Test conversion to TQt3 from Qt3 8c6fc1f8e35fd264dd01c582ca5e7549b32ab731

1 files changed, 2220 insertions, 0 deletions

diff --git a/src/3rdparty/sqlite/pager.c b/src/3rdparty/sqlite/pager.c
new file mode 100644
index 000000000..3b591bc05
--- /dev/null
+++ b/src/3rdparty/sqlite/pager.c
@@ -0,0 +1,2220 @@
+/*
+** 2001 September 15
+**
+** 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 is the implementation of the page cache subsystem or "pager".
+** 
+** The pager is used to access a database disk file.  It implements
+** atomic commit and rollback through the use of a journal file that
+** is separate from the database file.  The pager also implements file
+** locking to prevent two processes from writing the same database
+** file simultaneously, or one process from reading the database while
+** another is writing.
+**
+** @(#) $Id: pager.c,v 1.101 2004/02/25 02:20:41 drh Exp $
+*/
+#include "os.h"         /* Must be first to enable large file support */
+#include "sqliteInt.h"
+#include "pager.h"
+#include <assert.h>
+#include <string.h>
+
+/*
+** Macros for troubleshooting.  Normally turned off
+*/
+#if 0
+static Pager *mainPager = 0;
+#define SET_PAGER(X)  if( mainPager==0 ) mainPager = (X)
+#define CLR_PAGER(X)  if( mainPager==(X) ) mainPager = 0
+#define TRACE1(X)     if( pPager==mainPager ) fprintf(stderr,X)
+#define TRACE2(X,Y)   if( pPager==mainPager ) fprintf(stderr,X,Y)
+#define TRACE3(X,Y,Z) if( pPager==mainPager ) fprintf(stderr,X,Y,Z)
+#else
+#define SET_PAGER(X)
+#define CLR_PAGER(X)
+#define TRACE1(X)
+#define TRACE2(X,Y)
+#define TRACE3(X,Y,Z)
+#endif
+
+
+/*
+** The page cache as a whole is always in one of the following
+** states:
+**
+**   SQLITE_UNLOCK       The page cache is not currently reading or 
+**                       writing the database file.  There is no
+**                       data held in memory.  This is the initial
+**                       state.
+**
+**   SQLITE_READLOCK     The page cache is reading the database.
+**                       Writing is not permitted.  There can be
+**                       multiple readers accessing the same database
+**                       file at the same time.
+**
+**   SQLITE_WRITELOCK    The page cache is writing the database.
+**                       Access is exclusive.  No other processes or
+**                       threads can be reading or writing while one
+**                       process is writing.
+**
+** The page cache comes up in SQLITE_UNLOCK.  The first time a
+** sqlite_page_get() occurs, the state transitions to SQLITE_READLOCK.
+** After all pages have been released using sqlite_page_unref(),
+** the state transitions back to SQLITE_UNLOCK.  The first time
+** that sqlite_page_write() is called, the state transitions to
+** SQLITE_WRITELOCK.  (Note that sqlite_page_write() can only be
+** called on an outstanding page which means that the pager must
+** be in SQLITE_READLOCK before it transitions to SQLITE_WRITELOCK.)
+** The sqlite_page_rollback() and sqlite_page_commit() functions 
+** transition the state from SQLITE_WRITELOCK back to SQLITE_READLOCK.
+*/
+#define SQLITE_UNLOCK      0
+#define SQLITE_READLOCK    1
+#define SQLITE_WRITELOCK   2
+
+
+/*
+** Each in-memory image of a page begins with the following header.
+** This header is only visible to this pager module.  The client
+** code that calls pager sees only the data that follows the header.
+**
+** Client code should call sqlitepager_write() on a page prior to making
+** any modifications to that page.  The first time sqlitepager_write()
+** is called, the original page contents are written into the rollback
+** journal and PgHdr.inJournal and PgHdr.needSync are set.  Later, once
+** the journal page has made it onto the disk surface, PgHdr.needSync
+** is cleared.  The modified page cannot be written back into the original
+** database file until the journal pages has been synced to disk and the
+** PgHdr.needSync has been cleared.
+**
+** The PgHdr.dirty flag is set when sqlitepager_write() is called and
+** is cleared again when the page content is written back to the original
+** database file.
+*/
+typedef struct PgHdr PgHdr;
+struct PgHdr {
+  Pager *pPager;                 /* The pager to which this page belongs */
+  Pgno pgno;                     /* The page number for this page */
+  PgHdr *pNextHash, *pPrevHash;  /* Hash collision chain for PgHdr.pgno */
+  int nRef;                      /* Number of users of this page */
+  PgHdr *pNextFree, *pPrevFree;  /* Freelist of pages where nRef==0 */
+  PgHdr *pNextAll, *pPrevAll;    /* A list of all pages */
+  PgHdr *pNextCkpt, *pPrevCkpt;  /* List of pages in the checkpoint journal */
+  u8 inJournal;                  /* TRUE if has been written to journal */
+  u8 inCkpt;                     /* TRUE if written to the checkpoint journal */
+  u8 dirty;                      /* TRUE if we need to write back changes */
+  u8 needSync;                   /* Sync journal before writing this page */
+  u8 alwaysRollback;             /* Disable dont_rollback() for this page */
+  PgHdr *pDirty;                 /* Dirty pages sorted by PgHdr.pgno */
+  /* SQLITE_PAGE_SIZE bytes of page data follow this header */
+  /* Pager.nExtra bytes of local data follow the page data */
+};
+
+
+/*
+** A macro used for invoking the codec if there is one
+*/
+#ifdef SQLITE_HAS_CODEC
+# define CODEC(P,D,N,X) if( P->xCodec ){ P->xCodec(P->pCodecArg,D,N,X); }
+#else
+# define CODEC(P,D,N,X)
+#endif
+
+/*
+** Convert a pointer to a PgHdr into a pointer to its data
+** and back again.
+*/
+#define PGHDR_TO_DATA(P)  ((void*)(&(P)[1]))
+#define DATA_TO_PGHDR(D)  (&((PgHdr*)(D))[-1])
+#define PGHDR_TO_EXTRA(P) ((void*)&((char*)(&(P)[1]))[SQLITE_PAGE_SIZE])
+
+/*
+** How big to make the hash table used for locating in-memory pages
+** by page number.
+*/
+#define N_PG_HASH 2048
+
+/*
+** Hash a page number
+*/
+#define pager_hash(PN)  ((PN)&(N_PG_HASH-1))
+
+/*
+** A open page cache is an instance of the following structure.
+*/
+struct Pager {
+  char *zFilename;            /* Name of the database file */
+  char *zJournal;             /* Name of the journal file */
+  char *zDirectory;           /* Directory hold database and journal files */
+  OsFile fd, jfd;             /* File descriptors for database and journal */
+  OsFile cpfd;                /* File descriptor for the checkpoint journal */
+  int dbSize;                 /* Number of pages in the file */
+  int origDbSize;             /* dbSize before the current change */
+  int ckptSize;               /* Size of database (in pages) at ckpt_begin() */
+  off_t ckptJSize;            /* Size of journal at ckpt_begin() */
+  int nRec;                   /* Number of pages written to the journal */
+  u32 cksumInit;              /* Quasi-random value added to every checksum */
+  int ckptNRec;               /* Number of records in the checkpoint journal */
+  int nExtra;                 /* Add this many bytes to each in-memory page */
+  void (*xDestructor)(void*); /* Call this routine when freeing pages */
+  int nPage;                  /* Total number of in-memory pages */
+  int nRef;                   /* Number of in-memory pages with PgHdr.nRef>0 */
+  int mxPage;                 /* Maximum number of pages to hold in cache */
+  int nHit, nMiss, nOvfl;     /* Cache hits, missing, and LRU overflows */
+  void (*xCodec)(void*,void*,Pgno,int); /* Routine for en/decoding data */
+  void *pCodecArg;            /* First argument to xCodec() */
+  u8 journalOpen;             /* True if journal file descriptors is valid */
+  u8 journalStarted;          /* True if header of journal is synced */
+  u8 useJournal;              /* Use a rollback journal on this file */
+  u8 ckptOpen;                /* True if the checkpoint journal is open */
+  u8 ckptInUse;               /* True we are in a checkpoint */
+  u8 ckptAutoopen;            /* Open ckpt journal when main journal is opened*/
+  u8 noSync;                  /* Do not sync the journal if true */
+  u8 fullSync;                /* Do extra syncs of the journal for robustness */
+  u8 state;                   /* SQLITE_UNLOCK, _READLOCK or _WRITELOCK */
+  u8 errMask;                 /* One of several kinds of errors */
+  u8 tempFile;                /* zFilename is a temporary file */
+  u8 readOnly;                /* True for a read-only database */
+  u8 needSync;                /* True if an fsync() is needed on the journal */
+  u8 dirtyFile;               /* True if database file has changed in any way */
+  u8 alwaysRollback;          /* Disable dont_rollback() for all pages */
+  u8 *aInJournal;             /* One bit for each page in the database file */
+  u8 *aInCkpt;                /* One bit for each page in the database */
+  PgHdr *pFirst, *pLast;      /* List of free pages */
+  PgHdr *pFirstSynced;        /* First free page with PgHdr.needSync==0 */
+  PgHdr *pAll;                /* List of all pages */
+  PgHdr *pCkpt;               /* List of pages in the checkpoint journal */
+  PgHdr *aHash[N_PG_HASH];    /* Hash table to map page number of PgHdr */
+};
+
+/*
+** These are bits that can be set in Pager.errMask.
+*/
+#define PAGER_ERR_FULL     0x01  /* a write() failed */
+#define PAGER_ERR_MEM      0x02  /* malloc() failed */
+#define PAGER_ERR_LOCK     0x04  /* error in the locking protocol */
+#define PAGER_ERR_CORRUPT  0x08  /* database or journal corruption */
+#define PAGER_ERR_DISK     0x10  /* general disk I/O error - bad hard drive? */
+
+/*
+** The journal file contains page records in the following
+** format.
+**
+** Actually, this structure is the complete page record for pager
+** formats less than 3.  Beginning with format 3, this record is surrounded
+** by two checksums.
+*/
+typedef struct PageRecord PageRecord;
+struct PageRecord {
+  Pgno pgno;                      /* The page number */
+  char aData[SQLITE_PAGE_SIZE];   /* Original data for page pgno */
+};
+
+/*
+** Journal files begin with the following magic string.  The data
+** was obtained from /dev/random.  It is used only as a sanity check.
+**
+** There are three journal formats (so far). The 1st journal format writes
+** 32-bit integers in the byte-order of the host machine.  New
+** formats writes integers as big-endian.  All new journals use the
+** new format, but we have to be able to read an older journal in order
+** to rollback journals created by older versions of the library.
+**
+** The 3rd journal format (added for 2.8.0) adds additional sanity
+** checking information to the journal.  If the power fails while the
+** journal is being written, semi-random garbage data might appear in
+** the journal file after power is restored.  If an attempt is then made
+** to roll the journal back, the database could be corrupted.  The additional
+** sanity checking data is an attempt to discover the garbage in the
+** journal and ignore it.
