src/test_demovfs.c

   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     if( nRead<iAmt ){
 244       memset(&((char*)zBuf)[nRead], 0, iAmt-nRead);
 245     }
 246     return SQLITE_IOERR_SHORT_READ;
 247   }
 248
 249   return SQLITE_IOERR_READ;
 250 }
 251
 252 /*
 253 ** Write data to a crash-file.
 254 */
 255 static int demoWrite(
 256   sqlite3_file *pFile,
 257   const void *zBuf,
 258   int iAmt,
 259   sqlite_int64 iOfst
 260 ){
 261   DemoFile *p = (DemoFile*)pFile;
 262
 263   if( p->aBuffer ){
 264     char *z = (char *)zBuf;       /* Pointer to remaining data to write */
 265     int n = iAmt;                 /* Number of bytes at z */
 266     sqlite3_int64 i = iOfst;      /* File offset to write to */
 267
 268     while( n>0 ){
 269       int nCopy;                  /* Number of bytes to copy into buffer */
 270
 271       /* If the buffer is full, or if this data is not being written directly
 272       ** following the data already buffered, flush the buffer. Flushing
 273       ** the buffer is a no-op if it is empty.
 274       */
 275       if( p->nBuffer==SQLITE_DEMOVFS_BUFFERSZ || p->iBufferOfst+p->nBuffer!=i ){
 276         int rc = demoFlushBuffer(p);
 277         if( rc!=SQLITE_OK ){
 278           return rc;
 279         }
 280       }
 281       assert( p->nBuffer==0 || p->iBufferOfst+p->nBuffer==i );
 282       p->iBufferOfst = i - p->nBuffer;
 283
 284       /* Copy as much data as possible into the buffer. */
 285       nCopy = SQLITE_DEMOVFS_BUFFERSZ - p->nBuffer;
 286       if( nCopy>n ){
 287         nCopy = n;
 288       }
 289       memcpy(&p->aBuffer[p->nBuffer], z, nCopy);
 290       p->nBuffer += nCopy;
 291
 292       n -= nCopy;
 293       i += nCopy;
 294       z += nCopy;
 295     }
 296   }else{
 297     return demoDirectWrite(p, zBuf, iAmt, iOfst);
 298   }
 299
 300   return SQLITE_OK;
 301 }
 302
 303 /*
 304 ** Truncate a file. This is a no-op for this VFS (see header comments at
 305 ** the top of the file).
 306 */
 307 static int demoTruncate(sqlite3_file *pFile, sqlite_int64 size){
 308 #if 0
 309   if( ftruncate(((DemoFile *)pFile)->fd, size) ) return SQLITE_IOERR_TRUNCATE;
 310 #endif
 311   return SQLITE_OK;
 312 }
 313
 314 /*
 315 ** Sync the contents of the file to the persistent media.
 316 */
 317 static int demoSync(sqlite3_file *pFile, int flags){
 318   DemoFile *p = (DemoFile*)pFile;
 319   int rc;
 320
 321   rc = demoFlushBuffer(p);
 322   if( rc!=SQLITE_OK ){
 323     return rc;
 324   }
 325
 326   rc = fsync(p->fd);
 327   return (rc==0 ? SQLITE_OK : SQLITE_IOERR_FSYNC);
 328 }
 329
 330 /*
 331 ** Write the size of the file in bytes to *pSize.
 332 */
 333 static int demoFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
 334   DemoFile *p = (DemoFile*)pFile;
 335   int rc;                         /* Return code from fstat() call */
 336   struct stat sStat;              /* Output of fstat() call */
 337
 338   /* Flush the contents of the buffer to disk. As with the flush in the
 339   ** demoRead() method, it would be possible to avoid this and save a write
 340   ** here and there. But in practice this comes up so infrequently it is
 341   ** not worth the trouble.
 342   */
 343   rc = demoFlushBuffer(p);
 344   if( rc!=SQLITE_OK ){
 345     return rc;
 346   }
 347
 348   rc = fstat(p->fd, &sStat);
 349   if( rc!=0 ) return SQLITE_IOERR_FSTAT;
 350   *pSize = sStat.st_size;
 351   return SQLITE_OK;
 352 }
 353
 354 /*
 355 ** Locking functions. The xLock() and xUnlock() methods are both no-ops.
 356 ** The xCheckReservedLock() always indicates that no other process holds
 357 ** a reserved lock on the database file. This ensures that if a hot-journal
 358 ** file is found in the file-system it is rolled back.
