return pRet;
}

/*
** Register a callback to be invoked each time a transaction is written
** into the write-ahead-log by this database connection.
*/
void *sqlite3_log_hook(
  sqlite3 *db,                    /* Attach the hook to this db handle */
  int(*xCallback)(void *, sqlite3*, const char*, int),
  void *pArg                      /* First argument passed to xCallback() */
){
  void *pRet;
  sqlite3_mutex_enter(db->mutex);
  pRet = db->pLogArg;

  return pRet;
}

/*
** Register a callback to be invoked each time a transaction is written
** into the write-ahead-log by this database connection.
*/
void *sqlite3_wal_hook(
  sqlite3 *db,                    /* Attach the hook to this db handle */
  int(*xCallback)(void *, sqlite3*, const char*, int),
  void *pArg                      /* First argument passed to xCallback() */
){
  void *pRet;
  sqlite3_mutex_enter(db->mutex);
  pRet = db->pLogArg;

** a fixed-length buffer on the stack.  If the log message is longer than
** a few hundred characters, it will be truncated to the length of the
** buffer.
*/
void sqlite3_log(int iErrCode, const char *zFormat, ...);

/*
** Experimental WAL callback interface.
**
** The [sqlite3_log_hook()] function is used to register a callback that
** will be invoked each time a database connection commits data to a
** write-ahead-log (i.e. whenever a transaction is committed in
** journal_mode=WAL mode). 
**
** The callback is invoked by SQLite after the commit has taken place and 
** the associated write-lock on the database released, so the implementation 
** may read, write or checkpoint the database as required.
**
** The first parameter passed to the callback function when it is invoked
** is a copy of the third parameter passed to sqlite3_log_hook() when
** registering the callback. The second is a copy of the database handle.
** The third parameter is the name of the database that was written to -
** either "main" or the name of an ATTACHed database. The fourth parameter
** is the number of pages currently in the log file, including those that
** were just committed.
**
** If an invocation of the callback function returns non-zero, then a
** checkpoint is automatically run on the database. If zero is returned,
** no special action is taken.
**
** A single database handle may have at most a single log callback 
** registered at one time. Calling [sqlite3_log_hook()] replaces any
** previously registered log callback. 
*/
void *sqlite3_log_hook(
  sqlite3*, 
  int(*)(void *,sqlite3*,const char*,int),
  void*
);

/*
** Undo the hack that converts floating point types to integer for

** a fixed-length buffer on the stack.  If the log message is longer than
** a few hundred characters, it will be truncated to the length of the
** buffer.
*/
void sqlite3_log(int iErrCode, const char *zFormat, ...);

/*
** CAPI3REF: Write-Ahead Log Commit Hook
**
** The [sqlite3_wal_hook()] function is used to register a callback that
** will be invoked each time a database connection commits data to a
** write-ahead-log (i.e. whenever a transaction is committed in
** journal_mode=WAL mode). 
**
** The callback is invoked by SQLite after the commit has taken place and 
** the associated write-lock on the database released, so the implementation 
** may read, write or checkpoint the database as required.
**
** The first parameter passed to the callback function when it is invoked
** is a copy of the third parameter passed to sqlite3_wal_hook() when
** registering the callback. The second is a copy of the database handle.
** The third parameter is the name of the database that was written to -
** either "main" or the name of an ATTACHed database. The fourth parameter
** is the number of pages currently in the log file, including those that
** were just committed.
**
** If an invocation of the callback function returns non-zero, then a
** checkpoint is automatically run on the database. If zero is returned,
** no special action is taken.
**
** A single database handle may have at most a single log callback 
** registered at one time. Calling [sqlite3_wal_hook()] replaces any
** previously registered log callback. 
*/
void *sqlite3_wal_hook(
  sqlite3*, 
  int(*)(void *,sqlite3*,const char*,int),
  void*
);

