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Unified Diff: third_party/sqlite/sqlite-src-3080704/src/pcache.c

Issue 949043002: Add //third_party/sqlite to dirs_to_snapshot, remove net_sql.patch (Closed) Base URL: git@github.com:domokit/mojo.git@master
Patch Set: Created 5 years, 10 months ago
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Index: third_party/sqlite/sqlite-src-3080704/src/pcache.c
diff --git a/third_party/sqlite/sqlite-src-3080704/src/pcache.c b/third_party/sqlite/sqlite-src-3080704/src/pcache.c
new file mode 100644
index 0000000000000000000000000000000000000000..191a9d00f41ded328642e71fa5da12138f38bc35
--- /dev/null
+++ b/third_party/sqlite/sqlite-src-3080704/src/pcache.c
@@ -0,0 +1,666 @@
+/*
+** 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.
+*/
+#include "sqliteInt.h"
+
+/*
+** A complete page cache is an instance of this structure.
+*/
+struct PCache {
+ PgHdr *pDirty, *pDirtyTail; /* List of dirty pages in LRU order */
+ PgHdr *pSynced; /* Last synced page in dirty page list */
+ int nRef; /* Number of referenced pages */
+ int szCache; /* Configured cache size */
+ int szPage; /* Size of every page in this cache */
+ int szExtra; /* Size of extra space for each page */
+ u8 bPurgeable; /* True if pages are on backing store */
+ u8 eCreate; /* eCreate value for for xFetch() */
+ int (*xStress)(void*,PgHdr*); /* Call to try make a page clean */
+ void *pStress; /* Argument to xStress */
+ sqlite3_pcache *pCache; /* Pluggable cache module */
+ PgHdr *pPage1; /* Reference to page 1 */
+};
+
+/*
+** Some of the assert() macros in this code are too expensive to run
+** even during normal debugging. Use them only rarely on long-running
+** tests. Enable the expensive asserts using the
+** -DSQLITE_ENABLE_EXPENSIVE_ASSERT=1 compile-time option.
+*/
+#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
+# define expensive_assert(X) assert(X)
+#else
+# define expensive_assert(X)
+#endif
+
+/********************************** Linked List Management ********************/
+
+/* Allowed values for second argument to pcacheManageDirtyList() */
+#define PCACHE_DIRTYLIST_REMOVE 1 /* Remove pPage from dirty list */
+#define PCACHE_DIRTYLIST_ADD 2 /* Add pPage to the dirty list */
+#define PCACHE_DIRTYLIST_FRONT 3 /* Move pPage to the front of the list */
+
+/*
+** Manage pPage's participation on the dirty list. Bits of the addRemove
+** argument determines what operation to do. The 0x01 bit means first
+** remove pPage from the dirty list. The 0x02 means add pPage back to
+** the dirty list. Doing both moves pPage to the front of the dirty list.
+*/
+static void pcacheManageDirtyList(PgHdr *pPage, u8 addRemove){
+ PCache *p = pPage->pCache;
+
+ if( addRemove & PCACHE_DIRTYLIST_REMOVE ){
+ assert( pPage->pDirtyNext || pPage==p->pDirtyTail );
+ assert( pPage->pDirtyPrev || pPage==p->pDirty );
+
+ /* Update the PCache1.pSynced variable if necessary. */
+ if( p->pSynced==pPage ){
+ PgHdr *pSynced = pPage->pDirtyPrev;
+ while( pSynced && (pSynced->flags&PGHDR_NEED_SYNC) ){
+ pSynced = pSynced->pDirtyPrev;
+ }
+ p->pSynced = pSynced;
+ }
+
+ if( pPage->pDirtyNext ){
+ pPage->pDirtyNext->pDirtyPrev = pPage->pDirtyPrev;
+ }else{
+ assert( pPage==p->pDirtyTail );
+ p->pDirtyTail = pPage->pDirtyPrev;
+ }
+ if( pPage->pDirtyPrev ){
+ pPage->pDirtyPrev->pDirtyNext = pPage->pDirtyNext;
+ }else{
+ assert( pPage==p->pDirty );
+ p->pDirty = pPage->pDirtyNext;
+ if( p->pDirty==0 && p->bPurgeable ){
+ assert( p->eCreate==1 );
+ p->eCreate = 2;
+ }
+ }
+ pPage->pDirtyNext = 0;
+ pPage->pDirtyPrev = 0;
+ }
+ if( addRemove & PCACHE_DIRTYLIST_ADD ){
+ assert( pPage->pDirtyNext==0 && pPage->pDirtyPrev==0 && p->pDirty!=pPage );
+
+ pPage->pDirtyNext = p->pDirty;
+ if( pPage->pDirtyNext ){
+ assert( pPage->pDirtyNext->pDirtyPrev==0 );
+ pPage->pDirtyNext->pDirtyPrev = pPage;
+ }else{
+ p->pDirtyTail = pPage;
+ if( p->bPurgeable ){
+ assert( p->eCreate==2 );
+ p->eCreate = 1;
+ }
+ }
+ p->pDirty = pPage;
+ if( !p->pSynced && 0==(pPage->flags&PGHDR_NEED_SYNC) ){
+ p->pSynced = pPage;
+ }
+ }
+}
+
+/*
+** Wrapper around the pluggable caches xUnpin method. If the cache is
+** being used for an in-memory database, this function is a no-op.
