paho.mqtt.m2mqtt/M2Mqtt/Messages/MqttMsgPubrec.cs

/*
Copyright (c) 2013, 2014 Paolo Patierno

All rights reserved. This program and the accompanying materials
are made available under the terms of the Eclipse Public License v1.0
and Eclipse Distribution License v1.0 which accompany this distribution. 

The Eclipse Public License is available at 
   http://www.eclipse.org/legal/epl-v10.html
and the Eclipse Distribution License is available at 
   http://www.eclipse.org/org/documents/edl-v10.php.

Contributors:
   Paolo Patierno - initial API and implementation and/or initial documentation
*/

using uPLibrary.Networking.M2Mqtt.Exceptions;

namespace uPLibrary.Networking.M2Mqtt.Messages
{
    /// <summary>
    /// Class for PUBREC message from broker to client
    /// </summary>
    public class MqttMsgPubrec : MqttMsgBase
    {
        /// <summary>
        /// Constructor
        /// </summary>
        public MqttMsgPubrec()
        {
            this.type = MQTT_MSG_PUBREC_TYPE;
        }

        public override byte[] GetBytes(byte protocolVersion)
        {
            int fixedHeaderSize = 0;
            int varHeaderSize = 0;
            int payloadSize = 0;
            int remainingLength = 0;
            byte[] buffer;
            int index = 0;

            // message identifier
            varHeaderSize += MESSAGE_ID_SIZE;

            remainingLength += (varHeaderSize + payloadSize);

            // first byte of fixed header
            fixedHeaderSize = 1;

            int temp = remainingLength;
            // increase fixed header size based on remaining length
            // (each remaining length byte can encode until 128)
            do
            {
                fixedHeaderSize++;
                temp = temp / 128;
            } while (temp > 0);

            // allocate buffer for message
            buffer = new byte[fixedHeaderSize + varHeaderSize + payloadSize];

            // first fixed header byte
            if (protocolVersion == MqttMsgConnect.PROTOCOL_VERSION_V3_1_1)
                buffer[index++] = (MQTT_MSG_PUBREC_TYPE << MSG_TYPE_OFFSET) | MQTT_MSG_PUBREC_FLAG_BITS; // [v.3.1.1]
            else
                buffer[index++] = (MQTT_MSG_PUBREC_TYPE << MSG_TYPE_OFFSET);

            // encode remaining length
            index = this.encodeRemainingLength(remainingLength, buffer, index);

            // get message identifier
            buffer[index++] = (byte)((this.messageId >> 8) & 0x00FF); // MSB
            buffer[index++] = (byte)(this.messageId & 0x00FF); // LSB 

            return buffer;
        }

        /// <summary>
        /// Parse bytes for a PUBREC message
        /// </summary>
        /// <param name="fixedHeaderFirstByte">First fixed header byte</param>
        /// <param name="protocolVersion">Protocol Version</param>
        /// <param name="channel">Channel connected to the broker</param>
        /// <returns>PUBREC message instance</returns>
        public static MqttMsgPubrec Parse(byte fixedHeaderFirstByte, byte protocolVersion, IMqttNetworkChannel channel)
        {
            byte[] buffer;
            int index = 0;
            MqttMsgPubrec msg = new MqttMsgPubrec();

            if (protocolVersion == MqttMsgConnect.PROTOCOL_VERSION_V3_1_1)
            {
                // [v3.1.1] check flag bits
                if ((fixedHeaderFirstByte & MSG_FLAG_BITS_MASK) != MQTT_MSG_PUBREC_FLAG_BITS)
                    throw new MqttClientException(MqttClientErrorCode.InvalidFlagBits);
            }

            // get remaining length and allocate buffer
            int remainingLength = MqttMsgBase.decodeRemainingLength(channel);
            buffer = new byte[remainingLength];

            // read bytes from socket...
            channel.Receive(buffer);

            // message id
            msg.messageId = (ushort)((buffer[index++] << 8) & 0xFF00);
            msg.messageId |= (buffer[index++]);

            return msg;
        }

        public override string ToString()
        {
#if TRACE
            return this.GetTraceString(
                "PUBREC",
                new object[] { "messageId" },
                new object[] { this.messageId });
#else
            return base.ToString();
#endif
        }
    }
}