Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uunet!mitel!sce!klink
From: klink@sce.carleton.ca (Robert Klinkhammer)
Newsgroups: comp.sys.ibm.pc
Subject: Re: uncompress on PC - not there yet
Summary: It is compatible.
Keywords: PC compress
Message-ID: <716@sce.carleton.ca>
Date: 22 Nov 89 01:51:40 GMT
References: <824@dukempd.phy.duke.edu> <2565B872.3324@maccs.dcss.mcmaster.ca> <89Nov19.101032est.18571@me.utoronto.ca>
Organization: Systems & Computer Eng. Dept., Carleton University, Ottawa, Canada
Lines: 48

I'm posting this for ...!uunet!mitel!sce!tsmith!graham (Doug Graham)
who has only clandestine net access. :-)

In article <89Nov19.101032est.18571@me.utoronto.ca>, rwh@me.utoronto.ca (Russell Herman) writes:
> In article <2565B872.3324@maccs.dcss.mcmaster.ca> cs4g6ag@maccs.dcss.mcmaster.ca
>  (Stephen M. Dunn) writes:
> >In article <824@dukempd.phy.duke.edu> fang@dukempd.phy.duke.edu (Fang Zhong) writes:
> >$	Are there uudecode and uncompress on PC, which are compitible
> >$to the ones on Unix system?
> >   A new version just came across comp.binaries.ibm.pc sometime in the past
> >week or two.

I'm assuming that the compress referred to below, is the one that I posted
to comp.sources.misc about a week ago. I don't remember seeing one in
c.b.ibm.pc. If I'm wrong, please excuse the waste of network bandwidth.

> Yes, but it's still not 100% compatible.  I found a file that had been
> compressed elseware (don't know on what) which was accused of corruption
> by the recently posted compress 4.0.  I uploaded it to a SUN and it
> decompressed without any problems.  A careful reading of the comments
> supplied with the posted version brought me to conclude that a UNIX
> uncompress will handle files compressed by 4.0, but not necessarily
> the converse.

The converse is also true. That was the main point of the excercise.
It is possible though, that I was a bit over-zealous in adding error
checking. The original compress 4.0 depended on getting a SIGSEGV
if it was given a corrupt input file. This doesn't work on an 8088.
(And not very well on anything else for that matter). I added a bit
of code to try to avoid a system crash in the event of a bad input file.
I may have screwed up. I'll go have a closer look. See ya in comp.sources.bugs.
I would appreciate it, if you could send me a copy of the compressed
file that caused the trouble. (That is, if it's not too big)

If this really is the problem, removing the lines:

	if (code != freecode + 1)
		oops();

from the function decompress() will cure it, although you will then
have no protection against a bad input file.

Doug.
-- 
**********************************************************************
Robert Klinkhammer          "They recommended euthanasia 
<klink@sce.carleton.ca>     for noncomformists anywhere" -- Asia
**********************************************************************