+**
+** The sanity checking information for the 3rd journal format consists
+** of a 32-bit checksum on each page of data.  The checksum covers both
+** the page number and the SQLITE_PAGE_SIZE bytes of data for the page.
+** This cksum is initialized to a 32-bit random value that appears in the
+** journal file right after the header.  The random initializer is important,
+** because garbage data that appears at the end of a journal is likely
+** data that was once in other files that have now been deleted.  If the
+** garbage data came from an obsolete journal file, the checksums might
+** be correct.  But by initializing the checksum to random value which
+** is different for every journal, we minimize that risk.
+*/
+static const unsigned char aJournalMagic1[] = {
+  0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd4,
+};
+static const unsigned char aJournalMagic2[] = {
+  0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd5,
+};
+static const unsigned char aJournalMagic3[] = {
+  0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd6,
+};
+#define JOURNAL_FORMAT_1 1
+#define JOURNAL_FORMAT_2 2
+#define JOURNAL_FORMAT_3 3
+
+/*
+** The following integer determines what format to use when creating
+** new primary journal files.  By default we always use format 3.
+** When testing, we can set this value to older journal formats in order to
+** make sure that newer versions of the library are able to rollback older
+** journal files.
+**
+** Note that checkpoint journals always use format 2 and omit the header.
+*/
+#ifdef SQLITE_TEST
+int journal_format = 3;
+#else
+# define journal_format 3
+#endif
+
+/*
+** The size of the header and of each page in the journal varies according
+** to which journal format is being used.  The following macros figure out
+** the sizes based on format numbers.
+*/
+#define JOURNAL_HDR_SZ(X) \
+   (sizeof(aJournalMagic1) + sizeof(Pgno) + ((X)>=3)*2*sizeof(u32))
+#define JOURNAL_PG_SZ(X) \
+   (SQLITE_PAGE_SIZE + sizeof(Pgno) + ((X)>=3)*sizeof(u32))
+
+/*
+** Enable reference count tracking here:
+*/
+#ifdef SQLITE_TEST
+  int pager_refinfo_enable = 0;
+  static void pager_refinfo(PgHdr *p){
+    static int cnt = 0;
+    if( !pager_refinfo_enable ) return;
+    printf(
+       "REFCNT: %4d addr=0x%08x nRef=%d\n",
+       p->pgno, (int)PGHDR_TO_DATA(p), p->nRef
+    );
+    cnt++;   /* Something to set a breakpoint on */
+  }
+# define REFINFO(X)  pager_refinfo(X)
+#else
+# define REFINFO(X)
+#endif
+
+/*
+** Read a 32-bit integer from the given file descriptor.  Store the integer
+** that is read in *pRes.  Return SQLITE_OK if everything worked, or an
+** error code is something goes wrong.
+**
+** If the journal format is 2 or 3, read a big-endian integer.  If the
+** journal format is 1, read an integer in the native byte-order of the
+** host machine.
+*/
+static int read32bits(int format, OsFile *fd, u32 *pRes){
+  u32 res;
+  int rc;
+  rc = sqliteOsRead(fd, &res, sizeof(res));
+  if( rc==SQLITE_OK && format>JOURNAL_FORMAT_1 ){
+    unsigned char ac[4];
+    memcpy(ac, &res, 4);
+    res = (ac[0]<<24) | (ac[1]<<16) | (ac[2]<<8) | ac[3];
+  }
+  *pRes = res;
+  return rc;
+}
+
+/*
+** Write a 32-bit integer into the given file descriptor.  Return SQLITE_OK
+** on success or an error code is something goes wrong.
+**
+** If the journal format is 2 or 3, write the integer as 4 big-endian
+** bytes.  If the journal format is 1, write the integer in the native
+** byte order.  In normal operation, only formats 2 and 3 are used.
+** Journal format 1 is only used for testing.
+*/
+static int write32bits(OsFile *fd, u32 val){
+  unsigned char ac[4];
+  if( journal_format<=1 ){
+    return sqliteOsWrite(fd, &val, 4);
+  }
+  ac[0] = (val>>24) & 0xff;
+  ac[1] = (val>>16) & 0xff;
+  ac[2] = (val>>8) & 0xff;
+  ac[3] = val & 0xff;
+  return sqliteOsWrite(fd, ac, 4);
+}
+
+/*
+** Write a 32-bit integer into a page header right before the
+** page data.  This will overwrite the PgHdr.pDirty pointer.
+**
+** The integer is big-endian for formats 2 and 3 and native byte order
+** for journal format 1.
+*/
+static void store32bits(u32 val, PgHdr *p, int offset){
+  unsigned char *ac;
+  ac = &((unsigned char*)PGHDR_TO_DATA(p))[offset];
+  if( journal_format<=1 ){
+    memcpy(ac, &val, 4);
+  }else{
+    ac[0] = (val>>24) & 0xff;
+    ac[1] = (val>>16) & 0xff;
+    ac[2] = (val>>8) & 0xff;
+    ac[3] = val & 0xff;
+  }
+}
+
+
+/*
+** Convert the bits in the pPager->errMask into an approprate
+** return code.
+*/
+static int pager_errcode(Pager *pPager){
+  int rc = SQLITE_OK;
+  if( pPager->errMask & PAGER_ERR_LOCK )    rc = SQLITE_PROTOCOL;
+  if( pPager->errMask & PAGER_ERR_DISK )    rc = SQLITE_IOERR;
+  if( pPager->errMask & PAGER_ERR_FULL )    rc = SQLITE_FULL;
+  if( pPager->errMask & PAGER_ERR_MEM )     rc = SQLITE_NOMEM;
+  if( pPager->errMask & PAGER_ERR_CORRUPT ) rc = SQLITE_CORRUPT;
+  return rc;
+}
+
+/*
+** Add or remove a page from the list of all pages that are in the
+** checkpoint journal.
+**
+** The Pager keeps a separate list of pages that are currently in
+** the checkpoint journal.  This helps the sqlitepager_ckpt_commit()
+** routine run MUCH faster for the common case where there are many
+** pages in memory but only a few are in the checkpoint journal.
+*/
+static void page_add_to_ckpt_list(PgHdr *pPg){
+  Pager *pPager = pPg->pPager;
+  if( pPg->inCkpt ) return;
+  assert( pPg->pPrevCkpt==0 && pPg->pNextCkpt==0 );
+  pPg->pPrevCkpt = 0;
+  if( pPager->pCkpt ){
+    pPager->pCkpt->pPrevCkpt = pPg;
+  }
+  pPg->pNextCkpt = pPager->pCkpt;
+  pPager->pCkpt = pPg;
+  pPg->inCkpt = 1;
+}
+static void page_remove_from_ckpt_list(PgHdr *pPg){
+  if( !pPg->inCkpt ) return;
+  if( pPg->pPrevCkpt ){
+    assert( pPg->pPrevCkpt->pNextCkpt==pPg );
+    pPg->pPrevCkpt->pNextCkpt = pPg->pNextCkpt;
+  }else{
+    assert( pPg->pPager->pCkpt==pPg );
+    pPg->pPager->pCkpt = pPg->pNextCkpt;
+  }
+  if( pPg->pNextCkpt ){
+    assert( pPg->pNextCkpt->pPrevCkpt==pPg );
+    pPg->pNextCkpt->pPrevCkpt = pPg->pPrevCkpt;
+  }
+  pPg->pNextCkpt = 0;
+  pPg->pPrevCkpt = 0;
+  pPg->inCkpt = 0;
+}
+
+/*
+** Find a page in the hash table given its page number.  Return
+** a pointer to the page or NULL if not found.
+*/
+static PgHdr *pager_lookup(Pager *pPager, Pgno pgno){
+  PgHdr *p = pPager->aHash[pager_hash(pgno)];
+  while( p && p->pgno!=pgno ){
+    p = p->pNextHash;
+  }
+  return p;
+}
+
+/*
+** Unlock the database and clear the in-memory cache.  This routine
+** sets the state of the pager back to what it was when it was first
+** opened.  Any outstanding pages are invalidated and subsequent attempts
+** to access those pages will likely result in a coredump.
+*/
+static void pager_reset(Pager *pPager){
+  PgHdr *pPg, *pNext;
+  for(pPg=pPager->pAll; pPg; pPg=pNext){
+    pNext = pPg->pNextAll;
+    sqliteFree(pPg);
+  }
+  pPager->pFirst = 0;
+  pPager->pFirstSynced = 0;
+  pPager->pLast = 0;
+  pPager->pAll = 0;
+  memset(pPager->aHash, 0, sizeof(pPager->aHash));
+  pPager->nPage = 0;
+  if( pPager->state>=SQLITE_WRITELOCK ){
+    sqlitepager_rollback(pPager);
+  }
+  sqliteOsUnlock(&pPager->fd);
+  pPager->state = SQLITE_UNLOCK;
+  pPager->dbSize = -1;
+  pPager->nRef = 0;
+  assert( pPager->journalOpen==0 );
+}
+
+/*
+** When this routine is called, the pager has the journal file open and
+** a write lock on the database.  This routine releases the database
+** write lock and actquires a read lock in its place.  The journal file
+** is deleted and closed.
+**
+** TODO: Consider keeping the journal file open for temporary databases.
+** This might give a performance improvement on windows where opening
+** a file is an expensive operation.
+*/
+static int pager_unwritelock(Pager *pPager){
+  int rc;
+  PgHdr *pPg;
+  if( pPager->state<SQLITE_WRITELOCK ) return SQLITE_OK;
+  sqlitepager_ckpt_commit(pPager);
+  if( pPager->ckptOpen ){
+    sqliteOsClose(&pPager->cpfd);
+    pPager->ckptOpen = 0;
+  }
+  if( pPager->journalOpen ){
+    sqliteOsClose(&pPager->jfd);
+    pPager->journalOpen = 0;
+    sqliteOsDelete(pPager->zJournal);
+    sqliteFree( pPager->aInJournal );
+    pPager->aInJournal = 0;
+    for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
+      pPg->inJournal = 0;
+      pPg->dirty = 0;
+      pPg->needSync = 0;
+    }
+  }else{
+    assert( pPager->dirtyFile==0 || pPager->useJournal==0 );
+  }
+  rc = sqliteOsReadLock(&pPager->fd);
+  if( rc==SQLITE_OK ){
+    pPager->state = SQLITE_READLOCK;
+  }else{
+    /* This can only happen if a process does a BEGIN, then forks and the
+    ** child process does the COMMIT.  Because of the semantics of unix
+    ** file locking, the unlock will fail.
+    */
+    pPager->state = SQLITE_UNLOCK;
+  }
+  return rc;
+}
+
+/*
+** Compute and return a checksum for the page of data.
+**
+** This is not a real checksum.  It is really just the sum of the 
+** random initial value and the page number.  We considered do a checksum
+** of the database, but that was found to be too slow.
