aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorJulian Seward <jseward@acm.org>2005-02-15 22:13:13 +0100
committerJulian Seward <jseward@acm.org>2005-02-15 22:13:13 +0100
commit4d540bfc95a4b0eefc1d1f388ec33534aaeb3a2f (patch)
tree3b7e9c650b4c61d114e1716c4698e40d5c8d7ef7
parent099d844292f60f9d58914da29e5773204dc55e7a (diff)
downloadbzip2-1.0.3.tar.gz
bzip2-1.0.3.tar.bz2
bzip2-1.0.3.zip
bzip2-1.0.3bzip2-1.0.3
-rw-r--r--CHANGES22
-rw-r--r--LICENSE7
-rw-r--r--Makefile51
-rw-r--r--Makefile-libbz2_so12
-rw-r--r--README40
-rw-r--r--README.COMPILATION.PROBLEMS103
-rw-r--r--README.XML.STUFF31
-rw-r--r--blocksort.c4
-rw-r--r--bz-common.xsl39
-rw-r--r--bz-fo.xsl257
-rw-r--r--bz-html.xsl20
-rw-r--r--bzip.css74
-rw-r--r--bzip2.117
-rw-r--r--bzip2.1.preformatted247
-rw-r--r--bzip2.c20
-rw-r--r--bzip2.txt119
-rw-r--r--bzip2recover.c12
-rw-r--r--bzlib.c59
-rw-r--r--bzlib.h6
-rw-r--r--bzlib_private.h6
-rw-r--r--compress.c16
-rw-r--r--crctable.c4
-rw-r--r--decompress.c20
-rw-r--r--entities.xml9
-rwxr-xr-xformat.pl53
-rw-r--r--huffman.c23
-rw-r--r--manual.texi2243
-rw-r--r--manual.xml2966
-rw-r--r--randtable.c4
-rwxr-xr-xxmlproc.sh99
30 files changed, 3947 insertions, 2636 deletions
diff --git a/CHANGES b/CHANGES
index d984395..e31b03a 100644
--- a/CHANGES
+++ b/CHANGES
@@ -251,3 +251,25 @@ of bzip2:
251 251
252* added --fast and --best aliases for -1 -9 for gzip compatibility. 252* added --fast and --best aliases for -1 -9 for gzip compatibility.
253 253
254
2551.0.3 (15 Feb 05)
256~~~~~~~~~~~~~~~~~
257Fixes some minor bugs since the last version, 1.0.2.
258
259* Further robustification against corrupted compressed data.
260 There are currently no known bitstreams which can cause the
261 decompressor to crash, loop or access memory which does not
262 belong to it. If you are using bzip2 or the library to
263 decompress bitstreams from untrusted sources, an upgrade
264 to 1.0.3 is recommended.
265
266* The documentation has been converted to XML, from which html
267 and pdf can be derived.
268
269* Various minor bugs in the documentation have been fixed.
270
271* Fixes for various compilation warnings with newer versions of
272 gcc, and on 64-bit platforms.
273
274* The BZ_NO_STDIO cpp symbol was not properly observed in 1.0.2.
275 This has been fixed.
diff --git a/LICENSE b/LICENSE
index 9d4fa43..e60845b 100644
--- a/LICENSE
+++ b/LICENSE
@@ -1,6 +1,7 @@
1 1
2This program, "bzip2" and associated library "libbzip2", are 2This program, "bzip2", the associated library "libbzip2", and all
3copyright (C) 1996-2002 Julian R Seward. All rights reserved. 3documentation, are copyright (C) 1996-2005 Julian R Seward. All
4rights reserved.
4 5
5Redistribution and use in source and binary forms, with or without 6Redistribution and use in source and binary forms, with or without
6modification, are permitted provided that the following conditions 7modification, are permitted provided that the following conditions
@@ -35,5 +36,5 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
35 36
36Julian Seward, Cambridge, UK. 37Julian Seward, Cambridge, UK.
