chris@1: /*
chris@1:  *   SONEWS News Server
chris@1:  *   see AUTHORS for the list of contributors
chris@1:  *
chris@1:  *   This program is free software: you can redistribute it and/or modify
chris@1:  *   it under the terms of the GNU General Public License as published by
chris@1:  *   the Free Software Foundation, either version 3 of the License, or
chris@1:  *   (at your option) any later version.
chris@1:  *
chris@1:  *   This program is distributed in the hope that it will be useful,
chris@1:  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
chris@1:  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
chris@1:  *   GNU General Public License for more details.
chris@1:  *
chris@1:  *   You should have received a copy of the GNU General Public License
chris@1:  *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
chris@1:  */
chris@1: 
chris@1: package org.sonews.daemon;
chris@1: 
chris@1: import org.sonews.util.Log;
chris@1: import java.io.IOException;
chris@1: import java.nio.ByteBuffer;
chris@1: import java.nio.channels.CancelledKeyException;
chris@1: import java.nio.channels.SelectionKey;
chris@1: import java.nio.channels.Selector;
chris@1: import java.nio.channels.SocketChannel;
chris@1: import java.util.Iterator;
chris@1: 
chris@1: /**
chris@1:  * A Thread task that processes OP_WRITE events for SocketChannels.
chris@1:  * @author Christian Lins
chris@1:  * @since sonews/0.5.0
chris@1:  */
chris@1: class ChannelWriter extends AbstractDaemon
chris@1: {
chris@1: 
chris@1:   private static ChannelWriter instance = new ChannelWriter();
chris@1: 
chris@1:   /**
chris@1:    * @return Returns the active ChannelWriter instance.
chris@1:    */
chris@1:   public static ChannelWriter getInstance()
chris@1:   {
chris@1:     return instance;
chris@1:   }
chris@1:   
chris@1:   private Selector selector = null;
chris@1:   
chris@1:   protected ChannelWriter()
chris@1:   {
chris@1:   }
chris@1:   
chris@1:   /**
chris@1:    * @return Selector associated with this instance.
chris@1:    */
chris@1:   public Selector getSelector()
chris@1:   {
chris@1:     return this.selector;
chris@1:   }
chris@1:   
chris@1:   /**
chris@1:    * Sets the selector that is used by this ChannelWriter.
chris@1:    * @param selector
chris@1:    */
chris@1:   public void setSelector(final Selector selector)
chris@1:   {
chris@1:     this.selector = selector;
chris@1:   }
chris@1:   
chris@1:   /**
chris@1:    * Run loop.
chris@1:    */
chris@1:   @Override
chris@1:   public void run()
chris@1:   {
chris@1:     assert selector != null;
chris@1: 
chris@1:     while(isRunning())
chris@1:     {
chris@1:       try
chris@1:       {
chris@1:         SelectionKey   selKey        = null;
chris@1:         SocketChannel  socketChannel = null;
chris@1:         NNTPConnection connection    = null;
chris@1: 
chris@1:         // select() blocks until some SelectableChannels are ready for
chris@1:         // processing. There is no need to synchronize the selector as we
chris@1:         // have only one thread per selector.
chris@1:         selector.select(); // The return value of select can be ignored
chris@1: 
chris@1:         // Get list of selection keys with pending OP_WRITE events.
chris@1:         // The keySET is not thread-safe whereas the keys itself are.
chris@1:         Iterator it = selector.selectedKeys().iterator();
chris@1: 
chris@1:         while (it.hasNext())
chris@1:         {
chris@1:           // We remove the first event from the set and store it for
chris@1:           // later processing.
chris@1:           selKey = (SelectionKey) it.next();
chris@1:           socketChannel = (SocketChannel) selKey.channel();
chris@1:           connection = Connections.getInstance().get(socketChannel);
chris@1: 
chris@1:           it.remove();
chris@1:           if (connection != null)
chris@1:           {
chris@1:             break;
chris@1:           }
chris@1:           else
chris@1:           {
chris@1:             selKey = null;
chris@1:           }
chris@1:         }
chris@1:         
chris@1:         if (selKey != null)
chris@1:         {
chris@1:           try
chris@1:           {
chris@1:             // Process the selected key.
chris@1:             // As there is only one OP_WRITE key for a given channel, we need
chris@1:             // not to synchronize this processing to retain the order.
chris@1:             processSelectionKey(connection, socketChannel, selKey);
chris@1:           }
chris@1:           catch (IOException ex)
chris@1:           {
chris@1:             Log.msg("Error writing to channel: " + ex, false);
chris@1: 
chris@1:             // Cancel write events for this channel
chris@1:             selKey.cancel();
chris@1:             connection.shutdownInput();
chris@1:             connection.shutdownOutput();
chris@1:           }
chris@1:         }
chris@1:         
chris@1:         // Eventually wait for a register operation
chris@1:         synchronized(NNTPDaemon.RegisterGate) { /* do nothing */ }
chris@1:       }
chris@1:       catch(CancelledKeyException ex)
chris@1:       {
chris@1:         Log.msg("ChannelWriter.run(): " + ex, true);
chris@1:       }
chris@1:       catch(Exception ex)
chris@1:       {
chris@1:         ex.printStackTrace();
chris@1:       }
chris@1:     } // while(isRunning())
chris@1:   }
chris@1:   
chris@1:   private void processSelectionKey(final NNTPConnection connection,
chris@1:     final SocketChannel socketChannel, final SelectionKey selKey)
chris@1:     throws InterruptedException, IOException
chris@1:   {
chris@1:     assert connection != null;
chris@1:     assert socketChannel != null;
chris@1:     assert selKey != null;
chris@1:     assert selKey.isWritable();
chris@1: 
chris@1:     // SocketChannel is ready for writing
chris@1:     if(selKey.isValid())
chris@1:     {
chris@1:       // Lock the socket channel
chris@1:       synchronized(socketChannel)
chris@1:       {
chris@1:         // Get next output buffer
chris@1:         ByteBuffer buf = connection.getOutputBuffer();
chris@1:         if(buf == null)
chris@1:         {
chris@1:           // Currently we have nothing to write, so we stop the writeable
chris@1:           // events until we have something to write to the socket channel
chris@1:           //selKey.cancel();
chris@1:           selKey.interestOps(0);
chris@1:           return;
chris@1:         }
chris@1:  
chris@1:         while(buf != null) // There is data to be send
chris@1:         {
chris@1:           // Write buffer to socket channel; this method does not block
chris@1:           if(socketChannel.write(buf) <= 0)
chris@1:           {
chris@1:             // Perhaps there is data to be written, but the SocketChannel's
chris@1:             // buffer is full, so we stop writing to until the next event.
chris@1:             break;
chris@1:           }
chris@1:           else
chris@1:           {
chris@1:             // Retrieve next buffer if available; method may return the same
chris@1:             // buffer instance if it still have some bytes remaining
chris@1:             buf = connection.getOutputBuffer();
chris@1:           }
chris@1:         }
chris@1:       }
chris@1:     }
chris@1:     else
chris@1:     {
chris@1:       Log.msg("Invalid OP_WRITE key: " + selKey, false);
chris@1: 
chris@1:       if (socketChannel.socket().isClosed())
chris@1:       {
chris@1:         connection.shutdownInput();
chris@1:         connection.shutdownOutput();
chris@1:         socketChannel.close();
chris@1:         Log.msg("Connection closed.", true);
chris@1:       }
chris@1:     }
chris@1:   }
chris@1:   
chris@1: }