SQLite

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


/*
** This a more complex version of findCell() that works for
** pages that do contain overflow cells.
*/

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

  memset(&data[hdr+1], 0, 4);
  data[hdr+7] = 0;
  put2byte(&data[hdr+5], pBt->usableSize);
  pPage->nFree = (u16)(pBt->usableSize - first);
  decodeFlags(pPage, flags);
  pPage->hdrOffset = hdr;
  pPage->cellOffset = first;
  pPage->aDataEnd = &data[pBt->usableSize];
  pPage->aCellIdx = &data[first];
  pPage->nOverflow = 0;
  assert( pBt->pageSize>=512 && pBt->pageSize<=65536 );
  pPage->maskPage = (u16)(pBt->pageSize - 1);
  pPage->nCell = 0;
  pPage->isInit = 1;
}

        ** page is less than 16384 bytes and may be stored as a 2-byte
        ** varint. This information is used to attempt to avoid parsing 
        ** the entire cell by checking for the cases where the record is 
        ** stored entirely within the b-tree page by inspecting the first 
        ** 2 bytes of the cell.
        */
        int nCell = pCell[0];
        if( !(nCell & 0x80)
         && nCell<=pPage->maxLocal
         && (pCell+nCell+1)<=pPage->aDataEnd
        ){
          /* This branch runs if the record-size field of the cell is a
          ** single byte varint and the record fits entirely on the main
          ** b-tree page.  */
          testcase( pCell+nCell+1==pPage->aDataEnd );
          c = sqlite3VdbeRecordCompare(nCell, (void*)&pCell[1], pIdxKey);
        }else if( !(pCell[1] & 0x80) 
          && (nCell = ((nCell&0x7f)<<7) + pCell[1])<=pPage->maxLocal
          && (pCell+nCell+2)<=pPage->aDataEnd
        ){
          /* The record-size field is a 2 byte varint and the record 
          ** fits entirely on the main b-tree page.  */
          testcase( pCell+nCell+2==pPage->aDataEnd );
          c = sqlite3VdbeRecordCompare(nCell, (void*)&pCell[2], pIdxKey);
        }else{
          /* The record flows over onto one or more overflow pages. In
          ** this case the whole cell needs to be parsed, a buffer allocated
          ** and accessPayload() used to retrieve the record into the
          ** buffer before VdbeRecordCompare() can be called. */
          void *pCellKey;

  if( *pRC ) return;

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

            && (int)MX_CELL(pPage->pBt)<=10921);
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );

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

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

  u16 maskPage;        /* Mask for page offset */
  struct _OvflCell {   /* Cells that will not fit on aData[] */
    u8 *pCell;          /* Pointers to the body of the overflow cell */
    u16 idx;            /* Insert this cell before idx-th non-overflow cell */
  } aOvfl[5];
  BtShared *pBt;       /* Pointer to BtShared that this page is part of */
  u8 *aData;           /* Pointer to disk image of the page data */
  u8 *aDataEnd;        /* One byte past the end of usable data */
  u8 *aCellIdx;        /* The cell index area */
  DbPage *pDbPage;     /* Pager page handle */
  Pgno pgno;           /* Page number for this page */
};

/*
** The in-memory image of a disk page has the auxiliary information appended
** to the end.  EXTRA_SIZE is the number of bytes of space needed to hold

#include <winbase.h>

#ifdef __CYGWIN__
# include <sys/cygwin.h>
#endif








/*
** Include code that is common to all os_*.c files
*/
#include "os_common.h"

/*
** Some microsoft compilers lack this definition.

/*
** The return value of getLastErrorMsg
** is zero if the error message fits in the buffer, or non-zero
** otherwise (if the message was truncated).
*/
static int getLastErrorMsg(DWORD lastErrno, int nBuf, char *zBuf){
  /* FormatMessage returns 0 on failure.  Otherwise it
  ** returns the number of TCHARs written to the output
  ** buffer, excluding the terminating null char.
  */

