one.nio.lock.FairRWLock Maven / Gradle / Ivy

/*
 * Copyright 2015 Odnoklassniki Ltd, Mail.Ru Group
 *
 * 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 one.nio.lock;

public class FairRWLock extends RWLock {

    @Override
    protected int tryAcquireShared(int acquires) {
        for (;;) {
            if (hasQueuedPredecessors()) {
                return -1;
            }
            int state = getState();
            int remaining = state - acquires;
            if (remaining < 0 || compareAndSetState(state, remaining)) {
                return remaining;
            }
        }
    }
}