/**
* 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.operators;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
import rx.Observable.Operator;
import rx.Scheduler;
import rx.Scheduler.Worker;
import rx.Subscriber;
import rx.functions.Action0;
import rx.observers.SerializedSubscriber;
/**
* Returns an Observable that emits the results of sampling the items emitted by the source
* Observable at a specified time interval.
* <p>
* <img width="640" src="https://github.com/Netflix/RxJava/wiki/images/rx-operators/sample.png" alt="">
*
* @param <T> the value type
*/
public final class OperatorSampleWithTime<T> implements Operator<T, T> {
final long time;
final TimeUnit unit;
final Scheduler scheduler;
public OperatorSampleWithTime(long time, TimeUnit unit, Scheduler scheduler) {
this.time = time;
this.unit = unit;
this.scheduler = scheduler;
}
@Override
public Subscriber<? super T> call(Subscriber<? super T> child) {
final SerializedSubscriber<T> s = new SerializedSubscriber<T>(child);
final Worker worker = scheduler.createWorker();
child.add(worker);
SamplerSubscriber<T> sampler = new SamplerSubscriber<T>(s);
worker.schedulePeriodically(sampler, time, time, unit);
return sampler;
}
/**
* The source subscriber and sampler.
*/
static final class SamplerSubscriber<T> extends Subscriber<T> implements Action0 {
private final Subscriber<? super T> subscriber;
/** Indicates that no value is available. */
private static final Object EMPTY_TOKEN = new Object();
/** The shared value between the observer and the timed action. */
volatile Object value = EMPTY_TOKEN;
/** Updater for the value field. */
@SuppressWarnings("rawtypes")
static final AtomicReferenceFieldUpdater<SamplerSubscriber, Object> VALUE_UPDATER
= AtomicReferenceFieldUpdater.newUpdater(SamplerSubscriber.class, Object.class, "value");
public SamplerSubscriber(Subscriber<? super T> subscriber) {
this.subscriber = subscriber;
}
@Override
public void onStart() {
request(Long.MAX_VALUE);
}
@Override
public void onNext(T t) {
value = t;
}
@Override
public void onError(Throwable e) {
subscriber.onError(e);
unsubscribe();
}
@Override
public void onCompleted() {
subscriber.onCompleted();
unsubscribe();
}
@Override
public void call() {
Object localValue = VALUE_UPDATER.getAndSet(this, EMPTY_TOKEN);
if (localValue != EMPTY_TOKEN) {
try {
@SuppressWarnings("unchecked")
T v = (T)localValue;
subscriber.onNext(v);
} catch (Throwable e) {
onError(e);
}
}
}
}
}