Examples of LengthFieldBasedFrameDecoder

io.netty.handler.codec.LengthFieldBasedFrameDecoder
A decoder that splits the received {@link ByteBuf}s dynamically by the value of the length field in the message. It is particularly useful when you decode a binary message which has an integer header field that represents the length of the message body or the whole message.
{@link LengthFieldBasedFrameDecoder} has many configuration parameters sothat it can decode any message with a length field, which is often seen in proprietary client-server protocols. Here are some example that will give you the basic idea on which option does what.
2 bytes length field at offset 0, do not strip header
The value of the length field in this example is 12 (0x0C) which represents the length of "HELLO, WORLD". By default, the decoder assumes that the length field represents the number of the bytes that follows the length field. Therefore, it can be decoded with the simplistic parameter combination.
```
 lengthFieldOffset   = 0 lengthFieldLength   = 2 lengthAdjustment    = 0 initialBytesToStrip = 0 (= do not strip header) BEFORE DECODE (14 bytes)         AFTER DECODE (14 bytes) +--------+----------------+      +--------+----------------+ | Length | Actual Content |----->| Length | Actual Content | | 0x000C | "HELLO, WORLD" |      | 0x000C | "HELLO, WORLD" | +--------+----------------+      +--------+----------------+ 
```
2 bytes length field at offset 0, strip header
Because we can get the length of the content by calling {@link ByteBuf#readableBytes()}, you might want to strip the length field by specifying initialBytesToStrip. In this example, we specified 2, that is same with the length of the length field, to strip the first two bytes.
```
 lengthFieldOffset   = 0 lengthFieldLength   = 2 lengthAdjustment    = 0 initialBytesToStrip = 2 (= the length of the Length field) BEFORE DECODE (14 bytes)         AFTER DECODE (12 bytes) +--------+----------------+      +----------------+ | Length | Actual Content |----->| Actual Content | | 0x000C | "HELLO, WORLD" |      | "HELLO, WORLD" | +--------+----------------+      +----------------+ 
```
2 bytes length field at offset 0, do not strip header, the length field represents the length of the whole message
In most cases, the length field represents the length of the message body only, as shown in the previous examples. However, in some protocols, the length field represents the length of the whole message, including the message header. In such a case, we specify a non-zero lengthAdjustment. Because the length value in this example message is always greater than the body length by 2, we specify -2 as lengthAdjustment for compensation.
```
 lengthFieldOffset   =  0 lengthFieldLength   =  2 lengthAdjustment    = -2 (= the length of the Length field) initialBytesToStrip =  0 BEFORE DECODE (14 bytes)         AFTER DECODE (14 bytes) +--------+----------------+      +--------+----------------+ | Length | Actual Content |----->| Length | Actual Content | | 0x000E | "HELLO, WORLD" |      | 0x000E | "HELLO, WORLD" | +--------+----------------+      +--------+----------------+ 
```
3 bytes length field at the end of 5 bytes header, do not strip header
The following message is a simple variation of the first example. An extra header value is prepended to the message. lengthAdjustment is zero again because the decoder always takes the length of the prepended data into account during frame length calculation.
```
 lengthFieldOffset   = 2 (= the length of Header 1) lengthFieldLength   = 3 lengthAdjustment    = 0 initialBytesToStrip = 0 BEFORE DECODE (17 bytes)                      AFTER DECODE (17 bytes) +----------+----------+----------------+      +----------+----------+----------------+ | Header 1 |  Length  | Actual Content |----->| Header 1 |  Length  | Actual Content | |  0xCAFE  | 0x00000C | "HELLO, WORLD" |      |  0xCAFE  | 0x00000C | "HELLO, WORLD" | +----------+----------+----------------+      +----------+----------+----------------+ 
```
3 bytes length field at the beginning of 5 bytes header, do not strip header
This is an advanced example that shows the case where there is an extra header between the length field and the message body. You have to specify a positive lengthAdjustment so that the decoder counts the extra header into the frame length calculation.
```
 lengthFieldOffset   = 0 lengthFieldLength   = 3 lengthAdjustment    = 2 (= the length of Header 1) initialBytesToStrip = 0 BEFORE DECODE (17 bytes)                      AFTER DECODE (17 bytes) +----------+----------+----------------+      +----------+----------+----------------+ |  Length  | Header 1 | Actual Content |----->|  Length  | Header 1 | Actual Content | | 0x00000C |  0xCAFE  | "HELLO, WORLD" |      | 0x00000C |  0xCAFE  | "HELLO, WORLD" | +----------+----------+----------------+      +----------+----------+----------------+ 
```
2 bytes length field at offset 1 in the middle of 4 bytes header, strip the first header field and the length field
This is a combination of all the examples above. There are the prepended header before the length field and the extra header after the length field. The prepended header affects the lengthFieldOffset and the extra header affects the lengthAdjustment. We also specified a non-zero initialBytesToStrip to strip the length field and the prepended header from the frame. If you don't want to strip the prepended header, you could specify 0 for initialBytesToSkip.
```
 lengthFieldOffset   = 1 (= the length of HDR1) lengthFieldLength   = 2 lengthAdjustment    = 1 (= the length of HDR2) initialBytesToStrip = 3 (= the length of HDR1 + LEN) BEFORE DECODE (16 bytes)                       AFTER DECODE (13 bytes) +------+--------+------+----------------+      +------+----------------+ | HDR1 | Length | HDR2 | Actual Content |----->| HDR2 | Actual Content | | 0xCA | 0x000C | 0xFE | "HELLO, WORLD" |      | 0xFE | "HELLO, WORLD" | +------+--------+------+----------------+      +------+----------------+ 
```
2 bytes length field at offset 1 in the middle of 4 bytes header, strip the first header field and the length field, the length field represents the length of the whole message
Let's give another twist to the previous example. The only difference from the previous example is that the length field represents the length of the whole message instead of the message body, just like the third example. We have to count the length of HDR1 and Length into lengthAdjustment. Please note that we don't need to take the length of HDR2 into account because the length field already includes the whole header length.
```
 lengthFieldOffset   =  1 lengthFieldLength   =  2 lengthAdjustment    = -3 (= the length of HDR1 + LEN, negative) initialBytesToStrip =  3 BEFORE DECODE (16 bytes)                       AFTER DECODE (13 bytes) +------+--------+------+----------------+      +------+----------------+ | HDR1 | Length | HDR2 | Actual Content |----->| HDR2 | Actual Content | | 0xCA | 0x0010 | 0xFE | "HELLO, WORLD" |      | 0xFE | "HELLO, WORLD" | +------+--------+------+----------------+      +------+----------------+ 
```
@see LengthFieldPrepender

