break;
................................................................................
  sqliteFree(pPager);
  return SQLITE_OK;
}

/*
** Return the page number for the given page data.
*/
Pgno sqlitepager_pagenumber(void *pData){
  PgHdr *p = DATA_TO_PGHDR(pData);
  return p->pgno;
}

/*
** Increment the reference count for a page.  If the page is
** currently on the freelist (the reference count is zero) then
................................................................................
  REFINFO(pPg);
}

/*
** Increment the reference count for a page.  The input pointer is
** a reference to the page data.
*/
int sqlitepager_ref(void *pData){
  PgHdr *pPg = DATA_TO_PGHDR(pData);
  page_ref(pPg);
  return SQLITE_OK;
}

/*
** Sync the journal.  In other words, make sure all the pages that have
................................................................................
** read occurs and the memory image of the page is initialized to
** all zeros.  The extra data appended to a page is always initialized
** to zeros the first time a page is loaded into memory.
**
** The acquisition might fail for several reasons.  In all cases,
** an appropriate error code is returned and *ppPage is set to NULL.
**
** See also sqlitepager_lookup().  Both this routine and _lookup() attempt
** to find a page in the in-memory cache first.  If the page is not already
** in memory, this routine goes to disk to read it in whereas _lookup()
** just returns 0.  This routine acquires a read-lock the first time it
** has to go to disk, and could also playback an old journal if necessary.
** Since _lookup() never goes to disk, it never has to deal with locks
** or journal files.
*/
int sqlitepager_get(Pager *pPager, Pgno pgno, void **ppPage){
  PgHdr *pPg;
  int rc;

  /* Make sure we have not hit any critical errors.
  */ 
  assert( pPager!=0 );
  assert( pgno!=0 );
................................................................................
      ** on the journal file then fsync the journal file.  This is a
      ** very slow operation, so we work hard to avoid it.  But sometimes
      ** it can't be helped.
      */
      if( pPg==0 ){
        int rc = syncJournal(pPager);
        if( rc!=0 ){
          sqlitepager_rollback(pPager);
          return SQLITE_IOERR;
        }
        pPg = pPager->pFirst;
      }
      assert( pPg->nRef==0 );

      /* Write the page to the database file if it is dirty.
      */
      if( pPg->dirty ){
        assert( pPg->needSync==0 );
        pPg->pDirty = 0;
        rc = pager_write_pagelist( pPg );
        if( rc!=SQLITE_OK ){
          sqlitepager_rollback(pPager);
          return SQLITE_IOERR;
        }
      }
      assert( pPg->dirty==0 );

      /* If the page we are recycling is marked as alwaysRollback, then
      ** set the global alwaysRollback flag, thus disabling the
................................................................................
      pPg->needSync = 0;
    }else{
      pPg->inJournal = 0;
      pPg->needSync = 0;
    }
    if( pPager->aInCkpt && (int)pgno<=pPager->ckptSize
             && (pPager->aInCkpt[pgno/8] & (1<<(pgno&7)))!=0 ){
      page_add_to_ckpt_list(pPg);
    }else{
      page_remove_from_ckpt_list(pPg);
    }
    pPg->dirty = 0;
    pPg->nRef = 1;
    REFINFO(pPg);
    pPager->nRef++;
    h = pager_hash(pgno);
    pPg->pNextHash = pPager->aHash[h];
................................................................................
    if( pPg->pNextHash ){
      assert( pPg->pNextHash->pPrevHash==0 );
      pPg->pNextHash->pPrevHash = pPg;
    }
    if( pPager->nExtra>0 ){
      memset(PGHDR_TO_EXTRA(pPg), 0, pPager->nExtra);
    }
    if( pPager->dbSize<0 ) sqlitepager_pagecount(pPager);
    if( pPager->errMask!=0 ){
      sqlitepager_unref(PGHDR_TO_DATA(pPg));
      rc = pager_errcode(pPager);
      return rc;
    }
    if( pPager->dbSize<(int)pgno ){
      memset(PGHDR_TO_DATA(pPg), 0, SQLITE_PAGE_SIZE);
    }else{
      int rc;
................................................................................
      rc = sqliteOsRead(&pPager->fd, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE);
      TRACE2("FETCH %d\n", pPg->pgno);
      CODEC(pPager, PGHDR_TO_DATA(pPg), pPg->pgno, 3);
      if( rc!=SQLITE_OK ){
        off_t fileSize;
        if( sqliteOsFileSize(&pPager->fd,&fileSize)!=SQLITE_OK
               || fileSize>=pgno*SQLITE_PAGE_SIZE ){
          sqlitepager_unref(PGHDR_TO_DATA(pPg));
          return rc;
        }else{
          memset(PGHDR_TO_DATA(pPg), 0, SQLITE_PAGE_SIZE);
        }
      }
    }
  }else{
................................................................................
}

/*
** Acquire a page if it is already in the in-memory cache.  Do
** not read the page from disk.  Return a pointer to the page,
** or 0 if the page is not in cache.
**
** See also sqlitepager_get().  The difference between this routine
** and sqlitepager_get() is that _get() will go to the disk and read
** in the page if the page is not already in cache.  This routine
** returns NULL if the page is not in cache or if a disk I/O error 
** has ever happened.
*/
void *sqlitepager_lookup(Pager *pPager, Pgno pgno){
  PgHdr *pPg;

  assert( pPager!=0 );
  assert( pgno!=0 );
  if( pPager->errMask & ~(PAGER_ERR_FULL) ){
    return 0;
  }
................................................................................
** Release a page.
**
** If the number of references to the page drop to zero, then the
** page is added to the LRU list.  When all references to all pages
** are released, a rollback occurs and the lock on the database is
** removed.
*/
int sqlitepager_unref(void *pData){
  PgHdr *pPg;

  /* Decrement the reference count for this page
  */
  pPg = DATA_TO_PGHDR(pData);
  assert( pPg->nRef>0 );
  pPg->nRef--;
................................................................................
** write lock if anything goes wrong.
*/
static int pager_open_journal(Pager *pPager){
  int rc;
  assert( pPager->state==SQLITE_WRITELOCK );
  assert( pPager->journalOpen==0 );
  assert( pPager->useJournal );
  sqlitepager_pagecount(pPager);
  pPager->aInJournal = sqliteMalloc( pPager->dbSize/8 + 1 );
  if( pPager->aInJournal==0 ){
    sqliteOsReadLock(&pPager->fd);
    pPager->state = SQLITE_READLOCK;
    return SQLITE_NOMEM;
  }
  rc = sqliteOsOpenExclusive(pPager->zJournal, &pPager->jfd,pPager->tempFile);
................................................................................
    assert( journal_format==JOURNAL_FORMAT_1 );
    rc = sqliteOsWrite(&pPager->jfd, aJournalMagic1, sizeof(aJournalMagic1));
  }
  if( rc==SQLITE_OK ){
    rc = write32bits(&pPager->jfd, pPager->dbSize);
  }
  if( pPager->ckptAutoopen && rc==SQLITE_OK ){
    rc = sqlitepager_ckpt_begin(pPager);
  }
  if( rc!=SQLITE_OK ){
    rc = pager_unwritelock(pPager);
    if( rc==SQLITE_OK ){
      rc = SQLITE_FULL;
    }
  }
................................................................................
  return rc;  
}

/*
** Acquire a write-lock on the database.  The lock is removed when
** the any of the following happen:
**
**   *  sqlitepager_commit() is called.
**   *  sqlitepager_rollback() is called.
**   *  sqlitepager_close() is called.
**   *  sqlitepager_unref() is called to on every outstanding page.
**
** The parameter to this routine is a pointer to any open page of the
** database file.  Nothing changes about the page - it is used merely
** to acquire a pointer to the Pager structure and as proof that there
** is already a read-lock on the database.
**
** A journal file is opened if this is not a temporary file.  For
** temporary files, the opening of the journal file is deferred until
** there is an actual need to write to the journal.
**
** If the database is already write-locked, this routine is a no-op.
*/
int sqlitepager_begin(void *pData){
  PgHdr *pPg = DATA_TO_PGHDR(pData);
  Pager *pPager = pPg->pPager;
  int rc = SQLITE_OK;
  assert( pPg->nRef>0 );
  assert( pPager->state!=SQLITE_UNLOCK );
  if( pPager->state==SQLITE_READLOCK ){
    assert( pPager->aInJournal==0 );
................................................................................
** lock could not be acquired, this routine returns SQLITE_BUSY.  The
** calling routine must check for that return value and be careful not to
** change any page data until this routine returns SQLITE_OK.
**
** If the journal file could not be written because the disk is full,
** then this routine returns SQLITE_FULL and does an immediate rollback.
** All subsequent write attempts also return SQLITE_FULL until there
** is a call to sqlitepager_commit() or sqlitepager_rollback() to
** reset.
*/
int sqlitepager_write(void *pData){
  PgHdr *pPg = DATA_TO_PGHDR(pData);
  Pager *pPager = pPg->pPager;
  int rc = SQLITE_OK;

  /* Check for errors
  */
  if( pPager->errMask ){ 
................................................................................
  ** written to the transaction journal or the ckeckpoint journal
  ** or both.
  **
  ** First check to see that the transaction journal exists and
  ** create it if it does not.
  */
  assert( pPager->state!=SQLITE_UNLOCK );
  rc = sqlitepager_begin(pData);
  if( rc!=SQLITE_OK ){
    return rc;
  }
  assert( pPager->state==SQLITE_WRITELOCK );
  if( !pPager->journalOpen && pPager->useJournal ){
    rc = pager_open_journal(pPager);
    if( rc!=SQLITE_OK ) return rc;
................................................................................
      rc = sqliteOsWrite(&pPager->jfd, &((char*)pData)[-4], szPg);
      TRACE3("JOURNAL %d %d\n", pPg->pgno, pPg->needSync);
      CODEC(pPager, pData, pPg->pgno, 0);
      if( journal_format>=JOURNAL_FORMAT_3 ){
        *(u32*)PGHDR_TO_EXTRA(pPg) = saved;
      }
      if( rc!=SQLITE_OK ){
        sqlitepager_rollback(pPager);
        pPager->errMask |= PAGER_ERR_FULL;
        return rc;
      }
      pPager->nRec++;
      assert( pPager->aInJournal!=0 );
      pPager->aInJournal[pPg->pgno/8] |= 1<<(pPg->pgno&7);
      pPg->needSync = !pPager->noSync;
      pPg->inJournal = 1;
      if( pPager->ckptInUse ){
        pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
        page_add_to_ckpt_list(pPg);
      }
    }else{
      pPg->needSync = !pPager->journalStarted && !pPager->noSync;
      TRACE3("APPEND %d %d\n", pPg->pgno, pPg->needSync);
    }
    if( pPg->needSync ){
      pPager->needSync = 1;
................................................................................
    assert( pPg->inJournal || (int)pPg->pgno>pPager->origDbSize );
    store32bits(pPg->pgno, pPg, -4);
    CODEC(pPager, pData, pPg->pgno, 7);
    rc = sqliteOsWrite(&pPager->cpfd, &((char*)pData)[-4], SQLITE_PAGE_SIZE+4);
    TRACE2("CKPT-JOURNAL %d\n", pPg->pgno);
    CODEC(pPager, pData, pPg->pgno, 0);
    if( rc!=SQLITE_OK ){
      sqlitepager_rollback(pPager);
      pPager->errMask |= PAGER_ERR_FULL;
      return rc;
    }
    pPager->ckptNRec++;
    assert( pPager->aInCkpt!=0 );
    pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
    page_add_to_ckpt_list(pPg);
  }

