1 /* 2 ** 2008 August 05 3 ** 4 ** The author disclaims copyright to this source code. In place of 5 ** a legal notice, here is a blessing: 6 ** 7 ** May you do good and not evil. 8 ** May you find forgiveness for yourself and forgive others. 9 ** May you share freely, never taking more than you give. 10 ** 11 ************************************************************************* 12 ** This header file defines the interface that the sqlite page cache 13 ** subsystem. 14 */ 15 16 #ifndef _PCACHE_H_ 17 18 typedef struct PgHdr PgHdr; 19 typedef struct PCache PCache; 20 21 /* 22 ** Every page in the cache is controlled by an instance of the following 23 ** structure. 24 */ 25 struct PgHdr { 26 sqlite3_pcache_page *pPage; /* Pcache object page handle */ 27 void *pData; /* Page data */ 28 void *pExtra; /* Extra content */ 29 PgHdr *pDirty; /* Transient list of dirty pages */ 30 Pager *pPager; /* The pager this page is part of */ 31 Pgno pgno; /* Page number for this page */ 32 #ifdef SQLITE_CHECK_PAGES 33 u32 pageHash; /* Hash of page content */ 34 #endif 35 u16 flags; /* PGHDR flags defined below */ 36 37 /********************************************************************** 38 ** Elements above are public. All that follows is private to pcache.c 39 ** and should not be accessed by other modules. 40 */ 41 i16 nRef; /* Number of users of this page */ 42 PCache *pCache; /* Cache that owns this page */ 43 44 PgHdr *pDirtyNext; /* Next element in list of dirty pages */ 45 PgHdr *pDirtyPrev; /* Previous element in list of dirty pages */ 46 }; 47 48 /* Bit values for PgHdr.flags */ 49 #define PGHDR_DIRTY 0x002 /* Page has changed */ 50 #define PGHDR_NEED_SYNC 0x004 /* Fsync the rollback journal before 51 ** writing this page to the database */ 52 #define PGHDR_NEED_READ 0x008 /* Content is unread */ 53 #define PGHDR_REUSE_UNLIKELY 0x010 /* A hint that reuse is unlikely */ 54 #define PGHDR_DONT_WRITE 0x020 /* Do not write content to disk */ 55 56 #define PGHDR_MMAP 0x040 /* This is an mmap page object */ 57 58 /* Initialize and shutdown the page cache subsystem */ 59 int sqlite3PcacheInitialize(void); 60 void sqlite3PcacheShutdown(void); 61 62 /* Page cache buffer management: 63 ** These routines implement SQLITE_CONFIG_PAGECACHE. 64 */ 65 void sqlite3PCacheBufferSetup(void *, int sz, int n); 66 67 /* Create a new pager cache. 68 ** Under memory stress, invoke xStress to try to make pages clean. 69 ** Only clean and unpinned pages can be reclaimed. 70 */ 71 void sqlite3PcacheOpen( 72 int szPage, /* Size of every page */ 73 int szExtra, /* Extra space associated with each page */ 74 int bPurgeable, /* True if pages are on backing store */ 75 int (*xStress)(void*, PgHdr*), /* Call to try to make pages clean */ 76 void *pStress, /* Argument to xStress */ 77 PCache *pToInit /* Preallocated space for the PCache */ 78 ); 79 80 /* Modify the page-size after the cache has been created. */ 81 void sqlite3PcacheSetPageSize(PCache *, int); 82 83 /* Return the size in bytes of a PCache object. Used to preallocate 84 ** storage space. 85 */ 86 int sqlite3PcacheSize(void); 87 88 /* One release per successful fetch. Page is pinned until released. 89 ** Reference counted. 90 */ 91 int sqlite3PcacheFetch(PCache*, Pgno, int createFlag, PgHdr**); 92 void sqlite3PcacheRelease(PgHdr*); 93 94 void sqlite3PcacheDrop(PgHdr*); /* Remove page from cache */ 95 void sqlite3PcacheMakeDirty(PgHdr*); /* Make sure page is marked dirty */ 96 void sqlite3PcacheMakeClean(PgHdr*); /* Mark a single page as clean */ 97 void sqlite3PcacheCleanAll(PCache*); /* Mark all dirty list pages as clean */ 98 99 /* Change a page number. Used by incr-vacuum. */ 100 void sqlite3PcacheMove(PgHdr*, Pgno); 101 102 /* Remove all pages with pgno>x. Reset the cache if x==0 */ 103 void sqlite3PcacheTruncate(PCache*, Pgno x); 104 105 /* Get a list of all dirty pages in the cache, sorted by page number */ 106 PgHdr *sqlite3PcacheDirtyList(PCache*); 107 108 /* Reset and close the cache object */ 109 void sqlite3PcacheClose(PCache*); 110 111 /* Clear flags from pages of the page cache */ 112 void sqlite3PcacheClearSyncFlags(PCache *); 113 114 /* Discard the contents of the cache */ 115 void sqlite3PcacheClear(PCache*); 116 117 /* Return the total number of outstanding page references */ 118 int sqlite3PcacheRefCount(PCache*); 119 120 /* Increment the reference count of an existing page */ 121 void sqlite3PcacheRef(PgHdr*); 122 123 int sqlite3PcachePageRefcount(PgHdr*); 124 125 /* Return the total number of pages stored in the cache */ 126 int sqlite3PcachePagecount(PCache*); 127 128 #if defined(SQLITE_CHECK_PAGES) || defined(SQLITE_DEBUG) 129 /* Iterate through all dirty pages currently stored in the cache. This 130 ** interface is only available if SQLITE_CHECK_PAGES is defined when the 131 ** library is built. 132 */ 133 void sqlite3PcacheIterateDirty(PCache *pCache, void (*xIter)(PgHdr *)); 134 #endif 135 136 /* Set and get the suggested cache-size for the specified pager-cache. 137 ** 138 ** If no global maximum is configured, then the system attempts to limit 139 ** the total number of pages cached by purgeable pager-caches to the sum 140 ** of the suggested cache-sizes. 141 */ 142 void sqlite3PcacheSetCachesize(PCache *, int); 143 #ifdef SQLITE_TEST 144 int sqlite3PcacheGetCachesize(PCache *); 145 #endif 146 147 /* Free up as much memory as possible from the page cache */ 148 void sqlite3PcacheShrink(PCache*); 149 150 #ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT 151 /* Try to return memory used by the pcache module to the main memory heap */ 152 int sqlite3PcacheReleaseMemory(int); 153 #endif 154 155 #ifdef SQLITE_TEST 156 void sqlite3PcacheStats(int*,int*,int*,int*); 157 #endif 158 159 void sqlite3PCacheSetDefault(void); 160 161 #endif /* _PCACHE_H_ */ 162