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 1.455 2008/06/07 05:19:38 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include <assert.h>
#include <string.h>

/*

    IOTRACE(("JZEROHDR %p\n", pPager))
    if( doTruncate || iLimit==0 ){
      rc = sqlite3OsTruncate(pPager->jfd, 0);
    }else{
      rc = sqlite3OsWrite(pPager->jfd, zeroHdr, sizeof(zeroHdr), 0);
    }
    if( rc==SQLITE_OK && !pPager->noSync ){
      rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_DATAONLY|pPager->sync_flags);
    }

    /* At this point the transaction is committed but the write lock 
    ** is still held on the file. If there is a size limit configured for 
    ** the persistent journal and the journal file currently consumes more
    ** space than that limit allows for, truncate it now. There is no need

    rc = sqlite3OsAccess(pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &exists);
    if( rc==SQLITE_OK && exists ){
      rc = sqlite3OsCheckReservedLock(pPager->fd, &locked);
    }

    if( rc==SQLITE_OK && exists && !locked ){
      int nPage = sqlite3PagerPagecount(pPager);
      if( nPage==0 ){
        sqlite3OsDelete(pVfs, pPager->zJournal, 0);
        exists = 0;
      }else if( nPage<0 ){
        rc = SQLITE_IOERR;
      }
    }

    res = (rc!=SQLITE_OK ? -1 : (exists && !locked));
  }

  return res;

# 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 some common TCL routines used for regression
# testing the SQLite library
#
# $Id: tester.tcl,v 1.126 2008/06/07 05:19:38 danielk1977 Exp $

#
# What for user input before continuing.  This gives an opportunity
# to connect profiling tools to the process.
#
for {set i 0} {$i<[llength $argv]} {incr i} {
  if {[regexp {^-+pause$} [lindex $argv $i] all value]} {

    set ::sqlite_io_error_hit 0
    set ::sqlite_io_error_pending 0

    # Check that no page references were leaked. There should be 
    # a single reference if there is still an active transaction, 
    # or zero otherwise.
    #
    # UPDATE: If the IO error occurs after a 'BEGIN' but before any
    # locks are established on database files (i.e. if the error 
    # occurs while attempting to detect a hot-journal file), then
    # there may 0 page references and an active transaction according
    # to [sqlite3_get_autocommit].
    #
    if {$::go && $::sqlite_io_error_hardhit && $::ioerropts(-ckrefcount)} {
      do_test $testname.$n.4 {
        set bt [btree_from_db db]
        db_enter db
        array set stats [btree_pager_stats $bt]
        db_leave db
        set nRef $stats(ref)
        expr {$nRef == 0 || ([sqlite3_get_autocommit db]==0 && $nRef == 1)}
      } {1}
    }

    # If there is an open database handle and no open transaction, 
    # and the pager is not running in exclusive-locking mode,
    # check that the pager is in "unlocked" state. Theoretically,
    # if a call to xUnlock() failed due to an IO error the underlying
    # file may still be locked.