1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/org/sonews/daemon/ChannelWriter.java Fri Jun 26 16:48:50 2009 +0200
1.3 @@ -0,0 +1,207 @@
1.4 +/*
1.5 + * SONEWS News Server
1.6 + * see AUTHORS for the list of contributors
1.7 + *
1.8 + * This program is free software: you can redistribute it and/or modify
1.9 + * it under the terms of the GNU General Public License as published by
1.10 + * the Free Software Foundation, either version 3 of the License, or
1.11 + * (at your option) any later version.
1.12 + *
1.13 + * This program is distributed in the hope that it will be useful,
1.14 + * but WITHOUT ANY WARRANTY; without even the implied warranty of
1.15 + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
1.16 + * GNU General Public License for more details.
1.17 + *
1.18 + * You should have received a copy of the GNU General Public License
1.19 + * along with this program. If not, see <http://www.gnu.org/licenses/>.
1.20 + */
1.21 +
1.22 +package org.sonews.daemon;
1.23 +
1.24 +import org.sonews.util.Log;
1.25 +import java.io.IOException;
1.26 +import java.nio.ByteBuffer;
1.27 +import java.nio.channels.CancelledKeyException;
1.28 +import java.nio.channels.SelectionKey;
1.29 +import java.nio.channels.Selector;
1.30 +import java.nio.channels.SocketChannel;
1.31 +import java.util.Iterator;
1.32 +
1.33 +/**
1.34 + * A Thread task that processes OP_WRITE events for SocketChannels.
1.35 + * @author Christian Lins
1.36 + * @since sonews/0.5.0
1.37 + */
1.38 +class ChannelWriter extends AbstractDaemon
1.39 +{
1.40 +
1.41 + private static ChannelWriter instance = new ChannelWriter();
1.42 +
1.43 + /**
1.44 + * @return Returns the active ChannelWriter instance.
1.45 + */
1.46 + public static ChannelWriter getInstance()
1.47 + {
1.48 + return instance;
1.49 + }
1.50 +
1.51 + private Selector selector = null;
1.52 +
1.53 + protected ChannelWriter()
1.54 + {
1.55 + }
1.56 +
1.57 + /**
1.58 + * @return Selector associated with this instance.
1.59 + */
1.60 + public Selector getSelector()
1.61 + {
1.62 + return this.selector;
1.63 + }
1.64 +
1.65 + /**
1.66 + * Sets the selector that is used by this ChannelWriter.
1.67 + * @param selector
1.68 + */
1.69 + public void setSelector(final Selector selector)
1.70 + {
1.71 + this.selector = selector;
1.72 + }
1.73 +
1.74 + /**
1.75 + * Run loop.
1.76 + */
1.77 + @Override
1.78 + public void run()
1.79 + {
1.80 + assert selector != null;
1.81 +
1.82 + while(isRunning())
1.83 + {
1.84 + try
1.85 + {
1.86 + SelectionKey selKey = null;
1.87 + SocketChannel socketChannel = null;
1.88 + NNTPConnection connection = null;
1.89 +
1.90 + // select() blocks until some SelectableChannels are ready for
1.91 + // processing. There is no need to synchronize the selector as we
1.92 + // have only one thread per selector.
1.93 + selector.select(); // The return value of select can be ignored
1.94 +
1.95 + // Get list of selection keys with pending OP_WRITE events.
1.96 + // The keySET is not thread-safe whereas the keys itself are.
1.97 + Iterator it = selector.selectedKeys().iterator();
1.98 +
1.99 + while (it.hasNext())
1.100 + {
1.101 + // We remove the first event from the set and store it for
1.102 + // later processing.
1.103 + selKey = (SelectionKey) it.next();
1.104 + socketChannel = (SocketChannel) selKey.channel();
1.105 + connection = Connections.getInstance().get(socketChannel);
1.106 +
1.107 + it.remove();
1.108 + if (connection != null)
1.109 + {
1.110 + break;
1.111 + }
1.112 + else
1.113 + {
1.114 + selKey = null;
1.115 + }
1.116 + }
1.117 +
1.118 + if (selKey != null)
1.119 + {
1.120 + try
1.121 + {
1.122 + // Process the selected key.
1.123 + // As there is only one OP_WRITE key for a given channel, we need
1.124 + // not to synchronize this processing to retain the order.
1.125 + processSelectionKey(connection, socketChannel, selKey);
1.126 + }
1.127 + catch (IOException ex)
1.128 + {
1.129 + Log.msg("Error writing to channel: " + ex, false);
1.130 +
1.131 + // Cancel write events for this channel
1.132 + selKey.cancel();
1.133 + connection.shutdownInput();
1.134 + connection.shutdownOutput();
1.135 + }
1.136 + }
1.137 +
1.138 + // Eventually wait for a register operation
1.139 + synchronized(NNTPDaemon.RegisterGate) { /* do nothing */ }
1.140 + }
1.141 + catch(CancelledKeyException ex)
1.142 + {
1.143 + Log.msg("ChannelWriter.run(): " + ex, true);
1.144 + }
1.145 + catch(Exception ex)
1.146 + {
1.147 + ex.printStackTrace();
1.148 + }
1.149 + } // while(isRunning())
1.150 + }
1.151 +
1.152 + private void processSelectionKey(final NNTPConnection connection,
1.153 + final SocketChannel socketChannel, final SelectionKey selKey)
1.154 + throws InterruptedException, IOException
1.155 + {
1.156 + assert connection != null;
1.157 + assert socketChannel != null;
1.158 + assert selKey != null;
1.159 + assert selKey.isWritable();
1.160 +
1.161 + // SocketChannel is ready for writing
1.162 + if(selKey.isValid())
1.163 + {
1.164 + // Lock the socket channel
1.165 + synchronized(socketChannel)
1.166 + {
1.167 + // Get next output buffer
1.168 + ByteBuffer buf = connection.getOutputBuffer();
1.169 + if(buf == null)
1.170 + {
1.171 + // Currently we have nothing to write, so we stop the writeable
1.172 + // events until we have something to write to the socket channel
1.173 + //selKey.cancel();
1.174 + selKey.interestOps(0);
1.175 + return;
1.176 + }
1.177 +
1.178 + while(buf != null) // There is data to be send
1.179 + {
1.180 + // Write buffer to socket channel; this method does not block
1.181 + if(socketChannel.write(buf) <= 0)
1.182 + {
1.183 + // Perhaps there is data to be written, but the SocketChannel's
1.184 + // buffer is full, so we stop writing to until the next event.
1.185 + break;
1.186 + }
1.187 + else
1.188 + {
1.189 + // Retrieve next buffer if available; method may return the same
1.190 + // buffer instance if it still have some bytes remaining
1.191 + buf = connection.getOutputBuffer();
1.192 + }
1.193 + }
1.194 + }
1.195 + }
1.196 + else
1.197 + {
1.198 + Log.msg("Invalid OP_WRITE key: " + selKey, false);
1.199 +
1.200 + if (socketChannel.socket().isClosed())
1.201 + {
1.202 + connection.shutdownInput();
1.203 + connection.shutdownOutput();
1.204 + socketChannel.close();
1.205 + Log.msg("Connection closed.", true);
1.206 + }
1.207 + }
1.208 + }
1.209 +
1.210 +}