  /* Update the database size and return.
  */
  if( pPager->dbSize<(int)pPg->pgno ){
    pPager->dbSize = pPg->pgno;
  }
  return rc;
}

/*
** Return TRUE if the page given in the argument was previously passed
** to sqlitepager_write().  In other words, return TRUE if it is ok
** to change the content of the page.
*/
int sqlitepager_iswriteable(void *pData){
  PgHdr *pPg = DATA_TO_PGHDR(pData);
  return pPg->dirty;
}

/*
** Replace the content of a single page with the information in the third
** argument.
*/
int sqlitepager_overwrite(Pager *pPager, Pgno pgno, void *pData){
  void *pPage;
  int rc;

  rc = sqlitepager_get(pPager, pgno, &pPage);
  if( rc==SQLITE_OK ){
    rc = sqlitepager_write(pPage);
    if( rc==SQLITE_OK ){
      memcpy(pPage, pData, SQLITE_PAGE_SIZE);
    }
    sqlitepager_unref(pPage);
  }
  return rc;
}

/*
** A call to this routine tells the pager that it is not necessary to
** write the information on page "pgno" back to the disk, even though
................................................................................
** that page might be marked as dirty.
**
** The overlying software layer calls this routine when all of the data
** on the given page is unused.  The pager marks the page as clean so
** that it does not get written to disk.
**
** Tests show that this optimization, together with the
** sqlitepager_dont_rollback() below, more than double the speed
** of large INSERT operations and quadruple the speed of large DELETEs.
**
** When this routine is called, set the alwaysRollback flag to true.
** Subsequent calls to sqlitepager_dont_rollback() for the same page
** will thereafter be ignored.  This is necessary to avoid a problem
** where a page with data is added to the freelist during one part of
** a transaction then removed from the freelist during a later part
** of the same transaction and reused for some other purpose.  When it
** is first added to the freelist, this routine is called.  When reused,
** the dont_rollback() routine is called.  But because the page contains
** critical data, we still need to be sure it gets rolled back in spite
** of the dont_rollback() call.
*/
void sqlitepager_dont_write(Pager *pPager, Pgno pgno){
  PgHdr *pPg;

  pPg = pager_lookup(pPager, pgno);
  pPg->alwaysRollback = 1;
  if( pPg && pPg->dirty ){
    if( pPager->dbSize==(int)pPg->pgno && pPager->origDbSize<pPager->dbSize ){
      /* If this pages is the last page in the file and the file has grown
................................................................................

/*
** A call to this routine tells the pager that if a rollback occurs,
** it is not necessary to restore the data on the given page.  This
** means that the pager does not have to record the given page in the
** rollback journal.
*/
void sqlitepager_dont_rollback(void *pData){
  PgHdr *pPg = DATA_TO_PGHDR(pData);
  Pager *pPager = pPg->pPager;

  if( pPager->state!=SQLITE_WRITELOCK || pPager->journalOpen==0 ) return;
  if( pPg->alwaysRollback || pPager->alwaysRollback ) return;
  if( !pPg->inJournal && (int)pPg->pgno <= pPager->origDbSize ){
    assert( pPager->aInJournal!=0 );
    pPager->aInJournal[pPg->pgno/8] |= 1<<(pPg->pgno&7);
    pPg->inJournal = 1;
    if( pPager->ckptInUse ){
      pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
      page_add_to_ckpt_list(pPg);
    }
    TRACE2("DONT_ROLLBACK %d\n", pPg->pgno);
  }
  if( pPager->ckptInUse && !pPg->inCkpt && (int)pPg->pgno<=pPager->ckptSize ){
    assert( pPg->inJournal || (int)pPg->pgno>pPager->origDbSize );
    assert( pPager->aInCkpt!=0 );
    pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
    page_add_to_ckpt_list(pPg);
  }
}

/*
** Commit all changes to the database and release the write lock.
**
** If the commit fails for any reason, a rollback attempt is made
** and an error code is returned.  If the commit worked, SQLITE_OK
** is returned.
*/
int sqlitepager_commit(Pager *pPager){
  int rc;
  PgHdr *pPg;

  if( pPager->errMask==PAGER_ERR_FULL ){
    rc = sqlitepager_rollback(pPager);
    if( rc==SQLITE_OK ){
      rc = SQLITE_FULL;
    }
    return rc;
  }
  if( pPager->errMask!=0 ){
    rc = pager_errcode(pPager);
................................................................................
  rc = pager_unwritelock(pPager);
  pPager->dbSize = -1;
  return rc;

  /* Jump here if anything goes wrong during the commit process.
  */
commit_abort:
  rc = sqlitepager_rollback(pPager);
  if( rc==SQLITE_OK ){
    rc = SQLITE_FULL;
  }
  return rc;
}

/*
................................................................................
** This routine cannot fail unless some other process is not following
** the correct locking protocol (SQLITE_PROTOCOL) or unless some other
** process is writing trash into the journal file (SQLITE_CORRUPT) or
** unless a prior malloc() failed (SQLITE_NOMEM).  Appropriate error
** codes are returned for all these occasions.  Otherwise,
** SQLITE_OK is returned.
*/
int sqlitepager_rollback(Pager *pPager){
  int rc;
  TRACE1("ROLLBACK\n");
  if( !pPager->dirtyFile || !pPager->journalOpen ){
    rc = pager_unwritelock(pPager);
    pPager->dbSize = -1;
    return rc;
  }
................................................................................
  return rc;
}

/*
** Return TRUE if the database file is opened read-only.  Return FALSE
** if the database is (in theory) writable.
*/
int sqlitepager_isreadonly(Pager *pPager){
  return pPager->readOnly;
}

/*
** This routine is used for testing and analysis only.
*/
int *sqlitepager_stats(Pager *pPager){
  static int a[9];
  a[0] = pPager->nRef;
  a[1] = pPager->nPage;
  a[2] = pPager->mxPage;
  a[3] = pPager->dbSize;
  a[4] = pPager->state;
  a[5] = pPager->errMask;
................................................................................
/*
** Set the checkpoint.
**
** This routine should be called with the transaction journal already
** open.  A new checkpoint journal is created that can be used to rollback
** changes of a single SQL command within a larger transaction.
*/
int sqlitepager_ckpt_begin(Pager *pPager){
  int rc;
  char zTemp[SQLITE_TEMPNAME_SIZE];
  if( !pPager->journalOpen ){
    pPager->ckptAutoopen = 1;
    return SQLITE_OK;
  }
  assert( pPager->journalOpen );
................................................................................
  assert( pPager->ckptJSize == 
    pPager->nRec*JOURNAL_PG_SZ(journal_format)+JOURNAL_HDR_SZ(journal_format) );
#endif
  pPager->ckptJSize = pPager->nRec*JOURNAL_PG_SZ(journal_format)
                         + JOURNAL_HDR_SZ(journal_format);
  pPager->ckptSize = pPager->dbSize;
  if( !pPager->ckptOpen ){
    rc = sqlitepager_opentemp(zTemp, &pPager->cpfd);
    if( rc ) goto ckpt_begin_failed;
    pPager->ckptOpen = 1;
    pPager->ckptNRec = 0;
  }
  pPager->ckptInUse = 1;
  return SQLITE_OK;
 
................................................................................
  }
  return rc;
}

/*
** Commit a checkpoint.
*/
int sqlitepager_ckpt_commit(Pager *pPager){
  if( pPager->ckptInUse ){
    PgHdr *pPg, *pNext;
    sqliteOsSeek(&pPager->cpfd, 0);
    /* sqliteOsTruncate(&pPager->cpfd, 0); */
    pPager->ckptNRec = 0;
    pPager->ckptInUse = 0;
    sqliteFree( pPager->aInCkpt );
................................................................................
  pPager->ckptAutoopen = 0;
  return SQLITE_OK;
}

/*
** Rollback a checkpoint.
*/
int sqlitepager_ckpt_rollback(Pager *pPager){
  int rc;
  if( pPager->ckptInUse ){
    rc = pager_ckpt_playback(pPager);
    sqlitepager_ckpt_commit(pPager);
  }else{
    rc = SQLITE_OK;
  }
  pPager->ckptAutoopen = 0;
  return rc;
}

/*
** Return the full pathname of the database file.
*/
const char *sqlitepager_filename(Pager *pPager){
  return pPager->zFilename;
}

/*
** Set the codec for this pager
*/
void sqlitepager_set_codec(
  Pager *pPager,
  void (*xCodec)(void*,void*,Pgno,int),
  void *pCodecArg
){
  pPager->xCodec = xCodec;
  pPager->pCodecArg = pCodecArg;
}

#ifdef SQLITE_TEST
/*
** Print a listing of all referenced pages and their ref count.
*/
void sqlitepager_refdump(Pager *pPager){
  PgHdr *pPg;
  for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
    if( pPg->nRef<=0 ) continue;
    printf("PAGE %3d addr=0x%08x nRef=%d\n", 
       pPg->pgno, (int)PGHDR_TO_DATA(pPg), pPg->nRef);
  }
}
#endif







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** 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 1.102 2004/04/26 14:10:21 drh Exp $
*/
#include "os.h"         /* Must be first to enable large file support */
#include "sqliteInt.h"
#include "pager.h"
#include <assert.h>
#include <string.h>

................................................................................


/*
** Each in-memory image of a page begins with the following header.
** This header is only visible to this pager module.  The client
** code that calls pager sees only the data that follows the header.
**
** Client code should call sqlite3pager_write() on a page prior to making
** any modifications to that page.  The first time sqlite3pager_write()
** is called, the original page contents are written into the rollback
** journal and PgHdr.inJournal and PgHdr.needSync are set.  Later, once
** the journal page has made it onto the disk surface, PgHdr.needSync
** is cleared.  The modified page cannot be written back into the original
** database file until the journal pages has been synced to disk and the
** PgHdr.needSync has been cleared.
**
** The PgHdr.dirty flag is set when sqlite3pager_write() is called and
** is cleared again when the page content is written back to the original
** database file.
*/
typedef struct PgHdr PgHdr;
struct PgHdr {
  Pager *pPager;                 /* The pager to which this page belongs */
  Pgno pgno;                     /* The page number for this page */
................................................................................
#define JOURNAL_PG_SZ(X) \
   (SQLITE_PAGE_SIZE + sizeof(Pgno) + ((X)>=3)*sizeof(u32))

/*
** Enable reference count tracking here:
*/
#ifdef SQLITE_TEST
  int pager3_refinfo_enable = 0;
  static void pager_refinfo(PgHdr *p){
    static int cnt = 0;
    if( !pager3_refinfo_enable ) return;
    printf(
       "REFCNT: %4d addr=0x%08x nRef=%d\n",
       p->pgno, (int)PGHDR_TO_DATA(p), p->nRef
    );
    cnt++;   /* Something to set a breakpoint on */
  }
# define REFINFO(X)  pager_refinfo(X)
................................................................................
}

