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src/test_vfs.c
1 697 строк49 KB
stephan
Test app/script patches from Jan Nijtmans for cygwin. Add/replace many more sentinel arguments for TCL variadic functions which specifically need a NULL trailing argument. With this, 'make test' on cygwin runs to completion for me, with 134 of 329227 tests failing. MSC build fails the same 13 tests which fail for me in trunk.
08 мар 2025, 09:53
08 мар 2025, 09:53065c0a6
/*
** 2010 May 05
**
** 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 the implementation of the Tcl [testvfs] command,
** used to create SQLite VFS implementations with various properties and
** instrumentation to support testing SQLite.
**
**   testvfs VFSNAME ?OPTIONS?
**
** Available options are:
**
**   -noshm      BOOLEAN        (True to omit shm methods. Default false)
**   -default    BOOLEAN        (True to make the vfs default. Default false)
**   -szosfile   INTEGER        (Value for sqlite3_vfs.szOsFile)
**   -mxpathname INTEGER        (Value for sqlite3_vfs.mxPathname)
**   -iversion   INTEGER        (Value for sqlite3_vfs.iVersion)
*/
#if SQLITE_TEST          /* This file is used for testing only */

#include "sqlite3.h"
#include "sqliteInt.h"
#include "tclsqlite.h"

typedef struct Testvfs Testvfs;
typedef struct TestvfsShm TestvfsShm;
typedef struct TestvfsBuffer TestvfsBuffer;
typedef struct TestvfsFile TestvfsFile;
typedef struct TestvfsFd TestvfsFd;

/*
** An open file handle.
*/
struct TestvfsFile {
  sqlite3_file base;              /* Base class.  Must be first */
  TestvfsFd *pFd;                 /* File data */
};
#define tvfsGetFd(pFile) (((TestvfsFile *)pFile)->pFd)

struct TestvfsFd {
  sqlite3_vfs *pVfs;              /* The VFS */
  const char *zFilename;          /* Filename as passed to xOpen() */
  sqlite3_file *pReal;            /* The real, underlying file descriptor */
  Tcl_Obj *pShmId;                /* Shared memory id for Tcl callbacks */

  TestvfsBuffer *pShm;            /* Shared memory buffer */
  u32 excllock;                   /* Mask of exclusive locks */
  u32 sharedlock;                 /* Mask of shared locks */
  TestvfsFd *pNext;               /* Next handle opened on the same file */
};


#define FAULT_INJECT_NONE       0
#define FAULT_INJECT_TRANSIENT  1
#define FAULT_INJECT_PERSISTENT 2

typedef struct TestFaultInject TestFaultInject;
struct TestFaultInject {
  int iCnt;                       /* Remaining calls before fault injection */
  int eFault;                     /* A FAULT_INJECT_* value */
  int nFail;                      /* Number of faults injected */
};

/*
** An instance of this structure is allocated for each VFS created. The
** sqlite3_vfs.pAppData field of the VFS structure registered with SQLite
** is set to point to it.
*/
struct Testvfs {
  char *zName;                    /* Name of this VFS */
  sqlite3_vfs *pParent;           /* The VFS to use for file IO */
  sqlite3_vfs *pVfs;              /* The testvfs registered with SQLite */
  Tcl_Interp *interp;             /* Interpreter to run script in */
  Tcl_Obj *pScript;               /* Script to execute */
  TestvfsBuffer *pBuffer;         /* List of shared buffers */
  int isNoshm;
  int isFullshm;

  int mask;                       /* Mask controlling [script] and [ioerr] */

  TestFaultInject ioerr_err;
  TestFaultInject full_err;
  TestFaultInject cantopen_err;

#if 0
  int iIoerrCnt;
  int ioerr;
  int nIoerrFail;
  int iFullCnt;
  int fullerr;
  int nFullFail;
#endif

  int iDevchar;
  int iSectorsize;
};

/*
** The Testvfs.mask variable is set to a combination of the following.
** If a bit is clear in Testvfs.mask, then calls made by SQLite to the 
** corresponding VFS method is ignored for purposes of:
**
**   + Simulating IO errors, and
**   + Invoking the Tcl callback script.
*/
#define TESTVFS_SHMOPEN_MASK      0x00000001
#define TESTVFS_SHMLOCK_MASK      0x00000010
#define TESTVFS_SHMMAP_MASK       0x00000020
#define TESTVFS_SHMBARRIER_MASK   0x00000040
#define TESTVFS_SHMCLOSE_MASK     0x00000080

#define TESTVFS_OPEN_MASK         0x00000100
#define TESTVFS_SYNC_MASK         0x00000200
#define TESTVFS_DELETE_MASK       0x00000400
#define TESTVFS_CLOSE_MASK        0x00000800
#define TESTVFS_WRITE_MASK        0x00001000
#define TESTVFS_TRUNCATE_MASK     0x00002000
#define TESTVFS_ACCESS_MASK       0x00004000
#define TESTVFS_FULLPATHNAME_MASK 0x00008000
#define TESTVFS_READ_MASK         0x00010000
#define TESTVFS_UNLOCK_MASK       0x00020000
#define TESTVFS_LOCK_MASK         0x00040000
#define TESTVFS_CKLOCK_MASK       0x00080000
#define TESTVFS_FCNTL_MASK        0x00100000
#define TESTVFS_SLEEP_MASK        0x00200000

#define TESTVFS_ALL_MASK          0x003FFFFF


#define TESTVFS_MAX_PAGES 1024

/*
** A shared-memory buffer. There is one of these objects for each shared
** memory region opened by clients. If two clients open the same file,
** there are two TestvfsFile structures but only one TestvfsBuffer structure.
*/
struct TestvfsBuffer {
  char *zFile;                    /* Associated file name */
  int pgsz;                       /* Page size */
  u8 *aPage[TESTVFS_MAX_PAGES];   /* Array of ckalloc'd pages */
  TestvfsFd *pFile;               /* List of open handles */
  TestvfsBuffer *pNext;           /* Next in linked list of all buffers */
};


#define PARENTVFS(x) (((Testvfs *)((x)->pAppData))->pParent)

#define TESTVFS_MAX_ARGS 12


/*
** Method declarations for TestvfsFile.
*/
static int tvfsClose(sqlite3_file*);
static int tvfsRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
static int tvfsWrite(sqlite3_file*,const void*,int iAmt, sqlite3_int64 iOfst);
static int tvfsTruncate(sqlite3_file*, sqlite3_int64 size);
static int tvfsSync(sqlite3_file*, int flags);
static int tvfsFileSize(sqlite3_file*, sqlite3_int64 *pSize);
static int tvfsLock(sqlite3_file*, int);
static int tvfsUnlock(sqlite3_file*, int);
static int tvfsCheckReservedLock(sqlite3_file*, int *);
static int tvfsFileControl(sqlite3_file*, int op, void *pArg);
static int tvfsSectorSize(sqlite3_file*);
static int tvfsDeviceCharacteristics(sqlite3_file*);

