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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.internal.subscriptions;
/**
* 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.
*/
import java.util.concurrent.atomic.*;
import org.reactivestreams.Subscription;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.util.BackpressureHelper;
/**
* Arbitrates requests and cancellation between Subscriptions.
*/
public class SubscriptionArbiter extends AtomicInteger implements Subscription {
private static final long serialVersionUID = -2189523197179400958L;
/**
* The current subscription which may null if no Subscriptions have been set.
*/
Subscription actual;
/**
* The current outstanding request amount.
*/
long requested;
final AtomicReference missedSubscription;
final AtomicLong missedRequested;
final AtomicLong missedProduced;
final boolean cancelOnReplace;
volatile boolean cancelled;
protected boolean unbounded;
public SubscriptionArbiter(boolean cancelOnReplace) {
this.cancelOnReplace = cancelOnReplace;
missedSubscription = new AtomicReference();
missedRequested = new AtomicLong();
missedProduced = new AtomicLong();
}
/**
* Atomically sets a new subscription.
* @param s the subscription to set, not null (verified)
*/
public final void setSubscription(Subscription s) {
if (cancelled) {
s.cancel();
return;
}
ObjectHelper.requireNonNull(s, "s is null");
if (get() == 0 && compareAndSet(0, 1)) {
Subscription a = actual;
if (a != null && cancelOnReplace) {
a.cancel();
}
actual = s;
long r = requested;
if (decrementAndGet() != 0) {
drainLoop();
}
if (r != 0L) {
s.request(r);
}
return;
}
Subscription a = missedSubscription.getAndSet(s);
if (a != null && cancelOnReplace) {
a.cancel();
}
drain();
}
@Override
public final void request(long n) {
if (SubscriptionHelper.validate(n)) {
if (unbounded) {
return;
}
if (get() == 0 && compareAndSet(0, 1)) {
long r = requested;
if (r != Long.MAX_VALUE) {
r = BackpressureHelper.addCap(r, n);
requested = r;
if (r == Long.MAX_VALUE) {
unbounded = true;
}
}
Subscription a = actual;
if (decrementAndGet() != 0) {
drainLoop();
}
if (a != null) {
a.request(n);
}
return;
}
BackpressureHelper.add(missedRequested, n);
drain();
}
}
public final void produced(long n) {
if (unbounded) {
return;
}
if (get() == 0 && compareAndSet(0, 1)) {
long r = requested;
if (r != Long.MAX_VALUE) {
long u = r - n;
if (u < 0L) {
SubscriptionHelper.reportMoreProduced(u);
u = 0;
}
requested = u;
}
if (decrementAndGet() == 0) {
return;
}
drainLoop();
return;
}
BackpressureHelper.add(missedProduced, n);
drain();
}
@Override
public void cancel() {
if (!cancelled) {
cancelled = true;
drain();
}
}
final void drain() {
if (getAndIncrement() != 0) {
return;
}
drainLoop();
}
final void drainLoop() {
int missed = 1;
long requestAmount = 0L;
Subscription requestTarget = null;
for (; ; ) {
Subscription ms = missedSubscription.get();
if (ms != null) {
ms = missedSubscription.getAndSet(null);
}
long mr = missedRequested.get();
if (mr != 0L) {
mr = missedRequested.getAndSet(0L);
}
long mp = missedProduced.get();
if (mp != 0L) {
mp = missedProduced.getAndSet(0L);
}
Subscription a = actual;
if (cancelled) {
if (a != null) {
a.cancel();
actual = null;
}
if (ms != null) {
ms.cancel();
}
} else {
long r = requested;
if (r != Long.MAX_VALUE) {
long u = BackpressureHelper.addCap(r, mr);
if (u != Long.MAX_VALUE) {
long v = u - mp;
if (v < 0L) {
SubscriptionHelper.reportMoreProduced(v);
v = 0;
}
r = v;
} else {
r = u;
}
requested = r;
}
if (ms != null) {
if (a != null && cancelOnReplace) {
a.cancel();
}
actual = ms;
if (r != 0L) {
requestAmount = BackpressureHelper.addCap(requestAmount, r);
requestTarget = ms;
}
} else if (a != null && mr != 0L) {
requestAmount = BackpressureHelper.addCap(requestAmount, mr);
requestTarget = a;
}
}
missed = addAndGet(-missed);
if (missed == 0) {
if (requestAmount != 0L) {
requestTarget.request(requestAmount);
}
return;
}
}
}
/**
* Returns true if the arbiter runs in unbounded mode.
* @return true if the arbiter runs in unbounded mode
*/
public final boolean isUnbounded() {
return unbounded;
}
/**
* Returns true if the arbiter has been cancelled.
* @return true if the arbiter has been cancelled
*/
public final boolean isCancelled() {
return cancelled;
}
}