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

[Brendan Moran <[e-mail]>]

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

IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.