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SkyCapt's picture
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Joined: 2017 Jan 11
Can anybody identify the file-compression used in Apple diagnostics?

Such as in this dL (AHT-AIO_v0.6-PMG4) link:
http://macintoshgarden.org/apps/apple-hardware-test-powermac-g4

The software (AHT v1.2.6 thru v2.5.x) spans at least 5 years in the making, and all use the same one simple compression format upon some of their files which otherwise would be ascii text files.

Sample compressed ascii files are in at least all AHT versions mentioned, their folder "Localization/*" files.

This compression format looks like it always begins with the 32-bit word $7C5F7C5F which itself in ascii text is " |_|_ ". The 2nd 32-bit word might be a numerical value proportional to the size of the file.

When we arrive in time at AHT v2.2.5 (also found within the dL linked above) Apple began compressing additional files in AHTs. These files are everything in "Apps/Configs/*" in which these files had been uncompressed ascii within many older versions of AHT (v2.1.0 downto v2.0.0). So here are numerous examples of similar files found both compressed and uncompressed.

In AHT v2.2.5 there is a new ascii file in compressed form named "Apps/Configs/Indy.env" which is so short (41 bytes data fork) that it will make the compression format easy to crk if necessary.

Anybody know this compression format, and therefore how to read files stored this way?