io.reactivex.rxjava3.internal.operators.flowable.BlockingFlowableMostRecent Maven / Gradle / Ivy
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/*
* Copyright (c) 2016-present, RxJava Contributors.
*
* 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 io.reactivex.rxjava3.internal.operators.flowable;
import java.util.*;
import io.reactivex.rxjava3.core.Flowable;
import io.reactivex.rxjava3.internal.util.*;
import io.reactivex.rxjava3.subscribers.DefaultSubscriber;
/**
* Returns an Iterable that always returns the item most recently emitted by an Observable, or a
* seed value if no item has yet been emitted.
*
*
*
* @param the value type
*/
public final class BlockingFlowableMostRecent implements Iterable {
final Flowable source;
final T initialValue;
public BlockingFlowableMostRecent(Flowable source, T initialValue) {
this.source = source;
this.initialValue = initialValue;
}
@Override
public Iterator iterator() {
MostRecentSubscriber mostRecentSubscriber = new MostRecentSubscriber<>(initialValue);
source.subscribe(mostRecentSubscriber);
return mostRecentSubscriber.getIterable();
}
static final class MostRecentSubscriber extends DefaultSubscriber {
volatile Object value;
MostRecentSubscriber(T value) {
this.value = NotificationLite.next(value);
}
@Override
public void onComplete() {
value = NotificationLite.complete();
}
@Override
public void onError(Throwable e) {
value = NotificationLite.error(e);
}
@Override
public void onNext(T args) {
value = NotificationLite.next(args);
}
/**
* The {@link Iterator} return is not thread safe. In other words don't call {@link Iterator#hasNext()} in one
* thread expect {@link Iterator#next()} called from a different thread to work.
* @return the Iterator
*/
public Iterator getIterable() {
return new Iterator();
}
final class Iterator implements java.util.Iterator {
/**
* buffer to make sure that the state of the iterator doesn't change between calling hasNext() and next().
*/
private Object buf;
@Override
public boolean hasNext() {
buf = value;
return !NotificationLite.isComplete(buf);
}
@Override
public T next() {
try {
// if hasNext wasn't called before calling next.
if (buf == null) {
buf = value;
}
if (NotificationLite.isComplete(buf)) {
throw new NoSuchElementException();
}
if (NotificationLite.isError(buf)) {
throw ExceptionHelper.wrapOrThrow(NotificationLite.getError(buf));
}
return NotificationLite.getValue(buf);
}
finally {
buf = null;
}
}
@Override
public void remove() {
throw new UnsupportedOperationException("Read only iterator");
}
}
}
}