Package co.paralleluniverse.strands.channels

Source Code of co.paralleluniverse.strands.channels.DelayedVal

/*
* Quasar: lightweight threads and actors for the JVM.
* Copyright (C) 2013, Parallel Universe Software Co. All rights reserved.
*
* This program and the accompanying materials are dual-licensed under
* either the terms of the Eclipse Public License v1.0 as published by
* the Eclipse Foundation
*   or (per the licensee's choosing)
* under the terms of the GNU Lesser General Public License version 3.0
* as published by the Free Software Foundation.
*/
package co.paralleluniverse.strands.channels;

import co.paralleluniverse.fibers.SuspendExecution;
import co.paralleluniverse.fibers.Suspendable;
import co.paralleluniverse.strands.SimpleConditionSynchronizer;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

/**
*
* @author pron
*/
public class DelayedVal<V> implements Future<V> {
    private V value;
    private volatile SimpleConditionSynchronizer sync = new SimpleConditionSynchronizer(this);

    public final void set(V value) {
        if (sync == null)
            throw new IllegalStateException("Value has already been set (and can only be set once)");
        this.value = value;
        final SimpleConditionSynchronizer s = sync;
        sync = null; // must be done before signal
        s.signalAll();
    }

    @Override
    public boolean isDone() {
        return sync == null;
    }

    SimpleConditionSynchronizer getSync() {
        return sync;
    }

    V getValue() {
        return value;
    }

    @Override
    @Suspendable
    public V get() throws InterruptedException {
        try {
            final SimpleConditionSynchronizer s = sync;
            if (s != null) {
                s.register();
                try {
                    for (int i = 0; sync != null; i++)
                        s.await(i);
                } finally {
                    s.unregister();
                }
            }
            return value;
        } catch (SuspendExecution e) {
            throw new AssertionError(e);
        }
    }

    @Override
    @Suspendable
    public V get(long timeout, TimeUnit unit) throws InterruptedException, TimeoutException {
        try {
            final SimpleConditionSynchronizer s = sync;
            if (s != null) {
                s.register();
                try {
                    final long start = System.nanoTime();
                    long left = unit.toNanos(timeout);
                    final long deadline = start + left;
                    for (int i = 0; sync != null; i++) {
                        s.awaitNanos(i, left);
                        left = deadline - System.nanoTime();
                        if (left <= 0)
                            throw new TimeoutException();
                    }
                } finally {
                    s.unregister();
                }
            }
            return value;
        } catch (SuspendExecution e) {
            throw new AssertionError(e);
        }
    }

    @Override
    public boolean cancel(boolean mayInterruptIfRunning) {
        throw new UnsupportedOperationException();
    }

    @Override
    public boolean isCancelled() {
        return false;
    }
}
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