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Overview
Comment:Add part of the btree layer of the shared-cache feature. (CVS 2848)
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: 2afcad990190af97d1ad0010f211a5ca8f0fd745
User & Date: danielk1977 2005-12-30 16:28:02
Context
2005-12-30
16:31
Repair typo in previous commit. (CVS 2849) check-in: a4aa0911 user: danielk1977 tags: trunk
16:28
Add part of the btree layer of the shared-cache feature. (CVS 2848) check-in: 2afcad99 user: danielk1977 tags: trunk
2005-12-29
23:33
Add support for CREATE TABLE IF NOT EXISTS. (CVS 2847) check-in: 0bd9e35f user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/btree.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 1.276 2005/12/21 18:36:46 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.
................................................................................
** assumes a minimum cell size of 3 bytes.  Such small cells will be
** exceedingly rare, but they are possible.
*/
#define MX_CELL(pBt) ((pBt->pageSize-8)/3)

/* 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.
**
** You can change this value at compile-time by specifying a
** -DSQLITE_FILE_HEADER="..." on the compiler command-line.  The
................................................................................
  u16 maxLocal;        /* Copy of Btree.maxLocal or Btree.maxLeaf */
  u16 minLocal;        /* Copy of Btree.minLocal or Btree.minLeaf */
  u16 cellOffset;      /* Index in aData of first cell pointer */
  u16 idxParent;       /* Index in parent of this node */
  u16 nFree;           /* Number of free bytes on the page */
  u16 nCell;           /* Number of cells on this page, local and ovfl */
  struct _OvflCell {   /* Cells that will not fit on aData[] */
    u8 *pCell;           /* Pointers to the body of the overflow cell */
    u16 idx;             /* Insert this cell before idx-th non-overflow cell */
  } aOvfl[5];
  struct Btree *pBt;   /* Pointer back to BTree structure */
  u8 *aData;           /* Pointer back to the start of the page */
  Pgno pgno;           /* Page number for this page */
  MemPage *pParent;    /* The parent of this page.  NULL for root */
};

/*
** 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 we are in a statement subtransaction */
  u8 readOnly;          /* True if the underlying file is readonly */
  u8 maxEmbedFrac;      /* Maximum payload as % of total page size */
  u8 minEmbedFrac;      /* Minimum payload as % of total page size */
  u8 minLeafFrac;       /* Minimum leaf payload as % of total page size */
  u8 pageSizeFixed;     /* True if the page size can no longer be changed */
#ifndef SQLITE_OMIT_AUTOVACUUM
................................................................................
  u16 pageSize;         /* Total number of bytes on a page */
  u16 usableSize;       /* Number of usable bytes on each page */
  int maxLocal;         /* Maximum local payload in non-LEAFDATA tables */
  int minLocal;         /* Minimum local payload in non-LEAFDATA tables */
  int maxLeaf;          /* Maximum local payload in a LEAFDATA table */
  int minLeaf;          /* Minimum local payload in a LEAFDATA table */
  BusyHandler *pBusyHandler;   /* Callback for when there is lock contention */





};
typedef Btree Bt;

/*
** Btree.inTrans may take one of the following values.
*/
#define TRANS_NONE  0
#define TRANS_READ  1
#define TRANS_WRITE 2

/*
** An instance of the following structure is used to hold information
** about a cell.  The parseCellPtr() function fills in this structure
** based on information extract from the raw disk page.
*/
typedef struct CellInfo CellInfo;
................................................................................

/*
** A cursor is a pointer to a particular entry in the BTree.
** The entry is identified by its MemPage and the index in
** MemPage.aCell[] of the entry.
*/
struct BtCursor {
  Btree *pBt;               /* The Btree to which this cursor belongs */
  BtCursor *pNext, *pPrev;  /* Forms a linked list of all cursors */
  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[] */
  CellInfo info;            /* A parse of the cell we are pointing at */
................................................................................
# define TRACE(X)
#endif
int sqlite3_btree_trace=0;  /* True to enable tracing */

/*
** Forward declaration
*/
static int checkReadLocks(Btree*,Pgno,BtCursor*);

/*
** Read or write a two- and four-byte big-endian integer values.
*/
static u32 get2byte(unsigned char *p){
  return (p[0]<<8) | p[1];
}
................................................................................

/* The database page the PENDING_BYTE occupies. This page is never used.
** TODO: This macro is very similary to PAGER_MJ_PGNO() in pager.c. They
** should possibly be consolidated (presumably in pager.h).
*/
#define PENDING_BYTE_PAGE(pBt) ((PENDING_BYTE/(pBt)->pageSize)+1)





















































































































#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** These macros define the location of the pointer-map entry for a 
** database page. The first argument to each is the number of usable
** bytes on each page of the database (often 1024). The second is the
** page number to look up in the pointer map.
**
................................................................................
/*
** Write an entry into the pointer map.
**
** This routine updates the pointer map entry for page number 'key'
** so that it maps to type 'eType' and parent page number 'pgno'.
** An error code is returned if something goes wrong, otherwise SQLITE_OK.
*/
static int ptrmapPut(Btree *pBt, Pgno key, u8 eType, Pgno parent){
  u8 *pPtrmap;    /* The pointer map page */
  Pgno iPtrmap;   /* The pointer map page number */
  int offset;     /* Offset in pointer map page */
  int rc;

  assert( pBt->autoVacuum );
  if( key==0 ){
................................................................................
/*
** Read an entry from the pointer map.
**
** This routine retrieves the pointer map entry for page 'key', writing
** the type and parent page number to *pEType and *pPgno respectively.
** An error code is returned if something goes wrong, otherwise SQLITE_OK.
*/
static int ptrmapGet(Btree *pBt, Pgno key, u8 *pEType, Pgno *pPgno){
  int iPtrmap;       /* Pointer map page index */
  u8 *pPtrmap;       /* Pointer map page data */
  int offset;        /* Offset of entry in pointer map */
  int rc;

  iPtrmap = PTRMAP_PAGENO(pBt->usableSize, key);
  rc = sqlite3pager_get(pBt->pPager, iPtrmap, (void **)&pPtrmap);
................................................................................
  sqlite3pager_unref(pPtrmap);
  if( *pEType<1 || *pEType>5 ) return SQLITE_CORRUPT_BKPT;
  return SQLITE_OK;
}

#endif /* SQLITE_OMIT_AUTOVACUUM */






















/*
** Given a btree page and a cell index (0 means the first cell on
** the page, 1 means the second cell, and so forth) return a pointer
** to the cell content.
**
** This routine works only for pages that do not contain overflow cells.
*/
................................................................................
  sqliteFree(used);
}
#define pageIntegrity(X) _pageIntegrity(X)
#else
# define pageIntegrity(X)
#endif










/*
** Defragment the page given.  All Cells are moved to the
** end of the page and all free space is collected into one
** big FreeBlk that occurs in between the header and cell
** pointer array and the cell content area.
*/
static int defragmentPage(MemPage *pPage){
................................................................................
}

/*
** Decode the flags byte (the first byte of the header) for a page
** and initialize fields of the MemPage structure accordingly.
*/
static void decodeFlags(MemPage *pPage, int flagByte){
  Btree *pBt;     /* A copy of pPage->pBt */

  assert( pPage->hdrOffset==(pPage->pgno==1 ? 100 : 0) );
  pPage->intKey = (flagByte & (PTF_INTKEY|PTF_LEAFDATA))!=0;
  pPage->zeroData = (flagByte & PTF_ZERODATA)!=0;
  pPage->leaf = (flagByte & PTF_LEAF)!=0;
  pPage->childPtrSize = 4*(pPage->leaf==0);
  pBt = pPage->pBt;
................................................................................
static int initPage(
  MemPage *pPage,        /* The page to be initialized */
  MemPage *pParent       /* The parent.  Might be NULL */
){
  int pc;            /* Address of a freeblock within pPage->aData[] */
  int hdr;           /* Offset to beginning of page header */
  u8 *data;          /* Equal to pPage->aData */
  Btree *pBt;        /* The main btree structure */
  int usableSize;    /* Amount of usable space on each page */
  int cellOffset;    /* Offset from start of page to first cell pointer */
  int nFree;         /* Number of unused bytes on the page */
  int top;           /* First byte of the cell content area */

  pBt = pPage->pBt;
  assert( pBt!=0 );
................................................................................

/*
** 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( sqlite3pager_pagenumber(data)==pPage->pgno );
  assert( &data[pBt->pageSize] == (unsigned char*)pPage );
  assert( sqlite3pager_iswriteable(data) );
  memset(&data[hdr], 0, pBt->usableSize - hdr);
................................................................................
  pageIntegrity(pPage);
}

/*
** 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 = sqlite3pager_get(pBt->pPager, pgno, (void**)&aData);
  if( rc ) return rc;
  pPage = (MemPage*)&aData[pBt->pageSize];
  pPage->aData = aData;
................................................................................

/*
** Get a page from the pager and initialize it.  This routine
** is just a convenience wrapper around separate calls to
** getPage() and initPage().
*/
static int getAndInitPage(
  Btree *pBt,          /* The database file */
  Pgno pgno,           /* Number of the page to get */
  MemPage **ppPage,    /* Write the page pointer here */
  MemPage *pParent     /* Parent of the page */
){
  int rc;
  if( pgno==0 ){
    return SQLITE_CORRUPT_BKPT; 
................................................................................
** 
** 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 sqlite3BtreeClose() is called.
*/
int sqlite3BtreeOpen(
  const char *zFilename,  /* Name of the file containing the BTree database */

  Btree **ppBtree,        /* Pointer to new Btree object written here */
  int flags               /* Options */
){
  Btree *pBt;

  int rc;
  int nReserve;
  unsigned char zDbHeader[100];











































  /*
  ** The following asserts make sure that structures used by the btree are
  ** the right size.  This is to guard against size changes that result
  ** when compiling on a different architecture.
  */
  assert( sizeof(i64)==8 );
................................................................................
  assert( sizeof(u32)==4 );
  assert( sizeof(u16)==2 );
  assert( sizeof(Pgno)==4 );

  pBt = sqliteMalloc( sizeof(*pBt) );
  if( pBt==0 ){
    *ppBtree = 0;

    return SQLITE_NOMEM;
  }
  rc = sqlite3pager_open(&pBt->pPager, zFilename, EXTRA_SIZE, flags);
  if( rc!=SQLITE_OK ){
    if( pBt->pPager ) sqlite3pager_close(pBt->pPager);
    sqliteFree(pBt);

    *ppBtree = 0;
    return rc;
  }


  sqlite3pager_set_destructor(pBt->pPager, pageDestructor);
  sqlite3pager_set_reiniter(pBt->pPager, pageReinit);
  pBt->pCursor = 0;
  pBt->pPage1 = 0;
  pBt->readOnly = sqlite3pager_isreadonly(pBt->pPager);
  sqlite3pager_read_fileheader(pBt->pPager, sizeof(zDbHeader), zDbHeader);
  pBt->pageSize = get2byte(&zDbHeader[16]);
................................................................................
#ifndef SQLITE_OMIT_AUTOVACUUM
    /* If the magic name ":memory:" will create an in-memory database, then
    ** do not set the auto-vacuum flag, even if SQLITE_DEFAULT_AUTOVACUUM
    ** is true. On the other hand, if SQLITE_OMIT_MEMORYDB has been defined,
    ** then ":memory:" is just a regular file-name. Respect the auto-vacuum
    ** default in this case.
    */
#ifndef SQLITE_OMIT_MEMORYDB
    if( zFilename && strcmp(zFilename,":memory:") ){
#else
    if( zFilename ){
#endif
      pBt->autoVacuum = SQLITE_DEFAULT_AUTOVACUUM;
    }
#endif
    nReserve = 0;
  }else{
    nReserve = zDbHeader[20];
    pBt->maxEmbedFrac = zDbHeader[21];
................................................................................
#ifndef SQLITE_OMIT_AUTOVACUUM
    pBt->autoVacuum = (get4byte(&zDbHeader[36 + 4*4])?1:0);
#endif
  }
  pBt->usableSize = pBt->pageSize - nReserve;
  assert( (pBt->pageSize & 7)==0 );  /* 8-byte alignment of pageSize */
  sqlite3pager_set_pagesize(pBt->pPager, pBt->pageSize);









  *ppBtree = pBt;
  return SQLITE_OK;
}

/*
** Close an open database and invalidate all cursors.
*/
int sqlite3BtreeClose(Btree *pBt){








  while( pBt->pCursor ){




    sqlite3BtreeCloseCursor(pBt->pCursor);
  }





























  sqlite3pager_close(pBt->pPager);
  sqliteFree(pBt);
  return SQLITE_OK;
}

/*
** Change the busy handler callback function.
*/
int sqlite3BtreeSetBusyHandler(Btree *pBt, BusyHandler *pHandler){

  pBt->pBusyHandler = pHandler;
  sqlite3pager_set_busyhandler(pBt->pPager, pHandler);
  return SQLITE_OK;
}

/*
** Change the limit on the number of pages allowed in the cache.
................................................................................
** 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 sqlite3BtreeSetCacheSize(Btree *pBt, int mxPage){

  sqlite3pager_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.
*/
#ifndef SQLITE_OMIT_PAGER_PRAGMAS
int sqlite3BtreeSetSafetyLevel(Btree *pBt, int level){

  sqlite3pager_set_safety_level(pBt->pPager, level);
  return SQLITE_OK;
}
#endif

/*
** Return TRUE if the given btree is set to safety level 1.  In other
** words, return TRUE if no sync() occurs on the disk files.
*/
int sqlite3BtreeSyncDisabled(Btree *pBt){

  assert( pBt && pBt->pPager );
  return sqlite3pager_nosync(pBt->pPager);
}

#if !defined(SQLITE_OMIT_PAGER_PRAGMAS) || !defined(SQLITE_OMIT_VACUUM)
/*
** Change the default pages size and the number of reserved bytes per page.
................................................................................
** of the database file used for locking (beginning at PENDING_BYTE,
** the first byte past the 1GB boundary, 0x40000000) needs to occur
** at the beginning of a page.
**
** If parameter nReserve is less than zero, then the number of reserved
** bytes per page is left unchanged.
*/
int sqlite3BtreeSetPageSize(Btree *pBt, int pageSize, int nReserve){

  if( pBt->pageSizeFixed ){
    return SQLITE_READONLY;
  }
  if( nReserve<0 ){
    nReserve = pBt->pageSize - pBt->usableSize;
  }
  if( pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE &&
        ((pageSize-1)&pageSize)==0 ){
    assert( (pageSize & 7)==0 );

    pBt->pageSize = sqlite3pager_set_pagesize(pBt->pPager, pageSize);
  }
  pBt->usableSize = pBt->pageSize - nReserve;
  return SQLITE_OK;
}

/*
** Return the currently defined page size
*/
int sqlite3BtreeGetPageSize(Btree *pBt){
  return pBt->pageSize;
}
int sqlite3BtreeGetReserve(Btree *pBt){
  return pBt->pageSize - pBt->usableSize;
}
#endif /* !defined(SQLITE_OMIT_PAGER_PRAGMAS) || !defined(SQLITE_OMIT_VACUUM) */

/*
** Change the 'auto-vacuum' property of the database. If the 'autoVacuum'
** parameter is non-zero, then auto-vacuum mode is enabled. If zero, it
** is disabled. The default value for the auto-vacuum property is 
** determined by the SQLITE_DEFAULT_AUTOVACUUM macro.
*/
int sqlite3BtreeSetAutoVacuum(Btree *pBt, int autoVacuum){

#ifdef SQLITE_OMIT_AUTOVACUUM
  return SQLITE_READONLY;
#else
  if( pBt->pageSizeFixed ){
    return SQLITE_READONLY;
  }
  pBt->autoVacuum = (autoVacuum?1:0);
................................................................................
#endif
}

/*
** Return the value of the 'auto-vacuum' property. If auto-vacuum is 
** enabled 1 is returned. Otherwise 0.
*/
int sqlite3BtreeGetAutoVacuum(Btree *pBt){
#ifdef SQLITE_OMIT_AUTOVACUUM
  return 0;
#else
  return pBt->autoVacuum;
#endif
}


/*
** Get a reference to pPage1 of the database file.  This will
** also acquire a readlock on that file.
................................................................................
**
** SQLITE_OK is returned on success.  If the file is not a
** well-formed database file, then SQLITE_CORRUPT is returned.
** SQLITE_BUSY is returned if the database is locked.  SQLITE_NOMEM
** is returned if we run out of memory.  SQLITE_PROTOCOL is returned
** if there is a locking protocol violation.
*/
static int lockBtree(Btree *pBt){
  int rc, pageSize;
  MemPage *pPage1;
  if( pBt->pPage1 ) return SQLITE_OK;
  rc = getPage(pBt, 1, &pPage1);
  if( rc!=SQLITE_OK ) return rc;
  

................................................................................
  return rc;
}

/*
** This routine works like lockBtree() except that it also invokes the
** busy callback if there is lock contention.
*/
static int lockBtreeWithRetry(Btree *pBt){
  int rc = SQLITE_OK;
  if( pBt->inTrans==TRANS_NONE ){


    rc = sqlite3BtreeBeginTrans(pBt, 0);

    pBt->inTrans = TRANS_NONE;




  }
  return rc;
}
       

/*
** If there are no outstanding cursors and we are not in the middle
................................................................................
** 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==TRANS_NONE && pBt->pCursor==0 && pBt->pPage1!=0 ){
    if( pBt->pPage1->aData==0 ){
      MemPage *pPage = pBt->pPage1;
      pPage->aData = &((u8*)pPage)[-pBt->pageSize];
      pPage->pBt = pBt;
      pPage->pgno = 1;
    }
    releasePage(pBt->pPage1);
................................................................................
  }
}

/*
** 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( sqlite3pager_pagecount(pBt->pPager)>0 ) return SQLITE_OK;
  pP1 = pBt->pPage1;
  assert( pP1!=0 );
  data = pP1->aData;
................................................................................
** a reserved lock.  B tries to promote to exclusive but is blocked because
** of A's read lock.  A tries to promote to reserved but is blocked by B.
** One or the other of the two processes must give way or there can be
** no progress.  By returning SQLITE_BUSY and not invoking the busy callback
** when A already has a read lock, we encourage A to give up and let B
** proceed.
*/
int sqlite3BtreeBeginTrans(Btree *pBt, int wrflag){

  int rc = SQLITE_OK;



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

  /* Write transactions are not possible on a read-only database */
  if( pBt->readOnly && wrflag ){
    return SQLITE_READONLY;
  }









  do {
    if( pBt->pPage1==0 ){
      rc = lockBtree(pBt);
    }
  
    if( rc==SQLITE_OK && wrflag ){
................................................................................
      rc = sqlite3pager_begin(pBt->pPage1->aData, wrflag>1);
      if( rc==SQLITE_OK ){
        rc = newDatabase(pBt);
      }
    }
  
    if( rc==SQLITE_OK ){
      pBt->inTrans = (wrflag?TRANS_WRITE:TRANS_READ);
      if( wrflag ) pBt->inStmt = 0;
    }else{
      unlockBtreeIfUnused(pBt);
    }
  }while( rc==SQLITE_BUSY && pBt->inTrans==TRANS_NONE &&
          sqlite3InvokeBusyHandler(pBt->pBusyHandler) );












  return rc;
}

#ifndef SQLITE_OMIT_AUTOVACUUM

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

  initPage(pPage, 0);
  nCell = pPage->nCell;

  for(i=0; i<nCell; i++){
................................................................................


/*
** Move the open database page pDbPage to location iFreePage in the 
** database. The pDbPage reference remains valid.
*/
static int relocatePage(
  Btree *pBt,              /* Btree */
  MemPage *pDbPage,        /* Open page to move */
  u8 eType,                /* Pointer map 'type' entry for pDbPage */
  Pgno iPtrPage,           /* Pointer map 'page-no' entry for pDbPage */
  Pgno iFreePage           /* The location to move pDbPage to */
){
  MemPage *pPtrPage;   /* The page that contains a pointer to pDbPage */
  Pgno iDbPage = pDbPage->pgno;
................................................................................
      rc = ptrmapPut(pBt, iFreePage, eType, iPtrPage);
    }
  }
  return rc;
}

/* Forward declaration required by autoVacuumCommit(). */
static int allocatePage(Btree *, MemPage **, Pgno *, Pgno, u8);

/*
** This routine is called prior to sqlite3pager_commit when a transaction
** is commited for an auto-vacuum database.
*/
static int autoVacuumCommit(Btree *pBt, Pgno *nTrunc){
  Pager *pPager = pBt->pPager;
  Pgno nFreeList;   /* Number of pages remaining on the free-list. */
  int nPtrMap;      /* Number of pointer-map pages deallocated */
  Pgno origSize;  /* Pages in the database file */
  Pgno finSize;   /* Pages in the database file after truncation */
  int rc;           /* Return code */
  u8 eType;
................................................................................

