os.c

SQLite 2.8.6 源代码,用来在Linux/Unix/Windows上编译安装.它是一个小型的数据库,但是非常好用,速度也快,一般的数据库查询之类的操作据统计比MySQL,PostgreSQL

    return SQLITE_CANTOPEN;
  }
  sqliteOsEnterMutex();
  id->pLock = findLockInfo(id->fd);
  sqliteOsLeaveMutex();
  if( id->pLock==0 ){
    close(id->fd);
    return SQLITE_NOMEM;
  }
  id->locked = 0;
  TRACE3("OPEN-RO %-3d %s\n", id->fd, zFilename);
  OpenCounter(+1);
  return SQLITE_OK;
#endif
#if OS_WIN
  HANDLE h = CreateFile(zFilename,
     GENERIC_READ,
     0,
     NULL,
     OPEN_EXISTING,
     FILE_ATTRIBUTE_NORMAL | FILE_FLAG_RANDOM_ACCESS,
     NULL
  );
  if( h==INVALID_HANDLE_VALUE ){
    return SQLITE_CANTOPEN;
  }
  id->h = h;
  id->locked = 0;
  OpenCounter(+1);
  return SQLITE_OK;
#endif
#if OS_MAC
  FSSpec fsSpec;
# ifdef _LARGE_FILE
  HFSUniStr255 dfName;
  FSRef fsRef;
  if( __path2fss(zFilename, &fsSpec) != noErr )
    return SQLITE_CANTOPEN;
  if( FSpMakeFSRef(&fsSpec, &fsRef) != noErr )
    return SQLITE_CANTOPEN;
  FSGetDataForkName(&dfName);
  if( FSOpenFork(&fsRef, dfName.length, dfName.unicode,
                 fsRdPerm, &(id->refNum)) != noErr )
    return SQLITE_CANTOPEN;
# else
  __path2fss(zFilename, &fsSpec);
  if( HOpenDF(fsSpec.vRefNum, fsSpec.parID, fsSpec.name, fsRdPerm, &(id->refNum)) != noErr )
    return SQLITE_CANTOPEN;
# endif
  if( HOpenRF(fsSpec.vRefNum, fsSpec.parID, fsSpec.name, fsRdWrShPerm, &(id->refNumRF)) != noErr){
    id->refNumRF = -1;
  }
  id->locked = 0;
  id->delOnClose = 0;
  OpenCounter(+1);
  return SQLITE_OK;
#endif
}

/*
** Attempt to open a file descriptor for the directory that contains a
** file.  This file descriptor can be used to fsync() the directory
** in order to make sure the creation of a new file is actually written
** to disk.
**
** This routine is only meaningful for Unix.  It is a no-op under
** windows since windows does not support hard links.
**
** On success, a handle for a previously open file is at *id is
** updated with the new directory file descriptor and SQLITE_OK is
** returned.
**
** On failure, the function returns SQLITE_CANTOPEN and leaves
** *id unchanged.
*/
int sqliteOsOpenDirectory(
  const char *zDirname,
  OsFile *id
){
#if OS_UNIX
  if( id->fd<0 ){
    /* Do not open the directory if the corresponding file is not already
    ** open. */
    return SQLITE_CANTOPEN;
  }
  assert( id->dirfd<0 );
  id->dirfd = open(zDirname, O_RDONLY|O_BINARY, 0644);
  if( id->dirfd<0 ){
    return SQLITE_CANTOPEN; 
  }
  TRACE3("OPENDIR %-3d %s\n", id->dirfd, zDirname);
#endif
  return SQLITE_OK;
}

