clib/singleton.h

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/*
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*/

#ifndef CLIB_SINGLETON_H
#define CLIB_SINGLETON_H
namespace Pol {
  namespace Clib {
    template <typename T>
    class Singleton
    {
    private:
      static void _cleanup() { delete _instance; _instance = NULL; }
    public:
      static T* instance()
      {
        if( !_instance )
        {
          std::lock_guard<std::mutex> lock( _SingletonMutex ); //critical double check
          if( !_instance )
          {
            _instance = new T();
            atexit( &Singleton<T>::_cleanup );
          }
        }
        return _instance;
      }
    private:
      static T* _instance;
      static std::mutex _SingletonMutex;
    protected:
      Singleton() {}
      ~Singleton() {}
    private: // Forbid copies
      Singleton( Singleton& );
      Singleton& operator=( Singleton& );
    };
    template <typename T> T* Singleton <T>::_instance = NULL;
    template <typename T> std::mutex Singleton <T>::_SingletonMutex;
  }
}
#endif