Chih-Hung Hsieh | cc6e635 | 2020-10-26 19:08:21 -0700 | [diff] [blame] | 1 | /* |
| 2 | ** 2010 April 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 implements an example of a simple VFS implementation that |
| 14 | ** omits complex features often not required or not possible on embedded |
| 15 | ** platforms. Code is included to buffer writes to the journal file, |
| 16 | ** which can be a significant performance improvement on some embedded |
| 17 | ** platforms. |
| 18 | ** |
| 19 | ** OVERVIEW |
| 20 | ** |
| 21 | ** The code in this file implements a minimal SQLite VFS that can be |
| 22 | ** used on Linux and other posix-like operating systems. The following |
| 23 | ** system calls are used: |
| 24 | ** |
| 25 | ** File-system: access(), unlink(), getcwd() |
| 26 | ** File IO: open(), read(), write(), fsync(), close(), fstat() |
| 27 | ** Other: sleep(), usleep(), time() |
| 28 | ** |
| 29 | ** The following VFS features are omitted: |
| 30 | ** |
| 31 | ** 1. File locking. The user must ensure that there is at most one |
| 32 | ** connection to each database when using this VFS. Multiple |
| 33 | ** connections to a single shared-cache count as a single connection |
| 34 | ** for the purposes of the previous statement. |
| 35 | ** |
| 36 | ** 2. The loading of dynamic extensions (shared libraries). |
| 37 | ** |
| 38 | ** 3. Temporary files. The user must configure SQLite to use in-memory |
| 39 | ** temp files when using this VFS. The easiest way to do this is to |
| 40 | ** compile with: |
| 41 | ** |
| 42 | ** -DSQLITE_TEMP_STORE=3 |
| 43 | ** |
| 44 | ** 4. File truncation. As of version 3.6.24, SQLite may run without |
| 45 | ** a working xTruncate() call, providing the user does not configure |
| 46 | ** SQLite to use "journal_mode=truncate", or use both |
| 47 | ** "journal_mode=persist" and ATTACHed databases. |
| 48 | ** |
| 49 | ** It is assumed that the system uses UNIX-like path-names. Specifically, |
| 50 | ** that '/' characters are used to separate path components and that |
| 51 | ** a path-name is a relative path unless it begins with a '/'. And that |
| 52 | ** no UTF-8 encoded paths are greater than 512 bytes in length. |
| 53 | ** |
| 54 | ** JOURNAL WRITE-BUFFERING |
| 55 | ** |
| 56 | ** To commit a transaction to the database, SQLite first writes rollback |
| 57 | ** information into the journal file. This usually consists of 4 steps: |
| 58 | ** |
| 59 | ** 1. The rollback information is sequentially written into the journal |
| 60 | ** file, starting at the start of the file. |
| 61 | ** 2. The journal file is synced to disk. |
| 62 | ** 3. A modification is made to the first few bytes of the journal file. |
| 63 | ** 4. The journal file is synced to disk again. |
| 64 | ** |
| 65 | ** Most of the data is written in step 1 using a series of calls to the |
| 66 | ** VFS xWrite() method. The buffers passed to the xWrite() calls are of |
| 67 | ** various sizes. For example, as of version 3.6.24, when committing a |
| 68 | ** transaction that modifies 3 pages of a database file that uses 4096 |
| 69 | ** byte pages residing on a media with 512 byte sectors, SQLite makes |