 359 */
 360 static int demoLock(sqlite3_file *pFile, int eLock){
 361   return SQLITE_OK;
 362 }
 363 static int demoUnlock(sqlite3_file *pFile, int eLock){
 364   return SQLITE_OK;
 365 }
 366 static int demoCheckReservedLock(sqlite3_file *pFile, int *pResOut){
 367   *pResOut = 0;
 368   return SQLITE_OK;
 369 }
 370
 371 /*
 372 ** No xFileControl() verbs are implemented by this VFS.
 373 */
 374 static int demoFileControl(sqlite3_file *pFile, int op, void *pArg){
 375   return SQLITE_NOTFOUND;
 376 }
 377
 378 /*
 379 ** The xSectorSize() and xDeviceCharacteristics() methods. These two
 380 ** may return special values allowing SQLite to optimize file-system
 381 ** access to some extent. But it is also safe to simply return 0.
 382 */
 383 static int demoSectorSize(sqlite3_file *pFile){
 384   return 0;
 385 }
 386 static int demoDeviceCharacteristics(sqlite3_file *pFile){
 387   return 0;
 388 }
 389
 390 /*
 391 ** Open a file handle.
 392 */
 393 static int demoOpen(
 394   sqlite3_vfs *pVfs,              /* VFS */
 395   const char *zName,              /* File to open, or 0 for a temp file */
 396   sqlite3_file *pFile,            /* Pointer to DemoFile struct to populate */
 397   int flags,                      /* Input SQLITE_OPEN_XXX flags */
 398   int *pOutFlags                  /* Output SQLITE_OPEN_XXX flags (or NULL) */
 399 ){
 400   static const sqlite3_io_methods demoio = {
 401     1,                            /* iVersion */
 402     demoClose,                    /* xClose */
 403     demoRead,                     /* xRead */
 404     demoWrite,                    /* xWrite */
 405     demoTruncate,                 /* xTruncate */
 406     demoSync,                     /* xSync */
 407     demoFileSize,                 /* xFileSize */
 408     demoLock,                     /* xLock */
 409     demoUnlock,                   /* xUnlock */
 410     demoCheckReservedLock,        /* xCheckReservedLock */
 411     demoFileControl,              /* xFileControl */
 412     demoSectorSize,               /* xSectorSize */
 413     demoDeviceCharacteristics     /* xDeviceCharacteristics */
 414   };
 415
 416   DemoFile *p = (DemoFile*)pFile; /* Populate this structure */
 417   int oflags = 0;                 /* flags to pass to open() call */
 418   char *aBuf = 0;
 419
 420   if( zName==0 ){
 421     return SQLITE_IOERR;
 422   }
 423
 424   if( flags&SQLITE_OPEN_MAIN_JOURNAL ){
 425     aBuf = (char *)sqlite3_malloc(SQLITE_DEMOVFS_BUFFERSZ);
 426     if( !aBuf ){
 427       return SQLITE_NOMEM;
 428     }
 429   }
 430
 431   if( flags&SQLITE_OPEN_EXCLUSIVE ) oflags |= O_EXCL;
 432   if( flags&SQLITE_OPEN_CREATE )    oflags |= O_CREAT;
 433   if( flags&SQLITE_OPEN_READONLY )  oflags |= O_RDONLY;
 434   if( flags&SQLITE_OPEN_READWRITE ) oflags |= O_RDWR;
 435
 436   memset(p, 0, sizeof(DemoFile));
 437   p->fd = open(zName, oflags, 0600);
 438   if( p->fd<0 ){
 439     sqlite3_free(aBuf);
 440     return SQLITE_CANTOPEN;
 441   }
 442   p->aBuffer = aBuf;
 443
 444   if( pOutFlags ){
 445     *pOutFlags = flags;
 446   }
 447   p->base.pMethods = &demoio;
 448   return SQLITE_OK;
 449 }
 450
 451 /*
 452 ** Delete the file identified by argument zPath. If the dirSync parameter
 453 ** is non-zero, then ensure the file-system modification to delete the
 454 ** file has been synced to disk before returning.
