/**
* 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.subjects;
import io.reactivex.annotations.Experimental;
import io.reactivex.annotations.Nullable;
import io.reactivex.plugins.RxJavaPlugins;
import java.util.concurrent.atomic.*;
import io.reactivex.Observer;
import io.reactivex.annotations.CheckReturnValue;
import io.reactivex.disposables.Disposable;
import io.reactivex.internal.disposables.EmptyDisposable;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.fuseable.SimpleQueue;
import io.reactivex.internal.observers.BasicIntQueueDisposable;
import io.reactivex.internal.queue.SpscLinkedArrayQueue;
/**
* Subject that allows only a single Subscriber to subscribe to it during its lifetime.
*
* <p>This subject buffers notifications and replays them to the Subscriber as requested.
*
* <p>This subject holds an unbounded internal buffer.
*
* <p>If more than one Subscriber attempts to subscribe to this Subject, they
* will receive an IllegalStateException if this Subject hasn't terminated yet,
* or the Subscribers receive the terminal event (error or completion) if this
* Subject has terminated.
* <p>
* <img width="640" height="370" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/UnicastSubject.png" alt="">
*
* @param <T> the value type received and emitted by this Subject subclass
* @since 2.0
*/
public final class UnicastSubject<T> extends Subject<T> {
/** The queue that buffers the source events. */
final SpscLinkedArrayQueue<T> queue;
/** The single Observer. */
final AtomicReference<Observer<? super T>> actual;
/** The optional callback when the Subject gets cancelled or terminates. */
final AtomicReference<Runnable> onTerminate;
/** deliver onNext events before error event. */
final boolean delayError;
/** Indicates the single observer has cancelled. */
volatile boolean disposed;
/** Indicates the source has terminated. */
volatile boolean done;
/**
* The terminal error if not null.
* Must be set before writing to done and read after done == true.
*/
Throwable error;
/** Set to 1 atomically for the first and only Subscriber. */
final AtomicBoolean once;
/** The wip counter and QueueDisposable surface. */
final BasicIntQueueDisposable<T> wip;
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> UnicastSubject<T> create() {
return new UnicastSubject<T>(bufferSize(), true);
}
/**
* Creates an UnicastSubject with the given internal buffer capacity hint.
* @param <T> the value type
* @param capacityHint the hint to size the internal unbounded buffer
* @return an UnicastSubject instance
*/
@CheckReturnValue
public static <T> UnicastSubject<T> create(int capacityHint) {
return new UnicastSubject<T>(capacityHint, true);
}
/**
* Creates an UnicastSubject 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 onTerminate the callback to run when the Subject is terminated or cancelled, null not allowed
* @return an UnicastSubject instance
*/
@CheckReturnValue
public static <T> UnicastSubject<T> create(int capacityHint, Runnable onTerminate) {
return new UnicastSubject<T>(capacityHint, onTerminate, true);
}
/**
* Creates an UnicastSubject 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 onTerminate the callback to run when the Subject is terminated or cancelled, null not allowed
* @param delayError deliver pending onNext events before onError
* @return an UnicastSubject instance
* @since 2.0.8 - experimental
*/
@CheckReturnValue
@Experimental
public static <T> UnicastSubject<T> create(int capacityHint, Runnable onTerminate, boolean delayError) {
return new UnicastSubject<T>(capacityHint, onTerminate, delayError);
}
/**
* Creates an UnicastSubject with an internal buffer capacity hint 16 and given delay error flag.
*
* <p>The callback, if not null, is called exactly once and
* non-overlapped with any active replay.
*
* @param <T> the value type
* @param delayError deliver pending onNext events before onError
* @return an UnicastSubject instance
* @since 2.0.8 - experimental
*/
@CheckReturnValue
@Experimental
public static <T> UnicastSubject<T> create(boolean delayError) {
return new UnicastSubject<T>(bufferSize(), delayError);
}
/**
* Creates an UnicastSubject with the given capacity hint and delay error flag.
