** 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 1.407 2007/08/22 00:39:20 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "btreeInt.h"

................................................................................
** SQLITE_OK if the lock may be obtained (by calling lockTable()), or
** SQLITE_LOCKED if not.
*/
static int queryTableLock(Btree *p, Pgno iTab, u8 eLock){
  BtShared *pBt = p->pBt;
  BtLock *pIter;

  assert( sqlite3_mutex_held(pBt->mutex) );
  
  /* This is a no-op if the shared-cache is not enabled */
  if( !p->sharable ){
    return SQLITE_OK;
  }

  /* This (along with lockTable()) is where the ReadUncommitted flag is
................................................................................
** 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( sqlite3_mutex_held(pBt->mutex) );

  /* This is a no-op if the shared-cache is not enabled */
  if( !p->sharable ){
    return SQLITE_OK;
  }

  assert( SQLITE_OK==queryTableLock(p, iTable, eLock) );
................................................................................
/*
** 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;

  assert( sqlite3_mutex_held(p->pBt->mutex) );
  assert( p->sharable || 0==*ppIter );

  while( *ppIter ){
    BtLock *pLock = *ppIter;
    if( pLock->pBtree==p ){
      *ppIter = pLock->pNext;
      sqlite3_free(pLock);
................................................................................

/*
** Invalidate the overflow page-list cache for all cursors opened
** on the shared btree structure pBt.
*/
static void invalidateAllOverflowCache(BtShared *pBt){
  BtCursor *p;
  assert( sqlite3_mutex_held(pBt->mutex) );
  for(p=pBt->pCursor; p; p=p->pNext){
    invalidateOverflowCache(p);
  }
}
#else
  #define invalidateOverflowCache(x)
  #define invalidateAllOverflowCache(x)
................................................................................
** and BtCursor.pKey. The cursor's state is set to CURSOR_REQUIRESEEK.
*/
static int saveCursorPosition(BtCursor *pCur){
  int rc;

  assert( CURSOR_VALID==pCur->eState );
  assert( 0==pCur->pKey );
  assert( sqlite3_mutex_held(pCur->pBtree->pBt->mutex) );

  rc = sqlite3BtreeKeySize(pCur, &pCur->nKey);

  /* If this is an intKey table, then the above call to BtreeKeySize()
  ** stores the integer key in pCur->nKey. In this case this value is
  ** all that is required. Otherwise, if pCur is not open on an intKey
  ** table, then malloc space for and store the pCur->nKey bytes of key 
................................................................................
/*
** Save the positions of all cursors except pExcept open on the table 
** with root-page iRoot. Usually, this is called just before cursor
** pExcept is used to modify the table (BtreeDelete() or BtreeInsert()).
*/
static int saveAllCursors(BtShared *pBt, Pgno iRoot, BtCursor *pExcept){
  BtCursor *p;
  assert( sqlite3_mutex_held(pBt->mutex) );
  for(p=pBt->pCursor; p; p=p->pNext){
    if( p!=pExcept && (0==iRoot || p->pgnoRoot==iRoot) && 
        p->eState==CURSOR_VALID ){
      int rc = saveCursorPosition(p);
      if( SQLITE_OK!=rc ){
        return rc;
      }
................................................................................
  return SQLITE_OK;
}

/*
** Clear the current cursor position.
*/
static void clearCursorPosition(BtCursor *pCur){
  assert( sqlite3_mutex_held(pCur->pBtree->pBt->mutex) );
  sqlite3_free(pCur->pKey);
  pCur->pKey = 0;
  pCur->eState = CURSOR_INVALID;
}

/*
** Restore the cursor to the position it was in (or as close to as possible)
................................................................................
/*
** Given a page number of a regular database page, return the page
** number for the pointer-map page that contains the entry for the
** input page number.
*/
static Pgno ptrmapPageno(BtShared *pBt, Pgno pgno){
  int nPagesPerMapPage, iPtrMap, ret;
  assert( sqlite3_mutex_held(pBt->mutex) );
  nPagesPerMapPage = (pBt->usableSize/5)+1;
  iPtrMap = (pgno-2)/nPagesPerMapPage;
  ret = (iPtrMap*nPagesPerMapPage) + 2; 
  if( ret==PENDING_BYTE_PAGE(pBt) ){
    ret++;
  }
  return ret;
................................................................................
static int ptrmapPut(BtShared *pBt, Pgno key, u8 eType, Pgno parent){
  DbPage *pDbPage;  /* The pointer map page */
  u8 *pPtrmap;      /* The pointer map data */
  Pgno iPtrmap;     /* The pointer map page number */
  int offset;       /* Offset in pointer map page */
  int rc;

  assert( sqlite3_mutex_held(pBt->mutex) );
  /* The master-journal page number must never be used as a pointer map page */
  assert( 0==PTRMAP_ISPAGE(pBt, PENDING_BYTE_PAGE(pBt)) );

  assert( pBt->autoVacuum );
  if( key==0 ){
    return SQLITE_CORRUPT_BKPT;
  }
................................................................................
static int ptrmapGet(BtShared *pBt, Pgno key, u8 *pEType, Pgno *pPgno){
  DbPage *pDbPage;   /* The pointer map page */
  int iPtrmap;       /* Pointer map page index */
  u8 *pPtrmap;       /* Pointer map page data */
  int offset;        /* Offset of entry in pointer map */
  int rc;

  assert( sqlite3_mutex_held(pBt->mutex) );

  iPtrmap = PTRMAP_PAGENO(pBt, key);
  rc = sqlite3PagerGet(pBt->pPager, iPtrmap, &pDbPage);
  if( rc!=0 ){
    return rc;
  }
  pPtrmap = (u8 *)sqlite3PagerGetData(pDbPage);
................................................................................

/*
** This a more complex version of sqlite3BtreeFindCell() that works for
** pages that do contain overflow cells.  See insert
*/
static u8 *findOverflowCell(MemPage *pPage, int iCell){
  int i;
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  for(i=pPage->nOverflow-1; i>=0; i--){
    int k;
    struct _OvflCell *pOvfl;
    pOvfl = &pPage->aOvfl[i];
    k = pOvfl->idx;
    if( k<=iCell ){
      if( k==iCell ){
................................................................................
  MemPage *pPage,         /* Page containing the cell */
  u8 *pCell,              /* Pointer to the cell text. */
  CellInfo *pInfo         /* Fill in this structure */
){
  int n;                  /* Number bytes in cell content header */
  u32 nPayload;           /* Number of bytes of cell payload */

  assert( sqlite3_mutex_held(pPage->pBt->mutex) );

  pInfo->pCell = pCell;
  assert( pPage->leaf==0 || pPage->leaf==1 );
  n = pPage->childPtrSize;
  assert( n==4-4*pPage->leaf );
  if( pPage->hasData ){
    n += getVarint32(&pCell[n], &nPayload);
................................................................................
/*
** If the cell with index iCell on page pPage contains a pointer
** to an overflow page, insert an entry into the pointer-map
** for the overflow page.
*/
static int ptrmapPutOvfl(MemPage *pPage, int iCell){
  u8 *pCell;
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  pCell = findOverflowCell(pPage, iCell);
  return ptrmapPutOvflPtr(pPage, pCell);
}
#endif


/*
................................................................................
  unsigned char *data;       /* The page data */
  unsigned char *temp;       /* Temp area for cell content */

  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  assert( pPage->pBt!=0 );
  assert( pPage->pBt->usableSize <= SQLITE_MAX_PAGE_SIZE );
  assert( pPage->nOverflow==0 );
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  temp = sqlite3_malloc( pPage->pBt->pageSize );
  if( temp==0 ) return SQLITE_NOMEM;
  data = pPage->aData;
  hdr = pPage->hdrOffset;
  cellOffset = pPage->cellOffset;
  nCell = pPage->nCell;
  assert( nCell==get2byte(&data[hdr+3]) );
................................................................................
  int nCell;
  int cellOffset;
  unsigned char *data;
  
  data = pPage->aData;
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  assert( pPage->pBt );
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  if( nByte<4 ) nByte = 4;
  if( pPage->nFree<nByte || pPage->nOverflow>0 ) return 0;
  pPage->nFree -= nByte;
  hdr = pPage->hdrOffset;

  nFrag = data[hdr+7];
  if( nFrag<60 ){
................................................................................
  int addr, pbegin, hdr;
  unsigned char *data = pPage->aData;

  assert( pPage->pBt!=0 );
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  assert( start>=pPage->hdrOffset+6+(pPage->leaf?0:4) );
  assert( (start + size)<=pPage->pBt->usableSize );
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  if( size<4 ) size = 4;

#ifdef SQLITE_SECURE_DELETE
  /* Overwrite deleted information with zeros when the SECURE_DELETE 
  ** option is enabled at compile-time */
  memset(&data[start], 0, size);
#endif
................................................................................
** 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) );
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  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;
  if( flagByte & PTF_LEAFDATA ){
    pPage->leafData = 1;
................................................................................
  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 );
  assert( pParent==0 || pParent->pBt==pBt );
  assert( sqlite3_mutex_held(pBt->mutex) );
  assert( pPage->pgno==sqlite3PagerPagenumber(pPage->pDbPage) );
  assert( pPage->aData == &((unsigned char*)pPage)[-pBt->pageSize] );
  if( pPage->pParent!=pParent && (pPage->pParent!=0 || pPage->isInit) ){
    /* The parent page should never change unless the file is corrupt */
    return SQLITE_CORRUPT_BKPT;
  }
  if( pPage->isInit ) return SQLITE_OK;
................................................................................
  BtShared *pBt = pPage->pBt;
  int hdr = pPage->hdrOffset;
  int first;

  assert( sqlite3PagerPagenumber(pPage->pDbPage)==pPage->pgno );
  assert( &data[pBt->pageSize] == (unsigned char*)pPage );
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  assert( sqlite3_mutex_held(pBt->mutex) );
  memset(&data[hdr], 0, pBt->usableSize - hdr);
  data[hdr] = flags;
  first = hdr + 8 + 4*((flags&PTF_LEAF)==0);
  memset(&data[hdr+1], 0, 4);
  data[hdr+7] = 0;
  put2byte(&data[hdr+5], pBt->usableSize);
  pPage->nFree = pBt->usableSize - first;
................................................................................
  MemPage **ppPage,    /* Return the page in this parameter */
  int noContent        /* Do not load page content if true */
){
  int rc;
  MemPage *pPage;
  DbPage *pDbPage;

  assert( sqlite3_mutex_held(pBt->mutex) );
  rc = sqlite3PagerAcquire(pBt->pPager, pgno, (DbPage**)&pDbPage, noContent);
  if( rc ) return rc;
  pPage = (MemPage *)sqlite3PagerGetExtra(pDbPage);
  pPage->aData = sqlite3PagerGetData(pDbPage);
  pPage->pDbPage = pDbPage;
  pPage->pBt = pBt;
  pPage->pgno = pgno;
................................................................................
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;
  assert( sqlite3_mutex_held(pBt->mutex) );
  if( pgno==0 ){
    return SQLITE_CORRUPT_BKPT; 
  }
  rc = sqlite3BtreeGetPage(pBt, pgno, ppPage, 0);
  if( rc==SQLITE_OK && (*ppPage)->isInit==0 ){
    rc = sqlite3BtreeInitPage(*ppPage, pParent);
  }
................................................................................
** call to sqlite3BtreeGetPage.
*/
static void releasePage(MemPage *pPage){
  if( pPage ){
    assert( pPage->aData );
    assert( pPage->pBt );
    assert( &pPage->aData[pPage->pBt->pageSize]==(unsigned char*)pPage );
    assert( sqlite3_mutex_held(pPage->pBt->mutex) );
    sqlite3PagerUnref(pPage->pDbPage);
  }
}

/*
** This routine is called when the reference count for a page
** reaches zero.  We need to unref the pParent pointer when that
................................................................................
*/
static void pageDestructor(DbPage *pData, int pageSize){
  MemPage *pPage;
  assert( (pageSize & 7)==0 );
  pPage = (MemPage *)sqlite3PagerGetExtra(pData);
  if( pPage->pParent ){
    MemPage *pParent = pPage->pParent;
    assert( sqlite3_mutex_held(pPage->pBt->mutex) );
    pPage->pParent = 0;
    releasePage(pParent);
  }
  pPage->isInit = 0;
}

/*
................................................................................
** page to agree with the restored data.
*/
static void pageReinit(DbPage *pData, int pageSize){
  MemPage *pPage;
  assert( (pageSize & 7)==0 );
  pPage = (MemPage *)sqlite3PagerGetExtra(pData);
  if( pPage->isInit ){
    assert( sqlite3_mutex_held(pPage->pBt->mutex) );
    pPage->isInit = 0;
    sqlite3BtreeInitPage(pPage, pPage->pParent);
  }
}

/*
** Open a database file.
................................................................................
  unsigned char zDbHeader[100];

  if( pSqlite ){
    pVfs = pSqlite->pVfs;
  }else{
    pVfs = sqlite3_vfs_find(0);
  }
  assert( pSqlite==0 || sqlite3_mutex_held(pSqlite->mutex) );

  /* 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)
................................................................................
  assert( p->sharable || (p->pNext==0 && p->pPrev==0) );

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

  /* We should already hold a lock on the database connection */
  assert( sqlite3_mutex_held(p->pSqlite->mutex) );

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

  /* In most cases, we should be able to acquire the lock we
  ** want without having to go throught the ascending lock
................................................................................
** SQLITE_BUSY is returned if the database is locked.  SQLITE_NOMEM
** is returned if we run out of memory. 
*/
static int lockBtree(BtShared *pBt){
  int rc, pageSize;
  MemPage *pPage1;

  assert( sqlite3_mutex_held(pBt->mutex) );
  if( pBt->pPage1 ) return SQLITE_OK;
  rc = sqlite3BtreeGetPage(pBt, 1, &pPage1, 0);
  if( rc!=SQLITE_OK ) return rc;
  

  /* Do some checking to help insure the file we opened really is
  ** a valid database file. 
................................................................................
/*
** 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;

  assert( sqlite3_mutex_held(pRef->pSqlite->mutex) );
  assert( sqlite3_mutex_held(pRef->pBt->mutex) );
  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 ){
................................................................................
** 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){
  assert( sqlite3_mutex_held(pBt->mutex) );
  if( pBt->inTransaction==TRANS_NONE && pBt->pCursor==0 && pBt->pPage1!=0 ){
    if( sqlite3PagerRefcount(pBt->pPager)>=1 ){
      if( pBt->pPage1->aData==0 ){
        MemPage *pPage = pBt->pPage1;
        pPage->aData = &((u8*)pPage)[-pBt->pageSize];
        pPage->pBt = pBt;
        pPage->pgno = 1;
................................................................................
** file.
*/
static int newDatabase(BtShared *pBt){
  MemPage *pP1;
  unsigned char *data;
  int rc;

  assert( sqlite3_mutex_held(pBt->mutex) );
  if( sqlite3PagerPagecount(pBt->pPager)>0 ) return SQLITE_OK;
  pP1 = pBt->pPage1;
  assert( pP1!=0 );
  data = pP1->aData;
  rc = sqlite3PagerWrite(pP1->pDbPage);
  if( rc ) return rc;
  memcpy(data, zMagicHeader, sizeof(zMagicHeader));
................................................................................
  int i;                             /* Counter variable */
  int nCell;                         /* Number of cells in page pPage */
  int rc;                            /* Return code */
  BtShared *pBt = pPage->pBt;
  int isInitOrig = pPage->isInit;
  Pgno pgno = pPage->pgno;

