src/test6.c

   1 /*
   2 ** 2004 May 22
   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 that modified the OS layer in order to simulate
  14 ** the effect on the database file of an OS crash or power failure.  This
  15 ** is used to test the ability of SQLite to recover from those situations.
  16 */
  17 #if SQLITE_TEST          /* This file is used for testing only */
  18 #include "sqliteInt.h"
  19 #if defined(INCLUDE_SQLITE_TCL_H)
  20 #  include "sqlite_tcl.h"
  21 #else
  22 #  include "tcl.h"
  23 #endif
  24
  25 #ifndef SQLITE_OMIT_DISKIO  /* This file is a no-op if disk I/O is disabled */
  26
  27 /* #define TRACE_CRASHTEST */
  28
  29 typedef struct CrashFile CrashFile;
  30 typedef struct CrashGlobal CrashGlobal;
  31 typedef struct WriteBuffer WriteBuffer;
  32
  33 /*
  34 ** Method:
  35 **
  36 **   This layer is implemented as a wrapper around the "real"
  37 **   sqlite3_file object for the host system. Each time data is
  38 **   written to the file object, instead of being written to the
  39 **   underlying file, the write operation is stored in an in-memory
  40 **   structure (type WriteBuffer). This structure is placed at the
  41 **   end of a global ordered list (the write-list).
  42 **
  43 **   When data is read from a file object, the requested region is
  44 **   first retrieved from the real file. The write-list is then
  45 **   traversed and data copied from any overlapping WriteBuffer
  46 **   structures to the output buffer. i.e. a read() operation following
  47 **   one or more write() operations works as expected, even if no
  48 **   data has actually been written out to the real file.
  49 **
  50 **   When a fsync() operation is performed, an operating system crash
  51 **   may be simulated, in which case exit(-1) is called (the call to
  52 **   xSync() never returns). Whether or not a crash is simulated,
  53 **   the data associated with a subset of the WriteBuffer structures
  54 **   stored in the write-list is written to the real underlying files
  55 **   and the entries removed from the write-list. If a crash is simulated,
  56 **   a subset of the buffers may be corrupted before the data is written.
  57 **
  58 **   The exact subset of the write-list written and/or corrupted is
  59 **   determined by the simulated device characteristics and sector-size.
  60 **
  61 ** "Normal" mode:
  62 **
  63 **   Normal mode is used when the simulated device has none of the
  64 **   SQLITE_IOCAP_XXX flags set.
  65 **
  66 **   In normal mode, if the fsync() is not a simulated crash, the
  67 **   write-list is traversed from beginning to end. Each WriteBuffer
  68 **   structure associated with the file handle used to call xSync()
  69 **   is written to the real file and removed from the write-list.
  70 **
  71 **   If a crash is simulated, one of the following takes place for
  72 **   each WriteBuffer in the write-list, regardless of which
  73 **   file-handle it is associated with:
  74 **
  75 **     1. The buffer is correctly written to the file, just as if
  76 **        a crash were not being simulated.
  77 **
  78 **     2. Nothing is done.
  79 **
  80 **     3. Garbage data is written to all sectors of the file that
  81 **        overlap the region specified by the WriteBuffer. Or garbage
  82 **        data is written to some contiguous section within the
  83 **        overlapped sectors.
  84 **
  85 ** Device Characteristic flag handling:
  86 **
  87 **   If the IOCAP_ATOMIC flag is set, then option (3) above is
  88 **   never selected.
  89 **
  90 **   If the IOCAP_ATOMIC512 flag is set, and the WriteBuffer represents
  91 **   an aligned write() of an integer number of 512 byte regions, then
  92 **   option (3) above is never selected. Instead, each 512 byte region
  93 **   is either correctly written or left completely untouched. Similar
  94 **   logic governs the behavior if any of the other ATOMICXXX flags
  95 **   is set.
  96 **
  97 **   If either the IOCAP_SAFEAPPEND or IOCAP_SEQUENTIAL flags are set
  98 **   and a crash is being simulated, then an entry of the write-list is
  99 **   selected at random. Everything in the list after the selected entry
 100 **   is discarded before processing begins.
 101 **
 102 **   If IOCAP_SEQUENTIAL is set and a crash is being simulated, option
 103 **   (1) is selected for all write-list entries except the last. If a
 104 **   crash is not being simulated, then all entries in the write-list
 105 **   that occur before at least one write() on the file-handle specified
 106 **   as part of the xSync() are written to their associated real files.
 107 **
 108 **   If IOCAP_SAFEAPPEND is set and the first byte written by the write()
 109 **   operation is one byte past the current end of the file, then option
 110 **   (1) is always selected.
 111 */
 112
 113 /*
 114 ** Each write operation in the write-list is represented by an instance
 115 ** of the following structure.
 116 **
 117 ** If zBuf is 0, then this structure represents a call to xTruncate(),
 118 ** not xWrite(). In that case, iOffset is the size that the file is
 119 ** truncated to.
 120 */
 121 struct WriteBuffer {
 122   i64 iOffset;                 /* Byte offset of the start of this write() */
 123   int nBuf;                    /* Number of bytes written */
 124   u8 *zBuf;                    /* Pointer to copy of written data */
 125   CrashFile *pFile;            /* File this write() applies to */
 126
 127   WriteBuffer *pNext;          /* Next in CrashGlobal.pWriteList */
 128 };
 129
 130 struct CrashFile {
 131   const sqlite3_io_methods *pMethod;   /* Must be first */
 132   sqlite3_file *pRealFile;             /* Underlying "real" file handle */
 133   char *zName;
 134   int flags;                           /* Flags the file was opened with */
 135
 136   /* Cache of the entire file. This is used to speed up OsRead() and
 137   ** OsFileSize() calls. Although both could be done by traversing the
 138   ** write-list, in practice this is impractically slow.
