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 1.296 2007/03/26 10:27:19 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include "os.h"
#include "pager.h"
#include <assert.h>
#include <string.h>

  int rc = SQLITE_OK;
  assert( !MEMDB );
  if( pPager->state<PAGER_RESERVED ){
    return SQLITE_OK;
  }
  sqlite3PagerStmtCommit(pPager);
  if( pPager->stmtOpen && !pPager->exclusiveMode ){
    if( !pPager->exclusiveMode ){
      sqlite3OsClose(&pPager->stfd);
      pPager->stmtOpen = 0;
    }else{
      sqlite3OsTruncate(pPager->stfd, 0);
    }
  }
  if( pPager->journalOpen ){

** stored at byte 24 of the pager file.
*/
static int pager_incr_changecounter(Pager *pPager){
  PgHdr *pPgHdr;
  u32 change_counter;
  int rc;

  if( !pPager->changeCountDone ){
    /* Open page 1 of the file for writing. */
    rc = sqlite3PagerGet(pPager, 1, &pPgHdr);
    if( rc!=SQLITE_OK ) return rc;
    rc = sqlite3PagerWrite(pPgHdr);
    if( rc!=SQLITE_OK ) return rc;
  
    /* Read the current value at byte 24. */
    change_counter = retrieve32bits(pPgHdr, 24);
  
    /* Increment the value just read and write it back to byte 24. */
    change_counter++;
    put32bits(((char*)PGHDR_TO_DATA(pPgHdr))+24, change_counter);
    pPager->iChangeCount = change_counter;
  
    /* Release the page reference. */
    sqlite3PagerUnref(pPgHdr);
    pPager->changeCountDone = 1;
  }
  return SQLITE_OK;
}

/*
** 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

# 2007 March 24
#
# 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 these tests is exclusive access mode (i.e. the thing activated by 
# "PRAGMA locking_mode = EXCLUSIVE").
#
# $Id: exclusive.test,v 1.3 2007/03/26 10:27:19 danielk1977 Exp $

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

ifcapable {!pager_pragmas} {
  finish_test
  return

# 2007 March 24
#
# 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.
#
# $Id: exclusive2.test,v 1.1 2007/03/26 10:27:19 danielk1977 Exp $

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

ifcapable {!pager_pragmas} {
  finish_test
  return
}

proc pagerChangeCounter {filename {new ""}} {
  set fd [open $filename a+]
  fconfigure $fd -translation binary -encoding binary
  if {$new ne ""} {
    seek $fd 24
    set a [expr {($new&0xFF000000)>>24}]
    set b [expr {($new&0x00FF0000)>>16}]
    set c [expr {($new&0x0000FF00)>>8}]
    set d [expr {($new&0x000000FF)}]
    puts $fd [binary format cccc $a $b $c $d]
  }

  seek $fd 24
  foreach {a b c d} [list 0 0 0 0] {}
  binary scan [read $fd 4] cccc a b c d
  set  ret [expr ($a&0x000000FF)<<24]
  incr ret [expr ($b&0x000000FF)<<16]
  incr ret [expr ($c&0x000000FF)<<8]
  incr ret [expr ($d&0x000000FF)<<0]

  close $fd
  return $ret
}

proc t1sig {{db db}} {
  execsql {SELECT count(*), md5sum(a) FROM t1} $db
}
do_test exclusive2-1.0 {
  pagerChangeCounter test.db
} {0}

#-----------------------------------------------------------------------
# The following tests - exclusive2-1.X - check that:
#
# 1-3:   Build a database with connection 1, calculate a signature.
# 4-9:   Modify the database using a second connection, then reset
#        the pager change-counter to the value it had before the modifications.
# 8:     Check that using the first connection, the database signature
#        is still the same. This is because it uses the in-memory cache.
#        It can't tell the db has changed because we reset the change-counter.
# 9:     Increment the change-counter.
# 10:    Ensure that the first connection now sees the updated database. It
#        sees the change-counter has been incremented and discards the 
#        invalid in-memory cache.
#
do_test exclusive2-1.1 {
  execsql {
    BEGIN;
    CREATE TABLE t1(a UNIQUE);
    INSERT INTO t1 VALUES(randstr(10, 400));
    INSERT INTO t1 VALUES(randstr(10, 400));
    INSERT INTO t1 SELECT randstr(10, 400) FROM t1;
    INSERT INTO t1 SELECT randstr(10, 400) FROM t1;
    INSERT INTO t1 SELECT randstr(10, 400) FROM t1;
    INSERT INTO t1 SELECT randstr(10, 400) FROM t1;
    INSERT INTO t1 SELECT randstr(10, 400) FROM t1;
    COMMIT;
    SELECT count(*) FROM t1;
  }
} {64}
do_test exclusive2-1.2 {
  set ::sig [t1sig]
  pagerChangeCounter test.db
} {1}
do_test exclusive2-1.3 {
  t1sig
} $::sig
do_test exclusive2-1.4 {
  sqlite3 db2 test.db
  t1sig db2
} $::sig
do_test exclusive2-1.5 {
  execsql {
    DELETE FROM t1;
  } db2
  expr {[t1sig db2] eq $::sig}
} 0
do_test exclusive2-1.6 {
  pagerChangeCounter test.db
} {2}
do_test exclusive2-1.7 {
  pagerChangeCounter test.db 1
} {1}
do_test exclusive2-1.9 {
  t1sig
  expr {[t1sig] eq $::sig}
} {1}
do_test exclusive2-1.10 {
  pagerChangeCounter test.db 2
} {2}
do_test exclusive2-1.11 {
  expr {[t1sig] eq $::sig}
} {0}

