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/*
* Copyright (c) 2018-2023 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.Arrays;
import java.util.Comparator;
import java.util.Objects;
import java.util.Queue;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import java.util.concurrent.atomic.AtomicLongFieldUpdater;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
import org.reactivestreams.Publisher;
import org.reactivestreams.Subscriber;
import org.reactivestreams.Subscription;
import reactor.core.CoreSubscriber;
import reactor.core.Exceptions;
import reactor.util.annotation.Nullable;
import reactor.util.concurrent.Queues;
import reactor.util.context.Context;
/**
* Merges the provided sources {@link org.reactivestreams.Publisher}, assuming a total order
* of the values, by picking the smallest available value from each publisher, resulting in
* a single totally ordered {@link Flux} sequence. This operator considers its primary
* parent to be the first of the sources, for the purpose of {@link reactor.core.Scannable.Attr#PARENT}.
*
* @param the value type
* @author David Karnok
* @author Simon Baslé
*/
//source: https://akarnokd.blogspot.fr/2017/09/java-9-flow-api-ordered-merge.html
final class FluxMergeComparing extends Flux implements SourceProducer {
final int prefetch;
final Comparator valueComparator;
final Publisher[] sources;
final boolean delayError;
final boolean waitForAllSources;
@SafeVarargs
FluxMergeComparing(int prefetch, Comparator valueComparator, boolean delayError,
boolean waitForAllSources, Publisher... sources) {
if (prefetch <= 0) {
throw new IllegalArgumentException("prefetch > 0 required but it was " + prefetch);
}
this.sources = Objects.requireNonNull(sources, "sources must be non-null");
for (int i = 0; i < sources.length; i++) {
Publisher source = sources[i];
if (source == null) {
throw new NullPointerException("sources[" + i + "] is null");
}
}
Operators.toFluxOrMono(this.sources);
this.prefetch = prefetch;
this.valueComparator = valueComparator;
this.delayError = delayError;
this.waitForAllSources = waitForAllSources;
}
/**
* Returns a new instance which has the additional source to be merged together with
* the current array of sources. The provided {@link Comparator} is tested for equality
* with the current comparator, and if different is combined by {@link Comparator#thenComparing(Comparator)}.
*
* This operation doesn't change the current {@link FluxMergeComparing} instance.
*
* @param source the new source to merge with the others
* @return the new {@link FluxMergeComparing} instance
*/
FluxMergeComparing mergeAdditionalSource(Publisher source, Comparator otherComparator) {
int n = sources.length;
@SuppressWarnings("unchecked")
Publisher[] newArray = new Publisher[n + 1];
System.arraycopy(sources, 0, newArray, 0, n);
newArray[n] = source;
if (!valueComparator.equals(otherComparator)) {
@SuppressWarnings("unchecked")
Comparator currentComparator = (Comparator) this.valueComparator;
final Comparator newComparator = currentComparator.thenComparing(otherComparator);
return new FluxMergeComparing<>(prefetch, newComparator, delayError, waitForAllSources, newArray);
}
return new FluxMergeComparing<>(prefetch, valueComparator, delayError, waitForAllSources, newArray);
}
@Override
public int getPrefetch() {
return prefetch;
}
@Override
@Nullable
public Object scanUnsafe(Attr key) {
if (key == Attr.PARENT) return sources.length > 0 ? sources[0] : null;
if (key == Attr.PREFETCH) return prefetch;
if (key == Attr.DELAY_ERROR) return delayError;
if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC;
return SourceProducer.super.scanUnsafe(key);
}
@Override
public void subscribe(CoreSubscriber actual) {
MergeOrderedMainProducer main = new MergeOrderedMainProducer<>(actual, valueComparator, prefetch, sources.length, delayError, waitForAllSources);
