Re: [Suit] CBOR pull parsing vs. packed binary format extraction

Thanks for sharing!

Your code seems to assume a specific order of map elements, but as far as I know, CDDL (or even CBOR?) doesn't guarantee deterministic ordering.
Am I missing something?

Also, a full implementation will require the ability to fetch of most or all present elements (if not, why are the elements present?), so in practice the size will be larger, right?

Øyvind

> -----Original Message-----
> From: Suit <suit-bounces@ietf.org> On Behalf Of Brendan Moran
> Sent: 13. november 2018 13:24
> To: suit <suit@ietf.org>
> Subject: [Suit] CBOR pull parsing vs. packed binary format extraction
> 
> I have worked up an example pull parser for Class 1 devices. It is
> published in the suit-manifest-generator repo:
> 
> https://github.com/ARMmbed/suit-manifest-
> generator/tree/master/parser-example
> 
> This repo demonstrates constructing a highly specialised parser for the
> draft-moran-suit-manifest-03 draft (with one small modification that will
> be included in the 04 draft) as detailed in README.md.
> 
> The parser has been built for ARM Cortex-M4 to evaluate size:
> 
> The parser consumes 560 bytes of flash, uses only a single pointer of
> state between function calls, returns interpreted integers and references
> to byte strings to save memory when called, and uses no dynamic
> memory. It is guaranteed not to issue unaligned accesses, since all
> accesses are explicitly byte-wise.
> 
> The parser can be used in a low-resource mode, consuming 333 bytes of
> flash, but giving up structural validation of the CBOR, and assuming that
> any fixed components (such as containers) of the manifest are correct
> 
> 
> I have also provided, for comparison, an unserialised binary structure
> using the same information and the same parser API. In this instance, the
> parser consumes 102 bytes of flash. This is not the manifest as defined in
> draft-pagel-suit-manifest-00.
> 
> Martin, would you be able to offer an implementation of an updater for
> class 1 devices using your manifest draft so that we can compare the
> compiled size?
> 
> Best Regards,
> Brendan
> 
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