def by_indextype(self, index, dtype):
        """Lookup a register according to its `index` and `dtype`.

        Some examples of dtypes: idaapi.dt_byte, idaapi.dt_word, idaapi.dt_dword, idaapi.dt_qword
        """
        res = idaapi.ph.regnames[index]
        name = self.__cache__[res, dtype]
        return getattr(self.__register__, name) 

def dt_to_width(self, dt):
        '''
        returns OOFW_xxx flag given a dt_xxx
        '''
        return {
            idaapi.dt_byte:  idaapi.OOFW_8,
            idaapi.dt_word:  idaapi.OOFW_16,
            idaapi.dt_dword: idaapi.OOFW_32,
            idaapi.dt_qword: idaapi.OOFW_64,
        }[dt]