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

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Here is the source code for sas.systems.imflux.network.udp.UdpControlPacketEncoder.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.buffer.Unpooled;
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.handler.codec.MessageToMessageEncoder;
import sas.systems.imflux.packet.rtcp.CompoundControlPacket;
import sas.systems.imflux.packet.rtcp.ControlPacket;

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

/**
 * A class (singleton) for encoding {@link CompoundControlPacket}s to {@link ByteBuf}fers. For supporting sending to
 * multiple recipients from one {@link Channel} the {@code CompoundControlPacket} has to be wrapped into an 
 * {@link AddressedEnvelope}. The {@link ByteBuf} created from this encoder is also wrapped into an 
 * {@code AddressedEnvelope}. It extends {@link MessageToMessageEncoder} and can therefore be used in multiple 
 * {@link ChannelPipeline}s.
 * 
 * @see MessageToMessageEncoder
 * @author <a href="https://github.com/CodeLionX">CodeLionX</a>
 */
@Sharable
public class UdpControlPacketEncoder
        extends MessageToMessageEncoder<AddressedEnvelope<CompoundControlPacket, SocketAddress>> {

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

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

    // MessageToMessageEncoder ----------------------------------------------------------------------------------------
    /**
     * Encodes a {@link CompoundControlPacket} wrapped into an {@link AddressedEnvelope} to a {@link ByteBuf} also 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 encode(ChannelHandlerContext ctx, AddressedEnvelope<CompoundControlPacket, SocketAddress> msg,
            List<Object> out) throws Exception {
        // encode CompountControlPacket here and forward destination (recipient) of the packet
        final CompoundControlPacket compoundControlPacket = msg.content();
        final List<ControlPacket> packets = compoundControlPacket.getControlPackets();
        ByteBuf compoundBuffer = Unpooled.EMPTY_BUFFER;
        if (packets.isEmpty()) {
            final ByteBuf[] buffers = new ByteBuf[packets.size()];
            for (int i = 0; i < buffers.length; i++) {
                buffers[i] = packets.get(i).encode();
            }
            compoundBuffer = Unpooled.wrappedBuffer(buffers);
        }

        AddressedEnvelope<ByteBuf, SocketAddress> newMsg = new DefaultAddressedEnvelope<ByteBuf, SocketAddress>(
                compoundBuffer, msg.recipient(), ctx.channel().localAddress());
        out.add(newMsg);
    }

    // private classes ------------------------------------------------------------------------------------------------
    /**
     * Factory class for the {@link UdpControlPacketEncoder}.
     * 
     * @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 UdpControlPacketEncoder INSTANCE = new UdpControlPacketEncoder();
    }
}