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