rsc | ff3adf6 | 2004-04-14 20:09:21 +0000 | [diff] [blame] | 1 | |
| 2 | This is the README for bzip2, a block-sorting file compressor, version |
| 3 | 1.0. This version is fully compatible with the previous public |
| 4 | releases, bzip2-0.1pl2, bzip2-0.9.0 and bzip2-0.9.5. |
| 5 | |
| 6 | bzip2-1.0 is distributed under a BSD-style license. For details, |
| 7 | see the file LICENSE. |
| 8 | |
| 9 | Complete documentation is available in Postscript form (manual.ps) or |
| 10 | html (manual_toc.html). A plain-text version of the manual page is |
| 11 | available as bzip2.txt. A statement about Y2K issues is now included |
| 12 | in the file Y2K_INFO. |
| 13 | |
| 14 | |
| 15 | HOW TO BUILD -- UNIX |
| 16 | |
| 17 | Type `make'. This builds the library libbz2.a and then the |
| 18 | programs bzip2 and bzip2recover. Six self-tests are run. |
| 19 | If the self-tests complete ok, carry on to installation: |
| 20 | |
| 21 | To install in /usr/bin, /usr/lib, /usr/man and /usr/include, type |
| 22 | make install |
| 23 | To install somewhere else, eg, /xxx/yyy/{bin,lib,man,include}, type |
| 24 | make install PREFIX=/xxx/yyy |
| 25 | If you are (justifiably) paranoid and want to see what 'make install' |
| 26 | is going to do, you can first do |
| 27 | make -n install or |
| 28 | make -n install PREFIX=/xxx/yyy respectively. |
| 29 | The -n instructs make to show the commands it would execute, but |
| 30 | not actually execute them. |
| 31 | |
| 32 | |
| 33 | HOW TO BUILD -- UNIX, shared library libbz2.so. |
| 34 | |
| 35 | Do 'make -f Makefile-libbz2_so'. This Makefile seems to work for |
| 36 | Linux-ELF (RedHat 5.2 on an x86 box), with gcc. I make no claims |
| 37 | that it works for any other platform, though I suspect it probably |
| 38 | will work for most platforms employing both ELF and gcc. |
| 39 | |
| 40 | bzip2-shared, a client of the shared library, is also build, but |
| 41 | not self-tested. So I suggest you also build using the normal |
| 42 | Makefile, since that conducts a self-test. |
| 43 | |
| 44 | Important note for people upgrading .so's from 0.9.0/0.9.5 to |
| 45 | version 1.0. All the functions in the library have been renamed, |
| 46 | from (eg) bzCompress to BZ2_bzCompress, to avoid namespace pollution. |
| 47 | Unfortunately this means that the libbz2.so created by |
| 48 | Makefile-libbz2_so will not work with any program which used an |
| 49 | older version of the library. Sorry. I do encourage library |
| 50 | clients to make the effort to upgrade to use version 1.0, since |
| 51 | it is both faster and more robust than previous versions. |
| 52 | |
| 53 | |
| 54 | HOW TO BUILD -- Windows 95, NT, DOS, Mac, etc. |
| 55 | |
| 56 | It's difficult for me to support compilation on all these platforms. |
| 57 | My approach is to collect binaries for these platforms, and put them |
| 58 | on the master web page (http://sourceware.cygnus.com/bzip2). Look |
| 59 | there. However (FWIW), bzip2-1.0 is very standard ANSI C and should |
| 60 | compile unmodified with MS Visual C. For Win32, there is one |
| 61 | important caveat: in bzip2.c, you must set BZ_UNIX to 0 and |
| 62 | BZ_LCCWIN32 to 1 before building. If you have difficulties building, |
| 63 | you might want to read README.COMPILATION.PROBLEMS. |
| 64 | |
| 65 | |
| 66 | VALIDATION |
| 67 | |
| 68 | Correct operation, in the sense that a compressed file can always be |
| 69 | decompressed to reproduce the original, is obviously of paramount |
| 70 | importance. To validate bzip2, I used a modified version of Mark |
| 71 | Nelson's churn program. Churn is an automated test driver which |
| 72 | recursively traverses a directory structure, using bzip2 to compress |
| 73 | and then decompress each file it encounters, and checking that the |
| 74 | decompressed data is the same as the original. There are more details |
| 75 | in Section 4 of the user guide. |
| 76 | |
| 77 | |
| 78 | |