/*
** 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 = SQLITE_OK;








  if( pBt->inTrans==TRANS_WRITE ){


    rc = sqlite3pager_commit(pBt->pPager);


  }
















  pBt->inTrans = TRANS_NONE;
  pBt->inStmt = 0;
  unlockBtreeIfUnused(pBt);


  return rc;
}

#ifndef NDEBUG
/*
** Return the number of write-cursors open on this handle. This is for use
** in assert() expressions, so it is only compiled if NDEBUG is not
** defined.
*/
static int countWriteCursors(Btree *pBt){
  BtCursor *pCur;
  int r = 0;
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    if( pCur->wrFlag ) r++;
  }
  return r;
}
#endif

#ifdef SQLITE_TEST
/*
** Print debugging information about all cursors to standard output.
*/
void sqlite3BtreeCursorList(Btree *pBt){
  BtCursor *pCur;

  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    MemPage *pPage = pCur->pPage;
    char *zMode = pCur->wrFlag ? "rw" : "ro";
    sqlite3DebugPrintf("CURSOR %p rooted at %4d(%s) currently at %d.%d%s\n",
       pCur, pCur->pgnoRoot, zMode,
       pPage ? pPage->pgno : 0, pCur->idx,
       pCur->isValid ? "" : " eof"
................................................................................
** 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 = SQLITE_OK;

  MemPage *pPage1;




  if( pBt->inTrans==TRANS_WRITE ){


    rc = sqlite3pager_rollback(pBt->pPager);
    /* The rollback may have destroyed the pPage1->aData value.  So
    ** call getPage() on page 1 again to make sure pPage1->aData is
    ** set correctly. */
    if( getPage(pBt, 1, &pPage1)==SQLITE_OK ){
      releasePage(pPage1);
    }
    assert( countWriteCursors(pBt)==0 );

  }









  pBt->inTrans = TRANS_NONE;
  pBt->inStmt = 0;
  unlockBtreeIfUnused(pBt);


  return rc;
}

/*
** Start a statement subtransaction.  The subtransaction can
** can be rolled back independently of the main transaction.
** You must start a transaction before starting a subtransaction.
................................................................................
** to start a new subtransaction if another subtransaction is already active.
**
** Statement subtransactions are used around individual SQL statements
** that are contained within a BEGIN...COMMIT block.  If a constraint
** error occurs within the statement, the effect of that one statement
** can be rolled back without having to rollback the entire transaction.
*/
int sqlite3BtreeBeginStmt(Btree *pBt){
  int rc;

  if( (pBt->inTrans!=TRANS_WRITE) || pBt->inStmt ){
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }

  rc = pBt->readOnly ? SQLITE_OK : sqlite3pager_stmt_begin(pBt->pPager);
  pBt->inStmt = 1;
  return rc;
}


/*
** Commit the statment subtransaction currently in progress.  If no
** subtransaction is active, this is a no-op.
*/
int sqlite3BtreeCommitStmt(Btree *pBt){
  int rc;

  if( pBt->inStmt && !pBt->readOnly ){
    rc = sqlite3pager_stmt_commit(pBt->pPager);
  }else{
    rc = SQLITE_OK;
  }
  pBt->inStmt = 0;
  return rc;
................................................................................
** Rollback the active statement subtransaction.  If no subtransaction
** is active this routine is a no-op.
**
** All cursors will be invalidated 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;

  if( pBt->inStmt==0 || pBt->readOnly ) return SQLITE_OK;
  rc = sqlite3pager_stmt_rollback(pBt->pPager);
  assert( countWriteCursors(pBt)==0 );
  pBt->inStmt = 0;
  return rc;
}

................................................................................
** 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;


  *ppCur = 0;
  if( wrFlag ){
    if( pBt->readOnly ){
      return SQLITE_READONLY;
    }
    if( checkReadLocks(pBt, iTable, 0) ){
      return SQLITE_LOCKED;
    }
  }








  if( pBt->pPage1==0 ){
    rc = lockBtreeWithRetry(pBt);
    if( rc!=SQLITE_OK ){
      return rc;
    }
  }
  pCur = sqliteMallocRaw( sizeof(*pCur) );
  if( pCur==0 ){
    rc = SQLITE_NOMEM;
................................................................................
    rc = SQLITE_EMPTY;
    goto create_cursor_exception;
  }
  rc = getAndInitPage(pBt, pCur->pgnoRoot, &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;
  memset(&pCur->info, 0, sizeof(pCur->info));
  pCur->pNext = pBt->pCursor;
  if( pCur->pNext ){
    pCur->pNext->pPrev = pCur;
  }
  pCur->pPrev = 0;
  pBt->pCursor = pCur;
  pCur->isValid = 0;
  *ppCur = pCur;
  return SQLITE_OK;


create_cursor_exception:
  if( pCur ){
    releasePage(pCur->pPage);
    sqliteFree(pCur);
  }
  unlockBtreeIfUnused(pBt);
  return rc;
................................................................................
#endif

/*
** 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;
................................................................................
  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;
  int ovflSize;
  u32 nKey;

  assert( pCur!=0 && pCur->pPage!=0 );
  assert( pCur->isValid );
  pBt = pCur->pBt;
  pPage = pCur->pPage;
  pageIntegrity(pPage);
  assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
  getCellInfo(pCur);
  aPayload = pCur->info.pCell;
  aPayload += pCur->info.nHeader;
  if( pPage->intKey ){
................................................................................
** Move the cursor down to a new child page.  The newPgno argument is the
** page number of the child page to move to.
*/
static int moveToChild(BtCursor *pCur, u32 newPgno){
  int rc;
  MemPage *pNewPage;
  MemPage *pOldPage;
  Btree *pBt = pCur->pBt;

  assert( pCur->isValid );
  rc = getAndInitPage(pBt, newPgno, &pNewPage, pCur->pPage);
  if( rc ) return rc;
  pageIntegrity(pNewPage);
  pNewPage->idxParent = pCur->idx;
  pOldPage = pCur->pPage;
................................................................................

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

  rc = getAndInitPage(pBt, pCur->pgnoRoot, &pRoot, 0);
  if( rc ){
    pCur->isValid = 0;
    return rc;
  }
  releasePage(pCur->pPage);
................................................................................
** which in turn can make database access faster.
**
** If the "exact" parameter is not 0, and the page-number nearby exists 
** anywhere on the free-list, then it is guarenteed to be returned. This
** is only used by auto-vacuum databases when allocating a new table.
*/
static int allocatePage(
  Btree *pBt, 
  MemPage **ppPage, 
  Pgno *pPgno, 
  Pgno nearby,
  u8 exact
){
  MemPage *pPage1;
  int rc;
................................................................................

/*
** Add a page of the database file to the freelist.
**
** sqlite3pager_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);
................................................................................
  return rc;
}

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

  parseCellPtr(pPage, pCell, &info);
  if( info.iOverflow==0 ){
    return SQLITE_OK;  /* No overflow pages. Return without doing anything */
................................................................................
  const u8 *pSrc;
  int nSrc, n, rc;
  int spaceLeft;
  MemPage *pOvfl = 0;
  MemPage *pToRelease = 0;
  unsigned char *pPrior;
  unsigned char *pPayload;
  Btree *pBt = pPage->pBt;
  Pgno pgnoOvfl = 0;
  int nHeader;
  CellInfo info;

  /* Fill in the header. */
  nHeader = 0;
  if( !pPage->leaf ){
................................................................................
}

/*
** Change the MemPage.pParent pointer on the page whose number is
** given in the second argument so that MemPage.pParent holds the
** pointer in the third argument.
*/
static int reparentPage(Btree *pBt, Pgno pgno, MemPage *pNewParent, int idx){
  MemPage *pThis;
  unsigned char *aData;

  if( pgno==0 ) return SQLITE_OK;
  assert( pBt->pPager!=0 );
  aData = sqlite3pager_lookup(pBt->pPager, pgno);
  if( aData ){
................................................................................
** to make sure that each child knows that pPage is its parent.
**
** This routine gets called after you memcpy() one page into
** another.
*/
static int reparentChildPages(MemPage *pPage){
  int i;
  Btree *pBt = pPage->pBt;
  int rc = SQLITE_OK;

  if( pPage->leaf ) return SQLITE_OK;

  for(i=0; i<pPage->nCell; i++){
    u8 *pCell = findCell(pPage, i);
    if( !pPage->leaf ){
................................................................................
static int balance_quick(MemPage *pPage, MemPage *pParent){
  int rc;
  MemPage *pNew;
  Pgno pgnoNew;
  u8 *pCell;
  int szCell;
  CellInfo info;
  Btree *pBt = pPage->pBt;
  int parentIdx = pParent->nCell;   /* pParent new divider cell index */
  int parentSize;                   /* Size of new divider cell */
  u8 parentCell[64];                /* Space for the new divider cell */

  /* Allocate a new page. Insert the overflow cell from pPage
  ** into it. Then remove the overflow cell from pPage.
  */
................................................................................
**
** If this routine fails for any reason, it might leave the database
** in a corrupted state.  So if this routine fails, the database should
** be rolled back.
*/
static int balance_nonroot(MemPage *pPage){
  MemPage *pParent;            /* The parent of pPage */
  Btree *pBt;                  /* The whole database */
  int nCell = 0;               /* Number of cells in apCell[] */
  int nMaxCells = 0;           /* Allocated size of apCell, szCell, aFrom. */
  int nOld;                    /* Number of pages in apOld[] */
  int nNew;                    /* Number of pages in apNew[] */
  int nDiv;                    /* Number of cells in apDiv[] */
  int i, j, k;                 /* Loop counters */
  int idx;                     /* Index of pPage in pParent->aCell[] */
................................................................................
** page contains no cells.  This is an opportunity to make the tree
** shallower by one level.
*/
static int balance_shallower(MemPage *pPage){
  MemPage *pChild;             /* The only child page of pPage */
  Pgno pgnoChild;              /* Page number for pChild */
  int rc = SQLITE_OK;          /* Return code from subprocedures */
  Btree *pBt;                  /* The main BTree structure */
  int mxCellPerPage;           /* Maximum number of cells per page */
  u8 **apCell;                 /* All cells from pages being balanced */
  int *szCell;                 /* Local size of all cells */

  assert( pPage->pParent==0 );
  assert( pPage->nCell==0 );
  pBt = pPage->pBt;
................................................................................
** child.   Finally, call balance_internal() on the new child
** to cause it to split.
*/
static int balance_deeper(MemPage *pPage){
  int rc;             /* Return value from subprocedures */
  MemPage *pChild;    /* Pointer to a new child page */
  Pgno pgnoChild;     /* Page number of the new child page */
  Btree *pBt;         /* The BTree */
  int usableSize;     /* Total usable size of a page */
  u8 *data;           /* Content of the parent page */
  u8 *cdata;          /* Content of the child page */
  int hdr;            /* Offset to page header in parent */
  int brk;            /* Offset to content of first cell in parent */

  assert( pPage->pParent==0 );
................................................................................
** means a cursor opened with wrFlag==0) this routine also moves
** all cursors other than pExclude so that they are pointing to the 
** first Cell on root page.  This is necessary because an insert 
** or delete might change the number of cells on a page or delete
** a page entirely and we do not want to leave any cursors 
** pointing to non-existant pages or cells.
*/
static int checkReadLocks(Btree *pBt, Pgno pgnoRoot, BtCursor *pExclude){
  BtCursor *p;
  for(p=pBt->pCursor; p; p=p->pNext){
    if( p->pgnoRoot!=pgnoRoot || p==pExclude ) continue;
    if( p->wrFlag==0 ) return SQLITE_LOCKED;
    if( p->pPage->pgno!=p->pgnoRoot ){
      moveToRoot(p);
    }
................................................................................
  const void *pKey, i64 nKey,    /* The key of the new record */
  const void *pData, int nData   /* The data of the new record */
){
  int rc;
  int loc;
  int szNew;
  MemPage *pPage;
  Btree *pBt = pCur->pBt;
  unsigned char *oldCell;
  unsigned char *newCell = 0;

  if( pBt->inTrans!=TRANS_WRITE ){
    /* Must start a transaction before doing an insert */
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  assert( !pBt->readOnly );
  if( !pCur->wrFlag ){
    return SQLITE_PERM;   /* Cursor not open for writing */
  }
................................................................................
** is left pointing at a random location.
*/
int sqlite3BtreeDelete(BtCursor *pCur){
  MemPage *pPage = pCur->pPage;
  unsigned char *pCell;
  int rc;
  Pgno pgnoChild = 0;
  Btree *pBt = pCur->pBt;

  assert( pPage->isInit );
  if( pBt->inTrans!=TRANS_WRITE ){
    /* Must start a transaction before doing a delete */
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  assert( !pBt->readOnly );
  if( pCur->idx >= pPage->nCell ){
    return SQLITE_ERROR;  /* The cursor is not pointing to anything */
  }
................................................................................
** The type of type is determined by the flags parameter.  Only the
** following values of flags are currently in use.  Other values for
** flags might not work:
**
**     BTREE_INTKEY|BTREE_LEAFDATA     Used for SQL tables with rowid keys
**     BTREE_ZERODATA                  Used for SQL indices
*/
int sqlite3BtreeCreateTable(Btree *pBt, int *piTable, int flags){

  MemPage *pRoot;
  Pgno pgnoRoot;
  int rc;
  if( pBt->inTrans!=TRANS_WRITE ){
    /* Must start a transaction first */
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  assert( !pBt->readOnly );

  /* It is illegal to create a table if any cursors are open on the
  ** database. This is because in auto-vacuum mode the backend may
................................................................................
    Pgno pgnoMove;      /* Move a page here to make room for the root-page */
    MemPage *pPageMove; /* The page to move to. */

    /* Read the value of meta[3] from the database to determine where the
    ** root page of the new table should go. meta[3] is the largest root-page
    ** created so far, so the new root-page is (meta[3]+1).
    */
    rc = sqlite3BtreeGetMeta(pBt, 4, &pgnoRoot);
    if( rc!=SQLITE_OK ) return rc;
    pgnoRoot++;

    /* The new root-page may not be allocated on a pointer-map page, or the
    ** PENDING_BYTE page.
    */
    if( pgnoRoot==PTRMAP_PAGENO(pBt->usableSize, pgnoRoot) ||
................................................................................

    /* Update the pointer-map and meta-data with the new root-page number. */
    rc = ptrmapPut(pBt, pgnoRoot, PTRMAP_ROOTPAGE, 0);
    if( rc ){
      releasePage(pRoot);
      return rc;
    }
    rc = sqlite3BtreeUpdateMeta(pBt, 4, pgnoRoot);
    if( rc ){
      releasePage(pRoot);
      return rc;
    }

  }else{
    rc = allocatePage(pBt, &pRoot, &pgnoRoot, 1, 0);
................................................................................
}

/*
** Erase the given database page and all its children.  Return
** the page to the freelist.
*/
static int clearDatabasePage(
  Btree *pBt,           /* The BTree that contains the table */
  Pgno pgno,            /* Page number to clear */
  MemPage *pParent,     /* Parent page.  NULL for the root */
  int freePageFlag      /* Deallocate page if true */
){
  MemPage *pPage = 0;
  int rc;
  unsigned char *pCell;
................................................................................
** the page number of the root of the table.  After this routine returns,
** the root page is empty, but still exists.
**
** This routine will fail with SQLITE_LOCKED if there are any open
** read cursors on the table.  Open write cursors are moved to the
** root of the table.
*/
int sqlite3BtreeClearTable(Btree *pBt, int iTable){
  int rc;
  BtCursor *pCur;

  if( pBt->inTrans!=TRANS_WRITE ){
    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);
    }
................................................................................
** root pages are kept at the beginning of the database file, which
** is necessary for AUTOVACUUM to work right.  *piMoved is set to the 
** page number that used to be the last root page in the file before
** the move.  If no page gets moved, *piMoved is set to 0.
** The last root page is recorded in meta[3] and the value of
** meta[3] is updated by this procedure.
*/
int sqlite3BtreeDropTable(Btree *pBt, int iTable, int *piMoved){
  int rc;
  MemPage *pPage = 0;


  if( pBt->inTrans!=TRANS_WRITE ){
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }

  /* It is illegal to drop a table if any cursors are open on the
  ** database. This is because in auto-vacuum mode the backend may
  ** need to move another root-page to fill a gap left by the deleted
  ** root page. If an open cursor was using this page a problem would 
................................................................................
  */
  if( pBt->pCursor ){
    return SQLITE_LOCKED;
  }

  rc = getPage(pBt, (Pgno)iTable, &pPage);
  if( rc ) return rc;
  rc = sqlite3BtreeClearTable(pBt, iTable);
  if( rc ){
    releasePage(pPage);
    return rc;
  }

  *piMoved = 0;

................................................................................
  if( iTable>1 ){
#ifdef SQLITE_OMIT_AUTOVACUUM
    rc = freePage(pPage);
    releasePage(pPage);
#else
    if( pBt->autoVacuum ){
      Pgno maxRootPgno;
      rc = sqlite3BtreeGetMeta(pBt, 4, &maxRootPgno);
      if( rc!=SQLITE_OK ){
        releasePage(pPage);
        return rc;
      }

      if( iTable==maxRootPgno ){
        /* If the table being dropped is the table with the largest root-page
................................................................................
        maxRootPgno--;
      }
      if( maxRootPgno==PTRMAP_PAGENO(pBt->usableSize, maxRootPgno) ){
        maxRootPgno--;
      }
      assert( maxRootPgno!=PENDING_BYTE_PAGE(pBt) );

      rc = sqlite3BtreeUpdateMeta(pBt, 4, maxRootPgno);
    }else{
      rc = freePage(pPage);
      releasePage(pPage);
    }
#endif
  }else{
    /* If sqlite3BtreeDropTable was called on page 1. */
................................................................................
** through meta[15] are available for use by higher layers.  Meta[0]
** is read-only, the others are read/write.
** 
** The schema layer numbers meta values differently.  At the schema
** layer (and the SetCookie and ReadCookie opcodes) the number of
** free pages is not visible.  So Cookie[0] is the same as Meta[1].
*/
int sqlite3BtreeGetMeta(Btree *pBt, int idx, u32 *pMeta){
  int rc;
  unsigned char *pP1;


  assert( idx>=0 && idx<=15 );
  rc = sqlite3pager_get(pBt->pPager, 1, (void**)&pP1);
  if( rc ) return rc;
  *pMeta = get4byte(&pP1[36 + idx*4]);
  sqlite3pager_unref(pP1);

................................................................................
  return SQLITE_OK;
}

/*
** Write meta-information back into the database.  Meta[0] is
** read-only and may not be written.
*/
int sqlite3BtreeUpdateMeta(Btree *pBt, int idx, u32 iMeta){

  unsigned char *pP1;
  int rc;
  assert( idx>=1 && idx<=15 );
  if( pBt->inTrans!=TRANS_WRITE ){
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  assert( pBt->pPage1!=0 );
  pP1 = pBt->pPage1->aData;
  rc = sqlite3pager_write(pP1);
  if( rc ) return rc;
  put4byte(&pP1[36 + idx*4], iMeta);
................................................................................
}

#ifdef SQLITE_DEBUG
/*
** Print a disassembly of the given page on standard output.  This routine
** is used for debugging and testing only.
*/
static int btreePageDump(Btree *pBt, int pgno, int recursive, MemPage *pParent){
  int rc;
  MemPage *pPage;
  int i, j, c;
  int nFree;
  u16 idx;
  int hdr;
  int nCell;
................................................................................
    btreePageDump(pBt, get4byte(&data[hdr+8]), 1, pPage);
  }
  pPage->isInit = isInit;
  sqlite3pager_unref(data);
  fflush(stdout);
  return SQLITE_OK;
}
int sqlite3BtreePageDump(Btree *pBt, int pgno, int recursive){
  return btreePageDump(pBt, pgno, recursive, 0);
}
#endif

#ifdef SQLITE_TEST
/*
** Fill aResult[] with information about the entry and page that the
** cursor is pointing to.
................................................................................
}
#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.
*/
typedef struct IntegrityCk IntegrityCk;
struct IntegrityCk {
  Btree *pBt;    /* The tree being checked out */
  Pager *pPager; /* The associated pager.  Also accessible by pBt->pPager */
  int nPage;     /* Number of pages in the database */
  int *anRef;    /* Number of times each page is referenced */
  char *zErrMsg; /* An error message.  NULL of no errors seen. */
};

#ifndef SQLITE_OMIT_INTEGRITY_CHECK
................................................................................
  int nUpper            /* Number of characters in zUpperBound */
){
  MemPage *pPage;
  int i, rc, depth, d2, pgno, cnt;
  int hdr, cellStart;
  int nCell;
  u8 *data;
  Btree *pBt;
  int usableSize;
  char zContext[100];
  char *hit;

  sprintf(zContext, "Page %d: ", iPage);

  /* Check that the page exists
................................................................................
** 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 = *sqlite3pager_stats(pBt->pPager);
  if( lockBtreeWithRetry(pBt)!=SQLITE_OK ){
    return sqliteStrDup("Unable to acquire a read lock on the database");
  }
  sCheck.pBt = pBt;
  sCheck.pPager = pBt->pPager;
  sCheck.nPage = sqlite3pager_pagecount(sCheck.pPager);
  if( sCheck.nPage==0 ){
    unlockBtreeIfUnused(pBt);
................................................................................
  return sCheck.zErrMsg;
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */

/*
** Return the full pathname of the underlying database file.
*/
const char *sqlite3BtreeGetFilename(Btree *pBt){
  assert( pBt->pPager!=0 );
  return sqlite3pager_filename(pBt->pPager);
}

/*
** Return the pathname of the directory that contains the database file.
*/
const char *sqlite3BtreeGetDirname(Btree *pBt){
  assert( pBt->pPager!=0 );
  return sqlite3pager_dirname(pBt->pPager);
}

/*
** Return the pathname of the journal file for this database. The return
** value of this routine is the same regardless of whether the journal file
** has been created or not.
*/
const char *sqlite3BtreeGetJournalname(Btree *pBt){
  assert( pBt->pPager!=0 );
  return sqlite3pager_journalname(pBt->pPager);
}

#ifndef SQLITE_OMIT_VACUUM
/*
** 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, iSkip;




  if( pBtTo->inTrans!=TRANS_WRITE || pBtFrom->inTrans!=TRANS_WRITE ){
    return SQLITE_ERROR;
  }
  if( pBtTo->pCursor ) return SQLITE_BUSY;
  nToPage = sqlite3pager_pagecount(pBtTo->pPager);
  nPage = sqlite3pager_pagecount(pBtFrom->pPager);
  iSkip = PENDING_BYTE_PAGE(pBtTo);
  for(i=1; rc==SQLITE_OK && i<=nPage; i++){
................................................................................
    sqlite3pager_unref(pPage);
    sqlite3pager_dont_write(pBtTo->pPager, i);
  }
  if( !rc && nPage<nToPage ){
    rc = sqlite3pager_truncate(pBtTo->pPager, nPage);
  }
  if( rc ){
    sqlite3BtreeRollback(pBtTo);
  }
  return rc;  
}
#endif /* SQLITE_OMIT_VACUUM */

