mqtt/M2Mqtt/Messages/MqttMsgConnack.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 uPLibrary.Networking.M2Mqtt.Exceptions;

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

    // return codes for CONNACK message
    public const Byte CONN_ACCEPTED = 0x00;
    public const Byte CONN_REFUSED_PROT_VERS = 0x01;
    public const Byte CONN_REFUSED_IDENT_REJECTED = 0x02;
    public const Byte CONN_REFUSED_SERVER_UNAVAILABLE = 0x03;
    public const Byte CONN_REFUSED_USERNAME_PASSWORD = 0x04;
    public const Byte CONN_REFUSED_NOT_AUTHORIZED = 0x05;

    //private const Byte TOPIC_NAME_COMP_RESP_BYTE_OFFSET = 0;
    private const Byte TOPIC_NAME_COMP_RESP_BYTE_SIZE = 1;
    // [v3.1.1] connect acknowledge flags replace "old" topic name compression respone (not used in 3.1)
    private const Byte CONN_ACK_FLAGS_BYTE_OFFSET = 0;
    private const Byte CONN_ACK_FLAGS_BYTE_SIZE = 1;
    // [v3.1.1] session present flag
    private const Byte SESSION_PRESENT_FLAG_MASK = 0x01;
    private const Byte SESSION_PRESENT_FLAG_OFFSET = 0x00;
    //private const Byte SESSION_PRESENT_FLAG_SIZE = 0x01;
    private const Byte CONN_RETURN_CODE_BYTE_OFFSET = 1;
    private const Byte CONN_RETURN_CODE_BYTE_SIZE = 1;

    #endregion

    #region Properties...

    // [v3.1.1] session present flag
    /// <summary>
    /// Session present flag
    /// </summary>
    public Boolean SessionPresent { get; set; }

    /// <summary>
    /// Return Code
    /// </summary>
    public Byte ReturnCode { get; set; }

    #endregion

    // [v3.1.1] session present flag

    /// <summary>
    /// Constructor
    /// </summary>
    public MqttMsgConnack() => this.Type = MQTT_MSG_CONNACK_TYPE;

    /// <summary>
    /// Parse bytes for a CONNACK 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>CONNACK message instance</returns>
    public static MqttMsgConnack Parse(Byte fixedHeaderFirstByte, Byte protocolVersion, IMqttNetworkChannel channel) {
      Byte[] buffer;
      MqttMsgConnack msg = new MqttMsgConnack();

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

      // get remaining length and allocate buffer
      Int32 remainingLength = MqttMsgBase.DecodeRemainingLength(channel);
      buffer = new Byte[remainingLength];

      // read bytes from socket...
      _ = channel.Receive(buffer);
      if (protocolVersion == MqttMsgConnect.PROTOCOL_VERSION_V3_1_1) {
        // [v3.1.1] ... set session present flag ...
        msg.SessionPresent = (buffer[CONN_ACK_FLAGS_BYTE_OFFSET] & SESSION_PRESENT_FLAG_MASK) != 0x00;
      }
      // ...and set return code from broker
      msg.ReturnCode = buffer[CONN_RETURN_CODE_BYTE_OFFSET];

      return msg;
    }

    public override Byte[] GetBytes(Byte ProtocolVersion) {
      Int32 varHeaderSize = 0;
      Int32 payloadSize = 0;
      Int32 remainingLength = 0;
      Byte[] buffer;
      Int32 index = 0;

      if (ProtocolVersion == MqttMsgConnect.PROTOCOL_VERSION_V3_1_1) {
        // flags byte and connect return code
        varHeaderSize += CONN_ACK_FLAGS_BYTE_SIZE + CONN_RETURN_CODE_BYTE_SIZE;
      } else {
        // topic name compression response and connect return code
        varHeaderSize += TOPIC_NAME_COMP_RESP_BYTE_SIZE + CONN_RETURN_CODE_BYTE_SIZE;
      }

      remainingLength += varHeaderSize + payloadSize;

      // first byte of fixed header
      Int32 fixedHeaderSize = 1;

      Int32 temp = remainingLength;
      // increase fixed header size based on remaining length
      // (each remaining length byte can encode until 128)
      do {
        fixedHeaderSize++;
        temp /= 128;
      } while (temp > 0);

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

      // first fixed header byte
      buffer[index++] = ProtocolVersion == MqttMsgConnect.PROTOCOL_VERSION_V3_1_1
        ? (Byte)((MQTT_MSG_CONNACK_TYPE << MSG_TYPE_OFFSET) | MQTT_MSG_CONNACK_FLAG_BITS)
        : (Byte)(MQTT_MSG_CONNACK_TYPE << MSG_TYPE_OFFSET);

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

      if (ProtocolVersion == MqttMsgConnect.PROTOCOL_VERSION_V3_1_1) {
        // [v3.1.1] session present flag
        buffer[index++] = this.SessionPresent ? (Byte)(1 << SESSION_PRESENT_FLAG_OFFSET) : (Byte)0x00;
      } else {
        // topic name compression response (reserved values. not used);
        buffer[index++] = 0x00;
      }

      // connect return code
      buffer[index++] = this.ReturnCode;

      return buffer;
    }

    public override String ToString() =>
#if TRACE
      this.GetTraceString(
          "CONNACK",
          new Object[] { "returnCode" },
          new Object[] { this.ReturnCode });
#else
            base.ToString();
#endif

  }
}