root/third_party/sqlite/src/src/test6.c

DEFINITIONS

1. crash_malloc
2. crash_free
3. crash_realloc
4. writeDbFile
5. writeListSync
6. writeListAppend
7. cfClose
8. cfRead
9. cfWrite
10. cfTruncate
11. cfSync
12. cfFileSize
13. cfLock
14. cfUnlock
15. cfCheckReservedLock
16. cfFileControl
17. cfSectorSize
18. cfDeviceCharacteristics
19. cfShmLock
20. cfShmBarrier
21. cfShmUnmap
22. cfShmMap
23. cfOpen
24. cfDelete
25. cfAccess
26. cfFullPathname
27. cfDlOpen
28. cfDlError
29. cfDlSym
30. cfDlClose
31. cfRandomness
32. cfSleep
33. cfCurrentTime
34. processDevSymArgs
35. crashEnableCmd
36. crashParamsObjCmd
37. devSymObjCmd
38. jtObjCmd
39. jtUnregisterObjCmd
40. Sqlitetest6_Init

/*
** 2004 May 22
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
******************************************************************************
**
** This file contains code that modified the OS layer in order to simulate
** the effect on the database file of an OS crash or power failure.  This
** is used to test the ability of SQLite to recover from those situations.
*/
#if SQLITE_TEST          /* This file is used for testing only */
#include "sqliteInt.h"
#include "tcl.h"

#ifndef SQLITE_OMIT_DISKIO  /* This file is a no-op if disk I/O is disabled */

/* #define TRACE_CRASHTEST */

typedef struct CrashFile CrashFile;
typedef struct CrashGlobal CrashGlobal;
typedef struct WriteBuffer WriteBuffer;

/*
** Method:
**
**   This layer is implemented as a wrapper around the "real" 
**   sqlite3_file object for the host system. Each time data is 
**   written to the file object, instead of being written to the
**   underlying file, the write operation is stored in an in-memory 
**   structure (type WriteBuffer). This structure is placed at the
**   end of a global ordered list (the write-list).
**
**   When data is read from a file object, the requested region is
**   first retrieved from the real file. The write-list is then 
**   traversed and data copied from any overlapping WriteBuffer 
**   structures to the output buffer. i.e. a read() operation following
**   one or more write() operations works as expected, even if no
**   data has actually been written out to the real file.
**
**   When a fsync() operation is performed, an operating system crash 
**   may be simulated, in which case exit(-1) is called (the call to 
**   xSync() never returns). Whether or not a crash is simulated,
**   the data associated with a subset of the WriteBuffer structures 
**   stored in the write-list is written to the real underlying files 
**   and the entries removed from the write-list. If a crash is simulated,
**   a subset of the buffers may be corrupted before the data is written.
**
**   The exact subset of the write-list written and/or corrupted is
**   determined by the simulated device characteristics and sector-size.
**
** "Normal" mode:
**
**   Normal mode is used when the simulated device has none of the
**   SQLITE_IOCAP_XXX flags set.
**
**   In normal mode, if the fsync() is not a simulated crash, the 
**   write-list is traversed from beginning to end. Each WriteBuffer
**   structure associated with the file handle used to call xSync()
**   is written to the real file and removed from the write-list.
**
**   If a crash is simulated, one of the following takes place for 
**   each WriteBuffer in the write-list, regardless of which 
**   file-handle it is associated with:
**
**     1. The buffer is correctly written to the file, just as if
**        a crash were not being simulated.
**
**     2. Nothing is done.
**
**     3. Garbage data is written to all sectors of the file that 
**        overlap the region specified by the WriteBuffer. Or garbage
**        data is written to some contiguous section within the 
**        overlapped sectors.
**
** Device Characteristic flag handling:
**
**   If the IOCAP_ATOMIC flag is set, then option (3) above is 
**   never selected.
**
**   If the IOCAP_ATOMIC512 flag is set, and the WriteBuffer represents
**   an aligned write() of an integer number of 512 byte regions, then
**   option (3) above is never selected. Instead, each 512 byte region
**   is either correctly written or left completely untouched. Similar
**   logic governs the behaviour if any of the other ATOMICXXX flags
**   is set.
**
**   If either the IOCAP_SAFEAPPEND or IOCAP_SEQUENTIAL flags are set
**   and a crash is being simulated, then an entry of the write-list is
**   selected at random. Everything in the list after the selected entry 
**   is discarded before processing begins.
**
**   If IOCAP_SEQUENTIAL is set and a crash is being simulated, option 
**   (1) is selected for all write-list entries except the last. If a 
**   crash is not being simulated, then all entries in the write-list
**   that occur before at least one write() on the file-handle specified
**   as part of the xSync() are written to their associated real files.
**
**   If IOCAP_SAFEAPPEND is set and the first byte written by the write()
**   operation is one byte past the current end of the file, then option
**   (1) is always selected.
*/

