** 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 1.77 2003/02/15 23:09:17 drh Exp $
*/
#include "os.h"         /* Must be first to enable large file support */
#include "sqliteInt.h"
#include "pager.h"
#include <assert.h>
#include <string.h>

................................................................................
static int pager_playback_one_page(Pager *pPager, OsFile *jfd, int format){
  int rc;
  PgHdr *pPg;              /* An existing page in the cache */
  PageRecord pgRec;
  u32 cksum;

  rc = read32bits(format, jfd, &pgRec.pgno);
  if( rc!=SQLITE_OK ) return SQLITE_DONE;
  rc = sqliteOsRead(jfd, &pgRec.aData, sizeof(pgRec.aData));
  if( rc!=SQLITE_OK ) return SQLITE_DONE;

  /* Sanity checking on the page.  This is more important that I originally
  ** thought.  If a power failure occurs while the journal is being written,
  ** it could cause invalid data to be written into the journal.  We need to
  ** detect this invalid data (with high probability) and ignore it.
  */
  if( pgRec.pgno==0 ){
................................................................................
    return SQLITE_DONE;
  }
  if( pgRec.pgno>pPager->dbSize ){
    return SQLITE_OK;
  }
  if( format>=JOURNAL_FORMAT_3 ){
    rc = read32bits(format, jfd, &cksum);
    if( rc ) return SQLITE_DONE;
    if( pager_cksum(pPager, pgRec.pgno, pgRec.aData)!=cksum ){
      return SQLITE_DONE;
    }
  }

  /* Playback the page.  Update the in-memory copy of the page
  ** at the same time, if there is one.
  */
  pPg = pager_lookup(pPager, pgRec.pgno);
  if( pPg==0 || pPg->needSync==0 ){
    TRACE2("PLAYBACK %d\n", pgRec.pgno);
    sqliteOsSeek(&pPager->fd, (pgRec.pgno-1)*(off_t)SQLITE_PAGE_SIZE);
    rc = sqliteOsWrite(&pPager->fd, pgRec.aData, SQLITE_PAGE_SIZE);
  }
  if( pPg ){
    if( pPg->nRef==0 ||
        memcmp(PGHDR_TO_DATA(pPg), pgRec.aData, SQLITE_PAGE_SIZE)==0
    ){
      /* Do not update the data on this page if the page is in use
      ** and the page has never been modified.  This avoids resetting
      ** the "extra" data.  That in turn avoids invalidating BTree cursors
................................................................................
** journal file (as determined by looking at the magic number
** at the beginning) then this routine returns SQLITE_PROTOCOL.
** If any other errors occur during playback, the database will
** likely be corrupted, so the PAGER_ERR_CORRUPT bit is set in
** pPager->errMask and SQLITE_CORRUPT is returned.  If it all
** works, then this routine returns SQLITE_OK.
*/
static int pager_playback(Pager *pPager){
  off_t szJ;               /* Size of the journal file in bytes */
  int nRec;                /* Number of Records in the journal */
  int i;                   /* Loop counter */
  Pgno mxPg = 0;           /* Size of the original file in pages */
  int format;              /* Format of the journal file. */
  unsigned char aMagic[sizeof(aJournalMagic1)];
  int rc;
................................................................................
    goto end_playback;
  }
  if( format>=JOURNAL_FORMAT_3 ){
    rc = read32bits(format, &pPager->jfd, &nRec);
    if( rc ) goto end_playback;
    rc = read32bits(format, &pPager->jfd, &pPager->cksumInit);
    if( rc ) goto end_playback;
    if( nRec==0xffffffff ){
      nRec = (szJ - JOURNAL_HDR_SZ(3))/JOURNAL_PG_SZ(3);
    }
  }else{
    nRec = (szJ - JOURNAL_HDR_SZ(2))/JOURNAL_PG_SZ(2);
    assert( nRec*JOURNAL_PG_SZ(2)+JOURNAL_HDR_SZ(2)==szJ );
  }
  rc = read32bits(format, &pPager->jfd, &mxPg);
................................................................................
        off_t szJ;
        if( pPager->fullSync ){
          TRACE1("SYNC\n");
          rc = sqliteOsSync(&pPager->jfd);
          if( rc!=0 ) return rc;
        }
        sqliteOsSeek(&pPager->jfd, sizeof(aJournalMagic1));
        write32bits(&pPager->jfd, pPager->nRec);

        szJ = JOURNAL_HDR_SZ(journal_format) +
                 pPager->nRec*JOURNAL_PG_SZ(journal_format);
        sqliteOsSeek(&pPager->jfd, szJ);
      }
      TRACE1("SYNC\n");
      rc = sqliteOsSync(&pPager->jfd);
      if( rc!=0 ) return rc;
................................................................................
       }
       pPager->journalOpen = 1;
       pPager->journalStarted = 0;

