SQLite

  u8 exclusiveMode;           /* Boolean. True if locking_mode==EXCLUSIVE */
  u8 journalMode;             /* One of the PAGER_JOURNALMODE_* values */
  u8 useJournal;              /* Use a rollback journal on this file */
  u8 noReadlock;              /* Do not bother to obtain readlocks */
  u8 noSync;                  /* Do not sync the journal if true */
  u8 fullSync;                /* Do extra syncs of the journal for robustness */
  u8 ckptSyncFlags;           /* SYNC_NORMAL or SYNC_FULL for checkpoint */
  u8 walSyncFlags;            /* SYNC_NORMAL or SYNC_FULL for wal writes */
  u8 syncFlags;               /* SYNC_NORMAL or SYNC_FULL otherwise */
  u8 tempFile;                /* zFilename is a temporary file */
  u8 readOnly;                /* True for a read-only database */
  u8 memDb;                   /* True to inhibit all file I/O */

  /**************************************************************************
  ** The following block contains those class members that change during

#ifndef SQLITE_OMIT_WAL
static int pagerUseWal(Pager *pPager){
  return (pPager->pWal!=0);
}
#else
# define pagerUseWal(x) 0
# define pagerRollbackWal(x) 0
# define pagerWalFrames(v,w,x,y) 0
# define pagerOpenWalIfPresent(z) SQLITE_OK
# define pagerBeginReadTransaction(z) SQLITE_OK
#endif

#ifndef NDEBUG 
/*
** Usage:

** The list of pages passed into this routine is always sorted by page number.
** Hence, if page 1 appears anywhere on the list, it will be the first page.
*/ 
static int pagerWalFrames(
  Pager *pPager,                  /* Pager object */
  PgHdr *pList,                   /* List of frames to log */
  Pgno nTruncate,                 /* Database size after this commit */
  int isCommit                    /* True if this is a commit */

){
  int rc;                         /* Return code */
#if defined(SQLITE_DEBUG) || defined(SQLITE_CHECK_PAGES)
  PgHdr *p;                       /* For looping over pages */
#endif

  assert( pPager->pWal );

      if( p->pgno<=nTruncate ) ppNext = &p->pDirty;
    }
    assert( pList );
  }

  if( pList->pgno==1 ) pager_write_changecounter(pList);
  rc = sqlite3WalFrames(pPager->pWal, 
      pPager->pageSize, pList, nTruncate, isCommit, pPager->walSyncFlags
  );
  if( rc==SQLITE_OK && pPager->pBackup ){
    PgHdr *p;
    for(p=pList; p; p=p->pDirty){
      sqlite3BackupUpdate(pPager->pBackup, p->pgno, (u8 *)p->pData);
    }
  }

  }else if( bCkptFullFsync ){
    pPager->syncFlags = SQLITE_SYNC_NORMAL;
    pPager->ckptSyncFlags = SQLITE_SYNC_FULL;
  }else{
    pPager->syncFlags = SQLITE_SYNC_NORMAL;
    pPager->ckptSyncFlags = SQLITE_SYNC_NORMAL;
  }
  pPager->walSyncFlags = pPager->syncFlags;
  if( pPager->fullSync ){
    pPager->walSyncFlags |= WAL_SYNC_TRANSACTIONS;
  }
}
#endif

/*
** The following global variable is incremented whenever the library
** attempts to open a temporary file.  This information is used for
** testing and analysis only.  

  pPg->pDirty = 0;
  if( pagerUseWal(pPager) ){
    /* Write a single frame for this page to the log. */
    if( subjRequiresPage(pPg) ){ 
      rc = subjournalPage(pPg); 
    }
    if( rc==SQLITE_OK ){
      rc = pagerWalFrames(pPager, pPg, 0, 0);
    }
  }else{
  
