/**
* Copyright (c) 2016-present, RxJava Contributors.
*
* 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 io.reactivex.processors;
import io.reactivex.annotations.CheckReturnValue;
import java.util.concurrent.atomic.*;
import io.reactivex.annotations.Experimental;
import io.reactivex.annotations.Nullable;
import org.reactivestreams.*;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.fuseable.QueueSubscription;
import io.reactivex.internal.queue.SpscLinkedArrayQueue;
import io.reactivex.internal.subscriptions.*;
import io.reactivex.internal.util.BackpressureHelper;
import io.reactivex.plugins.RxJavaPlugins;
/**
* Processor that allows only a single Subscriber to subscribe to it during its lifetime.
*
* <p>This processor buffers notifications and replays them to the Subscriber as requested.
*
* <p>This processor holds an unbounded internal buffer.
*
* <p>If more than one Subscriber attempts to subscribe to this Processor, they
* will receive an IllegalStateException if this Processor hasn't terminated yet,
* or the Subscribers receive the terminal event (error or completion) if this
* Processor has terminated.
* <p>
* <img width="640" height="370" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/UnicastProcessor.png" alt="">
*
* @param <T> the value type received and emitted by this Processor subclass
* @since 2.0
*/
public final class UnicastProcessor<T> extends FlowableProcessor<T> {
final SpscLinkedArrayQueue<T> queue;
final AtomicReference<Runnable> onTerminate;
final boolean delayError;
volatile boolean done;
Throwable error;
final AtomicReference<Subscriber<? super T>> actual;
volatile boolean cancelled;
final AtomicBoolean once;
final BasicIntQueueSubscription<T> wip;
final AtomicLong requested;
boolean enableOperatorFusion;
/**
* Creates an UnicastSubject with an internal buffer capacity hint 16.
* @param <T> the value type
* @return an UnicastSubject instance
*/
@CheckReturnValue
public static <T> UnicastProcessor<T> create() {
return new UnicastProcessor<T>(bufferSize());
}
/**
* Creates an UnicastProcessor with the given internal buffer capacity hint.
* @param <T> the value type
* @param capacityHint the hint to size the internal unbounded buffer
* @return an UnicastProcessor instance
*/
@CheckReturnValue
public static <T> UnicastProcessor<T> create(int capacityHint) {
return new UnicastProcessor<T>(capacityHint);
}
/**
* Creates an UnicastProcessor with default internal buffer capacity hint and delay error flag.
* @param <T> the value type
* @param delayError deliver pending onNext events before onError
* @return an UnicastProcessor instance
* @since 2.0.8 - experimental
*/
@CheckReturnValue
@Experimental
public static <T> UnicastProcessor<T> create(boolean delayError) {
return new UnicastProcessor<T>(bufferSize(), null, delayError);
}
/**
* Creates an UnicastProcessor with the given internal buffer capacity hint and a callback for
* the case when the single Subscriber cancels its subscription.
*
* <p>The callback, if not null, is called exactly once and
* non-overlapped with any active replay.
*
* @param <T> the value type
* @param capacityHint the hint to size the internal unbounded buffer
* @param onCancelled the non null callback
* @return an UnicastProcessor instance
*/
@CheckReturnValue
public static <T> UnicastProcessor<T> create(int capacityHint, Runnable onCancelled) {
ObjectHelper.requireNonNull(onCancelled, "onTerminate");
return new UnicastProcessor<T>(capacityHint, onCancelled);
}
/**
* Creates an UnicastProcessor with the given internal buffer capacity hint, delay error flag and a callback for
* the case when the single Subscriber cancels its subscription.
*
* <p>The callback, if not null, is called exactly once and
* non-overlapped with any active replay.
*
* @param <T> the value type
* @param capacityHint the hint to size the internal unbounded buffer
* @param onCancelled the non null callback
* @param delayError deliver pending onNext events before onError
* @return an UnicastProcessor instance
* @since 2.0.8 - experimental
*/
@CheckReturnValue
@Experimental
public static <T> UnicastProcessor<T> create(int capacityHint, Runnable onCancelled, boolean delayError) {
ObjectHelper.requireNonNull(onCancelled, "onTerminate");
return new UnicastProcessor<T>(capacityHint, onCancelled, delayError);
}
/**
* Creates an UnicastProcessor with the given capacity hint.
* @param capacityHint the capacity hint for the internal, unbounded queue
* @since 2.0
*/
UnicastProcessor(int capacityHint) {
this(capacityHint,null, true);
}
/**
* Creates an UnicastProcessor with the given capacity hint and callback
* for when the Processor is terminated normally or its single Subscriber cancels.
* @param capacityHint the capacity hint for the internal, unbounded queue
* @param onTerminate the callback to run when the Processor is terminated or cancelled, null not allowed
* @since 2.0
*/
UnicastProcessor(int capacityHint, Runnable onTerminate) {
this(capacityHint, onTerminate, true);
}
/**
* Creates an UnicastProcessor with the given capacity hint and callback
* for when the Processor is terminated normally or its single Subscriber cancels.