  DWORD dwLen = 0;
  char *zOut = 0;

  if( isNT() ){
    WCHAR *zTempWide = NULL;
    dwLen = FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER |
                           FORMAT_MESSAGE_FROM_SYSTEM |
                           FORMAT_MESSAGE_IGNORE_INSERTS,
                           NULL,
                           lastErrno,
                           0,
                           (LPWSTR) &zTempWide,
                           0,
                           0);
    if( dwLen > 0 ){
      /* allocate a buffer and convert to UTF8 */
      zOut = unicodeToUtf8(zTempWide);
      /* free the system buffer allocated by FormatMessage */
      LocalFree(zTempWide);
    }
/* isNT() is 1 if SQLITE_OS_WINCE==1, so this else is never executed. 
** Since the ASCII version of these Windows API do not exist for WINCE,
** it's important to not reference them for WINCE builds.
*/
#if SQLITE_OS_WINCE==0
  }else{
    char *zTemp = NULL;
    dwLen = FormatMessageA(FORMAT_MESSAGE_ALLOCATE_BUFFER |
                           FORMAT_MESSAGE_FROM_SYSTEM |
                           FORMAT_MESSAGE_IGNORE_INSERTS,
                           NULL,
                           lastErrno,
                           0,
                           (LPSTR) &zTemp,
                           0,
                           0);
    if( dwLen > 0 ){
      /* allocate a buffer and convert to UTF8 */
      zOut = sqlite3_win32_mbcs_to_utf8(zTemp);
      /* free the system buffer allocated by FormatMessage */
      LocalFree(zTemp);
    }
#endif
  }
  if( 0 == dwLen ){
    sqlite3_snprintf(nBuf, zBuf, "OsError 0x%x (%u)", lastErrno, lastErrno);
  }else{
    /* copy a maximum of nBuf chars to output buffer */
    sqlite3_snprintf(nBuf, zBuf, "%s", zOut);
    /* free the UTF8 buffer */
    free(zOut);
  }
  return 0;

** FormatMessage.
**
** The first argument passed to the macro should be the error code that
** will be returned to SQLite (e.g. SQLITE_IOERR_DELETE, SQLITE_CANTOPEN). 
** The two subsequent arguments should be the name of the OS function that
** failed and the the associated file-system path, if any.
*/
#define winLogError(a,b,c,d)   winLogErrorAtLine(a,b,c,d,__LINE__)
static int winLogErrorAtLine(
  int errcode,                    /* SQLite error code */
  DWORD lastErrno,                /* Win32 last error */
  const char *zFunc,              /* Name of OS function that failed */
  const char *zPath,              /* File path associated with error */
  int iLine                       /* Source line number where error occurred */
){
  char zMsg[500];                 /* Human readable error text */
  int i;                          /* Loop counter */


  zMsg[0] = 0;
  getLastErrorMsg(lastErrno, sizeof(zMsg), zMsg);
  assert( errcode!=SQLITE_OK );
  if( zPath==0 ) zPath = "";
  for(i=0; zMsg[i] && zMsg[i]!='\r' && zMsg[i]!='\n'; i++){}
  zMsg[i] = 0;
  sqlite3_log(errcode,
      "os_win.c:%d: (%d) %s(%s) - %s",
      iLine, lastErrno, zFunc, zPath, zMsg
  );

  return errcode;
}

/*
** The number of times that a ReadFile(), WriteFile(), and DeleteFile()

    if (*zTok == '\\') *zTok = '_';
  }

  /* Create/open the named mutex */
  pFile->hMutex = CreateMutexW(NULL, FALSE, zName);
  if (!pFile->hMutex){
    pFile->lastErrno = GetLastError();
    winLogError(SQLITE_ERROR, pFile->lastErrno, "winceCreateLock1", zFilename);
    free(zName);
    return FALSE;
  }

  /* Acquire the mutex before continuing */
  winceMutexAcquire(pFile->hMutex);
  

  /* If we succeeded in making the shared memory handle, map it. */
  if (pFile->hShared){
    pFile->shared = (winceLock*)MapViewOfFile(pFile->hShared, 
             FILE_MAP_READ|FILE_MAP_WRITE, 0, 0, sizeof(winceLock));
    /* If mapping failed, close the shared memory handle and erase it */
    if (!pFile->shared){
      pFile->lastErrno = GetLastError();
      winLogError(SQLITE_ERROR, pFile->lastErrno,
               "winceCreateLock2", zFilename);
      CloseHandle(pFile->hShared);
      pFile->hShared = NULL;
    }
  }

  /* If shared memory could not be created, then close the mutex and fail */
  if (pFile->hShared == NULL){

