SQLite

/*
** 2004 April 6
**
** 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.
**
*************************************************************************
** $Id: btree.c,v 1.156 2004/06/03 16:08:41 danielk1977 Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
**
**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
**     "Sorting And Searching", pages 473-480. Addison-Wesley
**     Publishing Company, Reading, Massachusetts.

**      sqlite3BtreeCreateTable()
**      sqlite3BtreeCreateIndex()
**      sqlite3BtreeClearTable()
**      sqlite3BtreeDropTable()
**      sqlite3BtreeInsert()
**      sqlite3BtreeDelete()
**      sqlite3BtreeUpdateMeta()
**
** If wrflag is true, then nMaster specifies the maximum length of
** a master journal file name supplied later via sqlite3BtreeSync().
** This is so that appropriate space can be allocated in the journal file
** when it is created..
*/
int sqlite3BtreeBeginTrans(Btree *pBt, int wrflag, int nMaster){
  int rc = SQLITE_OK;

  /* If the btree is already in a write-transaction, or it
  ** is already in a read-transaction and a read-transaction
  ** is requested, this is a no-op.
  */
  if( pBt->inTrans==TRANS_WRITE || 
      (pBt->inTrans==TRANS_READ && !wrflag) ){
    return SQLITE_OK;
  }
  if( pBt->readOnly && wrflag ){
    return SQLITE_READONLY;
  }

  if( pBt->pPage1==0 ){
    rc = lockBtree(pBt);
  }

  if( rc==SQLITE_OK && wrflag ){
    rc = sqlite3pager_begin(pBt->pPage1->aData, 0);
    if( rc==SQLITE_OK ){
      rc = newDatabase(pBt);
    }
  }

  if( rc==SQLITE_OK ){
    pBt->inTrans = (wrflag?TRANS_WRITE:TRANS_READ);

    Pgno chldPg;
    MemPage *pPage = pCur->pPage;
    int c = -1;  /* pRes return if table is empty must be -1 */
    lwr = 0;
    upr = pPage->nCell-1;
    pageIntegrity(pPage);
    while( lwr<=upr ){
      void *pCellKey;
      i64 nCellKey;
      pCur->idx = (lwr+upr)/2;
      pCur->info.nSize = 0;
      sqlite3BtreeKeySize(pCur, &nCellKey);
      if( pPage->intKey ){
        if( nCellKey<nKey ){
          c = -1;
        }else if( nCellKey>nKey ){
          c = +1;
        }else{
          c = 0;
        }
      }else{
        int available;
        pCellKey = (void *)fetchPayload(pCur, &available, 0);
        if( available>=nCellKey ){
          c = pCur->xCompare(pCur->pArg, nCellKey, pCellKey, nKey, pKey);
        }else{
          pCellKey = sqliteMallocRaw( nCellKey );
          if( pCellKey==0 ) return SQLITE_NOMEM;
          rc = sqlite3BtreeKey(pCur, 0, nCellKey, (void *)pCellKey);
          c = pCur->xCompare(pCur->pArg, nCellKey, pCellKey, nKey, pKey);
          sqliteFree(pCellKey);
          if( rc ) return rc;
        }
      }
      if( c==0 ){
        if( pPage->leafData && !pPage->leaf ){

/*
** Return non-zero if a statement transaction is active.
*/
int sqlite3BtreeIsInStmt(Btree *pBt){
  return (pBt && pBt->inStmt);
}

/*
** This call is a no-op if no write-transaction is currently active on pBt.
**
** Otherwise, sync the database file for the btree pBt. zMaster points to
** the name of a master journal file that should be written into the
** individual journal file, or is NULL, indicating no master journal file 
** (single database transaction).
**
** When this is called, the master journal should already have been
** created, populated with this journal pointer and synced to disk.
**
** Once this is routine has returned, the only thing required to commit
** the write-transaction for this database file is to delete the journal.
*/
int sqlite3BtreeSync(Btree *pBt, const char *zMaster){
  if( pBt->inTrans==TRANS_WRITE ){
    return sqlite3pager_sync(pBt->pPager, zMaster);
  }
  return SQLITE_OK;
}

**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite B-Tree file
** subsystem.  See comments in the source code for a detailed description
** of what each interface routine does.
**
** @(#) $Id: btree.h,v 1.52 2004/06/03 16:08:41 danielk1977 Exp $
*/
#ifndef _BTREE_H_
#define _BTREE_H_

/* TODO: This definition is just included so other modules compile. It
** needs to be revisited.
*/

*/
#define BTREE_OMIT_JOURNAL  1  /* Do not use journal.  No argument */
#define BTREE_MEMORY        2  /* In-memory DB.  No argument */

int sqlite3BtreeClose(Btree*);
int sqlite3BtreeSetCacheSize(Btree*,int);
int sqlite3BtreeSetSafetyLevel(Btree*,int);
int sqlite3BtreeBeginTrans(Btree*,int,int);
int sqlite3BtreeCommit(Btree*);
int sqlite3BtreeRollback(Btree*);
int sqlite3BtreeBeginStmt(Btree*);
int sqlite3BtreeCommitStmt(Btree*);
int sqlite3BtreeRollbackStmt(Btree*);
int sqlite3BtreeCreateTable(Btree*, int*, int flags);
int sqlite3BtreeIsInTrans(Btree*);
int sqlite3BtreeIsInStmt(Btree*);
int sqlite3BtreeSync(Btree*, const char *zMaster);

const char *sqlite3BtreeGetFilename(Btree *);
int sqlite3BtreeCopyFile(Btree *, Btree *);

