OFMessageDecoder.java

/**
 *    Copyright 2011, Big Switch Networks, Inc.
 *    Originally created by David Erickson, Stanford University
 *
 *    Licensed under the Apache License, Version 2.0 (the "License"); you may
 *    not use this file except in compliance with the License. You may obtain
 *    a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 *    License for the specific language governing permissions and limitations
 *    under the License.
 **/

package net.floodlightcontroller.core.internal;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;

import org.projectfloodlight.openflow.protocol.OFFactories;
import org.projectfloodlight.openflow.protocol.OFFactory;
import org.projectfloodlight.openflow.protocol.OFMessage;
import org.projectfloodlight.openflow.protocol.OFMessageReader;
import org.projectfloodlight.openflow.protocol.OFVersion;

/**
 * Decode an openflow message from a channel, for use in a netty pipeline.
 *
 * @author Andreas Wundsam <andreas.wundsam@bigswitch.com>
 */
public class OFMessageDecoder extends ByteToMessageDecoder {

	private OFMessageReader<OFMessage> reader;

	public OFMessageDecoder() {
		setReader();
	}

	public OFMessageDecoder(OFVersion version) {
		setVersion(version);
		setReader();
	}

	private void setReader() {
		reader = OFFactories.getGenericReader();
	}

	public void setVersion(OFVersion version) {
		OFFactory factory = OFFactories.getFactory(version);
		this.reader = factory.getReader();
	}

	@Override
	protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
		if (!ctx.channel().isActive()) {
			// In testing, I see decode being called AFTER decode last.
			// This check avoids that from reading corrupted frames
			return;
		}

		// Note(andiw): netty4 adds support for more efficient handling of lists messages in the
		// pipeline itself.
		// Instead of constructing a list of messages here, we could also just add the individual
		// messages to the "out" list provided by netty. This would require changing all the handlers
		// in the pipeline to accept "OFMessage" instead of "Iterable<OFMessage>". Probably
		// a good idea, but left for a future cleanup.

		OFMessage singleMessage = null;
		List<OFMessage> list = null;
		boolean first = true;
		for (;;) {
			OFMessage message = reader.readFrom(in);
			if (message == null) {
				break;
			}
			if (first) {
				// first message read
				singleMessage = message;
				first = false;
			} else {
				// more messages read, use the list
				if (list == null) {
					list = new ArrayList<>();
					list.add(singleMessage);
					singleMessage = null;
				}
				list.add(message);
			}
		}
		if (list != null) {
			out.add(list);
		} else if (singleMessage != null) {
			out.add(Collections.singletonList(singleMessage));
		}
	}
}