SQLite

    char zBuf[_MAX_PATH+1];
      sqliteSetString(&zFull, getcwd(zBuf, sizeof(zBuf)), zRelative, 0);
    }
  }
  return zFull;
#endif
}

** 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 1.68 2003/01/16 13:42:43 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

  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 */
  /* SQLITE_PAGE_SIZE bytes of page data follow this header */
  /* Pager.nExtra bytes of local data follow the page data */
};

/*
** Convert a pointer to a PgHdr into a pointer to its data

  char *zJournal;             /* Name of the journal file */
  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() */
#ifndef NDEBUG
  off_t syncJSize;            /* Size of journal at last fsync() call */
#endif
  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 */
  u8 journalOpen;             /* True if journal file descriptors is valid */
  u8 journalStarted;          /* True if initial magic of journal is synced */
  u8 useJournal;              /* Do not 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 state;                   /* SQLITE_UNLOCK, _READLOCK or _WRITELOCK */
  u8 errMask;                 /* One of several kinds of errors */

    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;

  /* Sanity checking on the page */
  if( pgRec.pgno>pPager->dbSize || pgRec.pgno==0 ) return SQLITE_CORRUPT;

  /* 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);
  if( pPg==0 || pPg->needSync==0 ){
    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 ){
    memcpy(PGHDR_TO_DATA(pPg), pgRec.aData, SQLITE_PAGE_SIZE);
    memset(PGHDR_TO_EXTRA(pPg), 0, pPager->nExtra);



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

/*
** Playback the journal and thus restore the database file to
** the state it was in before we started making changes.  

  
  /* Copy original pages out of the journal and back into the database file.
  */
  for(i=nRec-1; i>=0; i--){
    rc = pager_playback_one_page(pPager, &pPager->jfd);
    if( rc!=SQLITE_OK ) break;
  }


end_playback:
#if !defined(NDEBUG) && defined(SQLITE_TEST)
  /* For pages that were never written into the journal, restore the
  ** memory copy from the original database file.
  **
  ** This is code is used during testing only.  It is necessary to
  ** compensate for the sqliteOsTruncate() call inside 
  ** sqlitepager_rollback().
  */
  if( rc==SQLITE_OK ){
    PgHdr *pPg;
    for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
      if( (int)pPg->pgno <= pPager->origDbSize ){
        sqliteOsSeek(&pPager->fd, SQLITE_PAGE_SIZE*(off_t)(pPg->pgno-1));
        rc = sqliteOsRead(&pPager->fd, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE);
        if( rc ) break;
      }else{
        memset(PGHDR_TO_DATA(pPg), 0, SQLITE_PAGE_SIZE);
      }
      memset(PGHDR_TO_EXTRA(pPg), 0, pPager->nExtra);
      pPg->needSync = 0;
      pPg->dirty = 0;
    }
  }
#endif
  if( rc!=SQLITE_OK ){
    pager_unwritelock(pPager);
    pPager->errMask |= PAGER_ERR_CORRUPT;
    rc = SQLITE_CORRUPT;
  }else{
    rc = pager_unwritelock(pPager);
  }

  nameLen = strlen(zFullPathname);
  pPager = sqliteMalloc( sizeof(*pPager) + nameLen*2 + 30 );
  if( pPager==0 ){
    sqliteOsClose(&fd);
    sqliteFree(zFullPathname);
    return SQLITE_NOMEM;
  }
  SET_PAGER(pPager);
  pPager->zFilename = (char*)&pPager[1];
  pPager->zJournal = &pPager->zFilename[nameLen+1];
  strcpy(pPager->zFilename, zFullPathname);
  strcpy(pPager->zJournal, zFullPathname);
  sqliteFree(zFullPathname);
  strcpy(&pPager->zJournal[nameLen], "-journal");
  pPager->fd = fd;

  sqliteOsClose(&pPager->fd);
  assert( pPager->journalOpen==0 );
  /* Temp files are automatically deleted by the OS
  ** if( pPager->tempFile ){
  **   sqliteOsDelete(pPager->zFilename);
  ** }
  */
  CLR_PAGER(pPager);
  sqliteFree(pPager);
  return SQLITE_OK;
}

/*
** Return the page number for the given page data.
*/

**
** If we are writing to temporary database, there is no need to preserve
** the integrity of the journal file, so we can save time and skip the
** fsync().
*/
static int syncAllPages(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 );
      TRACE1("SYNC\n");
      rc = sqliteOsSync(&pPager->jfd);
      if( rc!=0 ) return rc;
#ifndef NDEBUG
      rc = sqliteOsFileSize(&pPager->jfd, &pPager->syncJSize);
      if( rc!=0 ) return rc;
#endif
      pPager->journalStarted = 1;
    }
    pPager->needSync = 0;
  }

  /* Erase the needSync flag from every page.



