Is there an LZX-like archiver for the PC???

[Glaucus]

Greets Amiga fans!

Back in 1995 Jonathan Forbes and Tomi Poutanen released a new Amiga-only archiving tool called LZX. LZX had, at the time, a unique compression feature they called "file merging". Here's how they describe file merging in the official documentation for LZX:

File merging is a feature of LZX which enables compression to be increased, often very significantly, by allowing data from one file to be compressed using the knowledge of previous files in the archive.  This feature, unique to LZX on the Amiga, often improves compression by 300% or more!

This feature is very useful when compressing text files and source files, where there is often a large amount of text common to many files.

There is also a significant advantage to this feature when compressing a large number of small files, since the data overhead of re-starting compression for each file is now removed.  This is particularly true when compressing ".info" files

My question here is, are there file archiving utilities available for the PC (or other platforms) that employ this feature? My understanding is that zip (or WinZip) does not support such a feature, but I could be wrong here. Doing some quick googling around the net I noticed that WinZip 10 supports PPMd compression, but most docs I've found for it are Russian. Unfortunately for me, I can't read Russian. Does anyone know anything about this compression standard?

As for why I'm asking about this? Ummm... Not really sure, but a good buddy of mine has tasked me with figuring out the answer to this question - for reasons not yet clear to me. :-D If anyone could help, it would be greatly appreciated.

  - Mike

[Glaucus]

I suppose I should have mentioned that their use of the phrase "file merging" is quite different then what seems to be the norm. If you read their definition of "file merging" you'll quickly note that it's quite different from what tar does. In the LZX sense, "file merging" will compress identical files better then lha or zip, by magically merging the data before compressing it.

For example, if you have ten .info file, which are binary identical, and add them all to a zip file, WinZip will compress each file independently, and add them to the archive. LZX would note that the ten files are all the same and use advanced compression techniques to minimize the duplication of compressed data. This makes the compressed file size much smaller.

So I think we're talking about something slightly different then what tar does.

  - Mike

[Glaucus]

Ah, okay, I see what you're saying now.

Yes, I should have realized this right away. It's been a while since I've used a unix-like system, but I have used tar & gzip together in the past.

But yeah, LZX did have that advantage of allowing you to do things in one step instead of two. That's a good point.

So, are there any other options out there that perform similarly to LZX?

  - Mike

[Glaucus]

Okay, thanks guys!

  - Mike