/* The flags parameter to sqlite3BtreeCreateTable can be the bitwise OR
** of the following flags:
*/

**     DROP INDEX
**     creating ID lists
**     BEGIN TRANSACTION
**     COMMIT
**     ROLLBACK
**     PRAGMA
**
** $Id: build.c,v 1.206 2004/06/03 16:08:41 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** This routine is called when a new SQL statement is beginning to
** be parsed.  Check to see if the schema for the database needs

    if( rc!=SQLITE_OK ){
      sqlite3ErrorMsg(pParse, "unable to open a temporary database "
        "file for storing temporary tables");
      pParse->nErr++;
      return;
    }
    if( db->flags & !db->autoCommit ){
      rc = sqlite3BtreeBeginTrans(db->aDb[1].pBt, 1, 0);
      if( rc!=SQLITE_OK ){
        sqlite3ErrorMsg(pParse, "unable to get a write lock on "
          "the temporary database file");
        return;
      }
    }
  }

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle DELETE FROM statements.
**
** $Id: delete.c,v 1.72 2004/06/03 16:08:41 danielk1977 Exp $
*/
#include "sqliteInt.h"

/*
** Look up every table that is named in pSrc.  If any table is not found,
** add an error message to pParse->zErrMsg and return NULL.  If all tables
** are found, return a pointer to the last table.

  int iCur,          /* Cursor number for the table */
  char *aIdxUsed     /* Only delete if aIdxUsed!=0 && aIdxUsed[i]!=0 */
){
  int i;
  Index *pIdx;

  for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){

    if( aIdxUsed!=0 && aIdxUsed[i-1]==0 ) continue;
    sqlite3GenerateIndexKey(v, pIdx, iCur);
    sqlite3VdbeAddOp(v, OP_IdxDelete, iCur+i, 0);
  }
}

/*

int sqlite3OsRandomSeed(char*);
int sqlite3OsSleep(int ms);
int sqlite3OsCurrentTime(double*);
void sqlite3OsEnterMutex(void);
void sqlite3OsLeaveMutex(void);
char *sqlite3OsFullPathname(const char*);
int sqlite3OsLock(OsFile*, int);
int sqlite3OsCheckWriteLock(OsFile *id);

#endif /* _SQLITE_OS_H_ */

/*
** Include code that is common to all os_*.c files
*/
#include "os_common.h"

#if defined(THREADSAFE) && defined(__linux__)
#define getpid pthread_self
#endif

/*
** Here is the dirt on POSIX advisory locks:  ANSI STD 1003.1 (1996)
** section 6.5.2.2 lines 483 through 490 specify that when a process
** sets or clears a lock, that operation overrides any prior locks set
** by the same process.  It does not explicitly say so, but this implies
** that it overrides locks set by the same process using a different
** file descriptor.  Consider this test case:

**
** A single inode can have multiple file descriptors, so each OsFile
** structure contains a pointer to an instance of this object and this
** object keeps a count of the number of OsFiles pointing to it.
*/
struct lockInfo {
  struct lockKey key;  /* The lookup key */
  int cnt;             /* Number of locks held */
  int locktype;        /* One of SHARED_LOCK, RESERVED_LOCK etc. */
  int nRef;            /* Number of pointers to this structure */
};

/*
** An instance of the following structure serves as the key used
** to locate a particular openCnt structure given its inode.  This

  sqlite3OsEnterMutex();
  rc = findLockInfo(id->fd, &id->pLock, &id->pOpen);
  sqlite3OsLeaveMutex();
  if( rc ){
    close(id->fd);
    return SQLITE_NOMEM;
  }
  id->locktype = 0;
  TRACE3("OPEN    %-3d %s\n", id->fd, zFilename);
  OpenCounter(+1);
  return SQLITE_OK;
}


/*

  rc = findLockInfo(id->fd, &id->pLock, &id->pOpen);
  sqlite3OsLeaveMutex();
  if( rc ){
    close(id->fd);
    unlink(zFilename);
    return SQLITE_NOMEM;
  }
  id->locktype = 0;
  if( delFlag ){
    unlink(zFilename);
  }
  TRACE3("OPEN-EX %-3d %s\n", id->fd, zFilename);
  OpenCounter(+1);
  return SQLITE_OK;
}

  sqlite3OsEnterMutex();
  rc = findLockInfo(id->fd, &id->pLock, &id->pOpen);
  sqlite3OsLeaveMutex();
  if( rc ){
    close(id->fd);
    return SQLITE_NOMEM;
  }
  id->locktype = 0;
  TRACE3("OPEN-RO %-3d %s\n", id->fd, zFilename);
  OpenCounter(+1);
  return SQLITE_OK;
}

/*
** Attempt to open a file descriptor for the directory that contains a

** SQLITE_OK on success and SQLITE_BUSY on a failure.  If this
** library was compiled with large file support (LFS) but LFS is not
** available on the host, then an SQLITE_NOLFS is returned.
*/
int sqlite3OsWriteLock(OsFile *id){
  return sqlite3OsLock(id, EXCLUSIVE_LOCK);
}

