rx.operators.OperationSkipLast Maven / Gradle / Ivy
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/**
* 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.operators;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Deque;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReentrantLock;
import rx.Observable;
import rx.Observable.OnSubscribeFunc;
import rx.Observer;
import rx.Scheduler;
import rx.Subscription;
import rx.schedulers.Timestamped;
/**
* Bypasses a specified number of elements at the end of an observable sequence.
*/
public class OperationSkipLast {
/**
* Bypasses a specified number of elements at the end of an observable
* sequence.
*
* This operator accumulates a queue with a length enough to store the first
* count elements. As more elements are received, elements are taken from
* the front of the queue and produced on the result sequence. This causes
* elements to be delayed.
*
* @param source
* the source sequence.
* @param count
* number of elements to bypass at the end of the source
* sequence.
* @return An observable sequence containing the source sequence elements
* except for the bypassed ones at the end.
*
* @throws IndexOutOfBoundsException
* count is less than zero.
*/
public static OnSubscribeFunc skipLast(
Observable source, int count) {
return new SkipLast(source, count);
}
private static class SkipLast implements OnSubscribeFunc {
private final int count;
private final Observable source;
private SkipLast(Observable source, int count) {
this.count = count;
this.source = source;
}
public Subscription onSubscribe(final Observer observer) {
if (count < 0) {
throw new IndexOutOfBoundsException(
"count could not be negative");
}
final SafeObservableSubscription subscription = new SafeObservableSubscription();
return subscription.wrap(source.subscribe(new Observer() {
private final ReentrantLock lock = new ReentrantLock();
/**
* Store the last count elements until now.
*/
private final Deque deque = new LinkedList();
@Override
public void onCompleted() {
observer.onCompleted();
}
@Override
public void onError(Throwable e) {
observer.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 emit the value
// directly.
try {
observer.onNext(value);
} catch (Throwable ex) {
observer.onError(ex);
subscription.unsubscribe();
}
return;
}
lock.lock();
try {
deque.offerLast(value);
if (deque.size() > count) {
// Now deque has count + 1 elements, so the first
// element in the deque definitely does not belong
// to the last count elements of the source
// sequence. We can emit it now.
observer.onNext(deque.removeFirst());
}
} catch (Throwable ex) {
observer.onError(ex);
subscription.unsubscribe();
} finally {
lock.unlock();
}
}
}));
}
}
/**
* Skip delivering values in the time window before the values.
*
* @param
* the result value type
*/
public static final class SkipLastTimed implements OnSubscribeFunc {
final Observable source;
final long timeInMillis;
final Scheduler scheduler;
public SkipLastTimed(Observable source, long time, TimeUnit unit, Scheduler scheduler) {
this.source = source;
this.timeInMillis = unit.toMillis(time);
this.scheduler = scheduler;
}
@Override
public Subscription onSubscribe(Observer t1) {
return source.subscribe(new SourceObserver(t1, timeInMillis, scheduler));
}
/** Observes the source. */
private static final class SourceObserver implements Observer {
final Observer observer;
final long timeInMillis;
final Scheduler scheduler;
List> buffer = new ArrayList>();
public SourceObserver(Observer observer,
long timeInMillis, Scheduler scheduler) {
this.observer = observer;
this.timeInMillis = timeInMillis;
this.scheduler = scheduler;
}
@Override
public void onNext(T args) {
buffer.add(new Timestamped(scheduler.now(), args));
}
@Override
public void onError(Throwable e) {
buffer = Collections.emptyList();
observer.onError(e);
}
@Override
public void onCompleted() {
long limit = scheduler.now() - timeInMillis;
try {
for (Timestamped v : buffer) {
if (v.getTimestampMillis() < limit) {
try {
observer.onNext(v.getValue());
} catch (Throwable t) {
observer.onError(t);
return;
}
} else {
observer.onCompleted();
break;
}
}
} finally {
buffer = Collections.emptyList();
}
}
}
}
}