rx.internal.producers.SingleProducer Maven / Gradle / Ivy
/**
* Copyright 2015 Netflix, Inc.
*
* 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 rx.internal.producers;
import java.util.concurrent.atomic.AtomicBoolean;
import rx.*;
import rx.exceptions.*;
/**
* A producer which emits a single value and completes the child on the first positive request.
*
* @param the value type
*/
public final class SingleProducer extends AtomicBoolean implements Producer {
/** */
private static final long serialVersionUID = -3353584923995471404L;
/** The child subscriber. */
final Subscriber super T> child;
/** The value to be emitted. */
final T value;
/**
* Constructs the producer with the given target child and value to be emitted.
* @param child the child subscriber, non-null
* @param value the value to be emitted, may be null
*/
public SingleProducer(Subscriber super T> child, T value) {
this.child = child;
this.value = value;
}
@Override
public void request(long n) {
// negative requests are bugs
if (n < 0) {
throw new IllegalArgumentException("n >= 0 required");
}
// we ignore zero requests
if (n == 0) {
return;
}
// atomically change the state into emitting mode
if (compareAndSet(false, true)) {
// avoid re-reading the instance fields
final Subscriber super T> c = child;
// eagerly check for unsubscription
if (c.isUnsubscribed()) {
return;
}
T v = value;
// emit the value
try {
c.onNext(v);
} catch (Throwable e) {
Exceptions.throwOrReport(e, c, v);
return;
}
// eagerly check for unsubscription
if (c.isUnsubscribed()) {
return;
}
// complete the child
c.onCompleted();
}
}
}
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