  ** INVALID_SET_FILE_POINTER may also be a valid new offset. So to determine 
  ** whether an error has actually occured, it is also necessary to call 
  ** GetLastError().
  */
  dwRet = SetFilePointer(pFile->h, lowerBits, &upperBits, FILE_BEGIN);
  if( (dwRet==INVALID_SET_FILE_POINTER && GetLastError()!=NO_ERROR) ){
    pFile->lastErrno = GetLastError();
    winLogError(SQLITE_IOERR_SEEK, pFile->lastErrno,
             "seekWinFile", pFile->zPath);
    return 1;
  }

  return 0;
}

/*

    }
    free(pFile->zDeleteOnClose);
  }
#endif
  OSTRACE(("CLOSE %d %s\n", pFile->h, rc ? "ok" : "failed"));
  OpenCounter(-1);
  return rc ? SQLITE_OK
            : winLogError(SQLITE_IOERR_CLOSE, GetLastError(),
                          "winClose", pFile->zPath);
}

/*
** Read data from a file into a buffer.  Return SQLITE_OK if all
** bytes were read successfully and SQLITE_IOERR if anything goes
** wrong.
*/

  if( seekWinFile(pFile, offset) ){
    return SQLITE_FULL;
  }
  while( !ReadFile(pFile->h, pBuf, amt, &nRead, 0) ){
    if( retryIoerr(&nRetry) ) continue;
    pFile->lastErrno = GetLastError();
    return winLogError(SQLITE_IOERR_READ, pFile->lastErrno,
             "winRead", pFile->zPath);
  }
  logIoerr(nRetry);
  if( nRead<(DWORD)amt ){
    /* Unread parts of the buffer must be zero-filled */
    memset(&((char*)pBuf)[nRead], 0, amt-nRead);
    return SQLITE_IOERR_SHORT_READ;
  }

  }

  if( rc ){
    if(   ( pFile->lastErrno==ERROR_HANDLE_DISK_FULL )
       || ( pFile->lastErrno==ERROR_DISK_FULL )){
      return SQLITE_FULL;
    }
    return winLogError(SQLITE_IOERR_WRITE, pFile->lastErrno,
             "winWrite", pFile->zPath);
  }else{
    logIoerr(nRetry);
  }
  return SQLITE_OK;
}

/*

  */
  if( pFile->szChunk>0 ){
    nByte = ((nByte + pFile->szChunk - 1)/pFile->szChunk) * pFile->szChunk;
  }

  /* SetEndOfFile() returns non-zero when successful, or zero when it fails. */
  if( seekWinFile(pFile, nByte) ){
    rc = winLogError(SQLITE_IOERR_TRUNCATE, pFile->lastErrno,
             "winTruncate1", pFile->zPath);
  }else if( 0==SetEndOfFile(pFile->h) ){
    pFile->lastErrno = GetLastError();
    rc = winLogError(SQLITE_IOERR_TRUNCATE, pFile->lastErrno,
             "winTruncate2", pFile->zPath);
  }

  OSTRACE(("TRUNCATE %d %lld %s\n", pFile->h, nByte, rc ? "failed" : "ok"));
  return rc;
}

#ifdef SQLITE_TEST

#else
  rc = FlushFileBuffers(pFile->h);
  SimulateIOError( rc=FALSE );
  if( rc ){
    return SQLITE_OK;
  }else{
    pFile->lastErrno = GetLastError();
    return winLogError(SQLITE_IOERR_FSYNC, pFile->lastErrno,
             "winSync", pFile->zPath);
  }
#endif
}

/*
** Determine the current size of a file in bytes
*/
static int winFileSize(sqlite3_file *id, sqlite3_int64 *pSize){
  DWORD upperBits;
  DWORD lowerBits;
  winFile *pFile = (winFile*)id;
  DWORD error;

  assert( id!=0 );
  SimulateIOError(return SQLITE_IOERR_FSTAT);
  lowerBits = GetFileSize(pFile->h, &upperBits);
  if(   (lowerBits == INVALID_FILE_SIZE)
     && ((error = GetLastError()) != NO_ERROR) )
  {
    pFile->lastErrno = error;
    return winLogError(SQLITE_IOERR_FSTAT, pFile->lastErrno,
             "winFileSize", pFile->zPath);
  }
  *pSize = (((sqlite3_int64)upperBits)<<32) + lowerBits;
  return SQLITE_OK;
}

/*
** LOCKFILE_FAIL_IMMEDIATELY is undefined on some Windows systems.