/*
** Method declarations for tvfs_vfs.
*/
static int tvfsOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
static int tvfsDelete(sqlite3_vfs*, const char *zName, int syncDir);
static int tvfsAccess(sqlite3_vfs*, const char *zName, int flags, int *);
static int tvfsFullPathname(sqlite3_vfs*, const char *zName, int, char *zOut);
#ifndef SQLITE_OMIT_LOAD_EXTENSION
static void *tvfsDlOpen(sqlite3_vfs*, const char *zFilename);
static void tvfsDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
static void (*tvfsDlSym(sqlite3_vfs*,void*, const char *zSymbol))(void);
static void tvfsDlClose(sqlite3_vfs*, void*);
#endif /* SQLITE_OMIT_LOAD_EXTENSION */
static int tvfsRandomness(sqlite3_vfs*, int nByte, char *zOut);
static int tvfsSleep(sqlite3_vfs*, int microseconds);
static int tvfsCurrentTime(sqlite3_vfs*, double*);

static int tvfsShmOpen(sqlite3_file*);
static int tvfsShmLock(sqlite3_file*, int , int, int);
static int tvfsShmMap(sqlite3_file*,int,int,int, void volatile **);
static void tvfsShmBarrier(sqlite3_file*);
static int tvfsShmUnmap(sqlite3_file*, int);

static int tvfsFetch(sqlite3_file*, sqlite3_int64, int, void**);
static int tvfsUnfetch(sqlite3_file*, sqlite3_int64, void*);

static sqlite3_io_methods tvfs_io_methods = {
  3,                              /* iVersion */
  tvfsClose,                      /* xClose */
  tvfsRead,                       /* xRead */
  tvfsWrite,                      /* xWrite */
  tvfsTruncate,                   /* xTruncate */
  tvfsSync,                       /* xSync */
  tvfsFileSize,                   /* xFileSize */
  tvfsLock,                       /* xLock */
  tvfsUnlock,                     /* xUnlock */
  tvfsCheckReservedLock,          /* xCheckReservedLock */
  tvfsFileControl,                /* xFileControl */
  tvfsSectorSize,                 /* xSectorSize */
  tvfsDeviceCharacteristics,      /* xDeviceCharacteristics */
  tvfsShmMap,                     /* xShmMap */
  tvfsShmLock,                    /* xShmLock */
  tvfsShmBarrier,                 /* xShmBarrier */
  tvfsShmUnmap,                   /* xShmUnmap */
  tvfsFetch,
  tvfsUnfetch
};

static int tvfsResultCode(Testvfs *p, int *pRc){
  struct errcode {
    int eCode;
    const char *zCode;
  } aCode[] = {
    { SQLITE_OK,       "SQLITE_OK"     },
    { SQLITE_ERROR,    "SQLITE_ERROR"  },
    { SQLITE_IOERR,    "SQLITE_IOERR"  },
    { SQLITE_LOCKED,   "SQLITE_LOCKED" },
    { SQLITE_BUSY,     "SQLITE_BUSY"   },
    { SQLITE_READONLY, "SQLITE_READONLY"   },
    { SQLITE_READONLY_CANTINIT, "SQLITE_READONLY_CANTINIT"   },
    { SQLITE_NOTFOUND, "SQLITE_NOTFOUND"   },
    { -1,              "SQLITE_OMIT"   },
  };

  const char *z;
  int i;

  z = Tcl_GetStringResult(p->interp);
  for(i=0; i<ArraySize(aCode); i++){
    if( 0==strcmp(z, aCode[i].zCode) ){
      *pRc = aCode[i].eCode;
      return 1;
    }
  }

  return 0;
}

static int tvfsInjectFault(TestFaultInject *p){
  int ret = 0;
  if( p->eFault ){
    p->iCnt--;
    if( p->iCnt==0 || (p->iCnt<0 && p->eFault==FAULT_INJECT_PERSISTENT ) ){
      ret = 1;
      p->nFail++;
    }
  }
  return ret;
}


static int tvfsInjectIoerr(Testvfs *p){
  return tvfsInjectFault(&p->ioerr_err);
}

static int tvfsInjectFullerr(Testvfs *p){
  return tvfsInjectFault(&p->full_err);
}
static int tvfsInjectCantopenerr(Testvfs *p){
  return tvfsInjectFault(&p->cantopen_err);
}


static void tvfsExecTcl(
  Testvfs *p, 
  const char *zMethod,
  Tcl_Obj *arg1,
  Tcl_Obj *arg2,
  Tcl_Obj *arg3,
  Tcl_Obj *arg4
){
  int rc;                         /* Return code from Tcl_EvalObj() */
  Tcl_Obj *pEval;
  assert( p->pScript );

  assert( zMethod );
  assert( p );
  assert( arg2==0 || arg1!=0 );
  assert( arg3==0 || arg2!=0 );

  pEval = Tcl_DuplicateObj(p->pScript);
  Tcl_IncrRefCount(p->pScript);
  Tcl_ListObjAppendElement(p->interp, pEval, Tcl_NewStringObj(zMethod, -1));
  if( arg1 ) Tcl_ListObjAppendElement(p->interp, pEval, arg1);
  if( arg2 ) Tcl_ListObjAppendElement(p->interp, pEval, arg2);
  if( arg3 ) Tcl_ListObjAppendElement(p->interp, pEval, arg3);
  if( arg4 ) Tcl_ListObjAppendElement(p->interp, pEval, arg4);

  rc = Tcl_EvalObjEx(p->interp, pEval, TCL_EVAL_GLOBAL);
  if( rc!=TCL_OK ){
    Tcl_BackgroundError(p->interp);
    Tcl_ResetResult(p->interp);
  }
}


/*
** Close an tvfs-file.
*/
static int tvfsClose(sqlite3_file *pFile){
  TestvfsFile *pTestfile = (TestvfsFile *)pFile;
  TestvfsFd *pFd = pTestfile->pFd;
  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;

  if( p->pScript && p->mask&TESTVFS_CLOSE_MASK ){
    tvfsExecTcl(p, "xClose", 
        Tcl_NewStringObj(pFd->zFilename, -1), pFd->pShmId, 0, 0
    );
  }

  if( pFd->pShmId ){
    Tcl_DecrRefCount(pFd->pShmId);
    pFd->pShmId = 0;
  }
  if( pFile->pMethods ){
    ckfree((char *)pFile->pMethods);
  }
  sqlite3OsClose(pFd->pReal);
  ckfree((char *)pFd);
  pTestfile->pFd = 0;
  return SQLITE_OK;
}

/*
** Read data from an tvfs-file.
*/
static int tvfsRead(
  sqlite3_file *pFile, 
  void *zBuf, 
  int iAmt, 
  sqlite_int64 iOfst
){
  int rc = SQLITE_OK;
  TestvfsFd *pFd = tvfsGetFd(pFile);
  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
  if( p->pScript && p->mask&TESTVFS_READ_MASK ){
    tvfsExecTcl(p, "xRead", 
        Tcl_NewStringObj(pFd->zFilename, -1), pFd->pShmId, 0, 0
    );
    tvfsResultCode(p, &rc);
  }
  if( rc==SQLITE_OK && p->mask&TESTVFS_READ_MASK && tvfsInjectIoerr(p) ){
    rc = SQLITE_IOERR;
  }
  if( rc==SQLITE_OK ){
    rc = sqlite3OsRead(pFd->pReal, zBuf, iAmt, iOfst);
  }
  return rc;
}

/*
** Write data to an tvfs-file.
*/
static int tvfsWrite(
  sqlite3_file *pFile, 
  const void *zBuf, 
  int iAmt, 
  sqlite_int64 iOfst
){
  int rc = SQLITE_OK;
  TestvfsFd *pFd = tvfsGetFd(pFile);
  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;

  if( p->pScript && p->mask&TESTVFS_WRITE_MASK ){
    tvfsExecTcl(p, "xWrite", 
        Tcl_NewStringObj(pFd->zFilename, -1), pFd->pShmId, 
        Tcl_NewWideIntObj(iOfst), Tcl_NewIntObj(iAmt)
    );
    tvfsResultCode(p, &rc);
    if( rc<0 ) return SQLITE_OK;
  }

  if( rc==SQLITE_OK && tvfsInjectFullerr(p) ){
    rc = SQLITE_FULL;
  }
  if( rc==SQLITE_OK && p->mask&TESTVFS_WRITE_MASK && tvfsInjectIoerr(p) ){
    rc = SQLITE_IOERR;
  }
  
  if( rc==SQLITE_OK ){
    rc = sqlite3OsWrite(pFd->pReal, zBuf, iAmt, iOfst);
  }
  return rc;
}

/*
** Truncate an tvfs-file.
*/
static int tvfsTruncate(sqlite3_file *pFile, sqlite_int64 size){
  int rc = SQLITE_OK;
  TestvfsFd *pFd = tvfsGetFd(pFile);
  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;

  if( p->pScript && p->mask&TESTVFS_TRUNCATE_MASK ){
    tvfsExecTcl(p, "xTruncate", 
        Tcl_NewStringObj(pFd->zFilename, -1), pFd->pShmId, 0, 0
    );
    tvfsResultCode(p, &rc);
  }
  
  if( rc==SQLITE_OK ){
    rc = sqlite3OsTruncate(pFd->pReal, size);
  }
  return rc;
}