/*
** Add or remove a page from the list of all pages that are in the
** checkpoint journal.
**
** The Pager keeps a separate list of pages that are currently in
** the checkpoint journal.  This helps the sqlite3pager_stmt_commit()
** routine run MUCH faster for the common case where there are many
** pages in memory but only a few are in the checkpoint journal.
*/
static void page_add_to_stmt_list(PgHdr *pPg){
  Pager *pPager = pPg->pPager;
  if( pPg->inCkpt ) return;
  assert( pPg->pPrevCkpt==0 && pPg->pNextCkpt==0 );
  pPg->pPrevCkpt = 0;
  if( pPager->pCkpt ){
    pPager->pCkpt->pPrevCkpt = pPg;
  }
  pPg->pNextCkpt = pPager->pCkpt;
  pPager->pCkpt = pPg;
  pPg->inCkpt = 1;
}
static void page_remove_from_stmt_list(PgHdr *pPg){
  if( !pPg->inCkpt ) return;
  if( pPg->pPrevCkpt ){
    assert( pPg->pPrevCkpt->pNextCkpt==pPg );
    pPg->pPrevCkpt->pNextCkpt = pPg->pNextCkpt;
  }else{
    assert( pPg->pPager->pCkpt==pPg );
    pPg->pPager->pCkpt = pPg->pNextCkpt;
................................................................................
  pPager->pFirst = 0;
  pPager->pFirstSynced = 0;
  pPager->pLast = 0;
  pPager->pAll = 0;
  memset(pPager->aHash, 0, sizeof(pPager->aHash));
  pPager->nPage = 0;
  if( pPager->state>=SQLITE_WRITELOCK ){
    sqlite3pager_rollback(pPager);
  }
  sqliteOsUnlock(&pPager->fd);
  pPager->state = SQLITE_UNLOCK;
  pPager->dbSize = -1;
  pPager->nRef = 0;
  assert( pPager->journalOpen==0 );
}
................................................................................
** This might give a performance improvement on windows where opening
** a file is an expensive operation.
*/
static int pager_unwritelock(Pager *pPager){
  int rc;
  PgHdr *pPg;
  if( pPager->state<SQLITE_WRITELOCK ) return SQLITE_OK;
  sqlite3pager_stmt_commit(pPager);
  if( pPager->ckptOpen ){
    sqliteOsClose(&pPager->cpfd);
    pPager->ckptOpen = 0;
  }
  if( pPager->journalOpen ){
    sqliteOsClose(&pPager->jfd);
    pPager->journalOpen = 0;
................................................................................
**         the checkpoint is stored in pPager->ckptSize, not in the
**         journal file itself.
**
**    (2)  In addition to playing back the checkpoint journal, also
**         playback all pages of the transaction journal beginning
**         at offset pPager->ckptJSize.
*/
static int pager_stmt_playback(Pager *pPager){
  off_t szJ;               /* Size of the full journal */
  int nRec;                /* Number of Records */
  int i;                   /* Loop counter */
  int rc;

  /* Truncate the database back to its original size.
  */
................................................................................
  ** database file.  Note that the checkpoint journal always uses format
  ** 2 instead of format 3 since it does not need to be concerned with
  ** power failures corrupting the journal and can thus omit the checksums.
  */
  for(i=nRec-1; i>=0; i--){
    rc = pager_playback_one_page(pPager, &pPager->cpfd, 2);
    assert( rc!=SQLITE_DONE );
    if( rc!=SQLITE_OK ) goto end_stmt_playback;
  }

  /* Figure out how many pages need to be copied out of the transaction
  ** journal.
  */
  rc = sqliteOsSeek(&pPager->jfd, pPager->ckptJSize);
  if( rc!=SQLITE_OK ){
    goto end_stmt_playback;
  }
  rc = sqliteOsFileSize(&pPager->jfd, &szJ);
  if( rc!=SQLITE_OK ){
    goto end_stmt_playback;
  }
  nRec = (szJ - pPager->ckptJSize)/JOURNAL_PG_SZ(journal_format);
  for(i=nRec-1; i>=0; i--){
    rc = pager_playback_one_page(pPager, &pPager->jfd, journal_format);
    if( rc!=SQLITE_OK ){
      assert( rc!=SQLITE_DONE );
      goto end_stmt_playback;
    }
  }
  
end_stmt_playback:
  if( rc!=SQLITE_OK ){
    pPager->errMask |= PAGER_ERR_CORRUPT;
    rc = SQLITE_CORRUPT;
  }
  return rc;
}

................................................................................
** The maximum number is the absolute value of the mxPage parameter.
** If mxPage is negative, the noSync flag is also set.  noSync bypasses
** calls to sqliteOsSync().  The pager runs much faster with noSync on,
** but if the operating system crashes or there is an abrupt power 
** failure, the database file might be left in an inconsistent and
** unrepairable state.  
*/
void sqlite3pager_set_cachesize(Pager *pPager, int mxPage){
  if( mxPage>=0 ){
    pPager->noSync = pPager->tempFile;
    if( pPager->noSync==0 ) pPager->needSync = 0;
  }else{
    pPager->noSync = 1;
    mxPage = -mxPage;
  }
................................................................................
**              single disk sector is atomic, then this mode provides
**              assurance that the journal will not be corrupted to the
**              point of causing damage to the database during rollback.
**
** Numeric values associated with these states are OFF==1, NORMAL=2,
** and FULL=3.
*/
void sqlite3pager_set_safety_level(Pager *pPager, int level){
  pPager->noSync =  level==1 || pPager->tempFile;
  pPager->fullSync = level==3 && !pPager->tempFile;
  if( pPager->noSync==0 ) pPager->needSync = 0;
}

/*
** Open a temporary file.  Write the name of the file into zName
................................................................................
** (zName must be at least SQLITE_TEMPNAME_SIZE bytes long.)  Write
** the file descriptor into *fd.  Return SQLITE_OK on success or some
** other error code if we fail.
**
** The OS will automatically delete the temporary file when it is
** closed.
*/
static int sqlite3pager_opentemp(char *zFile, OsFile *fd){
  int cnt = 8;
  int rc;
  do{
    cnt--;
    sqliteOsTempFileName(zFile);
    rc = sqliteOsOpenExclusive(zFile, fd, 1);
  }while( cnt>0 && rc!=SQLITE_OK );
  return rc;
}

/*
** Create a new page cache and put a pointer to the page cache in *ppPager.
** The file to be cached need not exist.  The file is not locked until
** the first call to sqlite3pager_get() and is only held open until the
** last page is released using sqlite3pager_unref().
**
** If zFilename is NULL then a randomly-named temporary file is created
** and used as the file to be cached.  The file will be deleted
** automatically when it is closed.
*/
int sqlite3pager_open(
  Pager **ppPager,         /* Return the Pager structure here */
  const char *zFilename,   /* Name of the database file to open */
  int mxPage,              /* Max number of in-memory cache pages */
  int nExtra,              /* Extra bytes append to each in-memory page */
  int useJournal           /* TRUE to use a rollback journal on this file */
){
  Pager *pPager;
................................................................................
    return SQLITE_NOMEM;
  }
  if( zFilename && zFilename[0] ){
    zFullPathname = sqliteOsFullPathname(zFilename);
    rc = sqliteOsOpenReadWrite(zFullPathname, &fd, &readOnly);
    tempFile = 0;
  }else{
    rc = sqlite3pager_opentemp(zTemp, &fd);
    zFilename = zTemp;
    zFullPathname = sqliteOsFullPathname(zFilename);
    tempFile = 1;
  }
  if( sqlite_malloc_failed ){
    return SQLITE_NOMEM;
  }
................................................................................
}

/*
** Set the destructor for this pager.  If not NULL, the destructor is called
** when the reference count on each page reaches zero.  The destructor can
** be used to clean up information in the extra segment appended to each page.
**
** The destructor is not called as a result sqlite3pager_close().  
** Destructors are only called by sqlite3pager_unref().
*/
void sqlite3pager_set_destructor(Pager *pPager, void (*xDesc)(void*)){
  pPager->xDestructor = xDesc;
}

/*
** Return the total number of pages in the disk file associated with
** pPager.
*/
int sqlite3pager_pagecount(Pager *pPager){
  off_t n;
  assert( pPager!=0 );
  if( pPager->dbSize>=0 ){
    return pPager->dbSize;
  }
  if( sqliteOsFileSize(&pPager->fd, &n)!=SQLITE_OK ){
    pPager->errMask |= PAGER_ERR_DISK;
................................................................................
** Forward declaration
*/
static int syncJournal(Pager*);

/*
** Truncate the file to the number of pages specified.
*/
int sqlite3pager_truncate(Pager *pPager, Pgno nPage){
  int rc;
  if( pPager->dbSize<0 ){
    sqlite3pager_pagecount(pPager);
  }
  if( pPager->errMask!=0 ){
    rc = pager_errcode(pPager);
    return rc;
  }
  if( nPage>=(unsigned)pPager->dbSize ){
    return SQLITE_OK;
................................................................................
**
** If a transaction was in progress when this routine is called, that
** transaction is rolled back.  All outstanding pages are invalidated
** and their memory is freed.  Any attempt to use a page associated
** with this page cache after this function returns will likely
** result in a coredump.
*/
int sqlite3pager_close(Pager *pPager){
  PgHdr *pPg, *pNext;
  switch( pPager->state ){
    case SQLITE_WRITELOCK: {
      sqlite3pager_rollback(pPager);
      sqliteOsUnlock(&pPager->fd);
      assert( pPager->journalOpen==0 );
      break;
    }
    case SQLITE_READLOCK: {
      sqliteOsUnlock(&pPager->fd);
      break;
................................................................................
  sqliteFree(pPager);
  return SQLITE_OK;
}

/*
** Return the page number for the given page data.
*/
Pgno sqlite3pager_pagenumber(void *pData){
  PgHdr *p = DATA_TO_PGHDR(pData);
  return p->pgno;
}

/*
** Increment the reference count for a page.  If the page is
** currently on the freelist (the reference count is zero) then
................................................................................
  REFINFO(pPg);
}

/*
** Increment the reference count for a page.  The input pointer is
** a reference to the page data.
*/
int sqlite3pager_ref(void *pData){
  PgHdr *pPg = DATA_TO_PGHDR(pData);
  page_ref(pPg);
  return SQLITE_OK;
}

/*
** Sync the journal.  In other words, make sure all the pages that have
................................................................................
** read occurs and the memory image of the page is initialized to
** all zeros.  The extra data appended to a page is always initialized
** to zeros the first time a page is loaded into memory.
**
** The acquisition might fail for several reasons.  In all cases,
** an appropriate error code is returned and *ppPage is set to NULL.
**
** See also sqlite3pager_lookup().  Both this routine and _lookup() attempt
** to find a page in the in-memory cache first.  If the page is not already
** in memory, this routine goes to disk to read it in whereas _lookup()
** just returns 0.  This routine acquires a read-lock the first time it
** has to go to disk, and could also playback an old journal if necessary.
** Since _lookup() never goes to disk, it never has to deal with locks
** or journal files.
*/
int sqlite3pager_get(Pager *pPager, Pgno pgno, void **ppPage){
  PgHdr *pPg;
  int rc;

  /* Make sure we have not hit any critical errors.
  */ 
  assert( pPager!=0 );
  assert( pgno!=0 );
................................................................................
      ** on the journal file then fsync the journal file.  This is a
      ** very slow operation, so we work hard to avoid it.  But sometimes
      ** it can't be helped.
      */
      if( pPg==0 ){
        int rc = syncJournal(pPager);
        if( rc!=0 ){
          sqlite3pager_rollback(pPager);
          return SQLITE_IOERR;
        }
        pPg = pPager->pFirst;
      }
      assert( pPg->nRef==0 );