       /* Playback and delete the journal.  Drop the database write
       ** lock and reacquire the read lock.
       */
       rc = pager_playback(pPager);
       if( rc!=SQLITE_OK ){
         return rc;
       }
    }
    pPg = 0;
  }else{
    /* Search for page in cache */
................................................................................
        szPg = SQLITE_PAGE_SIZE+4;
      }
      store32bits(pPg->pgno, pPg, -4);
      rc = sqliteOsWrite(&pPager->jfd, &((char*)pData)[-4], szPg);
      if( journal_format>=JOURNAL_FORMAT_3 ){
        *(u32*)PGHDR_TO_EXTRA(pPg) = saved;
      }
      pPager->nRec++;
      if( rc!=SQLITE_OK ){
        sqlitepager_rollback(pPager);
        pPager->errMask |= PAGER_ERR_FULL;
        return rc;
      }

      assert( pPager->aInJournal!=0 );
      pPager->aInJournal[pPg->pgno/8] |= 1<<(pPg->pgno&7);
      pPg->needSync = !pPager->noSync;
      pPg->inJournal = 1;
      if( pPager->ckptInUse ){
        pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
        page_add_to_ckpt_list(pPg);
................................................................................
    rc = pager_unwritelock(pPager);
    pPager->dbSize = -1;
    return rc;
  }

  if( pPager->errMask!=0 && pPager->errMask!=PAGER_ERR_FULL ){
    if( pPager->state>=SQLITE_WRITELOCK ){
      pager_playback(pPager);
    }
    return pager_errcode(pPager);
  }
  if( pPager->state!=SQLITE_WRITELOCK ){
    return SQLITE_OK;
  }
  rc = pager_playback(pPager);
  if( rc!=SQLITE_OK ){
    rc = SQLITE_CORRUPT;
    pPager->errMask |= PAGER_ERR_CORRUPT;
  }
  pPager->dbSize = -1;
  return 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 1.78 2003/02/16 19:13:37 drh Exp $
*/
#include "os.h"         /* Must be first to enable large file support */
#include "sqliteInt.h"
#include "pager.h"
#include <assert.h>
#include <string.h>

................................................................................
static int pager_playback_one_page(Pager *pPager, OsFile *jfd, int format){
  int rc;
  PgHdr *pPg;              /* An existing page in the cache */
  PageRecord pgRec;
  u32 cksum;

  rc = read32bits(format, jfd, &pgRec.pgno);
  if( rc!=SQLITE_OK ) return rc;
  rc = sqliteOsRead(jfd, &pgRec.aData, sizeof(pgRec.aData));
  if( rc!=SQLITE_OK ) return rc;

  /* Sanity checking on the page.  This is more important that I originally
  ** thought.  If a power failure occurs while the journal is being written,
  ** it could cause invalid data to be written into the journal.  We need to
  ** detect this invalid data (with high probability) and ignore it.
  */
  if( pgRec.pgno==0 ){
................................................................................
    return SQLITE_DONE;
  }
  if( pgRec.pgno>pPager->dbSize ){
    return SQLITE_OK;
  }
  if( format>=JOURNAL_FORMAT_3 ){
    rc = read32bits(format, jfd, &cksum);
    if( rc ) return rc;
    if( pager_cksum(pPager, pgRec.pgno, pgRec.aData)!=cksum ){
      return SQLITE_DONE;
    }
  }

  /* Playback the page.  Update the in-memory copy of the page
  ** at the same time, if there is one.
  */
  pPg = pager_lookup(pPager, pgRec.pgno);

  TRACE2("PLAYBACK %d\n", pgRec.pgno);
  sqliteOsSeek(&pPager->fd, (pgRec.pgno-1)*(off_t)SQLITE_PAGE_SIZE);
  rc = sqliteOsWrite(&pPager->fd, pgRec.aData, SQLITE_PAGE_SIZE);