 139   */
 140   u8 *zData;                           /* Buffer containing file contents */
 141   int nData;                           /* Size of buffer allocated at zData */
 142   i64 iSize;                           /* Size of file in bytes */
 143 };
 144
 145 struct CrashGlobal {
 146   WriteBuffer *pWriteList;     /* Head of write-list */
 147   WriteBuffer *pWriteListEnd;  /* End of write-list */
 148
 149   int iSectorSize;             /* Value of simulated sector size */
 150   int iDeviceCharacteristics;  /* Value of simulated device characteristics */
 151
 152   int iCrash;                  /* Crash on the iCrash'th call to xSync() */
 153   char zCrashFile[500];        /* Crash during an xSync() on this file */
 154 };
 155
 156 static CrashGlobal g = {0, 0, SQLITE_DEFAULT_SECTOR_SIZE, 0, 0};
 157
 158 /*
 159 ** Set this global variable to 1 to enable crash testing.
 160 */
 161 static int sqlite3CrashTestEnable = 0;
 162
 163 static void *crash_malloc(int nByte){
 164   return (void *)Tcl_AttemptAlloc((size_t)nByte);
 165 }
 166 static void crash_free(void *p){
 167   Tcl_Free(p);
 168 }
 169 static void *crash_realloc(void *p, int n){
 170   return (void *)Tcl_AttemptRealloc(p, (size_t)n);
 171 }
 172
 173 /*
 174 ** Wrapper around the sqlite3OsWrite() function that avoids writing to the
 175 ** 512 byte block beginning at offset PENDING_BYTE.
 176 */
 177 static int writeDbFile(CrashFile *p, u8 *z, i64 iAmt, i64 iOff){
 178   int rc = SQLITE_OK;
 179   int iSkip = 0;
 180   if( (iAmt-iSkip)>0 ){
 181     rc = sqlite3OsWrite(p->pRealFile, &z[iSkip], (int)(iAmt-iSkip), iOff+iSkip);
 182   }
 183   return rc;
 184 }
 185
 186 /*
 187 ** Flush the write-list as if xSync() had been called on file handle
 188 ** pFile. If isCrash is true, simulate a crash.
 189 */
 190 static int writeListSync(CrashFile *pFile, int isCrash){
 191   int rc = SQLITE_OK;
 192   int iDc = g.iDeviceCharacteristics;
 193
 194   WriteBuffer *pWrite;
 195   WriteBuffer **ppPtr;
 196
 197   /* If this is not a crash simulation, set pFinal to point to the
 198   ** last element of the write-list that is associated with file handle
 199   ** pFile.
 200   **
 201   ** If this is a crash simulation, set pFinal to an arbitrarily selected
 202   ** element of the write-list.
 203   */
 204   WriteBuffer *pFinal = 0;
 205   if( !isCrash ){
 206     for(pWrite=g.pWriteList; pWrite; pWrite=pWrite->pNext){
 207       if( pWrite->pFile==pFile ){
 208         pFinal = pWrite;
 209       }
 210     }
 211   }else if( iDc&(SQLITE_IOCAP_SEQUENTIAL|SQLITE_IOCAP_SAFE_APPEND) ){
 212     int nWrite = 0;
 213     int iFinal;
 214     for(pWrite=g.pWriteList; pWrite; pWrite=pWrite->pNext) nWrite++;
 215     sqlite3_randomness(sizeof(int), &iFinal);
 216     iFinal = ((iFinal<0)?-1*iFinal:iFinal)%nWrite;
 217     for(pWrite=g.pWriteList; iFinal>0; pWrite=pWrite->pNext) iFinal--;
 218     pFinal = pWrite;
 219   }
 220
 221 #ifdef TRACE_CRASHTEST
 222   if( pFile ){
 223     printf("Sync %s (is %s crash)\n", pFile->zName, (isCrash?"a":"not a"));
 224   }
 225 #endif
 226
 227   ppPtr = &g.pWriteList;
 228   for(pWrite=*ppPtr; rc==SQLITE_OK && pWrite; pWrite=*ppPtr){
 229     sqlite3_file *pRealFile = pWrite->pFile->pRealFile;
 230
 231     /* (eAction==1)      -> write block out normally,
 232     ** (eAction==2)      -> do nothing,
 233     ** (eAction==3)      -> trash sectors.
 234     */
 235     int eAction = 0;
 236     if( !isCrash ){
 237       eAction = 2;
 238       if( (pWrite->pFile==pFile || iDc&SQLITE_IOCAP_SEQUENTIAL) ){
 239         eAction = 1;
 240       }
 241     }else{
 242       char random;
 243       sqlite3_randomness(1, &random);
 244
 245       /* Do not select option 3 (sector trashing) if the IOCAP_ATOMIC flag
 246       ** is set or this is an OsTruncate(), not an Oswrite().
 247       */
 248       if( (iDc&SQLITE_IOCAP_ATOMIC) || (pWrite->zBuf==0) ){
 249         random &= 0x01;
 250       }
 251
 252       /* If IOCAP_SEQUENTIAL is set and this is not the final entry
 253       ** in the truncated write-list, always select option 1 (write
 254       ** out correctly).
 255       */
 256       if( (iDc&SQLITE_IOCAP_SEQUENTIAL && pWrite!=pFinal) ){
 257         random = 0;
 258       }
 259
 260       /* If IOCAP_SAFE_APPEND is set and this OsWrite() operation is
 261       ** an append (first byte of the written region is 1 byte past the
 262       ** current EOF), always select option 1 (write out correctly).
