** If an IO error occurs, then the IO error is returned to the caller.
** Otherwise, SQLITE_OK is returned.
*/
static int readDbPage(PgHdr *pPg){
  Pager *pPager = pPg->pPager; /* Pager object associated with page pPg */
  Pgno pgno = pPg->pgno;       /* Page number to read */
  int rc = SQLITE_OK;          /* Return code */
  i64 iOffset;                 /* Byte offset of file to read from */
  int isInWal = 0;             /* True if page is in log file */


  assert( pPager->state>=PAGER_SHARED && !MEMDB );
  assert( isOpen(pPager->fd) );

  if( NEVER(!isOpen(pPager->fd)) ){
    assert( pPager->tempFile );
    memset(pPg->pData, 0, pPager->pageSize);
    return SQLITE_OK;
  }

  if( pagerUseWal(pPager) ){
    /* Try to pull the page from the write-ahead log. */
    rc = sqlite3WalRead(pPager->pWal, pgno, &isInWal, pPg->pData);
  }
  if( rc==SQLITE_OK && !isInWal ){
    iOffset = (pgno-1)*(i64)pPager->pageSize;
    rc = sqlite3OsRead(pPager->fd, pPg->pData, pPager->pageSize, iOffset);
    if( rc==SQLITE_IOERR_SHORT_READ ){
      rc = SQLITE_OK;
    }
  }

  if( pgno==1 ){
    if( rc ){
................................................................................
** the error code is returned to the caller and the contents of the
** output buffer undefined.
*/
int sqlite3PagerReadFileheader(Pager *pPager, int N, unsigned char *pDest){
  int rc = SQLITE_OK;
  memset(pDest, 0, N);
  assert( isOpen(pPager->fd) || pPager->tempFile );









  if( isOpen(pPager->fd) ){
    IOTRACE(("DBHDR %p 0 %d\n", pPager, N))
    rc = sqlite3OsRead(pPager->fd, pDest, N, 0);
    if( rc==SQLITE_IOERR_SHORT_READ ){
      rc = SQLITE_OK;
    }
  }
................................................................................

  disable_simulated_io_errors();
  sqlite3BeginBenignMalloc();
  pPager->errCode = 0;
  pPager->exclusiveMode = 0;
#ifndef SQLITE_OMIT_WAL
  sqlite3WalClose(pPager->pWal, pPager->fd, 
    (pPager->noSync ? 0 : pPager->sync_flags), pTmp

  );
  pPager->pWal = 0;
#endif
  pager_reset(pPager);
  if( MEMDB ){
    pager_unlock(pPager);
  }else{
................................................................................
*/
int sqlite3PagerCheckpoint(Pager *pPager){
  int rc = SQLITE_OK;
  if( pPager->pWal ){
    u8 *zBuf = (u8 *)pPager->pTmpSpace;
    rc = sqlite3WalCheckpoint(pPager->pWal, pPager->fd, 
        (pPager->noSync ? 0 : pPager->sync_flags),

        zBuf, pPager->xBusyHandler, pPager->pBusyHandlerArg
    );
  }
  return rc;
}

int sqlite3PagerWalCallback(Pager *pPager){
  return sqlite3WalCallback(pPager->pWal);
................................................................................
  ** the database file, the log and log-summary files will be deleted.
  */
  if( rc==SQLITE_OK && pPager->pWal ){
    rc = sqlite3OsLock(pPager->fd, SQLITE_LOCK_EXCLUSIVE);
    if( rc==SQLITE_OK ){
      rc = sqlite3WalClose(pPager->pWal, pPager->fd,
        (pPager->noSync ? 0 : pPager->sync_flags), 
        (u8*)pPager->pTmpSpace
      );
      pPager->pWal = 0;
    }
  }
  return rc;
}
#endif

#endif /* SQLITE_OMIT_DISKIO */

** If an IO error occurs, then the IO error is returned to the caller.
** Otherwise, SQLITE_OK is returned.
*/
static int readDbPage(PgHdr *pPg){
  Pager *pPager = pPg->pPager; /* Pager object associated with page pPg */
  Pgno pgno = pPg->pgno;       /* Page number to read */
  int rc = SQLITE_OK;          /* Return code */

  int isInWal = 0;             /* True if page is in log file */
  int pgsz = pPager->pageSize; /* Number of bytes to read */

  assert( pPager->state>=PAGER_SHARED && !MEMDB );
  assert( isOpen(pPager->fd) );

  if( NEVER(!isOpen(pPager->fd)) ){
    assert( pPager->tempFile );
    memset(pPg->pData, 0, pPager->pageSize);
    return SQLITE_OK;
  }

  if( pagerUseWal(pPager) ){
    /* Try to pull the page from the write-ahead log. */
    rc = sqlite3WalRead(pPager->pWal, pgno, &isInWal, pgsz, pPg->pData);
  }
  if( rc==SQLITE_OK && !isInWal ){
    i64 iOffset = (pgno-1)*(i64)pPager->pageSize;
    rc = sqlite3OsRead(pPager->fd, pPg->pData, pgsz, iOffset);
    if( rc==SQLITE_IOERR_SHORT_READ ){
      rc = SQLITE_OK;
    }
  }

  if( pgno==1 ){
    if( rc ){
................................................................................
** the error code is returned to the caller and the contents of the
** output buffer undefined.
*/
int sqlite3PagerReadFileheader(Pager *pPager, int N, unsigned char *pDest){
  int rc = SQLITE_OK;
  memset(pDest, 0, N);
  assert( isOpen(pPager->fd) || pPager->tempFile );

  if( pagerUseWal(pPager) ){
    int isInWal = 0;
    rc = sqlite3WalRead(pPager->pWal, 1, &isInWal, N, pDest);
    if( rc!=SQLITE_OK || isInWal ){
      return rc;
    }
  }

  if( isOpen(pPager->fd) ){
    IOTRACE(("DBHDR %p 0 %d\n", pPager, N))
    rc = sqlite3OsRead(pPager->fd, pDest, N, 0);
    if( rc==SQLITE_IOERR_SHORT_READ ){
      rc = SQLITE_OK;
    }
  }
................................................................................

  disable_simulated_io_errors();
  sqlite3BeginBenignMalloc();
  pPager->errCode = 0;
  pPager->exclusiveMode = 0;
#ifndef SQLITE_OMIT_WAL
  sqlite3WalClose(pPager->pWal, pPager->fd, 
    (pPager->noSync ? 0 : pPager->sync_flags), 
    pPager->pageSize, pTmp
  );
  pPager->pWal = 0;
#endif
  pager_reset(pPager);
  if( MEMDB ){
    pager_unlock(pPager);
  }else{
................................................................................
*/
int sqlite3PagerCheckpoint(Pager *pPager){
  int rc = SQLITE_OK;
  if( pPager->pWal ){
    u8 *zBuf = (u8 *)pPager->pTmpSpace;
    rc = sqlite3WalCheckpoint(pPager->pWal, pPager->fd, 
        (pPager->noSync ? 0 : pPager->sync_flags),
        pPager->pageSize, zBuf, 
        pPager->xBusyHandler, pPager->pBusyHandlerArg
    );
  }
  return rc;
}

int sqlite3PagerWalCallback(Pager *pPager){
  return sqlite3WalCallback(pPager->pWal);
................................................................................
  ** the database file, the log and log-summary files will be deleted.
  */
  if( rc==SQLITE_OK && pPager->pWal ){
    rc = sqlite3OsLock(pPager->fd, SQLITE_LOCK_EXCLUSIVE);
    if( rc==SQLITE_OK ){
      rc = sqlite3WalClose(pPager->pWal, pPager->fd,
        (pPager->noSync ? 0 : pPager->sync_flags), 
        pPager->pageSize, (u8*)pPager->pTmpSpace
      );
      pPager->pWal = 0;
    }
  }
  return rc;
}
#endif

