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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 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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import java.util.Set;
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import org.sonews.util.Log;
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/**
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* A Thread task listening for OP_READ events from 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 ChannelReader extends AbstractDaemon
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{
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private static ChannelReader instance = new ChannelReader();
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/**
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* @return Active ChannelReader instance.
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*/
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public static ChannelReader 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 ChannelReader()
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{
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}
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/**
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* Sets the selector which is used by this reader to determine the channel
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* to read from.
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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. Blocks until some data is available in a channel.
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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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{
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try
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{
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// select() blocks until some SelectableChannels are ready for
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// processing. There is no need to lock the selector as we have only
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// one thread per selector.
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selector.select();
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// Get list of selection keys with pending events.
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// Note: the selected key set is not thread-safe
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SocketChannel channel = null;
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NNTPConnection conn = null;
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final Set<SelectionKey> selKeys = selector.selectedKeys();
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SelectionKey selKey = null;
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synchronized (selKeys)
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{
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Iterator it = selKeys.iterator();
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// Process the first pending event
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while (it.hasNext())
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{
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selKey = (SelectionKey) it.next();
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channel = (SocketChannel) selKey.channel();
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conn = Connections.getInstance().get(channel);
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// Because we cannot lock the selKey as that would cause a deadlock
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// we lock the connection. To preserve the order of the received
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// byte blocks a selection key for a connection that has pending
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// read events is skipped.
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if (conn == null || conn.tryReadLock())
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{
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// Remove from set to indicate that it's being processed
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it.remove();
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if (conn != null)
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{
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break; // End while loop
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}
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}
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else
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{
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selKey = null;
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channel = null;
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conn = null;
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}
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}
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}
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// Do not lock the selKeys while processing because this causes
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// a deadlock in sun.nio.ch.SelectorImpl.lockAndDoSelect()
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if (selKey != null && channel != null && conn != null)
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{
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processSelectionKey(conn, channel, selKey);
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conn.unlockReadLock();
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}
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}
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catch(CancelledKeyException ex)
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{
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Log.msg("ChannelReader.run(): " + ex, false);
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if(Log.isDebug())
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{
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ex.printStackTrace();
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}
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}
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catch(Exception ex)
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{
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ex.printStackTrace();
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}
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// Eventually wait for a register operation
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synchronized (NNTPDaemon.RegisterGate)
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{
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// Do nothing; FindBugs may warn about an empty synchronized
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// statement, but we cannot use a wait()/notify() mechanism here.
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// If we used something like RegisterGate.wait() we block here
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// until the NNTPDaemon calls notify(). But the daemon only
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// calls notify() if itself is NOT blocked in the listening socket.
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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 selKey != null;
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assert selKey.isReadable();
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// Some bytes are available for reading
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if(selKey.isValid())
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{
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// Lock the channel
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//synchronized(socketChannel)
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{
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// Read the data into the appropriate buffer
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ByteBuffer buf = connection.getInputBuffer();
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int read = -1;
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try
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{
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read = socketChannel.read(buf);
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}
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catch(IOException ex)
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{
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// The connection was probably closed by the remote host
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// in a non-clean fashion
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Log.msg("ChannelReader.processSelectionKey(): " + ex, true);
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}
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catch(Exception ex)
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{
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Log.msg("ChannelReader.processSelectionKey(): " + ex, false);
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if(Log.isDebug())
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{
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ex.printStackTrace();
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}
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}
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if(read == -1) // End of stream
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{
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selKey.cancel();
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}
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else if(read > 0) // If some data was read
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{
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ConnectionWorker.addChannel(socketChannel);
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}
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}
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}
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else
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{
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// Should not happen
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Log.msg(selKey, false);
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}
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}
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}
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