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 1.376 2007/08/24 16:29:24 drh Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include <assert.h>
#include <string.h>

/*

/*
** Open a temporary file. 
**
** Write the file descriptor into *fd.  Return SQLITE_OK on success or some
** other error code if we fail. The OS will automatically delete the temporary
** file when it is closed.
**
** If zFilename is 0, then an appropriate temporary filename is
** generated automatically and  SQLITE_OPEN_SUBJOURNAL is passed to
** the OS layer as the file type.
**
** If zFilename is not 0, SQLITE_OPEN_TEMP_DB is passed as the file type.
*/
static int sqlite3PagerOpentemp(
  sqlite3_vfs *pVfs, 
  sqlite3_file *pFile, 
  char *zFilename
){

  int rc;
  int flags = (
     SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|
     SQLITE_OPEN_EXCLUSIVE|SQLITE_OPEN_DELETEONCLOSE
  );

  char *zFree = 0;
  if( zFilename==0 ){
    zFree = (char *)sqlite3_malloc(pVfs->mxPathname);
    if( !zFree ){
      return SQLITE_NOMEM;
    }
    zFilename = zFree;
    flags |= SQLITE_OPEN_SUBJOURNAL;
    rc = sqlite3OsGetTempName(pVfs, zFilename);
    if( rc!=SQLITE_OK ){
      sqlite3_free(zFree);
      return rc;
    }
  }else{
    flags |= SQLITE_OPEN_TEMP_DB;
  }

#ifdef SQLITE_TEST
  sqlite3_opentemp_count++;  /* Used for testing and analysis only */
#endif




  rc = sqlite3OsOpen(pVfs, zFilename, pFile, flags, 0);
    assert( rc!=SQLITE_OK || pFile->pMethods );


  sqlite3_free(zFree);
  return rc;
}

/*
** Create a new page cache and put a pointer to the page cache in *ppPager.
** The file to be cached need not exist.  The file is not locked until

    if( strcmp(zFilename,":memory:")==0 ){
      memDb = 1;
      zPathname[0] = 0;
    }else
#endif
    {
      rc = sqlite3OsFullPathname(pVfs, zFilename, zPathname);
    }
  }else{
    rc = sqlite3OsGetTempName(pVfs, zPathname);
  }
      if( rc!=SQLITE_OK ){
        sqlite3_free(zPathname);
        return rc;
      }




  nPathname = strlen(zPathname);

  /* Allocate memory for the pager structure */
  pPager = sqlite3MallocZero(
    sizeof(*pPager) +           /* Pager structure */
    journalFileSize +           /* The journal file structure */ 
    pVfs->szOsFile * 2 +        /* The db and stmt journal files */ 

  pPager->zJournal = &pPager->zDirectory[nPathname+1];
  pPager->pVfs = pVfs;
  memcpy(pPager->zFilename, zPathname, nPathname+1);
  sqlite3_free(zPathname);

  /* Open the pager file.
  */
  if( zFilename && zFilename[0] && !memDb ){
    if( nPathname>(pVfs->mxPathname - sizeof("-journal")) ){
      rc = SQLITE_CANTOPEN;
    }else{
/***  FIXME:  Might need to be SQLITE_OPEN_TEMP_DB.  Need to pass in
**** a flag from higher up.
****/
      int oflag = 

# 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 regression tests for SQLite library.  The
# focus of this script is page cache subsystem.
#
# $Id: pager.test,v 1.30 2007/08/24 16:29:24 drh Exp $


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

if {[info commands pager_open]!=""} {
db close

do_test pager-4.6.1 {
  pager_close [pager_open ptf2.db -15]
} {}

# Test truncate on an in-memory database is Ok.
ifcapable memorydb {
  do_test pager-4.6.2 {

    set ::p2 [pager_open :memory: 10]
    pager_truncate $::p2 5
  } {}
  do_test pager-4.6.3 {
    for {set i 1} {$i<5} {incr i} {
      set p [page_get $::p2 $i]
      page_write $p "Page $i"