SQLite

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** Memory allocation functions used throughout sqlite.
**
** $Id: malloc.c,v 1.35 2008/08/20 14:49:24 danielk1977 Exp $
** $Id: malloc.c,v 1.36 2008/08/21 12:19:44 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include <stdarg.h>
#include <ctype.h>

/*
** This routine runs when the memory allocator sees that the

/*
** Attempt to release up to n bytes of non-essential memory currently
** held by SQLite. An example of non-essential memory is memory used to
** cache database pages that are not currently in use.
*/
int sqlite3_release_memory(int n){
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
  int nRet = 0;
#if 0
  int nRet = sqlite3VdbeReleaseMemory(n);
  nRet += sqlite3PagerReleaseMemory(n-nRet);
  nRet += sqlite3VdbeReleaseMemory(n);
#endif
  nRet += sqlite3PcacheReleaseMemory(n-nRet);
  return nRet;
#else
  return SQLITE_OK;
#endif
}

/*

** 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 1.472 2008/08/21 04:35:19 danielk1977 Exp $
** @(#) $Id: pager.c,v 1.473 2008/08/21 12:19:44 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"

/*
** Macros for troubleshooting.  Normally turned off
*/

** by the pcache layer.
*/
static int pagerStress(void *p){
  Pager *pPager = (Pager *)p;
  PgHdr *pPg = sqlite3PcacheDirtyPage(pPager->pPCache);
  int rc = SQLITE_OK;

  if( pPg && pPager->errCode==SQLITE_OK ){
  if( pPg ){
    assert( pPg->flags&PGHDR_DIRTY );
    if( pPager->errCode==SQLITE_OK ){
    if( pPg->flags&PGHDR_NEED_SYNC ){
      rc = syncJournal(pPager);
      if( rc==SQLITE_OK && pPager->fullSync 
       && !(sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND)
      ){
        pPager->nRec = 0;
        rc = writeJournalHdr(pPager);
      }
    }
    if( rc==SQLITE_OK ){
      rc = pager_write_pagelist(pPg);
    }
    if( rc!=SQLITE_OK ){
      pager_error(pPager, rc);
      if( pPg->flags&PGHDR_NEED_SYNC ){
        rc = syncJournal(pPager);
        if( rc==SQLITE_OK && pPager->fullSync && 
          !(sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND)
        ){
          pPager->nRec = 0;
          rc = writeJournalHdr(pPager);
        }
      }
      if( rc==SQLITE_OK ){
        rc = pager_write_pagelist(pPg);
      }
      if( rc!=SQLITE_OK ){
        pager_error(pPager, rc);
      }
    }else{
      sqlite3PcacheMakeClean(pPg);
    }
  }
  return rc;
}


/*

      }
    }
  }

  return rc;
}

#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
/*
** This function is called to free superfluous dynamically allocated memory
** held by the pager system. Memory in use by any SQLite pager allocated
** by the current thread may be sqlite3_free()ed.
**
** nReq is the number of bytes of memory required. Once this much has
** been released, the function returns. The return value is the total number 
** of bytes of memory released.
*/
int sqlite3PagerReleaseMemory(int nReq){
  return 0;
}
#endif /* SQLITE_ENABLE_MEMORY_MANAGEMENT */

/*
** Read the content of page pPg out of the database file.
*/
static int readDbPage(Pager *pPager, PgHdr *pPg, Pgno pgno){
  int rc;
  i64 offset;
  assert( MEMDB==0 );

**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite page cache
** subsystem.  The page cache subsystem reads and writes a file a page
** at a time and provides a journal for rollback.
**
** @(#) $Id: pager.h,v 1.78 2008/08/20 14:49:25 danielk1977 Exp $
** @(#) $Id: pager.h,v 1.79 2008/08/21 12:19:44 danielk1977 Exp $
*/

#ifndef _PAGER_H_
#define _PAGER_H_

/*
** If defined as non-zero, auto-vacuum is enabled by default. Otherwise

int sqlite3PagerLockingMode(Pager *, int);
int sqlite3PagerJournalMode(Pager *, int);
i64 sqlite3PagerJournalSizeLimit(Pager *, i64);
void *sqlite3PagerTempSpace(Pager*);
int sqlite3PagerSync(Pager *pPager);
void sqlite3PagerAlwaysRollback(Pager *pPager);

#if defined(SQLITE_ENABLE_MEMORY_MANAGEMENT) && !defined(SQLITE_OMIT_DISKIO)
  int sqlite3PagerReleaseMemory(int);
#endif

#ifdef SQLITE_HAS_CODEC
  void sqlite3PagerSetCodec(Pager*,void*(*)(void*,void*,Pgno,int),void*);
#endif