 263       */
 264       if( iDc&SQLITE_IOCAP_SAFE_APPEND && pWrite->zBuf ){
 265         i64 iSize;
 266         sqlite3OsFileSize(pRealFile, &iSize);
 267         if( iSize==pWrite->iOffset ){
 268           random = 0;
 269         }
 270       }
 271
 272       if( (random&0x06)==0x06 ){
 273         eAction = 3;
 274       }else{
 275         eAction = ((random&0x01)?2:1);
 276       }
 277     }
 278
 279     switch( eAction ){
 280       case 1: {               /* Write out correctly */
 281         if( pWrite->zBuf ){
 282           rc = writeDbFile(
 283               pWrite->pFile, pWrite->zBuf, pWrite->nBuf, pWrite->iOffset
 284           );
 285         }else{
 286           rc = sqlite3OsTruncate(pRealFile, pWrite->iOffset);
 287         }
 288         *ppPtr = pWrite->pNext;
 289 #ifdef TRACE_CRASHTEST
 290         if( isCrash ){
 291           printf("Writing %d bytes @ %d (%s)\n",
 292             pWrite->nBuf, (int)pWrite->iOffset, pWrite->pFile->zName
 293           );
 294         }
 295 #endif
 296         crash_free(pWrite);
 297         break;
 298       }
 299       case 2: {               /* Do nothing */
 300         ppPtr = &pWrite->pNext;
 301 #ifdef TRACE_CRASHTEST
 302         if( isCrash ){
 303           printf("Omiting %d bytes @ %d (%s)\n",
 304             pWrite->nBuf, (int)pWrite->iOffset, pWrite->pFile->zName
 305           );
 306         }
 307 #endif
 308         break;
 309       }
 310       case 3: {               /* Trash sectors */
 311         u8 *zGarbage;
 312         int iFirst = (int)(pWrite->iOffset/g.iSectorSize);
 313         int iLast = (int)((pWrite->iOffset+pWrite->nBuf-1)/g.iSectorSize);
 314
 315         assert(pWrite->zBuf);
 316
 317 #ifdef TRACE_CRASHTEST
 318         printf("Trashing %d sectors (%d bytes) @ %lld (sector %d) (%s)\n",
 319             1+iLast-iFirst, (1+iLast-iFirst)*g.iSectorSize,
 320             pWrite->iOffset, iFirst, pWrite->pFile->zName
 321         );
 322 #endif
 323
 324         zGarbage = crash_malloc(g.iSectorSize);
 325         if( zGarbage ){
 326           sqlite3_int64 i;
 327           for(i=iFirst; rc==SQLITE_OK && i<=iLast; i++){
 328             sqlite3_randomness(g.iSectorSize, zGarbage);
 329             rc = writeDbFile(
 330               pWrite->pFile, zGarbage, g.iSectorSize, i*g.iSectorSize
 331             );
 332           }
 333           crash_free(zGarbage);
 334         }else{
 335           rc = SQLITE_NOMEM;
 336         }
 337
 338         ppPtr = &pWrite->pNext;
 339         break;
 340       }
 341
 342       default:
 343         assert(!"Cannot happen");
 344     }
 345
 346     if( pWrite==pFinal ) break;
 347   }
 348
 349   if( rc==SQLITE_OK && isCrash ){
 350     exit(-1);
 351   }
 352
 353   for(pWrite=g.pWriteList; pWrite && pWrite->pNext; pWrite=pWrite->pNext);
 354   g.pWriteListEnd = pWrite;
 355
 356   return rc;
 357 }
 358
 359 /*
 360 ** Add an entry to the end of the write-list.
 361 */
 362 static int writeListAppend(
 363   sqlite3_file *pFile,
 364   sqlite3_int64 iOffset,
 365   const u8 *zBuf,
 366   int nBuf
 367 ){
 368   WriteBuffer *pNew;
 369
 370   assert((zBuf && nBuf) || (!nBuf && !zBuf));
 371
 372   pNew = (WriteBuffer *)crash_malloc(sizeof(WriteBuffer) + nBuf);
 373   if( pNew==0 ){
 374     fprintf(stderr, "out of memory in the crash simulator\n");
 375   }
 376   memset(pNew, 0, sizeof(WriteBuffer)+nBuf);
 377   pNew->iOffset = iOffset;
 378   pNew->nBuf = nBuf;
 379   pNew->pFile = (CrashFile *)pFile;
 380   if( zBuf ){
 381     pNew->zBuf = (u8 *)&pNew[1];
 382     memcpy(pNew->zBuf, zBuf, nBuf);
 383   }
 384
 385   if( g.pWriteList ){
 386     assert(g.pWriteListEnd);
 387     g.pWriteListEnd->pNext = pNew;
 388   }else{
 389     g.pWriteList = pNew;
 390   }
 391   g.pWriteListEnd = pNew;
 392
 393   return SQLITE_OK;
 394 }
 395
 396 /*
 397 ** Close a crash-file.
 398 */
 399 static int cfClose(sqlite3_file *pFile){
 400   CrashFile *pCrash = (CrashFile *)pFile;
 401   writeListSync(pCrash, 0);
 402   sqlite3OsClose(pCrash->pRealFile);
 403   return SQLITE_OK;
 404 }
 405
 406 /*
 407 ** Read data from a crash-file.
 408 */
 409 static int cfRead(
 410   sqlite3_file *pFile,
 411   void *zBuf,
 412   int iAmt,
 413   sqlite_int64 iOfst
 414 ){
 415   CrashFile *pCrash = (CrashFile *)pFile;
 416   int nCopy = (int)MIN((i64)iAmt, (pCrash->iSize - iOfst));
 417
 418   if( nCopy>0 ){
 419     memcpy(zBuf, &pCrash->zData[iOfst], nCopy);
 420   }
 421
 422   /* Check the file-size to see if this is a short-read */
 423   if( nCopy<iAmt ){
 424     return SQLITE_IOERR_SHORT_READ;
 425   }
 426
 427   return SQLITE_OK;
 428 }
 429
 430 /*
 431 ** Write data to a crash-file.
