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Overview
Comment:Fix a race condition in the locking code that would sometimes cause SQLITE_PROTOCOL or SQLITE_CORRUPT to be returned when SQLITE_BUSY should have been returned. (CVS 326)
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SHA1: b0d218876442187af08161d989e6887b1cb4130c
User & Date: drh 2001-12-14 15:09:56.000
Context
2001-12-14
15:15
Version 2.1.6 (CVS 455) (check-in: 6ecd90b6c3 user: drh tags: trunk)
15:09
Fix a race condition in the locking code that would sometimes cause SQLITE_PROTOCOL or SQLITE_CORRUPT to be returned when SQLITE_BUSY should have been returned. (CVS 326) (check-in: b0d2188764 user: drh tags: trunk)
2001-12-06
13:30
Version 2.1.5 (CVS 456) (check-in: 8e90ad552f user: drh tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to VERSION.
1
2.1.5
|
1
2.1.6
Changes to src/btree.c.
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/*
** 2001 September 15
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.42 2001/12/05 00:21:20 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
**
**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
**     "Sorting And Searching", pages 473-480. Addison-Wesley
**     Publishing Company, Reading, Massachusetts.











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/*
** 2001 September 15
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.43 2001/12/14 15:09:57 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
**
**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
**     "Sorting And Searching", pages 473-480. Addison-Wesley
**     Publishing Company, Reading, Massachusetts.
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      amt -= a;
      zBuf += a;
    }else{
      offset -= OVERFLOW_SIZE;
    }
    sqlitepager_unref(pOvfl);
  }

  return amt==0 ? SQLITE_OK : SQLITE_CORRUPT;


}

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







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      amt -= a;
      zBuf += a;
    }else{
      offset -= OVERFLOW_SIZE;
    }
    sqlitepager_unref(pOvfl);
  }
  if( amt>0 ){
    return SQLITE_CORRUPT;
  }
  return SQLITE_OK;
}

/*
** Read part of the key associated with cursor pCur.  A maximum
** of "amt" bytes will be transfered into zBuf[].  The transfer
** begins at "offset".  The number of bytes actually read is
** returned.  The amount returned will be smaller than the
Changes to src/os.c.
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** An instance of the following structure is allocated for each inode.
** A single inode can have multiple file descriptors, so each OsFile
** structure contains a pointer to an instance of this object and this
** object keeps a count of the number of OsFiles pointing to it.
*/
struct lockInfo {
  struct inodeKey key;  /* The lookup key */
  int cnt;              /* 0: unlocked.  -1: write lock.  >=1: read lock */
  int nRef;             /* Number of pointers to this structure */
};

/* 
** This hash table maps inodes (in the form of inodeKey structures) into
** pointers to lockInfo structures.
*/







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** An instance of the following structure is allocated for each inode.
** A single inode can have multiple file descriptors, so each OsFile
** structure contains a pointer to an instance of this object and this
** object keeps a count of the number of OsFiles pointing to it.
*/
struct lockInfo {
  struct inodeKey key;  /* The lookup key */
  int cnt;              /* 0: unlocked.  -1: write lock.  1...: read lock. */
  int nRef;             /* Number of pointers to this structure */
};

/* 
** This hash table maps inodes (in the form of inodeKey structures) into
** pointers to lockInfo structures.
*/
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/*
** Attempt to open a file for both reading and writing.  If that
** fails, try opening it read-only.  If the file does not exist,
** try to create it.
**
** On success, a handle for the open file is written to *pResult
** and *pReadonly is set to 0 if the file was opened for reading and
** writing or 1 if the file was opened read-only.  The function returns
** SQLITE_OK.
**
** On failure, the function returns SQLITE_CANTOPEN and leaves
** *pResulst and *pReadonly unchanged.
*/
int sqliteOsOpenReadWrite(
  const char *zFilename,
  OsFile *pResult,
  int *pReadonly
){
#if OS_UNIX
  OsFile s;
  s.fd = open(zFilename, O_RDWR|O_CREAT, 0644);
  if( s.fd<0 ){
    s.fd = open(zFilename, O_RDONLY);
    if( s.fd<0 ){
      return SQLITE_CANTOPEN; 
    }
    *pReadonly = 1;
  }else{
    *pReadonly = 0;
  }
  sqliteOsEnterMutex();
  s.pLock = findLockInfo(s.fd);
  sqliteOsLeaveMutex();
  if( s.pLock==0 ){
    close(s.fd);
    return SQLITE_NOMEM;
  }
  *pResult = s;
  return SQLITE_OK;
#endif
#if OS_WIN
  HANDLE h = CreateFile(zFilename,
     GENERIC_READ | GENERIC_WRITE,
     FILE_SHARE_READ | FILE_SHARE_WRITE,
     NULL,







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/*
** Attempt to open a file for both reading and writing.  If that
** fails, try opening it read-only.  If the file does not exist,
** try to create it.
**
** On success, a handle for the open file is written to *id
** and *pReadonly is set to 0 if the file was opened for reading and
** writing or 1 if the file was opened read-only.  The function returns
** SQLITE_OK.
**
** On failure, the function returns SQLITE_CANTOPEN and leaves
** *pResulst and *pReadonly unchanged.
*/
int sqliteOsOpenReadWrite(
  const char *zFilename,
  OsFile *id,
  int *pReadonly
){
#if OS_UNIX

  id->fd = open(zFilename, O_RDWR|O_CREAT, 0644);
  if( id->fd<0 ){
    id->fd = open(zFilename, O_RDONLY);
    if( id->fd<0 ){
      return SQLITE_CANTOPEN; 
    }
    *pReadonly = 1;
  }else{
    *pReadonly = 0;
  }
  sqliteOsEnterMutex();
  id->pLock = findLockInfo(id->fd);
  sqliteOsLeaveMutex();
  if( id->pLock==0 ){
    close(id->fd);
    return SQLITE_NOMEM;
  }
  id->locked = 0;
  return SQLITE_OK;
#endif
#if OS_WIN
  HANDLE h = CreateFile(zFilename,
     GENERIC_READ | GENERIC_WRITE,
     FILE_SHARE_READ | FILE_SHARE_WRITE,
     NULL,
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    if( h==INVALID_HANDLE_VALUE ){
      return SQLITE_CANTOPEN;
    }
    *pReadonly = 1;
  }else{
    *pReadonly = 0;
  }
  *pResult = h;

  return SQLITE_OK;
#endif
}


/*
** Attempt to open a new file for exclusive access by this process.
** The file will be opened for both reading and writing.  To avoid
** a potential security problem, we do not allow the file to have
** previously existed.  Nor do we allow the file to be a symbolic
** link.
**
** On success, write the file handle into *pResult and return SQLITE_OK.
**
** On failure, return SQLITE_CANTOPEN.
*/
int sqliteOsOpenExclusive(const char *zFilename, OsFile *pResult){
#if OS_UNIX
  OsFile s;
  if( access(zFilename, 0)==0 ){
    return SQLITE_CANTOPEN;
  }
#ifndef O_NOFOLLOW
# define O_NOFOLLOW 0
#endif
  s.fd = open(zFilename, O_RDWR|O_CREAT|O_EXCL|O_NOFOLLOW, 0600);
  if( s.fd<0 ){
    return SQLITE_CANTOPEN;
  }
  sqliteOsEnterMutex();
  s.pLock = findLockInfo(s.fd);
  sqliteOsLeaveMutex();
  if( s.pLock==0 ){
    close(s.fd);
    unlink(zFilename);
    return SQLITE_NOMEM;
  }
  *pResult = s;
  return SQLITE_OK;
#endif
#if OS_WIN
  HANDLE h = CreateFile(zFilename,
     GENERIC_READ | GENERIC_WRITE,
     0,
     NULL,
     CREATE_ALWAYS,
     FILE_ATTRIBUTE_NORMAL | FILE_FLAG_RANDOM_ACCESS,
     NULL
  );
  if( h==INVALID_HANDLE_VALUE ){
    return SQLITE_CANTOPEN;
  }
  *pResult = h;

