paho.mqtt.m2mqtt/M2Mqtt/Messages/MqttMsgPuback.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
*/

namespace uPLibrary.Networking.M2Mqtt.Messages
{
    /// <summary>
    /// Class for PUBACK message from broker to client
    /// </summary>
    public class MqttMsgPuback : MqttMsgBase
    {
        #region Properties...

        /// <summary>
        /// Message identifier for the publish message
        /// that is acknowledged
        /// </summary>
        public ushort MessageId
        {
            get { return this.messageId; }
            set { this.messageId = value; }
        }

        #endregion

        // message identifier
        private ushort messageId;
        
        /// <summary>
        /// Constructor
        /// </summary>
        public MqttMsgPuback()
        {
            this.type = MQTT_MSG_PUBACK_TYPE;
        }

        public override byte[] GetBytes()
        {
            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
            buffer[index++] = (MQTT_MSG_PUBACK_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 PUBACK message
        /// </summary>
        /// <param name="fixedHeaderFirstByte">First fixed header byte</param>
        /// <param name="channel">Channel connected to the broker</param>
        /// <returns>PUBACK message instance</returns>
        public static MqttMsgPuback Parse(byte fixedHeaderFirstByte, IMqttNetworkChannel channel)
        {
            byte[] buffer;
            int index = 0;
            MqttMsgPuback msg = new MqttMsgPuback();

            // 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(
                "PUBACK",
                new object[] { "messageId" },
                new object[] { this.messageId });
#else
            return base.ToString();
#endif
        }
    }
}