 432 */
 433 static int cfWrite(
 434   sqlite3_file *pFile,
 435   const void *zBuf,
 436   int iAmt,
 437   sqlite_int64 iOfst
 438 ){
 439   CrashFile *pCrash = (CrashFile *)pFile;
 440   if( iAmt+iOfst>pCrash->iSize ){
 441     pCrash->iSize = (int)(iAmt+iOfst);
 442   }
 443   while( pCrash->iSize>pCrash->nData ){
 444     u8 *zNew;
 445     int nNew = (pCrash->nData*2) + 4096;
 446     zNew = crash_realloc(pCrash->zData, nNew);
 447     if( !zNew ){
 448       return SQLITE_NOMEM;
 449     }
 450     memset(&zNew[pCrash->nData], 0, nNew-pCrash->nData);
 451     pCrash->nData = nNew;
 452     pCrash->zData = zNew;
 453   }
 454   memcpy(&pCrash->zData[iOfst], zBuf, iAmt);
 455   return writeListAppend(pFile, iOfst, zBuf, iAmt);
 456 }
 457
 458 /*
 459 ** Truncate a crash-file.
 460 */
 461 static int cfTruncate(sqlite3_file *pFile, sqlite_int64 size){
 462   CrashFile *pCrash = (CrashFile *)pFile;
 463   assert(size>=0);
 464   if( pCrash->iSize>size ){
 465     pCrash->iSize = (int)size;
 466   }
 467   return writeListAppend(pFile, size, 0, 0);
 468 }
 469
 470 /*
 471 ** Sync a crash-file.
 472 */
 473 static int cfSync(sqlite3_file *pFile, int flags){
 474   CrashFile *pCrash = (CrashFile *)pFile;
 475   int isCrash = 0;
 476
 477   const char *zName = pCrash->zName;
 478   const char *zCrashFile = g.zCrashFile;
 479   int nName = (int)strlen(zName);
 480   int nCrashFile = (int)strlen(zCrashFile);
 481
 482   if( nCrashFile>0 && zCrashFile[nCrashFile-1]=='*' ){
 483     nCrashFile--;
 484     if( nName>nCrashFile ) nName = nCrashFile;
 485   }
 486
 487 #ifdef TRACE_CRASHTEST
 488   printf("cfSync(): nName = %d, nCrashFile = %d, zName = %s, zCrashFile = %s\n",
 489          nName, nCrashFile, zName, zCrashFile);
 490 #endif
 491
 492   if( nName==nCrashFile && 0==memcmp(zName, zCrashFile, nName) ){
 493 #ifdef TRACE_CRASHTEST
 494     printf("cfSync(): name matched, g.iCrash = %d\n", g.iCrash);
 495 #endif
 496     if( (--g.iCrash)==0 ) isCrash = 1;
 497   }
 498
 499   return writeListSync(pCrash, isCrash);
 500 }
 501
 502 /*
 503 ** Return the current file-size of the crash-file.
 504 */
 505 static int cfFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
 506   CrashFile *pCrash = (CrashFile *)pFile;
 507   *pSize = (i64)pCrash->iSize;
 508   return SQLITE_OK;
 509 }
 510
 511 /*
 512 ** Calls related to file-locks are passed on to the real file handle.
 513 */
 514 static int cfLock(sqlite3_file *pFile, int eLock){
 515   return sqlite3OsLock(((CrashFile *)pFile)->pRealFile, eLock);
 516 }
 517 static int cfUnlock(sqlite3_file *pFile, int eLock){
 518   return sqlite3OsUnlock(((CrashFile *)pFile)->pRealFile, eLock);
 519 }
 520 static int cfCheckReservedLock(sqlite3_file *pFile, int *pResOut){
 521   return sqlite3OsCheckReservedLock(((CrashFile *)pFile)->pRealFile, pResOut);
 522 }
 523 static int cfFileControl(sqlite3_file *pFile, int op, void *pArg){
 524   if( op==SQLITE_FCNTL_SIZE_HINT ){
 525     CrashFile *pCrash = (CrashFile *)pFile;
 526     i64 nByte = *(i64 *)pArg;
 527     if( nByte>pCrash->iSize ){
 528       if( SQLITE_OK==writeListAppend(pFile, nByte, 0, 0) ){
 529         pCrash->iSize = (int)nByte;
 530       }
 531     }
 532     return SQLITE_OK;
 533   }
 534   return sqlite3OsFileControl(((CrashFile *)pFile)->pRealFile, op, pArg);
 535 }
 536
 537 /*
 538 ** The xSectorSize() and xDeviceCharacteristics() functions return
 539 ** the global values configured by the [sqlite_crashparams] tcl
 540 *  interface.
 541 */
 542 static int cfSectorSize(sqlite3_file *pFile){
 543   return g.iSectorSize;
 544 }
 545 static int cfDeviceCharacteristics(sqlite3_file *pFile){
 546   return g.iDeviceCharacteristics;
 547 }
 548
 549 /*
 550 ** Pass-throughs for WAL support.
