/**
* 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 java.util.concurrent.atomic.*;
import io.reactivex.*;
import io.reactivex.annotations.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.plugins.RxJavaPlugins;
/**
* Represents a hot Maybe-like source and consumer of events similar to Subjects.
* <p>
* All methods are thread safe. Calling onSuccess or onComplete multiple
* times has no effect. Calling onError multiple times relays the Throwable to
* the RxJavaPlugins' error handler.
* <p>
* The MaybeSubject doesn't store the Disposables coming through onSubscribe but
* disposes them once the other onXXX methods were called (terminal state reached).
* <p>History: 2.0.5 - experimental
* @param <T> the value type received and emitted
* @since 2.1
*/
public final class MaybeSubject<T> extends Maybe<T> implements MaybeObserver<T> {
final AtomicReference<MaybeDisposable<T>[]> observers;
@SuppressWarnings("rawtypes")
static final MaybeDisposable[] EMPTY = new MaybeDisposable[0];
@SuppressWarnings("rawtypes")
static final MaybeDisposable[] TERMINATED = new MaybeDisposable[0];
final AtomicBoolean once;
T value;
Throwable error;
/**
* Creates a fresh MaybeSubject.
* @param <T> the value type received and emitted
* @return the new MaybeSubject instance
*/
@CheckReturnValue
public static <T> MaybeSubject<T> create() {
return new MaybeSubject<T>();
}
@SuppressWarnings("unchecked")
MaybeSubject() {
once = new AtomicBoolean();
observers = new AtomicReference<MaybeDisposable<T>[]>(EMPTY);
}
@Override
public void onSubscribe(Disposable d) {
if (observers.get() == TERMINATED) {
d.dispose();
}
}
@SuppressWarnings("unchecked")
@Override
public void onSuccess(T value) {
if (value == null) {
onError(new NullPointerException("Null values are not allowed in 2.x"));
return;
}
if (once.compareAndSet(false, true)) {
this.value = value;
for (MaybeDisposable<T> md : observers.getAndSet(TERMINATED)) {
md.actual.onSuccess(value);
}
}
}
@SuppressWarnings("unchecked")
@Override
public void onError(Throwable e) {
if (e == null) {
e = new NullPointerException("Null errors are not allowed in 2.x");
}
if (once.compareAndSet(false, true)) {
this.error = e;
for (MaybeDisposable<T> md : observers.getAndSet(TERMINATED)) {
md.actual.onError(e);
}
} else {
RxJavaPlugins.onError(e);
}
}
@SuppressWarnings("unchecked")
@Override
public void onComplete() {
if (once.compareAndSet(false, true)) {
for (MaybeDisposable<T> md : observers.getAndSet(TERMINATED)) {
md.actual.onComplete();
}
}
}
@Override
protected void subscribeActual(MaybeObserver<? super T> observer) {
MaybeDisposable<T> md = new MaybeDisposable<T>(observer, this);
observer.onSubscribe(md);
if (add(md)) {
if (md.isDisposed()) {
remove(md);
}
} else {
Throwable ex = error;
if (ex != null) {
observer.onError(ex);
} else {
T v = value;
if (v == null) {
observer.onComplete();
} else {
observer.onSuccess(v);
}
}
}
}
boolean add(MaybeDisposable<T> inner) {
for (;;) {
MaybeDisposable<T>[] a = observers.get();
if (a == TERMINATED) {
return false;
}
int n = a.length;
@SuppressWarnings("unchecked")
MaybeDisposable<T>[] b = new MaybeDisposable[n + 1];
System.arraycopy(a, 0, b, 0, n);
b[n] = inner;
if (observers.compareAndSet(a, b)) {
return true;
}
}
}
@SuppressWarnings("unchecked")
void remove(MaybeDisposable<T> inner) {
for (;;) {
MaybeDisposable<T>[] a = observers.get();
int n = a.length;
if (n == 0) {
return;
}
int j = -1;
for (int i = 0; i < n; i++) {
if (a[i] == inner) {
j = i;
break;
}
}
if (j < 0) {
return;
}
MaybeDisposable<T>[] b;
if (n == 1) {
b = EMPTY;
} else {
b = new MaybeDisposable[n - 1];
System.arraycopy(a, 0, b, 0, j);
System.arraycopy(a, j + 1, b, j, n - j - 1);
}
if (observers.compareAndSet(a, b)) {
return;
}
}
}
/**
* Returns the success value if this MaybeSubject was terminated with a success value.
* @return the success value or null
*/
public T getValue() {
if (observers.get() == TERMINATED) {
return value;
}
return null;
}
/**
* Returns true if this MaybeSubject was terminated with a success value.
* @return true if this MaybeSubject was terminated with a success value
*/
public boolean hasValue() {
return observers.get() == TERMINATED && value != null;
}
/**
* Returns the terminal error if this MaybeSubject has been terminated with an error, null otherwise.
* @return the terminal error or null if not terminated or not with an error
*/
public Throwable getThrowable() {
if (observers.get() == TERMINATED) {
return error;
}
return null;
}
/**
* Returns true if this MaybeSubject has been terminated with an error.
* @return true if this MaybeSubject has been terminated with an error
*/
public boolean hasThrowable() {
return observers.get() == TERMINATED && error != null;
}
/**
* Returns true if this MaybeSubject has been completed.
* @return true if this MaybeSubject has been completed
*/
public boolean hasComplete() {
return observers.get() == TERMINATED && value == null && error == null;
}
/**
* Returns true if this MaybeSubject has observers.
* @return true if this MaybeSubject has observers
*/
public boolean hasObservers() {
return observers.get().length != 0;
}
/**
* Returns the number of current observers.
* @return the number of current observers
*/
/* test */ int observerCount() {
return observers.get().length;
}
static final class MaybeDisposable<T>
extends AtomicReference<MaybeSubject<T>> implements Disposable {
private static final long serialVersionUID = -7650903191002190468L;
final MaybeObserver<? super T> actual;
MaybeDisposable(MaybeObserver<? super T> actual, MaybeSubject<T> parent) {
this.actual = actual;
lazySet(parent);
}
@Override
public void dispose() {
MaybeSubject<T> parent = getAndSet(null);
if (parent != null) {
parent.remove(this);
}
}
@Override
public boolean isDisposed() {
return get() == null;
}
}
}