More ASN.1...

Bruce Fitzsimons <>
Mon Nov 25 20:21:34 CET 2002


Thanks Bertil, its good to know how it supposed to work. It should be even
easier to do H.323 in the next release.

Thanks again,
Bruce

----- Original Message -----
From: "Bertil Karlsson" <>
To: <>
Sent: Tuesday, November 26, 2002 1:27 AM
Subject: Re: More ASN.1...


> You are absolutely right! The asn1 compiler should have generated a
> 'TransportAddress_ipAddress' record, and so also for each SEQUENCE/SET
> that is defined inside a "constructed type" (SEQUENCE, CHOICE, SET,
> SEQUENCE OF, SET OF) like in:
>
> MyType ::= CHOICE {
> a SEQUENCE {a INTEGER, b INTEGER}
> }
>
> This will result in a record 'MyType_a'.
>
> Due to a bug in the compiler no record is generated for a SEQUENCE in a
> CHOICE that has extensionmarks, like in:
> MyType2 ::= CHOICE {
> a SEQUENCE {a INTEGER, b INTEGER},
> ...
> }
> The TransportAddress is a CHOICE with an extension mark.
>
> There will be a fix of this bug in the next release.
> Maybe the easiest workaround is to define missing records by hand.
>
> Bruce Fitzsimons wrote:
> >
> > I have a few more questions about the Erlang ASN.1 compiler/runtime.
> >
> > Given an H.323 TransportAddress definition (used for addressing
> > packets'n'stuff, definition below) I can get packets decoded with items
such
> > as:
> >
> > {ipAddress,
> >     {'TransportAddress_ipAddress',
> >         [10,151,33,220],
> >         2634}},
> >
> > However there doesn't seem to be any way of decoding/interpreting this
> > directly, inasmuch as there is no auto-generated record definition
> > 'TransportAddress_ipAddress' (or for any of the other choices). This is
> > contrary to what I would have expected given that other choices do end
up
> > with records for their sub-sequences (such as, for example, the
RasMessage
> > choice - gives 'GatekeeperRequest' etc).
> >
> > I feel I must be missing something fundamental. I can of course define a
> > record for myself, but I thought I should ask the question.
> >
> > Thanks in advance
> >
> > /Bruce
> >
> > H323 ASN.1 definition:
> >
> > TransportAddress ::= CHOICE
> > {
> >  ipAddress SEQUENCE
> >  {
> >   ip   OCTET STRING (SIZE(4)),
> >   port   INTEGER(0..65535)
> >  },
> >  ipSourceRoute SEQUENCE
> >  {
> >   ip   OCTET STRING (SIZE(4)),
> >   port   INTEGER(0..65535),
> >   route   SEQUENCE OF OCTET STRING (SIZE(4)),
> >   routing   CHOICE
> >   {
> >    strict NULL,
> >    loose NULL,
> >    ...
> >   },
> >   ...
> >  },
> >  ipxAddress SEQUENCE
> >  {
> >   node  OCTET STRING (SIZE(6)),
> >   netnum  OCTET STRING (SIZE(4)),
> >   port  OCTET STRING (SIZE(2))
> >  },
> >  ip6Address SEQUENCE
> >  {
> >   ip  OCTET STRING (SIZE(16)),
> >   port  INTEGER(0..65535),
> >   ...
> >  },
> >  netBios   OCTET STRING (SIZE(16)),
> >  nsap   OCTET STRING (SIZE(1..20)),
> >  nonStandardAddress NonStandardParameter,
> >  ...
> > }
>
> --
> / Bertil Karlsson





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