/*
** Sync an tvfs-file.
*/
static int tvfsSync(sqlite3_file *pFile, int flags){
  int rc = SQLITE_OK;
  TestvfsFd *pFd = tvfsGetFd(pFile);
  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;

  if( p->pScript && p->mask&TESTVFS_SYNC_MASK ){
    char *zFlags = 0;

    switch( flags ){
      case SQLITE_SYNC_NORMAL:
        zFlags = "normal";
        break;
      case SQLITE_SYNC_FULL:
        zFlags = "full";
        break;
      case SQLITE_SYNC_NORMAL|SQLITE_SYNC_DATAONLY:
        zFlags = "normal|dataonly";
        break;
      case SQLITE_SYNC_FULL|SQLITE_SYNC_DATAONLY:
        zFlags = "full|dataonly";
        break;
      default:
        assert(0);
    }

    tvfsExecTcl(p, "xSync", 
        Tcl_NewStringObj(pFd->zFilename, -1), pFd->pShmId,
        Tcl_NewStringObj(zFlags, -1), 0
    );
    tvfsResultCode(p, &rc);
  }

  if( rc==SQLITE_OK && tvfsInjectFullerr(p) ) rc = SQLITE_FULL;

  if( rc==SQLITE_OK ){
    rc = sqlite3OsSync(pFd->pReal, flags);
  }

  return rc;
}

/*
** Return the current file-size of an tvfs-file.
*/
static int tvfsFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
  TestvfsFd *p = tvfsGetFd(pFile);
  return sqlite3OsFileSize(p->pReal, pSize);
}

/*
** Lock an tvfs-file.
*/
static int tvfsLock(sqlite3_file *pFile, int eLock){
  TestvfsFd *pFd = tvfsGetFd(pFile);
  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
  if( p->pScript && p->mask&TESTVFS_LOCK_MASK ){
    char zLock[30];
    sqlite3_snprintf(sizeof(zLock),zLock,"%d",eLock);
    tvfsExecTcl(p, "xLock", Tcl_NewStringObj(pFd->zFilename, -1), 
                   Tcl_NewStringObj(zLock, -1), 0, 0);
  }
  if( p->mask&TESTVFS_LOCK_MASK && tvfsInjectIoerr(p) ){
    return SQLITE_IOERR_LOCK;
  }
  return sqlite3OsLock(pFd->pReal, eLock);
}

/*
** Unlock an tvfs-file.
*/
static int tvfsUnlock(sqlite3_file *pFile, int eLock){
  TestvfsFd *pFd = tvfsGetFd(pFile);
  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
  if( p->pScript && p->mask&TESTVFS_UNLOCK_MASK ){
    char zLock[30];
    sqlite3_snprintf(sizeof(zLock),zLock,"%d",eLock);
    tvfsExecTcl(p, "xUnlock", Tcl_NewStringObj(pFd->zFilename, -1), 
                   Tcl_NewStringObj(zLock, -1), 0, 0);
  }
  if( p->mask&TESTVFS_UNLOCK_MASK && tvfsInjectIoerr(p) ){
    return SQLITE_IOERR_UNLOCK;
  }
  return sqlite3OsUnlock(pFd->pReal, eLock);
}

/*
** Check if another file-handle holds a RESERVED lock on an tvfs-file.
*/
static int tvfsCheckReservedLock(sqlite3_file *pFile, int *pResOut){
  TestvfsFd *pFd = tvfsGetFd(pFile);
  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
  if( p->pScript && p->mask&TESTVFS_CKLOCK_MASK ){
    tvfsExecTcl(p, "xCheckReservedLock", Tcl_NewStringObj(pFd->zFilename, -1),
                   0, 0, 0);
  }
  return sqlite3OsCheckReservedLock(pFd->pReal, pResOut);
}

/*
** File control method. For custom operations on an tvfs-file.
*/
static int tvfsFileControl(sqlite3_file *pFile, int op, void *pArg){
  TestvfsFd *pFd = tvfsGetFd(pFile);
  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
  if( op==SQLITE_FCNTL_PRAGMA ){
    char **argv = (char**)pArg;
    if( sqlite3_stricmp(argv[1],"error")==0 ){
      int rc = SQLITE_ERROR;
      if( argv[2] ){
        const char *z = argv[2];
        int x = atoi(z);
        if( x ){
          rc = x;
          while( sqlite3Isdigit(z[0]) ){ z++; }
          while( sqlite3Isspace(z[0]) ){ z++; }
        }
        if( z[0] ) argv[0] = sqlite3_mprintf("%s", z);
      }
      return rc;
    }
    if( sqlite3_stricmp(argv[1], "filename")==0 ){
      argv[0] = sqlite3_mprintf("%s", pFd->zFilename);
      return SQLITE_OK;
    }
  }
  if( p->pScript && (p->mask&TESTVFS_FCNTL_MASK) ){
    struct Fcntl {
      int iFnctl;
      const char *zFnctl;
    } aF[] = {
      { SQLITE_FCNTL_BEGIN_ATOMIC_WRITE, "BEGIN_ATOMIC_WRITE" },
      { SQLITE_FCNTL_COMMIT_ATOMIC_WRITE, "COMMIT_ATOMIC_WRITE" },
      { SQLITE_FCNTL_ZIPVFS, "ZIPVFS" },
    };
    int i;
    for(i=0; i<sizeof(aF)/sizeof(aF[0]); i++){
      if( op==aF[i].iFnctl ) break;
    }
    if( i<sizeof(aF)/sizeof(aF[0]) ){
      int rc = 0;
      tvfsExecTcl(p, "xFileControl", 
          Tcl_NewStringObj(pFd->zFilename, -1), 
          Tcl_NewStringObj(aF[i].zFnctl, -1),
          0, 0
      );
      tvfsResultCode(p, &rc);
      if( rc ) return (rc<0 ? SQLITE_OK : rc);
    }
  }
  return sqlite3OsFileControl(pFd->pReal, op, pArg);
}

/*
** Return the sector-size in bytes for an tvfs-file.
*/
static int tvfsSectorSize(sqlite3_file *pFile){
  TestvfsFd *pFd = tvfsGetFd(pFile);
  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
  if( p->iSectorsize>=0 ){
    return p->iSectorsize;
  }
  return sqlite3OsSectorSize(pFd->pReal);
}

/*
** Return the device characteristic flags supported by an tvfs-file.
*/
static int tvfsDeviceCharacteristics(sqlite3_file *pFile){
  TestvfsFd *pFd = tvfsGetFd(pFile);
  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
  if( p->iDevchar>=0 ){
    return p->iDevchar;
  }
  return sqlite3OsDeviceCharacteristics(pFd->pReal);
}

/*
** Open an tvfs file handle.
*/
static int tvfsOpen(
  sqlite3_vfs *pVfs,
  const char *zName,
  sqlite3_file *pFile,
  int flags,
  int *pOutFlags
){
  int rc;
  TestvfsFile *pTestfile = (TestvfsFile *)pFile;
  TestvfsFd *pFd;
  Tcl_Obj *pId = 0;
  Testvfs *p = (Testvfs *)pVfs->pAppData;

  pFd = (TestvfsFd *)ckalloc(sizeof(TestvfsFd) + PARENTVFS(pVfs)->szOsFile);
  memset(pFd, 0, sizeof(TestvfsFd) + PARENTVFS(pVfs)->szOsFile);
  pFd->pShm = 0;
  pFd->pShmId = 0;
  pFd->zFilename = zName;
  pFd->pVfs = pVfs;
  pFd->pReal = (sqlite3_file *)&pFd[1];
  memset(pTestfile, 0, sizeof(TestvfsFile));
  pTestfile->pFd = pFd;

