[sqlite] Remove obsolete reference version 3.8.7.4.

third_party/sqlite/sqlite-src-3080704/src/pcache1.c

Index: third_party/sqlite/sqlite-src-3080704/src/pcache1.c
diff --git a/third_party/sqlite/sqlite-src-3080704/src/pcache1.c b/third_party/sqlite/sqlite-src-3080704/src/pcache1.c
deleted file mode 100644
index a8c3217382a10b170f017a2648a8759e0dd28b5f..0000000000000000000000000000000000000000
--- a/third_party/sqlite/sqlite-src-3080704/src/pcache1.c
+++ /dev/null
@@ -1,1039 +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 overridden, then neither of
-** these two features are available.
-*/
-
-#include "sqliteInt.h"
-
-typedef struct PCache1 PCache1;
-typedef struct PgHdr1 PgHdr1;
-typedef struct PgFreeslot PgFreeslot;
-typedef struct PGroup PGroup;
-
-/* Each page cache (or PCache) belongs to a PGroup.  A PGroup is a set 
-** of one or more PCaches that are able to recycle each other's unpinned
-** pages when they are under memory pressure.  A PGroup is an instance of
-** the following object.
-**
-** This page cache implementation works in one of two modes:
-**
-**   (1)  Every PCache is the sole member of its own PGroup.  There is
-**        one PGroup per PCache.
-**
-**   (2)  There is a single global PGroup that all PCaches are a member
-**        of.
-**
-** Mode 1 uses more memory (since PCache instances are not able to rob
-** unused pages from other PCaches) but it also operates without a mutex,
-** and is therefore often faster.  Mode 2 requires a mutex in order to be
-** threadsafe, but recycles pages more efficiently.
-**
-** For mode (1), PGroup.mutex is NULL.  For mode (2) there is only a single
-** PGroup which is the pcache1.grp global variable and its mutex is
-** SQLITE_MUTEX_STATIC_LRU.
-*/
-struct PGroup {
-  sqlite3_mutex *mutex;          /* MUTEX_STATIC_LRU or NULL */
-  unsigned int nMaxPage;         /* Sum of nMax for purgeable caches */
-  unsigned int nMinPage;         /* Sum of nMin for purgeable caches */
-  unsigned int mxPinned;         /* nMaxpage + 10 - nMinPage */
-  unsigned int nCurrentPage;     /* Number of purgeable pages allocated */
-  PgHdr1 *pLruHead, *pLruTail;   /* LRU list of unpinned pages */
-};
-
-/* Each page cache is an instance of the following object.  Every
-** open database file (including each in-memory database and each
-** temporary or transient database) has a single page cache which
-** is an instance of this object.
-**
-** 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 PGroup mutex must be held when accessing nMax.
-  */
-  PGroup *pGroup;                     /* PGroup this cache belongs to */
-  int szPage;                         /* Size of allocated pages in bytes */
-  int szExtra;                        /* Size of extra space in bytes */
-  int bPurgeable;                     /* True if cache is purgeable */
-  unsigned int nMin;                  /* Minimum number of pages reserved */
-  unsigned int nMax;                  /* Configured "cache_size" value */
-  unsigned int n90pct;                /* nMax*9/10 */
-  unsigned int iMaxKey;               /* Largest key seen since xTruncate() */
-
-  /* Hash table of all pages. The following variables may only be accessed
-  ** when the accessor is holding the PGroup mutex.
-  */
-  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 */
-};
-
-/*
-** Each cache entry is represented by an instance of the following 
-** structure. Unless SQLITE_PCACHE_SEPARATE_HEADER is defined, a buffer of
-** PgHdr1.pCache->szPage bytes is allocated directly before this structure 
-** in memory.
-*/
-struct PgHdr1 {
-  sqlite3_pcache_page page;
-  unsigned int iKey;             /* Key value (page number) */
-  u8 isPinned;                   /* Page in use, not on the LRU list */
-  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 {
-  PGroup grp;                    /* The global PGroup for mode (2) */
-
-  /* Variables related to SQLITE_CONFIG_PAGECACHE settings.  The
-  ** szSlot, nSlot, pStart, pEnd, nReserve, and isInit values are all
-  ** fixed at sqlite3_initialize() time and do not require mutex protection.
