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- This is the README for bzip2, a block-sorting file compressor, version
- 1.0. This version is fully compatible with the previous public
- releases, bzip2-0.1pl2, bzip2-0.9.0 and bzip2-0.9.5.
- bzip2-1.0 is distributed under a BSD-style license. For details,
- see the file LICENSE.
- Complete documentation is available in Postscript form (manual.ps) or
- html (manual_toc.html). A plain-text version of the manual page is
- available as bzip2.txt. A statement about Y2K issues is now included
- in the file Y2K_INFO.
- HOW TO BUILD -- UNIX
- Type `make'. This builds the library libbz2.a and then the
- programs bzip2 and bzip2recover. Six self-tests are run.
- If the self-tests complete ok, carry on to installation:
- To install in /usr/bin, /usr/lib, /usr/man and /usr/include, type
- make install
- To install somewhere else, eg, /xxx/yyy/{bin,lib,man,include}, type
- make install PREFIX=/xxx/yyy
- If you are (justifiably) paranoid and want to see what 'make install'
- is going to do, you can first do
- make -n install or
- make -n install PREFIX=/xxx/yyy respectively.
- The -n instructs make to show the commands it would execute, but
- not actually execute them.
- HOW TO BUILD -- UNIX, shared library libbz2.so.
- Do 'make -f Makefile-libbz2_so'. This Makefile seems to work for
- Linux-ELF (RedHat 5.2 on an x86 box), with gcc. I make no claims
- that it works for any other platform, though I suspect it probably
- will work for most platforms employing both ELF and gcc.
- bzip2-shared, a client of the shared library, is also build, but
- not self-tested. So I suggest you also build using the normal
- Makefile, since that conducts a self-test.
- Important note for people upgrading .so's from 0.9.0/0.9.5 to
- version 1.0. All the functions in the library have been renamed,
- from (eg) bzCompress to BZ2_bzCompress, to avoid namespace pollution.
- Unfortunately this means that the libbz2.so created by
- Makefile-libbz2_so will not work with any program which used an
- older version of the library. Sorry. I do encourage library
- clients to make the effort to upgrade to use version 1.0, since
- it is both faster and more robust than previous versions.
- HOW TO BUILD -- Windows 95, NT, DOS, Mac, etc.
- It's difficult for me to support compilation on all these platforms.
- My approach is to collect binaries for these platforms, and put them
- on the master web page (http://sourceware.cygnus.com/bzip2). Look
- there. However (FWIW), bzip2-1.0 is very standard ANSI C and should
- compile unmodified with MS Visual C. For Win32, there is one
- important caveat: in bzip2.c, you must set BZ_UNIX to 0 and
- BZ_LCCWIN32 to 1 before building. If you have difficulties building,
- you might want to read README.COMPILATION.PROBLEMS.
- VALIDATION
- Correct 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. There are more details
- in Section 4 of the user guide.
- Please read and be aware of the following:
- WARNING:
- This program (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.
- DISCLAIMER:
- I TAKE NO RESPONSIBILITY FOR ANY LOSS OF DATA ARISING FROM THE
- USE OF THIS PROGRAM, HOWSOEVER CAUSED.
- 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. Indeed,
- I very much hope the opposite is true. bzip2 has been carefully
- constructed and extensively tested.
- PATENTS:
- To the best of my knowledge, bzip2 does not use any patented
- algorithms. However, I do not have the resources available to
- carry out a full patent search. Therefore I cannot give any
- guarantee of the above statement.
- End of legalities.
- 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)
- WHAT'S NEW IN 0.9.5 ?
- * 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.
- * A Y2K statement.
- WHAT'S NEW IN 1.0
- See the CHANGES file.
- I hope you find bzip2 useful. Feel free to contact me at
- jseward@acm.org
- 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, bzip2-0.1pl2 and bzip2-0.9.0, and the changes in bzip2 are
- largely a result of this feedback. I thank you for your comments.
- At least for the time being, bzip2's "home" is (or can be reached via)
- http://www.muraroa.demon.co.uk.
- Julian Seward
- jseward@acm.org
- Cambridge, UK
- 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)
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