hu.akarnokd.rxjava2.internal.operators.OperatorThrottleFirstTimed 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.*;

import org.reactivestreams.*;

import hu.akarnokd.rxjava2.Observable.Operator;
import hu.akarnokd.rxjava2.Scheduler;
import hu.akarnokd.rxjava2.Scheduler.Worker;
import hu.akarnokd.rxjava2.disposables.Disposable;
import hu.akarnokd.rxjava2.internal.subscriptions.SubscriptionHelper;
import hu.akarnokd.rxjava2.internal.util.BackpressureHelper;
import hu.akarnokd.rxjava2.plugins.RxJavaPlugins;
import hu.akarnokd.rxjava2.subscribers.SerializedSubscriber;

public final class OperatorThrottleFirstTimed implements Operator {
    final long timeout;
    final TimeUnit unit;
    final Scheduler scheduler;

    public OperatorThrottleFirstTimed(long timeout, TimeUnit unit, Scheduler scheduler) {
        this.timeout = timeout;
        this.unit = unit;
        this.scheduler = scheduler;
    }
    
    @Override
    public Subscriber apply(Subscriber t) {
        return new DebounceTimedSubscriber(
                new SerializedSubscriber(t), 
                timeout, unit, scheduler.createWorker());
    }
    
    static final class DebounceTimedSubscriber
    extends AtomicLong
    implements Subscriber, Subscription, Runnable {
        /** */
        private static final long serialVersionUID = -9102637559663639004L;
        final Subscriber actual;
        final long timeout;
        final TimeUnit unit;
        final Scheduler.Worker worker;
        
        Subscription s;
        
        volatile Disposable timer;
        @SuppressWarnings("rawtypes")
        static final AtomicReferenceFieldUpdater TIMER =
                AtomicReferenceFieldUpdater.newUpdater(DebounceTimedSubscriber.class, Disposable.class, "timer");

        static final Disposable CANCELLED = new Disposable() {
            @Override
            public void dispose() { }
        };

        static final Disposable NEW_TIMER = new Disposable() {
            @Override
            public void dispose() { }
        };

        volatile boolean gate;
        
        boolean done;
        
        public DebounceTimedSubscriber(Subscriber actual, long timeout, TimeUnit unit, Worker worker) {
            this.actual = actual;
            this.timeout = timeout;
            this.unit = unit;
            this.worker = worker;
        }
        
        public void disposeTimer() {
            Disposable d = timer;
            if (d != CANCELLED) {
                d = TIMER.getAndSet(this, CANCELLED);
                if (d != CANCELLED && d != null) {
                    d.dispose();
                }
            }
        }
        @Override
        public void onSubscribe(Subscription s) {
            if (SubscriptionHelper.validateSubscription(this.s, s)) {
                return;
            }
            
            this.s = s;
            actual.onSubscribe(this);
            s.request(Long.MAX_VALUE);
        }
        
        @Override
        public void onNext(T t) {
            if (done) {
                return;
            }

            if (!gate) {
                gate = true;
                long r = get();
                if (r != 0L) {
                    actual.onNext(t);
                    if (r != Long.MAX_VALUE) {
                        decrementAndGet();
                    }
                } else {
                    done = true;
                    cancel();
                    actual.onError(new IllegalStateException("Could not deliver value due to lack of requests"));
                    return;
                }
                
                // FIXME should this be a periodic blocking or a value-relative blocking?
                Disposable d = timer;
                if (d != null) {
                    d.dispose();
                }
                
                if (TIMER.compareAndSet(this, d, NEW_TIMER)) {
                    d = worker.schedule(this, timeout, unit);
                    if (!TIMER.compareAndSet(this, NEW_TIMER, d)) {
                        d.dispose();
                    }
                }
            }
            
            
        }
        
        @Override
        public void run() {
            gate = false;
        }
        
        @Override
        public void onError(Throwable t) {
            if (done) {
                RxJavaPlugins.onError(t);
                return;
            }
            done = true;
            disposeTimer();
            actual.onError(t);
        }
        
        @Override
        public void onComplete() {
            if (done) {
                return;
            }
            done = true;
            disposeTimer();
            worker.dispose();
            actual.onComplete();
        }
        
        @Override
        public void request(long n) {
            if (SubscriptionHelper.validateRequest(n)) {
                return;
            }
            BackpressureHelper.add(this, n);
        }
        
        @Override
        public void cancel() {
            disposeTimer();
            worker.dispose();
            s.cancel();
        }
    }
}