/*
** Return non-zero if a transaction is active.
*/
int sqlite3BtreeIsInTrans(Btree *pBt){
  return (pBt && (pBt->inTrans==TRANS_WRITE));
}

/*
** Return non-zero if a statement transaction is active.
*/
int sqlite3BtreeIsInStmt(Btree *pBt){
  return (pBt && pBt->inStmt);
}

/*
** This call is a no-op if no write-transaction is currently active on pBt.
**
** Otherwise, sync the database file for the btree pBt. zMaster points to
** the name of a master journal file that should be written into the
................................................................................
**
** When this is called, the master journal should already have been
** created, populated with this journal pointer and synced to disk.
**
** Once this is routine has returned, the only thing required to commit
** the write-transaction for this database file is to delete the journal.
*/
int sqlite3BtreeSync(Btree *pBt, const char *zMaster){
  if( pBt->inTrans==TRANS_WRITE ){

#ifndef SQLITE_OMIT_AUTOVACUUM
    Pgno nTrunc = 0;
    if( pBt->autoVacuum ){
      int rc = autoVacuumCommit(pBt, &nTrunc); 
      if( rc!=SQLITE_OK ) return rc;
    }
    return sqlite3pager_sync(pBt->pPager, zMaster, nTrunc);
#endif
    return sqlite3pager_sync(pBt->pPager, zMaster, 0);
  }
  return SQLITE_OK;
}






















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>
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5
6
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8
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13
14
15
16
17
18
19
...
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
...
282
283
284
285
286
287
288
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291
292
293
294
295
296
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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
...
340
341
342
343
344
345
346
347
348
349
350
351
352








353
354
355
356
357
358
359
...
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
...
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
...
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
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460
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464
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467
468
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527
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529
530
531
532
533
534
535
536
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539
540
541
542
543
544
545
546
547
548
549
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551
552
553
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555
556
557
558
559
560
561
562
563
...
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
...
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
...
674
675
676
677
678
679
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681
682
683
684
685
686
687
688
689
690
691
692
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700
701
702
703
704
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706
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708
...
939
940
941
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943
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946
947
948
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950
951
952
953
954
955
956
957
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959
960
961
....
1136
1137
1138
1139
1140
1141
1142
1143
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1146
1147
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1149
1150
....
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
....
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
....
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
....
1298
1299
1300
1301
1302
1303
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1308
1309
1310
1311
1312
....
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
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1403
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1405
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1414
1415
1416
1417
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1419
1420
1421
1422
1423
1424
1425
1426
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1428
1429
1430
1431
1432
1433
1434
1435
....
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
....
1470
1471
1472
1473
1474
1475
1476



1477

1478
1479
1480
1481
1482
1483
1484
....
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
1521
1522
1523
1524
1525
1526
1527
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
....
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
1612
1613
1614
1615
1616
1617
1618
1619
1620
....
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
....
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
....
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
....
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
....
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
....
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
....
1880
1881
1882
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
....
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
....
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
....
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288

2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
....
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
....
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
....
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
....
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
....
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573

2574
2575
2576
2577
2578
2579
2580
2581
2582
....
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
....
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
....
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
....
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
....
3326
3327
3328
3329
3330
3331
3332
3333
3334
3335
3336
3337
3338
3339
3340
....
3544
3545
3546
3547
3548
3549
3550
3551
3552
3553
3554
3555
3556
3557
3558
....
3612
3613
3614
3615
3616
3617
3618
3619
3620
3621
3622
3623
3624
3625
3626
....
3664
3665
3666
3667
3668
3669
3670
3671
3672
3673
3674
3675
3676
3677
3678
....
3753
3754
3755
3756
3757
3758
3759
3760
3761
3762
3763
3764
3765
3766
3767
....
3796
3797
3798
3799
3800
3801
3802
3803
3804
3805
3806
3807
3808
3809
3810
....
4029
4030
4031
4032
4033
4034
4035
4036
4037
4038
4039
4040
4041
4042
4043
....
4138
4139
4140
4141
4142
4143
4144
4145
4146
4147
4148
4149
4150
4151
4152
....
4687
4688
4689
4690
4691
4692
4693
4694
4695
4696
4697
4698
4699
4700
4701
....
4789
4790
4791
4792
4793
4794
4795
4796
4797
4798
4799
4800
4801
4802
4803
....
4878
4879
4880
4881
4882
4883
4884
4885
4886
4887
4888
4889
4890
4891
4892
....
4908
4909
4910
4911
4912
4913
4914
4915
4916
4917
4918
4919
4920
4921
4922
4923
4924
4925
4926
....
4980
4981
4982
4983
4984
4985
4986
4987
4988
4989
4990
4991
4992
4993
4994
4995
4996
4997
....
5083
5084
5085
5086
5087
5088
5089
5090
5091
5092
5093
5094
5095
5096
5097
5098
5099
5100
5101
5102
....
5115
5116
5117
5118
5119
5120
5121
5122
5123
5124
5125
5126
5127
5128
5129
....
5182
5183
5184
5185
5186
5187
5188
5189
5190
5191
5192
5193
5194
5195
5196
....
5205
5206
5207
5208
5209
5210
5211
5212
5213
5214
5215
5216
5217
5218
5219
....
5256
5257
5258
5259
5260
5261
5262
5263
5264
5265
5266
5267
5268
5269
5270
5271
5272
5273
5274
....
5298
5299
5300
5301
5302
5303
5304
5305
5306
5307
5308
5309
5310
5311
5312
5313
5314
5315
5316
5317
....
5319
5320
5321
5322
5323
5324
5325
5326
5327
5328
5329
5330
5331
5332
5333
....
5334
5335
5336
5337
5338
5339
5340
5341
5342
5343
5344
5345
5346
5347
5348
....
5391
5392
5393
5394
5395
5396
5397
5398
5399
5400
5401
5402
5403
5404
5405
....
5416
5417
5418
5419
5420
5421
5422
5423
5424
5425
5426
5427
5428
5429
5430
5431
5432
5433
....
5441
5442
5443
5444
5445
5446
5447
5448
5449
5450
5451
5452
5453
5454
5455
5456
5457
5458
5459
5460
....
5471
5472
5473
5474
5475
5476
5477
5478
5479
5480
5481
5482
5483
5484
5485
....
5567
5568
5569
5570
5571
5572
5573
5574
5575
5576
5577
5578
5579
5580
5581
5582
....
5641
5642
5643
5644
5645
5646
5647
5648
5649
5650
5651
5652
5653
5654
5655
5656
5657
5658
5659
5660
5661
5662
5663
5664
5665
....
5842
5843
5844
5845
5846
5847
5848
5849
5850
5851
5852
5853
5854
5855
5856
....
5984
5985
5986
5987
5988
5989
5990
5991
5992
5993
5994
5995
5996
5997
5998
5999
6000
6001
6002
6003
6004
6005
....
6073
6074
6075
6076
6077
6078
6079
6080
6081
6082
6083
6084
6085
6086
6087
6088
6089
6090
6091
6092
6093
6094
6095
6096
6097
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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 1.277 2005/12/30 16:28:02 danielk1977 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.
................................................................................
** assumes a minimum cell size of 3 bytes.  Such small cells will be
** exceedingly rare, but they are possible.
*/
#define MX_CELL(pBt) ((pBt->pageSize-8)/3)

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

/*
** This is a magic string that appears at the beginning of every
** SQLite database in order to identify the file as a real database.
**
** You can change this value at compile-time by specifying a
** -DSQLITE_FILE_HEADER="..." on the compiler command-line.  The
................................................................................
  u16 maxLocal;        /* Copy of Btree.maxLocal or Btree.maxLeaf */
  u16 minLocal;        /* Copy of Btree.minLocal or Btree.minLeaf */
  u16 cellOffset;      /* Index in aData of first cell pointer */
  u16 idxParent;       /* Index in parent of this node */
  u16 nFree;           /* Number of free bytes on the page */
  u16 nCell;           /* Number of cells on this page, local and ovfl */
  struct _OvflCell {   /* Cells that will not fit on aData[] */
    u8 *pCell;          /* Pointers to the body of the overflow cell */
    u16 idx;            /* Insert this cell before idx-th non-overflow cell */
  } aOvfl[5];
  BtShared *pBt;        /* Pointer back to BTree structure */
  u8 *aData;            /* Pointer back to the start of the page */
  Pgno pgno;            /* Page number for this page */
  MemPage *pParent;     /* The parent of this page.  NULL for root */
};

/*
** 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)

/* Btree handle */
struct Btree {
  sqlite3 *pSqlite;
  BtShared *pBt;
  u8 inTrans;            /* TRANS_NONE, TRANS_READ or TRANS_WRITE */
};

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

/*
** Everything we need to know about an open database
*/
struct BtShared {
  Pager *pPager;        /* The page cache */
  BtCursor *pCursor;    /* A list of all open cursors */
  MemPage *pPage1;      /* First page of the database */

  u8 inStmt;            /* True if we are in a statement subtransaction */
  u8 readOnly;          /* True if the underlying file is readonly */
  u8 maxEmbedFrac;      /* Maximum payload as % of total page size */
  u8 minEmbedFrac;      /* Minimum payload as % of total page size */
  u8 minLeafFrac;       /* Minimum leaf payload as % of total page size */
  u8 pageSizeFixed;     /* True if the page size can no longer be changed */
#ifndef SQLITE_OMIT_AUTOVACUUM
................................................................................
  u16 pageSize;         /* Total number of bytes on a page */
  u16 usableSize;       /* Number of usable bytes on each page */
  int maxLocal;         /* Maximum local payload in non-LEAFDATA tables */
  int minLocal;         /* Minimum local payload in non-LEAFDATA tables */
  int maxLeaf;          /* Maximum local payload in a LEAFDATA table */
  int minLeaf;          /* Minimum local payload in a LEAFDATA table */
  BusyHandler *pBusyHandler;   /* Callback for when there is lock contention */
  u8 inTransaction;     /* Transaction state */
  BtShared *pNext;      /* Next in SqliteTsd.pBtree linked list */
  int nRef;             /* Number of references to this structure */
  int nTransaction;     /* Number of open transactions (read + write) */
  BtLock *pLock;        /* List of locks held on this shared-btree struct */
};









/*
** An instance of the following structure is used to hold information
** about a cell.  The parseCellPtr() function fills in this structure
** based on information extract from the raw disk page.
*/
typedef struct CellInfo CellInfo;
................................................................................

/*
** A cursor is a pointer to a particular entry in the BTree.
** The entry is identified by its MemPage and the index in
** MemPage.aCell[] of the entry.
*/
struct BtCursor {
  Btree *pBtree;            /* The Btree to which this cursor belongs */
  BtCursor *pNext, *pPrev;  /* Forms a linked list of all cursors */
  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[] */
  CellInfo info;            /* A parse of the cell we are pointing at */
................................................................................
# define TRACE(X)
#endif
int sqlite3_btree_trace=0;  /* True to enable tracing */

/*
** Forward declaration
*/
static int checkReadLocks(BtShared*,Pgno,BtCursor*);

/*
** Read or write a two- and four-byte big-endian integer values.
*/
static u32 get2byte(unsigned char *p){
  return (p[0]<<8) | p[1];
}
................................................................................

/* The database page the PENDING_BYTE occupies. This page is never used.
** TODO: This macro is very similary to PAGER_MJ_PGNO() in pager.c. They
** should possibly be consolidated (presumably in pager.h).
*/
#define PENDING_BYTE_PAGE(pBt) ((PENDING_BYTE/(pBt)->pageSize)+1)

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

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

#ifdef SQLITE_OMIT_SHARED_CACHE
  /*
  ** The functions queryTableLock(), lockTable() and unlockAllTables()
  ** manipulate entries in the BtShared.pLock linked list used to store
  ** shared-cache table level locks. If the library is compiled with the
  ** shared-cache feature disabled, then there is only ever one user
  ** of each BtShared structure and so this locking is not required. 
  ** So define the three interface functions as no-ops.
  */
  #define queryTableLock(a,b,c) SQLITE_OK
  #define lockTable(a,b,c) SQLITE_OK
  #define unlockAllTables(a,b,c)
#else

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

  for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
    if( pIter->pBtree!=p && pIter->iTable==iTab && 
        (pIter->eLock!=READ_LOCK || eLock!=READ_LOCK) ){
      return SQLITE_BUSY;
    }
  }
  return SQLITE_OK;
}

/*
** Add a lock on the table with root-page iTable to the shared-btree used
** by Btree handle p. Parameter eLock must be either READ_LOCK or 
** WRITE_LOCK.
**
** SQLITE_OK is returned if the lock is added successfully. SQLITE_BUSY and
** SQLITE_NOMEM may also be returned.
*/
static int lockTable(Btree *p, Pgno iTable, u8 eLock){
  BtShared *pBt = p->pBt;
  BtLock *pLock = 0;
  BtLock *pIter;

  assert( SQLITE_OK==queryTableLock(p, iTable, eLock) );

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

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

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

  return SQLITE_OK;
}

/*
** Release all the table locks (locks obtained via calls to the lockTable()
** procedure) held by Btree handle p.
*/
static void unlockAllTables(Btree *p){
  BtLock **ppIter = &p->pBt->pLock;
  while( *ppIter ){
    BtLock *pLock = *ppIter;
    if( pLock->pBtree==p ){
      *ppIter = pLock->pNext;
      sqliteFree(pLock);
    }else{
      ppIter = &pLock->pNext;
    }
  }
}
#endif /* SQLITE_OMIT_SHARED_CACHE */

#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** These macros define the location of the pointer-map entry for a 
** database page. The first argument to each is the number of usable
** bytes on each page of the database (often 1024). The second is the
** page number to look up in the pointer map.
**
................................................................................
/*
** Write an entry into the pointer map.
**
** This routine updates the pointer map entry for page number 'key'
** so that it maps to type 'eType' and parent page number 'pgno'.
** An error code is returned if something goes wrong, otherwise SQLITE_OK.
*/
static int ptrmapPut(BtShared *pBt, Pgno key, u8 eType, Pgno parent){
  u8 *pPtrmap;    /* The pointer map page */
  Pgno iPtrmap;   /* The pointer map page number */
  int offset;     /* Offset in pointer map page */
  int rc;

  assert( pBt->autoVacuum );
  if( key==0 ){
................................................................................
/*
** Read an entry from the pointer map.
**
** This routine retrieves the pointer map entry for page 'key', writing
** the type and parent page number to *pEType and *pPgno respectively.
** An error code is returned if something goes wrong, otherwise SQLITE_OK.
*/
static int ptrmapGet(BtShared *pBt, Pgno key, u8 *pEType, Pgno *pPgno){
  int iPtrmap;       /* Pointer map page index */
  u8 *pPtrmap;       /* Pointer map page data */
  int offset;        /* Offset of entry in pointer map */
  int rc;

  iPtrmap = PTRMAP_PAGENO(pBt->usableSize, key);
  rc = sqlite3pager_get(pBt->pPager, iPtrmap, (void **)&pPtrmap);
................................................................................
  sqlite3pager_unref(pPtrmap);
  if( *pEType<1 || *pEType>5 ) return SQLITE_CORRUPT_BKPT;
  return SQLITE_OK;
}

#endif /* SQLITE_OMIT_AUTOVACUUM */

/*
** Return a pointer to the Btree structure associated with btree pBt
** and connection handle pSqlite.
*/
#if 0
static Btree *btree_findref(BtShared *pBt, sqlite3 *pSqlite){
#ifndef SQLITE_OMIT_SHARED_DATA
  if( pBt->aRef ){
    int i;
    for(i=0; i<pBt->nRef; i++){
      if( pBt->aRef[i].pSqlite==pSqlite ){
        return &pBt->aRef[i];
      }
    }
    assert(0);
  }
#endif
  return &pBt->ref;
}
#endif

/*
** Given a btree page and a cell index (0 means the first cell on
** the page, 1 means the second cell, and so forth) return a pointer
** to the cell content.
**
** This routine works only for pages that do not contain overflow cells.
*/
................................................................................
  sqliteFree(used);
}
#define pageIntegrity(X) _pageIntegrity(X)
#else
# define pageIntegrity(X)
#endif

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

/*
** Defragment the page given.  All Cells are moved to the
** end of the page and all free space is collected into one
** big FreeBlk that occurs in between the header and cell
** pointer array and the cell content area.
*/
static int defragmentPage(MemPage *pPage){
................................................................................
}

/*
** Decode the flags byte (the first byte of the header) for a page
** and initialize fields of the MemPage structure accordingly.
*/
static void decodeFlags(MemPage *pPage, int flagByte){
  BtShared *pBt;     /* A copy of pPage->pBt */

  assert( pPage->hdrOffset==(pPage->pgno==1 ? 100 : 0) );
  pPage->intKey = (flagByte & (PTF_INTKEY|PTF_LEAFDATA))!=0;
  pPage->zeroData = (flagByte & PTF_ZERODATA)!=0;
  pPage->leaf = (flagByte & PTF_LEAF)!=0;
  pPage->childPtrSize = 4*(pPage->leaf==0);
  pBt = pPage->pBt;
................................................................................
static int initPage(
  MemPage *pPage,        /* The page to be initialized */
  MemPage *pParent       /* The parent.  Might be NULL */
){
  int pc;            /* Address of a freeblock within pPage->aData[] */
  int hdr;           /* Offset to beginning of page header */
  u8 *data;          /* Equal to pPage->aData */
  BtShared *pBt;        /* The main btree structure */
  int usableSize;    /* Amount of usable space on each page */
  int cellOffset;    /* Offset from start of page to first cell pointer */
  int nFree;         /* Number of unused bytes on the page */
  int top;           /* First byte of the cell content area */

  pBt = pPage->pBt;
  assert( pBt!=0 );
................................................................................

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

  assert( sqlite3pager_pagenumber(data)==pPage->pgno );
  assert( &data[pBt->pageSize] == (unsigned char*)pPage );
  assert( sqlite3pager_iswriteable(data) );
  memset(&data[hdr], 0, pBt->usableSize - hdr);
................................................................................
  pageIntegrity(pPage);
}

/*
** Get a page from the pager.  Initialize the MemPage.pBt and
** MemPage.aData elements if needed.
*/
static int getPage(BtShared *pBt, Pgno pgno, MemPage **ppPage){
  int rc;
  unsigned char *aData;
  MemPage *pPage;
  rc = sqlite3pager_get(pBt->pPager, pgno, (void**)&aData);
  if( rc ) return rc;
  pPage = (MemPage*)&aData[pBt->pageSize];
  pPage->aData = aData;
................................................................................

/*
** Get a page from the pager and initialize it.  This routine
** is just a convenience wrapper around separate calls to
** getPage() and initPage().
*/
static int getAndInitPage(
  BtShared *pBt,          /* The database file */
  Pgno pgno,           /* Number of the page to get */
  MemPage **ppPage,    /* Write the page pointer here */
  MemPage *pParent     /* Parent of the page */
){
  int rc;
  if( pgno==0 ){
    return SQLITE_CORRUPT_BKPT; 
................................................................................
** 
** 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 sqlite3BtreeClose() is called.
*/
int sqlite3BtreeOpen(
  const char *zFilename,  /* Name of the file containing the BTree database */
  sqlite3 *pSqlite,       /* Associated database handle */
  Btree **ppBtree,        /* Pointer to new Btree object written here */
  int flags               /* Options */
){
  BtShared *pBt;          /* Shared part of btree structure */
  Btree *p;               /* Handle to return */
  int rc;
  int nReserve;
  unsigned char zDbHeader[100];
  SqliteTsd *pTsd = sqlite3Tsd();

  /* Set the variable isMemdb to true for an in-memory database, or 
  ** false for a file-based database. This symbol is only required if
  ** either of the shared-data or autovacuum features are compiled 
  ** into the library.
  */
#if !defined(SQLITE_OMIT_SHARED_CACHE) || !defined(SQLITE_OMIT_AUTOVACUUM)
  #ifdef SQLITE_OMIT_MEMORYDB
  const int isMemdb = !zFilename;
  #else
  const int isMemdb = !zFilename || (strcmp(zFilename, ":memory:")?0:1);
  #endif
#endif

  p = sqliteMalloc(sizeof(Btree));
  if( !p ){
    return SQLITE_NOMEM;
  }
  p->inTrans = TRANS_NONE;
  p->pSqlite = pSqlite;

  /* Try to find an existing Btree structure opened on zFilename. */
#ifndef SQLITE_OMIT_SHARED_CACHE
  if( pTsd->useSharedData && zFilename && !isMemdb ){
    char *zFullPathname = sqlite3Os.xFullPathname(zFilename);
    if( !zFullPathname ){
      sqliteFree(p);
      return SQLITE_NOMEM;
    }
    for(pBt=pTsd->pBtree; pBt; pBt=pBt->pNext){
      if( 0==strcmp(zFullPathname, sqlite3pager_filename(pBt->pPager)) ){
        p->pBt = pBt;
        *ppBtree = p;
        pBt->nRef++;
        sqliteFree(zFullPathname);
        return SQLITE_OK;
      }
    }
    sqliteFree(zFullPathname);
  }
#endif