/*
** Undo the hack that converts floating point types to integer for

  static const char *DB_strs[] = {
    "authorizer",         "backup",            "busy",
    "cache",              "changes",           "close",
    "collate",            "collation_needed",  "commit_hook",
    "complete",           "copy",              "enable_load_extension",
    "errorcode",          "eval",              "exists",
    "function",           "incrblob",          "interrupt",
    "last_insert_rowid",  "log_hook",          "nullvalue",
    "onecolumn",          "profile",           "progress",
    "rekey",              "restore",           "rollback_hook",     
    "status",             "timeout",           "total_changes",     
    "trace",              "transaction",       "unlock_notify",     
    "update_hook",        "version",            0                    
  };
  enum DB_enum {
    DB_AUTHORIZER,        DB_BACKUP,           DB_BUSY,
    DB_CACHE,             DB_CHANGES,          DB_CLOSE,
    DB_COLLATE,           DB_COLLATION_NEEDED, DB_COMMIT_HOOK,
    DB_COMPLETE,          DB_COPY,             DB_ENABLE_LOAD_EXTENSION,
    DB_ERRORCODE,         DB_EVAL,             DB_EXISTS,
    DB_FUNCTION,          DB_INCRBLOB,         DB_INTERRUPT,
    DB_LAST_INSERT_ROWID, DB_LOG_HOOK,         DB_NULLVALUE,
    DB_ONECOLUMN,         DB_PROFILE,          DB_PROGRESS,
    DB_REKEY,             DB_RESTORE,          DB_ROLLBACK_HOOK,    
    DB_STATUS,            DB_TIMEOUT,          DB_TOTAL_CHANGES,    
    DB_TRACE,             DB_TRANSACTION,      DB_UNLOCK_NOTIFY,    
    DB_UPDATE_HOOK,       DB_VERSION
  };
  /* don't leave trailing commas on DB_enum, it confuses the AIX xlc compiler */

  if( objc<2 ){
    Tcl_WrongNumArgs(interp, 1, objv, "SUBCOMMAND ...");
    return TCL_ERROR;
  }
................................................................................
      }
    }
#endif
    break;
  }

  /*
  **    $db log_hook ?script?
  **    $db update_hook ?script?
  **    $db rollback_hook ?script?
  */
  case DB_LOG_HOOK: 
  case DB_UPDATE_HOOK: 
  case DB_ROLLBACK_HOOK: {

    /* set ppHook to point at pUpdateHook or pRollbackHook, depending on 
    ** whether [$db update_hook] or [$db rollback_hook] was invoked.
    */
    Tcl_Obj **ppHook; 
    if( choice==DB_UPDATE_HOOK ){
      ppHook = &pDb->pUpdateHook;
    }else if( choice==DB_LOG_HOOK ){
      ppHook = &pDb->pLogHook;
    }else{
      ppHook = &pDb->pRollbackHook;
    }

    if( objc!=2 && objc!=3 ){
       Tcl_WrongNumArgs(interp, 2, objv, "?SCRIPT?");
................................................................................
        *ppHook = objv[2];
        Tcl_IncrRefCount(*ppHook);
      }
    }

    sqlite3_update_hook(pDb->db, (pDb->pUpdateHook?DbUpdateHandler:0), pDb);
    sqlite3_rollback_hook(pDb->db,(pDb->pRollbackHook?DbRollbackHandler:0),pDb);
    sqlite3_log_hook(pDb->db,(pDb->pLogHook?DbLogHandler:0),pDb);

    break;
  }

  /*    $db version
  **
  ** Return the version string for this database.

