content: /*
   * 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.distributed.util;
  
  import java.util.concurrent.CountDownLatch;
  import java.util.concurrent.TimeUnit;
  
  import com.google.common.util.concurrent.UncheckedTimeoutException;
  
  import org.apache.cassandra.utils.Shared;
  import org.apache.cassandra.utils.concurrent.UncheckedInterruptedException;
  
  @Shared
  public class TwoWay implements AutoCloseable
  {
      private volatile CountDownLatch first = new CountDownLatch(1);
      private final CountDownLatch second = new CountDownLatch(1);
  
      public void awaitAndEnter()
      {
          await();
          enter();
      }
  
      public void await()
      {
          await(first);
          first = null;
      }
  
      public void enter()
      {
          if (first != null)
          {
              first.countDown();
              await(second);
          }
          else
          {
              second.countDown();
          }
      }
  
      private void await(CountDownLatch latch)
      {
          try
          {
              if (!latch.await(1, TimeUnit.MINUTES))
                  throw new UncheckedTimeoutException("Timeout waiting on " + (latch == second ? "second" : "first") + " latch");
          }
          catch (InterruptedException e)
          {
              throw new UncheckedInterruptedException(e);
          }
      }
  
      @Override
      public void close()
      {
          if (first != null)
              first.countDown();
          first = null;
          second.countDown();
      }
  }
  