SQLite

  pCsr->iOffset = (i64)pCsr->szPage * (pCsr->iPageno - 1);

  /* If connected to a ZIPVFS backend, override the page size and
  ** offset with actual values obtained from ZIPVFS.
  */
  fd = sqlite3PagerFile(pPager);
  x[0] = pCsr->iPageno;
  if( fd->pMethods!=0 && sqlite3OsFileControl(fd, 230440, &x)==SQLITE_OK ){
    pCsr->iOffset = x[0];
    pCsr->szPage = (int)x[1];
  }
}

/*
** Move a statvfs cursor to the next entry in the file.

      rc = SQLITE_OK;
    }else if( op==SQLITE_FCNTL_VFS_POINTER ){
      *(sqlite3_vfs**)pArg = sqlite3PagerVfs(pPager);
      rc = SQLITE_OK;
    }else if( op==SQLITE_FCNTL_JOURNAL_POINTER ){
      *(sqlite3_file**)pArg = sqlite3PagerJrnlFile(pPager);
      rc = SQLITE_OK;
    }else if( fd->pMethods ){
      rc = sqlite3OsFileControl(fd, op, pArg);
    }else{
      rc = SQLITE_NOTFOUND;
    }
    sqlite3BtreeLeave(pBtree);
  }
  sqlite3_mutex_leave(db->mutex);
  return rc;
}

    ** The core must call OsFileControl() though, not OsFileControlHint(),
    ** as if a custom VFS (e.g. zipvfs) returns an error here, it probably
    ** means the commit really has failed and an error should be returned
    ** to the user.  */
    DO_OS_MALLOC_TEST(id);
  }
#endif

  return id->pMethods->xFileControl(id, op, pArg);
}
void sqlite3OsFileControlHint(sqlite3_file *id, int op, void *pArg){
  (void)id->pMethods->xFileControl(id, op, pArg);
}

int sqlite3OsSectorSize(sqlite3_file *id){
  int (*xSectorSize)(sqlite3_file*) = id->pMethods->xSectorSize;
  return (xSectorSize ? xSectorSize(id) : SQLITE_DEFAULT_SECTOR_SIZE);
}
int sqlite3OsDeviceCharacteristics(sqlite3_file *id){

    ** successfully committed, but the EXCLUSIVE lock is still held on the
    ** file. So it is safe to truncate the database file to its minimum
    ** required size.  */
    assert( pPager->eLock==EXCLUSIVE_LOCK );
    rc = pager_truncate(pPager, pPager->dbSize);
  }

  if( rc==SQLITE_OK && bCommit && isOpen(pPager->fd) ){
    rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_COMMIT_PHASETWO, 0);
    if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
  }

  if( !pPager->exclusiveMode 
   && (!pagerUseWal(pPager) || sqlite3WalExclusiveMode(pPager->pWal, 0))
  ){

  }
  /* Following a rollback, the database file should be back in its original
  ** state prior to the start of the transaction, so invoke the
  ** SQLITE_FCNTL_DB_UNCHANGED file-control method to disable the
  ** assertion that the transaction counter was modified.
  */
#ifdef SQLITE_DEBUG
  if( pPager->fd->pMethods ){
    sqlite3OsFileControlHint(pPager->fd,SQLITE_FCNTL_DB_UNCHANGED,0);
  }
#endif

  /* If this playback is happening automatically as a result of an IO or 
  ** malloc error that occurred after the change-counter was updated but 
  ** before the transaction was committed, then the change-counter 
  ** modification may just have been reverted. If this happens in exclusive 
  ** mode, then subsequent transactions performed by the connection will not

** returned to the caller of the pager API function.
*/
void sqlite3PagerSetBusyHandler(
  Pager *pPager,                       /* Pager object */
  int (*xBusyHandler)(void *),         /* Pointer to busy-handler function */
  void *pBusyHandlerArg                /* Argument to pass to xBusyHandler */
){

  pPager->xBusyHandler = xBusyHandler;
  pPager->pBusyHandlerArg = pBusyHandlerArg;

  if( isOpen(pPager->fd) ){
    void **ap = (void **)&pPager->xBusyHandler;
    assert( ((int(*)(void *))(ap[0]))==xBusyHandler );
    assert( ap[1]==pBusyHandlerArg );
    sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_BUSYHANDLER, (void *)ap);
  }
}

/*
** Change the page size used by the Pager object. The new page size 
** is passed in *pPageSize.
**
** If the pager is in the error state when this function is called, it

** or pages with the Pager.noSync flag set.
**
** If successful, or if called on a pager for which it is a no-op, this
** function returns SQLITE_OK. Otherwise, an IO error code is returned.
*/
int sqlite3PagerSync(Pager *pPager, const char *zMaster){
  int rc = SQLITE_OK;

  if( isOpen(pPager->fd) ){
    void *pArg = (void*)zMaster;
    rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_SYNC, pArg);
    if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
  }
  if( rc==SQLITE_OK && !pPager->noSync ){
    assert( !MEMDB );
    rc = sqlite3OsSync(pPager->fd, pPager->syncFlags);
  }
  return rc;
}

}

#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
/*
** Reset the lock timeout for pager.
*/
void sqlite3PagerResetLockTimeout(Pager *pPager){
  if( isOpen(pPager->fd) ){
    int x = 0;
    sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_LOCK_TIMEOUT, &x);
  }
}
#endif

/*
** Return the file handle for the journal file (if it exists).
** This will be either the rollback journal or the WAL file.
*/