  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  rc = sqlite3BtreeInitPage(pPage, pPage->pParent);
  if( rc!=SQLITE_OK ){
    goto set_child_ptrmaps_out;
  }
  nCell = pPage->nCell;

  for(i=0; i<nCell; i++){
................................................................................
** PTRMAP_OVERFLOW1: pPage is a btree-page. The pointer points at an overflow
**                   page pointed to by one of the cells on pPage.
**
** PTRMAP_OVERFLOW2: pPage is an overflow-page. The pointer points at the next
**                   overflow page in the list.
*/
static int modifyPagePointer(MemPage *pPage, Pgno iFrom, Pgno iTo, u8 eType){
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  if( eType==PTRMAP_OVERFLOW2 ){
    /* The pointer is always the first 4 bytes of the page in this case.  */
    if( get4byte(pPage->aData)!=iFrom ){
      return SQLITE_CORRUPT_BKPT;
    }
    put4byte(pPage->aData, iTo);
  }else{
................................................................................
  MemPage *pPtrPage;   /* The page that contains a pointer to pDbPage */
  Pgno iDbPage = pDbPage->pgno;
  Pager *pPager = pBt->pPager;
  int rc;

  assert( eType==PTRMAP_OVERFLOW2 || eType==PTRMAP_OVERFLOW1 || 
      eType==PTRMAP_BTREE || eType==PTRMAP_ROOTPAGE );
  assert( sqlite3_mutex_held(pBt->mutex) );

  /* Move page iDbPage from it's current location to page number iFreePage */
  TRACE(("AUTOVACUUM: Moving %d to free page %d (ptr page %d type %d)\n", 
      iDbPage, iFreePage, iPtrPage, eType));
  rc = sqlite3PagerMovepage(pPager, pDbPage->pDbPage, iFreePage);
  if( rc!=SQLITE_OK ){
    return rc;
................................................................................
** number of pages the database file will contain after this 
** process is complete.
*/
static int incrVacuumStep(BtShared *pBt, Pgno nFin){
  Pgno iLastPg;             /* Last page in the database */
  Pgno nFreeList;           /* Number of pages still on the free-list */

  assert( sqlite3_mutex_held(pBt->mutex) );
  iLastPg = pBt->nTrunc;
  if( iLastPg==0 ){
    iLastPg = sqlite3PagerPagecount(pBt->pPager);
  }

  if( !PTRMAP_ISPAGE(pBt, iLastPg) && iLastPg!=PENDING_BYTE_PAGE(pBt) ){
    int rc;
................................................................................
static int autoVacuumCommit(BtShared *pBt, Pgno *pnTrunc){
  int rc = SQLITE_OK;
  Pager *pPager = pBt->pPager;
#ifndef NDEBUG
  int nRef = sqlite3PagerRefcount(pPager);
#endif

  assert( sqlite3_mutex_held(pBt->mutex) );
  invalidateAllOverflowCache(pBt);
  assert(pBt->autoVacuum);
  if( !pBt->incrVacuum ){
    Pgno nFin = 0;

    if( pBt->nTrunc==0 ){
      Pgno nFree;
................................................................................
  void *pArg,                                 /* First arg to xCompare() */
  BtCursor **ppCur                            /* Write new cursor here */
){
  int rc;
  BtCursor *pCur;
  BtShared *pBt = p->pBt;

  assert( sqlite3_mutex_held(pBt->mutex) );
  *ppCur = 0;
  if( wrFlag ){
    if( pBt->readOnly ){
      return SQLITE_READONLY;
    }
    if( checkReadLocks(p, iTable, 0) ){
      return SQLITE_LOCKED;
................................................................................
  Pgno ovfl,                   /* Overflow page */
  MemPage **ppPage,            /* OUT: MemPage handle */
  Pgno *pPgnoNext              /* OUT: Next overflow page number */
){
  Pgno next = 0;
  int rc;

  assert( sqlite3_mutex_held(pBt->mutex) );
  /* One of these must not be NULL. Otherwise, why call this function? */
  assert(ppPage || pPgnoNext);

  /* If pPgnoNext is NULL, then this function is being called to obtain
  ** a MemPage* reference only. No page-data is required in this case.
  */
  if( !pPgnoNext ){
................................................................................
  MemPage *pPage = pCur->pPage;        /* Btree page of current cursor entry */
  BtShared *pBt = pCur->pBtree->pBt;   /* Btree this cursor belongs to */

  assert( pPage );
  assert( pCur->eState==CURSOR_VALID );
  assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
  assert( offset>=0 );
  assert( sqlite3_mutex_held(pCur->pBtree->pBt->mutex) );

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

  if( skipKey ){
    offset += nKey;
................................................................................
  unsigned char *aPayload;
  MemPage *pPage;
  u32 nKey;
  int nLocal;

  assert( pCur!=0 && pCur->pPage!=0 );
  assert( pCur->eState==CURSOR_VALID );
  assert( sqlite3_mutex_held(pCur->pBtree->pBt->mutex) );
  pPage = pCur->pPage;
  assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
  getCellInfo(pCur);
  aPayload = pCur->info.pCell;
  aPayload += pCur->info.nHeader;
  if( pPage->intKey ){
    nKey = 0;
................................................................................
** Hence, a mutex on the BtShared should be held prior to calling
** this routine.
**
** These routines is used to get quick access to key and data
** in the common case where no overflow pages are used.
*/
const void *sqlite3BtreeKeyFetch(BtCursor *pCur, int *pAmt){
  assert( sqlite3_mutex_held(pCur->pBtree->pBt->mutex) );
  if( pCur->eState==CURSOR_VALID ){
    return (const void*)fetchPayload(pCur, pAmt, 0);
  }
  return 0;
}
const void *sqlite3BtreeDataFetch(BtCursor *pCur, int *pAmt){
  assert( sqlite3_mutex_held(pCur->pBtree->pBt->mutex) );
  if( pCur->eState==CURSOR_VALID ){
    return (const void*)fetchPayload(pCur, pAmt, 1);
  }
  return 0;
}


................................................................................
*/
static int moveToChild(BtCursor *pCur, u32 newPgno){
  int rc;
  MemPage *pNewPage;
  MemPage *pOldPage;
  BtShared *pBt = pCur->pBtree->pBt;

  assert( sqlite3_mutex_held(pBt->mutex) );
  assert( pCur->eState==CURSOR_VALID );
  rc = getAndInitPage(pBt, newPgno, &pNewPage, pCur->pPage);
  if( rc ) return rc;
  pNewPage->idxParent = pCur->idx;
  pOldPage = pCur->pPage;
  pOldPage->idxShift = 0;
  releasePage(pOldPage);
................................................................................
** is empty except for the right-pointer.  In such cases the
** virtual root page is the page that the right-pointer of page
** 1 is pointing to.
*/
int sqlite3BtreeIsRootPage(MemPage *pPage){
  MemPage *pParent;

  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  pParent = pPage->pParent;
  if( pParent==0 ) return 1;
  if( pParent->pgno>1 ) return 0;
  if( get2byte(&pParent->aData[pParent->hdrOffset+3])==0 ) return 1;
  return 0;
}

................................................................................
*/
static int moveToRoot(BtCursor *pCur){
  MemPage *pRoot;
  int rc = SQLITE_OK;
  Btree *p = pCur->pBtree;
  BtShared *pBt = p->pBt;

  assert( sqlite3_mutex_held(p->pSqlite->mutex) );
  assert( sqlite3_mutex_held(pBt->mutex) );
  if( pCur->eState==CURSOR_REQUIRESEEK ){
    clearCursorPosition(pCur);
  }
  pRoot = pCur->pPage;
  if( pRoot && pRoot->pgno==pCur->pgnoRoot ){
    assert( pRoot->isInit );
  }else{
................................................................................
** in ascending order.
*/
static int moveToLeftmost(BtCursor *pCur){
  Pgno pgno;
  int rc = SQLITE_OK;
  MemPage *pPage;

  assert( sqlite3_mutex_held(pCur->pBtree->pBt->mutex) );
  assert( sqlite3_mutex_held(pCur->pBtree->pSqlite->mutex) );
  assert( pCur->eState==CURSOR_VALID );
  while( rc==SQLITE_OK && !(pPage = pCur->pPage)->leaf ){
    assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
    pgno = get4byte(findCell(pPage, pCur->idx));
    rc = moveToChild(pCur, pgno);
  }
  return rc;
................................................................................
** key in ascending order.
*/
static int moveToRightmost(BtCursor *pCur){
  Pgno pgno;
  int rc = SQLITE_OK;
  MemPage *pPage;

  assert( sqlite3_mutex_held(pCur->pBtree->pBt->mutex) );
  assert( sqlite3_mutex_held(pCur->pBtree->pSqlite->mutex) );
  assert( pCur->eState==CURSOR_VALID );
  while( rc==SQLITE_OK && !(pPage = pCur->pPage)->leaf ){
    pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
    pCur->idx = pPage->nCell;
    rc = moveToChild(pCur, pgno);
  }
  if( rc==SQLITE_OK ){
................................................................................
/* Move the cursor to the first entry in the table.  Return SQLITE_OK
** on success.  Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
int sqlite3BtreeFirst(BtCursor *pCur, int *pRes){
  int rc;

  assert( sqlite3_mutex_held(pCur->pBtree->pBt->mutex) );
  assert( sqlite3_mutex_held(pCur->pBtree->pSqlite->mutex) );
  rc = moveToRoot(pCur);
  if( rc==SQLITE_OK ){
    if( pCur->eState==CURSOR_INVALID ){
      assert( pCur->pPage->nCell==0 );
      *pRes = 1;
      rc = SQLITE_OK;
    }else{
................................................................................
/* Move the cursor to the last entry in the table.  Return SQLITE_OK
** on success.  Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
int sqlite3BtreeLast(BtCursor *pCur, int *pRes){
  int rc;
 
  assert( sqlite3_mutex_held(pCur->pBtree->pBt->mutex) );
  assert( sqlite3_mutex_held(pCur->pBtree->pSqlite->mutex) );
  rc = moveToRoot(pCur);
  if( rc==SQLITE_OK ){
    if( CURSOR_INVALID==pCur->eState ){
      assert( pCur->pPage->nCell==0 );
      *pRes = 1;
    }else{
      assert( pCur->eState==CURSOR_VALID );
................................................................................
  const void *pKey,      /* The key content for indices.  Not used by tables */
  i64 nKey,              /* Size of pKey.  Or the key for tables */
  int biasRight,         /* If true, bias the search to the high end */
  int *pRes              /* Search result flag */
){
  int rc;

  assert( sqlite3_mutex_held(pCur->pBtree->pBt->mutex) );
  assert( sqlite3_mutex_held(pCur->pBtree->pSqlite->mutex) );
  rc = moveToRoot(pCur);
  if( rc ){
    return rc;
  }
  assert( pCur->pPage );
  assert( pCur->pPage->isInit );
  if( pCur->eState==CURSOR_INVALID ){
................................................................................
  MemPage *pPage1;
  int rc;
  int n;     /* Number of pages on the freelist */
  int k;     /* Number of leaves on the trunk of the freelist */
  MemPage *pTrunk = 0;
  MemPage *pPrevTrunk = 0;

  assert( sqlite3_mutex_held(pBt->mutex) );
  pPage1 = pBt->pPage1;
  n = get4byte(&pPage1->aData[36]);
  if( n>0 ){
    /* There are pages on the freelist.  Reuse one of those pages. */
    Pgno iTrunk;
    u8 searchList = 0; /* If the free-list must be searched for 'nearby' */
    
................................................................................
*/
static int freePage(MemPage *pPage){
  BtShared *pBt = pPage->pBt;
  MemPage *pPage1 = pBt->pPage1;
  int rc, n, k;

  /* Prepare the page for freeing */
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  assert( pPage->pgno>1 );
  pPage->isInit = 0;
  releasePage(pPage->pParent);
  pPage->pParent = 0;

  /* Increment the free page count on pPage1 */
  rc = sqlite3PagerWrite(pPage1->pDbPage);
................................................................................
  BtShared *pBt = pPage->pBt;
  CellInfo info;
  Pgno ovflPgno;
  int rc;
  int nOvfl;
  int ovflPageSize;

  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  sqlite3BtreeParseCellPtr(pPage, pCell, &info);
  if( info.iOverflow==0 ){
    return SQLITE_OK;  /* No overflow pages. Return without doing anything */
  }
  ovflPgno = get4byte(&pCell[info.iOverflow]);
  ovflPageSize = pBt->usableSize - 4;
  nOvfl = (info.nPayload - info.nLocal + ovflPageSize - 1)/ovflPageSize;
................................................................................
  unsigned char *pPrior;
  unsigned char *pPayload;
  BtShared *pBt = pPage->pBt;
  Pgno pgnoOvfl = 0;
  int nHeader;
  CellInfo info;

  assert( sqlite3_mutex_held(pPage->pBt->mutex) );

  /* Fill in the header. */
  nHeader = 0;
  if( !pPage->leaf ){
    nHeader += 4;
  }
  if( pPage->hasData ){
................................................................................
** 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;
  DbPage *pDbPage;

  assert( sqlite3_mutex_held(pBt->mutex) );
  assert( pNewParent!=0 );
  if( pgno==0 ) return SQLITE_OK;
  assert( pBt->pPager!=0 );
  pDbPage = sqlite3PagerLookup(pBt->pPager, pgno);
  if( pDbPage ){
    pThis = (MemPage *)sqlite3PagerGetExtra(pDbPage);
    if( pThis->isInit ){
................................................................................
** another.
*/
static int reparentChildPages(MemPage *pPage){
  int i;
  BtShared *pBt = pPage->pBt;
  int rc = SQLITE_OK;

  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  if( pPage->leaf ) return SQLITE_OK;

  for(i=0; i<pPage->nCell; i++){
    u8 *pCell = findCell(pPage, i);
    if( !pPage->leaf ){
      rc = reparentPage(pBt, get4byte(pCell), pPage, i);
      if( rc!=SQLITE_OK ) return rc;
................................................................................
  int pc;         /* Offset to cell content of cell being deleted */
  u8 *data;       /* pPage->aData */
  u8 *ptr;        /* Used to move bytes around within data[] */

  assert( idx>=0 && idx<pPage->nCell );
  assert( sz==cellSize(pPage, idx) );
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  data = pPage->aData;
  ptr = &data[pPage->cellOffset + 2*idx];
  pc = get2byte(ptr);
  assert( pc>10 && pc+sz<=pPage->pBt->usableSize );
  freeSpace(pPage, pc, sz);
  for(i=idx+1; i<pPage->nCell; i++, ptr+=2){
    ptr[0] = ptr[2];
................................................................................
  int hdr;          /* Offset into data[] of the page header */
  int cellOffset;   /* Address of first cell pointer in data[] */
  u8 *data;         /* The content of the whole page */
  u8 *ptr;          /* Used for moving information around in data[] */

  assert( i>=0 && i<=pPage->nCell+pPage->nOverflow );
  assert( sz==cellSizePtr(pPage, pCell) );
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  if( pPage->nOverflow || sz+2>pPage->nFree ){
    if( pTemp ){
      memcpy(pTemp+nSkip, pCell+nSkip, sz-nSkip);
      pCell = pTemp;
    }
    j = pPage->nOverflow++;
    assert( j<sizeof(pPage->aOvfl)/sizeof(pPage->aOvfl[0]) );
................................................................................
  int totalSize;    /* Total size of all cells */
  int hdr;          /* Index of page header */
  int cellptr;      /* Address of next cell pointer */
  int cellbody;     /* Address of next cell body */
  u8 *data;         /* Data for the page */

  assert( pPage->nOverflow==0 );
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  totalSize = 0;
  for(i=0; i<nCell; i++){
    totalSize += aSize[i];
  }
  assert( totalSize+2*nCell<=pPage->nFree );
  assert( pPage->nCell==0 );
  cellptr = pPage->cellOffset;
................................................................................
  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 */

  assert( sqlite3_mutex_held(pPage->pBt->mutex) );

  /* Allocate a new page. Insert the overflow cell from pPage
  ** into it. Then remove the overflow cell from pPage.
  */
  rc = allocateBtreePage(pBt, &pNew, &pgnoNew, 0, 0);
  if( rc!=SQLITE_OK ){
    return rc;
................................................................................
  int *szCell;                 /* Local size of all cells in apCell[] */
  u8 *aCopy[NB];               /* Space for holding data of apCopy[] */
  u8 *aSpace;                  /* Space to hold copies of dividers cells */
#ifndef SQLITE_OMIT_AUTOVACUUM
  u8 *aFrom = 0;
#endif

  assert( sqlite3_mutex_held(pPage->pBt->mutex) );

  /* 
  ** Find the parent page.
  */
  assert( pPage->isInit );
  assert( sqlite3PagerIswriteable(pPage->pDbPage) || pPage->nOverflow==1 );
  pBt = pPage->pBt;
................................................................................
  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 );
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  pBt = pPage->pBt;
  mxCellPerPage = MX_CELL(pBt);
  apCell = sqlite3_malloc( mxCellPerPage*(sizeof(u8*)+sizeof(int)) );
  if( apCell==0 ) return SQLITE_NOMEM;
  szCell = (int*)&apCell[mxCellPerPage];
  if( pPage->leaf ){
    /* The table is completely empty */
................................................................................
  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 );
  assert( pPage->nOverflow>0 );
  pBt = pPage->pBt;
  assert( sqlite3_mutex_held(pBt->mutex) );
  rc = allocateBtreePage(pBt, &pChild, &pgnoChild, pPage->pgno, 0);
  if( rc ) return rc;
  assert( sqlite3PagerIswriteable(pChild->pDbPage) );
  usableSize = pBt->usableSize;
  data = pPage->aData;
  hdr = pPage->hdrOffset;
  brk = get2byte(&data[hdr+5]);
................................................................................