 551 */
 552 static int cfShmLock(sqlite3_file *pFile, int ofst, int n, int flags){
 553   sqlite3_file *pReal = ((CrashFile*)pFile)->pRealFile;
 554   return pReal->pMethods->xShmLock(pReal, ofst, n, flags);
 555 }
 556 static void cfShmBarrier(sqlite3_file *pFile){
 557   sqlite3_file *pReal = ((CrashFile*)pFile)->pRealFile;
 558   pReal->pMethods->xShmBarrier(pReal);
 559 }
 560 static int cfShmUnmap(sqlite3_file *pFile, int delFlag){
 561   sqlite3_file *pReal = ((CrashFile*)pFile)->pRealFile;
 562   return pReal->pMethods->xShmUnmap(pReal, delFlag);
 563 }
 564 static int cfShmMap(
 565   sqlite3_file *pFile,            /* Handle open on database file */
 566   int iRegion,                    /* Region to retrieve */
 567   int sz,                         /* Size of regions */
 568   int w,                          /* True to extend file if necessary */
 569   void volatile **pp              /* OUT: Mapped memory */
 570 ){
 571   sqlite3_file *pReal = ((CrashFile*)pFile)->pRealFile;
 572   return pReal->pMethods->xShmMap(pReal, iRegion, sz, w, pp);
 573 }
 574
 575 static const sqlite3_io_methods CrashFileVtab = {
 576   2,                            /* iVersion */
 577   cfClose,                      /* xClose */
 578   cfRead,                       /* xRead */
 579   cfWrite,                      /* xWrite */
 580   cfTruncate,                   /* xTruncate */
 581   cfSync,                       /* xSync */
 582   cfFileSize,                   /* xFileSize */
 583   cfLock,                       /* xLock */
 584   cfUnlock,                     /* xUnlock */
 585   cfCheckReservedLock,          /* xCheckReservedLock */
 586   cfFileControl,                /* xFileControl */
 587   cfSectorSize,                 /* xSectorSize */
 588   cfDeviceCharacteristics,      /* xDeviceCharacteristics */
 589   cfShmMap,                     /* xShmMap */
 590   cfShmLock,                    /* xShmLock */
 591   cfShmBarrier,                 /* xShmBarrier */
 592   cfShmUnmap                    /* xShmUnmap */
 593 };
 594
 595 /*
 596 ** Application data for the crash VFS
 597 */
 598 struct crashAppData {
 599   sqlite3_vfs *pOrig;                   /* Wrapped vfs structure */
 600 };
 601
 602 /*
 603 ** Open a crash-file file handle.
 604 **
 605 ** The caller will have allocated pVfs->szOsFile bytes of space
 606 ** at pFile. This file uses this space for the CrashFile structure
 607 ** and allocates space for the "real" file structure using
 608 ** sqlite3_malloc(). The assumption here is (pVfs->szOsFile) is
 609 ** equal or greater than sizeof(CrashFile).
 610 */
 611 static int cfOpen(
 612   sqlite3_vfs *pCfVfs,
 613   const char *zName,
 614   sqlite3_file *pFile,
 615   int flags,
 616   int *pOutFlags
 617 ){
 618   sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
 619   int rc;
 620   CrashFile *pWrapper = (CrashFile *)pFile;
 621   sqlite3_file *pReal = (sqlite3_file*)&pWrapper[1];
 622
 623   memset(pWrapper, 0, sizeof(CrashFile));
 624   rc = sqlite3OsOpen(pVfs, zName, pReal, flags, pOutFlags);
 625
 626   if( rc==SQLITE_OK ){
 627     i64 iSize;
 628     pWrapper->pMethod = &CrashFileVtab;
 629     pWrapper->zName = (char *)zName;
 630     pWrapper->pRealFile = pReal;
 631     rc = sqlite3OsFileSize(pReal, &iSize);
 632     pWrapper->iSize = (int)iSize;
 633     pWrapper->flags = flags;
 634   }
 635   if( rc==SQLITE_OK ){
 636     pWrapper->nData = (int)(4096 + pWrapper->iSize);
 637     pWrapper->zData = crash_malloc(pWrapper->nData);
 638     if( pWrapper->zData ){
 639       /* os_unix.c contains an assert() that fails if the caller attempts
 640       ** to read data from the 512-byte locking region of a file opened
 641       ** with the SQLITE_OPEN_MAIN_DB flag. This region of a database file
 642       ** never contains valid data anyhow. So avoid doing such a read here.
 643       **
 644       ** UPDATE: It also contains an assert() verifying that each call
 645       ** to the xRead() method reads less than 128KB of data.