actual.onSubscribe(main);
main.subscribe(sources);
}
static final class MergeOrderedMainProducer implements InnerProducer {
static final Object DONE = new Object();
final CoreSubscriber actual;
final MergeOrderedInnerSubscriber[] subscribers;
final Comparator comparator;
final Object[] values;
final boolean delayError;
final boolean waitForAllSources;
boolean done;
volatile Throwable error;
static final AtomicReferenceFieldUpdater ERROR =
AtomicReferenceFieldUpdater.newUpdater(MergeOrderedMainProducer.class, Throwable.class, "error");
volatile int cancelled;
static final AtomicIntegerFieldUpdater CANCELLED =
AtomicIntegerFieldUpdater.newUpdater(MergeOrderedMainProducer.class, "cancelled");
volatile long requested;
static final AtomicLongFieldUpdater REQUESTED =
AtomicLongFieldUpdater.newUpdater(MergeOrderedMainProducer.class, "requested");
volatile long emitted;
static final AtomicLongFieldUpdater EMITTED =
AtomicLongFieldUpdater.newUpdater(MergeOrderedMainProducer.class, "emitted");
volatile int wip;
static final AtomicIntegerFieldUpdater WIP =
AtomicIntegerFieldUpdater.newUpdater(MergeOrderedMainProducer.class, "wip");
MergeOrderedMainProducer(CoreSubscriber actual,
Comparator comparator, int prefetch, int n, boolean delayError, boolean waitForAllSources) {
this.actual = actual;
this.comparator = comparator;
this.delayError = delayError;
this.waitForAllSources = waitForAllSources;
@SuppressWarnings("unchecked")
MergeOrderedInnerSubscriber[] mergeOrderedInnerSub =
new MergeOrderedInnerSubscriber[n];
this.subscribers = mergeOrderedInnerSub;
for (int i = 0; i < n; i++) {
this.subscribers[i] = new MergeOrderedInnerSubscriber<>(this, prefetch);
}
this.values = new Object[n];
}
void subscribe(Publisher[] sources) {
if (sources.length != subscribers.length) {
throw new IllegalArgumentException("must subscribe with " + subscribers.length + " sources");
}
for (int i = 0; i < sources.length; i++) {
Objects.requireNonNull(sources[i], "subscribed with a null source: sources[" + i + "]");
sources[i].subscribe(subscribers[i]);
}
}
@Override
public CoreSubscriber actual() {
return this.actual;
}
@Override
public void request(long n) {
Operators.addCap(REQUESTED, this, n);
drain();
}
@Override
public void cancel() {
if (CANCELLED.compareAndSet(this, 0, 1)) {
for (MergeOrderedInnerSubscriber subscriber : subscribers) {
subscriber.cancel();
}
if (WIP.getAndIncrement(this) == 0) {
discardData();
}
}
}
void onInnerError(MergeOrderedInnerSubscriber inner, Throwable ex) {
Throwable e = Operators.onNextInnerError(ex, actual().currentContext(), this);
if (e != null) {
if (Exceptions.addThrowable(ERROR, this, e)) {
if (!delayError) {
done = true;
}
inner.done = true;
drain();
}
else {
inner.done = true;
Operators.onErrorDropped(e, actual.currentContext());
}
}
else {
inner.done = true;
drain();
}
}
void drain() {
if (WIP.getAndIncrement(this) != 0) {
return;
}
int missed = 1;
CoreSubscriber actual = this.actual;
Comparator comparator = this.comparator;
MergeOrderedInnerSubscriber[] subscribers = this.subscribers;
int n = subscribers.length;
Object[] values = this.values;
long e = emitted;
for (;;) {
long r = requested;
for (;;) {
boolean d = this.done;
if (cancelled != 0) {
Arrays.fill(values, null);
for (MergeOrderedInnerSubscriber inner : subscribers) {
inner.queue.clear();
}
return;
}
int innerDoneCount = 0;
int nonEmpty = 0;
for (int i = 0; i < n; i++) {
Object o = values[i];
if (o == DONE) {
innerDoneCount++;
nonEmpty++;
}
else if (o == null) {
boolean innerDone = subscribers[i].done;
o = subscribers[i].queue.poll();
if (o != null) {
values[i] = o;
nonEmpty++;
}
else if (innerDone) {
values[i] = DONE;
innerDoneCount++;
nonEmpty++;
}
}
else {
nonEmpty++;
}
}
if (checkTerminated(d || innerDoneCount == n, actual)) {
return;
}