  */
  for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){






    pPg->needSync = 0;

  }

  return rc;
}

/*
** Acquire a page.
**
** A read lock on the disk file is obtained when the first page is acquired. 

       if( rc!=SQLITE_OK ){
         rc = sqliteOsUnlock(&pPager->fd);
         assert( rc==SQLITE_OK );
         *ppPage = 0;
         return SQLITE_BUSY;
       }
       pPager->journalOpen = 1;
       pPager->journalStarted = 0;

       /* Playback and delete the journal.  Drop the database write
       ** lock and reacquire the read lock.
       */
       rc = pager_playback(pPager);
       if( rc!=SQLITE_OK ){
         return rc;

      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
      ** require us to do an fsync() on the journal.
      */
      pPg = pPager->pFirst;
      while( pPg && pPg->needSync ){
        pPg = pPg->pNextFree;
      }

      /* 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 = syncAllPages(pPager);
        if( rc!=0 ){
          sqlitepager_rollback(pPager);
          *ppPage = 0;
          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 );
        TRACE2("SAVE %d\n", pPg->pgno);
        sqliteOsSeek(&pPager->fd, (pPg->pgno-1)*(off_t)SQLITE_PAGE_SIZE);
        rc = sqliteOsWrite(&pPager->fd, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE);
        if( rc!=SQLITE_OK ){
          sqlitepager_rollback(pPager);
          *ppPage = 0;
          return SQLITE_IOERR;
        }
        pPg->dirty = 0;
      }
      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.
      */

      }
      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);
    }

    sqliteFree(pPager->aInJournal);
    pPager->aInJournal = 0;
    sqliteOsReadLock(&pPager->fd);
    pPager->state = SQLITE_READLOCK;
    return SQLITE_CANTOPEN;
  }
  pPager->journalOpen = 1;
  pPager->journalStarted = 0;
  pPager->needSync = 0;
  pPager->alwaysRollback = 0;
  sqlitepager_pagecount(pPager);
  pPager->origDbSize = pPager->dbSize;
  if( pager_old_format ){
    rc = sqliteOsWrite(&pPager->jfd, aOldJournalMagic,
                       sizeof(aOldJournalMagic));

  }
  if( rc!=SQLITE_OK ){
    rc = pager_unwritelock(pPager);
    if( rc==SQLITE_OK ){
      rc = SQLITE_FULL;
    }
  }
#ifndef NDEBUG
  pPager->syncJSize = 0;
#endif
  return rc;  
}

/*
** Acquire a write-lock on the database.  The lock is removed when
** the any of the following happen:
**

    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;
}

  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 ){
      rc = write32bits(&pPager->jfd, pPg->pgno);
      if( rc==SQLITE_OK ){
        rc = sqliteOsWrite(&pPager->jfd, pData, SQLITE_PAGE_SIZE);
      }
      if( rc!=SQLITE_OK ){
        sqlitepager_rollback(pPager);
        pPager->errMask |= PAGER_ERR_FULL;
        return rc;
      }
      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);
      }
      TRACE3("JOURNAL %d %d\n", pPg->pgno, pPg->needSync);
    }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.
  */
  if( pPager->ckptInUse && !pPg->inCkpt && (int)pPg->pgno<=pPager->ckptSize ){

      ** 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,

    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;
  int dbChanged;

  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. */
    rc = pager_unwritelock(pPager);
    pPager->dbSize = -1;
    return rc;
  }
  assert( pPager->journalOpen );
  if( !pPager->journalStarted && !pPager->noSync ) pPager->needSync = 1;
  assert( pPager->dirtyFile || !pPager->needSync );
  if( pPager->needSync && sqliteOsSync(&pPager->jfd)!=SQLITE_OK ){
    goto commit_abort;
  }
  dbChanged = 0;
  for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
    if( pPg->dirty==0 ) continue;
    TRACE2("COMMIT-PAGE %d\n", pPg->pgno);
    sqliteOsSeek(&pPager->fd, (pPg->pgno-1)*(off_t)SQLITE_PAGE_SIZE);

    rc = sqliteOsWrite(&pPager->fd, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE);
    if( rc!=SQLITE_OK ) goto commit_abort;
    dbChanged = 1;
  }
  if( dbChanged && !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.

** 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 defined(SQLITE_TEST) && !defined(NDEBUG)
  /* Truncate the journal to the size it was at the conclusion of the
  ** last sqliteOsSync() call.  This is really an error check.  If the
  ** rollback still works, it means that the rollback would have also
  ** worked if it had occurred after an OS crash or unexpected power
  ** loss.
  */
  if( pPager->syncJSize<sizeof(aJournalMagic)+sizeof(Pgno) ){
    pPager->syncJSize = sizeof(aJournalMagic)+sizeof(Pgno);
  }
  TRACE2("TRUNCATE JOURNAL %lld\n", pPager->syncJSize);
  rc =  sqliteOsTruncate(&pPager->jfd, pPager->syncJSize);
  if( rc ) return rc;
#endif

  if( pPager->errMask!=0 && pPager->errMask!=PAGER_ERR_FULL ){
    if( pPager->state>=SQLITE_WRITELOCK ){
      pager_playback(pPager);
    }
    return pager_errcode(pPager);
  }
  if( pPager->state!=SQLITE_WRITELOCK ){

**
** 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 1.198 2003/01/16 13:42:43 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** The makefile scans this source file and creates the following
** array of string constants which are the names of all VDBE opcodes.

/*
** Pop the stack N times.  Free any memory associated with the
** popped stack elements.
*/
static void PopStack(Vdbe *p, int N){
  assert( N>=0 );
  if( p->zStack==0 ) return;
  assert( p->aStack || sqlite_malloc_failed );
  if( p->aStack==0 ) return;
  while( N-- > 0 ){
    if( p->aStack[p->tos].flags & STK_Dyn ){
      sqliteFree(p->zStack[p->tos]);
    }
    p->aStack[p->tos].flags = 0;
    p->zStack[p->tos] = 0;
    p->tos--;

do_test trigger3-1.2 {
    execsql {
	SELECT * FROM tbl;
	ROLLBACK;
    }
} {5 5 6}
do_test trigger3-1.3 {
    execsql {SELECT * FROM tbl}
} {}

# FAIL
do_test trigger3-2.1 {
    catchsql {
	BEGIN;
        INSERT INTO tbl VALUES (5, 5, 6);
        INSERT INTO tbl VALUES (2, 5, 6);