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authorobrien <obrien@FreeBSD.org>2001-06-21 18:37:17 +0000
committerobrien <obrien@FreeBSD.org>2001-06-21 18:37:17 +0000
commitda41d3ce6ee0a7c399e6438525caf651b761080b (patch)
treedd474847b5cb872a4c00011987d2276b9e7075d0 /contrib/bzip2/README
downloadFreeBSD-src-da41d3ce6ee0a7c399e6438525caf651b761080b.zip
FreeBSD-src-da41d3ce6ee0a7c399e6438525caf651b761080b.tar.gz
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+
+This is the README for bzip2, a block-sorting file compressor, version
+1.0. This version is fully compatible with the previous public
+releases, bzip2-0.1pl2, bzip2-0.9.0 and bzip2-0.9.5.
+
+bzip2-1.0 is distributed under a BSD-style license. For details,
+see the file LICENSE.
+
+Complete documentation is available in Postscript form (manual.ps) 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 5.2 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 build, but
+not self-tested. So I suggest you also build using the normal
+Makefile, since that conducts a self-test.
+
+Important note for people upgrading .so's from 0.9.0/0.9.5 to
+version 1.0. 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://sourceware.cygnus.com/bzip2). Look
+there. However (FWIW), bzip2-1.0 is very standard ANSI C and should
+compile unmodified with MS Visual C. For Win32, there is one
+important caveat: in bzip2.c, you must set BZ_UNIX to 0 and
+BZ_LCCWIN32 to 1 before building. If you have difficulties building,
+you might want to read README.COMPILATION.PROBLEMS.
+
+
+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
+
+ 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, bzip2-0.1pl2 and bzip2-0.9.0, 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://www.muraroa.demon.co.uk.
+
+Julian Seward
+jseward@acm.org
+
+Cambridge, UK
+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)
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