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.concurrent;
  
  import java.util.concurrent.atomic.AtomicBoolean;
  
  import org.apache.cassandra.utils.concurrent.Future;
  
  public class SingleThreadExecutorPlus extends ThreadPoolExecutorPlus implements SequentialExecutorPlus
  {
      public static class AtLeastOnce extends AtomicBoolean implements AtLeastOnceTrigger, Runnable
      {
          private static final long serialVersionUID = 0;  // for simulator support
          protected final SequentialExecutorPlus executor;
          protected final Runnable run;
  
          public AtLeastOnce(SequentialExecutorPlus executor, Runnable run)
          {
              this.executor = executor;
              this.run = run;
          }
  
          public boolean trigger()
          {
              boolean success;
              if (success = compareAndSet(false, true))
                  executor.execute(this);
              return success;
          }
  
          public void runAfter(Runnable run)
          {
              executor.execute(run);
          }
  
          public void sync()
          {
              Future<?> done = executor.submit(() -> {});
              done.awaitThrowUncheckedOnInterrupt();
              done.rethrowIfFailed(); // executor might get shutdown before we execute; propagate cancellation exception
          }
  
          public void run()
          {
              set(false);
              run.run();
          }
  
          @Override
          public String toString()
          {
              return run.toString();
          }
      }
  
      SingleThreadExecutorPlus(ThreadPoolExecutorBuilder<? extends SingleThreadExecutorPlus> builder)
      {
          this(builder, TaskFactory.standard());
      }
  
      SingleThreadExecutorPlus(ThreadPoolExecutorBuilder<? extends SingleThreadExecutorPlus> builder, TaskFactory taskFactory)
      {
          super(builder, taskFactory);
      }
  
      @Override
      public int getCorePoolSize()
      {
          return 1;
      }
      @Override
      public void setCorePoolSize(int number)
      {
          throw new UnsupportedOperationException();
      }
      @Override
      public int getMaximumPoolSize()
      {
          return 1;
      }
      @Override
      public void setMaximumPoolSize(int number)
      {
          throw new UnsupportedOperationException();
      }
  
      @Override
      public AtLeastOnce atLeastOnceTrigger(Runnable run)
      {
          return new AtLeastOnce(this, run);
      }
  }
  