static int fseek(InputStream fis, long off, int whence){
    if(fis instanceof SeekableInputStream){
      SeekableInputStream sis=(SeekableInputStream)fis;
      try{
        if(whence==SEEK_SET){
          sis.seek(off);
        }
        else if(whence==SEEK_END){
          sis.seek(sis.getLength()-off);
        }
        else{
        }
      }
      catch(Exception e){
      }
      return 0;
    }
    try{
      if(whence==0){
        fis.reset();
      }
      fis.skip(off);
    }
    catch(Exception e){
      return -1;
    }
    return 0;
  }