org.redisson.pubsub.AsyncSemaphore Maven / Gradle / Ivy
/**
* Copyright 2018 Nikita Koksharov
*
* 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 org.redisson.pubsub;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Set;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
/**
*
* @author Nikita Koksharov
*
*/
public class AsyncSemaphore {
private int counter;
private final Set listeners = new LinkedHashSet();
public AsyncSemaphore(int permits) {
counter = permits;
}
public boolean tryAcquire(long timeoutMillis) {
final CountDownLatch latch = new CountDownLatch(1);
final Runnable listener = new Runnable() {
@Override
public void run() {
latch.countDown();
}
};
acquire(listener);
try {
boolean res = latch.await(timeoutMillis, TimeUnit.MILLISECONDS);
if (!res) {
if (!remove(listener)) {
release();
}
}
return res;
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
if (!remove(listener)) {
release();
}
return false;
}
}
public int queueSize() {
synchronized (this) {
return listeners.size();
}
}
public void removeListeners() {
synchronized (this) {
listeners.clear();
}
}
public void acquire(Runnable listener) {
boolean run = false;
synchronized (this) {
if (counter == 0) {
listeners.add(listener);
return;
}
if (counter > 0) {
counter--;
run = true;
}
}
if (run) {
listener.run();
}
}
public boolean remove(Runnable listener) {
synchronized (this) {
return listeners.remove(listener);
}
}
public int getCounter() {
return counter;
}
public void release() {
Runnable runnable = null;
synchronized (this) {
counter++;
Iterator iter = listeners.iterator();
if (iter.hasNext()) {
runnable = iter.next();
iter.remove();
}
}
if (runnable != null) {
acquire(runnable);
}
}
}