io.netty.handler.codec

Class LengthFieldPrepender

java.lang.Object

io.netty.channel.ChannelOperationHandlerAdapter

io.netty.channel.ChannelOutboundHandlerAdapter

io.netty.channel.ChannelOutboundMessageHandlerAdapter<I>

io.netty.handler.codec.MessageToByteEncoder<io.netty.buffer.ByteBuf>

io.netty.handler.codec.LengthFieldPrepender

All Implemented Interfaces:

io.netty.channel.ChannelHandler, io.netty.channel.ChannelOperationHandler, io.netty.channel.ChannelOutboundHandler, io.netty.channel.ChannelOutboundMessageHandler<io.netty.buffer.ByteBuf>

@ChannelHandler.Sharable
public class LengthFieldPrepender
extends MessageToByteEncoder<io.netty.buffer.ByteBuf>

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 ByteBufFactory.

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" |
 +--------+----------------+
 

Nested Class Summary

Nested classes/interfaces inherited from interface io.netty.channel.ChannelHandler

io.netty.channel.ChannelHandler.Sharable

Constructor Summary

Constructors

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

Method Summary

Methods

Modifier and Type	Method and Description
void	encode(io.netty.channel.ChannelHandlerContext ctx, io.netty.buffer.ByteBuf msg, io.netty.buffer.ByteBuf out)
boolean	isEncodable(Object msg) Returns true if and only if the specified message can be encoded by this encoder.

Methods inherited from class io.netty.handler.codec.MessageToByteEncoder

flush

Methods inherited from class io.netty.channel.ChannelOutboundMessageHandlerAdapter

newOutboundBuffer

Methods inherited from class io.netty.channel.ChannelOperationHandlerAdapter

afterAdd, afterRemove, beforeAdd, beforeRemove, bind, close, connect, deregister, disconnect, exceptionCaught, userEventTriggered

Methods inherited from class java.lang.Object

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

Methods inherited from interface io.netty.channel.ChannelOperationHandler

bind, close, connect, deregister, disconnect

Methods inherited from interface io.netty.channel.ChannelHandler

afterAdd, afterRemove, beforeAdd, beforeRemove, exceptionCaught, userEventTriggered

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

isEncodable

public boolean isEncodable(Object msg)
                    throws Exception

Description copied from class: MessageToByteEncoder

Returns true if and only if the specified message can be encoded by this encoder.

Overrides:

isEncodable in class MessageToByteEncoder<io.netty.buffer.ByteBuf>

Parameters:

msg - the message

Throws:

Exception

encode

public void encode(io.netty.channel.ChannelHandlerContext ctx,
          io.netty.buffer.ByteBuf msg,
          io.netty.buffer.ByteBuf out)
            throws Exception

Specified by:

encode in class MessageToByteEncoder<io.netty.buffer.ByteBuf>

Throws:

Exception