paho.mqtt.m2mqtt/M2Mqtt/Messages/MqttMsgPubrel.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 PUBREL message from client top broker
    /// </summary>
    public class MqttMsgPubrel : MqttMsgBase
    {
        #region Properties...

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

        #endregion

        // message identifier
        private ushort messageId;
        
        /// <summary>
        /// Constructor
        /// </summary>
        public MqttMsgPubrel()
        {
            this.type = MQTT_MSG_PUBREL_TYPE;
            // PUBREL message use QoS Level 1
            this.qosLevel = QOS_LEVEL_AT_LEAST_ONCE;
        }

        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] = (byte)((MQTT_MSG_PUBREL_TYPE << MSG_TYPE_OFFSET) |
                                   (this.qosLevel << QOS_LEVEL_OFFSET));
            buffer[index] |= this.dupFlag ? (byte)(1 << DUP_FLAG_OFFSET) : (byte)0x00;
            index++;
            
            // encode remaining length
            index = this.encodeRemainingLength(remainingLength, buffer, index);

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

            return buffer;
        }

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

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

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

            // read QoS level from fixed header (would be QoS Level 1)
            msg.qosLevel = (byte)((fixedHeaderFirstByte & QOS_LEVEL_MASK) >> QOS_LEVEL_OFFSET);
            // read DUP flag from fixed header
            msg.dupFlag = (((fixedHeaderFirstByte & DUP_FLAG_MASK) >> DUP_FLAG_OFFSET) == 0x01);

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

            return msg;
        }

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