37jseward@acm.org 38jseward@acm.org
38bzip2/libbzip2 version 1.0.2 of 30 December 2001 39bzip2/libbzip2 version 1.0.3 of 15 February 2005
39 40
diff --git a/Makefile b/Makefile
index 8305235..eea329a 100644
--- a/Makefile
+++ b/Makefile
@@ -7,9 +7,8 @@ AR=ar
7RANLIB=ranlib 7RANLIB=ranlib
8LDFLAGS= 8LDFLAGS=
9 9
10# Suitably paranoid flags to avoid bugs in gcc-2.7
11BIGFILES=-D_FILE_OFFSET_BITS=64 10BIGFILES=-D_FILE_OFFSET_BITS=64
12CFLAGS=-Wall -Winline -O2 -fomit-frame-pointer -fno-strength-reduce $(BIGFILES) 11CFLAGS=-Wall -Winline -O -g $(BIGFILES)
13 12
14# Where you want it installed when you do 'make install' 13# Where you want it installed when you do 'make install'
15PREFIX=/usr 14PREFIX=/usr
@@ -96,7 +95,6 @@ install: bzip2 bzip2recover
96 echo ".so man1/bzmore.1" > $(PREFIX)/man/man1/bzless.1 95 echo ".so man1/bzmore.1" > $(PREFIX)/man/man1/bzless.1
97 echo ".so man1/bzdiff.1" > $(PREFIX)/man/man1/bzcmp.1 96 echo ".so man1/bzdiff.1" > $(PREFIX)/man/man1/bzcmp.1
98 97
99distclean: clean
100clean: 98clean:
101 rm -f *.o libbz2.a bzip2 bzip2recover \ 99 rm -f *.o libbz2.a bzip2 bzip2recover \
102 sample1.rb2 sample2.rb2 sample3.rb2 \ 100 sample1.rb2 sample2.rb2 sample3.rb2 \
@@ -122,8 +120,12 @@ bzip2.o: bzip2.c
122bzip2recover.o: bzip2recover.c 120bzip2recover.o: bzip2recover.c
123 $(CC) $(CFLAGS) -c bzip2recover.c 121 $(CC) $(CFLAGS) -c bzip2recover.c
124 122
125DISTNAME=bzip2-1.0.2 123
126tarfile: 124distclean: clean
125 rm -f manual.ps manual.html manual.pdf
126
127DISTNAME=bzip2-1.0.3
128dist: check manual
127 rm -f $(DISTNAME) 129 rm -f $(DISTNAME)
128 ln -sf . $(DISTNAME) 130 ln -sf . $(DISTNAME)
129 tar cvf $(DISTNAME).tar \ 131 tar cvf $(DISTNAME).tar \
@@ -139,9 +141,6 @@ tarfile:
139 $(DISTNAME)/bzlib.h \ 141 $(DISTNAME)/bzlib.h \
140 $(DISTNAME)/bzlib_private.h \ 142 $(DISTNAME)/bzlib_private.h \
141 $(DISTNAME)/Makefile \ 143 $(DISTNAME)/Makefile \
142 $(DISTNAME)/manual.texi \
143 $(DISTNAME)/manual.ps \
144 $(DISTNAME)/manual.pdf \
145 $(DISTNAME)/LICENSE \ 144 $(DISTNAME)/LICENSE \
146 $(DISTNAME)/bzip2.1 \ 145 $(DISTNAME)/bzip2.1 \
147 $(DISTNAME)/bzip2.1.preformatted \ 146 $(DISTNAME)/bzip2.1.preformatted \
@@ -157,9 +156,12 @@ tarfile:
157 $(DISTNAME)/sample2.bz2 \ 156 $(DISTNAME)/sample2.bz2 \
158 $(DISTNAME)/sample3.bz2 \ 157 $(DISTNAME)/sample3.bz2 \