  /* Evaluate the Tcl script: 
  **
  **   SCRIPT xOpen FILENAME KEY-VALUE-ARGS
  **
  ** If the script returns an SQLite error code other than SQLITE_OK, an
  ** error is returned to the caller. If it returns SQLITE_OK, the new
  ** connection is named "anon". Otherwise, the value returned by the
  ** script is used as the connection name.
  */
  Tcl_ResetResult(p->interp);
  if( p->pScript && p->mask&TESTVFS_OPEN_MASK ){
    Tcl_Obj *pArg = Tcl_NewObj();
    Tcl_IncrRefCount(pArg);
    if( flags&SQLITE_OPEN_MAIN_DB ){
      const char *z = &zName[strlen(zName)+1];
      while( *z ){
        Tcl_ListObjAppendElement(0, pArg, Tcl_NewStringObj(z, -1));
        z += strlen(z) + 1;
        Tcl_ListObjAppendElement(0, pArg, Tcl_NewStringObj(z, -1));
        z += strlen(z) + 1;
      }
    }
    tvfsExecTcl(p, "xOpen", Tcl_NewStringObj(pFd->zFilename, -1), pArg, 0, 0);
    Tcl_DecrRefCount(pArg);
    if( tvfsResultCode(p, &rc) ){
      if( rc!=SQLITE_OK ) return rc;
    }else{
      pId = Tcl_GetObjResult(p->interp);
    }
  }

  if( (p->mask&TESTVFS_OPEN_MASK) &&  tvfsInjectIoerr(p) ) return SQLITE_IOERR;
  if( tvfsInjectCantopenerr(p) ) return SQLITE_CANTOPEN;
  if( tvfsInjectFullerr(p) ) return SQLITE_FULL;

  if( !pId ){
    pId = Tcl_NewStringObj("anon", -1);
  }
  Tcl_IncrRefCount(pId);
  pFd->pShmId = pId;
  Tcl_ResetResult(p->interp);

  rc = sqlite3OsOpen(PARENTVFS(pVfs), zName, pFd->pReal, flags, pOutFlags);
  if( pFd->pReal->pMethods ){
    sqlite3_io_methods *pMethods;
    int nByte;

    if( pVfs->iVersion>1 ){
      nByte = sizeof(sqlite3_io_methods);
    }else{
      nByte = offsetof(sqlite3_io_methods, xShmMap);
    }

    pMethods = (sqlite3_io_methods *)ckalloc(nByte);
    memcpy(pMethods, &tvfs_io_methods, nByte);
    pMethods->iVersion = pFd->pReal->pMethods->iVersion;
    if( pMethods->iVersion>pVfs->iVersion ){
      pMethods->iVersion = pVfs->iVersion;
    }
    if( pVfs->iVersion>1 && ((Testvfs *)pVfs->pAppData)->isNoshm ){
      pMethods->xShmUnmap = 0;
      pMethods->xShmLock = 0;
      pMethods->xShmBarrier = 0;
      pMethods->xShmMap = 0;
    }
    pFile->pMethods = pMethods;
  }

  return rc;
}

/*
** Delete the file located at zPath. If the dirSync argument is true,
** ensure the file-system modifications are synced to disk before
** returning.
*/
static int tvfsDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
  int rc = SQLITE_OK;
  Testvfs *p = (Testvfs *)pVfs->pAppData;

  if( p->pScript && p->mask&TESTVFS_DELETE_MASK ){
    tvfsExecTcl(p, "xDelete", 
        Tcl_NewStringObj(zPath, -1), Tcl_NewIntObj(dirSync), 0, 0
    );
    tvfsResultCode(p, &rc);
  }
  if( rc==SQLITE_OK ){
    rc = sqlite3OsDelete(PARENTVFS(pVfs), zPath, dirSync);
  }
  return rc;
}

/*
** Test for access permissions. Return true if the requested permission
** is available, or false otherwise.
*/
static int tvfsAccess(
  sqlite3_vfs *pVfs, 
  const char *zPath, 
  int flags, 
  int *pResOut
){
  Testvfs *p = (Testvfs *)pVfs->pAppData;
  if( p->pScript && p->mask&TESTVFS_ACCESS_MASK ){
    int rc;
    char *zArg = 0;
    if( flags==SQLITE_ACCESS_EXISTS ) zArg = "SQLITE_ACCESS_EXISTS";
    if( flags==SQLITE_ACCESS_READWRITE ) zArg = "SQLITE_ACCESS_READWRITE";
    if( flags==SQLITE_ACCESS_READ ) zArg = "SQLITE_ACCESS_READ";
    tvfsExecTcl(p, "xAccess", 
        Tcl_NewStringObj(zPath, -1), Tcl_NewStringObj(zArg, -1), 0, 0
    );
    if( tvfsResultCode(p, &rc) ){
      if( rc!=SQLITE_OK ) return rc;
    }else{
      Tcl_Interp *interp = p->interp;
      if( TCL_OK==Tcl_GetBooleanFromObj(0, Tcl_GetObjResult(interp), pResOut) ){
        return SQLITE_OK;
      }
    }
  }
  return sqlite3OsAccess(PARENTVFS(pVfs), zPath, flags, pResOut);
}

/*
** Populate buffer zOut with the full canonical pathname corresponding
** to the pathname in zPath. zOut is guaranteed to point to a buffer
** of at least (DEVSYM_MAX_PATHNAME+1) bytes.
*/
static int tvfsFullPathname(
  sqlite3_vfs *pVfs, 
  const char *zPath, 
  int nOut, 
  char *zOut
){
  Testvfs *p = (Testvfs *)pVfs->pAppData;
  if( p->pScript && p->mask&TESTVFS_FULLPATHNAME_MASK ){
    int rc;
    tvfsExecTcl(p, "xFullPathname", Tcl_NewStringObj(zPath, -1), 0, 0, 0);
    if( tvfsResultCode(p, &rc) ){
      if( rc!=SQLITE_OK ) return rc;
    }
  }
  return sqlite3OsFullPathname(PARENTVFS(pVfs), zPath, nOut, zOut);
}

#ifndef SQLITE_OMIT_LOAD_EXTENSION
/*
** Open the dynamic library located at zPath and return a handle.
*/
static void *tvfsDlOpen(sqlite3_vfs *pVfs, const char *zPath){
  return sqlite3OsDlOpen(PARENTVFS(pVfs), zPath);
}

/*
** Populate the buffer zErrMsg (size nByte bytes) with a human readable
** utf-8 string describing the most recent error encountered associated 
** with dynamic libraries.
*/
static void tvfsDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
  sqlite3OsDlError(PARENTVFS(pVfs), nByte, zErrMsg);
}

/*
** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
*/
static void (*tvfsDlSym(sqlite3_vfs *pVfs, void *p, const char *zSym))(void){
  return sqlite3OsDlSym(PARENTVFS(pVfs), p, zSym);
}

/*
** Close the dynamic library handle pHandle.
*/
static void tvfsDlClose(sqlite3_vfs *pVfs, void *pHandle){
  sqlite3OsDlClose(PARENTVFS(pVfs), pHandle);
}
#endif /* SQLITE_OMIT_LOAD_EXTENSION */

/*
** Populate the buffer pointed to by zBufOut with nByte bytes of 
** random data.
*/
static int tvfsRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
  return sqlite3OsRandomness(PARENTVFS(pVfs), nByte, zBufOut);
}

/*
** Sleep for nMicro microseconds. Return the number of microseconds 
** actually slept.
*/
static int tvfsSleep(sqlite3_vfs *pVfs, int nMicro){
  Testvfs *p = (Testvfs *)pVfs->pAppData;
  if( p->pScript && (p->mask&TESTVFS_SLEEP_MASK) ){
    tvfsExecTcl(p, "xSleep", Tcl_NewIntObj(nMicro), 0, 0, 0);
  }
  return sqlite3OsSleep(PARENTVFS(pVfs), nMicro);
}

/*
** Return the current time as a Julian Day number in *pTimeOut.
*/
static int tvfsCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
  return PARENTVFS(pVfs)->xCurrentTime(PARENTVFS(pVfs), pTimeOut);
}

static int tvfsShmOpen(sqlite3_file *pFile){
  Testvfs *p;
  int rc = SQLITE_OK;             /* Return code */
  TestvfsBuffer *pBuffer;         /* Buffer to open connection to */
  TestvfsFd *pFd;                 /* The testvfs file structure */

  pFd = tvfsGetFd(pFile);
  p = (Testvfs *)pFd->pVfs->pAppData;
  assert( 0==p->isFullshm );
  assert( pFd->pShmId && pFd->pShm==0 && pFd->pNext==0 );