      /* Write the page to the database file if it is dirty.
      */
      if( pPg->dirty ){
        assert( pPg->needSync==0 );
        pPg->pDirty = 0;
        rc = pager_write_pagelist( pPg );
        if( rc!=SQLITE_OK ){
          sqlite3pager_rollback(pPager);
          return SQLITE_IOERR;
        }
      }
      assert( pPg->dirty==0 );

      /* If the page we are recycling is marked as alwaysRollback, then
      ** set the global alwaysRollback flag, thus disabling the
................................................................................
      pPg->needSync = 0;
    }else{
      pPg->inJournal = 0;
      pPg->needSync = 0;
    }
    if( pPager->aInCkpt && (int)pgno<=pPager->ckptSize
             && (pPager->aInCkpt[pgno/8] & (1<<(pgno&7)))!=0 ){
      page_add_to_stmt_list(pPg);
    }else{
      page_remove_from_stmt_list(pPg);
    }
    pPg->dirty = 0;
    pPg->nRef = 1;
    REFINFO(pPg);
    pPager->nRef++;
    h = pager_hash(pgno);
    pPg->pNextHash = pPager->aHash[h];
................................................................................
    if( pPg->pNextHash ){
      assert( pPg->pNextHash->pPrevHash==0 );
      pPg->pNextHash->pPrevHash = pPg;
    }
    if( pPager->nExtra>0 ){
      memset(PGHDR_TO_EXTRA(pPg), 0, pPager->nExtra);
    }
    if( pPager->dbSize<0 ) sqlite3pager_pagecount(pPager);
    if( pPager->errMask!=0 ){
      sqlite3pager_unref(PGHDR_TO_DATA(pPg));
      rc = pager_errcode(pPager);
      return rc;
    }
    if( pPager->dbSize<(int)pgno ){
      memset(PGHDR_TO_DATA(pPg), 0, SQLITE_PAGE_SIZE);
    }else{
      int rc;
................................................................................
      rc = sqliteOsRead(&pPager->fd, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE);
      TRACE2("FETCH %d\n", pPg->pgno);
      CODEC(pPager, PGHDR_TO_DATA(pPg), pPg->pgno, 3);
      if( rc!=SQLITE_OK ){
        off_t fileSize;
        if( sqliteOsFileSize(&pPager->fd,&fileSize)!=SQLITE_OK
               || fileSize>=pgno*SQLITE_PAGE_SIZE ){
          sqlite3pager_unref(PGHDR_TO_DATA(pPg));
          return rc;
        }else{
          memset(PGHDR_TO_DATA(pPg), 0, SQLITE_PAGE_SIZE);
        }
      }
    }
  }else{
................................................................................
}

/*
** Acquire a page if it is already in the in-memory cache.  Do
** not read the page from disk.  Return a pointer to the page,
** or 0 if the page is not in cache.
**
** See also sqlite3pager_get().  The difference between this routine
** and sqlite3pager_get() is that _get() will go to the disk and read
** in the page if the page is not already in cache.  This routine
** returns NULL if the page is not in cache or if a disk I/O error 
** has ever happened.
*/
void *sqlite3pager_lookup(Pager *pPager, Pgno pgno){
  PgHdr *pPg;

  assert( pPager!=0 );
  assert( pgno!=0 );
  if( pPager->errMask & ~(PAGER_ERR_FULL) ){
    return 0;
  }
................................................................................
** Release a page.
**
** If the number of references to the page drop to zero, then the
** page is added to the LRU list.  When all references to all pages
** are released, a rollback occurs and the lock on the database is
** removed.
*/
int sqlite3pager_unref(void *pData){
  PgHdr *pPg;

  /* Decrement the reference count for this page
  */
  pPg = DATA_TO_PGHDR(pData);
  assert( pPg->nRef>0 );
  pPg->nRef--;
................................................................................
** write lock if anything goes wrong.
*/
static int pager_open_journal(Pager *pPager){
  int rc;
  assert( pPager->state==SQLITE_WRITELOCK );
  assert( pPager->journalOpen==0 );
  assert( pPager->useJournal );
  sqlite3pager_pagecount(pPager);
  pPager->aInJournal = sqliteMalloc( pPager->dbSize/8 + 1 );
  if( pPager->aInJournal==0 ){
    sqliteOsReadLock(&pPager->fd);
    pPager->state = SQLITE_READLOCK;
    return SQLITE_NOMEM;
  }
  rc = sqliteOsOpenExclusive(pPager->zJournal, &pPager->jfd,pPager->tempFile);
................................................................................
    assert( journal_format==JOURNAL_FORMAT_1 );
    rc = sqliteOsWrite(&pPager->jfd, aJournalMagic1, sizeof(aJournalMagic1));
  }
  if( rc==SQLITE_OK ){
    rc = write32bits(&pPager->jfd, pPager->dbSize);
  }
  if( pPager->ckptAutoopen && rc==SQLITE_OK ){
    rc = sqlite3pager_stmt_begin(pPager);
  }
  if( rc!=SQLITE_OK ){
    rc = pager_unwritelock(pPager);
    if( rc==SQLITE_OK ){
      rc = SQLITE_FULL;
    }
  }
................................................................................
  return rc;  
}

/*
** Acquire a write-lock on the database.  The lock is removed when
** the any of the following happen:
**
**   *  sqlite3pager_commit() is called.
**   *  sqlite3pager_rollback() is called.
**   *  sqlite3pager_close() is called.
**   *  sqlite3pager_unref() is called to on every outstanding page.
**
** The parameter to this routine is a pointer to any open page of the
** database file.  Nothing changes about the page - it is used merely
** to acquire a pointer to the Pager structure and as proof that there
** is already a read-lock on the database.
**
** A journal file is opened if this is not a temporary file.  For
** temporary files, the opening of the journal file is deferred until
** there is an actual need to write to the journal.
**
** If the database is already write-locked, this routine is a no-op.
*/
int sqlite3pager_begin(void *pData){
  PgHdr *pPg = DATA_TO_PGHDR(pData);
  Pager *pPager = pPg->pPager;
  int rc = SQLITE_OK;
  assert( pPg->nRef>0 );
  assert( pPager->state!=SQLITE_UNLOCK );
  if( pPager->state==SQLITE_READLOCK ){
    assert( pPager->aInJournal==0 );
................................................................................
** lock could not be acquired, this routine returns SQLITE_BUSY.  The
** calling routine must check for that return value and be careful not to
** change any page data until this routine returns SQLITE_OK.
**
** If the journal file could not be written because the disk is full,
** then this routine returns SQLITE_FULL and does an immediate rollback.
** All subsequent write attempts also return SQLITE_FULL until there
** is a call to sqlite3pager_commit() or sqlite3pager_rollback() to
** reset.
*/
int sqlite3pager_write(void *pData){
  PgHdr *pPg = DATA_TO_PGHDR(pData);
  Pager *pPager = pPg->pPager;
  int rc = SQLITE_OK;

  /* Check for errors
  */
  if( pPager->errMask ){ 
................................................................................
  ** written to the transaction journal or the ckeckpoint journal
  ** or both.
  **
  ** First check to see that the transaction journal exists and
  ** create it if it does not.
  */
  assert( pPager->state!=SQLITE_UNLOCK );
  rc = sqlite3pager_begin(pData);
  if( rc!=SQLITE_OK ){
    return rc;
  }
  assert( pPager->state==SQLITE_WRITELOCK );
  if( !pPager->journalOpen && pPager->useJournal ){
    rc = pager_open_journal(pPager);
    if( rc!=SQLITE_OK ) return rc;
................................................................................
      rc = sqliteOsWrite(&pPager->jfd, &((char*)pData)[-4], szPg);
      TRACE3("JOURNAL %d %d\n", pPg->pgno, pPg->needSync);
      CODEC(pPager, pData, pPg->pgno, 0);
      if( journal_format>=JOURNAL_FORMAT_3 ){
        *(u32*)PGHDR_TO_EXTRA(pPg) = saved;
      }
      if( rc!=SQLITE_OK ){
        sqlite3pager_rollback(pPager);
        pPager->errMask |= PAGER_ERR_FULL;
        return rc;
      }
      pPager->nRec++;
      assert( pPager->aInJournal!=0 );
      pPager->aInJournal[pPg->pgno/8] |= 1<<(pPg->pgno&7);
      pPg->needSync = !pPager->noSync;
      pPg->inJournal = 1;
      if( pPager->ckptInUse ){
        pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
        page_add_to_stmt_list(pPg);
      }
    }else{
      pPg->needSync = !pPager->journalStarted && !pPager->noSync;
      TRACE3("APPEND %d %d\n", pPg->pgno, pPg->needSync);
    }
    if( pPg->needSync ){
      pPager->needSync = 1;
................................................................................
    assert( pPg->inJournal || (int)pPg->pgno>pPager->origDbSize );
    store32bits(pPg->pgno, pPg, -4);
    CODEC(pPager, pData, pPg->pgno, 7);
    rc = sqliteOsWrite(&pPager->cpfd, &((char*)pData)[-4], SQLITE_PAGE_SIZE+4);
    TRACE2("CKPT-JOURNAL %d\n", pPg->pgno);
    CODEC(pPager, pData, pPg->pgno, 0);
    if( rc!=SQLITE_OK ){
      sqlite3pager_rollback(pPager);
      pPager->errMask |= PAGER_ERR_FULL;
      return rc;
    }
    pPager->ckptNRec++;
    assert( pPager->aInCkpt!=0 );
    pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
    page_add_to_stmt_list(pPg);
  }

  /* Update the database size and return.
  */
  if( pPager->dbSize<(int)pPg->pgno ){
    pPager->dbSize = pPg->pgno;
  }
  return rc;
}

/*
** Return TRUE if the page given in the argument was previously passed
** to sqlite3pager_write().  In other words, return TRUE if it is ok
** to change the content of the page.
*/
int sqlite3pager_iswriteable(void *pData){
  PgHdr *pPg = DATA_TO_PGHDR(pData);
  return pPg->dirty;
}

/*
** Replace the content of a single page with the information in the third
** argument.
*/
int sqlite3pager_overwrite(Pager *pPager, Pgno pgno, void *pData){
  void *pPage;
  int rc;

  rc = sqlite3pager_get(pPager, pgno, &pPage);
  if( rc==SQLITE_OK ){
    rc = sqlite3pager_write(pPage);
    if( rc==SQLITE_OK ){
      memcpy(pPage, pData, SQLITE_PAGE_SIZE);
    }
    sqlite3pager_unref(pPage);
  }
  return rc;
}

/*
** A call to this routine tells the pager that it is not necessary to
** write the information on page "pgno" back to the disk, even though
................................................................................
** that page might be marked as dirty.
**
** The overlying software layer calls this routine when all of the data
** on the given page is unused.  The pager marks the page as clean so
** that it does not get written to disk.
**
** Tests show that this optimization, together with the
** sqlite3pager_dont_rollback() below, more than double the speed
** of large INSERT operations and quadruple the speed of large DELETEs.
**
** When this routine is called, set the alwaysRollback flag to true.
** Subsequent calls to sqlite3pager_dont_rollback() for the same page
** will thereafter be ignored.  This is necessary to avoid a problem
** where a page with data is added to the freelist during one part of
** a transaction then removed from the freelist during a later part
** of the same transaction and reused for some other purpose.  When it
** is first added to the freelist, this routine is called.  When reused,
** the dont_rollback() routine is called.  But because the page contains
** critical data, we still need to be sure it gets rolled back in spite
** of the dont_rollback() call.
*/
void sqlite3pager_dont_write(Pager *pPager, Pgno pgno){
  PgHdr *pPg;

  pPg = pager_lookup(pPager, pgno);
  pPg->alwaysRollback = 1;
  if( pPg && pPg->dirty ){
    if( pPager->dbSize==(int)pPg->pgno && pPager->origDbSize<pPager->dbSize ){
      /* If this pages is the last page in the file and the file has grown
................................................................................

