src/main/java/rx/internal/operators/OperatorSwitch.java
/**
* 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.*;
import java.util.concurrent.atomic.AtomicLong;
import rx.*;
import rx.Observable;
import rx.Observable.Operator;
import rx.exceptions.CompositeException;
import rx.functions.Action0;
import rx.internal.util.RxRingBuffer;
import rx.internal.util.atomic.SpscLinkedArrayQueue;
import rx.plugins.RxJavaHooks;
import rx.subscriptions.*;
/**
* Transforms an Observable that emits Observables into a single Observable that
* emits the items emitted by the most recently published of those Observables.
* <p>
* <img width="640" src="https://github.com/ReactiveX/RxJava/wiki/images/rx-operators/switchDo.png" alt="">
*
* @param <T> the value type
*/
public final class OperatorSwitch<T> implements Operator<T, Observable<? extends T>> {
final boolean delayError;
/** Lazy initialization via inner-class holder. */
static final class Holder {
/** A singleton instance. */
static final OperatorSwitch<Object> INSTANCE = new OperatorSwitch<Object>(false);
}
/** Lazy initialization via inner-class holder. */
static final class HolderDelayError {
/** A singleton instance. */
static final OperatorSwitch<Object> INSTANCE = new OperatorSwitch<Object>(true);
}
/**
* Returns a singleton instance of the operator based on the delayError parameter.
* @param <T> the value type
* @param delayError should the errors of the inner sources delayed until the main sequence completes?
* @return a singleton instance of this stateless operator.
*/
@SuppressWarnings({ "unchecked" })
public static <T> OperatorSwitch<T> instance(boolean delayError) {
if (delayError) {
return (OperatorSwitch<T>)HolderDelayError.INSTANCE;
}
return (OperatorSwitch<T>)Holder.INSTANCE;
}
OperatorSwitch(boolean delayError) {
this.delayError = delayError;
}
@Override
public Subscriber<? super Observable<? extends T>> call(final Subscriber<? super T> child) {
SwitchSubscriber<T> sws = new SwitchSubscriber<T>(child, delayError);
child.add(sws);
sws.init();
return sws;
}
static final class SwitchSubscriber<T> extends Subscriber<Observable<? extends T>> {
final Subscriber<? super T> child;
final SerialSubscription serial;
final boolean delayError;
final AtomicLong index;
final SpscLinkedArrayQueue<Object> queue;
boolean emitting;
boolean missed;
long requested;
Producer producer;
volatile boolean mainDone;
Throwable error;
boolean innerActive;
static final Throwable TERMINAL_ERROR = new Throwable("Terminal error");
SwitchSubscriber(Subscriber<? super T> child, boolean delayError) {
this.child = child;
this.serial = new SerialSubscription();
this.delayError = delayError;
this.index = new AtomicLong();
this.queue = new SpscLinkedArrayQueue<Object>(RxRingBuffer.SIZE);
}
void init() {
child.add(serial);
child.add(Subscriptions.create(new Action0() {
@Override
public void call() {
clearProducer();
}
}));
child.setProducer(new Producer() {
@Override
public void request(long n) {
if (n > 0L) {
childRequested(n);
} else
if (n < 0L) {
throw new IllegalArgumentException("n >= 0 expected but it was " + n);
}
}
});
}
void clearProducer() {
synchronized (this) {
producer = null;
}
}
@Override
public void onNext(Observable<? extends T> t) {
long id = index.incrementAndGet();
Subscription s = serial.get();
if (s != null) {
s.unsubscribe();
}
InnerSubscriber<T> inner;
synchronized (this) {
inner = new InnerSubscriber<T>(id, this);
innerActive = true;
producer = null;
}
serial.set(inner);
t.unsafeSubscribe(inner);
}
@Override
public void onError(Throwable e) {
boolean success;
synchronized (this) {
success = updateError(e);
}
if (success) {
mainDone = true;
drain();
} else {
pluginError(e);
}
}
boolean updateError(Throwable next) {
Throwable e = error;
if (e == TERMINAL_ERROR) {
return false;
} else
if (e == null) {
error = next;
} else
if (e instanceof CompositeException) {
List<Throwable> list = new ArrayList<Throwable>(((CompositeException)e).getExceptions());