159 $(DISTNAME)/dlltest.c \ 158 $(DISTNAME)/dlltest.c \
160 $(DISTNAME)/*.html \ 159 $(DISTNAME)/manual.html \
160 $(DISTNAME)/manual.pdf \
161 $(DISTNAME)/manual.ps \
161 $(DISTNAME)/README \ 162 $(DISTNAME)/README \
162 $(DISTNAME)/README.COMPILATION.PROBLEMS \ 163 $(DISTNAME)/README.COMPILATION.PROBLEMS \
164 $(DISTNAME)/README.XML.STUFF \
163 $(DISTNAME)/CHANGES \ 165 $(DISTNAME)/CHANGES \
164 $(DISTNAME)/libbz2.def \ 166 $(DISTNAME)/libbz2.def \
165 $(DISTNAME)/libbz2.dsp \ 167 $(DISTNAME)/libbz2.dsp \
@@ -175,18 +177,29 @@ tarfile:
175 $(DISTNAME)/bzmore.1 \ 177 $(DISTNAME)/bzmore.1 \
176 $(DISTNAME)/bzgrep \ 178 $(DISTNAME)/bzgrep \
177 $(DISTNAME)/bzgrep.1 \ 179 $(DISTNAME)/bzgrep.1 \
178 $(DISTNAME)/Makefile-libbz2_so 180 $(DISTNAME)/Makefile-libbz2_so \
181 $(DISTNAME)/bz-common.xsl \
182 $(DISTNAME)/bz-fo.xsl \
183 $(DISTNAME)/bz-html.xsl \
184 $(DISTNAME)/bzip.css \
185 $(DISTNAME)/entities.xml \
186 $(DISTNAME)/manual.xml \
187 $(DISTNAME)/format.pl \
188 $(DISTNAME)/xmlproc.sh
179 gzip -v $(DISTNAME).tar 189 gzip -v $(DISTNAME).tar
180 190
181# For rebuilding the manual from sources on my RedHat 7.2 box 191# For rebuilding the manual from sources on my SuSE 9.1 box
182manual: manual.ps manual.pdf manual.html 192
193MANUAL_SRCS= bz-common.xsl bz-fo.xsl bz-html.xsl bzip.css \
194 entities.xml manual.xml
195
196manual: manual.html manual.ps manual.pdf
183 197
184manual.ps: manual.texi 198manual.ps: $(MANUAL_SRCS)
185 tex manual.texi 199 ./xmlproc.sh -ps manual.xml
186 dvips -o manual.ps manual.dvi
187 200
188manual.pdf: manual.ps 201manual.pdf: $(MANUAL_SRCS)
189 ps2pdf manual.ps 202 ./xmlproc.sh -pdf manual.xml
190 203
191manual.html: manual.texi 204manual.html: $(MANUAL_SRCS)
192 texi2html -split_chapter manual.texi 205 ./xmlproc.sh -html manual.xml
diff --git a/Makefile-libbz2_so b/Makefile-libbz2_so
index 4986fe2..458c5a1 100644
--- a/Makefile-libbz2_so
+++ b/Makefile-libbz2_so
@@ -1,6 +1,6 @@
1 1
2# This Makefile builds a shared version of the library, 2# This Makefile builds a shared version of the library,
3# libbz2.so.1.0.2, with soname libbz2.so.1.0, 3# libbz2.so.1.0.3, with soname libbz2.so.1.0,
4# at least on x86-Linux (RedHat 7.2), 4# at least on x86-Linux (RedHat 7.2),
5# with gcc-2.96 20000731 (Red Hat Linux 7.1 2.96-98). 5# with gcc-2.96 20000731 (Red Hat Linux 7.1 2.96-98).