| 70 | ** eleven calls to the xWrite() method to create the rollback journal, |
| 71 | ** as follows: |
| 72 | ** |
| 73 | ** Write offset | Bytes written |
| 74 | ** ---------------------------- |
| 75 | ** 0 512 |
| 76 | ** 512 4 |
| 77 | ** 516 4096 |
| 78 | ** 4612 4 |
| 79 | ** 4616 4 |
| 80 | ** 4620 4096 |
| 81 | ** 8716 4 |
| 82 | ** 8720 4 |
| 83 | ** 8724 4096 |
| 84 | ** 12820 4 |
| 85 | ** ++++++++++++SYNC+++++++++++ |
| 86 | ** 0 12 |
| 87 | ** ++++++++++++SYNC+++++++++++ |
| 88 | ** |
| 89 | ** On many operating systems, this is an efficient way to write to a file. |
| 90 | ** However, on some embedded systems that do not cache writes in OS |
| 91 | ** buffers it is much more efficient to write data in blocks that are |
| 92 | ** an integer multiple of the sector-size in size and aligned at the |
| 93 | ** start of a sector. |
| 94 | ** |
| 95 | ** To work around this, the code in this file allocates a fixed size |
| 96 | ** buffer of SQLITE_DEMOVFS_BUFFERSZ using sqlite3_malloc() whenever a |
| 97 | ** journal file is opened. It uses the buffer to coalesce sequential |
| 98 | ** writes into aligned SQLITE_DEMOVFS_BUFFERSZ blocks. When SQLite |
| 99 | ** invokes the xSync() method to sync the contents of the file to disk, |
| 100 | ** all accumulated data is written out, even if it does not constitute |
| 101 | ** a complete block. This means the actual IO to create the rollback |
| 102 | ** journal for the example transaction above is this: |
| 103 | ** |
| 104 | ** Write offset | Bytes written |
| 105 | ** ---------------------------- |
| 106 | ** 0 8192 |
| 107 | ** 8192 4632 |
| 108 | ** ++++++++++++SYNC+++++++++++ |
| 109 | ** 0 12 |
| 110 | ** ++++++++++++SYNC+++++++++++ |
| 111 | ** |
| 112 | ** Much more efficient if the underlying OS is not caching write |
| 113 | ** operations. |
| 114 | */ |
| 115 | |
| 116 | #if !defined(SQLITE_TEST) || SQLITE_OS_UNIX |
| 117 | |
| 118 | #include "sqlite3.h" |
| 119 | |
| 120 | #include <assert.h> |
| 121 | #include <string.h> |
| 122 | #include <sys/types.h> |
| 123 | #include <sys/stat.h> |
| 124 | #include <sys/file.h> |
| 125 | #include <sys/param.h> |
| 126 | #include <unistd.h> |
| 127 | #include <time.h> |
| 128 | #include <errno.h> |
| 129 | #include <fcntl.h> |
| 130 | |
| 131 | /* |
| 132 | ** Size of the write buffer used by journal files in bytes. |
| 133 | */ |
| 134 | #ifndef SQLITE_DEMOVFS_BUFFERSZ |
| 135 | # define SQLITE_DEMOVFS_BUFFERSZ 8192 |
| 136 | #endif |
| 137 | |
| 138 | /* |
| 139 | ** The maximum pathname length supported by this VFS. |
| 140 | */ |
| 141 | #define MAXPATHNAME 512 |
| 142 | |
| 143 | /* |
| 144 | ** When using this VFS, the sqlite3_file* handles that SQLite uses are |
| 145 | ** actually pointers to instances of type DemoFile. |
| 146 | */ |
| 147 | typedef struct DemoFile DemoFile; |
| 148 | struct DemoFile { |
| 149 | sqlite3_file base; /* Base class. Must be first. */ |
| 150 | int fd; /* File descriptor */ |
| 151 | |
| 152 | char *aBuffer; /* Pointer to malloc'd buffer */ |
| 153 | int nBuffer; /* Valid bytes of data in zBuffer */ |
