Move bundled copy of sqlite one level deeper to better separate it...

third_party/sqlite/src/pcache1.c

Index: third_party/sqlite/src/pcache1.c
===================================================================
--- third_party/sqlite/src/pcache1.c	(revision 56608)
+++ third_party/sqlite/src/pcache1.c	(working copy)
@@ -1,789 +0,0 @@
-/*
-** 2008 November 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 the default page cache implementation (the
-** sqlite3_pcache interface). It also contains part of the implementation
-** of the SQLITE_CONFIG_PAGECACHE and sqlite3_release_memory() features.
-** If the default page cache implementation is overriden, then neither of
-** these two features are available.
-**
-** @(#) $Id: pcache1.c,v 1.19 2009/07/17 11:44:07 drh Exp $
-*/
-
-#include "sqliteInt.h"
-
-typedef struct PCache1 PCache1;
-typedef struct PgHdr1 PgHdr1;
-typedef struct PgFreeslot PgFreeslot;
-
-/* Pointers to structures of this type are cast and returned as 
-** opaque sqlite3_pcache* handles
-*/
-struct PCache1 {
-  /* Cache configuration parameters. Page size (szPage) and the purgeable
-  ** flag (bPurgeable) are set when the cache is created. nMax may be 
-  ** modified at any time by a call to the pcache1CacheSize() method.
-  ** The global mutex must be held when accessing nMax.
-  */
-  int szPage;                         /* Size of allocated pages in bytes */
-  int bPurgeable;                     /* True if cache is purgeable */
-  unsigned int nMin;                  /* Minimum number of pages reserved */
-  unsigned int nMax;                  /* Configured "cache_size" value */
-
-  /* Hash table of all pages. The following variables may only be accessed
-  ** when the accessor is holding the global mutex (see pcache1EnterMutex() 
-  ** and pcache1LeaveMutex()).
-  */
-  unsigned int nRecyclable;           /* Number of pages in the LRU list */
-  unsigned int nPage;                 /* Total number of pages in apHash */
-  unsigned int nHash;                 /* Number of slots in apHash[] */
-  PgHdr1 **apHash;                    /* Hash table for fast lookup by key */
-
-  unsigned int iMaxKey;               /* Largest key seen since xTruncate() */
-};
-
-/*
-** Each cache entry is represented by an instance of the following 
-** structure. A buffer of PgHdr1.pCache->szPage bytes is allocated 
-** directly before this structure in memory (see the PGHDR1_TO_PAGE() 
-** macro below).
-*/
-struct PgHdr1 {
-  unsigned int iKey;             /* Key value (page number) */
-  PgHdr1 *pNext;                 /* Next in hash table chain */
-  PCache1 *pCache;               /* Cache that currently owns this page */
-  PgHdr1 *pLruNext;              /* Next in LRU list of unpinned pages */
-  PgHdr1 *pLruPrev;              /* Previous in LRU list of unpinned pages */
-};
-
-/*
-** Free slots in the allocator used to divide up the buffer provided using
-** the SQLITE_CONFIG_PAGECACHE mechanism.
-*/
-struct PgFreeslot {
-  PgFreeslot *pNext;  /* Next free slot */
-};
-
-/*
-** Global data used by this cache.
-*/
-static SQLITE_WSD struct PCacheGlobal {
-  sqlite3_mutex *mutex;               /* static mutex MUTEX_STATIC_LRU */
-
-  int nMaxPage;                       /* Sum of nMaxPage for purgeable caches */
-  int nMinPage;                       /* Sum of nMinPage for purgeable caches */
-  int nCurrentPage;                   /* Number of purgeable pages allocated */
-  PgHdr1 *pLruHead, *pLruTail;        /* LRU list of unpinned pages */
-
-  /* Variables related to SQLITE_CONFIG_PAGECACHE settings. */
-  int szSlot;                         /* Size of each free slot */
-  void *pStart, *pEnd;                /* Bounds of pagecache malloc range */
-  PgFreeslot *pFree;                  /* Free page blocks */
-  int isInit;                         /* True if initialized */
-} pcache1_g;
-
-/*
-** All code in this file should access the global structure above via the
-** alias "pcache1". This ensures that the WSD emulation is used when
-** compiling for systems that do not support real WSD.