/*
** Create a temporary file name in zBuf.  zBuf must be big enough to
** hold at least SQLITE_TEMPNAME_SIZE characters.
*/
int sqliteOsTempFileName(char *zBuf){
#if OS_UNIX
  static const char *azDirs[] = {
     "/var/tmp",
     "/usr/tmp",
     "/tmp",
     ".",
  };
  static char zChars[] =
    "abcdefghijklmnopqrstuvwxyz"
    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    "0123456789";
  int i, j;
  struct stat buf;
  const char *zDir = ".";
  for(i=0; i<sizeof(azDirs)/sizeof(azDirs[0]); i++){
    if( stat(azDirs[i], &buf) ) continue;
    if( !S_ISDIR(buf.st_mode) ) continue;
    if( access(azDirs[i], 07) ) continue;
    zDir = azDirs[i];
    break;
  }
  do{
    sprintf(zBuf, "%s/"TEMP_FILE_PREFIX, zDir);
    j = strlen(zBuf);
    for(i=0; i<15; i++){
      int n = sqliteRandomByte() % (sizeof(zChars)-1);
      zBuf[j++] = zChars[n];
    }
    zBuf[j] = 0;
  }while( access(zBuf,0)==0 );
#endif
#if OS_WIN
  static char zChars[] =
    "abcdefghijklmnopqrstuvwxyz"
    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    "0123456789";
  int i, j;
  char zTempPath[SQLITE_TEMPNAME_SIZE];
  GetTempPath(SQLITE_TEMPNAME_SIZE-30, zTempPath);
  for(i=strlen(zTempPath); i>0 && zTempPath[i-1]=='\\'; i--){}
  zTempPath[i] = 0;
  for(;;){
    sprintf(zBuf, "%s\\"TEMP_FILE_PREFIX, zTempPath);
    j = strlen(zBuf);
    for(i=0; i<15; i++){
      int n = sqliteRandomByte() % (sizeof(zChars) - 1);
      zBuf[j++] = zChars[n];
    }
    zBuf[j] = 0;
    if( !sqliteOsFileExists(zBuf) ) break;
  }
#endif
#if OS_MAC
  static char zChars[] =
    "abcdefghijklmnopqrstuvwxyz"
    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    "0123456789";
  int i, j;
  char zTempPath[SQLITE_TEMPNAME_SIZE];
  char zdirName[32];
  CInfoPBRec infoRec;
  Str31 dirName;
  memset(&infoRec, 0, sizeof(infoRec));
  memset(zTempPath, 0, SQLITE_TEMPNAME_SIZE);
  if( FindFolder(kOnSystemDisk, kTemporaryFolderType,  kCreateFolder,
       &(infoRec.dirInfo.ioVRefNum), &(infoRec.dirInfo.ioDrParID)) == noErr ){
    infoRec.dirInfo.ioNamePtr = dirName;
    do{
      infoRec.dirInfo.ioFDirIndex = -1;
      infoRec.dirInfo.ioDrDirID = infoRec.dirInfo.ioDrParID;
      if( PBGetCatInfoSync(&infoRec) == noErr ){
        CopyPascalStringToC(dirName, zdirName);
        i = strlen(zdirName);
        memmove(&(zTempPath[i+1]), zTempPath, strlen(zTempPath));
        strcpy(zTempPath, zdirName);
        zTempPath[i] = ':';
      }else{
        *zTempPath = 0;
        break;
      }
    } while( infoRec.dirInfo.ioDrDirID != fsRtDirID );
  }
  if( *zTempPath == 0 )
    getcwd(zTempPath, SQLITE_TEMPNAME_SIZE-24);
  for(;;){
    sprintf(zBuf, "%s"TEMP_FILE_PREFIX, zTempPath);
    j = strlen(zBuf);
    for(i=0; i<15; i++){
      int n = sqliteRandomByte() % sizeof(zChars);
      zBuf[j++] = zChars[n];
    }
    zBuf[j] = 0;
    if( !sqliteOsFileExists(zBuf) ) break;
  }
#endif
  return SQLITE_OK; 
}

/*
** Close a file
*/
int sqliteOsClose(OsFile *id){
#if OS_UNIX
  close(id->fd);
  if( id->dirfd>=0 ) close(id->dirfd);
  id->dirfd = -1;
  sqliteOsEnterMutex();
  releaseLockInfo(id->pLock);
  sqliteOsLeaveMutex();
  TRACE2("CLOSE   %-3d\n", id->fd);
  OpenCounter(-1);
  return SQLITE_OK;
#endif
#if OS_WIN
  CloseHandle(id->h);
  OpenCounter(-1);
  return SQLITE_OK;
#endif
#if OS_MAC
  if( id->refNumRF!=-1 )
    FSClose(id->refNumRF);
# ifdef _LARGE_FILE
  FSCloseFork(id->refNum);
# else
  FSClose(id->refNum);
# endif
  if( id->delOnClose ){
    unlink(id->pathToDel);
    sqliteFree(id->pathToDel);
  }
  OpenCounter(-1);
  return SQLITE_OK;
#endif
}

