When passed as True, only st_mode's type bits, st_size and st_mtime[_nsec] are guaranteed to be set. Other fields may also be set for a given Python version on a given platform version, but may change without warning (in the case of OS changes - Python will try to keep them stable). This first implementation uses a new Windows API that is significantly faster, provided the volume identifier is not required. Other optimizations may be added later.