Class Delay

src/jvm/clojure/lang/Delay.java:18–68

import java.util.concurrent.locks.ReentrantLock;

public class Delay implements IDeref, IPending{
Object val;
Throwable exception;
IFn fn;
volatile Lock lock;

public Delay(IFn f){
	fn = f;
	val = null;
	exception = null;
	lock = new ReentrantLock();
}

static public Object force(Object x) {
	return (x instanceof Delay) ?
	       ((Delay) x).deref()
	       : x;
}

private void realize() {
	Lock l = lock;
	if(l != null) {
		l.lock();
		try {
			if(fn!=null) {
				try {
					val = fn.invoke();
				} catch (Throwable t) {
					exception = t;
				}
				fn = null;
				lock = null;
			}
		} finally {
			l.unlock();
		}
	}
}

public Object deref() {
	if(lock != null)
		realize();
	if(exception != null)
		throw Util.sneakyThrow(exception);
	return val;
}

public boolean isRealized(){
	return lock == null;
}
}