/*
* 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.
Objects;
import java.util.concurrent.atomic.
AtomicLongFieldUpdater;
import java.util.concurrent.atomic.
AtomicReferenceFieldUpdater;
import java.util.stream.
Stream;
import org.reactivestreams.
Publisher;
import org.reactivestreams.
Subscription;
import reactor.core.
CoreSubscriber;
import reactor.core.
Exceptions;
import reactor.core.
Scannable;
import reactor.util.annotation.
Nullable;
import reactor.util.context.
Context;
/**
* Samples the main source and emits its latest value whenever the other Publisher
* signals a value.
* <p>
* <p>
* Termination of either Publishers will result in termination for the Subscriber
* as well.
* <p>
* <p>
* Both Publishers will run in unbounded mode because the backpressure
* would interfere with the sampling precision.
*
* @param <T> the input and output value type
* @param <U> the value type of the sampler (irrelevant)
* @see <a href="https://github.com/reactor/reactive-streams-commons">Reactive-Streams-Commons</a>
*/
final class
FluxSample<T, U> extends
FluxOperator<T, T> {
final
Publisher<U>
other;
FluxSample(
Flux<? extends T>
source,
Publisher<U>
other) {
super(
source);
this.
other =
Objects.
requireNonNull(
other, "other");
}
@
Override
public int
getPrefetch() {
return
Integer.
MAX_VALUE;
}
@
Override
public void
subscribe(
CoreSubscriber<? super T>
actual) {
CoreSubscriber<T>
serial =
Operators.
serialize(
actual);
SampleMainSubscriber<T>
main = new
SampleMainSubscriber<>(
serial);
actual.
onSubscribe(
main);
other.
subscribe(new
SampleOther<>(
main));
source.
subscribe(
main);
}
static final class
SampleMainSubscriber<T> implements
InnerOperator<T, T> {
final
CoreSubscriber<? super T>
actual;
final
Context ctx;
volatile T
value;
@
SuppressWarnings("rawtypes")
static final
AtomicReferenceFieldUpdater<
SampleMainSubscriber,
Object>
VALUE =
AtomicReferenceFieldUpdater.
newUpdater(
SampleMainSubscriber.class,
Object.class, "value");
volatile
Subscription main;
@
SuppressWarnings("rawtypes")
static final
AtomicReferenceFieldUpdater<
SampleMainSubscriber,
Subscription>
MAIN =
AtomicReferenceFieldUpdater.
newUpdater(
SampleMainSubscriber.class,
Subscription.class, "main");
volatile
Subscription other;
@
SuppressWarnings("rawtypes")
static final
AtomicReferenceFieldUpdater<
SampleMainSubscriber,
Subscription>
OTHER =
AtomicReferenceFieldUpdater.
newUpdater(
SampleMainSubscriber.class,
Subscription.class, "other");
volatile long
requested;
@
SuppressWarnings("rawtypes")
static final
AtomicLongFieldUpdater<
SampleMainSubscriber>
REQUESTED =
AtomicLongFieldUpdater.
newUpdater(
SampleMainSubscriber.class, "requested");
SampleMainSubscriber(
CoreSubscriber<? super T>
actual) {
this.
actual =
actual;
this.
ctx =
actual.
currentContext();
}
@
Override
public final
CoreSubscriber<? super T>
actual() {
return
actual;
}
@
Override
public
Stream<? extends
Scannable>
inners() {
return
Stream.
of(
Scannable.
from(
other));
}
@
Override
@
Nullable
public
Object scanUnsafe(
Attr key) {
if (
key ==
Attr.
REQUESTED_FROM_DOWNSTREAM) return
requested;
if (
key ==
Attr.
PARENT) return
main;
if (
key ==
Attr.
CANCELLED) return
main ==
Operators.
cancelledSubscription();
if (
key ==
Attr.
BUFFERED) return
value != null ? 1 : 0;
return
InnerOperator.super.scanUnsafe(
key);
}
@
Override
public void
onSubscribe(
Subscription s) {
if (!