/*
** Decide if the page pPage needs to be balanced.  If balancing is
** required, call the appropriate balancing routine.
*/
static int balance(MemPage *pPage, int insert){
  int rc = SQLITE_OK;
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  if( pPage->pParent==0 ){
    rc = sqlite3PagerWrite(pPage->pDbPage);
    if( rc==SQLITE_OK && pPage->nOverflow>0 ){
      rc = balance_deeper(pPage);
    }
    if( rc==SQLITE_OK && pPage->nCell==0 ){
      rc = balance_shallower(pPage);
................................................................................
** a page entirely and we do not want to leave any cursors 
** pointing to non-existant pages or cells.
*/
static int checkReadLocks(Btree *pBtree, Pgno pgnoRoot, BtCursor *pExclude){
  BtCursor *p;
  BtShared *pBt = pBtree->pBt;
  sqlite3 *db = pBtree->pSqlite;
  assert( sqlite3_mutex_held(pBt->mutex) );
  assert( sqlite3_mutex_held(db->mutex) );
  for(p=pBt->pCursor; p; p=p->pNext){
    if( p==pExclude ) continue;
    if( p->eState!=CURSOR_VALID ) continue;
    if( p->pgnoRoot!=pgnoRoot ) continue;
    if( p->wrFlag==0 ){
      sqlite3 *dbOther = p->pBtree->pSqlite;
      if( dbOther==0 ||
................................................................................
  int freePageFlag      /* Deallocate page if true */
){
  MemPage *pPage = 0;
  int rc;
  unsigned char *pCell;
  int i;

  assert( sqlite3_mutex_held(pBt->mutex) );
  if( pgno>sqlite3PagerPagecount(pBt->pPager) ){
    return SQLITE_CORRUPT_BKPT;
  }

  rc = getAndInitPage(pBt, pgno, &pPage, pParent);
  if( rc ) goto cleardatabasepage_out;
  for(i=0; i<pPage->nCell; i++){
................................................................................
** meta[3] is updated by this procedure.
*/
static int btreeDropTable(Btree *p, int iTable, int *piMoved){
  int rc;
  MemPage *pPage = 0;
  BtShared *pBt = p->pBt;

  assert( sqlite3_mutex_held(pBt->mutex) );
  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
................................................................................
** is currently pointing to.
*/
int sqlite3BtreeFlags(BtCursor *pCur){
  /* TODO: What about CURSOR_REQUIRESEEK state? Probably need to call
  ** restoreOrClearCursorPosition() here.
  */
  MemPage *pPage = pCur->pPage;
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  return pPage ? pPage->aData[pPage->hdrOffset] : 0;
}


/*
** Return the pager associated with a BTree.  This routine is used for
** testing and debugging only.
*/
Pager *sqlite3BtreePager(Btree *p){
  assert( sqlite3_mutex_held(p->pSqlite->mutex) );
  assert( sqlite3_mutex_held(p->pBt->mutex) );
  return p->pBt->pPager;
}

#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** Append a message to the error message string.
*/
................................................................................
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */

/*
** Return the full pathname of the underlying database file.
*/
const char *sqlite3BtreeGetFilename(Btree *p){
  assert( p->pBt->pPager!=0 );
  assert( sqlite3_mutex_held(p->pBt->mutex) );
  return sqlite3PagerFilename(p->pBt->pPager);
}

/*
** Return the pathname of the directory that contains the database file.
*/
const char *sqlite3BtreeGetDirname(Btree *p){
  assert( p->pBt->pPager!=0 );
  assert( sqlite3_mutex_held(p->pBt->mutex) );
  return sqlite3PagerDirname(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 );
  assert( sqlite3_mutex_held(p->pBt->mutex) );
  return sqlite3PagerJournalname(p->pBt->pPager);
}

#ifndef SQLITE_OMIT_VACUUM
/*
** Copy the complete content of pBtFrom into pBtTo.  A transaction
** must be active for both files.
................................................................................

#endif /* SQLITE_OMIT_VACUUM */

/*
** Return non-zero if a transaction is active.
*/
int sqlite3BtreeIsInTrans(Btree *p){
  assert( sqlite3_mutex_held(p->pBt->mutex) );
  assert( sqlite3_mutex_held(p->pSqlite->mutex) );
  return (p && (p->inTrans==TRANS_WRITE));
}

/*
** Return non-zero if a statement transaction is active.
*/
int sqlite3BtreeIsInStmt(Btree *p){
  assert( sqlite3_mutex_held(p->pBt->mutex) );
  assert( sqlite3_mutex_held(p->pSqlite->mutex) );
  return (p->pBt && p->pBt->inStmt);
}

/*
** Return non-zero if a read (or write) transaction is active.
*/
int sqlite3BtreeIsInReadTrans(Btree *p){
  assert( sqlite3_mutex_held(p->pBt->mutex) );
  assert( sqlite3_mutex_held(p->pSqlite->mutex) );
  return (p && (p->inTrans!=TRANS_NONE));
}

/*
** This function returns a pointer to a blob of memory associated with
** a single shared-btree. The memory is used by client code for it's own
** purposes (for example, to store a high-level schema associated with 
................................................................................
** Just before the shared-btree is closed, the function passed as the 
** xFree argument when the memory allocation was made is invoked on the 
** blob of allocated memory. This function should not call sqlite3_free()
** on the memory, the btree layer does that.
*/
void *sqlite3BtreeSchema(Btree *p, int nBytes, void(*xFree)(void *)){
  BtShared *pBt = p->pBt;
  assert( sqlite3_mutex_held(pBt->mutex) );
  assert( sqlite3_mutex_held(p->pSqlite->mutex) );
  if( !pBt->pSchema ){
    pBt->pSchema = sqlite3MallocZero(nBytes);
    pBt->xFreeSchema = xFree;
  }

  return pBt->pSchema;
}

/*
** Return true if another user of the same shared btree as the argument
** handle holds an exclusive lock on the sqlite_master table.
*/
int sqlite3BtreeSchemaLocked(Btree *p){
  assert( sqlite3_mutex_held(p->pBt->mutex) );
  assert( sqlite3_mutex_held(p->pSqlite->mutex) );

  return (queryTableLock(p, MASTER_ROOT, READ_LOCK)!=SQLITE_OK);


}


#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Obtain a lock on the table whose root page is iTab.  The
** lock is a write lock if isWritelock is true or a read lock
................................................................................
** Argument pCsr must be a cursor opened for writing on an 
** INTKEY table currently pointing at a valid table entry. 
** This function modifies the data stored as part of that entry.
** Only the data content may only be modified, it is not possible
** to change the length of the data stored.
*/
int sqlite3BtreePutData(BtCursor *pCsr, u32 offset, u32 amt, void *z){
  assert( sqlite3_mutex_held(pCsr->pBtree->pBt->mutex) );
  assert( sqlite3_mutex_held(pCsr->pBtree->pSqlite->mutex) );
  assert(pCsr->isIncrblobHandle);
  if( pCsr->eState==CURSOR_REQUIRESEEK ){
    return SQLITE_ABORT;
  }

  /* Check some preconditions: 
  **   (a) the cursor is open for writing,
................................................................................
**
** This function sets a flag only. The actual page location cache
** (stored in BtCursor.aOverflow[]) is allocated and used by function
** accessPayload() (the worker function for sqlite3BtreeData() and
** sqlite3BtreePutData()).
*/
void sqlite3BtreeCacheOverflow(BtCursor *pCur){
  assert( sqlite3_mutex_held(pCur->pBtree->pBt->mutex) );
  assert( sqlite3_mutex_held(pCur->pBtree->pSqlite->mutex) );
  assert(!pCur->isIncrblobHandle);
  assert(!pCur->aOverflow);
  pCur->isIncrblobHandle = 1;
}
#endif

** 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 1.408 2007/08/22 02:56:43 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "btreeInt.h"

................................................................................
** SQLITE_OK if the lock may be obtained (by calling lockTable()), or
** SQLITE_LOCKED if not.
*/
static int queryTableLock(Btree *p, Pgno iTab, u8 eLock){
  BtShared *pBt = p->pBt;
  BtLock *pIter;

  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  
  /* This is a no-op if the shared-cache is not enabled */
  if( !p->sharable ){
    return SQLITE_OK;
  }

  /* This (along with lockTable()) is where the ReadUncommitted flag is
................................................................................
** 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( sqlite3BtreeMutexHeld(pBt->mutex) );

  /* This is a no-op if the shared-cache is not enabled */
  if( !p->sharable ){
    return SQLITE_OK;
  }

  assert( SQLITE_OK==queryTableLock(p, iTable, eLock) );
................................................................................
/*
** 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;

  assert( sqlite3BtreeMutexHeld(p->pBt->mutex) );
  assert( p->sharable || 0==*ppIter );

  while( *ppIter ){
    BtLock *pLock = *ppIter;
    if( pLock->pBtree==p ){
      *ppIter = pLock->pNext;
      sqlite3_free(pLock);
................................................................................

/*
** Invalidate the overflow page-list cache for all cursors opened
** on the shared btree structure pBt.
*/
static void invalidateAllOverflowCache(BtShared *pBt){
  BtCursor *p;
  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  for(p=pBt->pCursor; p; p=p->pNext){
    invalidateOverflowCache(p);
  }
}
#else
  #define invalidateOverflowCache(x)
  #define invalidateAllOverflowCache(x)
................................................................................
** and BtCursor.pKey. The cursor's state is set to CURSOR_REQUIRESEEK.
*/
static int saveCursorPosition(BtCursor *pCur){
  int rc;

  assert( CURSOR_VALID==pCur->eState );
  assert( 0==pCur->pKey );
  assert( sqlite3BtreeMutexHeld(pCur->pBtree->pBt->mutex) );

  rc = sqlite3BtreeKeySize(pCur, &pCur->nKey);

  /* If this is an intKey table, then the above call to BtreeKeySize()
  ** stores the integer key in pCur->nKey. In this case this value is
  ** all that is required. Otherwise, if pCur is not open on an intKey
  ** table, then malloc space for and store the pCur->nKey bytes of key 
................................................................................
/*
** Save the positions of all cursors except pExcept open on the table 
** with root-page iRoot. Usually, this is called just before cursor
** pExcept is used to modify the table (BtreeDelete() or BtreeInsert()).
*/
static int saveAllCursors(BtShared *pBt, Pgno iRoot, BtCursor *pExcept){
  BtCursor *p;
  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  for(p=pBt->pCursor; p; p=p->pNext){
    if( p!=pExcept && (0==iRoot || p->pgnoRoot==iRoot) && 
        p->eState==CURSOR_VALID ){
      int rc = saveCursorPosition(p);
      if( SQLITE_OK!=rc ){
        return rc;
      }
................................................................................
  return SQLITE_OK;
}

/*
** Clear the current cursor position.
*/
static void clearCursorPosition(BtCursor *pCur){
  assert( sqlite3BtreeMutexHeld(pCur->pBtree->pBt->mutex) );
  sqlite3_free(pCur->pKey);
  pCur->pKey = 0;
  pCur->eState = CURSOR_INVALID;
}

/*
** Restore the cursor to the position it was in (or as close to as possible)
................................................................................
/*
** Given a page number of a regular database page, return the page
** number for the pointer-map page that contains the entry for the
** input page number.
*/
static Pgno ptrmapPageno(BtShared *pBt, Pgno pgno){
  int nPagesPerMapPage, iPtrMap, ret;
  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  nPagesPerMapPage = (pBt->usableSize/5)+1;
  iPtrMap = (pgno-2)/nPagesPerMapPage;
  ret = (iPtrMap*nPagesPerMapPage) + 2; 
  if( ret==PENDING_BYTE_PAGE(pBt) ){
    ret++;
  }
  return ret;
................................................................................
static int ptrmapPut(BtShared *pBt, Pgno key, u8 eType, Pgno parent){
  DbPage *pDbPage;  /* The pointer map page */
  u8 *pPtrmap;      /* The pointer map data */
  Pgno iPtrmap;     /* The pointer map page number */
  int offset;       /* Offset in pointer map page */
  int rc;

  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  /* The master-journal page number must never be used as a pointer map page */
  assert( 0==PTRMAP_ISPAGE(pBt, PENDING_BYTE_PAGE(pBt)) );

  assert( pBt->autoVacuum );
  if( key==0 ){
    return SQLITE_CORRUPT_BKPT;
  }
................................................................................
static int ptrmapGet(BtShared *pBt, Pgno key, u8 *pEType, Pgno *pPgno){
  DbPage *pDbPage;   /* The pointer map page */
  int iPtrmap;       /* Pointer map page index */
  u8 *pPtrmap;       /* Pointer map page data */
  int offset;        /* Offset of entry in pointer map */
  int rc;

  assert( sqlite3BtreeMutexHeld(pBt->mutex) );

  iPtrmap = PTRMAP_PAGENO(pBt, key);
  rc = sqlite3PagerGet(pBt->pPager, iPtrmap, &pDbPage);
  if( rc!=0 ){
    return rc;
  }
  pPtrmap = (u8 *)sqlite3PagerGetData(pDbPage);
................................................................................