  return SQLITE_OK;
#endif
}

/*
** Attempt to open a new file for read-only access.
**
** On success, write the file handle into *pResult and return SQLITE_OK.
**
** On failure, return SQLITE_CANTOPEN.
*/
int sqliteOsOpenReadOnly(const char *zFilename, OsFile *pResult){
#if OS_UNIX
  OsFile s;
  s.fd = open(zFilename, O_RDONLY);
  if( s.fd<0 ){
    return SQLITE_CANTOPEN;
  }
  sqliteOsEnterMutex();
  s.pLock = findLockInfo(s.fd);
  sqliteOsLeaveMutex();
  if( s.pLock==0 ){
    close(s.fd);
    return SQLITE_NOMEM;
  }
  *pResult = s;
  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;
  }
  *pResult = h;

  return SQLITE_OK;
#endif
}

/*
** Create a temporary file name in zBuf.  zBuf must be big enough to
** hold at least SQLITE_TEMPNAME_SIZE characters.







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    if( h==INVALID_HANDLE_VALUE ){
      return SQLITE_CANTOPEN;
    }
    *pReadonly = 1;
  }else{
    *pReadonly = 0;
  }
  id->h = h;
  id->locked = 0;
  return SQLITE_OK;
#endif
}


/*
** Attempt to open a new file for exclusive access by this process.
** The file will be opened for both reading and writing.  To avoid
** a potential security problem, we do not allow the file to have
** previously existed.  Nor do we allow the file to be a symbolic
** link.
**
** On success, write the file handle into *id and return SQLITE_OK.
**
** On failure, return SQLITE_CANTOPEN.
*/
int sqliteOsOpenExclusive(const char *zFilename, OsFile *id){
#if OS_UNIX

  if( access(zFilename, 0)==0 ){
    return SQLITE_CANTOPEN;
  }
#ifndef O_NOFOLLOW
# define O_NOFOLLOW 0
#endif
  id->fd = open(zFilename, O_RDWR|O_CREAT|O_EXCL|O_NOFOLLOW, 0600);
  if( id->fd<0 ){
    return SQLITE_CANTOPEN;
  }
  sqliteOsEnterMutex();
  id->pLock = findLockInfo(id->fd);
  sqliteOsLeaveMutex();
  if( id->pLock==0 ){
    close(id->fd);
    unlink(zFilename);
    return SQLITE_NOMEM;
  }
  id->locked = 0;
  return SQLITE_OK;
#endif
#if OS_WIN
  HANDLE h = CreateFile(zFilename,
     GENERIC_READ | GENERIC_WRITE,
     0,
     NULL,
     CREATE_ALWAYS,
     FILE_ATTRIBUTE_NORMAL | FILE_FLAG_RANDOM_ACCESS,
     NULL
  );
  if( h==INVALID_HANDLE_VALUE ){
    return SQLITE_CANTOPEN;
  }
  id->h = h;
  id->locked = 0;
  return SQLITE_OK;
#endif
}

/*
** Attempt to open a new file for read-only access.
**
** On success, write the file handle into *id and return SQLITE_OK.
**
** On failure, return SQLITE_CANTOPEN.
*/
int sqliteOsOpenReadOnly(const char *zFilename, OsFile *id){
#if OS_UNIX

  id->fd = open(zFilename, O_RDONLY);
  if( id->fd<0 ){
    return SQLITE_CANTOPEN;
  }
  sqliteOsEnterMutex();
  id->pLock = findLockInfo(id->fd);
  sqliteOsLeaveMutex();
  if( id->pLock==0 ){
    close(id->fd);
    return SQLITE_NOMEM;
  }
  id->locked = 0;
  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;
  return SQLITE_OK;
#endif
}

/*
** Create a temporary file name in zBuf.  zBuf must be big enough to
** hold at least SQLITE_TEMPNAME_SIZE characters.
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#endif
  return SQLITE_OK; 
}

/*
** Close a file
*/
int sqliteOsClose(OsFile id){
#if OS_UNIX
  close(id.fd);
  sqliteOsEnterMutex();
  releaseLockInfo(id.pLock);
  sqliteOsLeaveMutex();
  return SQLITE_OK;
#endif
#if OS_WIN
  CloseHandle(id);
  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);
  got = read(id.fd, pBuf, amt);
  if( got<0 ) got = 0;
  return got==amt ? SQLITE_OK : SQLITE_IOERR;
#endif
#if OS_WIN
  DWORD got;
  SimulateIOError(SQLITE_IOERR);
  if( !ReadFile(id, pBuf, amt, &got, 0) ){
    got = 0;
  }
  return got==amt ? SQLITE_OK : 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;
  SimulateIOError(SQLITE_IOERR);
  wrote = write(id.fd, pBuf, amt);
  if( wrote<amt ) return SQLITE_FULL;
  return SQLITE_OK;
#endif
#if OS_WIN
  DWORD wrote;
  SimulateIOError(SQLITE_IOERR);
  if( !WriteFile(id, pBuf, amt, &wrote, 0) || wrote<amt ){
    return SQLITE_FULL;
  }
  return SQLITE_OK;
#endif
}

/*
** Move the read/write pointer in a file.
*/
int sqliteOsSeek(OsFile id, int offset){
#if OS_UNIX
  lseek(id.fd, offset, SEEK_SET);
  return SQLITE_OK;
#endif
#if OS_WIN
  SetFilePointer(id, offset, 0, FILE_BEGIN);
  return SQLITE_OK;
#endif
}

/*
** Make sure all writes to a particular file are committed to disk.
*/
int sqliteOsSync(OsFile id){
  SimulateIOError(SQLITE_IOERR);
#if OS_UNIX
  return fsync(id.fd)==0 ? SQLITE_OK : SQLITE_IOERR;
#endif
#if OS_WIN
  return FlushFileBuffers(id) ? SQLITE_OK : SQLITE_IOERR;
#endif
}

/*
** Truncate an open file to a specified size
*/
int sqliteOsTruncate(OsFile id, int nByte){
  SimulateIOError(SQLITE_IOERR);
#if OS_UNIX
  return ftruncate(id.fd, nByte)==0 ? SQLITE_OK : SQLITE_IOERR;
#endif
#if OS_WIN
  SetFilePointer(id, nByte, 0, FILE_BEGIN);
  SetEndOfFile(id);
  return SQLITE_OK;
#endif
}