list.add(next);
error = new CompositeException(list);
} else {
error = new CompositeException(e, next);
}
return true;
}
@Override
public void onCompleted() {
mainDone = true;
drain();
}
void emit(T value, InnerSubscriber<T> inner) {
synchronized (this) {
if (index.get() != inner.id) {
return;
}
queue.offer(inner, NotificationLite.next(value));
}
drain();
}
void error(Throwable e, long id) {
boolean success;
synchronized (this) {
if (index.get() == id) {
success = updateError(e);
innerActive = false;
producer = null;
} else {
success = true;
}
}
if (success) {
drain();
} else {
pluginError(e);
}
}
void complete(long id) {
synchronized (this) {
if (index.get() != id) {
return;
}
innerActive = false;
producer = null;
}
drain();
}
void pluginError(Throwable e) {
RxJavaHooks.onError(e);
}
void innerProducer(Producer p, long id) {
long n;
synchronized (this) {
if (index.get() != id) {
return;
}
n = requested;
producer = p;
}
p.request(n);
}
void childRequested(long n) {
Producer p;
synchronized (this) {
p = producer;
requested = BackpressureUtils.addCap(requested, n);
}
if (p != null) {
p.request(n);
}
drain();
}
void drain() {
boolean localInnerActive;
long localRequested;
Throwable localError;
synchronized (this) {
if (emitting) {
missed = true;
return;
}
emitting = true;
localInnerActive = innerActive;
localRequested = requested;
localError = error;
if (localError != null && localError != TERMINAL_ERROR && !delayError) {
error = TERMINAL_ERROR;
}
}
final SpscLinkedArrayQueue<Object> localQueue = queue;
final AtomicLong localIndex = index;
final Subscriber<? super T> localChild = child;
boolean localMainDone = mainDone;
for (;;) {
long localEmission = 0L;
while (localEmission != localRequested) {
if (localChild.isUnsubscribed()) {
return;
}
boolean empty = localQueue.isEmpty();
if (checkTerminated(localMainDone, localInnerActive, localError,
localQueue, localChild, empty)) {
return;
}
if (empty) {
break;
}
@SuppressWarnings("unchecked")
InnerSubscriber<T> inner = (InnerSubscriber<T>)localQueue.poll();
T value = NotificationLite.getValue(localQueue.poll());
if (localIndex.get() == inner.id) {
localChild.onNext(value);
localEmission++;
}
}
if (localEmission == localRequested) {
if (localChild.isUnsubscribed()) {
return;
}
if (checkTerminated(mainDone, localInnerActive, localError, localQueue,
localChild, localQueue.isEmpty())) {
return;
}
}
synchronized (this) {
localRequested = requested;
if (localRequested != Long.MAX_VALUE) {
localRequested -= localEmission;
requested = localRequested;
}
if (!missed) {
emitting = false;
return;
}
missed = false;
localMainDone = mainDone;
localInnerActive = innerActive;
localError = error;
if (localError != null && localError != TERMINAL_ERROR && !delayError) {
error = TERMINAL_ERROR;
}
}
}
}
protected boolean checkTerminated(boolean localMainDone, boolean localInnerActive, Throwable localError,
final SpscLinkedArrayQueue<Object> localQueue, final Subscriber<? super T> localChild, boolean empty) {
if (delayError) {
if (localMainDone && !localInnerActive && empty) {
if (localError != null) {
localChild.onError(localError);
} else {
localChild.onCompleted();
}
return true;
}
} else {
if (localError != null) {
localQueue.clear();
localChild.onError(localError);
return true;
} else
if (localMainDone && !localInnerActive && empty) {
localChild.onCompleted();
return true;
}
}
return false;
}
}
static final class InnerSubscriber<T> extends Subscriber<T> {
private final long id;
private final SwitchSubscriber<T> parent;
InnerSubscriber(long id, SwitchSubscriber<T> parent) {
this.id = id;
this.parent = parent;
}
@Override
public void setProducer(Producer p) {
parent.innerProducer(p, id);
}
@Override
public void onNext(T t) {
parent.emit(t, this);
}
@Override
public void onError(Throwable e) {
parent.error(e, id);
}
@Override
public void onCompleted() {
parent.complete(id);
}
}
}