SQLite

  return pOta->nProgress;
}

/**************************************************************************
** Beginning of OTA VFS shim methods. The VFS shim modifies the behaviour
** of a standard VFS in the following ways:
**
**   1. Whenever the first page of an OTA target database file is read or 
**      written, the value of the change-counter cookie is stored in
**      sqlite3ota.iCookie. This ensures that, so long as a read transaction
**      is held on the db file, the value of sqlite3ota.iCookie matches
**      that stored on disk.
**
**   2. When the ota handle is in OTA_STAGE_OAL or OTA_STAGE_CKPT state, all
**      EXCLUSIVE lock attempts on the target database fail. This prevents
**      sqlite3_close() from running an automatic checkpoint. Until the
**      ota handle reaches OTA_STAGE_DONE - at that point the automatic
**      checkpoint may be required to delete the *-wal file.
**
**   3. In OTA_STAGE_OAL, the *-shm file is stored in memory. All xShmLock()

**      calls are noops.


**
**   4. In OTA_STAGE_OAL mode, when SQLite calls xAccess() to check if a
**      *-wal file associated with the target database exists, the following
**      special handling applies:
**
**        a) if the *-wal file does exist, return SQLITE_CANTOPEN. An OTA
**           target database may not be in wal mode already.
**
**        b) if the *-wal file does not exist, set the output parameter to
**           non-zero (to tell SQLite that it does exist) anyway.
**
**   5. In OTA_STAGE_OAL mode, if SQLite tries to open a *-wal file 
**      associated with a target database, open the corresponding *-oal file
**      instead.
*/

typedef struct ota_file ota_file;
typedef struct ota_vfs ota_vfs;

struct ota_file {
  sqlite3_file base;              /* sqlite3_file methods */
  sqlite3_file *pReal;            /* Underlying file handle */
  ota_vfs *pOtaVfs;               /* Pointer to the ota_vfs object */