| 154 | sqlite3_int64 iBufferOfst; /* Offset in file of zBuffer[0] */ |
| 155 | }; |
| 156 | |
| 157 | /* |
| 158 | ** Write directly to the file passed as the first argument. Even if the |
| 159 | ** file has a write-buffer (DemoFile.aBuffer), ignore it. |
| 160 | */ |
| 161 | static int demoDirectWrite( |
| 162 | DemoFile *p, /* File handle */ |
| 163 | const void *zBuf, /* Buffer containing data to write */ |
| 164 | int iAmt, /* Size of data to write in bytes */ |
| 165 | sqlite_int64 iOfst /* File offset to write to */ |
| 166 | ){ |
| 167 | off_t ofst; /* Return value from lseek() */ |
| 168 | size_t nWrite; /* Return value from write() */ |
| 169 | |
| 170 | ofst = lseek(p->fd, iOfst, SEEK_SET); |
| 171 | if( ofst!=iOfst ){ |
| 172 | return SQLITE_IOERR_WRITE; |
| 173 | } |
| 174 | |
| 175 | nWrite = write(p->fd, zBuf, iAmt); |
| 176 | if( nWrite!=iAmt ){ |
| 177 | return SQLITE_IOERR_WRITE; |
| 178 | } |
| 179 | |
| 180 | return SQLITE_OK; |
| 181 | } |
| 182 | |
| 183 | /* |
| 184 | ** Flush the contents of the DemoFile.aBuffer buffer to disk. This is a |
| 185 | ** no-op if this particular file does not have a buffer (i.e. it is not |
| 186 | ** a journal file) or if the buffer is currently empty. |
| 187 | */ |
| 188 | static int demoFlushBuffer(DemoFile *p){ |
| 189 | int rc = SQLITE_OK; |
| 190 | if( p->nBuffer ){ |
| 191 | rc = demoDirectWrite(p, p->aBuffer, p->nBuffer, p->iBufferOfst); |
| 192 | p->nBuffer = 0; |
| 193 | } |
| 194 | return rc; |
| 195 | } |
| 196 | |
| 197 | /* |
| 198 | ** Close a file. |
| 199 | */ |
| 200 | static int demoClose(sqlite3_file *pFile){ |
| 201 | int rc; |
| 202 | DemoFile *p = (DemoFile*)pFile; |
| 203 | rc = demoFlushBuffer(p); |
| 204 | sqlite3_free(p->aBuffer); |
| 205 | close(p->fd); |
| 206 | return rc; |
| 207 | } |
| 208 | |
| 209 | /* |
| 210 | ** Read data from a file. |
| 211 | */ |
| 212 | static int demoRead( |
| 213 | sqlite3_file *pFile, |
| 214 | void *zBuf, |
| 215 | int iAmt, |
| 216 | sqlite_int64 iOfst |
| 217 | ){ |
| 218 | DemoFile *p = (DemoFile*)pFile; |
| 219 | off_t ofst; /* Return value from lseek() */ |
| 220 | int nRead; /* Return value from read() */ |
| 221 | int rc; /* Return code from demoFlushBuffer() */ |
| 222 | |
| 223 | /* Flush any data in the write buffer to disk in case this operation |
| 224 | ** is trying to read data the file-region currently cached in the buffer. |
| 225 | ** It would be possible to detect this case and possibly save an |
| 226 | ** unnecessary write here, but in practice SQLite will rarely read from |
| 227 | ** a journal file when there is data cached in the write-buffer. |
| 228 | */ |
| 229 | rc = demoFlushBuffer(p); |
| 230 | if( rc!=SQLITE_OK ){ |
| 231 | return rc; |
| 232 | } |
| 233 | |
| 234 | ofst = lseek(p->fd, iOfst, SEEK_SET); |
| 235 | if( ofst!=iOfst ){ |
| 236 | return SQLITE_IOERR_READ; |
| 237 | } |
| 238 | nRead = read(p->fd, zBuf, iAmt); |
| 239 | |
| 240 | if( nRead==iAmt ){ |
| 241 | return SQLITE_OK; |
| 242 | }else if( nRead>=0 ){ |
| 243 | return SQLITE_IOERR_SHORT_READ; |
| 244 | } |
| 245 | |
| 246 | return SQLITE_IOERR_READ; |
| 247 | } |
