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rxjava2-extensions developed by David Karnok
/*
* Copyright 2016-2018 David Karnok
*
* 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 hu.akarnokd.rxjava2.operators;
import java.util.concurrent.atomic.*;
import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.functions.Function;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.util.AtomicThrowable;
import io.reactivex.plugins.RxJavaPlugins;
/**
* FlatMap only one {@link ObservableSource} at a time and keep the latest upstream value until it terminates
* and resume with the {@code ObservableSource} mapped for that latest upstream value.
* @param the upstream value type
* @param the output type
* @since 0.19.0
*/
final class ObservableFlatMapLatest extends Observable implements ObservableTransformer {
final Observable source;
final Function> mapper;
ObservableFlatMapLatest(Observable source,
Function> mapper) {
this.source = source;
this.mapper = mapper;
}
@Override
public ObservableSource apply(Observable upstream) {
return new ObservableFlatMapLatest(upstream, mapper);
}
@Override
protected void subscribeActual(Observer observer) {
source.subscribe(new FlatMapLatestObserver(observer, mapper));
}
static final class FlatMapLatestObserver
extends AtomicInteger
implements Observer, Disposable {
private static final long serialVersionUID = 1251911925259779985L;
final Observer downstream;
final Function> mapper;
final FlatMapLatestInnerObserver innerObserver;
final AtomicThrowable errors;
final AtomicReference latest;
Disposable upstream;
volatile boolean active;
volatile boolean done;
volatile boolean disposed;
FlatMapLatestObserver(Observer downstream,
Function> mapper) {
this.downstream = downstream;
this.mapper = mapper;
this.innerObserver = new FlatMapLatestInnerObserver();
this.errors = new AtomicThrowable();
this.latest = new AtomicReference();
}
@Override
public void onSubscribe(Disposable d) {
if (DisposableHelper.validate(upstream, d)) {
this.upstream = d;
downstream.onSubscribe(this);
}
}
@Override
public void onNext(T t) {
latest.set(t);
drain();
}
@Override
public void onError(Throwable e) {
if (errors.addThrowable(e)) {
onComplete();
} else {
RxJavaPlugins.onError(e);
}
}
@Override
public void onComplete() {
done = true;
drain();
}
@Override
public void dispose() {
disposed = true;
upstream.dispose();
DisposableHelper.dispose(innerObserver);
if (getAndIncrement() == 0) {
latest.lazySet(null);
}
}
@Override
public boolean isDisposed() {
return disposed;
}
void innerNext(R item) {
downstream.onNext(item);
}
void innerError(Throwable e) {
if (errors.addThrowable(e)) {
innerComplete();
} else {
RxJavaPlugins.onError(e);
}
}
void innerComplete() {
active = false;
drain();
}
void drain() {
if (getAndIncrement() != 0) {
return;
}
do {
if (disposed) {
latest.lazySet(null);
return;
}
if (!active) {
boolean d = done;
T v = latest.getAndSet(null);
if (d && v == null) {
Throwable ex = errors.terminate();
if (ex == null) {
downstream.onComplete();
} else {
downstream.onError(ex);
}
return;
}
if (v != null) {
ObservableSource o;
try {
o = ObjectHelper.requireNonNull(mapper.apply(v), "The mapper returned a null ObservableSource");
} catch (Throwable ex) {
Exceptions.throwIfFatal(ex);
upstream.dispose();
errors.addThrowable(ex);
ex = errors.terminate();
downstream.onError(ex);
return;
}
active = true;
o.subscribe(innerObserver);
}
}
} while (decrementAndGet() != 0);
}
final class FlatMapLatestInnerObserver
extends AtomicReference
implements Observer {
private static final long serialVersionUID = -3707363807296094399L;
@Override
public void onSubscribe(Disposable d) {
DisposableHelper.replace(this, d);
}
@Override
public void onNext(R t) {
innerNext(t);
}
@Override
public void onError(Throwable e) {
innerError(e);
}
@Override
public void onComplete() {
innerComplete();
}
}
}
}