io.reactivex.observable.subjects.AsyncSubject Maven / Gradle / Ivy
/**
* 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.observable.subjects;
import java.util.Arrays;
import java.util.concurrent.atomic.AtomicReference;
import io.reactivex.common.*;
import io.reactivex.common.annotations.CheckReturnValue;
import io.reactivex.observable.Observer;
import io.reactivex.observable.internal.observers.DeferredScalarDisposable;
/**
* An Subject that emits the very last value followed by a completion event or the received error to Observers.
*
* The implementation of onXXX methods are technically thread-safe but non-serialized calls
* to them may lead to undefined state in the currently subscribed Observers.
*
* @param the value type
*/
public final class AsyncSubject extends Subject {
@SuppressWarnings("rawtypes")
static final AsyncDisposable[] EMPTY = new AsyncDisposable[0];
@SuppressWarnings("rawtypes")
static final AsyncDisposable[] TERMINATED = new AsyncDisposable[0];
final AtomicReference[]> subscribers;
/** Write before updating subscribers, read after reading subscribers as TERMINATED. */
Throwable error;
/** Write before updating subscribers, read after reading subscribers as TERMINATED. */
T value;
/**
* Creates a new AsyncProcessor.
* @param the value type to be received and emitted
* @return the new AsyncProcessor instance
*/
@CheckReturnValue
public static AsyncSubject create() {
return new AsyncSubject();
}
/**
* Constructs an AsyncSubject.
* @since 2.0
*/
@SuppressWarnings("unchecked")
AsyncSubject() {
this.subscribers = new AtomicReference[]>(EMPTY);
}
@Override
public void onSubscribe(Disposable s) {
if (subscribers.get() == TERMINATED) {
s.dispose();
}
}
@Override
public void onNext(T t) {
if (subscribers.get() == TERMINATED) {
return;
}
if (t == null) {
nullOnNext();
return;
}
value = t;
}
@SuppressWarnings("unchecked")
void nullOnNext() {
value = null;
Throwable ex = new NullPointerException("onNext called with null. Null values are generally not allowed in 2.x operators and sources.");
error = ex;
for (AsyncDisposable as : subscribers.getAndSet(TERMINATED)) {
as.onError(ex);
}
}
@SuppressWarnings("unchecked")
@Override
public void onError(Throwable t) {
if (t == null) {
t = new NullPointerException("onError called with null. Null values are generally not allowed in 2.x operators and sources.");
}
if (subscribers.get() == TERMINATED) {
RxJavaCommonPlugins.onError(t);
return;
}
value = null;
error = t;
for (AsyncDisposable as : subscribers.getAndSet(TERMINATED)) {
as.onError(t);
}
}
@SuppressWarnings("unchecked")
@Override
public void onComplete() {
if (subscribers.get() == TERMINATED) {
return;
}
T v = value;
AsyncDisposable[] array = subscribers.getAndSet(TERMINATED);
if (v == null) {
for (AsyncDisposable as : array) {
as.onComplete();
}
} else {
for (AsyncDisposable as : array) {
as.complete(v);
}
}
}
@Override
public boolean hasObservers() {
return subscribers.get().length != 0;
}
@Override
public boolean hasThrowable() {
return subscribers.get() == TERMINATED && error != null;
}
@Override
public boolean hasComplete() {
return subscribers.get() == TERMINATED && error == null;
}
@Override
public Throwable getThrowable() {
return subscribers.get() == TERMINATED ? error : null;
}
@Override
protected void subscribeActual(Observer s) {
AsyncDisposable as = new AsyncDisposable(s, this);
s.onSubscribe(as);
if (add(as)) {
if (as.isDisposed()) {
remove(as);
}
} else {
Throwable ex = error;
if (ex != null) {
s.onError(ex);
} else {
T v = value;
if (v != null) {
as.complete(v);
} else {
as.onComplete();
}
}
}
}
/**
* Tries to add the given subscriber to the subscribers array atomically
* or returns false if the subject has terminated.
* @param ps the subscriber to add
* @return true if successful, false if the subject has terminated
*/
boolean add(AsyncDisposable ps) {
for (;;) {
AsyncDisposable[] a = subscribers.get();
if (a == TERMINATED) {
return false;
}
int n = a.length;
@SuppressWarnings("unchecked")
AsyncDisposable[] b = new AsyncDisposable[n + 1];
System.arraycopy(a, 0, b, 0, n);
b[n] = ps;
if (subscribers.compareAndSet(a, b)) {
return true;
}
}
}
/**
* Atomically removes the given subscriber if it is subscribed to the subject.
* @param ps the subject to remove
*/
@SuppressWarnings("unchecked")
void remove(AsyncDisposable ps) {
for (;;) {
AsyncDisposable[] a = subscribers.get();
int n = a.length;
if (n == 0) {
return;
}
int j = -1;
for (int i = 0; i < n; i++) {
if (a[i] == ps) {
j = i;
break;
}
}
if (j < 0) {
return;
}
AsyncDisposable[] b;
if (n == 1) {
b = EMPTY;
} else {
b = new AsyncDisposable[n - 1];
System.arraycopy(a, 0, b, 0, j);
System.arraycopy(a, j + 1, b, j, n - j - 1);
}
if (subscribers.compareAndSet(a, b)) {
return;
}
}
}
/**
* Returns true if the subject has any value.
* The method is thread-safe.
* @return true if the subject has any value
*/
public boolean hasValue() {
return subscribers.get() == TERMINATED && value != null;
}
/**
* Returns a single value the Subject currently has or null if no such value exists.
*
The method is thread-safe.
* @return a single value the Subject currently has or null if no such value exists
*/
public T getValue() {
return subscribers.get() == TERMINATED ? value : null;
}
/**
* Returns an Object array containing snapshot all values of the Subject.
*
The method is thread-safe.
* @return the array containing the snapshot of all values of the Subject
*/
public Object[] getValues() {
T v = getValue();
return v != null ? new Object[] { v } : new Object[0];
}
/**
* Returns a typed array containing a snapshot of all values of the Subject.
*
The method follows the conventions of Collection.toArray by setting the array element
* after the last value to null (if the capacity permits).
*
The method is thread-safe.
* @param array the target array to copy values into if it fits
* @return the given array if the values fit into it or a new array containing all values
*/
public T[] getValues(T[] array) {
T v = getValue();
if (v == null) {
if (array.length != 0) {
array[0] = null;
}
return array;
}
if (array.length == 0) {
array = Arrays.copyOf(array, 1);
}
array[0] = v;
if (array.length != 1) {
array[1] = null;
}
return array;
}
static final class AsyncDisposable extends DeferredScalarDisposable {
private static final long serialVersionUID = 5629876084736248016L;
final AsyncSubject parent;
AsyncDisposable(Observer actual, AsyncSubject parent) {
super(actual);
this.parent = parent;
}
@Override
public void dispose() {
if (super.tryDispose()) {
parent.remove(this);
}
}
void onComplete() {
if (!isDisposed()) {
actual.onComplete();
}
}
void onError(Throwable t) {
if (isDisposed()) {
RxJavaCommonPlugins.onError(t);
} else {
actual.onError(t);
}
}
}
}