    /* Sync the journal file if required. */
    if( pPg->flags&PGHDR_NEED_SYNC 
     || pPager->eState==PAGER_WRITER_CACHEMOD
    ){

  assert( PAGER_LOCKINGMODE_EXCLUSIVE==1 );
  pPager->exclusiveMode = (u8)tempFile; 
  pPager->changeCountDone = pPager->tempFile;
  pPager->memDb = (u8)memDb;
  pPager->readOnly = (u8)readOnly;
  assert( useJournal || pPager->tempFile );
  pPager->noSync = pPager->tempFile;
  if( pPager->noSync ){
    assert( pPager->fullSync==0 );
    assert( pPager->syncFlags==0 );
    assert( pPager->walSyncFlags==0 );
    assert( pPager->ckptSyncFlags==0 );
  }else{
    pPager->fullSync = 1;
    pPager->syncFlags = SQLITE_SYNC_NORMAL;
    pPager->walSyncFlags = SQLITE_SYNC_NORMAL | WAL_SYNC_TRANSACTIONS;
    pPager->ckptSyncFlags = SQLITE_SYNC_NORMAL;
  }
  /* pPager->pFirst = 0; */
  /* pPager->pFirstSynced = 0; */
  /* pPager->pLast = 0; */
  pPager->nExtra = (u16)nExtra;
  pPager->journalSizeLimit = SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT;
  assert( isOpen(pPager->fd) || tempFile );
  setSectorSize(pPager);

        ** Ticket [2d1a5c67dfc2363e44f29d9bbd57f] 2011-05-18 */
        rc = sqlite3PagerGet(pPager, 1, &pPageOne);
        pList = pPageOne;
        pList->pDirty = 0;
      }
      assert( rc==SQLITE_OK );
      if( ALWAYS(pList) ){
        rc = pagerWalFrames(pPager, pList, pPager->dbSize, 1);


      }
      sqlite3PagerUnref(pPageOne);
      if( rc==SQLITE_OK ){
        sqlite3PcacheCleanAll(pPager->pPCache);
      }
    }else{
      /* The following block updates the change-counter. Exactly how it

  u32 iCallback;             /* Value to pass to log callback (or 0) */
  i64 mxWalSize;             /* Truncate WAL to this size upon reset */
  int nWiData;               /* Size of array apWiData */
  int szFirstBlock;          /* Size of first block written to WAL file */
  volatile u32 **apWiData;   /* Pointer to wal-index content in memory */
  u32 szPage;                /* Database page size */
  i16 readLock;              /* Which read lock is being held.  -1 for none */
  u8 syncFlags;              /* Flags to use to sync header writes */
  u8 exclusiveMode;          /* Non-zero if connection is in exclusive mode */
  u8 writeLock;              /* True if in a write transaction */
  u8 ckptLock;               /* True if holding a checkpoint lock */
  u8 readOnly;               /* WAL_RDWR, WAL_RDONLY, or WAL_SHM_RDONLY */
  u8 truncateOnCommit;       /* True to truncate WAL file on commit */
  u8 noSyncHeader;           /* Avoid WAL header fsyncs if true */
  WalIndexHdr hdr;           /* Wal-index header for current transaction */
  const char *zWalName;      /* Name of WAL file */
  u32 nCkpt;                 /* Checkpoint sequence counter in the wal-header */
#ifdef SQLITE_DEBUG
  u8 lockError;              /* True if a locking error has occurred */
#endif
};

  }

  if( rc!=SQLITE_OK ){
    walIndexClose(pRet, 0);
    sqlite3OsClose(pRet->pWalFd);
    sqlite3_free(pRet);
  }else{
    int iDC = sqlite3OsDeviceCharacteristics(pRet->pWalFd);
    if( iDC & SQLITE_IOCAP_SEQUENTIAL ){ pRet->noSyncHeader = 1; }
    *ppWal = pRet;
    WALTRACE(("WAL%d: opened\n", pRet));
  }
  return rc;
}

