Regards
Brian Carpenter
On 10/01/2017 03:43, Michael Richardson wrote:
>
> Brian E Carpenter <brian.e.carpen...@gmail.com> wrote:
> >> When I read: divert-option = [O_DIVERT, +locator-option]
> >>
> >> I think that it means that +locator-option means that one can multiple
> >> options, and that they would be inside an array?
> >>
> >> So, for example:
> >>
> >> [O_DIVERT, [ [O_IPv6_LOCATOR, ipv6-address, transport-proto,
> >> port-number], [O_IPv4_LOCATOR, ipv6-address, transport-proto,
> >> port-number], [O_FQDN_LOCATOR, ipv6-address, transport-proto,
> >> port-number]]]
>
>
> > I'm not sure there's an additional array. CBOR can handle arrays of
> > undefined length, so I think that syntax generates
>
> > [O_DIVERT, [O_IPv6_LOCATOR, ipv6-address, transport-proto,
> > port-number], [O_IPv4_LOCATOR, ipv6-address, transport-proto,
> > port-number], [O_FQDN_LOCATOR, ipv6-address, transport-proto,
> > port-number]]
>
> > but I'd rather hear that from Carsten to be sure.
>
> But, have specification like:
>
> response-message = [M_RESPONSE, session-id, initiator, ttl,
> (+locator-option // divert-option), ?objective)]
>
> so unless the () implies a level of sub-array, then there would be
> some unknown number of location-options, and then the last item would be
> objective, *if* it exists.
In CDDL (...) is just a way of grouping items syntactically, it
doesn't represent anything in the data. [...] signals an array
and {...} signals a map, which we haven't used in GRASP.
So yes, there is a possible parsing problem in that syntax, because
the + signals "one or more" and the ? signals "0 or 1". So if there
are at least 2 elements, the last one might be a locator or an objective.
<pause to stare at my code for a while>
The reason I hadn't thought about this is in the comments at the
beginning of my code:
# - the spec allows an optional Objective option in
# Response messages: not implemented
To be honest I don't know what value this feature adds.
It can be parsed from the CBOR, however. All options *except* objectives
start with an integer. Objectives start with a text string. If you don't
like that, we'd have to change the syntax slightly.
Brian
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