-*/
-#define pcache1 (GLOBAL(struct PCacheGlobal, pcache1_g))
-
-/*
-** When a PgHdr1 structure is allocated, the associated PCache1.szPage
-** bytes of data are located directly before it in memory (i.e. the total
-** size of the allocation is sizeof(PgHdr1)+PCache1.szPage byte). The
-** PGHDR1_TO_PAGE() macro takes a pointer to a PgHdr1 structure as
-** an argument and returns a pointer to the associated block of szPage
-** bytes. The PAGE_TO_PGHDR1() macro does the opposite: its argument is
-** a pointer to a block of szPage bytes of data and the return value is
-** a pointer to the associated PgHdr1 structure.
-**
-**   assert( PGHDR1_TO_PAGE(PAGE_TO_PGHDR1(pCache, X))==X );
-*/
-#define PGHDR1_TO_PAGE(p)    (void*)(((char*)p) - p->pCache->szPage)
-#define PAGE_TO_PGHDR1(c, p) (PgHdr1*)(((char*)p) + c->szPage)
-
-/*
-** Macros to enter and leave the global LRU mutex.
-*/
-#define pcache1EnterMutex() sqlite3_mutex_enter(pcache1.mutex)
-#define pcache1LeaveMutex() sqlite3_mutex_leave(pcache1.mutex)
-
-/******************************************************************************/
-/******** Page Allocation/SQLITE_CONFIG_PCACHE Related Functions **************/
-
-/*
-** This function is called during initialization if a static buffer is 
-** supplied to use for the page-cache by passing the SQLITE_CONFIG_PAGECACHE
-** verb to sqlite3_config(). Parameter pBuf points to an allocation large
-** enough to contain 'n' buffers of 'sz' bytes each.
-*/
-void sqlite3PCacheBufferSetup(void *pBuf, int sz, int n){
-  if( pcache1.isInit ){
-    PgFreeslot *p;
-    sz = ROUNDDOWN8(sz);
-    pcache1.szSlot = sz;
-    pcache1.pStart = pBuf;
-    pcache1.pFree = 0;
-    while( n-- ){
-      p = (PgFreeslot*)pBuf;
-      p->pNext = pcache1.pFree;
-      pcache1.pFree = p;
-      pBuf = (void*)&((char*)pBuf)[sz];
-    }
-    pcache1.pEnd = pBuf;
-  }
-}
-
-/*
-** Malloc function used within this file to allocate space from the buffer
-** configured using sqlite3_config(SQLITE_CONFIG_PAGECACHE) option. If no 
-** such buffer exists or there is no space left in it, this function falls 
-** back to sqlite3Malloc().
-*/
-static void *pcache1Alloc(int nByte){
-  void *p;
-  assert( sqlite3_mutex_held(pcache1.mutex) );
-  if( nByte<=pcache1.szSlot && pcache1.pFree ){
-    assert( pcache1.isInit );
-    p = (PgHdr1 *)pcache1.pFree;
-    pcache1.pFree = pcache1.pFree->pNext;
-    sqlite3StatusSet(SQLITE_STATUS_PAGECACHE_SIZE, nByte);
-    sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_USED, 1);
-  }else{
-
-    /* Allocate a new buffer using sqlite3Malloc. Before doing so, exit the
-    ** global pcache mutex and unlock the pager-cache object pCache. This is 
-    ** so that if the attempt to allocate a new buffer causes the the 
-    ** configured soft-heap-limit to be breached, it will be possible to
-    ** reclaim memory from this pager-cache.
-    */
-    pcache1LeaveMutex();
-    p = sqlite3Malloc(nByte);
-    pcache1EnterMutex();
-    if( p ){
-      int sz = sqlite3MallocSize(p);
-      sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_OVERFLOW, sz);
-    }
-  }
-  return p;
-}
-
-/*
-** Free an allocated buffer obtained from pcache1Alloc().
-*/
-static void pcache1Free(void *p){
-  assert( sqlite3_mutex_held(pcache1.mutex) );
-  if( p==0 ) return;
-  if( p>=pcache1.pStart && p<pcache1.pEnd ){
-    PgFreeslot *pSlot;
-    sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_USED, -1);
-    pSlot = (PgFreeslot*)p;
-    pSlot->pNext = pcache1.pFree;
-    pcache1.pFree = pSlot;
-  }else{
-    int iSize = sqlite3MallocSize(p);
-    sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_OVERFLOW, -iSize);
-    sqlite3_free(p);
-  }
-}
-
-/*
-** Allocate a new page object initially associated with cache pCache.
