1 2This is the README for bzip2/libzip2. 3This version is fully compatible with the previous public releases. 4 5------------------------------------------------------------------ 6This file is part of bzip2/libbzip2, a program and library for 7lossless, block-sorting data compression. 8 9bzip2/libbzip2 version 1.0.8 of 13 July 2019 10Copyright (C) 1996-2019 Julian Seward <jseward@acm.org> 11 12Please read the WARNING, DISCLAIMER and PATENTS sections in this file. 13 14This program is released under the terms of the license contained 15in the file LICENSE. 16------------------------------------------------------------------ 17 18Complete documentation is available in Postscript form (manual.ps), 19PDF (manual.pdf) or html (manual.html). A plain-text version of the 20manual page is available as bzip2.txt. 21 22 23HOW TO BUILD -- UNIX 24 25Type 'make'. This builds the library libbz2.a and then the programs 26bzip2 and bzip2recover. Six self-tests are run. If the self-tests 27complete ok, carry on to installation: 28 29To install in /usr/local/bin, /usr/local/lib, /usr/local/man and 30/usr/local/include, type 31 32 make install 33 34To install somewhere else, eg, /xxx/yyy/{bin,lib,man,include}, type 35 36 make install PREFIX=/xxx/yyy 37 38If you are (justifiably) paranoid and want to see what 'make install' 39is going to do, you can first do 40 41 make -n install or 42 make -n install PREFIX=/xxx/yyy respectively. 43 44The -n instructs make to show the commands it would execute, but not 45actually execute them. 46 47 48HOW TO BUILD -- UNIX, shared library libbz2.so. 49 50Do 'make -f Makefile-libbz2_so'. This Makefile seems to work for 51Linux-ELF (RedHat 7.2 on an x86 box), with gcc. I make no claims 52that it works for any other platform, though I suspect it probably 53will work for most platforms employing both ELF and gcc. 54 55bzip2-shared, a client of the shared library, is also built, but not 56self-tested. So I suggest you also build using the normal Makefile, 57since that conducts a self-test. A second reason to prefer the 58version statically linked to the library is that, on x86 platforms, 59building shared objects makes a valuable register (%ebx) unavailable 60to gcc, resulting in a slowdown of 10%-20%, at least for bzip2. 61 62Important note for people upgrading .so's from 0.9.0/0.9.5 to version 631.0.X. All the functions in the library have been renamed, from (eg) 64bzCompress to BZ2_bzCompress, to avoid namespace pollution. 65Unfortunately this means that the libbz2.so created by 66Makefile-libbz2_so will not work with any program which used an older 67version of the library. I do encourage library clients to make the 68effort to upgrade to use version 1.0, since it is both faster and more 69robust than previous versions. 70 71 72HOW TO BUILD -- Windows 95, NT, DOS, Mac, etc. 73 74It's difficult for me to support compilation on all these platforms. 75My approach is to collect binaries for these platforms, and put them 76on the master web site (https://sourceware.org/bzip2/). Look there. However 77(FWIW), bzip2-1.0.X is very standard ANSI C and should compile 78unmodified with MS Visual C. If you have difficulties building, you 79might want to read README.COMPILATION.PROBLEMS. 80 81At least using MS Visual C++ 6, you can build from the unmodified 82sources by issuing, in a command shell: 83 84 nmake -f makefile.msc 85 86(you may need to first run the MSVC-provided script VCVARS32.BAT 87 so as to set up paths to the MSVC tools correctly). 88 89 90VALIDATION 91 92Correct operation, in the sense that a compressed file can always be 93decompressed to reproduce the original, is obviously of paramount 94importance. To validate bzip2, I used a modified version of Mark 95Nelson's churn program. Churn is an automated test driver which 96recursively traverses a directory structure, using bzip2 to compress 97and then decompress each file it encounters, and checking that the 98decompressed data is the same as the original. 