lang/cs/Org.Apache.REEF.Wake/Remote/Impl/Link.cs

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

using System;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using System.Threading.Tasks;
using Org.Apache.REEF.Tang.Exceptions;
using Org.Apache.REEF.Utilities.Diagnostics;
using Org.Apache.REEF.Utilities.Logging;
using Org.Apache.REEF.Wake.Util;

namespace Org.Apache.REEF.Wake.Remote.Impl
{
    /// <summary>
    /// Represents an open connection between remote hosts
    /// </summary>
    public class Link<T> : ILink<T>
    {
        private static readonly Logger LOGGER = Logger.GetLogger(typeof(Link<T>));

        private readonly IPEndPoint _localEndpoint;
        private readonly ICodec<T> _codec;
        private readonly Channel _channel;
        private bool _disposed;

        /// <summary>
        /// Constructs a Link object.
        /// Connects to the specified remote endpoint.
        /// </summary>
        /// <param name="remoteEndpoint">The remote endpoint to connect to</param>
        /// <param name="codec">The codec for serializing messages</param>
        /// <param name="tcpClientFactory">TcpClient factory</param>
        public Link(IPEndPoint remoteEndpoint, ICodec<T> codec, ITcpClientConnectionFactory tcpClientFactory)
        {
            if (remoteEndpoint == null)
            {
                throw new ArgumentNullException("remoteEndpoint");
            }
            if (codec == null)
            {
                throw new ArgumentNullException("codec");
            }

            Client = tcpClientFactory.Connect(remoteEndpoint);

            _codec = codec;
            _channel = new Channel(Client.GetStream());
            _localEndpoint = (IPEndPoint)Client.Client.LocalEndPoint;
            _disposed = false;
        }

        /// <summary>
        /// Constructs a Link object.
        /// Uses the already connected TcpClient.
        /// </summary>
        /// <param name="client">The already connected client</param>
        /// <param name="codec">The encoder and decoder</param>
        public Link(TcpClient client, ICodec<T> codec)
        {
            if (client == null)
            {
                throw new ArgumentNullException("client");
            }
            if (codec == null)
            {
                throw new ArgumentNullException("codec");
            }

            Client = client;
            _codec = codec;
            _channel = new Channel(Client.GetStream());
            _localEndpoint = (IPEndPoint)Client.Client.LocalEndPoint;
            _disposed = false;
        }

        /// <summary>
        /// Returns the local socket address
        /// </summary>
        public IPEndPoint LocalEndpoint
        {
            get { return _localEndpoint; }
        }

        /// <summary>
        /// Returns the remote socket address
        /// </summary>
        public IPEndPoint RemoteEndpoint
        {
            get { return (IPEndPoint)Client.Client.RemoteEndPoint; }
        }

        /// <summary>
        /// Gets the underlying TcpClient
        /// </summary>
        public TcpClient Client { get; private set; }

        /// <summary>
        /// Writes the message to the remote host
        /// </summary>
        /// <param name="value">The data to write</param>
        public void Write(T value)
        {
            if (value == null)
            {
                throw new ArgumentNullException("value");    
            }
            if (_disposed)
            {
                Exceptions.Throw(new IllegalStateException("Link has been closed."), LOGGER);
            }

            byte[] message = _codec.Encode(value);
            _channel.Write(message);
        }

        /// <summary>
        /// Writes the value to this link asynchronously
        /// </summary>
        /// <param name="value">The data to write</param>
        /// <param name="token">The cancellation token</param>
        public async Task WriteAsync(T value, CancellationToken token)
        {
            if (_disposed)
            {
                Exceptions.Throw(new IllegalStateException("Link has been closed."), LOGGER); 
            }

            byte[] message = _codec.Encode(value);
            await _channel.WriteAsync(message, token);
        }

        /// <summary>
        /// Reads the value from the link synchronously
        /// </summary>
        public T Read()
        {
            if (_disposed)
            {
                Exceptions.Throw(new IllegalStateException("Link has been disposed."), LOGGER);
            }

            byte[] message = _channel.Read();
            return (message == null) ? default(T) : _codec.Decode(message);
        }

        /// <summary>
        /// Reads the value from the link asynchronously
        /// </summary>
        /// <param name="token">The cancellation token</param>
        public async Task<T> ReadAsync(CancellationToken token)
        {
            if (_disposed)
            {
                Exceptions.Throw(new IllegalStateException("Link has been disposed."), LOGGER);
            }

            byte[] message = await _channel.ReadAsync(token);
            return (message == null) ? default(T) : _codec.Decode(message);
        }

        /// <summary>
        /// Close the client connection
        /// </summary>
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        /// <summary>
        /// Subclasses of Links should overwrite this to handle disposing
        /// of the link
        /// </summary>
        /// <param name="disposing">To dispose or not</param>
        public virtual void Dispose(bool disposing)
        {
            if (_disposed)
            {
                return;
            }

            if (disposing)
            {
                try
                {
                    Client.GetStream().Close();
                }
                catch (InvalidOperationException)
                {
                    LOGGER.Log(Level.Warning, "failed to close stream on a non-connected socket.");
                }

                Client.Close();
            }
            _disposed = true;
        }

        /// <summary>
        /// Overrides Equals. Two Link objects are equal if they are connected
        /// to the same remote endpoint.
        /// </summary>
        /// <param name="obj">The object to compare</param>
        /// <returns>True if the object is equal to this Link, otherwise false</returns>
        public override bool Equals(object obj)
        {
            Link<T> other = obj as Link<T>;
            if (other == null)
            {
                return false;
            }

            return other.RemoteEndpoint.Equals(RemoteEndpoint);
        }

        /// <summary>
        /// Gets the hash code for the Link object.
        /// </summary>
        /// <returns>The object's hash code</returns>
        public override int GetHashCode()
        {
            return RemoteEndpoint.GetHashCode();
        }
    }
}