-*/
-static PgHdr1 *pcache1AllocPage(PCache1 *pCache){
-  int nByte = sizeof(PgHdr1) + pCache->szPage;
-  void *pPg = pcache1Alloc(nByte);
-  PgHdr1 *p;
-  if( pPg ){
-    p = PAGE_TO_PGHDR1(pCache, pPg);
-    if( pCache->bPurgeable ){
-      pcache1.nCurrentPage++;
-    }
-  }else{
-    p = 0;
-  }
-  return p;
-}
-
-/*
-** Free a page object allocated by pcache1AllocPage().
-**
-** The pointer is allowed to be NULL, which is prudent.  But it turns out
-** that the current implementation happens to never call this routine
-** with a NULL pointer, so we mark the NULL test with ALWAYS().
-*/
-static void pcache1FreePage(PgHdr1 *p){
-  if( ALWAYS(p) ){
-    if( p->pCache->bPurgeable ){
-      pcache1.nCurrentPage--;
-    }
-    pcache1Free(PGHDR1_TO_PAGE(p));
-  }
-}
-
-/*
-** Malloc function used by SQLite to obtain space from the buffer configured
-** using sqlite3_config(SQLITE_CONFIG_PAGECACHE) option. If no such buffer
-** exists, this function falls back to sqlite3Malloc().
-*/
-void *sqlite3PageMalloc(int sz){
-  void *p;
-  pcache1EnterMutex();
-  p = pcache1Alloc(sz);
-  pcache1LeaveMutex();
-  return p;
-}
-
-/*
-** Free an allocated buffer obtained from sqlite3PageMalloc().
-*/
-void sqlite3PageFree(void *p){
-  pcache1EnterMutex();
-  pcache1Free(p);
-  pcache1LeaveMutex();
-}
-
-/******************************************************************************/
-/******** General Implementation Functions ************************************/
-
-/*
-** This function is used to resize the hash table used by the cache passed
-** as the first argument.
-**
-** The global mutex must be held when this function is called.
-*/
-static int pcache1ResizeHash(PCache1 *p){
-  PgHdr1 **apNew;
-  unsigned int nNew;
-  unsigned int i;
-
-  assert( sqlite3_mutex_held(pcache1.mutex) );
-
-  nNew = p->nHash*2;
-  if( nNew<256 ){
-    nNew = 256;
-  }
-
-  pcache1LeaveMutex();
-  if( p->nHash ){ sqlite3BeginBenignMalloc(); }
-  apNew = (PgHdr1 **)sqlite3_malloc(sizeof(PgHdr1 *)*nNew);
-  if( p->nHash ){ sqlite3EndBenignMalloc(); }
-  pcache1EnterMutex();
-  if( apNew ){
-    memset(apNew, 0, sizeof(PgHdr1 *)*nNew);
-    for(i=0; i<p->nHash; i++){
-      PgHdr1 *pPage;
-      PgHdr1 *pNext = p->apHash[i];
-      while( (pPage = pNext)!=0 ){
-        unsigned int h = pPage->iKey % nNew;
-        pNext = pPage->pNext;
-        pPage->pNext = apNew[h];
-        apNew[h] = pPage;
-      }
-    }
-    sqlite3_free(p->apHash);
-    p->apHash = apNew;
-    p->nHash = nNew;
-  }
-
-  return (p->apHash ? SQLITE_OK : SQLITE_NOMEM);
-}
-
-/*
-** This function is used internally to remove the page pPage from the 
-** global LRU list, if is part of it. If pPage is not part of the global
-** LRU list, then this function is a no-op.
-**
-** The global mutex must be held when this function is called.
-*/
-static void pcache1PinPage(PgHdr1 *pPage){
-  assert( sqlite3_mutex_held(pcache1.mutex) );
-  if( pPage && (pPage->pLruNext || pPage==pcache1.pLruTail) ){
-    if( pPage->pLruPrev ){
-      pPage->pLruPrev->pLruNext = pPage->pLruNext;
-    }
-    if( pPage->pLruNext ){
-      pPage->pLruNext->pLruPrev = pPage->pLruPrev;
-    }
-    if( pcache1.pLruHead==pPage ){
-      pcache1.pLruHead = pPage->pLruNext;
-    }
-    if( pcache1.pLruTail==pPage ){
-      pcache1.pLruTail = pPage->pLruPrev;
-    }
-    pPage->pLruNext = 0;
-    pPage->pLruPrev = 0;
-    pPage->pCache->nRecyclable--;
-  }
-}
-
-
-/*
-** Remove the page supplied as an argument from the hash table 
-** (PCache1.apHash structure) that it is currently stored in.