/*
** Read data from a file into a buffer.  Return SQLITE_OK if all
** bytes were read successfully and SQLITE_IOERR if anything goes
** wrong.
*/
int sqliteOsRead(OsFile *id, void *pBuf, int amt){
#if OS_UNIX
  int got;
  SimulateIOError(SQLITE_IOERR);
  TIMER_START;
  got = read(id->fd, pBuf, amt);
  TIMER_END;
  TRACE4("READ    %-3d %7d %d\n", id->fd, last_page, elapse);
  SEEK(0);
  /* if( got<0 ) got = 0; */
  if( got==amt ){
    return SQLITE_OK;
  }else{
    return SQLITE_IOERR;
  }
#endif
#if OS_WIN
  DWORD got;
  SimulateIOError(SQLITE_IOERR);
  TRACE2("READ %d\n", last_page);
  if( !ReadFile(id->h, pBuf, amt, &got, 0) ){
    got = 0;
  }
  if( got==(DWORD)amt ){
    return SQLITE_OK;
  }else{
    return SQLITE_IOERR;
  }
#endif
#if OS_MAC
  int got;
  SimulateIOError(SQLITE_IOERR);
  TRACE2("READ %d\n", last_page);
# ifdef _LARGE_FILE
  FSReadFork(id->refNum, fsAtMark, 0, (ByteCount)amt, pBuf, (ByteCount*)&got);
# else
  got = amt;
  FSRead(id->refNum, &got, pBuf);
# endif
  if( got==amt ){
    return SQLITE_OK;
  }else{
    return SQLITE_IOERR;
  }
#endif
}

/*
** Write data from a buffer into a file.  Return SQLITE_OK on success
** or some other error code on failure.
*/
int sqliteOsWrite(OsFile *id, const void *pBuf, int amt){
#if OS_UNIX
  int wrote = 0;
  SimulateIOError(SQLITE_IOERR);
  TIMER_START;
  while( amt>0 && (wrote = write(id->fd, pBuf, amt))>0 ){
    amt -= wrote;
    pBuf = &((char*)pBuf)[wrote];
  }
  TIMER_END;
  TRACE4("WRITE   %-3d %7d %d\n", id->fd, last_page, elapse);
  SEEK(0);
  if( amt>0 ){
    return SQLITE_FULL;
  }
  return SQLITE_OK;
#endif
#if OS_WIN
  int rc;
  DWORD wrote;
  SimulateIOError(SQLITE_IOERR);
  TRACE2("WRITE %d\n", last_page);
  while( amt>0 && (rc = WriteFile(id->h, pBuf, amt, &wrote, 0))!=0 && wrote>0 ){
    amt -= wrote;
    pBuf = &((char*)pBuf)[wrote];
  }
  if( !rc || amt>(int)wrote ){
    return SQLITE_FULL;
  }
  return SQLITE_OK;
#endif
#if OS_MAC
  OSErr oserr;
  int wrote = 0;
  SimulateIOError(SQLITE_IOERR);
  TRACE2("WRITE %d\n", last_page);
  while( amt>0 ){
# ifdef _LARGE_FILE
    oserr = FSWriteFork(id->refNum, fsAtMark, 0,
                        (ByteCount)amt, pBuf, (ByteCount*)&wrote);
# else
    wrote = amt;
    oserr = FSWrite(id->refNum, &wrote, pBuf);
# endif
    if( wrote == 0 || oserr != noErr)
      break;
    amt -= wrote;
    pBuf = &((char*)pBuf)[wrote];
  }
  if( oserr != noErr || amt>wrote ){
    return SQLITE_FULL;
  }
  return SQLITE_OK;
#endif
}

/*
** Move the read/write pointer in a file.
*/
int sqliteOsSeek(OsFile *id, off_t offset){
  SEEK(offset/1024 + 1);
#if OS_UNIX
  lseek(id->fd, offset, SEEK_SET);
  return SQLITE_OK;
#endif
#if OS_WIN
  {
    LONG upperBits = offset>>32;
    LONG lowerBits = offset & 0xffffffff;
    DWORD rc;
    rc = SetFilePointer(id->h, lowerBits, &upperBits, FILE_BEGIN);
    /* TRACE3("SEEK rc=0x%x upper=0x%x\n", rc, upperBits); */
  }
  return SQLITE_OK;
#endif
#if OS_MAC
  {
    off_t curSize;
    if( sqliteOsFileSize(id, &curSize) != SQLITE_OK ){
      return SQLITE_IOERR;
    }
    if( offset >= curSize ){
      if( sqliteOsTruncate(id, offset+1) != SQLITE_OK ){
        return SQLITE_IOERR;
      }
    }
# ifdef _LARGE_FILE
    if( FSSetForkPosition(id->refNum, fsFromStart, offset) != noErr ){
# else
    if( SetFPos(id->refNum, fsFromStart, offset) != noErr ){
# endif
      return SQLITE_IOERR;
    }else{
      return SQLITE_OK;
    }
  }
#endif
}

