| 1 |
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| 2 | This is the README for bzip2, a block-sorting file compressor, version
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| 3 | 1.0.3. This version is fully compatible with the previous public
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| 4 | releases, versions 0.1pl2, 0.9.0, 0.9.5, 1.0.0, 1.0.1 and 1.0.2.
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| 5 |
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| 6 | bzip2-1.0.3 is distributed under a BSD-style license. For details,
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| 7 | see the file LICENSE.
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| 8 |
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| 9 | Complete documentation is available in Postscript form (manual.ps),
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| 10 | PDF (manual.pdf) or html (manual.html). A plain-text version of the
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| 11 | manual page is available as bzip2.txt. A statement about Y2K issues
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| 12 | is now included in the file Y2K_INFO.
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| 13 |
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| 14 |
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| 15 | HOW TO BUILD -- UNIX
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| 16 |
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| 17 | Type `make'. This builds the library libbz2.a and then the
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| 18 | programs bzip2 and bzip2recover. Six self-tests are run.
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| 19 | If the self-tests complete ok, carry on to installation:
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| 20 |
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| 21 | To install in /usr/bin, /usr/lib, /usr/man and /usr/include, type
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| 22 | make install
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| 23 | To install somewhere else, eg, /xxx/yyy/{bin,lib,man,include}, type
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| 24 | make install PREFIX=/xxx/yyy
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| 25 | If you are (justifiably) paranoid and want to see what 'make install'
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| 26 | is going to do, you can first do
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| 27 | make -n install or
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| 28 | make -n install PREFIX=/xxx/yyy respectively.
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| 29 | The -n instructs make to show the commands it would execute, but
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| 30 | not actually execute them.
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| 31 |
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| 32 |
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| 33 | HOW TO BUILD -- UNIX, shared library libbz2.so.
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| 34 |
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| 35 | Do 'make -f Makefile-libbz2_so'. This Makefile seems to work for
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| 36 | Linux-ELF (RedHat 7.2 on an x86 box), with gcc. I make no claims
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| 37 | that it works for any other platform, though I suspect it probably
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| 38 | will work for most platforms employing both ELF and gcc.
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| 39 |
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| 40 | bzip2-shared, a client of the shared library, is also built, but not
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| 41 | self-tested. So I suggest you also build using the normal Makefile,
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| 42 | since that conducts a self-test. A second reason to prefer the
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| 43 | version statically linked to the library is that, on x86 platforms,
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| 44 | building shared objects makes a valuable register (%ebx) unavailable
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| 45 | to gcc, resulting in a slowdown of 10%-20%, at least for bzip2.
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| 46 |
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| 47 | Important note for people upgrading .so's from 0.9.0/0.9.5 to version
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| 48 | 1.0.X. All the functions in the library have been renamed, from (eg)
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| 49 | bzCompress to BZ2_bzCompress, to avoid namespace pollution.
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| 50 | Unfortunately this means that the libbz2.so created by
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| 51 | Makefile-libbz2_so will not work with any program which used an older
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| 52 | version of the library. Sorry. I do encourage library clients to
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| 53 | make the effort to upgrade to use version 1.0, since it is both faster
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| 54 | and more robust than previous versions.
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| 55 |
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| 56 |
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| 57 | HOW TO BUILD -- Windows 95, NT, DOS, Mac, etc.
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| 58 |
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| 59 | It's difficult for me to support compilation on all these platforms.
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| 60 | My approach is to collect binaries for these platforms, and put them
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| 61 | on the master web page (http://sources.redhat.com/bzip2). Look there.
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| 62 | However (FWIW), bzip2-1.0.X is very standard ANSI C and should compile
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| 63 | unmodified with MS Visual C. If you have difficulties building, you
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| 64 | might want to read README.COMPILATION.PROBLEMS.
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| 65 |
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| 66 | At least using MS Visual C++ 6, you can build from the unmodified
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| 67 | sources by issuing, in a command shell:
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| 68 | nmake -f makefile.msc
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| 69 | (you may need to first run the MSVC-provided script VCVARS32.BAT
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| 70 | so as to set up paths to the MSVC tools correctly).
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| 71 |
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| 72 |
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| 73 | VALIDATION
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| 74 |
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| 75 | Correct operation, in the sense that a compressed file can always be
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| 76 | decompressed to reproduce the original, is obviously of paramount
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| 77 | importance. To validate bzip2, I used a modified version of Mark
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| 78 | Nelson's churn program. Churn is an automated test driver which
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| 79 | recursively traverses a directory structure, using bzip2 to compress
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| 80 | and then decompress each file it encounters, and checking that the
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| 81 | decompressed data is the same as the original.
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| 82 |
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| 83 |
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| 84 |
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| 85 | Please read and be aware of the following:
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| 86 |
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| 87 | WARNING:
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| 88 |
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| 89 | This program (attempts to) compress data by performing several
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| 90 | non-trivial transformations on it. Unless you are 100% familiar
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| 91 | with *all* the algorithms contained herein, and with the
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| 92 | consequences of modifying them, you should NOT meddle with the
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| 93 | compression or decompression machinery. Incorrect changes can and
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| 94 | very likely *will* lead to disastrous loss of data.