/*
** Each write operation in the write-list is represented by an instance
** of the following structure.
**
** If zBuf is 0, then this structure represents a call to xTruncate(), 
** not xWrite(). In that case, iOffset is the size that the file is
** truncated to.
*/
struct WriteBuffer {
  i64 iOffset;                 /* Byte offset of the start of this write() */
  int nBuf;                    /* Number of bytes written */
  u8 *zBuf;                    /* Pointer to copy of written data */
  CrashFile *pFile;            /* File this write() applies to */

  WriteBuffer *pNext;          /* Next in CrashGlobal.pWriteList */
};

struct CrashFile {
  const sqlite3_io_methods *pMethod;   /* Must be first */
  sqlite3_file *pRealFile;             /* Underlying "real" file handle */
  char *zName;
  int flags;                           /* Flags the file was opened with */

  /* Cache of the entire file. This is used to speed up OsRead() and 
  ** OsFileSize() calls. Although both could be done by traversing the
  ** write-list, in practice this is impractically slow.
  */
  int iSize;                           /* Size of file in bytes */
  int nData;                           /* Size of buffer allocated at zData */
  u8 *zData;                           /* Buffer containing file contents */
};

struct CrashGlobal {
  WriteBuffer *pWriteList;     /* Head of write-list */
  WriteBuffer *pWriteListEnd;  /* End of write-list */

  int iSectorSize;             /* Value of simulated sector size */
  int iDeviceCharacteristics;  /* Value of simulated device characteristics */

  int iCrash;                  /* Crash on the iCrash'th call to xSync() */
  char zCrashFile[500];        /* Crash during an xSync() on this file */ 
};

static CrashGlobal g = {0, 0, SQLITE_DEFAULT_SECTOR_SIZE, 0, 0};

/*
** Set this global variable to 1 to enable crash testing.
*/
static int sqlite3CrashTestEnable = 0;

static void *crash_malloc(int nByte){
  return (void *)Tcl_Alloc((size_t)nByte);
}
static void crash_free(void *p){
  Tcl_Free(p);
}
static void *crash_realloc(void *p, int n){
  return (void *)Tcl_Realloc(p, (size_t)n);
}

/*
** Wrapper around the sqlite3OsWrite() function that avoids writing to the
** 512 byte block begining at offset PENDING_BYTE.
*/
static int writeDbFile(CrashFile *p, u8 *z, i64 iAmt, i64 iOff){
  int rc = SQLITE_OK;
  int iSkip = 0;
  if( iOff==PENDING_BYTE && (p->flags&SQLITE_OPEN_MAIN_DB) ){
    iSkip = 512;
  }
  if( (iAmt-iSkip)>0 ){
    rc = sqlite3OsWrite(p->pRealFile, &z[iSkip], iAmt-iSkip, iOff+iSkip);
  }
  return rc;
}

/*
** Flush the write-list as if xSync() had been called on file handle
** pFile. If isCrash is true, simulate a crash.
*/
static int writeListSync(CrashFile *pFile, int isCrash){
  int rc = SQLITE_OK;
  int iDc = g.iDeviceCharacteristics;

  WriteBuffer *pWrite;
  WriteBuffer **ppPtr;

  /* If this is not a crash simulation, set pFinal to point to the 
  ** last element of the write-list that is associated with file handle
  ** pFile.
  **
  ** If this is a crash simulation, set pFinal to an arbitrarily selected
  ** element of the write-list.
  */
  WriteBuffer *pFinal = 0;
  if( !isCrash ){
    for(pWrite=g.pWriteList; pWrite; pWrite=pWrite->pNext){
      if( pWrite->pFile==pFile ){
        pFinal = pWrite;
      }
    }
  }else if( iDc&(SQLITE_IOCAP_SEQUENTIAL|SQLITE_IOCAP_SAFE_APPEND) ){
    int nWrite = 0;
    int iFinal;
    for(pWrite=g.pWriteList; pWrite; pWrite=pWrite->pNext) nWrite++;
    sqlite3_randomness(sizeof(int), &iFinal);
    iFinal = ((iFinal<0)?-1*iFinal:iFinal)%nWrite;
    for(pWrite=g.pWriteList; iFinal>0; pWrite=pWrite->pNext) iFinal--;
    pFinal = pWrite;
  }

