SQLite

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains the implementation of the sqlite3_backup_XXX() 
** API functions and the related features.
**
** $Id: backup.c,v 1.13.2.1 2009/05/18 17:11:31 drh Exp $
*/
#include "sqliteInt.h"
#include "btreeInt.h"

/* Macro to find the minimum of two numeric values.
*/
#ifndef MIN

  /* These two variables are set by every call to backup_step(). They are
  ** read by calls to backup_remaining() and backup_pagecount().
  */
  Pgno nRemaining;         /* Number of pages left to copy */
  Pgno nPagecount;         /* Total number of pages to copy */

  int isAttached;          /* True once backup has been registered with pager */
  sqlite3_backup *pNext;   /* Next backup associated with source pager */
};

/*
** THREAD SAFETY NOTES:
**
**   Once it has been created using backup_init(), a single sqlite3_backup

  if( p ){
    memset(p, 0, sizeof(sqlite3_backup));
    p->pSrc = findBtree(pDestDb, pSrcDb, zSrcDb);
    p->pDest = findBtree(pDestDb, pDestDb, zDestDb);
    p->pDestDb = pDestDb;
    p->pSrcDb = pSrcDb;
    p->iNext = 1;
    p->isAttached = 0;

    if( 0==p->pSrc || 0==p->pDest ){
      /* One (or both) of the named databases did not exist. An error has
      ** already been written into the pDestDb handle. All that is left
      ** to do here is free the sqlite3_backup structure.
      */
      sqlite3_free(p);
      p = 0;
    }
  }





  if( p ){






    p->pSrc->nBackup++;
  }

  sqlite3_mutex_leave(pDestDb->mutex);
  sqlite3_mutex_leave(pSrcDb->mutex);
  return p;
}

  i64 iCurrent;
  int rc = sqlite3OsFileSize(pFile, &iCurrent);
  if( rc==SQLITE_OK && iCurrent>iSize ){
    rc = sqlite3OsTruncate(pFile, iSize);
  }
  return rc;
}

/*
** Register this backup object with the associated source pager for
** callbacks when pages are changed or the cache invalidated.
*/
static void attachBackupObject(sqlite3_backup *p){
  sqlite3_backup **pp;
  assert( sqlite3BtreeHoldsMutex(p->pSrc) );
  pp = sqlite3PagerBackupPtr(sqlite3BtreePager(p->pSrc));
  p->pNext = *pp;
  *pp = p;
  p->isAttached = 1;
}

/*
** Copy nPage pages from the source b-tree to the destination.
*/
int sqlite3_backup_step(sqlite3_backup *p, int nPage){
  int rc;

      p->iNext++;
    }
    if( rc==SQLITE_OK ){
      p->nPagecount = nSrcPage;
      p->nRemaining = nSrcPage+1-p->iNext;
      if( p->iNext>(Pgno)nSrcPage ){
        rc = SQLITE_DONE;
      }else if( !p->isAttached ){
        attachBackupObject(p);
      }
    }
  
    if( rc==SQLITE_DONE ){
      const int nSrcPagesize = sqlite3BtreeGetPageSize(p->pSrc);
      const int nDestPagesize = sqlite3BtreeGetPageSize(p->pDest);
      int nDestTruncate;

  mutex = p->pSrcDb->mutex;
  if( p->pDestDb ){
    sqlite3_mutex_enter(p->pDestDb->mutex);
  }

  /* Detach this backup from the source pager. */
  if( p->pDestDb ){
    p->pSrc->nBackup--;
  }
  if( p->isAttached ){
    pp = sqlite3PagerBackupPtr(sqlite3BtreePager(p->pSrc));
    while( *pp!=p ){
      pp = &(*pp)->pNext;
    }
    *pp = p->pNext;

  }

  /* If a transaction is still open on the Btree, roll it back. */
  sqlite3BtreeRollback(p->pDest);

  /* Set the error code of the destination database handle. */
  rc = (p->rc==SQLITE_DONE) ? SQLITE_OK : p->rc;

** 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 1.586.2.1 2009/05/18 17:11:31 drh Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"

/*
** Macros for troubleshooting.  Normally turned off
*/

        goto failed;
      }
      assert( (pPager->state==PAGER_SHARED)
           || (pPager->exclusiveMode && pPager->state>PAGER_SHARED)
      );
    }

    if( pPager->pBackup || sqlite3PcachePagecount(pPager->pPCache)>0 ){
      /* The shared-lock has just been acquired on the database file
      ** and there are already pages in the cache (from a previous
      ** read or write transaction).  Check to see if the database
      ** has been modified.  If the database has changed, flush the
      ** cache.
      **
      ** Database changes is detected by looking at 15 bytes beginning

# 2009 January 30
#
# 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 file is testing the sqlite3_backup_XXX API.
#
# $Id: backup.test,v 1.9.2.1 2009/05/18 17:11:31 drh Exp $

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

#---------------------------------------------------------------------
# Test organization:
#

do_test backup-9.2.2 {
  B remaining
} {0}
do_test backup-9.2.3 {
  B finish
} {SQLITE_OK}
catch {db2 close}

ifcapable memorymanage {
  db close
  file delete -force test.db
  file delete -force bak.db

  sqlite3 db test.db
  sqlite3 db2 test.db
  sqlite3 db3 bak.db

  do_test backup-10.1.1 {
    execsql {
      BEGIN;
      CREATE TABLE t1(a, b);
      INSERT INTO t1 VALUES(1, randstr(1000,1000));
      INSERT INTO t1 VALUES(2, randstr(1000,1000));
      INSERT INTO t1 VALUES(3, randstr(1000,1000));
      INSERT INTO t1 VALUES(4, randstr(1000,1000));
      INSERT INTO t1 VALUES(5, randstr(1000,1000));
      CREATE INDEX i1 ON t1(a, b);
      COMMIT;
    }
  } {}
  do_test backup-10.1.2 {
    sqlite3_backup B db3 main db2 main
    B step 5
  } {SQLITE_OK}
  do_test backup-10.1.3 {
    execsql {
      UPDATE t1 SET b = randstr(500,500);
    }
  } {}
  sqlite3_release_memory [expr 1024*1024]
  do_test backup-10.1.3 {
    B step 50
  } {SQLITE_DONE}
  do_test backup-10.1.4 {
    B finish
  } {SQLITE_OK}
  do_test backup-10.1.5 {
    execsql { PRAGMA integrity_check } db3
  } {ok}

  db2 close
  db3 close
}

finish_test