AFX (Atari ST)
AFX (Automatic File eXtractor) is a transparent file compression utility for Atari ST. It was developed primarily by Thomas Quester. Much of the information about it is in German.
Its native compressed file format is a single-file variant of LHarc format.
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Discussion
Some of the Atari ST versions of LHarc can create and decompress AFX-compressed files. Specifically:
- At least versions 2.01d and later by Quester. (The "c" command exists in v2.01d, though it's not in the "usage" message.)
- The LHarc software by Grunenberg and Mandel, and later Haun. Seems to be the successor to Quester's LHarc.
Format details
Compression
The compression method is Okumura's LZSS. It is evidently the same as the -lz5- method from LArc, except that the history buffer is initialized differently -- with LZSS's standard 4096-18 spaces, instead of lz5's special pattern. Whether the initialization makes any difference is unknown.
CRC issue
A number of AFX files found in the wild seem to have an incorrect CRC stored in the file. The cause of this problem is unknown. At least some of them seem to decompress correctly, if the CRC is ignored. That the CRC is incorrect is confirmed by the "test" or "extract" function of Quester's LHarc.
Identification
ASCII "-afx-" appears at offset 2. The byte at offset 20 (the LHA "header level") is evidently always 0.
Software
- LHarc for Atari ST - v2.01X by Thomas Quester
- 2.01d German: CSTEX4-2.ZOO → lzh.lzh → LHARC/LHARC.TTP
- 2.01L English: LZH201LE.TTP
- LZH_201L.LZH - Includes LHarc and AFX
- LZHSOURC.LZH - Source code for "LHarc 2.01m (c)Yoshi, Quester, 1988-91":
- LHarc for Atari ST - v2.20-3.xx by Grunenberg/Mandel(/Haun)
- v3.13a junior: [1]
