io.reactivex.internal.operators.flowable.FlowablePublishAlt Maven / Gradle / Ivy
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/**
* 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.internal.operators.flowable;
import java.util.concurrent.atomic.*;
import org.reactivestreams.*;
import io.reactivex.FlowableSubscriber;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.*;
import io.reactivex.flowables.ConnectableFlowable;
import io.reactivex.functions.Consumer;
import io.reactivex.internal.disposables.ResettableConnectable;
import io.reactivex.internal.fuseable.*;
import io.reactivex.internal.queue.SpscArrayQueue;
import io.reactivex.internal.subscriptions.SubscriptionHelper;
import io.reactivex.internal.util.*;
import io.reactivex.plugins.RxJavaPlugins;
/**
* Shares a single underlying connection to the upstream Publisher
* and multicasts events to all subscribed subscribers until the upstream
* completes or the connection is disposed.
*
* The difference to FlowablePublish is that when the upstream terminates,
* late subscriberss will receive that terminal event until the connection is
* disposed and the ConnectableFlowable is reset to its fresh state.
*
* @param the element type
* @since 2.2.10
*/
public final class FlowablePublishAlt extends ConnectableFlowable
implements HasUpstreamPublisher, ResettableConnectable {
final Publisher source;
final int bufferSize;
final AtomicReference> current;
public FlowablePublishAlt(Publisher source, int bufferSize) {
this.source = source;
this.bufferSize = bufferSize;
this.current = new AtomicReference>();
}
@Override
public Publisher source() {
return source;
}
/**
* The internal buffer size of this FloawblePublishAlt operator.
* @return The internal buffer size of this FloawblePublishAlt operator.
*/
public int publishBufferSize() {
return bufferSize;
}
@Override
public void connect(Consumer connection) {
PublishConnection conn;
boolean doConnect = false;
for (;;) {
conn = current.get();
if (conn == null || conn.isDisposed()) {
PublishConnection fresh = new PublishConnection(current, bufferSize);
if (!current.compareAndSet(conn, fresh)) {
continue;
}
conn = fresh;
}
doConnect = !conn.connect.get() && conn.connect.compareAndSet(false, true);
break;
}
try {
connection.accept(conn);
} catch (Throwable ex) {
Exceptions.throwIfFatal(ex);
throw ExceptionHelper.wrapOrThrow(ex);
}
if (doConnect) {
source.subscribe(conn);
}
}
@Override
protected void subscribeActual(Subscriber s) {
PublishConnection conn;
for (;;) {
conn = current.get();
// don't create a fresh connection if the current is disposed
if (conn == null) {
PublishConnection fresh = new PublishConnection(current, bufferSize);
if (!current.compareAndSet(conn, fresh)) {
continue;
}
conn = fresh;
}
break;
}
InnerSubscription inner = new InnerSubscription(s, conn);
s.onSubscribe(inner);
if (conn.add(inner)) {
if (inner.isCancelled()) {
conn.remove(inner);
} else {
conn.drain();
}
return;
}
Throwable ex = conn.error;
if (ex != null) {
s.onError(ex);
} else {
s.onComplete();
}
}
@SuppressWarnings("unchecked")
@Override
public void resetIf(Disposable connection) {
current.compareAndSet((PublishConnection)connection, null);
}
static final class PublishConnection
extends AtomicInteger
implements FlowableSubscriber, Disposable {
private static final long serialVersionUID = -1672047311619175801L;
final AtomicReference> current;
final AtomicReference upstream;
final AtomicBoolean connect;
final AtomicReference[]> subscribers;
final int bufferSize;
volatile SimpleQueue queue;
int sourceMode;
volatile boolean done;
Throwable error;
int consumed;
@SuppressWarnings("rawtypes")
static final InnerSubscription[] EMPTY = new InnerSubscription[0];
@SuppressWarnings("rawtypes")
static final InnerSubscription[] TERMINATED = new InnerSubscription[0];
@SuppressWarnings("unchecked")
PublishConnection(AtomicReference> current, int bufferSize) {
this.current = current;
this.upstream = new AtomicReference();
this.connect = new AtomicBoolean();
this.bufferSize = bufferSize;
this.subscribers = new AtomicReference[]>(EMPTY);
}
@SuppressWarnings("unchecked")
@Override
public void dispose() {
subscribers.getAndSet(TERMINATED);
current.compareAndSet(this, null);
SubscriptionHelper.cancel(upstream);
}
@Override
public boolean isDisposed() {
return subscribers.get() == TERMINATED;
}
@Override
public void onSubscribe(Subscription s) {
if (SubscriptionHelper.setOnce(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;
drain();
return;
}
if (m == QueueSubscription.ASYNC) {
sourceMode = m;
queue = qs;
s.request(bufferSize);
return;
}
}
queue = new SpscArrayQueue(bufferSize);
s.request(bufferSize);
}
}
@Override
public void onNext(T t) {
// we expect upstream to honor backpressure requests
if (sourceMode == QueueSubscription.NONE && !queue.offer(t)) {
onError(new MissingBackpressureException("Prefetch queue is full?!"));
return;
}
