[CDG5] Random questions

Max Poliakovski maximumspatium at googlemail.com
Sat Dec 1 22:22:40 AWST 2018


Hi Daniel,

email attachments work.

Thank you for sending me your disassembly. From what I see there, that PPC
code implements the same compression algorithm by Donn Denman from 1990 as
in DeCompressDefProc.a. This becomes apparent when looking at the table of
180 words at the beginning of the dump.

The overall algorithm looks like a mix of various well-known lossless
techniques: run-length coding (RLE), differential coding and dictionary
replacements (both static and dynamic).

Code resources will be compressed by replacing the most frequent words
found in 68k code with byte indexes. 0x0000 comes first, 0x4EBA (JSR) comes
next, followed by 0x0008 and 0x4E75 (RTS) and so on.

The whole stuff looks quite easy to understand and to reimplement in
Python. I'm prepared to give a try if someone could send me such a
compressed resource and its decompressed equivalent.

Cheers
Max


Am Sa., 1. Dez. 2018 um 05:00 Uhr schrieb Daniel B-J <
danielbj314 at verizon.net>:

> My "secret project" can do a half-decent job disassembling PEFs.
>
> Here's the partial disasm of the 'ncmp' 0 resource, which is called
> DonnDecompress0.
>
> You may or may not get the file, as I have no idea if this mailing list
> even lets you use attachments. Time to find out.
> _______________________________________________
> cdg5 mailing list
> cdg5 at ucc.asn.au
> https://lists.ucc.gu.uwa.edu.au/mailman/listinfo/cdg5
>
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