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rxjava2-extensions developed by David Karnok
/*
* Copyright 2016-2017 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.parallel;
import java.util.concurrent.atomic.*;
import org.reactivestreams.*;
import io.reactivex.Flowable;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.functions.BiFunction;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.subscriptions.*;
import io.reactivex.plugins.RxJavaPlugins;
/**
* Reduces all 'rails' into a single value which then gets reduced into a single
* Publisher sequence.
*
* @param the value type
*/
@SuppressWarnings("deprecation")
final class ParallelReduceFull extends Flowable {
final ParallelFlowable source;
final BiFunction reducer;
ParallelReduceFull(ParallelFlowable source, BiFunction reducer) {
this.source = source;
this.reducer = reducer;
}
@Override
protected void subscribeActual(Subscriber s) {
ParallelReduceFullMainSubscriber parent = new ParallelReduceFullMainSubscriber(s, source.parallelism(), reducer);
s.onSubscribe(parent);
source.subscribe(parent.subscribers);
}
static final class ParallelReduceFullMainSubscriber extends DeferredScalarSubscription {
private static final long serialVersionUID = -5370107872170712765L;
final ParallelReduceFullInnerSubscriber[] subscribers;
final BiFunction reducer;
final AtomicReference> current = new AtomicReference>();
final AtomicInteger remaining = new AtomicInteger();
final AtomicBoolean once = new AtomicBoolean();
ParallelReduceFullMainSubscriber(Subscriber subscriber, int n, BiFunction reducer) {
super(subscriber);
@SuppressWarnings("unchecked")
ParallelReduceFullInnerSubscriber[] a = new ParallelReduceFullInnerSubscriber[n];
for (int i = 0; i < n; i++) {
a[i] = new ParallelReduceFullInnerSubscriber(this, reducer);
}
this.subscribers = a;
this.reducer = reducer;
remaining.lazySet(n);
}
SlotPair addValue(T value) {
for (;;) {
SlotPair curr = current.get();
if (curr == null) {
curr = new SlotPair();
if (!current.compareAndSet(null, curr)) {
continue;
}
}
int c = curr.tryAcquireSlot();
if (c < 0) {
current.compareAndSet(curr, null);
continue;
}
if (c == 0) {
curr.first = value;
} else {
curr.second = value;
}
if (curr.releaseSlot()) {
current.compareAndSet(curr, null);
return curr;
}
return null;
}
}
@Override
public void cancel() {
for (ParallelReduceFullInnerSubscriber inner : subscribers) {
inner.cancel();
}
}
void innerError(Throwable ex) {
if (once.compareAndSet(false, true)) {
cancel();
actual.onError(ex);
} else {
RxJavaPlugins.onError(ex);
}
}
void innerComplete(T value) {
if (value != null) {
for (;;) {
SlotPair sp = addValue(value);
if (sp != null) {
try {
value = reducer.apply(sp.first, sp.second);
} catch (Throwable ex) {
Exceptions.throwIfFatal(ex);
innerError(ex);
return;
}
if (value == null) {
innerError(new NullPointerException("The reducer returned a null value"));
return;
}
} else {
break;
}
}
}
if (remaining.decrementAndGet() == 0) {
SlotPair sp = current.get();
current.lazySet(null);
if (sp != null) {
complete(sp.first);
} else {
actual.onComplete();
}
}
}
}
static final class ParallelReduceFullInnerSubscriber
extends AtomicReference
implements Subscriber {
private static final long serialVersionUID = -7954444275102466525L;
final ParallelReduceFullMainSubscriber parent;
final BiFunction reducer;
T value;
boolean done;
ParallelReduceFullInnerSubscriber(ParallelReduceFullMainSubscriber parent, BiFunction reducer) {
this.parent = parent;
this.reducer = reducer;
}
@Override
public void onSubscribe(Subscription s) {
if (SubscriptionHelper.setOnce(this, s)) {
s.request(Long.MAX_VALUE);
}
}
@Override
public void onNext(T t) {
if (done) {
return;
}
T v = value;
if (v == null) {
value = t;
} else {
try {
v = ObjectHelper.requireNonNull(reducer.apply(v, t), "The reducer returned a null value");
} catch (Throwable ex) {
Exceptions.throwIfFatal(ex);
get().cancel();
onError(ex);
return;
}
value = v;
}
}
@Override
public void onError(Throwable t) {
if (done) {
RxJavaPlugins.onError(t);
return;
}
done = true;
parent.innerError(t);
}
@Override
public void onComplete() {
if (done) {
return;
}
done = true;
parent.innerComplete(value);
}
void cancel() {
SubscriptionHelper.cancel(this);
}
}
static final class SlotPair {
T first;
T second;
volatile int acquireIndex;
@SuppressWarnings("rawtypes")
static final AtomicIntegerFieldUpdater ACQ =
AtomicIntegerFieldUpdater.newUpdater(SlotPair.class, "acquireIndex");
volatile int releaseIndex;
@SuppressWarnings("rawtypes")
static final AtomicIntegerFieldUpdater REL =
AtomicIntegerFieldUpdater.newUpdater(SlotPair.class, "releaseIndex");
int tryAcquireSlot() {
for (;;) {
int acquired = acquireIndex;
if (acquired >= 2) {
return -1;
}
if (ACQ.compareAndSet(this, acquired, acquired + 1)) {
return acquired;
}
}
}
boolean releaseSlot() {
return REL.incrementAndGet(this) == 2;
}
}
}
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