src/net/lightstone/net/MinecraftEncoder.java

/*
 * Copyright (c) 2010-2011 Graham Edgecombe.
 *
 * This file is part of Lightstone.
 *
 * Lightstone is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Lightstone is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Lightstone.  If not, see <http://www.gnu.org/licenses/>.
 */

package net.lightstone.net;

import java.io.IOException;

import net.lightstone.msg.Message;
import net.lightstone.net.codec.MessageCodec;

import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.oneone.OneToOneEncoder;

/**
 * A {@link OneToOneEncoder} which encodes Minecraft {@link Message}s into
 * {@link ChannelBuffer}s.
 */
public class MinecraftEncoder extends OneToOneEncoder {

	@SuppressWarnings("unchecked")
	@Override
	protected Object encode(ChannelHandlerContext ctx, Channel c, Object msg) throws Exception {
		if (msg instanceof Message) {
			Message message = (Message) msg;

			Class<? extends Message> clazz = message.getClass();
			MessageCodec<Message> codec = (MessageCodec<Message>) CodecLookupService.find(clazz);
			if (codec == null) {
				throw new IOException("Unknown message type: " + clazz + ".");
			}

			ChannelBuffer opcodeBuf = ChannelBuffers.buffer(1);
			opcodeBuf.writeByte(codec.getOpcode());

			return ChannelBuffers.wrappedBuffer(opcodeBuf, codec.encode(message));
		}
		return msg;
	}

}