/*
** Determine the current size of a file in bytes
*/
int sqliteOsFileSize(OsFile id, int *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
  SimulateIOError(SQLITE_IOERR);
  *pSize = GetFileSize(id, 0);
  return SQLITE_OK;
#endif
}


/*

** Get a read or write lock on a file.



*/
int sqliteOsLock(OsFile id, int wrlock){
#if OS_UNIX



























  int rc;
  int needSysLock;
  sqliteOsEnterMutex();
  if( wrlock ){
    if( id.pLock->cnt!=0 ){
      rc = SQLITE_BUSY;
    }else{
      rc = SQLITE_OK;
      id.pLock->cnt = -1;
      needSysLock = 1;
    }
  }else{
    if( id.pLock->cnt<0 ){
      rc = SQLITE_BUSY;
    }else{

      rc = SQLITE_OK;
      needSysLock = id.pLock->cnt==0;
      id.pLock->cnt++;

    }
  }


  if( rc==SQLITE_OK && needSysLock ){ 






    struct flock lock;
    lock.l_type = wrlock ? F_WRLCK : F_RDLCK;
    lock.l_whence = SEEK_SET;
    lock.l_start = lock.l_len = 0L;
    rc = fcntl(id.fd, F_SETLK, &lock)==0 ? SQLITE_OK : SQLITE_BUSY;


    if( rc ){
      id.pLock->cnt = 0;

    }


  }
  sqliteOsLeaveMutex();      
  return rc;
#endif
#if OS_WIN



  if( !LockFile(id, 0, 0, 1024, 0) ){



    return SQLITE_BUSY;
  }
  return SQLITE_OK;
#endif
}

/*
** Release the read or write lock from a file.

*/
int sqliteOsUnlock(OsFile id){
#if OS_UNIX
  int rc;
  int needSysUnlock;

  sqliteOsEnterMutex();
  if( id.pLock->cnt<0 ){
    needSysUnlock = 1;
    id.pLock->cnt = 0;
  }else if( id.pLock->cnt>0 ){
    id.pLock->cnt--;
    needSysUnlock = id.pLock->cnt==0;
  }else{
    rc = SQLITE_OK;
    needSysUnlock = 0;
  }
  if( needSysUnlock ){
    struct flock lock;
    lock.l_type = F_UNLCK;
    lock.l_whence = SEEK_SET;
    lock.l_start = lock.l_len = 0L;
    rc = fcntl(id.fd, F_SETLK, &lock)==0 ? SQLITE_OK : SQLITE_IOERR;




  }

  sqliteOsLeaveMutex();

  return rc;
#endif
#if OS_WIN



  return UnlockFile(id, 0, 0, 1024, 0) ? SQLITE_OK : SQLITE_IOERR;






#endif
}

/*
** Get information to seed the random number generator.
*/
int sqliteOsRandomSeed(char *zBuf){







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#endif
  return SQLITE_OK; 
}

/*
** Close a file
*/
int sqliteOsClose(OsFile *id){
#if OS_UNIX
  close(id->fd);
  sqliteOsEnterMutex();
  releaseLockInfo(id->pLock);
  sqliteOsLeaveMutex();
  return SQLITE_OK;
#endif
#if OS_WIN
  CloseHandle(id->h);
  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);
  got = read(id->fd, pBuf, amt);
  if( got<0 ) got = 0;
  return got==amt ? SQLITE_OK : SQLITE_IOERR;
#endif
#if OS_WIN
  DWORD got;
  SimulateIOError(SQLITE_IOERR);
  if( !ReadFile(id->h, pBuf, amt, &got, 0) ){
    got = 0;
  }
  return got==amt ? SQLITE_OK : 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;
  SimulateIOError(SQLITE_IOERR);
  wrote = write(id->fd, pBuf, amt);
  if( wrote<amt ) return SQLITE_FULL;
  return SQLITE_OK;
#endif
#if OS_WIN
  DWORD wrote;
  SimulateIOError(SQLITE_IOERR);
  if( !WriteFile(id->h, pBuf, amt, &wrote, 0) || wrote<amt ){
    return SQLITE_FULL;
  }
  return SQLITE_OK;
#endif
}

/*
** Move the read/write pointer in a file.
*/
int sqliteOsSeek(OsFile *id, int offset){
#if OS_UNIX
  lseek(id->fd, offset, SEEK_SET);
  return SQLITE_OK;
#endif
#if OS_WIN
  SetFilePointer(id->h, offset, 0, FILE_BEGIN);
  return SQLITE_OK;
#endif
}

/*
** Make sure all writes to a particular file are committed to disk.
*/
int sqliteOsSync(OsFile *id){
  SimulateIOError(SQLITE_IOERR);
#if OS_UNIX
  return fsync(id->fd)==0 ? SQLITE_OK : SQLITE_IOERR;
#endif
#if OS_WIN
  return FlushFileBuffers(id->h) ? SQLITE_OK : SQLITE_IOERR;
#endif
}

/*
** Truncate an open file to a specified size
*/
int sqliteOsTruncate(OsFile *id, int nByte){
  SimulateIOError(SQLITE_IOERR);
#if OS_UNIX
  return ftruncate(id->fd, nByte)==0 ? SQLITE_OK : SQLITE_IOERR;
#endif
#if OS_WIN
  SetFilePointer(id->h, nByte, 0, FILE_BEGIN);
  SetEndOfFile(id->h);
  return SQLITE_OK;
#endif
}

/*
** Determine the current size of a file in bytes
*/
int sqliteOsFileSize(OsFile *id, int *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
  SimulateIOError(SQLITE_IOERR);
  *pSize = GetFileSize(id->h, 0);
  return SQLITE_OK;
#endif
}


/*
** Change the status of the lock on the file "id" to be a readlock.
** If the file was write locked, then this reduces the lock to a read.
** If the file was read locked, then this acquires a new read lock.
**
** Return SQLITE_OK on success and SQLITE_BUSY on failure.
*/
int sqliteOsReadLock(OsFile *id){
#if OS_UNIX
  int rc;
  sqliteOsEnterMutex();
  if( id->pLock->cnt>0 ){
    if( !id->locked ){
      id->pLock->cnt++;
      id->locked = 1;
    }
    rc = SQLITE_OK;
  }else if( id->locked || id->pLock->cnt==0 ){
    struct flock lock;
    lock.l_type = F_RDLCK;
    lock.l_whence = SEEK_SET;
    lock.l_start = lock.l_len = 0L;
    if( fcntl(id->fd, F_SETLK, &lock)!=0 ){
      rc = SQLITE_BUSY;
    }else{
      rc = SQLITE_OK;
      id->pLock->cnt = 1;
      id->locked = 1;
    }
  }else{
    rc = SQLITE_BUSY;
  }
  sqliteOsLeaveMutex();
  return rc;
#endif
#if OS_WIN
  int rc;



  if( id->locked ){
    rc = SQLITE_OK;
  }else if( LockFile(id->h, 0, 0, 1024, 0) ){
    rc = SQLITE_OK;

    id->locked = 1;

  }else{

    rc = SQLITE_BUSY;

  }
  return rc;


