LZpackIT.DLL

© Copyright 1992, Ian Taylor. All rights reserved.

------------
INTRODUCTION
------------

I had to install a fairly large number of files during a setup program.
Not only where there a large number of files, but one of them was larger
than 1.4 Mb ! Accordingly there was no way that I could just use the copy
functions to get them across. I looked around for a DLL and couldn't find
one, and found that LZEXPAND.DLL from MS was no use, because I would
have to buy the SDK to get COMPRESS.EXE in the first place. Even then I
thought that this was not very satisfactory since I would not be able
to compress the files except by shelling to DOS.

So I wrote LZpackIT.DLL which does the job for me. Please bear in mind that
this is the first version ! I am not altogether happy with it's speed but
it's compression performance is fairly good. It compresses a file to
around the same size as PKZip, sometimes slightly smaller, sometimes bigger.

It will only compress/decompress 1 file at a time, so you will have to
invoke the functions over again to do another file.

The DLL is based on the Lempel-Ziv algorithm, modified by Adaptive Huffman
Encoding.

-----
USAGE
-----

The DLL contains 2 Subs:

packIT		'Compresses a file
unpackIT	'Decompresses a file

The VB Declares for these functions are:

Declare Sub PackIT Lib "LZpackIT.DLL" (ByVal SourceFile$, ByVal TargetFile$)
Declare Sub UnPackIT Lib "LZpackIT.DLL" (ByVal SourceFile$, ByVal TargetFile$)

At present the DLL does not give any progress indication, or return a
result code.

Please provide me with any feedback you may have, and I will bear it in
mind as I write future versions.

------
NOTICE
------

This software is provided free of charge and "as is". You may
distribute it freely providing you distribute this document along with it, 
and you do not modify either the software or this document in any way.

I have taken every care to test this program in as many situations and
under as many conditions as I can. Up to now I have not encountered any
errors in compression or decompression of files. You must, however,
satisfy yourself as to its suitability for your purpose:
I cannot accept any responsibility for any adverse results.

Ian Taylor 100025,557

Moorgate East Farm,
Broad Lane,
Rochdale,
England
OL16 4QL
Tel: (+44) 706-353-412

10/7/92