#endif /* SQLITE_OMIT_DISKIO */

/*
** Checkpoint the contents of the log file.
*/
static int walCheckpoint(
  Wal *pWal,                      /* Wal connection */
  sqlite3_file *pFd,              /* File descriptor open on db file */
  int sync_flags,                 /* Flags for OsSync() (or 0) */

  u8 *zBuf                        /* Temporary buffer to use */
){
  int rc;                         /* Return code */
  int pgsz = pWal->hdr.pgsz;      /* Database page-size */
  WalIterator *pIter = 0;         /* Wal iterator context */
  u32 iDbpage = 0;                /* Next database page to write */
  u32 iFrame = 0;                 /* Wal frame containing data for iDbpage */

  if( pWal->hdr.iLastPg==0 ){
    return SQLITE_OK;
  }

  /* Allocate the iterator */
  pIter = walIteratorInit(pWal);
  if( !pIter ) return SQLITE_NOMEM;











  /* Sync the log file to disk */
  if( sync_flags ){
    rc = sqlite3OsSync(pWal->pFd, sync_flags);
    if( rc!=SQLITE_OK ) goto out;
  }

................................................................................
/*
** Close a connection to a log file.
*/
int sqlite3WalClose(
  Wal *pWal,                      /* Wal to close */
  sqlite3_file *pFd,              /* Database file */
  int sync_flags,                 /* Flags to pass to OsSync() (or 0) */

  u8 *zBuf                        /* Buffer of at least page-size bytes */
){
  int rc = SQLITE_OK;
  if( pWal ){
    int isDelete = 0;             /* True to unlink wal and wal-index files */

    /* If an EXCLUSIVE lock can be obtained on the database file (using the
    ** ordinary, rollback-mode locking methods, this guarantees that the
................................................................................
    ** the database. In this case checkpoint the database and unlink both
    ** the wal and wal-index files.
    **
    ** The EXCLUSIVE lock is not released before returning.
    */
    rc = sqlite3OsLock(pFd, SQLITE_LOCK_EXCLUSIVE);
    if( rc==SQLITE_OK ){
      rc = walCheckpoint(pWal, pFd, sync_flags, zBuf);
      if( rc==SQLITE_OK ){
        isDelete = 1;
      }
      walIndexUnmap(pWal);
    }

    pWal->pVfs->xShmClose(pWal->pVfs, pWal->pWIndex, isDelete);
................................................................................
  );
  walSetLock(pWal, SQLITE_SHM_UNLOCK);
}

/*
** Read a page from the log, if it is present. 
*/
int sqlite3WalRead(Wal *pWal, Pgno pgno, int *pInWal, u8 *pOut){






  u32 iRead = 0;
  u32 *aData; 
  int iFrame = (pWal->hdr.iLastPg & 0xFFFFFF00);

  assert( pWal->lockState==SQLITE_SHM_READ||pWal->lockState==SQLITE_SHM_WRITE );
  walIndexMap(pWal, -1);

................................................................................

  /* If iRead is non-zero, then it is the log frame number that contains the
  ** required page. Read and return data from the log file.
  */
  if( iRead ){
    i64 iOffset = walFrameOffset(iRead, pWal->hdr.pgsz) + WAL_FRAME_HDRSIZE;
    *pInWal = 1;
    return sqlite3OsRead(pWal->pFd, pOut, pWal->hdr.pgsz, iOffset);
  }

  *pInWal = 0;
  return SQLITE_OK;
}


................................................................................
**   3. Zero the wal-index header (so new readers will ignore the log).
**   4. Drop the CHECKPOINT lock.
*/
int sqlite3WalCheckpoint(
  Wal *pWal,                      /* Wal connection */
  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 */
){
  int rc;                         /* Return code */
  int isChanged = 0;              /* True if a new wal-index header is loaded */

................................................................................
    walSetLock(pWal, SQLITE_SHM_UNLOCK);
    return rc;
  }

  /* Copy data from the log to the database file. */
  rc = walIndexReadHdr(pWal, &isChanged);
  if( rc==SQLITE_OK ){
    rc = walCheckpoint(pWal, pFd, sync_flags, zBuf);
  }
  if( isChanged ){
    /* If a new wal-index header was loaded before the checkpoint was 
    ** performed, then the pager-cache associated with log pWal is now
    ** out of date. So zero the cached wal-index header to ensure that
    ** next time the pager opens a snapshot on this database it knows that
    ** the cache needs to be reset.

