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Reactive Extensions for Java
/*
* Copyright (c) 2016-present, RxJava Contributors.
*
* 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 io.reactivex.rxjava3.internal.operators.parallel;
import java.util.concurrent.atomic.*;
import org.reactivestreams.*;
import io.reactivex.rxjava3.core.FlowableSubscriber;
import io.reactivex.rxjava3.exceptions.*;
import io.reactivex.rxjava3.internal.subscriptions.SubscriptionHelper;
import io.reactivex.rxjava3.internal.util.BackpressureHelper;
import io.reactivex.rxjava3.operators.QueueSubscription;
import io.reactivex.rxjava3.operators.SimpleQueue;
import io.reactivex.rxjava3.operators.SpscArrayQueue;
import io.reactivex.rxjava3.parallel.ParallelFlowable;
import io.reactivex.rxjava3.plugins.RxJavaPlugins;
/**
* Dispatches the values from upstream in a round robin fashion to subscribers which are
* ready to consume elements. A value from upstream is sent to only one of the subscribers.
*
* @param the value type
*/
public final class ParallelFromPublisher extends ParallelFlowable {
final Publisher source;
final int parallelism;
final int prefetch;
public ParallelFromPublisher(Publisher source, int parallelism, int prefetch) {
this.source = source;
this.parallelism = parallelism;
this.prefetch = prefetch;
}
@Override
public int parallelism() {
return parallelism;
}
@Override
public void subscribe(Subscriber[] subscribers) {
subscribers = RxJavaPlugins.onSubscribe(this, subscribers);
if (!validate(subscribers)) {
return;
}
source.subscribe(new ParallelDispatcher<>(subscribers, prefetch));
}
static final class ParallelDispatcher
extends AtomicInteger
implements FlowableSubscriber {
private static final long serialVersionUID = -4470634016609963609L;
final Subscriber[] subscribers;
final AtomicLongArray requests;
final long[] emissions;
final int prefetch;
final int limit;
Subscription upstream;
SimpleQueue queue;
Throwable error;
volatile boolean done;
int index;
volatile boolean cancelled;
/**
* Counts how many subscribers were setup to delay triggering the
* drain of upstream until all of them have been setup.
*/
final AtomicInteger subscriberCount = new AtomicInteger();
int produced;
int sourceMode;
ParallelDispatcher(Subscriber[] subscribers, int prefetch) {
this.subscribers = subscribers;
this.prefetch = prefetch;
this.limit = prefetch - (prefetch >> 2);
int m = subscribers.length;
this.requests = new AtomicLongArray(m + m + 1);
this.requests.lazySet(m + m, m);
this.emissions = new long[m];
}
@Override
public void onSubscribe(Subscription s) {
if (SubscriptionHelper.validate(this.upstream, s)) {
this.upstream = s;
if (s instanceof QueueSubscription) {
@SuppressWarnings("unchecked")
QueueSubscription qs = (QueueSubscription) s;
int m = qs.requestFusion(QueueSubscription.ANY | QueueSubscription.BOUNDARY);
if (m == QueueSubscription.SYNC) {
sourceMode = m;
queue = qs;
done = true;
setupSubscribers();
drain();
return;
} else
if (m == QueueSubscription.ASYNC) {
sourceMode = m;
queue = qs;
setupSubscribers();
s.request(prefetch);
return;
}
}
queue = new SpscArrayQueue<>(prefetch);
setupSubscribers();
s.request(prefetch);
}
}
void setupSubscribers() {
Subscriber[] subs = subscribers;
final int m = subs.length;
for (int i = 0; i < m; i++) {
subscriberCount.lazySet(i + 1);
subs[i].onSubscribe(new RailSubscription(i, m));
}
}
final class RailSubscription implements Subscription {
final int j;
