/*
** 2010 February 1
**
** 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.
**
*************************************************************************
** This header file defines the interface to the write-ahead logging
** system. Refer to the comments below and the header comment attached to
** the implementation of each function in log.c for further details.
*/
#ifndef _WAL_H_
#define _WAL_H_
#include "sqliteInt.h"
#ifdef SQLITE_OMIT_WAL
# define sqlite3WalOpen(x,y,z) 0
# define sqlite3WalClose(w,x,y,z) 0
# define sqlite3WalOpenSnapshot(y,z) 0
# define sqlite3WalCloseSnapshot(z)
# define sqlite3WalRead(v,w,x,y,z) 0
# define sqlite3WalDbsize(y,z)
# define sqlite3WalWriteLock(y,z) 0
# define sqlite3WalUndo(x,y,z) 0
# define sqlite3WalSavepoint(z) 0
# define sqlite3WalSavepointUndo(y,z) 0
# define sqlite3WalFrames(u,v,w,x,y,z) 0
# define sqlite3WalCheckpoint(u,v,w,x,y,z) 0
# define sqlite3WalCallback(z) 0
#else
/* Connection to a write-ahead log (WAL) file.
** There is one object of this type for each pager.
*/
typedef struct Wal Wal;
/* Open and close a connection to a write-ahead log. */
int sqlite3WalOpen(sqlite3_vfs*, const char *zDb, Wal **ppWal);
int sqlite3WalClose(Wal *pWal, sqlite3_file *pFd, int sync_flags, int, u8 *);
/* Used by readers to open (lock) and close (unlock) a snapshot. A
** snapshot is like a read-transaction. It is the state of the database
** at an instant in time. sqlite3WalOpenSnapshot gets a read lock and
** preserves the current state even if the other threads or processes
** write to or checkpoint the WAL. sqlite3WalCloseSnapshot() closes the
** transaction and releases the lock.
*/
int sqlite3WalOpenSnapshot(Wal *pWal, int *);
void sqlite3WalCloseSnapshot(Wal *pWal);
/* Read a page from the write-ahead log, if it is present. */
int sqlite3WalRead(Wal *pWal, Pgno pgno, int *pInWal, int nOut, u8 *pOut);
/* Return the size of the database as it existed at the beginning
** of the snapshot */
void sqlite3WalDbsize(Wal *pWal, Pgno *pPgno);
/* Obtain or release the WRITER lock. */
int sqlite3WalWriteLock(Wal *pWal, int op);
/* Undo any frames written (but not committed) to the log */
int sqlite3WalUndo(Wal *pWal, int (*xUndo)(void *, Pgno), void *pUndoCtx);
/* Return an integer that records the current (uncommitted) write
** position in the WAL */
u32 sqlite3WalSavepoint(Wal *pWal);
/* Move the write position of the WAL back to iFrame. Called in
** response to a ROLLBACK TO command. */
int sqlite3WalSavepointUndo(Wal *pWal, u32 iFrame);
/* Write a frame or frames to the log. */
int sqlite3WalFrames(Wal *pWal, int, PgHdr *, Pgno, int, int);
/* Copy pages from the log to the database file */
int sqlite3WalCheckpoint(
Wal *pWal, /* Write-ahead log connection */
sqlite3_file *pFd, /* File descriptor open on db file */
int sync_flags, /* Flags to sync db file with (or 0) */
int nBuf, /* Size of buffer nBuf */
u8 *zBuf, /* Temporary buffer to use */
int (*xBusyHandler)(void *), /* Pointer to busy-handler function */
void *pBusyHandlerArg /* Argument to pass to xBusyHandler */
);
/* Return the value to pass to a sqlite3_wal_hook callback, the
** number of frames in the WAL at the point of the last commit since
** sqlite3WalCallback() was called. If no commits have occurred since
** the last call, then return 0.
*/
int sqlite3WalCallback(Wal *pWal);
#endif /* ifndef SQLITE_OMIT_WAL */
#endif /* _WAL_H_ */