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Reactive Extensions for Java
/*
* 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.observable;
import java.util.Objects;
import java.util.concurrent.atomic.AtomicInteger;
import io.reactivex.rxjava3.annotations.Nullable;
import io.reactivex.rxjava3.core.*;
import io.reactivex.rxjava3.exceptions.Exceptions;
import io.reactivex.rxjava3.functions.*;
import io.reactivex.rxjava3.internal.disposables.EmptyDisposable;
import io.reactivex.rxjava3.operators.QueueDisposable;
import io.reactivex.rxjava3.plugins.RxJavaPlugins;
/**
* Utility classes to work with scalar-sourced XMap operators (where X == { flat, concat, switch }).
*/
public final class ObservableScalarXMap {
/** Utility class. */
private ObservableScalarXMap() {
throw new IllegalStateException("No instances!");
}
/**
* Tries to subscribe to a possibly Supplier source's mapped ObservableSource.
* @param the input value type
* @param the output value type
* @param source the source ObservableSource
* @param observer the subscriber
* @param mapper the function mapping a scalar value into an ObservableSource
* @return true if successful, false if the caller should continue with the regular path.
*/
@SuppressWarnings("unchecked")
public static boolean tryScalarXMapSubscribe(ObservableSource source,
Observer observer,
Function> mapper) {
if (source instanceof Supplier) {
T t;
try {
t = ((Supplier)source).get();
} catch (Throwable ex) {
Exceptions.throwIfFatal(ex);
EmptyDisposable.error(ex, observer);
return true;
}
if (t == null) {
EmptyDisposable.complete(observer);
return true;
}
ObservableSource r;
try {
r = Objects.requireNonNull(mapper.apply(t), "The mapper returned a null ObservableSource");
} catch (Throwable ex) {
Exceptions.throwIfFatal(ex);
EmptyDisposable.error(ex, observer);
return true;
}
if (r instanceof Supplier) {
R u;
try {
u = ((Supplier)r).get();
} catch (Throwable ex) {
Exceptions.throwIfFatal(ex);
EmptyDisposable.error(ex, observer);
return true;
}
if (u == null) {
EmptyDisposable.complete(observer);
return true;
}
ScalarDisposable sd = new ScalarDisposable<>(observer, u);
observer.onSubscribe(sd);
sd.run();
} else {
r.subscribe(observer);
}
return true;
}
return false;
}
/**
* Maps a scalar value into an Observable and emits its values.
*
* @param the scalar value type
* @param the output value type
* @param value the scalar value to map
* @param mapper the function that gets the scalar value and should return
* an ObservableSource that gets streamed
* @return the new Observable instance
*/
public static Observable scalarXMap(T value,
Function> mapper) {
return RxJavaPlugins.onAssembly(new ScalarXMapObservable<>(value, mapper));
}
/**
* Maps a scalar value to an ObservableSource and subscribes to it.
*
* @param the scalar value type
* @param the mapped ObservableSource's element type.
*/
static final class ScalarXMapObservable extends Observable {
final T value;
final Function> mapper;
ScalarXMapObservable(T value,
Function> mapper) {
this.value = value;
this.mapper = mapper;
}
@SuppressWarnings("unchecked")
@Override
public void subscribeActual(Observer observer) {
ObservableSource other;
try {
other = Objects.requireNonNull(mapper.apply(value), "The mapper returned a null ObservableSource");
} catch (Throwable e) {
Exceptions.throwIfFatal(e);
EmptyDisposable.error(e, observer);
return;
}
if (other instanceof Supplier) {
R u;
try {
u = ((Supplier)other).get();
} catch (Throwable ex) {
Exceptions.throwIfFatal(ex);
EmptyDisposable.error(ex, observer);
return;
}
if (u == null) {
EmptyDisposable.complete(observer);
return;
}
ScalarDisposable sd = new ScalarDisposable<>(observer, u);
observer.onSubscribe(sd);
sd.run();
} else {
other.subscribe(observer);
}
}
}
/**
* Represents a Disposable that signals one onNext followed by an onComplete.
*
* @param the value type
*/
public static final class ScalarDisposable
extends AtomicInteger
implements QueueDisposable, Runnable {
private static final long serialVersionUID = 3880992722410194083L;
final Observer observer;
final T value;
static final int START = 0;
static final int FUSED = 1;
static final int ON_NEXT = 2;
static final int ON_COMPLETE = 3;
public ScalarDisposable(Observer observer, T value) {
this.observer = observer;
this.value = value;
}
@Override
public boolean offer(T value) {
throw new UnsupportedOperationException("Should not be called!");
}
@Override
public boolean offer(T v1, T v2) {
throw new UnsupportedOperationException("Should not be called!");
}
@Nullable
@Override
public T poll() {
if (get() == FUSED) {
lazySet(ON_COMPLETE);
return value;
}
return null;
}
@Override
public boolean isEmpty() {
return get() != FUSED;
}
@Override
public void clear() {
lazySet(ON_COMPLETE);
}
@Override
public void dispose() {
set(ON_COMPLETE);
}
@Override
public boolean isDisposed() {
return get() == ON_COMPLETE;
}
@Override
public int requestFusion(int mode) {
if ((mode & SYNC) != 0) {
lazySet(FUSED);
return SYNC;
}
return NONE;
}
@Override
public void run() {
if (get() == START && compareAndSet(START, ON_NEXT)) {
observer.onNext(value);
if (get() == ON_NEXT) {
lazySet(ON_COMPLETE);
observer.onComplete();
}
}
}
}
}
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