+*/
+static u32 pager_cksum(Pager *pPager, Pgno pgno, const char *aData){
+  u32 cksum = pPager->cksumInit + pgno;
+  return cksum;
+}
+
+/*
+** Read a single page from the journal file opened on file descriptor
+** jfd.  Playback this one page.
+**
+** There are three different journal formats.  The format parameter determines
+** which format is used by the journal that is played back.
+*/
+static int pager_playback_one_page(Pager *pPager, OsFile *jfd, int format){
+  int rc;
+  PgHdr *pPg;              /* An existing page in the cache */
+  PageRecord pgRec;
+  u32 cksum;
+
+  rc = read32bits(format, jfd, &pgRec.pgno);
+  if( rc!=SQLITE_OK ) return rc;
+  rc = sqliteOsRead(jfd, &pgRec.aData, sizeof(pgRec.aData));
+  if( rc!=SQLITE_OK ) return rc;
+
+  /* Sanity checking on the page.  This is more important that I originally
+  ** thought.  If a power failure occurs while the journal is being written,
+  ** it could cause invalid data to be written into the journal.  We need to
+  ** detect this invalid data (with high probability) and ignore it.
+  */
+  if( pgRec.pgno==0 ){
+    return SQLITE_DONE;
+  }
+  if( pgRec.pgno>(unsigned)pPager->dbSize ){
+    return SQLITE_OK;
+  }
+  if( format>=JOURNAL_FORMAT_3 ){
+    rc = read32bits(format, jfd, &cksum);
+    if( rc ) return rc;
+    if( pager_cksum(pPager, pgRec.pgno, pgRec.aData)!=cksum ){
+      return SQLITE_DONE;
+    }
+  }
+
+  /* Playback the page.  Update the in-memory copy of the page
+  ** at the same time, if there is one.
+  */
+  pPg = pager_lookup(pPager, pgRec.pgno);
+  TRACE2("PLAYBACK %d\n", pgRec.pgno);
+  sqliteOsSeek(&pPager->fd, (pgRec.pgno-1)*(off_t)SQLITE_PAGE_SIZE);
+  rc = sqliteOsWrite(&pPager->fd, pgRec.aData, SQLITE_PAGE_SIZE);
+  if( pPg ){
+    /* No page should ever be rolled back that is in use, except for page
+    ** 1 which is held in use in order to keep the lock on the database
+    ** active.
+    */
+    assert( pPg->nRef==0 || pPg->pgno==1 );
+    memcpy(PGHDR_TO_DATA(pPg), pgRec.aData, SQLITE_PAGE_SIZE);
+    memset(PGHDR_TO_EXTRA(pPg), 0, pPager->nExtra);
+    pPg->dirty = 0;
+    pPg->needSync = 0;
+    CODEC(pPager, PGHDR_TO_DATA(pPg), pPg->pgno, 3);
+  }
+  return rc;
+}
+
+/*
+** Playback the journal and thus restore the database file to
+** the state it was in before we started making changes.  
+**
+** The journal file format is as follows: 
+**
+**    *  8 byte prefix.  One of the aJournalMagic123 vectors defined
+**       above.  The format of the journal file is determined by which
+**       of the three prefix vectors is seen.
+**    *  4 byte big-endian integer which is the number of valid page records
+**       in the journal.  If this value is 0xffffffff, then compute the
+**       number of page records from the journal size.  This field appears
+**       in format 3 only.
+**    *  4 byte big-endian integer which is the initial value for the 
+**       sanity checksum.  This field appears in format 3 only.
+**    *  4 byte integer which is the number of pages to truncate the
+**       database to during a rollback.
+**    *  Zero or more pages instances, each as follows:
+**        +  4 byte page number.
+**        +  SQLITE_PAGE_SIZE bytes of data.
+**        +  4 byte checksum (format 3 only)
+**
+** When we speak of the journal header, we mean the first 4 bullets above.
+** Each entry in the journal is an instance of the 5th bullet.  Note that
+** bullets 2 and 3 only appear in format-3 journals.
+**
+** Call the value from the second bullet "nRec".  nRec is the number of
+** valid page entries in the journal.  In most cases, you can compute the
+** value of nRec from the size of the journal file.  But if a power
+** failure occurred while the journal was being written, it could be the
+** case that the size of the journal file had already been increased but
+** the extra entries had not yet made it safely to disk.  In such a case,
+** the value of nRec computed from the file size would be too large.  For
+** that reason, we always use the nRec value in the header.
+**
+** If the nRec value is 0xffffffff it means that nRec should be computed
+** from the file size.  This value is used when the user selects the
+** no-sync option for the journal.  A power failure could lead to corruption
+** in this case.  But for things like temporary table (which will be
+** deleted when the power is restored) we don't care.  
+**
+** Journal formats 1 and 2 do not have an nRec value in the header so we
+** have to compute nRec from the file size.  This has risks (as described
+** above) which is why all persistent tables have been changed to use
+** format 3.
+**
+** If the file opened as the journal file is not a well-formed
+** journal file then the database will likely already be
+** corrupted, so the PAGER_ERR_CORRUPT bit is set in pPager->errMask
+** and SQLITE_CORRUPT is returned.  If it all works, then this routine
+** returns SQLITE_OK.
+*/
+static int pager_playback(Pager *pPager, int useJournalSize){
+  off_t szJ;               /* Size of the journal file in bytes */
+  int nRec;                /* Number of Records in the journal */
+  int i;                   /* Loop counter */
+  Pgno mxPg = 0;           /* Size of the original file in pages */
+  int format;              /* Format of the journal file. */
+  unsigned char aMagic[sizeof(aJournalMagic1)];
+  int rc;
+
+  /* Figure out how many records are in the journal.  Abort early if
+  ** the journal is empty.
+  */
+  assert( pPager->journalOpen );
+  sqliteOsSeek(&pPager->jfd, 0);
+  rc = sqliteOsFileSize(&pPager->jfd, &szJ);
+  if( rc!=SQLITE_OK ){
+    goto end_playback;
+  }
+
+  /* If the journal file is too small to contain a complete header,
+  ** it must mean that the process that created the journal was just
+  ** beginning to write the journal file when it died.  In that case,
+  ** the database file should have still been completely unchanged.
+  ** Nothing needs to be rolled back.  We can safely ignore this journal.
+  */
+  if( szJ < sizeof(aMagic)+sizeof(Pgno) ){
+    goto end_playback;
+  }
+
+  /* Read the beginning of the journal and truncate the
+  ** database file back to its original size.
+  */
+  rc = sqliteOsRead(&pPager->jfd, aMagic, sizeof(aMagic));
+  if( rc!=SQLITE_OK ){
+    rc = SQLITE_PROTOCOL;
+    goto end_playback;
+  }
+  if( memcmp(aMagic, aJournalMagic3, sizeof(aMagic))==0 ){
+    format = JOURNAL_FORMAT_3;
+  }else if( memcmp(aMagic, aJournalMagic2, sizeof(aMagic))==0 ){
+    format = JOURNAL_FORMAT_2;
+  }else if( memcmp(aMagic, aJournalMagic1, sizeof(aMagic))==0 ){
+    format = JOURNAL_FORMAT_1;
+  }else{
+    rc = SQLITE_PROTOCOL;
+    goto end_playback;
+  }
+  if( format>=JOURNAL_FORMAT_3 ){
+    if( szJ < sizeof(aMagic) + 3*sizeof(u32) ){
+      /* Ignore the journal if it is too small to contain a complete
+      ** header.  We already did this test once above, but at the prior
+      ** test, we did not know the journal format and so we had to assume
+      ** the smallest possible header.  Now we know the header is bigger
+      ** than the minimum so we test again.
+      */
+      goto end_playback;
+    }
+    rc = read32bits(format, &pPager->jfd, (u32*)&nRec);
+    if( rc ) goto end_playback;
+    rc = read32bits(format, &pPager->jfd, &pPager->cksumInit);
+    if( rc ) goto end_playback;
+    if( nRec==0xffffffff || useJournalSize ){
+      nRec = (szJ - JOURNAL_HDR_SZ(3))/JOURNAL_PG_SZ(3);
+    }
+  }else{
+    nRec = (szJ - JOURNAL_HDR_SZ(2))/JOURNAL_PG_SZ(2);
+    assert( nRec*JOURNAL_PG_SZ(2)+JOURNAL_HDR_SZ(2)==szJ );
+  }
+  rc = read32bits(format, &pPager->jfd, &mxPg);
+  if( rc!=SQLITE_OK ){
+    goto end_playback;
+  }
+  assert( pPager->origDbSize==0 || pPager->origDbSize==mxPg );
+  rc = sqliteOsTruncate(&pPager->fd, SQLITE_PAGE_SIZE*(off_t)mxPg);
+  if( rc!=SQLITE_OK ){
+    goto end_playback;
+  }
+  pPager->dbSize = mxPg;
+  
+  /* Copy original pages out of the journal and back into the database file.
+  */
+  for(i=0; i<nRec; i++){
+    rc = pager_playback_one_page(pPager, &pPager->jfd, format);
+    if( rc!=SQLITE_OK ){
+      if( rc==SQLITE_DONE ){
+        rc = SQLITE_OK;
+      }
+      break;
+    }
+  }
+
+  /* Pages that have been written to the journal but never synced
+  ** where not restored by the loop above.  We have to restore those
+  ** pages by reading them back from the original database.
+  */
+  if( rc==SQLITE_OK ){
+    PgHdr *pPg;
+    for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
+      char zBuf[SQLITE_PAGE_SIZE];
+      if( !pPg->dirty ) continue;
+      if( (int)pPg->pgno <= pPager->origDbSize ){
+        sqliteOsSeek(&pPager->fd, SQLITE_PAGE_SIZE*(off_t)(pPg->pgno-1));
+        rc = sqliteOsRead(&pPager->fd, zBuf, SQLITE_PAGE_SIZE);
+        TRACE2("REFETCH %d\n", pPg->pgno);
+        CODEC(pPager, zBuf, pPg->pgno, 2);
+        if( rc ) break;
+      }else{
+        memset(zBuf, 0, SQLITE_PAGE_SIZE);
+      }
+      if( pPg->nRef==0 || memcmp(zBuf, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE) ){
+        memcpy(PGHDR_TO_DATA(pPg), zBuf, SQLITE_PAGE_SIZE);
+        memset(PGHDR_TO_EXTRA(pPg), 0, pPager->nExtra);
+      }
+      pPg->needSync = 0;
+      pPg->dirty = 0;
+    }
+  }
+
+end_playback:
+  if( rc!=SQLITE_OK ){
+    pager_unwritelock(pPager);
+    pPager->errMask |= PAGER_ERR_CORRUPT;
+    rc = SQLITE_CORRUPT;
+  }else{
+    rc = pager_unwritelock(pPager);
+  }
+  return rc;
+}
+
+/*
+** Playback the checkpoint journal.
+**
+** This is similar to playing back the transaction journal but with
+** a few extra twists.
+**
+**    (1)  The number of pages in the database file at the start of
+**         the checkpoint is stored in pPager->ckptSize, not in the
+**         journal file itself.
