Re: [Cbor] Packed CBOR and dictionaries

[Michael Richardson <[e-mail]>]

I feel that the WG should adopt the document already.

Jim Schaad <[e-mail]> wrote:
    > * Should the dictionary expansion be separate or part of this draft?  I am
    > not sure how I want to address this.  If you have a dictionary w/ 50,000
    > entries in it, that is going to change how things should be done.  It may
    > also be that one might want to use a dictionary entry for something that
    > might otherwise be encoded as a prefix and the prefix might not be needed
    > anymore.

Once the dictionary is larger than 512, I guess 131072 is the next size.
That uses four-byte references, and so the dictionary ought to provide at
least four-byte substitutions, right?
Otherwise, we'd be expanding rather then compressing.
It seems that a (C,Python,etc.) array is probably always appropriate as the internal
datastructure to perform lookups into the dictionary. It shouldn't require a
sparse array, ever, should it?

    > Being able to do packed is going to be of importance for doing CoRAL, but
    > just as important is being able to do dictionaries.  Dictionaries do have
    > the downside that if they are not referenced internal to the structure then
    > from a security point of view they can be problematic as the
    > signed/encrypted CBOR byte stream is no longer self-contained.  This is not
    > a problem for packed CBOR as long as the packing does not cross the security
    > boundary.

Agreed.


--
Michael Richardson <[e-mail]>, Sandelman Software Works
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