/*
* Aleph Toolkit
*
* Copyright 1999, Brown University, Providence, RI.
*
* All Rights Reserved
*
* Permission to use, copy, modify, and distribute this software and its
* documentation for any purpose other than its incorporation into a
* commercial product is hereby granted without fee, provided that the
* above copyright notice appear in all copies and that both that
* copyright notice and this permission notice appear in supporting
* documentation, and that the name of Brown University not be used in
* advertising or publicity pertaining to distribution of the software
* without specific, written prior permission.
*
* BROWN UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
* INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR ANY
* PARTICULAR PURPOSE. IN NO EVENT SHALL BROWN UNIVERSITY BE LIABLE FOR
* ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
package aleph.comm.tcp;
import aleph.Aleph;
import aleph.AsynchMessage;
import aleph.Message;
import aleph.meter.Counter;
import aleph.thread.Scheduler;
import java.io.IOException;
import java.io.InterruptedIOException;
/**
* A Connection is a stream socket. A listener thread handles input, and a
* <code>send</code> method handles output.
*
* @author Maurice Herlihy
* @date August 1998
* @author Michael Rubin
* @date May 1998
**/
public abstract class Connection {
protected static Counter messagesSent = new Counter("Messages sent");
private static final boolean DEBUG = false; // Oy, va-voy!
private volatile boolean quit = false; // The pipes are calling ...
/**
* Start thread to process incoming messages.
* Must be called after calling the constructor.
**/
public void start () {
(new MessageHandler()).start();
}
/**
* Clean me up.
**/
public void close () {
quit = true;
}
/**
* Flush output stream.
**/
public abstract void flush() throws InterruptedIOException;
/**
* Ping output stream.
**/
public abstract boolean ping();
/**
* Blocking method that pulls in the next message.
* @returns next message
**/
protected abstract Message receive () throws IOException;
/**
* Send'em a message.
* @param message what to send
* @exception java.io.IOException something's wrong
**/
public abstract void send (Message message) throws IOException;
private class MessageHandler extends Thread {
public void run() {
try {
while(! quit) { // keep on keeping on
Message message = Connection.this.receive();
if (message != null) { // ignore spurious nulls
if (DEBUG)
Aleph.debug("Connection received " + message);
if (message instanceof AsynchMessage)
Scheduler.getScheduler().schedule(message); // maybe later
else
message.run();
}
}
} catch(IOException e) {
if (DEBUG)
Aleph.debug("tcp.Connection closing: " + e);
return;
} catch(Exception e) {
Aleph.panic(e);
}
}
}
}