  /*
  ** The following asserts make sure that structures used by the btree are
  ** the right size.  This is to guard against size changes that result
  ** when compiling on a different architecture.
  */
  assert( sizeof(i64)==8 );
................................................................................
  assert( sizeof(u32)==4 );
  assert( sizeof(u16)==2 );
  assert( sizeof(Pgno)==4 );

  pBt = sqliteMalloc( sizeof(*pBt) );
  if( pBt==0 ){
    *ppBtree = 0;
    sqliteFree(p);
    return SQLITE_NOMEM;
  }
  rc = sqlite3pager_open(&pBt->pPager, zFilename, EXTRA_SIZE, flags);
  if( rc!=SQLITE_OK ){
    if( pBt->pPager ) sqlite3pager_close(pBt->pPager);
    sqliteFree(pBt);
    sqliteFree(p);
    *ppBtree = 0;
    return rc;
  }
  p->pBt = pBt;

  sqlite3pager_set_destructor(pBt->pPager, pageDestructor);
  sqlite3pager_set_reiniter(pBt->pPager, pageReinit);
  pBt->pCursor = 0;
  pBt->pPage1 = 0;
  pBt->readOnly = sqlite3pager_isreadonly(pBt->pPager);
  sqlite3pager_read_fileheader(pBt->pPager, sizeof(zDbHeader), zDbHeader);
  pBt->pageSize = get2byte(&zDbHeader[16]);
................................................................................
#ifndef SQLITE_OMIT_AUTOVACUUM
    /* If the magic name ":memory:" will create an in-memory database, then
    ** do not set the auto-vacuum flag, even if SQLITE_DEFAULT_AUTOVACUUM
    ** is true. On the other hand, if SQLITE_OMIT_MEMORYDB has been defined,
    ** then ":memory:" is just a regular file-name. Respect the auto-vacuum
    ** default in this case.
    */



    if( zFilename && !isMemdb ){

      pBt->autoVacuum = SQLITE_DEFAULT_AUTOVACUUM;
    }
#endif
    nReserve = 0;
  }else{
    nReserve = zDbHeader[20];
    pBt->maxEmbedFrac = zDbHeader[21];
................................................................................
#ifndef SQLITE_OMIT_AUTOVACUUM
    pBt->autoVacuum = (get4byte(&zDbHeader[36 + 4*4])?1:0);
#endif
  }
  pBt->usableSize = pBt->pageSize - nReserve;
  assert( (pBt->pageSize & 7)==0 );  /* 8-byte alignment of pageSize */
  sqlite3pager_set_pagesize(pBt->pPager, pBt->pageSize);

#ifndef SQLITE_OMIT_SHARED_CACHE
  /* Add the new btree to the linked list starting at SqliteTsd.pBtree */
  if( pTsd->useSharedData && zFilename && !isMemdb ){
    pBt->pNext = pTsd->pBtree;
    pTsd->pBtree = pBt;
  }
  pBt->nRef = 1;
#endif
  *ppBtree = p;
  return SQLITE_OK;
}

/*
** Close an open database and invalidate all cursors.
*/
int sqlite3BtreeClose(Btree *p){
  SqliteTsd *pTsd = sqlite3Tsd();
  BtShared *pBt = p->pBt;
  BtCursor *pCur;

  /* Drop any table-locks */
  unlockAllTables(p);

  /* Close all cursors opened via this handle.  */
  pCur = pBt->pCursor;
  while( pCur ){
    BtCursor *pTmp = pCur;
    pCur = pCur->pNext;
    if( pTmp->pBtree==p ){
      sqlite3BtreeCloseCursor(pTmp);
    }
  }

  sqliteFree(p);

#ifndef SQLITE_OMIT_SHARED_CACHE
  /* If there are still other outstanding references to the shared-btree
  ** structure, return now. The remainder of this procedure cleans 
  ** up the shared-btree.
  */
  assert( pBt->nRef>0 );
  pBt->nRef--;
  if( pBt->nRef ){
    return SQLITE_OK;
  }

  /* Remove the shared-btree from the thread wide list */
  if( pTsd->pBtree==pBt ){
    pTsd->pBtree = pBt->pNext;
  }else{
    BtShared *pPrev;
    for(pPrev=pTsd->pBtree; pPrev && pPrev->pNext!=pBt; pPrev=pPrev->pNext);
    if( pPrev ){
      pPrev->pNext = pBt->pNext;
    }
  }
#endif

  /* Close the pager and free the shared-btree structure */
  assert( !pBt->pCursor );
  sqlite3pager_close(pBt->pPager);
  sqliteFree(pBt);
  return SQLITE_OK;
}

/*
** Change the busy handler callback function.
*/
int sqlite3BtreeSetBusyHandler(Btree *p, BusyHandler *pHandler){
  BtShared *pBt = p->pBt;
  pBt->pBusyHandler = pHandler;
  sqlite3pager_set_busyhandler(pBt->pPager, pHandler);
  return SQLITE_OK;
}

/*
** Change the limit on the number of pages allowed in the cache.
................................................................................
** 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 sqlite3BtreeSetCacheSize(Btree *p, int mxPage){
  BtShared *pBt = p->pBt;
  sqlite3pager_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.
*/
#ifndef SQLITE_OMIT_PAGER_PRAGMAS
int sqlite3BtreeSetSafetyLevel(Btree *p, int level){
  BtShared *pBt = p->pBt;
  sqlite3pager_set_safety_level(pBt->pPager, level);
  return SQLITE_OK;
}
#endif

/*
** Return TRUE if the given btree is set to safety level 1.  In other
** words, return TRUE if no sync() occurs on the disk files.
*/
int sqlite3BtreeSyncDisabled(Btree *p){
  BtShared *pBt = p->pBt;
  assert( pBt && pBt->pPager );
  return sqlite3pager_nosync(pBt->pPager);
}

#if !defined(SQLITE_OMIT_PAGER_PRAGMAS) || !defined(SQLITE_OMIT_VACUUM)
/*
** Change the default pages size and the number of reserved bytes per page.
................................................................................
** of the database file used for locking (beginning at PENDING_BYTE,
** the first byte past the 1GB boundary, 0x40000000) needs to occur
** at the beginning of a page.
**
** If parameter nReserve is less than zero, then the number of reserved
** bytes per page is left unchanged.
*/
int sqlite3BtreeSetPageSize(Btree *p, int pageSize, int nReserve){
  BtShared *pBt = p->pBt;
  if( pBt->pageSizeFixed ){
    return SQLITE_READONLY;
  }
  if( nReserve<0 ){
    nReserve = pBt->pageSize - pBt->usableSize;
  }
  if( pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE &&
        ((pageSize-1)&pageSize)==0 ){
    assert( (pageSize & 7)==0 );
    assert( !pBt->pPage1 && !pBt->pCursor );
    pBt->pageSize = sqlite3pager_set_pagesize(pBt->pPager, pageSize);
  }
  pBt->usableSize = pBt->pageSize - nReserve;
  return SQLITE_OK;
}

/*
** Return the currently defined page size
*/
int sqlite3BtreeGetPageSize(Btree *p){
  return p->pBt->pageSize;
}
int sqlite3BtreeGetReserve(Btree *p){
  return p->pBt->pageSize - p->pBt->usableSize;
}
#endif /* !defined(SQLITE_OMIT_PAGER_PRAGMAS) || !defined(SQLITE_OMIT_VACUUM) */

/*
** Change the 'auto-vacuum' property of the database. If the 'autoVacuum'
** parameter is non-zero, then auto-vacuum mode is enabled. If zero, it
** is disabled. The default value for the auto-vacuum property is 
** determined by the SQLITE_DEFAULT_AUTOVACUUM macro.
*/
int sqlite3BtreeSetAutoVacuum(Btree *p, int autoVacuum){
  BtShared *pBt = p->pBt;;
#ifdef SQLITE_OMIT_AUTOVACUUM
  return SQLITE_READONLY;
#else
  if( pBt->pageSizeFixed ){
    return SQLITE_READONLY;
  }
  pBt->autoVacuum = (autoVacuum?1:0);
................................................................................
#endif
}

/*
** Return the value of the 'auto-vacuum' property. If auto-vacuum is 
** enabled 1 is returned. Otherwise 0.
*/
int sqlite3BtreeGetAutoVacuum(Btree *p){
#ifdef SQLITE_OMIT_AUTOVACUUM
  return 0;
#else
  return p->pBt->autoVacuum;
#endif
}


/*
** Get a reference to pPage1 of the database file.  This will
** also acquire a readlock on that file.
................................................................................
**
** SQLITE_OK is returned on success.  If the file is not a
** well-formed database file, then SQLITE_CORRUPT is returned.
** SQLITE_BUSY is returned if the database is locked.  SQLITE_NOMEM
** is returned if we run out of memory.  SQLITE_PROTOCOL is returned
** if there is a locking protocol violation.
*/
static int lockBtree(BtShared *pBt){
  int rc, pageSize;
  MemPage *pPage1;
  if( pBt->pPage1 ) return SQLITE_OK;
  rc = getPage(pBt, 1, &pPage1);
  if( rc!=SQLITE_OK ) return rc;
  

................................................................................
  return rc;
}

/*
** This routine works like lockBtree() except that it also invokes the
** busy callback if there is lock contention.
*/
static int lockBtreeWithRetry(Btree *pRef){
  int rc = SQLITE_OK;
  if( pRef->inTrans==TRANS_NONE ){
    u8 inTransaction = pRef->pBt->inTransaction;
    btreeIntegrity(pRef);
    rc = sqlite3BtreeBeginTrans(pRef, 0);
    pRef->pBt->inTransaction = inTransaction;
    pRef->inTrans = TRANS_NONE;
    if( rc==SQLITE_OK ){
      pRef->pBt->nTransaction--;
    }
    btreeIntegrity(pRef);
  }
  return rc;
}
       

/*
** If there are no outstanding cursors and we are not in the middle
................................................................................
** 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(BtShared *pBt){
  if( pBt->inTransaction==TRANS_NONE && pBt->pCursor==0 && pBt->pPage1!=0 ){
    if( pBt->pPage1->aData==0 ){
      MemPage *pPage = pBt->pPage1;
      pPage->aData = &((u8*)pPage)[-pBt->pageSize];
      pPage->pBt = pBt;
      pPage->pgno = 1;
    }
    releasePage(pBt->pPage1);
................................................................................
  }
}

/*
** Create a new database by initializing the first page of the
** file.
*/
static int newDatabase(BtShared *pBt){
  MemPage *pP1;
  unsigned char *data;
  int rc;
  if( sqlite3pager_pagecount(pBt->pPager)>0 ) return SQLITE_OK;
  pP1 = pBt->pPage1;
  assert( pP1!=0 );
  data = pP1->aData;
................................................................................
** a reserved lock.  B tries to promote to exclusive but is blocked because
** of A's read lock.  A tries to promote to reserved but is blocked by B.
** One or the other of the two processes must give way or there can be
** no progress.  By returning SQLITE_BUSY and not invoking the busy callback
** when A already has a read lock, we encourage A to give up and let B
** proceed.
*/
int sqlite3BtreeBeginTrans(Btree *p, int wrflag){
  BtShared *pBt = p->pBt;
  int rc = SQLITE_OK;

  btreeIntegrity(p);

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

  /* Write transactions are not possible on a read-only database */
  if( pBt->readOnly && wrflag ){
    return SQLITE_READONLY;
  }

  /* If another database handle has already opened a write transaction 
  ** on this shared-btree structure and a second write transaction is
  ** requested, return SQLITE_BUSY.
  */
  if( pBt->inTransaction==TRANS_WRITE && wrflag ){
    return SQLITE_BUSY;
  }

  do {
    if( pBt->pPage1==0 ){
      rc = lockBtree(pBt);
    }
  
    if( rc==SQLITE_OK && wrflag ){
................................................................................
      rc = sqlite3pager_begin(pBt->pPage1->aData, wrflag>1);
      if( rc==SQLITE_OK ){
        rc = newDatabase(pBt);
      }
    }
  
    if( rc==SQLITE_OK ){

      if( wrflag ) pBt->inStmt = 0;
    }else{
      unlockBtreeIfUnused(pBt);
    }
  }while( rc==SQLITE_BUSY && pBt->inTransaction==TRANS_NONE &&
          sqlite3InvokeBusyHandler(pBt->pBusyHandler) );

  if( rc==SQLITE_OK ){
    if( p->inTrans==TRANS_NONE ){
      pBt->nTransaction++;
    }
    p->inTrans = (wrflag?TRANS_WRITE:TRANS_READ);
    if( p->inTrans>pBt->inTransaction ){
      pBt->inTransaction = p->inTrans;
    }
  }

  btreeIntegrity(p);
  return rc;
}

#ifndef SQLITE_OMIT_AUTOVACUUM

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

  initPage(pPage, 0);
  nCell = pPage->nCell;

  for(i=0; i<nCell; i++){
................................................................................


/*
** Move the open database page pDbPage to location iFreePage in the 
** database. The pDbPage reference remains valid.
*/
static int relocatePage(
  BtShared *pBt,           /* Btree */
  MemPage *pDbPage,        /* Open page to move */
  u8 eType,                /* Pointer map 'type' entry for pDbPage */
  Pgno iPtrPage,           /* Pointer map 'page-no' entry for pDbPage */
  Pgno iFreePage           /* The location to move pDbPage to */
){
  MemPage *pPtrPage;   /* The page that contains a pointer to pDbPage */
  Pgno iDbPage = pDbPage->pgno;
................................................................................
      rc = ptrmapPut(pBt, iFreePage, eType, iPtrPage);
    }
  }
  return rc;
}

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

/*
** This routine is called prior to sqlite3pager_commit when a transaction
** is commited for an auto-vacuum database.
*/
static int autoVacuumCommit(BtShared *pBt, Pgno *nTrunc){
  Pager *pPager = pBt->pPager;
  Pgno nFreeList;   /* Number of pages remaining on the free-list. */
  int nPtrMap;      /* Number of pointer-map pages deallocated */
  Pgno origSize;  /* Pages in the database file */
  Pgno finSize;   /* Pages in the database file after truncation */
  int rc;           /* Return code */
  u8 eType;
................................................................................

/*
** 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 *p){
  int rc = SQLITE_OK;
  BtShared *pBt = p->pBt;

  btreeIntegrity(p);
  unlockAllTables(p);

  /* If the handle has a write-transaction open, commit the shared-btrees 
  ** transaction and set the shared state to TRANS_READ.
  */
  if( p->inTrans==TRANS_WRITE ){
    assert( pBt->inTransaction==TRANS_WRITE );
    assert( pBt->nTransaction>0 );
    rc = sqlite3pager_commit(pBt->pPager);
    pBt->inTransaction = TRANS_READ;
    pBt->inStmt = 0;
  }

  /* If the handle has any kind of transaction open, decrement the transaction
  ** count of the shared btree. If the transaction count reaches 0, set
  ** the shared state to TRANS_NONE. The unlockBtreeIfUnused() call below
  ** will unlock the pager.
  */
  if( p->inTrans!=TRANS_NONE ){
    pBt->nTransaction--;
    if( 0==pBt->nTransaction ){
      pBt->inTransaction = TRANS_NONE;
    }
  }

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

  unlockBtreeIfUnused(pBt);

  btreeIntegrity(p);
  return rc;
}

#ifndef NDEBUG
/*
** Return the number of write-cursors open on this handle. This is for use
** in assert() expressions, so it is only compiled if NDEBUG is not
** defined.
*/
static int countWriteCursors(BtShared *pBt){
  BtCursor *pCur;
  int r = 0;
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    if( pCur->wrFlag ) r++; 
  }
  return r;
}
#endif

#ifdef SQLITE_TEST
/*
** Print debugging information about all cursors to standard output.
*/
void sqlite3BtreeCursorList(Btree *p){
  BtCursor *pCur;
  BtShared *pBt = p->pBt;
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    MemPage *pPage = pCur->pPage;
    char *zMode = pCur->wrFlag ? "rw" : "ro";
    sqlite3DebugPrintf("CURSOR %p rooted at %4d(%s) currently at %d.%d%s\n",
       pCur, pCur->pgnoRoot, zMode,
       pPage ? pPage->pgno : 0, pCur->idx,
       pCur->isValid ? "" : " eof"
................................................................................
** 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 *p){
  int rc = SQLITE_OK;
  BtShared *pBt = p->pBt;
  MemPage *pPage1;

  btreeIntegrity(p);
  unlockAllTables(p);

  if( p->inTrans==TRANS_WRITE ){
    assert( TRANS_WRITE==pBt->inTransaction );

    rc = sqlite3pager_rollback(pBt->pPager);
    /* The rollback may have destroyed the pPage1->aData value.  So
    ** call getPage() on page 1 again to make sure pPage1->aData is
    ** set correctly. */
    if( getPage(pBt, 1, &pPage1)==SQLITE_OK ){
      releasePage(pPage1);
    }
    assert( countWriteCursors(pBt)==0 );
    pBt->inTransaction = TRANS_READ;
  }

  if( p->inTrans!=TRANS_NONE ){
    assert( pBt->nTransaction>0 );
    pBt->nTransaction--;
    if( 0==pBt->nTransaction ){
      pBt->inTransaction = TRANS_NONE;
    }
  }

  p->inTrans = TRANS_NONE;
  pBt->inStmt = 0;
  unlockBtreeIfUnused(pBt);

  btreeIntegrity(p);
  return rc;
}

/*
** Start a statement subtransaction.  The subtransaction can
** can be rolled back independently of the main transaction.
** You must start a transaction before starting a subtransaction.
................................................................................
** to start a new subtransaction if another subtransaction is already active.
**
** Statement subtransactions are used around individual SQL statements
** that are contained within a BEGIN...COMMIT block.  If a constraint
** error occurs within the statement, the effect of that one statement
** can be rolled back without having to rollback the entire transaction.
*/
int sqlite3BtreeBeginStmt(Btree *p){
  int rc;
  BtShared *pBt = p->pBt;
  if( (p->inTrans!=TRANS_WRITE) || pBt->inStmt ){
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  assert( pBt->inTransaction==TRANS_WRITE );
  rc = pBt->readOnly ? SQLITE_OK : sqlite3pager_stmt_begin(pBt->pPager);
  pBt->inStmt = 1;
  return rc;
}


/*
** Commit the statment subtransaction currently in progress.  If no
** subtransaction is active, this is a no-op.
*/
int sqlite3BtreeCommitStmt(Btree *p){
  int rc;
  BtShared *pBt = p->pBt;
  if( pBt->inStmt && !pBt->readOnly ){
    rc = sqlite3pager_stmt_commit(pBt->pPager);
  }else{
    rc = SQLITE_OK;
  }
  pBt->inStmt = 0;
  return rc;
................................................................................
** Rollback the active statement subtransaction.  If no subtransaction
** is active this routine is a no-op.
**
** All cursors will be invalidated 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 *p){
  int rc;
  BtShared *pBt = p->pBt;
  if( pBt->inStmt==0 || pBt->readOnly ) return SQLITE_OK;
  rc = sqlite3pager_stmt_rollback(pBt->pPager);
  assert( countWriteCursors(pBt)==0 );
  pBt->inStmt = 0;
  return rc;
}

................................................................................
** 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 *p,                                   /* 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;
  BtShared *pBt = p->pBt;

  *ppCur = 0;
  if( wrFlag ){
    if( pBt->readOnly ){
      return SQLITE_READONLY;
    }
    if( checkReadLocks(pBt, iTable, 0) ){
      return SQLITE_LOCKED;
    }
  }

#ifndef SQLITE_OMIT_SHARED_CACHE
  rc = queryTableLock(p, iTable, wrFlag?WRITE_LOCK:READ_LOCK);
  if( rc!=SQLITE_OK ){
    return rc;
  }
#endif

  if( pBt->pPage1==0 ){
    rc = lockBtreeWithRetry(p);
    if( rc!=SQLITE_OK ){
      return rc;
    }
  }
  pCur = sqliteMallocRaw( sizeof(*pCur) );
  if( pCur==0 ){
    rc = SQLITE_NOMEM;
................................................................................
    rc = SQLITE_EMPTY;
    goto create_cursor_exception;
  }
  rc = getAndInitPage(pBt, pCur->pgnoRoot, &pCur->pPage, 0);
  if( rc!=SQLITE_OK ){
    goto create_cursor_exception;
  }

  /* Obtain the table-lock on the shared-btree. */
  rc = lockTable(p, iTable, wrFlag?WRITE_LOCK:READ_LOCK);
  if( rc!=SQLITE_OK ){
    assert( rc==SQLITE_NOMEM );
    goto create_cursor_exception;
  }

  /* Now that no other errors can occur, finish filling in the BtCursor
  ** variables, link the cursor into the BtShared list and set *ppCur (the
  ** output argument to this function).
  */
  pCur->xCompare = xCmp ? xCmp : dfltCompare;
  pCur->pArg = pArg;
  pCur->pBtree = p;
  pCur->wrFlag = wrFlag;
  pCur->idx = 0;
  memset(&pCur->info, 0, sizeof(pCur->info));
  pCur->pNext = pBt->pCursor;
  if( pCur->pNext ){
    pCur->pNext->pPrev = pCur;
  }
  pCur->pPrev = 0;
  pBt->pCursor = pCur;
  pCur->isValid = 0;
  *ppCur = pCur;


  return SQLITE_OK;
create_cursor_exception:
  if( pCur ){
    releasePage(pCur->pPage);
    sqliteFree(pCur);
  }
  unlockBtreeIfUnused(pBt);
  return rc;
................................................................................
#endif

/*
** Close a cursor.  The read lock on the database file is released
** when the last cursor is closed.
*/
int sqlite3BtreeCloseCursor(BtCursor *pCur){
  BtShared *pBt = pCur->pBtree->pBt;
  if( pCur->pPrev ){
    pCur->pPrev->pNext = pCur->pNext;
  }else{
    pBt->pCursor = pCur->pNext;
  }
  if( pCur->pNext ){
    pCur->pNext->pPrev = pCur->pPrev;
................................................................................
  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;
  BtShared *pBt;
  int ovflSize;
  u32 nKey;

  assert( pCur!=0 && pCur->pPage!=0 );
  assert( pCur->isValid );
  pBt = pCur->pBtree->pBt;
  pPage = pCur->pPage;
  pageIntegrity(pPage);
  assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
  getCellInfo(pCur);
  aPayload = pCur->info.pCell;
  aPayload += pCur->info.nHeader;
  if( pPage->intKey ){
................................................................................
** Move the cursor down to a new child page.  The newPgno argument is the
** page number of the child page to move to.
*/
static int moveToChild(BtCursor *pCur, u32 newPgno){
  int rc;
  MemPage *pNewPage;
  MemPage *pOldPage;
  BtShared *pBt = pCur->pBtree->pBt;

  assert( pCur->isValid );
  rc = getAndInitPage(pBt, newPgno, &pNewPage, pCur->pPage);
  if( rc ) return rc;
  pageIntegrity(pNewPage);
  pNewPage->idxParent = pCur->idx;
  pOldPage = pCur->pPage;
................................................................................

