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/*
* Copyright (c) 2017-2021 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.AtomicIntegerFieldUpdater;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
import java.util.function.Function;
import java.util.stream.Stream;
import org.reactivestreams.Subscription;
import reactor.core.CoreSubscriber;
import reactor.core.Fuseable;
import reactor.core.Scannable;
import reactor.util.annotation.Nullable;
import reactor.util.context.Context;
/**
* Shares a {@link Mono} for the duration of a function that may transform it and
* consume it as many times as necessary without causing multiple subscriptions
* to the upstream.
*
* @param the source value type
* @param the output value type
*
* @see Reactive-Streams-Commons
*/
final class MonoPublishMulticast extends InternalMonoOperator implements Fuseable {
final Function, ? extends Mono> transform;
MonoPublishMulticast(Mono source,
Function, ? extends Mono> transform) {
super(source);
this.transform = Objects.requireNonNull(transform, "transform");
}
@Override
public CoreSubscriber subscribeOrReturn(CoreSubscriber actual) {
MonoPublishMulticaster multicast = new MonoPublishMulticaster<>(actual.currentContext());
Mono out = Objects.requireNonNull(transform.apply(fromDirect(multicast)),
"The transform returned a null Mono");
if (out instanceof Fuseable) {
out.subscribe(new FluxPublishMulticast.CancelFuseableMulticaster<>(actual, multicast));
}
else {
out.subscribe(new FluxPublishMulticast.CancelMulticaster<>(actual, multicast));
}
return multicast;
}
@Override
public Object scanUnsafe(Attr key) {
if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC;
return super.scanUnsafe(key);
}
static final class MonoPublishMulticaster extends Mono
implements InnerConsumer, FluxPublishMulticast.PublishMulticasterParent {
volatile Subscription s;
static final AtomicReferenceFieldUpdater S =
AtomicReferenceFieldUpdater.newUpdater(MonoPublishMulticaster.class,
Subscription.class,
"s");
volatile int wip;
static final AtomicIntegerFieldUpdater WIP =
AtomicIntegerFieldUpdater.newUpdater(MonoPublishMulticaster.class, "wip");
volatile PublishMulticastInner[] subscribers;
@SuppressWarnings("rawtypes")
static final AtomicReferenceFieldUpdater SUBSCRIBERS =
AtomicReferenceFieldUpdater.newUpdater(MonoPublishMulticaster.class, PublishMulticastInner[].class, "subscribers");
@SuppressWarnings("rawtypes")
static final PublishMulticastInner[] EMPTY = new PublishMulticastInner[0];
@SuppressWarnings("rawtypes")
static final PublishMulticastInner[] TERMINATED = new PublishMulticastInner[0];
volatile boolean done;
@Nullable
T value;
Throwable error;
volatile boolean connected;
final Context context;
@SuppressWarnings("unchecked")
MonoPublishMulticaster(Context ctx) {
SUBSCRIBERS.lazySet(this, EMPTY);
this.context = ctx;
}
@Override
@Nullable
public Object scanUnsafe(Attr key) {
if (key == Attr.PARENT) {
return s;
}
if (key == Attr.ERROR) {
return error;
}
if (key == Attr.CANCELLED) {
return s == Operators.cancelledSubscription();
}
if (key == Attr.TERMINATED) {
return done;
}
if (key == Attr.PREFETCH) {
return 1;
}
if (key == Attr.BUFFERED) {
return value != null ? 1 : 0;
}
if (key == Attr.RUN_STYLE) {
return Attr.RunStyle.SYNC;
}
return null;
}
@Override
public Stream inners() {
return Stream.of(subscribers);
}
@Override
public Context currentContext() {
return context;
}
@Override
public void subscribe(CoreSubscriber actual) {
PublishMulticastInner pcs = new PublishMulticastInner<>(this, actual);
