NbpOnSubscribeTimerOnceSource.java

/**
 * Copyright 2016 Netflix, Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software distributed under the License is
 * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
 * the License for the specific language governing permissions and limitations under the License.
 */

package io.reactivex.internal.operators.observable;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.internal.disposables.DisposableHelper;

public final class NbpOnSubscribeTimerOnceSource implements ObservableConsumable<Long> {
    final Scheduler scheduler;
    final long delay;
    final TimeUnit unit;
    public NbpOnSubscribeTimerOnceSource(long delay, TimeUnit unit, Scheduler scheduler) {
        this.delay = delay;
        this.unit = unit;
        this.scheduler = scheduler;
    }
    
    @Override
    public void subscribe(Observer<? super Long> s) {
        IntervalOnceSubscriber ios = new IntervalOnceSubscriber(s);
        s.onSubscribe(ios);
        
        Disposable d = scheduler.scheduleDirect(ios, delay, unit);
        
        ios.setResource(d);
    }
    
    static final class IntervalOnceSubscriber extends AtomicReference<Disposable> 
    implements Disposable, Runnable {
        /** */
        private static final long serialVersionUID = -2809475196591179431L;

        final Observer<? super Long> actual;
        
        /** This state tells the setResource not to call dispose since the run is finishing anyway. */
        static final Disposable DONE = new Disposable() {
            @Override
            public void dispose() { }
        };
        
        volatile boolean cancelled;
        
        public IntervalOnceSubscriber(Observer<? super Long> actual) {
            this.actual = actual;
        }
        
        @Override
        public void dispose() {
            if (!cancelled) {
                cancelled = true;
                
                DisposableHelper.dispose(this);
            }
        }
        
        @Override
        public void run() {
            if (!cancelled) {
                actual.onNext(0L);
                actual.onComplete();
            }
            lazySet(DONE);
        }
        
        public void setResource(Disposable d) {
            DisposableHelper.setOnce(this, d);
        }
    }
}