/*
** This routine checks if there is a RESERVED lock held on the specified
** file by this or any other process. If such a lock is held, return
** non-zero, otherwise zero.
*/
int sqlite3OsCheckWriteLock(OsFile *id){
  int r = 0;

  sqlite3OsEnterMutex();

  /* Check if a thread in this process holds such a lock */
  if( id->pLock->locktype>SHARED_LOCK ){
    r = 1;
  }

  /* Otherwise see if some other process holds it. Just check the whole
  ** file for write-locks, rather than any specific bytes.
  */
  if( !r ){
    struct flock lock;
    lock.l_whence = SEEK_SET;
    lock.l_start = 0;
    lock.l_len = 0;
    lock.l_type = F_RDLCK;
    fcntl(id->fd, F_GETLK, &lock);
    if( lock.l_type!=F_UNLCK ){
      r = 1;
    }
  }
  
  sqlite3OsLeaveMutex();

  return r;
}

/*
** Lock the file with the lock specified by parameter locktype - one
** of the following:
**
** SHARED_LOCK
** RESERVED_LOCK
** PENDING_LOCK
** EXCLUSIVE_LOCK
*/
int sqlite3OsLock(OsFile *id, int locktype){
  int rc = SQLITE_OK;
  struct lockInfo *pLock = id->pLock;
  struct flock lock;
  int s;

  /* It is an error to request any kind of lock before a shared lock */
  if( locktype>SHARED_LOCK && id->locktype==0 ){
    rc = sqlite3OsLock(id, SHARED_LOCK);
    if( rc!=SQLITE_OK ) return rc;
  }
  assert( locktype==SHARED_LOCK || id->locktype!=0 );

  /* If there is already a lock of this type or more restrictive on the
  ** OsFile, do nothing. Don't use the end_lock: exit path, as
  ** sqlite3OsEnterMutex() hasn't been called yet.
  */
  if( id->locktype>=locktype ){
    return SQLITE_OK;
  }

  sqlite3OsEnterMutex();

  /* If some thread using this PID has a lock via a different OsFile*
  ** handle that precludes the requested lock, return BUSY.
  */
  if( (id->locktype!=pLock->locktype && 
      (pLock->locktype>RESERVED_LOCK || locktype!=SHARED_LOCK)) ||
      (locktype>RESERVED_LOCK && pLock->cnt>1)
  ){
    rc = SQLITE_BUSY;
    goto end_lock;
  }

  /* If a SHARED lock is requested, and some thread using this PID already
  ** has a SHARED or RESERVED lock, then increment reference counts and
  ** return SQLITE_OK.
  */
  if( locktype==SHARED_LOCK && 
      (pLock->locktype==SHARED_LOCK || pLock->locktype==RESERVED_LOCK) ){
    assert( locktype==SHARED_LOCK );
    assert( id->locktype==0 );
    assert( pLock->cnt>0 );
    id->locktype = SHARED_LOCK;
    pLock->cnt++;
    id->pOpen->nLock++;
    goto end_lock;
  }

  lock.l_len = 1L;
  lock.l_whence = SEEK_SET;

  /* If control gets to this point, then actually go ahead and make
  ** operating system calls for the specified lock.
  */
  if( locktype==SHARED_LOCK ){
    assert( pLock->cnt==0 );

    s = fcntl(id->fd, F_SETLK, &lock);
    lock.l_start = 2;
    lock.l_type = F_UNLCK;
    fcntl(id->fd, F_SETLK, &lock);
    if( s ){
      rc = (errno==EINVAL) ? SQLITE_NOLFS : SQLITE_BUSY;
    }else{
      id->locktype = SHARED_LOCK;
      id->pOpen->nLock++;
      pLock->cnt = 1;
    }
  }else{
    /* The request was for a RESERVED, PENDING or EXCLUSIVE lock.  It is
    ** assumed that there is a SHARED or greater lock on the file
    ** already.
    */
    assert( 0!=id->locktype );
    lock.l_type = F_WRLCK;
    switch( locktype ){
      case RESERVED_LOCK:
        lock.l_start = 1;
        break;
      case PENDING_LOCK:
        lock.l_start = 2;

    s = fcntl(id->fd, F_SETLK, &lock);
    if( s ){
      rc = (errno==EINVAL) ? SQLITE_NOLFS : SQLITE_BUSY;
    }
  }
  
  if( rc==SQLITE_OK ){
    id->locktype = locktype;
    pLock->locktype = locktype;
    assert( pLock->locktype==RESERVED_LOCK || pLock->cnt==1 );
  }

end_lock:
  sqlite3OsLeaveMutex();
  return rc;
}

/*
** Unlock the given file descriptor.  If the file descriptor was
** not previously locked, then this routine is a no-op.  If this
** library was compiled with large file support (LFS) but LFS is not
** available on the host, then an SQLITE_NOLFS is returned.
*/
int sqlite3OsUnlock(OsFile *id){
  int rc;
  if( !id->locktype ) return SQLITE_OK;
  id->locktype = 0;
  sqlite3OsEnterMutex();
  assert( id->pLock->cnt!=0 );
  if( id->pLock->cnt>1 ){
    id->pLock->cnt--;
    rc = SQLITE_OK;
  }else{
    struct flock lock;

      }
      sqliteFree(pOpen->aPending);
      pOpen->nPending = 0;
      pOpen->aPending = 0;
    }
  }
  sqlite3OsLeaveMutex();
  id->locktype = 0;
  return rc;
}

/*
** Get information to seed the random number generator.  The seed
** is written into the buffer zBuf[256].  The calling function must
** supply a sufficiently large buffer.

