---------- Forwarded message ----------
From: Yoshiki Ohshima <Yoshiki.Ohshima@acm.org>
Date: Tue, May 6, 2014 at 2:09 PM
Subject: [squeak-dev] A nitpick
To: The general-purpose Squeak developers list <squeak-dev@lists.squeakfoundation.org>


This can be a nitpick of the year, but there is a bug in
InflateStream>>decompressBlock:with:

There is a part that reads (toward the end):

------------------------
collection
�� �� �� �� replaceFrom: readLimit+1
�� �� �� �� to: readLimit + length + 1
�� �� �� �� with: collection
�� �� �� �� startingAt: readLimit - distance + 1.
------------------------

but here we want to replace "length" bytes in collection, as opposed
to length + 1 bytes, so it has to say:

------------------------
collection
�� �� �� �� replaceFrom: readLimit+1
�� �� �� �� to: readLimit + length
�� �� �� �� with: collection
�� �� �� �� startingAt: readLimit - distance + 1.
------------------------

(So is the non-primitive version in FastInflateStream.)

The reason it does not matter is that replaceFrom:to:with:startingAt:
does not care about the source and destination being the same and
overlap between them. ��Even when the above bug puts one extra bytes in
collection temporarily, the extra byte will be wiped out in the next
iteration of the loop surrounding it. ��However, if you try to port
this to a language that does the "right thing" when there is an
overlap, it manifests as a bug.

-- Yoshiki

P.S.
It was a "rare" delight to point out a bug in Andreas' code^^; We miss
you.