/*
** This a more complex version of sqlite3BtreeFindCell() that works for
** pages that do contain overflow cells.  See insert
*/
static u8 *findOverflowCell(MemPage *pPage, int iCell){
  int i;
  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );
  for(i=pPage->nOverflow-1; i>=0; i--){
    int k;
    struct _OvflCell *pOvfl;
    pOvfl = &pPage->aOvfl[i];
    k = pOvfl->idx;
    if( k<=iCell ){
      if( k==iCell ){
................................................................................
  MemPage *pPage,         /* Page containing the cell */
  u8 *pCell,              /* Pointer to the cell text. */
  CellInfo *pInfo         /* Fill in this structure */
){
  int n;                  /* Number bytes in cell content header */
  u32 nPayload;           /* Number of bytes of cell payload */

  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );

  pInfo->pCell = pCell;
  assert( pPage->leaf==0 || pPage->leaf==1 );
  n = pPage->childPtrSize;
  assert( n==4-4*pPage->leaf );
  if( pPage->hasData ){
    n += getVarint32(&pCell[n], &nPayload);
................................................................................
/*
** If the cell with index iCell on page pPage contains a pointer
** to an overflow page, insert an entry into the pointer-map
** for the overflow page.
*/
static int ptrmapPutOvfl(MemPage *pPage, int iCell){
  u8 *pCell;
  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );
  pCell = findOverflowCell(pPage, iCell);
  return ptrmapPutOvflPtr(pPage, pCell);
}
#endif


/*
................................................................................
  unsigned char *data;       /* The page data */
  unsigned char *temp;       /* Temp area for cell content */

  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  assert( pPage->pBt!=0 );
  assert( pPage->pBt->usableSize <= SQLITE_MAX_PAGE_SIZE );
  assert( pPage->nOverflow==0 );
  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );
  temp = sqlite3_malloc( pPage->pBt->pageSize );
  if( temp==0 ) return SQLITE_NOMEM;
  data = pPage->aData;
  hdr = pPage->hdrOffset;
  cellOffset = pPage->cellOffset;
  nCell = pPage->nCell;
  assert( nCell==get2byte(&data[hdr+3]) );
................................................................................
  int nCell;
  int cellOffset;
  unsigned char *data;
  
  data = pPage->aData;
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  assert( pPage->pBt );
  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );
  if( nByte<4 ) nByte = 4;
  if( pPage->nFree<nByte || pPage->nOverflow>0 ) return 0;
  pPage->nFree -= nByte;
  hdr = pPage->hdrOffset;

  nFrag = data[hdr+7];
  if( nFrag<60 ){
................................................................................
  int addr, pbegin, hdr;
  unsigned char *data = pPage->aData;

  assert( pPage->pBt!=0 );
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  assert( start>=pPage->hdrOffset+6+(pPage->leaf?0:4) );
  assert( (start + size)<=pPage->pBt->usableSize );
  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );
  if( size<4 ) size = 4;

#ifdef SQLITE_SECURE_DELETE
  /* Overwrite deleted information with zeros when the SECURE_DELETE 
  ** option is enabled at compile-time */
  memset(&data[start], 0, size);
#endif
................................................................................
** 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) );
  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );
  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;
  if( flagByte & PTF_LEAFDATA ){
    pPage->leafData = 1;
................................................................................
  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 );
  assert( pParent==0 || pParent->pBt==pBt );
  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  assert( pPage->pgno==sqlite3PagerPagenumber(pPage->pDbPage) );
  assert( pPage->aData == &((unsigned char*)pPage)[-pBt->pageSize] );
  if( pPage->pParent!=pParent && (pPage->pParent!=0 || pPage->isInit) ){
    /* The parent page should never change unless the file is corrupt */
    return SQLITE_CORRUPT_BKPT;
  }
  if( pPage->isInit ) return SQLITE_OK;
................................................................................
  BtShared *pBt = pPage->pBt;
  int hdr = pPage->hdrOffset;
  int first;

  assert( sqlite3PagerPagenumber(pPage->pDbPage)==pPage->pgno );
  assert( &data[pBt->pageSize] == (unsigned char*)pPage );
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  memset(&data[hdr], 0, pBt->usableSize - hdr);
  data[hdr] = flags;
  first = hdr + 8 + 4*((flags&PTF_LEAF)==0);
  memset(&data[hdr+1], 0, 4);
  data[hdr+7] = 0;
  put2byte(&data[hdr+5], pBt->usableSize);
  pPage->nFree = pBt->usableSize - first;
................................................................................
  MemPage **ppPage,    /* Return the page in this parameter */
  int noContent        /* Do not load page content if true */
){
  int rc;
  MemPage *pPage;
  DbPage *pDbPage;

  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  rc = sqlite3PagerAcquire(pBt->pPager, pgno, (DbPage**)&pDbPage, noContent);
  if( rc ) return rc;
  pPage = (MemPage *)sqlite3PagerGetExtra(pDbPage);
  pPage->aData = sqlite3PagerGetData(pDbPage);
  pPage->pDbPage = pDbPage;
  pPage->pBt = pBt;
  pPage->pgno = pgno;
................................................................................
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;
  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  if( pgno==0 ){
    return SQLITE_CORRUPT_BKPT; 
  }
  rc = sqlite3BtreeGetPage(pBt, pgno, ppPage, 0);
  if( rc==SQLITE_OK && (*ppPage)->isInit==0 ){
    rc = sqlite3BtreeInitPage(*ppPage, pParent);
  }
................................................................................
** call to sqlite3BtreeGetPage.
*/
static void releasePage(MemPage *pPage){
  if( pPage ){
    assert( pPage->aData );
    assert( pPage->pBt );
    assert( &pPage->aData[pPage->pBt->pageSize]==(unsigned char*)pPage );
    assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );
    sqlite3PagerUnref(pPage->pDbPage);
  }
}

/*
** This routine is called when the reference count for a page
** reaches zero.  We need to unref the pParent pointer when that
................................................................................
*/
static void pageDestructor(DbPage *pData, int pageSize){
  MemPage *pPage;
  assert( (pageSize & 7)==0 );
  pPage = (MemPage *)sqlite3PagerGetExtra(pData);
  if( pPage->pParent ){
    MemPage *pParent = pPage->pParent;
    assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );
    pPage->pParent = 0;
    releasePage(pParent);
  }
  pPage->isInit = 0;
}

/*
................................................................................
** page to agree with the restored data.
*/
static void pageReinit(DbPage *pData, int pageSize){
  MemPage *pPage;
  assert( (pageSize & 7)==0 );
  pPage = (MemPage *)sqlite3PagerGetExtra(pData);
  if( pPage->isInit ){
    assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );
    pPage->isInit = 0;
    sqlite3BtreeInitPage(pPage, pPage->pParent);
  }
}

/*
** Open a database file.
................................................................................
  unsigned char zDbHeader[100];

  if( pSqlite ){
    pVfs = pSqlite->pVfs;
  }else{
    pVfs = sqlite3_vfs_find(0);
  }
  assert( sqlite3BtreeMutexHeld(pSqlite->mutex) );

  /* 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)
................................................................................
  assert( p->sharable || (p->pNext==0 && p->pPrev==0) );

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

  /* We should already hold a lock on the database connection */
  assert( sqlite3BtreeMutexHeld(p->pSqlite->mutex) );

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

  /* In most cases, we should be able to acquire the lock we
  ** want without having to go throught the ascending lock
................................................................................
** SQLITE_BUSY is returned if the database is locked.  SQLITE_NOMEM
** is returned if we run out of memory. 
*/
static int lockBtree(BtShared *pBt){
  int rc, pageSize;
  MemPage *pPage1;

  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  if( pBt->pPage1 ) return SQLITE_OK;
  rc = sqlite3BtreeGetPage(pBt, 1, &pPage1, 0);
  if( rc!=SQLITE_OK ) return rc;
  

  /* Do some checking to help insure the file we opened really is
  ** a valid database file. 
................................................................................
/*
** 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;

  assert( sqlite3BtreeMutexHeld(pRef->pSqlite->mutex) );
  assert( sqlite3BtreeMutexHeld(pRef->pBt->mutex) );
  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 ){
................................................................................
** 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){
  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  if( pBt->inTransaction==TRANS_NONE && pBt->pCursor==0 && pBt->pPage1!=0 ){
    if( sqlite3PagerRefcount(pBt->pPager)>=1 ){
      if( pBt->pPage1->aData==0 ){
        MemPage *pPage = pBt->pPage1;
        pPage->aData = &((u8*)pPage)[-pBt->pageSize];
        pPage->pBt = pBt;
        pPage->pgno = 1;
................................................................................
** file.
*/
static int newDatabase(BtShared *pBt){
  MemPage *pP1;
  unsigned char *data;
  int rc;

  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  if( sqlite3PagerPagecount(pBt->pPager)>0 ) return SQLITE_OK;
  pP1 = pBt->pPage1;
  assert( pP1!=0 );
  data = pP1->aData;
  rc = sqlite3PagerWrite(pP1->pDbPage);
  if( rc ) return rc;
  memcpy(data, zMagicHeader, sizeof(zMagicHeader));
................................................................................
  int i;                             /* Counter variable */
  int nCell;                         /* Number of cells in page pPage */
  int rc;                            /* Return code */
  BtShared *pBt = pPage->pBt;
  int isInitOrig = pPage->isInit;
  Pgno pgno = pPage->pgno;

  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );
  rc = sqlite3BtreeInitPage(pPage, pPage->pParent);
  if( rc!=SQLITE_OK ){
    goto set_child_ptrmaps_out;
  }
  nCell = pPage->nCell;

  for(i=0; i<nCell; i++){
................................................................................
** PTRMAP_OVERFLOW1: pPage is a btree-page. The pointer points at an overflow
**                   page pointed to by one of the cells on pPage.
**
** PTRMAP_OVERFLOW2: pPage is an overflow-page. The pointer points at the next
**                   overflow page in the list.
*/
static int modifyPagePointer(MemPage *pPage, Pgno iFrom, Pgno iTo, u8 eType){
  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );
  if( eType==PTRMAP_OVERFLOW2 ){
    /* The pointer is always the first 4 bytes of the page in this case.  */
    if( get4byte(pPage->aData)!=iFrom ){
      return SQLITE_CORRUPT_BKPT;
    }
    put4byte(pPage->aData, iTo);
  }else{
................................................................................
  MemPage *pPtrPage;   /* The page that contains a pointer to pDbPage */
  Pgno iDbPage = pDbPage->pgno;
  Pager *pPager = pBt->pPager;
  int rc;

  assert( eType==PTRMAP_OVERFLOW2 || eType==PTRMAP_OVERFLOW1 || 
      eType==PTRMAP_BTREE || eType==PTRMAP_ROOTPAGE );
  assert( sqlite3BtreeMutexHeld(pBt->mutex) );

  /* Move page iDbPage from it's current location to page number iFreePage */
  TRACE(("AUTOVACUUM: Moving %d to free page %d (ptr page %d type %d)\n", 
      iDbPage, iFreePage, iPtrPage, eType));
  rc = sqlite3PagerMovepage(pPager, pDbPage->pDbPage, iFreePage);
  if( rc!=SQLITE_OK ){
    return rc;
................................................................................
** number of pages the database file will contain after this 
** process is complete.
*/
static int incrVacuumStep(BtShared *pBt, Pgno nFin){
  Pgno iLastPg;             /* Last page in the database */
  Pgno nFreeList;           /* Number of pages still on the free-list */

  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  iLastPg = pBt->nTrunc;
  if( iLastPg==0 ){
    iLastPg = sqlite3PagerPagecount(pBt->pPager);
  }

  if( !PTRMAP_ISPAGE(pBt, iLastPg) && iLastPg!=PENDING_BYTE_PAGE(pBt) ){
    int rc;
................................................................................
static int autoVacuumCommit(BtShared *pBt, Pgno *pnTrunc){
  int rc = SQLITE_OK;
  Pager *pPager = pBt->pPager;
#ifndef NDEBUG
  int nRef = sqlite3PagerRefcount(pPager);
#endif

  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  invalidateAllOverflowCache(pBt);
  assert(pBt->autoVacuum);
  if( !pBt->incrVacuum ){
    Pgno nFin = 0;

    if( pBt->nTrunc==0 ){
      Pgno nFree;
................................................................................
  void *pArg,                                 /* First arg to xCompare() */
  BtCursor **ppCur                            /* Write new cursor here */
){
  int rc;
  BtCursor *pCur;
  BtShared *pBt = p->pBt;

  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  *ppCur = 0;
  if( wrFlag ){
    if( pBt->readOnly ){
      return SQLITE_READONLY;
    }
    if( checkReadLocks(p, iTable, 0) ){
      return SQLITE_LOCKED;
................................................................................
  Pgno ovfl,                   /* Overflow page */
  MemPage **ppPage,            /* OUT: MemPage handle */
  Pgno *pPgnoNext              /* OUT: Next overflow page number */
){
  Pgno next = 0;
  int rc;

  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  /* One of these must not be NULL. Otherwise, why call this function? */
  assert(ppPage || pPgnoNext);

  /* If pPgnoNext is NULL, then this function is being called to obtain
  ** a MemPage* reference only. No page-data is required in this case.
  */
  if( !pPgnoNext ){
................................................................................
  MemPage *pPage = pCur->pPage;        /* Btree page of current cursor entry */
  BtShared *pBt = pCur->pBtree->pBt;   /* Btree this cursor belongs to */

  assert( pPage );
  assert( pCur->eState==CURSOR_VALID );
  assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
  assert( offset>=0 );
  assert( sqlite3BtreeMutexHeld(pCur->pBtree->pBt->mutex) );

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

  if( skipKey ){
    offset += nKey;
................................................................................
  unsigned char *aPayload;
  MemPage *pPage;
  u32 nKey;
  int nLocal;

  assert( pCur!=0 && pCur->pPage!=0 );
  assert( pCur->eState==CURSOR_VALID );
  assert( sqlite3BtreeMutexHeld(pCur->pBtree->pBt->mutex) );
  pPage = pCur->pPage;
  assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
  getCellInfo(pCur);
  aPayload = pCur->info.pCell;
  aPayload += pCur->info.nHeader;
  if( pPage->intKey ){
    nKey = 0;
................................................................................
** Hence, a mutex on the BtShared should be held prior to calling
** this routine.
**
** These routines is used to get quick access to key and data
** in the common case where no overflow pages are used.
*/
const void *sqlite3BtreeKeyFetch(BtCursor *pCur, int *pAmt){
  assert( sqlite3BtreeMutexHeld(pCur->pBtree->pBt->mutex) );
  if( pCur->eState==CURSOR_VALID ){
    return (const void*)fetchPayload(pCur, pAmt, 0);
  }
  return 0;
}
const void *sqlite3BtreeDataFetch(BtCursor *pCur, int *pAmt){
  assert( sqlite3BtreeMutexHeld(pCur->pBtree->pBt->mutex) );
  if( pCur->eState==CURSOR_VALID ){
    return (const void*)fetchPayload(pCur, pAmt, 1);
  }
  return 0;
}


................................................................................
*/
static int moveToChild(BtCursor *pCur, u32 newPgno){
  int rc;
  MemPage *pNewPage;
  MemPage *pOldPage;
  BtShared *pBt = pCur->pBtree->pBt;

  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  assert( pCur->eState==CURSOR_VALID );
  rc = getAndInitPage(pBt, newPgno, &pNewPage, pCur->pPage);
  if( rc ) return rc;
  pNewPage->idxParent = pCur->idx;
  pOldPage = pCur->pPage;
  pOldPage->idxShift = 0;
  releasePage(pOldPage);
................................................................................
** is empty except for the right-pointer.  In such cases the
** virtual root page is the page that the right-pointer of page
** 1 is pointing to.
*/
int sqlite3BtreeIsRootPage(MemPage *pPage){
  MemPage *pParent;

  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );
  pParent = pPage->pParent;
  if( pParent==0 ) return 1;
  if( pParent->pgno>1 ) return 0;
  if( get2byte(&pParent->aData[pParent->hdrOffset+3])==0 ) return 1;
  return 0;
}

