1 2This is the README for bzip2, a block-sorting file compressor, version 31.0. This version is fully compatible with the previous public 4releases, bzip2-0.1pl2, bzip2-0.9.0 and bzip2-0.9.5. 5 6bzip2-1.0 is distributed under a BSD-style license. For details, 7see the file LICENSE. 8 9Complete documentation is available in Postscript form (manual.ps) or 10html (manual_toc.html). A plain-text version of the manual page is 11available as bzip2.txt. A statement about Y2K issues is now included 12in the file Y2K_INFO. 13 14 15HOW TO BUILD -- UNIX 16 17Type `make'. This builds the library libbz2.a and then the 18programs bzip2 and bzip2recover. Six self-tests are run. 19If the self-tests complete ok, carry on to installation: 20 21To install in /usr/bin, /usr/lib, /usr/man and /usr/include, type 22 make install 23To install somewhere else, eg, /xxx/yyy/{bin,lib,man,include}, type 24 make install PREFIX=/xxx/yyy 25If you are (justifiably) paranoid and want to see what 'make install' 26is going to do, you can first do 27 make -n install or 28 make -n install PREFIX=/xxx/yyy respectively. 29The -n instructs make to show the commands it would execute, but 30not actually execute them. 31 32 33HOW TO BUILD -- UNIX, shared library libbz2.so. 34 35Do 'make -f Makefile-libbz2_so'. This Makefile seems to work for 36Linux-ELF (RedHat 5.2 on an x86 box), with gcc. I make no claims 37that it works for any other platform, though I suspect it probably 38will work for most platforms employing both ELF and gcc. 39 40bzip2-shared, a client of the shared library, is also build, but 41not self-tested. So I suggest you also build using the normal 42Makefile, since that conducts a self-test. 43 44Important note for people upgrading .so's from 0.9.0/0.9.5 to 45version 1.0. All the functions in the library have been renamed, 46from (eg) bzCompress to BZ2_bzCompress, to avoid namespace pollution. 47Unfortunately this means that the libbz2.so created by 48Makefile-libbz2_so will not work with any program which used an 49older version of the library. Sorry. I do encourage library 50clients to make the effort to upgrade to use version 1.0, since 51it is both faster and more robust than previous versions. 52 53 54HOW TO BUILD -- Windows 95, NT, DOS, Mac, etc. 55 56It's difficult for me to support compilation on all these platforms. 57My approach is to collect binaries for these platforms, and put them 58on the master web page (http://sourceware.cygnus.com/bzip2). Look 59there. However (FWIW), bzip2-1.0 is very standard ANSI C and should 60compile unmodified with MS Visual C. For Win32, there is one 61important caveat: in bzip2.c, you must set BZ_UNIX to 0 and 62BZ_LCCWIN32 to 1 before building. If you have difficulties building, 63you might want to read README.COMPILATION.PROBLEMS. 64 65 66VALIDATION 67 68Correct operation, in the sense that a compressed file can always be 69decompressed to reproduce the original, is obviously of paramount 70importance. To validate bzip2, I used a modified version of Mark 71Nelson's churn program. Churn is an automated test driver which 72recursively traverses a directory structure, using bzip2 to compress 73and then decompress each file it encounters, and checking that the 74decompressed data is the same as the original. There are more details 75in Section 4 of the user guide. 76 77 78 79Please read and be aware of the following: 80 81WARNING: 82 83 This program (attempts to) compress data by performing several 84 non-trivial transformations on it. Unless you are 100% familiar 85 with *all* the algorithms contained herein, and with the 86 consequences of modifying them, you should NOT meddle with the 87 compression or decompression machinery. Incorrect changes can and 88 very likely *will* lead to disastrous loss of data. 89 90 91DISCLAIMER: 92 93 I TAKE NO RESPONSIBILITY FOR ANY LOSS OF DATA ARISING FROM THE 94 USE OF THIS PROGRAM, HOWSOEVER CAUSED. 95 96 Every compression of a file implies an assumption that the 97 compressed file can be decompressed to reproduce the original. 98 Great efforts in design, coding and testing have been made to 99 ensure that this program works correctly. However, the complexity 100 of the algorithms, and, in particular, the presence of various 101 special cases in the code which occur with very low but non-zero 102 probability make it impossible to rule out the possibility of bugs 103 remaining in the program. DO NOT COMPRESS ANY DATA WITH THIS 104 PROGRAM UNLESS YOU ARE PREPARED TO ACCEPT THE POSSIBILITY, HOWEVER 105 SMALL, THAT THE DATA WILL NOT BE RECOVERABLE. 106 107 That is not to say this program is inherently unreliable. Indeed, 108 I very much hope the opposite is true. bzip2 has been carefully 109 constructed and extensively tested. 110 111 112PATENTS: 113 114 To the best of my knowledge, bzip2 does not use any patented 115 algorithms. However, I do not have the resources available to 116 carry out a full patent search. Therefore I cannot give any 117 guarantee of the above statement. 118 119End of legalities. 120 121 122WHAT'S NEW IN 0.9.0 (as compared to 0.1pl2) ? 123 124 * Approx 10% faster compression, 30% faster decompression 125 * -t (test mode) is a lot quicker 126 * Can decompress concatenated compressed files 127 * Programming interface, so programs can directly read/write .bz2 files 128 * Less restrictive (BSD-style) licensing 129 * Flag handling more compatible with GNU gzip 130 * Much more documentation, i.e., a proper user manual 131 * Hopefully, improved portability (at least of the library) 132 133WHAT'S NEW IN 0.9.5 ? 134 135 * Compression speed is much less sensitive to the input 136 data than in previous versions. Specifically, the very 137 slow performance caused by repetitive data is fixed. 138 * Many small improvements in file and flag handling. 139 * A Y2K statement. 140 141WHAT'S NEW IN 1.0 142 143 See the CHANGES file. 144 145I hope you find bzip2 useful. Feel free to contact me at 146 jseward@acm.org 147if you have any suggestions or queries. Many people mailed me with 148comments, suggestions and patches after the releases of bzip-0.15, 149bzip-0.21, bzip2-0.1pl2 and bzip2-0.9.0, and the changes in bzip2 are 150largely a result of this feedback. I thank you for your comments. 151 152At least for the time being, bzip2's "home" is (or can be reached via) 153http://www.muraroa.demon.co.uk. 154 155Julian Seward 156jseward@acm.org 157 158Cambridge, UK 15918 July 1996 (version 0.15) 16025 August 1996 (version 0.21) 161 7 August 1997 (bzip2, version 0.1) 16229 August 1997 (bzip2, version 0.1pl2) 16323 August 1998 (bzip2, version 0.9.0) 164 8 June 1999 (bzip2, version 0.9.5) 165 4 Sept 1999 (bzip2, version 0.9.5d) 166 5 May 2000 (bzip2, version 1.0pre8) 167