io.netty.handler.codec

Class LengthFieldPrepender

java.lang.Object

io.netty.channel.ChannelHandlerAdapter

io.netty.channel.ChannelOutboundHandlerAdapter

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

io.netty.handler.codec.LengthFieldPrepender

All Implemented Interfaces:

ChannelHandler, ChannelOutboundHandler

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

An encoder that prepends the length of the message. The length value is prepended as a binary form.

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

ChannelHandler.Sharable

Constructor Summary

Constructors

Constructor and Description
LengthFieldPrepender(java.nio.ByteOrder byteOrder, int lengthFieldLength, int lengthAdjustment, boolean lengthIncludesLengthFieldLength) Creates a new instance.
LengthFieldPrepender(int lengthFieldLength) Creates a new instance.
LengthFieldPrepender(int lengthFieldLength, boolean lengthIncludesLengthFieldLength) Creates a new instance.
LengthFieldPrepender(int lengthFieldLength, int lengthAdjustment) Creates a new instance.
LengthFieldPrepender(int lengthFieldLength, int lengthAdjustment, boolean lengthIncludesLengthFieldLength) Creates a new instance.

Method Summary

Modifier and Type	Method and Description
protected ByteBuf	allocateBuffer(ChannelHandlerContext ctx, ByteBuf msg, boolean preferDirect) Allocate a ByteBuf which will be used as argument of #encode(ChannelHandlerContext, I, ByteBuf).
protected void	encode(ChannelHandlerContext ctx, ByteBuf msg, ByteBuf out) Encode a message into a ByteBuf.

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

acceptOutboundMessage, write

Methods inherited from class io.netty.channel.ChannelOutboundHandlerAdapter

bind, close, connect, deregister, disconnect, flush, read

Methods inherited from class io.netty.channel.ChannelHandlerAdapter

ensureNotSharable, exceptionCaught, handlerAdded, handlerRemoved, isSharable

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.ChannelHandler

exceptionCaught, handlerAdded, handlerRemoved

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:

java.lang.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:

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

LengthFieldPrepender

public LengthFieldPrepender(int lengthFieldLength,
                            int lengthAdjustment)

Creates a new instance.

Parameters:

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

lengthAdjustment - the compensation value to add to the value of the length field

Throws:

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

LengthFieldPrepender

public LengthFieldPrepender(int lengthFieldLength,
                            int lengthAdjustment,
                            boolean lengthIncludesLengthFieldLength)

Creates a new instance.

Parameters:

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

lengthAdjustment - the compensation value to add to the value of the length field

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

Throws:

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

LengthFieldPrepender

public LengthFieldPrepender(java.nio.ByteOrder byteOrder,
                            int lengthFieldLength,
                            int lengthAdjustment,
                            boolean lengthIncludesLengthFieldLength)

Creates a new instance.

Parameters:

byteOrder - the ByteOrder of the length field

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

lengthAdjustment - the compensation value to add to the value of the length field

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

Throws:

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

Method Detail

encode

protected void encode(ChannelHandlerContext ctx,
                      ByteBuf msg,
                      ByteBuf out)
               throws java.lang.Exception

Description copied from class: MessageToByteEncoder

Encode a message into a ByteBuf. This method will be called for each written message that can be handled by this encoder.

Specified by:

encode in class MessageToByteEncoder<ByteBuf>

Parameters:

ctx - the ChannelHandlerContext which this MessageToByteEncoder belongs to

msg - the message to encode

out - the ByteBuf into which the encoded message will be written

Throws:

java.lang.Exception - is thrown if an error occurs

allocateBuffer

protected ByteBuf allocateBuffer(ChannelHandlerContext ctx,
                                 ByteBuf msg,
                                 boolean preferDirect)
                          throws java.lang.Exception

Description copied from class: MessageToByteEncoder

Allocate a ByteBuf which will be used as argument of #encode(ChannelHandlerContext, I, ByteBuf). Sub-classes may override this method to return ByteBuf with a perfect matching initialCapacity.

Overrides:

allocateBuffer in class MessageToByteEncoder<ByteBuf>

Throws:

java.lang.Exception