if ((waitForAllSources && nonEmpty != n) || (!waitForAllSources && (nonEmpty == 0 || nonEmpty == innerDoneCount)) || e >= r) {
break;
}
T min = null;
int minIndex = -1;
int i = 0;
for (Object o : values) {
if (o != DONE && o != null) {
boolean smaller;
try {
@SuppressWarnings("unchecked")
T t = (T) o;
smaller = min == null || comparator.compare(min, t) > 0;
} catch (Throwable ex) {
Exceptions.addThrowable(ERROR, this, ex);
cancel();
actual.onError(Exceptions.terminate(ERROR, this));
return;
}
if (smaller) {
@SuppressWarnings("unchecked")
T t = (T) o;
min = t;
minIndex = i;
}
}
i++;
}
if (minIndex >= 0) {
values[minIndex] = null;
actual.onNext(min);
e++;
subscribers[minIndex].request(1);
}
}
this.emitted = e;
missed = WIP.addAndGet(this, -missed);
if (missed == 0) {
break;
}
}
}
boolean checkTerminated(boolean d, Subscriber a) {
if (cancelled != 0) {
discardData();
return true;
}
if (!d) {
return false;
}
if (delayError) {
Throwable e = error;
if (e != null && e != Exceptions.TERMINATED) {
e = Exceptions.terminate(ERROR, this);
a.onError(e);
}
else {
a.onComplete();
}
}
else {
Throwable e = error;
if (e != null && e != Exceptions.TERMINATED) {
e = Exceptions.terminate(ERROR, this);
cancel();
discardData();
a.onError(e);
}
else {
a.onComplete();
}
}
return true;
}
private void discardData() {
Context ctx = actual().currentContext();
for (Object v : values) {
if (v != DONE) {
Operators.onDiscard(v, ctx);
}
}
Arrays.fill(values, null);
for (MergeOrderedInnerSubscriber subscriber : subscribers) {
Operators.onDiscardQueueWithClear(subscriber.queue, ctx, null);
}
}
@Override
public Object scanUnsafe(Attr key) {
if (key == Attr.ACTUAL) return actual;
if (key == Attr.CANCELLED) return this.cancelled > 0;
if (key == Attr.ERROR) return this.error;
if (key == Attr.DELAY_ERROR) return delayError;
if (key == Attr.REQUESTED_FROM_DOWNSTREAM) return requested - emitted;
if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC;
return InnerProducer.super.scanUnsafe(key);
}
}
static final class MergeOrderedInnerSubscriber implements InnerOperator {
final MergeOrderedMainProducer parent;
final int prefetch;
final int limit;
final Queue queue;
int consumed;
volatile boolean done;
volatile Subscription s;
@SuppressWarnings("rawtypes")
static final AtomicReferenceFieldUpdater S =
AtomicReferenceFieldUpdater.newUpdater(MergeOrderedInnerSubscriber.class, Subscription.class, "s");
MergeOrderedInnerSubscriber(MergeOrderedMainProducer parent, int prefetch) {
this.parent = parent;
this.prefetch = prefetch;
this.limit = prefetch - (prefetch >> 2);
this.queue = Queues.get(prefetch).get();
}
@Override
public void onSubscribe(Subscription s) {
if (Operators.setOnce(S, this, s)) {
s.request(prefetch);
}
}
@Override
public void onNext(T item) {
if (parent.done || done) {
Operators.onNextDropped(item, actual().currentContext());
return;
}
queue.offer(item);
parent.drain();
}
@Override
public void onError(Throwable throwable) {
parent.onInnerError(this, throwable);
}
@Override
public void onComplete() {
done = true;
parent.drain();
}
/**
* @param n is ignored and considered to be 1
*/
@Override
public void request(long n) {
int c = consumed + 1;
if (c == limit) {
consumed = 0;
Subscription sub = s;
if (sub != this) {
sub.request(c);
}
}
else {
consumed = c;
}
}
@Override
public void cancel() {
Subscription sub = S.getAndSet(this, this);
if (sub != null && sub != this) {
sub.cancel();
}
}
@Override
public CoreSubscriber actual() {
return parent.actual; //TODO check
}
@Override
@Nullable
public Object scanUnsafe(Attr key){
if (key == Attr.ACTUAL) return parent; //TODO does that check out?
if (key == Attr.PARENT) return s;
if (key == Attr.PREFETCH) return prefetch;
if (key == Attr.TERMINATED) return done;
if (key == Attr.BUFFERED) return queue.size();
if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC;
return InnerOperator.super.scanUnsafe(key);
}
}
}