backend_ctypes.py 文件源码

def typeoffsetof(self, BType, fieldname, num=0):
        if isinstance(fieldname, str):
            if num == 0 and issubclass(BType, CTypesGenericPtr):
                BType = BType._BItem
            if not issubclass(BType, CTypesBaseStructOrUnion):
                raise TypeError("expected a struct or union ctype")
            BField = BType._bfield_types[fieldname]
            if BField is Ellipsis:
                raise TypeError("not supported for bitfields")
            return (BField, BType._offsetof(fieldname))
        elif isinstance(fieldname, (int, long)):
            if issubclass(BType, CTypesGenericArray):
                BType = BType._CTPtr
            if not issubclass(BType, CTypesGenericPtr):
                raise TypeError("expected an array or ptr ctype")
            BItem = BType._BItem
            offset = BItem._get_size() * fieldname
            if offset > sys.maxsize:
                raise OverflowError
            return (BItem, offset)
        else:
            raise TypeError(type(fieldname))