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      1 
      2 This is the README for bzip2/libzip2.
      3 This version is fully compatible with the previous public releases.
      4 
      5 ------------------------------------------------------------------
      6 This file is part of bzip2/libbzip2, a program and library for
      7 lossless, block-sorting data compression.
      8 
      9 bzip2/libbzip2 version 1.0.6 of 6 September 2010
     10 Copyright (C) 1996-2010 Julian Seward <jseward (a] bzip.org>
     11 
     12 Please read the WARNING, DISCLAIMER and PATENTS sections in this file.
     13 
     14 This program is released under the terms of the license contained
     15 in the file LICENSE.
     16 ------------------------------------------------------------------
     17 
     18 Complete documentation is available in Postscript form (manual.ps),
     19 PDF (manual.pdf) or html (manual.html).  A plain-text version of the
     20 manual page is available as bzip2.txt.
     21 
     22 
     23 HOW TO BUILD -- UNIX
     24 
     25 Type 'make'.  This builds the library libbz2.a and then the programs
     26 bzip2 and bzip2recover.  Six self-tests are run.  If the self-tests
     27 complete ok, carry on to installation:
     28 
     29 To install in /usr/local/bin, /usr/local/lib, /usr/local/man and
     30 /usr/local/include, type
     31 
     32    make install
     33 
     34 To install somewhere else, eg, /xxx/yyy/{bin,lib,man,include}, type
     35 
     36    make install PREFIX=/xxx/yyy
     37 
     38 If you are (justifiably) paranoid and want to see what 'make install'
     39 is going to do, you can first do
     40 
     41    make -n install                      or
     42    make -n install PREFIX=/xxx/yyy      respectively.
     43 
     44 The -n instructs make to show the commands it would execute, but not
     45 actually execute them.
     46 
     47 
     48 HOW TO BUILD -- UNIX, shared library libbz2.so.
     49 
     50 Do 'make -f Makefile-libbz2_so'.  This Makefile seems to work for
     51 Linux-ELF (RedHat 7.2 on an x86 box), with gcc.  I make no claims
     52 that it works for any other platform, though I suspect it probably
     53 will work for most platforms employing both ELF and gcc.
     54 
     55 bzip2-shared, a client of the shared library, is also built, but not
     56 self-tested.  So I suggest you also build using the normal Makefile,
     57 since that conducts a self-test.  A second reason to prefer the
     58 version statically linked to the library is that, on x86 platforms,
     59 building shared objects makes a valuable register (%ebx) unavailable
     60 to gcc, resulting in a slowdown of 10%-20%, at least for bzip2.
     61 
     62 Important note for people upgrading .so's from 0.9.0/0.9.5 to version
     63 1.0.X.  All the functions in the library have been renamed, from (eg)
     64 bzCompress to BZ2_bzCompress, to avoid namespace pollution.
     65 Unfortunately this means that the libbz2.so created by
     66 Makefile-libbz2_so will not work with any program which used an older
     67 version of the library.  I do encourage library clients to make the
     68 effort to upgrade to use version 1.0, since it is both faster and more
     69 robust than previous versions.
     70 
     71 
     72 HOW TO BUILD -- Windows 95, NT, DOS, Mac, etc.
     73 
     74 It's difficult for me to support compilation on all these platforms.
     75 My approach is to collect binaries for these platforms, and put them
     76 on the master web site (http://www.bzip.org).  Look there.  However
     77 (FWIW), bzip2-1.0.X is very standard ANSI C and should compile
     78 unmodified with MS Visual C.  If you have difficulties building, you
     79 might want to read README.COMPILATION.PROBLEMS.
     80 
     81 At least using MS Visual C++ 6, you can build from the unmodified
     82 sources by issuing, in a command shell: 
     83 
     84    nmake -f makefile.msc
     85 
     86 (you may need to first run the MSVC-provided script VCVARS32.BAT
     87  so as to set up paths to the MSVC tools correctly).
     88 
     89 
     90 VALIDATION
     91 
     92 Correct operation, in the sense that a compressed file can always be
     93 decompressed to reproduce the original, is obviously of paramount
     94 importance.  To validate bzip2, I used a modified version of Mark
     95 Nelson's churn program.  Churn is an automated test driver which
     96 recursively traverses a directory structure, using bzip2 to compress
     97 and then decompress each file it encounters, and checking that the
     98 decompressed data is the same as the original.
     99 
    100 
    101 
    102 Please read and be aware of the following:
    103 
    104 WARNING:
    105 
    106    This program and library (attempts to) compress data by 
    107    performing several non-trivial transformations on it.  
