SQLite

** 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 1.115 2004/06/09 17:37:28 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>

*/
#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 statement 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_HDR_SZ(pPager, X) (\
   sizeof(aJournalMagic1) + \
   sizeof(Pgno) + \
   ((X)>=3?3*sizeof(u32)+(pPager)->nMaster:0) )
#define JOURNAL_PG_SZ(X) \
   (SQLITE_PAGE_SIZE + sizeof(Pgno) + ((X)>=3)*sizeof(u32))


/*
** Enable reference count tracking here:
*/
#ifdef SQLITE_TEST
  int pager3_refinfo_enable = 0;

# 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 = sqlite3OsRead(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 sqlite3OsWrite(fd, &val, 4);
  }
  ac[0] = (val>>24) & 0xff;
  ac[1] = (val>>16) & 0xff;
  ac[2] = (val>>8) & 0xff;
  ac[3] = val & 0xff;
  return sqlite3OsWrite(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.
*/

  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 = sqlite3OsRead(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 page %d\n", pgRec.pgno);
  sqlite3OsSeek(&pPager->fd, (pgRec.pgno-1)*(off_t)SQLITE_PAGE_SIZE);
  rc = sqlite3OsWrite(&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.
    */
    void *pData;
    assert( pPg->nRef==0 || pPg->pgno==1 );
    pData = PGHDR_TO_DATA(pPg);
    memcpy(pData, pgRec.aData, pPager->pageSize);
    if( pPager->xDestructor ){
      pPager->xDestructor(pData, pPager->pageSize);
    }
    pPg->dirty = 0;
    pPg->needSync = 0;
    CODEC(pPager, pData, pPg->pgno, 3);
  }

        rc = sqlite3OsOpenReadOnly(zJournal, &journal);
        sqliteFree(zJournal);
        if( rc!=SQLITE_OK ){
          sqlite3OsClose(&journal);
          goto delmaster_out;
        }

	/* Check if the file is big enough to be a format 3 journal file
        ** with the required master journal name. If not, ignore it.
        */
        rc = sqlite3OsFileSize(&journal, &jsz);
        if( rc!=SQLITE_OK ){
          sqlite3OsClose(&journal);
          goto delmaster_out;
        }
        if( jsz<(sizeof(aJournalMagic3)+4*sizeof(u32)+strlen(zMaster)+1) ){
          sqlite3OsClose(&journal);
          continue;
        }
        
        /* Seek to the point in the journal where the master journal name
        ** is stored. Read the master journal name into memory obtained
        ** from malloc.
        */
        rc = sqlite3OsSeek(&journal, sizeof(aJournalMagic3)+2*sizeof(u32));
        if( rc!=SQLITE_OK ) goto delmaster_out;
        rc = read32bits(3, &journal, (u32 *)&nMaster);
        if( rc!=SQLITE_OK ) goto delmaster_out;
        if( nMaster>0 && nMaster==strlen(zMaster)+1 ){
          char *zMasterPtr = (char *)sqliteMalloc(nMaster);
          if( !zMasterPtr ){
            rc = SQLITE_NOMEM;
          }
          rc = sqlite3OsRead(&journal, zMasterPtr, nMaster);
          if( rc!=SQLITE_OK ){
            sqliteFree(zMasterPtr);

/*
** 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;

  char *zMaster = 0;       /* Name of master journal file if any */

  /* Figure out how many records are in the journal.  Abort early if
  ** the journal is empty.
  */
  assert( pPager->journalOpen );
  sqlite3OsSeek(&pPager->jfd, 0);
  rc = sqlite3OsFileSize(&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 = sqlite3OsRead(&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) + 4*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(pPager, 3))/JOURNAL_PG_SZ(3);
    }