+*/
+static void pcacheUnpin(PgHdr *p){
+ if( p->pCache->bPurgeable ){
+ if( p->pgno==1 ){
+ p->pCache->pPage1 = 0;
+ }
+ sqlite3GlobalConfig.pcache2.xUnpin(p->pCache->pCache, p->pPage, 0);
+ }
+}
+
+/*
+** Compute the number of pages of cache requested.
+*/
+static int numberOfCachePages(PCache *p){
+ if( p->szCache>=0 ){
+ return p->szCache;
+ }else{
+ return (int)((-1024*(i64)p->szCache)/(p->szPage+p->szExtra));
+ }
+}
+
+/*************************************************** General Interfaces ******
+**
+** Initialize and shutdown the page cache subsystem. Neither of these
+** functions are threadsafe.
+*/
+int sqlite3PcacheInitialize(void){
+ if( sqlite3GlobalConfig.pcache2.xInit==0 ){
+ /* IMPLEMENTATION-OF: R-26801-64137 If the xInit() method is NULL, then the
+ ** built-in default page cache is used instead of the application defined
+ ** page cache. */
+ sqlite3PCacheSetDefault();
+ }
+ return sqlite3GlobalConfig.pcache2.xInit(sqlite3GlobalConfig.pcache2.pArg);
+}
+void sqlite3PcacheShutdown(void){
+ if( sqlite3GlobalConfig.pcache2.xShutdown ){
+ /* IMPLEMENTATION-OF: R-26000-56589 The xShutdown() method may be NULL. */
+ sqlite3GlobalConfig.pcache2.xShutdown(sqlite3GlobalConfig.pcache2.pArg);
+ }
+}
+
+/*
+** Return the size in bytes of a PCache object.
+*/
+int sqlite3PcacheSize(void){ return sizeof(PCache); }
+
+/*
+** Create a new PCache object. Storage space to hold the object
+** has already been allocated and is passed in as the p pointer.
+** The caller discovers how much space needs to be allocated by
+** calling sqlite3PcacheSize().
+*/
+int sqlite3PcacheOpen(
+ int szPage, /* Size of every page */
+ int szExtra, /* Extra space associated with each page */
+ int bPurgeable, /* True if pages are on backing store */
+ int (*xStress)(void*,PgHdr*),/* Call to try to make pages clean */
+ void *pStress, /* Argument to xStress */
+ PCache *p /* Preallocated space for the PCache */
+){
+ memset(p, 0, sizeof(PCache));
+ p->szPage = 1;
+ p->szExtra = szExtra;
+ p->bPurgeable = bPurgeable;
+ p->eCreate = 2;
+ p->xStress = xStress;
+ p->pStress = pStress;
+ p->szCache = 100;
+ return sqlite3PcacheSetPageSize(p, szPage);
+}
+
+/*
+** Change the page size for PCache object. The caller must ensure that there
+** are no outstanding page references when this function is called.
+*/
+int sqlite3PcacheSetPageSize(PCache *pCache, int szPage){
+ assert( pCache->nRef==0 && pCache->pDirty==0 );
+ if( pCache->szPage ){
+ sqlite3_pcache *pNew;
+ pNew = sqlite3GlobalConfig.pcache2.xCreate(
+ szPage, pCache->szExtra + sizeof(PgHdr), pCache->bPurgeable
+ );
+ if( pNew==0 ) return SQLITE_NOMEM;
+ sqlite3GlobalConfig.pcache2.xCachesize(pNew, numberOfCachePages(pCache));
+ if( pCache->pCache ){
+ sqlite3GlobalConfig.pcache2.xDestroy(pCache->pCache);
+ }
+ pCache->pCache = pNew;
+ pCache->pPage1 = 0;
+ pCache->szPage = szPage;
+ }
+ return SQLITE_OK;
+}
+
+/*
+** Try to obtain a page from the cache.