#if SQLITE_OS_WINCE==0
  }else{
    res = UnlockFile(pFile->h, SHARED_FIRST + pFile->sharedLockByte, 0, 1, 0);
#endif
  }
  if( res==0 && GetLastError()!=ERROR_NOT_LOCKED ){
    pFile->lastErrno = GetLastError();
    winLogError(SQLITE_IOERR_UNLOCK, pFile->lastErrno,
             "unlockReadLock", pFile->zPath);
  }
  return res;
}

/*
** Lock the file with the lock specified by parameter locktype - one
** of the following:

  newLocktype = pFile->locktype;
  if(   (pFile->locktype==NO_LOCK)
     || (   (locktype==EXCLUSIVE_LOCK)
         && (pFile->locktype==RESERVED_LOCK))
  ){
    int cnt = 3;
    while( cnt-->0 && (res = LockFile(pFile->h, PENDING_BYTE, 0, 1, 0))==0 ){
      /* Try 3 times to get the pending lock.  This is needed to work
      ** around problems caused by anti-virus software on windows system.
      ** If you are using this code as a model for alternative VFSes, do not
      ** copy this retry logic.  It is a hack intended for windows only.
      */
      OSTRACE(("could not get a PENDING lock. cnt=%d\n", cnt));
      if( cnt ) Sleep(1);
    }
    gotPendingLock = res;
    if( !res ){
      error = GetLastError();
    }
  }

          pFile->locktype, pFile->sharedLockByte));
  type = pFile->locktype;
  if( type>=EXCLUSIVE_LOCK ){
    UnlockFile(pFile->h, SHARED_FIRST, 0, SHARED_SIZE, 0);
    if( locktype==SHARED_LOCK && !getReadLock(pFile) ){
      /* This should never happen.  We should always be able to
      ** reacquire the read lock */
      rc = winLogError(SQLITE_IOERR_UNLOCK, GetLastError(),
               "winUnlock", pFile->zPath);
    }
  }
  if( type>=RESERVED_LOCK ){
    UnlockFile(pFile->h, RESERVED_BYTE, 0, 1, 0);
  }
  if( locktype==NO_LOCK && type>=SHARED_LOCK ){
    unlockReadLock(pFile);

    /* Check to see if another process is holding the dead-man switch.
    ** If not, truncate the file to zero length. 
    */
    if( winShmSystemLock(pShmNode, _SHM_WRLCK, WIN_SHM_DMS, 1)==SQLITE_OK ){
      rc = winTruncate((sqlite3_file *)&pShmNode->hFile, 0);
      if( rc!=SQLITE_OK ){
        rc = winLogError(SQLITE_IOERR_SHMOPEN, GetLastError(),
                 "winOpenShm", pDbFd->zPath);
      }
    }
    if( rc==SQLITE_OK ){
      winShmSystemLock(pShmNode, _SHM_UNLCK, WIN_SHM_DMS, 1);
      rc = winShmSystemLock(pShmNode, _SHM_RDLCK, WIN_SHM_DMS, 1);
    }
    if( rc ) goto shm_open_err;

    /* The requested region is not mapped into this processes address space.
    ** Check to see if it has been allocated (i.e. if the wal-index file is
    ** large enough to contain the requested region).
    */
    rc = winFileSize((sqlite3_file *)&pShmNode->hFile, &sz);
    if( rc!=SQLITE_OK ){
      rc = winLogError(SQLITE_IOERR_SHMSIZE, GetLastError(),
               "winShmMap1", pDbFd->zPath);
      goto shmpage_out;
    }

    if( sz<nByte ){
      /* The requested memory region does not exist. If isWrite is set to
      ** zero, exit early. *pp will be set to NULL and SQLITE_OK returned.
      **
      ** Alternatively, if isWrite is non-zero, use ftruncate() to allocate
      ** the requested memory region.
      */
      if( !isWrite ) goto shmpage_out;
      rc = winTruncate((sqlite3_file *)&pShmNode->hFile, nByte);
      if( rc!=SQLITE_OK ){
        rc = winLogError(SQLITE_IOERR_SHMSIZE, GetLastError(),
                 "winShmMap2", pDbFd->zPath);
        goto shmpage_out;
      }
    }