    /* Check if a master journal file is specified. If one is specified, 
    ** only proceed with the playback if it still exists.
    */
    rc = read32bits(format, &pPager->jfd, &pPager->nMaster);
    if( rc ) goto end_playback;
    if( pPager->nMaster>0 ){
      zMaster = sqliteMalloc(pPager->nMaster);
      if( !zMaster ){
        rc = SQLITE_NOMEM;
        goto end_playback;
      }
      rc = sqlite3OsRead(&pPager->jfd, zMaster, pPager->nMaster);
      if( rc!=SQLITE_OK || (strlen(zMaster) && !sqlite3OsFileExists(zMaster)) ){
        goto end_playback;
      }
    }
  }else{
    nRec = (szJ - JOURNAL_HDR_SZ(pPager, 2))/JOURNAL_PG_SZ(2);
    assert( nRec*JOURNAL_PG_SZ(2)+JOURNAL_HDR_SZ(pPager, 2)==szJ );
  }
  rc = read32bits(format, &pPager->jfd, &mxPg);
  if( rc!=SQLITE_OK ){
    goto end_playback;
  }

  assert( pPager->origDbSize==0 || pPager->origDbSize==mxPg );
  rc = sqlite3OsTruncate(&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;
    }
  }

  /* Figure out how many records are in the statement journal.
  */
  assert( pPager->stmtInUse && pPager->journalOpen );
  sqlite3OsSeek(&pPager->stfd, 0);
  nRec = pPager->stmtNRec;
  
  /* Copy original pages out of the statement journal and back into the
  ** database file.  Note that the statement 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->stfd, 2);
    assert( rc!=SQLITE_DONE );
    if( rc!=SQLITE_OK ) goto end_stmt_playback;
  }

  /* Figure out how many pages need to be copied out of the transaction
  ** journal.
  */
  rc = sqlite3OsSeek(&pPager->jfd, pPager->stmtJSize);
  if( rc!=SQLITE_OK ){
    goto end_stmt_playback;
  }
  rc = sqlite3OsFileSize(&pPager->jfd, &szJ);
  if( rc!=SQLITE_OK ){
    goto end_stmt_playback;
  }
  nRec = (szJ - pPager->stmtJSize)/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_stmt_playback;
    }
  }
  
end_stmt_playback:

  if( sqlite3_malloc_failed ){
    return SQLITE_NOMEM;
  }
  if( zFilename && zFilename[0] ){
    if( strcmp(zFilename,":memory:")==0 ){
      memDb = 1;
      zFullPathname = sqliteMalloc(4);
      if( zFullPathname ) strcpy(zFullPathname, "nil");
      rc = SQLITE_OK;
    }else{
      zFullPathname = sqlite3OsFullPathname(zFilename);
      rc = sqlite3OsOpenReadWrite(zFullPathname, &fd, &readOnly);
      tempFile = 0;
    }
  }else{

      ** 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(pPager, journal_format);
        pgSz = JOURNAL_PG_SZ(journal_format);
        rc = sqlite3OsFileSize(&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 ){
          TRACE2("SYNC journal of %d\n", pPager->fd.h);
          rc = sqlite3OsSync(&pPager->jfd);
          if( rc!=0 ) return rc;
        }
        sqlite3OsSeek(&pPager->jfd, sizeof(aJournalMagic1));
        rc = write32bits(&pPager->jfd, pPager->nRec);
        if( rc ) return rc;

        /* Write the name of the master journal file if one is specified */
        if( zMaster ){
          assert( strlen(zMaster)<pPager->nMaster );
          rc = sqlite3OsSeek(&pPager->jfd, sizeof(aJournalMagic3) + 3*4);
          if( rc ) return rc;
          rc = sqlite3OsWrite(&pPager->jfd, zMaster, strlen(zMaster)+1);
          if( rc ) return rc;
        }

        szJ = JOURNAL_HDR_SZ(pPager, journal_format) +
                 pPager->nRec*JOURNAL_PG_SZ(journal_format);
        sqlite3OsSeek(&pPager->jfd, szJ);
      }
      TRACE2("SYNC journal of %d\n", pPager->fd.h);
      rc = sqlite3OsSync(&pPager->jfd);
      if( rc!=0 ) return rc;
      pPager->journalStarted = 1;
    }

  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 ){
    /* Create the header for a format 3 journal:
    ** - 8 bytes: Magic identifying journal format 3.
    ** - 4 bytes: Number of records in journal, or -1 no-sync mode is on.
    ** - 4 bytes: Magic used for page checksums.

