rice.pastry.wire
Class SocketChannelWriter

java.lang.Object
  |
  +--rice.pastry.wire.SocketChannelWriter

public class SocketChannelWriter

extends java.lang.Object

Class which serves as an "writer" for all of the messages sent across the wire in Pastry. This class serializes and properly formats all messages, and then waits to be called with an available SocketChannel in order to write the message out. If the messagae could not be written in one go, subsequent calls to the write() method will finish writing out the message. This class also maintains an internal queue of messages waiting to be sent across the wire. Calling isEmpty() will tell clients if it is safe to mark the SelectionKey as not being interested in writing.

Version:

$Id: SocketChannelWriter.java,v 1.13 2003/10/01 06:35:10 amislove Exp $

Author:

Alan Mislove

Field Summary

protected static byte[]	MAGIC_NUMBER
static int	MAXIMUM_QUEUE_LENGTH

Constructor Summary

SocketChannelWriter(rice.pastry.wire.WirePastryNode spn, rice.pastry.wire.messaging.socket.SocketCommandMessage msg)
Constructor which creates this SocketChannelWriter with a pastry node and an object to write out.

Method Summary

void	enqueue(java.lang.Object o) Adds an object to this SocketChannelWriter's queue of pending objects to write.
java.util.LinkedList	getQueue() Returns the queue of writes for the remote address
void	greetingReceived()
boolean	isEmpty() Returns whether or not there are objects in the queue on in writing.
void	reset(rice.pastry.wire.messaging.socket.SocketCommandMessage msg) Resets the SocketChannelWriter, by clearing both the buffer and the queue.
static java.nio.ByteBuffer	serialize(java.lang.Object o) Method which serializes a given object into a ByteBuffer, in order to prepare it for writing.
boolean	write(java.nio.channels.SocketChannel sc) Method which is designed to be called when this writer should write out its data.

Methods inherited from class java.lang.Object

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

Field Detail

MAXIMUM_QUEUE_LENGTH

public static int MAXIMUM_QUEUE_LENGTH

MAGIC_NUMBER

protected static byte[] MAGIC_NUMBER

Constructor Detail

SocketChannelWriter

public SocketChannelWriter(rice.pastry.wire.WirePastryNode spn,
                           rice.pastry.wire.messaging.socket.SocketCommandMessage msg)

Constructor which creates this SocketChannelWriter with a pastry node and an object to write out.

Parameters:

spn - The PastryNode the SocketChannelWriter servers

Method Detail

enqueue

public void enqueue(java.lang.Object o)

Adds an object to this SocketChannelWriter's queue of pending objects to write. This methos is synchronized and therefore safe for use by multiple threads.

Parameters:

o - The object to be written.

isEmpty

public boolean isEmpty()

Returns whether or not there are objects in the queue on in writing. If the result is true, it the safe to mark the SelectionKey as not being interested in writing.

Returns:

Whether or not there are objects still to be written.

getQueue

public java.util.LinkedList getQueue()

Returns the queue of writes for the remote address

Returns:

the queue of writes for the remote address

reset

public void reset(rice.pastry.wire.messaging.socket.SocketCommandMessage msg)

Resets the SocketChannelWriter, by clearing both the buffer and the queue. Should not be used except when a socket has just been opened.

Parameters:

msg - The greeting message that should be enqueued first

greetingReceived

public void greetingReceived()

write

public boolean write(java.nio.channels.SocketChannel sc)
              throws java.io.IOException

Method which is designed to be called when this writer should write out its data. Returns whether or not the message was completely written. If false is returns, write() will need to be called again when the SocketChannel is ready for data to be written.

Parameters:

sc - The SocketChannel to write to

Returns:

true if this output stream is done, false otherwise

java.io.IOException

serialize

public static java.nio.ByteBuffer serialize(java.lang.Object o)
                                     throws java.io.IOException

Method which serializes a given object into a ByteBuffer, in order to prepare it for writing. This is necessary because the size of the object must be prepended to the to the front of the buffer in order to tell the reciever how long the object is.

Parameters:

o - The object to serialize

Returns:

A ByteBuffer containing the object prepended with its size.

java.io.IOException