* @param capacityHint the capacity hint for the internal, unbounded queue
* @param onTerminate the callback to run when the Processor is terminated or cancelled, null not allowed
* @param delayError deliver pending onNext events before onError
* @since 2.0.8 - experimental
*/
UnicastProcessor(int capacityHint, Runnable onTerminate, boolean delayError) {
this.queue = new SpscLinkedArrayQueue<T>(ObjectHelper.verifyPositive(capacityHint, "capacityHint"));
this.onTerminate = new AtomicReference<Runnable>(onTerminate);
this.delayError = delayError;
this.actual = new AtomicReference<Subscriber<? super T>>();
this.once = new AtomicBoolean();
this.wip = new UnicastQueueSubscription();
this.requested = new AtomicLong();
}
void doTerminate() {
Runnable r = onTerminate.get();
if (r != null && onTerminate.compareAndSet(r, null)) {
r.run();
}
}
void drainRegular(Subscriber<? super T> a) {
int missed = 1;
final SpscLinkedArrayQueue<T> q = queue;
final boolean failFast = !delayError;
for (;;) {
long r = requested.get();
long e = 0L;
while (r != e) {
boolean d = done;
T t = q.poll();
boolean empty = t == null;
if (checkTerminated(failFast, d, empty, a, q)) {
return;
}
if (empty) {
break;
}
a.onNext(t);
e++;
}
if (r == e && checkTerminated(failFast, done, q.isEmpty(), a, q)) {
return;
}
if (e != 0 && r != Long.MAX_VALUE) {
requested.addAndGet(-e);
}
missed = wip.addAndGet(-missed);
if (missed == 0) {
break;
}
}
}
void drainFused(Subscriber<? super T> a) {
int missed = 1;
final SpscLinkedArrayQueue<T> q = queue;
final boolean failFast = !delayError;
for (;;) {
if (cancelled) {
q.clear();
actual.lazySet(null);
return;
}
boolean d = done;
if (failFast && d && error != null) {
q.clear();
actual.lazySet(null);
a.onError(error);
return;
}
a.onNext(null);
if (d) {
actual.lazySet(null);
Throwable ex = error;
if (ex != null) {
a.onError(ex);
} else {
a.onComplete();
}
return;
}
missed = wip.addAndGet(-missed);
if (missed == 0) {
break;
}
}
}
void drain() {
if (wip.getAndIncrement() != 0) {
return;
}
int missed = 1;
Subscriber<? super T> a = actual.get();
for (;;) {
if (a != null) {
if (enableOperatorFusion) {
drainFused(a);
} else {
drainRegular(a);
}
return;
}
missed = wip.addAndGet(-missed);
if (missed == 0) {
break;
}
a = actual.get();
}
}
boolean checkTerminated(boolean failFast, boolean d, boolean empty, Subscriber<? super T> a, SpscLinkedArrayQueue<T> q) {
if (cancelled) {
q.clear();
actual.lazySet(null);
return true;
}
if (d) {
if (failFast && error != null) {
q.clear();
actual.lazySet(null);
a.onError(error);
return true;
}
if (empty) {
Throwable e = error;
actual.lazySet(null);
if (e != null) {
a.onError(e);
} else {
a.onComplete();
}
return true;
}
}
return false;
}
@Override
public void onSubscribe(Subscription s) {
if (done || cancelled) {
s.cancel();
} else {
s.request(Long.MAX_VALUE);
}
}
@Override
public void onNext(T t) {
if (done || cancelled) {
return;
}
if (t == null) {
onError(new NullPointerException("onNext called with null. Null values are generally not allowed in 2.x operators and sources."));
return;
}
queue.offer(t);
drain();
}
@Override
public void onError(Throwable t) {
if (done || cancelled) {
RxJavaPlugins.onError(t);
return;
}
if (t == null) {
t = new NullPointerException("onError called with null. Null values are generally not allowed in 2.x operators and sources.");
}
error = t;
done = true;
doTerminate();
drain();
}
@Override
public void onComplete() {
if (done || cancelled) {
return;
}
done = true;
doTerminate();
drain();
}
@Override
protected void subscribeActual(Subscriber<? super T> s) {
if (!once.get() && once.compareAndSet(false, true)) {
s.onSubscribe(wip);
actual.set(s);
if (cancelled) {
actual.lazySet(null);
} else {
drain();
}
} else {
EmptySubscription.error(new IllegalStateException("This processor allows only a single Subscriber"), s);
}
}
final class UnicastQueueSubscription extends BasicIntQueueSubscription<T> {
private static final long serialVersionUID = -4896760517184205454L;
@Nullable
@Override
public T poll() {
return queue.poll();
}
@Override
public boolean isEmpty() {
return queue.isEmpty();
}
@Override
public void clear() {
queue.clear();
}
@Override
public int requestFusion(int requestedMode) {
if ((requestedMode & QueueSubscription.ASYNC) != 0) {
enableOperatorFusion = true;
return QueueSubscription.ASYNC;
}
return QueueSubscription.NONE;
}
@Override
public void request(long n) {
if (SubscriptionHelper.validate(n)) {
BackpressureHelper.add(requested, n);
drain();
}
}
@Override
public void cancel() {
if (cancelled) {
return;
}
cancelled = true;
doTerminate();
if (!enableOperatorFusion) {
if (wip.getAndIncrement() == 0) {
queue.clear();
actual.lazySet(null);
}
}
}
}
@Override
public boolean hasSubscribers() {
return actual.get() != null;
}
@Override
public Throwable getThrowable() {
if (done) {
return error;
}
return null;
}
@Override
public boolean hasComplete() {
return done && error == null;
}
@Override
public boolean hasThrowable() {
return done && error != null;
}
}