#include <unistd.h>

/*
** The OsFile structure is a operating-system independing representation
** of an open file handle.  It is defined differently for each architecture.
**
** This is the definition for Unix.
**
** OsFile.locktype takes one of the values SHARED_LOCK, RESERVED_LOCK,
** PENDING_LOCK or EXCLUSIVE_LOCK.
*/
typedef struct OsFile OsFile;
struct OsFile {
  struct openCnt *pOpen;    /* Info about all open fd's on this inode */
  struct lockInfo *pLock;   /* Info about locks on this inode */
  int fd;                   /* The file descriptor */
  int locktype;             /* The type of lock held on this fd */
  int dirfd;                /* File descriptor for the directory */
};

/*
** Maximum number of characters in a temporary file name
*/
#define SQLITE_TEMPNAME_SIZE 200

** 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 1.110 2004/06/03 16:08:42 danielk1977 Exp $
*/
#include "os.h"         /* Must be first to enable large file support */
#include "sqliteInt.h"
#include "pager.h"
#include <assert.h>
#include <string.h>

  u8 *aInJournal;             /* One bit for each page in the database file */
  u8 *aInStmt;                /* 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 *pStmt;               /* List of pages in the statement subjournal */
  PgHdr *aHash[N_PG_HASH];    /* Hash table to map page number of PgHdr */
  int nMaster;                /* Number of bytes to reserve for master j.p */
};

/*
** 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 */

#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;
  static void pager_refinfo(PgHdr *p){

    }
    pPg->dirty = 0;
    pPg->needSync = 0;
    CODEC(pPager, pData, pPg->pgno, 3);
  }
  return rc;
}

/*
** Parameter zMaster is the name of a master journal file. A single journal
** file that referred to the master journal file has just been rolled back.
** This routine checks if it is possible to delete the master journal file,
** and does so if it is.
*/
static int pager_delmaster(const char *zMaster){
  int rc;
  int master_open = 0;
  OsFile master;
  char *zMasterJournal = 0; /* Contents of master journal file */
  off_t nMasterJournal;     /* Size of master journal file */

  /* Open the master journal file exclusively in case some other process
  ** is running this routine also. Not that it makes too much difference.
  */
  rc = sqlite3OsOpenExclusive(zMaster, &master, 0);
  if( rc!=SQLITE_OK ) goto delmaster_out;
  master_open = 1;

  rc = sqlite3OsFileSize(&master, &nMasterJournal);
  if( rc!=SQLITE_OK ) goto delmaster_out;

  if( nMasterJournal>0 ){
    char *zDb;
    zMasterJournal = (char *)sqliteMalloc(nMasterJournal);
    if( !zMasterJournal ){
      rc = SQLITE_NOMEM;
      goto delmaster_out;
    }
    rc = sqlite3OsRead(&master, zMasterJournal, nMasterJournal);
    if( rc!=SQLITE_OK ) goto delmaster_out;

    zDb = zMasterJournal;
    while( (zDb-zMasterJournal)<nMasterJournal ){
      char *zJournal = 0;
      sqlite3SetString(&zJournal, zDb, "-journal", 0);
      if( !zJournal ){
        rc = SQLITE_NOMEM;
        goto delmaster_out;
      }
      if( sqlite3OsFileExists(zJournal) ){
        /* One of the journals pointed to by the master journal exists.
        ** Open it and check if it points at the master journal. If
        ** so, return without deleting the master journal file.
        */
        OsFile journal;
        int nMaster;

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

        /* 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);
            goto delmaster_out;
          }
          if( 0==strncmp(zMasterPtr, zMaster, nMaster) ){
            /* We have a match. Do not delete the master journal file. */
            sqliteFree(zMasterPtr);
            goto delmaster_out;
          }
        }
      }
      zDb += (strlen(zDb)+1);
    }
  }
  
  sqlite3OsDelete(zMaster);

delmaster_out:
  if( zMasterJournal ){
    sqliteFree(zMasterJournal);
  }  
  if( master_open ){
    sqlite3OsClose(&master);
  }
  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: 
**

  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);

  }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);

      }
      pPg->needSync = 0;
      pPg->dirty = 0;
    }
  }

end_playback:
  if( zMaster ){
    /* If there was a master journal and this routine will return true,
    ** see if it is possible to delete the master journal. If errors 
    ** occur during this process, ignore them.
    */
    if( rc==SQLITE_OK ){
      pager_delmaster(zMaster);
    }
    sqliteFree(zMaster);
  }
  if( rc!=SQLITE_OK ){
    /* FIX ME: We shouldn't delete the journal if an error occured during
    ** rollback. It may have been a transient error and the rollback may
    ** succeed next time it is attempted.
    */
    pager_unwritelock(pPager);
    pPager->errMask |= PAGER_ERR_CORRUPT;
    rc = SQLITE_CORRUPT;
  }else{
    rc = pager_unwritelock(pPager);
  }
  return rc;

