87 lines
3.0 KiB
Plaintext
87 lines
3.0 KiB
Plaintext
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#------------------------------------------------------------------------------
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# compress: file(1) magic for pure-compression formats (no archives)
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#
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# compress, gzip, pack, compact, huf, squeeze, crunch, freeze, yabba, etc.
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#
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# Formats for various forms of compressed data
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# Formats for "compress" proper have been moved into "compress.c",
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# because it tries to uncompress it to figure out what's inside.
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# standard unix compress
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0 string \037\235 compress'd data
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>2 byte&0x80 >0 block compressed
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>2 byte&0x1f x %d bits
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# gzip (GNU zip, not to be confused with Info-ZIP or PKWARE zip archiver)
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0 string \037\213 gzip compressed data
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>2 byte <8 \b, reserved method,
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>2 byte 8 \b, deflated,
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>3 byte &0x01 ASCII,
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>3 byte &0x02 continuation,
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>3 byte &0x04 extra field,
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>3 byte &0x08 original filename,
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>3 byte &0x10 comment,
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>3 byte &0x20 encrypted,
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>4 ledate x last modified: %s,
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>8 byte 2 max compression,
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>8 byte 4 max speed,
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>9 byte =0x00 os: MS-DOS
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>9 byte =0x01 os: Amiga
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>9 byte =0x02 os: VMS
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>9 byte =0x03 os: Unix
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>9 byte =0x05 os: Atari
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>9 byte =0x06 os: OS/2
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>9 byte =0x07 os: MacOS
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>9 byte =0x0A os: Tops/20
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>9 byte =0x0B os: Win/32
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# packed data, Huffman (minimum redundancy) codes on a byte-by-byte basis
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0 string \037\036 packed data
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>2 belong >1 \b, %d characters originally
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>2 belong =1 \b, %d character originally
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#
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# This magic number is byte-order-independent. XXX - Does that mean this
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# is big-endian, little-endian, either, or that you can't tell?
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# this short is valid for SunOS
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0 short 017437 old packed data
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# XXX - why *two* entries for "compacted data", one of which is
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# byte-order independent, and one of which is byte-order dependent?
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#
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0 short 0x1fff compacted data
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# This string is valid for SunOS (BE) and a matching "short" is listed
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# in the Ultrix (LE) magic file.
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0 string \377\037 compacted data
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0 short 0145405 huf output
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# Squeeze and Crunch...
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# These numbers were gleaned from the Unix versions of the programs to
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# handle these formats. Note that I can only uncrunch, not crunch, and
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# I didn't have a crunched file handy, so the crunch number is untested.
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# Keith Waclena <keith@cerberus.uchicago.edu>
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0 leshort 0x76FF squeezed data (CP/M, DOS)
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0 leshort 0x76FE crunched data (CP/M, DOS)
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# Freeze
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0 string \037\237 frozen file 2.1
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0 string \037\236 frozen file 1.0 (or gzip 0.5)
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# SCO compress -H (LZH)
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0 string \037\240 SCO compress -H (LZH) data
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# European GSM 06.10 is a provisional standard for full-rate speech
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# transcoding, prI-ETS 300 036, which uses RPE/LTP (residual pulse
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# excitation/long term prediction) coding at 13 kbit/s.
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#
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# There's only a magic nibble (4 bits); that nibble repeats every 33
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# bytes. This isn't suited for use, but maybe we can use it someday.
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#
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# This will cause very short GSM files to be declared as data and
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# mismatches to be declared as data too!
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#0 byte&0xF0 0xd0 data
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#>33 byte&0xF0 0xd0
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#>66 byte&0xF0 0xd0
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#>99 byte&0xF0 0xd0
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#>132 byte&0xF0 0xd0 GSM 06.10 compressed audio
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