// util/kaldi-semaphore.h

// Copyright 2012  Karel Vesely (Brno University of Technology)
//           2017  Dogan Can (University of Southern California)

// See ../../COPYING for clarification regarding multiple authors
//
// Licensed 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
//
// THIS CODE IS PROVIDED *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED
// WARRANTIES OR CONDITIONS OF TITLE, FITNESS FOR A PARTICULAR PURPOSE,
// MERCHANTABLITY OR NON-INFRINGEMENT.
// See the Apache 2 License for the specific language governing permissions and
// limitations under the License.


#ifndef KALDI_THREAD_KALDI_SEMAPHORE_H_
#define KALDI_THREAD_KALDI_SEMAPHORE_H_ 1

#include <mutex>
#include <condition_variable>

namespace kaldi {

class Semaphore {
 public:
  Semaphore(int32 count = 0);

  ~Semaphore();

  bool TryWait();  ///< Returns true if Wait() goes through
  void Wait();     ///< decrease the counter
  void Signal();   ///< increase the counter

 private:
  int32 count_;    ///< the semaphore counter, 0 means block on Wait()

  std::mutex mutex_;
  std::condition_variable condition_variable_;
  KALDI_DISALLOW_COPY_AND_ASSIGN(Semaphore);
};

} //namespace

#endif // KALDI_THREAD_KALDI_SEMAPHORE_H_