code: public int read(byte []buf, int offset, int length) throws IOException
    {
      if (_is == null)
        return -1;
  
      int len = _is.read(buf, offset, length);
  
      return len;
    }
docs: Reads bytes from the file.
  
  @param buf a byte array receiving the data.
  @param offset starting index to receive data.
  @param length number of bytes to read.
  
  @return the number of bytes read or -1 on end of file.