  }
  return n;
}

/*
** Forward declaration
*/
static int syncJournal(Pager*, const char*);


/*
** Unlink a page from the free list (the list of all pages where nRef==0)
** and from its hash collision chain.
*/
static void unlinkPage(PgHdr *pPg){

    return SQLITE_OK;
  }
  if( pPager->memDb ){
    pPager->dbSize = nPage;
    memoryTruncate(pPager);
    return SQLITE_OK;
  }
  syncJournal(pPager, 0);
  rc = sqlite3OsTruncate(&pPager->fd, SQLITE_PAGE_SIZE*(off_t)nPage);
  if( rc==SQLITE_OK ){
    pPager->dbSize = nPage;
  }
  return rc;
}

**
** 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, const char *zMaster){
  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 || zMaster ){
    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(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 ){
          TRACE1("SYNC\n");
          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);
      }
      TRACE1("SYNC\n");
      rc = sqlite3OsSync(&pPager->jfd);
      if( rc!=0 ) return rc;
      pPager->journalStarted = 1;

  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 SHARED lock
  ** on the database file.
  */
  if( pPager->nRef==0 && !pPager->memDb ){
    rc = sqlite3OsReadLock(&pPager->fd);
    if( rc!=SQLITE_OK ){
      return rc;
    }
    pPager->state = SQLITE_READLOCK;

    /* If a journal file exists, and there is no RESERVED lock on the
    ** database file, then it either needs to be played back or deleted.
    */
    if( pPager->useJournal && 
        sqlite3OsFileExists(pPager->zJournal) &&
        !sqlite3OsCheckWriteLock(&pPager->fd) 
    ){
       int rc;

       /* Get an EXCLUSIVE lock on the database file. */

       rc = sqlite3OsLock(&pPager->fd, EXCLUSIVE_LOCK);
       if( rc!=SQLITE_OK ){
         if( sqlite3OsUnlock(&pPager->fd)!=SQLITE_OK ){
           /* This should never happen! */
           rc = SQLITE_INTERNAL;
         }
         return rc;
       }

      /* If we could not find a page that does not require 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, 0);
        if( rc!=0 ){
          sqlite3pager_rollback(pPager);
          return SQLITE_IOERR;
        }
        pPg = pPager->pFirst;
      }
      assert( pPg->nRef==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 ){

** the any of the following happen:
**
**   *  sqlite3pager_commit() is called.
**   *  sqlite3pager_rollback() is called.
**   *  sqlite3pager_close() is called.
**   *  sqlite3pager_unref() is called to on every outstanding page.
**
** The first 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
** acquire a pointer to the Pager structure and as proof that there is
** already a read-lock on the database.
**
** The second parameter indicates how much space in bytes to reserve for a
** master journal file-name at the start of the journal when it is created.
**
** 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 sqlite3pager_begin(void *pData, int nMaster){
  PgHdr *pPg = DATA_TO_PGHDR(pData);
  Pager *pPager = pPg->pPager;
  int rc = SQLITE_OK;
  assert( pPg->nRef>0 );
  assert( nMaster>=0 );
  assert( pPager->state!=SQLITE_UNLOCK );
  if( pPager->state==SQLITE_READLOCK ){
    assert( pPager->aInJournal==0 );
    if( pPager->memDb ){
      pPager->state = SQLITE_WRITELOCK;
      pPager->origDbSize = pPager->dbSize;
    }else{
      rc = sqlite3OsWriteLock(&pPager->fd);
      if( rc!=SQLITE_OK ){
        return rc;
      }
      pPager->nMaster = nMaster;
      pPager->state = SQLITE_WRITELOCK;
      pPager->dirtyFile = 0;
      TRACE1("TRANSACTION\n");
      if( pPager->useJournal && !pPager->tempFile ){
        rc = pager_open_journal(pPager);
      }
    }

  ** 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 = sqlite3pager_begin(pData, 0);
  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;

        TRACE2("JOURNAL %d\n", pPg->pgno);
        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;

      pPg->pPrevStmt = pPg->pNextStmt = 0;
      pPg = pPg->pDirty;
    }
    pPager->pStmt = 0;
    pPager->state = SQLITE_READLOCK;
    return SQLITE_OK;
  }
#if 0
  if( pPager->dirtyFile==0 ){
    /* Exit early (without doing the time-consuming sqlite3OsSync() 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, 0);
  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 && sqlite3OsSync(&pPager->fd)!=SQLITE_OK) ){
      goto commit_abort;
    }
  }
#endif
  rc = sqlite3pager_sync(pPager, 0);
  if( rc!=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:

    sqlite3OsReadLock(&pPager->fd);
    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;
  }

  Pager *pPager,
  void (*xCodec)(void*,void*,Pgno,int),
  void *pCodecArg
){
  pPager->xCodec = xCodec;
  pPager->pCodecArg = pCodecArg;
}

/*
** Sync the database file for the pager pPager. zMaster points to the name
** of a master journal file that should be written into the individual
** journal file. zMaster may be NULL, which is interpreted as no master
** journal (a single database transaction).
**
** This routine ensures that the journal is synced, all dirty pages written
** to the database file and the database file synced. The only thing that
** remains to commit the transaction is to delete the journal file (or
** master journal file if specified).
**
** Note that if zMaster==NULL, this does not overwrite a previous value
** passed to an sqlite3pager_sync() call.
*/
int sqlite3pager_sync(Pager *pPager, const char *zMaster){
  int rc = SQLITE_OK;

