/**
* 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.concurrent.atomic.
AtomicLong;
import rx.*;
import rx.
Observable.
Operator;
import rx.functions.
Func1;
/**
* Returns an Observable that emits the at most 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="">
*
* @param <T> the value type
*/
public final class
OperatorTakeLast<T> implements
Operator<T, T> {
final int
count;
public
OperatorTakeLast(int
count) {
if (
count < 0) {
throw new
IndexOutOfBoundsException("count cannot be negative");
}
this.
count =
count;
}
@
Override
public
Subscriber<? super T>
call(final
Subscriber<? super T>
subscriber) {
final
TakeLastSubscriber<T>
parent = new
TakeLastSubscriber<T>(
subscriber,
count);
subscriber.
add(
parent);
subscriber.
setProducer(new
Producer() {
@
Override
public void
request(long
n) {
parent.
requestMore(
n);
}
});
return
parent;
}
static final class
TakeLastSubscriber<T> extends
Subscriber<T> implements
Func1<
Object, T> {
final
Subscriber<? super T>
actual;
final
AtomicLong requested;
final
ArrayDeque<
Object>
queue;
final int
count;
public
TakeLastSubscriber(
Subscriber<? super T>
actual, int
count) {
this.
actual =
actual;
this.
count =
count;
this.
requested = new
AtomicLong();
this.
queue = new
ArrayDeque<
Object>();
}
@
Override
public void
onNext(T
t) {
if (
queue.
size() ==
count) {
queue.
poll();
}
queue.
offer(
NotificationLite.
next(
t));
}
@
Override
public void
onError(
Throwable e) {
queue.
clear();
actual.
onError(
e);
}
@
Override
public void
onCompleted() {
BackpressureUtils.
postCompleteDone(
requested,
queue,
actual, this);
}
@
Override
public T
call(
Object t) {
return
NotificationLite.
getValue(
t);
}
void
requestMore(long
n) {
if (
n > 0L) {
BackpressureUtils.
postCompleteRequest(
requested,
n,
queue,
actual, this);
}
}
}
}