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#ifndef BASE_SINGLETON_INTERNAL_H__
#define BASE_SINGLETON_INTERNAL_H__

// Define the storage of the singleton pointer.
template <typename Type, typename DifferentiatingType, bool kVolatile>
class SingletonStorage {
 protected:
  // The actual pointer. Note that it is a volatile pointer.
  static Type* volatile instance_;
};

// Partial specialization.
template <typename Type, typename DifferentiatingType>
class SingletonStorage<Type, DifferentiatingType, false> {
 protected:
  // The pointer does not need to be volatile for use with pthread_once or
  // locked initialization.
  static Type* instance_;
};

template <typename Type, typename DifferentiatingType, bool kVolatile>
Type* volatile SingletonStorage<Type, DifferentiatingType,
                                kVolatile>::instance_ = NULL;

template <typename Type, typename DifferentiatingType>
Type* SingletonStorage<Type, DifferentiatingType, false>::instance_ = NULL;

template<bool kUseVolatile>
struct UseVolatileSingleton {
#ifdef WIN32
  static const bool value = kUseVolatile;
#else
  static const bool value = false;
#endif  // WIN32
};

#endif  // BASE_SINGLETON_INTERNAL_H__