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| 95 |
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| 96 |
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| 97 | DISCLAIMER:
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| 98 |
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| 99 | I TAKE NO RESPONSIBILITY FOR ANY LOSS OF DATA ARISING FROM THE
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| 100 | USE OF THIS PROGRAM, HOWSOEVER CAUSED.
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| 101 |
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| 102 | Every compression of a file implies an assumption that the
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| 103 | compressed file can be decompressed to reproduce the original.
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| 104 | Great efforts in design, coding and testing have been made to
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| 105 | ensure that this program works correctly. However, the complexity
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| 106 | of the algorithms, and, in particular, the presence of various
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| 107 | special cases in the code which occur with very low but non-zero
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| 108 | probability make it impossible to rule out the possibility of bugs
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| 109 | remaining in the program. DO NOT COMPRESS ANY DATA WITH THIS
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| 110 | PROGRAM UNLESS YOU ARE PREPARED TO ACCEPT THE POSSIBILITY, HOWEVER
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| 111 | SMALL, THAT THE DATA WILL NOT BE RECOVERABLE.
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| 112 |
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| 113 | That is not to say this program is inherently unreliable. Indeed,
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| 114 | I very much hope the opposite is true. bzip2 has been carefully
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| 115 | constructed and extensively tested.
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| 116 |
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| 117 |
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| 118 | PATENTS:
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| 119 |
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| 120 | To the best of my knowledge, bzip2 does not use any patented
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| 121 | algorithms. However, I do not have the resources to carry out
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| 122 | a patent search. Therefore I cannot give any guarantee of the
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| 123 | above statement.
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| 124 |
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| 125 | End of legalities.
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| 126 |
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| 127 |
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| 128 | WHAT'S NEW IN 0.9.0 (as compared to 0.1pl2) ?
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| 129 |
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| 130 | * Approx 10% faster compression, 30% faster decompression
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| 131 | * -t (test mode) is a lot quicker
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| 132 | * Can decompress concatenated compressed files
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| 133 | * Programming interface, so programs can directly read/write .bz2 files
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| 134 | * Less restrictive (BSD-style) licensing
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| 135 | * Flag handling more compatible with GNU gzip
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| 136 | * Much more documentation, i.e., a proper user manual
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| 137 | * Hopefully, improved portability (at least of the library)
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| 138 |
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| 139 | WHAT'S NEW IN 0.9.5 ?
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| 140 |
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| 141 | * Compression speed is much less sensitive to the input
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| 142 | data than in previous versions. Specifically, the very
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| 143 | slow performance caused by repetitive data is fixed.
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| 144 | * Many small improvements in file and flag handling.
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| 145 | * A Y2K statement.
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| 146 |
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| 147 | WHAT'S NEW IN 1.0.0 ?
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| 148 |
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| 149 | See the CHANGES file.
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| 150 |
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| 151 | WHAT'S NEW IN 1.0.2 ?
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| 152 |
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| 153 | See the CHANGES file.
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| 154 |
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| 155 | WHAT'S NEW IN 1.0.3 ?
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| 156 |
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| 157 | See the CHANGES file.
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| 158 |
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| 159 |
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| 160 | I hope you find bzip2 useful. Feel free to contact me at
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| 161 | jseward@bzip.org
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| 162 | if you have any suggestions or queries. Many people mailed me with
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| 163 | comments, suggestions and patches after the releases of bzip-0.15,
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| 164 | bzip-0.21, and bzip2 versions 0.1pl2, 0.9.0, 0.9.5, 1.0.0, 1.0.1 and
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| 165 | 1.0.2, and the changes in bzip2 are largely a result of this feedback.
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| 166 | I thank you for your comments.
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| 167 |
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| 168 | At least for the time being, bzip2's "home" is (or can be reached via)
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| 169 | http://www.bzip.org
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| 170 |
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| 171 | Julian Seward
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| 172 | jseward@bzip.org
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| 173 |
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| 174 | Cambridge, UK.
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| 175 |
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| 176 | 18 July 1996 (version 0.15)
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| 177 | 25 August 1996 (version 0.21)
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| 178 | 7 August 1997 (bzip2, version 0.1)
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| 179 | 29 August 1997 (bzip2, version 0.1pl2)
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| 180 | 23 August 1998 (bzip2, version 0.9.0)
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| 181 | 8 June 1999 (bzip2, version 0.9.5)
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| 182 | 4 Sept 1999 (bzip2, version 0.9.5d)
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| 183 | 5 May 2000 (bzip2, version 1.0pre8)
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| 184 | 30 December 2001 (bzip2, version 1.0.2pre1)
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| 185 | 15 February 2005 (bzip2, version 1.0.3)
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