io.helidon.security.jersey.RequestedCounter Maven / Gradle / Ivy
/*
* Copyright (c) 2018 Oracle and/or its affiliates. All rights reserved.
*
* 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.helidon.security.jersey;
import java.util.concurrent.atomic.AtomicLong;
import java.util.function.Consumer;
/**
* Requested event counter.
*
* This utility class helps to safely track and process the back-pressure of {@link java.util.concurrent.Flow.Subscriber}s.
*/
@SuppressWarnings("WeakerAccess")
class RequestedCounter {
private final AtomicLong requested = new AtomicLong();
/**
* Increments safely a requested event counter to prevent {@code Long.MAX_VALUE} overflow.
*
* @param increment amount of additional events to request.
*/
public void increment(long increment, Consumer errorHandler) {
if (increment <= 0) {
errorHandler.accept(new IllegalArgumentException("Unsupported requested event increment: " + increment));
return;
}
requested.updateAndGet(original -> {
if (original == Long.MAX_VALUE) {
return Long.MAX_VALUE;
}
long r = original + increment;
// HD 2-12 Overflow iff both arguments have the opposite sign of the result; inspired by Math.addExact(long, long)
if (r == Long.MAX_VALUE || ((original ^ r) & (increment ^ r)) < 0) {
// unbounded reached
return Long.MAX_VALUE;
} else {
return r;
}
});
}
/**
* Tries to safely decrement a positive requested counter value, making sure the value does not drop below zero.
*
* @return {@code true} if the initial positive value has been decremented successfully, {@code false} in case the initial
* counter value was already set to zero.
*/
public boolean tryDecrement() {
return requested.getAndUpdate(val -> val > 0 ? val - 1 : 0) > 0;
}
/**
* Gets the current requested event counter value.
*
* @return current value of the requested event counter.
*/
public long get() {
return requested.get();
}
}