condvar.java

Java Threads, 2Ed (Source）

/*
 *
 * Copyright (c) 1997-1999 Scott Oaks and Henry Wong. All Rights Reserved.
 *
 * Permission to use, copy, modify, and distribute this software
 * and its documentation for NON-COMMERCIAL purposes and
 * without fee is hereby granted.
 *
 * This sample source code is provided for example only,
 * on an unsupported, as-is basis. 
 *
 * AUTHOR MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF
 * THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
 * TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE, OR NON-INFRINGEMENT. AUTHOR SHALL NOT BE LIABLE FOR
 * ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
 * DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
 *
 * THIS SOFTWARE IS NOT DESIGNED OR INTENDED FOR USE OR RESALE AS ON-LINE
 * CONTROL EQUIPMENT IN HAZARDOUS ENVIRONMENTS REQUIRING FAIL-SAFE
 * PERFORMANCE, SUCH AS IN THE OPERATION OF NUCLEAR FACILITIES, AIRCRAFT
 * NAVIGATION OR COMMUNICATION SYSTEMS, AIR TRAFFIC CONTROL, DIRECT LIFE
 * SUPPORT MACHINES, OR WEAPONS SYSTEMS, IN WHICH THE FAILURE OF THE
 * SOFTWARE COULD LEAD DIRECTLY TO DEATH, PERSONAL INJURY, OR SEVERE
 * PHYSICAL OR ENVIRONMENTAL DAMAGE ("HIGH RISK ACTIVITIES").  AUTHOR
 * SPECIFICALLY DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY OF FITNESS FOR
 * HIGH RISK ACTIVITIES.
 */


public class CondVar {
private BusyFlag SyncVar;

	public CondVar() {
		this(new BusyFlag());
	}

	public CondVar(BusyFlag sv) {
		SyncVar = sv;
	}

	public void cvWait() throws InterruptedException {
		cvTimedWait(SyncVar, 0);
	}

	public void cvWait(BusyFlag sv) throws InterruptedException {
		cvTimedWait(sv, 0);
	}

	public void cvTimedWait(int millis) throws InterruptedException {
		cvTimedWait(SyncVar, millis);
	}

	public void cvTimedWait(BusyFlag sv, int millis) throws InterruptedException {
		int i = 0;
		InterruptedException errex = null;

		synchronized (this) {
			// You must own the lock in order to use this method
			if (sv.getBusyFlagOwner() != Thread.currentThread()) {
				throw new IllegalMonitorStateException("current thread not owner");
			}

			// Release the lock (Completely)
			while (sv.getBusyFlagOwner() == Thread.currentThread()) {
				i++;
				sv.freeBusyFlag();
			}
		
			// Use wait() method	
			try {
				if (millis == 0) {
					wait();
				} else {
					wait(millis);
				}
			} catch (InterruptedException iex) {
				errex = iex;
			}
		}
	 
		// Obtain the lock (Return to original state)
		for (; i>0; i--) {
			sv.getBusyFlag();
		}

		if (errex != null) throw errex;
		return;
	}

	public void cvSignal() {
		cvSignal(SyncVar);
	}

	public synchronized void cvSignal(BusyFlag sv) {
		// You must own the lock in order to use this method
		if (sv.getBusyFlagOwner() != Thread.currentThread()) {
			throw new IllegalMonitorStateException("current thread not owner");
		}
		notify();
	}

	public void cvBroadcast() {
		cvBroadcast(SyncVar);
	}

	public synchronized void cvBroadcast(BusyFlag sv) {
		// You must own the lock in order to use this method
		if (sv.getBusyFlagOwner() != Thread.currentThread()) {
			throw new IllegalMonitorStateException("current thread not owner");
		}
		notifyAll();
	}
}