code: func DecimalPeak(b []byte) (int, error) {
  	if len(b) < 3 {
  		return 0, ErrBadNumber
  	}
  	precision := int(b[0])
  	frac := int(b[1])
  	return decimalBinSize(precision, frac) + 2, nil
  }
docs: // DecimalPeak returns the length of the encoded decimal.