  /* Evaluate the Tcl script: 
  **
  **   SCRIPT xShmOpen FILENAME
  */
  Tcl_ResetResult(p->interp);
  if( p->pScript && p->mask&TESTVFS_SHMOPEN_MASK ){
    tvfsExecTcl(p, "xShmOpen", Tcl_NewStringObj(pFd->zFilename, -1), 0, 0, 0);
    if( tvfsResultCode(p, &rc) ){
      if( rc!=SQLITE_OK ) return rc;
    }
  }

  assert( rc==SQLITE_OK );
  if( p->mask&TESTVFS_SHMOPEN_MASK && tvfsInjectIoerr(p) ){
    return SQLITE_IOERR;
  }

  /* Search for a TestvfsBuffer. Create a new one if required. */
  for(pBuffer=p->pBuffer; pBuffer; pBuffer=pBuffer->pNext){
    if( 0==strcmp(pFd->zFilename, pBuffer->zFile) ) break;
  }
  if( !pBuffer ){
    int szName = (int)strlen(pFd->zFilename);
    int nByte = sizeof(TestvfsBuffer) + szName + 1;
    pBuffer = (TestvfsBuffer *)ckalloc(nByte);
    memset(pBuffer, 0, nByte);
    pBuffer->zFile = (char *)&pBuffer[1];
    memcpy(pBuffer->zFile, pFd->zFilename, szName+1);
    pBuffer->pNext = p->pBuffer;
    p->pBuffer = pBuffer;
  }

  /* Connect the TestvfsBuffer to the new TestvfsShm handle and return. */
  pFd->pNext = pBuffer->pFile;
  pBuffer->pFile = pFd;
  pFd->pShm = pBuffer;
  return rc;
}

static void tvfsAllocPage(TestvfsBuffer *p, int iPage, int pgsz){
  assert( iPage<TESTVFS_MAX_PAGES );
  if( p->aPage[iPage]==0 ){
    p->aPage[iPage] = (u8 *)ckalloc(pgsz);
    memset(p->aPage[iPage], 0, pgsz);
    p->pgsz = pgsz;
  }
}

static int tvfsShmMap(
  sqlite3_file *pFile,            /* Handle open on database file */
  int iPage,                      /* Page to retrieve */
  int pgsz,                       /* Size of pages */
  int isWrite,                    /* True to extend file if necessary */
  void volatile **pp              /* OUT: Mapped memory */
){
  int rc = SQLITE_OK;
  TestvfsFd *pFd = tvfsGetFd(pFile);
  Testvfs *p = (Testvfs *)(pFd->pVfs->pAppData);

  if( p->isFullshm ){
    sqlite3_file *pReal = pFd->pReal;
    return pReal->pMethods->xShmMap(pReal, iPage, pgsz, isWrite, pp);
  }

  if( 0==pFd->pShm ){
    rc = tvfsShmOpen(pFile);
    if( rc!=SQLITE_OK ){
      return rc;
    }
  }

  if( p->pScript && p->mask&TESTVFS_SHMMAP_MASK ){
    Tcl_Obj *pArg = Tcl_NewObj();
    Tcl_IncrRefCount(pArg);
    Tcl_ListObjAppendElement(p->interp, pArg, Tcl_NewIntObj(iPage));
    Tcl_ListObjAppendElement(p->interp, pArg, Tcl_NewIntObj(pgsz));
    Tcl_ListObjAppendElement(p->interp, pArg, Tcl_NewIntObj(isWrite));
    tvfsExecTcl(p, "xShmMap", 
        Tcl_NewStringObj(pFd->pShm->zFile, -1), pFd->pShmId, pArg, 0
    );
    tvfsResultCode(p, &rc);
    Tcl_DecrRefCount(pArg);
  }
  if( rc==SQLITE_OK && p->mask&TESTVFS_SHMMAP_MASK && tvfsInjectIoerr(p) ){
    rc = SQLITE_IOERR;
  }

  if( rc==SQLITE_OK && isWrite && !pFd->pShm->aPage[iPage] ){
    tvfsAllocPage(pFd->pShm, iPage, pgsz);
  }
  if( rc==SQLITE_OK || rc==SQLITE_READONLY ){
    *pp = (void volatile *)pFd->pShm->aPage[iPage];
  }

  return rc;
}


static int tvfsShmLock(
  sqlite3_file *pFile,
  int ofst,
  int n,
  int flags
){
  int rc = SQLITE_OK;
  TestvfsFd *pFd = tvfsGetFd(pFile);
  Testvfs *p = (Testvfs *)(pFd->pVfs->pAppData);
  int nLock;
  char zLock[80];

  if( p->isFullshm ){
    sqlite3_file *pReal = pFd->pReal;
    return pReal->pMethods->xShmLock(pReal, ofst, n, flags);
  }

  if( p->pScript && p->mask&TESTVFS_SHMLOCK_MASK ){
    sqlite3_snprintf(sizeof(zLock), zLock, "%d %d", ofst, n);
    nLock = (int)strlen(zLock);
    if( flags & SQLITE_SHM_LOCK ){
      strcpy(&zLock[nLock], " lock");
    }else{
      strcpy(&zLock[nLock], " unlock");
    }
    nLock += (int)strlen(&zLock[nLock]);
    if( flags & SQLITE_SHM_SHARED ){
      strcpy(&zLock[nLock], " shared");
    }else{
      strcpy(&zLock[nLock], " exclusive");
    }
    tvfsExecTcl(p, "xShmLock", 
        Tcl_NewStringObj(pFd->pShm->zFile, -1), pFd->pShmId,
        Tcl_NewStringObj(zLock, -1), 0
    );
    tvfsResultCode(p, &rc);
  }

  if( rc==SQLITE_OK && p->mask&TESTVFS_SHMLOCK_MASK && tvfsInjectIoerr(p) ){
    rc = SQLITE_IOERR;
  }

  if( rc==SQLITE_OK ){
    int isLock = (flags & SQLITE_SHM_LOCK);
    int isExcl = (flags & SQLITE_SHM_EXCLUSIVE);
    u32 mask = (((1<<n)-1) << ofst);
    if( isLock ){
      TestvfsFd *p2;
      for(p2=pFd->pShm->pFile; p2; p2=p2->pNext){
        if( p2==pFd ) continue;
        if( (p2->excllock&mask) || (isExcl && p2->sharedlock&mask) ){
          rc = SQLITE_BUSY;
          break;
        }
      }
      if( rc==SQLITE_OK ){
        if( isExcl )  pFd->excllock |= mask;
        if( !isExcl ) pFd->sharedlock |= mask;
      }
    }else{
      if( isExcl )  pFd->excllock &= (~mask);
      if( !isExcl ) pFd->sharedlock &= (~mask);
    }
  }

  return rc;
}

static void tvfsShmBarrier(sqlite3_file *pFile){
  TestvfsFd *pFd = tvfsGetFd(pFile);
  Testvfs *p = (Testvfs *)(pFd->pVfs->pAppData);

  if( p->pScript && p->mask&TESTVFS_SHMBARRIER_MASK ){
    const char *z = pFd->pShm ? pFd->pShm->zFile : "";
    tvfsExecTcl(p, "xShmBarrier", Tcl_NewStringObj(z, -1), pFd->pShmId, 0, 0);
  }

  if( p->isFullshm ){
    sqlite3_file *pReal = pFd->pReal;
    pReal->pMethods->xShmBarrier(pReal);
    return;
  }
}

static int tvfsShmUnmap(
  sqlite3_file *pFile,
  int deleteFlag
){
  int rc = SQLITE_OK;
  TestvfsFd *pFd = tvfsGetFd(pFile);
  Testvfs *p = (Testvfs *)(pFd->pVfs->pAppData);
  TestvfsBuffer *pBuffer = pFd->pShm;
  TestvfsFd **ppFd;

  if( p->isFullshm ){
    sqlite3_file *pReal = pFd->pReal;
    return pReal->pMethods->xShmUnmap(pReal, deleteFlag);
  }

  if( !pBuffer ) return SQLITE_OK;
  assert( pFd->pShmId && pFd->pShm );

