/**
* 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.atomic.AtomicLong;
import rx.*;
import rx.Observable.Operator;
import rx.plugins.RxJavaHooks;
/**
* Turns all of the notifications from an Observable into {@code onNext} emissions, and marks
* them with their original notification types within {@link Notification} objects.
* <p>
* <img width="640" src="https://github.com/ReactiveX/RxJava/wiki/images/rx-operators/materialize.png" alt="">
* <p>
* See <a href="http://msdn.microsoft.com/en-us/library/hh229453.aspx">here</a> for the Microsoft Rx equivalent.
* @param <T> the value type
*/
public final class OperatorMaterialize<T> implements Operator<Notification<T>, T> {
/** Lazy initialization via inner-class holder. */
static final class Holder {
/** A singleton instance. */
static final OperatorMaterialize<Object> INSTANCE = new OperatorMaterialize<Object>();
}
/**
* @param <T> the value type
* @return a singleton instance of this stateless operator.
*/
@SuppressWarnings("unchecked")
public static <T> OperatorMaterialize<T> instance() {
return (OperatorMaterialize<T>) Holder.INSTANCE;
}
OperatorMaterialize() {
// singleton instances
}
@Override
public Subscriber<? super T> call(final Subscriber<? super Notification<T>> child) {
final ParentSubscriber<T> parent = new ParentSubscriber<T>(child);
child.add(parent);
child.setProducer(new Producer() {
@Override
public void request(long n) {
if (n > 0) {
parent.requestMore(n);
}
}
});
return parent;
}
static class ParentSubscriber<T> extends Subscriber<T> {
private final Subscriber<? super Notification<T>> child;
private volatile Notification<T> terminalNotification;
// guarded by this
private boolean busy;
// guarded by this
private boolean missed;
private final AtomicLongrequested = new AtomicLong();
ParentSubscriber(Subscriber<? super Notification<T>> child) {
this.child = child;
}
@Override
public void onStart() {
request(0);
}
void requestMore(long n) {
BackpressureUtils.getAndAddRequest(requested, n);
request(n);
drain();
}
@Override
public void onCompleted() {
terminalNotification = Notification.createOnCompleted();
drain();
}
@Override
public void onError(Throwablee) {
terminalNotification = Notification.createOnError(e);
RxJavaHooks.onError(e);
drain();
}
@Override
public void onNext(T t) {
child.onNext(Notification.createOnNext(t));
decrementRequested();
}
private void decrementRequested() {
// atomically decrement requested
AtomicLonglocalRequested = this.requested;
while (true) {
long r = localRequested.get();
if (r == Long.MAX_VALUE) {
// don't decrement if unlimited requested
return;
} else if (localRequested.compareAndSet(r, r - 1)) {
return;
}
}
}
private void drain() {
synchronized (this) {
if (busy) {
// set flag to force extra loop if drain loop running
missed = true;
return;
}
busy = true;
}
// drain loop
final AtomicLonglocalRequested = this.requested;
while (!child.isUnsubscribed()) {
Notification<T> tn;
tn = terminalNotification;
if (tn != null) {
if (localRequested.get() > 0) {
// allow tn to be GC'd after the onNext call
terminalNotification = null;
// emit the terminal notification
child.onNext(tn);
if (!child.isUnsubscribed()) {
child.onCompleted();
}
// note that we leave busy=true here
// which will prevent further drains
return;
}
}
// continue looping if drain() was called while in
// this loop
synchronized (this) {
if (!missed) {
busy = false;
return;
}
}
}
}
}
}