-**
-** The global mutex must be held when this function is called.
-*/
-static void pcache1RemoveFromHash(PgHdr1 *pPage){
-  unsigned int h;
-  PCache1 *pCache = pPage->pCache;
-  PgHdr1 **pp;
-
-  h = pPage->iKey % pCache->nHash;
-  for(pp=&pCache->apHash[h]; (*pp)!=pPage; pp=&(*pp)->pNext);
-  *pp = (*pp)->pNext;
-
-  pCache->nPage--;
-}
-
-/*
-** If there are currently more than pcache.nMaxPage pages allocated, try
-** to recycle pages to reduce the number allocated to pcache.nMaxPage.
-*/
-static void pcache1EnforceMaxPage(void){
-  assert( sqlite3_mutex_held(pcache1.mutex) );
-  while( pcache1.nCurrentPage>pcache1.nMaxPage && pcache1.pLruTail ){
-    PgHdr1 *p = pcache1.pLruTail;
-    pcache1PinPage(p);
-    pcache1RemoveFromHash(p);
-    pcache1FreePage(p);
-  }
-}
-
-/*
-** Discard all pages from cache pCache with a page number (key value) 
-** greater than or equal to iLimit. Any pinned pages that meet this 
-** criteria are unpinned before they are discarded.
-**
-** The global mutex must be held when this function is called.
-*/
-static void pcache1TruncateUnsafe(
-  PCache1 *pCache, 
-  unsigned int iLimit 
-){
-  TESTONLY( unsigned int nPage = 0; )      /* Used to assert pCache->nPage is correct */
-  unsigned int h;
-  assert( sqlite3_mutex_held(pcache1.mutex) );
-  for(h=0; h<pCache->nHash; h++){
-    PgHdr1 **pp = &pCache->apHash[h]; 
-    PgHdr1 *pPage;
-    while( (pPage = *pp)!=0 ){
-      if( pPage->iKey>=iLimit ){
-        pCache->nPage--;
-        *pp = pPage->pNext;
-        pcache1PinPage(pPage);
-        pcache1FreePage(pPage);
-      }else{
-        pp = &pPage->pNext;
-        TESTONLY( nPage++; )
-      }
-    }
-  }
-  assert( pCache->nPage==nPage );
-}
-
-/******************************************************************************/
-/******** sqlite3_pcache Methods **********************************************/
-
-/*
-** Implementation of the sqlite3_pcache.xInit method.
-*/
-static int pcache1Init(void *NotUsed){
-  UNUSED_PARAMETER(NotUsed);
-  assert( pcache1.isInit==0 );
-  memset(&pcache1, 0, sizeof(pcache1));
-  if( sqlite3GlobalConfig.bCoreMutex ){
-    pcache1.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_LRU);
-  }
-  pcache1.isInit = 1;
-  return SQLITE_OK;
-}
-
-/*
-** Implementation of the sqlite3_pcache.xShutdown method.
-** Note that the static mutex allocated in xInit does 
-** not need to be freed.
-*/
-static void pcache1Shutdown(void *NotUsed){
-  UNUSED_PARAMETER(NotUsed);
-  assert( pcache1.isInit!=0 );
-  memset(&pcache1, 0, sizeof(pcache1));
-}
-
-/*
-** Implementation of the sqlite3_pcache.xCreate method.
-**
-** Allocate a new cache.
-*/
-static sqlite3_pcache *pcache1Create(int szPage, int bPurgeable){
-  PCache1 *pCache;
-
-  pCache = (PCache1 *)sqlite3_malloc(sizeof(PCache1));
-  if( pCache ){
-    memset(pCache, 0, sizeof(PCache1));
-    pCache->szPage = szPage;
-    pCache->bPurgeable = (bPurgeable ? 1 : 0);
-    if( bPurgeable ){
-      pCache->nMin = 10;
-      pcache1EnterMutex();
-      pcache1.nMinPage += pCache->nMin;
-      pcache1LeaveMutex();
-    }
-  }
-  return (sqlite3_pcache *)pCache;
-}
-
-/*
-** Implementation of the sqlite3_pcache.xCachesize method. 
