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 1.284 2007/03/01 00:29:14 drh Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include "os.h"
#include "pager.h"
#include <assert.h>
#include <string.h>

  ** sqlite_dont_rollback() optimization for the rest of this transaction.
  ** It is necessary to do this because the page marked alwaysRollback
  ** might be reloaded at a later time but at that point we won't remember
  ** that is was marked alwaysRollback.  This means that all pages must
  ** be marked as alwaysRollback from here on out.
  */
  if( pPg->alwaysRollback ){
    IOTRACE(("ALWAYS_ROLLBACK %p\n", pPager))
    pPager->alwaysRollback = 1;
  }

  /* Unlink the old page from the free list and the hash table
  */
  unlinkPage(pPg);
  TEST_INCR(pPager->nOvfl);

/*
** 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.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.540 2007/03/01 00:29:14 drh Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_

/*
** Extra interface definitions for those who need them
*/

/*
** If the SQLITE_ENABLE IOTRACE exists then the global variable
** sqlite3_io_trace is a pointer to a printf-like routine used to
** print I/O tracing messages. 
*/
#ifdef SQLITE_ENABLE_IOTRACE
# define IOTRACE(A)  if( sqlite3_io_trace ){ sqlite3_io_trace A; }
  void sqlite3VdbeIOTrace(Vdbe*);
#else
# define IOTRACE(A)
# define sqlite3VdbeIOTrace(X)
#endif
extern void (*sqlite3_io_trace)(const char*,...);

#endif

**
** Various scripts scan this source file in order to generate HTML
** documentation, headers files, or other derived files.  The formatting
** of the code in this file is, therefore, important.  See other comments
** in this file for details.  If in doubt, do not deviate from existing
** commenting and indentation practices when changing or adding code.
**
** $Id: vdbe.c,v 1.590 2007/03/01 00:29:14 drh Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>
#include "vdbeInt.h"

/*

  if( p->popStack ){
    popStack(&pTos, p->popStack);
    p->popStack = 0;
  }
  p->resOnStack = 0;
  db->busyHandler.nBusy = 0;
  CHECK_FOR_INTERRUPT;
  sqlite3VdbeIOTraceSql(p);
#ifdef SQLITE_DEBUG
  if( (p->db->flags & SQLITE_VdbeListing)!=0
    || sqlite3OsFileExists("vdbe_explain")
  ){
    int i;
    printf("VDBE Program Listing:\n");
    sqlite3VdbePrintSql(p);

  if( pOp->opcode==OP_Noop && pOp->p3!=0 ){
    const char *z = pOp->p3;
    while( isspace(*(u8*)z) ) z++;
    printf("SQL: [%s]\n", z);
  }
#endif
}

#if !defined(SQLITE_OMIT_TRACE) && defined(SQLITE_ENABLE_IOTRACE)
/*
** Print an IOTRACE message showing SQL content.
*/
void sqlite3VdbeIOTraceSql(Vdbe *p){
  int nOp = p->nOp;
  VdbeOp *pOp;
  if( sqlite3_io_trace==0 ) return;
  if( nOp<1 ) return;
  pOp = &p->aOp[nOp-1];
  if( pOp->opcode==OP_Noop && pOp->p3!=0 ){
    char *z = sqlite3StrDup(pOp->p3);
    int i, j;
    for(i=0; isspace(z[i]); i++){}
    for(j=0; z[i]; i++){
      if( isspace(z[i]) ){
        if( z[i-1]!=' ' ){
          z[j++] = ' ';
        }
      }else{
        z[j++] = z[i];
      }
    }
    z[j] = 0;
    sqlite3_io_trace("SQL %s\n", z);
    sqliteFree(z);
  }
}
#endif /* !SQLITE_OMIT_TRACE && SQLITE_ENABLE_IOTRACE */


/*
** Prepare a virtual machine for execution.  This involves things such
** as allocating stack space and initializing the program counter.
** After the VDBE has be prepped, it can be executed by one or more
** calls to sqlite3VdbeExec().  
**