#ifdef TRACE_CRASHTEST
  printf("Sync %s (is %s crash)\n", pFile->zName, (isCrash?"a":"not a"));
#endif

  ppPtr = &g.pWriteList;
  for(pWrite=*ppPtr; rc==SQLITE_OK && pWrite; pWrite=*ppPtr){
    sqlite3_file *pRealFile = pWrite->pFile->pRealFile;

    /* (eAction==1)      -> write block out normally,
    ** (eAction==2)      -> do nothing,
    ** (eAction==3)      -> trash sectors.
    */
    int eAction = 0;
    if( !isCrash ){
      eAction = 2;
      if( (pWrite->pFile==pFile || iDc&SQLITE_IOCAP_SEQUENTIAL) ){
        eAction = 1;
      }
    }else{
      char random;
      sqlite3_randomness(1, &random);

      /* Do not select option 3 (sector trashing) if the IOCAP_ATOMIC flag 
      ** is set or this is an OsTruncate(), not an Oswrite().
      */
      if( (iDc&SQLITE_IOCAP_ATOMIC) || (pWrite->zBuf==0) ){
        random &= 0x01;
      }

      /* If IOCAP_SEQUENTIAL is set and this is not the final entry
      ** in the truncated write-list, always select option 1 (write
      ** out correctly).
      */
      if( (iDc&SQLITE_IOCAP_SEQUENTIAL && pWrite!=pFinal) ){
        random = 0;
      }

      /* If IOCAP_SAFE_APPEND is set and this OsWrite() operation is
      ** an append (first byte of the written region is 1 byte past the
      ** current EOF), always select option 1 (write out correctly).
      */
      if( iDc&SQLITE_IOCAP_SAFE_APPEND && pWrite->zBuf ){
        i64 iSize;
        sqlite3OsFileSize(pRealFile, &iSize);
        if( iSize==pWrite->iOffset ){
          random = 0;
        }
      }

      if( (random&0x06)==0x06 ){
        eAction = 3;
      }else{
        eAction = ((random&0x01)?2:1);
      }
    }

    switch( eAction ){
      case 1: {               /* Write out correctly */
        if( pWrite->zBuf ){
          rc = writeDbFile(
              pWrite->pFile, pWrite->zBuf, pWrite->nBuf, pWrite->iOffset
          );
        }else{
          rc = sqlite3OsTruncate(pRealFile, pWrite->iOffset);
        }
        *ppPtr = pWrite->pNext;
#ifdef TRACE_CRASHTEST
        if( isCrash ){
          printf("Writing %d bytes @ %d (%s)\n", 
            pWrite->nBuf, (int)pWrite->iOffset, pWrite->pFile->zName
          );
        }
#endif
        crash_free(pWrite);
        break;
      }
      case 2: {               /* Do nothing */
        ppPtr = &pWrite->pNext;
#ifdef TRACE_CRASHTEST
        if( isCrash ){
          printf("Omiting %d bytes @ %d (%s)\n", 
            pWrite->nBuf, (int)pWrite->iOffset, pWrite->pFile->zName
          );
        }
#endif
        break;
      }
      case 3: {               /* Trash sectors */
        u8 *zGarbage;
        int iFirst = (pWrite->iOffset/g.iSectorSize);
        int iLast = (pWrite->iOffset+pWrite->nBuf-1)/g.iSectorSize;

        assert(pWrite->zBuf);

#ifdef TRACE_CRASHTEST
        printf("Trashing %d sectors @ sector %d (%s)\n", 
            1+iLast-iFirst, iFirst, pWrite->pFile->zName
        );
#endif

        zGarbage = crash_malloc(g.iSectorSize);
        if( zGarbage ){
          sqlite3_int64 i;
          for(i=iFirst; rc==SQLITE_OK && i<=iLast; i++){
            sqlite3_randomness(g.iSectorSize, zGarbage); 
            rc = writeDbFile(
              pWrite->pFile, zGarbage, g.iSectorSize, i*g.iSectorSize
            );
          }
          crash_free(zGarbage);
        }else{
          rc = SQLITE_NOMEM;
        }