-**
-** Configure the cache_size limit for a cache.
-*/
-static void pcache1Cachesize(sqlite3_pcache *p, int nMax){
-  PCache1 *pCache = (PCache1 *)p;
-  if( pCache->bPurgeable ){
-    pcache1EnterMutex();
-    pcache1.nMaxPage += (nMax - pCache->nMax);
-    pCache->nMax = nMax;
-    pcache1EnforceMaxPage();
-    pcache1LeaveMutex();
-  }
-}
-
-/*
-** Implementation of the sqlite3_pcache.xPagecount method. 
-*/
-static int pcache1Pagecount(sqlite3_pcache *p){
-  int n;
-  pcache1EnterMutex();
-  n = ((PCache1 *)p)->nPage;
-  pcache1LeaveMutex();
-  return n;
-}
-
-/*
-** Implementation of the sqlite3_pcache.xFetch method. 
-**
-** Fetch a page by key value.
-**
-** Whether or not a new page may be allocated by this function depends on
-** the value of the createFlag argument.  0 means do not allocate a new
-** page.  1 means allocate a new page if space is easily available.  2 
-** means to try really hard to allocate a new page.
-**
-** For a non-purgeable cache (a cache used as the storage for an in-memory
-** database) there is really no difference between createFlag 1 and 2.  So
-** the calling function (pcache.c) will never have a createFlag of 1 on
-** a non-purgable cache.
-**
-** There are three different approaches to obtaining space for a page,
-** depending on the value of parameter createFlag (which may be 0, 1 or 2).
-**
-**   1. Regardless of the value of createFlag, the cache is searched for a 
-**      copy of the requested page. If one is found, it is returned.
-**
-**   2. If createFlag==0 and the page is not already in the cache, NULL is
-**      returned.
-**
-**   3. If createFlag is 1, and the page is not already in the cache,
-**      and if either of the following are true, return NULL:
-**
-**       (a) the number of pages pinned by the cache is greater than
-**           PCache1.nMax, or
-**       (b) the number of pages pinned by the cache is greater than
-**           the sum of nMax for all purgeable caches, less the sum of 
-**           nMin for all other purgeable caches. 
-**
-**   4. If none of the first three conditions apply and the cache is marked
-**      as purgeable, and if one of the following is true:
-**
-**       (a) The number of pages allocated for the cache is already 
-**           PCache1.nMax, or
-**
-**       (b) The number of pages allocated for all purgeable caches is
-**           already equal to or greater than the sum of nMax for all
-**           purgeable caches,
-**
-**      then attempt to recycle a page from the LRU list. If it is the right
-**      size, return the recycled buffer. Otherwise, free the buffer and
-**      proceed to step 5. 
-**
-**   5. Otherwise, allocate and return a new page buffer.
-*/
-static void *pcache1Fetch(sqlite3_pcache *p, unsigned int iKey, int createFlag){
-  unsigned int nPinned;
-  PCache1 *pCache = (PCache1 *)p;
-  PgHdr1 *pPage = 0;
-
-  assert( pCache->bPurgeable || createFlag!=1 );
-  pcache1EnterMutex();
-  if( createFlag==1 ) sqlite3BeginBenignMalloc();
-
-  /* Search the hash table for an existing entry. */
-  if( pCache->nHash>0 ){
-    unsigned int h = iKey % pCache->nHash;
-    for(pPage=pCache->apHash[h]; pPage&&pPage->iKey!=iKey; pPage=pPage->pNext);
-  }
-
-  if( pPage || createFlag==0 ){
-    pcache1PinPage(pPage);
-    goto fetch_out;
-  }
-
-  /* Step 3 of header comment. */
-  nPinned = pCache->nPage - pCache->nRecyclable;
-  if( createFlag==1 && (
-        nPinned>=(pcache1.nMaxPage+pCache->nMin-pcache1.nMinPage)
-     || nPinned>=(pCache->nMax * 9 / 10)
-  )){
-    goto fetch_out;
-  }
-
-  if( pCache->nPage>=pCache->nHash && pcache1ResizeHash(pCache) ){
-    goto fetch_out;
-  }
-
-  /* Step 4. Try to recycle a page buffer if appropriate. */
-  if( pCache->bPurgeable && pcache1.pLruTail && (
-     (pCache->nPage+1>=pCache->nMax) || pcache1.nCurrentPage>=pcache1.nMaxPage
-  )){
-    pPage = pcache1.pLruTail;
-    pcache1RemoveFromHash(pPage);
-    pcache1PinPage(pPage);
-    if( pPage->pCache->szPage!=pCache->szPage ){
-      pcache1FreePage(pPage);
-      pPage = 0;
-    }else{
-      pcache1.nCurrentPage -= (pPage->pCache->bPurgeable - pCache->bPurgeable);
-    }
-  }
-
-  /* Step 5. If a usable page buffer has still not been found, 
-  ** attempt to allocate a new one. 