    /* Map the requested memory region into this processes address space. */
    apNew = (struct ShmRegion *)sqlite3_realloc(
        pShmNode->aRegion, (iRegion+1)*sizeof(apNew[0])

        );
        OSTRACE(("SHM-MAP pid-%d map region=%d offset=%d size=%d %s\n",
                 (int)GetCurrentProcessId(), pShmNode->nRegion, iOffset, szRegion,
                 pMap ? "ok" : "failed"));
      }
      if( !pMap ){
        pShmNode->lastErrno = GetLastError();
        rc = winLogError(SQLITE_IOERR_SHMMAP, pShmNode->lastErrno,
                 "winShmMap3", pDbFd->zPath);
        if( hMap ) CloseHandle(hMap);
        goto shmpage_out;
      }

      pShmNode->aRegion[pShmNode->nRegion].pMap = pMap;
      pShmNode->aRegion[pShmNode->nRegion].hMap = hMap;
      pShmNode->nRegion++;

  OSTRACE(("OPEN %d %s 0x%lx %s\n", 
           h, zName, dwDesiredAccess, 
           h==INVALID_HANDLE_VALUE ? "failed" : "ok"));

  if( h==INVALID_HANDLE_VALUE ){
    pFile->lastErrno = GetLastError();
    winLogError(SQLITE_CANTOPEN, pFile->lastErrno, "winOpen", zUtf8Name);
    free(zConverted);
    if( isReadWrite && !isExclusive ){
      return winOpen(pVfs, zName, id, 
             ((flags|SQLITE_OPEN_READONLY)&~(SQLITE_OPEN_CREATE|SQLITE_OPEN_READWRITE)), pOutFlags);
    }else{
      return SQLITE_CANTOPEN_BKPT;
    }

    rc = 1;
    while( GetFileAttributesA(zConverted)!=INVALID_FILE_ATTRIBUTES &&
           (rc = DeleteFileA(zConverted))==0 && retryIoerr(&cnt) ){}
    rc = rc ? SQLITE_OK : SQLITE_ERROR;
#endif
  }
  if( rc ){
    rc = winLogError(SQLITE_IOERR_DELETE, GetLastError(),
             "winDelete", zFilename);
  }else{
    logIoerr(cnt);
  }
  free(zConverted);
  OSTRACE(("DELETE \"%s\" %s\n", zFilename, (rc ? "failed" : "ok" )));
  return rc;
}

          && sAttrData.nFileSizeHigh==0 
          && sAttrData.nFileSizeLow==0 ){
        attr = INVALID_FILE_ATTRIBUTES;
      }else{
        attr = sAttrData.dwFileAttributes;
      }
    }else{
      DWORD lastErrno = GetLastError();
      logIoerr(cnt);
      if( lastErrno!=ERROR_FILE_NOT_FOUND ){
        winLogError(SQLITE_IOERR_ACCESS, lastErrno, "winAccess", zFilename);
        free(zConverted);
        return SQLITE_IOERR_ACCESS;
      }else{
        attr = INVALID_FILE_ATTRIBUTES;
      }
    }
/* isNT() is 1 if SQLITE_OS_WINCE==1, so this else is never executed. 

#endif
  }
  free(zConverted);
  return (void*)h;
}
static void winDlError(sqlite3_vfs *pVfs, int nBuf, char *zBufOut){
  UNUSED_PARAMETER(pVfs);
  getLastErrorMsg(GetLastError(), nBuf, zBufOut);
}
static void (*winDlSym(sqlite3_vfs *pVfs, void *pHandle, const char *zSymbol))(void){
  UNUSED_PARAMETER(pVfs);
#if SQLITE_OS_WINCE
  /* The GetProcAddressA() routine is only available on wince. */
  return (void(*)(void))GetProcAddressA((HANDLE)pHandle, zSymbol);
#else

**
** However if an error message is supplied, it will be incorporated
** by sqlite into the error message available to the user using
** sqlite3_errmsg(), possibly making IO errors easier to debug.
*/
static int winGetLastError(sqlite3_vfs *pVfs, int nBuf, char *zBuf){
  UNUSED_PARAMETER(pVfs);
  return getLastErrorMsg(GetLastError(), nBuf, zBuf);
}



/*
** Initialize and deinitialize the operating system interface.
*/