src/org/sonews/daemon/ChannelReader.java
author František Kučera <franta-hg@frantovo.cz>
Sun, 06 Nov 2011 00:08:05 +0100
changeset 116 4ddc1020a154
parent 37 74139325d305
permissions -rwxr-xr-x
Podpora Markdown syntaxe
na začátek odesílané zprávy stačí přidat:
#!markdown
a zpráva se pak prožene Markdown procesorem (spouštěno přes sudo pod jiným uživatelem)
a pak teprve přes standardní XSL transformaci.

1) Vytvořit uživatele a skupinu markdown

2) Do /etc/sudoers přidat:
Cmnd_Alias MARKDOWN = /usr/bin/markdown
%markdown ALL = (%markdown) NOPASSWD : MARKDOWN

3) Uivatele, pod kterým běží NNTP démon, přidat do skupiny markdown
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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 java.util.logging.Level;
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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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			try {
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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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					Iterator it = selKeys.iterator();
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					// Process the first pending event
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					while (it.hasNext()) {
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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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							// 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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								break; // End while loop
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							}
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						} else {
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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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					processSelectionKey(conn, channel, selKey);
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					conn.unlockReadLock();
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				}
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			} catch (CancelledKeyException ex) {
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				Log.get().warning("ChannelReader.run(): " + ex);
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				Log.get().log(Level.INFO, "", ex);
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			} catch (Exception ex) {
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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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				// 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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			// 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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					read = socketChannel.read(buf);
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				} catch (IOException ex) {
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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.get().info("ChannelReader.processSelectionKey(): " + ex);
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				} catch (Exception ex) {
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					Log.get().warning("ChannelReader.processSelectionKey(): " + ex);
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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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				} 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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		} else {
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			// Should not happen
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			Log.get().severe("Should not happen: " + selKey.toString());
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		}
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	}
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}