    ** - 4 bytes: Number of bytes reserved for master journal ptr (nMaster)
    ** - nMaster bytes: Space for a master journal pointer.
    ** - 4 bytes: Initial database page count.
    */
    rc = sqlite3OsWrite(&pPager->jfd, aJournalMagic3, sizeof(aJournalMagic3));
    if( rc==SQLITE_OK ){
      rc = write32bits(&pPager->jfd, pPager->noSync ? 0xffffffff : 0);
    }
    if( rc==SQLITE_OK ){
      sqlite3Randomness(sizeof(pPager->cksumInit), &pPager->cksumInit);
      rc = write32bits(&pPager->jfd, pPager->cksumInit);
    }
    if( rc==SQLITE_OK ){
      rc = write32bits(&pPager->jfd, pPager->nMaster);
    }
   
    /* Unless the size reserved for the master-journal pointer is 0, set
    ** the first byte of the master journal pointer to 0x00.  Either way,
    ** this is interpreted as 'no master journal' in the event of a
    ** rollback after a crash.
    */
    if( rc==SQLITE_OK && pPager->nMaster>0 ){
      rc = sqlite3OsWrite(&pPager->jfd, "", 1);
    }
    if( rc==SQLITE_OK ){
      rc = sqlite3OsSeek(&pPager->jfd, 
          sizeof(aJournalMagic3) + 3*4 + pPager->nMaster);
    }
  }else if( journal_format==JOURNAL_FORMAT_2 ){
    rc = sqlite3OsWrite(&pPager->jfd, aJournalMagic2, sizeof(aJournalMagic2));
  }else{
    assert( journal_format==JOURNAL_FORMAT_1 );
    rc = sqlite3OsWrite(&pPager->jfd, aJournalMagic1, sizeof(aJournalMagic1));
  }
  if( rc==SQLITE_OK ){
    rc = write32bits(&pPager->jfd, pPager->dbSize);
  }
  if( pPager->stmtAutoopen && rc==SQLITE_OK ){
    rc = sqlite3pager_stmt_begin(pPager);
  }
  if( rc!=SQLITE_OK ){
    rc = pager_unwritelock(pPager);
    if( rc==SQLITE_OK ){
      rc = SQLITE_FULL;

        assert( pHist->pOrig==0 );
        pHist->pOrig = sqliteMallocRaw( pPager->pageSize );
        if( pHist->pOrig ){
          memcpy(pHist->pOrig, PGHDR_TO_DATA(pPg), pPager->pageSize);
        }
        pPg->inJournal = 1;
      }else{
        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 = sqlite3OsWrite(&pPager->jfd, &((char*)pData)[-4], szPg);
        TRACE3("JOURNAL page %d needSync=%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 ){
          sqlite3pager_rollback(pPager);
          pPager->errMask |= PAGER_ERR_FULL;
          return rc;
        }
        pPager->nRec++;
        assert( pPager->aInJournal!=0 );

    if( pPg->needSync ){
      pPager->needSync = 1;
    }
  }

  /* If the statement journal is open and the page is not in it,
  ** then write the current page to the statement journal.  Note that
  ** the statement journal always uses the simplier format 2 that lacks
  ** checksums.  The header is also omitted from the statement journal.
  */
  if( pPager->stmtInUse && !pPg->inStmt && (int)pPg->pgno<=pPager->stmtSize ){
    assert( pPg->inJournal || (int)pPg->pgno>pPager->origDbSize );
    if( pPager->memDb ){
      PgHistory *pHist = PGHDR_TO_HIST(pPg, pPager);
      assert( pHist->pStmt==0 );
      pHist->pStmt = sqliteMallocRaw( pPager->pageSize );

