func PeekMessageType()

in internal/encoding/types.go [202:234]

• 26 lines of code
• 8 McCabe index (conditional complexity)

func PeekMessageType(buf []byte) (uint8, uint8, error) {
	if len(buf) < 3 {
		return 0, 0, errors.New("invalid message")
	}

	if buf[0] != 0 {
		return 0, 0, fmt.Errorf("invalid composite header %02x", buf[0])
	}

	// copied from readUlong to avoid allocations
	t := AMQPType(buf[1])
	if t == TypeCodeUlong0 {
		return 0, 2, nil
	}

	if t == TypeCodeSmallUlong {
		if len(buf[2:]) == 0 {
			return 0, 0, errors.New("invalid ulong")
		}
		return buf[2], 3, nil
	}

	if t != TypeCodeUlong {
		return 0, 0, fmt.Errorf("invalid type for uint32 %02x", t)
	}

	if len(buf[2:]) < 8 {
		return 0, 0, errors.New("invalid ulong")
	}
	v := binary.BigEndian.Uint64(buf[2:10])

	return uint8(v), 10, nil
}