/*

 ** 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.

 **

 ** $Id: test6.c,v 1.39 2008/06/06 11:11:26 danielk1977 Exp $

 */

 #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;

   /* 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);

 }

 /*

 ** 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 = sqlite3OsWrite(

               pRealFile, 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 = sqlite3OsWrite(

               pRealFile, zGarbage, g.iSectorSize, i*g.iSectorSize

             );

           }

           crash_free(zGarbage);

         }else{

           rc = SQLITE_NOMEM;

         }

         ppPtr = &pWrite->pNext;

         break;

       }

       default:

         assert(0); /* 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;

 }

 static const sqlite3_io_methods CrashFileVtab = {

   1,                            /* 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 */

 };

 /*

 ** 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;

   }

   if( rc==SQLITE_OK ){

     pWrapper->nData = (4096 + pWrapper->iSize);

     pWrapper->zData = crash_malloc(pWrapper->nData);

     if( pWrapper->zData ){

       memset(pWrapper->zData, 0, pWrapper->nData);

       rc = sqlite3OsRead(pReal, pWrapper->zData, pWrapper->iSize, 0); 

     }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 *pHandle, const char *zSymbol){

   sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;

   return pVfs->xDlSym(pVfs, pHandle, zSymbol);

 }

 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 = {

     1,                  /* 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 */

   };

   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;

 }

 #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);

 #endif

   return TCL_OK;

 }

 #endif /* SQLITE_TEST */