Newsgroups: comp.sys.mac.apps Path: utzoo!utgpu!watserv1!watnow.waterloo.edu!jlee From: jlee@watnow.waterloo.edu (Johnny Lee) Subject: Re: Compactor - A reason not to use Message-ID: <1991Jan15.062305.4215@watserv1.waterloo.edu> Sender: daemon@watserv1.waterloo.edu Organization: University of Waterloo References: <41470@nigel.ee.udel.edu> Date: Tue, 15 Jan 91 06:23:05 GMT Lines: 36 In article vd09+@andrew.cmu.edu (Vincent M. Del Vecchio) writes: > >I disagree somewhat with your interpretation. I believe that Bill Goodman >would be more than willing to disclose header-type information for >incorporation into programs like FileList and CatStuff; this information should >not be hard to deduce anyway and disclosing it doesn't give an advantage to >your competitors. On the other hand, in light of what I have heard about his It wasn't that hard. One just needs to get a decent sampling of Compactor archives and one doesn't have to be Sherlock Holmes to deduce 99% of all the fields. Actually, the information that Mr. Goodman sends out doesn't seem to reveal the Compactor-specific information, i.e. Compressed lengths, location of compressed data. >negotations with CompuServe, he seems to be reluctant to disclose the actual >compression format with which the files in the archive are compressed or >decompressed (typically, the filenames, orig. and compressed sizes, etc. of the >compressed files are stored in plaintext (uncompressed) in the data fork of the >archive file). Perhaps a good way to put it would be to say that the archive >format is known, but the compression format is still not. > From a preliminary look at the resulting archives, Compactor seems to use a couple of types of compression including run-length encoding. I've never heard any stories about reverse-engineering a compressed file, but it should be nice late-night fodder. Compactor is a nice Mac archiving program, but I don't use it because I talk more to/thru Unix boxes than Macs. Besides, for real compression, COMIC beats most with one hand tied behind its back (though you'll have to wait a long time). Johnny Lee jlee@watnow.waterloo.edu