/*
** Checkpoint the contents of the log file.
*/
static int walCheckpoint(
  Wal *pWal,                      /* Wal connection */
  sqlite3_file *pFd,              /* File descriptor open on db file */
  int sync_flags,                 /* Flags for OsSync() (or 0) */
  int nBuf,                       /* Size of zBuf in bytes */
  u8 *zBuf                        /* Temporary buffer to use */
){
  int rc;                         /* Return code */
  int pgsz = pWal->hdr.pgsz;      /* Database page-size */
  WalIterator *pIter = 0;         /* Wal iterator context */
  u32 iDbpage = 0;                /* Next database page to write */
  u32 iFrame = 0;                 /* Wal frame containing data for iDbpage */





  /* Allocate the iterator */
  pIter = walIteratorInit(pWal);
  if( !pIter ) return SQLITE_NOMEM;

  if( pWal->hdr.iLastPg==0 ){
    rc = SQLITE_OK;
    goto out;
  }

  if( pWal->hdr.pgsz!=nBuf ){
    rc = SQLITE_CORRUPT_BKPT;
    goto out;
  }

  /* Sync the log file to disk */
  if( sync_flags ){
    rc = sqlite3OsSync(pWal->pFd, sync_flags);
    if( rc!=SQLITE_OK ) goto out;
  }

................................................................................
/*
** Close a connection to a log file.
*/
int sqlite3WalClose(
  Wal *pWal,                      /* Wal to close */
  sqlite3_file *pFd,              /* Database file */
  int sync_flags,                 /* Flags to pass to OsSync() (or 0) */
  int nBuf,
  u8 *zBuf                        /* Buffer of at least nBuf bytes */
){
  int rc = SQLITE_OK;
  if( pWal ){
    int isDelete = 0;             /* True to unlink wal and wal-index files */

    /* If an EXCLUSIVE lock can be obtained on the database file (using the
    ** ordinary, rollback-mode locking methods, this guarantees that the
................................................................................
    ** the database. In this case checkpoint the database and unlink both
    ** the wal and wal-index files.
    **
    ** The EXCLUSIVE lock is not released before returning.
    */
    rc = sqlite3OsLock(pFd, SQLITE_LOCK_EXCLUSIVE);
    if( rc==SQLITE_OK ){
      rc = walCheckpoint(pWal, pFd, sync_flags, nBuf, zBuf);
      if( rc==SQLITE_OK ){
        isDelete = 1;
      }
      walIndexUnmap(pWal);
    }

    pWal->pVfs->xShmClose(pWal->pVfs, pWal->pWIndex, isDelete);
................................................................................
  );
  walSetLock(pWal, SQLITE_SHM_UNLOCK);
}

/*
** Read a page from the log, if it is present. 
*/
int sqlite3WalRead(
  Wal *pWal, 
  Pgno pgno, 
  int *pInWal, 
  int nOut,
  u8 *pOut
){
  u32 iRead = 0;
  u32 *aData; 
  int iFrame = (pWal->hdr.iLastPg & 0xFFFFFF00);

  assert( pWal->lockState==SQLITE_SHM_READ||pWal->lockState==SQLITE_SHM_WRITE );
  walIndexMap(pWal, -1);

................................................................................