-  ** The nFreeSlot and pFree values do require mutex protection.
-  */
-  int isInit;                    /* True if initialized */
-  int szSlot;                    /* Size of each free slot */
-  int nSlot;                     /* The number of pcache slots */
-  int nReserve;                  /* Try to keep nFreeSlot above this */
-  void *pStart, *pEnd;           /* Bounds of pagecache malloc range */
-  /* Above requires no mutex.  Use mutex below for variable that follow. */
-  sqlite3_mutex *mutex;          /* Mutex for accessing the following: */
-  PgFreeslot *pFree;             /* Free page blocks */
-  int nFreeSlot;                 /* Number of unused pcache slots */
-  /* The following value requires a mutex to change.  We skip the mutex on
-  ** reading because (1) most platforms read a 32-bit integer atomically and
-  ** (2) even if an incorrect value is read, no great harm is done since this
-  ** is really just an optimization. */
-  int bUnderPressure;            /* True if low on PAGECACHE memory */
-} 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))
-
-/*
-** Macros to enter and leave the PCache LRU mutex.
-*/
-#define pcache1EnterMutex(X) sqlite3_mutex_enter((X)->mutex)
-#define pcache1LeaveMutex(X) sqlite3_mutex_leave((X)->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.
-**
-** This routine is called from sqlite3_initialize() and so it is guaranteed
-** to be serialized already.  There is no need for further mutexing.
-*/
-void sqlite3PCacheBufferSetup(void *pBuf, int sz, int n){
-  if( pcache1.isInit ){
-    PgFreeslot *p;
-    sz = ROUNDDOWN8(sz);
-    pcache1.szSlot = sz;
-    pcache1.nSlot = pcache1.nFreeSlot = n;
-    pcache1.nReserve = n>90 ? 10 : (n/10 + 1);
-    pcache1.pStart = pBuf;
-    pcache1.pFree = 0;
-    pcache1.bUnderPressure = 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().
-**
-** Multiple threads can run this routine at the same time.  Global variables
-** in pcache1 need to be protected via mutex.
-*/
-static void *pcache1Alloc(int nByte){
-  void *p = 0;
-  assert( sqlite3_mutex_notheld(pcache1.grp.mutex) );
-  sqlite3StatusSet(SQLITE_STATUS_PAGECACHE_SIZE, nByte);
-  if( nByte<=pcache1.szSlot ){
-    sqlite3_mutex_enter(pcache1.mutex);
-    p = (PgHdr1 *)pcache1.pFree;
-    if( p ){
-      pcache1.pFree = pcache1.pFree->pNext;
-      pcache1.nFreeSlot--;
-      pcache1.bUnderPressure = pcache1.nFreeSlot<pcache1.nReserve;
-      assert( pcache1.nFreeSlot>=0 );
-      sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_USED, 1);
-    }
-    sqlite3_mutex_leave(pcache1.mutex);
-  }
-  if( p==0 ){
-    /* Memory is not available in the SQLITE_CONFIG_PAGECACHE pool.  Get
-    ** it from sqlite3Malloc instead.
-    */
-    p = sqlite3Malloc(nByte);
-#ifndef SQLITE_DISABLE_PAGECACHE_OVERFLOW_STATS
-    if( p ){
-      int sz = sqlite3MallocSize(p);
-      sqlite3_mutex_enter(pcache1.mutex);
-      sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_OVERFLOW, sz);
-      sqlite3_mutex_leave(pcache1.mutex);
-    }
-#endif
-    sqlite3MemdebugSetType(p, MEMTYPE_PCACHE);
-  }
-  return p;
-}
-
-/*
-** Free an allocated buffer obtained from pcache1Alloc().
