Re: [Cbor] Ordering of items in the prefix table

Michael Richardson <mcr+ietf@sandelman.ca> Fri, 28 August 2020 18:24 UTC

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From: Michael Richardson <mcr+ietf@sandelman.ca>
To: Jim Schaad <ietf@augustcellars.com>, draft-bormann-cbor-packed@ietf.org, cbor@ietf.org
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Date: Fri, 28 Aug 2020 14:24:46 -0400
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Subject: Re: [Cbor] Ordering of items in the prefix table
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Jim Schaad <ietf@augustcellars.com> wrote:
    > I was just going through an expansion algorithm and I started to wonder if
    > we should have a requirement about order of items in the prefix table.
    > Specifically if an entry in the prefix table uses a prefix itself  (i.e.
    > entry 3 in the table is 6.2872("foo")), does that entry need to occur after
    > the entry it references?

I also asked that question.
If we don't enforce that rule, then the decoder has to take care of dealing
with loops.

This means either having a maximum loop depth, or, using a mark to refuse to
expand any specific dictionary item more than once.
I would prefer that all references are forward references.

--
Michael Richardson <mcr+IETF@sandelman.ca>ca>, Sandelman Software Works
 -= IPv6 IoT consulting =-