6# Please see the README file for some 6# Please see the README file for some
@@ -9,7 +9,7 @@
9SHELL=/bin/sh 9SHELL=/bin/sh
10CC=gcc 10CC=gcc
11BIGFILES=-D_FILE_OFFSET_BITS=64 11BIGFILES=-D_FILE_OFFSET_BITS=64
12CFLAGS=-fpic -fPIC -Wall -Winline -O2 -fomit-frame-pointer -fno-strength-reduce $(BIGFILES) 12CFLAGS=-fpic -fPIC -Wall -Winline -O -g
13 13
14OBJS= blocksort.o \ 14OBJS= blocksort.o \
15 huffman.o \ 15 huffman.o \
@@ -20,13 +20,13 @@ OBJS= blocksort.o \
20 bzlib.o 20 bzlib.o
21 21
22all: $(OBJS) 22all: $(OBJS)
23 $(CC) -shared -Wl,-soname -Wl,libbz2.so.1.0 -o libbz2.so.1.0.2 $(OBJS) 23 $(CC) -shared -Wl,-soname -Wl,libbz2.so.1.0 -o libbz2.so.1.0.3 $(OBJS)
24 $(CC) $(CFLAGS) -o bzip2-shared bzip2.c libbz2.so.1.0.2 24 $(CC) $(CFLAGS) -o bzip2-shared bzip2.c libbz2.so.1.0.3
25 rm -f libbz2.so.1.0 25 rm -f libbz2.so.1.0
26 ln -s libbz2.so.1.0.2 libbz2.so.1.0 26 ln -s libbz2.so.1.0.3 libbz2.so.1.0
27 27
28clean: 28clean:
29 rm -f $(OBJS) bzip2.o libbz2.so.1.0.2 libbz2.so.1.0 bzip2-shared 29 rm -f $(OBJS) bzip2.o libbz2.so.1.0.3 libbz2.so.1.0 bzip2-shared
30 30
31blocksort.o: blocksort.c 31blocksort.o: blocksort.c
32 $(CC) $(CFLAGS) -c blocksort.c 32 $(CC) $(CFLAGS) -c blocksort.c
diff --git a/README b/README
index 07505d8..1aff448 100644
--- a/README
+++ b/README
@@ -1,15 +1,15 @@
1 1
2This is the README for bzip2, a block-sorting file compressor, version 2This is the README for bzip2, a block-sorting file compressor, version
31.0.2. This version is fully compatible with the previous public 31.0.3. This version is fully compatible with the previous public
4releases, versions 0.1pl2, 0.9.0, 0.9.5, 1.0.0 and 1.0.1. 4releases, versions 0.1pl2, 0.9.0, 0.9.5, 1.0.0, 1.0.1 and 1.0.2.
5 5
6bzip2-1.0.2 is distributed under a BSD-style license. For details, 6bzip2-1.0.3 is distributed under a BSD-style license. For details,
7see the file LICENSE. 7see the file LICENSE.
8 8
9Complete documentation is available in Postscript form (manual.ps), 9Complete documentation is available in Postscript form (manual.ps),
10PDF (manual.pdf, amazingly enough) or html (manual_toc.html). A 10PDF (manual.pdf) or html (manual.html). A plain-text version of the
11plain-text version of the manual page is available as bzip2.txt. 11manual page is available as bzip2.txt. A statement about Y2K issues
12A statement about Y2K issues is now included in the file Y2K_INFO. 12is now included in the file Y2K_INFO.
13 13
14 14
15HOW TO BUILD -- UNIX 15HOW TO BUILD -- UNIX
@@ -78,8 +78,7 @@ importance. To validate bzip2, I used a modified version of Mark
78Nelson's churn program. Churn is an automated test driver which 78Nelson's churn program. Churn is an automated test driver which
79recursively traverses a directory structure, using bzip2 to compress 79recursively traverses a directory structure, using bzip2 to compress
80and then decompress each file it encounters, and checking that the 80and then decompress each file it encounters, and checking that the
81decompressed data is the same as the original. There are more details 81decompressed data is the same as the original.
82in Section 4 of the user guide.
83 82
84 83
85 84
@@ -119,9 +118,9 @@ DISCLAIMER:
119PATENTS: 118PATENTS:
120 119
121 To the best of my knowledge, bzip2 does not use any patented 120 To the best of my knowledge, bzip2 does not use any patented
122 algorithms. However, I do not have the resources available to 121 algorithms. However, I do not have the resources to carry out
123 carry out a full patent search. Therefore I cannot give any 122 a patent search. Therefore I cannot give any guarantee of the
124 guarantee of the above statement. 123 above statement.
125 124
126End of legalities. 125End of legalities.
127 126
@@ -153,22 +152,26 @@ WHAT'S NEW IN 1.0.2 ?
153 152
154 See the CHANGES file. 153 See the CHANGES file.
155 154
155WHAT'S NEW IN 1.0.3 ?
