** 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 1.540 2009/01/07 18:08:49 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"

/*
** Macros for troubleshooting.  Normally turned off
*/
................................................................................
    ** The third term of the test was added to fix ticket #2565.
    ** When rolling back a hot journal, nRec==0 always means that the next
    ** chunk of the journal contains zero pages to be rolled back.  But
    ** when doing a ROLLBACK and the nRec==0 chunk is the last chunk in
    ** the journal, it means that the journal might contain additional
    ** pages that need to be rolled back and that the number of pages 
    ** should be computed based on the journal file size.
    **
    ** 2009-01-07:  We think #2565 is now unreachable due to changes
    ** in the pcache.  The assert that follows will fire if we are wrong.
    */
    assert( !(nRec==0 && !isHot
         && pPager->journalHdr+JOURNAL_HDR_SZ(pPager)!=pPager->journalOff
         && ((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager))>0
         && pagerNextJournalPageIsValid(pPager))
    );
    if( nRec==0 && !isHot &&
        pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff ){
      nRec = (int)((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager));
    }

    /* If this is the first header read from the journal, truncate the

** 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 1.541 2009/01/08 15:24:02 drh Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"

/*
** Macros for troubleshooting.  Normally turned off
*/
................................................................................
    ** The third term of the test was added to fix ticket #2565.
    ** When rolling back a hot journal, nRec==0 always means that the next
    ** chunk of the journal contains zero pages to be rolled back.  But
    ** when doing a ROLLBACK and the nRec==0 chunk is the last chunk in
    ** the journal, it means that the journal might contain additional
    ** pages that need to be rolled back and that the number of pages 
    ** should be computed based on the journal file size.



    */
    testcase( nRec==0 && !isHot
         && pPager->journalHdr+JOURNAL_HDR_SZ(pPager)!=pPager->journalOff
         && ((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager))>0
         && pagerNextJournalPageIsValid(pPager)
    );
    if( nRec==0 && !isHot &&
        pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff ){
      nRec = (int)((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager));
    }

    /* If this is the first header read from the journal, truncate the

# 2009 January 8
#
# 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 script attempts to reproduce the circumstances of ticket #2565.
#
# More specifically, this script attempts to generate rollback journals
# that contain headers with nRec==0 that are followed by additional
# valid headers.
#
# $Id: tkt2565.test,v 1.1 2009/01/08 15:24:02 drh Exp $

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

# Use the alternative pcache and rig it to call pagerStress()
# very frequently.
#
db close
sqlite3_shutdown
sqlite3_config_alt_pcache 1 100 0 1

# Open two database connections to database "test.db".
#
proc reopen_database {} {
  catch {db close}
  sqlite3 db test.db
  db cache size 0
  execsql {
    pragma page_size=512;
    pragma auto_vacuum=2;
    pragma cache_size=16;
  }
}

# Open two database connections and create a single table in the db.
#
do_test tkt2565-1.0 {
  reopen_database
  execsql { CREATE TABLE A(Id INTEGER, Name TEXT) }
} {}

for {set iFail 1} {$iFail<200} {incr iFail} {
  reopen_database
  execsql { pragma locking_mode=exclusive }
  set nRow [db one {SELECT count(*) FROM a}]
  
  # Dirty (at least) one of the pages in the cache.
  do_test tkt2565-1.$iFail.1 {
    execsql {
      BEGIN EXCLUSIVE;
      INSERT INTO a VALUES(1, 'ABCDEFGHIJKLMNOP');
    }
  } {}
  
  # Now try to commit the transaction. Cause an IO error to occur
  # within this operation, which moves the pager into the error state.
  #
  set ::sqlite_io_error_persist 1
  set ::sqlite_io_error_pending $iFail
  do_test tkt2565-1.$iFail.2 {
    set rc [catchsql {COMMIT}]
    list
  } {}
  set ::sqlite_io_error_persist 0
  set ::sqlite_io_error_pending 0
  if {!$::sqlite_io_error_hit} break
  set ::sqlite_io_error_hit 0
}

# Make sure this test script doesn't leave any files open.
#
do_test tkt2565-1.X {
  catch { db close }
  set sqlite_open_file_count
} 0

# Restore the pcache configuration for subsequent tests.
#
sqlite3_shutdown
sqlite3_config_alt_pcache 0

finish_test