  if( pPg ){
    if( pPg->nRef==0 ||
        memcmp(PGHDR_TO_DATA(pPg), pgRec.aData, SQLITE_PAGE_SIZE)==0
    ){
      /* Do not update the data on this page if the page is in use
      ** and the page has never been modified.  This avoids resetting
      ** the "extra" data.  That in turn avoids invalidating BTree cursors
................................................................................
** journal file (as determined by looking at the magic number
** at the beginning) then this routine returns SQLITE_PROTOCOL.
** If any other errors occur during playback, the database will
** likely be corrupted, so the PAGER_ERR_CORRUPT bit is set in
** pPager->errMask and SQLITE_CORRUPT is returned.  If it all
** works, then this routine returns SQLITE_OK.
*/
static int pager_playback(Pager *pPager, int useJournalSize){
  off_t szJ;               /* Size of the journal file in bytes */
  int nRec;                /* Number of Records in the journal */
  int i;                   /* Loop counter */
  Pgno mxPg = 0;           /* Size of the original file in pages */
  int format;              /* Format of the journal file. */
  unsigned char aMagic[sizeof(aJournalMagic1)];
  int rc;
................................................................................
    goto end_playback;
  }
  if( format>=JOURNAL_FORMAT_3 ){
    rc = read32bits(format, &pPager->jfd, &nRec);
    if( rc ) goto end_playback;
    rc = read32bits(format, &pPager->jfd, &pPager->cksumInit);
    if( rc ) goto end_playback;
    if( nRec==0xffffffff || useJournalSize ){
      nRec = (szJ - JOURNAL_HDR_SZ(3))/JOURNAL_PG_SZ(3);
    }
  }else{
    nRec = (szJ - JOURNAL_HDR_SZ(2))/JOURNAL_PG_SZ(2);
    assert( nRec*JOURNAL_PG_SZ(2)+JOURNAL_HDR_SZ(2)==szJ );
  }
  rc = read32bits(format, &pPager->jfd, &mxPg);
................................................................................
        off_t szJ;
        if( pPager->fullSync ){
          TRACE1("SYNC\n");
          rc = sqliteOsSync(&pPager->jfd);
          if( rc!=0 ) return rc;
        }
        sqliteOsSeek(&pPager->jfd, sizeof(aJournalMagic1));
        rc = write32bits(&pPager->jfd, pPager->nRec);
        if( rc ) return rc;
        szJ = JOURNAL_HDR_SZ(journal_format) +
                 pPager->nRec*JOURNAL_PG_SZ(journal_format);
        sqliteOsSeek(&pPager->jfd, szJ);
      }
      TRACE1("SYNC\n");
      rc = sqliteOsSync(&pPager->jfd);
      if( rc!=0 ) return rc;
................................................................................
       }
       pPager->journalOpen = 1;
       pPager->journalStarted = 0;

       /* Playback and delete the journal.  Drop the database write
       ** lock and reacquire the read lock.
       */
       rc = pager_playback(pPager, 0);
       if( rc!=SQLITE_OK ){
         return rc;
       }
    }
    pPg = 0;
  }else{
    /* Search for page in cache */
................................................................................
        szPg = SQLITE_PAGE_SIZE+4;
      }
      store32bits(pPg->pgno, pPg, -4);
      rc = sqliteOsWrite(&pPager->jfd, &((char*)pData)[-4], szPg);
      if( journal_format>=JOURNAL_FORMAT_3 ){
        *(u32*)PGHDR_TO_EXTRA(pPg) = saved;
      }

      if( rc!=SQLITE_OK ){
        sqlitepager_rollback(pPager);
        pPager->errMask |= PAGER_ERR_FULL;
        return rc;
      }
      pPager->nRec++;
      assert( pPager->aInJournal!=0 );
      pPager->aInJournal[pPg->pgno/8] |= 1<<(pPg->pgno&7);
      pPg->needSync = !pPager->noSync;
      pPg->inJournal = 1;
      if( pPager->ckptInUse ){
        pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
        page_add_to_ckpt_list(pPg);
................................................................................
    rc = pager_unwritelock(pPager);
    pPager->dbSize = -1;
    return rc;
  }

  if( pPager->errMask!=0 && pPager->errMask!=PAGER_ERR_FULL ){
    if( pPager->state>=SQLITE_WRITELOCK ){
      pager_playback(pPager, 1);
    }
    return pager_errcode(pPager);
  }
  if( pPager->state!=SQLITE_WRITELOCK ){
    return SQLITE_OK;
  }
  rc = pager_playback(pPager, 1);
  if( rc!=SQLITE_OK ){
    rc = SQLITE_CORRUPT;
    pPager->errMask |= PAGER_ERR_CORRUPT;
  }
  pPager->dbSize = -1;
  return rc;
}

**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing the printf() interface to SQLite.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test1.c,v 1.20 2003/01/29 22:58:26 drh Exp $
*/
#include "sqliteInt.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>