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

  rc = getAndInitPage(pBt, pCur->pgnoRoot, &pRoot, 0);
  if( rc ){
    pCur->isValid = 0;
    return rc;
  }
  releasePage(pCur->pPage);
................................................................................
** which in turn can make database access faster.
**
** If the "exact" parameter is not 0, and the page-number nearby exists 
** anywhere on the free-list, then it is guarenteed to be returned. This
** is only used by auto-vacuum databases when allocating a new table.
*/
static int allocatePage(
  BtShared *pBt, 
  MemPage **ppPage, 
  Pgno *pPgno, 
  Pgno nearby,
  u8 exact
){
  MemPage *pPage1;
  int rc;
................................................................................

/*
** Add a page of the database file to the freelist.
**
** sqlite3pager_unref() is NOT called for pPage.
*/
static int freePage(MemPage *pPage){
  BtShared *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);
................................................................................
  return rc;
}

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

  parseCellPtr(pPage, pCell, &info);
  if( info.iOverflow==0 ){
    return SQLITE_OK;  /* No overflow pages. Return without doing anything */
................................................................................
  const u8 *pSrc;
  int nSrc, n, rc;
  int spaceLeft;
  MemPage *pOvfl = 0;
  MemPage *pToRelease = 0;
  unsigned char *pPrior;
  unsigned char *pPayload;
  BtShared *pBt = pPage->pBt;
  Pgno pgnoOvfl = 0;
  int nHeader;
  CellInfo info;

  /* Fill in the header. */
  nHeader = 0;
  if( !pPage->leaf ){
................................................................................
}

/*
** Change the MemPage.pParent pointer on the page whose number is
** given in the second argument so that MemPage.pParent holds the
** pointer in the third argument.
*/
static int reparentPage(BtShared *pBt, Pgno pgno, MemPage *pNewParent, int idx){
  MemPage *pThis;
  unsigned char *aData;

  if( pgno==0 ) return SQLITE_OK;
  assert( pBt->pPager!=0 );
  aData = sqlite3pager_lookup(pBt->pPager, pgno);
  if( aData ){
................................................................................
** to make sure that each child knows that pPage is its parent.
**
** This routine gets called after you memcpy() one page into
** another.
*/
static int reparentChildPages(MemPage *pPage){
  int i;
  BtShared *pBt = pPage->pBt;
  int rc = SQLITE_OK;

  if( pPage->leaf ) return SQLITE_OK;

  for(i=0; i<pPage->nCell; i++){
    u8 *pCell = findCell(pPage, i);
    if( !pPage->leaf ){
................................................................................
static int balance_quick(MemPage *pPage, MemPage *pParent){
  int rc;
  MemPage *pNew;
  Pgno pgnoNew;
  u8 *pCell;
  int szCell;
  CellInfo info;
  BtShared *pBt = pPage->pBt;
  int parentIdx = pParent->nCell;   /* pParent new divider cell index */
  int parentSize;                   /* Size of new divider cell */
  u8 parentCell[64];                /* Space for the new divider cell */

  /* Allocate a new page. Insert the overflow cell from pPage
  ** into it. Then remove the overflow cell from pPage.
  */
................................................................................
**
** If this routine fails for any reason, it might leave the database
** in a corrupted state.  So if this routine fails, the database should
** be rolled back.
*/
static int balance_nonroot(MemPage *pPage){
  MemPage *pParent;            /* The parent of pPage */
  BtShared *pBt;                  /* The whole database */
  int nCell = 0;               /* Number of cells in apCell[] */
  int nMaxCells = 0;           /* Allocated size of apCell, szCell, aFrom. */
  int nOld;                    /* Number of pages in apOld[] */
  int nNew;                    /* Number of pages in apNew[] */
  int nDiv;                    /* Number of cells in apDiv[] */
  int i, j, k;                 /* Loop counters */
  int idx;                     /* Index of pPage in pParent->aCell[] */
................................................................................
** page contains no cells.  This is an opportunity to make the tree
** shallower by one level.
*/
static int balance_shallower(MemPage *pPage){
  MemPage *pChild;             /* The only child page of pPage */
  Pgno pgnoChild;              /* Page number for pChild */
  int rc = SQLITE_OK;          /* Return code from subprocedures */
  BtShared *pBt;                  /* The main BTree structure */
  int mxCellPerPage;           /* Maximum number of cells per page */
  u8 **apCell;                 /* All cells from pages being balanced */
  int *szCell;                 /* Local size of all cells */

  assert( pPage->pParent==0 );
  assert( pPage->nCell==0 );
  pBt = pPage->pBt;
................................................................................
** child.   Finally, call balance_internal() on the new child
** to cause it to split.
*/
static int balance_deeper(MemPage *pPage){
  int rc;             /* Return value from subprocedures */
  MemPage *pChild;    /* Pointer to a new child page */
  Pgno pgnoChild;     /* Page number of the new child page */
  BtShared *pBt;         /* The BTree */
  int usableSize;     /* Total usable size of a page */
  u8 *data;           /* Content of the parent page */
  u8 *cdata;          /* Content of the child page */
  int hdr;            /* Offset to page header in parent */
  int brk;            /* Offset to content of first cell in parent */

  assert( pPage->pParent==0 );
................................................................................
** means a cursor opened with wrFlag==0) this routine also moves
** all cursors other than pExclude so that they are pointing to the 
** first Cell on root page.  This is necessary because an insert 
** or delete might change the number of cells on a page or delete
** a page entirely and we do not want to leave any cursors 
** pointing to non-existant pages or cells.
*/
static int checkReadLocks(BtShared *pBt, Pgno pgnoRoot, BtCursor *pExclude){
  BtCursor *p;
  for(p=pBt->pCursor; p; p=p->pNext){
    if( p->pgnoRoot!=pgnoRoot || p==pExclude ) continue;
    if( p->wrFlag==0 ) return SQLITE_LOCKED;
    if( p->pPage->pgno!=p->pgnoRoot ){
      moveToRoot(p);
    }
................................................................................
  const void *pKey, i64 nKey,    /* The key of the new record */
  const void *pData, int nData   /* The data of the new record */
){
  int rc;
  int loc;
  int szNew;
  MemPage *pPage;
  BtShared *pBt = pCur->pBtree->pBt;
  unsigned char *oldCell;
  unsigned char *newCell = 0;

  if( pBt->inTransaction!=TRANS_WRITE ){
    /* Must start a transaction before doing an insert */
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  assert( !pBt->readOnly );
  if( !pCur->wrFlag ){
    return SQLITE_PERM;   /* Cursor not open for writing */
  }
................................................................................
** is left pointing at a random location.
*/
int sqlite3BtreeDelete(BtCursor *pCur){
  MemPage *pPage = pCur->pPage;
  unsigned char *pCell;
  int rc;
  Pgno pgnoChild = 0;
  BtShared *pBt = pCur->pBtree->pBt;

  assert( pPage->isInit );
  if( pBt->inTransaction!=TRANS_WRITE ){
    /* Must start a transaction before doing a delete */
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  assert( !pBt->readOnly );
  if( pCur->idx >= pPage->nCell ){
    return SQLITE_ERROR;  /* The cursor is not pointing to anything */
  }
................................................................................
** The type of type is determined by the flags parameter.  Only the
** following values of flags are currently in use.  Other values for
** flags might not work:
**
**     BTREE_INTKEY|BTREE_LEAFDATA     Used for SQL tables with rowid keys
**     BTREE_ZERODATA                  Used for SQL indices
*/
int sqlite3BtreeCreateTable(Btree *p, int *piTable, int flags){
  BtShared *pBt = p->pBt;
  MemPage *pRoot;
  Pgno pgnoRoot;
  int rc;
  if( pBt->inTransaction!=TRANS_WRITE ){
    /* Must start a transaction first */
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  assert( !pBt->readOnly );

  /* It is illegal to create a table if any cursors are open on the
  ** database. This is because in auto-vacuum mode the backend may
................................................................................
    Pgno pgnoMove;      /* Move a page here to make room for the root-page */
    MemPage *pPageMove; /* The page to move to. */

    /* Read the value of meta[3] from the database to determine where the
    ** root page of the new table should go. meta[3] is the largest root-page
    ** created so far, so the new root-page is (meta[3]+1).
    */
    rc = sqlite3BtreeGetMeta(p, 4, &pgnoRoot);
    if( rc!=SQLITE_OK ) return rc;
    pgnoRoot++;

    /* The new root-page may not be allocated on a pointer-map page, or the
    ** PENDING_BYTE page.
    */
    if( pgnoRoot==PTRMAP_PAGENO(pBt->usableSize, pgnoRoot) ||
................................................................................

    /* Update the pointer-map and meta-data with the new root-page number. */
    rc = ptrmapPut(pBt, pgnoRoot, PTRMAP_ROOTPAGE, 0);
    if( rc ){
      releasePage(pRoot);
      return rc;
    }
    rc = sqlite3BtreeUpdateMeta(p, 4, pgnoRoot);
    if( rc ){
      releasePage(pRoot);
      return rc;
    }

  }else{
    rc = allocatePage(pBt, &pRoot, &pgnoRoot, 1, 0);
................................................................................
}

/*
** Erase the given database page and all its children.  Return
** the page to the freelist.
*/
static int clearDatabasePage(
  BtShared *pBt,           /* The BTree that contains the table */
  Pgno pgno,            /* Page number to clear */
  MemPage *pParent,     /* Parent page.  NULL for the root */
  int freePageFlag      /* Deallocate page if true */
){
  MemPage *pPage = 0;
  int rc;
  unsigned char *pCell;
................................................................................
** the page number of the root of the table.  After this routine returns,
** the root page is empty, but still exists.
**
** This routine will fail with SQLITE_LOCKED if there are any open
** read cursors on the table.  Open write cursors are moved to the
** root of the table.
*/
int sqlite3BtreeClearTable(Btree *p, int iTable){
  int rc;
  BtCursor *pCur;
  BtShared *pBt = p->pBt;
  if( p->inTrans!=TRANS_WRITE ){
    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);
    }
................................................................................
** root pages are kept at the beginning of the database file, which
** is necessary for AUTOVACUUM to work right.  *piMoved is set to the 
** page number that used to be the last root page in the file before
** the move.  If no page gets moved, *piMoved is set to 0.
** The last root page is recorded in meta[3] and the value of
** meta[3] is updated by this procedure.
*/
int sqlite3BtreeDropTable(Btree *p, int iTable, int *piMoved){
  int rc;
  MemPage *pPage = 0;
  BtShared *pBt = p->pBt;

  if( p->inTrans!=TRANS_WRITE ){
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }

  /* It is illegal to drop a table if any cursors are open on the
  ** database. This is because in auto-vacuum mode the backend may
  ** need to move another root-page to fill a gap left by the deleted
  ** root page. If an open cursor was using this page a problem would 
................................................................................
  */
  if( pBt->pCursor ){
    return SQLITE_LOCKED;
  }

  rc = getPage(pBt, (Pgno)iTable, &pPage);
  if( rc ) return rc;
  rc = sqlite3BtreeClearTable(p, iTable);
  if( rc ){
    releasePage(pPage);
    return rc;
  }

  *piMoved = 0;

................................................................................
  if( iTable>1 ){
#ifdef SQLITE_OMIT_AUTOVACUUM
    rc = freePage(pPage);
    releasePage(pPage);
#else
    if( pBt->autoVacuum ){
      Pgno maxRootPgno;
      rc = sqlite3BtreeGetMeta(p, 4, &maxRootPgno);
      if( rc!=SQLITE_OK ){
        releasePage(pPage);
        return rc;
      }

      if( iTable==maxRootPgno ){
        /* If the table being dropped is the table with the largest root-page
................................................................................
        maxRootPgno--;
      }
      if( maxRootPgno==PTRMAP_PAGENO(pBt->usableSize, maxRootPgno) ){
        maxRootPgno--;
      }
      assert( maxRootPgno!=PENDING_BYTE_PAGE(pBt) );

      rc = sqlite3BtreeUpdateMeta(p, 4, maxRootPgno);
    }else{
      rc = freePage(pPage);
      releasePage(pPage);
    }
#endif
  }else{
    /* If sqlite3BtreeDropTable was called on page 1. */
................................................................................
** through meta[15] are available for use by higher layers.  Meta[0]
** is read-only, the others are read/write.
** 
** The schema layer numbers meta values differently.  At the schema
** layer (and the SetCookie and ReadCookie opcodes) the number of
** free pages is not visible.  So Cookie[0] is the same as Meta[1].
*/
int sqlite3BtreeGetMeta(Btree *p, int idx, u32 *pMeta){
  int rc;
  unsigned char *pP1;
  BtShared *pBt = p->pBt;

  assert( idx>=0 && idx<=15 );
  rc = sqlite3pager_get(pBt->pPager, 1, (void**)&pP1);
  if( rc ) return rc;
  *pMeta = get4byte(&pP1[36 + idx*4]);
  sqlite3pager_unref(pP1);

................................................................................
  return SQLITE_OK;
}

/*
** Write meta-information back into the database.  Meta[0] is
** read-only and may not be written.
*/
int sqlite3BtreeUpdateMeta(Btree *p, int idx, u32 iMeta){
  BtShared *pBt = p->pBt;
  unsigned char *pP1;
  int rc;
  assert( idx>=1 && idx<=15 );
  if( p->inTrans!=TRANS_WRITE ){
    return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }
  assert( pBt->pPage1!=0 );
  pP1 = pBt->pPage1->aData;
  rc = sqlite3pager_write(pP1);
  if( rc ) return rc;
  put4byte(&pP1[36 + idx*4], iMeta);
................................................................................
}

#ifdef SQLITE_DEBUG
/*
** Print a disassembly of the given page on standard output.  This routine
** is used for debugging and testing only.
*/
static int btreePageDump(BtShared *pBt, int pgno, int recursive, MemPage *pParent){
  int rc;
  MemPage *pPage;
  int i, j, c;
  int nFree;
  u16 idx;
  int hdr;
  int nCell;
................................................................................
    btreePageDump(pBt, get4byte(&data[hdr+8]), 1, pPage);
  }
  pPage->isInit = isInit;
  sqlite3pager_unref(data);
  fflush(stdout);
  return SQLITE_OK;
}
int sqlite3BtreePageDump(Btree *p, int pgno, int recursive){
  return btreePageDump(p->pBt, pgno, recursive, 0);
}
#endif

#ifdef SQLITE_TEST
/*
** Fill aResult[] with information about the entry and page that the
** cursor is pointing to.
................................................................................
}
#endif

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

/*
** This structure is passed around through all the sanity checking routines
** in order to keep track of some global state information.
*/
typedef struct IntegrityCk IntegrityCk;
struct IntegrityCk {
  BtShared *pBt;    /* The tree being checked out */
  Pager *pPager; /* The associated pager.  Also accessible by pBt->pPager */
  int nPage;     /* Number of pages in the database */
  int *anRef;    /* Number of times each page is referenced */
  char *zErrMsg; /* An error message.  NULL of no errors seen. */
};

#ifndef SQLITE_OMIT_INTEGRITY_CHECK
................................................................................
  int nUpper            /* Number of characters in zUpperBound */
){
  MemPage *pPage;
  int i, rc, depth, d2, pgno, cnt;
  int hdr, cellStart;
  int nCell;
  u8 *data;
  BtShared *pBt;
  int usableSize;
  char zContext[100];
  char *hit;

  sprintf(zContext, "Page %d: ", iPage);

  /* Check that the page exists
................................................................................
** 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 *p, int *aRoot, int nRoot){
  int i;
  int nRef;
  IntegrityCk sCheck;
  BtShared *pBt = p->pBt;

  nRef = *sqlite3pager_stats(pBt->pPager);
  if( lockBtreeWithRetry(p)!=SQLITE_OK ){
    return sqliteStrDup("Unable to acquire a read lock on the database");
  }
  sCheck.pBt = pBt;
  sCheck.pPager = pBt->pPager;
  sCheck.nPage = sqlite3pager_pagecount(sCheck.pPager);
  if( sCheck.nPage==0 ){
    unlockBtreeIfUnused(pBt);
................................................................................
  return sCheck.zErrMsg;
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */

/*
** Return the full pathname of the underlying database file.
*/
const char *sqlite3BtreeGetFilename(Btree *p){
  assert( p->pBt->pPager!=0 );
  return sqlite3pager_filename(p->pBt->pPager);
}

/*
** Return the pathname of the directory that contains the database file.
*/
const char *sqlite3BtreeGetDirname(Btree *p){
  assert( p->pBt->pPager!=0 );
  return sqlite3pager_dirname(p->pBt->pPager);
}

/*
** Return the pathname of the journal file for this database. The return
** value of this routine is the same regardless of whether the journal file
** has been created or not.
*/
const char *sqlite3BtreeGetJournalname(Btree *p){
  assert( p->pBt->pPager!=0 );
  return sqlite3pager_journalname(p->pBt->pPager);
}

#ifndef SQLITE_OMIT_VACUUM
/*
** 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 *pTo, Btree *pFrom){
  int rc = SQLITE_OK;
  Pgno i, nPage, nToPage, iSkip;

  BtShared *pBtTo = pTo->pBt;
  BtShared *pBtFrom = pFrom->pBt;

  if( pTo->inTrans!=TRANS_WRITE || pFrom->inTrans!=TRANS_WRITE ){
    return SQLITE_ERROR;
  }
  if( pBtTo->pCursor ) return SQLITE_BUSY;
  nToPage = sqlite3pager_pagecount(pBtTo->pPager);
  nPage = sqlite3pager_pagecount(pBtFrom->pPager);
  iSkip = PENDING_BYTE_PAGE(pBtTo);
  for(i=1; rc==SQLITE_OK && i<=nPage; i++){
................................................................................
    sqlite3pager_unref(pPage);
    sqlite3pager_dont_write(pBtTo->pPager, i);
  }
  if( !rc && nPage<nToPage ){
    rc = sqlite3pager_truncate(pBtTo->pPager, nPage);
  }
  if( rc ){
    sqlite3BtreeRollback(pTo);
  }
  return rc;  
}
#endif /* SQLITE_OMIT_VACUUM */

/*
** Return non-zero if a transaction is active.
*/
int sqlite3BtreeIsInTrans(Btree *p){
  return (p && (p->inTrans==TRANS_WRITE));
}

/*
** Return non-zero if a statement transaction is active.
*/
int sqlite3BtreeIsInStmt(Btree *p){
  return (p->pBt && p->pBt->inStmt);
}

/*
** This call is a no-op if no write-transaction is currently active on pBt.
**
** Otherwise, sync the database file for the btree pBt. zMaster points to
** the name of a master journal file that should be written into the
................................................................................
**
** When this is called, the master journal should already have been
** created, populated with this journal pointer and synced to disk.
**
** Once this is routine has returned, the only thing required to commit
** the write-transaction for this database file is to delete the journal.
*/
int sqlite3BtreeSync(Btree *p, const char *zMaster){
  if( p->inTrans==TRANS_WRITE ){
    BtShared *pBt = p->pBt;
#ifndef SQLITE_OMIT_AUTOVACUUM
    Pgno nTrunc = 0;
    if( pBt->autoVacuum ){
      int rc = autoVacuumCommit(pBt, &nTrunc); 
      if( rc!=SQLITE_OK ) return rc;
    }
    return sqlite3pager_sync(pBt->pPager, zMaster, nTrunc);
#endif
    return sqlite3pager_sync(pBt->pPager, zMaster, 0);
  }
  return SQLITE_OK;
}

#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Enable the shared pager and schema features.
*/
int sqlite3_enable_shared_cache(int enable){
  SqliteTsd *pTsd = sqlite3Tsd();
  if( pTsd->pPager ){
    return SQLITE_MISUSE;
  }
  pTsd->useSharedData = enable;
  return SQLITE_OK;
}
#endif

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 1.65 2005/12/16 15:24:29 danielk1977 Exp $
*/
#ifndef _BTREE_H_
#define _BTREE_H_

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

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



int sqlite3BtreeOpen(
  const char *zFilename,   /* Name of database file to open */

  Btree **,                /* Return open Btree* here */
  int flags                /* Flags */
);

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







|







 







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>







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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 1.66 2005/12/30 16:28:02 danielk1977 Exp $
*/
#ifndef _BTREE_H_
#define _BTREE_H_

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

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


int sqlite3BtreeOpen(
  const char *zFilename,   /* Name of database file to open */
  sqlite3 *db,             /* Associated database connection */
  Btree **,                /* Return open Btree* here */
  int flags                /* Flags */
);

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

Changes to src/main.c.

