software.amazon.awssdk.utils.internal.async.EmptySubscription Maven / Gradle / Ivy
/*
* Copyright Amazon.com, Inc. or its affiliates. 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.
* A copy of the License is located at
*
* http://aws.amazon.com/apache2.0
*
* or in the "license" file accompanying this file. This file 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 software.amazon.awssdk.utils.internal.async;
import java.util.concurrent.atomic.AtomicBoolean;
import org.reactivestreams.Subscriber;
import org.reactivestreams.Subscription;
import software.amazon.awssdk.annotations.SdkInternalApi;
/**
* A NoOp implementation of {@link Subscription} interface.
*
* This subscription calls {@link Subscriber#onComplete()} on first request for data and then terminates the subscription.
*/
@SdkInternalApi
public final class EmptySubscription implements Subscription {
private final AtomicBoolean isTerminated = new AtomicBoolean(false);
private final Subscriber subscriber;
public EmptySubscription(Subscriber subscriber) {
this.subscriber = subscriber;
}
@Override
public void request(long n) {
if (isTerminated()) {
return;
}
if (n <= 0) {
throw new IllegalArgumentException("Non-positive request signals are illegal");
}
if (terminate()) {
subscriber.onComplete();
}
}
@Override
public void cancel() {
terminate();
}
private boolean terminate() {
return isTerminated.compareAndSet(false, true);
}
private boolean isTerminated() {
return isTerminated.get();
}
}