    sqlite3OsLock(&pPager->fd, SHARED_LOCK);
    return SQLITE_NOMEM;
  }
#ifndef NDEBUG
  rc = sqlite3OsFileSize(&pPager->jfd, &pPager->stmtJSize);
  if( rc ) goto stmt_begin_failed;
  assert( pPager->stmtJSize == 
    pPager->nRec*JOURNAL_PG_SZ(journal_format) + 
    JOURNAL_HDR_SZ(pPager, journal_format) );
#endif
  pPager->stmtJSize = pPager->nRec*JOURNAL_PG_SZ(journal_format)
                         + JOURNAL_HDR_SZ(pPager, journal_format);
  pPager->stmtSize = pPager->dbSize;
  if( !pPager->stmtOpen ){
    rc = sqlite3pager_opentemp(zTemp, &pPager->stfd);
    if( rc ) goto stmt_begin_failed;
    pPager->stmtOpen = 1;
    pPager->stmtNRec = 0;
  }

**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing the pager.c module in SQLite.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test2.c,v 1.20 2004/06/04 06:22:02 danielk1977 Exp $
*/
#include "os.h"
#include "sqliteInt.h"
#include "pager.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>

  };
  int i;
  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
    Tcl_CreateCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
  }
  Tcl_LinkVar(interp, "sqlite3_io_error_pending",
     (char*)&sqlite3_io_error_pending, TCL_LINK_INT);
#ifdef SQLITE_TEST
  {
    extern int journal_format;
    Tcl_LinkVar(interp, "journal_format",
       (char*)&journal_format, TCL_LINK_INT);
  }
#endif
  sprintf(zBuf, "%d", SQLITE_PAGE_SIZE);
  Tcl_SetVar(interp, "SQLITE_PAGE_SIZE", zBuf, TCL_GLOBAL_ONLY); 
  sprintf(zBuf, "%d", SQLITE_PAGE_RESERVE);
  Tcl_SetVar(interp, "SQLITE_PAGE_RESERVE", zBuf, TCL_GLOBAL_ONLY); 
  sprintf(zBuf, "%d", SQLITE_USABLE_SIZE);
  Tcl_SetVar(interp, "SQLITE_USABLE_SIZE", zBuf, TCL_GLOBAL_ONLY); 
  return TCL_OK;
}

# 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 file implements regression tests for SQLite library.  The
# focus of this script is in-memory database backend.
#
# $Id: memdb.test,v 1.6 2003/08/05 13:13:39 drh Exp $


set testdir [file dirname $argv0]
source $testdir/tester.tcl

# In the following sequence of tests, compute the MD5 sum of the content
# of a table, make lots of modifications to that table, then do a rollback.

# Do rollbacks.  Make sure the signature does not change.
#
set limit 10
for {set i 2} {$i<=$limit} {incr i} {
  set ::sig [signature one]
  # puts "sig=$sig"
  set cnt [lindex $::sig 0]
  set ::journal_format [expr {($i%3)+1}]
  if {$i%2==0} {
    execsql {PRAGMA synchronous=FULL}
  } else {
    execsql {PRAGMA synchronous=NORMAL}
  }
  do_test memdb-1.$i.1-$cnt {
     execsql {

# 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 file implements regression tests for SQLite library.  The
# focus of this script is database locks.
#
# $Id: trans.test,v 1.20 2004/05/31 08:26:50 danielk1977 Exp $


set testdir [file dirname $argv0]
source $testdir/tester.tcl


# Create several tables to work with.

}

# Do rollbacks.  Make sure the signature does not change.
#
for {set i 2} {$i<=$limit} {incr i} {
  set ::sig [signature]
  set cnt [lindex $::sig 0]
  set ::journal_format [expr {($i%3)+1}]
  if {$i%2==0} {
    execsql {PRAGMA synchronous=FULL}
  } else {
    execsql {PRAGMA synchronous=NORMAL}
  }
  do_test trans-9.$i.1-$cnt {
     execsql {