libosmo-gtlv: add auto dec/enc to/from structs

Add osmo_gtlv_coding: describe the value part of a TLV (decode and
encode), describe a struct with its members, and get/put readily decoded
structs from/to a raw PDU, directly.

With osmo_gtlv_coding defined for a protocol's tags, we only deal with
encoded PDUs or fully decoded C structs, no TLV related
re-implementations clutter up the message handling code.

A usage example is given in gtlv_dec_enc_test. The first real use will be
the PFCP protocol in osmo-upf.git.

With osmo_gtlv_coding, there still is a lot of monkey work involved in
describing the decoded structs. A subsequent patch adds a generator for
osmo_gtlv_coding and message structs from tag value lists.

Related: SYS#5599
Change-Id: I65de793105882a452124ee58adb0e58469e6e796

0 files changed, 0 insertions, 0 deletions