/**
* Copyright 2015 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 java.util.concurrent.atomic.AtomicLongFieldUpdater;
/**
* Utility functions for use with backpressure.
*
*/
final class BackpressureUtils {
/**
* Adds {@code n} to {@code requested} field and returns the value prior to
* addition once the addition is successful (uses CAS semantics). If
* overflows then sets {@code requested} field to {@code Long.MAX_VALUE}.
*
* @param requested
* atomic field updater for a request count
* @param object
* contains the field updated by the updater
* @param n
* the number of requests to add to the requested count
* @return requested value just prior to successful addition
*/
static <T> long getAndAddRequest(AtomicLongFieldUpdater<T> requested, T object, long n) {
// add n to field but check for overflow
while (true) {
long current = requested.get(object);
long next = current + n;
// check for overflow
if (next < 0)
next = Long.MAX_VALUE;
if (requested.compareAndSet(object, current, next))
return current;
}
}
/**
* Adds {@code n} to {@code requested} and returns the value prior to addition once the
* addition is successful (uses CAS semantics). If overflows then sets
* {@code requested} field to {@code Long.MAX_VALUE}.
*
* @param requested
* atomic field updater for a request count
* @param object
* contains the field updated by the updater
* @param n
* the number of requests to add to the requested count
* @return requested value just prior to successful addition
*/
static <T> long getAndAddRequest(AtomicLong requested, long n) {
// add n to field but check for overflow
while (true) {
long current = requested.get();
long next = current + n;
// check for overflow
if (next < 0)
next = Long.MAX_VALUE;
if (requested.compareAndSet(current, next))
return current;
}
}
}