+**
+**    (2)  In addition to playing back the checkpoint journal, also
+**         playback all pages of the transaction journal beginning
+**         at offset pPager->ckptJSize.
+*/
+static int pager_ckpt_playback(Pager *pPager){
+  off_t szJ;               /* Size of the full journal */
+  int nRec;                /* Number of Records */
+  int i;                   /* Loop counter */
+  int rc;
+
+  /* Truncate the database back to its original size.
+  */
+  rc = sqliteOsTruncate(&pPager->fd, SQLITE_PAGE_SIZE*(off_t)pPager->ckptSize);
+  pPager->dbSize = pPager->ckptSize;
+
+  /* Figure out how many records are in the checkpoint journal.
+  */
+  assert( pPager->ckptInUse && pPager->journalOpen );
+  sqliteOsSeek(&pPager->cpfd, 0);
+  nRec = pPager->ckptNRec;
+  
+  /* Copy original pages out of the checkpoint journal and back into the
+  ** database file.  Note that the checkpoint journal always uses format
+  ** 2 instead of format 3 since it does not need to be concerned with
+  ** power failures corrupting the journal and can thus omit the checksums.
+  */
+  for(i=nRec-1; i>=0; i--){
+    rc = pager_playback_one_page(pPager, &pPager->cpfd, 2);
+    assert( rc!=SQLITE_DONE );
+    if( rc!=SQLITE_OK ) goto end_ckpt_playback;
+  }
+
+  /* Figure out how many pages need to be copied out of the transaction
+  ** journal.
+  */
+  rc = sqliteOsSeek(&pPager->jfd, pPager->ckptJSize);
+  if( rc!=SQLITE_OK ){
+    goto end_ckpt_playback;
+  }
+  rc = sqliteOsFileSize(&pPager->jfd, &szJ);
+  if( rc!=SQLITE_OK ){
+    goto end_ckpt_playback;
+  }
+  nRec = (szJ - pPager->ckptJSize)/JOURNAL_PG_SZ(journal_format);
+  for(i=nRec-1; i>=0; i--){
+    rc = pager_playback_one_page(pPager, &pPager->jfd, journal_format);
+    if( rc!=SQLITE_OK ){
+      assert( rc!=SQLITE_DONE );
+      goto end_ckpt_playback;
+    }
+  }
+  
+end_ckpt_playback:
+  if( rc!=SQLITE_OK ){
+    pPager->errMask |= PAGER_ERR_CORRUPT;
+    rc = SQLITE_CORRUPT;
+  }
+  return rc;
+}
+
+/*
+** Change the maximum number of in-memory pages that are allowed.
+**
+** The maximum number is the absolute value of the mxPage parameter.
+** If mxPage is negative, the noSync flag is also set.  noSync bypasses
+** calls to sqliteOsSync().  The pager runs much faster with noSync on,
+** but if the operating system crashes or there is an abrupt power 
+** failure, the database file might be left in an inconsistent and
+** unrepairable state.  
+*/
+void sqlitepager_set_cachesize(Pager *pPager, int mxPage){
+  if( mxPage>=0 ){
+    pPager->noSync = pPager->tempFile;
+    if( pPager->noSync==0 ) pPager->needSync = 0;
+  }else{
+    pPager->noSync = 1;
+    mxPage = -mxPage;
+  }
+  if( mxPage>10 ){
+    pPager->mxPage = mxPage;
+  }
+}
+
+/*
+** Adjust the robustness of the database to damage due to OS crashes
+** or power failures by changing the number of syncs()s when writing
+** the rollback journal.  There are three levels:
+**
+**    OFF       sqliteOsSync() is never called.  This is the default
+**              for temporary and transient files.
+**
+**    NORMAL    The journal is synced once before writes begin on the
+**              database.  This is normally adequate protection, but
+**              it is theoretically possible, though very unlikely,
+**              that an inopertune power failure could leave the journal
+**              in a state which would cause damage to the database
+**              when it is rolled back.
+**
+**    FULL      The journal is synced twice before writes begin on the
+**              database (with some additional information - the nRec field
+**              of the journal header - being written in between the two
+**              syncs).  If we assume that writing a
+**              single disk sector is atomic, then this mode provides
+**              assurance that the journal will not be corrupted to the
+**              point of causing damage to the database during rollback.
+**
+** Numeric values associated with these states are OFF==1, NORMAL=2,
+** and FULL=3.
+*/
+void sqlitepager_set_safety_level(Pager *pPager, int level){
+  pPager->noSync =  level==1 || pPager->tempFile;
+  pPager->fullSync = level==3 && !pPager->tempFile;
+  if( pPager->noSync==0 ) pPager->needSync = 0;
+}
+
+/*
+** Open a temporary file.  Write the name of the file into zName
+** (zName must be at least SQLITE_TEMPNAME_SIZE bytes long.)  Write
+** the file descriptor into *fd.  Return SQLITE_OK on success or some
+** other error code if we fail.
+**
+** The OS will automatically delete the temporary file when it is
+** closed.
+*/
+static int sqlitepager_opentemp(char *zFile, OsFile *fd){
+  int cnt = 8;
+  int rc;
+  do{
+    cnt--;
+    sqliteOsTempFileName(zFile);
+    rc = sqliteOsOpenExclusive(zFile, fd, 1);
+  }while( cnt>0 && rc!=SQLITE_OK );
+  return rc;
+}
+
+/*
+** Create a new page cache and put a pointer to the page cache in *ppPager.
+** The file to be cached need not exist.  The file is not locked until
+** the first call to sqlitepager_get() and is only held open until the
+** last page is released using sqlitepager_unref().
+**
+** If zFilename is NULL then a randomly-named temporary file is created
+** and used as the file to be cached.  The file will be deleted
+** automatically when it is closed.
+*/
+int sqlitepager_open(
+  Pager **ppPager,         /* Return the Pager structure here */
+  const char *zFilename,   /* Name of the database file to open */
+  int mxPage,              /* Max number of in-memory cache pages */
+  int nExtra,              /* Extra bytes append to each in-memory page */
+  int useJournal           /* TRUE to use a rollback journal on this file */
+){
+  Pager *pPager;
+  char *zFullPathname;
+  int nameLen;
+  OsFile fd;
+  int rc, i;
+  int tempFile;
+  int readOnly = 0;
+  char zTemp[SQLITE_TEMPNAME_SIZE];
+
+  *ppPager = 0;
+  if( sqlite_malloc_failed ){
+    return SQLITE_NOMEM;
+  }
+  if( zFilename && zFilename[0] ){
+    zFullPathname = sqliteOsFullPathname(zFilename);
+    rc = sqliteOsOpenReadWrite(zFullPathname, &fd, &readOnly);
+    tempFile = 0;
+  }else{
+    rc = sqlitepager_opentemp(zTemp, &fd);
+    zFilename = zTemp;
+    zFullPathname = sqliteOsFullPathname(zFilename);
+    tempFile = 1;
+  }
+  if( sqlite_malloc_failed ){
+    return SQLITE_NOMEM;
+  }
+  if( rc!=SQLITE_OK ){
+    sqliteFree(zFullPathname);
+    return SQLITE_CANTOPEN;
+  }
+  nameLen = strlen(zFullPathname);
+  pPager = sqliteMalloc( sizeof(*pPager) + nameLen*3 + 30 );
+  if( pPager==0 ){
+    sqliteOsClose(&fd);
+    sqliteFree(zFullPathname);
+    return SQLITE_NOMEM;
+  }
+  SET_PAGER(pPager);
+  pPager->zFilename = (char*)&pPager[1];
+  pPager->zDirectory = &pPager->zFilename[nameLen+1];
+  pPager->zJournal = &pPager->zDirectory[nameLen+1];
+  strcpy(pPager->zFilename, zFullPathname);
+  strcpy(pPager->zDirectory, zFullPathname);
+  for(i=nameLen; i>0 && pPager->zDirectory[i-1]!='/'; i--){}
+  if( i>0 ) pPager->zDirectory[i-1] = 0;
+  strcpy(pPager->zJournal, zFullPathname);
+  sqliteFree(zFullPathname);
+  strcpy(&pPager->zJournal[nameLen], "-journal");
+  pPager->fd = fd;
+  pPager->journalOpen = 0;
+  pPager->useJournal = useJournal;
+  pPager->ckptOpen = 0;
+  pPager->ckptInUse = 0;
+  pPager->nRef = 0;
+  pPager->dbSize = -1;
+  pPager->ckptSize = 0;
+  pPager->ckptJSize = 0;
+  pPager->nPage = 0;
+  pPager->mxPage = mxPage>5 ? mxPage : 10;
+  pPager->state = SQLITE_UNLOCK;
+  pPager->errMask = 0;
+  pPager->tempFile = tempFile;
+  pPager->readOnly = readOnly;
+  pPager->needSync = 0;
+  pPager->noSync = pPager->tempFile || !useJournal;
+  pPager->pFirst = 0;
+  pPager->pFirstSynced = 0;
+  pPager->pLast = 0;
+  pPager->nExtra = nExtra;
+  memset(pPager->aHash, 0, sizeof(pPager->aHash));
+  *ppPager = pPager;
+  return SQLITE_OK;
+}
+
+/*
+** Set the destructor for this pager.  If not NULL, the destructor is called
+** when the reference count on each page reaches zero.  The destructor can
+** be used to clean up information in the extra segment appended to each page.
+**
+** The destructor is not called as a result sqlitepager_close().  
+** Destructors are only called by sqlitepager_unref().
+*/
+void sqlitepager_set_destructor(Pager *pPager, void (*xDesc)(void*)){
+  pPager->xDestructor = xDesc;
+}
+
+/*
+** Return the total number of pages in the disk file associated with
+** pPager.
+*/
+int sqlitepager_pagecount(Pager *pPager){
+  off_t n;
+  assert( pPager!=0 );
+  if( pPager->dbSize>=0 ){
+    return pPager->dbSize;
+  }
+  if( sqliteOsFileSize(&pPager->fd, &n)!=SQLITE_OK ){
+    pPager->errMask |= PAGER_ERR_DISK;
+    return 0;
+  }
+  n /= SQLITE_PAGE_SIZE;
+  if( pPager->state!=SQLITE_UNLOCK ){
+    pPager->dbSize = n;
+  }
+  return n;
+}
+
+/*
+** Forward declaration
+*/
+static int syncJournal(Pager*);
+
+/*
+** Truncate the file to the number of pages specified.
+*/
+int sqlitepager_truncate(Pager *pPager, Pgno nPage){
+  int rc;
+  if( pPager->dbSize<0 ){
+    sqlitepager_pagecount(pPager);
+  }
+  if( pPager->errMask!=0 ){
+    rc = pager_errcode(pPager);
+    return rc;
+  }
+  if( nPage>=(unsigned)pPager->dbSize ){
+    return SQLITE_OK;
+  }
+  syncJournal(pPager);
+  rc = sqliteOsTruncate(&pPager->fd, SQLITE_PAGE_SIZE*(off_t)nPage);
+  if( rc==SQLITE_OK ){
+    pPager->dbSize = nPage;
+  }
+  return rc;
+}
+
+/*
+** Shutdown the page cache.  Free all memory and close all files.
