SQLite

    unixDlError,          /* xDlError */                    \
    unixDlSym,            /* xDlSym */                      \
    unixDlClose,          /* xDlClose */                    \
    unixRandomness,       /* xRandomness */                 \
    unixSleep,            /* xSleep */                      \
    unixCurrentTime,      /* xCurrentTime */                \
    unixGetLastError,     /* xGetLastError */               \
    0,                    /* xRename */                     \
    unixCurrentTimeInt64, /* xCurrentTimeInt64 */           \
  }

  /*
  ** All default VFSes for unix are contained in the following array.
  **
  ** Note that the sqlite3_vfs.pNext field of the VFS object is modified

    winDlError,          /* xDlError */
    winDlSym,            /* xDlSym */
    winDlClose,          /* xDlClose */
    winRandomness,       /* xRandomness */
    winSleep,            /* xSleep */
    winCurrentTime,      /* xCurrentTime */
    winGetLastError,     /* xGetLastError */
    0,                   /* xRename */
    winCurrentTimeInt64, /* xCurrentTimeInt64 */
  };

  sqlite3_vfs_register(&winVfs, 1);
  return SQLITE_OK; 
}
int sqlite3_os_end(void){ 

** SQLite will always allocate at least mxPathname+1 bytes for the
** output buffer xFullPathname.  The exact size of the output buffer
** is also passed as a parameter to both  methods. If the output buffer
** is not large enough, [SQLITE_CANTOPEN] should be returned. Since this is
** handled as a fatal error by SQLite, vfs implementations should endeavor
** to prevent this by setting mxPathname to a sufficiently large value.
**
** The xRandomness(), xSleep(), and xCurrentTime() interfaces
** are not strictly a part of the filesystem, but they are
** included in the VFS structure for completeness.
** The xRandomness() function attempts to return nBytes bytes
** of good-quality randomness into zOut.  The return value is
** the actual number of bytes of randomness obtained.
** The xSleep() method causes the calling thread to sleep for at
** least the number of microseconds given.  The xCurrentTime()
** method returns a Julian Day Number for the current date and time.



**




*/
typedef struct sqlite3_vfs sqlite3_vfs;
struct sqlite3_vfs {
  int iVersion;            /* Structure version number (currently 2) */
  int szOsFile;            /* Size of subclassed sqlite3_file */
  int mxPathname;          /* Maximum file pathname length */
  sqlite3_vfs *pNext;      /* Next registered VFS */

  int (*xSleep)(sqlite3_vfs*, int microseconds);
  int (*xCurrentTime)(sqlite3_vfs*, double*);
  int (*xGetLastError)(sqlite3_vfs*, int, char *);
  /*
  ** The methods above are in version 1 of the sqlite_vfs object
  ** definition.  Those that follow are added in version 2 or later
  */
  int (*xRename)(sqlite3_vfs*, const char *zOld, const char *zNew, int dirSync);
  int (*xCurrentTimeInt64)(sqlite3_vfs*, sqlite3_int64*);
  /*
  ** The methods above are in versions 1 and 2 of the sqlite_vfs object.
  ** New fields may be appended in figure versions.  The iVersion
  ** value will increment whenever this happens. 
  */
};

    cfDlError,            /* xDlError */
    cfDlSym,              /* xDlSym */
    cfDlClose,            /* xDlClose */
    cfRandomness,         /* xRandomness */
    cfSleep,              /* xSleep */
    cfCurrentTime,        /* xCurrentTime */
    0,                    /* xGetlastError */
    0,                    /* xRename */
    0,                    /* xCurrentTimeInt64 */
  };

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

  0,                        /* xDlSym */
  0,                        /* xDlClose */
#endif /* SQLITE_OMIT_LOAD_EXTENSION */
  devsymRandomness,         /* xRandomness */
  devsymSleep,              /* xSleep */
  devsymCurrentTime,        /* xCurrentTime */
  0,                        /* xGetLastError */
  0,                        /* xRename */
  0                         /* xCurrentTimeInt64 */
};

static sqlite3_io_methods devsym_io_methods = {
  2,                                /* iVersion */
  devsymClose,                      /* xClose */
  devsymRead,                       /* xRead */