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**
*************************************************************************
** Main file for the SQLite library.  The routines in this file
** implement the programmer interface to the library.  Routines in
** other files are for internal use by SQLite and should not be
** accessed by users of the library.
**
** $Id: main.c,v 1.312 2005/12/16 15:24:29 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>

/*
** The following constant value is used by the SQLITE_BIGENDIAN and
** SQLITE_LITTLEENDIAN macros.
*/
const int sqlite3one = 1;

#ifndef SQLITE_OMIT_GLOBALRECOVER
/*
** Linked list of all open database handles. This is used by the 
** sqlite3_global_recover() function. Entries are added to the list
** by openDatabase() and removed by sqlite3_close().
*/
static sqlite3 *pDbList = 0;
#endif

/*
** The version of the library
*/
const char rcsid3[] = "@(#) \044Id: SQLite version " SQLITE_VERSION " $";
const char sqlite3_version[] = SQLITE_VERSION;
const char *sqlite3_libversion(void){ return sqlite3_version; }
int sqlite3_libversion_number(void){ return SQLITE_VERSION_NUMBER; }
................................................................................
#endif
#if TEMP_STORE==3
    zFilename = ":memory:";
#endif
#endif /* SQLITE_OMIT_MEMORYDB */
  }

  rc = sqlite3BtreeOpen(zFilename, ppBtree, btree_flags);
  if( rc==SQLITE_OK ){
    sqlite3BtreeSetBusyHandler(*ppBtree, (void*)&db->busyHandler);
    sqlite3BtreeSetCacheSize(*ppBtree, nCache);
  }
  return rc;
}








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**
*************************************************************************
** Main file for the SQLite library.  The routines in this file
** implement the programmer interface to the library.  Routines in
** other files are for internal use by SQLite and should not be
** accessed by users of the library.
**
** $Id: main.c,v 1.313 2005/12/30 16:28:02 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>

/*
** The following constant value is used by the SQLITE_BIGENDIAN and
** SQLITE_LITTLEENDIAN macros.
*/
const int sqlite3one = 1;










/*
** The version of the library
*/
const char rcsid3[] = "@(#) \044Id: SQLite version " SQLITE_VERSION " $";
const char sqlite3_version[] = SQLITE_VERSION;
const char *sqlite3_libversion(void){ return sqlite3_version; }
int sqlite3_libversion_number(void){ return SQLITE_VERSION_NUMBER; }
................................................................................
#endif
#if TEMP_STORE==3
    zFilename = ":memory:";
#endif
#endif /* SQLITE_OMIT_MEMORYDB */
  }

  rc = sqlite3BtreeOpen(zFilename, db, ppBtree, btree_flags);
  if( rc==SQLITE_OK ){
    sqlite3BtreeSetBusyHandler(*ppBtree, (void*)&db->busyHandler);
    sqlite3BtreeSetCacheSize(*ppBtree, nCache);
  }
  return rc;
}

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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 1.228 2005/12/20 09:19:37 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include "os.h"
#include "pager.h"
#include <assert.h>
#include <string.h>
................................................................................
# define TEST_INCR(x)  x++
#else
# define TEST_INCR(x)
#endif

/*
** These are bits that can be set in Pager.errMask.

























*/
#define PAGER_ERR_FULL     0x01  /* a write() failed */
#define PAGER_ERR_MEM      0x02  /* malloc() failed */
#define PAGER_ERR_LOCK     0x04  /* error in the locking protocol */
#define PAGER_ERR_CORRUPT  0x08  /* database or journal corruption */
#define PAGER_ERR_DISK     0x10  /* general disk I/O error - bad hard drive? */

/*
** Journal files begin with the following magic string.  The data
** was obtained from /dev/random.  It is used only as a sanity check.
**
** Since version 2.8.0, the journal format contains additional sanity
** checking information.  If the power fails while the journal is begin
................................................................................
** return code.
*/
static int pager_errcode(Pager *pPager){
  int rc = SQLITE_OK;
  if( pPager->errMask & PAGER_ERR_LOCK )    rc = SQLITE_PROTOCOL;
  if( pPager->errMask & PAGER_ERR_DISK )    rc = SQLITE_IOERR;
  if( pPager->errMask & PAGER_ERR_FULL )    rc = SQLITE_FULL;
  if( pPager->errMask & PAGER_ERR_MEM )     rc = SQLITE_NOMEM;
  if( pPager->errMask & PAGER_ERR_CORRUPT ) rc = SQLITE_CORRUPT;
  return rc;
}























#ifdef SQLITE_CHECK_PAGES
/*
** Return a 32-bit hash of the page data for pPage.
*/
static u32 pager_pagehash(PgHdr *pPage){
  u32 hash = 0;
................................................................................
** + N bytes: length of master journal name.
** + 4 bytes: N
** + 4 bytes: Master journal name checksum.
** + 8 bytes: aJournalMagic[].
**
** The master journal page checksum is the sum of the bytes in the master
** journal name.



*/
static int writeMasterJournal(Pager *pPager, const char *zMaster){
  int rc;
  int len; 
  int i; 
  u32 cksum = 0; 

................................................................................
  }
  sqlite3OsUnlock(pPager->fd, NO_LOCK);
  pPager->state = PAGER_UNLOCK;
  pPager->dbSize = -1;
  pPager->nRef = 0;
  assert( pPager->journalOpen==0 );
}

/*
** This function is used to reset the pager after a malloc() failure. This
** doesn't work with in-memory databases. If a malloc() fails when an 
** in-memory database is in use it is not possible to recover.
**
** If a transaction or statement transaction is active, it is rolled back.
**
** It is an error to call this function if any pages are in use.
*/
#ifndef SQLITE_OMIT_GLOBALRECOVER
int sqlite3pager_reset(Pager *pPager){
  if( pPager ){
    if( pPager->nRef || MEMDB ){
      return SQLITE_ERROR;
    }
    pPager->errMask &= ~(PAGER_ERR_MEM);
    pager_reset(pPager);
  }
  return SQLITE_OK;
}
#endif


/*
** When this routine is called, the pager has the journal file open and
** a RESERVED or EXCLUSIVE lock on the database.  This routine releases
** the database lock and acquires a SHARED lock in its place.  The journal
** file is deleted and closed.
**
................................................................................
*/
int sqlite3pager_open(
  Pager **ppPager,         /* Return the Pager structure here */
  const char *zFilename,   /* Name of the database file to open */
  int nExtra,              /* Extra bytes append to each in-memory page */
  int flags                /* flags controlling this file */
){
  Pager *pPager;
  char *zFullPathname = 0;
  int nameLen;
  OsFile *fd;
  int rc = SQLITE_OK;
  int i;
  int tempFile = 0;
  int memDb = 0;
  int readOnly = 0;
  int useJournal = (flags & PAGER_OMIT_JOURNAL)==0;
  int noReadlock = (flags & PAGER_NO_READLOCK)!=0;
  char zTemp[SQLITE_TEMPNAME_SIZE];
  SqliteTsd *pTsd = sqlite3Tsd();





  *ppPager = 0;
  memset(&fd, 0, sizeof(fd));
  if( sqlite3Tsd()->mallocFailed ){
    return SQLITE_NOMEM;
  }





  if( zFilename && zFilename[0] ){
#ifndef SQLITE_OMIT_MEMORYDB
    if( strcmp(zFilename,":memory:")==0 ){
      memDb = 1;
      zFullPathname = sqliteStrDup("");
      rc = SQLITE_OK;
    }else
#endif
    {
      zFullPathname = sqlite3Os.xFullPathname(zFilename);
      if( zFullPathname ){
        rc = sqlite3Os.xOpenReadWrite(zFullPathname, &fd, &readOnly);
      }
................................................................................
    rc = sqlite3pager_opentemp(zTemp, &fd);
    zFilename = zTemp;
    zFullPathname = sqlite3Os.xFullPathname(zFilename);
    if( rc==SQLITE_OK ){
      tempFile = 1;
    }
  }
  if( !zFullPathname ){
    sqlite3OsClose(&fd);
    return SQLITE_NOMEM;
  }
  if( rc!=SQLITE_OK ){
    sqlite3OsClose(&fd);




    sqliteFree(zFullPathname);
    return rc;
  }
  nameLen = strlen(zFullPathname);
  pPager = sqliteMalloc( sizeof(*pPager) + nameLen*3 + 30 );



  if( pPager==0 ){




    sqlite3OsClose(&fd);
    sqliteFree(zFullPathname);

    return SQLITE_NOMEM;
  }

  TRACE3("OPEN %d %s\n", FILEHANDLEID(fd), zFullPathname);
  pPager->zFilename = (char*)&pPager[1];
  pPager->zDirectory = &pPager->zFilename[nameLen+1];
  pPager->zJournal = &pPager->zDirectory[nameLen+1];
  strcpy(pPager->zFilename, zFullPathname);
  strcpy(pPager->zDirectory, zFullPathname);

  for(i=nameLen; i>0 && pPager->zDirectory[i-1]!='/'; i--){}
  if( i>0 ) pPager->zDirectory[i-1] = 0;
  strcpy(pPager->zJournal, zFullPathname);
  sqliteFree(zFullPathname);
  strcpy(&pPager->zJournal[nameLen], "-journal");
  pPager->fd = fd;
  pPager->journalOpen = 0;
................................................................................
# define clear_simulated_io_error()
# define disable_simulated_io_errors()
# define enable_simulated_io_errors()
#endif

/*
** Read the first N bytes from the beginning of the file into memory
** that pDest points to.  No error checking is done.






*/
void sqlite3pager_read_fileheader(Pager *pPager, int N, unsigned char *pDest){
  memset(pDest, 0, N);
  if( MEMDB==0 ){
    sqlite3OsSeek(pPager->fd, 0);
    sqlite3OsRead(pPager->fd, pDest, N);
    clear_simulated_io_error();
................................................................................
** Shutdown the page cache.  Free all memory and close all files.
**
** 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;
#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
  SqliteTsd *pTsd = sqlite3Tsd();
#endif

................................................................................
  /* Temp files are automatically deleted by the OS
  ** if( pPager->tempFile ){
  **   sqlite3Os.xDelete(pPager->zFilename);
  ** }
  */

#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT



  if( pPager==pTsd->pPager ){
    pTsd->pPager = pPager->pNext;
  }else{
    Pager *pTmp;
    for(pTmp = pTsd->pPager; pTmp->pNext!=pPager; pTmp=pTmp->pNext);
    pTmp->pNext = pPager->pNext;
  }
................................................................................
    return 0;
  }else{
    return 1;
  }
}

/*
** Try to find a page in the cache that can be recycled.



*/
static int pager_recycle(Pager *pPager, int syncOk, PgHdr **ppPg){
  PgHdr *pPg;
  *ppPg = 0;

  /* Find a page to recycle.  Try to locate a page that does not
  ** require us to do an fsync() on the journal.
................................................................................
  ** 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 && pPager->pFirst && syncOk && !MEMDB){
    int rc = syncJournal(pPager);
    if( rc!=0 ){
      sqlite3pager_rollback(pPager);
      return SQLITE_IOERR;
    }
    if( pPager->fullSync ){
      /* If in full-sync mode, write a new journal header into the
      ** journal file. This is done to avoid ever modifying a journal
      ** header that is involved in the rollback of pages that have
      ** already been written to the database (in case the header is
      ** trashed when the nRec field is updated).
      */
      pPager->nRec = 0;
      assert( pPager->journalOff > 0 );
      rc = writeJournalHdr(pPager);
      if( rc!=0 ){
        sqlite3pager_rollback(pPager);
        return SQLITE_IOERR;
      }
    }
    pPg = pPager->pFirst;
  }
  if( pPg==0 ){
    return SQLITE_OK;
  }
................................................................................
  */
  if( pPg->dirty ){
    int rc;
    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
  ** sqlite_dont_rollback() optimization for the rest of this transaction.
................................................................................
      int rc;

      /* For each pager, try to free as many pages as possible (without 
      ** calling fsync() if this is the first iteration of the outermost 
      ** loop).
      */
      while( SQLITE_OK==(rc = pager_recycle(p, i, &pPg)) && pPg) {
	/* We've found a page to free. At this point the page has been 
        ** removed from the page hash-table, free-list and synced-list 
	** (pFirstSynced). It is still in the all pages (pAll) list. 
        ** Remove it from this list before freeing.
        **
        ** Todo: Check the Pager.pStmt list to make sure this is Ok. It 
        ** probably is though.
        */
        PgHdr *pTmp;
        assert( pPg );

        if( pPg==p->pAll ){
           p->pAll = pPg->pNextAll;
        }else{
          for( pTmp=p->pAll; pTmp->pNextAll!=pPg; pTmp=pTmp->pNextAll );
          pTmp->pNextAll = pPg->pNextAll;
        }
        nReleased += sqliteAllocSize(pPg);
        sqliteFree(pPg);
      }

      if( rc!=SQLITE_OK ){
        /* Assert that fsync() was enabled and the error was an io-error
        ** or a full database. Nothing else should be able to wrong in 
        ** pager_recycle.
        */
        assert( i && (rc==SQLITE_IOERR || rc==SQLITE_FULL) );

        /* TODO: Figure out what to do about this. The IO-error
        ** belongs to the connection that is executing a transaction. 
        */
        assert(0);
      }
    }
  }
  
  return nReleased;
}
#endif

/*
** Acquire a page.
**
** A read lock on the disk file is obtained when the first page is acquired. 
** This read lock is dropped when the last page is released.
**
................................................................................
  /* If this is the first page accessed, then get a SHARED lock
  ** on the database file.
  */
  if( pPager->nRef==0 && !MEMDB ){
    if( !pPager->noReadlock ){
      rc = pager_wait_on_lock(pPager, SHARED_LOCK);
      if( rc!=SQLITE_OK ){
        return rc;
      }
    }

    /* If a journal file exists, and there is no RESERVED lock on the
    ** database file, then it either needs to be played back or deleted.
    */
    if( hasHotJournal(pPager) ){
................................................................................
       ** second process will get to this point in the code and fail to
       ** obtain it's own EXCLUSIVE lock on the database file.
       */
       rc = sqlite3OsLock(pPager->fd, EXCLUSIVE_LOCK);
       if( rc!=SQLITE_OK ){
         sqlite3OsUnlock(pPager->fd, NO_LOCK);
         pPager->state = PAGER_UNLOCK;
         return rc;
       }
       pPager->state = PAGER_EXCLUSIVE;

       /* Open the journal for reading only.  Return SQLITE_BUSY if
       ** we are unable to open the journal file. 
       **
       ** The journal file does not need to be locked itself.  The
................................................................................
       pPager->journalHdr = 0;

       /* Playback and delete the journal.  Drop the database write
       ** lock and reacquire the read lock.
       */
       rc = pager_playback(pPager);
       if( rc!=SQLITE_OK ){
         return rc;
       }
    }
    pPg = 0;
  }else{
    /* Search for page in cache */
    pPg = pager_lookup(pPager, pgno);
    if( MEMDB && pPager->state==PAGER_UNLOCK ){
................................................................................
    TEST_INCR(pPager->nMiss);
    if( pPager->nPage<pPager->mxPage || pPager->pFirst==0 || MEMDB ){
      /* Create a new page */
      pPg = sqliteMallocRaw( sizeof(*pPg) + pPager->pageSize
                              + sizeof(u32) + pPager->nExtra
                              + MEMDB*sizeof(PgHistory) );
      if( pPg==0 ){
        // pPager->errMask |= PAGER_ERR_MEM;
        return SQLITE_NOMEM;
      }
      memset(pPg, 0, sizeof(*pPg));
      if( MEMDB ){
        memset(PGHDR_TO_HIST(pPg, pPager), 0, sizeof(PgHistory));
      }
      pPg->pPager = pPager;
................................................................................
      if( pPager->nPage>pPager->nMaxPage ){
        assert( pPager->nMaxPage==(pPager->nPage-1) );
        pPager->nMaxPage++;
      }
    }else{
      rc = pager_recycle(pPager, 1, &pPg);
      if( rc!=SQLITE_OK ){
        return rc;
      }
      assert(pPg) ;
    }
    pPg->pgno = pgno;
    if( pPager->aInJournal && (int)pgno<=pPager->origDbSize ){
      sqlite3CheckMemory(pPager->aInJournal, pgno/8);
      assert( pPager->journalOpen );
................................................................................
      TRACE3("FETCH %d page %d\n", PAGERID(pPager), pPg->pgno);
      CODEC(pPager, PGHDR_TO_DATA(pPg), pPg->pgno, 3);
      if( rc!=SQLITE_OK ){
        i64 fileSize;
        if( sqlite3OsFileSize(pPager->fd,&fileSize)!=SQLITE_OK
               || fileSize>=pgno*pPager->pageSize ){
          sqlite3pager_unref(PGHDR_TO_DATA(pPg));
          return rc;
        }else{
          clear_simulated_io_error();
          memset(PGHDR_TO_DATA(pPg), 0, pPager->pageSize);
        }
      }else{
        TEST_INCR(pPager->nRead);
      }







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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 1.229 2005/12/30 16:28:02 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include "os.h"
#include "pager.h"
#include <assert.h>
#include <string.h>
................................................................................
# define TEST_INCR(x)  x++
#else
# define TEST_INCR(x)
#endif

/*
** These are bits that can be set in Pager.errMask.
**
** TODO: Maybe we just want a variable - Pager.errCode. Can we really 
**       have two simultaneous error conditions?
**
** Recovering from an SQLITE_FULL, SQLITE_LOCK, SQLITE_CORRUPT or 
** SQLITE_IOERR error is not a simple matter, particularly if the pager 
** cache is shared between multiple connections.
**
** SQLITE_FULL (PAGER_ERR_FULL):
**     Cleared when the transaction is rolled back.
**
** SQLITE_CORRUPT (PAGER_ERR_CORRUPT):
**     Cannot be cleared. The upper layer must close the current pager 
**     and open a new one on the same file to continue.
**
** SQLITE_PROTOCOL (PAGER_ERR_LOCK):
**     This error only occurs if an internal error occurs or another process 
**     is not following the sqlite locking protocol (i.e. someone is 
**     manipulating the database file using something other than sqlite).
**     This is handled in the same way as database corruption - the error 
**     cannot be cleared except by closing the current pager and opening 
**     a brand new one on the same file.
**
** SQLITE_IOERR (PAGER_ERR_DISK):
**     Cleared when the transaction is rolled back.
*/
#define PAGER_ERR_FULL     0x01  /* a write() failed */

#define PAGER_ERR_LOCK     0x02  /* error in the locking protocol */
#define PAGER_ERR_CORRUPT  0x04  /* database or journal corruption */
#define PAGER_ERR_DISK     0x08  /* general disk I/O error - bad hard drive? */

/*
** Journal files begin with the following magic string.  The data
** was obtained from /dev/random.  It is used only as a sanity check.
**
** Since version 2.8.0, the journal format contains additional sanity
** checking information.  If the power fails while the journal is begin
................................................................................
** return code.
*/
static int pager_errcode(Pager *pPager){
  int rc = SQLITE_OK;
  if( pPager->errMask & PAGER_ERR_LOCK )    rc = SQLITE_PROTOCOL;
  if( pPager->errMask & PAGER_ERR_DISK )    rc = SQLITE_IOERR;
  if( pPager->errMask & PAGER_ERR_FULL )    rc = SQLITE_FULL;

  if( pPager->errMask & PAGER_ERR_CORRUPT ) rc = SQLITE_CORRUPT;
  return rc;
}

/*
** This function should be called when an error occurs within the pager
** code to set the appropriate bits in Pager.errMask.
*/
static int pager_error(Pager *pPager, int rc){
  switch( rc ){
    case SQLITE_PROTOCOL:
      pPager->errMask |= PAGER_ERR_LOCK;
      break;
    case SQLITE_IOERR:
      pPager->errMask |= PAGER_ERR_DISK;
      break;
    case SQLITE_FULL:
      pPager->errMask |= PAGER_ERR_FULL;
      break;
    case SQLITE_CORRUPT:
      pPager->errMask |= PAGER_ERR_CORRUPT;
      break;
  }
  return rc;
}

#ifdef SQLITE_CHECK_PAGES
/*
** Return a 32-bit hash of the page data for pPage.
*/
static u32 pager_pagehash(PgHdr *pPage){
  u32 hash = 0;
................................................................................
** + N bytes: length of master journal name.
** + 4 bytes: N
** + 4 bytes: Master journal name checksum.
** + 8 bytes: aJournalMagic[].
**
** The master journal page checksum is the sum of the bytes in the master
** journal name.
**
** If zMaster is a NULL pointer (occurs for a single database transaction), 
** this call is a no-op.
*/
static int writeMasterJournal(Pager *pPager, const char *zMaster){
  int rc;
  int len; 
  int i; 
  u32 cksum = 0; 

................................................................................
  }
  sqlite3OsUnlock(pPager->fd, NO_LOCK);
  pPager->state = PAGER_UNLOCK;
  pPager->dbSize = -1;
  pPager->nRef = 0;
  assert( pPager->journalOpen==0 );
}
























/*
** When this routine is called, the pager has the journal file open and
** a RESERVED or EXCLUSIVE lock on the database.  This routine releases
** the database lock and acquires a SHARED lock in its place.  The journal
** file is deleted and closed.
**
................................................................................
*/
int sqlite3pager_open(
  Pager **ppPager,         /* Return the Pager structure here */
  const char *zFilename,   /* Name of the database file to open */
  int nExtra,              /* Extra bytes append to each in-memory page */
  int flags                /* flags controlling this file */
){
  Pager *pPager = 0;
  char *zFullPathname = 0;
  int nameLen;
  OsFile *fd;
  int rc = SQLITE_OK;
  int i;
  int tempFile = 0;
  int memDb = 0;
  int readOnly = 0;
  int useJournal = (flags & PAGER_OMIT_JOURNAL)==0;
  int noReadlock = (flags & PAGER_NO_READLOCK)!=0;
  char zTemp[SQLITE_TEMPNAME_SIZE];
  SqliteTsd *pTsd = sqlite3Tsd();

  /* If malloc() has already failed return SQLITE_NOMEM. Before even
  ** testing for this, set *ppPager to NULL so the caller knows the pager
  ** structure was never allocated. 
  */
  *ppPager = 0;

  if( sqlite3Tsd()->mallocFailed ){
    return SQLITE_NOMEM;
  }
  memset(&fd, 0, sizeof(fd));

  /* Open the pager file and set zFullPathname to point at malloc()ed 
  ** memory containing the complete filename (i.e. including the directory).
  */
  if( zFilename && zFilename[0] ){
#ifndef SQLITE_OMIT_MEMORYDB
    if( strcmp(zFilename,":memory:")==0 ){
      memDb = 1;
      zFullPathname = sqliteStrDup("");

    }else
#endif
    {
      zFullPathname = sqlite3Os.xFullPathname(zFilename);
      if( zFullPathname ){
        rc = sqlite3Os.xOpenReadWrite(zFullPathname, &fd, &readOnly);
      }
................................................................................
    rc = sqlite3pager_opentemp(zTemp, &fd);
    zFilename = zTemp;
    zFullPathname = sqlite3Os.xFullPathname(zFilename);
    if( rc==SQLITE_OK ){
      tempFile = 1;
    }
  }






