rx.subscriptions.SerialSubscription 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.subscriptions;
import java.util.concurrent.atomic.AtomicReference;
import rx.Subscription;
/**
* Represents a subscription whose underlying subscription can be swapped for another subscription which causes
* the previous underlying subscription to be unsubscribed.
*/
public final class SerialSubscription implements Subscription {
final AtomicReference state = new AtomicReference(new State(false, Subscriptions.empty()));
private static final class State {
final boolean isUnsubscribed;
final Subscription subscription;
State(boolean u, Subscription s) {
this.isUnsubscribed = u;
this.subscription = s;
}
State unsubscribe() {
return new State(true, subscription);
}
State set(Subscription s) {
return new State(isUnsubscribed, s);
}
}
@Override
public boolean isUnsubscribed() {
return state.get().isUnsubscribed;
}
@Override
public void unsubscribe() {
State oldState;
State newState;
final AtomicReference localState = this.state;
do {
oldState = localState.get();
if (oldState.isUnsubscribed) {
return;
} else {
newState = oldState.unsubscribe();
}
} while (!localState.compareAndSet(oldState, newState));
oldState.subscription.unsubscribe();
}
/**
* Swaps out the old {@link Subscription} for the specified {@code Subscription}.
*
* @param s
* the new {@code Subscription} to swap in
* @throws IllegalArgumentException
* if {@code s} is {@code null}
*/
public void set(Subscription s) {
if (s == null) {
throw new IllegalArgumentException("Subscription can not be null");
}
State oldState;
State newState;
final AtomicReference localState = this.state;
do {
oldState = localState.get();
if (oldState.isUnsubscribed) {
s.unsubscribe();
return;
} else {
newState = oldState.set(s);
}
} while (!localState.compareAndSet(oldState, newState));
oldState.subscription.unsubscribe();
}
/**
* Retrieves the current {@link Subscription} that is being represented by this {@code SerialSubscription}.
*
* @return the current {@link Subscription} that is being represented by this {@code SerialSubscription}
*/
public Subscription get() {
return state.get().subscription;
}
}