#endif
}

/*
** Change the lock status to be an exclusive or write lock.  Return
** SQLITE_OK on success and SQLITE_BUSY on a failure.
*/
int sqliteOsWriteLock(OsFile *id){
#if OS_UNIX
  int rc;
  sqliteOsEnterMutex();
  if( id->pLock->cnt==0 || (id->pLock->cnt==1 && id->locked==1) ){
    struct flock lock;
    lock.l_type = F_WRLCK;
    lock.l_whence = SEEK_SET;
    lock.l_start = lock.l_len = 0L;
    if( fcntl(id->fd, F_SETLK, &lock)!=0 ){
      rc = SQLITE_BUSY;
    }else{
      rc = SQLITE_OK;
      id->pLock->cnt = -1;
      id->locked = 1;
    }
  }else{
    rc = SQLITE_BUSY;
  }
  sqliteOsLeaveMutex();
  return rc;
#endif
#if OS_WIN
  int rc;
  if( id->locked ){
    rc = SQLITE_OK;
  }else if( LockFile(id->h, 0, 0, 1024, 0) ){
    rc = SQLITE_OK;
    id->locked = 1;
  }else{
    rc = SQLITE_BUSY;
  }
  return rc;
#endif
}

/*
** Unlock the given file descriptor.  If the file descriptor was
** not previously locked, then this routine is a no-op.
*/
int sqliteOsUnlock(OsFile *id){
#if OS_UNIX
  int rc;

  if( !id->locked ) return SQLITE_OK;
  sqliteOsEnterMutex();
  assert( id->pLock->cnt!=0 );

  if( id->pLock->cnt>1 ){

    id->pLock->cnt--;


    rc = SQLITE_OK;

  }else{

    struct flock lock;
    lock.l_type = F_UNLCK;
    lock.l_whence = SEEK_SET;
    lock.l_start = lock.l_len = 0L;
    if( fcntl(id->fd, F_SETLK, &lock)!=0 ){
      rc = SQLITE_BUSY;
    }else{
      rc = SQLITE_OK;
      id->pLock->cnt = 0;
    }
  }
  sqliteOsLeaveMutex();
  id->locked = 0;
  return rc;
#endif
#if OS_WIN
  int rc;
  if( !id->locked ){
    rc = SQLITE_OK;
  }else if( UnlockFile(id->h, 0, 0, 1024, 0) ){
    rc = SQLITE_OK;
    id->locked = 0;
  }else{
    rc = SQLITE_BUSY;
  }
  return rc;
#endif
}

/*
** Get information to seed the random number generator.
*/
int sqliteOsRandomSeed(char *zBuf){
Changes to src/os.h.
21
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** A handle for an open file is stored in an OsFile object.
*/
#if OS_UNIX
  typedef struct OsFile OsFile;
  struct OsFile {
    struct lockInfo *pLock;  /* Information about locks on this inode */
    int fd;                  /* The file descriptor */

  };
# define SQLITE_TEMPNAME_SIZE 200
# if defined(HAVE_USLEEP) && HAVE_USLEEP
#  define SQLITE_MIN_SLEEP_MS 1
# else
#  define SQLITE_MIN_SLEEP_MS 1000
# endif
#endif

#if OS_WIN
#include <windows.h>
#include <winbase.h>


  typedef HANDLE OsFile;


# define SQLITE_TEMPNAME_SIZE (MAX_PATH+50)
# define SQLITE_MIN_SLEEP_MS 1
#endif

int sqliteOsDelete(const char*);
int sqliteOsFileExists(const char*);
int sqliteOsOpenReadWrite(const char*, OsFile*, int*);
int sqliteOsOpenExclusive(const char*, OsFile*);
int sqliteOsOpenReadOnly(const char*, OsFile*);
int sqliteOsTempFileName(char*);
int sqliteOsClose(OsFile);
int sqliteOsRead(OsFile, void*, int amt);
int sqliteOsWrite(OsFile, const void*, int amt);
int sqliteOsSeek(OsFile, int offset);
int sqliteOsSync(OsFile);
int sqliteOsTruncate(OsFile, int size);
int sqliteOsFileSize(OsFile, int *pSize);
int sqliteOsLock(OsFile, int wrlock);

int sqliteOsUnlock(OsFile);
int sqliteOsRandomSeed(char*);
int sqliteOsSleep(int ms);
void sqliteOsEnterMutex(void);
void sqliteOsLeaveMutex(void);










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** A handle for an open file is stored in an OsFile object.
*/
#if OS_UNIX
  typedef struct OsFile OsFile;
  struct OsFile {
    struct lockInfo *pLock;  /* Information about locks on this inode */
    int fd;                  /* The file descriptor */
    int locked;              /* True if this user holds the lock */
  };
# define SQLITE_TEMPNAME_SIZE 200
# if defined(HAVE_USLEEP) && HAVE_USLEEP
#  define SQLITE_MIN_SLEEP_MS 1
# else
#  define SQLITE_MIN_SLEEP_MS 1000
# endif
#endif

#if OS_WIN
#include <windows.h>
#include <winbase.h>
  typedef struct OsFile OsFile;
  struct OsFile {
    HANDLE h;
    int locked;
  };
# define SQLITE_TEMPNAME_SIZE (MAX_PATH+50)
# define SQLITE_MIN_SLEEP_MS 1
#endif

int sqliteOsDelete(const char*);
int sqliteOsFileExists(const char*);
int sqliteOsOpenReadWrite(const char*, OsFile*, int*);
int sqliteOsOpenExclusive(const char*, OsFile*);
int sqliteOsOpenReadOnly(const char*, OsFile*);
int sqliteOsTempFileName(char*);
int sqliteOsClose(OsFile*);
int sqliteOsRead(OsFile*, void*, int amt);
int sqliteOsWrite(OsFile*, const void*, int amt);
int sqliteOsSeek(OsFile*, int offset);
int sqliteOsSync(OsFile*);
int sqliteOsTruncate(OsFile*, int size);
int sqliteOsFileSize(OsFile*, int *pSize);
int sqliteOsReadLock(OsFile*);
int sqliteOsWriteLock(OsFile*);
int sqliteOsUnlock(OsFile*);
int sqliteOsRandomSeed(char*);
int sqliteOsSleep(int ms);
void sqliteOsEnterMutex(void);
void sqliteOsLeaveMutex(void);



Changes to src/pager.c.
14
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28
** The pager is used to access a database disk file.  It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file.  The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.32 2001/12/05 00:21:20 drh Exp $
*/
#include "sqliteInt.h"
#include "pager.h"
#include "os.h"
#include <assert.h>
#include <string.h>








|







14
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28
** The pager is used to access a database disk file.  It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file.  The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.33 2001/12/14 15:09:57 drh Exp $
*/
#include "sqliteInt.h"
#include "pager.h"
#include "os.h"
#include <assert.h>
#include <string.h>

214
215
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228
  pPager->pLast = 0;
  pPager->pAll = 0;
  memset(pPager->aHash, 0, sizeof(pPager->aHash));
  pPager->nPage = 0;
  if( pPager->state==SQLITE_WRITELOCK ){
    sqlitepager_rollback(pPager);
  }
  sqliteOsUnlock(pPager->fd);
  pPager->state = SQLITE_UNLOCK;
  pPager->dbSize = -1;
  pPager->nRef = 0;
  assert( pPager->journalOpen==0 );
}