  /* If this is an in-memory db, or no pages have been written to, this
  ** function is a no-op.
  */
  if( !pPager->memDb && pPager->dirtyFile ){
    PgHdr *pPg;
    assert( pPager->journalOpen );

    /* Sync the journal file */
    rc = syncJournal(pPager, zMaster);
    if( rc!=SQLITE_OK ) goto sync_exit;

    /* Write all dirty pages to the database file */
    pPg = pager_get_all_dirty_pages(pPager);
    rc = pager_write_pagelist(pPg);
    if( rc!=SQLITE_OK ) goto sync_exit;

    /* If any pages were actually written, sync the database file */
    if( pPg && !pPager->noSync ){
      rc = sqlite3OsSync(&pPager->fd);
    }
  }

sync_exit:
  return rc;
}

#ifdef SQLITE_TEST
/*
** Print a listing of all referenced pages and their ref count.
*/
void sqlite3pager_refdump(Pager *pPager){
  PgHdr *pPg;

**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite page cache
** subsystem.  The page cache subsystem reads and writes a file a page
** at a time and provides a journal for rollback.
**
** @(#) $Id: pager.h,v 1.30 2004/06/03 16:08:42 danielk1977 Exp $
*/

/*
** The size of a page.
**
** You can change this value to another (reasonable) value you want.
** It need not be a power of two, though the interface to the disk

int sqlite3pager_unref(void*);
Pgno sqlite3pager_pagenumber(void*);
int sqlite3pager_write(void*);
int sqlite3pager_iswriteable(void*);
int sqlite3pager_overwrite(Pager *pPager, Pgno pgno, void*);
int sqlite3pager_pagecount(Pager*);
int sqlite3pager_truncate(Pager*,Pgno);
int sqlite3pager_begin(void*,int);
int sqlite3pager_commit(Pager*);
int sqlite3pager_sync(Pager*,const char *zMaster);
int sqlite3pager_rollback(Pager*);
int sqlite3pager_isreadonly(Pager*);
int sqlite3pager_stmt_begin(Pager*);
int sqlite3pager_stmt_commit(Pager*);
int sqlite3pager_stmt_rollback(Pager*);
void sqlite3pager_dont_rollback(void*);
void sqlite3pager_dont_write(Pager*, Pgno);

/*
** 2003 April 6
**
** 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 contains code used to implement the PRAGMA command.
**
** $Id: pragma.c,v 1.36 2004/06/03 16:08:42 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** Interpret the given string as a boolean value.
*/

                         (char*)&pIdx->keyInfo, P3_KEYINFO);
        }
        sqlite3VdbeAddOp(v, OP_Integer, 0, 0);
        sqlite3VdbeAddOp(v, OP_MemStore, 1, 1);
        loopTop = sqlite3VdbeAddOp(v, OP_Rewind, 1, 0);
        sqlite3VdbeAddOp(v, OP_MemIncr, 1, 0);
        for(j=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, j++){
          int jmp2;
          static VdbeOpList idxErr[] = {
            { OP_MemIncr,     0,  0,  0},
            { OP_String8,      0,  0,  "rowid "},
            { OP_Recno,       1,  0,  0},
            { OP_String8,      0,  0,  " missing from index "},
            { OP_String8,      0,  0,  0},    /* 4 */
            { OP_Concat,      4,  0,  0},

**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing the btree.c module in SQLite.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test3.c,v 1.42 2004/06/03 16:08:42 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "pager.h"
#include "btree.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>

  int rc;
  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[1], (int*)&pBt) ) return TCL_ERROR;
  rc = sqlite3BtreeBeginTrans(pBt, 1, 0);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  return TCL_OK;
}

**
*************************************************************************
** This file contains code used to implement the VACUUM command.
**
** Most of the code in this file may be omitted by defining the
** SQLITE_OMIT_VACUUM macro.
**
** $Id: vacuum.c,v 1.21 2004/06/03 16:08:42 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "os.h"

#if !defined(SQLITE_OMIT_VACUUM) || SQLITE_OMIT_VACUUM
/*
** Generate a random name of 20 character in length.

  */
  pTemp = db->aDb[db->nDb-1].pBt;
  if( sqlite3BtreeIsInTrans(pTemp) ){
    Btree *pMain = db->aDb[0].pBt;
    u32 meta;

    assert( 0==sqlite3BtreeIsInTrans(pMain) );
    rc = sqlite3BtreeBeginTrans(db->aDb[0].pBt, 1, 0);
    if( rc!=SQLITE_OK ) goto end_of_vacuum;

    /* Copy Btree meta values 3 and 4. These correspond to SQL layer meta 
    ** values 2 and 3, the default values of a couple of pragmas.
    */
    rc = sqlite3BtreeGetMeta(pMain, 3, &meta);
    if( rc!=SQLITE_OK ) goto end_of_vacuum;