    108    Unless you are 100% familiar with *all* the algorithms 
    109    contained herein, and with the consequences of modifying them, 
    110    you should NOT meddle with the compression or decompression 
    111    machinery.  Incorrect changes can and very likely *will* 
    112    lead to disastrous loss of data.
    113 
    114 
    115 DISCLAIMER:
    116 
    117    I TAKE NO RESPONSIBILITY FOR ANY LOSS OF DATA ARISING FROM THE
    118    USE OF THIS PROGRAM/LIBRARY, HOWSOEVER CAUSED.
    119 
    120    Every compression of a file implies an assumption that the
    121    compressed file can be decompressed to reproduce the original.
    122    Great efforts in design, coding and testing have been made to
    123    ensure that this program works correctly.  However, the complexity
    124    of the algorithms, and, in particular, the presence of various
    125    special cases in the code which occur with very low but non-zero
    126    probability make it impossible to rule out the possibility of bugs
    127    remaining in the program.  DO NOT COMPRESS ANY DATA WITH THIS
    128    PROGRAM UNLESS YOU ARE PREPARED TO ACCEPT THE POSSIBILITY, HOWEVER
    129    SMALL, THAT THE DATA WILL NOT BE RECOVERABLE.
    130 
    131    That is not to say this program is inherently unreliable.  
    132    Indeed, I very much hope the opposite is true.  bzip2/libbzip2 
    133    has been carefully constructed and extensively tested.
    134 
    135 
    136 PATENTS:
    137 
    138    To the best of my knowledge, bzip2/libbzip2 does not use any 
    139    patented algorithms.  However, I do not have the resources 
    140    to carry out a patent search.  Therefore I cannot give any 
    141    guarantee of the above statement.
    142 
    143 
    144 
    145 WHAT'S NEW IN 0.9.0 (as compared to 0.1pl2) ?
    146 
    147    * Approx 10% faster compression, 30% faster decompression
    148    * -t (test mode) is a lot quicker
    149    * Can decompress concatenated compressed files
    150    * Programming interface, so programs can directly read/write .bz2 files
    151    * Less restrictive (BSD-style) licensing
    152    * Flag handling more compatible with GNU gzip
    153    * Much more documentation, i.e., a proper user manual
    154    * Hopefully, improved portability (at least of the library)
    155 
    156 WHAT'S NEW IN 0.9.5 ?
    157 
    158    * Compression speed is much less sensitive to the input
    159      data than in previous versions.  Specifically, the very
    160      slow performance caused by repetitive data is fixed.
    161    * Many small improvements in file and flag handling.
    162    * A Y2K statement.
    163 
    164 WHAT'S NEW IN 1.0.0 ?
    165 
    166    See the CHANGES file.
    167 
    168 WHAT'S NEW IN 1.0.2 ?
    169 
    170    See the CHANGES file.
    171 
    172 WHAT'S NEW IN 1.0.3 ?
    173 
    174    See the CHANGES file.
    175 
    176 WHAT'S NEW IN 1.0.4 ?
    177 
    178    See the CHANGES file.
    179 
    180 WHAT'S NEW IN 1.0.5 ?
    181 
    182    See the CHANGES file.
    183 
    184 WHAT'S NEW IN 1.0.6 ?
    185 
    186    See the CHANGES file.
    187 
    188 
    189 I hope you find bzip2 useful.  Feel free to contact me at
    190    jseward (a] bzip.org
    191 if you have any suggestions or queries.  Many people mailed me with
    192 comments, suggestions and patches after the releases of bzip-0.15,
    193 bzip-0.21, and bzip2 versions 0.1pl2, 0.9.0, 0.9.5, 1.0.0, 1.0.1,
    194 1.0.2 and 1.0.3, and the changes in bzip2 are largely a result of this
    195 feedback.  I thank you for your comments.
    196 
    197 bzip2's "home" is http://www.bzip.org/
    198 
    199 Julian Seward
    200 jseward (a] bzip.org
    201 Cambridge, UK.
    202 
    203 18     July 1996 (version 0.15)
    204 25   August 1996 (version 0.21)
    205  7   August 1997 (bzip2, version 0.1)
    206 29   August 1997 (bzip2, version 0.1pl2)
    207 23   August 1998 (bzip2, version 0.9.0)
    208  8     June 1999 (bzip2, version 0.9.5)
    209  4     Sept 1999 (bzip2, version 0.9.5d)
    210  5      May 2000 (bzip2, version 1.0pre8)
    211 30 December 2001 (bzip2, version 1.0.2pre1)
    212 15 February 2005 (bzip2, version 1.0.3)
    213 20 December 2006 (bzip2, version 1.0.4)
    214 10 December 2007 (bzip2, version 1.0.5)
    215  6     Sept 2010 (bzip2, version 1.0.6)
    216