  /* If iRead is non-zero, then it is the log frame number that contains the
  ** required page. Read and return data from the log file.
  */
  if( iRead ){
    i64 iOffset = walFrameOffset(iRead, pWal->hdr.pgsz) + WAL_FRAME_HDRSIZE;
    *pInWal = 1;
    return sqlite3OsRead(pWal->pFd, pOut, nOut, iOffset);
  }

  *pInWal = 0;
  return SQLITE_OK;
}


................................................................................
**   3. Zero the wal-index header (so new readers will ignore the log).
**   4. Drop the CHECKPOINT lock.
*/
int sqlite3WalCheckpoint(
  Wal *pWal,                      /* Wal connection */
  sqlite3_file *pFd,              /* File descriptor open on db file */
  int sync_flags,                 /* Flags to sync db file with (or 0) */
  int nBuf,                       /* Size of temporary buffer */
  u8 *zBuf,                       /* Temporary buffer to use */
  int (*xBusyHandler)(void *),    /* Pointer to busy-handler function */
  void *pBusyHandlerArg           /* Argument to pass to xBusyHandler */
){
  int rc;                         /* Return code */
  int isChanged = 0;              /* True if a new wal-index header is loaded */

................................................................................
    walSetLock(pWal, SQLITE_SHM_UNLOCK);
    return rc;
  }

  /* Copy data from the log to the database file. */
  rc = walIndexReadHdr(pWal, &isChanged);
  if( rc==SQLITE_OK ){
    rc = walCheckpoint(pWal, pFd, sync_flags, nBuf, zBuf);
  }
  if( isChanged ){
    /* If a new wal-index header was loaded before the checkpoint was 
    ** performed, then the pager-cache associated with log pWal is now
    ** out of date. So zero the cached wal-index header to ensure that
    ** next time the pager opens a snapshot on this database it knows that
    ** the cache needs to be reset.

#include "sqliteInt.h"

#ifdef SQLITE_OMIT_WAL
# define sqlite3WalOpen(x,y,z)             0
# define sqlite3WalClose(w,x,y,z)          0
# define sqlite3WalOpenSnapshot(y,z)       0
# define sqlite3WalCloseSnapshot(z) 
# define sqlite3WalRead(w,x,y,z)           0
# define sqlite3WalDbsize(y,z)
# define sqlite3WalWriteLock(y,z)          0
# define sqlite3WalUndo(x,y,z)             0
# define sqlite3WalSavepoint(z)            0
# define sqlite3WalSavepointUndo(y,z)      0
# define sqlite3WalFrames(u,v,w,x,y,z)     0
# define sqlite3WalCheckpoint(u,v,w,x,y,z) 0
................................................................................
/* 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*, const char *zDb, Wal **ppWal);
int sqlite3WalClose(Wal *pWal, 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(Wal *pWal, int *);
void sqlite3WalCloseSnapshot(Wal *pWal);

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

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

/* Obtain or release the WRITER lock. */
int sqlite3WalWriteLock(Wal *pWal, int op);
................................................................................
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_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

#include "sqliteInt.h"

#ifdef SQLITE_OMIT_WAL
# define sqlite3WalOpen(x,y,z)             0
# define sqlite3WalClose(w,x,y,z)          0
# define sqlite3WalOpenSnapshot(y,z)       0
# define sqlite3WalCloseSnapshot(z) 
# define sqlite3WalRead(v,w,x,y,z)         0
# define sqlite3WalDbsize(y,z)
# define sqlite3WalWriteLock(y,z)          0
# define sqlite3WalUndo(x,y,z)             0
# define sqlite3WalSavepoint(z)            0
# define sqlite3WalSavepointUndo(y,z)      0
# define sqlite3WalFrames(u,v,w,x,y,z)     0
# define sqlite3WalCheckpoint(u,v,w,x,y,z) 0
................................................................................
/* 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*, const char *zDb, Wal **ppWal);
int sqlite3WalClose(Wal *pWal, sqlite3_file *pFd, 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 sqlite3WalOpenSnapshot(Wal *pWal, int *);
void sqlite3WalCloseSnapshot(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);