        ppPtr = &pWrite->pNext;
        break;
      }

      default:
        assert(!"Cannot happen");
    }

    if( pWrite==pFinal ) break;
  }

  if( rc==SQLITE_OK && isCrash ){
    exit(-1);
  }

  for(pWrite=g.pWriteList; pWrite && pWrite->pNext; pWrite=pWrite->pNext);
  g.pWriteListEnd = pWrite;

  return rc;
}

/*
** Add an entry to the end of the write-list.
*/
static int writeListAppend(
  sqlite3_file *pFile,
  sqlite3_int64 iOffset,
  const u8 *zBuf,
  int nBuf
){
  WriteBuffer *pNew;

  assert((zBuf && nBuf) || (!nBuf && !zBuf));

  pNew = (WriteBuffer *)crash_malloc(sizeof(WriteBuffer) + nBuf);
  if( pNew==0 ){
    fprintf(stderr, "out of memory in the crash simulator\n");
  }
  memset(pNew, 0, sizeof(WriteBuffer)+nBuf);
  pNew->iOffset = iOffset;
  pNew->nBuf = nBuf;
  pNew->pFile = (CrashFile *)pFile;
  if( zBuf ){
    pNew->zBuf = (u8 *)&pNew[1];
    memcpy(pNew->zBuf, zBuf, nBuf);
  }

  if( g.pWriteList ){
    assert(g.pWriteListEnd);
    g.pWriteListEnd->pNext = pNew;
  }else{
    g.pWriteList = pNew;
  }
  g.pWriteListEnd = pNew;
  
  return SQLITE_OK;
}

/*
** Close a crash-file.
*/
static int cfClose(sqlite3_file *pFile){
  CrashFile *pCrash = (CrashFile *)pFile;
  writeListSync(pCrash, 0);
  sqlite3OsClose(pCrash->pRealFile);
  return SQLITE_OK;
}

/*
** Read data from a crash-file.
*/
static int cfRead(
  sqlite3_file *pFile, 
  void *zBuf, 
  int iAmt, 
  sqlite_int64 iOfst
){
  CrashFile *pCrash = (CrashFile *)pFile;

  /* Check the file-size to see if this is a short-read */
  if( pCrash->iSize<(iOfst+iAmt) ){
    return SQLITE_IOERR_SHORT_READ;
  }

  memcpy(zBuf, &pCrash->zData[iOfst], iAmt);
  return SQLITE_OK;
}

/*
** Write data to a crash-file.
*/
static int cfWrite(
  sqlite3_file *pFile, 
  const void *zBuf, 
  int iAmt, 
  sqlite_int64 iOfst
){
  CrashFile *pCrash = (CrashFile *)pFile;
  if( iAmt+iOfst>pCrash->iSize ){
    pCrash->iSize = iAmt+iOfst;
  }
  while( pCrash->iSize>pCrash->nData ){
    u8 *zNew;
    int nNew = (pCrash->nData*2) + 4096;
    zNew = crash_realloc(pCrash->zData, nNew);
    if( !zNew ){
      return SQLITE_NOMEM;
    }
    memset(&zNew[pCrash->nData], 0, nNew-pCrash->nData);
    pCrash->nData = nNew;
    pCrash->zData = zNew;
  }
  memcpy(&pCrash->zData[iOfst], zBuf, iAmt);
  return writeListAppend(pFile, iOfst, zBuf, iAmt);
}

/*
** Truncate a crash-file.
*/
static int cfTruncate(sqlite3_file *pFile, sqlite_int64 size){
  CrashFile *pCrash = (CrashFile *)pFile;
  assert(size>=0);
  if( pCrash->iSize>size ){
    pCrash->iSize = size;
  }
  return writeListAppend(pFile, size, 0, 0);
}

/*
** Sync a crash-file.
*/
static int cfSync(sqlite3_file *pFile, int flags){
  CrashFile *pCrash = (CrashFile *)pFile;
  int isCrash = 0;

  const char *zName = pCrash->zName;
  const char *zCrashFile = g.zCrashFile;
  int nName = strlen(zName);
  int nCrashFile = strlen(zCrashFile);

  if( nCrashFile>0 && zCrashFile[nCrashFile-1]=='*' ){
    nCrashFile--;
    if( nName>nCrashFile ) nName = nCrashFile;
  }

  if( nName==nCrashFile && 0==memcmp(zName, zCrashFile, nName) ){
    if( (--g.iCrash)==0 ) isCrash = 1;
  }

  return writeListSync(pCrash, isCrash);
}

/*
** Return the current file-size of the crash-file.
*/
static int cfFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
  CrashFile *pCrash = (CrashFile *)pFile;
  *pSize = (i64)pCrash->iSize;
  return SQLITE_OK;
}

