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william |
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This is the README for bzip2/libzip2. |
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This version is fully compatible with the previous public releases. |
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------------------------------------------------------------------ |
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This file is part of bzip2/libbzip2, a program and library for |
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lossless, block-sorting data compression. |
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bzip2/libbzip2 version 1.0.4 of 20 December 2006 |
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Copyright (C) 1996-2006 Julian Seward <jseward@bzip.org> |
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Please read the WARNING, DISCLAIMER and PATENTS sections in this file. |
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This program is released under the terms of the license contained |
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in the file LICENSE. |
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------------------------------------------------------------------ |
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Complete documentation is available in Postscript form (manual.ps), |
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PDF (manual.pdf) or html (manual.html). A plain-text version of the |
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manual page is available as bzip2.txt. |
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HOW TO BUILD -- UNIX |
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Type 'make'. This builds the library libbz2.a and then the programs |
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bzip2 and bzip2recover. Six self-tests are run. If the self-tests |
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complete ok, carry on to installation: |
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To install in /usr/local/bin, /usr/local/lib, /usr/local/man and |
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/usr/local/include, type |
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make install |
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To install somewhere else, eg, /xxx/yyy/{bin,lib,man,include}, type |
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make install PREFIX=/xxx/yyy |
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If you are (justifiably) paranoid and want to see what 'make install' |
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is going to do, you can first do |
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make -n install or |
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make -n install PREFIX=/xxx/yyy respectively. |
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The -n instructs make to show the commands it would execute, but not |
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actually execute them. |
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HOW TO BUILD -- UNIX, shared library libbz2.so. |
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Do 'make -f Makefile-libbz2_so'. This Makefile seems to work for |
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Linux-ELF (RedHat 7.2 on an x86 box), with gcc. I make no claims |
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that it works for any other platform, though I suspect it probably |
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will work for most platforms employing both ELF and gcc. |
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bzip2-shared, a client of the shared library, is also built, but not |
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self-tested. So I suggest you also build using the normal Makefile, |
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since that conducts a self-test. A second reason to prefer the |
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version statically linked to the library is that, on x86 platforms, |
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building shared objects makes a valuable register (%ebx) unavailable |
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to gcc, resulting in a slowdown of 10%-20%, at least for bzip2. |
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Important note for people upgrading .so's from 0.9.0/0.9.5 to version |
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1.0.X. All the functions in the library have been renamed, from (eg) |
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bzCompress to BZ2_bzCompress, to avoid namespace pollution. |
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Unfortunately this means that the libbz2.so created by |
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Makefile-libbz2_so will not work with any program which used an older |
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version of the library. I do encourage library clients to make the |
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effort to upgrade to use version 1.0, since it is both faster and more |
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robust than previous versions. |
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HOW TO BUILD -- Windows 95, NT, DOS, Mac, etc. |
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It's difficult for me to support compilation on all these platforms. |
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My approach is to collect binaries for these platforms, and put them |
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on the master web site (http://www.bzip.org). Look there. However |
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(FWIW), bzip2-1.0.X is very standard ANSI C and should compile |
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unmodified with MS Visual C. If you have difficulties building, you |
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might want to read README.COMPILATION.PROBLEMS. |
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At least using MS Visual C++ 6, you can build from the unmodified |
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sources by issuing, in a command shell: |
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nmake -f makefile.msc |
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(you may need to first run the MSVC-provided script VCVARS32.BAT |
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so as to set up paths to the MSVC tools correctly). |
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VALIDATION |
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Correct operation, in the sense that a compressed file can always be |
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decompressed to reproduce the original, is obviously of paramount |
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importance. To validate bzip2, I used a modified version of Mark |
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Nelson's churn program. Churn is an automated test driver which |
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recursively traverses a directory structure, using bzip2 to compress |
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and then decompress each file it encounters, and checking that the |
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decompressed data is the same as the original. |
