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 ** @(#) $Id: pcache.h,v 1.17 2009/01/16 15:21:06 danielk1977 Exp $ 16 */ 17 18 #ifndef _PCACHE_H_ 19 20 typedef struct PgHdr PgHdr; 21 typedef struct PCache PCache; 22 23 /* 24 ** Every page in the cache is controlled by an instance of the following 25 ** structure. 26 */ 27 struct PgHdr { 28 void *pData; /* Content of this page */ 29 void *pExtra; /* Extra content */ 30 PgHdr *pDirty; /* Transient list of dirty pages */ 31 Pgno pgno; /* Page number for this page */ 32 Pager *pPager; /* The pager this page is part of */ 33 #ifdef SQLITE_CHECK_PAGES 34 u32 pageHash; /* Hash of page content */ 35 #endif 36 u16 flags; /* PGHDR flags defined below */ 37 38 /********************************************************************** 39 ** Elements above are public. All that follows is private to pcache.c 40 ** and should not be accessed by other modules. 41 */ 42 i16 nRef; /* Number of users of this page */ 43 PCache *pCache; /* Cache that owns this page */ 44 45 PgHdr *pDirtyNext; /* Next element in list of dirty pages */ 46 PgHdr *pDirtyPrev; /* Previous element in list of dirty pages */ 47 }; 48 49 /* Bit values for PgHdr.flags */ 50 #define PGHDR_DIRTY 0x002 /* Page has changed */ 51 #define PGHDR_NEED_SYNC 0x004 /* Fsync the rollback journal before 52 ** writing this page to the database */ 53 #define PGHDR_NEED_READ 0x008 /* Content is unread */ 54 #define PGHDR_REUSE_UNLIKELY 0x010 /* A hint that reuse is unlikely */ 55 #define PGHDR_DONT_WRITE 0x020 /* Do not write content to disk */ 56 57 /* Initialize and shutdown the page cache subsystem */ 58 int sqlite3PcacheInitialize(void); 59 void sqlite3PcacheShutdown(void); 60 61 /* Page cache buffer management: 62 ** These routines implement SQLITE_CONFIG_PAGECACHE. 63 */ 64 void sqlite3PCacheBufferSetup(void *, int sz, int n); 65 66 /* Create a new pager cache. 67 ** Under memory stress, invoke xStress to try to make pages clean. 68 ** Only clean and unpinned pages can be reclaimed. 69 */ 70 void sqlite3PcacheOpen( 71 int szPage, /* Size of every page */ 72 int szExtra, /* Extra space associated with each page */ 73 int bPurgeable, /* True if pages are on backing store */ 74 int (*xStress)(void*, PgHdr*), /* Call to try to make pages clean */ 75 void *pStress, /* Argument to xStress */ 76 PCache *pToInit /* Preallocated space for the PCache */ 77 ); 78 79 /* Modify the page-size after the cache has been created. */ 80 void sqlite3PcacheSetPageSize(PCache *, int); 81 82 /* Return the size in bytes of a PCache object. Used to preallocate 83 ** storage space. 84 */ 85 int sqlite3PcacheSize(void); 86 87 /* One release per successful fetch. Page is pinned until released. 88 ** Reference counted. 89 */ 90 int sqlite3PcacheFetch(PCache*, Pgno, int createFlag, PgHdr**); 91 void sqlite3PcacheRelease(PgHdr*); 92 93 void sqlite3PcacheDrop(PgHdr*); /* Remove page from cache */ 94 void sqlite3PcacheMakeDirty(PgHdr*); /* Make sure page is marked dirty */ 95 void sqlite3PcacheMakeClean(PgHdr*); /* Mark a single page as clean */ 96 void sqlite3PcacheCleanAll(PCache*); /* Mark all dirty list pages as clean */ 97 98 /* Change a page number. Used by incr-vacuum. */ 99 void sqlite3PcacheMove(PgHdr*, Pgno); 100 101 /* Remove all pages with pgno>x. Reset the cache if x==0 */ 102 void sqlite3PcacheTruncate(PCache*, Pgno x); 103 104 /* Get a list of all dirty pages in the cache, sorted by page number */ 105 PgHdr *sqlite3PcacheDirtyList(PCache*); 106 107 /* Reset and close the cache object */ 108 void sqlite3PcacheClose(PCache*); 109 110 /* Clear flags from pages of the page cache */ 111 void sqlite3PcacheClearSyncFlags(PCache *); 112 113 /* Discard the contents of the cache */ 114 void sqlite3PcacheClear(PCache*); 115 116 /* Return the total number of outstanding page references */ 117 int sqlite3PcacheRefCount(PCache*); 118 119 /* Increment the reference count of an existing page */ 120 void sqlite3PcacheRef(PgHdr*); 121 122 int sqlite3PcachePageRefcount(PgHdr*); 123 124 /* Return the total number of pages stored in the cache */ 125 int sqlite3PcachePagecount(PCache*); 126 127 #ifdef SQLITE_CHECK_PAGES 128 /* Iterate through all dirty pages currently stored in the cache. This 129 ** interface is only available if SQLITE_CHECK_PAGES is defined when the 130 ** library is built. 131 */ 132 void sqlite3PcacheIterateDirty(PCache *pCache, void (*xIter)(PgHdr *)); 133 #endif 134 135 /* Set and get the suggested cache-size for the specified pager-cache. 136 ** 137 ** If no global maximum is configured, then the system attempts to limit 138 ** the total number of pages cached by purgeable pager-caches to the sum 139 ** of the suggested cache-sizes. 140 */ 141 void sqlite3PcacheSetCachesize(PCache *, int); 142 #ifdef SQLITE_TEST 143 int sqlite3PcacheGetCachesize(PCache *); 144 #endif 145 146 #ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT 147 /* Try to return memory used by the pcache module to the main memory heap */ 148 int sqlite3PcacheReleaseMemory(int); 149 #endif 150 151 #ifdef SQLITE_TEST 152 void sqlite3PcacheStats(int*,int*,int*,int*); 153 #endif 154 155 void sqlite3PCacheSetDefault(void); 156 157 #endif /* _PCACHE_H_ */ 158