/*
** Calls related to file-locks are passed on to the real file handle.
*/
static int cfLock(sqlite3_file *pFile, int eLock){
  return sqlite3OsLock(((CrashFile *)pFile)->pRealFile, eLock);
}
static int cfUnlock(sqlite3_file *pFile, int eLock){
  return sqlite3OsUnlock(((CrashFile *)pFile)->pRealFile, eLock);
}
static int cfCheckReservedLock(sqlite3_file *pFile, int *pResOut){
  return sqlite3OsCheckReservedLock(((CrashFile *)pFile)->pRealFile, pResOut);
}
static int cfFileControl(sqlite3_file *pFile, int op, void *pArg){
  return sqlite3OsFileControl(((CrashFile *)pFile)->pRealFile, op, pArg);
}

/*
** The xSectorSize() and xDeviceCharacteristics() functions return
** the global values configured by the [sqlite_crashparams] tcl
*  interface.
*/
static int cfSectorSize(sqlite3_file *pFile){
  return g.iSectorSize;
}
static int cfDeviceCharacteristics(sqlite3_file *pFile){
  return g.iDeviceCharacteristics;
}

/*
** Pass-throughs for WAL support.
*/
static int cfShmLock(sqlite3_file *pFile, int ofst, int n, int flags){
  return sqlite3OsShmLock(((CrashFile*)pFile)->pRealFile, ofst, n, flags);
}
static void cfShmBarrier(sqlite3_file *pFile){
  sqlite3OsShmBarrier(((CrashFile*)pFile)->pRealFile);
}
static int cfShmUnmap(sqlite3_file *pFile, int delFlag){
  return sqlite3OsShmUnmap(((CrashFile*)pFile)->pRealFile, delFlag);
}
static int cfShmMap(
  sqlite3_file *pFile,            /* Handle open on database file */
  int iRegion,                    /* Region to retrieve */
  int sz,                         /* Size of regions */
  int w,                          /* True to extend file if necessary */
  void volatile **pp              /* OUT: Mapped memory */
){
  return sqlite3OsShmMap(((CrashFile*)pFile)->pRealFile, iRegion, sz, w, pp);
}

static const sqlite3_io_methods CrashFileVtab = {
  2,                            /* iVersion */
  cfClose,                      /* xClose */
  cfRead,                       /* xRead */
  cfWrite,                      /* xWrite */
  cfTruncate,                   /* xTruncate */
  cfSync,                       /* xSync */
  cfFileSize,                   /* xFileSize */
  cfLock,                       /* xLock */
  cfUnlock,                     /* xUnlock */
  cfCheckReservedLock,          /* xCheckReservedLock */
  cfFileControl,                /* xFileControl */
  cfSectorSize,                 /* xSectorSize */
  cfDeviceCharacteristics,      /* xDeviceCharacteristics */
  cfShmMap,                     /* xShmMap */
  cfShmLock,                    /* xShmLock */
  cfShmBarrier,                 /* xShmBarrier */
  cfShmUnmap                    /* xShmUnmap */
};

/*
** Application data for the crash VFS
*/
struct crashAppData {
  sqlite3_vfs *pOrig;                   /* Wrapped vfs structure */
};

/*
** Open a crash-file file handle.
**
** The caller will have allocated pVfs->szOsFile bytes of space
** at pFile. This file uses this space for the CrashFile structure
** and allocates space for the "real" file structure using 
** sqlite3_malloc(). The assumption here is (pVfs->szOsFile) is
** equal or greater than sizeof(CrashFile).
*/
static int cfOpen(
  sqlite3_vfs *pCfVfs,
  const char *zName,
  sqlite3_file *pFile,
  int flags,
  int *pOutFlags
){
  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
  int rc;
  CrashFile *pWrapper = (CrashFile *)pFile;
  sqlite3_file *pReal = (sqlite3_file*)&pWrapper[1];

  memset(pWrapper, 0, sizeof(CrashFile));
  rc = sqlite3OsOpen(pVfs, zName, pReal, flags, pOutFlags);