 646       */
 647       i64 iOff;
 648
 649       memset(pWrapper->zData, 0, pWrapper->nData);
 650       for(iOff=0; iOff<pWrapper->iSize; iOff += 512){
 651         int nRead = (int)(pWrapper->iSize - iOff);
 652         if( nRead>512 ) nRead = 512;
 653         rc = sqlite3OsRead(pReal, &pWrapper->zData[iOff], nRead, iOff);
 654       }
 655     }else{
 656       rc = SQLITE_NOMEM;
 657     }
 658   }
 659   if( rc!=SQLITE_OK && pWrapper->pMethod ){
 660     sqlite3OsClose(pFile);
 661   }
 662   return rc;
 663 }
 664
 665 static int cfDelete(sqlite3_vfs *pCfVfs, const char *zPath, int dirSync){
 666   sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
 667   return pVfs->xDelete(pVfs, zPath, dirSync);
 668 }
 669 static int cfAccess(
 670   sqlite3_vfs *pCfVfs,
 671   const char *zPath,
 672   int flags,
 673   int *pResOut
 674 ){
 675   sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
 676   return pVfs->xAccess(pVfs, zPath, flags, pResOut);
 677 }
 678 static int cfFullPathname(
 679   sqlite3_vfs *pCfVfs,
 680   const char *zPath,
 681   int nPathOut,
 682   char *zPathOut
 683 ){
 684   sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
 685   return pVfs->xFullPathname(pVfs, zPath, nPathOut, zPathOut);
 686 }
 687 static void *cfDlOpen(sqlite3_vfs *pCfVfs, const char *zPath){
 688   sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
 689   return pVfs->xDlOpen(pVfs, zPath);
 690 }
 691 static void cfDlError(sqlite3_vfs *pCfVfs, int nByte, char *zErrMsg){
 692   sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
 693   pVfs->xDlError(pVfs, nByte, zErrMsg);
 694 }
 695 static void (*cfDlSym(sqlite3_vfs *pCfVfs, void *pH, const char *zSym))(void){
 696   sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
 697   return pVfs->xDlSym(pVfs, pH, zSym);
 698 }
 699 static void cfDlClose(sqlite3_vfs *pCfVfs, void *pHandle){
 700   sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
 701   pVfs->xDlClose(pVfs, pHandle);
 702 }
 703 static int cfRandomness(sqlite3_vfs *pCfVfs, int nByte, char *zBufOut){
 704   sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
 705   return pVfs->xRandomness(pVfs, nByte, zBufOut);
 706 }
 707 static int cfSleep(sqlite3_vfs *pCfVfs, int nMicro){
 708   sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
 709   return pVfs->xSleep(pVfs, nMicro);
 710 }
 711 static int cfCurrentTime(sqlite3_vfs *pCfVfs, double *pTimeOut){
 712   sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
 713   return pVfs->xCurrentTime(pVfs, pTimeOut);
 714 }
 715 static int cfGetLastError(sqlite3_vfs *pCfVfs, int n, char *z){
 716   sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
 717   return pVfs->xGetLastError(pVfs, n, z);
 718 }
 719
 720 static int processDevSymArgs(
 721   Tcl_Interp *interp,
 722   int objc,
 723   Tcl_Obj *CONST objv[],
 724   int *piDeviceChar,
 725   int *piSectorSize
 726 ){
 727   struct DeviceFlag {
 728     char *zName;
 729     int iValue;
 730   } aFlag[] = {
 731     { "atomic",              SQLITE_IOCAP_ATOMIC                },
 732     { "atomic512",           SQLITE_IOCAP_ATOMIC512             },
 733     { "atomic1k",            SQLITE_IOCAP_ATOMIC1K              },
 734     { "atomic2k",            SQLITE_IOCAP_ATOMIC2K              },
 735     { "atomic4k",            SQLITE_IOCAP_ATOMIC4K              },
 736     { "atomic8k",            SQLITE_IOCAP_ATOMIC8K              },
 737     { "atomic16k",           SQLITE_IOCAP_ATOMIC16K             },
 738     { "atomic32k",           SQLITE_IOCAP_ATOMIC32K             },
 739     { "atomic64k",           SQLITE_IOCAP_ATOMIC64K             },
 740     { "sequential",          SQLITE_IOCAP_SEQUENTIAL            },
 741     { "safe_append",         SQLITE_IOCAP_SAFE_APPEND           },
 742     { "powersafe_overwrite", SQLITE_IOCAP_POWERSAFE_OVERWRITE   },
 743     { "batch-atomic",        SQLITE_IOCAP_BATCH_ATOMIC          },
 744     { 0, 0 }
 745   };
 746
 747   int i;
 748   int iDc = 0;
 749   int iSectorSize = 0;
 750   int setSectorsize = 0;
 751   int setDeviceChar = 0;
 752
 753   for(i=0; i<objc; i+=2){
 754     int nOpt;
 755     char *zOpt = Tcl_GetStringFromObj(objv[i], &nOpt);
 756
 757     if( (nOpt>11 || nOpt<2 || strncmp("-sectorsize", zOpt, nOpt))
 758      && (nOpt>16 || nOpt<2 || strncmp("-characteristics", zOpt, nOpt))
 759     ){
 760       Tcl_AppendResult(interp,
 761         "Bad option: \"", zOpt,
 762         "\" - must be \"-characteristics\" or \"-sectorsize\"", 0
 763       );
 764       return TCL_ERROR;
 765     }
 766     if( i==objc-1 ){
 767       Tcl_AppendResult(interp, "Option requires an argument: \"", zOpt, "\"",0);
 768       return TCL_ERROR;
 769     }
 770
 771     if( zOpt[1]=='s' ){
 772       if( Tcl_GetIntFromObj(interp, objv[i+1], &iSectorSize) ){
 773         return TCL_ERROR;
 774       }
 775       setSectorsize = 1;
 776     }else{
 777       int j;
 778       Tcl_Obj **apObj;
 779       int nObj;
 780       if( Tcl_ListObjGetElements(interp, objv[i+1], &nObj, &apObj) ){
 781         return TCL_ERROR;
 782       }
 783       for(j=0; j<nObj; j++){
 784         int rc;
 785         int iChoice;
 786         Tcl_Obj *pFlag = Tcl_DuplicateObj(apObj[j]);
 787         Tcl_IncrRefCount(pFlag);
 788         Tcl_UtfToLower(Tcl_GetString(pFlag));
 789
 790         rc = Tcl_GetIndexFromObjStruct(
 791             interp, pFlag, aFlag, sizeof(aFlag[0]), "no such flag", 0, &iChoice
 792         );
 793         Tcl_DecrRefCount(pFlag);
 794         if( rc ){
 795           return TCL_ERROR;
 796         }
 797
 798         iDc |= aFlag[iChoice].iValue;
 799       }
 800       setDeviceChar = 1;
 801     }
 802   }
 803
 804   if( setDeviceChar ){
 805     *piDeviceChar = iDc;
 806   }
 807   if( setSectorsize ){
 808     *piSectorSize = iSectorSize;
 809   }
 810
 811   return TCL_OK;
 812 }
 813
 814 /*
 815 ** tclcmd:   sqlite3_crash_now
 816 **
 817 ** Simulate a crash immediately. This function does not return
 818 ** (writeListSync() calls exit(-1)).
