1
2
3This is the README for bzip2, a block-sorting file compressor, version
40.9.0. This version is fully compatible with the previous public
5release, bzip2-0.1pl2.
6
7bzip2-0.9.0 is distributed under a BSD-style license. For details,
8see the file LICENSE.
9
10Complete documentation is available in Postscript form (manual.ps)
11or html (manual_toc.html). A plain-text version of the manual page is
12available as bzip2.txt.
13
14
15HOW TO BUILD -- UNIX
16
17Type `make'.
18
19This creates binaries "bzip2" and "bzip2recover".
20
21It also runs four compress-decompress tests to make sure things are
22working properly. If all goes well, you should be up & running.
23Please be sure to read the output from `make' just to be sure that the
24tests went ok.
25
26To install bzip2 properly:
27
28* Copy the binaries "bzip2" and "bzip2recover" to a publically visible
29 place, possibly /usr/bin or /usr/local/bin.
30
31* In that directory, make "bunzip2" and "bzcat" be symbolic links
32 to "bzip2".
33
34* Copy the manual page, bzip2.1, to the relevant place.
35 Probably the right place is /usr/man/man1/.
36
37If you want to program with the library, you'll need to copy libbz2.a
38and bzlib.h to /usr/lib and /usr/include respectively.
39
40
41HOW TO BUILD -- Windows 95, NT, DOS, Mac, etc.
42
43It's difficult for me to support compilation on all these platforms.
44My approach is to collect binaries for these platforms, and put them
45on my web page (http://www.muraroa.demon.co.uk). Look there.
46
47
48VALIDATION
49
50Correct operation, in the sense that a compressed file can always be
51decompressed to reproduce the original, is obviously of paramount
52importance. To validate bzip2, I used a modified version of Mark
53Nelson's churn program. Churn is an automated test driver which
54recursively traverses a directory structure, using bzip2 to compress
55and then decompress each file it encounters, and checking that the
56decompressed data is the same as the original. There are more details
57in Section 4 of the user guide.
58
59
60
61Please read and be aware of the following:
62
63WARNING:
64
65 This program (attempts to) compress data by performing several
66 non-trivial transformations on it. Unless you are 100% familiar
67 with *all* the algorithms contained herein, and with the
68 consequences of modifying them, you should NOT meddle with the
69 compression or decompression machinery. Incorrect changes can and
70 very likely *will* lead to disastrous loss of data.
71
72
73DISCLAIMER:
74
75 I TAKE NO RESPONSIBILITY FOR ANY LOSS OF DATA ARISING FROM THE
76 USE OF THIS PROGRAM, HOWSOEVER CAUSED.
77
78 Every compression of a file implies an assumption that the
79 compressed file can be decompressed to reproduce the original.
80 Great efforts in design, coding and testing have been made to
81 ensure that this program works correctly. However, the complexity
82 of the algorithms, and, in particular, the presence of various
83 special cases in the code which occur with very low but non-zero
84 probability make it impossible to rule out the possibility of bugs
85 remaining in the program. DO NOT COMPRESS ANY DATA WITH THIS
86 PROGRAM UNLESS YOU ARE PREPARED TO ACCEPT THE POSSIBILITY, HOWEVER
87 SMALL, THAT THE DATA WILL NOT BE RECOVERABLE.
88
89 That is not to say this program is inherently unreliable. Indeed,
90 I very much hope the opposite is true. bzip2 has been carefully
91 constructed and extensively tested.
92
93
94PATENTS:
95
96 To the best of my knowledge, bzip2 does not use any patented
97 algorithms. However, I do not have the resources available to
98 carry out a full patent search. Therefore I cannot give any
99 guarantee of the above statement.
100
101End of legalities.
102
103
104WHAT'S NEW IN 0.9.0 (as compared to 0.1pl2) ?
105
106 * Approx 10% faster compression, 30% faster decompression
107 * -t (test mode) is a lot quicker
108 * Can decompress concatenated compressed files
109 * Programming interface, so programs can directly read/write .bz2 files
110 * Less restrictive (BSD-style) licensing
111 * Flag handling more compatible with GNU gzip
112 * Much more documentation, i.e., a proper user manual
113 * Hopefully, improved portability (at least of the library)
114
115
116I hope you find bzip2 useful. Feel free to contact me at
117 jseward@acm.org
118if you have any suggestions or queries. Many people mailed me with
119comments, suggestions and patches after the releases of bzip-0.15,
120bzip-0.21 and bzip2-0.1pl2, and the changes in bzip2 are largely a
121result of this feedback. I thank you for your comments.
122
123At least for the time being, bzip2's "home" is
124http://www.muraroa.demon.co.uk.
125
126Julian Seward
127jseward@acm.org
128
129Manchester, UK
13018 July 1996 (version 0.15)
13125 August 1996 (version 0.21)
132
133Guildford, Surrey, UK
1347 August 1997 (bzip2, version 0.1)
13529 August 1997 (bzip2, version 0.1pl2)
13623 August 1998 (bzip2, version 0.9.0)
137
138