| |
| This is the README for bzip2, a block-sorting file compressor, version |
| 1.0.2. This version is fully compatible with the previous public |
| releases, versions 0.1pl2, 0.9.0, 0.9.5, 1.0.0 and 1.0.1. |
| |
| bzip2-1.0.2 is distributed under a BSD-style license. For details, |
| see the file LICENSE. |
| |
| Complete documentation is available in Postscript form (manual.ps), |
| PDF (manual.pdf, amazingly enough) 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 7.2 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 built, but not |
| self-tested. So I suggest you also build using the normal Makefile, |
| since that conducts a self-test. A second reason to prefer the |
| version statically linked to the library is that, on x86 platforms, |
| building shared objects makes a valuable register (%ebx) unavailable |
| to gcc, resulting in a slowdown of 10%-20%, at least for bzip2. |
| |
| Important note for people upgrading .so's from 0.9.0/0.9.5 to version |
| 1.0.X. 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://sources.redhat.com/bzip2). Look there. |
| However (FWIW), bzip2-1.0.X is very standard ANSI C and should compile |
| unmodified with MS Visual C. If you have difficulties building, you |
| might want to read README.COMPILATION.PROBLEMS. |
| |
| At least using MS Visual C++ 6, you can build from the unmodified |
| sources by issuing, in a command shell: |
| nmake -f makefile.msc |
| (you may need to first run the MSVC-provided script VCVARS32.BAT |
| so as to set up paths to the MSVC tools correctly). |
| |
| |
| 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 1.0.0 ? |
| |
| See the CHANGES file. |
| |
| WHAT'S NEW IN 1.0.2 ? |
| |
| 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, and bzip2 versions 0.1pl2, 0.9.0, 0.9.5, 1.0.0 and 1.0.1, |
| 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://sources.redhat.com/bzip2. |
| |
| Julian Seward |
| jseward@acm.org |
| |
| Cambridge, UK (and what a great town this is!) |
| |
| 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) |