+**
+** If a transaction was in progress when this routine is called, that
+** transaction is rolled back.  All outstanding pages are invalidated
+** and their memory is freed.  Any attempt to use a page associated
+** with this page cache after this function returns will likely
+** result in a coredump.
+*/
+int sqlitepager_close(Pager *pPager){
+  PgHdr *pPg, *pNext;
+  switch( pPager->state ){
+    case SQLITE_WRITELOCK: {
+      sqlitepager_rollback(pPager);
+      sqliteOsUnlock(&pPager->fd);
+      assert( pPager->journalOpen==0 );
+      break;
+    }
+    case SQLITE_READLOCK: {
+      sqliteOsUnlock(&pPager->fd);
+      break;
+    }
+    default: {
+      /* Do nothing */
+      break;
+    }
+  }
+  for(pPg=pPager->pAll; pPg; pPg=pNext){
+    pNext = pPg->pNextAll;
+    sqliteFree(pPg);
+  }
+  sqliteOsClose(&pPager->fd);
+  assert( pPager->journalOpen==0 );
+  /* Temp files are automatically deleted by the OS
+  ** if( pPager->tempFile ){
+  **   sqliteOsDelete(pPager->zFilename);
+  ** }
+  */
+  CLR_PAGER(pPager);
+  if( pPager->zFilename!=(char*)&pPager[1] ){
+    assert( 0 );  /* Cannot happen */
+    sqliteFree(pPager->zFilename);
+    sqliteFree(pPager->zJournal);
+    sqliteFree(pPager->zDirectory);
+  }
+  sqliteFree(pPager);
+  return SQLITE_OK;
+}
+
+/*
+** Return the page number for the given page data.
+*/
+Pgno sqlitepager_pagenumber(void *pData){
+  PgHdr *p = DATA_TO_PGHDR(pData);
+  return p->pgno;
+}
+
+/*
+** Increment the reference count for a page.  If the page is
+** currently on the freelist (the reference count is zero) then
+** remove it from the freelist.
+*/
+#define page_ref(P)   ((P)->nRef==0?_page_ref(P):(void)(P)->nRef++)
+static void _page_ref(PgHdr *pPg){
+  if( pPg->nRef==0 ){
+    /* The page is currently on the freelist.  Remove it. */
+    if( pPg==pPg->pPager->pFirstSynced ){
+      PgHdr *p = pPg->pNextFree;
+      while( p && p->needSync ){ p = p->pNextFree; }
+      pPg->pPager->pFirstSynced = p;
+    }
+    if( pPg->pPrevFree ){
+      pPg->pPrevFree->pNextFree = pPg->pNextFree;
+    }else{
+      pPg->pPager->pFirst = pPg->pNextFree;
+    }
+    if( pPg->pNextFree ){
+      pPg->pNextFree->pPrevFree = pPg->pPrevFree;
+    }else{
+      pPg->pPager->pLast = pPg->pPrevFree;
+    }
+    pPg->pPager->nRef++;
+  }
+  pPg->nRef++;
+  REFINFO(pPg);
+}
+
+/*
+** Increment the reference count for a page.  The input pointer is
+** a reference to the page data.
+*/
+int sqlitepager_ref(void *pData){
+  PgHdr *pPg = DATA_TO_PGHDR(pData);
+  page_ref(pPg);
+  return SQLITE_OK;
+}
+
+/*
+** Sync the journal.  In other words, make sure all the pages that have
+** been written to the journal have actually reached the surface of the
+** disk.  It is not safe to modify the original database file until after
+** the journal has been synced.  If the original database is modified before
+** the journal is synced and a power failure occurs, the unsynced journal
+** data would be lost and we would be unable to completely rollback the
+** database changes.  Database corruption would occur.
+** 
+** This routine also updates the nRec field in the header of the journal.
+** (See comments on the pager_playback() routine for additional information.)
+** If the sync mode is FULL, two syncs will occur.  First the whole journal
+** is synced, then the nRec field is updated, then a second sync occurs.
+**
+** For temporary databases, we do not care if we are able to rollback
+** after a power failure, so sync occurs.
+**
+** This routine clears the needSync field of every page current held in
+** memory.
+*/
+static int syncJournal(Pager *pPager){
+  PgHdr *pPg;
+  int rc = SQLITE_OK;
+
+  /* Sync the journal before modifying the main database
+  ** (assuming there is a journal and it needs to be synced.)
+  */
+  if( pPager->needSync ){
+    if( !pPager->tempFile ){
+      assert( pPager->journalOpen );
+      /* assert( !pPager->noSync ); // noSync might be set if synchronous
+      ** was turned off after the transaction was started.  Ticket #615 */
+#ifndef NDEBUG
+      {
+        /* Make sure the pPager->nRec counter we are keeping agrees
+        ** with the nRec computed from the size of the journal file.
+        */
+        off_t hdrSz, pgSz, jSz;
+        hdrSz = JOURNAL_HDR_SZ(journal_format);
+        pgSz = JOURNAL_PG_SZ(journal_format);
+        rc = sqliteOsFileSize(&pPager->jfd, &jSz);
+        if( rc!=0 ) return rc;
+        assert( pPager->nRec*pgSz+hdrSz==jSz );
+      }
+#endif
+      if( journal_format>=3 ){
+        /* Write the nRec value into the journal file header */
+        off_t szJ;
+        if( pPager->fullSync ){
+          TRACE1("SYNC\n");
+          rc = sqliteOsSync(&pPager->jfd);
+          if( rc!=0 ) return rc;
+        }
+        sqliteOsSeek(&pPager->jfd, sizeof(aJournalMagic1));
+        rc = write32bits(&pPager->jfd, pPager->nRec);
+        if( rc ) return rc;
+        szJ = JOURNAL_HDR_SZ(journal_format) +
+                 pPager->nRec*JOURNAL_PG_SZ(journal_format);
+        sqliteOsSeek(&pPager->jfd, szJ);
+      }
+      TRACE1("SYNC\n");
+      rc = sqliteOsSync(&pPager->jfd);
+      if( rc!=0 ) return rc;
+      pPager->journalStarted = 1;
+    }
+    pPager->needSync = 0;
+
+    /* Erase the needSync flag from every page.
+    */
+    for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
+      pPg->needSync = 0;
+    }
+    pPager->pFirstSynced = pPager->pFirst;
+  }
+
+#ifndef NDEBUG
+  /* If the Pager.needSync flag is clear then the PgHdr.needSync
+  ** flag must also be clear for all pages.  Verify that this
+  ** invariant is true.
+  */
+  else{
+    for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
+      assert( pPg->needSync==0 );
+    }
+    assert( pPager->pFirstSynced==pPager->pFirst );
+  }
+#endif
+
+  return rc;
+}
+
+/*
+** Given a list of pages (connected by the PgHdr.pDirty pointer) write
+** every one of those pages out to the database file and mark them all
+** as clean.
+*/
+static int pager_write_pagelist(PgHdr *pList){
+  Pager *pPager;
+  int rc;
+
+  if( pList==0 ) return SQLITE_OK;
+  pPager = pList->pPager;
+  while( pList ){
+    assert( pList->dirty );
+    sqliteOsSeek(&pPager->fd, (pList->pgno-1)*(off_t)SQLITE_PAGE_SIZE);
+    CODEC(pPager, PGHDR_TO_DATA(pList), pList->pgno, 6);
+    TRACE2("STORE %d\n", pList->pgno);
+    rc = sqliteOsWrite(&pPager->fd, PGHDR_TO_DATA(pList), SQLITE_PAGE_SIZE);
+    CODEC(pPager, PGHDR_TO_DATA(pList), pList->pgno, 0);
+    if( rc ) return rc;
+    pList->dirty = 0;
+    pList = pList->pDirty;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Collect every dirty page into a dirty list and
+** return a pointer to the head of that list.  All pages are
+** collected even if they are still in use.
+*/
+static PgHdr *pager_get_all_dirty_pages(Pager *pPager){
+  PgHdr *p, *pList;
+  pList = 0;
+  for(p=pPager->pAll; p; p=p->pNextAll){
+    if( p->dirty ){
+      p->pDirty = pList;
+      pList = p;
+    }
+  }
+  return pList;
+}
+
+/*
+** Actquire a page.
+**
+** A read lock on the disk file is obtained when the first page is actquired. 
+** This read lock is dropped when the last page is released.
+**
+** A _get works for any page number greater than 0.  If the database
+** file is smaller than the requested page, then no actual disk
+** read occurs and the memory image of the page is initialized to
+** all zeros.  The extra data appended to a page is always initialized
+** to zeros the first time a page is loaded into memory.
+**
+** The actquisition might fail for several reasons.  In all cases,
+** an appropriate error code is returned and *ppPage is set to NULL.
+**
+** See also sqlitepager_lookup().  Both this routine and _lookup() attempt
+** to find a page in the in-memory cache first.  If the page is not already
+** in memory, this routine goes to disk to read it in whereas _lookup()
+** just returns 0.  This routine actquires a read-lock the first time it
+** has to go to disk, and could also playback an old journal if necessary.
+** Since _lookup() never goes to disk, it never has to deal with locks
+** or journal files.
+*/
+int sqlitepager_get(Pager *pPager, Pgno pgno, void **ppPage){
+  PgHdr *pPg;
+  int rc;
+
+  /* Make sure we have not hit any critical errors.
+  */ 
+  assert( pPager!=0 );
+  assert( pgno!=0 );
+  *ppPage = 0;
+  if( pPager->errMask & ~(PAGER_ERR_FULL) ){
+    return pager_errcode(pPager);
+  }
+
+  /* If this is the first page accessed, then get a read lock
+  ** on the database file.
+  */
+  if( pPager->nRef==0 ){
+    rc = sqliteOsReadLock(&pPager->fd);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    pPager->state = SQLITE_READLOCK;
+
+    /* If a journal file exists, try to play it back.
+    */
+    if( pPager->useJournal && sqliteOsFileExists(pPager->zJournal) ){
+       int rc;
+
+       /* Get a write lock on the database
+       */
+       rc = sqliteOsWriteLock(&pPager->fd);
+       if( rc!=SQLITE_OK ){
+         if( sqliteOsUnlock(&pPager->fd)!=SQLITE_OK ){
+           /* This should never happen! */
+           rc = SQLITE_INTERNAL;
+         }
+         return rc;
+       }
+       pPager->state = SQLITE_WRITELOCK;
+
+       /* Open the journal for reading only.  Return SQLITE_BUSY if
+       ** we are unable to open the journal file. 
+       **
+       ** The journal file does not need to be locked itself.  The
+       ** journal file is never open unless the main database file holds
+       ** a write lock, so there is never any chance of two or more
+       ** processes opening the journal at the same time.