| 248 | |
| 249 | /* |
| 250 | ** Write data to a crash-file. |
| 251 | */ |
| 252 | static int demoWrite( |
| 253 | sqlite3_file *pFile, |
| 254 | const void *zBuf, |
| 255 | int iAmt, |
| 256 | sqlite_int64 iOfst |
| 257 | ){ |
| 258 | DemoFile *p = (DemoFile*)pFile; |
| 259 | |
| 260 | if( p->aBuffer ){ |
| 261 | char *z = (char *)zBuf; /* Pointer to remaining data to write */ |
| 262 | int n = iAmt; /* Number of bytes at z */ |
| 263 | sqlite3_int64 i = iOfst; /* File offset to write to */ |
| 264 | |
| 265 | while( n>0 ){ |
| 266 | int nCopy; /* Number of bytes to copy into buffer */ |
| 267 | |
| 268 | /* If the buffer is full, or if this data is not being written directly |
| 269 | ** following the data already buffered, flush the buffer. Flushing |
| 270 | ** the buffer is a no-op if it is empty. |
| 271 | */ |
| 272 | if( p->nBuffer==SQLITE_DEMOVFS_BUFFERSZ || p->iBufferOfst+p->nBuffer!=i ){ |
| 273 | int rc = demoFlushBuffer(p); |
| 274 | if( rc!=SQLITE_OK ){ |
| 275 | return rc; |
| 276 | } |
| 277 | } |
| 278 | assert( p->nBuffer==0 || p->iBufferOfst+p->nBuffer==i ); |
| 279 | p->iBufferOfst = i - p->nBuffer; |
| 280 | |
| 281 | /* Copy as much data as possible into the buffer. */ |
| 282 | nCopy = SQLITE_DEMOVFS_BUFFERSZ - p->nBuffer; |
| 283 | if( nCopy>n ){ |
| 284 | nCopy = n; |
| 285 | } |
| 286 | memcpy(&p->aBuffer[p->nBuffer], z, nCopy); |
| 287 | p->nBuffer += nCopy; |
| 288 | |
| 289 | n -= nCopy; |
| 290 | i += nCopy; |
| 291 | z += nCopy; |
| 292 | } |
| 293 | }else{ |
| 294 | return demoDirectWrite(p, zBuf, iAmt, iOfst); |
| 295 | } |
| 296 | |
| 297 | return SQLITE_OK; |
| 298 | } |
| 299 | |
| 300 | /* |
| 301 | ** Truncate a file. This is a no-op for this VFS (see header comments at |
| 302 | ** the top of the file). |
| 303 | */ |
| 304 | static int demoTruncate(sqlite3_file *pFile, sqlite_int64 size){ |
| 305 | #if 0 |
| 306 | if( ftruncate(((DemoFile *)pFile)->fd, size) ) return SQLITE_IOERR_TRUNCATE; |
| 307 | #endif |
| 308 | return SQLITE_OK; |
| 309 | } |
| 310 | |
| 311 | /* |
| 312 | ** Sync the contents of the file to the persistent media. |
| 313 | */ |
| 314 | static int demoSync(sqlite3_file *pFile, int flags){ |
| 315 | DemoFile *p = (DemoFile*)pFile; |
| 316 | int rc; |
| 317 | |
| 318 | rc = demoFlushBuffer(p); |
| 319 | if( rc!=SQLITE_OK ){ |
| 320 | return rc; |
| 321 | } |
| 322 | |
| 323 | rc = fsync(p->fd); |
| 324 | return (rc==0 ? SQLITE_OK : SQLITE_IOERR_FSYNC); |
| 325 | } |
| 326 | |
| 327 | /* |
| 328 | ** Write the size of the file in bytes to *pSize. |
| 329 | */ |
| 330 | static int demoFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){ |
| 331 | DemoFile *p = (DemoFile*)pFile; |
| 332 | int rc; /* Return code from fstat() call */ |
| 333 | struct stat sStat; /* Output of fstat() call */ |
| 334 | |
| 335 | /* Flush the contents of the buffer to disk. As with the flush in the |
| 336 | ** demoRead() method, it would be possible to avoid this and save a write |
| 337 | ** here and there. But in practice this comes up so infrequently it is |
| 338 | ** not worth the trouble. |
| 339 | */ |
| 340 | rc = demoFlushBuffer(p); |
