sas.systems.imflux.network.udp.UdpControlPacketDecoder.java Source code

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Here is the source code for sas.systems.imflux.network.udp.UdpControlPacketDecoder.java

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/*
 * Copyright 2015 Sebastian Schmidl
 *
 * 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 sas.systems.imflux.network.udp;

import io.netty.buffer.ByteBuf;
import io.netty.channel.AddressedEnvelope;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandler.Sharable;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.DefaultAddressedEnvelope;
import io.netty.channel.socket.DatagramPacket;
import io.netty.handler.codec.MessageToMessageDecoder;
import sas.systems.imflux.logging.Logger;
import sas.systems.imflux.packet.rtcp.CompoundControlPacket;
import sas.systems.imflux.packet.rtcp.ControlPacket;

import java.net.SocketAddress;
import java.util.ArrayList;
import java.util.List;

/**
 * A class (singleton) for decoding {@link DatagramPacket}s to {@link CompoundControlPacket}s. For supporting sending to
 * multiple recipients from one {@link Channel} the {@code CompoundControlPacket} is wrapped into an 
 * {@link AddressedEnvelope}. You can access the {@link SocketAddress} from this packets source with
 * {@link AddressedEnvelope#sender()}. This class extends {@link MessageToMessageDecoder} and can therefore be used in multiple 
 * {@link ChannelPipeline}s.
 * 
 * @see MessageToMessageDecoder
 * @author <a href="https://github.com/CodeLionX">CodeLionX</a>
 */
@Sharable
public class UdpControlPacketDecoder extends MessageToMessageDecoder<DatagramPacket> {

    // constants ------------------------------------------------------------------------------------------------------
    protected static final Logger LOG = Logger.getLogger(UdpControlPacketDecoder.class);

    // constructor ----------------------------------------------------------------------------------------------------
    private UdpControlPacketDecoder() {
    }

    // public static methods ------------------------------------------------------------------------------------------
    /**
     * 
     * @return instance of UdpControlPacketDecoder
     */
    public static UdpControlPacketDecoder getInstance() {
        return InstanceHolder.INSTANCE;
    }

    // MessageToMessageEncoder ----------------------------------------------------------------------------------------
    /**
     * Decodes a {@link DatagramPacket} to a {@link CompoundControlPacket} wrapped into an {@link AddressedEnvelope}.
     * 
     * @param ctx The context of the ChannelHandler
     * @param message the message which should be encoded
     * @param out a list where all messages are written to
     */
    @Override
    protected void decode(ChannelHandlerContext ctx, DatagramPacket msg, List<Object> out) throws Exception {
        final ByteBuf content = msg.content();
        final SocketAddress sender = msg.sender();
        final SocketAddress recipient = msg.recipient();

        if ((content.readableBytes() % 4) != 0) {
            LOG.debug("Invalid RTCP packet received: total length should be multiple of 4 but is {}",
                    content.readableBytes());
            return;
        }

        // Usually 2 packets per UDP frame...
        final List<ControlPacket> controlPacketList = new ArrayList<>(2);

        // While there's data to read, keep on decoding.
        while (content.readableBytes() > 0) {
            try {
                // prevent adding null
                final ControlPacket packet = ControlPacket.decode(content);
                if (packet != null) {
                    controlPacketList.add(packet);
                }
            } catch (Exception e1) {
                LOG.debug("Exception caught while decoding RTCP packet.", e1);
                break;
            }
        }

        if (!controlPacketList.isEmpty()) {
            // Only forward to next ChannelHandler when there were more than one valid decoded packets.
            // TODO shouldn't the whole compound packet be discarded when one of them has errors?!
            final AddressedEnvelope<CompoundControlPacket, SocketAddress> newMsg = new DefaultAddressedEnvelope<>(
                    new CompoundControlPacket(controlPacketList), recipient, sender);
            out.add(newMsg);
        }
    }

    // private classes ------------------------------------------------------------------------------------------------
    /**
     * Factory class for the {@link UdpControlPacketDecoder}.
     * 
     * @author <a href="https://github.com/CodeLionX">CodeLionX</a>
     */
    private static final class InstanceHolder {
        /**
         * Private constructor for hiding the implicit default one.
         */
        private InstanceHolder() {
        };

        private static final UdpControlPacketDecoder INSTANCE = new UdpControlPacketDecoder();
    }
}