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| 1 /* | |
| 2 ** 2008 October 7 | |
| 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 ** | |
| 13 ** This file contains code use to implement an in-memory rollback journal. | |
| 14 ** The in-memory rollback journal is used to journal transactions for | |
| 15 ** ":memory:" databases and when the journal_mode=MEMORY pragma is used. | |
| 16 */ | |
| 17 #include "sqliteInt.h" | |
| 18 | |
| 19 /* Forward references to internal structures */ | |
| 20 typedef struct MemJournal MemJournal; | |
| 21 typedef struct FilePoint FilePoint; | |
| 22 typedef struct FileChunk FileChunk; | |
| 23 | |
| 24 /* Space to hold the rollback journal is allocated in increments of | |
| 25 ** this many bytes. | |
| 26 ** | |
| 27 ** The size chosen is a little less than a power of two. That way, | |
| 28 ** the FileChunk object will have a size that almost exactly fills | |
| 29 ** a power-of-two allocation. This minimizes wasted space in power-of-two | |
| 30 ** memory allocators. | |
| 31 */ | |
| 32 #define JOURNAL_CHUNKSIZE ((int)(1024-sizeof(FileChunk*))) | |
| 33 | |
| 34 /* | |
| 35 ** The rollback journal is composed of a linked list of these structures. | |
| 36 */ | |
| 37 struct FileChunk { | |
| 38 FileChunk *pNext; /* Next chunk in the journal */ | |
| 39 u8 zChunk[JOURNAL_CHUNKSIZE]; /* Content of this chunk */ | |
| 40 }; | |
| 41 | |
| 42 /* | |
| 43 ** An instance of this object serves as a cursor into the rollback journal. | |
| 44 ** The cursor can be either for reading or writing. | |
| 45 */ | |
| 46 struct FilePoint { | |
| 47 sqlite3_int64 iOffset; /* Offset from the beginning of the file */ | |
| 48 FileChunk *pChunk; /* Specific chunk into which cursor points */ | |
| 49 }; | |
| 50 | |
| 51 /* | |
| 52 ** This subclass is a subclass of sqlite3_file. Each open memory-journal | |
| 53 ** is an instance of this class. | |
| 54 */ | |
| 55 struct MemJournal { | |
| 56 sqlite3_io_methods *pMethod; /* Parent class. MUST BE FIRST */ | |
| 57 FileChunk *pFirst; /* Head of in-memory chunk-list */ | |
| 58 FilePoint endpoint; /* Pointer to the end of the file */ | |
| 59 FilePoint readpoint; /* Pointer to the end of the last xRead() */ | |
| 60 }; | |
| 61 | |
| 62 /* | |
| 63 ** Read data from the in-memory journal file. This is the implementation | |
| 64 ** of the sqlite3_vfs.xRead method. | |
| 65 */ | |
| 66 static int memjrnlRead( | |
| 67 sqlite3_file *pJfd, /* The journal file from which to read */ | |
| 68 void *zBuf, /* Put the results here */ | |
| 69 int iAmt, /* Number of bytes to read */ | |
| 70 sqlite_int64 iOfst /* Begin reading at this offset */ | |
| 71 ){ | |
| 72 MemJournal *p = (MemJournal *)pJfd; | |
| 73 u8 *zOut = zBuf; | |
| 74 int nRead = iAmt; | |
| 75 int iChunkOffset; | |
| 76 FileChunk *pChunk; | |
| 77 | |
| 78 /* SQLite never tries to read past the end of a rollback journal file */ | |
| 79 assert( iOfst+iAmt<=p->endpoint.iOffset ); | |
