[quicwg/base-drafts] QPACK instruction code points are inconsistent (#1471)

afrind <notifications@github.com> Fri, 22 June 2018 15:43 UTC

Date: Fri, 22 Jun 2018 08:43:33 -0700
From: afrind <notifications@github.com>
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Subject: [quicwg/base-drafts] QPACK instruction code points are inconsistent (#1471)
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HPACK/QPACK can encode N different instructions in N-1 bits.  Both HPACK and the QPACK encoder stream use the same style fore code points - each instruction has either one or zero '1' bits (eg: 1, 01, 001, 0001, 0000).  The QPACK decoder stream and request/push streams however use (0, 10, 11) and (1, 00, 011, 0100, 0101), each of which have instructions with more than one '1'.  The logic to decode the instruction is slightly simpler when using the HPACK form, eg:

```
if byte & shortest_instruction:
  ...
else if byte & next_shortest_instruction:
  ...
else:  # it's the all-zero instruction
  ...
```

This logic doesn't work on the other two streams right now, you need to mask and check for equality.


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[quicwg/base-drafts] QPACK instruction code point… afrind
Re: [quicwg/base-drafts] QPACK instruction code p… afrind
Re: [quicwg/base-drafts] QPACK instruction code p… Mike Bishop