/*
** A call to this routine tells the pager that if a rollback occurs,
** it is not necessary to restore the data on the given page.  This
** means that the pager does not have to record the given page in the
** rollback journal.
*/
void sqlite3pager_dont_rollback(void *pData){
  PgHdr *pPg = DATA_TO_PGHDR(pData);
  Pager *pPager = pPg->pPager;

  if( pPager->state!=SQLITE_WRITELOCK || pPager->journalOpen==0 ) return;
  if( pPg->alwaysRollback || pPager->alwaysRollback ) return;
  if( !pPg->inJournal && (int)pPg->pgno <= pPager->origDbSize ){
    assert( pPager->aInJournal!=0 );
    pPager->aInJournal[pPg->pgno/8] |= 1<<(pPg->pgno&7);
    pPg->inJournal = 1;
    if( pPager->ckptInUse ){
      pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
      page_add_to_stmt_list(pPg);
    }
    TRACE2("DONT_ROLLBACK %d\n", pPg->pgno);
  }
  if( pPager->ckptInUse && !pPg->inCkpt && (int)pPg->pgno<=pPager->ckptSize ){
    assert( pPg->inJournal || (int)pPg->pgno>pPager->origDbSize );
    assert( pPager->aInCkpt!=0 );
    pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
    page_add_to_stmt_list(pPg);
  }
}

/*
** Commit all changes to the database and release the write lock.
**
** If the commit fails for any reason, a rollback attempt is made
** and an error code is returned.  If the commit worked, SQLITE_OK
** is returned.
*/
int sqlite3pager_commit(Pager *pPager){
  int rc;
  PgHdr *pPg;

  if( pPager->errMask==PAGER_ERR_FULL ){
    rc = sqlite3pager_rollback(pPager);
    if( rc==SQLITE_OK ){
      rc = SQLITE_FULL;
    }
    return rc;
  }
  if( pPager->errMask!=0 ){
    rc = pager_errcode(pPager);
................................................................................
  rc = pager_unwritelock(pPager);
  pPager->dbSize = -1;
  return rc;

  /* Jump here if anything goes wrong during the commit process.
  */
commit_abort:
  rc = sqlite3pager_rollback(pPager);
  if( rc==SQLITE_OK ){
    rc = SQLITE_FULL;
  }
  return rc;
}

/*
................................................................................
** This routine cannot fail unless some other process is not following
** the correct locking protocol (SQLITE_PROTOCOL) or unless some other
** process is writing trash into the journal file (SQLITE_CORRUPT) or
** unless a prior malloc() failed (SQLITE_NOMEM).  Appropriate error
** codes are returned for all these occasions.  Otherwise,
** SQLITE_OK is returned.
*/
int sqlite3pager_rollback(Pager *pPager){
  int rc;
  TRACE1("ROLLBACK\n");
  if( !pPager->dirtyFile || !pPager->journalOpen ){
    rc = pager_unwritelock(pPager);
    pPager->dbSize = -1;
    return rc;
  }
................................................................................
  return rc;
}

/*
** Return TRUE if the database file is opened read-only.  Return FALSE
** if the database is (in theory) writable.
*/
int sqlite3pager_isreadonly(Pager *pPager){
  return pPager->readOnly;
}

/*
** This routine is used for testing and analysis only.
*/
int *sqlite3pager_stats(Pager *pPager){
  static int a[9];
  a[0] = pPager->nRef;
  a[1] = pPager->nPage;
  a[2] = pPager->mxPage;
  a[3] = pPager->dbSize;
  a[4] = pPager->state;
  a[5] = pPager->errMask;
................................................................................
/*
** Set the checkpoint.
**
** This routine should be called with the transaction journal already
** open.  A new checkpoint journal is created that can be used to rollback
** changes of a single SQL command within a larger transaction.
*/
int sqlite3pager_stmt_begin(Pager *pPager){
  int rc;
  char zTemp[SQLITE_TEMPNAME_SIZE];
  if( !pPager->journalOpen ){
    pPager->ckptAutoopen = 1;
    return SQLITE_OK;
  }
  assert( pPager->journalOpen );
................................................................................
  assert( pPager->ckptJSize == 
    pPager->nRec*JOURNAL_PG_SZ(journal_format)+JOURNAL_HDR_SZ(journal_format) );
#endif
  pPager->ckptJSize = pPager->nRec*JOURNAL_PG_SZ(journal_format)
                         + JOURNAL_HDR_SZ(journal_format);
  pPager->ckptSize = pPager->dbSize;
  if( !pPager->ckptOpen ){
    rc = sqlite3pager_opentemp(zTemp, &pPager->cpfd);
    if( rc ) goto ckpt_begin_failed;
    pPager->ckptOpen = 1;
    pPager->ckptNRec = 0;
  }
  pPager->ckptInUse = 1;
  return SQLITE_OK;
 
................................................................................
  }
  return rc;
}

/*
** Commit a checkpoint.
*/
int sqlite3pager_stmt_commit(Pager *pPager){
  if( pPager->ckptInUse ){
    PgHdr *pPg, *pNext;
    sqliteOsSeek(&pPager->cpfd, 0);
    /* sqliteOsTruncate(&pPager->cpfd, 0); */
    pPager->ckptNRec = 0;
    pPager->ckptInUse = 0;
    sqliteFree( pPager->aInCkpt );
................................................................................
  pPager->ckptAutoopen = 0;
  return SQLITE_OK;
}

/*
** Rollback a checkpoint.
*/
int sqlite3pager_stmt_rollback(Pager *pPager){
  int rc;
  if( pPager->ckptInUse ){
    rc = pager_stmt_playback(pPager);
    sqlite3pager_stmt_commit(pPager);
  }else{
    rc = SQLITE_OK;
  }
  pPager->ckptAutoopen = 0;
  return rc;
}

/*
** Return the full pathname of the database file.
*/
const char *sqlite3pager_filename(Pager *pPager){
  return pPager->zFilename;
}

/*
** Set the codec for this pager
*/
void sqlite3pager_set_codec(
  Pager *pPager,
  void (*xCodec)(void*,void*,Pgno,int),
  void *pCodecArg
){
  pPager->xCodec = xCodec;
  pPager->pCodecArg = pCodecArg;
}

#ifdef SQLITE_TEST
/*
** Print a listing of all referenced pages and their ref count.
*/
void sqlite3pager_refdump(Pager *pPager){
  PgHdr *pPg;
  for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
    if( pPg->nRef<=0 ) continue;
    printf("PAGE %3d addr=0x%08x nRef=%d\n", 
       pPg->pgno, (int)PGHDR_TO_DATA(pPg), pPg->nRef);
  }
}
#endif

Changes to src/pager.h.

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**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite page cache
** subsystem.  The page cache subsystem reads and writes a file a page
** at a time and provides a journal for rollback.
**
** @(#) $Id: pager.h,v 1.26 2004/02/11 02:18:07 drh Exp $
*/

/*
** The size of one page
**
** You can change this value to another (reasonable) value you want.
** It need not be a power of two, though the interface to the disk
................................................................................
** The total number of usable bytes stored on disk for each page.
** The usable bytes come at the beginning of the page and the reserve
** bytes come at the end.
*/
#define SQLITE_USABLE_SIZE (SQLITE_PAGE_SIZE-SQLITE_PAGE_RESERVE)

/*
** Maximum number of pages in one database.  (This is a limitation of
** imposed by 4GB files size limits.)
*/
#define SQLITE_MAX_PAGE 1073741823

/*
** The type used to represent a page number.  The first page in a file
** is called page 1.  0 is used to represent "not a page".
*/
................................................................................
*/
typedef struct Pager Pager;

/*
** See source code comments for a detailed description of the following
** routines:
*/
int sqlitepager_open(Pager **ppPager, const char *zFilename,
                     int nPage, int nExtra, int useJournal);
void sqlitepager_set_destructor(Pager*, void(*)(void*));
void sqlitepager_set_cachesize(Pager*, int);
int sqlitepager_close(Pager *pPager);
int sqlitepager_get(Pager *pPager, Pgno pgno, void **ppPage);
void *sqlitepager_lookup(Pager *pPager, Pgno pgno);
int sqlitepager_ref(void*);
int sqlitepager_unref(void*);
Pgno sqlitepager_pagenumber(void*);
int sqlitepager_write(void*);
int sqlitepager_iswriteable(void*);
int sqlitepager_overwrite(Pager *pPager, Pgno pgno, void*);
int sqlitepager_pagecount(Pager*);
int sqlitepager_truncate(Pager*,Pgno);
int sqlitepager_begin(void*);
int sqlitepager_commit(Pager*);
int sqlitepager_rollback(Pager*);
int sqlitepager_isreadonly(Pager*);
int sqlitepager_ckpt_begin(Pager*);
int sqlitepager_ckpt_commit(Pager*);
int sqlitepager_ckpt_rollback(Pager*);
void sqlitepager_dont_rollback(void*);
void sqlitepager_dont_write(Pager*, Pgno);
int *sqlitepager_stats(Pager*);
void sqlitepager_set_safety_level(Pager*,int);
const char *sqlitepager_filename(Pager*);
int sqlitepager_rename(Pager*, const char *zNewName);
void sqlitepager_set_codec(Pager*,void(*)(void*,void*,Pgno,int),void*);

#ifdef SQLITE_TEST
void sqlitepager_refdump(Pager*);
int pager_refinfo_enable;
int journal_format;
#endif







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105
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite page cache
** subsystem.  The page cache subsystem reads and writes a file a page
** at a time and provides a journal for rollback.
**
** @(#) $Id: pager.h,v 1.27 2004/04/26 14:10:22 drh Exp $
*/

/*
** The size of one page
**
** You can change this value to another (reasonable) value you want.
** It need not be a power of two, though the interface to the disk
................................................................................
** The total number of usable bytes stored on disk for each page.
** The usable bytes come at the beginning of the page and the reserve
** bytes come at the end.
*/
#define SQLITE_USABLE_SIZE (SQLITE_PAGE_SIZE-SQLITE_PAGE_RESERVE)

/*
** Maximum number of pages in one database.

