883N/AThis version is fully compatible with the previous public releases.
883N/A------------------------------------------------------------------
883N/Alossless, block-sorting data compression.
883N/ACopyright (C) 1996-2010 Julian Seward <jseward@bzip.org>
883N/APlease read the WARNING, DISCLAIMER and PATENTS sections in this file.
883N/AThis program is released under the terms of the license contained
883N/A------------------------------------------------------------------
883N/AType 'make'. This builds the library
libbz2.a and then the programs
883N/Abzip2 and bzip2recover. Six self-tests are run. If the self-tests
883N/Acomplete ok, carry on to installation:
883N/ATo install somewhere else, eg,
/xxx/yyy/{bin,lib,man,include}, type
883N/AIf you are (justifiably) paranoid and want to see what 'make install'
883N/Ais going to do, you can first do
883N/AThe -n instructs make to show the commands it would execute, but not
883N/ADo 'make -f Makefile-libbz2_so'. This Makefile seems to work for
883N/ALinux-ELF (RedHat 7.2 on an x86 box), with gcc. I make no claims
883N/Athat it works for any other platform, though I suspect it probably
883N/Awill work for most platforms employing both ELF and gcc.
883N/Abzip2-shared, a client of the shared library, is also built, but not
883N/Aself-tested. So I suggest you also build using the normal Makefile,
883N/Asince that conducts a self-test. A second reason to prefer the
883N/Aversion statically linked to the library is that, on x86 platforms,
883N/Abuilding shared objects makes a valuable register (%ebx) unavailable
883N/Ato gcc, resulting in a slowdown of 10%-20%, at least for bzip2.
883N/AImportant note for people upgrading .so's from 0.9.0/0.9.5 to version
883N/A1.0.X. All the functions in the library have been renamed, from (eg)
883N/AbzCompress to BZ2_bzCompress, to avoid namespace pollution.
883N/AMakefile-libbz2_so will not work with any program which used an older
883N/Aversion of the library. I do encourage library clients to make the
883N/Aeffort to upgrade to use version 1.0, since it is both faster and more
883N/Arobust than previous versions.
883N/AHOW TO BUILD -- Windows 95, NT, DOS, Mac, etc.
883N/AIt's difficult for me to support compilation on all these platforms.
883N/AMy approach is to collect binaries for these platforms, and put them
883N/Aunmodified with MS Visual C. If you have difficulties building, you
883N/AAt least using MS Visual C++ 6, you can build from the unmodified
883N/Asources by issuing, in a command shell:
883N/A so as to set up paths to the MSVC tools correctly).
883N/ACorrect operation, in the sense that a compressed file can always be
decompressed to reproduce the original, is obviously of paramount
importance. To validate bzip2, I used a modified version of Mark
Nelson's churn program. Churn is an automated test driver which
recursively traverses a directory structure, using bzip2 to compress
and then decompress each file it encounters, and checking that the
decompressed data is the same as the original.
Please read and be aware of the following:
This program and library (attempts to) compress data by
performing several non-trivial transformations on it.
Unless you are 100% familiar with *all* the algorithms
contained herein, and with the consequences of modifying them,
you should NOT meddle with the compression or decompression
machinery. Incorrect changes can and very likely *will*
lead to disastrous loss of data.
I TAKE NO RESPONSIBILITY FOR ANY LOSS OF DATA ARISING FROM THE
Every compression of a file implies an assumption that the
compressed file can be decompressed to reproduce the original.
Great efforts in design, coding and testing have been made to
ensure that this program works correctly. However, the complexity
of the algorithms, and, in particular, the presence of various
special cases in the code which occur with very low but non-zero
probability make it impossible to rule out the possibility of bugs
remaining in the program. DO NOT COMPRESS ANY DATA WITH THIS
PROGRAM UNLESS YOU ARE PREPARED TO ACCEPT THE POSSIBILITY, HOWEVER
SMALL, THAT THE DATA WILL NOT BE RECOVERABLE.
That is not to say this program is inherently unreliable.
has been carefully constructed and extensively tested.
patented algorithms. However, I do not have the resources
to carry out a patent search. Therefore I cannot give any
guarantee of the above statement.
WHAT'S NEW IN 0.9.0 (as compared to 0.1pl2) ?
* Approx 10% faster compression, 30% faster decompression
* -t (test mode) is a lot quicker
* Can decompress concatenated compressed files
* Programming interface, so programs can directly
read/write .bz2 files
* Less restrictive (BSD-style) licensing
* Flag handling more compatible with GNU gzip
* Much more documentation,
i.e., a proper user manual
* Hopefully, improved portability (at least of the library)
* Compression speed is much less sensitive to the input
data than in previous versions. Specifically, the very
slow performance caused by repetitive data is fixed.
* Many small improvements in file and flag handling.
I hope you find bzip2 useful. Feel free to contact me at
if you have any suggestions or queries. Many people mailed me with
comments, suggestions and patches after the releases of bzip-0.15,
bzip-0.21, and bzip2 versions 0.1pl2, 0.9.0, 0.9.5, 1.0.0, 1.0.1,
1.0.2 and 1.0.3, and the changes in bzip2 are largely a result of this
feedback. 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)