 455 */
 456 static int demoDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
 457   int rc;                         /* Return code */
 458
 459   rc = unlink(zPath);
 460   if( rc!=0 && errno==ENOENT ) return SQLITE_OK;
 461
 462   if( rc==0 && dirSync ){
 463     int dfd;                      /* File descriptor open on directory */
 464     int i;                        /* Iterator variable */
 465     char zDir[MAXPATHNAME+1];     /* Name of directory containing file zPath */
 466
 467     /* Figure out the directory name from the path of the file deleted. */
 468     sqlite3_snprintf(MAXPATHNAME, zDir, "%s", zPath);
 469     zDir[MAXPATHNAME] = '\0';
 470     for(i=strlen(zDir); i>1 && zDir[i]!='/'; i++);
 471     zDir[i] = '\0';
 472
 473     /* Open a file-descriptor on the directory. Sync. Close. */
 474     dfd = open(zDir, O_RDONLY, 0);
 475     if( dfd<0 ){
 476       rc = -1;
 477     }else{
 478       rc = fsync(dfd);
 479       close(dfd);
 480     }
 481   }
 482   return (rc==0 ? SQLITE_OK : SQLITE_IOERR_DELETE);
 483 }
 484
 485 #ifndef F_OK
 486 # define F_OK 0
 487 #endif
 488 #ifndef R_OK
 489 # define R_OK 4
 490 #endif
 491 #ifndef W_OK
 492 # define W_OK 2
 493 #endif
 494
 495 /*
 496 ** Query the file-system to see if the named file exists, is readable or
 497 ** is both readable and writable.
 498 */
 499 static int demoAccess(
 500   sqlite3_vfs *pVfs,
 501   const char *zPath,
 502   int flags,
 503   int *pResOut
 504 ){
 505   int rc;                         /* access() return code */
 506   int eAccess = F_OK;             /* Second argument to access() */
 507
 508   assert( flags==SQLITE_ACCESS_EXISTS       /* access(zPath, F_OK) */
 509        || flags==SQLITE_ACCESS_READ         /* access(zPath, R_OK) */
 510        || flags==SQLITE_ACCESS_READWRITE    /* access(zPath, R_OK|W_OK) */
 511   );
 512
 513   if( flags==SQLITE_ACCESS_READWRITE ) eAccess = R_OK|W_OK;
 514   if( flags==SQLITE_ACCESS_READ )      eAccess = R_OK;
 515
 516   rc = access(zPath, eAccess);
 517   *pResOut = (rc==0);
 518   return SQLITE_OK;
 519 }
 520
 521 /*
 522 ** Argument zPath points to a nul-terminated string containing a file path.
 523 ** If zPath is an absolute path, then it is copied as is into the output
 524 ** buffer. Otherwise, if it is a relative path, then the equivalent full
 525 ** path is written to the output buffer.
 526 **
 527 ** This function assumes that paths are UNIX style. Specifically, that:
 528 **
 529 **   1. Path components are separated by a '/'. and
 530 **   2. Full paths begin with a '/' character.
 531 */
 532 static int demoFullPathname(
 533   sqlite3_vfs *pVfs,              /* VFS */
 534   const char *zPath,              /* Input path (possibly a relative path) */
 535   int nPathOut,                   /* Size of output buffer in bytes */
 536   char *zPathOut                  /* Pointer to output buffer */
 537 ){
 538   char zDir[MAXPATHNAME+1];
 539   if( zPath[0]=='/' ){
 540     zDir[0] = '\0';
 541   }else{
 542     if( getcwd(zDir, sizeof(zDir))==0 ) return SQLITE_IOERR;
 543   }
 544   zDir[MAXPATHNAME] = '\0';
 545
 546   sqlite3_snprintf(nPathOut, zPathOut, "%s/%s", zDir, zPath);
 547   zPathOut[nPathOut-1] = '\0';
 548
 549   return SQLITE_OK;
 550 }
 551
 552 /*
 553 ** The following four VFS methods:
 554 **
 555 **   xDlOpen
 556 **   xDlError
 557 **   xDlSym
 558 **   xDlClose
 559 **
 560 ** are supposed to implement the functionality needed by SQLite to load
 561 ** extensions compiled as shared objects. This simple VFS does not support
 562 ** this functionality, so the following functions are no-ops.
 563 */
 564 static void *demoDlOpen(sqlite3_vfs *pVfs, const char *zPath){
 565   return 0;
 566 }
 567 static void demoDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
 568   sqlite3_snprintf(nByte, zErrMsg, "Loadable extensions are not supported");
 569   zErrMsg[nByte-1] = '\0';
 570 }
 571 static void (*demoDlSym(sqlite3_vfs *pVfs, void *pH, const char *z))(void){
 572   return 0;
 573 }
 574 static void demoDlClose(sqlite3_vfs *pVfs, void *pHandle){
 575   return;
 576 }
 577
 578 /*
 579 ** Parameter zByte points to a buffer nByte bytes in size. Populate this
 580 ** buffer with pseudo-random data.
