/*
** 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;
}
}
/*
** 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;
}
/*
** 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;
}
/*
** 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;
}
/*
** 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(pPg);
PgHdr1 **pp;
unsigned int h;
assert( pPage->iKey==iOld );
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;
if( iNew>pCache->iMaxKey ){
pCache->iMaxKey = iNew;
}
pcache1LeaveMutex();
}
/*
** 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(pPg);
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.xPagecount method.
*/
static int pcache1Pagecount(sqlite3_pcache *p){
int n;
pcache1EnterMutex();
n = ((PCache1 *)p)->nPage;
pcache1LeaveMutex();
return n;
}
/*
** 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.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.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 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(p);
pcache1PinPage(p);
pcache1RemoveFromHash(p);
pcache1FreePage(p);
}
pcache1LeaveMutex();
}
return nFree;
}
/*
** Allocate a new page object initially associated with cache pCache.
*/
static PgHdr1 *pcache1AllocPage(PCache1 *pCache, int benignMalloc){
PgHdr1 *p = 0;
void *pPg;
assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
if( pCache->pFree || (pCache->nPage==0 && pcache1InitBulk(pCache)) ){
p = pCache->pFree;
pCache->pFree = p->pNext;
p->pNext = 0;
}else{
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
/* The group mutex must be released before pcache1Alloc() is called. This
** is because it might call sqlite3_release_memory(), which assumes that
** this mutex is not held. */
assert( pcache1.separateCache==0 );
assert( pCache->pGroup==&pcache1.grp );
pcache1LeaveMutex(pCache->pGroup);
#endif
if( benignMalloc ){ sqlite3BeginBenignMalloc(); }
#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(pCache->szAlloc);
p = (PgHdr1 *)&((u8 *)pPg)[pCache->szPage];
#endif
if( benignMalloc ){ sqlite3EndBenignMalloc(); }
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
pcache1EnterMutex(pCache->pGroup);
#endif
if( pPg==0 ) return 0;
p->page.pBuf = pPg;
p->page.pExtra = &p[1];
p->isBulkLocal = 0;
p->isAnchor = 0;
}
if( pCache->bPurgeable ){
pCache->pGroup->nCurrentPage++;
}
return p;
}
/*
** 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;
}
/*
** 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);
}
/*
** Free an allocated buffer obtained from sqlite3PageMalloc().
*/
void sqlite3PageFree(void *p){
pcache1EnterMutex();
pcache1Free(p);
pcache1LeaveMutex();
}
/*
** 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.
**
** 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, the cache is marked as purgeable 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;
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 && pCache->bPurgeable && (
nPinned>=(pcache1.nMaxPage+pCache->nMin-pcache1.nMinPage)
|| nPinned>=(pCache->nMax)
)){
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>=pCache->nMax-1 || 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;
*(void **)(PGHDR1_TO_PAGE(pPage)) = 0;
pCache->nPage++;
pPage->iKey = iKey;
pPage->pNext = pCache->apHash[h];
pPage->pCache = pCache;
pPage->pLruPrev = 0;
pPage->pLruNext = 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);
}