/*







|







214
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228
  pPager->pLast = 0;
  pPager->pAll = 0;
  memset(pPager->aHash, 0, sizeof(pPager->aHash));
  pPager->nPage = 0;
  if( pPager->state==SQLITE_WRITELOCK ){
    sqlitepager_rollback(pPager);
  }
  sqliteOsUnlock(&pPager->fd);
  pPager->state = SQLITE_UNLOCK;
  pPager->dbSize = -1;
  pPager->nRef = 0;
  assert( pPager->journalOpen==0 );
}

/*
242
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253


254
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274
** is set in pPager->errMask, and this routine returns SQLITE_PROTOCOL.
** SQLITE_OK is returned on success.
*/
static int pager_unwritelock(Pager *pPager){
  int rc;
  PgHdr *pPg;
  if( pPager->state!=SQLITE_WRITELOCK ) return SQLITE_OK;
  sqliteOsUnlock(pPager->fd);
  rc = sqliteOsLock(pPager->fd, 0);
  sqliteOsClose(pPager->jfd);
  pPager->journalOpen = 0;
  sqliteOsDelete(pPager->zJournal);


  sqliteFree( pPager->aInJournal );
  pPager->aInJournal = 0;
  for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
    pPg->inJournal = 0;
    pPg->dirty = 0;
  }
  if( rc!=SQLITE_OK ){
    pPager->state = SQLITE_UNLOCK;
    rc = SQLITE_PROTOCOL;
    pPager->errMask |= PAGER_ERR_LOCK;
  }else{
    rc = SQLITE_OK;
    pPager->state = SQLITE_READLOCK;
  }
  return rc;
}

/*
** Playback the journal and thus restore the database file to
** the state it was in before we started making changes.  
**







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249
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260

261
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267
** is set in pPager->errMask, and this routine returns SQLITE_PROTOCOL.
** SQLITE_OK is returned on success.
*/
static int pager_unwritelock(Pager *pPager){
  int rc;
  PgHdr *pPg;
  if( pPager->state!=SQLITE_WRITELOCK ) return SQLITE_OK;


  sqliteOsClose(&pPager->jfd);
  pPager->journalOpen = 0;
  sqliteOsDelete(pPager->zJournal);
  rc = sqliteOsReadLock(&pPager->fd);
  assert( rc==SQLITE_OK );
  sqliteFree( pPager->aInJournal );
  pPager->aInJournal = 0;
  for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
    pPg->inJournal = 0;
    pPg->dirty = 0;
  }






  pPager->state = SQLITE_READLOCK;

  return rc;
}

/*
** Playback the journal and thus restore the database file to
** the state it was in before we started making changes.  
**
300
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  unsigned char aMagic[sizeof(aJournalMagic)];
  int rc;

  /* Figure out how many records are in the journal.  Abort early if
  ** the journal is empty.
  */
  assert( pPager->journalOpen );
  sqliteOsSeek(pPager->jfd, 0);
  rc = sqliteOsFileSize(pPager->jfd, &nRec);
  if( rc!=SQLITE_OK ){
    goto end_playback;
  }
  nRec = (nRec - (sizeof(aMagic)+sizeof(Pgno))) / sizeof(PageRecord);
  if( nRec<=0 ){
    goto end_playback;
  }

  /* Read the beginning of the journal and truncate the
  ** database file back to its original size.
  */
  rc = sqliteOsRead(pPager->jfd, aMagic, sizeof(aMagic));
  if( rc!=SQLITE_OK || memcmp(aMagic,aJournalMagic,sizeof(aMagic))!=0 ){
    rc = SQLITE_PROTOCOL;
    goto end_playback;
  }
  rc = sqliteOsRead(pPager->jfd, &mxPg, sizeof(mxPg));
  if( rc!=SQLITE_OK ){
    goto end_playback;
  }
  rc = sqliteOsTruncate(pPager->fd, mxPg*SQLITE_PAGE_SIZE);
  if( rc!=SQLITE_OK ){
    goto end_playback;
  }
  pPager->dbSize = mxPg;
  
  /* Process segments beginning with the last and working backwards
  ** to the first.
  */
  for(i=nRec-1; i>=0; i--){
    /* Seek to the beginning of the segment */
    int ofst;
    ofst = i*sizeof(PageRecord) + sizeof(aMagic) + sizeof(Pgno);
    rc = sqliteOsSeek(pPager->jfd, ofst);
    if( rc!=SQLITE_OK ) break;
    rc = sqliteOsRead(pPager->jfd, &pgRec, sizeof(pgRec));
    if( rc!=SQLITE_OK ) break;

    /* Sanity checking on the page */
    if( pgRec.pgno>mxPg || pgRec.pgno==0 ){
      rc = SQLITE_CORRUPT;
      break;
    }

    /* Playback the page.  Update the in-memory copy of the page
    ** at the same time, if there is one.
    */
    pPg = pager_lookup(pPager, pgRec.pgno);
    if( pPg ){
      memcpy(PGHDR_TO_DATA(pPg), pgRec.aData, SQLITE_PAGE_SIZE);
      memset(PGHDR_TO_EXTRA(pPg), 0, pPager->nExtra);
    }
    rc = sqliteOsSeek(pPager->fd, (pgRec.pgno-1)*SQLITE_PAGE_SIZE);
    if( rc!=SQLITE_OK ) break;
    rc = sqliteOsWrite(pPager->fd, pgRec.aData, SQLITE_PAGE_SIZE);
    if( rc!=SQLITE_OK ) break;
  }

end_playback:
  if( rc!=SQLITE_OK ){
    pager_unwritelock(pPager);
    pPager->errMask |= PAGER_ERR_CORRUPT;







|
|











|




|



|












|

|
















|

|







293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
  unsigned char aMagic[sizeof(aJournalMagic)];
  int rc;

  /* Figure out how many records are in the journal.  Abort early if
  ** the journal is empty.
  */
  assert( pPager->journalOpen );
  sqliteOsSeek(&pPager->jfd, 0);
  rc = sqliteOsFileSize(&pPager->jfd, &nRec);
  if( rc!=SQLITE_OK ){
    goto end_playback;
  }
  nRec = (nRec - (sizeof(aMagic)+sizeof(Pgno))) / sizeof(PageRecord);
  if( nRec<=0 ){
    goto end_playback;
  }

  /* Read the beginning of the journal and truncate the
  ** database file back to its original size.
  */
  rc = sqliteOsRead(&pPager->jfd, aMagic, sizeof(aMagic));
  if( rc!=SQLITE_OK || memcmp(aMagic,aJournalMagic,sizeof(aMagic))!=0 ){
    rc = SQLITE_PROTOCOL;
    goto end_playback;
  }
  rc = sqliteOsRead(&pPager->jfd, &mxPg, sizeof(mxPg));
  if( rc!=SQLITE_OK ){
    goto end_playback;
  }
  rc = sqliteOsTruncate(&pPager->fd, mxPg*SQLITE_PAGE_SIZE);
  if( rc!=SQLITE_OK ){
    goto end_playback;
  }
  pPager->dbSize = mxPg;
  