-*/
-static int pcache1Free(void *p){
-  int nFreed = 0;
-  if( p==0 ) return 0;
-  if( p>=pcache1.pStart && p<pcache1.pEnd ){
-    PgFreeslot *pSlot;
-    sqlite3_mutex_enter(pcache1.mutex);
-    sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_USED, -1);
-    pSlot = (PgFreeslot*)p;
-    pSlot->pNext = pcache1.pFree;
-    pcache1.pFree = pSlot;
-    pcache1.nFreeSlot++;
-    pcache1.bUnderPressure = pcache1.nFreeSlot<pcache1.nReserve;
-    assert( pcache1.nFreeSlot<=pcache1.nSlot );
-    sqlite3_mutex_leave(pcache1.mutex);
-  }else{
-    assert( sqlite3MemdebugHasType(p, MEMTYPE_PCACHE) );
-    sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
-    nFreed = sqlite3MallocSize(p);
-#ifndef SQLITE_DISABLE_PAGECACHE_OVERFLOW_STATS
-    sqlite3_mutex_enter(pcache1.mutex);
-    sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_OVERFLOW, -nFreed);
-    sqlite3_mutex_leave(pcache1.mutex);
-#endif
-    sqlite3_free(p);
-  }
-  return nFreed;
-}
-
-#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
-/*
-** Return the size of a pcache allocation
-*/
-static int pcache1MemSize(void *p){
-  if( p>=pcache1.pStart && p<pcache1.pEnd ){
-    return pcache1.szSlot;
-  }else{
-    int iSize;
-    assert( sqlite3MemdebugHasType(p, MEMTYPE_PCACHE) );
-    sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
-    iSize = sqlite3MallocSize(p);
-    sqlite3MemdebugSetType(p, MEMTYPE_PCACHE);
-    return iSize;
-  }
-}
-#endif /* SQLITE_ENABLE_MEMORY_MANAGEMENT */
-
-/*
-** Allocate a new page object initially associated with cache pCache.
-*/
-static PgHdr1 *pcache1AllocPage(PCache1 *pCache){
-  PgHdr1 *p = 0;
-  void *pPg;
-
-  /* The group mutex must be released before pcache1Alloc() is called. This
-  ** is because it may call sqlite3_release_memory(), which assumes that 
-  ** this mutex is not held. */
-  assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
-  pcache1LeaveMutex(pCache->pGroup);
-#ifdef SQLITE_PCACHE_SEPARATE_HEADER
-  pPg = pcache1Alloc(pCache->szPage);
-  p = sqlite3Malloc(sizeof(PgHdr1) + pCache->szExtra);
-  if( !pPg || !p ){
-    pcache1Free(pPg);
-    sqlite3_free(p);
-    pPg = 0;
-  }
-#else
-  pPg = pcache1Alloc(sizeof(PgHdr1) + pCache->szPage + pCache->szExtra);
-  p = (PgHdr1 *)&((u8 *)pPg)[pCache->szPage];
-#endif
-  pcache1EnterMutex(pCache->pGroup);
-
-  if( pPg ){
-    p->page.pBuf = pPg;
-    p->page.pExtra = &p[1];
-    if( pCache->bPurgeable ){
-      pCache->pGroup->nCurrentPage++;
-    }
-    return p;
-  }
-  return 0;
-}
-
-/*
-** 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) ){
-    PCache1 *pCache = p->pCache;
-    assert( sqlite3_mutex_held(p->pCache->pGroup->mutex) );
-    pcache1Free(p->page.pBuf);
-#ifdef SQLITE_PCACHE_SEPARATE_HEADER
-    sqlite3_free(p);
-#endif
-    if( pCache->bPurgeable ){
-      pCache->pGroup->nCurrentPage--;
-    }
-  }
-}
-
-/*
-** 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){
-  return pcache1Alloc(sz);
-}
-
-/*
-** Free an allocated buffer obtained from sqlite3PageMalloc().
-*/
-void sqlite3PageFree(void *p){
-  pcache1Free(p);
-}
-
-
-/*
-** Return true if it desirable to avoid allocating a new page cache
-** entry.