final int m;
RailSubscription(int j, int m) {
this.j = j;
this.m = m;
}
@Override
public void request(long n) {
if (SubscriptionHelper.validate(n)) {
AtomicLongArray ra = requests;
for (;;) {
long r = ra.get(j);
if (r == Long.MAX_VALUE) {
return;
}
long u = BackpressureHelper.addCap(r, n);
if (ra.compareAndSet(j, r, u)) {
break;
}
}
if (subscriberCount.get() == m) {
drain();
}
}
}
@Override
public void cancel() {
if (requests.compareAndSet(m + j, 0L, 1L)) {
ParallelDispatcher.this.cancel(m + m);
}
}
}
@Override
public void onNext(T t) {
if (sourceMode == QueueSubscription.NONE) {
if (!queue.offer(t)) {
upstream.cancel();
onError(new MissingBackpressureException("Queue is full?"));
return;
}
}
drain();
}
@Override
public void onError(Throwable t) {
error = t;
done = true;
drain();
}
@Override
public void onComplete() {
done = true;
drain();
}
void cancel(int m) {
if (requests.decrementAndGet(m) == 0L) {
cancelled = true;
this.upstream.cancel();
if (getAndIncrement() == 0) {
queue.clear();
}
}
}
void drainAsync() {
int missed = 1;
SimpleQueue q = queue;
Subscriber[] a = this.subscribers;
AtomicLongArray r = this.requests;
long[] e = this.emissions;
int n = e.length;
int idx = index;
int consumed = produced;
for (;;) {
int notReady = 0;
for (;;) {
if (cancelled) {
q.clear();
return;
}
boolean d = done;
if (d) {
Throwable ex = error;
if (ex != null) {
q.clear();
for (Subscriber s : a) {
s.onError(ex);
}
return;
}
}
boolean empty = q.isEmpty();
if (d && empty) {
for (Subscriber s : a) {
s.onComplete();
}
return;
}
if (empty) {
break;
}
long requestAtIndex = r.get(idx);
long emissionAtIndex = e[idx];
if (requestAtIndex != emissionAtIndex && r.get(n + idx) == 0) {
T v;
try {
v = q.poll();
} catch (Throwable ex) {
Exceptions.throwIfFatal(ex);
upstream.cancel();
for (Subscriber s : a) {
s.onError(ex);
}
return;
}
if (v == null) {
break;
}
a[idx].onNext(v);
e[idx] = emissionAtIndex + 1;
int c = ++consumed;
if (c == limit) {
consumed = 0;
upstream.request(c);
}
notReady = 0;
} else {
notReady++;
}
idx++;
if (idx == n) {
idx = 0;
}
if (notReady == n) {
break;
}
}
int w = get();
if (w == missed) {
index = idx;
produced = consumed;
missed = addAndGet(-missed);
if (missed == 0) {
break;
}
} else {
missed = w;
}
}
}
void drainSync() {
int missed = 1;
SimpleQueue q = queue;
Subscriber[] a = this.subscribers;
AtomicLongArray r = this.requests;
long[] e = this.emissions;
int n = e.length;
int idx = index;
for (;;) {
int notReady = 0;
for (;;) {
if (cancelled) {
q.clear();
return;
}
boolean empty = q.isEmpty();
if (empty) {
for (Subscriber s : a) {
s.onComplete();
}
return;
}
long requestAtIndex = r.get(idx);
long emissionAtIndex = e[idx];
if (requestAtIndex != emissionAtIndex && r.get(n + idx) == 0) {
T v;
try {
v = q.poll();
} catch (Throwable ex) {
Exceptions.throwIfFatal(ex);
upstream.cancel();
for (Subscriber s : a) {
s.onError(ex);
}
return;
}
if (v == null) {
for (Subscriber s : a) {
s.onComplete();
}
return;
}
a[idx].onNext(v);
e[idx] = emissionAtIndex + 1;
notReady = 0;
} else {
notReady++;
}
idx++;
if (idx == n) {
idx = 0;
}
if (notReady == n) {
break;
}
}
int w = get();
if (w == missed) {
index = idx;
missed = addAndGet(-missed);
if (missed == 0) {
break;
}
} else {
missed = w;
}
}
}
void drain() {
if (getAndIncrement() != 0) {
return;
}
if (sourceMode == QueueSubscription.SYNC) {
drainSync();
} else {
drainAsync();
}
}
}
}
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