Beware, the LZRW algorithms are patented. Quoting Dr. Ross:

Unfortunately, during this happy rollout, some patents popped out of the US patent system that cast a shadow over the LZRW series algorithms, and they became effectively unuseable in any practical application. If you want to use them in any product (whether free or commercial), you will have to do some in-depth patent homework and algorithm development/modification so as to avoid infringement. If you think that''s easy, then you should be aware that Microsoft tried to use an LZ77/LZRW1/etc variant, specifically designed not to infringe existing patents, in its MS-DOS V6 operating system, and ended up having to pay Stac about $80m in the resulting patent lawsuit. For this reason, I would like to take this opportunity to state that the code provided in this web (and FTP site) is provided with the intention that it be used for educational and recreational use only.

I read the patents on www.ross.net and RZW3-A is not named in any of the patents. Also in my source-files the string "public domain" exists.
And look at the ownership of the patents: No Ross N. Williams, although he invented the LZRW algorithms. Who stole the code? And never heard of "open source"?

And regarding Microsoft, I don''t think MS pays for all components used in WIN2K because nobody knows the complete source and could claim it hurts any patents.

Let''s just say I wrote a compression algorithm resulting in the same source-code.



B.o.t.G.
--------

Writer of
- VQAtoAVI, the conversation utility for C&C
- Golden Cow, the BO2K attacher

The following off www.ross.net:

quote:
LZRW Algorithms And Patents

It is possible that the algorithms LZRW1, LZRW1-A, LZRW2,
LZRW3, and LZRW3-A may be partially or fully covered by one
or more of the following patents:

US Patent 4701745 - The Waterworth LZ77 Patent.
US Patent 5049881 - Gibson and Graybill LZ77 patent.
US Patent 5051745 - Phil Katz LZ77 patent.
US Patent 5140321 - Robert Jung LZ77 limited search
patent.

The patent is on the LZ77 *algorithm* that the LZRW3-A is descended from.

Of course you didn''t find LZRW3-A in the patents, Ross Williams took the LZ algorithm and modified it slightly (and I mean slightly). He didn''t invent LZ, just modified it. So no one "stole his code".

Oh and his C source *implementation* is in the public domain, but the algorithm isn''t.

And if you wrote a compression algorithm that resulted in the same source code it would still infringe on the LZ77 patents. And yes, they can do an analysis that would show that you''re using an LZ77 style compression. LZ77 has a unique "fingerprint". And if you read Staffan''s post carefully, writing a similar compression algorithm was what landed MS paying $80 milliion.

I think I download an encryptionengine, too.
So knowbody can analyze the packed files *G*

And what is with zLib? Falls it under any patents or not?


B.o.t.G.
--------

Writer of
- VQAtoAVI, the conversation utility for C&C
- Golden Cow, the BO2K attacher

zlib is completely open source that was the point behind it''s development. I believe it''s under GPL, not LGPL though.

And B.o.t.G., if you encrypt an LZ77, as it sounds like you''re trying to do, almost any court in the world find you guilty of deliberatly trying to subvert patent laws. In such a case you may face criminal as well as civil charges. I''m not a lawyer, so feel free to ignore me, but don''t say no one tried to warn you.

I now know the difficulties with LZ77
But 1 hour after my previous post I find out how to set the Linker options so that my program can use zLib. It''s even packing better than anything else I tried! I now have to modify all the code to increase speed further and to reduce the size of the library.

But nobody can change my opinion: patents are f***ing b***sh**



B.o.t.G.
--------

Writer of
- VQAtoAVI, the conversation utility for C&C
- Golden Cow, the BO2K attacher

Use one of the OpenSource Zip libraries. Why reinvent the wheel?

--Rick