  static const char *DB_strs[] = {
    "authorizer",         "backup",            "busy",
    "cache",              "changes",           "close",
    "collate",            "collation_needed",  "commit_hook",
    "complete",           "copy",              "enable_load_extension",
    "errorcode",          "eval",              "exists",
    "function",           "incrblob",          "interrupt",
    "last_insert_rowid",  "nullvalue",         "onecolumn",
    "profile",            "progress",          "rekey",
    "restore",            "rollback_hook",     "status",
    "timeout",            "total_changes",     "trace",
    "transaction",        "unlock_notify",     "update_hook",
    "version",            "wal_hook",          0
  };
  enum DB_enum {
    DB_AUTHORIZER,        DB_BACKUP,           DB_BUSY,
    DB_CACHE,             DB_CHANGES,          DB_CLOSE,
    DB_COLLATE,           DB_COLLATION_NEEDED, DB_COMMIT_HOOK,
    DB_COMPLETE,          DB_COPY,             DB_ENABLE_LOAD_EXTENSION,
    DB_ERRORCODE,         DB_EVAL,             DB_EXISTS,
    DB_FUNCTION,          DB_INCRBLOB,         DB_INTERRUPT,
    DB_LAST_INSERT_ROWID, DB_NULLVALUE,        DB_ONECOLUMN,
    DB_PROFILE,           DB_PROGRESS,         DB_REKEY,
    DB_RESTORE,           DB_ROLLBACK_HOOK,    DB_STATUS,
    DB_TIMEOUT,           DB_TOTAL_CHANGES,    DB_TRACE,
    DB_TRANSACTION,       DB_UNLOCK_NOTIFY,    DB_UPDATE_HOOK,
    DB_VERSION,           DB_WAL_HOOK
  };
  /* don't leave trailing commas on DB_enum, it confuses the AIX xlc compiler */

  if( objc<2 ){
    Tcl_WrongNumArgs(interp, 1, objv, "SUBCOMMAND ...");
    return TCL_ERROR;
  }
................................................................................
      }
    }
#endif
    break;
  }

  /*
  **    $db wal_hook ?script?
  **    $db update_hook ?script?
  **    $db rollback_hook ?script?
  */
  case DB_WAL_HOOK: 
  case DB_UPDATE_HOOK: 
  case DB_ROLLBACK_HOOK: {

    /* set ppHook to point at pUpdateHook or pRollbackHook, depending on 
    ** whether [$db update_hook] or [$db rollback_hook] was invoked.
    */
    Tcl_Obj **ppHook; 
    if( choice==DB_UPDATE_HOOK ){
      ppHook = &pDb->pUpdateHook;
    }else if( choice==DB_WAL_HOOK ){
      ppHook = &pDb->pLogHook;
    }else{
      ppHook = &pDb->pRollbackHook;
    }

    if( objc!=2 && objc!=3 ){
       Tcl_WrongNumArgs(interp, 2, objv, "?SCRIPT?");
................................................................................
        *ppHook = objv[2];
        Tcl_IncrRefCount(*ppHook);
      }
    }

    sqlite3_update_hook(pDb->db, (pDb->pUpdateHook?DbUpdateHandler:0), pDb);
    sqlite3_rollback_hook(pDb->db,(pDb->pRollbackHook?DbRollbackHandler:0),pDb);
    sqlite3_wal_hook(pDb->db,(pDb->pLogHook?DbLogHandler:0),pDb);

    break;
  }

  /*    $db version
  **
  ** Return the version string for this database.

*/

#ifndef _WAL_H_
#define _WAL_H_

#include "sqliteInt.h"


/* Connection to a log file. There is one object of this type for each pager. */

typedef struct Log Log;

/* Open and close a connection to a log file. */
int sqlite3WalOpen(sqlite3_vfs*, const char *zDb, Log **ppLog);
int sqlite3WalClose(Log *pLog, sqlite3_file *pFd, int sync_flags, u8 *zBuf);

/* Used by readers to open (lock) and close (unlock) a snapshot. */






int sqlite3WalOpenSnapshot(Log *pLog, int *);
void sqlite3WalCloseSnapshot(Log *pLog);

/* Read a page from the log, if it is present. */
int sqlite3WalRead(Log *pLog, Pgno pgno, int *pInLog, u8 *pOut);



void sqlite3WalDbsize(Log *pLog, Pgno *pPgno);

