org.jboss.netty.handler.codec.frame
Class LengthFieldPrepender

java.lang.Object
  org.jboss.netty.handler.codec.oneone.OneToOneEncoder
      org.jboss.netty.handler.codec.frame.LengthFieldPrepender

All Implemented Interfaces:

ChannelDownstreamHandler, ChannelHandler

@ChannelPipelineCoverage(value="all")
public class LengthFieldPrepender
extends OneToOneEncoder

An encoder that prepends the length of the message. The length value is prepended as a binary form. It is encoded in either big endian or little endian depending on the default ByteOrder of the current ChannelBufferFactory.

For example, LengthFieldPrepender(2) will encode the following 12-bytes string:

 +----------------+
 | "HELLO, WORLD" |
 +----------------+
 

into the following:

 +--------+----------------+
 + 0x000C | "HELLO, WORLD" |
 +--------+----------------+
 

If you turned on the lengthIncludesLengthFieldLength flag in the constructor, the encoded data would look like the following (12 (original data) + 2 (prepended data) = 14 (0xE)):

 +--------+----------------+
 + 0x000E | "HELLO, WORLD" |
 +--------+----------------+
 

Version:

$Rev: 1685 $, $Date: 2009-08-28 16:15:49 +0900 (금, 28 8 2009) $

Author:

The Netty Project (netty-dev@lists.jboss.org), Trustin Lee (tlee@redhat.com)

Constructor Summary

LengthFieldPrepender(int lengthFieldLength)
Creates a new instance.

LengthFieldPrepender(int lengthFieldLength, boolean lengthIncludesLengthFieldLength)
Creates a new instance.

Method Summary

protected Object

encode(ChannelHandlerContext ctx, Channel channel, Object msg)

Methods inherited from class org.jboss.netty.handler.codec.oneone.OneToOneEncoder

handleDownstream

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

LengthFieldPrepender

public LengthFieldPrepender(int lengthFieldLength)

Creates a new instance.

Parameters:

lengthFieldLength - the length of the prepended length field. Only 1, 2, 3, 4, and 8 are allowed.

Throws:

IllegalArgumentException - if lengthFieldLength is not 1, 2, 3, 4, or 8

LengthFieldPrepender

public LengthFieldPrepender(int lengthFieldLength,
                            boolean lengthIncludesLengthFieldLength)

Creates a new instance.

Parameters:

lengthFieldLength - the length of the prepended length field. Only 1, 2, 3, 4, and 8 are allowed.

lengthIncludesLengthFieldLength - if true, the length of the prepended length field is added to the value of the prepended length field.

Throws:

IllegalArgumentException - if lengthFieldLength is not 1, 2, 3, 4, or 8

Method Detail

encode

protected Object encode(ChannelHandlerContext ctx,
                        Channel channel,
                        Object msg)
                 throws Exception

Specified by:

encode in class OneToOneEncoder

Throws:

Exception