get member id id - structure type ID member_offset - member offset. The offset can be any offset in the member. For example, is a member is 4 bytes long and starts at offset 2, then 2, 3, 4, 5 denote the same structure member. returns: -1 if bad structure type ID is passed or there is no member at the specified offset. otherwise returns the member id.
long get_member_id(long id, long member_offset);