_region_offset
*(uint8_t *)_region_offset(r, *rofs) = val;
memcpy(_region_offset(r, *rofs), &val, 4);
memcpy(_region_offset(r, keyofs),
memcpy(_region_offset(r, dataofs),
head = _region_offset(&ms->ms_region, ms->ms_pos);
h = p = (uint8_t *)_region_offset(&ms->ms_region, ms->ms_pos);