[Zlib-devel] Causality question

[Arjan van de Ven]

Hi,

I'm working on a variation of the deflate_fast/deflate_slow code
(currently I'm calling it deflate_medium), and as part of that I've
been instrumenting deflate_slow to see and compare what it emits.

One of the things I am noticing, and that makes me wonder, is
something that appears to violate causality:

Emitting match for pos 1703, length 6 from 1699

e.g. deflate_slow emits a match that appears to go into the "future".
(my current code emits
Emitting match for pos 1702, length 3 from 1694
Emitting match for pos 1705, length 4 from 1701
for this which does keep causality)

now.. since arguably deflate_slow actually works, how is such
anti-causal behavior defined?
is it defined that the decompressor must put zeros there?