................................................................................
*/
static int moveToRoot(BtCursor *pCur){
  MemPage *pRoot;
  int rc = SQLITE_OK;
  Btree *p = pCur->pBtree;
  BtShared *pBt = p->pBt;

  assert( sqlite3BtreeMutexHeld(p->pSqlite->mutex) );
  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  if( pCur->eState==CURSOR_REQUIRESEEK ){
    clearCursorPosition(pCur);
  }
  pRoot = pCur->pPage;
  if( pRoot && pRoot->pgno==pCur->pgnoRoot ){
    assert( pRoot->isInit );
  }else{
................................................................................
** in ascending order.
*/
static int moveToLeftmost(BtCursor *pCur){
  Pgno pgno;
  int rc = SQLITE_OK;
  MemPage *pPage;

  assert( sqlite3BtreeMutexHeld(pCur->pBtree->pBt->mutex) );
  assert( sqlite3BtreeMutexHeld(pCur->pBtree->pSqlite->mutex) );
  assert( pCur->eState==CURSOR_VALID );
  while( rc==SQLITE_OK && !(pPage = pCur->pPage)->leaf ){
    assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
    pgno = get4byte(findCell(pPage, pCur->idx));
    rc = moveToChild(pCur, pgno);
  }
  return rc;
................................................................................
** key in ascending order.
*/
static int moveToRightmost(BtCursor *pCur){
  Pgno pgno;
  int rc = SQLITE_OK;
  MemPage *pPage;

  assert( sqlite3BtreeMutexHeld(pCur->pBtree->pBt->mutex) );
  assert( sqlite3BtreeMutexHeld(pCur->pBtree->pSqlite->mutex) );
  assert( pCur->eState==CURSOR_VALID );
  while( rc==SQLITE_OK && !(pPage = pCur->pPage)->leaf ){
    pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
    pCur->idx = pPage->nCell;
    rc = moveToChild(pCur, pgno);
  }
  if( rc==SQLITE_OK ){
................................................................................
/* Move the cursor to the first entry in the table.  Return SQLITE_OK
** on success.  Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
int sqlite3BtreeFirst(BtCursor *pCur, int *pRes){
  int rc;

  assert( sqlite3BtreeMutexHeld(pCur->pBtree->pBt->mutex) );
  assert( sqlite3BtreeMutexHeld(pCur->pBtree->pSqlite->mutex) );
  rc = moveToRoot(pCur);
  if( rc==SQLITE_OK ){
    if( pCur->eState==CURSOR_INVALID ){
      assert( pCur->pPage->nCell==0 );
      *pRes = 1;
      rc = SQLITE_OK;
    }else{
................................................................................
/* Move the cursor to the last entry in the table.  Return SQLITE_OK
** on success.  Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
int sqlite3BtreeLast(BtCursor *pCur, int *pRes){
  int rc;
 
  assert( sqlite3BtreeMutexHeld(pCur->pBtree->pBt->mutex) );
  assert( sqlite3BtreeMutexHeld(pCur->pBtree->pSqlite->mutex) );
  rc = moveToRoot(pCur);
  if( rc==SQLITE_OK ){
    if( CURSOR_INVALID==pCur->eState ){
      assert( pCur->pPage->nCell==0 );
      *pRes = 1;
    }else{
      assert( pCur->eState==CURSOR_VALID );
................................................................................
  const void *pKey,      /* The key content for indices.  Not used by tables */
  i64 nKey,              /* Size of pKey.  Or the key for tables */
  int biasRight,         /* If true, bias the search to the high end */
  int *pRes              /* Search result flag */
){
  int rc;

  assert( sqlite3BtreeMutexHeld(pCur->pBtree->pBt->mutex) );
  assert( sqlite3BtreeMutexHeld(pCur->pBtree->pSqlite->mutex) );
  rc = moveToRoot(pCur);
  if( rc ){
    return rc;
  }
  assert( pCur->pPage );
  assert( pCur->pPage->isInit );
  if( pCur->eState==CURSOR_INVALID ){
................................................................................
  MemPage *pPage1;
  int rc;
  int n;     /* Number of pages on the freelist */
  int k;     /* Number of leaves on the trunk of the freelist */
  MemPage *pTrunk = 0;
  MemPage *pPrevTrunk = 0;

  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  pPage1 = pBt->pPage1;
  n = get4byte(&pPage1->aData[36]);
  if( n>0 ){
    /* There are pages on the freelist.  Reuse one of those pages. */
    Pgno iTrunk;
    u8 searchList = 0; /* If the free-list must be searched for 'nearby' */
    
................................................................................
*/
static int freePage(MemPage *pPage){
  BtShared *pBt = pPage->pBt;
  MemPage *pPage1 = pBt->pPage1;
  int rc, n, k;

  /* Prepare the page for freeing */
  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );
  assert( pPage->pgno>1 );
  pPage->isInit = 0;
  releasePage(pPage->pParent);
  pPage->pParent = 0;

  /* Increment the free page count on pPage1 */
  rc = sqlite3PagerWrite(pPage1->pDbPage);
................................................................................
  BtShared *pBt = pPage->pBt;
  CellInfo info;
  Pgno ovflPgno;
  int rc;
  int nOvfl;
  int ovflPageSize;

  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );
  sqlite3BtreeParseCellPtr(pPage, pCell, &info);
  if( info.iOverflow==0 ){
    return SQLITE_OK;  /* No overflow pages. Return without doing anything */
  }
  ovflPgno = get4byte(&pCell[info.iOverflow]);
  ovflPageSize = pBt->usableSize - 4;
  nOvfl = (info.nPayload - info.nLocal + ovflPageSize - 1)/ovflPageSize;
................................................................................
  unsigned char *pPrior;
  unsigned char *pPayload;
  BtShared *pBt = pPage->pBt;
  Pgno pgnoOvfl = 0;
  int nHeader;
  CellInfo info;

  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );

  /* Fill in the header. */
  nHeader = 0;
  if( !pPage->leaf ){
    nHeader += 4;
  }
  if( pPage->hasData ){
................................................................................
** 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;
  DbPage *pDbPage;

  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  assert( pNewParent!=0 );
  if( pgno==0 ) return SQLITE_OK;
  assert( pBt->pPager!=0 );
  pDbPage = sqlite3PagerLookup(pBt->pPager, pgno);
  if( pDbPage ){
    pThis = (MemPage *)sqlite3PagerGetExtra(pDbPage);
    if( pThis->isInit ){
................................................................................
** another.
*/
static int reparentChildPages(MemPage *pPage){
  int i;
  BtShared *pBt = pPage->pBt;
  int rc = SQLITE_OK;

  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );
  if( pPage->leaf ) return SQLITE_OK;

  for(i=0; i<pPage->nCell; i++){
    u8 *pCell = findCell(pPage, i);
    if( !pPage->leaf ){
      rc = reparentPage(pBt, get4byte(pCell), pPage, i);
      if( rc!=SQLITE_OK ) return rc;
................................................................................
  int pc;         /* Offset to cell content of cell being deleted */
  u8 *data;       /* pPage->aData */
  u8 *ptr;        /* Used to move bytes around within data[] */

  assert( idx>=0 && idx<pPage->nCell );
  assert( sz==cellSize(pPage, idx) );
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );
  data = pPage->aData;
  ptr = &data[pPage->cellOffset + 2*idx];
  pc = get2byte(ptr);
  assert( pc>10 && pc+sz<=pPage->pBt->usableSize );
  freeSpace(pPage, pc, sz);
  for(i=idx+1; i<pPage->nCell; i++, ptr+=2){
    ptr[0] = ptr[2];
................................................................................
  int hdr;          /* Offset into data[] of the page header */
  int cellOffset;   /* Address of first cell pointer in data[] */
  u8 *data;         /* The content of the whole page */
  u8 *ptr;          /* Used for moving information around in data[] */

  assert( i>=0 && i<=pPage->nCell+pPage->nOverflow );
  assert( sz==cellSizePtr(pPage, pCell) );
  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );
  if( pPage->nOverflow || sz+2>pPage->nFree ){
    if( pTemp ){
      memcpy(pTemp+nSkip, pCell+nSkip, sz-nSkip);
      pCell = pTemp;
    }
    j = pPage->nOverflow++;
    assert( j<sizeof(pPage->aOvfl)/sizeof(pPage->aOvfl[0]) );
................................................................................
  int totalSize;    /* Total size of all cells */
  int hdr;          /* Index of page header */
  int cellptr;      /* Address of next cell pointer */
  int cellbody;     /* Address of next cell body */
  u8 *data;         /* Data for the page */

  assert( pPage->nOverflow==0 );
  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );
  totalSize = 0;
  for(i=0; i<nCell; i++){
    totalSize += aSize[i];
  }
  assert( totalSize+2*nCell<=pPage->nFree );
  assert( pPage->nCell==0 );
  cellptr = pPage->cellOffset;
................................................................................
  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 */

  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );

  /* Allocate a new page. Insert the overflow cell from pPage
  ** into it. Then remove the overflow cell from pPage.
  */
  rc = allocateBtreePage(pBt, &pNew, &pgnoNew, 0, 0);
  if( rc!=SQLITE_OK ){
    return rc;
................................................................................
  int *szCell;                 /* Local size of all cells in apCell[] */
  u8 *aCopy[NB];               /* Space for holding data of apCopy[] */
  u8 *aSpace;                  /* Space to hold copies of dividers cells */
#ifndef SQLITE_OMIT_AUTOVACUUM
  u8 *aFrom = 0;
#endif

  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );

  /* 
  ** Find the parent page.
  */
  assert( pPage->isInit );
  assert( sqlite3PagerIswriteable(pPage->pDbPage) || pPage->nOverflow==1 );
  pBt = pPage->pBt;
................................................................................
  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 );
  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );
  pBt = pPage->pBt;
  mxCellPerPage = MX_CELL(pBt);
  apCell = sqlite3_malloc( mxCellPerPage*(sizeof(u8*)+sizeof(int)) );
  if( apCell==0 ) return SQLITE_NOMEM;
  szCell = (int*)&apCell[mxCellPerPage];
  if( pPage->leaf ){
    /* The table is completely empty */
................................................................................
  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 );
  assert( pPage->nOverflow>0 );
  pBt = pPage->pBt;
  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  rc = allocateBtreePage(pBt, &pChild, &pgnoChild, pPage->pgno, 0);
  if( rc ) return rc;
  assert( sqlite3PagerIswriteable(pChild->pDbPage) );
  usableSize = pBt->usableSize;
  data = pPage->aData;
  hdr = pPage->hdrOffset;
  brk = get2byte(&data[hdr+5]);
................................................................................

/*
** Decide if the page pPage needs to be balanced.  If balancing is
** required, call the appropriate balancing routine.
*/
static int balance(MemPage *pPage, int insert){
  int rc = SQLITE_OK;
  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );
  if( pPage->pParent==0 ){
    rc = sqlite3PagerWrite(pPage->pDbPage);
    if( rc==SQLITE_OK && pPage->nOverflow>0 ){
      rc = balance_deeper(pPage);
    }
    if( rc==SQLITE_OK && pPage->nCell==0 ){
      rc = balance_shallower(pPage);
................................................................................
** a page entirely and we do not want to leave any cursors 
** pointing to non-existant pages or cells.
*/
static int checkReadLocks(Btree *pBtree, Pgno pgnoRoot, BtCursor *pExclude){
  BtCursor *p;
  BtShared *pBt = pBtree->pBt;
  sqlite3 *db = pBtree->pSqlite;
  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  assert( sqlite3BtreeMutexHeld(db->mutex) );
  for(p=pBt->pCursor; p; p=p->pNext){
    if( p==pExclude ) continue;
    if( p->eState!=CURSOR_VALID ) continue;
    if( p->pgnoRoot!=pgnoRoot ) continue;
    if( p->wrFlag==0 ){
      sqlite3 *dbOther = p->pBtree->pSqlite;
      if( dbOther==0 ||
................................................................................
  int freePageFlag      /* Deallocate page if true */
){
  MemPage *pPage = 0;
  int rc;
  unsigned char *pCell;
  int i;

  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  if( pgno>sqlite3PagerPagecount(pBt->pPager) ){
    return SQLITE_CORRUPT_BKPT;
  }

  rc = getAndInitPage(pBt, pgno, &pPage, pParent);
  if( rc ) goto cleardatabasepage_out;
  for(i=0; i<pPage->nCell; i++){
................................................................................
** meta[3] is updated by this procedure.
*/
static int btreeDropTable(Btree *p, int iTable, int *piMoved){
  int rc;
  MemPage *pPage = 0;
  BtShared *pBt = p->pBt;

  assert( sqlite3BtreeMutexHeld(pBt->mutex) );
  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
................................................................................
** is currently pointing to.
*/
int sqlite3BtreeFlags(BtCursor *pCur){
  /* TODO: What about CURSOR_REQUIRESEEK state? Probably need to call
  ** restoreOrClearCursorPosition() here.
  */
  MemPage *pPage = pCur->pPage;
  assert( sqlite3BtreeMutexHeld(pPage->pBt->mutex) );
  return pPage ? pPage->aData[pPage->hdrOffset] : 0;
}


/*
** Return the pager associated with a BTree.  This routine is used for
** testing and debugging only.
*/
Pager *sqlite3BtreePager(Btree *p){
  assert( sqlite3BtreeMutexHeld(p->pSqlite->mutex) );
  assert( sqlite3BtreeMutexHeld(p->pBt->mutex) );
  return p->pBt->pPager;
}

#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** Append a message to the error message string.
*/
................................................................................
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */

/*
** Return the full pathname of the underlying database file.
*/
const char *sqlite3BtreeGetFilename(Btree *p){
  assert( p->pBt->pPager!=0 );
  assert( sqlite3BtreeMutexHeld(p->pBt->mutex) );
  return sqlite3PagerFilename(p->pBt->pPager);
}

/*
** Return the pathname of the directory that contains the database file.
*/
const char *sqlite3BtreeGetDirname(Btree *p){
  assert( p->pBt->pPager!=0 );
  assert( sqlite3BtreeMutexHeld(p->pBt->mutex) );
  return sqlite3PagerDirname(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 );
  assert( sqlite3BtreeMutexHeld(p->pBt->mutex) );
  return sqlite3PagerJournalname(p->pBt->pPager);
}

#ifndef SQLITE_OMIT_VACUUM
/*
** Copy the complete content of pBtFrom into pBtTo.  A transaction
** must be active for both files.
................................................................................