MAIN.
compareAndSet(this, null,
s)) {
s.
cancel();
if (
main !=
Operators.
cancelledSubscription()) {
Operators.
reportSubscriptionSet();
}
return;
}
s.
request(
Long.
MAX_VALUE);
}
void
cancelMain() {
Subscription s =
main;
if (
s !=
Operators.
cancelledSubscription()) {
s =
MAIN.
getAndSet(this,
Operators.
cancelledSubscription());
if (
s != null &&
s !=
Operators.
cancelledSubscription()) {
s.
cancel();
}
}
}
void
cancelOther() {
Subscription s =
other;
if (
s !=
Operators.
cancelledSubscription()) {
s =
OTHER.
getAndSet(this,
Operators.
cancelledSubscription());
if (
s != null &&
s !=
Operators.
cancelledSubscription()) {
s.
cancel();
}
}
}
void
setOther(
Subscription s) {
if (!
OTHER.
compareAndSet(this, null,
s)) {
s.
cancel();
if (
other !=
Operators.
cancelledSubscription()) {
Operators.
reportSubscriptionSet();
}
return;
}
s.
request(
Long.
MAX_VALUE);
}
@
Override
public void
request(long
n) {
if (
Operators.
validate(
n)) {
Operators.
addCap(
REQUESTED, this,
n);
}
}
@
Override
public void
cancel() {
cancelMain();
cancelOther();
}
@
Override
public void
onNext(T
t) {
Object old =
VALUE.
getAndSet(this,
t);
if (
old != null) {
Operators.
onDiscard(
old,
ctx);
}
}
@
Override
public void
onError(
Throwable t) {
cancelOther();
actual.
onError(
t);
}
@
Override
public void
onComplete() {
cancelOther();
//implementation note: if the sampler triggers at the exact same time as the
// last source value being emitted, it could be that the sampler "wins" and
// suppresses the value by cancelling the main. In any other case, the block
// below ensures last source value is always part of the sample.
T
v =
value;
if (
v != null) {
actual.
onNext(
value);
}
actual.
onComplete();
}
@
SuppressWarnings("unchecked")
@
Nullable
T
getAndNullValue() {
return (T)
VALUE.
getAndSet(this, null);
}
void
decrement() {
REQUESTED.
decrementAndGet(this);
}
}
static final class
SampleOther<T, U> implements
InnerConsumer<U> {
final
SampleMainSubscriber<T>
main;
SampleOther(
SampleMainSubscriber<T>
main) {
this.
main =
main;
}
@
Override
@
Nullable
public
Object scanUnsafe(
Attr key) {
if (
key ==
Attr.
PARENT) return
main.
other;
if (
key ==
Attr.
ACTUAL) return
main;
if (
key ==
Attr.
CANCELLED) return
main.
other ==
Operators.
cancelledSubscription();
if (
key ==
Attr.
PREFETCH) return
Integer.
MAX_VALUE;
return null;
}
@
Override
public
Context currentContext() {
return
main.
currentContext();
}
@
Override
public void
onSubscribe(
Subscription s) {
main.
setOther(
s);
}
@
Override
public void
onNext(U
t) {
SampleMainSubscriber<T>
m =
main;
T
v =
m.
getAndNullValue();
if (
v != null) {
if (
m.
requested != 0L) {
m.
actual.
onNext(
v);
if (
m.
requested !=
Long.
MAX_VALUE) {
m.
decrement();
}
return;
}
m.
cancel();
m.
actual.
onError(
Exceptions.
failWithOverflow("Can't signal value due to lack of requests"));
Operators.
onDiscard(
v,
m.
ctx);
}
}
@
Override
public void
onError(
Throwable t) {
SampleMainSubscriber<T>
m =
main;
m.
cancelMain();
m.
actual.
onError(
t);
}
@
Override
public void
onComplete() {
SampleMainSubscriber<T>
m =
main;
m.
cancelMain();
m.
actual.
onComplete();
}
}
}