#if !defined(NDEBUG) || defined(SQLITE_TEST)
  Pgno sqlite3PagerPagenumber(DbPage*);
  int sqlite3PagerIswriteable(DbPage*);

/*
** 2008 August 05
**
** 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 that page cache.
**
** @(#) $Id: pcache.c,v 1.3 2008/08/21 04:41:02 danielk1977 Exp $
** @(#) $Id: pcache.c,v 1.4 2008/08/21 12:19:44 danielk1977 Exp $
*/
#include "sqliteInt.h"

/*
** A complete page cache is an instance of this structure.
*/
struct PCache {

  if( sz<=pcache.szSlot && pcache.pFree ){
    PgFreeslot *p = pcache.pFree;
    pcache.pFree = p->pNext;
    sqlite3StatusSet(SQLITE_STATUS_PAGECACHE_SIZE, sz);
    sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_USED, 1);
    return (void*)p;
  }else{
    void *p;
    pcacheExitGlobal();
    void *p = sqlite3Malloc(sz);
    p = sqlite3Malloc(sz);
    pcacheEnterGlobal();
    if( p ){
      sz = sqlite3MallocSize(p);
      sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_OVERFLOW, sz);
    }
    return p;
  }
}

  if( p->pCache->bPurgeable ){
    pcache.nPurgeable--;
  }
  pcacheFree(p->apSave[0]);
  pcacheFree(p->apSave[1]);
  pcacheFree(p);
}

/*
** Return the number of bytes that will be returned to the heap when
** the argument is passed to pcachePageFree().
*/
static int pcachePageSize(PgHdr *p){
  assert( sqlite3_mutex_held(pcache.mutex_lru) );
  assert( !pcache.pStart );
  assert( p->apSave[0]==0 );
  assert( p->apSave[1]==0 );
  assert( p && p->pCache );
  return sqlite3MallocSize(p);
}

static PgHdr *pcacheRecycle(PCache *pCache){
  PCache *pCsr;
  PgHdr *p = 0;

  assert( pcache.isInit );
  assert( sqlite3_mutex_held(pcache.mutex_lru) );

  if( !pcache.pLruTail && SQLITE_OK==sqlite3_mutex_try(pcache.mutex_mem2) ){

    /* Invoke xStress() callbacks until the LRU list contains at least one
    ** page that can be reused or until the xStress() callback of all
    ** caches has been invoked.
    */
    for(pCsr=pcache.pAll; pCsr&&!pcache.pLruTail; pCsr=pCsr->pNextAll){
      assert( pCsr->iInUseMM==0 );
      pCsr->iInUseMM = 1;
      if( pCsr->xStress && (pCsr->iInUseDB==0 || pCache==pCsr) ){
        pcacheExitGlobal();
        pCsr->xStress(pCsr->pStress);
        pcacheEnterGlobal();
      }
      pCsr->iInUseMM = 0;
    }

    sqlite3_mutex_leave(pcache.mutex_mem2);
  }

  p = pcache.pLruTail;

  if( p ){
    pcacheRemoveFromLruList(p);
    pcacheRemoveFromHash(p);
    pcacheRemoveFromList(&p->pCache->pClean, p);

    /* If the always-rollback flag is set on the page being recycled, set 
    ** the always-rollback flag on the corresponding pager.
    */
    if( p->flags&PGHDR_ALWAYS_ROLLBACK ){
      assert(p->pPager);
      sqlite3PagerAlwaysRollback(p->pPager);
    }
  }

  return p;
}

/*
** Obtain space for a page. Try to recycle an old page if the limit on the 
** number of pages has been reached. If the limit has not been reached or
** there are no pages eligible for recycling, allocate a new page.
**
** Return a pointer to the new page, or NULL if an OOM condition occurs.

  assert( sqlite3_mutex_notheld(pcache.mutex_lru) );

  pcacheEnterGlobal();

  if( (pcache.mxPage && pcache.nPage>=pcache.mxPage) 
   || (!pcache.mxPage && bPurg && pcache.nPurgeable>=pcache.mxPagePurgeable)
  ){
    PCache *pCsr;

    /* If the above test succeeds, then a page will be obtained by recycling
    ** an existing page.
    /* If the above test succeeds, then try to obtain a buffer by recycling
    ** an existing page. */
    */
    if( !pcache.pLruTail && SQLITE_OK==sqlite3_mutex_try(pcache.mutex_mem2) ){