 581 */
 582 static int demoRandomness(sqlite3_vfs *pVfs, int nByte, char *zByte){
 583   return SQLITE_OK;
 584 }
 585
 586 /*
 587 ** Sleep for at least nMicro microseconds. Return the (approximate) number
 588 ** of microseconds slept for.
 589 */
 590 static int demoSleep(sqlite3_vfs *pVfs, int nMicro){
 591   sleep(nMicro / 1000000);
 592   usleep(nMicro % 1000000);
 593   return nMicro;
 594 }
 595
 596 /*
 597 ** Set *pTime to the current UTC time expressed as a Julian day. Return
 598 ** SQLITE_OK if successful, or an error code otherwise.
 599 **
 600 **   http://en.wikipedia.org/wiki/Julian_day
 601 **
 602 ** This implementation is not very good. The current time is rounded to
 603 ** an integer number of seconds. Also, assuming time_t is a signed 32-bit
 604 ** value, it will stop working some time in the year 2038 AD (the so-called
 605 ** "year 2038" problem that afflicts systems that store time this way).
 606 */
 607 static int demoCurrentTime(sqlite3_vfs *pVfs, double *pTime){
 608   time_t t = time(0);
 609   *pTime = t/86400.0 + 2440587.5;
 610   return SQLITE_OK;
 611 }
 612
 613 /*
 614 ** This function returns a pointer to the VFS implemented in this file.
 615 ** To make the VFS available to SQLite:
 616 **
 617 **   sqlite3_vfs_register(sqlite3_demovfs(), 0);
 618 */
 619 sqlite3_vfs *sqlite3_demovfs(void){
 620   static sqlite3_vfs demovfs = {
 621     1,                            /* iVersion */
 622     sizeof(DemoFile),             /* szOsFile */
 623     MAXPATHNAME,                  /* mxPathname */
 624     0,                            /* pNext */
 625     "demo",                       /* zName */
 626     0,                            /* pAppData */
 627     demoOpen,                     /* xOpen */
 628     demoDelete,                   /* xDelete */
 629     demoAccess,                   /* xAccess */
 630     demoFullPathname,             /* xFullPathname */
 631     demoDlOpen,                   /* xDlOpen */
 632     demoDlError,                  /* xDlError */
 633     demoDlSym,                    /* xDlSym */
 634     demoDlClose,                  /* xDlClose */
 635     demoRandomness,               /* xRandomness */
 636     demoSleep,                    /* xSleep */
 637     demoCurrentTime,              /* xCurrentTime */
 638   };
 639   return &demovfs;
 640 }
 641
 642 #endif /* !defined(SQLITE_TEST) || SQLITE_OS_UNIX */
 643
 644
 645 #ifdef SQLITE_TEST
 646
 647 #if defined(INCLUDE_SQLITE_TCL_H)
 648 #  include "sqlite_tcl.h"
 649 #else
 650 #  include "tcl.h"
 651 #  ifndef SQLITE_TCLAPI
 652 #    define SQLITE_TCLAPI
 653 #  endif
 654 #endif
 655
 656 #if SQLITE_OS_UNIX
 657 static int SQLITE_TCLAPI register_demovfs(
 658   ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
 659   Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
 660   int objc,              /* Number of arguments */
 661   Tcl_Obj *CONST objv[]  /* Command arguments */
 662 ){
 663   sqlite3_vfs_register(sqlite3_demovfs(), 1);
 664   return TCL_OK;
 665 }
 666 static int SQLITE_TCLAPI unregister_demovfs(
 667   ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
 668   Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
 669   int objc,              /* Number of arguments */
 670   Tcl_Obj *CONST objv[]  /* Command arguments */
 671 ){
 672   sqlite3_vfs_unregister(sqlite3_demovfs());
 673   return TCL_OK;
 674 }
 675
 676 /*
 677 ** Register commands with the TCL interpreter.
 678 */
 679 int Sqlitetest_demovfs_Init(Tcl_Interp *interp){
 680   Tcl_CreateObjCommand(interp, "register_demovfs", register_demovfs, 0, 0);
 681   Tcl_CreateObjCommand(interp, "unregister_demovfs", unregister_demovfs, 0, 0);
 682   return TCL_OK;
 683 }
 684
 685 #else
 686 int Sqlitetest_demovfs_Init(Tcl_Interp *interp){ return TCL_OK; }
 687 #endif
 688
 689 #endif /* SQLITE_TEST */