  /* Process segments beginning with the last and working backwards
  ** to the first.
  */
  for(i=nRec-1; i>=0; i--){
    /* Seek to the beginning of the segment */
    int ofst;
    ofst = i*sizeof(PageRecord) + sizeof(aMagic) + sizeof(Pgno);
    rc = sqliteOsSeek(&pPager->jfd, ofst);
    if( rc!=SQLITE_OK ) break;
    rc = sqliteOsRead(&pPager->jfd, &pgRec, sizeof(pgRec));
    if( rc!=SQLITE_OK ) break;

    /* Sanity checking on the page */
    if( pgRec.pgno>mxPg || pgRec.pgno==0 ){
      rc = SQLITE_CORRUPT;
      break;
    }

    /* Playback the page.  Update the in-memory copy of the page
    ** at the same time, if there is one.
    */
    pPg = pager_lookup(pPager, pgRec.pgno);
    if( pPg ){
      memcpy(PGHDR_TO_DATA(pPg), pgRec.aData, SQLITE_PAGE_SIZE);
      memset(PGHDR_TO_EXTRA(pPg), 0, pPager->nExtra);
    }
    rc = sqliteOsSeek(&pPager->fd, (pgRec.pgno-1)*SQLITE_PAGE_SIZE);
    if( rc!=SQLITE_OK ) break;
    rc = sqliteOsWrite(&pPager->fd, pgRec.aData, SQLITE_PAGE_SIZE);
    if( rc!=SQLITE_OK ) break;
  }

end_playback:
  if( rc!=SQLITE_OK ){
    pager_unwritelock(pPager);
    pPager->errMask |= PAGER_ERR_CORRUPT;
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
  }
  if( rc!=SQLITE_OK ){
    return SQLITE_CANTOPEN;
  }
  nameLen = strlen(zFilename);
  pPager = sqliteMalloc( sizeof(*pPager) + nameLen*2 + 30 );
  if( pPager==0 ){
    sqliteOsClose(fd);
    return SQLITE_NOMEM;
  }
  pPager->zFilename = (char*)&pPager[1];
  pPager->zJournal = &pPager->zFilename[nameLen+1];
  strcpy(pPager->zFilename, zFilename);
  strcpy(pPager->zJournal, zFilename);
  strcpy(&pPager->zJournal[nameLen], "-journal");







|







421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
  }
  if( rc!=SQLITE_OK ){
    return SQLITE_CANTOPEN;
  }
  nameLen = strlen(zFilename);
  pPager = sqliteMalloc( sizeof(*pPager) + nameLen*2 + 30 );
  if( pPager==0 ){
    sqliteOsClose(&fd);
    return SQLITE_NOMEM;
  }
  pPager->zFilename = (char*)&pPager[1];
  pPager->zJournal = &pPager->zFilename[nameLen+1];
  strcpy(pPager->zFilename, zFilename);
  strcpy(pPager->zJournal, zFilename);
  strcpy(&pPager->zJournal[nameLen], "-journal");
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
*/
int sqlitepager_pagecount(Pager *pPager){
  int n;
  assert( pPager!=0 );
  if( pPager->dbSize>=0 ){
    return pPager->dbSize;
  }
  if( sqliteOsFileSize(pPager->fd, &n)!=SQLITE_OK ){
    pPager->errMask |= PAGER_ERR_DISK;
    return 0;
  }
  n /= SQLITE_PAGE_SIZE;
  if( pPager->state!=SQLITE_UNLOCK ){
    pPager->dbSize = n;
  }







|







470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
*/
int sqlitepager_pagecount(Pager *pPager){
  int n;
  assert( pPager!=0 );
  if( pPager->dbSize>=0 ){
    return pPager->dbSize;
  }
  if( sqliteOsFileSize(&pPager->fd, &n)!=SQLITE_OK ){
    pPager->errMask |= PAGER_ERR_DISK;
    return 0;
  }
  n /= SQLITE_PAGE_SIZE;
  if( pPager->state!=SQLITE_UNLOCK ){
    pPager->dbSize = n;
  }
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
** result in a coredump.
*/
int sqlitepager_close(Pager *pPager){
  PgHdr *pPg, *pNext;
  switch( pPager->state ){
    case SQLITE_WRITELOCK: {
      sqlitepager_rollback(pPager);
      sqliteOsUnlock(pPager->fd);
      assert( pPager->journalOpen==0 );
      break;
    }
    case SQLITE_READLOCK: {
      sqliteOsUnlock(pPager->fd);
      break;
    }
    default: {
      /* Do nothing */
      break;
    }
  }
  for(pPg=pPager->pAll; pPg; pPg=pNext){
    pNext = pPg->pNextAll;
    sqliteFree(pPg);
  }
  sqliteOsClose(pPager->fd);
  assert( pPager->journalOpen==0 );
  if( pPager->tempFile ){
    sqliteOsDelete(pPager->zFilename);
  }
  sqliteFree(pPager);
  return SQLITE_OK;
}







|




|











|







495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
** result in a coredump.
*/
int sqlitepager_close(Pager *pPager){
  PgHdr *pPg, *pNext;
  switch( pPager->state ){
    case SQLITE_WRITELOCK: {
      sqlitepager_rollback(pPager);
      sqliteOsUnlock(&pPager->fd);
      assert( pPager->journalOpen==0 );
      break;
    }
    case SQLITE_READLOCK: {
      sqliteOsUnlock(&pPager->fd);
      break;
    }
    default: {
      /* Do nothing */
      break;
    }
  }
  for(pPg=pPager->pAll; pPg; pPg=pNext){
    pNext = pPg->pNextAll;
    sqliteFree(pPg);
  }
  sqliteOsClose(&pPager->fd);
  assert( pPager->journalOpen==0 );
  if( pPager->tempFile ){
    sqliteOsDelete(pPager->zFilename);
  }
  sqliteFree(pPager);
  return SQLITE_OK;
}
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
** of having to do another fsync() later on.  Writing dirty free pages
** in this way make database operations go up to 10 times faster.
*/
static int syncAllPages(Pager *pPager){
  PgHdr *pPg;
  int rc = SQLITE_OK;
  if( pPager->needSync ){
    rc = sqliteOsSync(pPager->jfd);
    if( rc!=0 ) return rc;
    pPager->needSync = 0;
  }
  for(pPg=pPager->pFirst; pPg; pPg=pPg->pNextFree){
    if( pPg->dirty ){
      sqliteOsSeek(pPager->fd, (pPg->pgno-1)*SQLITE_PAGE_SIZE);
      rc = sqliteOsWrite(pPager->fd, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE);
      if( rc!=SQLITE_OK ) break;
      pPg->dirty = 0;
    }
  }
  return rc;
}








|





|
|







579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
** of having to do another fsync() later on.  Writing dirty free pages
** in this way make database operations go up to 10 times faster.
*/
static int syncAllPages(Pager *pPager){
  PgHdr *pPg;
  int rc = SQLITE_OK;
  if( pPager->needSync ){
    rc = sqliteOsSync(&pPager->jfd);
    if( rc!=0 ) return rc;
    pPager->needSync = 0;
  }
  for(pPg=pPager->pFirst; pPg; pPg=pPg->pNextFree){
    if( pPg->dirty ){
      sqliteOsSeek(&pPager->fd, (pPg->pgno-1)*SQLITE_PAGE_SIZE);
      rc = sqliteOsWrite(&pPager->fd, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE);
      if( rc!=SQLITE_OK ) break;
      pPg->dirty = 0;
    }
  }
  return rc;
}

