138 lines
5.2 KiB
C
138 lines
5.2 KiB
C
/*
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** 2010 February 1
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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*************************************************************************
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** This header file defines the interface to the write-ahead logging
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** system. Refer to the comments below and the header comment attached to
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** the implementation of each function in log.c for further details.
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*/
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#ifndef _WAL_H_
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#define _WAL_H_
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#include "sqliteInt.h"
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/* Additional values that can be added to the sync_flags argument of
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** sqlite3WalFrames():
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*/
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#define WAL_SYNC_TRANSACTIONS 0x20 /* Sync at the end of each transaction */
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#define SQLITE_SYNC_MASK 0x13 /* Mask off the SQLITE_SYNC_* values */
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#ifdef SQLITE_OMIT_WAL
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# define sqlite3WalOpen(x,y,z) 0
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# define sqlite3WalLimit(x,y)
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# define sqlite3WalClose(w,x,y,z) 0
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# define sqlite3WalBeginReadTransaction(y,z) 0
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# define sqlite3WalEndReadTransaction(z)
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# define sqlite3WalDbsize(y) 0
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# define sqlite3WalBeginWriteTransaction(y) 0
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# define sqlite3WalEndWriteTransaction(x) 0
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# define sqlite3WalUndo(x,y,z) 0
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# define sqlite3WalSavepoint(y,z)
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# define sqlite3WalSavepointUndo(y,z) 0
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# define sqlite3WalFrames(u,v,w,x,y,z) 0
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# define sqlite3WalCheckpoint(r,s,t,u,v,w,x,y,z) 0
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# define sqlite3WalCallback(z) 0
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# define sqlite3WalExclusiveMode(y,z) 0
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# define sqlite3WalHeapMemory(z) 0
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# define sqlite3WalFramesize(z) 0
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# define sqlite3WalFindFrame(x,y,z) 0
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#else
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#define WAL_SAVEPOINT_NDATA 4
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/* Connection to a write-ahead log (WAL) file.
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** There is one object of this type for each pager.
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*/
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typedef struct Wal Wal;
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/* Open and close a connection to a write-ahead log. */
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int sqlite3WalOpen(sqlite3_vfs*, sqlite3_file*, const char *, int, i64, Wal**);
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int sqlite3WalClose(Wal *pWal, int sync_flags, int, u8 *);
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/* Set the limiting size of a WAL file. */
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void sqlite3WalLimit(Wal*, i64);
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/* Used by readers to open (lock) and close (unlock) a snapshot. A
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** snapshot is like a read-transaction. It is the state of the database
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** at an instant in time. sqlite3WalOpenSnapshot gets a read lock and
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** preserves the current state even if the other threads or processes
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** write to or checkpoint the WAL. sqlite3WalCloseSnapshot() closes the
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** transaction and releases the lock.
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*/
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int sqlite3WalBeginReadTransaction(Wal *pWal, int *);
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void sqlite3WalEndReadTransaction(Wal *pWal);
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/* Read a page from the write-ahead log, if it is present. */
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int sqlite3WalFindFrame(Wal *, Pgno, u32 *);
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int sqlite3WalReadFrame(Wal *, u32, int, u8 *);
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/* If the WAL is not empty, return the size of the database. */
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Pgno sqlite3WalDbsize(Wal *pWal);
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/* Obtain or release the WRITER lock. */
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int sqlite3WalBeginWriteTransaction(Wal *pWal);
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int sqlite3WalEndWriteTransaction(Wal *pWal);
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/* Undo any frames written (but not committed) to the log */
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int sqlite3WalUndo(Wal *pWal, int (*xUndo)(void *, Pgno), void *pUndoCtx);
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/* Return an integer that records the current (uncommitted) write
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** position in the WAL */
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void sqlite3WalSavepoint(Wal *pWal, u32 *aWalData);
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/* Move the write position of the WAL back to iFrame. Called in
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** response to a ROLLBACK TO command. */
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int sqlite3WalSavepointUndo(Wal *pWal, u32 *aWalData);
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/* Write a frame or frames to the log. */
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int sqlite3WalFrames(Wal *pWal, int, PgHdr *, Pgno, int, int);
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/* Copy pages from the log to the database file */
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int sqlite3WalCheckpoint(
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Wal *pWal, /* Write-ahead log connection */
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int eMode, /* One of PASSIVE, FULL and RESTART */
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int (*xBusy)(void*), /* Function to call when busy */
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void *pBusyArg, /* Context argument for xBusyHandler */
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int sync_flags, /* Flags to sync db file with (or 0) */
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int nBuf, /* Size of buffer nBuf */
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u8 *zBuf, /* Temporary buffer to use */
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int *pnLog, /* OUT: Number of frames in WAL */
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int *pnCkpt /* OUT: Number of backfilled frames in WAL */
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);
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/* Return the value to pass to a sqlite3_wal_hook callback, the
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** number of frames in the WAL at the point of the last commit since
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** sqlite3WalCallback() was called. If no commits have occurred since
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** the last call, then return 0.
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*/
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int sqlite3WalCallback(Wal *pWal);
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/* Tell the wal layer that an EXCLUSIVE lock has been obtained (or released)
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** by the pager layer on the database file.
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*/
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int sqlite3WalExclusiveMode(Wal *pWal, int op);
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/* Return true if the argument is non-NULL and the WAL module is using
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** heap-memory for the wal-index. Otherwise, if the argument is NULL or the
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** WAL module is using shared-memory, return false.
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*/
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int sqlite3WalHeapMemory(Wal *pWal);
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#ifdef SQLITE_ENABLE_ZIPVFS
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/* If the WAL file is not empty, return the number of bytes of content
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** stored in each frame (i.e. the db page-size when the WAL was created).
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*/
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int sqlite3WalFramesize(Wal *pWal);
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#endif
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#endif /* ifndef SQLITE_OMIT_WAL */
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#endif /* _WAL_H_ */
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