**
** Various scripts scan this source file in order to generate HTML
** documentation, headers files, or other derived files.  The formatting
** of the code in this file is, therefore, important.  See other comments
** in this file for details.  If in doubt, do not deviate from existing
** commenting and indentation practices when changing or adding code.
**
** $Id: vdbe.c,v 1.356 2004/06/03 16:08:42 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>
#include "vdbeInt.h"

/*

  int i = pOp->p1;
  Btree *pBt;

  assert( i>=0 && i<db->nDb );
  pBt = db->aDb[i].pBt;

  while( pBt && busy ){
    int nMaster = strlen(sqlite3BtreeGetFilename(db->aDb[0].pBt))+11;
    rc = sqlite3BtreeBeginTrans(db->aDb[i].pBt, pOp->p2, nMaster);
    switch( rc ){
      case SQLITE_BUSY: {
        if( db->xBusyCallback==0 ){
          p->pc = pc;
          p->rc = SQLITE_BUSY;
          p->pTos = pTos;
          return SQLITE_BUSY;

  pCx = p->apCsr[i];
  sqlite3VdbeCleanupCursor(pCx);
  memset(pCx, 0, sizeof(*pCx));
  pCx->nullRow = 1;
  rc = sqlite3BtreeFactory(db, 0, 1, TEMP_PAGES, &pCx->pBt);

  if( rc==SQLITE_OK ){
    rc = sqlite3BtreeBeginTrans(pCx->pBt, 1, 0);
  }
  if( rc==SQLITE_OK ){
    /* If a transient index is required, create it by calling
    ** sqlite3BtreeCreateTable() with the BTREE_ZERODATA flag before
    ** opening it. If a transient table is required, just use the
    ** automatically created table with root-page 1 (an INTKEY table).
    */

** intToKey() and keyToInt() used to transform the rowid.  But with
** the latest versions of the design they are no-ops.
*/
#define keyToInt(X)   (X)
#define intToKey(X)   (X)

/*
** The makefile scans the vdbe.c source file and creates the following
** array of string constants which are the names of all VDBE opcodes.  This
** array is defined in a separate source code file named opcode.c which is
** automatically generated by the makefile.
*/
extern char *sqlite3OpcodeNames[];

/*
** SQL is translated into a sequence of instructions to be
** executed by a virtual machine.  Each instruction is an instance
** of the following structure.

    rc = sqlite3VdbeMemSetStr(pColName, zName, N, TEXT_Utf8, N>0);
  }
  if( rc==SQLITE_OK && N==P3_DYNAMIC ){
    pColName->flags = (pColName->flags&(~MEM_Static))|MEM_Dyn;
  }
  return rc;
}

/*
** A read or write transaction may or may not be active on database handle
** db. If a transaction is active, commit it. If there is a
** write-transaction spanning more than one database file, this routine
** takes care of the master journal trickery.
*/
static int vdbeCommit(sqlite *db){
  int i;
  int nTrans = 0;  /* Number of databases with an active write-transaction */
  int rc = SQLITE_OK;
  int needXcommit = 0;

  for(i=0; i<db->nDb; i++){ 
    Btree *pBt = db->aDb[i].pBt;
    if( pBt && sqlite3BtreeIsInTrans(pBt) ){
      needXcommit = 1;
      if( i!=1 ) nTrans++;
    }
  }

  /* If there are any write-transactions at all, invoke the commit hook */
  if( needXcommit && db->xCommitCallback ){
    if( db->xCommitCallback(db->pCommitArg) ){
      return SQLITE_CONSTRAINT;
    }
  }

  /* The simple case - if less than two databases have write-transactions
  ** active, there is no need for the master-journal.
  */
  if( nTrans<2 ){
    for(i=0; i<db->nDb; i++){ 
      Btree *pBt = db->aDb[i].pBt;
      if( pBt ){
        int rc2 = sqlite3BtreeCommit(db->aDb[i].pBt);
        if( rc==SQLITE_OK ) rc = rc2;
      }
    }
  }

  /* The complex case - There is a multi-file write-transaction active.
  ** This requires a master journal file to ensure the transaction is
  ** committed atomicly.
  */
  else{
    char *zMaster = 0;   /* File-name for the master journal */
    char const *zMainFile = sqlite3BtreeGetFilename(db->aDb[0].pBt);
    OsFile master;

    /* Select a master journal file name */
    do {
      int random;
      if( zMaster ){
        sqliteFree(zMaster);
      }    
      sqlite3Randomness(sizeof(random), &random);
      zMaster = sqlite3_mprintf("%s%d", zMainFile, random);
      if( !zMaster ){
        return SQLITE_NOMEM;
      }
    }while( sqlite3OsFileExists(zMaster) );

    /* Open the master journal. */
    rc = sqlite3OsOpenExclusive(zMaster, &master, 0);
    if( rc!=SQLITE_OK ){
      sqliteFree(zMaster);
      return rc;
    }
 
    /* Write the name of each database file in the transaction into the new
    ** master journal file. If an error occurs at this point close
    ** and delete the master journal file. All the individual journal files
    ** still have 'null' as the master journal pointer, so they will roll
    ** back independantly if a failure occurs.
    */
    for(i=0; i<db->nDb; i++){ 
      Btree *pBt = db->aDb[i].pBt;
      if( pBt && sqlite3BtreeIsInTrans(pBt) ){
        char const *zFile = sqlite3BtreeGetFilename(pBt);
        rc = sqlite3OsWrite(&master, zFile, strlen(zFile));
        if( rc!=SQLITE_OK ){
          sqlite3OsClose(&master);
          sqlite3OsDelete(zMaster);
          sqliteFree(zMaster);
          return rc;
        }
        rc = sqlite3OsWrite(&master, "\0", 1);
        if( rc!=SQLITE_OK ){
          sqlite3OsClose(&master);
          sqlite3OsDelete(zMaster);
          sqliteFree(zMaster);
          return rc;
        }
      }
    }