/*
** Make sure all writes to a particular file are committed to disk.
**
** Under Unix, also make sure that the directory entry for the file
** has been created by fsync-ing the directory that contains the file.
** If we do not do this and we encounter a power failure, the directory
** entry for the journal might not exist after we reboot.  The next
** SQLite to access the file will not know that the journal exists (because
** the directory entry for the journal was never created) and the transaction
** will not roll back - possibly leading to database corruption.
*/
int sqliteOsSync(OsFile *id){
#if OS_UNIX
  SimulateIOError(SQLITE_IOERR);
  TRACE2("SYNC    %-3d\n", id->fd);
  if( fsync(id->fd) ){
    return SQLITE_IOERR;
  }else{
    if( id->dirfd>=0 ){
      TRACE2("DIRSYNC %-3d\n", id->dirfd);
      fsync(id->dirfd);
      close(id->dirfd);  /* Only need to sync once, so close the directory */
      id->dirfd = -1;    /* when we are done. */
    }
    return SQLITE_OK;
  }
#endif
#if OS_WIN
  if( FlushFileBuffers(id->h) ){
    return SQLITE_OK;
  }else{
    return SQLITE_IOERR;
  }
#endif
#if OS_MAC
# ifdef _LARGE_FILE
  if( FSFlushFork(id->refNum) != noErr ){
# else
  ParamBlockRec params;
  memset(&params, 0, sizeof(ParamBlockRec));
  params.ioParam.ioRefNum = id->refNum;
  if( PBFlushFileSync(&params) != noErr ){
# endif
    return SQLITE_IOERR;
  }else{
    return SQLITE_OK;
  }
#endif
}

/*
** Truncate an open file to a specified size
*/
int sqliteOsTruncate(OsFile *id, off_t nByte){
  SimulateIOError(SQLITE_IOERR);
#if OS_UNIX
  return ftruncate(id->fd, nByte)==0 ? SQLITE_OK : SQLITE_IOERR;
#endif
#if OS_WIN
  {
    LONG upperBits = nByte>>32;
    SetFilePointer(id->h, nByte, &upperBits, FILE_BEGIN);
    SetEndOfFile(id->h);
  }
  return SQLITE_OK;
#endif
#if OS_MAC
# ifdef _LARGE_FILE
  if( FSSetForkSize(id->refNum, fsFromStart, nByte) != noErr){
# else
  if( SetEOF(id->refNum, nByte) != noErr ){
# endif
    return SQLITE_IOERR;
  }else{
    return SQLITE_OK;
  }
#endif
}

/*
** Determine the current size of a file in bytes
*/
int sqliteOsFileSize(OsFile *id, off_t *pSize){
#if OS_UNIX
  struct stat buf;
  SimulateIOError(SQLITE_IOERR);
  if( fstat(id->fd, &buf)!=0 ){
    return SQLITE_IOERR;
  }
  *pSize = buf.st_size;
  return SQLITE_OK;
#endif
#if OS_WIN
  DWORD upperBits, lowerBits;
  SimulateIOError(SQLITE_IOERR);
  lowerBits = GetFileSize(id->h, &upperBits);
  *pSize = (((off_t)upperBits)<<32) + lowerBits;
  return SQLITE_OK;
#endif
#if OS_MAC
# ifdef _LARGE_FILE
  if( FSGetForkSize(id->refNum, pSize) != noErr){
# else
  if( GetEOF(id->refNum, pSize) != noErr ){
# endif
    return SQLITE_IOERR;
  }else{
    return SQLITE_OK;
  }
#endif
}

#if OS_WIN
/*
** Return true (non-zero) if we are running under WinNT, Win2K or WinXP.
** Return false (zero) for Win95, Win98, or WinME.
**
** Here is an interesting observation:  Win95, Win98, and WinME lack
** the LockFileEx() API.  But we can still statically link against that
** API as long as we don't call it win running Win95/98/ME.  A call to
** this routine is used to determine if the host is Win95/98/ME or
** WinNT/2K/XP so that we will know whether or not we can safely call
** the LockFileEx() API.
*/
int isNT(void){
  static osType = 0;   /* 0=unknown 1=win95 2=winNT */
  if( osType==0 ){
    OSVERSIONINFO sInfo;
    sInfo.dwOSVersionInfoSize = sizeof(sInfo);
    GetVersionEx(&sInfo);
    osType = sInfo.dwPlatformId==VER_PLATFORM_WIN32_NT ? 2 : 1;
  }
  return osType==2;
}
#endif

/*
** Windows file locking notes:  [similar issues apply to MacOS]
**
** We cannot use LockFileEx() or UnlockFileEx() on Win95/98/ME because
** those functions are not available.  So we use only LockFile() and
** UnlockFile().
**
** LockFile() prevents not just writing but also reading by other processes.
** (This is a design error on the part of Windows, but there is nothing
** we can do about that.)  So the region used for locking is at the
** end of the file where it is unlikely to ever interfere with an
** actual read attempt.
**
** A database read lock is obtained by locking a single randomly-chosen 
** byte out of a specific range of bytes. The lock byte is obtained at 
** random so two separate readers can probably access the file at the 
** same time, unless they are unlucky and choose the same lock byte.