| 79 | Please read and be aware of the following: |
| 80 | |
| 81 | WARNING: |
| 82 | |
| 83 | This program (attempts to) compress data by performing several |
| 84 | non-trivial transformations on it. Unless you are 100% familiar |
| 85 | with *all* the algorithms contained herein, and with the |
| 86 | consequences of modifying them, you should NOT meddle with the |
| 87 | compression or decompression machinery. Incorrect changes can and |
| 88 | very likely *will* lead to disastrous loss of data. |
| 89 | |
| 90 | |
| 91 | DISCLAIMER: |
| 92 | |
| 93 | I TAKE NO RESPONSIBILITY FOR ANY LOSS OF DATA ARISING FROM THE |
| 94 | USE OF THIS PROGRAM, HOWSOEVER CAUSED. |
| 95 | |
| 96 | Every compression of a file implies an assumption that the |
| 97 | compressed file can be decompressed to reproduce the original. |
| 98 | Great efforts in design, coding and testing have been made to |
| 99 | ensure that this program works correctly. However, the complexity |
| 100 | of the algorithms, and, in particular, the presence of various |
| 101 | special cases in the code which occur with very low but non-zero |
| 102 | probability make it impossible to rule out the possibility of bugs |
| 103 | remaining in the program. DO NOT COMPRESS ANY DATA WITH THIS |
| 104 | PROGRAM UNLESS YOU ARE PREPARED TO ACCEPT THE POSSIBILITY, HOWEVER |
| 105 | SMALL, THAT THE DATA WILL NOT BE RECOVERABLE. |
| 106 | |
| 107 | That is not to say this program is inherently unreliable. Indeed, |
| 108 | I very much hope the opposite is true. bzip2 has been carefully |
| 109 | constructed and extensively tested. |
| 110 | |
| 111 | |
| 112 | PATENTS: |
| 113 | |
| 114 | To the best of my knowledge, bzip2 does not use any patented |
| 115 | algorithms. However, I do not have the resources available to |
| 116 | carry out a full patent search. Therefore I cannot give any |
| 117 | guarantee of the above statement. |
| 118 | |
| 119 | End of legalities. |
| 120 | |
| 121 | |
| 122 | WHAT'S NEW IN 0.9.0 (as compared to 0.1pl2) ? |
| 123 | |
| 124 | * Approx 10% faster compression, 30% faster decompression |
| 125 | * -t (test mode) is a lot quicker |
| 126 | * Can decompress concatenated compressed files |
| 127 | * Programming interface, so programs can directly read/write .bz2 files |
| 128 | * Less restrictive (BSD-style) licensing |
| 129 | * Flag handling more compatible with GNU gzip |
| 130 | * Much more documentation, i.e., a proper user manual |
| 131 | * Hopefully, improved portability (at least of the library) |
| 132 | |
| 133 | WHAT'S NEW IN 0.9.5 ? |
| 134 | |
| 135 | * Compression speed is much less sensitive to the input |
| 136 | data than in previous versions. Specifically, the very |
| 137 | slow performance caused by repetitive data is fixed. |
| 138 | * Many small improvements in file and flag handling. |
| 139 | * A Y2K statement. |
| 140 | |
| 141 | WHAT'S NEW IN 1.0 |
| 142 | |
| 143 | See the CHANGES file. |
| 144 | |
| 145 | I hope you find bzip2 useful. Feel free to contact me at |
| 146 | jseward@acm.org |
| 147 | if you have any suggestions or queries. Many people mailed me with |
| 148 | comments, suggestions and patches after the releases of bzip-0.15, |
| 149 | bzip-0.21, bzip2-0.1pl2 and bzip2-0.9.0, and the changes in bzip2 are |
| 150 | largely a result of this feedback. I thank you for your comments. |
| 151 | |
| 152 | At least for the time being, bzip2's "home" is (or can be reached via) |
| 153 | http://www.muraroa.demon.co.uk. |
| 154 | |
| 155 | Julian Seward |
| 156 | jseward@acm.org |
| 157 | |
| 158 | Cambridge, UK |
| 159 | 18 July 1996 (version 0.15) |
| 160 | 25 August 1996 (version 0.21) |
| 161 | 7 August 1997 (bzip2, version 0.1) |
| 162 | 29 August 1997 (bzip2, version 0.1pl2) |
| 163 | 23 August 1998 (bzip2, version 0.9.0) |
| 164 | 8 June 1999 (bzip2, version 0.9.5) |
| 165 | 4 Sept 1999 (bzip2, version 0.9.5d) |
| 166 | 5 May 2000 (bzip2, version 1.0pre8) |