-**
-** If memory was allocated specifically to the page cache using
-** SQLITE_CONFIG_PAGECACHE but that memory has all been used, then
-** it is desirable to avoid allocating a new page cache entry because
-** presumably SQLITE_CONFIG_PAGECACHE was suppose to be sufficient
-** for all page cache needs and we should not need to spill the
-** allocation onto the heap.
-**
-** Or, the heap is used for all page cache memory but the heap is
-** under memory pressure, then again it is desirable to avoid
-** allocating a new page cache entry in order to avoid stressing
-** the heap even further.
-*/
-static int pcache1UnderMemoryPressure(PCache1 *pCache){
-  if( pcache1.nSlot && (pCache->szPage+pCache->szExtra)<=pcache1.szSlot ){
-    return pcache1.bUnderPressure;
-  }else{
-    return sqlite3HeapNearlyFull();
-  }
-}
-
-/******************************************************************************/
-/******** General Implementation Functions ************************************/
-
-/*
-** This function is used to resize the hash table used by the cache passed
-** as the first argument.
-**
-** The PCache mutex must be held when this function is called.
-*/
-static void pcache1ResizeHash(PCache1 *p){
-  PgHdr1 **apNew;
-  unsigned int nNew;
-  unsigned int i;
-
-  assert( sqlite3_mutex_held(p->pGroup->mutex) );
-
-  nNew = p->nHash*2;
-  if( nNew<256 ){
-    nNew = 256;
-  }
-
-  pcache1LeaveMutex(p->pGroup);
-  if( p->nHash ){ sqlite3BeginBenignMalloc(); }
-  apNew = (PgHdr1 **)sqlite3MallocZero(sizeof(PgHdr1 *)*nNew);
-  if( p->nHash ){ sqlite3EndBenignMalloc(); }
-  pcache1EnterMutex(p->pGroup);
-  if( apNew ){
-    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;
-  }
-}
-
-/*
-** This function is used internally to remove the page pPage from the 
-** PGroup LRU list, if is part of it. If pPage is not part of the PGroup
-** LRU list, then this function is a no-op.
-**
-** The PGroup mutex must be held when this function is called.
-*/
-static void pcache1PinPage(PgHdr1 *pPage){
-  PCache1 *pCache;
-  PGroup *pGroup;
-
-  assert( pPage!=0 );
-  assert( pPage->isPinned==0 );
-  pCache = pPage->pCache;
-  pGroup = pCache->pGroup;
-  assert( pPage->pLruNext || pPage==pGroup->pLruTail );
-  assert( pPage->pLruPrev || pPage==pGroup->pLruHead );
-  assert( sqlite3_mutex_held(pGroup->mutex) );
-  if( pPage->pLruPrev ){
-    pPage->pLruPrev->pLruNext = pPage->pLruNext;
-  }else{
-    pGroup->pLruHead = pPage->pLruNext;
-  }
-  if( pPage->pLruNext ){
-    pPage->pLruNext->pLruPrev = pPage->pLruPrev;
-  }else{
-    pGroup->pLruTail = pPage->pLruPrev;
-  }
-  pPage->pLruNext = 0;
-  pPage->pLruPrev = 0;
-  pPage->isPinned = 1;
-  pCache->nRecyclable--;
-}
-
-
-/*
-** Remove the page supplied as an argument from the hash table 
-** (PCache1.apHash structure) that it is currently stored in.
-**
-** The PGroup mutex must be held when this function is called.
-*/
-static void pcache1RemoveFromHash(PgHdr1 *pPage){
-  unsigned int h;
-  PCache1 *pCache = pPage->pCache;
-  PgHdr1 **pp;
-
-  assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
-  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 nMaxPage pages allocated, try
-** to recycle pages to reduce the number allocated to nMaxPage.