+       */
+       rc = sqliteOsOpenReadOnly(pPager->zJournal, &pPager->jfd);
+       if( rc!=SQLITE_OK ){
+         rc = sqliteOsUnlock(&pPager->fd);
+         assert( rc==SQLITE_OK );
+         return SQLITE_BUSY;
+       }
+       pPager->journalOpen = 1;
+       pPager->journalStarted = 0;
+
+       /* Playback and delete the journal.  Drop the database write
+       ** lock and reactquire the read lock.
+       */
+       rc = pager_playback(pPager, 0);
+       if( rc!=SQLITE_OK ){
+         return rc;
+       }
+    }
+    pPg = 0;
+  }else{
+    /* Search for page in cache */
+    pPg = pager_lookup(pPager, pgno);
+  }
+  if( pPg==0 ){
+    /* The requested page is not in the page cache. */
+    int h;
+    pPager->nMiss++;
+    if( pPager->nPage<pPager->mxPage || pPager->pFirst==0 ){
+      /* Create a new page */
+      pPg = sqliteMallocRaw( sizeof(*pPg) + SQLITE_PAGE_SIZE 
+                              + sizeof(u32) + pPager->nExtra );
+      if( pPg==0 ){
+        pager_unwritelock(pPager);
+        pPager->errMask |= PAGER_ERR_MEM;
+        return SQLITE_NOMEM;
+      }
+      memset(pPg, 0, sizeof(*pPg));
+      pPg->pPager = pPager;
+      pPg->pNextAll = pPager->pAll;
+      if( pPager->pAll ){
+        pPager->pAll->pPrevAll = pPg;
+      }
+      pPg->pPrevAll = 0;
+      pPager->pAll = pPg;
+      pPager->nPage++;
+    }else{
+      /* Find a page to recycle.  Try to locate a page that does not
+      ** retquire us to do an fsync() on the journal.
+      */
+      pPg = pPager->pFirstSynced;
+
+      /* If we could not find a page that does not retquire an fsync()
+      ** on the journal file then fsync the journal file.  This is a
+      ** very slow operation, so we work hard to avoid it.  But sometimes
+      ** it can't be helped.
+      */
+      if( pPg==0 ){
+        int rc = syncJournal(pPager);
+        if( rc!=0 ){
+          sqlitepager_rollback(pPager);
+          return SQLITE_IOERR;
+        }
+        pPg = pPager->pFirst;
+      }
+      assert( pPg->nRef==0 );
+
+      /* Write the page to the database file if it is dirty.
+      */
+      if( pPg->dirty ){
+        assert( pPg->needSync==0 );
+        pPg->pDirty = 0;
+        rc = pager_write_pagelist( pPg );
+        if( rc!=SQLITE_OK ){
+          sqlitepager_rollback(pPager);
+          return SQLITE_IOERR;
+        }
+      }
+      assert( pPg->dirty==0 );
+
+      /* If the page we are recycling is marked as alwaysRollback, then
+      ** set the global alwaysRollback flag, thus disabling the
+      ** sqlite_dont_rollback() optimization for the rest of this transaction.
+      ** It is necessary to do this because the page marked alwaysRollback
+      ** might be reloaded at a later time but at that point we won't remember
+      ** that is was marked alwaysRollback.  This means that all pages must
+      ** be marked as alwaysRollback from here on out.
+      */
+      if( pPg->alwaysRollback ){
+        pPager->alwaysRollback = 1;
+      }
+
+      /* Unlink the old page from the free list and the hash table
+      */
+      if( pPg==pPager->pFirstSynced ){
+        PgHdr *p = pPg->pNextFree;
+        while( p && p->needSync ){ p = p->pNextFree; }
+        pPager->pFirstSynced = p;
+      }
+      if( pPg->pPrevFree ){
+        pPg->pPrevFree->pNextFree = pPg->pNextFree;
+      }else{
+        assert( pPager->pFirst==pPg );
+        pPager->pFirst = pPg->pNextFree;
+      }
+      if( pPg->pNextFree ){
+        pPg->pNextFree->pPrevFree = pPg->pPrevFree;
+      }else{
+        assert( pPager->pLast==pPg );
+        pPager->pLast = pPg->pPrevFree;
+      }
+      pPg->pNextFree = pPg->pPrevFree = 0;
+      if( pPg->pNextHash ){
+        pPg->pNextHash->pPrevHash = pPg->pPrevHash;
+      }
+      if( pPg->pPrevHash ){
+        pPg->pPrevHash->pNextHash = pPg->pNextHash;
+      }else{
+        h = pager_hash(pPg->pgno);
+        assert( pPager->aHash[h]==pPg );
+        pPager->aHash[h] = pPg->pNextHash;
+      }
+      pPg->pNextHash = pPg->pPrevHash = 0;
+      pPager->nOvfl++;
+    }
+    pPg->pgno = pgno;
+    if( pPager->aInJournal && (int)pgno<=pPager->origDbSize ){
+      sqliteCheckMemory(pPager->aInJournal, pgno/8);
+      assert( pPager->journalOpen );
+      pPg->inJournal = (pPager->aInJournal[pgno/8] & (1<<(pgno&7)))!=0;
+      pPg->needSync = 0;
+    }else{
+      pPg->inJournal = 0;
+      pPg->needSync = 0;
+    }
+    if( pPager->aInCkpt && (int)pgno<=pPager->ckptSize
+             && (pPager->aInCkpt[pgno/8] & (1<<(pgno&7)))!=0 ){
+      page_add_to_ckpt_list(pPg);
+    }else{
+      page_remove_from_ckpt_list(pPg);
+    }
+    pPg->dirty = 0;
+    pPg->nRef = 1;
+    REFINFO(pPg);
+    pPager->nRef++;
+    h = pager_hash(pgno);
+    pPg->pNextHash = pPager->aHash[h];
+    pPager->aHash[h] = pPg;
+    if( pPg->pNextHash ){
+      assert( pPg->pNextHash->pPrevHash==0 );
+      pPg->pNextHash->pPrevHash = pPg;
+    }
+    if( pPager->nExtra>0 ){
+      memset(PGHDR_TO_EXTRA(pPg), 0, pPager->nExtra);
+    }
+    if( pPager->dbSize<0 ) sqlitepager_pagecount(pPager);
+    if( pPager->errMask!=0 ){
+      sqlitepager_unref(PGHDR_TO_DATA(pPg));
+      rc = pager_errcode(pPager);
+      return rc;
+    }
+    if( pPager->dbSize<(int)pgno ){
+      memset(PGHDR_TO_DATA(pPg), 0, SQLITE_PAGE_SIZE);
+    }else{
+      int rc;
+      sqliteOsSeek(&pPager->fd, (pgno-1)*(off_t)SQLITE_PAGE_SIZE);
+      rc = sqliteOsRead(&pPager->fd, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE);
+      TRACE2("FETCH %d\n", pPg->pgno);
+      CODEC(pPager, PGHDR_TO_DATA(pPg), pPg->pgno, 3);
+      if( rc!=SQLITE_OK ){
+        off_t fileSize;
+        if( sqliteOsFileSize(&pPager->fd,&fileSize)!=SQLITE_OK
+               || fileSize>=pgno*SQLITE_PAGE_SIZE ){
+          sqlitepager_unref(PGHDR_TO_DATA(pPg));
+          return rc;
+        }else{
+          memset(PGHDR_TO_DATA(pPg), 0, SQLITE_PAGE_SIZE);
+        }
+      }
+    }
+  }else{
+    /* The requested page is in the page cache. */
+    pPager->nHit++;
+    page_ref(pPg);
+  }
+  *ppPage = PGHDR_TO_DATA(pPg);
+  return SQLITE_OK;
+}
+
+/*
+** Actquire a page if it is already in the in-memory cache.  Do
+** not read the page from disk.  Return a pointer to the page,
+** or 0 if the page is not in cache.
+**
+** See also sqlitepager_get().  The difference between this routine
+** and sqlitepager_get() is that _get() will go to the disk and read
+** in the page if the page is not already in cache.  This routine
+** returns NULL if the page is not in cache or if a disk I/O error 
+** has ever happened.
+*/
+void *sqlitepager_lookup(Pager *pPager, Pgno pgno){
+  PgHdr *pPg;
+
+  assert( pPager!=0 );
+  assert( pgno!=0 );
+  if( pPager->errMask & ~(PAGER_ERR_FULL) ){
+    return 0;
+  }
+  /* if( pPager->nRef==0 ){
+  **  return 0;
+  ** }
+  */
+  pPg = pager_lookup(pPager, pgno);
+  if( pPg==0 ) return 0;
+  page_ref(pPg);
+  return PGHDR_TO_DATA(pPg);
+}
+
+/*
+** Release a page.
+**
+** If the number of references to the page drop to zero, then the
+** page is added to the LRU list.  When all references to all pages
+** are released, a rollback occurs and the lock on the database is
+** removed.
+*/
+int sqlitepager_unref(void *pData){
+  PgHdr *pPg;
+
+  /* Decrement the reference count for this page
+  */
+  pPg = DATA_TO_PGHDR(pData);
+  assert( pPg->nRef>0 );
+  pPg->nRef--;
+  REFINFO(pPg);
+
+  /* When the number of references to a page reach 0, call the
+  ** destructor and add the page to the freelist.
+  */
+  if( pPg->nRef==0 ){
+    Pager *pPager;
+    pPager = pPg->pPager;
+    pPg->pNextFree = 0;
+    pPg->pPrevFree = pPager->pLast;
+    pPager->pLast = pPg;
+    if( pPg->pPrevFree ){
+      pPg->pPrevFree->pNextFree = pPg;
+    }else{
+      pPager->pFirst = pPg;
+    }
+    if( pPg->needSync==0 && pPager->pFirstSynced==0 ){
+      pPager->pFirstSynced = pPg;
+    }
+    if( pPager->xDestructor ){
+      pPager->xDestructor(pData);
+    }
+  
+    /* When all pages reach the freelist, drop the read lock from
+    ** the database file.
+    */
+    pPager->nRef--;
+    assert( pPager->nRef>=0 );
+    if( pPager->nRef==0 ){
+      pager_reset(pPager);
+    }
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Create a journal file for pPager.  There should already be a write
+** lock on the database file when this routine is called.
+**
+** Return SQLITE_OK if everything.  Return an error code and release the
+** write lock if anything goes wrong.
