| /* |
| * 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.apache.cassandra.utils.concurrent; |
| |
| import java.util.concurrent.atomic.AtomicIntegerFieldUpdater; |
| |
| import org.apache.cassandra.utils.Intercept; |
| import org.apache.cassandra.utils.Shared; |
| |
| import static org.apache.cassandra.utils.Shared.Scope.SIMULATION; |
| |
| @Shared(scope = SIMULATION) |
| public interface CountDownLatch extends Awaitable |
| { |
| /** |
| * Count down by 1, signalling waiters if we have reached zero |
| */ |
| void decrement(); |
| |
| /** |
| * @return the current count |
| */ |
| int count(); |
| |
| /** |
| * Factory method used to capture and redirect instantiations for simulation |
| */ |
| @Intercept |
| static CountDownLatch newCountDownLatch(int count) |
| { |
| return new Async(count); |
| } |
| |
| static class Async extends AsyncAwaitable implements CountDownLatch |
| { |
| private static final AtomicIntegerFieldUpdater<CountDownLatch.Async> countUpdater = AtomicIntegerFieldUpdater.newUpdater(CountDownLatch.Async.class, "count"); |
| private volatile int count; |
| |
| // WARNING: if extending this class, consider simulator interactions |
| protected Async(int count) |
| { |
| this.count = count; |
| if (count == 0) |
| signal(); |
| } |
| |
| public void decrement() |
| { |
| if (countUpdater.decrementAndGet(this) == 0) |
| signal(); |
| } |
| |
| public int count() |
| { |
| return count; |
| } |
| |
| @Override |
| protected boolean isSignalled() |
| { |
| return count <= 0; |
| } |
| } |
| |
| static final class Sync extends SyncAwaitable implements CountDownLatch |
| { |
| private int count; |
| |
| public Sync(int count) |
| { |
| this.count = count; |
| } |
| |
| public synchronized void decrement() |
| { |
| if (count > 0 && --count == 0) |
| notifyAll(); |
| } |
| |
| public synchronized int count() |
| { |
| return count; |
| } |
| |
| /** |
| * not synchronized as only intended for internal usage by externally synchronized methods |
| */ |
| |
| @Override |
| protected boolean isSignalled() |
| { |
| return count <= 0; |
| } |
| } |
| } |