      /* Invoke xStress() callbacks until the LRU list contains at least one
      ** page that can be reused or until the xStress() callback of all
      ** caches has been invoked.
      */
      for(pCsr=pcache.pAll; pCsr&&!pcache.pLruTail; pCsr=pCsr->pNextAll){
        assert( pCsr->iInUseMM==0 );
        pCsr->iInUseMM = 1;
        if( pCsr->xStress && (pCsr->iInUseDB==0 || pCache==pCsr) ){
          pcacheExitGlobal();
          pCsr->xStress(pCsr->pStress);
          pcacheEnterGlobal();
        }
        pCsr->iInUseMM = 0;
      }

      sqlite3_mutex_leave(pcache.mutex_mem2);
    }

    p = pcache.pLruTail;
    p = pcacheRecycle(pCache);
  }

  if( p ){
    pcacheRemoveFromLruList(p);
    pcacheRemoveFromHash(p);
    pcacheRemoveFromList(&p->pCache->pClean, p);

    /* If the always-rollback flag is set on the page being recycled, set 
    ** the always-rollback flag on the corresponding pager.
    */
    if( p->flags&PGHDR_ALWAYS_ROLLBACK ){
      assert(p->pPager);
      sqlite3PagerAlwaysRollback(p->pPager);
    }

    if( p->pCache->szPage!=szPage || p->pCache->szExtra!=szExtra ){
      pcachePageFree(p);
      p = 0;
  if( p && (p->pCache->szPage!=szPage || p->pCache->szExtra!=szExtra) ){
    pcachePageFree(p);
    p = 0;
    }
  }

  if( !p ){
    /* Allocate a new page object. */
    p = pcachePageAlloc(szPage, szExtra, bPurg);
  }

/*
** Unlock a pager-cache.
*/
void sqlite3PcacheUnlock(PCache *pCache){
  pCache->iInUseDB--;
  assert( pCache->iInUseDB>=0 );
}

#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
/*
** This function is called to free superfluous dynamically allocated memory
** held by the pager system. Memory in use by any SQLite pager allocated
** by the current thread may be sqlite3_free()ed.
**
** nReq is the number of bytes of memory required. Once this much has
** been released, the function returns. The return value is the total number 
** of bytes of memory released.
*/
int sqlite3PcacheReleaseMemory(int nReq){
  int nFree = 0;
  if( pcache.pStart==0 ){
    PgHdr *p;
    pcacheEnterGlobal();
    while( (nReq<0 || nFree<nReq) && (p=pcacheRecycle(0)) ){
      nFree += pcachePageSize(p);
      pcachePageFree(p);
    }
    pcacheExitGlobal();
  }
  return nFree;
}
#endif /* SQLITE_ENABLE_MEMORY_MANAGEMENT */

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite page cache
** subsystem. 
**
** @(#) $Id: pcache.h,v 1.1 2008/08/20 14:49:25 danielk1977 Exp $
** @(#) $Id: pcache.h,v 1.2 2008/08/21 12:19:44 danielk1977 Exp $
*/

#ifndef _PCACHE_H_

typedef struct PgHdr PgHdr;
typedef struct PCache PCache;

/* Lock and unlock a pager-cache object. The PcacheLock() function may 
** block if the lock is temporarily available. While a pager-cache is locked,
** the system guarantees that any configured xStress() callback will not
** be invoked by any thread other than the one holding the lock.
*/
void sqlite3PcacheLock(PCache *);
void sqlite3PcacheUnlock(PCache *);

int sqlite3PcacheReleaseMemory(int);

#endif /* _PCACHE_H_ */

**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file contains code use to implement APIs that are part of the
** VDBE.
**
** $Id: vdbeapi.c,v 1.139 2008/08/11 18:44:58 drh Exp $
** $Id: vdbeapi.c,v 1.140 2008/08/21 12:19:44 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "vdbeInt.h"

#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
#if 0 && defined(SQLITE_ENABLE_MEMORY_MANAGEMENT)
/*
** The following structure contains pointers to the end points of a
** doubly-linked list of all compiled SQL statements that may be holding
** buffers eligible for release when the sqlite3_release_memory() interface is
** invoked. Access to this list is protected by the SQLITE_MUTEX_STATIC_LRU2
** mutex.
**

# 2008 June 17
#
# 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.
#
#***********************************************************************
#
# $Id: mutex1.test,v 1.11 2008/08/20 14:49:25 danielk1977 Exp $
# $Id: mutex1.test,v 1.12 2008/08/21 12:19:44 danielk1977 Exp $

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

if {[info exists tester_do_binarylog]} {
  finish_test
  return

set enable_shared_cache [sqlite3_enable_shared_cache 1]
ifcapable threadsafe {
  foreach {mode mutexes} {
    singlethread {}
    multithread  {fast static_lru static_master static_mem static_mem2 static_prng }
    serialized   {fast recursive static_lru static_master static_mem static_mem2 static_prng }
  } {
    ifcapable memorymanage {
      if {$mode ne "singlethread"} {
        lappend mutexes static_lru static_lru2 static_mem2
      }
    }

    do_test mutex1.2.$mode.1 {
      catch {db close}
      sqlite3_shutdown
      sqlite3_config $mode
    } SQLITE_OK