/**
* Copyright 2014 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.operators;
import java.util.ArrayDeque;
import java.util.Deque;
import rx.Observable.Operator;
import rx.Subscriber;
/**
* Returns an Observable that emits the last <code>count</code> items emitted by the source Observable.
* <p>
* <img width="640" src="https://github.com/ReactiveX/RxJava/wiki/images/rx-operators/last.png" alt="">
*/
public final class OperatorTakeLast<T> implements Operator<T, T> {
private final int count;
public OperatorTakeLast(int count) {
if (count < 0) {
throw new IndexOutOfBoundsException("count could not be negative");
}
this.count = count;
}
@Override
public Subscriber<? super T> call(final Subscriber<? super T> subscriber) {
final Deque<Object> deque = new ArrayDeque<Object>();
final NotificationLite<T> notification = NotificationLite.instance();
final TakeLastQueueProducer<T> producer = new TakeLastQueueProducer<T>(notification, deque, subscriber);
subscriber.setProducer(producer);
return new Subscriber<T>(subscriber) {
// no backpressure up as it wants to receive and discard all but the last
@Override
public void onStart() {
// we do this to break the chain of the child subscriber being passed through
request(Long.MAX_VALUE);
}
@Override
public void onCompleted() {
deque.offer(notification.completed());
producer.startEmitting();
}
@Override
public void onError(Throwable e) {
deque.clear();
subscriber.onError(e);
}
@Override
public void onNext(T value) {
if (count == 0) {
// If count == 0, we do not need to put value into deque and
// remove it at once. We can ignore the value directly.
return;
}
if (deque.size() == count) {
deque.removeFirst();
}
deque.offerLast(notification.next(value));
}
};
}
}