#endif /* SQLITE_OMIT_VACUUM */

/*
** Return non-zero if a transaction is active.
*/
int sqlite3BtreeIsInTrans(Btree *p){
  assert( sqlite3BtreeMutexHeld(p->pBt->mutex) );
  assert( sqlite3BtreeMutexHeld(p->pSqlite->mutex) );
  return (p && (p->inTrans==TRANS_WRITE));
}

/*
** Return non-zero if a statement transaction is active.
*/
int sqlite3BtreeIsInStmt(Btree *p){
  assert( sqlite3BtreeMutexHeld(p->pBt->mutex) );
  assert( sqlite3BtreeMutexHeld(p->pSqlite->mutex) );
  return (p->pBt && p->pBt->inStmt);
}

/*
** Return non-zero if a read (or write) transaction is active.
*/
int sqlite3BtreeIsInReadTrans(Btree *p){
  assert( sqlite3BtreeMutexHeld(p->pBt->mutex) );
  assert( sqlite3BtreeMutexHeld(p->pSqlite->mutex) );
  return (p && (p->inTrans!=TRANS_NONE));
}

/*
** This function returns a pointer to a blob of memory associated with
** a single shared-btree. The memory is used by client code for it's own
** purposes (for example, to store a high-level schema associated with 
................................................................................
** Just before the shared-btree is closed, the function passed as the 
** xFree argument when the memory allocation was made is invoked on the 
** blob of allocated memory. This function should not call sqlite3_free()
** on the memory, the btree layer does that.
*/
void *sqlite3BtreeSchema(Btree *p, int nBytes, void(*xFree)(void *)){
  BtShared *pBt = p->pBt;
  assert( sqlite3BtreeMutexHeld(p->pSqlite->mutex) );
  sqlite3BtreeEnter(p);
  if( !pBt->pSchema ){
    pBt->pSchema = sqlite3MallocZero(nBytes);
    pBt->xFreeSchema = xFree;
  }
  sqlite3BtreeLeave(p);
  return pBt->pSchema;
}

/*
** Return true if another user of the same shared btree as the argument
** handle holds an exclusive lock on the sqlite_master table.
*/
int sqlite3BtreeSchemaLocked(Btree *p){
  int rc;
  assert( sqlite3BtreeMutexHeld(p->pSqlite->mutex) );
  sqlite3BtreeEnter(p);
  rc = (queryTableLock(p, MASTER_ROOT, READ_LOCK)!=SQLITE_OK);
  sqlite3BtreeLeave(p);
  return rc;
}


#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Obtain a lock on the table whose root page is iTab.  The
** lock is a write lock if isWritelock is true or a read lock
................................................................................
** Argument pCsr must be a cursor opened for writing on an 
** INTKEY table currently pointing at a valid table entry. 
** This function modifies the data stored as part of that entry.
** Only the data content may only be modified, it is not possible
** to change the length of the data stored.
*/
int sqlite3BtreePutData(BtCursor *pCsr, u32 offset, u32 amt, void *z){
  assert( sqlite3BtreeMutexHeld(pCsr->pBtree->pBt->mutex) );
  assert( sqlite3BtreeMutexHeld(pCsr->pBtree->pSqlite->mutex) );
  assert(pCsr->isIncrblobHandle);
  if( pCsr->eState==CURSOR_REQUIRESEEK ){
    return SQLITE_ABORT;
  }

  /* Check some preconditions: 
  **   (a) the cursor is open for writing,
................................................................................
**
** This function sets a flag only. The actual page location cache
** (stored in BtCursor.aOverflow[]) is allocated and used by function
** accessPayload() (the worker function for sqlite3BtreeData() and
** sqlite3BtreePutData()).
*/
void sqlite3BtreeCacheOverflow(BtCursor *pCur){
  assert( sqlite3BtreeMutexHeld(pCur->pBtree->pBt->mutex) );
  assert( sqlite3BtreeMutexHeld(pCur->pBtree->pSqlite->mutex) );
  assert(!pCur->isIncrblobHandle);
  assert(!pCur->aOverflow);
  pCur->isIncrblobHandle = 1;
}
#endif

**    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 1.85 2007/08/21 19:33:56 drh Exp $
*/
#ifndef _BTREE_H_
#define _BTREE_H_

/* TODO: This definition is just included so other modules compile. It
** needs to be revisited.
*/
................................................................................
** If we are not using shared cache, then there is no need to
** use mutexes to access the BtShared structures.  So make the
** Enter and Leave procedures no-ops.
*/
#if SQLITE_THREADSAFE && !defined(SQLITE_OMIT_SHARED_CACHE)
  void sqlite3BtreeEnter(Btree*);
  void sqlite3BtreeLeave(Btree*);

#else
# define sqlite3BtreeEnter(X)
# define sqlite3BtreeLeave(X)

#endif

const char *sqlite3BtreeGetFilename(Btree *);
const char *sqlite3BtreeGetDirname(Btree *);
const char *sqlite3BtreeGetJournalname(Btree *);
int sqlite3BtreeCopyFile(Btree *, Btree *);

**    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 1.86 2007/08/22 02:56:43 drh Exp $
*/
#ifndef _BTREE_H_
#define _BTREE_H_

/* TODO: This definition is just included so other modules compile. It
** needs to be revisited.
*/
................................................................................
** If we are not using shared cache, then there is no need to
** use mutexes to access the BtShared structures.  So make the
** Enter and Leave procedures no-ops.
*/
#if SQLITE_THREADSAFE && !defined(SQLITE_OMIT_SHARED_CACHE)
  void sqlite3BtreeEnter(Btree*);
  void sqlite3BtreeLeave(Btree*);
# define sqlite3BtreeMutexHeld(X) sqlite3_mutex_held(X)
#else
# define sqlite3BtreeEnter(X)
# define sqlite3BtreeLeave(X)
# define sqlite3BtreeMutexHeld(X) 1
#endif

const char *sqlite3BtreeGetFilename(Btree *);
const char *sqlite3BtreeGetDirname(Btree *);
const char *sqlite3BtreeGetJournalname(Btree *);
int sqlite3BtreeCopyFile(Btree *, Btree *);

**
*************************************************************************
** 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 1.394 2007/08/22 00:39:20 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** The version of the library
*/
................................................................................
  */
  sqlite3VtabRollback(db);

  /* If there are any outstanding VMs, return SQLITE_BUSY. */
  if( db->pVdbe ){
    sqlite3Error(db, SQLITE_BUSY, 
        "Unable to close due to unfinalised statements");

    return SQLITE_BUSY;
  }
  assert( !sqlite3SafetyCheck(db) );

  /* FIX ME: db->magic may be set to SQLITE_MAGIC_CLOSED if the database
  ** cannot be opened for some reason. So this routine needs to run in
  ** that case. But maybe there should be an extra magic value for the
................................................................................
  ** "failed to open" state.
  **
  ** TODO: Coverage tests do not test the case where this condition is
  ** true. It's hard to see how to cause it without messing with threads.
  */
  if( db->magic!=SQLITE_MAGIC_CLOSED && sqlite3SafetyOn(db) ){
    /* printf("DID NOT CLOSE\n"); fflush(stdout); */

    return SQLITE_ERROR;
  }

  for(j=0; j<db->nDb; j++){
    struct Db *pDb = &db->aDb[j];
    if( pDb->pBt ){
      sqlite3BtreeClose(pDb->pBt);
................................................................................
** error.
*/
const char *sqlite3_errmsg(sqlite3 *db){
  const char *z;
  if( !db ){
    return sqlite3ErrStr(SQLITE_NOMEM);
  }
  sqlite3_mutex_enter(db->mutex);
  if( sqlite3SafetyCheck(db) || db->errCode==SQLITE_MISUSE ){
    return sqlite3ErrStr(SQLITE_MISUSE);
  }

  assert( !db->mallocFailed );
  z = (char*)sqlite3_value_text(db->pErr);
  if( z==0 ){
    z = sqlite3ErrStr(db->errCode);
  }
  sqlite3_mutex_leave(db->mutex);
  return z;
................................................................................
  db = sqlite3MallocZero( sizeof(sqlite3) );
  if( db==0 ) goto opendb_out;
  db->mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_RECURSIVE);
  if( db->mutex==0 ){
    db->mallocFailed = 1;
    goto opendb_out;
  }

  db->pVfs = sqlite3_vfs_find(zVfs);
  db->errMask = 0xff;
  db->priorNewRowid = 0;
  db->magic = SQLITE_MAGIC_BUSY;
  db->nDb = 2;
  db->aDb = db->aDbStatic;
  db->autoCommit = 1;
................................................................................
#ifdef SQLITE_DEFAULT_LOCKING_MODE
  db->dfltLockMode = SQLITE_DEFAULT_LOCKING_MODE;
  sqlite3PagerLockingMode(sqlite3BtreePager(db->aDb[0].pBt),
                          SQLITE_DEFAULT_LOCKING_MODE);
#endif

opendb_out:

  if( SQLITE_NOMEM==(rc = sqlite3_errcode(db)) ){
    sqlite3_close(db);
    db = 0;
  }
  *ppDb = db;
  return sqlite3ApiExit(0, rc);
}

**
*************************************************************************
** 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 1.395 2007/08/22 02:56:44 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** The version of the library
*/
................................................................................
  */
  sqlite3VtabRollback(db);

  /* If there are any outstanding VMs, return SQLITE_BUSY. */
  if( db->pVdbe ){
    sqlite3Error(db, SQLITE_BUSY, 
        "Unable to close due to unfinalised statements");
    sqlite3_mutex_leave(db->mutex);
    return SQLITE_BUSY;
  }
  assert( !sqlite3SafetyCheck(db) );

  /* FIX ME: db->magic may be set to SQLITE_MAGIC_CLOSED if the database
  ** cannot be opened for some reason. So this routine needs to run in
  ** that case. But maybe there should be an extra magic value for the
................................................................................
  ** "failed to open" state.
  **
  ** TODO: Coverage tests do not test the case where this condition is
  ** true. It's hard to see how to cause it without messing with threads.
  */
  if( db->magic!=SQLITE_MAGIC_CLOSED && sqlite3SafetyOn(db) ){
    /* printf("DID NOT CLOSE\n"); fflush(stdout); */
    sqlite3_mutex_leave(db->mutex);
    return SQLITE_ERROR;
  }

  for(j=0; j<db->nDb; j++){
    struct Db *pDb = &db->aDb[j];
    if( pDb->pBt ){
      sqlite3BtreeClose(pDb->pBt);
................................................................................
** error.
*/
const char *sqlite3_errmsg(sqlite3 *db){
  const char *z;
  if( !db ){
    return sqlite3ErrStr(SQLITE_NOMEM);
  }

  if( sqlite3SafetyCheck(db) || db->errCode==SQLITE_MISUSE ){
    return sqlite3ErrStr(SQLITE_MISUSE);
  }
  sqlite3_mutex_enter(db->mutex);
  assert( !db->mallocFailed );
  z = (char*)sqlite3_value_text(db->pErr);
  if( z==0 ){
    z = sqlite3ErrStr(db->errCode);
  }
  sqlite3_mutex_leave(db->mutex);
  return z;
................................................................................
  db = sqlite3MallocZero( sizeof(sqlite3) );
  if( db==0 ) goto opendb_out;
  db->mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_RECURSIVE);
  if( db->mutex==0 ){
    db->mallocFailed = 1;
    goto opendb_out;
  }
  sqlite3_mutex_enter(db->mutex);
  db->pVfs = sqlite3_vfs_find(zVfs);
  db->errMask = 0xff;
  db->priorNewRowid = 0;
  db->magic = SQLITE_MAGIC_BUSY;
  db->nDb = 2;
  db->aDb = db->aDbStatic;
  db->autoCommit = 1;
................................................................................
#ifdef SQLITE_DEFAULT_LOCKING_MODE
  db->dfltLockMode = SQLITE_DEFAULT_LOCKING_MODE;
  sqlite3PagerLockingMode(sqlite3BtreePager(db->aDb[0].pBt),
                          SQLITE_DEFAULT_LOCKING_MODE);
#endif

opendb_out:
  sqlite3_mutex_leave(db->mutex);
  if( SQLITE_NOMEM==(rc = sqlite3_errcode(db)) ){
    sqlite3_close(db);
    db = 0;
  }
  *ppDb = db;
  return sqlite3ApiExit(0, rc);
}

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains the C functions that implement mutexes for
** use by the SQLite core.
**
** $Id: mutex.c,v 1.7 2007/08/22 00:39:20 drh Exp $
*/
/*
** If SQLITE_MUTEX_APPDEF is defined, then this whole module is
** omitted and equivalent functionality must be provided by the
** application that links against the SQLite library.
*/
#ifndef SQLITE_MUTEX_APPDEF
................................................................................
*/
#include "sqliteInt.h"

/*
** Figure out what version of the code to use
*/
#define SQLITE_MUTEX_NOOP 1   /* The default */
#if 0
#if defined(SQLITE_DEBUG) && !SQLITE_THREADSAFE
# undef SQLITE_MUTEX_NOOP
# define SQLITE_MUTEX_NOOP_DEBUG
#endif

#if defined(SQLITE_MUTEX_NOOP) && SQLITE_THREADSAFE && OS_UNIX
# undef SQLITE_MUTEX_NOOP
# define SQLITE_MUTEX_PTHREAD
#endif
#if defined(SQLITE_MUTEX_NOOP) && SQLITE_THREADSAFE && OS_WIN
# undef SQLITE_MUTEX_NOOP
# define SQLITE_MUTEX_WIN
................................................................................
      if( pNew ){
        pNew->id = id;
        pNew->cnt = 0;
      }
      break;
    }
    default: {
      assert( id-SQLITE_MUTEX_STATIC_MASTER >= 0 );
      assert( id-SQLITE_MUTEX_STATIC_MASTER < count(aStatic) );
      pNew = &aStatic[id-SQLITE_MUTEX_STATIC_MASTER];
      pNew->id = id;
      break;
    }
  }
  return pNew;
}

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains the C functions that implement mutexes for
** use by the SQLite core.
**
** $Id: mutex.c,v 1.8 2007/08/22 02:56:44 drh Exp $
*/
/*
** If SQLITE_MUTEX_APPDEF is defined, then this whole module is
** omitted and equivalent functionality must be provided by the
** application that links against the SQLite library.
*/
#ifndef SQLITE_MUTEX_APPDEF
................................................................................
*/
#include "sqliteInt.h"

/*
** Figure out what version of the code to use
*/
#define SQLITE_MUTEX_NOOP 1   /* The default */

#if defined(SQLITE_DEBUG) && !SQLITE_THREADSAFE
# undef SQLITE_MUTEX_NOOP
# define SQLITE_MUTEX_NOOP_DEBUG
#endif
#if 0
#if defined(SQLITE_MUTEX_NOOP) && SQLITE_THREADSAFE && OS_UNIX
# undef SQLITE_MUTEX_NOOP
# define SQLITE_MUTEX_PTHREAD
#endif
#if defined(SQLITE_MUTEX_NOOP) && SQLITE_THREADSAFE && OS_WIN
# undef SQLITE_MUTEX_NOOP
# define SQLITE_MUTEX_WIN
................................................................................
      if( pNew ){
        pNew->id = id;
        pNew->cnt = 0;
      }
      break;
    }
    default: {
      assert( id-2 >= 0 );
      assert( id-2 < sizeof(aStatic)/sizeof(aStatic[0]) );
      pNew = &aStatic[id-2];
      pNew->id = id;
      break;
    }
  }
  return pNew;
}

**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains the implementation of the sqlite3_prepare()
** interface, and routines that contribute to loading the database schema
** from disk.
**
** $Id: prepare.c,v 1.57 2007/08/22 00:39:20 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** Fill the InitData structure with an error message that indicates
** that the database is corrupt.
................................................................................
  const char *zSql,         /* UTF-8 encoded SQL statement. */
  int nBytes,               /* Length of zSql in bytes. */
  int saveSqlFlag,          /* True to copy SQL text into the sqlite3_stmt */
  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
  const char **pzTail       /* OUT: End of parsed string */
){
  int rc;



  sqlite3_mutex_enter(db->mutex);
  rc = sqlite3Prepare(db, zSql, nBytes, saveSqlFlag, ppStmt, pzTail);
  sqlite3_mutex_leave(db->mutex);
  return rc;
}

/*

**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains the implementation of the sqlite3_prepare()
** interface, and routines that contribute to loading the database schema
** from disk.
**
** $Id: prepare.c,v 1.58 2007/08/22 02:56:44 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** Fill the InitData structure with an error message that indicates
** that the database is corrupt.
................................................................................
  const char *zSql,         /* UTF-8 encoded SQL statement. */
  int nBytes,               /* Length of zSql in bytes. */
  int saveSqlFlag,          /* True to copy SQL text into the sqlite3_stmt */
  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
  const char **pzTail       /* OUT: End of parsed string */
){
  int rc;
  if( sqlite3SafetyCheck(db) ){
    return SQLITE_MISUSE;
  }
  sqlite3_mutex_enter(db->mutex);
  rc = sqlite3Prepare(db, zSql, nBytes, saveSqlFlag, ppStmt, pzTail);
  sqlite3_mutex_leave(db->mutex);
  return rc;
}