99 100 101 102Please read and be aware of the following: 103 104WARNING: 105 106 This program and library (attempts to) compress data by 107 performing several non-trivial transformations on it. 108 Unless you are 100% familiar with *all* the algorithms 109 contained herein, and with the consequences of modifying them, 110 you should NOT meddle with the compression or decompression 111 machinery. Incorrect changes can and very likely *will* 112 lead to disastrous loss of data. 113 114 115DISCLAIMER: 116 117 I TAKE NO RESPONSIBILITY FOR ANY LOSS OF DATA ARISING FROM THE 118 USE OF THIS PROGRAM/LIBRARY, HOWSOEVER CAUSED. 119 120 Every compression of a file implies an assumption that the 121 compressed file can be decompressed to reproduce the original. 122 Great efforts in design, coding and testing have been made to 123 ensure that this program works correctly. However, the complexity 124 of the algorithms, and, in particular, the presence of various 125 special cases in the code which occur with very low but non-zero 126 probability make it impossible to rule out the possibility of bugs 127 remaining in the program. DO NOT COMPRESS ANY DATA WITH THIS 128 PROGRAM UNLESS YOU ARE PREPARED TO ACCEPT THE POSSIBILITY, HOWEVER 129 SMALL, THAT THE DATA WILL NOT BE RECOVERABLE. 130 131 That is not to say this program is inherently unreliable. 132 Indeed, I very much hope the opposite is true. bzip2/libbzip2 133 has been carefully constructed and extensively tested. 134 135 136PATENTS: 137 138 To the best of my knowledge, bzip2/libbzip2 does not use any 139 patented algorithms. However, I do not have the resources 140 to carry out a patent search. Therefore I cannot give any 141 guarantee of the above statement. 142 143 144 145WHAT'S NEW IN 0.9.0 (as compared to 0.1pl2) ? 146 147 * Approx 10% faster compression, 30% faster decompression 148 * -t (test mode) is a lot quicker 149 * Can decompress concatenated compressed files 150 * Programming interface, so programs can directly read/write .bz2 files 151 * Less restrictive (BSD-style) licensing 152 * Flag handling more compatible with GNU gzip 153 * Much more documentation, i.e., a proper user manual 154 * Hopefully, improved portability (at least of the library) 155 156WHAT'S NEW IN 0.9.5 ? 157 158 * Compression speed is much less sensitive to the input 159 data than in previous versions. Specifically, the very 160 slow performance caused by repetitive data is fixed. 161 * Many small improvements in file and flag handling. 162 * A Y2K statement. 163 164WHAT'S NEW IN 1.0.x ? 165 166 See the CHANGES file. 167 168I hope you find bzip2 useful. Feel free to contact the developers at 169 bzip2-devel@sourceware.org 170if you have any suggestions or queries. Many people mailed me with 171comments, suggestions and patches after the releases of bzip-0.15, 172bzip-0.21, and bzip2 versions 0.1pl2, 0.9.0, 0.9.5, 1.0.0, 1.0.1, 1731.0.2 and 1.0.3, and the changes in bzip2 are largely a result of this 174feedback. I thank you for your comments. 175 176bzip2's "home" is https://sourceware.org/bzip2/ 177 178Julian Seward 179jseward@acm.org 180Cambridge, UK. 181 18218 July 1996 (version 0.15) 18325 August 1996 (version 0.21) 184 7 August 1997 (bzip2, version 0.1) 18529 August 1997 (bzip2, version 0.1pl2) 18623 August 1998 (bzip2, version 0.9.0) 187 8 June 1999 (bzip2, version 0.9.5) 188 4 Sept 1999 (bzip2, version 0.9.5d) 189 5 May 2000 (bzip2, version 1.0pre8) 19030 December 2001 (bzip2, version 1.0.2pre1) 19115 February 2005 (bzip2, version 1.0.3) 19220 December 2006 (bzip2, version 1.0.4) 19310 December 2007 (bzip2, version 1.0.5) 194 6 Sept 2010 (bzip2, version 1.0.6) 19527 June 2019 (bzip2, version 1.0.7) 19613 July 2019 (bzip2, version 1.0.8) 197