* @param capacityHint the capacity hint for the internal, unbounded queue
* @param delayError deliver pending onNext events before onError
* @since 2.0.8 - experimental
*/
UnicastSubject(int capacityHint, boolean delayError) {
this.queue = new SpscLinkedArrayQueue<T>(ObjectHelper.verifyPositive(capacityHint, "capacityHint"));
this.onTerminate = new AtomicReference<Runnable>();
this.delayError = delayError;
this.actual = new AtomicReference<Observer<? super T>>();
this.once = new AtomicBoolean();
this.wip = new UnicastQueueDisposable();
}
/**
* Creates an UnicastSubject with the given capacity hint and callback
* for when the Subject 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 Subject is terminated or cancelled, null not allowed
* @since 2.0
*
* */
UnicastSubject(int capacityHint, Runnable onTerminate) {
this(capacityHint, onTerminate, true);
}
/**
* Creates an UnicastSubject with the given capacity hint, delay error flag and callback
* for when the Subject 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 Subject is terminated or cancelled, null not allowed
* @param delayError deliver pending onNext events before onError
* @since 2.0.8 - experimental
*/
UnicastSubject(int capacityHint, Runnable onTerminate, boolean delayError) {
this.queue = new SpscLinkedArrayQueue<T>(ObjectHelper.verifyPositive(capacityHint, "capacityHint"));
this.onTerminate = new AtomicReference<Runnable>(ObjectHelper.requireNonNull(onTerminate, "onTerminate"));
this.delayError = delayError;
this.actual = new AtomicReference<Observer<? super T>>();
this.once = new AtomicBoolean();
this.wip = new UnicastQueueDisposable();
}
@Override
protected void subscribeActual(Observer<? super T> observer) {
if (!once.get() && once.compareAndSet(false, true)) {
observer.onSubscribe(wip);
actual.lazySet(observer); // full barrier in drain
if (disposed) {
actual.lazySet(null);
return;
}
drain();
} else {
EmptyDisposable.error(new IllegalStateException("Only a single observer allowed."), observer);
}
}
void doTerminate() {
Runnable r = onTerminate.get();
if (r != null && onTerminate.compareAndSet(r, null)) {
r.run();
}
}
@Override
public void onSubscribe(Disposable s) {
if (done || disposed) {
s.dispose();
}
}
@Override
public void onNext(T t) {
if (done || disposed) {
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 || disposed) {
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 || disposed) {
return;
}
done = true;
doTerminate();
drain();
}
void drainNormal(Observer<? super T> a) {
int missed = 1;
SimpleQueue<T> q = queue;
boolean failFast = !this.delayError;
boolean canBeError = true;
for (;;) {
for (;;) {
if (disposed) {
actual.lazySet(null);
q.clear();
return;
}
boolean d = this.done;
T v = queue.poll();
boolean empty = v == null;
if (d) {
if (failFast && canBeError) {
if (failedFast(q, a)) {
return;
} else {
canBeError = false;
}
}
if (empty) {
errorOrComplete(a);
return;
}
}
if (empty) {
break;
}
a.onNext(v);
}
missed = wip.addAndGet(-missed);
if (missed == 0) {
break;
}
}
}
void drainFused(Observer<? super T> a) {
int missed = 1;
final SpscLinkedArrayQueue<T> q = queue;
final boolean failFast = !delayError;
for (;;) {
if (disposed) {
actual.lazySet(null);
q.clear();
return;
}
boolean d = done;
if (failFast && d) {
if (failedFast(q, a)) {
return;
}
}
a.onNext(null);
if (d) {
errorOrComplete(a);
return;
}
missed = wip.addAndGet(-missed);
if (missed == 0) {
break;
}
}
}
void errorOrComplete(Observer<? super T> a) {
actual.lazySet(null);
Throwable ex = error;
if (ex != null) {
a.onError(ex);
} else {
a.onComplete();
}
}
boolean failedFast(final SimpleQueue<T> q, Observer<? super T> a) {
Throwable ex = error;
if (ex != null) {
actual.lazySet(null);
q.clear();
a.onError(ex);
return true;
} else {
return false;
}
}
void drain() {
if (wip.getAndIncrement() != 0) {
return;
}
Observer<? super T> a = actual.get();
int missed = 1;
for (;;) {
if (a != null) {
if (enableOperatorFusion) {
drainFused(a);
} else {
drainNormal(a);
}
return;
}
missed = wip.addAndGet(-missed);
if (missed == 0) {
break;
}
a = actual.get();
}
}
@Override
public boolean hasObservers() {
return actual.get() != null;
}
@Override
public Throwable getThrowable() {
if (done) {
return error;
}
return null;
}
@Override
public boolean hasThrowable() {
return done && error != null;
}
@Override
public boolean hasComplete() {
return done && error == null;
}
final class UnicastQueueDisposable extends BasicIntQueueDisposable<T> {
private static final long serialVersionUID = 7926949470189395511L;
@Override
public int requestFusion(int mode) {
if ((mode & ASYNC) != 0) {
enableOperatorFusion = true;
return ASYNC;
}
return NONE;
}
@Nullable
@Override
public T poll() throws Exception {
return queue.poll();
}
@Override
public boolean isEmpty() {
return queue.isEmpty();
}
@Override
public void clear() {
queue.clear();
}
@Override
public void dispose() {
if (!disposed) {
disposed = true;
doTerminate();
actual.lazySet(null);
if (wip.getAndIncrement() == 0) {
actual.lazySet(null);
queue.clear();
}
}
}
@Override
public boolean isDisposed() {
return disposed;
}
}
}