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/*
* Copyright (c) 2016-2021 VMware Inc. or its affiliates, 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
*
* https://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.Objects;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
import java.util.function.BiFunction;
import java.util.stream.Stream;
import org.reactivestreams.Publisher;
import org.reactivestreams.Subscription;
import reactor.core.CoreSubscriber;
import reactor.core.Scannable;
import reactor.util.annotation.Nullable;
import reactor.util.context.Context;
import static reactor.core.Scannable.Attr.RUN_STYLE;
import static reactor.core.Scannable.Attr.RunStyle.SYNC;
/**
* Combines values from a main Publisher with values from another
* Publisher through a bi-function and emits the result.
*
*
* The operator will drop values from the main source until the other
* Publisher produces any value.
*
* If the other Publisher completes without any value, the sequence is completed.
*
* @param the main source type
* @param the alternate source type
* @param the output type
*
* @see Reactive-Streams-Commons
*/
final class FluxWithLatestFrom extends InternalFluxOperator {
final Publisher other;
final BiFunction combiner;
FluxWithLatestFrom(Flux source,
Publisher other,
BiFunction combiner) {
super(source);
this.other = Objects.requireNonNull(other, "other");
this.combiner = Objects.requireNonNull(combiner, "combiner");
}
@Override
public CoreSubscriber subscribeOrReturn(CoreSubscriber actual) {
CoreSubscriber serial = Operators.serialize(actual);
WithLatestFromSubscriber main =
new WithLatestFromSubscriber<>(serial, combiner);
WithLatestFromOtherSubscriber secondary =
new WithLatestFromOtherSubscriber<>(main);
other.subscribe(secondary);
return main;
}
@Override
public Object scanUnsafe(Attr key) {
if (key == RUN_STYLE) return SYNC;
return super.scanUnsafe(key);
}
static final class WithLatestFromSubscriber implements InnerOperator {
final CoreSubscriber actual;
final BiFunction combiner;
volatile Subscription main;
@SuppressWarnings("rawtypes")
static final AtomicReferenceFieldUpdater
MAIN =
AtomicReferenceFieldUpdater.newUpdater(WithLatestFromSubscriber.class,
Subscription.class,
"main");
volatile Subscription other;
@SuppressWarnings("rawtypes")
static final AtomicReferenceFieldUpdater
OTHER =
AtomicReferenceFieldUpdater.newUpdater(WithLatestFromSubscriber.class,
Subscription.class,
"other");
volatile U otherValue;
WithLatestFromSubscriber(CoreSubscriber actual,
BiFunction combiner) {
this.actual = actual;
this.combiner = combiner;
}
void setOther(Subscription s) {
if (!OTHER.compareAndSet(this, null, s)) {
s.cancel();
if (other != Operators.cancelledSubscription()) {
Operators.reportSubscriptionSet();
}
}
}
@Override
public CoreSubscriber actual() {
return actual;
}
@Override
@Nullable
public Object scanUnsafe(Attr key) {
if (key == Attr.CANCELLED) return main == Operators.cancelledSubscription();
if (key == Attr.PARENT) return main;
if (key == RUN_STYLE) return SYNC;
return InnerOperator.super.scanUnsafe(key);
}
@Override
public Stream inners() {
return Stream.of(Scannable.from(other));
}
@Override
public void request(long n) {
main.request(n);
}
void cancelMain() {
Subscription s = main;
if (s != Operators.cancelledSubscription()) {
s = MAIN.getAndSet(this, Operators.cancelledSubscription());
if (s != null && s != Operators.cancelledSubscription()) {
s.cancel();
}
}
}
void cancelOther() {
Subscription s = other;
if (s != Operators.cancelledSubscription()) {
s = OTHER.getAndSet(this, Operators.cancelledSubscription());
if (s != null && s != Operators.cancelledSubscription()) {
s.cancel();
}
}
}
@Override
public void cancel() {
cancelMain();
cancelOther();
}
@Override
public void onSubscribe(Subscription s) {
if (!MAIN.compareAndSet(this, null, s)) {
s.cancel();
if (main != Operators.cancelledSubscription()) {
Operators.reportSubscriptionSet();
}
}
else {
actual.onSubscribe(this);
}
}
@Override
public void onNext(T t) {
U u = otherValue;
if (u != null) {
R r;
try {
r = Objects.requireNonNull(combiner.apply(t, u),
"The combiner returned a null value");
}
catch (Throwable e) {
onError(Operators.onOperatorError(this, e, t, actual.currentContext()));
return;
}
actual.onNext(r);
}
else {
main.request(1);
}
}
@Override
public void onError(Throwable t) {
if (main == null) {
if (MAIN.compareAndSet(this, null, Operators.cancelledSubscription())) {
cancelOther();
Operators.error(actual, t);
return;
}
}
cancelOther();
otherValue = null;
actual.onError(t);
}
@Override
public void onComplete() {
cancelOther();
otherValue = null;
actual.onComplete();
}
void otherError(Throwable t) {
if (main == null) {
if (MAIN.compareAndSet(this, null, Operators.cancelledSubscription())) {
cancelMain();
Operators.error(actual, t);
return;
}
}
cancelMain();
otherValue = null;
actual.onError(t);
}
void otherComplete() {
if (otherValue == null) {
if (main == null) {
if (MAIN.compareAndSet(this,
null,
Operators.cancelledSubscription())) {
cancelMain();
Operators.complete(actual);
return;
}
}
cancelMain();
actual.onComplete();
}
}
}
static final class WithLatestFromOtherSubscriber implements InnerConsumer {
final WithLatestFromSubscriber main;
WithLatestFromOtherSubscriber(WithLatestFromSubscriber main) {
this.main = main;
}
@Override
public void onSubscribe(Subscription s) {
main.setOther(s);
s.request(Long.MAX_VALUE);
}
@Override
@Nullable
public Object scanUnsafe(Attr key) {
if (key == Attr.ACTUAL) {
return main;
}
if (key == RUN_STYLE) {
return SYNC;
}
return null;
}
@Override
public Context currentContext() {
return main.currentContext();
}
@Override
public void onNext(U t) {
main.otherValue = t;
}
@Override
public void onError(Throwable t) {
main.otherError(t);
}
@Override
public void onComplete() {
main.otherComplete();
}
}
}