**    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 1.30 2008/09/18 17:34:44 danielk1977 Exp $
*/
#include "sqliteInt.h"

/*
** A complete page cache is an instance of this structure.
**
** A cache may only be deleted by its owner and while holding the
................................................................................
}

/*
** Allocate a page cache line.  Look in the page cache memory pool first
** and use an element from it first if available.  If nothing is available
** in the page cache memory pool, go to the general purpose memory allocator.
*/
void *pcacheMalloc(int sz, PCache *pCache){
  assert( sqlite3_mutex_held(pcache_g.mutex) );
  if( sz<=pcache_g.szSlot && pcache_g.pFree ){
    PgFreeslot *p = pcache_g.pFree;
    pcache_g.pFree = p->pNext;
    sqlite3StatusSet(SQLITE_STATUS_PAGECACHE_SIZE, sz);
    sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_USED, 1);
    return (void*)p;
................................................................................
  pcacheExitMutex();
  return p;
}

/*
** Release a pager memory allocation
*/
void pcacheFree(void *p){
  assert( sqlite3_mutex_held(pcache_g.mutex) );
  if( p==0 ) return;
  if( p>=pcache_g.pStart && p<pcache_g.pEnd ){
    PgFreeslot *pSlot;
    sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_USED, -1);
    pSlot = (PgFreeslot*)p;
    pSlot->pNext = pcache_g.pFree;
................................................................................
  pcacheEnterMutex();
  pcacheRemoveFromList(&pCache->pClean, p);
  pcacheAddToList(&pCache->pDirty, p);
  pcacheExitMutex();
  p->flags |= PGHDR_DIRTY;
}

void pcacheMakeClean(PgHdr *p){
  PCache *pCache = p->pCache;
  assert( p->apSave[0]==0 && p->apSave[1]==0 );
  assert( p->flags & PGHDR_DIRTY );
  pcacheRemoveFromList(&pCache->pDirty, p);
  pcacheAddToList(&pCache->pClean, p);
  p->flags &= ~PGHDR_DIRTY;
  if( p->nRef==0 ){
................................................................................
  pcacheAddToHash(p);
  pcacheExitMutex();
}

/*
** Remove all content from a page cache
*/
void pcacheClear(PCache *pCache){
  PgHdr *p, *pNext;
  assert( sqlite3_mutex_held(pcache_g.mutex) );
  for(p=pCache->pClean; p; p=pNext){
    pNext = p->pNext;
    pcacheRemoveFromLruList(p);
    pcachePageFree(p);
  }

**    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 1.31 2008/09/21 15:14:04 drh Exp $
*/
#include "sqliteInt.h"

/*
** A complete page cache is an instance of this structure.
**
** A cache may only be deleted by its owner and while holding the
................................................................................
}

/*
** Allocate a page cache line.  Look in the page cache memory pool first
** and use an element from it first if available.  If nothing is available
** in the page cache memory pool, go to the general purpose memory allocator.
*/
static void *pcacheMalloc(int sz, PCache *pCache){
  assert( sqlite3_mutex_held(pcache_g.mutex) );
  if( sz<=pcache_g.szSlot && pcache_g.pFree ){
    PgFreeslot *p = pcache_g.pFree;
    pcache_g.pFree = p->pNext;
    sqlite3StatusSet(SQLITE_STATUS_PAGECACHE_SIZE, sz);
    sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_USED, 1);
    return (void*)p;
................................................................................
  pcacheExitMutex();
  return p;
}

/*
** Release a pager memory allocation
*/
static void pcacheFree(void *p){
  assert( sqlite3_mutex_held(pcache_g.mutex) );
  if( p==0 ) return;
  if( p>=pcache_g.pStart && p<pcache_g.pEnd ){
    PgFreeslot *pSlot;
    sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_USED, -1);
    pSlot = (PgFreeslot*)p;
    pSlot->pNext = pcache_g.pFree;
................................................................................
  pcacheEnterMutex();
  pcacheRemoveFromList(&pCache->pClean, p);
  pcacheAddToList(&pCache->pDirty, p);
  pcacheExitMutex();
  p->flags |= PGHDR_DIRTY;
}

static void pcacheMakeClean(PgHdr *p){
  PCache *pCache = p->pCache;
  assert( p->apSave[0]==0 && p->apSave[1]==0 );
  assert( p->flags & PGHDR_DIRTY );
  pcacheRemoveFromList(&pCache->pDirty, p);
  pcacheAddToList(&pCache->pClean, p);
  p->flags &= ~PGHDR_DIRTY;
  if( p->nRef==0 ){
................................................................................
  pcacheAddToHash(p);
  pcacheExitMutex();
}

/*
** Remove all content from a page cache
*/
static void pcacheClear(PCache *pCache){
  PgHdr *p, *pNext;
  assert( sqlite3_mutex_held(pcache_g.mutex) );
  for(p=pCache->pClean; p; p=pNext){
    pNext = p->pNext;
    pcacheRemoveFromLruList(p);
    pcachePageFree(p);
  }