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Merge pull request #1907 from benjchristensen/onBackpressureBlock
Experimental: onBackpressureBlock
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src/main/java/rx/internal/operators/OperatorOnBackpressureBlock.java
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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.internal.operators; | ||
|
|
||
| import java.util.concurrent.ArrayBlockingQueue; | ||
| import java.util.concurrent.BlockingQueue; | ||
|
|
||
| import rx.Observable.Operator; | ||
| import rx.Producer; | ||
| import rx.Subscriber; | ||
|
|
||
| /** | ||
| * Operator that blocks the producer thread in case a backpressure is needed. | ||
| */ | ||
| public class OperatorOnBackpressureBlock<T> implements Operator<T, T> { | ||
| final int max; | ||
| public OperatorOnBackpressureBlock(int max) { | ||
| this.max = max; | ||
| } | ||
| @Override | ||
| public Subscriber<? super T> call(Subscriber<? super T> child) { | ||
| BlockingSubscriber<T> s = new BlockingSubscriber<T>(max, child); | ||
| s.init(); | ||
| return s; | ||
| } | ||
|
|
||
| static final class BlockingSubscriber<T> extends Subscriber<T> { | ||
| final NotificationLite<T> nl = NotificationLite.instance(); | ||
| final BlockingQueue<Object> queue; | ||
| final Subscriber<? super T> child; | ||
| /** Guarded by this. */ | ||
| long requestedCount; | ||
| /** Guarded by this. */ | ||
| boolean emitting; | ||
| volatile boolean terminated; | ||
| /** Set before terminated, read after terminated. */ | ||
| Throwable exception; | ||
| public BlockingSubscriber(int max, Subscriber<? super T> child) { | ||
| this.queue = new ArrayBlockingQueue<Object>(max); | ||
| this.child = child; | ||
| } | ||
| void init() { | ||
| child.add(this); | ||
| child.setProducer(new Producer() { | ||
| @Override | ||
| public void request(long n) { | ||
| synchronized (BlockingSubscriber.this) { | ||
| if (n == Long.MAX_VALUE || requestedCount == Long.MAX_VALUE) { | ||
| requestedCount = Long.MAX_VALUE; | ||
| } else { | ||
| requestedCount += n; | ||
| } | ||
| } | ||
| drain(); | ||
| } | ||
| }); | ||
| } | ||
| @Override | ||
| public void onNext(T t) { | ||
| try { | ||
| queue.put(nl.next(t)); | ||
| drain(); | ||
| } catch (InterruptedException ex) { | ||
| if (!isUnsubscribed()) { | ||
| onError(ex); | ||
| } | ||
| } | ||
| } | ||
| @Override | ||
| public void onError(Throwable e) { | ||
| if (!terminated) { | ||
| exception = e; | ||
| terminated = true; | ||
| drain(); | ||
| } | ||
| } | ||
| @Override | ||
| public void onCompleted() { | ||
| terminated = true; | ||
| drain(); | ||
| } | ||
| void drain() { | ||
| long n; | ||
| synchronized (this) { | ||
| if (emitting) { | ||
| return; | ||
| } | ||
| emitting = true; | ||
| n = requestedCount; | ||
| } | ||
| boolean skipFinal = false; | ||
| try { | ||
| while (true) { | ||
| int emitted = 0; | ||
| while (n > 0) { | ||
| Object o = queue.poll(); | ||
| if (o == null) { | ||
| if (terminated) { | ||
| if (exception != null) { | ||
| child.onError(exception); | ||
| } else { | ||
| child.onCompleted(); | ||
| } | ||
| return; | ||
| } | ||
| break; | ||
| } else { | ||
| child.onNext(nl.getValue(o)); | ||
| n--; | ||
| emitted++; | ||
| } | ||
| } | ||
| synchronized (this) { | ||
| // if no backpressure below | ||
| if (requestedCount == Long.MAX_VALUE) { | ||
| // no new data arrived since the last poll | ||
| if (queue.peek() == null) { | ||
| skipFinal = true; | ||
| emitting = false; | ||
| return; | ||
| } | ||
| n = Long.MAX_VALUE; | ||
| } else { | ||
| if (emitted == 0) { | ||
| skipFinal = true; | ||
| emitting = false; | ||
| return; | ||
| } | ||
| requestedCount -= emitted; | ||
| n = requestedCount; | ||
| } | ||
| } | ||
| } | ||
| } finally { | ||
| if (!skipFinal) { | ||
| synchronized (this) { | ||
| emitting = false; | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } |
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