-  */
-  if( !pPage ){
-    pPage = pcache1AllocPage(pCache);
-  }
-
-  if( pPage ){
-    unsigned int h = iKey % pCache->nHash;
-    pCache->nPage++;
-    pPage->iKey = iKey;
-    pPage->pNext = pCache->apHash[h];
-    pPage->pCache = pCache;
-    pPage->pLruPrev = 0;
-    pPage->pLruNext = 0;
-    *(void **)(PGHDR1_TO_PAGE(pPage)) = 0;
-    pCache->apHash[h] = pPage;
-  }
-
-fetch_out:
-  if( pPage && iKey>pCache->iMaxKey ){
-    pCache->iMaxKey = iKey;
-  }
-  if( createFlag==1 ) sqlite3EndBenignMalloc();
-  pcache1LeaveMutex();
-  return (pPage ? PGHDR1_TO_PAGE(pPage) : 0);
-}
-
-
-/*
-** Implementation of the sqlite3_pcache.xUnpin method.
-**
-** Mark a page as unpinned (eligible for asynchronous recycling).
-*/
-static void pcache1Unpin(sqlite3_pcache *p, void *pPg, int reuseUnlikely){
-  PCache1 *pCache = (PCache1 *)p;
-  PgHdr1 *pPage = PAGE_TO_PGHDR1(pCache, pPg);
- 
-  assert( pPage->pCache==pCache );
-  pcache1EnterMutex();
-
-  /* It is an error to call this function if the page is already 
-  ** part of the global LRU list.
-  */
-  assert( pPage->pLruPrev==0 && pPage->pLruNext==0 );
-  assert( pcache1.pLruHead!=pPage && pcache1.pLruTail!=pPage );
-
-  if( reuseUnlikely || pcache1.nCurrentPage>pcache1.nMaxPage ){
-    pcache1RemoveFromHash(pPage);
-    pcache1FreePage(pPage);
-  }else{
-    /* Add the page to the global LRU list. Normally, the page is added to
-    ** the head of the list (last page to be recycled). However, if the 
-    ** reuseUnlikely flag passed to this function is true, the page is added
-    ** to the tail of the list (first page to be recycled).
-    */
-    if( pcache1.pLruHead ){
-      pcache1.pLruHead->pLruPrev = pPage;
-      pPage->pLruNext = pcache1.pLruHead;
-      pcache1.pLruHead = pPage;
-    }else{
-      pcache1.pLruTail = pPage;
-      pcache1.pLruHead = pPage;
-    }
-    pCache->nRecyclable++;
-  }
-
-  pcache1LeaveMutex();
-}
-
-/*
-** Implementation of the sqlite3_pcache.xRekey method. 
-*/
-static void pcache1Rekey(
-  sqlite3_pcache *p,
-  void *pPg,
-  unsigned int iOld,
-  unsigned int iNew
-){
-  PCache1 *pCache = (PCache1 *)p;
-  PgHdr1 *pPage = PAGE_TO_PGHDR1(pCache, pPg);
-  PgHdr1 **pp;
-  unsigned int h; 
-  assert( pPage->iKey==iOld );
-  assert( pPage->pCache==pCache );
-
-  pcache1EnterMutex();
-
-  h = iOld%pCache->nHash;
-  pp = &pCache->apHash[h];
-  while( (*pp)!=pPage ){
-    pp = &(*pp)->pNext;
-  }
-  *pp = pPage->pNext;
-
-  h = iNew%pCache->nHash;
-  pPage->iKey = iNew;
-  pPage->pNext = pCache->apHash[h];
-  pCache->apHash[h] = pPage;
-
-  /* The xRekey() interface is only used to move pages earlier in the
-  ** database file (in order to move all free pages to the end of the
-  ** file where they can be truncated off.)  Hence, it is not possible
-  ** for the new page number to be greater than the largest previously
-  ** fetched page.  But we retain the following test in case xRekey()
-  ** begins to be used in different ways in the future.
