/*
 * Operation.java February 2007
 *
 * Copyright (C) 2007, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or 
 * implied. See the License for the specific language governing 
 * permissions and limitations under the License.
 */

package org.simpleframework.transport.reactor;

import java.nio.channels.SelectableChannel;

/**
 * The <code>Operation</code> interface is used to describe a task that can be
 * executed when the associated channel is ready for some operation. Typically
 * the <code>SelectableChannel</code> is used to register with a selector with a
 * set of given interested operations when those operations can be performed
 * this is executed.
 * 
 * @author Niall Gallagher
 * 
 * @see org.simpleframework.transport.reactor.Reactor
 */
public interface Operation extends Runnable {

    /**
     * This is the <code>SelectableChannel</code> which is used to determine if
     * the operation should be executed. If the channel is ready for a given I/O
     * event it can be run. For instance if the operation is used to perform
     * some form of read operation it can be executed when ready to read data
     * from the channel.
     * 
     * @return this returns the channel used to govern execution
     */
    SelectableChannel getChannel();

    /**
     * This is used to cancel the operation if it has timed out. This is
     * typically invoked when it has been waiting in a selector for an extended
     * duration of time without any active operations on it. In such a case the
     * reactor must purge the operation to free the memory and open channels
     * associated with the operation.
     */
    void cancel();
}