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  1
  2This is the README for bzip2/libzip2.
  3This version is fully compatible with the previous public releases.
  4
  5------------------------------------------------------------------
  6This file is part of bzip2/libbzip2, a program and library for
  7lossless, block-sorting data compression.
  8
  9bzip2/libbzip2 version 1.0.5 of 10 December 2007
 10Copyright (C) 1996-2007 Julian Seward <jseward@bzip.org>
 11
 12Please read the WARNING, DISCLAIMER and PATENTS sections in this file.
 13
 14This program is released under the terms of the license contained
 15in the file LICENSE.
 16------------------------------------------------------------------
 17
 18Complete documentation is available in Postscript form (manual.ps),
 19PDF (manual.pdf) or html (manual.html).  A plain-text version of the
 20manual page is available as bzip2.txt.
 21
 22
 23HOW TO BUILD -- UNIX
 24
 25Type 'make'.  This builds the library libbz2.a and then the programs
 26bzip2 and bzip2recover.  Six self-tests are run.  If the self-tests
 27complete ok, carry on to installation:
 28
 29To install in /usr/local/bin, /usr/local/lib, /usr/local/man and
 30/usr/local/include, type
 31
 32   make install
 33
 34To install somewhere else, eg, /xxx/yyy/{bin,lib,man,include}, type
 35
 36   make install PREFIX=/xxx/yyy
 37
 38If you are (justifiably) paranoid and want to see what 'make install'
 39is going to do, you can first do
 40
 41   make -n install                      or
 42   make -n install PREFIX=/xxx/yyy      respectively.
 43
 44The -n instructs make to show the commands it would execute, but not
 45actually execute them.
 46
 47
 48HOW TO BUILD -- UNIX, shared library libbz2.so.
 49
 50Do 'make -f Makefile-libbz2_so'.  This Makefile seems to work for
 51Linux-ELF (RedHat 7.2 on an x86 box), with gcc.  I make no claims
 52that it works for any other platform, though I suspect it probably
 53will work for most platforms employing both ELF and gcc.
 54
 55bzip2-shared, a client of the shared library, is also built, but not
 56self-tested.  So I suggest you also build using the normal Makefile,
 57since that conducts a self-test.  A second reason to prefer the
 58version statically linked to the library is that, on x86 platforms,
 59building shared objects makes a valuable register (%ebx) unavailable
 60to gcc, resulting in a slowdown of 10%-20%, at least for bzip2.
 61
 62Important note for people upgrading .so's from 0.9.0/0.9.5 to version
 631.0.X.  All the functions in the library have been renamed, from (eg)
 64bzCompress to BZ2_bzCompress, to avoid namespace pollution.
 65Unfortunately this means that the libbz2.so created by
 66Makefile-libbz2_so will not work with any program which used an older
 67version of the library.  I do encourage library clients to make the
 68effort to upgrade to use version 1.0, since it is both faster and more
 69robust than previous versions.
 70
 71
 72HOW TO BUILD -- Windows 95, NT, DOS, Mac, etc.
 73
 74It's difficult for me to support compilation on all these platforms.
 75My approach is to collect binaries for these platforms, and put them
 76on 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
 78unmodified with MS Visual C.  If you have difficulties building, you
 79might want to read README.COMPILATION.PROBLEMS.
 80
 81At least using MS Visual C++ 6, you can build from the unmodified
 82sources 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
 90VALIDATION
 91
 92Correct operation, in the sense that a compressed file can always be
 93decompressed to reproduce the original, is obviously of paramount
 94importance.  To validate bzip2, I used a modified version of Mark
 95Nelson's churn program.  Churn is an automated test driver which
 96recursively traverses a directory structure, using bzip2 to compress
 97and then decompress each file it encounters, and checking that the
 98decompressed data is the same as the original.
 99
100
101
102Please read and be aware of the following:
103
104WARNING:
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
115DISCLAIMER:
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
136PATENTS:
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
145WHAT'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
156WHAT'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
164WHAT'S NEW IN 1.0.0 ?
165
166   See the CHANGES file.
167
168WHAT'S NEW IN 1.0.2 ?
169
170   See the CHANGES file.
171
172WHAT'S NEW IN 1.0.3 ?
173
174   See the CHANGES file.
175
176WHAT'S NEW IN 1.0.4 ?
177
178   See the CHANGES file.
179
180WHAT'S NEW IN 1.0.5 ?
181
182   See the CHANGES file.
183
184
185I hope you find bzip2 useful.  Feel free to contact me at
186   jseward@bzip.org
187if you have any suggestions or queries.  Many people mailed me with
188comments, suggestions and patches after the releases of bzip-0.15,
189bzip-0.21, and bzip2 versions 0.1pl2, 0.9.0, 0.9.5, 1.0.0, 1.0.1,
1901.0.2 and 1.0.3, and the changes in bzip2 are largely a result of this
191feedback.  I thank you for your comments.
192
193bzip2's "home" is http://www.bzip.org/
194
195Julian Seward
196jseward@bzip.org
197Cambridge, UK.
198
19918     July 1996 (version 0.15)
20025   August 1996 (version 0.21)
201 7   August 1997 (bzip2, version 0.1)
20229   August 1997 (bzip2, version 0.1pl2)
20323   August 1998 (bzip2, version 0.9.0)
204 8     June 1999 (bzip2, version 0.9.5)
205 4     Sept 1999 (bzip2, version 0.9.5d)
206 5      May 2000 (bzip2, version 1.0pre8)
20730 December 2001 (bzip2, version 1.0.2pre1)
20815 February 2005 (bzip2, version 1.0.3)
20920 December 2006 (bzip2, version 1.0.4)
21010 December 2007 (bzip2, version 1.0.5)