156
157 See the CHANGES file.
158
156 159
157I hope you find bzip2 useful. Feel free to contact me at 160I hope you find bzip2 useful. Feel free to contact me at
158 jseward@acm.org 161 jseward@bzip.org
159if you have any suggestions or queries. Many people mailed me with 162if you have any suggestions or queries. Many people mailed me with
160comments, suggestions and patches after the releases of bzip-0.15, 163comments, suggestions and patches after the releases of bzip-0.15,
161bzip-0.21, and bzip2 versions 0.1pl2, 0.9.0, 0.9.5, 1.0.0 and 1.0.1, 164bzip-0.21, and bzip2 versions 0.1pl2, 0.9.0, 0.9.5, 1.0.0, 1.0.1 and
162and the changes in bzip2 are largely a result of this feedback. 1651.0.2, and the changes in bzip2 are largely a result of this feedback.
163I thank you for your comments. 166I thank you for your comments.
164 167
165At least for the time being, bzip2's "home" is (or can be reached via) 168At least for the time being, bzip2's "home" is (or can be reached via)
166http://sources.redhat.com/bzip2. 169http://www.bzip.org
167 170
168Julian Seward 171Julian Seward
169jseward@acm.org 172jseward@bzip.org
170 173
171Cambridge, UK (and what a great town this is!) 174Cambridge, UK.
172 175
17318 July 1996 (version 0.15) 17618 July 1996 (version 0.15)
17425 August 1996 (version 0.21) 17725 August 1996 (version 0.21)
@@ -178,4 +181,5 @@ Cambridge, UK (and what a great town this is!)
178 8 June 1999 (bzip2, version 0.9.5) 181 8 June 1999 (bzip2, version 0.9.5)
179 4 Sept 1999 (bzip2, version 0.9.5d) 182 4 Sept 1999 (bzip2, version 0.9.5d)
180 5 May 2000 (bzip2, version 1.0pre8) 183 5 May 2000 (bzip2, version 1.0pre8)
18130 December 2001 (bzip2, version 1.0.2pre1) \ No newline at end of file 18430 December 2001 (bzip2, version 1.0.2pre1)
18515 February 2005 (bzip2, version 1.0.3)
diff --git a/README.COMPILATION.PROBLEMS b/README.COMPILATION.PROBLEMS
index bd1822d..f1bc396 100644
--- a/README.COMPILATION.PROBLEMS
+++ b/README.COMPILATION.PROBLEMS
@@ -1,11 +1,10 @@
1 1
2bzip2-1.0 should compile without problems on the vast majority of 2bzip2-1.0.3 should compile without problems on the vast majority of
3platforms. Using the supplied Makefile, I've built and tested it 3platforms. Using the supplied Makefile, I've built and tested it
4myself for x86-linux, sparc-solaris, alpha-linux, x86-cygwin32 and 4myself for x86-linux and x86_64-linux. With makefile.msc, Visual C++
5alpha-tru64unix. With makefile.msc, Visual C++ 6.0 and nmake, you can 56.0 and nmake, you can build a native Win32 version too. Large file
6build a native Win32 version too. Large file support seems to work 6support seems to work correctly on at least alpha-tru64unix and
7correctly on at least alpha-tru64unix and x86-cygwin32 (on Windows 7x86-cygwin32 (on Windows 2000).
82000).
9 8
10When I say "large file" I mean a file of size 2,147,483,648 (2^31) 9When I say "large file" I mean a file of size 2,147,483,648 (2^31)
11bytes or above. Many older OSs can't handle files above this size, 10bytes or above. Many older OSs can't handle files above this size,
@@ -22,7 +21,7 @@ The technique of adding -D_FILE_OFFSET_BITS=64 to get large file
22support is, as far as I know, the Recommended Way to get correct large 21support is, as far as I know, the Recommended Way to get correct large
23file support. For more details, see the Large File Support 22file support. For more details, see the Large File Support
24Specification, published by the Large File Summit, at 23Specification, published by the Large File Summit, at
25 http://www.sas.com/standard/large.file/ 24 http://ftp.sas.com/standards/large.file
26 25
27As a general comment, if you get compilation errors which you think 26As a general comment, if you get compilation errors which you think
28are related to large file support, try removing the above define from 27are related to large file support, try removing the above define from
@@ -38,93 +37,3 @@ You can use the spewG.c program to generate huge files to test bzip2's
38large file support, if you are feeling paranoid. Be aware though that 37large file support, if you are feeling paranoid. Be aware though that
39any compilation problems which affect bzip2 will also affect spewG.c, 38any compilation problems which affect bzip2 will also affect spewG.c,
40alas. 39alas.
