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JdkFlowAdapters.java
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/
JdkFlowAdapters.java
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/*
* Copyright © 2019 Apple Inc. and the ServiceTalk project authors
*
* 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 io.servicetalk.concurrent.jdkflow;
import io.servicetalk.concurrent.PublisherSource;
import io.servicetalk.concurrent.api.Publisher;
import java.util.concurrent.Flow.Subscriber;
import java.util.concurrent.Flow.Subscription;
import static io.servicetalk.concurrent.api.SourceAdapters.toSource;
import static java.util.Objects.requireNonNull;
/**
* A set of adapter methods for converting to and from
* <a href="https://docs.oracle.com/javase/9/docs/api/java/util/concurrent/Flow.html">JDK Flow</a>
* APIs and ServiceTalk APIs.
*/
public final class JdkFlowAdapters {
private JdkFlowAdapters() {
// No instances.
}
/**
* Converts the passed {@link Publisher} to a
* <a href="https://docs.oracle.com/javase/9/docs/api/java/util/concurrent/Flow.html">JDK Flow</a>
* {@link java.util.concurrent.Flow.Publisher}.
*
* @param source {@link java.util.concurrent.Flow.Publisher} to convert to a {@link Publisher}.
* @param <T> Type of items emitted from the {@code source} and the returned {@link Publisher}.
* @return A {@link Publisher} representation of the passed {@link java.util.concurrent.Flow.Publisher}.
*/
public static <T> Publisher<T> fromFlowPublisher(java.util.concurrent.Flow.Publisher<T> source) {
return new FlowToStPublisher<>(source);
}
/**
* Converts the passed {@link Publisher} to a
* <a href="https://docs.oracle.com/javase/9/docs/api/java/util/concurrent/Flow.html">JDK Flow</a>
* {@link java.util.concurrent.Flow.Publisher}.
*
* @param publisher {@link Publisher} to convert to a {@link Publisher}.
* @param <T> Type of items emitted from the {@code source} and the returned {@link Publisher}.
* @return A {@link java.util.concurrent.Flow.Publisher} representation of the passed {@link Publisher}.
*/
public static <T> java.util.concurrent.Flow.Publisher<T> toFlowPublisher(Publisher<T> publisher) {
return new StToFlowPublisher<>(toSource(publisher));
}
/**
* Converts the passed {@link PublisherSource} to a
* <a href="https://docs.oracle.com/javase/9/docs/api/java/util/concurrent/Flow.html">JDK Flow</a>
* {@link java.util.concurrent.Flow.Publisher}.
*
* @param source {@link PublisherSource} to convert to a {@link java.util.concurrent.Flow.Publisher}.
* @param <T> Type of items emitted from the {@code source} and the returned
* {@link java.util.concurrent.Flow.Publisher}.
* @return A {@link java.util.concurrent.Flow.Publisher} representation of the passed {@link PublisherSource}.
*/
public static <T> java.util.concurrent.Flow.Publisher<T> toFlowPublisher(PublisherSource<T> source) {
return new StToFlowPublisher<>(source);
}
private static final class StToFlowPublisher<T> implements java.util.concurrent.Flow.Publisher<T> {
private final PublisherSource<T> source;
StToFlowPublisher(final PublisherSource<T> source) {
this.source = requireNonNull(source);
}
@Override
public void subscribe(final Subscriber<? super T> subscriber) {
source.subscribe(new FlowToStSubscriber<>(subscriber));
}
}
private static final class FlowToStSubscriber<T> implements PublisherSource.Subscriber<T> {
private final Subscriber<? super T> subscriber;
FlowToStSubscriber(final Subscriber<? super T> subscriber) {
this.subscriber = requireNonNull(subscriber);
}
@Override
public void onSubscribe(final PublisherSource.Subscription subscription) {
subscriber.onSubscribe(new Subscription() {
@Override
public void request(final long n) {
subscription.request(n);
}
@Override
public void cancel() {
subscription.cancel();
}
});
}
@Override
public void onNext(final T next) {
subscriber.onNext(next);
}
@Override
public void onError(final Throwable t) {
subscriber.onError(t);
}
@Override
public void onComplete() {
subscriber.onComplete();
}
}
private static final class FlowToStPublisher<T> extends Publisher<T> {
private final java.util.concurrent.Flow.Publisher<T> source;
FlowToStPublisher(final java.util.concurrent.Flow.Publisher<T> source) {
this.source = requireNonNull(source);
}
@Override
protected void handleSubscribe(final PublisherSource.Subscriber<? super T> subscriber) {
source.subscribe(new StToFlowSubscriber<>(subscriber));
}
}
private static final class FlowToSTSubscription implements PublisherSource.Subscription {
private final Subscription s;
FlowToSTSubscription(final Subscription s) {
this.s = s;
}
@Override
public void request(final long n) {
s.request(n);
}
@Override
public void cancel() {
s.cancel();
}
}
private static final class StToFlowSubscriber<T> implements Subscriber<T> {
private final PublisherSource.Subscriber<? super T> subscriber;
StToFlowSubscriber(final PublisherSource.Subscriber<? super T> subscriber) {
this.subscriber = subscriber;
}
@Override
public void onSubscribe(final Subscription s) {
subscriber.onSubscribe(new FlowToSTSubscription(s));
}
@Override
public void onNext(final T t) {
subscriber.onNext(t);
}
@Override
public void onError(final Throwable t) {
subscriber.onError(t);
}
@Override
public void onComplete() {
subscriber.onComplete();
}
}
}