/*
 * (c) Copyright 2009 Hewlett-Packard Development Company, LP
 * All rights reserved.
 * [See end of file]
 */

package jenaplus;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.concurrent.atomic.AtomicInteger;

import org.openjena.atlas.logging.Log;

import com.hp.hpl.jena.shared.Lock;
import com.hp.hpl.jena.shared.LockMRSW;

public class TestMRSW
{
    static { Log.setLog4j() ; }
    
    static Lock lock = new LockMRSW() ;
    static AtomicInteger readerCount = new AtomicInteger(0) ;
    static AtomicInteger writerCount = new AtomicInteger(0) ;
    
    public static void main(String... args) throws Exception
    {
        //Log.enable(LockMRSW.class) ;
        
        int wThreads = 3 ;
        int rThreads = 5 ;
        
        List<Thread> threads = new ArrayList<Thread>();
        
        for ( int i = 0 ; i < rThreads ; i++ )
            threads.add(new Thread(new ReaderRunner())) ;

        for ( int i = 0 ; i < wThreads ; i++ )
            threads.add(new Thread(new WriterRunner())) ;
        

        for (Thread thread: threads)
            thread.start();
        
        for (Thread thread: threads)
            thread.join();
    }
    
    static void check()
    {
        // Not perfect when called from outside the critical region. 
        // Can see r = 1, then [threads run, r -> 0, w -> 1] read w = 1 => check fails.  
        int r = readerCount.intValue() ;
        int w = writerCount.intValue() ;
        
        if ( r > 0 && w > 0 )
            System.err.printf("r=%d w=%d", r, w) ;

        if ( r == 0 && w > 1 )
            System.err.printf("r=%d w=%d", r, w) ;

        if ( r < 0 || w < 0 )
            System.err.printf("r=%d w=%d", r, w) ;
    }
    
    
    static class ReaderRunner implements Runnable
    {

        @Override
        public void run()
        {
            while(true)
            {
                //Checks here may see inconsistency.
                randomWait(5) ;
                try {
                    lock.enterCriticalSection(Lock.READ) ;
                    readerCount.incrementAndGet() ;
                    check() ;
                    randomWait(10) ;
                    check() ;
                } finally
                { 
                    readerCount.decrementAndGet() ;
                    lock.leaveCriticalSection() ; 
                } 
            }
        }
    }

    static class WriterRunner implements Runnable
    {

        @Override
        public void run()
        {
            while(true)
            {
                //Bad - check() ;
                randomWait(5) ;
                try {
                    lock.enterCriticalSection(Lock.WRITE) ;
                    writerCount.incrementAndGet() ;
                    check() ;
                    randomWait(10) ;
                    check() ;
                } finally
                { 
                    writerCount.decrementAndGet() ;
                    lock.leaveCriticalSection() ; 
                }
            }
        }
    }
    
    
    static Random random = new Random() ; 
    static int randomWait(int milliseconds)
    {
        return random.nextInt(milliseconds) ;
    }
}


/*
 * (c) Copyright 2009 Hewlett-Packard Development Company, LP
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */