public CoapMessage decode()

in coap/src/main/java/org/apache/mina/coap/codec/CoapDecoder.java [62:116]
41 lines of code
6 McCabe index (conditional complexity)

    public CoapMessage decode(ByteBuffer input, Void context) {
        LOG.debug("decode");

        if (input.remaining() <= 0) {
            LOG.debug("nothing to decode");
            return null;
        }
        int byte0 = input.get() & 0xFF;
        int version = (byte0 >> 6) & 0x3;
        MessageType type = MessageType.fromCode((byte0 >> 4) & 0x3);
        byte[] token = new byte[byte0 & 0xF];
        int code = input.get() & 0xFF;
        int id = input.getShort() & 0xFFFF;
        input.get(token);

        // decode options
        int optionCode = 0;
        byte[] payload = EMPTY_PAYLOAD;
        List<CoapOption> options = new ArrayList<CoapOption>();
        while (input.hasRemaining()) {
            int next = input.get() & 0xFF;

            // start of payload ?
            if (next == 0xFF) {
                payload = new byte[input.remaining()];
                input.get(payload);
                break;
            } else {
                int optionDeltaQuartet = (next >> 4) & 0xF;

                optionCode += optionFromQuartet(optionDeltaQuartet, input);

                // decode the option length
                int optionLenQuartet = next & 0x0F;
                int optionLength = optionFromQuartet(optionLenQuartet, input);

                // create the option DTO
                CoapOptionType optType = CoapOptionType.fromCode(optionCode);
                if (optType == null) {
                    throw new ProtocolDecoderException("unknown option code : " + optionCode);
                }

                // get the value
                byte[] optionValue = new byte[optionLength];
                input.get(optionValue);

                options.add(new CoapOption(optType, optionValue));
            }
        }

        if (input.hasRemaining()) {
            throw new ProtocolDecoderException("trailling " + input.remaining() + " bytes in the UDP datagram");
        }
        return new CoapMessage(version, type, code, id, token, options.toArray(EMPTY_OPTION), payload);
    }