Argument of template as method of the object (How to replace the macros)

[unDEFER]

Hello!
Say me please, what the best way to replace the next C++ macros (code from
BerkeleyDB) in D:

#define WRAPPED_CLASS(_WRAPPER_CLASS, _IMP_CLASS, _WRAPPED_TYPE)           \
        class _IMP_CLASS {};                                               \
                                                                           \
        inline _WRAPPED_TYPE *unwrap(_WRAPPER_CLASS *val)                  \
        {                                                                  \
                if (!val) return (0);                                      \
                return (val->get_##_WRAPPED_TYPE());                       \
        }                                                                  \
                                                                           \
        inline const _WRAPPED_TYPE *unwrapConst(const _WRAPPER_CLASS *val) \
        {                                                                  \
                if (!val) return (0);                                      \
                return (val->get_const_##_WRAPPED_TYPE());                 \
        }

I'm already search several hours but can't find good example in the
documentation.
Thank you in advance.