+**
+** This routine returns a pointer to an sqlite3_pcache_page object if
+** such an object is already in cache, or if a new one is created.
+** This routine returns a NULL pointer if the object was not in cache
+** and could not be created.
+**
+** The createFlags should be 0 to check for existing pages and should
+** be 3 (not 1, but 3) to try to create a new page.
+**
+** If the createFlag is 0, then NULL is always returned if the page
+** is not already in the cache. If createFlag is 1, then a new page
+** is created only if that can be done without spilling dirty pages
+** and without exceeding the cache size limit.
+**
+** The caller needs to invoke sqlite3PcacheFetchFinish() to properly
+** initialize the sqlite3_pcache_page object and convert it into a
+** PgHdr object. The sqlite3PcacheFetch() and sqlite3PcacheFetchFinish()
+** routines are split this way for performance reasons. When separated
+** they can both (usually) operate without having to push values to
+** the stack on entry and pop them back off on exit, which saves a
+** lot of pushing and popping.
+*/
+sqlite3_pcache_page *sqlite3PcacheFetch(
+ PCache *pCache, /* Obtain the page from this cache */
+ Pgno pgno, /* Page number to obtain */
+ int createFlag /* If true, create page if it does not exist already */
+){
+ int eCreate;
+
+ assert( pCache!=0 );
+ assert( pCache->pCache!=0 );
+ assert( createFlag==3 || createFlag==0 );
+ assert( pgno>0 );
+
+ /* eCreate defines what to do if the page does not exist.
+ ** 0 Do not allocate a new page. (createFlag==0)
+ ** 1 Allocate a new page if doing so is inexpensive.
+ ** (createFlag==1 AND bPurgeable AND pDirty)
+ ** 2 Allocate a new page even it doing so is difficult.
+ ** (createFlag==1 AND !(bPurgeable AND pDirty)
+ */
+ eCreate = createFlag & pCache->eCreate;
+ assert( eCreate==0 || eCreate==1 || eCreate==2 );
+ assert( createFlag==0 || pCache->eCreate==eCreate );
+ assert( createFlag==0 || eCreate==1+(!pCache->bPurgeable||!pCache->pDirty) );
+ return sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, pgno, eCreate);
+}
+
+/*
+** If the sqlite3PcacheFetch() routine is unable to allocate a new
+** page because new clean pages are available for reuse and the cache
+** size limit has been reached, then this routine can be invoked to
+** try harder to allocate a page. This routine might invoke the stress
+** callback to spill dirty pages to the journal. It will then try to
+** allocate the new page and will only fail to allocate a new page on
+** an OOM error.
+**
+** This routine should be invoked only after sqlite3PcacheFetch() fails.
+*/
+int sqlite3PcacheFetchStress(
+ PCache *pCache, /* Obtain the page from this cache */
+ Pgno pgno, /* Page number to obtain */
+ sqlite3_pcache_page **ppPage /* Write result here */
+){
+ PgHdr *pPg;
+ if( pCache->eCreate==2 ) return 0;
+
+
+ /* Find a dirty page to write-out and recycle. First try to find a
+ ** page that does not require a journal-sync (one with PGHDR_NEED_SYNC
+ ** cleared), but if that is not possible settle for any other
+ ** unreferenced dirty page.
+ */
+ for(pPg=pCache->pSynced;
+ pPg && (pPg->nRef || (pPg->flags&PGHDR_NEED_SYNC));
+ pPg=pPg->pDirtyPrev
+ );
+ pCache->pSynced = pPg;
+ if( !pPg ){
+ for(pPg=pCache->pDirtyTail; pPg && pPg->nRef; pPg=pPg->pDirtyPrev);
+ }
+ if( pPg ){
+ int rc;
+#ifdef SQLITE_LOG_CACHE_SPILL
+ sqlite3_log(SQLITE_FULL,
+ "spill page %d making room for %d - cache used: %d/%d",
+ pPg->pgno, pgno,
+ sqlite3GlobalConfig.pcache.xPagecount(pCache->pCache),
+ numberOfCachePages(pCache));
+#endif
+ rc = pCache->xStress(pCache->pStress, pPg);
+ if( rc!=SQLITE_OK && rc!=SQLITE_BUSY ){
+ return rc;
+ }
+ }
+ *ppPage = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, pgno, 2);
+ return *ppPage==0 ? SQLITE_NOMEM : SQLITE_OK;
+}
+
+/*
+** This is a helper routine for sqlite3PcacheFetchFinish()
+**
+** In the uncommon case where the page being fetched has not been
+** initialized, this routine is invoked to do the initialization.
