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/*
* Copyright (c) 2011-2017 Pivotal Software Inc, All Rights Reserved.
*
* 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 reactor.core.publisher;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import org.reactivestreams.Subscription;
import reactor.core.CoreSubscriber;
import reactor.util.annotation.Nullable;
/**
* Emits a single item at most from the source.
*
* @param the value type
*
* @see Reactive-Streams-Commons
*/
final class MonoNext extends MonoFromFluxOperator {
MonoNext(Flux source) {
super(source);
}
@Override
public void subscribe(CoreSubscriber actual) {
source.subscribe(new NextSubscriber<>(actual));
}
static final class NextSubscriber implements InnerOperator {
final CoreSubscriber actual;
Subscription s;
boolean done;
volatile int wip;
@SuppressWarnings("rawtypes")
static final AtomicIntegerFieldUpdater WIP =
AtomicIntegerFieldUpdater.newUpdater(NextSubscriber.class, "wip");
NextSubscriber(CoreSubscriber actual) {
this.actual = actual;
}
@Override
public void onSubscribe(Subscription s) {
if (Operators.validate(this.s, s)) {
this.s = s;
actual.onSubscribe(this);
}
}
@Override
public void onNext(T t) {
if (done) {
Operators.onNextDropped(t, actual.currentContext());
return;
}
s.cancel();
actual.onNext(t);
onComplete();
}
@Override
public void onError(Throwable t) {
if (done) {
Operators.onErrorDropped(t, actual.currentContext());
return;
}
done = true;
actual.onError(t);
}
@Override
public void onComplete() {
if (done) {
return;
}
done = true;
actual.onComplete();
}
@Override
public void request(long n) {
if (WIP.compareAndSet(this, 0, 1)) {
s.request(Long.MAX_VALUE);
}
}
@Override
public void cancel() {
s.cancel();
}
@Override
@Nullable
public Object scanUnsafe(Attr key) {
if (key == Attr.TERMINATED) return done;
if (key == Attr.PARENT) return s;
return InnerOperator.super.scanUnsafe(key);
}
@Override
public CoreSubscriber actual() {
return actual;
}
}
}