| 341 | if( rc!=SQLITE_OK ){ |
| 342 | return rc; |
| 343 | } |
| 344 | |
| 345 | rc = fstat(p->fd, &sStat); |
| 346 | if( rc!=0 ) return SQLITE_IOERR_FSTAT; |
| 347 | *pSize = sStat.st_size; |
| 348 | return SQLITE_OK; |
| 349 | } |
| 350 | |
| 351 | /* |
| 352 | ** Locking functions. The xLock() and xUnlock() methods are both no-ops. |
| 353 | ** The xCheckReservedLock() always indicates that no other process holds |
| 354 | ** a reserved lock on the database file. This ensures that if a hot-journal |
| 355 | ** file is found in the file-system it is rolled back. |
| 356 | */ |
| 357 | static int demoLock(sqlite3_file *pFile, int eLock){ |
| 358 | return SQLITE_OK; |
| 359 | } |
| 360 | static int demoUnlock(sqlite3_file *pFile, int eLock){ |
| 361 | return SQLITE_OK; |
| 362 | } |
| 363 | static int demoCheckReservedLock(sqlite3_file *pFile, int *pResOut){ |
| 364 | *pResOut = 0; |
| 365 | return SQLITE_OK; |
| 366 | } |
| 367 | |
| 368 | /* |
| 369 | ** No xFileControl() verbs are implemented by this VFS. |
| 370 | */ |
| 371 | static int demoFileControl(sqlite3_file *pFile, int op, void *pArg){ |
| 372 | return SQLITE_OK; |
| 373 | } |
| 374 | |
| 375 | /* |
| 376 | ** The xSectorSize() and xDeviceCharacteristics() methods. These two |
| 377 | ** may return special values allowing SQLite to optimize file-system |
| 378 | ** access to some extent. But it is also safe to simply return 0. |
| 379 | */ |
| 380 | static int demoSectorSize(sqlite3_file *pFile){ |
| 381 | return 0; |
| 382 | } |
| 383 | static int demoDeviceCharacteristics(sqlite3_file *pFile){ |
| 384 | return 0; |
| 385 | } |
| 386 | |
| 387 | /* |
| 388 | ** Open a file handle. |
| 389 | */ |
| 390 | static int demoOpen( |
| 391 | sqlite3_vfs *pVfs, /* VFS */ |
| 392 | const char *zName, /* File to open, or 0 for a temp file */ |
| 393 | sqlite3_file *pFile, /* Pointer to DemoFile struct to populate */ |
| 394 | int flags, /* Input SQLITE_OPEN_XXX flags */ |
| 395 | int *pOutFlags /* Output SQLITE_OPEN_XXX flags (or NULL) */ |
| 396 | ){ |
| 397 | static const sqlite3_io_methods demoio = { |
| 398 | 1, /* iVersion */ |
| 399 | demoClose, /* xClose */ |
| 400 | demoRead, /* xRead */ |
| 401 | demoWrite, /* xWrite */ |
| 402 | demoTruncate, /* xTruncate */ |
| 403 | demoSync, /* xSync */ |
| 404 | demoFileSize, /* xFileSize */ |
| 405 | demoLock, /* xLock */ |
| 406 | demoUnlock, /* xUnlock */ |
| 407 | demoCheckReservedLock, /* xCheckReservedLock */ |
| 408 | demoFileControl, /* xFileControl */ |
| 409 | demoSectorSize, /* xSectorSize */ |
| 410 | demoDeviceCharacteristics /* xDeviceCharacteristics */ |
| 411 | }; |
| 412 | |
| 413 | DemoFile *p = (DemoFile*)pFile; /* Populate this structure */ |
| 414 | int oflags = 0; /* flags to pass to open() call */ |
| 415 | char *aBuf = 0; |
| 416 | |
| 417 | if( zName==0 ){ |
| 418 | return SQLITE_IOERR; |
| 419 | } |
| 420 | |
| 421 | if( flags&SQLITE_OPEN_MAIN_JOURNAL ){ |
| 422 | aBuf = (char *)sqlite3_malloc(SQLITE_DEMOVFS_BUFFERSZ); |
| 423 | if( !aBuf ){ |
| 424 | return SQLITE_NOMEM; |
| 425 | } |
| 426 | } |
| 427 | |
