Re: [Cbor] [COSE] CBOR magic number, file format and tags
Michael Richardson <mcr+ietf@sandelman.ca> Thu, 21 January 2021 13:44 UTC
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From: Michael Richardson <mcr+ietf@sandelman.ca>
To: Carsten Bormann <cabo@tzi.org>, Josef 'Jeff' Sipek <jeffpc@josefsipek.net>, cbor@ietf.org
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Date: Thu, 21 Jan 2021 08:44:51 -0500
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Subject: Re: [Cbor] [COSE] CBOR magic number, file format and tags
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I think this belongs in CBOR, not COSE. It sounds like this is something that a few people are interested in persuing. Is it a BCP or a Standard? Carsten Bormann <cabo@tzi.org> wrote: > Challenge accepted. CBOR diagnostic notation is quite versatile, you > just have to tell cbor2diag.rb what you want. okay. > cbor2diag.rb -t: bytes_as_text, i.e., use text form for bytes if > possible. > $ printf cbor | cbor2diag.rb -t "bor" $ printf CBOR | cbor2diag.rb -t > ‘BOR' > Oh, and, BTW: > cbor2diag.rb -e: try_decode_embedded, i.e., try embedded CBOR. > $ printf CBOR | cbor2diag.rb -te << 'OR' >> alright, I award full cool points. > Back to the magic number issue: > For CBOR data items, I prefer registering a tag and prefixing with that > head (*) over prefixing with an array head and a string. See, we have > a magic number registry built right into CBOR... I can live with this, but here are my concerns. If we go this way, then it just becomes a BCP on good CBOR protocol design. 1) when transmitting over the wire, shorter tags are preferred, and I'm concerned that they will be too short to useful *on-disk* magic numbers. The same short sequence could occur in other kinds of files rather easily. 2) I wanted a structure that made it rather easy for an application that is reading from the disk to know what part they can omit when transmitting. That's why I initially looked at the two-element array, with the second element being the actual "thing" > For CBOR sequences, obviously prefixing the sequence with a > CBOR-encoded (text or byte) string sounds quite good. Making that > optional (to save bytes when you don’t need it) requires that the > sequence otherwise cannot start with that kind of string. For on-disk files, if one uses a CBOR Sequence, I wasn't thinking about ever having the prefix be optional. But, we could go that way easily if do Tag<per-protocol-tag>CBOR or Tag<CBOR-protocol-tag>Per-protocol-Value. As the prefix, as I think that would be quite easily not part of any protocol. -- Michael Richardson <mcr+IETF@sandelman.ca> . o O ( IPv6 IøT consulting ) Sandelman Software Works Inc, Ottawa and Worldwide
- Re: [Cbor] [COSE] CBOR magic number, file format … Michael Richardson
- Re: [Cbor] CBOR magic number, file format and tags Michael Richardson
- [Cbor] CBOR magic number, file format and tags Michael Richardson
- Re: [Cbor] CBOR magic number, file format and tags Josef 'Jeff' Sipek
- Re: [Cbor] [COSE] CBOR magic number, file format … David Waite
- Re: [Cbor] CBOR magic number, file format and tags Michael Richardson
- Re: [Cbor] CBOR magic number, file format and tags Michael Richardson
- Re: [Cbor] CBOR magic number, file format and tags Doug Ewell
- Re: [Cbor] CBOR magic number, file format and tags Josef 'Jeff' Sipek
- Re: [Cbor] CBOR magic number, file format and tags worley
- Re: [Cbor] [COSE] CBOR magic number, file format … Carsten Bormann
- Re: [Cbor] [COSE] CBOR magic number, file format … Michael Richardson
- Re: [Cbor] [COSE] CBOR magic number, file format … Michael Richardson
- Re: [Cbor] [COSE] CBOR magic number, file format … Carsten Bormann
- Re: [Cbor] [COSE] CBOR magic number, file format … Carsten Bormann
- Re: [Cbor] [COSE] CBOR magic number, file format … Michael Richardson
- Re: [Cbor] [COSE] CBOR magic number, file format … Michael Richardson
- Re: [Cbor] [COSE] CBOR magic number, file format … John Mattsson
- Re: [Cbor] [COSE] CBOR magic number, file format … Michael Richardson
- Re: [Cbor] [COSE] CBOR magic number, file format … worley
- Re: [Cbor] [COSE] CBOR magic number, file format … Michael Richardson
- Re: [Cbor] [COSE] CBOR magic number, file format … worley
- Re: [Cbor] [COSE] CBOR magic number, file format … Carsten Bormann
- Re: [Cbor] [COSE] CBOR magic number, file format … Laurence Lundblade
- Re: [Cbor] [COSE] CBOR magic number, file format … Carsten Bormann
- Re: [Cbor] [COSE] CBOR magic number, file format … Michael Richardson
- Re: [Cbor] [COSE] CBOR magic number, file format … Carsten Bormann
- Re: [Cbor] [COSE] CBOR magic number, file format … Michael Richardson
- Re: [Cbor] [COSE] CBOR magic number, file format … Carsten Bormann
- Re: [Cbor] [COSE] CBOR magic number, file format … Michael Richardson
- Re: [Cbor] [COSE] CBOR magic number, file format … worley