 819 */
 820 static int SQLITE_TCLAPI crashNowCmd(
 821   void * clientData,
 822   Tcl_Interp *interp,
 823   int objc,
 824   Tcl_Obj *CONST objv[]
 825 ){
 826   if( objc!=1 ){
 827     Tcl_WrongNumArgs(interp, 1, objv, "");
 828     return TCL_ERROR;
 829   }
 830   writeListSync(0, 1);
 831   assert( 0 );
 832   return TCL_OK;
 833 }
 834
 835 /*
 836 ** tclcmd:   sqlite_crash_enable ENABLE ?DEFAULT?
 837 **
 838 ** Parameter ENABLE must be a boolean value. If true, then the "crash"
 839 ** vfs is added to the system. If false, it is removed.
 840 */
 841 static int SQLITE_TCLAPI crashEnableCmd(
 842   void * clientData,
 843   Tcl_Interp *interp,
 844   int objc,
 845   Tcl_Obj *CONST objv[]
 846 ){
 847   int isEnable;
 848   int isDefault = 0;
 849   static sqlite3_vfs crashVfs = {
 850     2,                  /* iVersion */
 851     0,                  /* szOsFile */
 852     0,                  /* mxPathname */
 853     0,                  /* pNext */
 854     "crash",            /* zName */
 855     0,                  /* pAppData */
 856
 857     cfOpen,               /* xOpen */
 858     cfDelete,             /* xDelete */
 859     cfAccess,             /* xAccess */
 860     cfFullPathname,       /* xFullPathname */
 861     cfDlOpen,             /* xDlOpen */
 862     cfDlError,            /* xDlError */
 863     cfDlSym,              /* xDlSym */
 864     cfDlClose,            /* xDlClose */
 865     cfRandomness,         /* xRandomness */
 866     cfSleep,              /* xSleep */
 867     cfCurrentTime,        /* xCurrentTime */
 868     cfGetLastError,       /* xGetLastError */
 869     0,                    /* xCurrentTimeInt64 */
 870   };
 871
 872   if( objc!=2 && objc!=3 ){
 873     Tcl_WrongNumArgs(interp, 1, objv, "ENABLE ?DEFAULT?");
 874     return TCL_ERROR;
 875   }
 876
 877   if( Tcl_GetBooleanFromObj(interp, objv[1], &isEnable) ){
 878     return TCL_ERROR;
 879   }
 880   if( objc==3 && Tcl_GetBooleanFromObj(interp, objv[2], &isDefault) ){
 881     return TCL_ERROR;
 882   }
 883
 884   if( (isEnable && crashVfs.pAppData) || (!isEnable && !crashVfs.pAppData) ){
 885     return TCL_OK;
 886   }
 887
 888   if( crashVfs.pAppData==0 ){
 889     sqlite3_vfs *pOriginalVfs = sqlite3_vfs_find(0);
 890     crashVfs.mxPathname = pOriginalVfs->mxPathname;
 891     crashVfs.pAppData = (void *)pOriginalVfs;
 892     crashVfs.szOsFile = sizeof(CrashFile) + pOriginalVfs->szOsFile;
 893     sqlite3_vfs_register(&crashVfs, isDefault);
 894   }else{
 895     crashVfs.pAppData = 0;
 896     sqlite3_vfs_unregister(&crashVfs);
 897   }
 898
 899   return TCL_OK;
 900 }
 901
 902 /*
 903 ** tclcmd:   sqlite_crashparams ?OPTIONS? DELAY CRASHFILE
 904 **
 905 ** This procedure implements a TCL command that enables crash testing
 906 ** in testfixture.  Once enabled, crash testing cannot be disabled.
 907 **
 908 ** Available options are "-characteristics" and "-sectorsize". Both require
 909 ** an argument. For -sectorsize, this is the simulated sector size in
 910 ** bytes. For -characteristics, the argument must be a list of io-capability
 911 ** flags to simulate. Valid flags are "atomic", "atomic512", "atomic1K",
 912 ** "atomic2K", "atomic4K", "atomic8K", "atomic16K", "atomic32K",
 913 ** "atomic64K", "sequential" and "safe_append".
