FrameDecoder.java

package com.dianping.pigeon.remoting.netty.codec;

import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;

/**
 * @author qi.yin
 *         2016/06/16  下午2:38.
 */
public class FrameDecoder extends org.jboss.netty.handler.codec.frame.FrameDecoder {


    @Override
    protected Object decode(ChannelHandlerContext ctx, Channel channel, ChannelBuffer buffer)
            throws Exception {

        Object message = null;

        if (buffer.readableBytes() <= 2) {
            return message;
        }

        byte[] headMsgs = new byte[2];

        buffer.getBytes(buffer.readerIndex(), headMsgs);

        if ((0x39 == headMsgs[0] && 0x3A == headMsgs[1])) {
            //old protocol
            message = doDecode(buffer);

        } else if ((byte) 0xAB == headMsgs[0] && (byte) 0xBA == headMsgs[1]) {
            //new protocol
            message = _doDecode(buffer);

        } else {
            throw new IllegalArgumentException("Decode invalid message head:" +
                    headMsgs[0] + " " + headMsgs[1] + ", " + "message:" + buffer);
        }

        return message;

    }

    protected Object doDecode(ChannelBuffer buffer)
            throws Exception {

        CodecEvent codecEvent = null;

        if (buffer.readableBytes() <= CodecConstants.FRONT_LENGTH) {
            return codecEvent;
        }

        int totalLength = (int) buffer.getUnsignedInt(
                buffer.readerIndex() +
                        CodecConstants.HEAD_LENGTH);

        int frameLength = totalLength + CodecConstants.FRONT_LENGTH;

        if (buffer.readableBytes() >= frameLength) {

            ChannelBuffer frame = buffer.slice(buffer.readerIndex(), frameLength);
            buffer.readerIndex(buffer.readerIndex() + frameLength);

            codecEvent = new CodecEvent(frame, false);
            codecEvent.setReceiveTime(System.currentTimeMillis());
        }

        return codecEvent;
    }

    protected Object _doDecode(ChannelBuffer buffer)
            throws Exception {
        CodecEvent codecEvent = null;

        if (buffer.readableBytes() <= CodecConstants._FRONT_LENGTH) {
            return codecEvent;
        }

        int totalLength = (int) (buffer.getUnsignedInt(
                buffer.readerIndex() +
                        CodecConstants._HEAD_LENGTH));

        int frameLength = totalLength + CodecConstants._FRONT_LENGTH_;

        if (buffer.readableBytes() >= frameLength) {

            ChannelBuffer frame = buffer.slice(buffer.readerIndex(), frameLength);
            buffer.readerIndex(buffer.readerIndex() + frameLength);

            codecEvent = new CodecEvent(frame, true);
            codecEvent.setReceiveTime(System.currentTimeMillis());
        }

        return codecEvent;
    }

}