| 80 | |
| 81 if( p->readpoint.iOffset!=iOfst || iOfst==0 ){ | |
| 82 sqlite3_int64 iOff = 0; | |
| 83 for(pChunk=p->pFirst; | |
| 84 ALWAYS(pChunk) && (iOff+JOURNAL_CHUNKSIZE)<=iOfst; | |
| 85 pChunk=pChunk->pNext | |
| 86 ){ | |
| 87 iOff += JOURNAL_CHUNKSIZE; | |
| 88 } | |
| 89 }else{ | |
| 90 pChunk = p->readpoint.pChunk; | |
| 91 } | |
| 92 | |
| 93 iChunkOffset = (int)(iOfst%JOURNAL_CHUNKSIZE); | |
| 94 do { | |
| 95 int iSpace = JOURNAL_CHUNKSIZE - iChunkOffset; | |
| 96 int nCopy = MIN(nRead, (JOURNAL_CHUNKSIZE - iChunkOffset)); | |
| 97 memcpy(zOut, &pChunk->zChunk[iChunkOffset], nCopy); | |
| 98 zOut += nCopy; | |
| 99 nRead -= iSpace; | |
| 100 iChunkOffset = 0; | |
| 101 } while( nRead>=0 && (pChunk=pChunk->pNext)!=0 && nRead>0 ); | |
| 102 p->readpoint.iOffset = iOfst+iAmt; | |
| 103 p->readpoint.pChunk = pChunk; | |
| 104 | |
| 105 return SQLITE_OK; | |
| 106 } | |
| 107 | |
| 108 /* | |
| 109 ** Write data to the file. | |
| 110 */ | |
| 111 static int memjrnlWrite( | |
| 112 sqlite3_file *pJfd, /* The journal file into which to write */ | |
| 113 const void *zBuf, /* Take data to be written from here */ | |
| 114 int iAmt, /* Number of bytes to write */ | |
| 115 sqlite_int64 iOfst /* Begin writing at this offset into the file */ | |
| 116 ){ | |
| 117 MemJournal *p = (MemJournal *)pJfd; | |
| 118 int nWrite = iAmt; | |
| 119 u8 *zWrite = (u8 *)zBuf; | |
| 120 | |
| 121 /* An in-memory journal file should only ever be appended to. Random | |
| 122 ** access writes are not required by sqlite. | |
| 123 */ | |
| 124 assert( iOfst==p->endpoint.iOffset ); | |
| 125 UNUSED_PARAMETER(iOfst); | |
| 126 | |
| 127 while( nWrite>0 ){ | |
| 128 FileChunk *pChunk = p->endpoint.pChunk; | |
| 129 int iChunkOffset = (int)(p->endpoint.iOffset%JOURNAL_CHUNKSIZE); | |
| 130 int iSpace = MIN(nWrite, JOURNAL_CHUNKSIZE - iChunkOffset); | |
| 131 | |
| 132 if( iChunkOffset==0 ){ | |
| 133 /* New chunk is required to extend the file. */ | |
| 134 FileChunk *pNew = sqlite3_malloc(sizeof(FileChunk)); | |
| 135 if( !pNew ){ | |
| 136 return SQLITE_IOERR_NOMEM; | |
| 137 } | |
| 138 pNew->pNext = 0; | |
| 139 if( pChunk ){ | |
| 140 assert( p->pFirst ); | |
| 141 pChunk->pNext = pNew; | |
| 142 }else{ | |
| 143 assert( !p->pFirst ); | |
| 144 p->pFirst = pNew; | |
| 145 } | |
| 146 p->endpoint.pChunk = pNew; | |
| 147 } | |
| 148 | |
| 149 memcpy(&p->endpoint.pChunk->zChunk[iChunkOffset], zWrite, iSpace); | |
| 150 zWrite += iSpace; | |
| 151 nWrite -= iSpace; | |
| 152 p->endpoint.iOffset += iSpace; | |
| 153 } | |
| 154 | |
| 155 return SQLITE_OK; | |
| 156 } | |
| 157 | |
| 158 /* | |
| 159 ** Truncate the file. | |
| 160 */ | |
| 161 static int memjrnlTruncate(sqlite3_file *pJfd, sqlite_int64 size){ | |
| 162 MemJournal *p = (MemJournal *)pJfd; | |
| 163 FileChunk *pChunk; | |
| 164 assert(size==0); | |
| 165 UNUSED_PARAMETER(size); | |
| 166 pChunk = p->pFirst; | |
| 167 while( pChunk ){ | |
| 168 FileChunk *pTmp = pChunk; | |