+** This routine is broken out into a separate function since it
+** requires extra stack manipulation that can be avoided in the common
+** case.
+*/
+static SQLITE_NOINLINE PgHdr *pcacheFetchFinishWithInit(
+ PCache *pCache, /* Obtain the page from this cache */
+ Pgno pgno, /* Page number obtained */
+ sqlite3_pcache_page *pPage /* Page obtained by prior PcacheFetch() call */
+){
+ PgHdr *pPgHdr;
+ assert( pPage!=0 );
+ pPgHdr = (PgHdr*)pPage->pExtra;
+ assert( pPgHdr->pPage==0 );
+ memset(pPgHdr, 0, sizeof(PgHdr));
+ pPgHdr->pPage = pPage;
+ pPgHdr->pData = pPage->pBuf;
+ pPgHdr->pExtra = (void *)&pPgHdr[1];
+ memset(pPgHdr->pExtra, 0, pCache->szExtra);
+ pPgHdr->pCache = pCache;
+ pPgHdr->pgno = pgno;
+ return sqlite3PcacheFetchFinish(pCache,pgno,pPage);
+}
+
+/*
+** This routine converts the sqlite3_pcache_page object returned by
+** sqlite3PcacheFetch() into an initialized PgHdr object. This routine
+** must be called after sqlite3PcacheFetch() in order to get a usable
+** result.
+*/
+PgHdr *sqlite3PcacheFetchFinish(
+ PCache *pCache, /* Obtain the page from this cache */
+ Pgno pgno, /* Page number obtained */
+ sqlite3_pcache_page *pPage /* Page obtained by prior PcacheFetch() call */
+){
+ PgHdr *pPgHdr;
+
+ if( pPage==0 ) return 0;
+ pPgHdr = (PgHdr *)pPage->pExtra;
+
+ if( !pPgHdr->pPage ){
+ return pcacheFetchFinishWithInit(pCache, pgno, pPage);
+ }
+ if( 0==pPgHdr->nRef ){
+ pCache->nRef++;
+ }
+ pPgHdr->nRef++;
+ if( pgno==1 ){
+ pCache->pPage1 = pPgHdr;
+ }
+ return pPgHdr;
+}
+
+/*
+** Decrement the reference count on a page. If the page is clean and the
+** reference count drops to 0, then it is made eligible for recycling.
+*/
+void SQLITE_NOINLINE sqlite3PcacheRelease(PgHdr *p){
+ assert( p->nRef>0 );
+ p->nRef--;
+ if( p->nRef==0 ){
+ p->pCache->nRef--;
+ if( (p->flags&PGHDR_DIRTY)==0 ){
+ pcacheUnpin(p);
+ }else if( p->pDirtyPrev!=0 ){
+ /* Move the page to the head of the dirty list. */
+ pcacheManageDirtyList(p, PCACHE_DIRTYLIST_FRONT);
+ }
+ }
+}
+
+/*
+** Increase the reference count of a supplied page by 1.
+*/
+void sqlite3PcacheRef(PgHdr *p){
+ assert(p->nRef>0);
+ p->nRef++;
+}
+
+/*
+** Drop a page from the cache. There must be exactly one reference to the
+** page. This function deletes that reference, so after it returns the
+** page pointed to by p is invalid.
+*/
+void sqlite3PcacheDrop(PgHdr *p){
+ assert( p->nRef==1 );
+ if( p->flags&PGHDR_DIRTY ){
+ pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE);
+ }
+ p->pCache->nRef--;
+ if( p->pgno==1 ){
+ p->pCache->pPage1 = 0;
+ }
+ sqlite3GlobalConfig.pcache2.xUnpin(p->pCache->pCache, p->pPage, 1);
+}
+
+/*
+** Make sure the page is marked as dirty. If it isn't dirty already,
+** make it so.