*/
#define SQLITE_MAX_PAGE 1073741823

/*
** The type used to represent a page number.  The first page in a file
** is called page 1.  0 is used to represent "not a page".
*/
................................................................................
*/
typedef struct Pager Pager;

/*
** See source code comments for a detailed description of the following
** routines:
*/
int sqlite3pager_open(Pager **ppPager, const char *zFilename,
                     int nPage, int nExtra, int useJournal);
void sqlite3pager_set_destructor(Pager*, void(*)(void*));
void sqlite3pager_set_cachesize(Pager*, int);
int sqlite3pager_close(Pager *pPager);
int sqlite3pager_get(Pager *pPager, Pgno pgno, void **ppPage);
void *sqlite3pager_lookup(Pager *pPager, Pgno pgno);
int sqlite3pager_ref(void*);
int sqlite3pager_unref(void*);
Pgno sqlite3pager_pagenumber(void*);
int sqlite3pager_write(void*);
int sqlite3pager_iswriteable(void*);
int sqlite3pager_overwrite(Pager *pPager, Pgno pgno, void*);
int sqlite3pager_pagecount(Pager*);
int sqlite3pager_truncate(Pager*,Pgno);
int sqlite3pager_begin(void*);
int sqlite3pager_commit(Pager*);
int sqlite3pager_rollback(Pager*);
int sqlite3pager_isreadonly(Pager*);
int sqlite3pager_stmt_begin(Pager*);
int sqlite3pager_stmt_commit(Pager*);
int sqlite3pager_stmt_rollback(Pager*);
void sqlite3pager_dont_rollback(void*);
void sqlite3pager_dont_write(Pager*, Pgno);
int *sqlite3pager_stats(Pager*);
void sqlite3pager_set_safety_level(Pager*,int);
const char *sqlite3pager_filename(Pager*);
int sqlite3pager_rename(Pager*, const char *zNewName);
void sqlite3pager_set_codec(Pager*,void(*)(void*,void*,Pgno,int),void*);

#ifdef SQLITE_TEST
void sqlite3pager_refdump(Pager*);
int pager3_refinfo_enable;

#endif

Changes to src/sqliteInt.h.

7
8
9
10
11
12
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21
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24
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99
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...
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117

118
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135
**    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 1.220 2004/02/25 13:47:33 drh Exp $
*/
#include "config.h"
#include "sqlite.h"
#include "hash.h"
#include "parse.h"
#include "btree.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>

/*
** The maximum number of in-memory pages to use for the main database
................................................................................
/*
** Integers of known sizes.  These typedefs might change for architectures
** where the sizes very.  Preprocessor macros are available so that the
** types can be conveniently redefined at compile-type.  Like this:
**
**         cc '-DUINTPTR_TYPE=long long int' ...
*/



#ifndef UINT32_TYPE
# define UINT32_TYPE unsigned int
#endif
#ifndef UINT16_TYPE
# define UINT16_TYPE unsigned short int
#endif
#ifndef UINT8_TYPE
................................................................................
#ifndef INTPTR_TYPE
# if SQLITE_PTR_SZ==4
#   define INTPTR_TYPE int
# else
#   define INTPTR_TYPE long long
# endif
#endif

typedef UINT32_TYPE u32;           /* 4-byte unsigned integer */
typedef UINT16_TYPE u16;           /* 2-byte unsigned integer */
typedef UINT8_TYPE u8;             /* 1-byte unsigned integer */
typedef UINT8_TYPE i8;             /* 1-byte signed integer */
typedef INTPTR_TYPE ptr;           /* Big enough to hold a pointer */
typedef unsigned INTPTR_TYPE uptr; /* Big enough to hold a pointer */

/*
** Defer sourcing vdbe.h until after the "u8" typedef is defined.
*/
#include "vdbe.h"


/*
** Most C compilers these days recognize "long double", don't they?
** Just in case we encounter one that does not, we will create a macro
** for long double so that it can be easily changed to just "double".
*/
#ifndef LONGDOUBLE_TYPE







|





<







 







>
>
>







 







>











>







7
8
9
10
11
12
13
14
15
16
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20
21
22
23
24
25
26
..
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
...
113
114
115
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120
121
122
123
124
125
126
127
128
129
130
131
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134
135
136
137
138
139
**    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 1.221 2004/04/26 14:10:22 drh Exp $
*/
#include "config.h"
#include "sqlite.h"
#include "hash.h"
#include "parse.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>

/*
** The maximum number of in-memory pages to use for the main database
................................................................................
/*
** Integers of known sizes.  These typedefs might change for architectures
** where the sizes very.  Preprocessor macros are available so that the
** types can be conveniently redefined at compile-type.  Like this:
**
**         cc '-DUINTPTR_TYPE=long long int' ...
*/
#ifndef UINT64_TYPE
# define UINT64_TYPE unsigned long long int
#endif
#ifndef UINT32_TYPE
# define UINT32_TYPE unsigned int
#endif
#ifndef UINT16_TYPE
# define UINT16_TYPE unsigned short int
#endif
#ifndef UINT8_TYPE
................................................................................
#ifndef INTPTR_TYPE
# if SQLITE_PTR_SZ==4
#   define INTPTR_TYPE int
# else
#   define INTPTR_TYPE long long
# endif
#endif
typedef UINT64_TYPE u64;           /* 8-byte unsigned integer */
typedef UINT32_TYPE u32;           /* 4-byte unsigned integer */
typedef UINT16_TYPE u16;           /* 2-byte unsigned integer */
typedef UINT8_TYPE u8;             /* 1-byte unsigned integer */
typedef UINT8_TYPE i8;             /* 1-byte signed integer */
typedef INTPTR_TYPE ptr;           /* Big enough to hold a pointer */
typedef unsigned INTPTR_TYPE uptr; /* Big enough to hold a pointer */

/*
** Defer sourcing vdbe.h until after the "u8" typedef is defined.
*/
#include "vdbe.h"
#include "btree.h"

/*
** Most C compilers these days recognize "long double", don't they?
** Just in case we encounter one that does not, we will create a macro
** for long double so that it can be easily changed to just "double".
*/
#ifndef LONGDOUBLE_TYPE

Changes to src/tclsqlite.c.

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8
9
10
11
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14
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17
18
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20
21
22
23

24
25
26
27
28
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30
....
1151
1152
1153
1154
1155
1156
1157

1158
1159
1160
1161
1162
1163
1164
....
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
**    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.
**
*************************************************************************
** A TCL Interface to SQLite
**
** $Id: tclsqlite.c,v 1.59 2004/02/25 22:51:06 rdc Exp $
*/
#ifndef NO_TCL     /* Omit this whole file if TCL is unavailable */

#include "sqliteInt.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>
#include <assert.h>


/*
** If TCL uses UTF-8 and SQLite is configured to use iso8859, then we
** have to do a translation when going between the two.  Set the 
** UTF_TRANSLATION_NEEDED macro to indicate that we need to do
** this translation.  
*/
#if defined(TCL_UTF_MAX) && !defined(SQLITE_UTF8)
................................................................................
}
int Sqlite_SafeInit(Tcl_Interp *interp){
  return TCL_OK;
}
int Tclsqlite_SafeInit(Tcl_Interp *interp){
  return TCL_OK;
}


#if 0
/*
** If compiled using mktclapp, this routine runs to initialize
** everything.
*/
int Et_AppInit(Tcl_Interp *interp){
................................................................................
;

#define TCLSH_MAIN main   /* Needed to fake out mktclapp */
int TCLSH_MAIN(int argc, char **argv){
  Tcl_Interp *interp;
  Tcl_FindExecutable(argv[0]);
  interp = Tcl_CreateInterp();
  Sqlite_Init(interp);
#ifdef SQLITE_TEST
  {
    extern int Sqlitetest1_Init(Tcl_Interp*);
    extern int Sqlitetest2_Init(Tcl_Interp*);
    extern int Sqlitetest3_Init(Tcl_Interp*);
    extern int Sqlitetest4_Init(Tcl_Interp*);
    extern int Md5_Init(Tcl_Interp*);
    Sqlitetest1_Init(interp);
    Sqlitetest2_Init(interp);
    Sqlitetest3_Init(interp);
    Sqlitetest4_Init(interp);
    Md5_Init(interp);
  }
#endif
  if( argc>=2 ){
    int i;
    Tcl_SetVar(interp,"argv0",argv[1],TCL_GLOBAL_ONLY);
    Tcl_SetVar(interp,"argv", "", TCL_GLOBAL_ONLY);







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7
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23
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25
26
27
28
29
30
31
....
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
....
1197
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1199
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1218
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1221
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**    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.
**
*************************************************************************
** A TCL Interface to SQLite
**
** $Id: tclsqlite.c,v 1.60 2004/04/26 14:10:22 drh Exp $
*/
#ifndef NO_TCL     /* Omit this whole file if TCL is unavailable */

#include "sqliteInt.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>
#include <assert.h>

#if 0
/*
** If TCL uses UTF-8 and SQLite is configured to use iso8859, then we
** have to do a translation when going between the two.  Set the 
** UTF_TRANSLATION_NEEDED macro to indicate that we need to do
** this translation.  
*/
#if defined(TCL_UTF_MAX) && !defined(SQLITE_UTF8)
................................................................................
}
int Sqlite_SafeInit(Tcl_Interp *interp){
  return TCL_OK;
}
int Tclsqlite_SafeInit(Tcl_Interp *interp){
  return TCL_OK;
}
#endif

#if 0
/*
** If compiled using mktclapp, this routine runs to initialize
** everything.
*/
int Et_AppInit(Tcl_Interp *interp){
................................................................................
;

#define TCLSH_MAIN main   /* Needed to fake out mktclapp */
int TCLSH_MAIN(int argc, char **argv){
  Tcl_Interp *interp;
  Tcl_FindExecutable(argv[0]);
  interp = Tcl_CreateInterp();
  /* Sqlite_Init(interp); */
#ifdef SQLITE_TEST
  {
    extern int Sqlitetest1_Init(Tcl_Interp*);
    extern int Sqlitetest2_Init(Tcl_Interp*);
    extern int Sqlitetest3_Init(Tcl_Interp*);
    extern int Sqlitetest4_Init(Tcl_Interp*);
    extern int Md5_Init(Tcl_Interp*);
    /* Sqlitetest1_Init(interp); */
    Sqlitetest2_Init(interp);
    /* Sqlitetest3_Init(interp); */
    /* Sqlitetest4_Init(interp); */
    Md5_Init(interp);
  }
#endif
  if( argc>=2 ){
    int i;
    Tcl_SetVar(interp,"argv0",argv[1],TCL_GLOBAL_ONLY);
    Tcl_SetVar(interp,"argv", "", TCL_GLOBAL_ONLY);

Changes to src/test2.c.

