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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.eclipse.aether.named.support;
import java.util.ArrayDeque;
import java.util.Deque;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReadWriteLock;
/**
* Named lock support implementation that is using {@link ReadWriteLock} instances. The adapted lock MUST SUPPORT
* reentrancy, non re-entrant locks will NOT work. It is the responsibility of an adapting lock, to ensure that
* above lock requirement stands.
*/
public class ReadWriteLockNamedLock extends NamedLockSupport {
private enum Step {
/**
* Step when {@link ReadWriteLock#readLock()} was locked
*/
SHARED,
/**
* Step when {@link ReadWriteLock#writeLock()} was locked
*/
EXCLUSIVE
}
private final ThreadLocal> threadSteps;
private final ReadWriteLock readWriteLock;
public ReadWriteLockNamedLock(
final String name, final NamedLockFactorySupport factory, final ReadWriteLock readWriteLock) {
super(name, factory);
this.threadSteps = ThreadLocal.withInitial(ArrayDeque::new);
this.readWriteLock = readWriteLock;
}
@Override
protected boolean doLockShared(final long time, final TimeUnit unit) throws InterruptedException {
Deque steps = threadSteps.get();
if (readWriteLock.readLock().tryLock(time, unit)) {
steps.push(Step.SHARED);
return true;
}
return false;
}
@Override
protected boolean doLockExclusively(final long time, final TimeUnit unit) throws InterruptedException {
Deque steps = threadSteps.get();
if (!steps.isEmpty()) { // we already own shared or exclusive lock
if (!steps.contains(Step.EXCLUSIVE)) {
throw new LockUpgradeNotSupportedException(this); // Lock upgrade not supported
}
}
if (readWriteLock.writeLock().tryLock(time, unit)) {
steps.push(Step.EXCLUSIVE);
return true;
}
return false;
}
@Override
protected void doUnlock() {
Deque steps = threadSteps.get();
if (steps.isEmpty()) {
throw new IllegalStateException("Wrong API usage: unlock without lock");
}
Step step = steps.pop();
if (Step.SHARED == step) {
readWriteLock.readLock().unlock();
} else if (Step.EXCLUSIVE == step) {
readWriteLock.writeLock().unlock();
}
}
}