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rxjava2-extensions developed by David Karnok
/*
* Copyright 2016-2018 David Karnok
*
* 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 hu.akarnokd.rxjava2.operators;
import java.util.Arrays;
import java.util.Comparator;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import org.reactivestreams.Publisher;
import org.reactivestreams.Subscriber;
import org.reactivestreams.Subscription;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.internal.fuseable.SimpleQueue;
import io.reactivex.internal.subscribers.InnerQueuedSubscriber;
import io.reactivex.internal.subscribers.InnerQueuedSubscriberSupport;
import io.reactivex.internal.subscriptions.EmptySubscription;
import io.reactivex.internal.subscriptions.SubscriptionHelper;
import io.reactivex.internal.util.AtomicThrowable;
import io.reactivex.internal.util.BackpressureHelper;
import io.reactivex.parallel.ParallelFlowable;
import io.reactivex.plugins.RxJavaPlugins;
/**
* Subscription coordinator that merges items from a fixed set of source Publishers by
* picking the smallest available next item from them based on a Comparator.
*
* @param the value type
* @since 0.17.9
*/
public final class BasicMergeSubscription
extends AtomicInteger
implements Subscription, InnerQueuedSubscriberSupport {
private static final long serialVersionUID = -8467324377226330554L;
final Subscriber actual;
final Comparator comparator;
final InnerQueuedSubscriber[] subscribers;
final boolean delayErrors;
final AtomicThrowable errors;
final AtomicLong requested;
final Object[] latest;
volatile boolean cancelled;
@SuppressWarnings("unchecked")
public BasicMergeSubscription(Subscriber actual, Comparator comparator, int n, int prefetch, boolean delayErrors) {
this.actual = actual;
this.comparator = comparator;
this.delayErrors = delayErrors;
InnerQueuedSubscriber[] subs = new InnerQueuedSubscriber[n];
for (int i = 0; i < n; i++) {
subs[i] = new InnerQueuedSubscriber(this, prefetch);
}
this.subscribers = subs;
this.requested = new AtomicLong();
this.errors = new AtomicThrowable();
this.latest = new Object[n];
}
public void subscribe(Publisher[] sources, int n) {
InnerQueuedSubscriber[] subs = subscribers;
for (int i = 0; i < n && !cancelled; i++) {
Publisher p = sources[i];
if (p != null) {
p.subscribe(subs[i]);
} else {
EmptySubscription.error(new NullPointerException("The " + i + "th source is null"), subs[i]);
if (!delayErrors) {
break;
}
}
}
}
public void subscribe(ParallelFlowable source) {
source.subscribe(subscribers);
}
@Override
public void request(long n) {
if (SubscriptionHelper.validate(n)) {
BackpressureHelper.add(requested, n);
drain();
}
}
void cancelSources() {
for (InnerQueuedSubscriber d : subscribers) {
d.cancel();
}
}
void clearSources() {
Arrays.fill(latest, this);
for (InnerQueuedSubscriber d : subscribers) {
SimpleQueue q = d.queue();
if (q != null) {
q.clear();
}
}
}
void cancelAndClearSources() {
Arrays.fill(latest, this);
for (InnerQueuedSubscriber d : subscribers) {
d.cancel();
SimpleQueue q = d.queue();
if (q != null) {
q.clear();
}
}
}
@Override
public void cancel() {
if (!cancelled) {
cancelled = true;
cancelSources();
if (getAndIncrement() == 0) {
clearSources();
}
}
}
@Override
public void innerNext(InnerQueuedSubscriber inner, T value) {
inner.queue().offer(value);
drain();
}
@Override
public void innerError(InnerQueuedSubscriber inner, Throwable e) {
if (errors.addThrowable(e)) {
if (!delayErrors) {
cancelSources();
} else {
inner.setDone();
}
drain();
} else {
RxJavaPlugins.onError(e);
}
}
@Override
public void innerComplete(InnerQueuedSubscriber inner) {
inner.setDone();
drain();
}
@SuppressWarnings("unchecked")
@Override
public void drain() {
if (getAndIncrement() != 0) {
return;
}
int missed = 1;
Subscriber a = actual;
AtomicThrowable err = errors;
InnerQueuedSubscriber[] subs = subscribers;
int n = subs.length;
Object[] latest = this.latest;
Comparator comp = comparator;
for (;;) {
long r = requested.get();
long e = 0L;
while (e != r) {
if (cancelled) {
clearSources();
return;
}
if (!delayErrors && err.get() != null) {
cancelAndClearSources();
a.onError(err.terminate());
return;
}
boolean d = true;
int hasValue = 0;
boolean empty = true;
T smallest = null;
int pick = -1;
for (int i = 0; i < n; i++) {
InnerQueuedSubscriber inner = subs[i];
boolean innerDone = inner.isDone();
if (!innerDone) {
d = false;
}
Object v = latest[i];
if (v == null) {
SimpleQueue q = inner.queue();
try {
v = q != null ? q.poll() : null;
} catch (Throwable ex) {
Exceptions.throwIfFatal(ex);
err.addThrowable(ex);
inner.setDone();
if (!delayErrors) {
cancelAndClearSources();
a.onError(err.terminate());
return;
}
v = this;
}
if (v != null) {
latest[i] = v;
hasValue++;
empty = false;
} else
if (innerDone) {
latest[i] = this;
hasValue++;
}
} else {
hasValue++;
if (v != this) {
empty = false;
}
}
if (v != null && v != this) {
boolean smaller;
try {
if (smallest != null) {
smaller = comp.compare(smallest, (T)v) > 0;
} else {
smaller = true;
}
} catch (Throwable ex) {
Exceptions.throwIfFatal(ex);
err.addThrowable(ex);
cancelAndClearSources();
a.onError(err.terminate());
return;
}
if (smaller) {
smallest = (T)v;
pick = i;
}
}
}
if (hasValue == n && pick >= 0) {
a.onNext(smallest);
latest[pick] = null;
subs[pick].requestOne();
e++;
} else {
if (d && empty) {
if (err.get() != null) {
a.onError(err.terminate());
} else {
a.onComplete();
}
return;
}
break;
}
}
if (e == r) {
if (cancelled) {
clearSources();
return;
}
if (!delayErrors && err.get() != null) {
cancelAndClearSources();
a.onError(err.terminate());
return;
}
boolean d = true;
boolean empty = true;
for (int i = 0; i < subs.length; i++) {
InnerQueuedSubscriber inner = subs[i];
if (!inner.isDone()) {
d = false;
break;
}
Object o = latest[i];
SimpleQueue q = inner.queue();
if (o == null && q != null) {
try {
o = q.poll();
} catch (Throwable ex) {
Exceptions.throwIfFatal(ex);
err.addThrowable(ex);
if (!delayErrors) {
cancelAndClearSources();
a.onError(ex);
return;
}
o = this;
}
latest[i] = o;
}
if (o != null && o != this) {
empty = false;
break;
}
}
if (d && empty) {
if (err.get() != null) {
a.onError(err.terminate());
} else {
a.onComplete();
}
return;
}
}
if (e != 0L) {
BackpressureHelper.produced(requested, e);
}
missed = addAndGet(-missed);
if (missed == 0) {
break;
}
}
}
}