hu.akarnokd.rxjava2.internal.operators.PublisherIntervalOnceSource Maven / Gradle / Ivy

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rxjava2-backport developed by David Karnok
There is a newer version: 2.0.0-RC3
/**
 * Copyright 2015 David Karnok and 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 hu.akarnokd.rxjava2.internal.operators;

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

import org.reactivestreams.*;

import hu.akarnokd.rxjava2.Scheduler;
import hu.akarnokd.rxjava2.disposables.Disposable;
import hu.akarnokd.rxjava2.plugins.RxJavaPlugins;

public final class PublisherIntervalOnceSource implements Publisher {
    final Scheduler scheduler;
    final long delay;
    final TimeUnit unit;
    public PublisherIntervalOnceSource(long delay, TimeUnit unit, Scheduler scheduler) {
        this.delay = delay;
        this.unit = unit;
        this.scheduler = scheduler;
    }
    
    @Override
    public void subscribe(Subscriber 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 
    implements Subscription, Runnable {
        /** */
        private static final long serialVersionUID = -2809475196591179431L;

        final Subscriber actual;
        
        static final Disposable DISPOSED = new Disposable() {
            @Override
            public void dispose() { }
        };

        /** 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 requested;
        
        volatile boolean cancelled;
        
        public IntervalOnceSubscriber(Subscriber actual) {
            this.actual = actual;
        }
        
        @Override
        public void request(long n) {
            if (n <= 0) {
                RxJavaPlugins.onError(new IllegalArgumentException("n > 0 required but it was " + n));
                return;
            }
            requested = true;
        }
        
        @Override
        public void cancel() {
            if (!cancelled) {
                cancelled = true;
                
                Disposable d = get();
                if (d != DISPOSED && d != DONE) {
                    d = getAndSet(DISPOSED);
                    if (d != DISPOSED && d != null) {
                        d.dispose();
                    }
                }
            }
        }
        
        @Override
        public void run() {
            if (!cancelled) {
                if (requested) {
                    actual.onNext(0L);
                    actual.onComplete();
                } else {
                    actual.onError(new IllegalStateException("Can't deliver value due to lack of requests"));
                }
            }
            lazySet(DONE);
        }
        
        public void setResource(Disposable d) {
            for (;;) {
                Disposable current = get();
                if (current == DISPOSED) {
                    d.dispose();
                    return;
                }
                if (current == DONE) {
                    return;
                }
                if (current != null) {
                    RxJavaPlugins.onError(new IllegalStateException("Resource already set!"));
                    return;
                }
                if (compareAndSet(null, d)) {
                    return;
                }
            }
        }
    }
}