/*
................................................................................
    sprintf(zBuf, "(%d) ", rc);
    Tcl_AppendResult(interp, zBuf, zErrMsg, 0);
    sqlite_freemem(zErrMsg);
    return TCL_ERROR;
  }
  return TCL_OK;
}























/*
** Register commands with the TCL interpreter.
*/
int Sqlitetest1_Init(Tcl_Interp *interp){
  extern int sqlite_search_count;
  static struct {
................................................................................
#ifdef MEMORY_DEBUG
     { "sqlite_malloc_fail",             (Tcl_CmdProc*)sqlite_malloc_fail    },
     { "sqlite_malloc_stat",             (Tcl_CmdProc*)sqlite_malloc_stat    },
#endif
     { "sqlite_compile",                 (Tcl_CmdProc*)test_compile          },
     { "sqlite_step",                    (Tcl_CmdProc*)test_step             },
     { "sqlite_finalize",                (Tcl_CmdProc*)test_finalize         },

  };
  int i;

  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
    Tcl_CreateCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
  }
  Tcl_LinkVar(interp, "sqlite_search_count", 
      (char*)&sqlite_search_count, TCL_LINK_INT);
  return TCL_OK;
}

**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing the printf() interface to SQLite.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test1.c,v 1.21 2003/02/16 19:13:37 drh Exp $
*/
#include "sqliteInt.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>

/*
................................................................................
    sprintf(zBuf, "(%d) ", rc);
    Tcl_AppendResult(interp, zBuf, zErrMsg, 0);
    sqlite_freemem(zErrMsg);
    return TCL_ERROR;
  }
  return TCL_OK;
}

/*
** Usage:    breakpoint
**
** This routine exists for one purpose - to provide a place to put a
** breakpoint with GDB that can be triggered using TCL code.  The use
** for this is when a particular test fails on (say) the 1485th iteration.
** In the TCL test script, we can add code like this:
**
**     if {$i==1485} breakpoint
**
** Then run testfixture in the debugger and wait for the breakpoint to
** fire.  Then additional breakpoints can be set to trace down the bug.
*/
static int test_breakpoint(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  char **argv            /* Text of each argument */
){
  return TCL_OK;         /* Do nothing */
}

/*
** Register commands with the TCL interpreter.
*/
int Sqlitetest1_Init(Tcl_Interp *interp){
  extern int sqlite_search_count;
  static struct {
................................................................................
#ifdef MEMORY_DEBUG
     { "sqlite_malloc_fail",             (Tcl_CmdProc*)sqlite_malloc_fail    },
     { "sqlite_malloc_stat",             (Tcl_CmdProc*)sqlite_malloc_stat    },
#endif
     { "sqlite_compile",                 (Tcl_CmdProc*)test_compile          },
     { "sqlite_step",                    (Tcl_CmdProc*)test_step             },
     { "sqlite_finalize",                (Tcl_CmdProc*)test_finalize         },
     { "breakpoint",                     (Tcl_CmdProc*)test_breakpoint       },
  };
  int i;

  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
    Tcl_CreateCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
  }
  Tcl_LinkVar(interp, "sqlite_search_count", 
      (char*)&sqlite_search_count, TCL_LINK_INT);
  return TCL_OK;
}

#    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 1.12 2003/01/11 14:19:52 drh Exp $


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

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


# Basic sanity check.  Open and close a pager.
#
do_test pager-1.0 {
  catch {file delete -force ptf1.db}
  catch {file delete -force ptf1.db-journal}
  set v [catch {
................................................................................
do_test pager-2.28 {
  set v [catch {
    pager_rollback $::p1
  } msg]
  lappend v $msg
} {0 {}}
do_test pager-2.29 {


  page_read $::g1
} {Page-One}
do_test pager-2.99 {
  pager_close $::p1
} {}

do_test pager-3.1 {

#    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 1.13 2003/02/16 19:13:37 drh Exp $


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

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

# Basic sanity check.  Open and close a pager.
#
do_test pager-1.0 {
  catch {file delete -force ptf1.db}
  catch {file delete -force ptf1.db-journal}
  set v [catch {
................................................................................
do_test pager-2.28 {
  set v [catch {
    pager_rollback $::p1
  } msg]
  lappend v $msg
} {0 {}}
do_test pager-2.29 {
  page_unref $::g1
  set ::g1 [page_get $::p1 1]
  page_read $::g1
} {Page-One}
do_test pager-2.99 {
  pager_close $::p1
} {}

do_test pager-3.1 {