/*
** 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 SQLITE_WAL_H
#define SQLITE_WAL_H

#include "sqliteInt.h"

/* Macros for extracting appropriate sync flags for either transaction
** commits (WAL_SYNC_FLAGS(X)) or for checkpoint ops (CKPT_SYNC_FLAGS(X)):
*/
#define WAL_SYNC_FLAGS(X) ((X)&0x03)
#define CKPT_SYNC_FLAGS(X) (((X)>>2)&0x03)

#ifdef SQLITE_OMIT_WAL
# define sqlite3WalOpen(x,y,z) 0
# define sqlite3WalLimit(x,y)
# define sqlite3WalClose(v,w,x,y,z) 0
# define sqlite3WalBeginReadTransaction(y,z) 0
# define sqlite3WalEndReadTransaction(z)
# define sqlite3WalDbsize(y) 0
# define sqlite3WalBeginWriteTransaction(y) 0
# define sqlite3WalEndWriteTransaction(x) 0
# define sqlite3WalUndo(x,y,z) 0
# define sqlite3WalSavepoint(y,z)
# define sqlite3WalSavepointUndo(y,z) 0
# define sqlite3WalFrames(u,v,w,x,y,z) 0
# define sqlite3WalCheckpoint(q,r,s,t,u,v,w,x,y,z) 0
# define sqlite3WalCallback(z) 0
# define sqlite3WalExclusiveMode(y,z) 0
# define sqlite3WalHeapMemory(z) 0
# define sqlite3WalFramesize(z) 0
# define sqlite3WalFindFrame(x,y,z) 0
# define sqlite3WalFile(x) 0
# undef SQLITE_USE_SEH
#else

#define WAL_SAVEPOINT_NDATA 4

/* 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*, sqlite3_file*, const char *, int, i64, Wal**);
int sqlite3WalClose(Wal *pWal, sqlite3*, int sync_flags, int, u8 *);

/* Set the limiting size of a WAL file. */
void sqlite3WalLimit(Wal*, i64);

/* 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 sqlite3WalBeginReadTransaction(Wal *pWal, int *);
void sqlite3WalEndReadTransaction(Wal *pWal);

/* Read a page from the write-ahead log, if it is present. */
int sqlite3WalFindFrame(Wal *, Pgno, u32 *);
int sqlite3WalReadFrame(Wal *, u32, int, u8 *);

/* If the WAL is not empty, return the size of the database. */
Pgno sqlite3WalDbsize(Wal *pWal);

/* Obtain or release the WRITER lock. */
int sqlite3WalBeginWriteTransaction(Wal *pWal);
int sqlite3WalEndWriteTransaction(Wal *pWal);

/* 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 */
void sqlite3WalSavepoint(Wal *pWal, u32 *aWalData);

/* Move the write position of the WAL back to iFrame. Called in
** response to a ROLLBACK TO command. */
int sqlite3WalSavepointUndo(Wal *pWal, u32 *aWalData);

/* 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 *db, /* Check this handle's interrupt flag */
 int eMode, /* One of PASSIVE, FULL and RESTART */
 int (*xBusy)(void*), /* Function to call when busy */
 void *pBusyArg, /* Context argument for xBusyHandler */
 int sync_flags, /* Flags to sync db file with (or 0) */
 int nBuf, /* Size of buffer nBuf */
 u8 *zBuf, /* Temporary buffer to use */
 int *pnLog, /* OUT: Number of frames in WAL */
 int *pnCkpt /* OUT: Number of backfilled frames in WAL */
);

/* 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);

/* Tell the wal layer that an EXCLUSIVE lock has been obtained (or released)
** by the pager layer on the database file.
*/
int sqlite3WalExclusiveMode(Wal *pWal, int op);

/* Return true if the argument is non-NULL and the WAL module is using
** heap-memory for the wal-index. Otherwise, if the argument is NULL or the
** WAL module is using shared-memory, return false. 
*/
int sqlite3WalHeapMemory(Wal *pWal);

#ifdef SQLITE_ENABLE_SNAPSHOT
int sqlite3WalSnapshotGet(Wal *pWal, sqlite3_snapshot **ppSnapshot);
void sqlite3WalSnapshotOpen(Wal *pWal, sqlite3_snapshot *pSnapshot);
int sqlite3WalSnapshotRecover(Wal *pWal);
int sqlite3WalSnapshotCheck(Wal *pWal, sqlite3_snapshot *pSnapshot);
void sqlite3WalSnapshotUnlock(Wal *pWal);
#endif

#ifdef SQLITE_ENABLE_ZIPVFS
/* If the WAL file is not empty, return the number of bytes of content
** stored in each frame (i.e. the db page-size when the WAL was created).
*/
int sqlite3WalFramesize(Wal *pWal);
#endif

/* Return the sqlite3_file object for the WAL file */
sqlite3_file *sqlite3WalFile(Wal *pWal);

#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
int sqlite3WalWriteLock(Wal *pWal, int bLock);
void sqlite3WalDb(Wal *pWal, sqlite3 *db);
#endif

#ifdef SQLITE_USE_SEH
int sqlite3WalSystemErrno(Wal*);
#endif

#endif /* ifndef SQLITE_OMIT_WAL */
#endif /* SQLITE_WAL_H */