640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656











657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
    return pager_errcode(pPager);
  }

  /* If this is the first page accessed, then get a read lock
  ** on the database file.
  */
  if( pPager->nRef==0 ){
    if( sqliteOsLock(pPager->fd, 0)!=SQLITE_OK ){
      *ppPage = 0;
      return SQLITE_BUSY;
    }
    pPager->state = SQLITE_READLOCK;

    /* If a journal file exists, try to play it back.
    */
    if( sqliteOsFileExists(pPager->zJournal) ){
       int rc, dummy;












       /* Open the journal for exclusive access.  Return SQLITE_BUSY if
       ** we cannot get exclusive access to the journal file. 
       **
       ** Even though we will only be reading from the journal, not writing,
       ** we have to open the journal for writing in order to obtain an
       ** exclusive access lock.
       */
       rc = sqliteOsOpenReadWrite(pPager->zJournal, &pPager->jfd, &dummy);
       if( rc==SQLITE_OK ){
         pPager->journalOpen = 1;
       }
       if( rc!=SQLITE_OK || sqliteOsLock(pPager->jfd, 1)!=SQLITE_OK ){
         if( pPager->journalOpen ){
           sqliteOsClose(pPager->jfd);
           pPager->journalOpen = 0;
         }
         sqliteOsUnlock(pPager->fd);
         *ppPage = 0;
         return SQLITE_BUSY;
       }

       /* Get a write lock on the database */
       sqliteOsUnlock(pPager->fd);
       if( sqliteOsLock(pPager->fd, 1)!=SQLITE_OK ){
         sqliteOsClose(pPager->jfd);
         pPager->journalOpen = 0;
         *ppPage = 0;
         return SQLITE_PROTOCOL;
       }
       pPager->state = SQLITE_WRITELOCK;

       /* Playback and delete the journal.  Drop the database write
       ** lock and reacquire the read lock.
       */
       rc = pager_playback(pPager);
       if( rc!=SQLITE_OK ){
         return rc;







|









>
>
>
>
>
>
>
>
>
>
>









|
|
<
|
<
<
<
<
<



<
<
<
<
<
|
<
<
<
<







633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671

672





673
674
675





676




677
678
679
680
681
682
683
    return pager_errcode(pPager);
  }

  /* If this is the first page accessed, then get a read lock
  ** on the database file.
  */
  if( pPager->nRef==0 ){
    if( sqliteOsReadLock(&pPager->fd)!=SQLITE_OK ){
      *ppPage = 0;
      return SQLITE_BUSY;
    }
    pPager->state = SQLITE_READLOCK;

    /* If a journal file exists, try to play it back.
    */
    if( sqliteOsFileExists(pPager->zJournal) ){
       int rc, dummy;

       /* Get a write lock on the database
       */
       rc = sqliteOsWriteLock(&pPager->fd);
       if( rc!=SQLITE_OK ){
         rc = sqliteOsReadLock(&pPager->fd);
         assert( rc==SQLITE_OK );
         *ppPage = 0;
         return SQLITE_BUSY;
       }
       pPager->state = SQLITE_WRITELOCK;

       /* Open the journal for exclusive access.  Return SQLITE_BUSY if
       ** we cannot get exclusive access to the journal file. 
       **
       ** Even though we will only be reading from the journal, not writing,
       ** we have to open the journal for writing in order to obtain an
       ** exclusive access lock.
       */
       rc = sqliteOsOpenReadWrite(pPager->zJournal, &pPager->jfd, &dummy);
       if( rc!=SQLITE_OK ){
         rc = sqliteOsUnlock(&pPager->fd);

         assert( rc==SQLITE_OK );





         *ppPage = 0;
         return SQLITE_BUSY;
       }





       pPager->journalOpen = 1;





       /* Playback and delete the journal.  Drop the database write
       ** lock and reacquire the read lock.
       */
       rc = pager_playback(pPager);
       if( rc!=SQLITE_OK ){
         return rc;
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
      pPg->pNextHash->pPrevHash = pPg;
    }
    if( pPager->dbSize<0 ) sqlitepager_pagecount(pPager);
    if( pPager->dbSize<pgno ){
      memset(PGHDR_TO_DATA(pPg), 0, SQLITE_PAGE_SIZE);
    }else{
      int rc;
      sqliteOsSeek(pPager->fd, (pgno-1)*SQLITE_PAGE_SIZE);
      rc = sqliteOsRead(pPager->fd, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE);
      if( rc!=SQLITE_OK ){
        return rc;
      }
    }
    if( pPager->nExtra>0 ){
      memset(PGHDR_TO_EXTRA(pPg), 0, pPager->nExtra);
    }







|
|







789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
      pPg->pNextHash->pPrevHash = pPg;
    }
    if( pPager->dbSize<0 ) sqlitepager_pagecount(pPager);
    if( pPager->dbSize<pgno ){
      memset(PGHDR_TO_DATA(pPg), 0, SQLITE_PAGE_SIZE);
    }else{
      int rc;
      sqliteOsSeek(&pPager->fd, (pgno-1)*SQLITE_PAGE_SIZE);
      rc = sqliteOsRead(&pPager->fd, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE);
      if( rc!=SQLITE_OK ){
        return rc;
      }
    }
    if( pPager->nExtra>0 ){
      memset(PGHDR_TO_EXTRA(pPg), 0, pPager->nExtra);
    }
930
931
932
933
934
935
936




937
938
939
940
941
942
943
944


945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
    return SQLITE_PERM;
  }
  pPg->dirty = 1;
  if( pPg->inJournal ){ return SQLITE_OK; }
  assert( pPager->state!=SQLITE_UNLOCK );
  if( pPager->state==SQLITE_READLOCK ){
    assert( pPager->aInJournal==0 );




    pPager->aInJournal = sqliteMalloc( pPager->dbSize/8 + 1 );
    if( pPager->aInJournal==0 ){
      sqliteFree(pPager->aInJournal);
      return SQLITE_NOMEM;
    }
    rc = sqliteOsOpenExclusive(pPager->zJournal, &pPager->jfd);
    if( rc!=SQLITE_OK ){
      sqliteFree(pPager->aInJournal);