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..
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...
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...
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...
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...
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...
357
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...
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398
...
435
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449
...
459
460
461
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468
469
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471
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473
...
530
531
532
533
534
535
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538
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541
542
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544
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546
...
550
551
552
553
554
555
556


557
558

559
560
561
562
563
564
565
566
567
**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing the pager.c module in SQLite.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test2.c,v 1.16 2004/02/10 01:54:28 drh Exp $
*/
#include "os.h"
#include "sqliteInt.h"
#include "pager.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>
................................................................................
  char zBuf[100];
  if( argc!=3 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " FILENAME N-PAGE\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[2], &nPage) ) return TCL_ERROR;
  rc = sqlitepager_open(&pPager, argv[1], nPage, 0, 1);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  sprintf(zBuf,"0x%x",(int)pPager);
  Tcl_AppendResult(interp, zBuf, 0);
  return TCL_OK;
................................................................................
  int rc;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPager) ) return TCL_ERROR;
  rc = sqlitepager_close(pPager);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  return TCL_OK;
}

................................................................................
  int rc;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPager) ) return TCL_ERROR;
  rc = sqlitepager_rollback(pPager);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  return TCL_OK;
}

................................................................................
  int rc;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPager) ) return TCL_ERROR;
  rc = sqlitepager_commit(pPager);



























  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  return TCL_OK;
}

/*
** Usage:   pager_ckpt_begin ID
**
** Start a new checkpoint.
*/
static int pager_ckpt_begin(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  const char **argv      /* Text of each argument */
){
  Pager *pPager;
  int rc;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPager) ) return TCL_ERROR;
  rc = sqlitepager_ckpt_begin(pPager);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  return TCL_OK;
}

/*
** Usage:   pager_ckpt_rollback ID
**
** Rollback changes to a checkpoint
*/
static int pager_ckpt_rollback(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  const char **argv      /* Text of each argument */
){
  Pager *pPager;
  int rc;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPager) ) return TCL_ERROR;
  rc = sqlitepager_ckpt_rollback(pPager);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  return TCL_OK;
}

/*
** Usage:   pager_ckpt_commit ID
**
** Commit changes to a checkpoint
*/
static int pager_ckpt_commit(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  const char **argv      /* Text of each argument */
){
  Pager *pPager;
  int rc;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPager) ) return TCL_ERROR;
  rc = sqlitepager_ckpt_commit(pPager);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  return TCL_OK;
}

................................................................................
  int i, *a;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPager) ) return TCL_ERROR;
  a = sqlitepager_stats(pPager);
  for(i=0; i<9; i++){
    static char *zName[] = {
      "ref", "page", "max", "size", "state", "err",
      "hit", "miss", "ovfl",
    };
    char zBuf[100];
    Tcl_AppendElement(interp, zName[i]);
................................................................................
  char zBuf[100];
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPager) ) return TCL_ERROR;
  sprintf(zBuf,"%d",sqlitepager_pagecount(pPager));
  Tcl_AppendResult(interp, zBuf, 0);
  return TCL_OK;
}

/*
** Usage:   page_get ID PGNO
**
................................................................................
  if( argc!=3 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID PGNO\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPager) ) return TCL_ERROR;
  if( Tcl_GetInt(interp, argv[2], &pgno) ) return TCL_ERROR;
  rc = sqlitepager_get(pPager, pgno, &pPage);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  sprintf(zBuf,"0x%x",(int)pPage);
  Tcl_AppendResult(interp, zBuf, 0);
  return TCL_OK;
................................................................................
  if( argc!=3 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID PGNO\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPager) ) return TCL_ERROR;
  if( Tcl_GetInt(interp, argv[2], &pgno) ) return TCL_ERROR;
  pPage = sqlitepager_lookup(pPager, pgno);
  if( pPage ){
    sprintf(zBuf,"0x%x",(int)pPage);
    Tcl_AppendResult(interp, zBuf, 0);
  }
  return TCL_OK;
}

................................................................................
  int rc;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " PAGE\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPage) ) return TCL_ERROR;
  rc = sqlitepager_unref(pPage);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  return TCL_OK;
}

................................................................................
  void *pPage;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " PAGE\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPage) ) return TCL_ERROR;
  sprintf(zBuf, "%d", sqlitepager_pagenumber(pPage));
  Tcl_AppendResult(interp, zBuf, 0);
  return TCL_OK;
}

/*
** Usage:   page_write PAGE DATA
**
................................................................................
  int rc;
  if( argc!=3 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " PAGE DATA\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPage) ) return TCL_ERROR;
  rc = sqlitepager_write(pPage);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  strncpy((char*)pPage, argv[2], SQLITE_USABLE_SIZE-1);
  ((char*)pPage)[SQLITE_USABLE_SIZE-1] = 0;
  return TCL_OK;
................................................................................
    char *zName;
    Tcl_CmdProc *xProc;
  } aCmd[] = {
    { "pager_open",              (Tcl_CmdProc*)pager_open          },
    { "pager_close",             (Tcl_CmdProc*)pager_close         },
    { "pager_commit",            (Tcl_CmdProc*)pager_commit        },
    { "pager_rollback",          (Tcl_CmdProc*)pager_rollback      },
    { "pager_ckpt_begin",        (Tcl_CmdProc*)pager_ckpt_begin    },
    { "pager_ckpt_commit",       (Tcl_CmdProc*)pager_ckpt_commit   },
    { "pager_ckpt_rollback",     (Tcl_CmdProc*)pager_ckpt_rollback },
    { "pager_stats",             (Tcl_CmdProc*)pager_stats         },
    { "pager_pagecount",         (Tcl_CmdProc*)pager_pagecount     },
    { "page_get",                (Tcl_CmdProc*)page_get            },
    { "page_lookup",             (Tcl_CmdProc*)page_lookup         },
    { "page_unref",              (Tcl_CmdProc*)page_unref          },
    { "page_read",               (Tcl_CmdProc*)page_read           },
    { "page_write",              (Tcl_CmdProc*)page_write          },
................................................................................
  int i;
  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
    Tcl_CreateCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
  }
  Tcl_LinkVar(interp, "sqlite_io_error_pending",
     (char*)&sqlite_io_error_pending, TCL_LINK_INT);
#ifdef SQLITE_TEST


  Tcl_LinkVar(interp, "journal_format",
     (char*)&journal_format, TCL_LINK_INT);

#endif
  sprintf(zBuf, "%d", SQLITE_PAGE_SIZE);
  Tcl_SetVar(interp, "SQLITE_PAGE_SIZE", zBuf, TCL_GLOBAL_ONLY); 
  sprintf(zBuf, "%d", SQLITE_PAGE_RESERVE);
  Tcl_SetVar(interp, "SQLITE_PAGE_RESERVE", zBuf, TCL_GLOBAL_ONLY); 
  sprintf(zBuf, "%d", SQLITE_USABLE_SIZE);
  Tcl_SetVar(interp, "SQLITE_USABLE_SIZE", zBuf, TCL_GLOBAL_ONLY); 
  return TCL_OK;
}







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**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing the pager.c module in SQLite.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test2.c,v 1.17 2004/04/26 14:10:22 drh Exp $
*/
#include "os.h"
#include "sqliteInt.h"
#include "pager.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>
................................................................................
  char zBuf[100];
  if( argc!=3 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " FILENAME N-PAGE\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[2], &nPage) ) return TCL_ERROR;
  rc = sqlite3pager_open(&pPager, argv[1], nPage, 0, 1);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  sprintf(zBuf,"0x%x",(int)pPager);
  Tcl_AppendResult(interp, zBuf, 0);
  return TCL_OK;
................................................................................
  int rc;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPager) ) return TCL_ERROR;
  rc = sqlite3pager_close(pPager);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  return TCL_OK;
}

................................................................................
  int rc;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPager) ) return TCL_ERROR;
  rc = sqlite3pager_rollback(pPager);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  return TCL_OK;
}

................................................................................
  int rc;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPager) ) return TCL_ERROR;
  rc = sqlite3pager_commit(pPager);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  return TCL_OK;
}

/*
** Usage:   pager_stmt_begin ID
**
** Start a new checkpoint.
*/
static int pager_stmt_begin(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  const char **argv      /* Text of each argument */
){
  Pager *pPager;
  int rc;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPager) ) return TCL_ERROR;
  rc = sqlite3pager_stmt_begin(pPager);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  return TCL_OK;
}

/*
** Usage:   pager_stmt_rollback ID
**
** Rollback changes to a checkpoint
*/
static int pager_stmt_rollback(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  const char **argv      /* Text of each argument */
){
  Pager *pPager;
  int rc;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPager) ) return TCL_ERROR;
  rc = sqlite3pager_stmt_rollback(pPager);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  return TCL_OK;
}

/*
** Usage:   pager_stmt_commit ID
**
** Commit changes to a checkpoint
*/
static int pager_stmt_commit(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  const char **argv      /* Text of each argument */
){
  Pager *pPager;
  int rc;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPager) ) return TCL_ERROR;



























  rc = sqlite3pager_stmt_commit(pPager);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  return TCL_OK;
}

................................................................................
  int i, *a;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPager) ) return TCL_ERROR;
  a = sqlite3pager_stats(pPager);
  for(i=0; i<9; i++){
    static char *zName[] = {
      "ref", "page", "max", "size", "state", "err",
      "hit", "miss", "ovfl",
    };
    char zBuf[100];
    Tcl_AppendElement(interp, zName[i]);
................................................................................
  char zBuf[100];
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPager) ) return TCL_ERROR;
  sprintf(zBuf,"%d",sqlite3pager_pagecount(pPager));
  Tcl_AppendResult(interp, zBuf, 0);
  return TCL_OK;
}

/*
** Usage:   page_get ID PGNO
**
................................................................................
  if( argc!=3 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID PGNO\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPager) ) return TCL_ERROR;
  if( Tcl_GetInt(interp, argv[2], &pgno) ) return TCL_ERROR;
  rc = sqlite3pager_get(pPager, pgno, &pPage);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  sprintf(zBuf,"0x%x",(int)pPage);
  Tcl_AppendResult(interp, zBuf, 0);
  return TCL_OK;
................................................................................
  if( argc!=3 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID PGNO\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPager) ) return TCL_ERROR;
  if( Tcl_GetInt(interp, argv[2], &pgno) ) return TCL_ERROR;
  pPage = sqlite3pager_lookup(pPager, pgno);
  if( pPage ){
    sprintf(zBuf,"0x%x",(int)pPage);
    Tcl_AppendResult(interp, zBuf, 0);
  }
  return TCL_OK;
}

................................................................................
  int rc;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " PAGE\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPage) ) return TCL_ERROR;
  rc = sqlite3pager_unref(pPage);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  return TCL_OK;
}

................................................................................
  void *pPage;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " PAGE\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPage) ) return TCL_ERROR;
  sprintf(zBuf, "%d", sqlite3pager_pagenumber(pPage));
  Tcl_AppendResult(interp, zBuf, 0);
  return TCL_OK;
}

/*
** Usage:   page_write PAGE DATA
**
................................................................................
  int rc;
  if( argc!=3 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " PAGE DATA\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pPage) ) return TCL_ERROR;
  rc = sqlite3pager_write(pPage);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  strncpy((char*)pPage, argv[2], SQLITE_USABLE_SIZE-1);
  ((char*)pPage)[SQLITE_USABLE_SIZE-1] = 0;
  return TCL_OK;
................................................................................
    char *zName;
    Tcl_CmdProc *xProc;
  } aCmd[] = {
    { "pager_open",              (Tcl_CmdProc*)pager_open          },
    { "pager_close",             (Tcl_CmdProc*)pager_close         },
    { "pager_commit",            (Tcl_CmdProc*)pager_commit        },
    { "pager_rollback",          (Tcl_CmdProc*)pager_rollback      },
    { "pager_stmt_begin",        (Tcl_CmdProc*)pager_stmt_begin    },
    { "pager_stmt_commit",       (Tcl_CmdProc*)pager_stmt_commit   },
    { "pager_stmt_rollback",     (Tcl_CmdProc*)pager_stmt_rollback },
    { "pager_stats",             (Tcl_CmdProc*)pager_stats         },
    { "pager_pagecount",         (Tcl_CmdProc*)pager_pagecount     },
    { "page_get",                (Tcl_CmdProc*)page_get            },
    { "page_lookup",             (Tcl_CmdProc*)page_lookup         },
    { "page_unref",              (Tcl_CmdProc*)page_unref          },
    { "page_read",               (Tcl_CmdProc*)page_read           },
    { "page_write",              (Tcl_CmdProc*)page_write          },
................................................................................
  int i;
  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
    Tcl_CreateCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
  }
  Tcl_LinkVar(interp, "sqlite_io_error_pending",
     (char*)&sqlite_io_error_pending, TCL_LINK_INT);
#ifdef SQLITE_TEST
  {
    extern int journal_format;
    Tcl_LinkVar(interp, "journal_format",
       (char*)&journal_format, TCL_LINK_INT);
  }
#endif
  sprintf(zBuf, "%d", SQLITE_PAGE_SIZE);
  Tcl_SetVar(interp, "SQLITE_PAGE_SIZE", zBuf, TCL_GLOBAL_ONLY); 
  sprintf(zBuf, "%d", SQLITE_PAGE_RESERVE);
  Tcl_SetVar(interp, "SQLITE_PAGE_RESERVE", zBuf, TCL_GLOBAL_ONLY); 
  sprintf(zBuf, "%d", SQLITE_USABLE_SIZE);
  Tcl_SetVar(interp, "SQLITE_USABLE_SIZE", zBuf, TCL_GLOBAL_ONLY); 
  return TCL_OK;
}

Changes to src/util.c.