-*/
-static void pcache1EnforceMaxPage(PGroup *pGroup){
-  assert( sqlite3_mutex_held(pGroup->mutex) );
-  while( pGroup->nCurrentPage>pGroup->nMaxPage && pGroup->pLruTail ){
-    PgHdr1 *p = pGroup->pLruTail;
-    assert( p->pCache->pGroup==pGroup );
-    assert( p->isPinned==0 );
-    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 PCache mutex must be held when this function is called.
-*/
-static void pcache1TruncateUnsafe(
-  PCache1 *pCache,             /* The cache to truncate */
-  unsigned int iLimit          /* Drop pages with this pgno or larger */
-){
-  TESTONLY( unsigned int nPage = 0; )  /* To assert pCache->nPage is correct */
-  unsigned int h;
-  assert( sqlite3_mutex_held(pCache->pGroup->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;
-        if( !pPage->isPinned ) 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.grp.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_LRU);
-    pcache1.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_PMEM);
-  }
-  pcache1.grp.mxPinned = 10;
-  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));
-}
-
-/* forward declaration */
-static void pcache1Destroy(sqlite3_pcache *p);
-
-/*
-** Implementation of the sqlite3_pcache.xCreate method.
-**
-** Allocate a new cache.
-*/
-static sqlite3_pcache *pcache1Create(int szPage, int szExtra, int bPurgeable){
-  PCache1 *pCache;      /* The newly created page cache */
-  PGroup *pGroup;       /* The group the new page cache will belong to */
-  int sz;               /* Bytes of memory required to allocate the new cache */
-
-  /*
-  ** The separateCache variable is true if each PCache has its own private
-  ** PGroup.  In other words, separateCache is true for mode (1) where no
-  ** mutexing is required.
-  **
-  **   *  Always use a unified cache (mode-2) if ENABLE_MEMORY_MANAGEMENT
-  **
-  **   *  Always use a unified cache in single-threaded applications
-  **
-  **   *  Otherwise (if multi-threaded and ENABLE_MEMORY_MANAGEMENT is off)
-  **      use separate caches (mode-1)
-  */
-#if defined(SQLITE_ENABLE_MEMORY_MANAGEMENT) || SQLITE_THREADSAFE==0
-  const int separateCache = 0;
-#else
-  int separateCache = sqlite3GlobalConfig.bCoreMutex>0;
-#endif
-
-  assert( (szPage & (szPage-1))==0 && szPage>=512 && szPage<=65536 );
-  assert( szExtra < 300 );
-
-  sz = sizeof(PCache1) + sizeof(PGroup)*separateCache;
-  pCache = (PCache1 *)sqlite3MallocZero(sz);
-  if( pCache ){
-    if( separateCache ){
-      pGroup = (PGroup*)&pCache[1];
-      pGroup->mxPinned = 10;
-    }else{
-      pGroup = &pcache1.grp;
-    }
-    pCache->pGroup = pGroup;
-    pCache->szPage = szPage;
-    pCache->szExtra = szExtra;
-    pCache->bPurgeable = (bPurgeable ? 1 : 0);
-    pcache1EnterMutex(pGroup);
-    pcache1ResizeHash(pCache);
-    if( bPurgeable ){
-      pCache->nMin = 10;
-      pGroup->nMinPage += pCache->nMin;
-      pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage;
-    }
-    pcache1LeaveMutex(pGroup);
-    if( pCache->nHash==0 ){
-      pcache1Destroy((sqlite3_pcache*)pCache);
-      pCache = 0;
-    }
-  }
-  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 ){
-    PGroup *pGroup = pCache->pGroup;
-    pcache1EnterMutex(pGroup);
-    pGroup->nMaxPage += (nMax - pCache->nMax);
-    pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage;
-    pCache->nMax = nMax;
-    pCache->n90pct = pCache->nMax*9/10;
-    pcache1EnforceMaxPage(pGroup);
-    pcache1LeaveMutex(pGroup);
-  }
-}
-
-/*
-** Implementation of the sqlite3_pcache.xShrink method. 
-**
-** Free up as much memory as possible.