  if( rc==SQLITE_OK ){
    i64 iSize;
    pWrapper->pMethod = &CrashFileVtab;
    pWrapper->zName = (char *)zName;
    pWrapper->pRealFile = pReal;
    rc = sqlite3OsFileSize(pReal, &iSize);
    pWrapper->iSize = (int)iSize;
    pWrapper->flags = flags;
  }
  if( rc==SQLITE_OK ){
    pWrapper->nData = (4096 + pWrapper->iSize);
    pWrapper->zData = crash_malloc(pWrapper->nData);
    if( pWrapper->zData ){
      /* os_unix.c contains an assert() that fails if the caller attempts
      ** to read data from the 512-byte locking region of a file opened
      ** with the SQLITE_OPEN_MAIN_DB flag. This region of a database file
      ** never contains valid data anyhow. So avoid doing such a read here.
      */
      const int isDb = (flags&SQLITE_OPEN_MAIN_DB);
      i64 iChunk = pWrapper->iSize;
      if( iChunk>PENDING_BYTE && isDb ){
        iChunk = PENDING_BYTE;
      }
      memset(pWrapper->zData, 0, pWrapper->nData);
      rc = sqlite3OsRead(pReal, pWrapper->zData, iChunk, 0); 
      if( SQLITE_OK==rc && pWrapper->iSize>(PENDING_BYTE+512) && isDb ){
        i64 iOff = PENDING_BYTE+512;
        iChunk = pWrapper->iSize - iOff;
        rc = sqlite3OsRead(pReal, &pWrapper->zData[iOff], iChunk, iOff);
      }
    }else{
      rc = SQLITE_NOMEM;
    }
  }
  if( rc!=SQLITE_OK && pWrapper->pMethod ){
    sqlite3OsClose(pFile);
  }
  return rc;
}

static int cfDelete(sqlite3_vfs *pCfVfs, const char *zPath, int dirSync){
  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
  return pVfs->xDelete(pVfs, zPath, dirSync);
}
static int cfAccess(
  sqlite3_vfs *pCfVfs, 
  const char *zPath, 
  int flags, 
  int *pResOut
){
  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
  return pVfs->xAccess(pVfs, zPath, flags, pResOut);
}
static int cfFullPathname(
  sqlite3_vfs *pCfVfs, 
  const char *zPath, 
  int nPathOut,
  char *zPathOut
){
  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
  return pVfs->xFullPathname(pVfs, zPath, nPathOut, zPathOut);
}
static void *cfDlOpen(sqlite3_vfs *pCfVfs, const char *zPath){
  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
  return pVfs->xDlOpen(pVfs, zPath);
}
static void cfDlError(sqlite3_vfs *pCfVfs, int nByte, char *zErrMsg){
  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
  pVfs->xDlError(pVfs, nByte, zErrMsg);
}
static void (*cfDlSym(sqlite3_vfs *pCfVfs, void *pH, const char *zSym))(void){
  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
  return pVfs->xDlSym(pVfs, pH, zSym);
}
static void cfDlClose(sqlite3_vfs *pCfVfs, void *pHandle){
  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
  pVfs->xDlClose(pVfs, pHandle);
}
static int cfRandomness(sqlite3_vfs *pCfVfs, int nByte, char *zBufOut){
  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
  return pVfs->xRandomness(pVfs, nByte, zBufOut);
}
static int cfSleep(sqlite3_vfs *pCfVfs, int nMicro){
  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
  return pVfs->xSleep(pVfs, nMicro);
}
static int cfCurrentTime(sqlite3_vfs *pCfVfs, double *pTimeOut){
  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
  return pVfs->xCurrentTime(pVfs, pTimeOut);
}

static int processDevSymArgs(
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[],
  int *piDeviceChar,
  int *piSectorSize
){
  struct DeviceFlag {
    char *zName;
    int iValue;
  } aFlag[] = {
    { "atomic",      SQLITE_IOCAP_ATOMIC      },
    { "atomic512",   SQLITE_IOCAP_ATOMIC512   },
    { "atomic1k",    SQLITE_IOCAP_ATOMIC1K    },
    { "atomic2k",    SQLITE_IOCAP_ATOMIC2K    },
    { "atomic4k",    SQLITE_IOCAP_ATOMIC4K    },
    { "atomic8k",    SQLITE_IOCAP_ATOMIC8K    },
    { "atomic16k",   SQLITE_IOCAP_ATOMIC16K   },
    { "atomic32k",   SQLITE_IOCAP_ATOMIC32K   },
    { "atomic64k",   SQLITE_IOCAP_ATOMIC64K   },
    { "sequential",  SQLITE_IOCAP_SEQUENTIAL  },
    { "safe_append", SQLITE_IOCAP_SAFE_APPEND },
    { 0, 0 }
  };

