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