| 428 | if( flags&SQLITE_OPEN_EXCLUSIVE ) oflags |= O_EXCL; |
| 429 | if( flags&SQLITE_OPEN_CREATE ) oflags |= O_CREAT; |
| 430 | if( flags&SQLITE_OPEN_READONLY ) oflags |= O_RDONLY; |
| 431 | if( flags&SQLITE_OPEN_READWRITE ) oflags |= O_RDWR; |
| 432 | |
| 433 | memset(p, 0, sizeof(DemoFile)); |
| 434 | p->fd = open(zName, oflags, 0600); |
| 435 | if( p->fd<0 ){ |
| 436 | sqlite3_free(aBuf); |
| 437 | return SQLITE_CANTOPEN; |
| 438 | } |
| 439 | p->aBuffer = aBuf; |
| 440 | |
| 441 | if( pOutFlags ){ |
| 442 | *pOutFlags = flags; |
| 443 | } |
| 444 | p->base.pMethods = &demoio; |
| 445 | return SQLITE_OK; |
| 446 | } |
| 447 | |
| 448 | /* |
| 449 | ** Delete the file identified by argument zPath. If the dirSync parameter |
| 450 | ** is non-zero, then ensure the file-system modification to delete the |
| 451 | ** file has been synced to disk before returning. |
| 452 | */ |
| 453 | static int demoDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){ |
| 454 | int rc; /* Return code */ |
| 455 | |
| 456 | rc = unlink(zPath); |
| 457 | if( rc!=0 && errno==ENOENT ) return SQLITE_OK; |
| 458 | |
| 459 | if( rc==0 && dirSync ){ |
| 460 | int dfd; /* File descriptor open on directory */ |
| 461 | int i; /* Iterator variable */ |
| 462 | char zDir[MAXPATHNAME+1]; /* Name of directory containing file zPath */ |
| 463 | |
| 464 | /* Figure out the directory name from the path of the file deleted. */ |
| 465 | sqlite3_snprintf(MAXPATHNAME, zDir, "%s", zPath); |
| 466 | zDir[MAXPATHNAME] = '\0'; |
| 467 | for(i=strlen(zDir); i>1 && zDir[i]!='/'; i++); |
| 468 | zDir[i] = '\0'; |
| 469 | |
| 470 | /* Open a file-descriptor on the directory. Sync. Close. */ |
| 471 | dfd = open(zDir, O_RDONLY, 0); |
| 472 | if( dfd<0 ){ |
| 473 | rc = -1; |
| 474 | }else{ |
| 475 | rc = fsync(dfd); |
| 476 | close(dfd); |
| 477 | } |
| 478 | } |
| 479 | return (rc==0 ? SQLITE_OK : SQLITE_IOERR_DELETE); |
| 480 | } |
| 481 | |
| 482 | #ifndef F_OK |
| 483 | # define F_OK 0 |
| 484 | #endif |
| 485 | #ifndef R_OK |
| 486 | # define R_OK 4 |
| 487 | #endif |
| 488 | #ifndef W_OK |
| 489 | # define W_OK 2 |
| 490 | #endif |
| 491 | |
| 492 | /* |
| 493 | ** Query the file-system to see if the named file exists, is readable or |
| 494 | ** is both readable and writable. |
| 495 | */ |
| 496 | static int demoAccess( |
| 497 | sqlite3_vfs *pVfs, |
| 498 | const char *zPath, |
| 499 | int flags, |
| 500 | int *pResOut |
| 501 | ){ |
| 502 | int rc; /* access() return code */ |
| 503 | int eAccess = F_OK; /* Second argument to access() */ |
| 504 | |
| 505 | assert( flags==SQLITE_ACCESS_EXISTS /* access(zPath, F_OK) */ |
| 506 | || flags==SQLITE_ACCESS_READ /* access(zPath, R_OK) */ |
| 507 | || flags==SQLITE_ACCESS_READWRITE /* access(zPath, R_OK|W_OK) */ |
| 508 | ); |
| 509 | |
| 510 | if( flags==SQLITE_ACCESS_READWRITE ) eAccess = R_OK|W_OK; |
| 511 | if( flags==SQLITE_ACCESS_READ ) eAccess = R_OK; |
| 512 | |
| 513 | rc = access(zPath, eAccess); |
| 514 | *pResOut = (rc==0); |
| 515 | return SQLITE_OK; |
| 516 | } |
| 517 | |
| 518 | /* |
| 519 | ** Argument zPath points to a nul-terminated string containing a file path. |