#--------------------------------------------------------------------
# These tests - exclusive2-2.X - are similar to exclusive2-1.X, 
# except that they are run with locking_mode=EXCLUSIVE.
#
# 1-3:   Build a database with exclusive-access connection 1, 
#        calculate a signature.
# 4:     Corrupt the database by writing 10000 bytes of garbage
#        starting at the beginning of page 2. Check that connection 1
#        still works. It should be accessing the in-memory cache.
# 5-6:   Modify the dataase change-counter. Connection 1 still works
#        entirely from in-memory cache, because it doesn't check the
#        change-counter.
# 7-8    Set the locking-mode back to normal. After the db is unlocked,
#        SQLite detects the modified change-counter and discards the
#        in-memory cache. Then it finds the corruption caused in step 4....
#
do_test exclusive2-2.1 {
  execsql {PRAGMA locking_mode = exclusive;}
  execsql {
    BEGIN;
    INSERT INTO t1 VALUES(randstr(10, 400));
    INSERT INTO t1 VALUES(randstr(10, 400));
    INSERT INTO t1 SELECT randstr(10, 400) FROM t1;
    INSERT INTO t1 SELECT randstr(10, 400) FROM t1;
    INSERT INTO t1 SELECT randstr(10, 400) FROM t1;
    INSERT INTO t1 SELECT randstr(10, 400) FROM t1;
    INSERT INTO t1 SELECT randstr(10, 400) FROM t1;
    COMMIT;
    SELECT count(*) FROM t1;
  }
} {64}
do_test exclusive2-2.2 {
  set ::sig [t1sig]
  pagerChangeCounter test.db
} {3}
do_test exclusive2-2.3 {
  t1sig
} $::sig

do_test exclusive2-2.4 {
  set fd [open test.db a]
  seek $fd 1024
  puts -nonewline $fd [string repeat [binary format c 0] 10000]
  t1sig
} $::sig

do_test exclusive2-2.5 {
  pagerChangeCounter test.db 5
} {5}
do_test exclusive2-2.6 {
  t1sig
} $::sig
do_test exclusive2-2.7 {
  execsql {PRAGMA locking_mode = normal}
  t1sig
} $::sig

do_test exclusive2-2.8 {
  set rc [catch {t1sig} msg]
  list $rc $msg
} {1 {database disk image is malformed}}

#--------------------------------------------------------------------
# These tests - exclusive2-3.X - verify that the pager change-counter
# is only incremented by the first change when in exclusive access
# mode. In normal mode, the change-counter is incremented once
# per write-transaction.
#

db close
db2 close
file delete -force test.db
file delete -force test.db-journal

do_test exclusive2-3.0 {
  sqlite3 db test.db
  execsql {
    BEGIN;
    CREATE TABLE t1(a UNIQUE);
    INSERT INTO t1 VALUES(randstr(10, 400));
    INSERT INTO t1 VALUES(randstr(10, 400));
    COMMIT;
  }
  pagerChangeCounter test.db
} {1}
do_test exclusive2-3.1 {
  execsql {
    INSERT INTO t1 VALUES(randstr(10, 400));
  }
  pagerChangeCounter test.db
} {2}
do_test exclusive2-3.2 {
  execsql {
    INSERT INTO t1 VALUES(randstr(10, 400));
  }
  pagerChangeCounter test.db
} {3}
do_test exclusive2-3.3 {
  execsql {
    PRAGMA locking_mode = exclusive;
    INSERT INTO t1 VALUES(randstr(10, 400));
  }
  pagerChangeCounter test.db
} {4}
do_test exclusive2-3.4 {
  execsql {
    INSERT INTO t1 VALUES(randstr(10, 400));
  }
  pagerChangeCounter test.db
} {4}
do_test exclusive2-3.5 {
  execsql {
    PRAGMA locking_mode = normal;
    INSERT INTO t1 VALUES(randstr(10, 400));
  }
  pagerChangeCounter test.db
} {4}
do_test exclusive2-3.6 {
  execsql {
    INSERT INTO t1 VALUES(randstr(10, 400));
  }
  pagerChangeCounter test.db
} {5}

finish_test