  jtDlError,                     /* xDlError */
  jtDlSym,                       /* xDlSym */
  jtDlClose,                     /* xDlClose */
  jtRandomness,                  /* xRandomness */
  jtSleep,                       /* xSleep */
  jtCurrentTime,                 /* xCurrentTime */
  0,                             /* xGetLastError */
  0,                             /* xRename */
  jtCurrentTimeInt64             /* xCurrentTimeInt64 */
};

static sqlite3_io_methods jt_io_methods = {
  1,                             /* iVersion */
  jtClose,                       /* xClose */
  jtRead,                        /* xRead */

    fsDlOpen,                                   /* xDlOpen */
    fsDlError,                                  /* xDlError */
    fsDlSym,                                    /* xDlSym */
    fsDlClose,                                  /* xDlClose */
    fsRandomness,                               /* xRandomness */
    fsSleep,                                    /* xSleep */
    fsCurrentTime,                              /* xCurrentTime */
    0,                                          /* xRename */
    0                                           /* xCurrentTimeInt64 */
  }, 
  0,                                            /* pFileList */
  0                                             /* pParent */
};

static sqlite3_io_methods fs_io_methods = {

/*
** This module contains code for a wrapper VFS that causes a log of
** most VFS calls to be written into a nominated file on disk. The log 
** is stored in a compressed binary format to reduce the amount of IO 
** overhead introduced into the application by logging.
**
** All calls on sqlite3_file objects except xFileControl() are logged.
** Additionally, calls to the xAccess(), xOpen(), xDelete() and xRename() 
** methods are logged. The other sqlite3_vfs object methods (xDlXXX,
** xRandomness, xSleep, xCurrentTime, xGetLastError and xCurrentTimeInt64) 
** are not logged.
**
** The binary log files are read using a virtual table implementation
** also contained in this file. 
**

static void (*vfslogDlSym(sqlite3_vfs *pVfs, void *p, const char*zSym))(void);
static void vfslogDlClose(sqlite3_vfs*, void*);
static int vfslogRandomness(sqlite3_vfs*, int nByte, char *zOut);
static int vfslogSleep(sqlite3_vfs*, int microseconds);
static int vfslogCurrentTime(sqlite3_vfs*, double*);

static int vfslogGetLastError(sqlite3_vfs*, int, char *);
static int vfslogRename(sqlite3_vfs*, const char *, const char *, int);
static int vfslogCurrentTimeInt64(sqlite3_vfs*, sqlite3_int64*);

static sqlite3_vfs vfslog_vfs = {
  1,                              /* iVersion */
  sizeof(VfslogFile),             /* szOsFile */
  INST_MAX_PATHNAME,              /* mxPathname */
  0,                              /* pNext */

  vfslogDlError,                  /* xDlError */
  vfslogDlSym,                    /* xDlSym */
  vfslogDlClose,                  /* xDlClose */
  vfslogRandomness,               /* xRandomness */
  vfslogSleep,                    /* xSleep */
  vfslogCurrentTime,              /* xCurrentTime */
  vfslogGetLastError,             /* xGetLastError */
  vfslogRename,                   /* xRename */
  vfslogCurrentTimeInt64          /* xCurrentTime */
};

static sqlite3_io_methods vfslog_io_methods = {
  2,                              /* iVersion */
  vfslogClose,                    /* xClose */
  vfslogRead,                     /* xRead */

static int vfslogCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
  return REALVFS(pVfs)->xCurrentTime(REALVFS(pVfs), pTimeOut);
}

static int vfslogGetLastError(sqlite3_vfs *pVfs, int a, char *b){
  return REALVFS(pVfs)->xGetLastError(REALVFS(pVfs), a, b);
}
static int vfslogRename(sqlite3_vfs *pVfs, const char *a, const char *b, int c){
  return REALVFS(pVfs)->xRename(REALVFS(pVfs), a, b, c);
}
static int vfslogCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *p){
  return REALVFS(pVfs)->xCurrentTimeInt64(REALVFS(pVfs), p);
}

static void vfslog_flush(VfslogVfs *p){
#ifdef SQLITE_TEST
  extern int sqlite3_io_error_pending;

    0,                            /* xDlSym */
    0,                            /* xDlClose */
#endif /* SQLITE_OMIT_LOAD_EXTENSION */
    tvfsRandomness,               /* xRandomness */
    tvfsSleep,                    /* xSleep */
    tvfsCurrentTime,              /* xCurrentTime */
    0,                            /* xGetLastError */
    0,
    0,
  };

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