Subject: [quicwg/base-drafts] 6ed602: Avoid having multiple ways to encode Delta Base In...

From: Kazuho Oku <[email-masked]>
Date: Tue, 04 Dec 2018 13:33:18 -0800

Branch: refs/heads/master
  Home:   https://github.com/quicwg/base-drafts
  Commit: 6ed6021ebdf6f688b330c3e16bbacfc1d0464f3b
      https://github.com/quicwg/base-drafts/commit/6ed6021ebdf6f688b330c3e16bbacfc1d0464f3b
  Author: Kazuho Oku <[email-masked]>
  Date:   2018-12-04 (Tue, 04 Dec 2018)

  Changed paths:
    M draft-ietf-quic-qpack.md

  Log Message:
  -----------
  Avoid having multiple ways to encode Delta Base Index of zero. (#2005)

As discussed in #2002, there are two ways to encode Delta Base
Index of zero at the wire level; i.e. (sign-bit, delta-base-index)
= (0, 0) and (1, 0).

To avoid having multiple ways to represent one value, we prohibit
the latter form from being used.  A receiver is required to raise
an error when it sees the latter.

This is not only an unnecessary complexity but also contradicts
from the approach we use for Post-Base Indexes.  In case of Post-
Base Indexes, we introduce an offset of one so that the Post-Base
Index of zero and a non-Post-Base Index of zero do not overlap.

The commit adopts the approach to Delta Base Index; giving us
consistency in the design and also removing an error check at the
cost of requiring one subtraction.

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