reactor.core.publisher.FluxBufferPredicate Maven / Gradle / Ivy
/*
* 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.AbstractQueue;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.Objects;
import java.util.concurrent.atomic.AtomicLongFieldUpdater;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
import java.util.function.BooleanSupplier;
import java.util.function.Predicate;
import java.util.function.Supplier;
import org.reactivestreams.Subscription;
import reactor.core.CoreSubscriber;
import reactor.core.Exceptions;
import reactor.core.Fuseable.ConditionalSubscriber;
import reactor.util.annotation.Nullable;
/**
* Buffers elements into custom collections where the buffer boundary is determined by
* a {@link java.util.function.Predicate} on the values. The predicate can be used in
* several modes:
*
* - {@code Until}: A new buffer starts when the predicate returns true. The
* element that just matched the predicate is the last in the previous buffer.
* - {@code UntilOther}: A new buffer starts when the predicate returns true. The
* element that just matched the predicate is the first in the new buffer.
* - {@code While}: A new buffer starts when the predicate stops matching. The
* non-matching elements are simply discarded.
*
*
* @param the source value type
* @param the output collection type
* @see Reactive-Streams-Commons
*/
final class FluxBufferPredicate>
extends FluxOperator {
public enum Mode {
UNTIL, UNTIL_CUT_BEFORE, WHILE
}
final Predicate predicate;
final Supplier bufferSupplier;
final Mode mode;
FluxBufferPredicate(Flux source, Predicate predicate,
Supplier bufferSupplier, Mode mode) {
super(source);
this.predicate = Objects.requireNonNull(predicate, "predicate");
this.bufferSupplier = Objects.requireNonNull(bufferSupplier, "bufferSupplier");
this.mode = mode;
}
@Override
public int getPrefetch() {
return 1; //this operator changes the downstream request to 1 in the source
}
@Override
public void subscribe(CoreSubscriber actual) {
C initialBuffer;
try {
initialBuffer = Objects.requireNonNull(bufferSupplier.get(),
"The bufferSupplier returned a null initial buffer");
}
catch (Throwable e) {
Operators.error(actual, Operators.onOperatorError(e, actual.currentContext()));
return;
}
BufferPredicateSubscriber parent = new BufferPredicateSubscriber<>(actual,
initialBuffer, bufferSupplier, predicate, mode);
source.subscribe(parent);
}
static final class BufferPredicateSubscriber>
extends AbstractQueue
implements ConditionalSubscriber, InnerOperator, BooleanSupplier {
final CoreSubscriber actual;
final Supplier bufferSupplier;
final Mode mode;
final Predicate predicate;
C buffer;
boolean done;
volatile boolean fastpath;
volatile long requested;
@SuppressWarnings("rawtypes")
static final AtomicLongFieldUpdater REQUESTED =
AtomicLongFieldUpdater.newUpdater(BufferPredicateSubscriber.class,
"requested");
volatile Subscription s;
static final AtomicReferenceFieldUpdater S = AtomicReferenceFieldUpdater.newUpdater
(BufferPredicateSubscriber.class, Subscription.class, "s");
BufferPredicateSubscriber(CoreSubscriber actual, C initialBuffer,
Supplier bufferSupplier, Predicate predicate, Mode mode) {
this.actual = actual;
this.buffer = initialBuffer;
this.bufferSupplier = bufferSupplier;
this.predicate = predicate;
this.mode = mode;
}
@Override
public void request(long n) {
if (Operators.validate(n)) {
if (n == Long.MAX_VALUE) {
// here we request everything from the source. switching to
// fastpath will avoid unnecessary request(1) during filling
fastpath = true;
requested = Long.MAX_VALUE;
s.request(Long.MAX_VALUE);
}
else {
