func()

in nmxact/nmserial/serial_xport.go [303:372]

• 55 lines of code
• 19 McCabe index (conditional complexity)

func (sx *SerialXport) Rx() ([]byte, error) {
	for sx.scanner.Scan() {
		line := []byte(sx.scanner.Text())

		for {
			if len(line) > 1 && line[0] == '\r' {
				line = line[1:]
			} else {
				break
			}
		}
		log.Debugf("Rx serial:\n%s", hex.Dump(line))
		if len(line) < 2 || ((line[0] != 4 || line[1] != 20) &&
			(line[0] != 6 || line[1] != 9)) {
			continue
		}

		base64Data := string(line[2:])

		data, err := base64.StdEncoding.DecodeString(base64Data)
		if err != nil {
			return nil, fmt.Errorf("Couldn't decode base64 string:"+
				" %s\nPacket hex dump:\n%s",
				base64Data, hex.Dump(line))
		}

		if line[0] == 6 && line[1] == 9 {
			if len(data) < 2 {
				continue
			}

			pktLen := binary.BigEndian.Uint16(data[0:2])
			sx.pkt, err = NewPacket(pktLen)
			if err != nil {
				return nil, err
			}
			data = data[2:]
		}

		if sx.pkt == nil {
			continue
		}

		full := sx.pkt.AddBytes(data)
		if full {
			if crc16.Crc16(sx.pkt.GetBytes()) != 0 {
				return nil, fmt.Errorf("CRC error")
			}

			/*
			 * Trim away the 2 bytes of CRC
			 */
			sx.pkt.TrimEnd(2)
			b := sx.pkt.GetBytes()
			sx.pkt = nil

			log.Debugf("Decoded input:\n%s", hex.Dump(b))
			return b, nil
		}
	}

	err := sx.scanner.Err()
	if err == nil {
		// Scanner hit EOF, so we'll need to create a new one.  This only
		// happens on timeouts.
		err = errTimeout
		sx.scanner = bufio.NewScanner(sx.port)
	}
	return nil, err
}