+*/
+void sqlite3PcacheMakeDirty(PgHdr *p){
+ p->flags &= ~PGHDR_DONT_WRITE;
+ assert( p->nRef>0 );
+ if( 0==(p->flags & PGHDR_DIRTY) ){
+ p->flags |= PGHDR_DIRTY;
+ pcacheManageDirtyList(p, PCACHE_DIRTYLIST_ADD);
+ }
+}
+
+/*
+** Make sure the page is marked as clean. If it isn't clean already,
+** make it so.
+*/
+void sqlite3PcacheMakeClean(PgHdr *p){
+ if( (p->flags & PGHDR_DIRTY) ){
+ pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE);
+ p->flags &= ~(PGHDR_DIRTY|PGHDR_NEED_SYNC);
+ if( p->nRef==0 ){
+ pcacheUnpin(p);
+ }
+ }
+}
+
+/*
+** Make every page in the cache clean.
+*/
+void sqlite3PcacheCleanAll(PCache *pCache){
+ PgHdr *p;
+ while( (p = pCache->pDirty)!=0 ){
+ sqlite3PcacheMakeClean(p);
+ }
+}
+
+/*
+** Clear the PGHDR_NEED_SYNC flag from all dirty pages.
+*/
+void sqlite3PcacheClearSyncFlags(PCache *pCache){
+ PgHdr *p;
+ for(p=pCache->pDirty; p; p=p->pDirtyNext){
+ p->flags &= ~PGHDR_NEED_SYNC;
+ }
+ pCache->pSynced = pCache->pDirtyTail;
+}
+
+/*
+** Change the page number of page p to newPgno.
+*/
+void sqlite3PcacheMove(PgHdr *p, Pgno newPgno){
+ PCache *pCache = p->pCache;
+ assert( p->nRef>0 );
+ assert( newPgno>0 );
+ sqlite3GlobalConfig.pcache2.xRekey(pCache->pCache, p->pPage, p->pgno,newPgno);
+ p->pgno = newPgno;
+ if( (p->flags&PGHDR_DIRTY) && (p->flags&PGHDR_NEED_SYNC) ){
+ pcacheManageDirtyList(p, PCACHE_DIRTYLIST_FRONT);
+ }
+}
+
+/*
+** Drop every cache entry whose page number is greater than "pgno". The
+** caller must ensure that there are no outstanding references to any pages
+** other than page 1 with a page number greater than pgno.
+**
+** If there is a reference to page 1 and the pgno parameter passed to this
+** function is 0, then the data area associated with page 1 is zeroed, but
+** the page object is not dropped.
+*/
+void sqlite3PcacheTruncate(PCache *pCache, Pgno pgno){
+ if( pCache->pCache ){
+ PgHdr *p;
+ PgHdr *pNext;
+ for(p=pCache->pDirty; p; p=pNext){
+ pNext = p->pDirtyNext;
+ /* This routine never gets call with a positive pgno except right
+ ** after sqlite3PcacheCleanAll(). So if there are dirty pages,
+ ** it must be that pgno==0.
+ */
+ assert( p->pgno>0 );
+ if( ALWAYS(p->pgno>pgno) ){
+ assert( p->flags&PGHDR_DIRTY );
+ sqlite3PcacheMakeClean(p);
+ }
+ }
+ if( pgno==0 && pCache->pPage1 ){
+ memset(pCache->pPage1->pData, 0, pCache->szPage);
+ pgno = 1;
+ }
+ sqlite3GlobalConfig.pcache2.xTruncate(pCache->pCache, pgno+1);
+ }
+}
+
+/*
+** Close a cache.
+*/
+void sqlite3PcacheClose(PCache *pCache){
+ assert( pCache->pCache!=0 );
+ sqlite3GlobalConfig.pcache2.xDestroy(pCache->pCache);
+}
+
+/*
+** Discard the contents of the cache.
+*/
+void sqlite3PcacheClear(PCache *pCache){
+ sqlite3PcacheTruncate(pCache, 0);
+}
+
+/*
+** Merge two lists of pages connected by pDirty and in pgno order.
+** Do not both fixing the pDirtyPrev pointers.