  if( p->pScript && p->mask&TESTVFS_SHMCLOSE_MASK ){
    tvfsExecTcl(p, "xShmUnmap", 
        Tcl_NewStringObj(pFd->pShm->zFile, -1), pFd->pShmId, 0, 0
    );
    tvfsResultCode(p, &rc);
  }

  for(ppFd=&pBuffer->pFile; *ppFd!=pFd; ppFd=&((*ppFd)->pNext));
  assert( (*ppFd)==pFd );
  *ppFd = pFd->pNext;
  pFd->pNext = 0;

  if( pBuffer->pFile==0 ){
    int i;
    TestvfsBuffer **pp;
    for(pp=&p->pBuffer; *pp!=pBuffer; pp=&((*pp)->pNext));
    *pp = (*pp)->pNext;
    for(i=0; pBuffer->aPage[i]; i++){
      ckfree((char *)pBuffer->aPage[i]);
    }
    ckfree((char *)pBuffer);
  }
  pFd->pShm = 0;

  return rc;
}

static int tvfsFetch(
    sqlite3_file *pFile, 
    sqlite3_int64 iOfst, 
    int iAmt, 
    void **pp
){
  TestvfsFd *pFd = tvfsGetFd(pFile);
  return sqlite3OsFetch(pFd->pReal, iOfst, iAmt, pp);
}

static int tvfsUnfetch(sqlite3_file *pFile, sqlite3_int64 iOfst, void *p){
  TestvfsFd *pFd = tvfsGetFd(pFile);
  return sqlite3OsUnfetch(pFd->pReal, iOfst, p);
}

static int SQLITE_TCLAPI testvfs_obj_cmd(
  ClientData cd,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
  Testvfs *p = (Testvfs *)cd;

  enum DB_enum { 
    CMD_SHM, CMD_DELETE, CMD_FILTER, CMD_IOERR, CMD_SCRIPT, 
    CMD_DEVCHAR, CMD_SECTORSIZE, CMD_FULLERR, CMD_CANTOPENERR
  };
  struct TestvfsSubcmd {
    char *zName;
    enum DB_enum eCmd;
  } aSubcmd[] = {
    { "shm",         CMD_SHM         },
    { "delete",      CMD_DELETE      },
    { "filter",      CMD_FILTER      },
    { "ioerr",       CMD_IOERR       },
    { "fullerr",     CMD_FULLERR     },
    { "cantopenerr", CMD_CANTOPENERR },
    { "script",      CMD_SCRIPT      },
    { "devchar",     CMD_DEVCHAR     },
    { "sectorsize",  CMD_SECTORSIZE  },
    { 0, 0 }
  };
  int i;
  
  if( objc<2 ){
    Tcl_WrongNumArgs(interp, 1, objv, "SUBCOMMAND ...");
    return TCL_ERROR;
  }
  if( Tcl_GetIndexFromObjStruct(
        interp, objv[1], aSubcmd, sizeof(aSubcmd[0]), "subcommand", 0, &i) 
  ){
    return TCL_ERROR;
  }
  Tcl_ResetResult(interp);

  switch( aSubcmd[i].eCmd ){
    case CMD_SHM: {
      Tcl_Obj *pObj;
      int rc;
      TestvfsBuffer *pBuffer;
      char *zName;
      if( objc!=3 && objc!=4 ){
        Tcl_WrongNumArgs(interp, 2, objv, "FILE ?VALUE?");
        return TCL_ERROR;
      }
      zName = ckalloc(p->pParent->mxPathname);
      rc = p->pParent->xFullPathname(
          p->pParent, Tcl_GetString(objv[2]), 
          p->pParent->mxPathname, zName
      );
      if( rc!=SQLITE_OK ){
        Tcl_AppendResult(interp, "failed to get full path: ",
                         Tcl_GetString(objv[2]), NULL);
        ckfree(zName);
        return TCL_ERROR;
      }
      for(pBuffer=p->pBuffer; pBuffer; pBuffer=pBuffer->pNext){
        if( 0==strcmp(pBuffer->zFile, zName) ) break;
      }
      ckfree(zName);
      if( !pBuffer ){
        Tcl_AppendResult(interp, "no such file: ", Tcl_GetString(objv[2]), NULL);
        return TCL_ERROR;
      }
      if( objc==4 ){
        Tcl_Size n;
        u8 *a = Tcl_GetByteArrayFromObj(objv[3], &n);
        int pgsz = pBuffer->pgsz;
        if( pgsz==0 ) pgsz = 65536;
        for(i=0; i*pgsz<(int)n; i++){
          int nByte = pgsz;
          tvfsAllocPage(pBuffer, i, pgsz);
          if( n-i*pgsz<pgsz ){
            nByte = (int)n;
          }
          memcpy(pBuffer->aPage[i], &a[i*pgsz], nByte);
        }
      }

      pObj = Tcl_NewObj();
      for(i=0; pBuffer->aPage[i]; i++){
        int pgsz = pBuffer->pgsz;
        if( pgsz==0 ) pgsz = 65536;
        Tcl_AppendObjToObj(pObj, Tcl_NewByteArrayObj(pBuffer->aPage[i], pgsz));
      }
      Tcl_SetObjResult(interp, pObj);
      break;
    }

    /*  TESTVFS filter METHOD-LIST
    **
    **     Activate special processing for those methods contained in the list
    */
    case CMD_FILTER: {
      static struct VfsMethod {
        char *zName;
        int mask;
      } vfsmethod [] = {
        { "xShmOpen",           TESTVFS_SHMOPEN_MASK },
        { "xShmLock",           TESTVFS_SHMLOCK_MASK },
        { "xShmBarrier",        TESTVFS_SHMBARRIER_MASK },
        { "xShmUnmap",          TESTVFS_SHMCLOSE_MASK },
        { "xShmMap",            TESTVFS_SHMMAP_MASK },
        { "xSync",              TESTVFS_SYNC_MASK },
        { "xDelete",            TESTVFS_DELETE_MASK },
        { "xWrite",             TESTVFS_WRITE_MASK },
        { "xRead",              TESTVFS_READ_MASK },
        { "xTruncate",          TESTVFS_TRUNCATE_MASK },
        { "xOpen",              TESTVFS_OPEN_MASK },
        { "xClose",             TESTVFS_CLOSE_MASK },
        { "xAccess",            TESTVFS_ACCESS_MASK },
        { "xFullPathname",      TESTVFS_FULLPATHNAME_MASK },
        { "xUnlock",            TESTVFS_UNLOCK_MASK },
        { "xLock",              TESTVFS_LOCK_MASK },
        { "xCheckReservedLock", TESTVFS_CKLOCK_MASK },
        { "xFileControl",       TESTVFS_FCNTL_MASK },
        { "xSleep",             TESTVFS_SLEEP_MASK },
      };
      Tcl_Obj **apElem = 0;
      Tcl_Size nElem = 0;
      int mask = 0;
      if( objc!=3 ){
        Tcl_WrongNumArgs(interp, 2, objv, "LIST");
        return TCL_ERROR;
      }
      if( Tcl_ListObjGetElements(interp, objv[2], &nElem, &apElem) ){
        return TCL_ERROR;
      }
      Tcl_ResetResult(interp);
      for(i=0; i<(int)nElem; i++){
        int iMethod;
        char *zElem = Tcl_GetString(apElem[i]);
        for(iMethod=0; iMethod<ArraySize(vfsmethod); iMethod++){
          if( strcmp(zElem, vfsmethod[iMethod].zName)==0 ){
            mask |= vfsmethod[iMethod].mask;
            break;
          }
        }
        if( iMethod==ArraySize(vfsmethod) ){
          Tcl_AppendResult(interp, "unknown method: ", zElem, NULL);
          return TCL_ERROR;
        }
      }
      p->mask = mask;
      break;
    }

    /*
    **  TESTVFS script ?SCRIPT?
    **
    **  Query or set the script to be run when filtered VFS events
    **  occur.
    */
    case CMD_SCRIPT: {
      if( objc==3 ){
        Tcl_Size nByte;
        if( p->pScript ){
          Tcl_DecrRefCount(p->pScript);
          p->pScript = 0;
        }
        Tcl_GetStringFromObj(objv[2], &nByte);
        if( nByte>0 ){
          p->pScript = Tcl_DuplicateObj(objv[2]);
          Tcl_IncrRefCount(p->pScript);
        }
      }else if( objc!=2 ){
        Tcl_WrongNumArgs(interp, 2, objv, "?SCRIPT?");
        return TCL_ERROR;
      }