org.jboss.netty.handler.codec.frame.LengthFieldBasedFrameDecoder

A decoder that splits the received {@link ChannelBuffer}s dynamically by the value of the length field in the message. It is particularly useful when you decode a binary message which has an integer header field that represents the length of the message body or the whole message.

{@link LengthFieldBasedFrameDecoder} has many configuration parameters sothat it can decode any message with a length field, which is often seen in proprietary client-server protocols. Here are some example that will give you the basic idea on which option does what.

2 bytes length field at offset 0, do not strip header

 lengthFieldOffset   = 0 lengthFieldLength   = 2 lengthAdjustment    = 0 (default) initialBytesToStrip = 0 (default) BEFORE DECODE (14 bytes)         AFTER DECODE (14 bytes) +--------+----------------+      +--------+----------------+ | Length | Actual Content |----->| Length | Actual Content | | 0x000C | "HELLO, WORLD" |      | 0x000C | "HELLO, WORLD" | +--------+----------------+      +--------+----------------+

2 bytes length field at offset 0, strip header

 lengthFieldOffset   = 0 lengthFieldLength   = 2 lengthAdjustment    = 0 initialBytesToStrip = 2 BEFORE DECODE (14 bytes)         AFTER DECODE (12 bytes) +--------+----------------+      +----------------+ | Length | Actual Content |----->| Actual Content | | 0x000C | "HELLO, WORLD" |      | "HELLO, WORLD" | +--------+----------------+      +----------------+

3 bytes length field at the end of 5 bytes header, strip header

 lengthFieldOffset   = 2 (= 5 - 3) lengthFieldLength   = 3 lengthAdjustment    = 0 initialBytesToStrip = 5 BEFORE DECODE (17 bytes)                      AFTER DECODE (12 bytes) +----------+----------+----------------+      +----------------+ | Header 1 |  Length  | Actual Content |----->| Actual Content | |  0xCAFE  | 0x00000C | "HELLO, WORLD" |      | "HELLO, WORLD" | +----------+----------+----------------+      +----------------+