-*/
-static void pcache1Shrink(sqlite3_pcache *p){
-  PCache1 *pCache = (PCache1*)p;
-  if( pCache->bPurgeable ){
-    PGroup *pGroup = pCache->pGroup;
-    int savedMaxPage;
-    pcache1EnterMutex(pGroup);
-    savedMaxPage = pGroup->nMaxPage;
-    pGroup->nMaxPage = 0;
-    pcache1EnforceMaxPage(pGroup);
-    pGroup->nMaxPage = savedMaxPage;
-    pcache1LeaveMutex(pGroup);
-  }
-}
-
-/*
-** Implementation of the sqlite3_pcache.xPagecount method. 
-*/
-static int pcache1Pagecount(sqlite3_pcache *p){
-  int n;
-  PCache1 *pCache = (PCache1*)p;
-  pcache1EnterMutex(pCache->pGroup);
-  n = pCache->nPage;
-  pcache1LeaveMutex(pCache->pGroup);
-  return n;
-}
-
-
-/*
-** Implement steps 3, 4, and 5 of the pcache1Fetch() algorithm described
-** in the header of the pcache1Fetch() procedure.
-**
-** This steps are broken out into a separate procedure because they are
-** usually not needed, and by avoiding the stack initialization required
-** for these steps, the main pcache1Fetch() procedure can run faster.
-*/
-static SQLITE_NOINLINE PgHdr1 *pcache1FetchStage2(
-  PCache1 *pCache, 
-  unsigned int iKey, 
-  int createFlag
-){
-  unsigned int nPinned;
-  PGroup *pGroup = pCache->pGroup;
-  PgHdr1 *pPage = 0;
-
-  /* Step 3: Abort if createFlag is 1 but the cache is nearly full */
-  assert( pCache->nPage >= pCache->nRecyclable );
-  nPinned = pCache->nPage - pCache->nRecyclable;
-  assert( pGroup->mxPinned == pGroup->nMaxPage + 10 - pGroup->nMinPage );
-  assert( pCache->n90pct == pCache->nMax*9/10 );
-  if( createFlag==1 && (
-        nPinned>=pGroup->mxPinned
-     || nPinned>=pCache->n90pct
-     || (pcache1UnderMemoryPressure(pCache) && pCache->nRecyclable<nPinned)
-  )){
-    return 0;
-  }
-
-  if( pCache->nPage>=pCache->nHash ) pcache1ResizeHash(pCache);
-  assert( pCache->nHash>0 && pCache->apHash );
-
-  /* Step 4. Try to recycle a page. */
-  if( pCache->bPurgeable && pGroup->pLruTail && (
-         (pCache->nPage+1>=pCache->nMax)
-      || pGroup->nCurrentPage>=pGroup->nMaxPage
-      || pcache1UnderMemoryPressure(pCache)
-  )){
-    PCache1 *pOther;
-    pPage = pGroup->pLruTail;
-    assert( pPage->isPinned==0 );
-    pcache1RemoveFromHash(pPage);
-    pcache1PinPage(pPage);
-    pOther = pPage->pCache;
-
-    /* We want to verify that szPage and szExtra are the same for pOther
-    ** and pCache.  Assert that we can verify this by comparing sums. */
-    assert( (pCache->szPage & (pCache->szPage-1))==0 && pCache->szPage>=512 );
-    assert( pCache->szExtra<512 );
-    assert( (pOther->szPage & (pOther->szPage-1))==0 && pOther->szPage>=512 );
-    assert( pOther->szExtra<512 );
-
-    if( pOther->szPage+pOther->szExtra != pCache->szPage+pCache->szExtra ){
-      pcache1FreePage(pPage);
-      pPage = 0;
-    }else{
-      pGroup->nCurrentPage -= (pOther->bPurgeable - pCache->bPurgeable);
-    }
-  }
-
-  /* Step 5. If a usable page buffer has still not been found, 
-  ** attempt to allocate a new one. 