      Tcl_ResetResult(interp);
      if( p->pScript ) Tcl_SetObjResult(interp, p->pScript);

      break;
    }

    /*
    ** TESTVFS ioerr ?IFAIL PERSIST?
    **
    **   Where IFAIL is an integer and PERSIST is boolean.
    */
    case CMD_CANTOPENERR:
    case CMD_IOERR:
    case CMD_FULLERR: {
      TestFaultInject *pTest = 0;
      int iRet;

      switch( aSubcmd[i].eCmd ){
        case CMD_IOERR: pTest = &p->ioerr_err; break;
        case CMD_FULLERR: pTest = &p->full_err; break;
        case CMD_CANTOPENERR: pTest = &p->cantopen_err; break;
        default: assert(0);
      }
      iRet = pTest->nFail;
      pTest->nFail = 0;
      pTest->eFault = 0;
      pTest->iCnt = 0;

      if( objc==4 ){
        int iCnt, iPersist;
        if( TCL_OK!=Tcl_GetIntFromObj(interp, objv[2], &iCnt)
         || TCL_OK!=Tcl_GetBooleanFromObj(interp, objv[3], &iPersist)
        ){
          return TCL_ERROR;
        }
        pTest->eFault = iPersist?FAULT_INJECT_PERSISTENT:FAULT_INJECT_TRANSIENT;
        pTest->iCnt = iCnt;
      }else if( objc!=2 ){
        Tcl_WrongNumArgs(interp, 2, objv, "?CNT PERSIST?");
        return TCL_ERROR;
      }
      Tcl_SetObjResult(interp, Tcl_NewIntObj(iRet));
      break;
    }

    case CMD_DELETE: {
      Tcl_DeleteCommand(interp, Tcl_GetString(objv[0]));
      break;
    }

    case CMD_DEVCHAR: {
      struct DeviceFlag {
        char *zName;
        int iValue;
      } aFlag[] = {
        { "default",               -1 },
        { "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           },
        { "undeletable_when_open", SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN },
        { "powersafe_overwrite",   SQLITE_IOCAP_POWERSAFE_OVERWRITE   },
        { "immutable",             SQLITE_IOCAP_IMMUTABLE             },
        { 0, 0 }
      };
      Tcl_Obj *pRet;
      int iFlag;

      if( objc>3 ){
        Tcl_WrongNumArgs(interp, 2, objv, "?ATTR-LIST?");
        return TCL_ERROR;
      }
      if( objc==3 ){
        int j;
        int iNew = 0;
        Tcl_Obj **flags = 0;
        Tcl_Size nFlags = 0;

        if( Tcl_ListObjGetElements(interp, objv[2], &nFlags, &flags) ){
          return TCL_ERROR;
        }

        for(j=0; j<(int)nFlags; j++){
          int idx = 0;
          if( Tcl_GetIndexFromObjStruct(interp, flags[j], aFlag, 
                sizeof(aFlag[0]), "flag", 0, &idx) 
          ){
            return TCL_ERROR;
          }
          if( aFlag[idx].iValue<0 && nFlags>1 ){
            Tcl_AppendResult(interp, "bad flags: ", Tcl_GetString(objv[2]), NULL);
            return TCL_ERROR;
          }
          iNew |= aFlag[idx].iValue;
        }

        p->iDevchar = iNew| 0x10000000;
      }

      pRet = Tcl_NewObj();
      for(iFlag=0; iFlag<sizeof(aFlag)/sizeof(aFlag[0]); iFlag++){
        if( p->iDevchar & aFlag[iFlag].iValue ){
          Tcl_ListObjAppendElement(
              interp, pRet, Tcl_NewStringObj(aFlag[iFlag].zName, -1)
          );
        }
      }
      Tcl_SetObjResult(interp, pRet);

      break;
    }

    case CMD_SECTORSIZE: {
      if( objc>3 ){
        Tcl_WrongNumArgs(interp, 2, objv, "?VALUE?");
        return TCL_ERROR;
      }
      if( objc==3 ){
        int iNew = 0;
        if( Tcl_GetIntFromObj(interp, objv[2], &iNew) ){
          return TCL_ERROR;
        }
        p->iSectorsize = iNew;
      }
      Tcl_SetObjResult(interp, Tcl_NewIntObj(p->iSectorsize));
      break;
    }
  }

  return TCL_OK;
}

static void SQLITE_TCLAPI testvfs_obj_del(ClientData cd){
  Testvfs *p = (Testvfs *)cd;
  if( p->pScript ) Tcl_DecrRefCount(p->pScript);
  sqlite3_vfs_unregister(p->pVfs);
  memset(p->pVfs, 0, sizeof(sqlite3_vfs));
  ckfree((char *)p->pVfs);
  memset(p, 0, sizeof(Testvfs));
  ckfree((char *)p);
}

/*
** Usage:  testvfs VFSNAME ?SWITCHES?
**
** Switches are:
**
**   -noshm   BOOLEAN             (True to omit shm methods. Default false)
**   -default BOOLEAN             (True to make the vfs default. Default false)
**
** This command creates two things when it is invoked: an SQLite VFS, and
** a Tcl command. Both are named VFSNAME. The VFS is installed. It is not
** installed as the default VFS.
**
** The VFS passes all file I/O calls through to the underlying VFS.
**
** Whenever the xShmMap method of the VFS
** is invoked, the SCRIPT is executed as follows:
**
**   SCRIPT xShmMap    FILENAME ID
**
** The value returned by the invocation of SCRIPT above is interpreted as
** an SQLite error code and returned to SQLite. Either a symbolic 
** "SQLITE_OK" or numeric "0" value may be returned.
**
** The contents of the shared-memory buffer associated with a given file
** may be read and set using the following command:
**
**   VFSNAME shm FILENAME ?NEWVALUE?
**
** When the xShmLock method is invoked by SQLite, the following script is
** run:
**
**   SCRIPT xShmLock    FILENAME ID LOCK
**
** where LOCK is of the form "OFFSET NBYTE lock/unlock shared/exclusive"
*/
static int SQLITE_TCLAPI testvfs_cmd(
  ClientData cd,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
  static sqlite3_vfs tvfs_vfs = {
    3,                            /* iVersion */
    0,                            /* szOsFile */
    0,                            /* mxPathname */
    0,                            /* pNext */
    0,                            /* zName */
    0,                            /* pAppData */
    tvfsOpen,                     /* xOpen */
    tvfsDelete,                   /* xDelete */
    tvfsAccess,                   /* xAccess */
    tvfsFullPathname,             /* xFullPathname */
#ifndef SQLITE_OMIT_LOAD_EXTENSION
    tvfsDlOpen,                   /* xDlOpen */
    tvfsDlError,                  /* xDlError */
    tvfsDlSym,                    /* xDlSym */
    tvfsDlClose,                  /* xDlClose */
#else
    0,                            /* xDlOpen */
    0,                            /* xDlError */
    0,                            /* xDlSym */
    0,                            /* xDlClose */
#endif /* SQLITE_OMIT_LOAD_EXTENSION */
    tvfsRandomness,               /* xRandomness */
    tvfsSleep,                    /* xSleep */
    tvfsCurrentTime,              /* xCurrentTime */
    0,                            /* xGetLastError */
    0,                            /* xCurrentTimeInt64 */
    0,                            /* xSetSystemCall */
    0,                            /* xGetSystemCall */
    0,                            /* xNextSystemCall */
  };