+*/
+static PgHdr *pcacheMergeDirtyList(PgHdr *pA, PgHdr *pB){
+ PgHdr result, *pTail;
+ pTail = &result;
+ while( pA && pB ){
+ if( pA->pgno<pB->pgno ){
+ pTail->pDirty = pA;
+ pTail = pA;
+ pA = pA->pDirty;
+ }else{
+ pTail->pDirty = pB;
+ pTail = pB;
+ pB = pB->pDirty;
+ }
+ }
+ if( pA ){
+ pTail->pDirty = pA;
+ }else if( pB ){
+ pTail->pDirty = pB;
+ }else{
+ pTail->pDirty = 0;
+ }
+ return result.pDirty;
+}
+
+/*
+** Sort the list of pages in accending order by pgno. Pages are
+** connected by pDirty pointers. The pDirtyPrev pointers are
+** corrupted by this sort.
+**
+** Since there cannot be more than 2^31 distinct pages in a database,
+** there cannot be more than 31 buckets required by the merge sorter.
+** One extra bucket is added to catch overflow in case something
+** ever changes to make the previous sentence incorrect.
+*/
+#define N_SORT_BUCKET 32
+static PgHdr *pcacheSortDirtyList(PgHdr *pIn){
+ PgHdr *a[N_SORT_BUCKET], *p;
+ int i;
+ memset(a, 0, sizeof(a));
+ while( pIn ){
+ p = pIn;
+ pIn = p->pDirty;
+ p->pDirty = 0;
+ for(i=0; ALWAYS(i<N_SORT_BUCKET-1); i++){
+ if( a[i]==0 ){
+ a[i] = p;
+ break;
+ }else{
+ p = pcacheMergeDirtyList(a[i], p);
+ a[i] = 0;
+ }
+ }
+ if( NEVER(i==N_SORT_BUCKET-1) ){
+ /* To get here, there need to be 2^(N_SORT_BUCKET) elements in
+ ** the input list. But that is impossible.
+ */
+ a[i] = pcacheMergeDirtyList(a[i], p);
+ }
+ }
+ p = a[0];
+ for(i=1; i<N_SORT_BUCKET; i++){
+ p = pcacheMergeDirtyList(p, a[i]);
+ }
+ return p;
+}
+
+/*
+** Return a list of all dirty pages in the cache, sorted by page number.
+*/
+PgHdr *sqlite3PcacheDirtyList(PCache *pCache){
+ PgHdr *p;
+ for(p=pCache->pDirty; p; p=p->pDirtyNext){
+ p->pDirty = p->pDirtyNext;
+ }
+ return pcacheSortDirtyList(pCache->pDirty);
+}
+
+/*
+** Return the total number of referenced pages held by the cache.
+*/
+int sqlite3PcacheRefCount(PCache *pCache){
+ return pCache->nRef;
+}
+
+/*
+** Return the number of references to the page supplied as an argument.
+*/
+int sqlite3PcachePageRefcount(PgHdr *p){
+ return p->nRef;
+}
+
+/*
+** Return the total number of pages in the cache.
+*/
+int sqlite3PcachePagecount(PCache *pCache){
+ assert( pCache->pCache!=0 );
+ return sqlite3GlobalConfig.pcache2.xPagecount(pCache->pCache);
+}
+
+#ifdef SQLITE_TEST
+/*
+** Get the suggested cache-size value.
+*/
+int sqlite3PcacheGetCachesize(PCache *pCache){
+ return numberOfCachePages(pCache);
+}
+#endif
+
+/*
+** Set the suggested cache-size value.
+*/
+void sqlite3PcacheSetCachesize(PCache *pCache, int mxPage){
+ assert( pCache->pCache!=0 );
+ pCache->szCache = mxPage;
+ sqlite3GlobalConfig.pcache2.xCachesize(pCache->pCache,
+ numberOfCachePages(pCache));
+}
+
+/*
+** Free up as much memory as possible from the page cache.
+*/
+void sqlite3PcacheShrink(PCache *pCache){
+ assert( pCache->pCache!=0 );
+ sqlite3GlobalConfig.pcache2.xShrink(pCache->pCache);
+}
+
+#if defined(SQLITE_CHECK_PAGES) || defined(SQLITE_DEBUG)
+/*
+** For all dirty pages currently in the cache, invoke the specified
+** callback. This is only used if the SQLITE_CHECK_PAGES macro is
+** defined.
+*/
+void sqlite3PcacheIterateDirty(PCache *pCache, void (*xIter)(PgHdr *)){
+ PgHdr *pDirty;
+ for(pDirty=pCache->pDirty; pDirty; pDirty=pDirty->pDirtyNext){
+ xIter(pDirty);
+ }
+}
+#endif
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