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.utils.concurrent;
  
  import java.util.ArrayList;
  import java.util.List;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Executors;
  import java.util.concurrent.Future;
  import java.util.concurrent.TimeoutException;
  
  import org.junit.Assert;
  import org.junit.Test;
  
  import static java.util.concurrent.TimeUnit.MILLISECONDS;
  import static java.util.concurrent.TimeUnit.MINUTES;
  import static org.apache.cassandra.utils.Clock.Global.nanoTime;
  
  public class SemaphoreTest
  {
  
      @Test
      public void testUnfair() throws InterruptedException
      {
          Semaphore s = Semaphore.newSemaphore(2);
          List<Future<Boolean>> fs = start(s);
          s.release(1);
          while (s.permits() == 1) Thread.yield();
          Assert.assertEquals(1, fs.stream().filter(Future::isDone).count());
          s.release(1);
          while (s.permits() == 1) Thread.yield();
          Assert.assertEquals(2, fs.stream().filter(Future::isDone).count());
          s.release(1);
          while (s.permits() == 1) Thread.yield();
          Assert.assertEquals(3, fs.stream().filter(Future::isDone).count());
          s.release(1);
          Assert.assertEquals(1, s.permits());
      }
  
      @Test
      public void testFair() throws InterruptedException, ExecutionException, TimeoutException
      {
          Semaphore s = Semaphore.newFairSemaphore(2);
          List<Future<Boolean>> fs = start(s);
          s.release(1);
          fs.get(0).get(1L, MINUTES);
          s.release(1);
          fs.get(1).get(1L, MINUTES);
          s.release(1);
          fs.get(2).get(1L, MINUTES);
          s.release(1);
          Assert.assertEquals(1, s.permits());
      }
  
      private List<java.util.concurrent.Future<Boolean>> start(Semaphore s) throws InterruptedException
      {
          ExecutorService exec = Executors.newCachedThreadPool();
          try
          {
              Assert.assertTrue(s.tryAcquire(1));
              s.drain();
              Assert.assertFalse(s.tryAcquire(1));
              Assert.assertFalse(s.tryAcquire(1, 1L, MILLISECONDS));
              Thread.currentThread().interrupt();
              try { s.acquireThrowUncheckedOnInterrupt(1); Assert.fail(); } catch (UncheckedInterruptedException ignore) { }
              Thread.currentThread().interrupt();
              try { s.tryAcquire(1, 1L, MILLISECONDS); Assert.fail(); } catch (InterruptedException ignore) { }
              Thread.currentThread().interrupt();
              try { s.tryAcquireUntil(1, nanoTime() + MILLISECONDS.toNanos(1L)); Assert.fail(); } catch (InterruptedException ignore) { }
              List<Future<Boolean>> fs = new ArrayList<>();
              fs.add(exec.submit(() -> s.tryAcquire(1, 1L, MINUTES)));
              while (s instanceof Semaphore.Standard && ((Semaphore.Standard) s).waiting() == 0) Thread.yield();
              fs.add(exec.submit(() -> s.tryAcquireUntil(1, System.nanoTime() + MINUTES.toNanos(1L))));
              while (s instanceof Semaphore.Standard && ((Semaphore.Standard) s).waiting() == 1) Thread.yield();
              fs.add(exec.submit(() -> { s.acquire(1); return true; } ));
              return fs;
          }
          finally
          {
              exec.shutdown();
          }
      }
  
  }
  