actual.onSubscribe(pcs);
if (add(pcs)) {
if (pcs.cancelled == 1) {
remove(pcs);
return;
}
drain();
}
else {
Throwable ex = error;
if (ex != null) {
actual.onError(ex);
}
else {
actual.onComplete();
}
}
}
@Override
public void onSubscribe(Subscription s) {
if (Operators.setOnce(S, this, s)) {
connected = true;
s.request(Long.MAX_VALUE);
}
}
@Override
public void onNext(T t) {
if (done) {
Operators.onNextDropped(t, context);
return;
}
value = t;
done = true;
drain();
}
@Override
public void onError(Throwable t) {
if (done) {
Operators.onErrorDropped(t, context);
return;
}
error = t;
done = true;
drain();
}
@Override
public void onComplete() {
done = true;
drain();
}
void drain() {
if (WIP.getAndIncrement(this) != 0) {
return;
}
int missed = 1;
for (; ; ) {
if (connected) {
if (s == Operators.cancelledSubscription()) {
value = null;
return;
}
final T v = value;
PublishMulticastInner[] a = subscribers;
int n = a.length;
if (n != 0) {
if (s == Operators.cancelledSubscription()) {
value = null;
return;
}
@SuppressWarnings("unchecked")
PublishMulticastInner[] castedArray = SUBSCRIBERS.getAndSet(this, TERMINATED);
a = castedArray;
n = a.length;
Throwable ex = error;
if (ex != null) {
for (int i = 0; i < n; i++) {
a[i].actual.onError(ex);
}
}
else if (v == null) {
for (int i = 0; i < n; i++) {
a[i].actual.onComplete();
}
}
else {
for (int i = 0; i < n; i++) {
a[i].actual.onNext(v);
a[i].actual.onComplete();
}
value = null;
}
return;
}
}
missed = WIP.addAndGet(this, -missed);
if (missed == 0) {
break;
}
}
}
boolean add(PublishMulticastInner s) {
for (; ; ) {
PublishMulticastInner[] a = subscribers;
if (a == TERMINATED) {
return false;
}
int n = a.length;
@SuppressWarnings("unchecked")
PublishMulticastInner[] b = new PublishMulticastInner[n + 1];
System.arraycopy(a, 0, b, 0, n);
b[n] = s;
if (SUBSCRIBERS.compareAndSet(this, a, b)) {
return true;
}
}
}
@SuppressWarnings("unchecked")
void remove(PublishMulticastInner s) {
for (; ; ) {
PublishMulticastInner[] a = subscribers;
if (a == TERMINATED || a == EMPTY) {
return;
}
int n = a.length;
int j = -1;
for (int i = 0; i < n; i++) {
if (a[i] == s) {
j = i;
break;
}
}
if (j < 0) {
return;
}
PublishMulticastInner[] b;
if (n == 1) {
b = EMPTY;
}
else {
b = new PublishMulticastInner[n - 1];
System.arraycopy(a, 0, b, 0, j);
System.arraycopy(a, j + 1, b, j, n - j - 1);
}
if (SUBSCRIBERS.compareAndSet(this, a, b)) {
return;
}
}
}
@Override
public void terminate() {
Operators.terminate(S, this);
if (WIP.getAndIncrement(this) == 0) {
if (connected) {
value = null;
}
}
}
}
static final class PublishMulticastInner implements InnerProducer {
final MonoPublishMulticaster parent;
final CoreSubscriber actual;
volatile int cancelled;
static final AtomicIntegerFieldUpdater CANCELLED = AtomicIntegerFieldUpdater.newUpdater(PublishMulticastInner.class, "cancelled");
PublishMulticastInner(MonoPublishMulticaster parent,
CoreSubscriber actual) {
this.parent = parent;
this.actual = actual;
}
@Override
@Nullable
public Object scanUnsafe(Attr key) {
if (key == Attr.PARENT) {
return parent;
}
if (key == Attr.CANCELLED) {
return cancelled == 1;
}
if (key == Attr.RUN_STYLE) {
return Attr.RunStyle.SYNC;
}
return InnerProducer.super.scanUnsafe(key);
}
@Override
public CoreSubscriber actual() {
return actual;
}
@Override
public void request(long n) {
if (Operators.validate(n)) {
parent.drain();
}
}
@Override
public void cancel() {
if (CANCELLED.compareAndSet(this, 0, 1)) {
parent.remove(this);
parent.drain();
}
}
}
}
