1 2 This is the README for bzip2/libzip2. 3 This version is fully compatible with the previous public releases. 4 5 ------------------------------------------------------------------ 6 This file is part of bzip2/libbzip2, a program and library for 7 lossless, block-sorting data compression. 8 9 bzip2/libbzip2 version 1.0.6 of 6 September 2010 10 Copyright (C) 1996-2010 Julian Seward <jseward (a] bzip.org> 11 12 Please read the WARNING, DISCLAIMER and PATENTS sections in this file. 13 14 This program is released under the terms of the license contained 15 in the file LICENSE. 16 ------------------------------------------------------------------ 17 18 Complete documentation is available in Postscript form (manual.ps), 19 PDF (manual.pdf) or html (manual.html). A plain-text version of the 20 manual page is available as bzip2.txt. 21 22 23 HOW TO BUILD -- UNIX 24 25 Type 'make'. This builds the library libbz2.a and then the programs 26 bzip2 and bzip2recover. Six self-tests are run. If the self-tests 27 complete ok, carry on to installation: 28 29 To install in /usr/local/bin, /usr/local/lib, /usr/local/man and 30 /usr/local/include, type 31 32 make install 33 34 To install somewhere else, eg, /xxx/yyy/{bin,lib,man,include}, type 35 36 make install PREFIX=/xxx/yyy 37 38 If you are (justifiably) paranoid and want to see what 'make install' 39 is going to do, you can first do 40 41 make -n install or 42 make -n install PREFIX=/xxx/yyy respectively. 43 44 The -n instructs make to show the commands it would execute, but not 45 actually execute them. 46 47 48 HOW TO BUILD -- UNIX, shared library libbz2.so. 49 50 Do 'make -f Makefile-libbz2_so'. This Makefile seems to work for 51 Linux-ELF (RedHat 7.2 on an x86 box), with gcc. I make no claims 52 that it works for any other platform, though I suspect it probably 53 will work for most platforms employing both ELF and gcc. 54 55 bzip2-shared, a client of the shared library, is also built, but not 56 self-tested. So I suggest you also build using the normal Makefile, 57 since that conducts a self-test. A second reason to prefer the 58 version statically linked to the library is that, on x86 platforms, 59 building shared objects makes a valuable register (%ebx) unavailable 60 to gcc, resulting in a slowdown of 10%-20%, at least for bzip2. 61 62 Important note for people upgrading .so's from 0.9.0/0.9.5 to version 63 1.0.X. All the functions in the library have been renamed, from (eg) 64 bzCompress to BZ2_bzCompress, to avoid namespace pollution. 65 Unfortunately this means that the libbz2.so created by 66 Makefile-libbz2_so will not work with any program which used an older 67 version of the library. I do encourage library clients to make the 68 effort to upgrade to use version 1.0, since it is both faster and more 69 robust than previous versions. 70 71 72 HOW TO BUILD -- Windows 95, NT, DOS, Mac, etc. 73 74 It's difficult for me to support compilation on all these platforms. 75 My approach is to collect binaries for these platforms, and put them 76 on the master web site (http://www.bzip.org). Look there. However 77 (FWIW), bzip2-1.0.X is very standard ANSI C and should compile 78 unmodified with MS Visual C. If you have difficulties building, you 79 might want to read README.COMPILATION.PROBLEMS. 80 81 At least using MS Visual C++ 6, you can build from the unmodified 82 sources 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 90 VALIDATION 91 92 Correct operation, in the sense that a compressed file can always be 93 decompressed to reproduce the original, is obviously of paramount 94 importance. To validate bzip2, I used a modified version of Mark 95 Nelson's churn program. Churn is an automated test driver which 96 recursively traverses a directory structure, using bzip2 to compress 97 and then decompress each file it encounters, and checking that the 98 decompressed data is the same as the original. 99 100 101 102 Please read and be aware of the following: 103 104 WARNING: 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. 113 114 115 DISCLAIMER: 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. 134 135 136 PATENTS: 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. 142 143 144 145 WHAT'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) 155 156 WHAT'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. 163 164 WHAT'S NEW IN 1.0.0 ? 165 166 See the CHANGES file. 167 168 WHAT'S NEW IN 1.0.2 ? 169 170 See the CHANGES file. 171 172 WHAT'S NEW IN 1.0.3 ? 173 174 See the CHANGES file. 175 176 WHAT'S NEW IN 1.0.4 ? 177 178 See the CHANGES file. 179 180 WHAT'S NEW IN 1.0.5 ? 181 182 See the CHANGES file. 183 184 WHAT'S NEW IN 1.0.6 ? 185 186 See the CHANGES file. 187 188 189 I hope you find bzip2 useful. Feel free to contact me at 190 jseward (a] bzip.org 191 if you have any suggestions or queries. Many people mailed me with 192 comments, suggestions and patches after the releases of bzip-0.15, 193 bzip-0.21, and bzip2 versions 0.1pl2, 0.9.0, 0.9.5, 1.0.0, 1.0.1, 194 1.0.2 and 1.0.3, and the changes in bzip2 are largely a result of this 195 feedback. I thank you for your comments. 196 197 bzip2's "home" is http://www.bzip.org/ 198 199 Julian Seward 200 jseward (a] bzip.org 201 Cambridge, UK. 202 203 18 July 1996 (version 0.15) 204 25 August 1996 (version 0.21) 205 7 August 1997 (bzip2, version 0.1) 206 29 August 1997 (bzip2, version 0.1pl2) 207 23 August 1998 (bzip2, version 0.9.0) 208 8 June 1999 (bzip2, version 0.9.5) 209 4 Sept 1999 (bzip2, version 0.9.5d) 210 5 May 2000 (bzip2, version 1.0pre8) 211 30 December 2001 (bzip2, version 1.0.2pre1) 212 15 February 2005 (bzip2, version 1.0.3) 213 20 December 2006 (bzip2, version 1.0.4) 214 10 December 2007 (bzip2, version 1.0.5) 215 6 Sept 2010 (bzip2, version 1.0.6) 216
