TreiberClient00.java

/******************************************************************************
 * Copyright (c) 2009 - 2015 IBM Corporation.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *****************************************************************************/
package data.linearizability;

final public class TreiberClient00 {
    final private static Object item = new Object();
    
    final public static void thread1() {
        final Object i = item;
        final Object o = TreiberClient00.pop();
        assert o == i;
    }
    
    final public static void thread2() {
        final Object i = item;
        TreiberClient00.push(i);
        assert true;
    }
    
    private static class Lock {
        
        public Lock() { super(); }
    }
    
    final private static Object lock = new Lock();
    static Node head = null;
    
    public static Object pop() {
        Node oldHead;
        Node newHead;
        do  {
            oldHead = head;
            if (oldHead == null) return null;
            newHead = oldHead.next;
        }while(!TreiberClient00.casHead(oldHead, newHead)); 
        return oldHead.item;
    }
    
    public static void push(Object item) {
        Node oldHead;
        Node newHead = new Node(item);
        do  {
            oldHead = head;
            newHead.next = oldHead;
        }while(!TreiberClient00.casHead(oldHead, newHead)); 
    }
    
    private static boolean casHead(Node oldHead, Node newHead) {
        synchronized (lock)  {
            final Node curHead = head;
            if (curHead == oldHead) {
                head = newHead;
                return true;
            } else {
                return false;
            }
        }
    }
    
    private static class Node {
        final Object item;
        Node next;
        
        Node(Object item) {
            super();
            this.item = item;
            this.next = null;
        }
    }
    
    
    public TreiberClient00() { super(); }
}