/*

static int walWriteToLog(
  Wal *pWal,                 /* WAL to write to */
  void *pContent,            /* Content to be written */
  int iAmt,                  /* Number of bytes to write */
  sqlite3_int64 iOffset      /* Start writing at this offset */
){
  int rc;
  if( iOffset>=pWal->szFirstBlock
   || iOffset+iAmt<pWal->szFirstBlock
   || pWal->syncFlags==0
  ){
    /* The common and fast case.  Just write the data. */
    rc = sqlite3OsWrite(pWal->pWalFd, pContent, iAmt, iOffset);
  }else{
    /* If this write will cross the first sector boundary, it has to
    ** be split it two with a sync in between. */
    int iFirstAmt = pWal->szFirstBlock - iOffset;
    assert( iFirstAmt>0 && iFirstAmt<iAmt );
    rc = sqlite3OsWrite(pWal->pWalFd, pContent, iFirstAmt, iOffset);
    if( rc ) return rc;
    assert( pWal->syncFlags & (SQLITE_SYNC_NORMAL|SQLITE_SYNC_FULL) );
    rc = sqlite3OsSync(pWal->pWalFd, pWal->syncFlags);
    if( rc ) return rc;
    pContent = (void*)(iFirstAmt + (char*)pContent);
    rc = sqlite3OsWrite(pWal->pWalFd, pContent,
                        iAmt-iFirstAmt, iOffset+iFirstAmt);
  }
  return rc;
}

    WALTRACE(("WAL%p: wal-header write %s\n", pWal, rc ? "failed" : "ok"));
    if( rc!=SQLITE_OK ){
      return rc;
    }
  }
  assert( (int)pWal->szPage==szPage );

  /* Setup information needed to do the WAL header sync */
  if( pWal->noSyncHeader ){
    assert( pWal->szFirstBlock==0 );
    assert( pWal->syncFlags==0 );
  }else{
    pWal->szFirstBlock = sqlite3OsSectorSize(pWal->pWalFd);
    if( szPage>pWal->szFirstBlock ) pWal->szFirstBlock = szPage;
    pWal->syncFlags = sync_flags & SQLITE_SYNC_MASK;
  }

  /* Write the log file. */
  for(p=pList; p; p=p->pDirty){
    u32 nDbsize;                  /* Db-size field for frame header */
    i64 iOffset;                  /* Write offset in log file */
    void *pData;
   

    if( rc!=SQLITE_OK ){
      return rc;
    }
    pLast = p;
  }

  /* Sync the log file if the 'isSync' flag was specified. */
  if( isCommit && (sync_flags & WAL_SYNC_TRANSACTIONS)!=0 ){
    i64 iSegment = sqlite3OsSectorSize(pWal->pWalFd);
    i64 iOffset = walFrameOffset(iFrame+1, szPage);


    assert( iSegment>0 );

    iSegment = (((iOffset+iSegment-1)/iSegment) * iSegment);
    while( iOffset<iSegment ){
      void *pData;
#if defined(SQLITE_HAS_CODEC)
      if( (pData = sqlite3PagerCodec(pLast))==0 ) return SQLITE_NOMEM;

      if( rc!=SQLITE_OK ){
        return rc;
      }
      nLast++;
      iOffset += szPage;
    }

    rc = sqlite3OsSync(pWal->pWalFd, sync_flags & SQLITE_SYNC_MASK);
  }

  if( isCommit && pWal->truncateOnCommit && pWal->mxWalSize>=0 ){
    i64 sz = pWal->mxWalSize;
    if( walFrameOffset(iFrame+nLast+1, szPage)>pWal->mxWalSize ){
      sz = walFrameOffset(iFrame+nLast+1, szPage);
    }

/* 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);

/* Additional values that can be added to the sync_flags argument of
** sqlite3WalFrames():
*/
#define WAL_SYNC_TRANSACTIONS  0x20   /* Sync at the end of each transaction */
#define SQLITE_SYNC_MASK       0x13   /* Mask off the SQLITE_SYNC_* values */

/* 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) */

  }
}

#-------------------------------------------------------------------------
# Test that "PRAGMA checkpoint_fullsync" appears to be working.
#
foreach {tn sql reslist} {
  1 { }                                 {10 0 4 0 6 0}
  2 { PRAGMA checkpoint_fullfsync = 1 } {10 4 4 2 6 2}
  3 { PRAGMA checkpoint_fullfsync = 0 } {10 0 4 0 6 0}
} {
  faultsim_delete_and_reopen

  execsql {PRAGMA auto_vacuum = 0}
  execsql $sql
  do_execsql_test wal2-14.$tn.1 { PRAGMA journal_mode = WAL } {wal}

  set sqlite_sync_count 0
  set sqlite_fullsync_count 0

  do_execsql_test wal2-14.$tn.2 {
    PRAGMA wal_autocheckpoint = 10;
    CREATE TABLE t1(a, b);                -- 2 wal syncs
    INSERT INTO t1 VALUES(1, 2);          -- 2 wal sync
    PRAGMA wal_checkpoint;                -- 1 wal sync, 1 db sync
    BEGIN;
      INSERT INTO t1 VALUES(3, 4);
      INSERT INTO t1 VALUES(5, 6);
    COMMIT;                               -- 2 wal sync
    PRAGMA wal_checkpoint;                -- 1 wal sync, 1 db sync
  } {10 0 5 5 0 2 2}

  do_test wal2-14.$tn.3 {
    cond_incr_sync_count 1
    list $sqlite_sync_count $sqlite_fullsync_count
  } [lrange $reslist 0 1]

catch { db close }

# PRAGMA checkpoint_fullsync
# PRAGMA fullfsync
# PRAGMA synchronous
#
foreach {tn settings restart_sync commit_sync ckpt_sync} {
  1  {0 0 off}     {0 0}  {0 0}  {0 0}
  2  {0 0 normal}  {1 0}  {0 0}  {2 0}
  3  {0 0 full}    {2 0}  {1 0}  {2 0}

  4  {0 1 off}     {0 0}  {0 0}  {0 0}
  5  {0 1 normal}  {0 1}  {0 0}  {0 2}
  6  {0 1 full}    {0 2}  {0 1}  {0 2}

  7  {1 0 off}     {0 0}  {0 0}  {0 0}
  8  {1 0 normal}  {1 0}  {0 0}  {0 2}
  9  {1 0 full}    {2 0}  {1 0}  {0 2}

  10 {1 1 off}     {0 0}  {0 0}  {0 0}
  11 {1 1 normal}  {0 1}  {0 0}  {0 2}
  12 {1 1 full}    {0 2}  {0 1}  {0 2}
} {
  forcedelete test.db

  testvfs tvfs -default 1
  tvfs filter xSync
  tvfs script xSyncCb
  proc xSyncCb {method file fileid flags} {
    incr ::sync($flags)
  }

  sqlite3 db test.db
  do_execsql_test 15.$tn.1 "
    CREATE TABLE t1(x);
    PRAGMA wal_autocheckpoint = OFF;
    PRAGMA journal_mode = WAL;
    PRAGMA checkpoint_fullfsync = [lindex $settings 0];
    PRAGMA fullfsync = [lindex $settings 1];
    PRAGMA synchronous = [lindex $settings 2];
  " {0 wal}

  do_test 15.$tn.2 {
    set sync(normal) 0
    set sync(full) 0
    execsql { INSERT INTO t1 VALUES('abc') }
    list $::sync(normal) $::sync(full)
  } $restart_sync

  do_test 15.$tn.3 {
    set sync(normal) 0
    set sync(full) 0
    execsql { INSERT INTO t1 VALUES('abc') }
    list $::sync(normal) $::sync(full)
  } $commit_sync

  do_test 15.$tn.4 {
    set sync(normal) 0
    set sync(full) 0
    execsql { INSERT INTO t1 VALUES('def') }
    list $::sync(normal) $::sync(full)
  } $commit_sync

  do_test 15.$tn.5 {
    set sync(normal) 0
    set sync(full) 0
    execsql { PRAGMA wal_checkpoint }
    list $::sync(normal) $::sync(full)
  } $ckpt_sync
  
  db close
  tvfs delete
}



finish_test

    testvfs T
    T filter {} 
    T script sync_counter
    sqlite3 db test.db -vfs T
  
    execsql "PRAGMA synchronous = $syncmode"
    execsql { PRAGMA journal_mode = WAL }
    execsql { CREATE TABLE filler(a,b,c); }

    set ::syncs [list]
    T filter xSync
    execsql {
      CREATE TABLE x(y);
      INSERT INTO x VALUES('z');
      PRAGMA wal_checkpoint;