/*
* Copyright (c) 2011-2017 Pivotal Software Inc, 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
*
* 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 reactor.core.publisher;
import java.util.Queue;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import java.util.concurrent.atomic.AtomicLongFieldUpdater;
import java.util.function.Consumer;
import org.reactivestreams.Subscriber;
import org.reactivestreams.Subscription;
import reactor.core.Exceptions;
import reactor.core.Fuseable;
import reactor.util.concurrent.QueueSupplier;
/**
* @author Stephane Maldini
*/
final class FluxOnBackpressureBuffer<O> extends FluxSource<O, O> implements Fuseable {
final Consumer<? super O> onOverflow;
final int bufferSize;
final boolean unbounded;
final boolean delayError;
FluxOnBackpressureBuffer(Flux<? extends O> source,
int bufferSize,
boolean unbounded,
Consumer<? super O> onOverflow) {
super(source);
if (bufferSize < 1) {
throw new IllegalArgumentException("Buffer Size must be strictly positive");
}
this.bufferSize = bufferSize;
this.unbounded = unbounded;
this.onOverflow = onOverflow;
this.delayError = unbounded || onOverflow != null;
}
@Override
public void subscribe(Subscriber<? super O> s) {
source.subscribe(new BackpressureBufferSubscriber<>(s,
bufferSize,
unbounded,
delayError,
onOverflow));
}
@Override
public int getPrefetch() {
return Integer.MAX_VALUE;
}
static final class BackpressureBufferSubscriber<T>
implements QueueSubscription<T>, InnerOperator<T, T> {
final Subscriber<? super T> actual;
final Queue<T> queue;
final Consumer<? super T> onOverflow;
final boolean delayError;
Subscription s;
volatile boolean cancelled;
volatile boolean enabledFusion;
volatile boolean done;
Throwable error;
volatile int wip;
static final AtomicIntegerFieldUpdater<BackpressureBufferSubscriber> WIP =
AtomicIntegerFieldUpdater.newUpdater(BackpressureBufferSubscriber.class,
"wip");
volatile long requested;
static final AtomicLongFieldUpdater<BackpressureBufferSubscriber> REQUESTED =
AtomicLongFieldUpdater.newUpdater(BackpressureBufferSubscriber.class,
"requested");
BackpressureBufferSubscriber(Subscriber<? super T> actual,
int bufferSize,
boolean unbounded,
boolean delayError,
Consumer<? super T> onOverflow) {
this.actual = actual;
this.delayError = delayError;
this.onOverflow = onOverflow;
Queue<T> q;
if (unbounded) {
q = QueueSupplier.<T>unbounded(bufferSize).get();
}
else {
q = QueueSupplier.<T>get(bufferSize).get();
}
this.queue = q;
}
@Override
public Object scan(Attr key) {
switch (key) {
case PARENT:
return s;
case REQUESTED_FROM_DOWNSTREAM:
return requested;
case TERMINATED:
return done && queue.isEmpty();
case CANCELLED:
return cancelled;
case BUFFERED:
return queue.size();
case ERROR:
return error;
case PREFETCH:
return Integer.MAX_VALUE;
case DELAY_ERROR:
return delayError;
}
return InnerOperator.super.scan(key);
}
@Override
public void onSubscribe(Subscription s) {
if (Operators.validate(this.s, s)) {
this.s = s;
actual.onSubscribe(this);
s.request(Long.MAX_VALUE);
}
}
@Override
public void onNext(T t) {
if (done) {
Operators.onNextDropped(t);
return;
}
if (!queue.offer(t)) {
Throwable ex =
Operators.onOperatorError(s, Exceptions.failWithOverflow(), t);
if (onOverflow != null) {
try {
onOverflow.accept(t);
}
catch (Throwable e) {
Exceptions.throwIfFatal(e);
ex.initCause(e);
}
}
onError(ex);
return;
}
drain();
}
@Override
public void onError(Throwable t) {
if (done) {
Operators.onErrorDropped(t);
return;
}
error = t;
done = true;
drain();
}
@Override
public void onComplete() {
if (done) {
return;
}
done = true;
drain();
}
void drain() {
if (WIP.getAndIncrement(this) != 0) {
return;
}
int missed = 1;
for (; ; ) {
Subscriber<? super T> a = actual;
if (a != null) {
if (enabledFusion) {
drainFused(a);
}
else {
drainRegular(a);
}
return;
}
missed = WIP.addAndGet(this, -missed);
if (missed == 0) {
break;
}
}
}
void drainRegular(Subscriber<? super T> a) {
int missed = 1;
final Queue<T> q = queue;
for (; ; ) {
long r = requested;
long e = 0L;
while (r != e) {
boolean d = done;
T t = q.poll();
boolean empty = t == null;
if (checkTerminated(d, empty, a)) {
return;
}
if (empty) {
break;
}
a.onNext(t);
e++;
}
if (r == e) {
if (checkTerminated(done, q.isEmpty(), a)) {
return;
}
}
if (e != 0 && r != Long.MAX_VALUE) {
REQUESTED.addAndGet(this, -e);
}
missed = WIP.addAndGet(this, -missed);
if (missed == 0) {
break;
}
}
}
void drainFused(Subscriber<? super T> a) {
int missed = 1;
final Queue<T> q = queue;
for (; ; ) {
if (cancelled) {
s.cancel();
q.clear();
return;
}
boolean d = done;
a.onNext(null);
if (d) {
Throwable ex = error;
if (ex != null) {
a.onError(ex);
}
else {
a.onComplete();
}
return;
}
missed = WIP.addAndGet(this, -missed);
if (missed == 0) {
break;
}
}
}
@Override
public void request(long n) {
if (Operators.validate(n)) {
Operators.getAndAddCap(REQUESTED, this, n);
drain();
}
}
@Override
public void cancel() {
if (!cancelled) {
cancelled = true;
s.cancel();
if (!enabledFusion) {
if (WIP.getAndIncrement(this) == 0) {
queue.clear();
}
}
}
}
@Override
public T poll() {
return queue.poll();
}
@Override
public int size() {
return queue.size();
}
@Override
public boolean isEmpty() {
return queue.isEmpty();
}
@Override
public void clear() {
queue.clear();
}
@Override
public int requestFusion(int requestedMode) {
if ((requestedMode & Fuseable.ASYNC) != 0) {
enabledFusion = true;
return Fuseable.ASYNC;
}
return Fuseable.NONE;
}
@Override
public Subscriber<? super T> actual() {
return actual;
}
boolean checkTerminated(boolean d, boolean empty, Subscriber<? super T> a) {
if (cancelled) {
s.cancel();
queue.clear();
return true;
}
if (d) {
if (delayError) {
if (empty) {
Throwable e = error;
if (e != null) {
a.onError(e);
}
else {
a.onComplete();
}
return true;
}
}
else {
Throwable e = error;
if (e != null) {
queue.clear();
a.onError(e);
return true;
}
else if (empty) {
a.onComplete();
return true;
}
}
}
return false;
}
}
}