/*
 * Copyright 2007-2010 Sun Microsystems, Inc.
 *
 * This file is part of Project Darkstar Server.
 *
 * Project Darkstar Server is free software: you can redistribute it
 * and/or modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation and
 * distributed hereunder to you.
 *
 * Project Darkstar Server is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * Sun designates this particular file as subject to the "Classpath"
 * exception as provided by Sun in the LICENSE file that accompanied
 * this code.
 *
 * --
 */

package com.sun.sgs.nio.channels;

/**
 * A handler for consuming the result of an asynchronous operation.
 * <p>
 * The asynchronous channels defined in this package allow a completion
 * handler to be specified to consume the result of an asynchronous
 * operation. When an operation completes the handler's
 * {@link #completed completed} method is invoked with the result.
 *
 * <h3>Usage Example</h3>
 * <pre>
 *    InetSocketAddress addr = ...
 *    AsynchronousSocketChannel ch = AsynchronousSocketChannel.open();
 * 
 *    ch.connect(addr, new CompletionHandler<Void,Void>() {
 *        public void completed(IoFuture<Void,Void> result) {
 *            try {  
 *                result.getNow();
 *                // connection established
 * 
 *            } catch (ExecutionException x) { 
 *                ...
 *            }
 *        }
 *    });
 * </pre>
 * 
 * @param <R> the result type
 * @param <A> the attachment type
 */
public interface CompletionHandler<R, A> {

    /**
     * Invoked when an operation has completed.
     * <p>
     * The {@code result} parameter is an {@link IoFuture} representing the
     * result of the operation. Its {@link IoFuture#getNow() getNow} method 
     * should be invoked to retrieve the result.
     * <p>
     * This method should complete in a timely manner so as to avoid keeping
     * this thread from dispatching to other completion handlers.
     * 
     * @param result the {@code IoFuture} representing the result of the
     *               operation
     */
    void completed(IoFuture<R, A> result);
}