// Requesting from source may have been interrupted if downstream
// received enough buffer (requested == 0), so this new request for
// buffer should resume progressive filling from upstream. We can
// directly request the same as the number of needed buffers (if
// buffers turn out 1-sized then we'll have everything, otherwise
// we'll continue requesting one by one)
if (!DrainUtils.postCompleteRequest(n,
actual,
this,
REQUESTED,
this,
this)) {
s.request(1);
}
}
}
}
@Override
public void cancel() {
Operators.terminate(S, this);
}
@Override
public void onSubscribe(Subscription s) {
if (Operators.setOnce(S, this, s)) {
actual.onSubscribe(this);
}
}
@Override
public void onNext(T t) {
if (!tryOnNext(t)) {
s.request(1);
}
}
@Override
public boolean tryOnNext(T t) {
if (done) {
Operators.onNextDropped(t, actual.currentContext());
return true;
}
C b = buffer;
boolean match;
try {
match = predicate.test(t);
}
catch (Throwable e) {
onError(Operators.onOperatorError(s, e, t, actual.currentContext()));
return true;
}
boolean requestMore;
if (mode == Mode.UNTIL && match) {
b.add(t);
requestMore = onNextNewBuffer();
}
else if (mode == Mode.UNTIL_CUT_BEFORE && match) {
requestMore = onNextNewBuffer();
b = buffer;
b.add(t);
}
else if (mode == Mode.WHILE && !match) {
requestMore = onNextNewBuffer();
}
else {
b.add(t);
return !(!fastpath && requested != 0);
}
return !requestMore;
}
@Nullable
private C triggerNewBuffer() {
C b = buffer;
if (b.isEmpty()) {
//emit nothing and we'll reuse the same buffer
return null;
}
//we'll create a new buffer
C c;
try {
c = Objects.requireNonNull(bufferSupplier.get(),
"The bufferSupplier returned a null buffer");
}
catch (Throwable e) {
onError(Operators.onOperatorError(s, e, actual.currentContext()));
return null;
}
buffer = c;
return b;
}
private boolean onNextNewBuffer() {
C b = triggerNewBuffer();
if (b != null) {
return emit(b);
}
return true;
}
@Override
public CoreSubscriber actual() {
return actual;
}
@Override
public void onError(Throwable t) {
if (done) {
Operators.onErrorDropped(t, actual.currentContext());
return;
}
done = true;
buffer = null;
actual.onError(t);
}
@Override
public void onComplete() {
if (done) {
return;
}
done = true;
DrainUtils.postComplete(actual, this, REQUESTED, this, this);
}
boolean emit(C b) {
if (fastpath) {
actual.onNext(b);
return false;
}
long r = REQUESTED.getAndDecrement(this);
if(r > 0){
actual.onNext(b);
return requested > 0;
}
cancel();
actual.onError(Exceptions.failWithOverflow("Could not emit buffer due to lack of requests"));
return false;
}
@Override
public Object scanUnsafe(Attr key) {
if (key == Attr.PARENT) return s;
if (key == Attr.TERMINATED) return done;
if (key == Attr.CANCELLED) return getAsBoolean();
if (key == Attr.CAPACITY) {
C b = buffer;
return b != null ? b.size() : 0;
}
if (key == Attr.REQUESTED_FROM_DOWNSTREAM) return requested;
return InnerOperator.super.scanUnsafe(key);
}
@Override
public boolean getAsBoolean() {
return s == Operators.cancelledSubscription();
}
@Override
public Iterator iterator() {
if (isEmpty()) {
return Collections.emptyIterator();
}
return Collections.singleton(buffer).iterator();
}
@Override
public boolean offer(C objects) {
throw new IllegalArgumentException();
}
@Override
@Nullable
public C poll() {
C b = buffer;
if (b != null && !b.isEmpty()) {
buffer = null;
return b;
}
return null;
}
@Override
@Nullable
public C peek() {
return buffer;
}
@Override
public int size() {
return buffer == null || buffer.isEmpty() ? 0 : 1;
}
@Override
public String toString() {
return "FluxBufferPredicate";
}
}
}
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