get_member_id

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);