/* Obtain or release the WRITER lock. */
int sqlite3WalWriteLock(Log *pLog, int op);

/* Undo any frames written (but not committed) to the log */
int sqlite3WalUndo(Log *pLog, int (*xUndo)(void *, Pgno), void *pUndoCtx);



u32 sqlite3WalSavepoint(Log *pLog);



int sqlite3WalSavepointUndo(Log *pLog, u32 iFrame);

/* Return true if data has been written but not committed to the log file. */
int sqlite3WalDirty(Log *pLog);

/* Write a frame or frames to the log. */
int sqlite3WalFrames(Log *pLog, int, PgHdr *, Pgno, int, int);
................................................................................
  sqlite3_file *pFd,              /* File descriptor open on db file */
  int sync_flags,                 /* Flags to sync db file with (or 0) */
  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 log callback. Or 0 for no callback. */




int sqlite3WalCallback(Log *pLog);

#endif /* _WAL_H_ */

*/

#ifndef _WAL_H_
#define _WAL_H_

#include "sqliteInt.h"

/* Connection to a write-ahead log (WAL) file. 
** There is one object of this type for each pager. 
*/
typedef struct Log Log;

/* Open and close a connection to a write-ahead log. */
int sqlite3WalOpen(sqlite3_vfs*, const char *zDb, Log **ppLog);
int sqlite3WalClose(Log *pLog, sqlite3_file *pFd, int sync_flags, u8 *zBuf);

/* 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(Log *pLog, int *);
void sqlite3WalCloseSnapshot(Log *pLog);

/* Read a page from the write-ahead log, if it is present. */
int sqlite3WalRead(Log *pLog, Pgno pgno, int *pInLog, u8 *pOut);

/* Return the size of the database as it existed at the beginning
** of the snapshot */
void sqlite3WalDbsize(Log *pLog, Pgno *pPgno);

/* Obtain or release the WRITER lock. */
int sqlite3WalWriteLock(Log *pLog, int op);

/* Undo any frames written (but not committed) to the log */
int sqlite3WalUndo(Log *pLog, int (*xUndo)(void *, Pgno), void *pUndoCtx);

/* Return an integer that records the current (uncommitted) write
** position in the WAL */
u32 sqlite3WalSavepoint(Log *pLog);

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

/* Return true if data has been written but not committed to the log file. */
int sqlite3WalDirty(Log *pLog);

/* Write a frame or frames to the log. */
int sqlite3WalFrames(Log *pLog, int, PgHdr *, Pgno, int, int);
................................................................................
  sqlite3_file *pFd,              /* File descriptor open on db file */
  int sync_flags,                 /* Flags to sync db file with (or 0) */
  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(Log *pLog);

#endif /* _WAL_H_ */

  set v [catch {sqlite3 bogus} msg]
  regsub {really_sqlite3} $msg {sqlite3} msg
  lappend v $msg
} [list 1 "wrong # args: should be \"$r\""]
do_test tcl-1.2 {
  set v [catch {db bogus} msg]
  lappend v $msg
} {1 {bad option "bogus": must be authorizer, backup, busy, cache, changes, close, collate, collation_needed, commit_hook, complete, copy, enable_load_extension, errorcode, eval, exists, function, incrblob, interrupt, last_insert_rowid, log_hook, nullvalue, onecolumn, profile, progress, rekey, restore, rollback_hook, status, timeout, total_changes, trace, transaction, unlock_notify, update_hook, or version}}
do_test tcl-1.2.1 {
  set v [catch {db cache bogus} msg]
  lappend v $msg
} {1 {bad option "bogus": must be flush or size}}
do_test tcl-1.2.2 {
  set v [catch {db cache} msg]
  lappend v $msg

