Re: [quicwg/base-drafts] Add an appendix related to packet number decoding. (#1493)

Martin Thomson <notifications@github.com> Thu, 28 June 2018 01:04 UTC

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Subject: Re: [quicwg/base-drafts] Add an appendix related to packet number decoding. (#1493)
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Note that you can avoid one if statement with:

  decoded_pktn -= ((rcv_nxt + pktn_win) & (pktn_len - 1) + pktn) & (pktn_len - 1)

But no one wants to see that in a spec.

@maskit, are you suggesting the simpler code:

```python
expected = next + 1
range = 1 << nbits
mask = range - 1
candidate = (expected & mask) | truncated
if candidate <= expected - range/2:
  return candidate + range
if candidate > expected + range/2 and candidate > range:
  return candidate - range
return candidate
```

That might be better, I agree.

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