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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.internal.operators;
import java.util.Iterator;
import java.util.concurrent.atomic.AtomicLongFieldUpdater;
import rx.Observable.OnSubscribe;
import rx.Producer;
import rx.Subscriber;
/**
* Converts an {@code Iterable} sequence into an {@code Observable}.
*
* 
*
* You can convert any object that supports the Iterable interface into an Observable that emits each item in
* the object, with the {@code toObservable} operation.
*/
public final class OnSubscribeFromIterable implements OnSubscribe {
final Iterable is;
public OnSubscribeFromIterable(Iterable iterable) {
this.is = iterable;
}
@Override
public void call(final Subscriber o) {
if (is == null) {
o.onCompleted();
}
final Iterator it = is.iterator();
o.setProducer(new IterableProducer(o, it));
}
private static final class IterableProducer implements Producer {
private final Subscriber o;
private final Iterator it;
private volatile long requested = 0;
@SuppressWarnings("rawtypes")
private static final AtomicLongFieldUpdater REQUESTED_UPDATER = AtomicLongFieldUpdater.newUpdater(IterableProducer.class, "requested");
private IterableProducer(Subscriber o, Iterator it) {
this.o = o;
this.it = it;
}
@Override
public void request(long n) {
if (REQUESTED_UPDATER.get(this) == Long.MAX_VALUE) {
// already started with fast-path
return;
}
if (n == Long.MAX_VALUE) {
REQUESTED_UPDATER.set(this, n);
// fast-path without backpressure
while (it.hasNext()) {
if (o.isUnsubscribed()) {
return;
}
o.onNext(it.next());
}
if (!o.isUnsubscribed()) {
o.onCompleted();
}
} else if(n > 0) {
// backpressure is requested
long _c = REQUESTED_UPDATER.getAndAdd(this, n);
if (_c == 0) {
while (true) {
/*
* This complicated logic is done to avoid touching the volatile `requested` value
* during the loop itself. If it is touched during the loop the performance is impacted significantly.
*/
long r = requested;
long numToEmit = r;
while (it.hasNext() && --numToEmit >= 0) {
if (o.isUnsubscribed()) {
return;
}
o.onNext(it.next());
}
if (!it.hasNext()) {
o.onCompleted();
return;
}
if (REQUESTED_UPDATER.addAndGet(this, -r) == 0) {
// we're done emitting the number requested so return
return;
}
}
}
}
}
}
}