//******************************************************************************
   //
   // File:    NetworkChannel.java
   // Package: edu.rit.mp
   // Unit:    Class edu.rit.mp.NetworkChannel
   //
   // This Java source file is copyright (C) 2008 by Alan Kaminsky. All rights
   // reserved. For further information, contact the author, Alan Kaminsky, at
   // ark@cs.rit.edu.
  //
  // This Java source file is part of the Parallel Java Library ("PJ"). PJ is free
  // software; you can redistribute it and/or modify it under the terms of the GNU
  // General Public License as published by the Free Software Foundation; either
  // version 3 of the License, or (at your option) any later version.
  //
  // PJ is distributed in the hope that it will be useful, but WITHOUT ANY
  // WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
  // A PARTICULAR PURPOSE. See the GNU General Public License for more details.
  //
  // Linking this library statically or dynamically with other modules is making a
  // combined work based on this library. Thus, the terms and conditions of the GNU
  // General Public License cover the whole combination.
  //
  // As a special exception, the copyright holders of this library give you
  // permission to link this library with independent modules to produce an
  // executable, regardless of the license terms of these independent modules, and
  // to copy and distribute the resulting executable under terms of your choice,
  // provided that you also meet, for each linked independent module, the terms
  // and conditions of the license of that module. An independent module is a module
  // which is not derived from or based on this library. If you modify this library,
  // you may extend this exception to your version of the library, but you are not
  // obligated to do so. If you do not wish to do so, delete this exception
  // statement from your version.
  //
  // A copy of the GNU General Public License is provided in the file gpl.txt. You
  // may also obtain a copy of the GNU General Public License on the World Wide
  // Web at http://www.gnu.org/licenses/gpl.html.
  //
  //******************************************************************************
  package edu.rit.mp;
  
  import java.io.IOException;
  import java.net.InetSocketAddress;
  import java.nio.channels.SocketChannel;
  import java.util.concurrent.LinkedBlockingQueue;
  
  /**
   * Class NetworkChannel provides a channel for sending and receiving messages
   * over the network in the Message Protocol (MP).
   *
   * @author Alan Kaminsky
   * @version 23-Apr-2008
   */
  class NetworkChannel
          extends Channel {
  
  // Hidden data members.
      // Underlying socket channel.
      private SocketChannel mySocketChannel;
  
      // Far end channel group ID.
      private int myFarChannelGroupId;
  
      // Queue of outgoing I/O requests.
      private LinkedBlockingQueue<IORequest> myOutgoingQueue;
  
      // Network channel send and receive threads.
      private NetworkChannelSendThread myNetworkChannelSendThread;
      private NetworkChannelReceiveThread myNetworkChannelReceiveThread;
  
  // Hidden constructors.
      /**
       * Construct a new network channel.
       *
       * @param theChannelGroup Enclosing channel group.
       * @param theSocketChannel Underlying socket channel.
       * @param theFarChannelGroupId Far end channel group ID.
       */
      NetworkChannel(ChannelGroup theChannelGroup,
              SocketChannel theSocketChannel,
              int theFarChannelGroupId) {
          super(theChannelGroup);
          mySocketChannel = theSocketChannel;
          myFarChannelGroupId = theFarChannelGroupId;
          myOutgoingQueue = new LinkedBlockingQueue<IORequest>();
      }
  
  // Exported operations.
      /**
       * Obtain the channel group ID of this channel's near end channel group.
       *
       * @return Near end channel group ID.
       */
      public int nearEndChannelGroupId() {
          return myChannelGroup.myChannelGroupId;
      }
  
      /**
       * Obtain the channel group ID of this channel's far end channel group.
      *
      * @return Far end channel group ID.
      */
     public int farEndChannelGroupId() {
         return myFarChannelGroupId;
     }
 
     /**
      * Obtain this channel's near end address. This is the host and port of the
      * near end of this channel's connection.
      *
      * @return Near end address.
      */
     public InetSocketAddress nearEndAddress() {
         return (InetSocketAddress) mySocketChannel.socket().getLocalSocketAddress();
     }
 
     /**
      * Obtain this channel's far end address. This is the host and port of the
      * far end of this channel's connection.
      *
      * @return Far end address.
      */
     public InetSocketAddress farEndAddress() {
         return (InetSocketAddress) mySocketChannel.socket().getRemoteSocketAddress();
     }
 
 // Hidden operations.
     /**
      * Start sending and receiving messages via this channel.
      */
     void start() {
         myNetworkChannelSendThread
                 = new NetworkChannelSendThread(this,
                         mySocketChannel,
                         myOutgoingQueue);
         myNetworkChannelReceiveThread
                 = new NetworkChannelReceiveThread(this,
                         mySocketChannel);
     }
 
     /**
      * Send a message via this channel. The I/O request object must be newly
      * constructed with the message tag and source buffer fields filled in. This
      * method is allowed to return immediately and let the message be sent in a
      * separate thread. The calling thread should use the I/O request object to
      * wait for the message send to complete.
      *
      * @param theIORequest I/O request object.
      *
      * @exception IOException Thrown if an I/O error occurred.
      */
     synchronized void send(IORequest theIORequest)
             throws IOException {
         // Check whether channel is closed.
         if (myWriteState == WRITE_CLOSED) {
             throw new IOException("NetworkChannel.send(): Channel closed");
         }
 
         // Put I/O request in outgoing queue. Send thread will actually send the
         // message.
         myOutgoingQueue.add(theIORequest);
     }
 
     /**
      * Perform additional close actions in a subclass.
      */
     void subclassClose() {
         // Close socket channel.
         if (mySocketChannel != null) {
             try {
                 mySocketChannel.close();
             } catch (IOException ignored) {
             }
         }
 
         // Interrupt the send and receive threads, which will cause them to
         // terminate.
         if (myNetworkChannelSendThread != null) {
             myNetworkChannelSendThread.interrupt();
         }
         if (myNetworkChannelReceiveThread != null) {
             myNetworkChannelReceiveThread.interrupt();
         }
 
         // Enable garbage collection of data members.
         mySocketChannel = null;
         myOutgoingQueue = null;
         myNetworkChannelSendThread = null;
         myNetworkChannelReceiveThread = null;
     }
 
     /**
      * Shut down the input side of this network channel.
      */
     synchronized void shutdownInput() {
         myReadState = READ_CLOSED;
         myNetworkChannelReceiveThread = null;
     }
 
 }