/*
* 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.function.
BiFunction;
import org.reactivestreams.
Subscription;
import reactor.core.
CoreSubscriber;
import reactor.util.annotation.
Nullable;
/**
* Accumulates the source values with an accumulator function and
* returns the intermediate results of this function.
* <p>
* Unlike {@link FluxScan}, this operator doesn't take an initial value
* but treats the first source value as initial value.
* <br>
* The accumulation works as follows:
* <pre><code>
* result[0] = accumulator(source[0], source[1])
* result[1] = accumulator(result[0], source[2])
* result[2] = accumulator(result[1], source[3])
* ...
* </code></pre>
*
* @param <T> the input and accumulated value type
* @see <a href="https://github.com/reactor/reactive-streams-commons">Reactive-Streams-Commons</a>
*/
final class
FluxScan<T> extends
FluxOperator<T, T> {
final
BiFunction<T, ? super T, T>
accumulator;
FluxScan(
Flux<? extends T>
source,
BiFunction<T, ? super T, T>
accumulator) {
super(
source);
this.
accumulator =
Objects.
requireNonNull(
accumulator, "accumulator");
}
@
Override
public void
subscribe(
CoreSubscriber<? super T>
actual) {
source.
subscribe(new
ScanSubscriber<>(
actual,
accumulator));
}
static final class
ScanSubscriber<T>
implements
InnerOperator<T, T> {
final
CoreSubscriber<? super T>
actual;
final
BiFunction<T, ? super T, T>
accumulator;
Subscription s;
T
value;
boolean
done;
ScanSubscriber(
CoreSubscriber<? super T>
actual,
BiFunction<T, ? super T, T>
accumulator) {
this.
actual =
actual;
this.
accumulator =
accumulator;
}
@
Override
public void
onSubscribe(
Subscription s) {
if (
Operators.
validate(this.
s,
s)) {
this.
s =
s;
actual.
onSubscribe(this);
}
}
@
Override
public void
onNext(T
t) {
if (
done) {
Operators.
onNextDropped(
t,
actual.
currentContext());
return;
}
T
v =
value;
if (
v != null) {
try {
t =
Objects.
requireNonNull(
accumulator.
apply(
v,
t),
"The accumulator returned a null value");
}
catch (
Throwable e) {
onError(
Operators.
onOperatorError(
s,
e,
t,
actual.
currentContext()));
return;
}
}
value =
t;
actual.
onNext(
t);
}
@
Override
public void
onError(
Throwable t) {
if (
done) {
Operators.
onErrorDropped(
t,
actual.
currentContext());
return;
}
done = true;
actual.
onError(
t);
}
@
Override
public void
onComplete() {
if (
done) {
return;
}
done = true;
actual.
onComplete();
}
@
Override
@
Nullable
public
Object scanUnsafe(
Attr key) {
if (
key ==
Attr.
PARENT) return
s;
if (
key ==
Attr.
TERMINATED) return
done;
if (
key ==
Attr.
BUFFERED) return
value != null ? 1 : 0;
return
InnerOperator.super.scanUnsafe(
key);
}
@
Override
public
CoreSubscriber<? super T>
actual() {
return
actual;
}
@
Override
public void
request(long
n) {
s.
request(
n);
}
@
Override
public void
cancel() {
s.
cancel();
}
}
}