// since many things can happen concurrently, we have a common dispatch
// loop to act on the current state serially
drain();
}
@Override
public void onError(Throwable t) {
if (done) {
RxJavaPlugins.onError(t);
} else {
error = t;
done = true;
drain();
}
}
@Override
public void onComplete() {
done = true;
drain();
}
void drain() {
if (getAndIncrement() != 0) {
return;
}
int missed = 1;
SimpleQueue queue = this.queue;
int consumed = this.consumed;
int limit = this.bufferSize - (this.bufferSize >> 2);
boolean async = this.sourceMode != QueueSubscription.SYNC;
outer:
for (;;) {
if (queue != null) {
long minDemand = Long.MAX_VALUE;
boolean hasDemand = false;
InnerSubscription[] innerSubscriptions = subscribers.get();
for (InnerSubscription inner : innerSubscriptions) {
long request = inner.get();
if (request != Long.MIN_VALUE) {
hasDemand = true;
minDemand = Math.min(request - inner.emitted, minDemand);
}
}
if (!hasDemand) {
minDemand = 0L;
}
while (minDemand != 0L) {
boolean d = done;
T v;
try {
v = queue.poll();
} catch (Throwable ex) {
Exceptions.throwIfFatal(ex);
upstream.get().cancel();
queue.clear();
done = true;
signalError(ex);
return;
}
boolean empty = v == null;
if (checkTerminated(d, empty)) {
return;
}
if (empty) {
break;
}
for (InnerSubscription inner : innerSubscriptions) {
if (!inner.isCancelled()) {
inner.downstream.onNext(v);
inner.emitted++;
}
}
if (async && ++consumed == limit) {
consumed = 0;
upstream.get().request(limit);
}
minDemand--;
if (innerSubscriptions != subscribers.get()) {
continue outer;
}
}
if (checkTerminated(done, queue.isEmpty())) {
return;
}
}
this.consumed = consumed;
missed = addAndGet(-missed);
if (missed == 0) {
break;
}
if (queue == null) {
queue = this.queue;
}
}
}
@SuppressWarnings("unchecked")
boolean checkTerminated(boolean isDone, boolean isEmpty) {
if (isDone && isEmpty) {
Throwable ex = error;
if (ex != null) {
signalError(ex);
} else {
for (InnerSubscription inner : subscribers.getAndSet(TERMINATED)) {
if (!inner.isCancelled()) {
inner.downstream.onComplete();
}
}
}
return true;
}
return false;
}
@SuppressWarnings("unchecked")
void signalError(Throwable ex) {
for (InnerSubscription inner : subscribers.getAndSet(TERMINATED)) {
if (!inner.isCancelled()) {
inner.downstream.onError(ex);
}
}
}
boolean add(InnerSubscription inner) {
// the state can change so we do a CAS loop to achieve atomicity
for (;;) {
// get the current producer array
InnerSubscription[] c = subscribers.get();
// if this subscriber-to-source reached a terminal state by receiving
// an onError or onComplete, just refuse to add the new producer
if (c == TERMINATED) {
return false;
}
// we perform a copy-on-write logic
int len = c.length;
@SuppressWarnings("unchecked")
InnerSubscription[] u = new InnerSubscription[len + 1];
System.arraycopy(c, 0, u, 0, len);
u[len] = inner;
// try setting the subscribers array
if (subscribers.compareAndSet(c, u)) {
return true;
}
// if failed, some other operation succeeded (another add, remove or termination)
// so retry
}
}
@SuppressWarnings("unchecked")
void remove(InnerSubscription inner) {
// the state can change so we do a CAS loop to achieve atomicity
for (;;) {
// let's read the current subscribers array
InnerSubscription[] c = subscribers.get();
int len = c.length;
// if it is either empty or terminated, there is nothing to remove so we quit
if (len == 0) {
break;
}
// let's find the supplied producer in the array
// although this is O(n), we don't expect too many child subscribers in general
int j = -1;
for (int i = 0; i < len; i++) {
if (c[i] == inner) {
j = i;
break;
}
}
// we didn't find it so just quit
if (j < 0) {
return;
}
// we do copy-on-write logic here
InnerSubscription[] u;
// we don't create a new empty array if producer was the single inhabitant
// but rather reuse an empty array
if (len == 1) {
u = EMPTY;
} else {
// otherwise, create a new array one less in size
u = new InnerSubscription[len - 1];
// copy elements being before the given producer
System.arraycopy(c, 0, u, 0, j);
// copy elements being after the given producer
System.arraycopy(c, j + 1, u, j, len - j - 1);
}
// try setting this new array as
if (subscribers.compareAndSet(c, u)) {
break;
}
// if we failed, it means something else happened
// (a concurrent add/remove or termination), we need to retry
}
}
}
static final class InnerSubscription extends AtomicLong
implements Subscription {
private static final long serialVersionUID = 2845000326761540265L;
final Subscriber downstream;
final PublishConnection parent;
long emitted;
InnerSubscription(Subscriber downstream, PublishConnection parent) {
this.downstream = downstream;
this.parent = parent;
}
@Override
public void request(long n) {
BackpressureHelper.addCancel(this, n);
parent.drain();
}
@Override
public void cancel() {
if (getAndSet(Long.MIN_VALUE) != Long.MIN_VALUE) {
parent.remove(this);
parent.drain();
}
}
public boolean isCancelled() {
return get() == Long.MIN_VALUE;
}
}
}