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

/* Obtain or release the WRITER lock. */
int sqlite3WalWriteLock(Wal *pWal, int op);
................................................................................
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_file *pFd,              /* File descriptor open on db file */
  int sync_flags,                 /* Flags to sync db file with (or 0) */
  int nBuf,                       /* Size of buffer nBuf */
  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

  do_test wal-17.$tn.3 {
    db close
    file size test.db
  } [expr 512*171]
}
sqlite3_test_control_pending_byte $old_pending_byte


















































































































































catch { db2 close }
catch { db close }
finish_test

  do_test wal-17.$tn.3 {
    db close
    file size test.db
  } [expr 512*171]
}
sqlite3_test_control_pending_byte $old_pending_byte

#-------------------------------------------------------------------------
# This test - wal-18.* - verifies a couple of specific conditions that
# may be encountered while recovering a log file are handled correctly:
#
#   wal-18.1.* When the first 32-bits of a frame checksum is correct but 
#              the second 32-bits are false, and
#
#   wal-18.2.* When the page-size field that occurs at the start of a log
#              file is a power of 2 greater than 16384 or smaller than 512.
#
file delete -force test.db test.db-wal test.db-journal
do_test wal-18.0 {
  sqlite3 db test.db
  execsql {
    PRAGMA page_size = 1024;
    PRAGMA auto_vacuum = 0;
    PRAGMA journal_mode = WAL;
    PRAGMA synchronous = OFF;

    CREATE TABLE t1(a, b, UNIQUE(a, b));
    INSERT INTO t1 VALUES(0, 0);
    PRAGMA wal_checkpoint;

    INSERT INTO t1 VALUES(1, 2);          -- frames 1 and 2
    INSERT INTO t1 VALUES(3, 4);          -- frames 3 and 4
    INSERT INTO t1 VALUES(5, 6);          -- frames 5 and 6
  }

  file copy -force test.db testX.db
  file copy -force test.db-wal testX.db-wal
  db close
  list [file size testX.db] [file size testX.db-wal]
} [list [expr 3*1024] [log_file_size 6 1024]]

foreach {nFrame result} {
         0      {0 0}
         1      {0 0}
         2      {0 0 1 2}
         3      {0 0 1 2}
         4      {0 0 1 2 3 4}
         5      {0 0 1 2 3 4}
         6      {0 0 1 2 3 4 5 6}
} {
  do_test wal-18.1.$nFrame {
    file copy -force testX.db test.db
    file copy -force testX.db-wal test.db-wal

    hexio_write test.db-wal [expr 12 + $nFrame*(16+1024) + 12] 00000000

    sqlite3 db test.db
    execsql { 
      SELECT * FROM t1;
      PRAGMA integrity_check; 
    }
  } [concat $result ok]
  db close
} 

proc randomblob {pgsz} {
  sqlite3 rbdb :memory:
  set blob [rbdb one {SELECT randomblob($pgsz)}]
  rbdb close
  set blob
}

proc logcksum {ckv1 ckv2 blob} {
  upvar $ckv1 c1
  upvar $ckv2 c2

  binary scan $blob iu* values
  foreach v $values {
    incr c1 $v
    incr c2 $c1
  }

  set c1 [expr ($c1 + ($c1>>24))&0xFFFFFFFF]
  set c2 [expr ($c2 + ($c2>>24))&0xFFFFFFFF]
}

file copy -force test.db testX.db
foreach {tn pgsz works} { 
  1    128    0
  2    256    0
  3    512    1
  4   1024    1
  5   2048    1
  6   4096    1
  7   8192    1
  8  16384    1
  9  32768    1
 10  65536    0
} {

  for {set pg 1} {$pg <= 3} {incr pg} {
    file copy -force testX.db test.db
    file delete -force test.db-wal
  