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Please read and be aware of the following: |
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WARNING: |
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This program and library (attempts to) compress data by |
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performing several non-trivial transformations on it. |
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Unless you are 100% familiar with *all* the algorithms |
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contained herein, and with the consequences of modifying them, |
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you should NOT meddle with the compression or decompression |
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machinery. Incorrect changes can and very likely *will* |
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lead to disastrous loss of data. |
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DISCLAIMER: |
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I TAKE NO RESPONSIBILITY FOR ANY LOSS OF DATA ARISING FROM THE |
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USE OF THIS PROGRAM/LIBRARY, HOWSOEVER CAUSED. |
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Every compression of a file implies an assumption that the |
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compressed file can be decompressed to reproduce the original. |
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Great efforts in design, coding and testing have been made to |
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ensure that this program works correctly. However, the complexity |
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of the algorithms, and, in particular, the presence of various |
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special cases in the code which occur with very low but non-zero |
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probability make it impossible to rule out the possibility of bugs |
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remaining in the program. DO NOT COMPRESS ANY DATA WITH THIS |
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PROGRAM UNLESS YOU ARE PREPARED TO ACCEPT THE POSSIBILITY, HOWEVER |
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SMALL, THAT THE DATA WILL NOT BE RECOVERABLE. |
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That is not to say this program is inherently unreliable. |
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Indeed, I very much hope the opposite is true. bzip2/libbzip2 |
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has been carefully constructed and extensively tested. |
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PATENTS: |
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To the best of my knowledge, bzip2/libbzip2 does not use any |
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patented algorithms. However, I do not have the resources |
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to carry out a patent search. Therefore I cannot give any |
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guarantee of the above statement. |
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WHAT'S NEW IN 0.9.0 (as compared to 0.1pl2) ? |
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* Approx 10% faster compression, 30% faster decompression |
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* -t (test mode) is a lot quicker |
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* Can decompress concatenated compressed files |
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* Programming interface, so programs can directly read/write .bz2 files |
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* Less restrictive (BSD-style) licensing |
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* Flag handling more compatible with GNU gzip |
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* Much more documentation, i.e., a proper user manual |
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* Hopefully, improved portability (at least of the library) |
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WHAT'S NEW IN 0.9.5 ? |
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* Compression speed is much less sensitive to the input |
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data than in previous versions. Specifically, the very |
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slow performance caused by repetitive data is fixed. |
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* Many small improvements in file and flag handling. |
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* A Y2K statement. |
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WHAT'S NEW IN 1.0.0 ? |
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See the CHANGES file. |
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WHAT'S NEW IN 1.0.2 ? |
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See the CHANGES file. |
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WHAT'S NEW IN 1.0.3 ? |
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See the CHANGES file. |
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WHAT'S NEW IN 1.0.4 ? |
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See the CHANGES file. |
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I hope you find bzip2 useful. Feel free to contact me at |
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jseward@bzip.org |
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if you have any suggestions or queries. Many people mailed me with |
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comments, suggestions and patches after the releases of bzip-0.15, |
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bzip-0.21, and bzip2 versions 0.1pl2, 0.9.0, 0.9.5, 1.0.0, 1.0.1, |
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1.0.2 and 1.0.3, and the changes in bzip2 are largely a result of this |
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feedback. I thank you for your comments. |
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bzip2's "home" is http://www.bzip.org/ |
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Julian Seward |
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jseward@bzip.org |
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Cambridge, UK. |
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18 July 1996 (version 0.15) |
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25 August 1996 (version 0.21) |
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7 August 1997 (bzip2, version 0.1) |
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29 August 1997 (bzip2, version 0.1pl2) |
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23 August 1998 (bzip2, version 0.9.0) |
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8 June 1999 (bzip2, version 0.9.5) |
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4 Sept 1999 (bzip2, version 0.9.5d) |
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5 May 2000 (bzip2, version 1.0pre8) |
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30 December 2001 (bzip2, version 1.0.2pre1) |
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15 February 2005 (bzip2, version 1.0.3) |
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20 December 2006 (bzip2, version 1.0.4) |
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Parent Directory
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Revision Log