  set v [catch {sqlite3 bogus} msg]
  regsub {really_sqlite3} $msg {sqlite3} msg
  lappend v $msg
} [list 1 "wrong # args: should be \"$r\""]
do_test tcl-1.2 {
  set v [catch {db bogus} msg]
  lappend v $msg
} {1 {bad option "bogus": must be authorizer, backup, busy, cache, changes, close, collate, collation_needed, commit_hook, complete, copy, enable_load_extension, errorcode, eval, exists, function, incrblob, interrupt, last_insert_rowid, nullvalue, onecolumn, profile, progress, rekey, restore, rollback_hook, status, timeout, total_changes, trace, transaction, unlock_notify, update_hook, version, or wal_hook}}
do_test tcl-1.2.1 {
  set v [catch {db cache bogus} msg]
  lappend v $msg
} {1 {bad option "bogus": must be flush or size}}
do_test tcl-1.2.2 {
  set v [catch {db cache} msg]
  lappend v $msg

  [lindex $args 0] eval { 
    PRAGMA journal_mode = wal;
    PRAGMA synchronous = normal;
    PRAGMA page_size = 1024;
  }
}
sqlite3_wal db test.db
db log_hook log_hook

set ::log_hook [list]
proc log_hook {zDb nEntry} {
  lappend ::log_hook $zDb $nEntry
  return 0
}

do_test walhook-1.1 {
  execsql { CREATE TABLE t1(i PRIMARY KEY, j) }
  set ::log_hook
} {main 3}
do_test walhook-1.2 {
  set ::log_hook [list]
  execsql { INSERT INTO t1 VALUES(1, 'one') }
  set ::log_hook
} {main 5}
do_test walhook-1.3 {
  proc log_hook {args} { return 1 }
  execsql { INSERT INTO t1 VALUES(2, 'two') }
  file size test.db
} [expr 3*1024]

do_test walhook-1.4 {
  proc log_hook {zDb nEntry} { 
    execsql { PRAGMA checkpoint }
    return 0
  }
  execsql { CREATE TABLE t2(a, b) }
  file size test.db
} [expr 4*1024]

do_test walhook-1.5 {
  sqlite3_wal db2 test.db
  proc log_hook {zDb nEntry} { 
    execsql { PRAGMA checkpoint } db2
    return 0
  }
  execsql { CREATE TABLE t3(a PRIMARY KEY, b) }
  file size test.db
} [expr 6*1024]

catch { db2 close }
catch { db close }
finish_test

  [lindex $args 0] eval { 
    PRAGMA journal_mode = wal;
    PRAGMA synchronous = normal;
    PRAGMA page_size = 1024;
  }
}
sqlite3_wal db test.db
db wal_hook wal_hook

set ::wal_hook [list]
proc wal_hook {zDb nEntry} {
  lappend ::wal_hook $zDb $nEntry
  return 0
}

do_test walhook-1.1 {
  execsql { CREATE TABLE t1(i PRIMARY KEY, j) }
  set ::wal_hook
} {main 3}
do_test walhook-1.2 {
  set ::wal_hook [list]
  execsql { INSERT INTO t1 VALUES(1, 'one') }
  set ::wal_hook
} {main 5}
do_test walhook-1.3 {
  proc wal_hook {args} { return 1 }
  execsql { INSERT INTO t1 VALUES(2, 'two') }
  file size test.db
} [expr 3*1024]

do_test walhook-1.4 {
  proc wal_hook {zDb nEntry} { 
    execsql { PRAGMA checkpoint }
    return 0
  }
  execsql { CREATE TABLE t2(a, b) }
  file size test.db
} [expr 4*1024]

do_test walhook-1.5 {
  sqlite3_wal db2 test.db
  proc wal_hook {zDb nEntry} { 
    execsql { PRAGMA checkpoint } db2
    return 0
  }
  execsql { CREATE TABLE t3(a PRIMARY KEY, b) }
  file size test.db
} [expr 6*1024]

catch { db2 close }
catch { db close }
finish_test