+*/
+static int pager_open_journal(Pager *pPager){
+  int rc;
+  assert( pPager->state==SQLITE_WRITELOCK );
+  assert( pPager->journalOpen==0 );
+  assert( pPager->useJournal );
+  sqlitepager_pagecount(pPager);
+  pPager->aInJournal = sqliteMalloc( pPager->dbSize/8 + 1 );
+  if( pPager->aInJournal==0 ){
+    sqliteOsReadLock(&pPager->fd);
+    pPager->state = SQLITE_READLOCK;
+    return SQLITE_NOMEM;
+  }
+  rc = sqliteOsOpenExclusive(pPager->zJournal, &pPager->jfd,pPager->tempFile);
+  if( rc!=SQLITE_OK ){
+    sqliteFree(pPager->aInJournal);
+    pPager->aInJournal = 0;
+    sqliteOsReadLock(&pPager->fd);
+    pPager->state = SQLITE_READLOCK;
+    return SQLITE_CANTOPEN;
+  }
+  sqliteOsOpenDirectory(pPager->zDirectory, &pPager->jfd);
+  pPager->journalOpen = 1;
+  pPager->journalStarted = 0;
+  pPager->needSync = 0;
+  pPager->alwaysRollback = 0;
+  pPager->nRec = 0;
+  if( pPager->errMask!=0 ){
+    rc = pager_errcode(pPager);
+    return rc;
+  }
+  pPager->origDbSize = pPager->dbSize;
+  if( journal_format==JOURNAL_FORMAT_3 ){
+    rc = sqliteOsWrite(&pPager->jfd, aJournalMagic3, sizeof(aJournalMagic3));
+    if( rc==SQLITE_OK ){
+      rc = write32bits(&pPager->jfd, pPager->noSync ? 0xffffffff : 0);
+    }
+    if( rc==SQLITE_OK ){
+      sqliteRandomness(sizeof(pPager->cksumInit), &pPager->cksumInit);
+      rc = write32bits(&pPager->jfd, pPager->cksumInit);
+    }
+  }else if( journal_format==JOURNAL_FORMAT_2 ){
+    rc = sqliteOsWrite(&pPager->jfd, aJournalMagic2, sizeof(aJournalMagic2));
+  }else{
+    assert( journal_format==JOURNAL_FORMAT_1 );
+    rc = sqliteOsWrite(&pPager->jfd, aJournalMagic1, sizeof(aJournalMagic1));
+  }
+  if( rc==SQLITE_OK ){
+    rc = write32bits(&pPager->jfd, pPager->dbSize);
+  }
+  if( pPager->ckptAutoopen && rc==SQLITE_OK ){
+    rc = sqlitepager_ckpt_begin(pPager);
+  }
+  if( rc!=SQLITE_OK ){
+    rc = pager_unwritelock(pPager);
+    if( rc==SQLITE_OK ){
+      rc = SQLITE_FULL;
+    }
+  }
+  return rc;  
+}
+
+/*
+** Actquire a write-lock on the database.  The lock is removed when
+** the any of the following happen:
+**
+**   *  sqlitepager_commit() is called.
+**   *  sqlitepager_rollback() is called.
+**   *  sqlitepager_close() is called.
+**   *  sqlitepager_unref() is called to on every outstanding page.
+**
+** The parameter to this routine is a pointer to any open page of the
+** database file.  Nothing changes about the page - it is used merely
+** to actquire a pointer to the Pager structure and as proof that there
+** is already a read-lock on the database.
+**
+** A journal file is opened if this is not a temporary file.  For
+** temporary files, the opening of the journal file is deferred until
+** there is an actual need to write to the journal.
+**
+** If the database is already write-locked, this routine is a no-op.
+*/
+int sqlitepager_begin(void *pData){
+  PgHdr *pPg = DATA_TO_PGHDR(pData);
+  Pager *pPager = pPg->pPager;
+  int rc = SQLITE_OK;
+  assert( pPg->nRef>0 );
+  assert( pPager->state!=SQLITE_UNLOCK );
+  if( pPager->state==SQLITE_READLOCK ){
+    assert( pPager->aInJournal==0 );
+    rc = sqliteOsWriteLock(&pPager->fd);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    pPager->state = SQLITE_WRITELOCK;
+    pPager->dirtyFile = 0;
+    TRACE1("TRANSACTION\n");
+    if( pPager->useJournal && !pPager->tempFile ){
+      rc = pager_open_journal(pPager);
+    }
+  }
+  return rc;
+}
+
+/*
+** Mark a data page as writeable.  The page is written into the journal 
+** if it is not there already.  This routine must be called before making
+** changes to a page.
+**
+** The first time this routine is called, the pager creates a new
+** journal and actquires a write lock on the database.  If the write
+** lock could not be actquired, this routine returns SQLITE_BUSY.  The
+** calling routine must check for that return value and be careful not to
+** change any page data until this routine returns SQLITE_OK.
+**
+** If the journal file could not be written because the disk is full,
+** then this routine returns SQLITE_FULL and does an immediate rollback.
+** All subsequent write attempts also return SQLITE_FULL until there
+** is a call to sqlitepager_commit() or sqlitepager_rollback() to
+** reset.
+*/
+int sqlitepager_write(void *pData){
+  PgHdr *pPg = DATA_TO_PGHDR(pData);
+  Pager *pPager = pPg->pPager;
+  int rc = SQLITE_OK;
+
+  /* Check for errors
+  */
+  if( pPager->errMask ){ 
+    return pager_errcode(pPager);
+  }
+  if( pPager->readOnly ){
+    return SQLITE_PERM;
+  }
+
+  /* Mark the page as dirty.  If the page has already been written
+  ** to the journal then we can return right away.
+  */
+  pPg->dirty = 1;
+  if( pPg->inJournal && (pPg->inCkpt || pPager->ckptInUse==0) ){
+    pPager->dirtyFile = 1;
+    return SQLITE_OK;
+  }
+
+  /* If we get this far, it means that the page needs to be
+  ** written to the transaction journal or the ckeckpoint journal
+  ** or both.
+  **
+  ** First check to see that the transaction journal exists and
+  ** create it if it does not.
+  */
+  assert( pPager->state!=SQLITE_UNLOCK );
+  rc = sqlitepager_begin(pData);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+  assert( pPager->state==SQLITE_WRITELOCK );
+  if( !pPager->journalOpen && pPager->useJournal ){
+    rc = pager_open_journal(pPager);
+    if( rc!=SQLITE_OK ) return rc;
+  }
+  assert( pPager->journalOpen || !pPager->useJournal );
+  pPager->dirtyFile = 1;
+
+  /* The transaction journal now exists and we have a write lock on the
+  ** main database file.  Write the current page to the transaction 
+  ** journal if it is not there already.
+  */
+  if( !pPg->inJournal && pPager->useJournal ){
+    if( (int)pPg->pgno <= pPager->origDbSize ){
+      int szPg;
+      u32 saved;
+      if( journal_format>=JOURNAL_FORMAT_3 ){
+        u32 cksum = pager_cksum(pPager, pPg->pgno, pData);
+        saved = *(u32*)PGHDR_TO_EXTRA(pPg);
+        store32bits(cksum, pPg, SQLITE_PAGE_SIZE);
+        szPg = SQLITE_PAGE_SIZE+8;
+      }else{
+        szPg = SQLITE_PAGE_SIZE+4;
+      }
+      store32bits(pPg->pgno, pPg, -4);
+      CODEC(pPager, pData, pPg->pgno, 7);
+      rc = sqliteOsWrite(&pPager->jfd, &((char*)pData)[-4], szPg);
+      TRACE3("JOURNAL %d %d\n", pPg->pgno, pPg->needSync);
+      CODEC(pPager, pData, pPg->pgno, 0);
+      if( journal_format>=JOURNAL_FORMAT_3 ){
+        *(u32*)PGHDR_TO_EXTRA(pPg) = saved;
+      }
+      if( rc!=SQLITE_OK ){
+        sqlitepager_rollback(pPager);
+        pPager->errMask |= PAGER_ERR_FULL;
+        return rc;
+      }
+      pPager->nRec++;
+      assert( pPager->aInJournal!=0 );
+      pPager->aInJournal[pPg->pgno/8] |= 1<<(pPg->pgno&7);
+      pPg->needSync = !pPager->noSync;
+      pPg->inJournal = 1;
+      if( pPager->ckptInUse ){
+        pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
+        page_add_to_ckpt_list(pPg);
+      }
+    }else{
+      pPg->needSync = !pPager->journalStarted && !pPager->noSync;
+      TRACE3("APPEND %d %d\n", pPg->pgno, pPg->needSync);
+    }
+    if( pPg->needSync ){
+      pPager->needSync = 1;
+    }
+  }
+
+  /* If the checkpoint journal is open and the page is not in it,
+  ** then write the current page to the checkpoint journal.  Note that
+  ** the checkpoint journal always uses the simplier format 2 that lacks
+  ** checksums.  The header is also omitted from the checkpoint journal.
+  */
+  if( pPager->ckptInUse && !pPg->inCkpt && (int)pPg->pgno<=pPager->ckptSize ){
+    assert( pPg->inJournal || (int)pPg->pgno>pPager->origDbSize );
+    store32bits(pPg->pgno, pPg, -4);
+    CODEC(pPager, pData, pPg->pgno, 7);
+    rc = sqliteOsWrite(&pPager->cpfd, &((char*)pData)[-4], SQLITE_PAGE_SIZE+4);
+    TRACE2("CKPT-JOURNAL %d\n", pPg->pgno);
+    CODEC(pPager, pData, pPg->pgno, 0);
+    if( rc!=SQLITE_OK ){
+      sqlitepager_rollback(pPager);
+      pPager->errMask |= PAGER_ERR_FULL;
+      return rc;
+    }
+    pPager->ckptNRec++;
+    assert( pPager->aInCkpt!=0 );
+    pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
+    page_add_to_ckpt_list(pPg);
+  }
+
+  /* Update the database size and return.
+  */
+  if( pPager->dbSize<(int)pPg->pgno ){
+    pPager->dbSize = pPg->pgno;
+  }
+  return rc;
+}
+
+/*
+** Return TRUE if the page given in the argument was previously passed
+** to sqlitepager_write().  In other words, return TRUE if it is ok
+** to change the content of the page.
+*/
+int sqlitepager_iswriteable(void *pData){
+  PgHdr *pPg = DATA_TO_PGHDR(pData);
+  return pPg->dirty;
+}
+
+/*
+** Replace the content of a single page with the information in the third
+** argument.
+*/
+int sqlitepager_overwrite(Pager *pPager, Pgno pgno, void *pData){
+  void *pPage;
+  int rc;
+
+  rc = sqlitepager_get(pPager, pgno, &pPage);
+  if( rc==SQLITE_OK ){
+    rc = sqlitepager_write(pPage);
+    if( rc==SQLITE_OK ){
+      memcpy(pPage, pData, SQLITE_PAGE_SIZE);
+    }
+    sqlitepager_unref(pPage);
+  }
+  return rc;
+}
+
+/*
+** A call to this routine tells the pager that it is not necessary to
+** write the information on page "pgno" back to the disk, even though
+** that page might be marked as dirty.
+**
+** The overlying software layer calls this routine when all of the data
+** on the given page is unused.  The pager marks the page as clean so
+** that it does not get written to disk.
+**
+** Tests show that this optimization, together with the
+** sqlitepager_dont_rollback() below, more than double the speed
+** of large INSERT operations and quadruple the speed of large DELETEs.
+**
+** When this routine is called, set the alwaysRollback flag to true.
+** Subsequent calls to sqlitepager_dont_rollback() for the same page
+** will thereafter be ignored.  This is necessary to avoid a problem
+** where a page with data is added to the freelist during one part of
+** a transaction then removed from the freelist during a later part
+** of the same transaction and reused for some other purpose.  When it
+** is first added to the freelist, this routine is called.  When reused,
+** the dont_rollback() routine is called.  But because the page contains
+** critical data, we still need to be sure it gets rolled back in spite
+** of the dont_rollback() call.
