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May 23, 2014 07:58
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/** | |
* Copyright 2014 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 rx.operators; | |
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater; | |
import java.util.concurrent.atomic.AtomicLong; | |
import rx.Observable.Operator; | |
import rx.Scheduler; | |
import rx.Subscriber; | |
import rx.Subscription; | |
import rx.functions.Action0; | |
import rx.schedulers.ImmediateScheduler; | |
import rx.schedulers.TrampolineScheduler; | |
/** | |
* Delivers events on the specified Scheduler asynchronously via an unbounded buffer. | |
* | |
* <img width="640" src="https://github.com/Netflix/RxJava/wiki/images/rx-operators/observeOn.png"> | |
*/ | |
public final class OperatorObserveOn<T> implements Operator<T, T> { | |
private final Scheduler scheduler; | |
/** | |
* @param scheduler | |
*/ | |
public OperatorObserveOn(Scheduler scheduler) { | |
this.scheduler = scheduler; | |
} | |
@Override | |
public Subscriber<? super T> call(Subscriber<? super T> child) { | |
if (scheduler instanceof ImmediateScheduler) { | |
// avoid overhead, execute directly | |
return child; | |
} else if (scheduler instanceof TrampolineScheduler) { | |
// avoid overhead, execute directly | |
return child; | |
} else { | |
return new ObserveOnSubscriber<T>(scheduler, child); | |
} | |
} | |
/** Observe through individual queue per observer. */ | |
private static final class ObserveOnSubscriber<T> extends Subscriber<T> { | |
private final NotificationLite<T> on = NotificationLite.instance(); | |
final Subscriber<? super T> observer; | |
private final Scheduler.Worker recursiveScheduler; | |
private final UnsubscribeScheduler unsubscribeScheduler; | |
private FastList queue = new FastList(); | |
final AtomicLong counter = new AtomicLong(0); | |
public ObserveOnSubscriber(Scheduler scheduler, Subscriber<? super T> subscriber) { | |
super(subscriber); | |
this.observer = subscriber; | |
this.recursiveScheduler = scheduler.createWorker(); | |
this.unsubscribeScheduler = new UnsubscribeScheduler(recursiveScheduler); | |
subscriber.add(unsubscribeScheduler); | |
} | |
@Override | |
public void onNext(final T t) { | |
if (unsubscribeScheduler.isUnsubscribed()) { | |
return; | |
} | |
synchronized (this) { | |
queue.add(on.next(t)); | |
} | |
schedule(); | |
} | |
@Override | |
public void onCompleted() { | |
if (unsubscribeScheduler.isUnsubscribed()) { | |
return; | |
} | |
synchronized (this) { | |
queue.add(on.completed()); | |
} | |
schedule(); | |
} | |
@Override | |
public void onError(final Throwable e) { | |
if (unsubscribeScheduler.isUnsubscribed()) { | |
return; | |
} | |
synchronized (this) { | |
queue.add(on.error(e)); | |
} | |
schedule(); | |
} | |
protected void schedule() { | |
if (counter.getAndIncrement() == 0) { | |
recursiveScheduler.schedule(new Action0() { | |
@Override | |
public void call() { | |
pollQueue(); | |
} | |
}); | |
} | |
} | |
private void pollQueue() { | |
do { | |
FastList vs; | |
synchronized (this) { | |
vs = queue; | |
queue = new FastList(); | |
} | |
for (Object v : vs.array) { | |
if (v == null) { | |
break; | |
} | |
on.accept(observer, v); | |
} | |
if (counter.addAndGet(-vs.size) == 0) { | |
break; | |
} | |
} while (true); | |
} | |
} | |
static final class UnsubscribeScheduler implements Subscription { | |
final Scheduler.Worker worker; | |
volatile int once; | |
static final AtomicIntegerFieldUpdater<UnsubscribeScheduler> ONCE_UPDATER | |
= AtomicIntegerFieldUpdater.newUpdater(UnsubscribeScheduler.class, "once"); | |
public UnsubscribeScheduler(Scheduler.Worker worker) { | |
this.worker = worker; | |
} | |
@Override | |
public boolean isUnsubscribed() { | |
return once != 0; | |
} | |
@Override | |
public void unsubscribe() { | |
if (ONCE_UPDATER.getAndSet(this, 1) == 0) { | |
worker.schedule(new Action0() { | |
@Override | |
public void call() { | |
worker.unsubscribe(); | |
} | |
}); | |
} | |
} | |
} | |
static final class FastList { | |
Object[] array; | |
int size; | |
public void add(Object o) { | |
int s = size; | |
Object[] a = array; | |
if (a == null) { | |
a = new Object[16]; | |
array = a; | |
} else if (s == a.length) { | |
Object[] array2 = new Object[s + (s >> 2)]; | |
System.arraycopy(a, 0, array2, 0, s); | |
a = array2; | |
array = a; | |
} | |
a[s] = o; | |
size = s + 1; | |
} | |
} | |
} |
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