paho.mqtt.m2mqtt/M2Mqtt/Messages/MqttMsgBase.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 System;
using System.Text;

namespace uPLibrary.Networking.M2Mqtt.Messages
{
    /// <summary>
    /// Base class for all MQTT messages
    /// </summary>
    public abstract class MqttMsgBase
    {
        #region Constants...

        // mask, offset and size for fixed header fields
        internal const byte MSG_TYPE_MASK = 0xF0;
        internal const byte MSG_TYPE_OFFSET = 0x04;
        internal const byte MSG_TYPE_SIZE = 0x04;
        internal const byte DUP_FLAG_MASK = 0x08;
        internal const byte DUP_FLAG_OFFSET = 0x03;
        internal const byte DUP_FLAG_SIZE = 0x01;
        internal const byte QOS_LEVEL_MASK = 0x06;
        internal const byte QOS_LEVEL_OFFSET = 0x01;
        internal const byte QOS_LEVEL_SIZE = 0x02;
        internal const byte RETAIN_FLAG_MASK = 0x01;
        internal const byte RETAIN_FLAG_OFFSET = 0x00;
        internal const byte RETAIN_FLAG_SIZE = 0x01;

        // MQTT message types
        internal const byte MQTT_MSG_CONNECT_TYPE = 0x01;
        internal const byte MQTT_MSG_CONNACK_TYPE = 0x02;
        internal const byte MQTT_MSG_PUBLISH_TYPE = 0x03;
        internal const byte MQTT_MSG_PUBACK_TYPE = 0x04;
        internal const byte MQTT_MSG_PUBREC_TYPE = 0x05;
        internal const byte MQTT_MSG_PUBREL_TYPE = 0x06;
        internal const byte MQTT_MSG_PUBCOMP_TYPE = 0x07;
        internal const byte MQTT_MSG_SUBSCRIBE_TYPE = 0x08;
        internal const byte MQTT_MSG_SUBACK_TYPE = 0x09;
        internal const byte MQTT_MSG_UNSUBSCRIBE_TYPE = 0x0A;
        internal const byte MQTT_MSG_UNSUBACK_TYPE = 0x0B;
        internal const byte MQTT_MSG_PINGREQ_TYPE = 0x0C;
        internal const byte MQTT_MSG_PINGRESP_TYPE = 0x0D;
        internal const byte MQTT_MSG_DISCONNECT_TYPE = 0x0E;

        // QOS levels
        public const byte QOS_LEVEL_AT_MOST_ONCE = 0x00;
        public const byte QOS_LEVEL_AT_LEAST_ONCE = 0x01;
        public const byte QOS_LEVEL_EXACTLY_ONCE = 0x02;

        internal const ushort MAX_TOPIC_LENGTH = 65535;
        internal const ushort MIN_TOPIC_LENGTH = 1;
        internal const byte MESSAGE_ID_SIZE = 2;

        #endregion

        #region Properties...

        /// <summary>
        /// Message type
        /// </summary>
        public byte Type
        {
            get { return this.type; }
            set { this.type = value; }
        }

        /// <summary>
        /// Duplicate message flag
        /// </summary>
        public bool DupFlag
        {
            get { return this.dupFlag; }
            set { this.dupFlag = value; }
        }

        /// <summary>
        /// Quality of Service level
        /// </summary>
        public byte QosLevel
        {
            get { return this.qosLevel; }
            set { this.qosLevel = value; }
        }

        /// <summary>
        /// Retain message flag
        /// </summary>
        public bool Retain
        {
            get { return this.retain; }
            set { this.retain = value; }
        }

        #endregion

        // message type
        protected byte type;
        // duplicate delivery
        protected bool dupFlag;
        // quality of service level
        protected byte qosLevel;
        // retain flag
        protected bool retain;

        /// <summary>
        /// Returns message bytes rapresentation
        /// </summary>
        /// <returns>Bytes rapresentation</returns>
        public abstract byte[] GetBytes();
        
        /// <summary>
        /// Encode remaining length and insert it into message buffer
        /// </summary>
        /// <param name="remainingLength">Remaining length value to encode</param>
        /// <param name="buffer">Message buffer for inserting encoded value</param>
        /// <param name="index">Index from which insert encoded value into buffer</param>
        /// <returns>Index updated</returns>
        protected int encodeRemainingLength(int remainingLength, byte[] buffer, int index)
        {
            int digit = 0;
            do
            {
                digit = remainingLength % 128;
                remainingLength /= 128;
                if (remainingLength > 0)
                    digit = digit | 0x80;
                buffer[index++] = (byte)digit;
            } while (remainingLength > 0);
            return index;
        }

        /// <summary>
        /// Decode remaining length reading bytes from socket
        /// </summary>
        /// <param name="channel">Channel from reading bytes</param>
        /// <returns>Decoded remaining length</returns>
        protected static int decodeRemainingLength(IMqttNetworkChannel channel)
        {
            int multiplier = 1;
            int value = 0;
            int digit = 0;
            byte[] nextByte = new byte[1];
            do
            {
                // next digit from stream
                channel.Receive(nextByte);
                digit = nextByte[0];
                value += ((digit & 127) * multiplier);
                multiplier *= 128;
            } while ((digit & 128) != 0);
            return value;
        }

#if TRACE
        /// <summary>
        /// Returns a string representation of the message for tracing
        /// </summary>
        /// <param name="name">Message name</param>
        /// <param name="fieldNames">Message fields name</param>
        /// <param name="fieldValues">Message fields value</param>
        /// <returns>String representation of the message</returns>
        protected string GetTraceString(string name, object[] fieldNames, object[] fieldValues)
        {
            StringBuilder sb = new StringBuilder();
            sb.Append(name);
            
            if ((fieldNames != null) && (fieldValues != null))
            {
                sb.Append("(");
                bool addComma = false;
                for (int i = 0; i < fieldValues.Length; i++)
                {
                    if (fieldValues[i] != null)
                    {
                        if (addComma)
                        {
                            sb.Append(",");
                        }

                        sb.Append(fieldNames[i]);
                        sb.Append(":");
                        sb.Append(GetStringObject(fieldValues[i]));
                        addComma = true;
                    }
                }
                sb.Append(")");
            }
            
            return sb.ToString();
        }

        object GetStringObject(object value)
        {
            byte[] binary = value as byte[];
            if (binary != null)
            {
                string hexChars = "0123456789ABCDEF";
                StringBuilder sb = new StringBuilder(binary.Length * 2);
                for (int i = 0; i < binary.Length; ++i)
                {
                    sb.Append(hexChars[binary[i] >> 4]);
                    sb.Append(hexChars[binary[i] & 0x0F]);
                }

                return sb.ToString();
            }

            object[] list = value as object[];
            if (list != null)
            {
                StringBuilder sb = new StringBuilder();
                sb.Append('[');
                for (int i = 0; i < list.Length; ++i)
                {
                    if (i > 0) sb.Append(',');
                    sb.Append(list[i]);
                }
                sb.Append(']');

                return sb.ToString();
            }

            return value;
        }
#endif
    }
}