rx.internal.operators.OnSubscribeRange Maven / Gradle / Ivy
/**
* 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.concurrent.atomic.AtomicLong;
import rx.*;
import rx.Observable.OnSubscribe;
/**
* Emit ints from start to end inclusive.
*/
public final class OnSubscribeRange implements OnSubscribe {
private final int start;
private final int end;
public OnSubscribeRange(int start, int end) {
this.start = start;
this.end = end;
}
@Override
public void call(final Subscriber o) {
o.setProducer(new RangeProducer(o, start, end));
}
private static final class RangeProducer extends AtomicLong implements Producer {
/** */
private static final long serialVersionUID = 4114392207069098388L;
private final Subscriber o;
private final int end;
private long index;
private RangeProducer(Subscriber o, int start, int end) {
this.o = o;
this.index = start;
this.end = end;
}
@Override
public void request(long n) {
if (get() == Long.MAX_VALUE) {
// already started with fast-path
return;
}
if (n == Long.MAX_VALUE && compareAndSet(0L, Long.MAX_VALUE)) {
// fast-path without backpressure
fastpath();
} else if (n > 0L) {
long c = BackpressureUtils.getAndAddRequest(this, n);
if (c == 0L) {
// backpressure is requested
slowpath(n);
}
}
}
/**
*
*/
void slowpath(long r) {
long idx = index;
while (true) {
/*
* This complicated logic is done to avoid touching the volatile `index` and `requested` values
* during the loop itself. If they are touched during the loop the performance is impacted significantly.
*/
long fs = end - idx + 1;
long e = Math.min(fs, r);
final boolean complete = fs <= r;
fs = e + idx;
final Subscriber o = this.o;
for (long i = idx; i != fs; i++) {
if (o.isUnsubscribed()) {
return;
}
o.onNext((int) i);
}
if (complete) {
if (o.isUnsubscribed()) {
return;
}
o.onCompleted();
return;
}
idx = fs;
index = fs;
r = addAndGet(-e);
if (r == 0L) {
// we're done emitting the number requested so return
return;
}
}
}
/**
*
*/
void fastpath() {
final long end = this.end + 1L;
final Subscriber o = this.o;
for (long i = index; i != end; i++) {
if (o.isUnsubscribed()) {
return;
}
o.onNext((int) i);
}
if (!o.isUnsubscribed()) {
o.onCompleted();
}
}
}
}