2 bytes length field at offset 1 in the middle of 4 bytes header, strip the first header field and the length field

 lengthFieldOffset   = 1 lengthFieldLength   = 2 lengthAdjustment    = 1 (= the length of HDR2) initialBytesToStrip = 3 (= the length of HDR1 + LEN) BEFORE DECODE (16 bytes)                       AFTER DECODE (13 bytes) +------+--------+------+----------------+      +------+----------------+ | HDR1 | Length | HDR2 | Actual Content |----->| HDR2 | Actual Content | | 0xCA | 0x000C | 0xFE | "HELLO, WORLD" |      | 0xFE | "HELLO, WORLD" | +------+--------+------+----------------+      +------+----------------+

2 bytes length field at offset 1 in the middle of 4 bytes header, strip the first header field and the length field, the length field includes the header length

 lengthFieldOffset   =  1 lengthFieldLength   =  2 lengthAdjustment    = -3 (= the length of HDR1 + LEN, negative) initialBytesToStrip =  3 BEFORE DECODE (16 bytes)                       AFTER DECODE (13 bytes) +------+--------+------+----------------+      +------+----------------+ | HDR1 | Length | HDR2 | Actual Content |----->| HDR2 | Actual Content | | 0xCA | 0x0010 | 0xFE | "HELLO, WORLD" |      | 0xFE | "HELLO, WORLD" | +------+--------+------+----------------+      +------+----------------+

@author The Netty Project (netty-dev@lists.jboss.org) @author Trustin Lee (tlee@redhat.com) @version $Rev:231 $, $Date:2008-06-12 16:44:50 +0900 (목, 12 6월 2008) $ @see LengthFieldPrepender

Examples of org.jboss.netty.handler.codec.frame.LengthFieldBasedFrameDecoder

    @Override
    protected JndiRegistry createRegistry() throws Exception {
        JndiRegistry registry = super.createRegistry();


        // START SNIPPET: registry-beans
        LengthFieldBasedFrameDecoder lengthDecoder = new LengthFieldBasedFrameDecoder(1048576, 0, 4, 0, 4);
        StringDecoder stringDecoder = new StringDecoder();
        registry.bind("length-decoder", lengthDecoder);
        registry.bind("string-decoder", stringDecoder);


        LengthFieldPrepender lengthEncoder = new LengthFieldPrepender(4);

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Examples of org.jboss.netty.handler.codec.frame.LengthFieldBasedFrameDecoder

     */
    @Override
    public ChannelPipeline getPipeline() throws Exception {
        ChannelPipeline pipeline = Channels.pipeline();


        pipeline.addLast("lengthbasedframedecoder", new LengthFieldBasedFrameDecoder(MAX_FRAME_LENGTH, 0, 4, 0, 4));
        pipeline.addLast("mainhandler", this);
        return pipeline;
    }

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Examples of org.jboss.netty.handler.codec.frame.LengthFieldBasedFrameDecoder

          // pipeline components SaslServerHandler and ResponseEncoder are
          // removed, leaving the pipeline the same as in the non-authenticated
          // configuration except for the presence of the Authorize component.
          return Channels.pipeline(
              byteCounter,
              new LengthFieldBasedFrameDecoder(1024 * 1024 * 1024, 0, 4, 0, 4),
              new RequestDecoder(conf, byteCounter),
              // Removed after authentication completes:
              saslServerHandlerFactory.newHandler(conf),
              new AuthorizeServerHandler(),
              requestServerHandlerFactory.newHandler(workerRequestReservedMap,
                  conf, myTaskInfo),
              // Removed after authentication completes:
              new ResponseEncoder());
        } else {
          LOG.info("start: Using Netty without authentication.");
/*end[HADOOP_NON_SECURE]*/
          ChannelPipeline pipeline = pipeline();


          // Store all connected channels in order to ensure that we can close
          // them on stop(), or else stop() may hang waiting for the
          // connections to close on their own
          pipeline.addLast("connectedChannels",
              new SimpleChannelUpstreamHandler() {
                @Override
                public void channelConnected(ChannelHandlerContext ctx,
                    ChannelStateEvent e) throws Exception {
                  super.channelConnected(ctx, e);
                  accepted.add(e.getChannel());
                }
              });
          pipeline.addLast("serverByteCounter", byteCounter);
          pipeline.addLast("requestFrameDecoder",
              new LengthFieldBasedFrameDecoder(
                  1024 * 1024 * 1024, 0, 4, 0, 4));
          pipeline.addLast("requestDecoder",
              new RequestDecoder(conf, byteCounter));
          pipeline.addLast("requestProcessor",
              requestServerHandlerFactory.newHandler(

