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rxjava2-backport developed by David Karnok
/**
* Copyright 2015 David Karnok and 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 hu.akarnokd.rxjava2.internal.subscriptions;
/**
* Copyright 2015 David Karnok and 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.
*/
import java.util.Queue;
import java.util.concurrent.atomic.*;
import org.reactivestreams.Subscription;
import hu.akarnokd.rxjava2.internal.functions.Objects;
import hu.akarnokd.rxjava2.internal.queue.MpscLinkedQueue;
import hu.akarnokd.rxjava2.internal.util.BackpressureHelper;
import hu.akarnokd.rxjava2.plugins.RxJavaPlugins;
/**
* Arbitrates requests and cancellation between Subscriptions.
*/
public final class SubscriptionArbiter extends AtomicInteger implements Subscription {
/** */
private static final long serialVersionUID = -2189523197179400958L;
final Queue missedSubscription = new MpscLinkedQueue();
Subscription actual;
long requested;
volatile boolean cancelled;
volatile long missedRequested;
static final AtomicLongFieldUpdater MISSED_REQUESTED =
AtomicLongFieldUpdater.newUpdater(SubscriptionArbiter.class, "missedRequested");
volatile long missedProduced;
static final AtomicLongFieldUpdater MISSED_PRODUCED =
AtomicLongFieldUpdater.newUpdater(SubscriptionArbiter.class, "missedProduced");
private long addRequested(long n) {
long r = requested;
long u = BackpressureHelper.addCap(r, n);
requested = u;
return r;
}
@Override
public void request(final long n) {
if (SubscriptionHelper.validateRequest(n)) {
return;
}
if (cancelled) {
return;
}
if (get() == 0 && compareAndSet(0, 1)) {
addRequested(n);
Subscription s = actual;
if (s != null) {
s.request(n);
}
if (decrementAndGet() == 0) {
return;
}
} else {
BackpressureHelper.add(MISSED_REQUESTED, SubscriptionArbiter.this, n);
if (getAndIncrement() != 0) {
return;
}
}
int missed = 1;
for (;;) {
SubscriptionArbiter.this.drain();
missed = addAndGet(-missed);
if (missed == 0) {
return;
}
}
}
public void produced(final long n) {
if (n <= 0) {
RxJavaPlugins.onError(new IllegalArgumentException("n > 0 required but it was " + n));
return;
}
if (get() == 0 && compareAndSet(0, 1)) {
long r = requested;
if (r != Long.MAX_VALUE) {
long u = r - n;
if (u < 0L) {
RxJavaPlugins.onError(new IllegalArgumentException("More produced than requested: " + u));
u = 0;
}
requested = u;
}
if (decrementAndGet() == 0) {
return;
}
} else {
BackpressureHelper.add(MISSED_PRODUCED, SubscriptionArbiter.this, n);
if (getAndIncrement() != 0) {
return;
}
}
int missed = 1;
for (;;) {
SubscriptionArbiter.this.drain();
missed = addAndGet(-missed);
if (missed == 0) {
return;
}
}
}
public void setSubscription(final Subscription s) {
Objects.requireNonNull(s, "s is null");
if (cancelled) {
s.cancel();
return;
}
if (get() == 0 && compareAndSet(0, 1)) {
Subscription a = actual;
if (a != null) {
a.cancel();
}
actual = s;
long r = requested;
if (r != 0L) {
s.request(r);
}
if (decrementAndGet() == 0) {
return;
}
} else {
missedSubscription.offer(s);
if (getAndIncrement() != 0) {
return;
}
}
int missed = 1;
for (;;) {
SubscriptionArbiter.this.drain();
missed = addAndGet(-missed);
if (missed == 0) {
return;
}
}
}
@Override
public void cancel() {
if (cancelled) {
return;
}
cancelled = true;
if (get() == 0 && compareAndSet(0, 1)) {
Subscription a = actual;
if (a != null) {
actual = null;
a.cancel();
}
if (decrementAndGet() == 0) {
return;
}
} else {
if (getAndIncrement() != 0) {
return;
}
}
int missed = 1;
for (;;) {
SubscriptionArbiter.this.drain();
missed = addAndGet(-missed);
if (missed == 0) {
return;
}
}
}
public boolean isCancelled() {
return cancelled;
}
void drain() {
long mr = MISSED_REQUESTED.getAndSet(this, 0L);
long mp = MISSED_PRODUCED.getAndSet(this, 0L);
Subscription ms = missedSubscription.poll();
boolean c = cancelled;
long r = requested;
if (r != Long.MAX_VALUE && !c) {
long u = r + mr;
if (u < 0L) {
r = Long.MAX_VALUE;
requested = Long.MAX_VALUE;
} else {
long v = u - mp;
if (v < 0L) {
RxJavaPlugins.onError(new IllegalStateException("More produced than requested: " + v));
v = 0L;
}
r = v;
requested = v;
}
}
Subscription a = actual;
if (c && a != null) {
actual = null;
a.cancel();
}
if (ms == null) {
if (a != null && mr != 0L) {
a.request(mr);
}
} else {
if (c) {
ms.cancel();
} else {
if (a != null) {
a.cancel();
}
actual = ms;
if (r != 0L) {
ms.request(r);
}
}
}
}
}
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