/*

**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing all sorts of SQLite interfaces.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test1.c,v 1.268 2007/08/22 00:39:21 drh Exp $
*/
#include "sqliteInt.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>

/*
................................................................................
  Tcl_AppendElement(interp, zBuf);
  Tcl_AppendElement(interp, rc==SQLITE_OK ? Tcl_DStringValue(&str) : zErr);
  Tcl_DStringFree(&str);
  if( zErr ) sqlite3_free(zErr);
  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
  return TCL_OK;
}








































/*
** Usage:  sqlite3_exec  DB  SQL
**
** Invoke the sqlite3_exec interface using the open database DB
*/
static int test_exec(
................................................................................
  }

#ifndef SQLITE_OMIT_UTF16
  /* Use the sqlite3_create_function16() API here. Mainly for fun, but also 
  ** because it is not tested anywhere else. */
  if( rc==SQLITE_OK ){
    sqlite3_value *pVal;
    pVal = sqlite3ValueNew(db);
    sqlite3ValueSetStr(pVal, -1, "x_sqlite_exec", SQLITE_UTF8, SQLITE_STATIC);
    rc = sqlite3_create_function16(db, 
              sqlite3ValueText(pVal, SQLITE_UTF16NATIVE),
              1, SQLITE_UTF16, db, sqlite3ExecFunc, 0, 0);
    sqlite3ValueFree(pVal);
  }
#endif
................................................................................
  }
  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
  pResult = Tcl_NewObj();
  for(i=0; i<db->nDb; i++){
    if( db->aDb[i].pBt==0 ){
      v = -1;
    }else{

      a = sqlite3PagerStats(sqlite3BtreePager(db->aDb[i].pBt));
      v = a[0];

    }
    Tcl_ListObjAppendElement(0, pResult, Tcl_NewIntObj(v));
  }
  Tcl_SetObjResult(interp, pResult);
  return TCL_OK;
}

................................................................................
  extern int sqlite3_max_blobsize;
  extern int sqlite3BtreeSharedCacheReport(void*,
                                          Tcl_Interp*,int,Tcl_Obj*CONST*);
  static struct {
     char *zName;
     Tcl_CmdProc *xProc;
  } aCmd[] = {


     { "sqlite3_mprintf_int",           (Tcl_CmdProc*)sqlite3_mprintf_int    },
     { "sqlite3_mprintf_int64",         (Tcl_CmdProc*)sqlite3_mprintf_int64  },
     { "sqlite3_mprintf_str",           (Tcl_CmdProc*)sqlite3_mprintf_str    },
     { "sqlite3_snprintf_str",          (Tcl_CmdProc*)sqlite3_snprintf_str   },
     { "sqlite3_mprintf_stronly",       (Tcl_CmdProc*)sqlite3_mprintf_stronly},
     { "sqlite3_mprintf_double",        (Tcl_CmdProc*)sqlite3_mprintf_double },
     { "sqlite3_mprintf_scaled",        (Tcl_CmdProc*)sqlite3_mprintf_scaled },

**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing all sorts of SQLite interfaces.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test1.c,v 1.269 2007/08/22 02:56:44 drh Exp $
*/
#include "sqliteInt.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>

/*
................................................................................
  Tcl_AppendElement(interp, zBuf);
  Tcl_AppendElement(interp, rc==SQLITE_OK ? Tcl_DStringValue(&str) : zErr);
  Tcl_DStringFree(&str);
  if( zErr ) sqlite3_free(zErr);
  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
  return TCL_OK;
}

/*
** Usage:  db_enter DB
**         db_leave DB
**
** Enter or leave the mutex on a database connection.
*/
static int db_enter(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  char **argv            /* Text of each argument */
){
  sqlite3 *db;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
       " DB", 0);
    return TCL_ERROR;
  }
  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
  sqlite3_mutex_enter(db->mutex);
  return TCL_OK;
}
static int db_leave(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  char **argv            /* Text of each argument */
){
  sqlite3 *db;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
       " DB", 0);
    return TCL_ERROR;
  }
  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
  sqlite3_mutex_leave(db->mutex);
  return TCL_OK;
}

/*
** Usage:  sqlite3_exec  DB  SQL
**
** Invoke the sqlite3_exec interface using the open database DB
*/
static int test_exec(
................................................................................
  }

#ifndef SQLITE_OMIT_UTF16
  /* Use the sqlite3_create_function16() API here. Mainly for fun, but also 
  ** because it is not tested anywhere else. */
  if( rc==SQLITE_OK ){
    sqlite3_value *pVal;
    pVal = sqlite3ValueNew(0);
    sqlite3ValueSetStr(pVal, -1, "x_sqlite_exec", SQLITE_UTF8, SQLITE_STATIC);
    rc = sqlite3_create_function16(db, 
              sqlite3ValueText(pVal, SQLITE_UTF16NATIVE),
              1, SQLITE_UTF16, db, sqlite3ExecFunc, 0, 0);
    sqlite3ValueFree(pVal);
  }
#endif
................................................................................
  }
  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
  pResult = Tcl_NewObj();
  for(i=0; i<db->nDb; i++){
    if( db->aDb[i].pBt==0 ){
      v = -1;
    }else{
      sqlite3_mutex_enter(db->mutex);
      a = sqlite3PagerStats(sqlite3BtreePager(db->aDb[i].pBt));
      v = a[0];
      sqlite3_mutex_leave(db->mutex);
    }
    Tcl_ListObjAppendElement(0, pResult, Tcl_NewIntObj(v));
  }
  Tcl_SetObjResult(interp, pResult);
  return TCL_OK;
}

................................................................................
  extern int sqlite3_max_blobsize;
  extern int sqlite3BtreeSharedCacheReport(void*,
                                          Tcl_Interp*,int,Tcl_Obj*CONST*);
  static struct {
     char *zName;
     Tcl_CmdProc *xProc;
  } aCmd[] = {
     { "db_enter",                      (Tcl_CmdProc*)db_enter               },
     { "db_leave",                      (Tcl_CmdProc*)db_leave               },
     { "sqlite3_mprintf_int",           (Tcl_CmdProc*)sqlite3_mprintf_int    },
     { "sqlite3_mprintf_int64",         (Tcl_CmdProc*)sqlite3_mprintf_int64  },
     { "sqlite3_mprintf_str",           (Tcl_CmdProc*)sqlite3_mprintf_str    },
     { "sqlite3_snprintf_str",          (Tcl_CmdProc*)sqlite3_snprintf_str   },
     { "sqlite3_mprintf_stronly",       (Tcl_CmdProc*)sqlite3_mprintf_stronly},
     { "sqlite3_mprintf_double",        (Tcl_CmdProc*)sqlite3_mprintf_double },
     { "sqlite3_mprintf_scaled",        (Tcl_CmdProc*)sqlite3_mprintf_scaled },

**    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 1.80 2007/08/21 10:44:16 drh Exp $
*/
#include "sqliteInt.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>

/*
................................................................................
  }
  if( Tcl_GetInt(interp, argv[2], &nCache) ) return TCL_ERROR;
  if( Tcl_GetInt(interp, argv[3], &flags) ) return TCL_ERROR;
  nRefSqlite3++;
  if( nRefSqlite3==1 ){
    sDb.pVfs = sqlite3_vfs_find(0);
    sDb.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_RECURSIVE);

  }
  rc = sqlite3BtreeOpen(argv[1], &sDb, &pBt, flags);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  sqlite3BtreeSetCacheSize(pBt, nCache);
................................................................................
  rc = sqlite3BtreeClose(pBt);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  nRefSqlite3--;
  if( nRefSqlite3==0 ){

    sqlite3_mutex_free(sDb.mutex);
    sDb.mutex = 0;
    sqlite3_vfs_release(sDb.pVfs);
    sDb.pVfs = 0;
  }
  return TCL_OK;
}


/*
** Usage:   btree_begin_transaction ID
**
** Start a new transaction
*/
static int btree_begin_transaction(
................................................................................

  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  pBt = sqlite3TextToPtr(argv[1]);

  a = sqlite3PagerStats(sqlite3BtreePager(pBt));
  for(i=0; i<11; i++){
    static char *zName[] = {
      "ref", "page", "max", "size", "state", "err",
      "hit", "miss", "ovfl", "read", "write"
    };
    char zBuf[100];
    Tcl_AppendElement(interp, zName[i]);
    sqlite3_snprintf(sizeof(zBuf), zBuf,"%d",a[i]);
    Tcl_AppendElement(interp, zBuf);
  }

  return TCL_OK;
}

/*
** Usage:   btree_pager_ref_dump ID
**
** Print out all outstanding pages.

**    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 1.81 2007/08/22 02:56:44 drh Exp $
*/
#include "sqliteInt.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>

/*
................................................................................
  }
  if( Tcl_GetInt(interp, argv[2], &nCache) ) return TCL_ERROR;
  if( Tcl_GetInt(interp, argv[3], &flags) ) return TCL_ERROR;
  nRefSqlite3++;
  if( nRefSqlite3==1 ){
    sDb.pVfs = sqlite3_vfs_find(0);
    sDb.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_RECURSIVE);
    sqlite3_mutex_enter(sDb.mutex);
  }
  rc = sqlite3BtreeOpen(argv[1], &sDb, &pBt, flags);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  sqlite3BtreeSetCacheSize(pBt, nCache);
................................................................................
  rc = sqlite3BtreeClose(pBt);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  nRefSqlite3--;
  if( nRefSqlite3==0 ){
    sqlite3_mutex_leave(sDb.mutex);
    sqlite3_mutex_free(sDb.mutex);
    sDb.mutex = 0;
    sqlite3_vfs_release(sDb.pVfs);
    sDb.pVfs = 0;
  }
  return TCL_OK;
}


/*
** Usage:   btree_begin_transaction ID
**
** Start a new transaction
*/
static int btree_begin_transaction(
................................................................................

  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  pBt = sqlite3TextToPtr(argv[1]);
  sqlite3BtreeEnter(pBt);
  a = sqlite3PagerStats(sqlite3BtreePager(pBt));
  for(i=0; i<11; i++){
    static char *zName[] = {
      "ref", "page", "max", "size", "state", "err",
      "hit", "miss", "ovfl", "read", "write"
    };
    char zBuf[100];
    Tcl_AppendElement(interp, zName[i]);
    sqlite3_snprintf(sizeof(zBuf), zBuf,"%d",a[i]);
    Tcl_AppendElement(interp, zBuf);
  }
  sqlite3BtreeLeave(pBt);
  return TCL_OK;
}

/*
** Usage:   btree_pager_ref_dump ID
**
** Print out all outstanding pages.

  pVm = (Vdbe *)pStmt;
  if( pVm && pVm->resOnStack && i<pVm->nResColumn && i>=0 ){
    sqlite3_mutex_enter(pVm->db->mutex);
    vals = sqlite3_data_count(pStmt);
    pOut = &pVm->pTos[(1-vals)+i];
  }else{
    static const Mem nullMem = {{0}, 0.0, 0, "", 0, MEM_Null, SQLITE_NULL };


    sqlite3Error(pVm->db, SQLITE_RANGE, 0);

    pOut = (Mem*)&nullMem;
  }
  return pOut;
}

/*
** This function is called after invoking an sqlite3_value_XXX function on a 
................................................................................
  int rc;

  if( p==0 ){
    return SQLITE_MISUSE;
  }
  sqlite3_mutex_enter(p->db->mutex);
  rc = vdbeUnbind(p, i);
  if( rc || zData==0 ){
    return rc;
  }
  pVar = &p->aVar[i-1];
  rc = sqlite3VdbeMemSetStr(pVar, zData, nData, encoding, xDel);
  if( rc==SQLITE_OK && encoding!=0 ){
    rc = sqlite3VdbeChangeEncoding(pVar, ENC(p->db));
  }
  sqlite3Error(p->db, rc, 0);
  rc = sqlite3ApiExit(p->db, rc);

  sqlite3_mutex_leave(p->db->mutex);
  return rc;
}


/*
** Bind a blob value to an SQL statement variable.
................................................................................
** an SQLITE_ERROR is returned.
*/
int sqlite3_transfer_bindings(sqlite3_stmt *pFromStmt, sqlite3_stmt *pToStmt){
  Vdbe *pFrom = (Vdbe*)pFromStmt;
  Vdbe *pTo = (Vdbe*)pToStmt;
  int i, rc = SQLITE_OK;
  if( (pFrom->magic!=VDBE_MAGIC_RUN && pFrom->magic!=VDBE_MAGIC_HALT)
    || (pTo->magic!=VDBE_MAGIC_RUN && pTo->magic!=VDBE_MAGIC_HALT) ){

    return SQLITE_MISUSE;
  }
  if( pFrom->nVar!=pTo->nVar ){
    return SQLITE_ERROR;
  }

  for(i=0; rc==SQLITE_OK && i<pFrom->nVar; i++){
    sqlite3MallocDisallow();
    rc = sqlite3VdbeMemMove(&pTo->aVar[i], &pFrom->aVar[i]);
    sqlite3MallocAllow();
  }

  assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
  return rc;
}

/*
** Return the sqlite3* database handle to which the prepared statement given
** in the argument belongs.  This is the same database handle that was
** the first argument to the sqlite3_prepare() that was used to create
** the statement in the first place.
*/
sqlite3 *sqlite3_db_handle(sqlite3_stmt *pStmt){
  return pStmt ? ((Vdbe*)pStmt)->db : 0;
}

  pVm = (Vdbe *)pStmt;
  if( pVm && pVm->resOnStack && i<pVm->nResColumn && i>=0 ){
    sqlite3_mutex_enter(pVm->db->mutex);
    vals = sqlite3_data_count(pStmt);
    pOut = &pVm->pTos[(1-vals)+i];
  }else{
    static const Mem nullMem = {{0}, 0.0, 0, "", 0, MEM_Null, SQLITE_NULL };
    if( pVm->db ){
      sqlite3_mutex_enter(pVm->db->mutex);
      sqlite3Error(pVm->db, SQLITE_RANGE, 0);
    }
    pOut = (Mem*)&nullMem;
  }
  return pOut;
}

/*
** This function is called after invoking an sqlite3_value_XXX function on a 
................................................................................
  int rc;

  if( p==0 ){
    return SQLITE_MISUSE;
  }
  sqlite3_mutex_enter(p->db->mutex);
  rc = vdbeUnbind(p, i);
  if( rc==SQLITE_OK && zData!=0 ){


    pVar = &p->aVar[i-1];
    rc = sqlite3VdbeMemSetStr(pVar, zData, nData, encoding, xDel);
    if( rc==SQLITE_OK && encoding!=0 ){
      rc = sqlite3VdbeChangeEncoding(pVar, ENC(p->db));
    }
    sqlite3Error(p->db, rc, 0);
    rc = sqlite3ApiExit(p->db, rc);
  }
  sqlite3_mutex_leave(p->db->mutex);
  return rc;
}


