pausablefiber.java

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//
// This file is part of the OpenNMS(R) Application.
//
// OpenNMS(R) is Copyright (C) 2002-2003 The OpenNMS Group, Inc.  All rights reserved.
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// code that was published under the GNU General Public License. Copyrights for modified 
// and included code are below.
//
// OpenNMS(R) is a registered trademark of The OpenNMS Group, Inc.
// 
// Copyright (C) 1999-2001 Oculan Corp.  All rights reserved.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
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// This program is distributed in the hope that it will be useful,
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package org.opennms.core.fiber;

/**
 * <p>
 * This interface defines an extension to the core {@link Fiber Fiber}interface
 * and adds the methods for pausing and resuming an executable context. The base
 * interface class defines an execution environment, this interface extends the
 * core interface to provide methods for suspending and resuming the
 * <code>Fiber</code>.
 * </p>
 * 
 * @author <a href="mailto:[e-mail]">Brian Weaver </a>
 * @author <a href="http://www.opennms.org/">OpenNMS </a>
 */
public interface PausableFiber extends Fiber {
    /**
     * This state is used to define when a <code>Fiber</code> has begun the
     * process of pausing its operations. This is the intermedate period where
     * the thread is no longer in the <code>RUNNING</code> status, but not yet
     * to a <code>PAUSED</code> status.
     */
    public static final int PAUSE_PENDING = 5;

    /**
     * This state is used to denote a paused, or otherwise suspended
     * <code>Fiber</code>. When a <code>Fiber</code> is in this state it
     * should not be preforming any work.
     */
    public static final int PAUSED = 6;

    /**
     * This state is used to denote a <code>Fiber</code> recovering from a
     * paused state to a running status. During this status the
     * <code>Fiber</code> is reinitializing any necessary internal elements to
     * re-enter the <code>RUNNING</code> state.
     */
    public static final int RESUME_PENDING = 7;

    /**
     * This method is used to suspend a currently running <code>Fiber<code>.
     * When invoked the <code>Fiber</code> will begin the transition to
     * a <code>PAUSED</code> status after changing its internal state, if 
     * applicable.
     */
    public void pause();

    /**
     * This method is used to resume a suspeneded <code>Fiber</code>. If the
     * thread is already running then this method should have no effect on the
     * current <code>Fiber</code>.
     */
    public void resume();
}