      return SQLITE_CANTOPEN;
    }
    pPager->journalOpen = 1;
    pPager->needSync = 0;
    if( sqliteOsLock(pPager->jfd, 1)!=SQLITE_OK ){
      sqliteFree(pPager->aInJournal);
      sqliteOsClose(pPager->jfd);
      sqliteOsDelete(pPager->zJournal);
      pPager->journalOpen = 0;
      return SQLITE_BUSY;
    }
    sqliteOsUnlock(pPager->fd);
    if( sqliteOsLock(pPager->fd, 1)!=SQLITE_OK ){
      sqliteOsUnlock(pPager->fd);
      rc = sqliteOsLock(pPager->fd, 0);
      sqliteFree(pPager->aInJournal);
      sqliteOsClose(pPager->jfd);
      sqliteOsDelete(pPager->zJournal);
      pPager->journalOpen = 0;
      if( rc ){
        pPager->state = SQLITE_UNLOCK;
        pPager->errMask |= PAGER_ERR_LOCK;
        return SQLITE_PROTOCOL;
      }else{
        pPager->state = SQLITE_READLOCK;
        return SQLITE_BUSY;
      }
    }
    pPager->state = SQLITE_WRITELOCK;
    sqlitepager_pagecount(pPager);
    pPager->origDbSize = pPager->dbSize;
    rc = sqliteOsWrite(pPager->jfd, aJournalMagic, sizeof(aJournalMagic));
    if( rc==SQLITE_OK ){
      rc = sqliteOsWrite(pPager->jfd, &pPager->dbSize, sizeof(Pgno));
    }
    if( rc!=SQLITE_OK ){
      rc = pager_unwritelock(pPager);
      if( rc==SQLITE_OK ) rc = SQLITE_FULL;
      return rc;
    }
  }
  assert( pPager->state==SQLITE_WRITELOCK );
  assert( pPager->journalOpen );
  if( pPg->pgno <= pPager->origDbSize ){
    rc = sqliteOsWrite(pPager->jfd, &pPg->pgno, sizeof(Pgno));
    if( rc==SQLITE_OK ){
      rc = sqliteOsWrite(pPager->jfd, pData, SQLITE_PAGE_SIZE);
    }
    if( rc!=SQLITE_OK ){
      sqlitepager_rollback(pPager);
      pPager->errMask |= PAGER_ERR_FULL;
      return rc;
    }
    assert( pPager->aInJournal!=0 );







>
>
>
>


|





>
>




<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<



|

|










|

|







919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
























944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
    return SQLITE_PERM;
  }
  pPg->dirty = 1;
  if( pPg->inJournal ){ return SQLITE_OK; }
  assert( pPager->state!=SQLITE_UNLOCK );
  if( pPager->state==SQLITE_READLOCK ){
    assert( pPager->aInJournal==0 );
    rc = sqliteOsWriteLock(&pPager->fd);
    if( rc!=SQLITE_OK ){
      return rc;
    }
    pPager->aInJournal = sqliteMalloc( pPager->dbSize/8 + 1 );
    if( pPager->aInJournal==0 ){
      sqliteOsReadLock(&pPager->fd);
      return SQLITE_NOMEM;
    }
    rc = sqliteOsOpenExclusive(pPager->zJournal, &pPager->jfd);
    if( rc!=SQLITE_OK ){
      sqliteFree(pPager->aInJournal);
      pPager->aInJournal = 0;
      sqliteOsReadLock(&pPager->fd);
      return SQLITE_CANTOPEN;
    }
    pPager->journalOpen = 1;
    pPager->needSync = 0;
























    pPager->state = SQLITE_WRITELOCK;
    sqlitepager_pagecount(pPager);
    pPager->origDbSize = pPager->dbSize;
    rc = sqliteOsWrite(&pPager->jfd, aJournalMagic, sizeof(aJournalMagic));
    if( rc==SQLITE_OK ){
      rc = sqliteOsWrite(&pPager->jfd, &pPager->dbSize, sizeof(Pgno));
    }
    if( rc!=SQLITE_OK ){
      rc = pager_unwritelock(pPager);
      if( rc==SQLITE_OK ) rc = SQLITE_FULL;
      return rc;
    }
  }
  assert( pPager->state==SQLITE_WRITELOCK );
  assert( pPager->journalOpen );
  if( pPg->pgno <= pPager->origDbSize ){
    rc = sqliteOsWrite(&pPager->jfd, &pPg->pgno, sizeof(Pgno));
    if( rc==SQLITE_OK ){
      rc = sqliteOsWrite(&pPager->jfd, pData, SQLITE_PAGE_SIZE);
    }
    if( rc!=SQLITE_OK ){
      sqlitepager_rollback(pPager);
      pPager->errMask |= PAGER_ERR_FULL;
      return rc;
    }
    assert( pPager->aInJournal!=0 );
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
    rc = pager_errcode(pPager);
    return rc;
  }
  if( pPager->state!=SQLITE_WRITELOCK ){
    return SQLITE_ERROR;
  }
  assert( pPager->journalOpen );
  if( pPager->needSync && sqliteOsSync(pPager->jfd)!=SQLITE_OK ){
    goto commit_abort;
  }
  for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
    if( pPg->dirty==0 ) continue;
    rc = sqliteOsSeek(pPager->fd, (pPg->pgno-1)*SQLITE_PAGE_SIZE);
    if( rc!=SQLITE_OK ) goto commit_abort;
    rc = sqliteOsWrite(pPager->fd, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE);
    if( rc!=SQLITE_OK ) goto commit_abort;
  }
  if( sqliteOsSync(pPager->fd)!=SQLITE_OK ) goto commit_abort;
  rc = pager_unwritelock(pPager);
  pPager->dbSize = -1;
  return rc;

  /* Jump here if anything goes wrong during the commit process.
  */
commit_abort:







|




|

|


|







1007
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1031
    rc = pager_errcode(pPager);
    return rc;
  }
  if( pPager->state!=SQLITE_WRITELOCK ){
    return SQLITE_ERROR;
  }
  assert( pPager->journalOpen );
  if( pPager->needSync && sqliteOsSync(&pPager->jfd)!=SQLITE_OK ){
    goto commit_abort;
  }
  for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
    if( pPg->dirty==0 ) continue;
    rc = sqliteOsSeek(&pPager->fd, (pPg->pgno-1)*SQLITE_PAGE_SIZE);
    if( rc!=SQLITE_OK ) goto commit_abort;
    rc = sqliteOsWrite(&pPager->fd, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE);
    if( rc!=SQLITE_OK ) goto commit_abort;
  }
  if( sqliteOsSync(&pPager->fd)!=SQLITE_OK ) goto commit_abort;
  rc = pager_unwritelock(pPager);
  pPager->dbSize = -1;
  return rc;

  /* Jump here if anything goes wrong during the commit process.
  */
commit_abort:
Changes to www/changes.tcl.
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}


proc chng {date desc} {
  puts "<DT><B>$date</B></DT>"
  puts "<DD><P><UL>$desc</UL></P></DD>"
}








chng {2001 Dec 6 (2.1.5)} {
<li>Fix for another problem (unrelated to the one fixed in 2.1.4) 
    that sometimes causes <b>sqlite_exec()</b> to return SQLITE_PROTOCOL
    unnecessarily.  This time the bug was
    in the POSIX locking code and should not effect windows users.</li>
}







>
>
>
>
>
>
>







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16
17
18
19
20
21
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30
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32
}


proc chng {date desc} {
  puts "<DT><B>$date</B></DT>"
  puts "<DD><P><UL>$desc</UL></P></DD>"
}

chng {2001 Dec 14 (2.1.6)} {
<li>Fix the locking mechanism yet again to prevent
    <b>sqlite_exec()</b> from returning SQLITE_PROTOCOL
    unnecessarily.  This time the bug was a race condition in
    the locking code.  This change effects both POSIX and Windows users.</li>
}

chng {2001 Dec 6 (2.1.5)} {
<li>Fix for another problem (unrelated to the one fixed in 2.1.4) 
    that sometimes causes <b>sqlite_exec()</b> to return SQLITE_PROTOCOL
    unnecessarily.  This time the bug was
    in the POSIX locking code and should not effect windows users.</li>
}