io.reactivex.rxjava3.internal.operators.completable.CompletableCache Maven / Gradle / Ivy
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/*
* 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.rxjava3.internal.operators.completable;
import java.util.concurrent.atomic.*;
import io.reactivex.rxjava3.core.*;
import io.reactivex.rxjava3.disposables.Disposable;
/**
* Consume the upstream source exactly once and cache its terminal event.
* History: 2.0.4 - experimental
* @since 2.1
*/
public final class CompletableCache extends Completable implements CompletableObserver {
static final InnerCompletableCache[] EMPTY = new InnerCompletableCache[0];
static final InnerCompletableCache[] TERMINATED = new InnerCompletableCache[0];
final CompletableSource source;
final AtomicReference observers;
final AtomicBoolean once;
Throwable error;
public CompletableCache(CompletableSource source) {
this.source = source;
this.observers = new AtomicReference<>(EMPTY);
this.once = new AtomicBoolean();
}
@Override
protected void subscribeActual(CompletableObserver observer) {
InnerCompletableCache inner = new InnerCompletableCache(observer);
observer.onSubscribe(inner);
if (add(inner)) {
if (inner.isDisposed()) {
remove(inner);
}
if (once.compareAndSet(false, true)) {
source.subscribe(this);
}
} else {
Throwable ex = error;
if (ex != null) {
observer.onError(ex);
} else {
observer.onComplete();
}
}
}
@Override
public void onSubscribe(Disposable d) {
// not used
}
@Override
public void onError(Throwable e) {
error = e;
for (InnerCompletableCache inner : observers.getAndSet(TERMINATED)) {
if (!inner.get()) {
inner.downstream.onError(e);
}
}
}
@Override
public void onComplete() {
for (InnerCompletableCache inner : observers.getAndSet(TERMINATED)) {
if (!inner.get()) {
inner.downstream.onComplete();
}
}
}
boolean add(InnerCompletableCache inner) {
for (;;) {
InnerCompletableCache[] a = observers.get();
if (a == TERMINATED) {
return false;
}
int n = a.length;
InnerCompletableCache[] b = new InnerCompletableCache[n + 1];
System.arraycopy(a, 0, b, 0, n);
b[n] = inner;
if (observers.compareAndSet(a, b)) {
return true;
}
}
}
void remove(InnerCompletableCache inner) {
for (;;) {
InnerCompletableCache[] 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;
}
InnerCompletableCache[] b;
if (n == 1) {
b = EMPTY;
} else {
b = new InnerCompletableCache[n - 1];
System.arraycopy(a, 0, b, 0, j);
System.arraycopy(a, j + 1, b, j, n - j - 1);
}
if (observers.compareAndSet(a, b)) {
break;
}
}
}
final class InnerCompletableCache
extends AtomicBoolean
implements Disposable {
private static final long serialVersionUID = 8943152917179642732L;
final CompletableObserver downstream;
InnerCompletableCache(CompletableObserver downstream) {
this.downstream = downstream;
}
@Override
public boolean isDisposed() {
return get();
}
@Override
public void dispose() {
if (compareAndSet(false, true)) {
remove(this);
}
}
}
}