1 /* 2 * [The "BSD license"] 3 * Copyright (c) 2010 Terence Parr 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. The name of the author may not be used to endorse or promote products 15 * derived from this software without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 package org.antlr.misc; 29 30 /**A very simple barrier wait. Once a thread has requested a 31 * wait on the barrier with waitForRelease, it cannot fool the 32 * barrier into releasing by "hitting" the barrier multiple times-- 33 * the thread is blocked on the wait(). 34 */ 35 public class Barrier { 36 protected int threshold; 37 protected int count = 0; 38 39 public Barrier(int t) { 40 threshold = t; 41 } 42 43 public synchronized void waitForRelease() 44 throws InterruptedException 45 { 46 count++; 47 // The final thread to reach barrier resets barrier and 48 // releases all threads 49 if ( count==threshold ) { 50 // notify blocked threads that threshold has been reached 51 action(); // perform the requested operation 52 notifyAll(); 53 } 54 else while ( count<threshold ) { 55 wait(); 56 } 57 } 58 59 /** What to do when everyone reaches barrier */ 60 public void action() { 61 } 62 } 63