-  */
-  if( !pPage ){
-    if( createFlag==1 ) sqlite3BeginBenignMalloc();
-    pPage = pcache1AllocPage(pCache);
-    if( createFlag==1 ) sqlite3EndBenignMalloc();
-  }
-
-  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;
-    pPage->isPinned = 1;
-    *(void **)pPage->page.pExtra = 0;
-    pCache->apHash[h] = pPage;
-    if( iKey>pCache->iMaxKey ){
-      pCache->iMaxKey = iKey;
-    }
-  }
-  return pPage;
-}
-
-/*
-** 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-purgeable 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, then
-**      return NULL (do not allocate a new page) if any of the following
-**      conditions are true:
-**
-**       (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, or
-**
-**   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,
-**
-**       (c) The system is under memory pressure and wants to avoid
-**           unnecessary pages cache entry allocations
-**
-**      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 sqlite3_pcache_page *pcache1Fetch(
-  sqlite3_pcache *p, 
-  unsigned int iKey, 
-  int createFlag
-){
-  PCache1 *pCache = (PCache1 *)p;
-  PgHdr1 *pPage = 0;
-
-  assert( offsetof(PgHdr1,page)==0 );
-  assert( pCache->bPurgeable || createFlag!=1 );
-  assert( pCache->bPurgeable || pCache->nMin==0 );
-  assert( pCache->bPurgeable==0 || pCache->nMin==10 );
-  assert( pCache->nMin==0 || pCache->bPurgeable );
-  assert( pCache->nHash>0 );
-  pcache1EnterMutex(pCache->pGroup);
-
-  /* Step 1: Search the hash table for an existing entry. */
-  pPage = pCache->apHash[iKey % pCache->nHash];
-  while( pPage && pPage->iKey!=iKey ){ pPage = pPage->pNext; }
-
-  /* Step 2: Abort if no existing page is found and createFlag is 0 */
-  if( pPage ){
-    if( !pPage->isPinned ) pcache1PinPage(pPage);
-  }else if( createFlag ){
-    /* Steps 3, 4, and 5 implemented by this subroutine */
-    pPage = pcache1FetchStage2(pCache, iKey, createFlag);
-  }
-  assert( pPage==0 || pCache->iMaxKey>=iKey );
-  pcache1LeaveMutex(pCache->pGroup);
-  return (sqlite3_pcache_page*)pPage;
-}
-
-
-/*
-** Implementation of the sqlite3_pcache.xUnpin method.
-**
-** Mark a page as unpinned (eligible for asynchronous recycling).
-*/
-static void pcache1Unpin(
-  sqlite3_pcache *p, 
-  sqlite3_pcache_page *pPg, 
-  int reuseUnlikely
-){
-  PCache1 *pCache = (PCache1 *)p;
-  PgHdr1 *pPage = (PgHdr1 *)pPg;
-  PGroup *pGroup = pCache->pGroup;
- 
-  assert( pPage->pCache==pCache );
-  pcache1EnterMutex(pGroup);
-
-  /* It is an error to call this function if the page is already 
-  ** part of the PGroup LRU list.
-  */
-  assert( pPage->pLruPrev==0 && pPage->pLruNext==0 );
-  assert( pGroup->pLruHead!=pPage && pGroup->pLruTail!=pPage );
-  assert( pPage->isPinned==1 );
-
-  if( reuseUnlikely || pGroup->nCurrentPage>pGroup->nMaxPage ){
-    pcache1RemoveFromHash(pPage);
-    pcache1FreePage(pPage);
-  }else{
-    /* Add the page to the PGroup LRU list. */
-    if( pGroup->pLruHead ){
-      pGroup->pLruHead->pLruPrev = pPage;
-      pPage->pLruNext = pGroup->pLruHead;
-      pGroup->pLruHead = pPage;
-    }else{
-      pGroup->pLruTail = pPage;
-      pGroup->pLruHead = pPage;
-    }
-    pCache->nRecyclable++;
-    pPage->isPinned = 0;
-  }
-
-  pcache1LeaveMutex(pCache->pGroup);
-}
-
-/*
-** Implementation of the sqlite3_pcache.xRekey method. 
-*/
-static void pcache1Rekey(
-  sqlite3_pcache *p,
-  sqlite3_pcache_page *pPg,
-  unsigned int iOld,
-  unsigned int iNew
-){
-  PCache1 *pCache = (PCache1 *)p;
-  PgHdr1 *pPage = (PgHdr1 *)pPg;
-  PgHdr1 **pp;
-  unsigned int h; 
-  assert( pPage->iKey==iOld );
-  assert( pPage->pCache==pCache );
-
-  pcache1EnterMutex(pCache->pGroup);
-
-  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;
-  if( iNew>pCache->iMaxKey ){
-    pCache->iMaxKey = iNew;
-  }
-
-  pcache1LeaveMutex(pCache->pGroup);
-}
-
-/*
-** 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(pCache->pGroup);
-  if( iLimit<=pCache->iMaxKey ){
-    pcache1TruncateUnsafe(pCache, iLimit);
-    pCache->iMaxKey = iLimit-1;
-  }
-  pcache1LeaveMutex(pCache->pGroup);
-}
-
-/*
-** Implementation of the sqlite3_pcache.xDestroy method. 
-**
-** Destroy a cache allocated using pcache1Create().
-*/
-static void pcache1Destroy(sqlite3_pcache *p){
-  PCache1 *pCache = (PCache1 *)p;
-  PGroup *pGroup = pCache->pGroup;
-  assert( pCache->bPurgeable || (pCache->nMax==0 && pCache->nMin==0) );
-  pcache1EnterMutex(pGroup);
-  pcache1TruncateUnsafe(pCache, 0);
-  assert( pGroup->nMaxPage >= pCache->nMax );
-  pGroup->nMaxPage -= pCache->nMax;
-  assert( pGroup->nMinPage >= pCache->nMin );
-  pGroup->nMinPage -= pCache->nMin;
-  pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage;
-  pcache1EnforceMaxPage(pGroup);
-  pcache1LeaveMutex(pGroup);
-  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 const sqlite3_pcache_methods2 defaultMethods = {
-    1,                       /* iVersion */
-    0,                       /* pArg */
-    pcache1Init,             /* xInit */
-    pcache1Shutdown,         /* xShutdown */
-    pcache1Create,           /* xCreate */
-    pcache1Cachesize,        /* xCachesize */
-    pcache1Pagecount,        /* xPagecount */
-    pcache1Fetch,            /* xFetch */
-    pcache1Unpin,            /* xUnpin */
-    pcache1Rekey,            /* xRekey */
-    pcache1Truncate,         /* xTruncate */
-    pcache1Destroy,          /* xDestroy */
-    pcache1Shrink            /* xShrink */
-  };
-  sqlite3_config(SQLITE_CONFIG_PCACHE2, &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;
-  assert( sqlite3_mutex_notheld(pcache1.grp.mutex) );
-  assert( sqlite3_mutex_notheld(pcache1.mutex) );
-  if( pcache1.pStart==0 ){
-    PgHdr1 *p;
-    pcache1EnterMutex(&pcache1.grp);
-    while( (nReq<0 || nFree<nReq) && ((p=pcache1.grp.pLruTail)!=0) ){
-      nFree += pcache1MemSize(p->page.pBuf);
-#ifdef SQLITE_PCACHE_SEPARATE_HEADER
-      nFree += sqlite3MemSize(p);
-#endif
-      assert( p->isPinned==0 );
-      pcache1PinPage(p);
-      pcache1RemoveFromHash(p);
-      pcache1FreePage(p);
-    }
-    pcache1LeaveMutex(&pcache1.grp);
-  }
-  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.grp.pLruHead; p; p=p->pLruNext){
-    assert( p->isPinned==0 );
-    nRecyclable++;
-  }
-  *pnCurrent = pcache1.grp.nCurrentPage;
-  *pnMax = (int)pcache1.grp.nMaxPage;
-  *pnMin = (int)pcache1.grp.nMinPage;
-  *pnRecyclable = nRecyclable;
-}
-#endif