// 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_