Module io.netty5.codec

Package io.netty5.handler.codec

Class LengthFieldPrepender

java.lang.Object

io.netty5.channel.ChannelHandlerAdapter

io.netty5.handler.codec.MessageToMessageEncoder<Buffer>

io.netty5.handler.codec.LengthFieldPrepender

All Implemented Interfaces:

ChannelHandler

public class LengthFieldPrepender
extends MessageToMessageEncoder<Buffer>

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

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method	Description
protected void	encode(ChannelHandlerContext ctx, Buffer buffer, List<Object> out)	Encode from one message to another.
protected Buffer	getLengthFieldBuffer(ChannelHandlerContext ctx, int length, int lengthFieldLength, ByteOrder byteOrder)	Encodes the length into a buffer which will be prepended as the length field.
boolean	isSharable()	Returns true if this handler is sharable and thus can be added to more than one ChannelPipeline.

Methods inherited from class io.netty5.handler.codec.MessageToMessageEncoder

acceptOutboundMessage, encodeAndClose, write

Methods inherited from class java.lang.Object

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

Methods inherited from interface io.netty5.channel.ChannelHandler

bind, channelActive, channelExceptionCaught, channelInactive, channelInboundEvent, channelRead, channelReadComplete, channelRegistered, channelShutdown, channelUnregistered, channelWritabilityChanged, close, connect, deregister, disconnect, flush, handlerAdded, handlerRemoved, pendingOutboundBytes, read, register, sendOutboundEvent, shutdown

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 supported by default.

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 supported by default.

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

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 supported by default.

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

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 supported by default.

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.

LengthFieldPrepender

public LengthFieldPrepender(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 supported by default.

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.

Method Detail

isSharable

public boolean isSharable()

Description copied from interface: ChannelHandler

Returns true if this handler is sharable and thus can be added to more than one ChannelPipeline. By default, this method returns false. If this method returns false, you have to create a new handler instance every time you add it to a pipeline because it has unshared state such as member variables.

encode

protected void encode(ChannelHandlerContext ctx,
                      Buffer buffer,
                      List<Object> out)
               throws Exception

Description copied from class: MessageToMessageEncoder

Encode from one message to another. This method will be called for each written message that can be handled by this encoder.

The message will be disposed of after this call.

Subclasses that wish to sometimes pass messages through, should instead override the MessageToMessageEncoder.encodeAndClose(ChannelHandlerContext, Object, List) method.

Overrides:

encode in class MessageToMessageEncoder<Buffer>

Parameters:

ctx - the ChannelHandlerContext which this MessageToMessageEncoder belongs to.

buffer - the message to encode to another one.

out - the List into which produced output messages should be added.

Throws:

Exception - is thrown if an error occurs.

getLengthFieldBuffer

protected Buffer getLengthFieldBuffer(ChannelHandlerContext ctx,
                                      int length,
                                      int lengthFieldLength,
                                      ByteOrder byteOrder)

Encodes the length into a buffer which will be prepended as the length field. The default implementation is capable of encoding the length into an 8/16/24/32/64 bit integer. Override this method to encode the length field differently.

Parameters:

ctx - the ChannelHandlerContext which this LengthFieldPrepender belongs to

length - the length which should be encoded in the length field

lengthFieldLength - the length of the prepended length field

byteOrder - the ByteOrder of the length field

Returns:

A buffer containing the encoded length

Throws:

EncoderException - if failed to encode the length