  /* Allocate the Pager structure. As part of the same allocation, allocate
  ** space for the full paths of the file, directory and journal 
  ** (Pager.zFilename, Pager.zDirectory and Pager.zJournal).
  */
  if( zFullPathname ){


    nameLen = strlen(zFullPathname);
    pPager = sqliteMalloc( sizeof(*pPager) + nameLen*3 + 30 );
  }

  /* If an error occured in either of the blocks above, free the memory 
  ** pointed to by zFullPathname, free the Pager structure and close the 
  ** file. Since the pager is not allocated there is no need to set 
  ** any Pager.errMask variables.
  */
  if( !pPager || !zFullPathname || rc!=SQLITE_OK ){
    sqlite3OsClose(&fd);
    sqliteFree(zFullPathname);
    sqliteFree(pPager);
    return ((rc==SQLITE_OK)?SQLITE_NOMEM:rc);
  }

  TRACE3("OPEN %d %s\n", FILEHANDLEID(fd), zFullPathname);
  pPager->zFilename = (char*)&pPager[1];
  pPager->zDirectory = &pPager->zFilename[nameLen+1];
  pPager->zJournal = &pPager->zDirectory[nameLen+1];
  strcpy(pPager->zFilename, zFullPathname);
  strcpy(pPager->zDirectory, zFullPathname);

  for(i=nameLen; i>0 && pPager->zDirectory[i-1]!='/'; i--){}
  if( i>0 ) pPager->zDirectory[i-1] = 0;
  strcpy(pPager->zJournal, zFullPathname);
  sqliteFree(zFullPathname);
  strcpy(&pPager->zJournal[nameLen], "-journal");
  pPager->fd = fd;
  pPager->journalOpen = 0;
................................................................................
# define clear_simulated_io_error()
# define disable_simulated_io_errors()
# define enable_simulated_io_errors()
#endif

/*
** Read the first N bytes from the beginning of the file into memory
** that pDest points to. 
**
** No error checking is done. The rational for this is that this function 
** may be called even if the file does not exist or contain a header. In 
** these cases sqlite3OsRead() will return an error, to which the correct 
** response is to zero the memory at pDest and continue.  A real IO error 
** will presumably recur and be picked up later (Todo: Think about this).
*/
void sqlite3pager_read_fileheader(Pager *pPager, int N, unsigned char *pDest){
  memset(pDest, 0, N);
  if( MEMDB==0 ){
    sqlite3OsSeek(pPager->fd, 0);
    sqlite3OsRead(pPager->fd, pDest, N);
    clear_simulated_io_error();
................................................................................
** Shutdown the page cache.  Free all memory and close all files.
**
** 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.
**
** This function always succeeds. If a transaction is active an attempt
** is made to roll it back. If an error occurs during the rollback 
** a hot journal may be left in the filesystem but no error is returned
** to the caller.
*/
int sqlite3pager_close(Pager *pPager){
  PgHdr *pPg, *pNext;
#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
  SqliteTsd *pTsd = sqlite3Tsd();
#endif

................................................................................
  /* Temp files are automatically deleted by the OS
  ** if( pPager->tempFile ){
  **   sqlite3Os.xDelete(pPager->zFilename);
  ** }
  */

#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
  /* Remove the pager from the linked list of pagers starting at 
  ** SqliteTsd.pPager.
  */
  if( pPager==pTsd->pPager ){
    pTsd->pPager = pPager->pNext;
  }else{
    Pager *pTmp;
    for(pTmp = pTsd->pPager; pTmp->pNext!=pPager; pTmp=pTmp->pNext);
    pTmp->pNext = pPager->pNext;
  }
................................................................................
    return 0;
  }else{
    return 1;
  }
}

/*
** Try to find a page in the cache that can be recycled. 
**
** This routine may return SQLITE_IOERR, SQLITE_FULL or SQLITE_OK. It 
** does not set the pPager->errMask variable.
*/
static int pager_recycle(Pager *pPager, int syncOk, PgHdr **ppPg){
  PgHdr *pPg;
  *ppPg = 0;

  /* Find a page to recycle.  Try to locate a page that does not
  ** require us to do an fsync() on the journal.
................................................................................
  ** 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 && pPager->pFirst && syncOk && !MEMDB){
    int rc = syncJournal(pPager);
    if( rc!=0 ){

      return rc;
    }
    if( pPager->fullSync ){
      /* If in full-sync mode, write a new journal header into the
      ** journal file. This is done to avoid ever modifying a journal
      ** header that is involved in the rollback of pages that have
      ** already been written to the database (in case the header is
      ** trashed when the nRec field is updated).
      */
      pPager->nRec = 0;
      assert( pPager->journalOff > 0 );
      rc = writeJournalHdr(pPager);
      if( rc!=0 ){

        return rc;
      }
    }
    pPg = pPager->pFirst;
  }
  if( pPg==0 ){
    return SQLITE_OK;
  }
................................................................................
  */
  if( pPg->dirty ){
    int rc;
    assert( pPg->needSync==0 );
    pPg->pDirty = 0;
    rc = pager_write_pagelist( pPg );
    if( rc!=SQLITE_OK ){

      return rc;
    }
  }
  assert( pPg->dirty==0 );

  /* If the page we are recycling is marked as alwaysRollback, then
  ** set the global alwaysRollback flag, thus disabling the
  ** sqlite_dont_rollback() optimization for the rest of this transaction.
................................................................................
      int rc;

      /* For each pager, try to free as many pages as possible (without 
      ** calling fsync() if this is the first iteration of the outermost 
      ** loop).
      */
      while( SQLITE_OK==(rc = pager_recycle(p, i, &pPg)) && pPg) {
        /* We've found a page to free. At this point the page has been 
        ** removed from the page hash-table, free-list and synced-list 
        ** (pFirstSynced). It is still in the all pages (pAll) list. 
        ** Remove it from this list before freeing.
        **
        ** Todo: Check the Pager.pStmt list to make sure this is Ok. It 
        ** probably is though.
        */
        PgHdr *pTmp;
        assert( pPg );
        page_remove_from_stmt_list(pPg);
        if( pPg==p->pAll ){
           p->pAll = pPg->pNextAll;
        }else{
          for( pTmp=p->pAll; pTmp->pNextAll!=pPg; pTmp=pTmp->pNextAll );
          pTmp->pNextAll = pPg->pNextAll;
        }
        nReleased += sqliteAllocSize(pPg);
        sqliteFree(pPg);
      }

      if( rc!=SQLITE_OK ){
        /* An error occured whilst writing to the database file or 
        ** journal in pager_recycle(). The error is not returned to the 
        ** caller of this function. Instead, set the Pager.errMask variable.
        ** The error will be returned to the user (or users, in the case 
        ** of a shared pager cache) of the pager for which the error occured.
        */
        assert( rc==SQLITE_IOERR || rc==SQLITE_FULL );
        assert( p->state>=PAGER_RESERVED );
        pager_error(p, rc);

      }
    }
  }

  return nReleased;
}
#endif /* SQLITE_OMIT_MEMORY_MANAGEMENT */

/*
** Acquire a page.
**
** A read lock on the disk file is obtained when the first page is acquired. 
** This read lock is dropped when the last page is released.
**
................................................................................
  /* If this is the first page accessed, then get a SHARED lock
  ** on the database file.
  */
  if( pPager->nRef==0 && !MEMDB ){
    if( !pPager->noReadlock ){
      rc = pager_wait_on_lock(pPager, SHARED_LOCK);
      if( rc!=SQLITE_OK ){
        return pager_error(pPager, rc);
      }
    }

    /* If a journal file exists, and there is no RESERVED lock on the
    ** database file, then it either needs to be played back or deleted.
    */
    if( hasHotJournal(pPager) ){
................................................................................
       ** second process will get to this point in the code and fail to
       ** obtain it's own EXCLUSIVE lock on the database file.
       */
       rc = sqlite3OsLock(pPager->fd, EXCLUSIVE_LOCK);
       if( rc!=SQLITE_OK ){
         sqlite3OsUnlock(pPager->fd, NO_LOCK);
         pPager->state = PAGER_UNLOCK;
         return pager_error(pPager, rc);
       }
       pPager->state = PAGER_EXCLUSIVE;

       /* Open the journal for reading only.  Return SQLITE_BUSY if
       ** we are unable to open the journal file. 
       **
       ** The journal file does not need to be locked itself.  The
................................................................................
       pPager->journalHdr = 0;

       /* Playback and delete the journal.  Drop the database write
       ** lock and reacquire the read lock.
       */
       rc = pager_playback(pPager);
       if( rc!=SQLITE_OK ){
         return pager_error(pPager, rc);
       }
    }
    pPg = 0;
  }else{
    /* Search for page in cache */
    pPg = pager_lookup(pPager, pgno);
    if( MEMDB && pPager->state==PAGER_UNLOCK ){
................................................................................
    TEST_INCR(pPager->nMiss);
    if( pPager->nPage<pPager->mxPage || pPager->pFirst==0 || MEMDB ){
      /* Create a new page */
      pPg = sqliteMallocRaw( sizeof(*pPg) + pPager->pageSize
                              + sizeof(u32) + pPager->nExtra
                              + MEMDB*sizeof(PgHistory) );
      if( pPg==0 ){

        return SQLITE_NOMEM;
      }
      memset(pPg, 0, sizeof(*pPg));
      if( MEMDB ){
        memset(PGHDR_TO_HIST(pPg, pPager), 0, sizeof(PgHistory));
      }
      pPg->pPager = pPager;
................................................................................
      if( pPager->nPage>pPager->nMaxPage ){
        assert( pPager->nMaxPage==(pPager->nPage-1) );
        pPager->nMaxPage++;
      }
    }else{
      rc = pager_recycle(pPager, 1, &pPg);
      if( rc!=SQLITE_OK ){
        return pager_error(pPager, rc);
      }
      assert(pPg) ;
    }
    pPg->pgno = pgno;
    if( pPager->aInJournal && (int)pgno<=pPager->origDbSize ){
      sqlite3CheckMemory(pPager->aInJournal, pgno/8);
      assert( pPager->journalOpen );
................................................................................
      TRACE3("FETCH %d page %d\n", PAGERID(pPager), pPg->pgno);
      CODEC(pPager, PGHDR_TO_DATA(pPg), pPg->pgno, 3);
      if( rc!=SQLITE_OK ){
        i64 fileSize;
        if( sqlite3OsFileSize(pPager->fd,&fileSize)!=SQLITE_OK
               || fileSize>=pgno*pPager->pageSize ){
          sqlite3pager_unref(PGHDR_TO_DATA(pPg));
          return pager_error(pPager, rc);
        }else{
          clear_simulated_io_error();
          memset(PGHDR_TO_DATA(pPg), 0, pPager->pageSize);
        }
      }else{
        TEST_INCR(pPager->nRead);
      }

Changes to src/sqlite.h.in.

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**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the SQLite library
** presents to client programs.
**
** @(#) $Id: sqlite.h.in,v 1.151 2005/12/20 09:19:37 danielk1977 Exp $
*/
#ifndef _SQLITE3_H_
#define _SQLITE3_H_
#include <stdarg.h>     /* Needed for the definition of va_list */

/*
** Make sure we can call this stuff from C++.
................................................................................
** callback is not invoked if a transaction is automatically rolled
** back because the database connection is closed.
*/
void *sqlite3_rollback_hook(sqlite3*, void(*)(void *), void*);

int sqlite3_release_memory(int);









/*
** Undo the hack that converts floating point types to integer for
** builds on processors without floating point support.
*/
#ifdef SQLITE_OMIT_FLOATING_POINT
# undef double
#endif

#ifdef __cplusplus
}  /* End of the 'extern "C"' block */
#endif
#endif







|







 







>
>
>
>
>
>
>
>












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**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the SQLite library
** presents to client programs.
**
** @(#) $Id: sqlite.h.in,v 1.152 2005/12/30 16:28:02 danielk1977 Exp $
*/
#ifndef _SQLITE3_H_
#define _SQLITE3_H_
#include <stdarg.h>     /* Needed for the definition of va_list */

/*
** Make sure we can call this stuff from C++.
................................................................................
** callback is not invoked if a transaction is automatically rolled
** back because the database connection is closed.
*/
void *sqlite3_rollback_hook(sqlite3*, void(*)(void *), void*);

int sqlite3_release_memory(int);

/*
** This function is only available if the library is compiled without
** the SQLITE_OMIT_SHARED_CACHE macro defined. It is used to enable or
** disable (if the argument is true or false, respectively) the 
** "shared pager" feature.
*/
int sqlite3_enable_shared_cache(int);

/*
** Undo the hack that converts floating point types to integer for
** builds on processors without floating point support.
*/
#ifdef SQLITE_OMIT_FLOATING_POINT
# undef double
#endif

#ifdef __cplusplus
}  /* End of the 'extern "C"' block */
#endif
#endif

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296
297
**    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 1.445 2005/12/29 23:33:54 drh Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_

/*
** Many people are failing to set -DNDEBUG=1 when compiling SQLite.
** Setting NDEBUG makes the code smaller and run faster.  So the following
................................................................................
  u8 mallocFailed;         /* True after a malloc() has failed */

#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
  i64 nSoftHeapLimit;      /* -ve for unlimited */
  i64 nAlloc;              /* Number of bytes currently allocated */
  Pager *pPager;           /* Linked list of all pagers in this thread */
#endif






#ifdef SQLITE_MEMDEBUG
  i64 nMaxAlloc;           /* High water mark of SqliteTsd.nAlloc */
  int mallocAllowed;       /* assert() in sqlite3Malloc() if not set */
  int isFail;              /* True if all malloc() calls should fail */
  const char *zFile;       /* Filename to associate debugging info with */
  int iLine;               /* Line number to associate debugging info with */







|







 







>
>
>
>
>







7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
...
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
**    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 1.446 2005/12/30 16:28:02 danielk1977 Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_

/*
** Many people are failing to set -DNDEBUG=1 when compiling SQLite.
** Setting NDEBUG makes the code smaller and run faster.  So the following
................................................................................
  u8 mallocFailed;         /* True after a malloc() has failed */

#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
  i64 nSoftHeapLimit;      /* -ve for unlimited */
  i64 nAlloc;              /* Number of bytes currently allocated */
  Pager *pPager;           /* Linked list of all pagers in this thread */
#endif

#ifndef SQLITE_OMIT_SHARED_CACHE
  u8 useSharedData;        /* True if shared pagers and schemas are enabled */
  BtShared *pBtree;
#endif

#ifdef SQLITE_MEMDEBUG
  i64 nMaxAlloc;           /* High water mark of SqliteTsd.nAlloc */
  int mallocAllowed;       /* assert() in sqlite3Malloc() if not set */
  int isFail;              /* True if all malloc() calls should fail */
  const char *zFile;       /* Filename to associate debugging info with */
  int iLine;               /* Line number to associate debugging info with */

Changes to src/tclsqlite.c.

7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
....
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761

1762
1763
1764
1765
1766
1767
1768

1769
1770
1771
1772
1773
1774
1775
1776
1777
**    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 1.141 2005/12/19 14:18:11 danielk1977 Exp $
*/
#ifndef NO_TCL     /* Omit this whole file if TCL is unavailable */

#include "sqliteInt.h"
#include "hash.h"
#include "tcl.h"
#include <stdlib.h>
................................................................................
    break;
  }

  /*
  **     $db soft_heap_limit N
  **
  ** Set the soft-heap-limit for this thread. Note that the limit is 
  ** per-thread, not per-database. An empty string is returned.
  */
  case DB_SOFT_HEAP_LIMIT: {
#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
    int n;

    if( objc!=3 ){
      Tcl_WrongNumArgs(interp, 2, objv, "BYTES");
      return TCL_ERROR;
    }
    if( Tcl_GetIntFromObj(interp, objv[2], &n) ){
      return TCL_ERROR;
    }

    sqlite3_soft_heap_limit(n);
    Tcl_ResetResult(interp);
#endif
    break;
  }

  /*
  **     $db release_memory ?N?
  **







|







 







|




>







>

|







7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
....
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
**    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 1.142 2005/12/30 16:28:02 danielk1977 Exp $
*/
#ifndef NO_TCL     /* Omit this whole file if TCL is unavailable */

#include "sqliteInt.h"
#include "hash.h"
#include "tcl.h"
#include <stdlib.h>
................................................................................
    break;
  }

  /*
  **     $db soft_heap_limit N
  **
  ** Set the soft-heap-limit for this thread. Note that the limit is 
  ** per-thread, not per-database. The previous limit is returned.
  */
  case DB_SOFT_HEAP_LIMIT: {
#ifndef SQLITE_OMIT_MEMORY_MANAGEMENT
    int n;
    int ret;
    if( objc!=3 ){
      Tcl_WrongNumArgs(interp, 2, objv, "BYTES");
      return TCL_ERROR;
    }
    if( Tcl_GetIntFromObj(interp, objv[2], &n) ){
      return TCL_ERROR;
    }
    ret = sqlite3Tsd()->nSoftHeapLimit;
    sqlite3_soft_heap_limit(n);
    Tcl_SetObjResult(interp, Tcl_NewIntObj(ret));
#endif
    break;
  }

  /*
  **     $db release_memory ?N?
  **

Changes to src/test1.c.

9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
...
886
887
888
889
890
891
892
































893
894
895
896
897
898
899
....
3069
3070
3071
3072
3073
3074
3075






3076
3077
3078
3079
3080
3081
3082
....
3246
3247
3248
3249
3250
3251
3252



3253
3254
3255
3256
3257
3258
3259
**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing the printf() interface to SQLite.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test1.c,v 1.177 2005/12/20 09:19:37 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "tcl.h"
#include "os.h"
#include <stdlib.h>
#include <string.h>

................................................................................
    return TCL_OK;
  }

  return sqlite3OutstandingMallocs(interp);
}
#endif

































/*
** Usage:  sqlite_abort
**
** Shutdown the process immediately.  This is not a clean shutdown.
** This command is used to test the recoverability of a database in
** the event of a program crash.
*/
................................................................................
#endif

#ifdef SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS
  Tcl_SetVar2(interp, "sqlite_options", "schema_version", "0", TCL_GLOBAL_ONLY);
#else
  Tcl_SetVar2(interp, "sqlite_options", "schema_version", "1", TCL_GLOBAL_ONLY);
#endif







#ifdef SQLITE_OMIT_SUBQUERY
  Tcl_SetVar2(interp, "sqlite_options", "subquery", "0", TCL_GLOBAL_ONLY);
#else
  Tcl_SetVar2(interp, "sqlite_options", "subquery", "1", TCL_GLOBAL_ONLY);
#endif

................................................................................
     { "add_test_function",       test_function, 0           },
#endif
#ifdef SQLITE_MEMDEBUG
     { "sqlite_malloc_outstanding", sqlite_malloc_outstanding, 0},
#endif
     { "sqlite3_test_errstr",     test_errstr, 0             },
     { "tcl_variable_type",       tcl_variable_type, 0       },



  };
  static int bitmask_size = sizeof(Bitmask)*8;
  int i;
  extern int sqlite3_os_trace;
  extern int sqlite3_where_trace;
  extern int sqlite3_sync_count, sqlite3_fullsync_count;
  extern int sqlite3_opentemp_count;







|







 







>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>







 







>
>
>
>
>
>







 







>
>
>







9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
...
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
....
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
....
3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing the printf() interface to SQLite.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test1.c,v 1.178 2005/12/30 16:28:02 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "tcl.h"
#include "os.h"
#include <stdlib.h>
#include <string.h>

................................................................................
    return TCL_OK;
  }

  return sqlite3OutstandingMallocs(interp);
}
#endif

/*
** Usage: sqlite3_enable_shared_cache BOOLEAN
**
*/
#ifndef SQLITE_OMIT_SHARED_CACHE
static int test_enable_shared_cache(
  ClientData clientData,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int objc,              /* Number of arguments */
  Tcl_Obj *CONST objv[]  /* Command arguments */
){
  int rc;
  int enable;
  SqliteTsd *pTsd = sqlite3Tsd();
  Tcl_SetObjResult(interp, Tcl_NewBooleanObj(pTsd->useSharedData));

  if( objc!=2 ){
    Tcl_WrongNumArgs(interp, 1, objv, "BOOLEAN");
    return TCL_ERROR;
  }
  if( Tcl_GetBooleanFromObj(interp, objv[1], &enable) ){
    return TCL_ERROR;
  }
  rc = sqlite3_enable_shared_cache(enable);
  if( rc!=SQLITE_OK ){
    Tcl_SetResult(interp, (char *)sqlite3ErrStr(rc), TCL_STATIC);
    return TCL_ERROR;
  }
  return TCL_OK;
}
#endif

/*
** Usage:  sqlite_abort
**
** Shutdown the process immediately.  This is not a clean shutdown.
** This command is used to test the recoverability of a database in
** the event of a program crash.
*/
................................................................................
#endif

#ifdef SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS
  Tcl_SetVar2(interp, "sqlite_options", "schema_version", "0", TCL_GLOBAL_ONLY);
#else
  Tcl_SetVar2(interp, "sqlite_options", "schema_version", "1", TCL_GLOBAL_ONLY);
#endif

#ifdef SQLITE_OMIT_SHARED_CACHE
  Tcl_SetVar2(interp, "sqlite_options", "shared_cache", "0", TCL_GLOBAL_ONLY);
#else
  Tcl_SetVar2(interp, "sqlite_options", "shared_cache", "1", TCL_GLOBAL_ONLY);
#endif

#ifdef SQLITE_OMIT_SUBQUERY
  Tcl_SetVar2(interp, "sqlite_options", "subquery", "0", TCL_GLOBAL_ONLY);
#else
  Tcl_SetVar2(interp, "sqlite_options", "subquery", "1", TCL_GLOBAL_ONLY);
#endif

................................................................................
     { "add_test_function",       test_function, 0           },
#endif
#ifdef SQLITE_MEMDEBUG
     { "sqlite_malloc_outstanding", sqlite_malloc_outstanding, 0},
#endif
     { "sqlite3_test_errstr",     test_errstr, 0             },
     { "tcl_variable_type",       tcl_variable_type, 0       },
#ifndef SQLITE_OMIT_SHARED_CACHE
     { "sqlite3_enable_shared_cache", test_enable_shared_cache, 0},
#endif
  };
  static int bitmask_size = sizeof(Bitmask)*8;
  int i;
  extern int sqlite3_os_trace;
  extern int sqlite3_where_trace;
  extern int sqlite3_sync_count, sqlite3_fullsync_count;
  extern int sqlite3_opentemp_count;

Changes to src/test3.c.