 914 **
 915 ** Example:
 916 **
 917 **   sqlite_crashparams -sect 1024 -char {atomic sequential} ./test.db 1
 918 **
 919 */
 920 static int SQLITE_TCLAPI crashParamsObjCmd(
 921   void * clientData,
 922   Tcl_Interp *interp,
 923   int objc,
 924   Tcl_Obj *CONST objv[]
 925 ){
 926   int iDelay;
 927   const char *zCrashFile;
 928   int nCrashFile, iDc, iSectorSize;
 929
 930   iDc = -1;
 931   iSectorSize = -1;
 932
 933   if( objc<3 ){
 934     Tcl_WrongNumArgs(interp, 1, objv, "?OPTIONS? DELAY CRASHFILE");
 935     goto error;
 936   }
 937
 938   zCrashFile = Tcl_GetStringFromObj(objv[objc-1], &nCrashFile);
 939   if( nCrashFile>=sizeof(g.zCrashFile) ){
 940     Tcl_AppendResult(interp, "Filename is too long: \"", zCrashFile, "\"", 0);
 941     goto error;
 942   }
 943   if( Tcl_GetIntFromObj(interp, objv[objc-2], &iDelay) ){
 944     goto error;
 945   }
 946
 947   if( processDevSymArgs(interp, objc-3, &objv[1], &iDc, &iSectorSize) ){
 948     return TCL_ERROR;
 949   }
 950
 951   if( iDc>=0 ){
 952     g.iDeviceCharacteristics = iDc;
 953   }
 954   if( iSectorSize>=0 ){
 955     g.iSectorSize = iSectorSize;
 956   }
 957
 958   g.iCrash = iDelay;
 959   memcpy(g.zCrashFile, zCrashFile, nCrashFile+1);
 960   sqlite3CrashTestEnable = 1;
 961   return TCL_OK;
 962
 963 error:
 964   return TCL_ERROR;
 965 }
 966
 967 static int SQLITE_TCLAPI devSymObjCmd(
 968   void * clientData,
 969   Tcl_Interp *interp,
 970   int objc,
 971   Tcl_Obj *CONST objv[]
 972 ){
 973   void devsym_register(int iDeviceChar, int iSectorSize);
 974
 975   int iDc = -1;
 976   int iSectorSize = -1;
 977
 978   if( processDevSymArgs(interp, objc-1, &objv[1], &iDc, &iSectorSize) ){
 979     return TCL_ERROR;
 980   }
 981   devsym_register(iDc, iSectorSize);
 982
 983   return TCL_OK;
 984 }
 985
 986 /*
 987 ** tclcmd: sqlite3_crash_on_write N
 988 */
 989 static int SQLITE_TCLAPI writeCrashObjCmd(
 990   void * clientData,
 991   Tcl_Interp *interp,
 992   int objc,
 993   Tcl_Obj *CONST objv[]
 994 ){
 995   void devsym_crash_on_write(int);
 996   int nWrite = 0;
 997
 998   if( objc!=2 ){
 999     Tcl_WrongNumArgs(interp, 1, objv, "NWRITE");
1000     return TCL_ERROR;
1001   }
1002   if( Tcl_GetIntFromObj(interp, objv[1], &nWrite) ){
1003     return TCL_ERROR;
1004   }
1005
1006   devsym_crash_on_write(nWrite);
1007   return TCL_OK;
1008 }
1009
1010 /*
1011 ** tclcmd: unregister_devsim
1012 */
1013 static int SQLITE_TCLAPI dsUnregisterObjCmd(
1014   void * clientData,
1015   Tcl_Interp *interp,
1016   int objc,
1017   Tcl_Obj *CONST objv[]
1018 ){
1019   void devsym_unregister(void);
1020
1021   if( objc!=1 ){
1022     Tcl_WrongNumArgs(interp, 1, objv, "");
1023     return TCL_ERROR;
1024   }
1025
1026   devsym_unregister();
1027   return TCL_OK;
1028 }
1029
1030 /*
1031 ** tclcmd: register_jt_vfs ?-default? PARENT-VFS
1032 */
1033 static int SQLITE_TCLAPI jtObjCmd(
1034   void * clientData,
1035   Tcl_Interp *interp,
1036   int objc,
1037   Tcl_Obj *CONST objv[]
1038 ){
1039   int jt_register(char *, int);
1040   char *zParent = 0;
1041
1042   if( objc!=2 && objc!=3 ){
1043     Tcl_WrongNumArgs(interp, 1, objv, "?-default? PARENT-VFS");
1044     return TCL_ERROR;
1045   }
1046   zParent = Tcl_GetString(objv[1]);
1047   if( objc==3 ){
1048     if( strcmp(zParent, "-default") ){
1049       Tcl_AppendResult(interp,
1050           "bad option \"", zParent, "\": must be -default", 0
1051       );
1052       return TCL_ERROR;
1053     }
1054     zParent = Tcl_GetString(objv[2]);
1055   }
1056
1057   if( !(*zParent) ){
1058     zParent = 0;
1059   }
1060   if( jt_register(zParent, objc==3) ){
1061     Tcl_AppendResult(interp, "Error in jt_register", 0);
1062     return TCL_ERROR;
1063   }
1064
1065   return TCL_OK;
1066 }
1067
1068 /*
1069 ** tclcmd: unregister_jt_vfs
1070 */
1071 static int SQLITE_TCLAPI jtUnregisterObjCmd(
1072   void * clientData,
1073   Tcl_Interp *interp,
1074   int objc,
1075   Tcl_Obj *CONST objv[]
1076 ){
1077   void jt_unregister(void);
1078
1079   if( objc!=1 ){
1080     Tcl_WrongNumArgs(interp, 1, objv, "");
1081     return TCL_ERROR;
1082   }
1083
1084   jt_unregister();
1085   return TCL_OK;
1086 }
1087
1088 #endif /* SQLITE_OMIT_DISKIO */
1089
1090 /*
1091 ** This procedure registers the TCL procedures defined in this file.
1092 */
1093 int Sqlitetest6_Init(Tcl_Interp *interp){
1094 #ifndef SQLITE_OMIT_DISKIO
1095   Tcl_CreateObjCommand(interp, "sqlite3_crash_enable", crashEnableCmd, 0, 0);
1096   Tcl_CreateObjCommand(interp, "sqlite3_crashparams", crashParamsObjCmd, 0, 0);
1097   Tcl_CreateObjCommand(interp, "sqlite3_crash_now", crashNowCmd, 0, 0);
1098   Tcl_CreateObjCommand(interp, "sqlite3_simulate_device", devSymObjCmd, 0, 0);
1099   Tcl_CreateObjCommand(interp, "sqlite3_crash_on_write", writeCrashObjCmd,0,0);
1100   Tcl_CreateObjCommand(interp, "unregister_devsim", dsUnregisterObjCmd, 0, 0);
1101   Tcl_CreateObjCommand(interp, "register_jt_vfs", jtObjCmd, 0, 0);
1102   Tcl_CreateObjCommand(interp, "unregister_jt_vfs", jtUnregisterObjCmd, 0, 0);
1103 #endif
1104   return TCL_OK;
1105 }
1106
1107 #endif /* SQLITE_TEST */