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Examples of org.jboss.netty.handler.codec.frame.LengthFieldBasedFrameDecoder

          // The following pipeline component is needed to decode the server's
          // SASL tokens. It is replaced with a FixedLengthFrameDecoder (same
          // as used with the non-authenticated pipeline) after authentication
          // completes (as in non-auth pipeline below).
          pipeline.addLast("length-field-based-frame-decoder",
              new LengthFieldBasedFrameDecoder(1024, 0, 4, 0, 4));
          pipeline.addLast("request-encoder", new RequestEncoder(conf));
          // The following pipeline component responds to the server's SASL
          // tokens with its own responses. Both client and server share the
          // same Hadoop Job token, which is used to create the SASL tokens to
          // authenticate with each other.

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Examples of org.jboss.netty.handler.codec.frame.LengthFieldBasedFrameDecoder

     * prepending the length to outgoing packets etc.
     */
    @Override
    public ChannelPipeline getPipeline() throws Exception {
        ChannelPipeline pipeline = Channels.pipeline();
        pipeline.addLast("lengthbasedframedecoder", new LengthFieldBasedFrameDecoder(MAX_FRAME_LENGTH, 0, 4, 0, 4));
        pipeline.addLast("mainhandler", this);
        return pipeline;
    }

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Examples of org.jboss.netty.handler.codec.frame.LengthFieldBasedFrameDecoder

    @Override
    protected JndiRegistry createRegistry() throws Exception {
        JndiRegistry registry = super.createRegistry();


        // START SNIPPET: registry-beans
        LengthFieldBasedFrameDecoder lengthDecoder = new LengthFieldBasedFrameDecoder(1048576, 0, 4, 0, 4);
        StringDecoder stringDecoder = new StringDecoder();
        registry.bind("length-decoder", lengthDecoder);
        registry.bind("string-decoder", stringDecoder);


        LengthFieldPrepender lengthEncoder = new LengthFieldPrepender(4);

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Examples of org.jboss.netty.handler.codec.frame.LengthFieldBasedFrameDecoder

                                                                        final int lengthFieldLength, final int lengthAdjustment,
                                                                        final int initialBytesToStrip) {
        return new ChannelHandlerFactory() {
            @Override
            public ChannelHandler newChannelHandler() {
                return new LengthFieldBasedFrameDecoder(maxFrameLength, lengthFieldOffset, lengthFieldLength, lengthAdjustment, initialBytesToStrip);
            }
        };
    }

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Examples of org.jboss.netty.handler.codec.frame.LengthFieldBasedFrameDecoder

            readTimeoutTimer = new HashedWheelTimer();
        }


        pipeline.addLast("readTimeout", new ReadTimeoutHandler(readTimeoutTimer, 
                                                               conf.getReadTimeout()));
        pipeline.addLast("lengthbasedframedecoder", new LengthFieldBasedFrameDecoder(MAX_FRAME_LENGTH, 0, 4, 0, 4));
        pipeline.addLast("mainhandler", this);
        return pipeline;
    }

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Examples of org.jboss.netty.handler.codec.frame.LengthFieldBasedFrameDecoder

        ChannelPipeline pipeline = Channels.pipeline();
        if (sslFactory != null) {
            pipeline.addLast("ssl", new SslHandler(sslFactory.getEngine()));
        }
        pipeline.addLast("lengthbaseddecoder",
                         new LengthFieldBasedFrameDecoder(maxMessageSize, 0, 4, 0, 4));
        pipeline.addLast("lengthprepender", new LengthFieldPrepender(4));


        pipeline.addLast("protobufdecoder", new ProtobufDecoder(PubSubProtocol.PubSubRequest.getDefaultInstance()));
        pipeline.addLast("protobufencoder", new ProtobufEncoder());

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Examples of org.jboss.netty.handler.codec.frame.LengthFieldBasedFrameDecoder


    @Override
    public ChannelPipeline getPipeline() throws Exception {
        ChannelPipeline pipeline = Channels.pipeline();
        pipeline.addLast("lengthbaseddecoder",
                         new LengthFieldBasedFrameDecoder(1024 * 1024, 0, 4, 0, 4));
        pipeline.addLast("lengthprepender", new LengthFieldPrepender(4));
        pipeline.addLast("main", this);
        return pipeline;
    }

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