third_party/sqlite/sqlite-src-3080704/src/wal.h

   1 /*
   2 ** 2010 February 1
   3 **
   4 ** The author disclaims copyright to this source code.  In place of
   5 ** a legal notice, here is a blessing:
   6 **
   7 **    May you do good and not evil.
   8 **    May you find forgiveness for yourself and forgive others.
   9 **    May you share freely, never taking more than you give.
  10 **
  11 *************************************************************************
  12 ** This header file defines the interface to the write-ahead logging
  13 ** system. Refer to the comments below and the header comment attached to
  14 ** the implementation of each function in log.c for further details.
  15 */
  16
  17 #ifndef _WAL_H_
  18 #define _WAL_H_
  19
  20 #include "sqliteInt.h"
  21
  22 /* Additional values that can be added to the sync_flags argument of
  23 ** sqlite3WalFrames():
  24 */
  25 #define WAL_SYNC_TRANSACTIONS  0x20   /* Sync at the end of each transaction */
  26 #define SQLITE_SYNC_MASK       0x13   /* Mask off the SQLITE_SYNC_* values */
  27
  28 #ifdef SQLITE_OMIT_WAL
  29 # define sqlite3WalOpen(x,y,z)                   0
  30 # define sqlite3WalLimit(x,y)
  31 # define sqlite3WalClose(w,x,y,z)                0
  32 # define sqlite3WalBeginReadTransaction(y,z)     0
  33 # define sqlite3WalEndReadTransaction(z)
  34 # define sqlite3WalDbsize(y)                     0
  35 # define sqlite3WalBeginWriteTransaction(y)      0
  36 # define sqlite3WalEndWriteTransaction(x)        0
  37 # define sqlite3WalUndo(x,y,z)                   0
  38 # define sqlite3WalSavepoint(y,z)
  39 # define sqlite3WalSavepointUndo(y,z)            0
  40 # define sqlite3WalFrames(u,v,w,x,y,z)           0
  41 # define sqlite3WalCheckpoint(r,s,t,u,v,w,x,y,z) 0
  42 # define sqlite3WalCallback(z)                   0
  43 # define sqlite3WalExclusiveMode(y,z)            0
  44 # define sqlite3WalHeapMemory(z)                 0
  45 # define sqlite3WalFramesize(z)                  0
  46 # define sqlite3WalFindFrame(x,y,z)              0
  47 #else
  48
  49 #define WAL_SAVEPOINT_NDATA 4
  50
  51 /* Connection to a write-ahead log (WAL) file.
  52 ** There is one object of this type for each pager.
  53 */
  54 typedef struct Wal Wal;
  55
  56 /* Open and close a connection to a write-ahead log. */
  57 int sqlite3WalOpen(sqlite3_vfs*, sqlite3_file*, const char *, int, i64, Wal**);
  58 int sqlite3WalClose(Wal *pWal, int sync_flags, int, u8 *);
  59
  60 /* Set the limiting size of a WAL file. */
  61 void sqlite3WalLimit(Wal*, i64);
  62
  63 /* Used by readers to open (lock) and close (unlock) a snapshot.  A
  64 ** snapshot is like a read-transaction.  It is the state of the database
  65 ** at an instant in time.  sqlite3WalOpenSnapshot gets a read lock and
  66 ** preserves the current state even if the other threads or processes
  67 ** write to or checkpoint the WAL.  sqlite3WalCloseSnapshot() closes the
  68 ** transaction and releases the lock.
  69 */
  70 int sqlite3WalBeginReadTransaction(Wal *pWal, int *);
  71 void sqlite3WalEndReadTransaction(Wal *pWal);
  72
  73 /* Read a page from the write-ahead log, if it is present. */
  74 int sqlite3WalFindFrame(Wal *, Pgno, u32 *);
  75 int sqlite3WalReadFrame(Wal *, u32, int, u8 *);
  76
  77 /* If the WAL is not empty, return the size of the database. */
  78 Pgno sqlite3WalDbsize(Wal *pWal);
  79
  80 /* Obtain or release the WRITER lock. */
  81 int sqlite3WalBeginWriteTransaction(Wal *pWal);
  82 int sqlite3WalEndWriteTransaction(Wal *pWal);
  83
  84 /* Undo any frames written (but not committed) to the log */
  85 int sqlite3WalUndo(Wal *pWal, int (*xUndo)(void *, Pgno), void *pUndoCtx);
  86
  87 /* Return an integer that records the current (uncommitted) write
  88 ** position in the WAL */
  89 void sqlite3WalSavepoint(Wal *pWal, u32 *aWalData);
  90
  91 /* Move the write position of the WAL back to iFrame.  Called in
  92 ** response to a ROLLBACK TO command. */
  93 int sqlite3WalSavepointUndo(Wal *pWal, u32 *aWalData);
  94
  95 /* Write a frame or frames to the log. */
  96 int sqlite3WalFrames(Wal *pWal, int, PgHdr *, Pgno, int, int);
  97
  98 /* Copy pages from the log to the database file */
  99 int sqlite3WalCheckpoint(
 100   Wal *pWal,                      /* Write-ahead log connection */
 101   int eMode,                      /* One of PASSIVE, FULL and RESTART */
 102   int (*xBusy)(void*),            /* Function to call when busy */
 103   void *pBusyArg,                 /* Context argument for xBusyHandler */
 104   int sync_flags,                 /* Flags to sync db file with (or 0) */
 105   int nBuf,                       /* Size of buffer nBuf */
 106   u8 *zBuf,                       /* Temporary buffer to use */
 107   int *pnLog,                     /* OUT: Number of frames in WAL */
 108   int *pnCkpt                     /* OUT: Number of backfilled frames in WAL */
 109 );
 110
 111 /* Return the value to pass to a sqlite3_wal_hook callback, the
 112 ** number of frames in the WAL at the point of the last commit since
 113 ** sqlite3WalCallback() was called.  If no commits have occurred since
 114 ** the last call, then return 0.
 115 */
 116 int sqlite3WalCallback(Wal *pWal);
 117
 118 /* Tell the wal layer that an EXCLUSIVE lock has been obtained (or released)
 119 ** by the pager layer on the database file.
 120 */
 121 int sqlite3WalExclusiveMode(Wal *pWal, int op);
 122
 123 /* Return true if the argument is non-NULL and the WAL module is using
 124 ** heap-memory for the wal-index. Otherwise, if the argument is NULL or the
 125 ** WAL module is using shared-memory, return false.
 126 */
 127 int sqlite3WalHeapMemory(Wal *pWal);
 128
 129 #ifdef SQLITE_ENABLE_ZIPVFS
 130 /* If the WAL file is not empty, return the number of bytes of content
 131 ** stored in each frame (i.e. the db page-size when the WAL was created).
 132 */
 133 int sqlite3WalFramesize(Wal *pWal);
 134 #endif
 135
 136 #endif /* ifndef SQLITE_OMIT_WAL */
 137 #endif /* _WAL_H_ */