  int i;
  int iDc = 0;
  int iSectorSize = 0;
  int setSectorsize = 0;
  int setDeviceChar = 0;

  for(i=0; i<objc; i+=2){
    int nOpt;
    char *zOpt = Tcl_GetStringFromObj(objv[i], &nOpt);

    if( (nOpt>11 || nOpt<2 || strncmp("-sectorsize", zOpt, nOpt)) 
     && (nOpt>16 || nOpt<2 || strncmp("-characteristics", zOpt, nOpt))
    ){
      Tcl_AppendResult(interp, 
        "Bad option: \"", zOpt, 
        "\" - must be \"-characteristics\" or \"-sectorsize\"", 0
      );
      return TCL_ERROR;
    }
    if( i==objc-1 ){
      Tcl_AppendResult(interp, "Option requires an argument: \"", zOpt, "\"",0);
      return TCL_ERROR;
    }

    if( zOpt[1]=='s' ){
      if( Tcl_GetIntFromObj(interp, objv[i+1], &iSectorSize) ){
        return TCL_ERROR;
      }
      setSectorsize = 1;
    }else{
      int j;
      Tcl_Obj **apObj;
      int nObj;
      if( Tcl_ListObjGetElements(interp, objv[i+1], &nObj, &apObj) ){
        return TCL_ERROR;
      }
      for(j=0; j<nObj; j++){
        int rc;
        int iChoice;
        Tcl_Obj *pFlag = Tcl_DuplicateObj(apObj[j]);
        Tcl_IncrRefCount(pFlag);
        Tcl_UtfToLower(Tcl_GetString(pFlag));
 
        rc = Tcl_GetIndexFromObjStruct(
            interp, pFlag, aFlag, sizeof(aFlag[0]), "no such flag", 0, &iChoice
        );
        Tcl_DecrRefCount(pFlag);
        if( rc ){
          return TCL_ERROR;
        }

        iDc |= aFlag[iChoice].iValue;
      }
      setDeviceChar = 1;
    }
  }

  if( setDeviceChar ){
    *piDeviceChar = iDc;
  }
  if( setSectorsize ){
    *piSectorSize = iSectorSize;
  }

  return TCL_OK;
}

/*
** tclcmd:   sqlite_crash_enable ENABLE
**
** Parameter ENABLE must be a boolean value. If true, then the "crash"
** vfs is added to the system. If false, it is removed.
*/
static int crashEnableCmd(
  void * clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
  int isEnable;
  static sqlite3_vfs crashVfs = {
    2,                  /* iVersion */
    0,                  /* szOsFile */
    0,                  /* mxPathname */
    0,                  /* pNext */
    "crash",            /* zName */
    0,                  /* pAppData */
  
    cfOpen,               /* xOpen */
    cfDelete,             /* xDelete */
    cfAccess,             /* xAccess */
    cfFullPathname,       /* xFullPathname */
    cfDlOpen,             /* xDlOpen */
    cfDlError,            /* xDlError */
    cfDlSym,              /* xDlSym */
    cfDlClose,            /* xDlClose */
    cfRandomness,         /* xRandomness */
    cfSleep,              /* xSleep */
    cfCurrentTime,        /* xCurrentTime */
    0,                    /* xGetlastError */
    0,                    /* xCurrentTimeInt64 */
  };

  if( objc!=2 ){
    Tcl_WrongNumArgs(interp, 1, objv, "ENABLE");
    return TCL_ERROR;
  }

  if( Tcl_GetBooleanFromObj(interp, objv[1], &isEnable) ){
    return TCL_ERROR;
  }

  if( (isEnable && crashVfs.pAppData) || (!isEnable && !crashVfs.pAppData) ){
    return TCL_OK;
  }

  if( crashVfs.pAppData==0 ){
    sqlite3_vfs *pOriginalVfs = sqlite3_vfs_find(0);
    crashVfs.mxPathname = pOriginalVfs->mxPathname;
    crashVfs.pAppData = (void *)pOriginalVfs;
    crashVfs.szOsFile = sizeof(CrashFile) + pOriginalVfs->szOsFile;
    sqlite3_vfs_register(&crashVfs, 0);
  }else{
    crashVfs.pAppData = 0;
    sqlite3_vfs_unregister(&crashVfs);
  }

