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.simulator.systems;
  
  import java.util.Queue;
  import java.util.concurrent.ConcurrentLinkedQueue;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicInteger;
  
  import org.apache.cassandra.utils.concurrent.Semaphore;
  import org.apache.cassandra.utils.concurrent.UncheckedInterruptedException;
  
  import static org.apache.cassandra.simulator.systems.InterceptorOfGlobalMethods.Global.ifIntercepted;
  
  public class InterceptingSemaphore extends Semaphore.Standard
  {
      final Queue<SemaphoreSignal> interceptible = new ConcurrentLinkedQueue<>();
      final AtomicInteger permits;
      final boolean fair;
  
      private static class SemaphoreSignal extends InterceptingAwaitable.InterceptingSignal<Void>
      {
          private final int permits;
  
          private SemaphoreSignal(int permits)
          {
              this.permits = permits;
          }
      }
  
      public InterceptingSemaphore(int permits, boolean fair)
      {
          super(permits);
          this.permits = new AtomicInteger(permits);
          this.fair = fair;
      }
  
      @Override
      public int permits()
      {
          if (ifIntercepted() == null)
              return super.permits();
  
          return permits.get();
      }
  
      @Override
      public int drain()
      {
          if (ifIntercepted() == null)
              return super.drain();
  
          for (int i = 0; i < 10; i++)
          {
              int current = permits.get();
              if (permits.compareAndSet(current, 0))
                  return current;
          }
  
          throw new IllegalStateException("Too much contention");
      }
  
      @Override
      public void release(int release)
      {
          if (ifIntercepted() == null)
          {
              super.release(release);
              return;
          }
  
          int remaining = permits.addAndGet(release);
          while (!interceptible.isEmpty() && remaining > 0)
          {
              SemaphoreSignal signal = interceptible.peek();
              if (signal.permits >= remaining)
                  interceptible.poll().signal();
              else if (fair)
                  // Do not break enqueue order if using fair scheduler
                  break;
          }
      }
  
      @Override
      public boolean tryAcquire(int acquire)
      {
          if (ifIntercepted() == null)
              return super.tryAcquire(acquire);
  
          for (int i = 0; i < 10; i++)
          {
              int current = permits.get();
              if (current >= acquire)
              {
                  if (permits.compareAndSet(current, current - acquire))
                      return true;
              }
              else
              {
                  return false;
              }
          }
          throw new IllegalStateException("Too much contention");
      }
  
      @Override
      public boolean tryAcquire(int acquire, long time, TimeUnit unit) throws InterruptedException
      {
          if (ifIntercepted() == null)
              return super.tryAcquire(acquire, time, unit);
  
          while (true)
          {
              int current = permits.get();
              if (current >= acquire && permits.compareAndSet(current, current - acquire))
                  return true;
  
              SemaphoreSignal signal = new SemaphoreSignal(acquire);
              interceptible.add(signal);
              boolean res = signal.await(time, unit);
              interceptible.remove(signal);
              if (!res)
                  return false;
          }
      }
  
      @Override
      public boolean tryAcquireUntil(int acquire, long deadline) throws InterruptedException
      {
          if (ifIntercepted() == null)
              return super.tryAcquireUntil(acquire, deadline);
  
          while (true)
          {
              int current = permits.get();
              if (current >= acquire && permits.compareAndSet(current, current - acquire))
                      return true;
  
              SemaphoreSignal signal = new SemaphoreSignal(acquire);
              interceptible.add(signal);
              boolean res = signal.awaitUntil(deadline);
              interceptible.remove(signal);
              if (!res)
                  return false;
          }
      }
  
      @Override
      public void acquire(int acquire) throws InterruptedException
      {
          if (ifIntercepted() == null)
          {
              super.acquire(acquire);
              return;
          }
  
          while (true)
          {
              if (tryAcquire(acquire))
                  return;
  
              SemaphoreSignal signal = new SemaphoreSignal(acquire);
              interceptible.add(signal);
              signal.await();
              interceptible.remove(signal);
          }
      }
  
      @Override
      public void acquireThrowUncheckedOnInterrupt(int acquire) throws UncheckedInterruptedException
      {
          try
          {
              acquire(acquire);
          }
          catch (InterruptedException e)
          {
              throw new UncheckedInterruptedException(e);
          }
      }
  }
  