/*
** Bind a blob value to an SQL statement variable.
................................................................................
** an SQLITE_ERROR is returned.
*/
int sqlite3_transfer_bindings(sqlite3_stmt *pFromStmt, sqlite3_stmt *pToStmt){
  Vdbe *pFrom = (Vdbe*)pFromStmt;
  Vdbe *pTo = (Vdbe*)pToStmt;
  int i, rc = SQLITE_OK;
  if( (pFrom->magic!=VDBE_MAGIC_RUN && pFrom->magic!=VDBE_MAGIC_HALT)
    || (pTo->magic!=VDBE_MAGIC_RUN && pTo->magic!=VDBE_MAGIC_HALT)
    || pTo->db!=pFrom->db ){
    return SQLITE_MISUSE;
  }
  if( pFrom->nVar!=pTo->nVar ){
    return SQLITE_ERROR;
  }
  sqlite3_mutex_enter(pTo->db->mutex);
  for(i=0; rc==SQLITE_OK && i<pFrom->nVar; i++){
    sqlite3MallocDisallow();
    rc = sqlite3VdbeMemMove(&pTo->aVar[i], &pFrom->aVar[i]);
    sqlite3MallocAllow();
  }
  sqlite3_mutex_leave(pTo->db->mutex);
  assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
  return rc;
}

/*
** Return the sqlite3* database handle to which the prepared statement given
** in the argument belongs.  This is the same database handle that was
** the first argument to the sqlite3_prepare() that was used to create
** the statement in the first place.
*/
sqlite3 *sqlite3_db_handle(sqlite3_stmt *pStmt){
  return pStmt ? ((Vdbe*)pStmt)->db : 0;
}

**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains code used to help implement virtual tables.
**
** $Id: vtab.c,v 1.51 2007/08/17 01:14:39 drh Exp $
*/
#ifndef SQLITE_OMIT_VIRTUALTABLE
#include "sqliteInt.h"

static int createModule(
  sqlite3 *db,                    /* Database in which module is registered */
  const char *zName,              /* Name assigned to this module */
  const sqlite3_module *pModule,  /* The definition of the module */
  void *pAux,                     /* Context pointer for xCreate/xConnect */
  void (*xDestroy)(void *)        /* Module destructor function */
) {



  int nName = strlen(zName);
  Module *pMod = (Module *)sqlite3DbMallocRaw(db, sizeof(Module) + nName + 1);
  if( pMod ){
    char *zCopy = (char *)(&pMod[1]);
    memcpy(zCopy, zName, nName+1);
    pMod->zName = zCopy;
    pMod->pModule = pModule;
    pMod->pAux = pAux;
................................................................................
    pMod = (Module *)sqlite3HashInsert(&db->aModule, zCopy, nName, (void*)pMod);
    if( pMod && pMod->xDestroy ){
      pMod->xDestroy(pMod->pAux);
    }
    sqlite3_free(pMod);
    sqlite3ResetInternalSchema(db, 0);
  }
  return sqlite3ApiExit(db, SQLITE_OK);


}


/*
** External API function used to create a new virtual-table module.
*/
int sqlite3_create_module(
................................................................................
** valid to call this function from within the xCreate() or xConnect() of a
** virtual table module.
*/
int sqlite3_declare_vtab(sqlite3 *db, const char *zCreateTable){
  Parse sParse;

  int rc = SQLITE_OK;
  Table *pTab = db->pVTab;
  char *zErr = 0;



  if( !pTab ){
    sqlite3Error(db, SQLITE_MISUSE, 0);

    return SQLITE_MISUSE;
  }
  assert(pTab->isVirtual && pTab->nCol==0 && pTab->aCol==0);

  memset(&sParse, 0, sizeof(Parse));
  sParse.declareVtab = 1;
  sParse.db = db;
................................................................................
  sParse.declareVtab = 0;

  sqlite3_finalize((sqlite3_stmt*)sParse.pVdbe);
  sqlite3DeleteTable(sParse.pNewTable);
  sParse.pNewTable = 0;

  assert( (rc&0xff)==rc );
  return sqlite3ApiExit(db, rc);


}

/*
** This function is invoked by the vdbe to call the xDestroy method
** of the virtual table named zTab in database iDb. This occurs
** when a DROP TABLE is mentioned.
**

**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains code used to help implement virtual tables.
**
** $Id: vtab.c,v 1.52 2007/08/22 02:56:44 drh Exp $
*/
#ifndef SQLITE_OMIT_VIRTUALTABLE
#include "sqliteInt.h"

static int createModule(
  sqlite3 *db,                    /* Database in which module is registered */
  const char *zName,              /* Name assigned to this module */
  const sqlite3_module *pModule,  /* The definition of the module */
  void *pAux,                     /* Context pointer for xCreate/xConnect */
  void (*xDestroy)(void *)        /* Module destructor function */
) {
  int rc, nName;

  sqlite3_mutex_enter(db->mutex);
  nName = strlen(zName);
  Module *pMod = (Module *)sqlite3DbMallocRaw(db, sizeof(Module) + nName + 1);
  if( pMod ){
    char *zCopy = (char *)(&pMod[1]);
    memcpy(zCopy, zName, nName+1);
    pMod->zName = zCopy;
    pMod->pModule = pModule;
    pMod->pAux = pAux;
................................................................................
    pMod = (Module *)sqlite3HashInsert(&db->aModule, zCopy, nName, (void*)pMod);
    if( pMod && pMod->xDestroy ){
      pMod->xDestroy(pMod->pAux);
    }
    sqlite3_free(pMod);
    sqlite3ResetInternalSchema(db, 0);
  }
  rc = sqlite3ApiExit(db, SQLITE_OK);
  sqlite3_mutex_leave(db->mutex);
  return rc;
}


/*
** External API function used to create a new virtual-table module.
*/
int sqlite3_create_module(
................................................................................
** valid to call this function from within the xCreate() or xConnect() of a
** virtual table module.
*/
int sqlite3_declare_vtab(sqlite3 *db, const char *zCreateTable){
  Parse sParse;

  int rc = SQLITE_OK;
  Table *pTab;
  char *zErr = 0;

  sqlite3_mutex_enter(db->mutex);
  pTab = db->pVTab;
  if( !pTab ){
    sqlite3Error(db, SQLITE_MISUSE, 0);
    sqlite3_mutex_leave(db->mutex);
    return SQLITE_MISUSE;
  }
  assert(pTab->isVirtual && pTab->nCol==0 && pTab->aCol==0);

  memset(&sParse, 0, sizeof(Parse));
  sParse.declareVtab = 1;
  sParse.db = db;
................................................................................
  sParse.declareVtab = 0;

  sqlite3_finalize((sqlite3_stmt*)sParse.pVdbe);
  sqlite3DeleteTable(sParse.pNewTable);
  sParse.pNewTable = 0;

  assert( (rc&0xff)==rc );
  rc = sqlite3ApiExit(db, rc);
  sqlite3_mutex_leave(db->mutex);
  return rc;
}

/*
** This function is invoked by the vdbe to call the xDestroy method
** of the virtual table named zTab in database iDb. This occurs
** when a DROP TABLE is mentioned.
**

#
#    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: cache.test,v 1.3 2007/08/12 20:07:59 drh Exp $

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

ifcapable {!pager_pragmas} {
  finish_test
  return
}
sqlite3_soft_heap_limit 0

proc pager_cache_size {db} {
  set bt [btree_from_db $db]

  array set stats [btree_pager_stats $bt]

  return $stats(page)
}

do_test cache-1.1 {
  pager_cache_size db
} {0}

#
#    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: cache.test,v 1.4 2007/08/22 02:56:44 drh Exp $

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

ifcapable {!pager_pragmas} {
  finish_test
  return
}
sqlite3_soft_heap_limit 0

proc pager_cache_size {db} {
  set bt [btree_from_db $db]
  db_enter $db
  array set stats [btree_pager_stats $bt]
  db_leave $db
  return $stats(page)
}

do_test cache-1.1 {
  pager_cache_size db
} {0}

#    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 testing the callback-free C/C++ API.
#
# $Id: capi3.test,v 1.51 2007/08/12 20:07:59 drh Exp $
#

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

# Return the UTF-16 representation of the supplied UTF-8 string $str.
# If $nt is true, append two 0x00 bytes as a nul terminator.
................................................................................
} SQLITE_OK


set ::ENC [execsql {pragma encoding}]
db close

do_test capi3-6.0 {
btree_breakpoint
  sqlite3 db test.db
  set DB [sqlite3_connection_pointer db]
btree_breakpoint
  sqlite3_key $DB xyzzy
  set sql {SELECT a FROM t1 order by rowid}
  set STMT [sqlite3_prepare $DB $sql -1 TAIL]
  expr 0
} {0}
do_test capi3-6.1 {
  db cache flush

#    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 testing the callback-free C/C++ API.
#
# $Id: capi3.test,v 1.52 2007/08/22 02:56:44 drh Exp $
#

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

# Return the UTF-16 representation of the supplied UTF-8 string $str.
# If $nt is true, append two 0x00 bytes as a nul terminator.
................................................................................
} SQLITE_OK


set ::ENC [execsql {pragma encoding}]
db close

do_test capi3-6.0 {

  sqlite3 db test.db
  set DB [sqlite3_connection_pointer db]

  sqlite3_key $DB xyzzy
  set sql {SELECT a FROM t1 order by rowid}
  set STMT [sqlite3_prepare $DB $sql -1 TAIL]
  expr 0
} {0}
do_test capi3-6.1 {
  db cache flush

#
#    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: incrblob.test,v 1.13 2007/08/12 20:07:59 drh Exp $
#

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

ifcapable {!autovacuum || !pragma || !incrblob} {
  finish_test
................................................................................
#
#     * Reading near the end of a blob,
#     * Writing near the end of a blob, and
#     * SELECT a column value that is located on an overflow page.
#
proc nRead {db} {
  set bt [btree_from_db $db]

  array set stats [btree_pager_stats $bt]

  return $stats(read)
}
proc nWrite {db} {
  set bt [btree_from_db $db]

  array set stats [btree_pager_stats $bt]

  return $stats(write)
}

sqlite3_soft_heap_limit 0

foreach AutoVacuumMode [list 0 1] {

#
#    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: incrblob.test,v 1.14 2007/08/22 02:56:44 drh Exp $
#

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

ifcapable {!autovacuum || !pragma || !incrblob} {
  finish_test
................................................................................
#
#     * Reading near the end of a blob,
#     * Writing near the end of a blob, and
#     * SELECT a column value that is located on an overflow page.
#
proc nRead {db} {
  set bt [btree_from_db $db]
  db_enter $db
  array set stats [btree_pager_stats $bt]
  db_leave $db
  return $stats(read)
}
proc nWrite {db} {
  set bt [btree_from_db $db]
  db_enter $db
  array set stats [btree_pager_stats $bt]
  db_leave $db
  return $stats(write)
}

sqlite3_soft_heap_limit 0

foreach AutoVacuumMode [list 0 1] {

#
#***********************************************************************
#
# The focus of this file is testing some specific characteristics of the 
# IO traffic generated by SQLite (making sure SQLite is not writing out
# more database pages than it has to, stuff like that).
#
# $Id: io.test,v 1.1 2007/08/21 13:30:07 danielk1977 Exp $

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

set ::nWrite 0
proc nWrite {db} {
  set bt [btree_from_db $db]

  array set stats [btree_pager_stats $bt]


  set res [expr $stats(write) - $::nWrite]
  set ::nWrite $stats(write)
  set res
}

do_test io-1.1 {
  execsql {
................................................................................
  execsql { INSERT INTO abc VALUES(9,randstr(230,230)); }
  nWrite db
} {3}

#db eval {select * from sqlite_master} {btree_tree_dump [btree_from_db db] 2}

finish_test

#
#***********************************************************************
#
# The focus of this file is testing some specific characteristics of the 
# IO traffic generated by SQLite (making sure SQLite is not writing out
# more database pages than it has to, stuff like that).
#
# $Id: io.test,v 1.2 2007/08/22 02:56:44 drh Exp $

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

set ::nWrite 0
proc nWrite {db} {
  set bt [btree_from_db $db]
  db_enter $db
  array set stats [btree_pager_stats $bt]

  db_leave $db
  set res [expr $stats(write) - $::nWrite]
  set ::nWrite $stats(write)
  set res
}

do_test io-1.1 {
  execsql {
................................................................................
  execsql { INSERT INTO abc VALUES(9,randstr(230,230)); }
  nWrite db
} {3}

#db eval {select * from sqlite_master} {btree_tree_dump [btree_from_db db] 2}

finish_test

#    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 that the overflow-page related
# enhancements added after version 3.3.17 speed things up.
#
# $Id: speed3.test,v 1.2 2007/05/17 18:28:11 danielk1977 Exp $
#

#---------------------------------------------------------------------
# Test plan:
#
# If auto-vacuum is enabled for the database, the following cases
# should show performance improvement with respect to 3.3.17.
................................................................................
    }
    $db eval {INSERT INTO aux.t1 SELECT * FROM main.t1}
  }
}


proc io_log {db} {

  array set stats1 [btree_pager_stats [btree_from_db db]]
  array set stats2 [btree_pager_stats [btree_from_db db 2]]

# puts "1: [array get stats1]"
# puts "2: [array get stats2]"
  puts "Incrvacuum: Read $stats1(read), wrote $stats1(write)"
  puts "Normal    : Read $stats2(read), wrote $stats2(write)"
}

proc overflow_report {db} {
................................................................................
#overflow_report db
reset_db
speed_trial speed3-2.incrvacuum $::NROW row {SELECT c FROM main.t1}
speed_trial speed3-2.normal     $::NROW row {SELECT c FROM aux.t1}
io_log db

finish_test

#    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 that the overflow-page related
# enhancements added after version 3.3.17 speed things up.
#
# $Id: speed3.test,v 1.3 2007/08/22 02:56:44 drh Exp $
#

#---------------------------------------------------------------------
# Test plan:
#
# If auto-vacuum is enabled for the database, the following cases
# should show performance improvement with respect to 3.3.17.
................................................................................
    }
    $db eval {INSERT INTO aux.t1 SELECT * FROM main.t1}
  }
}


proc io_log {db} {
  db_enter db
  array set stats1 [btree_pager_stats [btree_from_db db]]
  array set stats2 [btree_pager_stats [btree_from_db db 2]]
  db_leave db
# puts "1: [array get stats1]"
# puts "2: [array get stats2]"
  puts "Incrvacuum: Read $stats1(read), wrote $stats1(write)"
  puts "Normal    : Read $stats2(read), wrote $stats2(write)"
}

proc overflow_report {db} {
................................................................................
#overflow_report db
reset_db
speed_trial speed3-2.incrvacuum $::NROW row {SELECT c FROM main.t1}
speed_trial speed3-2.normal     $::NROW row {SELECT c FROM aux.t1}
io_log db

finish_test

#    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 creating and dropping virtual tables.
#
# $Id: vtab1.test,v 1.43 2007/06/27 15:53:35 danielk1977 Exp $

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

ifcapable !vtab||!schema_pragmas {
  finish_test
  return
................................................................................
  catchsql {
    SELECT * FROM e2;
  }
} {1 {vtable constructor failed: e2}}
do_test vtab1.10-2 {
  set rc [catch {
    set ptr [sqlite3_connection_pointer db]

    sqlite3_declare_vtab $ptr {CREATE TABLE abc(a, b, c)}
  } msg]
  list $rc $msg
} {1 {library routine called out of sequence}}
do_test vtab1.10-3 {
  set ::echo_module_begin_fail r
  catchsql {

#    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 creating and dropping virtual tables.
#
# $Id: vtab1.test,v 1.44 2007/08/22 02:56:44 drh Exp $

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

ifcapable !vtab||!schema_pragmas {
  finish_test
  return
................................................................................
  catchsql {
    SELECT * FROM e2;
  }
} {1 {vtable constructor failed: e2}}
do_test vtab1.10-2 {
  set rc [catch {
    set ptr [sqlite3_connection_pointer db]
btree_breakpoint
    sqlite3_declare_vtab $ptr {CREATE TABLE abc(a, b, c)}
  } msg]
  list $rc $msg
} {1 {library routine called out of sequence}}
do_test vtab1.10-3 {
  set ::echo_module_begin_fail r
  catchsql {