| 520 | ** If zPath is an absolute path, then it is copied as is into the output |
| 521 | ** buffer. Otherwise, if it is a relative path, then the equivalent full |
| 522 | ** path is written to the output buffer. |
| 523 | ** |
| 524 | ** This function assumes that paths are UNIX style. Specifically, that: |
| 525 | ** |
| 526 | ** 1. Path components are separated by a '/'. and |
| 527 | ** 2. Full paths begin with a '/' character. |
| 528 | */ |
| 529 | static int demoFullPathname( |
| 530 | sqlite3_vfs *pVfs, /* VFS */ |
| 531 | const char *zPath, /* Input path (possibly a relative path) */ |
| 532 | int nPathOut, /* Size of output buffer in bytes */ |
| 533 | char *zPathOut /* Pointer to output buffer */ |
| 534 | ){ |
| 535 | sqlite3_snprintf(nPathOut, zPathOut, "%s", zPath); |
| 536 | zPathOut[nPathOut-1] = '\0'; |
| 537 | |
| 538 | return SQLITE_OK; |
| 539 | } |
| 540 | |
| 541 | /* |
| 542 | ** The following four VFS methods: |
| 543 | ** |
| 544 | ** xDlOpen |
| 545 | ** xDlError |
| 546 | ** xDlSym |
| 547 | ** xDlClose |
| 548 | ** |
| 549 | ** are supposed to implement the functionality needed by SQLite to load |
| 550 | ** extensions compiled as shared objects. This simple VFS does not support |
| 551 | ** this functionality, so the following functions are no-ops. |
| 552 | */ |
| 553 | static void *demoDlOpen(sqlite3_vfs *pVfs, const char *zPath){ |
| 554 | return 0; |
| 555 | } |
| 556 | static void demoDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){ |
| 557 | sqlite3_snprintf(nByte, zErrMsg, "Loadable extensions are not supported"); |
| 558 | zErrMsg[nByte-1] = '\0'; |
| 559 | } |
| 560 | static void (*demoDlSym(sqlite3_vfs *pVfs, void *pH, const char *z))(void){ |
| 561 | return 0; |
| 562 | } |
| 563 | static void demoDlClose(sqlite3_vfs *pVfs, void *pHandle){ |
| 564 | return; |
| 565 | } |
| 566 | |
| 567 | /* |
| 568 | ** Parameter zByte points to a buffer nByte bytes in size. Populate this |
| 569 | ** buffer with pseudo-random data. |
| 570 | */ |
| 571 | static int demoRandomness(sqlite3_vfs *pVfs, int nByte, char *zByte){ |
| 572 | return SQLITE_OK; |
| 573 | } |
| 574 | |
| 575 | /* |
| 576 | ** Sleep for at least nMicro microseconds. Return the (approximate) number |
| 577 | ** of microseconds slept for. |
| 578 | */ |
| 579 | static int demoSleep(sqlite3_vfs *pVfs, int nMicro){ |
| 580 | sleep(nMicro / 1000000); |
| 581 | usleep(nMicro % 1000000); |
| 582 | return nMicro; |
| 583 | } |
| 584 | |
| 585 | /* |
| 586 | ** Set *pTime to the current UTC time expressed as a Julian day. Return |
| 587 | ** SQLITE_OK if successful, or an error code otherwise. |
| 588 | ** |
| 589 | ** http://en.wikipedia.org/wiki/Julian_day |
| 590 | ** |
| 591 | ** This implementation is not very good. The current time is rounded to |
| 592 | ** an integer number of seconds. Also, assuming time_t is a signed 32-bit |
| 593 | ** value, it will stop working some time in the year 2038 AD (the so-called |
| 594 | ** "year 2038" problem that afflicts systems that store time this way). |
| 595 | */ |
| 596 | static int demoCurrentTime(sqlite3_vfs *pVfs, double *pTime){ |
