file_cmds-60.tar.gz

[apple/file_cmds.git] / file / magdir / compress

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