Semaphore.H

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// JeVois Smart Embedded Machine Vision Toolkit - Copyright (C) 2016 by Laurent Itti, the University of Southern
// California (USC), and iLab at USC. See http://iLab.usc.edu and http://jevois.org for information about this project.
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/*! \file */
 
// This file has been modified / imported from the Neuromorphic Robotics Toolkit (NRT). Original copyright is:
 
/* author Randolph Voorhies
   copyright GNU Public License (GPL v3)
    // ////////////////////////////////////////////////////////////////////////
    //              The iLab Neuromorphic Robotics Toolkit (NRT)             //
    // Copyright 2010-2012 by the University of Southern California (USC)    //
    //                          and the iLab at USC.                         //
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    // ////////////////////////////////////////////////////////////////////////
    // This file is part of The iLab Neuromorphic Robotics Toolkit.          //
    //                                                                       //
    // The iLab Neuromorphic Robotics Toolkit is free software: you can      //
    // redistribute it and/or modify it under the terms of the GNU General   //
    // Public License as published by the Free Software Foundation, either   //
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    // The iLab Neuromorphic Robotics Toolkit is distributed in the hope     //
    // that it will be useful, but WITHOUT ANY WARRANTY; without even the    //
    // implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR       //
    // PURPOSE.  See the GNU General Public License for more details.        //
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*/
 
#pragma once
 
#include <thread>
#include <condition_variable>
#include <jevois/Types/BlockingBehavior.H>
 
namespace jevois
{
  //! A simple semaphore
  /*! A semaphore is a thread-safe mechanism to share resources between multiple threads of execution.
 
      See this Wikipedia page for basic information: http://en.wikipedia.org/wiki/Semaphore_%28programming%29 
 
      This code is derived from the Neuromorphic Robotics Toolkit (NRT).
 
      @tparam BB defines the blocking behavior and should be a value from jevois::BlockingBehavior
 
      \ingroup types */
  template <BlockingBehavior BB>
  class Semaphore
  {
    public:
      //! Create a semaphore with n initial resources
      Semaphore(size_t n = 0);
 
      //! Release n resources to the semaphore
      void increment(size_t n);
 
      //! Remove n resources from the semaphore, blocking until they are available or throwing if they are not
      void decrement(size_t n);
 
      //! Get the current count
      size_t count() const;
 
    private:
      size_t itsCount;
      mutable std::mutex itsMutex;
      std::condition_variable itsCondVar;
  };
} // namespace jevois
 
// Include implementation details of no interest to users:
#include <jevois/Types/details/SemaphoreImpl.H>