| 597 | time_t t = time(0); |
| 598 | *pTime = t/86400.0 + 2440587.5; |
| 599 | return SQLITE_OK; |
| 600 | } |
| 601 | |
| 602 | /* |
| 603 | ** This function returns a pointer to the VFS implemented in this file. |
| 604 | ** To make the VFS available to SQLite: |
| 605 | ** |
| 606 | ** sqlite3_vfs_register(sqlite3_demovfs(), 0); |
| 607 | */ |
| 608 | sqlite3_vfs *sqlite3_demovfs(void){ |
| 609 | static sqlite3_vfs demovfs = { |
| 610 | 1, /* iVersion */ |
| 611 | sizeof(DemoFile), /* szOsFile */ |
| 612 | MAXPATHNAME, /* mxPathname */ |
| 613 | 0, /* pNext */ |
| 614 | "demo", /* zName */ |
| 615 | 0, /* pAppData */ |
| 616 | demoOpen, /* xOpen */ |
| 617 | demoDelete, /* xDelete */ |
| 618 | demoAccess, /* xAccess */ |
| 619 | demoFullPathname, /* xFullPathname */ |
| 620 | demoDlOpen, /* xDlOpen */ |
| 621 | demoDlError, /* xDlError */ |
| 622 | demoDlSym, /* xDlSym */ |
| 623 | demoDlClose, /* xDlClose */ |
| 624 | demoRandomness, /* xRandomness */ |
| 625 | demoSleep, /* xSleep */ |
| 626 | demoCurrentTime, /* xCurrentTime */ |
| 627 | }; |
| 628 | return &demovfs; |
| 629 | } |
| 630 | |
| 631 | #endif /* !defined(SQLITE_TEST) || SQLITE_OS_UNIX */ |
| 632 | |
| 633 | |
| 634 | #ifdef SQLITE_TEST |
| 635 | |
| 636 | #if defined(INCLUDE_SQLITE_TCL_H) |
| 637 | # include "sqlite_tcl.h" |
| 638 | #else |
| 639 | # include "tcl.h" |
| 640 | # ifndef SQLITE_TCLAPI |
| 641 | # define SQLITE_TCLAPI |
| 642 | # endif |
| 643 | #endif |
| 644 | |
| 645 | #if SQLITE_OS_UNIX |
| 646 | static int SQLITE_TCLAPI register_demovfs( |
| 647 | ClientData clientData, /* Pointer to sqlite3_enable_XXX function */ |
| 648 | Tcl_Interp *interp, /* The TCL interpreter that invoked this command */ |
| 649 | int objc, /* Number of arguments */ |
| 650 | Tcl_Obj *CONST objv[] /* Command arguments */ |
| 651 | ){ |
| 652 | sqlite3_vfs_register(sqlite3_demovfs(), 1); |
| 653 | return TCL_OK; |
| 654 | } |
| 655 | static int SQLITE_TCLAPI unregister_demovfs( |
| 656 | ClientData clientData, /* Pointer to sqlite3_enable_XXX function */ |
| 657 | Tcl_Interp *interp, /* The TCL interpreter that invoked this command */ |
| 658 | int objc, /* Number of arguments */ |
| 659 | Tcl_Obj *CONST objv[] /* Command arguments */ |
| 660 | ){ |
| 661 | sqlite3_vfs_unregister(sqlite3_demovfs()); |
| 662 | return TCL_OK; |
| 663 | } |
| 664 | |
| 665 | /* |
| 666 | ** Register commands with the TCL interpreter. |
| 667 | */ |
| 668 | int Sqlitetest_demovfs_Init(Tcl_Interp *interp){ |
| 669 | Tcl_CreateObjCommand(interp, "register_demovfs", register_demovfs, 0, 0); |
| 670 | Tcl_CreateObjCommand(interp, "unregister_demovfs", unregister_demovfs, 0, 0); |
| 671 | return TCL_OK; |
| 672 | } |
| 673 | |
| 674 | #else |
| 675 | int Sqlitetest_demovfs_Init(Tcl_Interp *interp){ return TCL_OK; } |
| 676 | #endif |
| 677 | |
| 678 | #endif /* SQLITE_TEST */ |
| 679 | |
| 680 | // Register sqlite3_demovfs |
| 681 | int sqlite3_os_init() |
| 682 | { |
| 683 | sqlite3_vfs_register(sqlite3_demovfs(), 0); |
| 684 | return 0; |
| 685 | } |
| 686 | |
| 687 | int sqlite3_os_end() |
| 688 | { |
| 689 | return 0; |
| 690 | } |