/**
* 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.internal.util;
import rx.*;
import rx.Scheduler.Worker;
import rx.functions.Action0;
import rx.internal.schedulers.EventLoopsScheduler;
public final class ScalarSynchronousObservable<T> extends Observable<T> {
public static final <T> ScalarSynchronousObservable<T> create(T t) {
return new ScalarSynchronousObservable<T>(t);
}
private final T t;
protected ScalarSynchronousObservable(final T t) {
super(new OnSubscribe<T>() {
@Override
public void call(Subscriber<? super T> s) {
/*
* We don't check isUnsubscribed as it is a significant performance impact in the fast-path use cases.
* See PerfBaseline tests and https://github.com/ReactiveX/RxJava/issues/1383 for more information.
* The assumption here is that when asking for a single item we should emit it and not concern ourselves with
* being unsubscribed already. If the Subscriber unsubscribes at 0, they shouldn't have subscribed, or it will
* filter it out (such as take(0)). This prevents us from paying the price on every subscription.
*/
s.onNext(t);
s.onCompleted();
}
});
this.t = t;
}
public T get() {
return t;
}
/**
* Customized observeOn/subscribeOn implementation which emits the scalar
* value directly or with less overhead on the specified scheduler.
* @param scheduler the target scheduler
* @return the new observable
*/
public Observable<T> scalarScheduleOn(Scheduler scheduler) {
if (scheduler instanceof EventLoopsScheduler) {
EventLoopsScheduler es = (EventLoopsScheduler) scheduler;
return create(new DirectScheduledEmission<T>(es, t));
}
return create(new NormalScheduledEmission<T>(scheduler, t));
}
/** Optimized observeOn for scalar value observed on the EventLoopsScheduler. */
static final class DirectScheduledEmission<T> implements OnSubscribe<T> {
private final EventLoopsScheduler es;
private final T value;
DirectScheduledEmission(EventLoopsScheduler es, T value) {
this.es = es;
this.value = value;
}
@Override
public void call(final Subscriber<? super T> child) {
child.add(es.scheduleDirect(new ScalarSynchronousAction<T>(child, value)));
}
}
/** Emits a scalar value on a general scheduler. */
static final class NormalScheduledEmission<T> implements OnSubscribe<T> {
private final Scheduler scheduler;
private final T value;
NormalScheduledEmission(Scheduler scheduler, T value) {
this.scheduler = scheduler;
this.value = value;
}
@Override
public void call(final Subscriber<? super T> subscriber) {
Worker worker = scheduler.createWorker();
subscriber.add(worker);
worker.schedule(new ScalarSynchronousAction<T>(subscriber, value));
}
}
/** Action that emits a single value when called. */
static final class ScalarSynchronousAction<T> implements Action0 {
private final Subscriber<? super T> subscriber;
private final T value;
private ScalarSynchronousAction(Subscriber<? super T> subscriber,
T value) {
this.subscriber = subscriber;
this.value = value;
}
@Override
public void call() {
try {
subscriber.onNext(value);
} catch (Throwable t) {
subscriber.onError(t);
return;
}
subscriber.onCompleted();
}
}
}