/*
* 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.concurrent.atomic.
AtomicIntegerFieldUpdater;
import java.util.concurrent.atomic.
AtomicLongFieldUpdater;
import java.util.concurrent.atomic.
AtomicReferenceFieldUpdater;
import org.reactivestreams.
Subscriber;
import org.reactivestreams.
Subscription;
import reactor.core.
CoreSubscriber;
import reactor.util.annotation.
Nullable;
import reactor.util.context.
Context;
/**
* Runs the source in unbounded mode and emits only the latest value
* if the subscriber can't keep up properly.
*
* @param <T> the value type
* @see <a href="https://github.com/reactor/reactive-streams-commons">Reactive-Streams-Commons</a>
*/
final class
FluxOnBackpressureLatest<T> extends
FluxOperator<T, T> {
FluxOnBackpressureLatest(
Flux<? extends T>
source) {
super(
source);
}
@
Override
public void
subscribe(
CoreSubscriber<? super T>
actual) {
source.
subscribe(new
LatestSubscriber<>(
actual));
}
@
Override
public int
getPrefetch() {
return
Integer.
MAX_VALUE;
}
static final class
LatestSubscriber<T>
implements
InnerOperator<T, T> {
final
CoreSubscriber<? super T>
actual;
final
Context ctx;
volatile long
requested;
@
SuppressWarnings("rawtypes")
static final
AtomicLongFieldUpdater<
LatestSubscriber>
REQUESTED =
AtomicLongFieldUpdater.
newUpdater(
LatestSubscriber.class, "requested");
volatile int
wip;
@
SuppressWarnings("rawtypes")
static final
AtomicIntegerFieldUpdater<
LatestSubscriber>
WIP =
AtomicIntegerFieldUpdater.
newUpdater(
LatestSubscriber.class, "wip");
Subscription s;
Throwable error;
volatile boolean
done;
volatile boolean
cancelled;
volatile T
value;
@
SuppressWarnings("rawtypes")
static final
AtomicReferenceFieldUpdater<
LatestSubscriber,
Object>
VALUE =
AtomicReferenceFieldUpdater.
newUpdater(
LatestSubscriber.class,
Object.class, "value");
LatestSubscriber(
CoreSubscriber<? super T>
actual) {
this.
actual =
actual;
this.
ctx =
actual.
currentContext();
}
@
Override
public void
request(long
n) {
if (
Operators.
validate(
n)) {
Operators.
addCap(
REQUESTED, this,
n);
drain();
}
}
@
Override
public void
cancel() {
if (!
cancelled) {
cancelled = true;
s.
cancel();
if (
WIP.
getAndIncrement(this) == 0) {
Object toDiscard =
VALUE.
getAndSet(this, null);
if (
toDiscard != null) {
Operators.
onDiscard(
toDiscard,
ctx);
}
}
}
}
@
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) {
Object toDiscard =
VALUE.
getAndSet(this,
t);
if (
toDiscard != null) {
Operators.
onDiscard(
toDiscard,
ctx);
}
drain();
}
@
Override
public void
onError(
Throwable t) {
error =
t;
done = true;
drain();
}
@
Override
public void
onComplete() {
done = true;
drain();
}
void
drain() {
if (
WIP.
getAndIncrement(this) != 0) {
return;
}
final
Subscriber<? super T>
a =
actual;
int
missed = 1;
for (; ; ) {
if (
checkTerminated(
done,
value == null,
a)) {
return;
}
long
r =
requested;
long
e = 0L;
while (
r !=
e) {
boolean
d =
done;
@
SuppressWarnings("unchecked")
T
v = (T)
VALUE.
getAndSet(this, null);
boolean
empty =
v == null;
if (
checkTerminated(
d,
empty,
a)) {
return;
}
if (
empty) {
break;
}
a.
onNext(
v);
e++;
}
if (
r ==
e &&
checkTerminated(
done,
value == null,
a)) {
return;
}
if (
e != 0L &&
r !=
Long.
MAX_VALUE) {
Operators.
produced(
REQUESTED, this, 1);
}
missed =
WIP.
addAndGet(this, -
missed);
if (
missed == 0) {
break;
}
}
}
boolean
checkTerminated(boolean
d, boolean
empty,
Subscriber<? super T>
a) {
if (
cancelled) {
Object toDiscard =
VALUE.
getAndSet(this, null);
if (
toDiscard != null) {
Operators.
onDiscard(
toDiscard,
ctx);
}return true;
}
if (
d) {
Throwable e =
error;
if (
e != null) {
Object toDiscard =
VALUE.
getAndSet(this, null);
if (
toDiscard != null) {
Operators.
onDiscard(
toDiscard,
ctx);
}
a.
onError(
e);
return true;
} else if (
empty) {
a.
onComplete();
return true;
}
}
return false;
}
@
Override
public
CoreSubscriber<? super T>
actual() {
return
actual;
}
@
Override
@
Nullable
public
Object scanUnsafe(
Attr key) {
if (
key ==
Attr.
PARENT) return
s;
if (
key ==
Attr.
REQUESTED_FROM_DOWNSTREAM) return
requested;
if (
key ==
Attr.
TERMINATED) return
done;
if (
key ==
Attr.
CANCELLED) return
cancelled;
if (
key ==
Attr.
BUFFERED) return
value != null ? 1 : 0;
if (
key ==
Attr.
ERROR) return
error;
if (
key ==
Attr.
PREFETCH) return
Integer.
MAX_VALUE;
return
InnerOperator.super.scanUnsafe(
key);
}
}
}