0N/AThis version is fully compatible with the previous public releases.
0N/A------------------------------------------------------------------
0N/Alossless, block-sorting data compression.
0N/ACopyright (C) 1996-2010 Julian Seward <jseward@bzip.org>
0N/APlease read the WARNING, DISCLAIMER and PATENTS sections in this file.
0N/AThis program is released under the terms of the license contained
0N/A------------------------------------------------------------------
0N/AComplete documentation is available in Postscript form (
manual.ps),
0N/AType 'make'. This builds the library
libbz2.a and then the programs
328N/Abzip2 and bzip2recover. Six self-tests are run. If the self-tests
0N/Acomplete ok, carry on to installation:
0N/ATo install somewhere else, eg,
/xxx/yyy/{bin,lib,man,include}, type
0N/AIf you are (justifiably) paranoid and want to see what 'make install'
0N/Ais going to do, you can first do
0N/AThe -n instructs make to show the commands it would execute, but not
0N/Aactually execute them.
328N/ADo 'make -f Makefile-libbz2_so'. This Makefile seems to work for
0N/ALinux-ELF (RedHat 7.2 on an x86 box), with gcc. I make no claims
0N/Athat it works for any other platform, though I suspect it probably
328N/Awill work for most platforms employing both ELF and gcc.
0N/Abzip2-shared, a client of the shared library, is also built, but not
328N/Aself-tested. So I suggest you also build using the normal Makefile,
0N/Asince that conducts a self-test. A second reason to prefer the
328N/Aversion statically linked to the library is that, on x86 platforms,
0N/Abuilding shared objects makes a valuable register (%ebx) unavailable
0N/Ato gcc, resulting in a slowdown of 10%-20%, at least for bzip2.
328N/AImportant note for people upgrading .so's from 0.9.0/0.9.5 to version
0N/A1.0.X. All the functions in the library have been renamed, from (eg)
0N/AbzCompress to BZ2_bzCompress, to avoid namespace pollution.
328N/AMakefile-libbz2_so will not work with any program which used an older
328N/Aversion of the library. I do encourage library clients to make the
328N/Aeffort to upgrade to use version 1.0, since it is both faster and more
328N/Arobust than previous versions.
328N/AHOW TO BUILD -- Windows 95, NT, DOS, Mac, etc.
0N/AIt's difficult for me to support compilation on all these platforms.
0N/AMy approach is to collect binaries for these platforms, and put them
0N/Aunmodified with MS Visual C. If you have difficulties building, you
328N/AAt least using MS Visual C++ 6, you can build from the unmodified
328N/Asources by issuing, in a command shell:
328N/A so as to set up paths to the MSVC tools correctly).
328N/ACorrect operation, in the sense that a compressed file can always be
328N/Adecompressed to reproduce the original, is obviously of paramount
328N/Aimportance. To validate bzip2, I used a modified version of Mark
328N/ANelson's churn program. Churn is an automated test driver which
328N/Arecursively traverses a directory structure, using bzip2 to compress
0N/Aand then decompress each file it encounters, and checking that the
328N/Adecompressed data is the same as the original.
328N/APlease read and be aware of the following:
328N/A This program and library (attempts to) compress data by
328N/A performing several non-trivial transformations on it.
328N/A Unless you are 100% familiar with *all* the algorithms
328N/A contained herein, and with the consequences of modifying them,
328N/A you should NOT meddle with the compression or decompression
328N/A machinery. Incorrect changes can and very likely *will*
328N/A lead to disastrous loss of data.
328N/A I TAKE NO RESPONSIBILITY FOR ANY LOSS OF DATA ARISING FROM THE
0N/A Every compression of a file implies an assumption that the
0N/A compressed file can be decompressed to reproduce the original.
0N/A Great efforts in design, coding and testing have been made to
328N/A ensure that this program works correctly. However, the complexity
328N/A of the algorithms, and, in particular, the presence of various
328N/A special cases in the code which occur with very low but non-zero
328N/A probability make it impossible to rule out the possibility of bugs
328N/A remaining in the program. DO NOT COMPRESS ANY DATA WITH THIS
328N/A PROGRAM UNLESS YOU ARE PREPARED TO ACCEPT THE POSSIBILITY, HOWEVER
328N/A SMALL, THAT THE DATA WILL NOT BE RECOVERABLE.
328N/A That is not to say this program is inherently unreliable.
328N/A has been carefully constructed and extensively tested.
328N/A patented algorithms. However, I do not have the resources
328N/A to carry out a patent search. Therefore I cannot give any
328N/A guarantee of the above statement.
328N/AWHAT'S NEW IN 0.9.0 (as compared to 0.1pl2) ?
328N/A * Approx 10% faster compression, 30% faster decompression
328N/A * -t (test mode) is a lot quicker
328N/A * Can decompress concatenated compressed files
328N/A * Less restrictive (BSD-style) licensing
328N/A * Flag handling more compatible with GNU gzip
0N/A * Much more documentation,
i.e., a proper user manual
328N/A * Hopefully, improved portability (at least of the library)
328N/A * Compression speed is much less sensitive to the input
328N/A data than in previous versions. Specifically, the very
328N/A slow performance caused by repetitive data is fixed.
328N/A * Many small improvements in file and flag handling.
328N/AI hope you find bzip2 useful. Feel free to contact me at
328N/Aif you have any suggestions or queries. Many people mailed me with
328N/Acomments, suggestions and patches after the releases of bzip-0.15,
328N/Abzip-0.21, and bzip2 versions 0.1pl2, 0.9.0, 0.9.5, 1.0.0, 1.0.1,
328N/A1.0.2 and 1.0.3, and the changes in bzip2 are largely a result of this
328N/Afeedback. I thank you for your comments.
18 July 1996 (version 0.15)
25 August 1996 (version 0.21)
7 August 1997 (bzip2, version 0.1)
29 August 1997 (bzip2, version 0.1pl2)
23 August 1998 (bzip2, version 0.9.0)
8 June 1999 (bzip2, version 0.9.5)
4 Sept 1999 (bzip2, version 0.9.5d)
5 May 2000 (bzip2, version 1.0pre8)
30 December 2001 (bzip2, version 1.0.2pre1)
15 February 2005 (bzip2, version 1.0.3)
20 December 2006 (bzip2, version 1.0.4)
10 December 2007 (bzip2, version 1.0.5)
6 Sept 2010 (bzip2, version 1.0.6)