+*/
+void sqlitepager_dont_write(Pager *pPager, Pgno pgno){
+  PgHdr *pPg;
+
+  pPg = pager_lookup(pPager, pgno);
+  pPg->alwaysRollback = 1;
+  if( pPg && pPg->dirty ){
+    if( pPager->dbSize==(int)pPg->pgno && pPager->origDbSize<pPager->dbSize ){
+      /* If this pages is the last page in the file and the file has grown
+      ** during the current transaction, then do NOT mark the page as clean.
+      ** When the database file grows, we must make sure that the last page
+      ** gets written at least once so that the disk file will be the correct
+      ** size. If you do not write this page and the size of the file
+      ** on the disk ends up being too small, that can lead to database
+      ** corruption during the next transaction.
+      */
+    }else{
+      TRACE2("DONT_WRITE %d\n", pgno);
+      pPg->dirty = 0;
+    }
+  }
+}
+
+/*
+** A call to this routine tells the pager that if a rollback occurs,
+** it is not necessary to restore the data on the given page.  This
+** means that the pager does not have to record the given page in the
+** rollback journal.
+*/
+void sqlitepager_dont_rollback(void *pData){
+  PgHdr *pPg = DATA_TO_PGHDR(pData);
+  Pager *pPager = pPg->pPager;
+
+  if( pPager->state!=SQLITE_WRITELOCK || pPager->journalOpen==0 ) return;
+  if( pPg->alwaysRollback || pPager->alwaysRollback ) return;
+  if( !pPg->inJournal && (int)pPg->pgno <= pPager->origDbSize ){
+    assert( pPager->aInJournal!=0 );
+    pPager->aInJournal[pPg->pgno/8] |= 1<<(pPg->pgno&7);
+    pPg->inJournal = 1;
+    if( pPager->ckptInUse ){
+      pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
+      page_add_to_ckpt_list(pPg);
+    }
+    TRACE2("DONT_ROLLBACK %d\n", pPg->pgno);
+  }
+  if( pPager->ckptInUse && !pPg->inCkpt && (int)pPg->pgno<=pPager->ckptSize ){
+    assert( pPg->inJournal || (int)pPg->pgno>pPager->origDbSize );
+    assert( pPager->aInCkpt!=0 );
+    pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
+    page_add_to_ckpt_list(pPg);
+  }
+}
+
+/*
+** Commit all changes to the database and release the write lock.
+**
+** If the commit fails for any reason, a rollback attempt is made
+** and an error code is returned.  If the commit worked, SQLITE_OK
+** is returned.
+*/
+int sqlitepager_commit(Pager *pPager){
+  int rc;
+  PgHdr *pPg;
+
+  if( pPager->errMask==PAGER_ERR_FULL ){
+    rc = sqlitepager_rollback(pPager);
+    if( rc==SQLITE_OK ){
+      rc = SQLITE_FULL;
+    }
+    return rc;
+  }
+  if( pPager->errMask!=0 ){
+    rc = pager_errcode(pPager);
+    return rc;
+  }
+  if( pPager->state!=SQLITE_WRITELOCK ){
+    return SQLITE_ERROR;
+  }
+  TRACE1("COMMIT\n");
+  if( pPager->dirtyFile==0 ){
+    /* Exit early (without doing the time-consuming sqliteOsSync() calls)
+    ** if there have been no changes to the database file. */
+    assert( pPager->needSync==0 );
+    rc = pager_unwritelock(pPager);
+    pPager->dbSize = -1;
+    return rc;
+  }
+  assert( pPager->journalOpen );
+  rc = syncJournal(pPager);
+  if( rc!=SQLITE_OK ){
+    goto commit_abort;
+  }
+  pPg = pager_get_all_dirty_pages(pPager);
+  if( pPg ){
+    rc = pager_write_pagelist(pPg);
+    if( rc || (!pPager->noSync && sqliteOsSync(&pPager->fd)!=SQLITE_OK) ){
+      goto commit_abort;
+    }
+  }
+  rc = pager_unwritelock(pPager);
+  pPager->dbSize = -1;
+  return rc;
+
+  /* Jump here if anything goes wrong during the commit process.
+  */
+commit_abort:
+  rc = sqlitepager_rollback(pPager);
+  if( rc==SQLITE_OK ){
+    rc = SQLITE_FULL;
+  }
+  return rc;
+}
+
+/*
+** Rollback all changes.  The database falls back to read-only mode.
+** All in-memory cache pages revert to their original data contents.
+** The journal is deleted.
+**
+** This routine cannot fail unless some other process is not following
+** the correct locking protocol (SQLITE_PROTOCOL) or unless some other
+** process is writing trash into the journal file (SQLITE_CORRUPT) or
+** unless a prior malloc() failed (SQLITE_NOMEM).  Appropriate error
+** codes are returned for all these occasions.  Otherwise,
+** SQLITE_OK is returned.
+*/
+int sqlitepager_rollback(Pager *pPager){
+  int rc;
+  TRACE1("ROLLBACK\n");
+  if( !pPager->dirtyFile || !pPager->journalOpen ){
+    rc = pager_unwritelock(pPager);
+    pPager->dbSize = -1;
+    return rc;
+  }
+
+  if( pPager->errMask!=0 && pPager->errMask!=PAGER_ERR_FULL ){
+    if( pPager->state>=SQLITE_WRITELOCK ){
+      pager_playback(pPager, 1);
+    }
+    return pager_errcode(pPager);
+  }
+  if( pPager->state!=SQLITE_WRITELOCK ){
+    return SQLITE_OK;
+  }
+  rc = pager_playback(pPager, 1);
+  if( rc!=SQLITE_OK ){
+    rc = SQLITE_CORRUPT;
+    pPager->errMask |= PAGER_ERR_CORRUPT;
+  }
+  pPager->dbSize = -1;
+  return rc;
+}
+
+/*
+** Return TRUE if the database file is opened read-only.  Return FALSE
+** if the database is (in theory) writable.
+*/
+int sqlitepager_isreadonly(Pager *pPager){
+  return pPager->readOnly;
+}
+
+/*
+** This routine is used for testing and analysis only.
+*/
+int *sqlitepager_stats(Pager *pPager){
+  static int a[9];
+  a[0] = pPager->nRef;
+  a[1] = pPager->nPage;
+  a[2] = pPager->mxPage;
+  a[3] = pPager->dbSize;
+  a[4] = pPager->state;
+  a[5] = pPager->errMask;
+  a[6] = pPager->nHit;
+  a[7] = pPager->nMiss;
+  a[8] = pPager->nOvfl;
+  return a;
+}
+
+/*
+** Set the checkpoint.
+**
+** This routine should be called with the transaction journal already
+** open.  A new checkpoint journal is created that can be used to rollback
+** changes of a single SQL command within a larger transaction.
+*/
+int sqlitepager_ckpt_begin(Pager *pPager){
+  int rc;
+  char zTemp[SQLITE_TEMPNAME_SIZE];
+  if( !pPager->journalOpen ){
+    pPager->ckptAutoopen = 1;
+    return SQLITE_OK;
+  }
+  assert( pPager->journalOpen );
+  assert( !pPager->ckptInUse );
+  pPager->aInCkpt = sqliteMalloc( pPager->dbSize/8 + 1 );
+  if( pPager->aInCkpt==0 ){
+    sqliteOsReadLock(&pPager->fd);
+    return SQLITE_NOMEM;
+  }
+#ifndef NDEBUG
+  rc = sqliteOsFileSize(&pPager->jfd, &pPager->ckptJSize);
+  if( rc ) goto ckpt_begin_failed;
+  assert( pPager->ckptJSize == 
+    pPager->nRec*JOURNAL_PG_SZ(journal_format)+JOURNAL_HDR_SZ(journal_format) );
+#endif
+  pPager->ckptJSize = pPager->nRec*JOURNAL_PG_SZ(journal_format)
+                         + JOURNAL_HDR_SZ(journal_format);
+  pPager->ckptSize = pPager->dbSize;
+  if( !pPager->ckptOpen ){
+    rc = sqlitepager_opentemp(zTemp, &pPager->cpfd);
+    if( rc ) goto ckpt_begin_failed;
+    pPager->ckptOpen = 1;
+    pPager->ckptNRec = 0;
+  }
+  pPager->ckptInUse = 1;
+  return SQLITE_OK;
+ 
+ckpt_begin_failed:
+  if( pPager->aInCkpt ){
+    sqliteFree(pPager->aInCkpt);
+    pPager->aInCkpt = 0;
+  }
+  return rc;
+}
+
+/*
+** Commit a checkpoint.
+*/
+int sqlitepager_ckpt_commit(Pager *pPager){
+  if( pPager->ckptInUse ){
+    PgHdr *pPg, *pNext;
+    sqliteOsSeek(&pPager->cpfd, 0);
+    /* sqliteOsTruncate(&pPager->cpfd, 0); */
+    pPager->ckptNRec = 0;
+    pPager->ckptInUse = 0;
+    sqliteFree( pPager->aInCkpt );
+    pPager->aInCkpt = 0;
+    for(pPg=pPager->pCkpt; pPg; pPg=pNext){
+      pNext = pPg->pNextCkpt;
+      assert( pPg->inCkpt );
+      pPg->inCkpt = 0;
+      pPg->pPrevCkpt = pPg->pNextCkpt = 0;
+    }
+    pPager->pCkpt = 0;
+  }
+  pPager->ckptAutoopen = 0;
+  return SQLITE_OK;
+}
+
+/*
+** Rollback a checkpoint.
+*/
+int sqlitepager_ckpt_rollback(Pager *pPager){
+  int rc;
+  if( pPager->ckptInUse ){
+    rc = pager_ckpt_playback(pPager);
+    sqlitepager_ckpt_commit(pPager);
+  }else{
+    rc = SQLITE_OK;
+  }
+  pPager->ckptAutoopen = 0;
+  return rc;
+}
+
+/*
+** Return the full pathname of the database file.
+*/
+const char *sqlitepager_filename(Pager *pPager){
+  return pPager->zFilename;
+}
+
+/*
+** Set the codec for this pager
+*/
+void sqlitepager_set_codec(
+  Pager *pPager,
+  void (*xCodec)(void*,void*,Pgno,int),
+  void *pCodecArg
+){
+  pPager->xCodec = xCodec;
+  pPager->pCodecArg = pCodecArg;
+}
+
+#ifdef SQLITE_TEST
+/*
+** Print a listing of all referenced pages and their ref count.
+*/
+void sqlitepager_refdump(Pager *pPager){
+  PgHdr *pPg;
+  for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
+    if( pPg->nRef<=0 ) continue;
+    printf("PAGE %3d addr=0x%08x nRef=%d\n", 
+       pPg->pgno, (int)PGHDR_TO_DATA(pPg), pPg->nRef);
+  }
+}
+#endif