Singleton.hxx

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#ifndef _UTILS_SINGLETON_HXX_
#define _UTILS_SINGLETON_HXX_
 
#include "utils/macros.h"
 
template<class T> class Singleton {
public:
  Singleton() {
    HASSERT(instance_ == nullptr);
    instance_ = static_cast<T*>(this);
  }
 
  ~Singleton() {
    instance_ = nullptr;
  }
 
  static T* instance() {
    HASSERT(instance_ != nullptr);
    return instance_;
  }
 
  static bool exists() {
    return (instance_ != nullptr);
  }
 
private:
  static T* instance_;
};
 
template<class T> T* Singleton<T>::instance_ = nullptr;
 
#define DEFINE_SINGLETON_INSTANCE(T) template<> T* Singleton<T>::instance_ = nullptr
 
#endif // _UTILS_SINGLETON_HXX_