// util/kaldi-semaphore.cc
  
  // 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.
  
  
  
  #include "base/kaldi-error.h"
  #include "util/kaldi-semaphore.h"
  
  namespace kaldi {
  
  Semaphore::Semaphore(int32 count) {
    KALDI_ASSERT(count >= 0);
    count_ = count;
  }
  
  Semaphore::~Semaphore() {}
  
  bool Semaphore::TryWait() {
    std::unique_lock<std::mutex> lock(mutex_);
    if(count_) {
        count_--;
        return true;
    }
    return false;
  }
  
  void Semaphore::Wait() {
    std::unique_lock<std::mutex> lock(mutex_);
    while(!count_)
      condition_variable_.wait(lock);
    count_--;
  }
  
  void Semaphore::Signal() {
    std::unique_lock<std::mutex> lock(mutex_);
    count_++;
    condition_variable_.notify_one();
  }
  
  } // namespace kaldi