    /* Sync the master journal file */
    rc = sqlite3OsSync(&master);
    sqlite3OsClose(&master);

    /* Sync all the db files involved in the transaction. The same call
    ** sets the master journal pointer in each individual journal. If
    ** an error occurs here, do not delete the master journal file.
    **
    ** If the error occurs during the first call to sqlite3BtreeSync(),
    ** then there is a chance that the master journal file will be
    ** orphaned. But we cannot delete it, in case the master journal
    ** file name was written into the journal file before the failure
    ** occured.
    */
    for(i=0; i<db->nDb; i++){ 
      Btree *pBt = db->aDb[i].pBt;
      if( pBt && sqlite3BtreeIsInTrans(pBt) ){
        rc = sqlite3BtreeSync(pBt, zMaster);
        if( rc!=SQLITE_OK ){
          sqliteFree(zMaster);
          return rc;
        }
      }
    }
    sqliteFree(zMaster);
    zMaster = 0;

    /* Delete the master journal file. This commits the transaction. */
    rc = sqlite3OsDelete(zMaster);
    assert( rc==SQLITE_OK );

    /* All files and directories have already been synced, so the following
    ** calls to sqlite3BtreeCommit() are only closing files and deleting
    ** journals. If something goes wrong while this is happening we don't
    ** really care. The integrity of the transaction is already guarenteed,
    ** but some stray 'cold' journals may be lying around. Returning an
    ** error code won't help matters.
    */
    for(i=0; i<db->nDb; i++){ 
      Btree *pBt = db->aDb[i].pBt;
      if( pBt ){
        sqlite3BtreeCommit(pBt);
      }
    }
  }
  return SQLITE_OK;
}

/* 
** This routine checks that the sqlite3.activeVdbeCnt count variable
** matches the number of vdbe's in the list sqlite3.pVdbe that are
** currently active. An assertion fails if the two counts do not match.
**
** This is a no-op if NDEBUG is defined.

** After this routine is run, the VDBE should be ready to be executed
** again.
*/
int sqlite3VdbeReset(Vdbe *p, char **pzErrMsg){
  sqlite *db = p->db;
  int i;
  int (*xFunc)(Btree *pBt) = 0;  /* Function to call on each btree backend */


  if( p->magic!=VDBE_MAGIC_RUN && p->magic!=VDBE_MAGIC_HALT ){
    sqlite3SetString(pzErrMsg, sqlite3ErrStr(SQLITE_MISUSE), (char*)0);
    sqlite3Error(p->db, SQLITE_MISUSE, 0 ,0);
    db->activeVdbeCnt--;
    return SQLITE_MISUSE;
  }

    sqlite3SetString(pzErrMsg, sqlite3ErrStr(p->rc), (char*)0);
    sqlite3Error(p->db, p->rc, 0);
  }else{
    sqlite3Error(p->db, SQLITE_OK, 0);
  }
  Cleanup(p);

  /* What is done now depends on the exit status of the vdbe, the value of
  ** the sqlite.autoCommit flag and whether or not there are any other
  ** queries in progress. A transaction or statement transaction may need
  ** to be committed or rolled back on each open database file.
  */
  checkActiveVdbeCnt(db);
  if( db->autoCommit && db->activeVdbeCnt==1 ){
    if( p->rc==SQLITE_OK || p->errorAction==OE_Fail ){
      /* The auto-commit flag is true, there are no other active queries
      ** using this handle and the vdbe program was successful or hit an
      ** 'OR FAIL' constraint. This means a commit is required, which is
      ** handled a little differently from the other options.
      */
      p->rc = vdbeCommit(db);
      if( p->rc!=SQLITE_OK ){
        sqlite3Error(p->db, p->rc, 0);
        xFunc = sqlite3BtreeRollback;

      }
    }else{
      xFunc = sqlite3BtreeRollback;
    }
  }else{
    if( p->rc==SQLITE_OK || p->errorAction==OE_Fail ){
      xFunc = sqlite3BtreeCommitStmt;
    }else if( p->errorAction==OE_Abort ){
      xFunc = sqlite3BtreeRollbackStmt;
    }else{
      xFunc = sqlite3BtreeRollback;
      db->autoCommit = 1;
    }
  }

  /* If xFunc is not NULL, then it is one of sqlite3BtreeRollback,
  ** sqlite3BtreeRollbackStmt or sqlite3BtreeCommitStmt. Call it once on
  ** each backend. If an error occurs and the return code is still
  ** SQLITE_OK, set the return code to the new error value.
  */
  for(i=0; xFunc && i<db->nDb; i++){ 
    int rc;
    Btree *pBt = db->aDb[i].pBt;










    if( pBt ){
      rc = xFunc(pBt);
      if( p->rc==SQLITE_OK ) p->rc = rc;
    }
  }