jcsp-master/src/main/java/jcsp/net2/Mutex.java

//////////////////////////////////////////////////////////////////////
//                                                                  //
//  JCSP ("CSP for Java") Libraries                                 //
//  Copyright (C) 1996-2018 Peter Welch, Paul Austin and Neil Brown //
//                2001-2004 Quickstone Technologies Limited         //
//                2005-2018 Kevin Chalmers                          //
//                                                                  //
//  You may use this work under the terms of either                 //
//  1. The Apache License, Version 2.0                              //
//  2. or (at your option), the GNU Lesser General Public License,  //
//       version 2.1 or greater.                                    //
//                                                                  //
//  Full licence texts are included in the LICENCE file with        //
//  this library.                                                   //
//                                                                  //
//  Author contacts: P.H.Welch@kent.ac.uk K.Chalmers@napier.ac.uk   //
//                                                                  //
//////////////////////////////////////////////////////////////////////

package jcsp.net2;

import jcsp.lang.ProcessInterruptedException;

/**
 * A package-visible class that implements a straightforward mutex, for use by Net2AnyChannel
 * 
 * @author Neil Brown
 */
class Mutex
{
    /**
     * Flag to mark the mutex as claimed
     */
    private boolean claimed = false;

    /**
     * Claims the mutex for exclusive access
     */
    void claim()
    {
        synchronized (this)
        {
            while (this.claimed)
            {
                try
                {
                    wait();
                }
                catch (InterruptedException e)
                {
                    throw new ProcessInterruptedException("*** Thrown from Mutex.claim()\n" + e.toString());
                }
            }
            this.claimed = true;
        }
    }

    /**
     * Releases the mutex for exclusive access
     */
    void release()
    {
        synchronized (this)
        {
            this.claimed = false;
            notify();
        }
    }
}
