| /* |
| ** 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 sqlite3WalBeginReadTransaction(y,z) 0 |
| # define sqlite3WalEndReadTransaction(z) |
| # define sqlite3WalRead(v,w,x,y,z) 0 |
| # 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(r,s,t,u,v,w,x,y,z) 0 |
| # define sqlite3WalCallback(z) 0 |
| # define sqlite3WalExclusiveMode(y,z) 0 |
| # define sqlite3WalHeapMemory(z) 0 |
| #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 *zName, int, Wal**); |
| int sqlite3WalClose(Wal *pWal, 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 sqlite3WalBeginReadTransaction(Wal *pWal, int *); |
| void sqlite3WalEndReadTransaction(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); |
| |
| /* 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 */ |
| 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); |
| |
| #endif /* ifndef SQLITE_OMIT_WAL */ |
| #endif /* _WAL_H_ */ |