-  */
-  if( NEVER(iNew>pCache->iMaxKey) ){
-    pCache->iMaxKey = iNew;
-  }
-
-  pcache1LeaveMutex();
-}
-
-/*
-** Implementation of the sqlite3_pcache.xTruncate method. 
-**
-** Discard all unpinned pages in the cache with a page number equal to
-** or greater than parameter iLimit. Any pinned pages with a page number
-** equal to or greater than iLimit are implicitly unpinned.
-*/
-static void pcache1Truncate(sqlite3_pcache *p, unsigned int iLimit){
-  PCache1 *pCache = (PCache1 *)p;
-  pcache1EnterMutex();
-  if( iLimit<=pCache->iMaxKey ){
-    pcache1TruncateUnsafe(pCache, iLimit);
-    pCache->iMaxKey = iLimit-1;
-  }
-  pcache1LeaveMutex();
-}
-
-/*
-** Implementation of the sqlite3_pcache.xDestroy method. 
-**
-** Destroy a cache allocated using pcache1Create().
-*/
-static void pcache1Destroy(sqlite3_pcache *p){
-  PCache1 *pCache = (PCache1 *)p;
-  pcache1EnterMutex();
-  pcache1TruncateUnsafe(pCache, 0);
-  pcache1.nMaxPage -= pCache->nMax;
-  pcache1.nMinPage -= pCache->nMin;
-  pcache1EnforceMaxPage();
-  pcache1LeaveMutex();
-  sqlite3_free(pCache->apHash);
-  sqlite3_free(pCache);
-}
-
-/*
-** This function is called during initialization (sqlite3_initialize()) to
-** install the default pluggable cache module, assuming the user has not
-** already provided an alternative.
-*/
-void sqlite3PCacheSetDefault(void){
-  static sqlite3_pcache_methods defaultMethods = {
-    0,                       /* pArg */
-    pcache1Init,             /* xInit */
-    pcache1Shutdown,         /* xShutdown */
-    pcache1Create,           /* xCreate */
-    pcache1Cachesize,        /* xCachesize */
-    pcache1Pagecount,        /* xPagecount */
-    pcache1Fetch,            /* xFetch */
-    pcache1Unpin,            /* xUnpin */
-    pcache1Rekey,            /* xRekey */
-    pcache1Truncate,         /* xTruncate */
-    pcache1Destroy           /* xDestroy */
-  };
-  sqlite3_config(SQLITE_CONFIG_PCACHE, &defaultMethods);
-}
-
-#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( pcache1.pStart==0 ){
-    PgHdr1 *p;
-    pcache1EnterMutex();
-    while( (nReq<0 || nFree<nReq) && (p=pcache1.pLruTail) ){
-      nFree += sqlite3MallocSize(PGHDR1_TO_PAGE(p));
-      pcache1PinPage(p);
-      pcache1RemoveFromHash(p);
-      pcache1FreePage(p);
-    }
-    pcache1LeaveMutex();
-  }
-  return nFree;
-}
-#endif /* SQLITE_ENABLE_MEMORY_MANAGEMENT */
-
-#ifdef SQLITE_TEST
-/*
-** This function is used by test procedures to inspect the internal state
-** of the global cache.
-*/
-void sqlite3PcacheStats(
-  int *pnCurrent,      /* OUT: Total number of pages cached */
-  int *pnMax,          /* OUT: Global maximum cache size */
-  int *pnMin,          /* OUT: Sum of PCache1.nMin for purgeable caches */
-  int *pnRecyclable    /* OUT: Total number of pages available for recycling */
-){
-  PgHdr1 *p;
-  int nRecyclable = 0;
-  for(p=pcache1.pLruHead; p; p=p->pLruNext){
-    nRecyclable++;
-  }
-  *pnCurrent = pcache1.nCurrentPage;
-  *pnMax = pcache1.nMaxPage;
-  *pnMin = pcache1.nMinPage;
-  *pnRecyclable = nRecyclable;
-}
-#endif