  return TCL_OK;
}

/*
** tclcmd:   sqlite_crashparams ?OPTIONS? DELAY CRASHFILE
**
** This procedure implements a TCL command that enables crash testing
** in testfixture.  Once enabled, crash testing cannot be disabled.
**
** Available options are "-characteristics" and "-sectorsize". Both require
** an argument. For -sectorsize, this is the simulated sector size in
** bytes. For -characteristics, the argument must be a list of io-capability
** flags to simulate. Valid flags are "atomic", "atomic512", "atomic1K",
** "atomic2K", "atomic4K", "atomic8K", "atomic16K", "atomic32K", 
** "atomic64K", "sequential" and "safe_append".
**
** Example:
**
**   sqlite_crashparams -sect 1024 -char {atomic sequential} ./test.db 1
**
*/
static int crashParamsObjCmd(
  void * clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
  int iDelay;
  const char *zCrashFile;
  int nCrashFile, iDc, iSectorSize;

  iDc = -1;
  iSectorSize = -1;

  if( objc<3 ){
    Tcl_WrongNumArgs(interp, 1, objv, "?OPTIONS? DELAY CRASHFILE");
    goto error;
  }

  zCrashFile = Tcl_GetStringFromObj(objv[objc-1], &nCrashFile);
  if( nCrashFile>=sizeof(g.zCrashFile) ){
    Tcl_AppendResult(interp, "Filename is too long: \"", zCrashFile, "\"", 0);
    goto error;
  }
  if( Tcl_GetIntFromObj(interp, objv[objc-2], &iDelay) ){
    goto error;
  }

  if( processDevSymArgs(interp, objc-3, &objv[1], &iDc, &iSectorSize) ){
    return TCL_ERROR;
  }

  if( iDc>=0 ){
    g.iDeviceCharacteristics = iDc;
  }
  if( iSectorSize>=0 ){
    g.iSectorSize = iSectorSize;
  }

  g.iCrash = iDelay;
  memcpy(g.zCrashFile, zCrashFile, nCrashFile+1);
  sqlite3CrashTestEnable = 1;
  return TCL_OK;

error:
  return TCL_ERROR;
}

static int devSymObjCmd(
  void * clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
  void devsym_register(int iDeviceChar, int iSectorSize);

  int iDc = -1;
  int iSectorSize = -1;

  if( processDevSymArgs(interp, objc-1, &objv[1], &iDc, &iSectorSize) ){
    return TCL_ERROR;
  }
  devsym_register(iDc, iSectorSize);

  return TCL_OK;
}

/*
** tclcmd: register_jt_vfs ?-default? PARENT-VFS
*/
static int jtObjCmd(
  void * clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
  int jt_register(char *, int);
  char *zParent = 0;

  if( objc!=2 && objc!=3 ){
    Tcl_WrongNumArgs(interp, 1, objv, "?-default? PARENT-VFS");
    return TCL_ERROR;
  }
  zParent = Tcl_GetString(objv[1]);
  if( objc==3 ){
    if( strcmp(zParent, "-default") ){
      Tcl_AppendResult(interp, 
          "bad option \"", zParent, "\": must be -default", 0
      );
      return TCL_ERROR;
    }
    zParent = Tcl_GetString(objv[2]);
  }

  if( !(*zParent) ){
    zParent = 0;
  }
  if( jt_register(zParent, objc==3) ){
    Tcl_AppendResult(interp, "Error in jt_register", 0);
    return TCL_ERROR;
  }

  return TCL_OK;
}

/*
** tclcmd: unregister_jt_vfs
*/
static int jtUnregisterObjCmd(
  void * clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
  void jt_unregister(void);

  if( objc!=1 ){
    Tcl_WrongNumArgs(interp, 1, objv, "");
    return TCL_ERROR;
  }

  jt_unregister();
  return TCL_OK;
}

#endif /* SQLITE_OMIT_DISKIO */

/*
** This procedure registers the TCL procedures defined in this file.
*/
int Sqlitetest6_Init(Tcl_Interp *interp){
#ifndef SQLITE_OMIT_DISKIO
  Tcl_CreateObjCommand(interp, "sqlite3_crash_enable", crashEnableCmd, 0, 0);
  Tcl_CreateObjCommand(interp, "sqlite3_crashparams", crashParamsObjCmd, 0, 0);
  Tcl_CreateObjCommand(interp, "sqlite3_simulate_device", devSymObjCmd, 0, 0);
  Tcl_CreateObjCommand(interp, "register_jt_vfs", jtObjCmd, 0, 0);
  Tcl_CreateObjCommand(interp, "unregister_jt_vfs", jtUnregisterObjCmd, 0, 0);
#endif
  return TCL_OK;
}

#endif /* SQLITE_TEST */