Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!sdd.hp.com!hp-pcd!hplsla!ericb
From: ericb@hplsla.HP.COM (Eric Backus)
Newsgroups: comp.binaries.ibm.pc.d
Subject: Re: PKLITE, what's the catch???
Message-ID: <11230004@hplsla.HP.COM>
Date: 26 Jun 91 22:56:37 GMT
References: <1991Jun26.141813.29418@midway.uchicago.edu>
Organization: HP Lake Stevens, WA
Lines: 48

>>I just got a neat program called PKLITE version 1.05 and have decreased
>>my hard disk usage by 4 Meg.  What's tha catch (aside from the obvious
>>extra second or two it take to load a exe)?  Are there any gotcha's
>>associated with using PKLITE?  E-mail responses are fine, let's not
>>clutter the net.

>As far as I know, no catches.  Obviously, it doesn't work with some files.

Catches:
	1. Compressed files take longer to execute (the bigger the
	   executable, the bigger the delay).
	2. Files which try to modify their own executable (to create a
	   registered version, for example) will probably no longer work.
	   But you can just uncompress them when you want to do this.
	3. Windows 3.0 executables can't be compressed.
	4. Some executables with overlays can't be compressed - but I've
	   found that many of them work fine.
	5. If the uncompressed version has a virus, compressing it probably
	   hides the virus from most virus scanners.
	6. Files which check for virus contamination usually refuse to run
	   if you compress them.

>What I'd like to know is what the comparison (on the usual criteria) is
>between the various EXE compressors.  (Diet, PKlite, LHEXE)
>I've been using LHEXE (I think that's the name; it seems to have slipped
>my mind - ANyway, it's the one from France) and it seems to work OK.
>Just wondering if any of the others are any better...

I've never done a REAL test, but here are my impressions based on playing
with Diet, PKLite, and LZEXE.  They will all compress within a few percent
of each other.  LZEXE seems to do slightly worse.  PKLite seems to do
slightly better.  PKLite seems to be slightly faster at unpacking when you
execute the file.  Diet seems to be slightly faster at compressing the
original.  All three can be undone if you decide that you don't want the
executable compressed anymore, but LZEXE does NOT restore the original
exactly.  Diet understands about disk cluster sizes and won't bother
replacing a file if the compressed version uses the same number of disk
clusters (not sure if PKLite or LZEXE do this).

I believe that Diet provides a TSR which intercepts disk reads and writes,
allowing you to keep data files in compressed form on disk, but I've never
tested that.

Personally, I use Diet.  It works very well.
--
				Eric Backus
				ericb%hplsla@hplabs.hp.com
				(206) 335-2495