9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
..
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing the btree.c module in SQLite.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test3.c,v 1.63 2005/12/09 20:21:59 drh Exp $
*/
#include "sqliteInt.h"
#include "pager.h"
#include "btree.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>
................................................................................
  if( argc!=4 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " FILENAME NCACHE FLAGS\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[2], &nCache) ) return TCL_ERROR;
  if( Tcl_GetInt(interp, argv[3], &flags) ) return TCL_ERROR;
  rc = sqlite3BtreeOpen(argv[1], &pBt, flags);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  sqlite3BtreeSetCacheSize(pBt, nCache);
  sqlite3_snprintf(sizeof(zBuf), zBuf,"%p", pBt);
  Tcl_AppendResult(interp, zBuf, 0);







|







 







|







9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
..
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing the btree.c module in SQLite.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test3.c,v 1.64 2005/12/30 16:28:02 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "pager.h"
#include "btree.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>
................................................................................
  if( argc!=4 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " FILENAME NCACHE FLAGS\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[2], &nCache) ) return TCL_ERROR;
  if( Tcl_GetInt(interp, argv[3], &flags) ) return TCL_ERROR;
  rc = sqlite3BtreeOpen(argv[1], 0, &pBt, flags);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  sqlite3BtreeSetCacheSize(pBt, nCache);
  sqlite3_snprintf(sizeof(zBuf), zBuf,"%p", pBt);
  Tcl_AppendResult(interp, zBuf, 0);

Changes to src/vdbeaux.c.

922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
      needXcommit = 1;
      if( i!=1 ) nTrans++;
    }
  }

  /* If there are any write-transactions at all, invoke the commit hook */
  if( needXcommit && db->xCommitCallback ){
    int rc;
    sqlite3SafetyOff(db);
    rc = db->xCommitCallback(db->pCommitArg);
    sqlite3SafetyOn(db);
    if( rc ){
      return SQLITE_CONSTRAINT;
    }
  }







<







922
923
924
925
926
927
928

929
930
931
932
933
934
935
      needXcommit = 1;
      if( i!=1 ) nTrans++;
    }
  }

  /* If there are any write-transactions at all, invoke the commit hook */
  if( needXcommit && db->xCommitCallback ){

    sqlite3SafetyOff(db);
    rc = db->xCommitCallback(db->pCommitArg);
    sqlite3SafetyOn(db);
    if( rc ){
      return SQLITE_CONSTRAINT;
    }
  }

Changes to test/alter3.test.

9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
...
356
357
358
359
360
361
362

363
364
365
366
367
368
369
#
#*************************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this script is testing that SQLite can handle a subtle 
# file format change that may be used in the future to implement
# "ALTER TABLE ... ADD COLUMN".
#
# $Id: alter3.test,v 1.6 2005/03/29 03:11:00 danielk1977 Exp $
#

set testdir [file dirname $argv0]

source $testdir/tester.tcl

# If SQLITE_OMIT_ALTERTABLE is defined, omit this file.
................................................................................
# Ticket #1183 - Make sure adding columns to large tables does not cause
# memory corruption (as was the case before this bug was fixed).
do_test alter3-8.1 {
  execsql {
    CREATE TABLE t4(c1);
  }
} {}

do_test alter3-8.2 {
  set cols c1
  for {set i 2} {$i < 100} {incr i} {
    execsql "
      ALTER TABLE t4 ADD c$i
    "
    lappend cols c$i







|







 







>







9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
...
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
#
#*************************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this script is testing that SQLite can handle a subtle 
# file format change that may be used in the future to implement
# "ALTER TABLE ... ADD COLUMN".
#
# $Id: alter3.test,v 1.7 2005/12/30 16:28:02 danielk1977 Exp $
#

set testdir [file dirname $argv0]

source $testdir/tester.tcl

# If SQLITE_OMIT_ALTERTABLE is defined, omit this file.
................................................................................
# Ticket #1183 - Make sure adding columns to large tables does not cause
# memory corruption (as was the case before this bug was fixed).
do_test alter3-8.1 {
  execsql {
    CREATE TABLE t4(c1);
  }
} {}
set ::sql ""
do_test alter3-8.2 {
  set cols c1
  for {set i 2} {$i < 100} {incr i} {
    execsql "
      ALTER TABLE t4 ADD c$i
    "
    lappend cols c$i

Changes to test/attach2.test.

8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
...
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this script is testing the ATTACH and DETACH commands
# and related functionality.
#
# $Id: attach2.test,v 1.33 2005/12/06 17:19:12 danielk1977 Exp $
#

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


# Ticket #354
#
# Databases test.db and test2.db contain identical schemas.  Make
# sure we can attach test2.db from test.db.
#
do_test attach2-1.1 {
................................................................................

# A procedure to verify the status of locks on a database.
#
proc lock_status {testnum db expected_result} {
  # If the database was compiled with OMIT_TEMPDB set, then 
  # the lock_status list will not contain an entry for the temp
  # db. But the test code doesn't know this, so it's easiest 
  # to filter it out here.
  ifcapable !tempdb {
    set expected_result [concat \
        [lrange $expected_result 0 1] \
        [lrange $expected_result 4 end] \
    ]
  }
  do_test attach2-$testnum [subst {







|




<







 







|







8
9
10
11
12
13
14
15
16
17
18
19

20
21
22
23
24
25
26
...
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this script is testing the ATTACH and DETACH commands
# and related functionality.
#
# $Id: attach2.test,v 1.34 2005/12/30 16:28:02 danielk1977 Exp $
#

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


# Ticket #354
#
# Databases test.db and test2.db contain identical schemas.  Make
# sure we can attach test2.db from test.db.
#
do_test attach2-1.1 {
................................................................................

# A procedure to verify the status of locks on a database.
#
proc lock_status {testnum db expected_result} {
  # If the database was compiled with OMIT_TEMPDB set, then 
  # the lock_status list will not contain an entry for the temp
  # db. But the test code doesn't know this, so it's easiest 
  # to filter it out of the $expected_result list here.
  ifcapable !tempdb {
    set expected_result [concat \
        [lrange $expected_result 0 1] \
        [lrange $expected_result 4 end] \
    ]
  }
  do_test attach2-$testnum [subst {

Changes to test/malloc5.test.

5
6
7
8
9
10
11



12
13
14
15
16
17
18
19
20







21
22
23
24
25
26
27
...
155
156
157
158
159
160
161





162
163
164
165
166
167
168
...
184
185
186
187
188
189
190
191
192
193
194
195
196
#
#    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: malloc5.test,v 1.2 2005/12/20 09:19:38 danielk1977 Exp $

#---------------------------------------------------------------------------
# NOTES ON EXPECTED BEHAVIOUR
#
#---------------------------------------------------------------------------

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








do_test malloc5-1.1 {
  # Simplest possible test. Call [db release_memory] when there is exactly
  # one unused page in a single pager cache. This test case set's the 
  # value of the ::pgalloc variable, which is used in subsequent tests.
  #
  # Note: Even though executing this statement on an empty database 
................................................................................
# to ensure that more than 1MB of dynamic memory is used to perform
# the transaction. 
#
# The second test case sets the "soft-heap-limit" to 100,000 bytes (0.1 MB)
# and tests to see that this limit is not exceeded at any point during 
# transaction execution.
#





do_test malloc5-4.1 {
  execsql {BEGIN;}
  execsql {DELETE FROM abc;}
  for {set i 0} {$i < 10000} {incr i} {
    execsql "INSERT INTO abc VALUES($i, $i, '[string repeat X 100]');"
  }
  execsql {COMMIT;}
................................................................................
do_test malloc5-4.3 {
  # Check that the content of table abc is at least roughly as expected.
  execsql {
    SELECT count(*), sum(a), sum(b) FROM abc;
  }
} [list 20000 [expr int(20000.0 * 4999.5)] [expr int(20000.0 * 4999.5)]]

# Unset the soft-heap-limit value.
db soft_heap_limit -1

finish_test









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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.
#
#***********************************************************************
#
# This file contains test cases focused on the two memory-management APIs, 
# sqlite3_soft_heap_limit() and sqlite3_release_memory().
#
# $Id: malloc5.test,v 1.3 2005/12/30 16:28:02 danielk1977 Exp $

#---------------------------------------------------------------------------
# NOTES ON EXPECTED BEHAVIOUR
#
#---------------------------------------------------------------------------

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

# Only run these tests if memory debugging is turned on.
if {[info command sqlite_malloc_stat]==""} {
   puts "Skipping malloc tests: not compiled with -DSQLITE_MEMDEBUG..."
   finish_test
   return
}

do_test malloc5-1.1 {
  # Simplest possible test. Call [db release_memory] when there is exactly
  # one unused page in a single pager cache. This test case set's the 
  # value of the ::pgalloc variable, which is used in subsequent tests.
  #
  # Note: Even though executing this statement on an empty database 
................................................................................
# to ensure that more than 1MB of dynamic memory is used to perform
# the transaction. 
#
# The second test case sets the "soft-heap-limit" to 100,000 bytes (0.1 MB)
# and tests to see that this limit is not exceeded at any point during 
# transaction execution.
#
# Before executing malloc5-4.* we save the value of the current soft heap 
# limit in variable ::soft_limit. The original value is restored after 
# running the tests.
#
set ::soft_limit [db soft_heap_limit -1]
do_test malloc5-4.1 {
  execsql {BEGIN;}
  execsql {DELETE FROM abc;}
  for {set i 0} {$i < 10000} {incr i} {
    execsql "INSERT INTO abc VALUES($i, $i, '[string repeat X 100]');"
  }
  execsql {COMMIT;}
................................................................................
do_test malloc5-4.3 {
  # Check that the content of table abc is at least roughly as expected.
  execsql {
    SELECT count(*), sum(a), sum(b) FROM abc;
  }
} [list 20000 [expr int(20000.0 * 4999.5)] [expr int(20000.0 * 4999.5)]]

# Restore the soft heap limit.
db soft_heap_limit $::soft_limit

finish_test


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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.
#
#***********************************************************************
# This file runs all tests.
#
# $Id: quick.test,v 1.38 2005/12/15 10:11:32 danielk1977 Exp $



















set testdir [file dirname $argv0]
source $testdir/tester.tcl
rename finish_test really_finish_test
proc finish_test {} {}
set ISQUICK 1








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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.
#
#***********************************************************************
# This file runs all tests.
#
# $Id: quick.test,v 1.39 2005/12/30 16:28:02 danielk1977 Exp $

proc lshift {lvar} {
  upvar $lvar l
  set ret [lindex $l 0]
  set l [lrange $l 1 end]
  return $ret
}
while {[set arg [lshift argv]] != ""} {
  switch -- $arg {
    -sharedpagercache {
      sqlite3_enable_shared_cache 1
    }
    default {
      set argv [linsert $argv 0 $arg]
      break
    }
  }
}

set testdir [file dirname $argv0]
source $testdir/tester.tcl
rename finish_test really_finish_test
proc finish_test {} {}
set ISQUICK 1

Added test/shared.test.



























































































































































































































































































































































































































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# 2005 December 30
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this file is testing the SELECT statement.
#
# $Id: shared.test,v 1.1 2005/12/30 16:28:02 danielk1977 Exp $

set ::enable_shared_cache [sqlite3_enable_shared_cache 1]

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

ifcapable !shared_cache {
  finish_test
  return
}

# Test organization:
#
# shared-1.*: Simple test to verify basic sanity of table level locking when
#             two connections share a pager cache.
# shared-2.*: Test that a read transaction can co-exist with a 
#             write-transaction, including a simple test to ensure the 
#             external locking protocol is still working.
#

do_test shared-1.1 {
  # Open a second database on the file test.db. It should use the same pager
  # cache and schema as the original connection. Verify that only 1 file is 
  # opened.
  sqlite3 db2 test.db
  sqlite3 db  test.db
  set ::sqlite_open_file_count
} {1}
do_test shared-1.2 {
  # Add a table and a single row of data via the first connection. 
  # Ensure that the second connection can see them.
  execsql {
    CREATE TABLE abc(a, b, c);
    INSERT INTO abc VALUES(1, 2, 3);
  } db
  execsql {
    SELECT * FROM abc;
  } db2
} {1 2 3}
do_test shared-1.3 {
  # Have the first connection begin a transaction and obtain a read-lock
  # on table abc. This should not prevent the second connection from 
  # querying abc.
  execsql {
    BEGIN;
    SELECT * FROM abc;
  }
  execsql {
    SELECT * FROM abc;
  } db2
} {1 2 3}
do_test shared-1.4 {
  # Try to insert a row into abc via connection 2. This should fail because
  # of the read-lock connection 1 is holding on table abc (obtained in the
  # previous test case).
  catchsql {
    INSERT INTO abc VALUES(4, 5, 6);
  } db2
} {1 {database is locked}}
do_test shared-1.5 {
  # Using connection 2 (the one without the open transaction), create a 
  # new table and add a row to it. This is permitted as the transaction
  # started by connection 1 is currently a read transaction.
  execsql {
    CREATE TABLE def(d, e, f);
    INSERT INTO def VALUES('I', 'II', 'III');
  } db2
} {}
do_test shared-1.6 {
  # Upgrade connection 1's transaction to a write transaction. Insert
  # a row into table def - the table just created by connection 2.
  #
  # Connection 1 is able to see table def, even though it was created 
  # "after" the connection 1 transaction was started. This is because no
  # lock was established on the sqlite_master table.

# Todo: Remove this. Because the implementation does not include
# shared-schemas yet, we need to run some query (that will fail at 
# OP_VerifyCookie) so that connection 1 picks up the schema change
# made via connection 2. Otherwise the sqlite3_prepare("INSERT INTO def...")
# below will fail.
execsql {
  SELECT * FROM sqlite_master;
}

  execsql {
    INSERT INTO def VALUES('IV', 'V', 'VI');
  }
} {}
do_test shared-1.7 {
  # Read from the sqlite_master table with connection 1 (inside the 
  # transaction). Then test that we can no longer create a table 
  # with connection 2. This is because of the read-lock on sqlite_master.
  execsql {
    SELECT * FROM sqlite_master;
  }
  catchsql {
    CREATE TABLE ghi(g, h, i);
  } db2
} {1 {database is locked}}
do_test shared-1.8 {
  # Check that connection 2 can read the sqlite_master table. Then
  # create a table using connection 1 (this should write-lock the 
  # sqlite_master table). Then try to read sqlite_master again using 
  # connection 2 and verify that the write-lock prevents this.
  execsql {
    SELECT * FROM sqlite_master;
  } db2
  execsql {
    CREATE TABLE ghi(g, h, i);
  } 
  catchsql {
    SELECT * FROM sqlite_master;
  } db2
} {1 {database is locked}}
do_test shared-1.9 {
  # Commit the connection 1 transaction.
  execsql {
    COMMIT;
  }
} {}

do_test shared-2.1 {
  # Open connection db3 to the database. Use a different path to the same
  # file so that db3 does *not* share the same pager cache as db and db2
  # (there should be two open file handles).
  sqlite3 db3 ./test.db
  set ::sqlite_open_file_count
} {2}
do_test shared-2.2 {
  # Start read transactions on db and db2 (the shared pager cache). Ensure
  # db3 cannot write to the database.
  execsql {
    BEGIN;
    SELECT * FROM abc;
  }
  execsql {
    BEGIN;
    SELECT * FROM abc;
  } db2
  catchsql {
    INSERT INTO abc VALUES(1, 2, 3);
  } db2
} {1 {database is locked}}
do_test shared-2.3 {
  # Turn db's transaction into a write-transaction. db3 should still be
  # able to read from table def (but will not see the new row). Connection
  # db2 should not be able to read def (because of the write-lock).

# Todo: The failed "INSERT INTO abc ..." statement in the above test
# has started a write-transaction on db2 (should this be so?). This 
# would prevent connection db from starting a write-transaction. So roll the
# db2 transaction back and replace it with a new read transaction.
  execsql {
    ROLLBACK;
    BEGIN;
    SELECT * FROM abc;
  } db2

  execsql {
    INSERT INTO def VALUES('VII', 'VIII', 'IX');
  }
  concat [
    catchsql { SELECT * FROM def; } db3
  ] [
    catchsql { SELECT * FROM def; } db2
  ]
} {0 {I II III IV V VI} 1 {database is locked}}
do_test shared-2.4 {
  # Commit the open transaction on db. db2 still holds a read-transaction.
  # This should prevent db3 from writing to the database, but not from 
  # reading.
  execsql {
    COMMIT;
  }
  concat [
    catchsql { SELECT * FROM def; } db3
  ] [
    catchsql { INSERT INTO def VALUES('X', 'XI', 'XII'); } db3
  ]
} {0 {I II III IV V VI VII VIII IX} 1 {database is locked}}


catch {db close}
catch {db2 close}
catch {db3 close}

finish_test
sqlite3_enable_shared_cache $::enable_shared_cache

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 1.54 2005/12/09 14:39:05 danielk1977 Exp $

# Make sure tclsqlite3 was compiled correctly.  Abort now with an
# error message if not.
#
if {[sqlite3 -tcl-uses-utf]} {
  if {"\u1234"=="u1234"} {
    puts stderr "***** BUILD PROBLEM *****"
................................................................................
# the current thread. A list is returned with one entry for each outstanding
# malloc. Each list entry is itself a list of 5 items, as follows:
#
#     { <number-bytes> <file-name> <line-number> <test-case> <stack-dump> }
#
proc check_for_leaks {} {
  set ret [list]

  foreach alloc [sqlite_malloc_outstanding] {
    foreach {nBytes file iLine userstring backtrace} $alloc {}
    set stack [list]
    set skip 0

    # The first command in this block will probably fail on windows. This
    # means there will be no stack dump available.

    catch {
      set stuff [eval "exec addr2line -e ./testfixture -f $backtrace"]
      foreach {func line} $stuff {
        if {$func != "??" || $line != "??:0"} {
          regexp {.*/(.*)} $line dummy line
          lappend stack "${func}() $line"
        } else {
          if {[lindex $stack end] != "..."} {
            lappend stack "..."

          }
        }
      }

    }

    if {!$skip} {
      lappend ret [list $nBytes $file $iLine $userstring $stack]
    }
  }
  return $ret







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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 1.55 2005/12/30 16:28:02 danielk1977 Exp $

# Make sure tclsqlite3 was compiled correctly.  Abort now with an
# error message if not.
#
if {[sqlite3 -tcl-uses-utf]} {
  if {"\u1234"=="u1234"} {
    puts stderr "***** BUILD PROBLEM *****"
................................................................................
# the current thread. A list is returned with one entry for each outstanding
# malloc. Each list entry is itself a list of 5 items, as follows:
#
#     { <number-bytes> <file-name> <line-number> <test-case> <stack-dump> }
#
proc check_for_leaks {} {
  set ret [list]
  set cnt 0
  foreach alloc [sqlite_malloc_outstanding] {
    foreach {nBytes file iLine userstring backtrace} $alloc {}
    set stack [list]
    set skip 0

    # The first command in this block will probably fail on windows. This
    # means there will be no stack dump available.
    if {$cnt < 25} {
      catch {
        set stuff [eval "exec addr2line -e ./testfixture -f $backtrace"]
        foreach {func line} $stuff {
          if {$func != "??" || $line != "??:0"} {
            regexp {.*/(.*)} $line dummy line
            lappend stack "${func}() $line"
          } else {
            if {[lindex $stack end] != "..."} {
              lappend stack "..."
            }
          }
        }
      }
      incr cnt
    }

    if {!$skip} {
      lappend ret [list $nBytes $file $iLine $userstring $stack]
    }
  }
  return $ret

Changes to test/trans.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 database locks.
#
# $Id: trans.test,v 1.26 2005/03/29 03:11:00 danielk1977 Exp $


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


# Create several tables to work with.
................................................................................
  }
} {1 2 3}
do_test trans-3.2 {
  catchsql {
    SELECT a FROM two ORDER BY a;
  } altdb
} {0 {1 5 10}}

do_test trans-3.3 {
  catchsql {
    SELECT a FROM one ORDER BY a;
  } altdb
} {0 {1 2 3}}
do_test trans-3.4 {
  catchsql {
................................................................................
  catchsql {
    SELECT a FROM one ORDER BY a;
  } altdb
} {0 {1 2 3}}
do_test trans-3.10 {
  execsql {END TRANSACTION}
} {}

do_test trans-3.11 {
  set v [catch {execsql {
    SELECT a FROM two ORDER BY a;
  } altdb} msg]
  lappend v $msg
} {0 {1 4 5 10}}
do_test trans-3.12 {







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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 database locks.
#
# $Id: trans.test,v 1.27 2005/12/30 16:28:02 danielk1977 Exp $


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


# Create several tables to work with.
................................................................................
  }
} {1 2 3}
do_test trans-3.2 {
  catchsql {
    SELECT a FROM two ORDER BY a;
  } altdb
} {0 {1 5 10}}

do_test trans-3.3 {
  catchsql {
    SELECT a FROM one ORDER BY a;
  } altdb
} {0 {1 2 3}}
do_test trans-3.4 {
  catchsql {
................................................................................
  catchsql {
    SELECT a FROM one ORDER BY a;
  } altdb
} {0 {1 2 3}}
do_test trans-3.10 {
  execsql {END TRANSACTION}
} {}

do_test trans-3.11 {
  set v [catch {execsql {
    SELECT a FROM two ORDER BY a;
  } altdb} msg]
  lappend v $msg
} {0 {1 4 5 10}}
do_test trans-3.12 {