  Testvfs *p;                     /* New object */
  sqlite3_vfs *pVfs;              /* New VFS */
  char *zVfs;
  int nByte;                      /* Bytes of space to allocate at p */

  int i;
  int isNoshm = 0;                /* True if -noshm is passed */
  int isFullshm = 0;              /* True if -fullshm is passed */
  int isDefault = 0;              /* True if -default is passed */
  int szOsFile = 0;               /* Value passed to -szosfile */
  int mxPathname = -1;            /* Value passed to -mxpathname */
  int iVersion = 3;               /* Value passed to -iversion */

  if( objc<2 || 0!=(objc%2) ) goto bad_args;
  for(i=2; i<objc; i += 2){
    Tcl_Size nSwitch;
    char *zSwitch;
    zSwitch = Tcl_GetStringFromObj(objv[i], &nSwitch); 

    if( nSwitch>2 && 0==strncmp("-noshm", zSwitch, nSwitch) ){
      if( Tcl_GetBooleanFromObj(interp, objv[i+1], &isNoshm) ){
        return TCL_ERROR;
      }
      if( isNoshm ) isFullshm = 0;
    }
    else if( nSwitch>2 && 0==strncmp("-default", zSwitch, nSwitch) ){
      if( Tcl_GetBooleanFromObj(interp, objv[i+1], &isDefault) ){
        return TCL_ERROR;
      }
    }
    else if( nSwitch>2 && 0==strncmp("-szosfile", zSwitch, nSwitch) ){
      if( Tcl_GetIntFromObj(interp, objv[i+1], &szOsFile) ){
        return TCL_ERROR;
      }
    }
    else if( nSwitch>2 && 0==strncmp("-mxpathname", zSwitch, nSwitch) ){
      if( Tcl_GetIntFromObj(interp, objv[i+1], &mxPathname) ){
        return TCL_ERROR;
      }
    }
    else if( nSwitch>2 && 0==strncmp("-iversion", zSwitch, nSwitch) ){
      if( Tcl_GetIntFromObj(interp, objv[i+1], &iVersion) ){
        return TCL_ERROR;
      }
    }
    else if( nSwitch>2 && 0==strncmp("-fullshm", zSwitch, nSwitch) ){
      if( Tcl_GetBooleanFromObj(interp, objv[i+1], &isFullshm) ){
        return TCL_ERROR;
      }
      if( isFullshm ) isNoshm = 0;
    }
    else{
      goto bad_args;
    }
  }

  if( szOsFile<sizeof(TestvfsFile) ){
    szOsFile = sizeof(TestvfsFile);
  }

  zVfs = Tcl_GetString(objv[1]);
  nByte = sizeof(Testvfs) + (int)strlen(zVfs)+1;
  p = (Testvfs *)ckalloc(nByte);
  memset(p, 0, nByte);
  p->iDevchar = -1;
  p->iSectorsize = -1;

  /* Create the new object command before querying SQLite for a default VFS
  ** to use for 'real' IO operations. This is because creating the new VFS
  ** may delete an existing [testvfs] VFS of the same name. If such a VFS
  ** is currently the default, the new [testvfs] may end up calling the 
  ** methods of a deleted object.
  */
  Tcl_CreateObjCommand(interp, zVfs, testvfs_obj_cmd, p, testvfs_obj_del);
  p->pParent = sqlite3_vfs_find(0);
  p->interp = interp;

  p->zName = (char *)&p[1];
  memcpy(p->zName, zVfs, strlen(zVfs)+1);

  pVfs = (sqlite3_vfs *)ckalloc(sizeof(sqlite3_vfs));
  memcpy(pVfs, &tvfs_vfs, sizeof(sqlite3_vfs));
  pVfs->pAppData = (void *)p;
  pVfs->iVersion = iVersion;
  pVfs->zName = p->zName;
  pVfs->mxPathname = p->pParent->mxPathname;
  if( mxPathname>=0 && mxPathname<pVfs->mxPathname ){
    pVfs->mxPathname = mxPathname;
  }
  pVfs->szOsFile = szOsFile;
  p->pVfs = pVfs;
  p->isNoshm = isNoshm;
  p->isFullshm = isFullshm;
  p->mask = TESTVFS_ALL_MASK;

  sqlite3_vfs_register(pVfs, isDefault);

  return TCL_OK;

 bad_args:
  Tcl_WrongNumArgs(interp, 1, objv, "VFSNAME ?-noshm BOOL? ?-fullshm BOOL? ?-default BOOL? ?-mxpathname INT? ?-szosfile INT? ?-iversion INT?");
  return TCL_ERROR;
}

extern int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb);
extern const char *sqlite3ErrName(int);

/*
** tclcmd: vfs_shmlock DB DBNAME (shared|exclusive) (lock|unlock) OFFSET N
*/
static int SQLITE_TCLAPI test_vfs_shmlock(
  void * clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
  const char *azArg1[] = {"shared", "exclusive", 0};
  const char *azArg2[] = {"lock", "unlock", 0};
  sqlite3 *db = 0;
  int rc = SQLITE_OK;
  const char *zDbname = 0;
  int iArg1 = 0;
  int iArg2 = 0;
  int iOffset = 0;
  int n = 0;
  sqlite3_file *pFd;

  if( objc!=7 ){
    Tcl_WrongNumArgs(interp, 1, objv, 
        "DB DBNAME (shared|exclusive) (lock|unlock) OFFSET N"
    );
    return TCL_ERROR;
  }

  zDbname = Tcl_GetString(objv[2]);
  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) 
   || Tcl_GetIndexFromObj(interp, objv[3], azArg1, "ARG", 0, &iArg1) 
   || Tcl_GetIndexFromObj(interp, objv[4], azArg2, "ARG", 0, &iArg2) 
   || Tcl_GetIntFromObj(interp, objv[5], &iOffset)
   || Tcl_GetIntFromObj(interp, objv[6], &n)
  ){
    return TCL_ERROR;
  }

  sqlite3_file_control(db, zDbname, SQLITE_FCNTL_FILE_POINTER, (void*)&pFd);
  if( pFd==0 ){
    return TCL_ERROR;
  }
  rc = pFd->pMethods->xShmLock(pFd, iOffset, n, 
      (iArg1==0 ? SQLITE_SHM_SHARED : SQLITE_SHM_EXCLUSIVE)
    | (iArg2==0 ? SQLITE_SHM_LOCK : SQLITE_SHM_UNLOCK)
  );
  Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
  return TCL_OK;
}

static int SQLITE_TCLAPI test_vfs_set_readmark(
  void * clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
  sqlite3 *db = 0;
  int rc = SQLITE_OK;
  const char *zDbname = 0;
  int iSlot = 0;
  int iVal = -1;
  sqlite3_file *pFd;
  void volatile *pShm = 0;
  u32 *aShm;
  int iOff;

  if( objc!=4 && objc!=5 ){
    Tcl_WrongNumArgs(interp, 1, objv, "DB DBNAME SLOT ?VALUE?");
    return TCL_ERROR;
  }

  zDbname = Tcl_GetString(objv[2]);
  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) 
   || Tcl_GetIntFromObj(interp, objv[3], &iSlot)
   || (objc==5 && Tcl_GetIntFromObj(interp, objv[4], &iVal))
  ){
    return TCL_ERROR;
  }

  sqlite3_file_control(db, zDbname, SQLITE_FCNTL_FILE_POINTER, (void*)&pFd);
  if( pFd==0 ){
    return TCL_ERROR;
  }
  rc = pFd->pMethods->xShmMap(pFd, 0, 32*1024, 0, &pShm);
  if( rc!=SQLITE_OK ){
    Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
    return TCL_ERROR;
  }
  if( pShm==0 ){
    Tcl_AppendResult(interp, "*-shm is not yet mapped", NULL);
    return TCL_ERROR;
  }
  aShm = (u32*)pShm;
  iOff = 12*2+1+iSlot;

  if( objc==5 ){
    aShm[iOff] = iVal;
  }
  Tcl_SetObjResult(interp, Tcl_NewIntObj(aShm[iOff]));

  return TCL_OK;
}

int Sqlitetestvfs_Init(Tcl_Interp *interp){
  Tcl_CreateObjCommand(interp, "testvfs", testvfs_cmd, 0, 0);
  Tcl_CreateObjCommand(interp, "vfs_shmlock", test_vfs_shmlock, 0, 0);
  Tcl_CreateObjCommand(interp, "vfs_set_readmark", test_vfs_set_readmark, 0, 0);
  return TCL_OK;
}

#endif