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**
*************************************************************************
** Utility functions used throughout sqlite.
**
** This file contains functions for allocating memory, comparing
** strings, and stuff like that.
**
** $Id: util.c,v 1.74 2004/02/22 17:49:34 drh Exp $
*/
#include "sqliteInt.h"
#include <stdarg.h>
#include <ctype.h>

/*
** If malloc() ever fails, this global variable gets set to 1.
................................................................................
#if MEMORY_DEBUG>1
  fprintf(stderr,"string at 0x%x is %s\n", (int)*pz, *pz);
#endif
#endif
  va_end(ap);
}


/*
** Add an error message to pParse->zErrMsg and increment pParse->nErr.
** The following formatting characters are allowed:
**
**      %s      Insert a string
**      %z      A string that should be freed after use
**      %d      Insert an integer
................................................................................
  va_list ap;
  pParse->nErr++;
  sqliteFree(pParse->zErrMsg);
  va_start(ap, zFormat);
  pParse->zErrMsg = sqliteVMPrintf(zFormat, ap);
  va_end(ap);
}


/*
** Convert an SQL-style quoted string into a normal string by removing
** the quote characters.  The conversion is done in-place.  If the
** input does not begin with a quote character, then this routine
** is a no-op.
**







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**
*************************************************************************
** Utility functions used throughout sqlite.
**
** This file contains functions for allocating memory, comparing
** strings, and stuff like that.
**
** $Id: util.c,v 1.75 2004/04/26 14:10:22 drh Exp $
*/
#include "sqliteInt.h"
#include <stdarg.h>
#include <ctype.h>

/*
** If malloc() ever fails, this global variable gets set to 1.
................................................................................
#if MEMORY_DEBUG>1
  fprintf(stderr,"string at 0x%x is %s\n", (int)*pz, *pz);
#endif
#endif
  va_end(ap);
}

#if 0
/*
** Add an error message to pParse->zErrMsg and increment pParse->nErr.
** The following formatting characters are allowed:
**
**      %s      Insert a string
**      %z      A string that should be freed after use
**      %d      Insert an integer
................................................................................
  va_list ap;
  pParse->nErr++;
  sqliteFree(pParse->zErrMsg);
  va_start(ap, zFormat);
  pParse->zErrMsg = sqliteVMPrintf(zFormat, ap);
  va_end(ap);
}
#endif

/*
** Convert an SQL-style quoted string into a normal string by removing
** the quote characters.  The conversion is done in-place.  If the
** input does not begin with a quote character, then this routine
** is a no-op.
**

Changes to test/pager.test.

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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 implements regression tests for SQLite library.  The
# focus of this script is page cache subsystem.
#
# $Id: pager.test,v 1.14 2004/02/25 02:20:42 drh Exp $


set testdir [file dirname $argv0]
source $testdir/tester.tcl

if {[info commands pager_open]!=""} {
db close
................................................................................
  } {state 2}
  do_test pager-4.5.$i.2 {
    for {set j 2} {$j<=20} {incr j} {
      set gx [page_get $p1 $j]
      page_write $gx "Page-$j v$i"
      page_unref $gx
      if {$j==$i} {
        pager_ckpt_begin $p1
      }
    }
  } {}
  do_test pager-4.5.$i.3 {
    set res {}
    for {set j 2} {$j<=20} {incr j} {
      set gx [page_get $p1 $j]
................................................................................
  } {state 2}
  do_test pager-4.5.$i.6 {
    for {set j 2} {$j<=20} {incr j} {
      set gx [page_get $p1 $j]
      page_write $gx "Page-$j v$i"
      page_unref $gx
      if {$j==$i} {
        pager_ckpt_begin $p1
      }
    }
  } {}
  do_test pager-4.5.$i.7 {
    pager_ckpt_rollback $p1
    for {set j 2} {$j<=20} {incr j} {
      set gx [page_get $p1 $j]
      set value [page_read $gx]
      page_unref $gx
      if {$j<=$i || $i==1} {
        set shouldbe "Page-$j v$i"
      } else {
................................................................................
  } {}
  do_test pager-4.5.$i.8 {
    for {set j 2} {$j<=20} {incr j} {
      set gx [page_get $p1 $j]
      page_write $gx "Page-$j v$i"
      page_unref $gx
      if {$j==$i} {
        pager_ckpt_begin $p1
      }
    }
  } {}
  do_test pager-4.5.$i.9 {
    pager_ckpt_commit $p1
    for {set j 2} {$j<=20} {incr j} {
      set gx [page_get $p1 $j]
      set value [page_read $gx]
      page_unref $gx
      set shouldbe "Page-$j v$i"
      if {$value!=$shouldbe} {
        lappend res $value $shouldbe
................................................................................



  file delete -force ptf1.db

} ;# end if( not mem: and has pager_open command );


# Ticket #615: an assertion fault inside the pager.  It is a benign
# fault, but we might as well test for it.
#
do_test pager-5.1 {
  sqlite db test.db
  execsql {
    BEGIN;
    CREATE TABLE t1(x);
    PRAGMA synchronous=off;
    COMMIT;
  }
} {}


finish_test







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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 implements regression tests for SQLite library.  The
# focus of this script is page cache subsystem.
#
# $Id: pager.test,v 1.15 2004/04/26 14:10:22 drh Exp $


set testdir [file dirname $argv0]
source $testdir/tester.tcl

if {[info commands pager_open]!=""} {
db close
................................................................................
  } {state 2}
  do_test pager-4.5.$i.2 {
    for {set j 2} {$j<=20} {incr j} {
      set gx [page_get $p1 $j]
      page_write $gx "Page-$j v$i"
      page_unref $gx
      if {$j==$i} {
        pager_stmt_begin $p1
      }
    }
  } {}
  do_test pager-4.5.$i.3 {
    set res {}
    for {set j 2} {$j<=20} {incr j} {
      set gx [page_get $p1 $j]
................................................................................
  } {state 2}
  do_test pager-4.5.$i.6 {
    for {set j 2} {$j<=20} {incr j} {
      set gx [page_get $p1 $j]
      page_write $gx "Page-$j v$i"
      page_unref $gx
      if {$j==$i} {
        pager_stmt_begin $p1
      }
    }
  } {}
  do_test pager-4.5.$i.7 {
    pager_stmt_rollback $p1
    for {set j 2} {$j<=20} {incr j} {
      set gx [page_get $p1 $j]
      set value [page_read $gx]
      page_unref $gx
      if {$j<=$i || $i==1} {
        set shouldbe "Page-$j v$i"
      } else {
................................................................................
  } {}
  do_test pager-4.5.$i.8 {
    for {set j 2} {$j<=20} {incr j} {
      set gx [page_get $p1 $j]
      page_write $gx "Page-$j v$i"
      page_unref $gx
      if {$j==$i} {
        pager_stmt_begin $p1
      }
    }
  } {}
  do_test pager-4.5.$i.9 {
    pager_stmt_commit $p1
    for {set j 2} {$j<=20} {incr j} {
      set gx [page_get $p1 $j]
      set value [page_read $gx]
      page_unref $gx
      set shouldbe "Page-$j v$i"
      if {$value!=$shouldbe} {
        lappend res $value $shouldbe
................................................................................



  file delete -force ptf1.db

} ;# end if( not mem: and has pager_open command );

if 0 {
# Ticket #615: an assertion fault inside the pager.  It is a benign
# fault, but we might as well test for it.
#
do_test pager-5.1 {
  sqlite db test.db
  execsql {
    BEGIN;
    CREATE TABLE t1(x);
    PRAGMA synchronous=off;
    COMMIT;
  }
} {}
}

finish_test

Changes to test/tester.tcl.

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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 implements some common TCL routines used for regression
# testing the SQLite library
#
# $Id: tester.tcl,v 1.28 2004/02/14 01:39:50 drh Exp $


# Make sure tclsqlite was compiled correctly.  Abort now with an
# error message if not.
#
if {[sqlite -tcl-uses-utf]} {
  if {"\u1234"=="u1234"} {
    puts stderr "***** BUILD PROBLEM *****"
    puts stderr "$argv0 was linked against an older version"
................................................................................
catch {db close}
file delete -force test.db
file delete -force test.db-journal
sqlite db ./test.db
if {[info exists ::SETUP_SQL]} {
  db eval $::SETUP_SQL
}



# Abort early if this script has been run before.
#
if {[info exists nTest]} return

# Set the test counters to zero
#
................................................................................
  catch {db close}
  puts "$nErr errors out of $nTest tests"
  puts "Failures on these tests: $::failList"
  if {$nProb>0} {
    puts "$nProb probabilistic tests also failed, but this does"
    puts "not necessarily indicate a malfunction."
  }

  if {$sqlite_open_file_count} {
    puts "$sqlite_open_file_count files were left open"
    incr nErr

  }
  exit [expr {$nErr>0}]
}

# A procedure to execute SQL
#
proc execsql {sql {db db}} {







|

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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 implements some common TCL routines used for regression
# testing the SQLite library
#
# $Id: tester.tcl,v 1.29 2004/04/26 14:10:22 drh Exp $

if 0 {
# Make sure tclsqlite was compiled correctly.  Abort now with an
# error message if not.
#
if {[sqlite -tcl-uses-utf]} {
  if {"\u1234"=="u1234"} {
    puts stderr "***** BUILD PROBLEM *****"
    puts stderr "$argv0 was linked against an older version"
................................................................................
catch {db close}
file delete -force test.db
file delete -force test.db-journal
sqlite db ./test.db
if {[info exists ::SETUP_SQL]} {
  db eval $::SETUP_SQL
}
}
proc db {args} {}

# Abort early if this script has been run before.
#
if {[info exists nTest]} return

# Set the test counters to zero
#
................................................................................
  catch {db close}
  puts "$nErr errors out of $nTest tests"
  puts "Failures on these tests: $::failList"
  if {$nProb>0} {
    puts "$nProb probabilistic tests also failed, but this does"
    puts "not necessarily indicate a malfunction."
  }
  if 0 {
  if {$sqlite_open_file_count} {
    puts "$sqlite_open_file_count files were left open"
    incr nErr
  }
  }
  exit [expr {$nErr>0}]
}

# A procedure to execute SQL
#
proc execsql {sql {db db}} {