Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!mailrus!tut.cis.ohio-state.edu!ucbvax!CSL.SRI.COM!auerbach
From: auerbach@CSL.SRI.COM (Karl Auerbach)
Newsgroups: comp.protocols.iso
Subject: An ASN.1 question
Message-ID: <8906051632.AA00970@Hercules.csl.sri.com>
Date: 5 Jun 89 16:32:21 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 31

Hi --  My original posting of this seems to have gone astray (it will
certainly pop-up seconds after I do this reposting.  Such are the 
whims of the network gods.)

Last night I was playing about with my ASN.1 tools (my own, not
those in ISODE) and I tried something with surprising results.

What I did was this: I added an encoding strategy flag, much like
PS_LEN_INDF in ISODE which (in my code) is supposed to mean "whenever
legally possible use indefinite length encoding."

What happened, and what I am not sure is legal, is that everything
that has an explicit tag got an indefinite length encoding.  For
example, [12] INTEGER with a value of 127 came out encoded as:

[12] LENGTH  INTEGER  LENGTH  CONTENTS  END-OF-CONTENTS
AC   80      02       01      7F        00 00

I find ISO 8825 to be a bit ambiguous on this point:

Section 6.3.2 (b) and (c) seem to say that anything that is constructued
can be done with indefinite length.

But section 18.2 (regarding non-implicit tags) says that the "contents
octets shall be the complete base encoding."  (A very restrictive reading
of that could mean "the complete base encoding and nothing more -- such
as end-of-contents".)

Anyway, I'd sure like to hear whether the form I generated is legal.

					--karl--