compress

早期freebsd实现

#
# 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.

# According to gzip.h, this is the correct byte order for packed data.
#
0	string		\037\036	packed data

#
# This magic number is byte-order-independent.
#
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
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 <[e-mail]>
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)
#
# Standard unix compress
#
0	string		\037\235	compressed data
>2	byte&0x80	>0		block compressed
>2	byte&0x1f	x		%d bits