| 169 pChunk = pChunk->pNext; | |
| 170 sqlite3_free(pTmp); | |
| 171 } | |
| 172 sqlite3MemJournalOpen(pJfd); | |
| 173 return SQLITE_OK; | |
| 174 } | |
| 175 | |
| 176 /* | |
| 177 ** Close the file. | |
| 178 */ | |
| 179 static int memjrnlClose(sqlite3_file *pJfd){ | |
| 180 memjrnlTruncate(pJfd, 0); | |
| 181 return SQLITE_OK; | |
| 182 } | |
| 183 | |
| 184 | |
| 185 /* | |
| 186 ** Sync the file. | |
| 187 ** | |
| 188 ** Syncing an in-memory journal is a no-op. And, in fact, this routine | |
| 189 ** is never called in a working implementation. This implementation | |
| 190 ** exists purely as a contingency, in case some malfunction in some other | |
| 191 ** part of SQLite causes Sync to be called by mistake. | |
| 192 */ | |
| 193 static int memjrnlSync(sqlite3_file *NotUsed, int NotUsed2){ | |
| 194 UNUSED_PARAMETER2(NotUsed, NotUsed2); | |
| 195 return SQLITE_OK; | |
| 196 } | |
| 197 | |
| 198 /* | |
| 199 ** Query the size of the file in bytes. | |
| 200 */ | |
| 201 static int memjrnlFileSize(sqlite3_file *pJfd, sqlite_int64 *pSize){ | |
| 202 MemJournal *p = (MemJournal *)pJfd; | |
| 203 *pSize = (sqlite_int64) p->endpoint.iOffset; | |
| 204 return SQLITE_OK; | |
| 205 } | |
| 206 | |
| 207 /* | |
| 208 ** Table of methods for MemJournal sqlite3_file object. | |
| 209 */ | |
| 210 static const struct sqlite3_io_methods MemJournalMethods = { | |
| 211 1, /* iVersion */ | |
| 212 memjrnlClose, /* xClose */ | |
| 213 memjrnlRead, /* xRead */ | |
| 214 memjrnlWrite, /* xWrite */ | |
| 215 memjrnlTruncate, /* xTruncate */ | |
| 216 memjrnlSync, /* xSync */ | |
| 217 memjrnlFileSize, /* xFileSize */ | |
| 218 0, /* xLock */ | |
| 219 0, /* xUnlock */ | |
| 220 0, /* xCheckReservedLock */ | |
| 221 0, /* xFileControl */ | |
| 222 0, /* xSectorSize */ | |
| 223 0, /* xDeviceCharacteristics */ | |
| 224 0, /* xShmMap */ | |
| 225 0, /* xShmLock */ | |
| 226 0, /* xShmBarrier */ | |
| 227 0, /* xShmUnmap */ | |
| 228 0, /* xFetch */ | |
| 229 0 /* xUnfetch */ | |
| 230 }; | |
| 231 | |
| 232 /* | |
| 233 ** Open a journal file. | |
| 234 */ | |
| 235 void sqlite3MemJournalOpen(sqlite3_file *pJfd){ | |
| 236 MemJournal *p = (MemJournal *)pJfd; | |
| 237 assert( EIGHT_BYTE_ALIGNMENT(p) ); | |
| 238 memset(p, 0, sqlite3MemJournalSize()); | |
| 239 p->pMethod = (sqlite3_io_methods*)&MemJournalMethods; | |
| 240 } | |
| 241 | |
| 242 /* | |
| 243 ** Return true if the file-handle passed as an argument is | |
| 244 ** an in-memory journal | |
| 245 */ | |
| 246 int sqlite3IsMemJournal(sqlite3_file *pJfd){ | |
| 247 return pJfd->pMethods==&MemJournalMethods; | |
| 248 } | |
| 249 | |
| 250 /* | |
| 251 ** Return the number of bytes required to store a MemJournal file descriptor. | |
| 252 */ | |
| 253 int sqlite3MemJournalSize(void){ | |
| 254 return sizeof(MemJournal); | |
| 255 } | |
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Chromium Code Reviews
Issue 2846743003:
[sql] Remove SQLite 3.10.2 reference directory. (Closed)
