code: func ReadVarintCode(buf []byte) (int, int, error) {
  	num, n := binary.Uvarint(buf)
  	if n < 0 {
  		return 0, 0, fmt.Errorf("varints larger than uint64 not yet supported")
  	}
  	return int(num), n, nil
  }
docs: // ReadVarintCode reads a varint code from the beginning of buf.
  // returns the code, and the number of bytes read.