    # Check that the database now exists and consists of three pages. And
    # that there is no associated wal file.
    #
    do_test wal-18.2.$tn.$pg.1 { file exists test.db-wal } 0
    do_test wal-18.2.$tn.$pg.2 { file exists test.db } 1
    do_test wal-18.2.$tn.$pg.3 { file size test.db } [expr 1024*3]
  
    do_test wal-18.2.$tn.$pg.4 {

      # Create a wal file that contains a single frame (database page
      # number $pg) with the commit flag set. The frame checksum is
      # correct, but the contents of the database page are corrupt.
      #
      # The page-size in the log file header is set to $pgsz. If the
      # WAL code considers $pgsz to be a valid SQLite database file page-size,
      # the database will be corrupt (because the garbage frame contents
      # will be treated as valid content). If $pgsz is invalid (too small
      # or too large), the db will not be corrupt as the log file will
      # be ignored.
      #
      set c1 22
      set c2 23
      set walhdr [binary format III $pgsz $c1 $c2]
      set framebody [randomblob $pgsz]
      set framehdr  [binary format II $pg 5]
      logcksum c1 c2 $framehdr
      logcksum c1 c2 $framebody
      set framehdr [binary format IIII $pg 5 $c1 $c2]
      set fd [open test.db-wal w]
      fconfigure $fd -encoding binary -translation binary
      puts -nonewline $fd $walhdr
      puts -nonewline $fd $framehdr
      puts -nonewline $fd $framebody
      close $fd
  
      file size test.db-wal
    } [log_file_size 1 $pgsz]
  
    do_test wal-18.2.$tn.$pg.5 {
      sqlite3 db test.db
      set rc [catch { db one {PRAGMA integrity_check} } msg]
      expr { $rc!=0 || $msg!="ok" }
    } $works
  
    db close
  }
}

catch { db2 close }
catch { db close }
finish_test

  } {1}
  do_test walcrash-6.$i.3 { execsql { PRAGMA main.integrity_check } } {ok}
  do_test walcrash-6.$i.4 { execsql { PRAGMA main.journal_mode } } {wal}

  db close
}












for {set i 1} {$i < $REPEATS} {incr i} {
  file delete -force test.db test.db-wal





  do_test walcrash-7.$i.1 {
    crashsql -delay 3 -file test.db -seed [incr seed] -blocksize 512 {

      PRAGMA journal_mode = wal;
      BEGIN;
        CREATE TABLE t1(a, b);
        INSERT INTO t1 VALUES(1, 2);
      COMMIT;
      PRAGMA wal_checkpoint;
      CREATE INDEX i1 ON t1(a);
      PRAGMA wal_checkpoint;
    }
  } {1 {child process exited abnormally}}

  do_test walcrash-7.$i.2 {
    sqlite3 db test.db
    execsql { SELECT b FROM t1 WHERE a = 1 }
  } {2}
  do_test walcrash-7.$i.3 { execsql { PRAGMA main.integrity_check } } {ok}

  } {1}
  do_test walcrash-6.$i.3 { execsql { PRAGMA main.integrity_check } } {ok}
  do_test walcrash-6.$i.4 { execsql { PRAGMA main.journal_mode } } {wal}

  db close
}

#-------------------------------------------------------------------------
# This test case simulates a crash while checkpointing the database. Page
# 1 is one of the pages overwritten by the checkpoint. This is a special
# case because it means the content of page 1 may be damaged. SQLite will
# have to determine:
#
#   (a) that the database is a WAL database, and 
#   (b) the database page-size
#
# based on the log file.
#
for {set i 1} {$i < $REPEATS} {incr i} {
  file delete -force test.db test.db-wal

  # Select a page-size for this test.
  #
  set pgsz [lindex {512 1024 2048 4096 8192 16384} [expr $i%6]]

  do_test walcrash-7.$i.1 {
    crashsql -delay 3 -file test.db -seed [incr seed] -blocksize 512 "
      PRAGMA page_size = $pgsz;
      PRAGMA journal_mode = wal;
      BEGIN;
        CREATE TABLE t1(a, b);
        INSERT INTO t1 VALUES(1, 2);
      COMMIT;
      PRAGMA wal_checkpoint;
      CREATE INDEX i1 ON t1(a);
      PRAGMA wal_checkpoint;
    "
  } {1 {child process exited abnormally}}

  do_test walcrash-7.$i.2 {
    sqlite3 db test.db
    execsql { SELECT b FROM t1 WHERE a = 1 }
  } {2}
  do_test walcrash-7.$i.3 { execsql { PRAGMA main.integrity_check } } {ok}