41
42
43Known problems as of 1.0pre8:
44~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
45
46* HP/UX 10.20 and 11.00, using gcc (2.7.2.3 and 2.95.2): A large
47 number of warnings appear, including the following:
48
49 /usr/include/sys/resource.h: In function `getrlimit':
50 /usr/include/sys/resource.h:168:
51 warning: implicit declaration of function `__getrlimit64'
52 /usr/include/sys/resource.h: In function `setrlimit':
53 /usr/include/sys/resource.h:170:
54 warning: implicit declaration of function `__setrlimit64'
55
56 This would appear to be a problem with large file support, header
57 files and gcc. gcc may or may not give up at this point. If it
58 fails, you might be able to improve matters by adding
59 -D__STDC_EXT__=1
60 to the BIGFILES variable in the Makefile (ie, change its definition
61 to
62 BIGFILES=-D_FILE_OFFSET_BITS=64 -D__STDC_EXT__=1
63
64 Even if gcc does produce a binary which appears to work (ie passes
65 its self-tests), you might want to test it to see if it works properly
66 on large files.
67
68
69* HP/UX 10.20 and 11.00, using HP's cc compiler.
70
71 No specific problems for this combination, except that you'll need to
72 specify the -Ae flag, and zap the gcc-specific stuff
73 -Wall -Winline -O2 -fomit-frame-pointer -fno-strength-reduce.
74 You should retain -D_FILE_OFFSET_BITS=64 in order to get large
75 file support -- which is reported to work ok for this HP/UX + cc
76 combination.
77
78
79* SunOS 4.1.X.
80
81 Amazingly, there are still people out there using this venerable old
82 banger. I shouldn't be too rude -- I started life on SunOS, and
83 it was a pretty darn good OS, way back then. Anyway:
84
85 SunOS doesn't seem to have strerror(), so you'll have to use
86 perror(), perhaps by doing adding this (warning: UNTESTED CODE):
87
88 char* strerror ( int errnum )
89 {
90 if (errnum < 0 || errnum >= sys_nerr)
91 return "Unknown error";
92 else
93 return sys_errlist[errnum];
94 }
95
96 Or you could comment out the relevant calls to strerror; they're
97 not mission-critical. Or you could upgrade to Solaris. Ha ha ha!
98 (what?? you think I've got Bad Attitude?)
99
100
101* Making a shared library on Solaris. (Not really a compilation
102 problem, but many people ask ...)
103
104 Firstly, if you have Solaris 8, either you have libbz2.so already
105 on your system, or you can install it from the Solaris CD.
106
107 Secondly, be aware that there are potential naming conflicts
108 between the .so file supplied with Solaris 8, and the .so file
109 which Makefile-libbz2_so will make. Makefile-libbz2_so creates
110 a .so which has the names which I intend to be "official" as
111 of version 1.0.0 and onwards. Unfortunately, the .so in
112 Solaris 8 appeared before I decided on the final names, so
113 the two libraries are incompatible. We have since communicated
114 and I hope that the problems will have been solved in the next
115 version of Solaris, whenever that might appear.
116
117 All that said: you might be able to get somewhere
118 by finding the line in Makefile-libbz2_so which says
119
120 $(CC) -shared -Wl,-soname -Wl,libbz2.so.1.0 -o libbz2.so.1.0.2 $(OBJS)
121
122 and replacing with
123
124 $(CC) -G -shared -o libbz2.so.1.0.2 -h libbz2.so.1.0 $(OBJS)
125
126 If gcc objects to the combination -fpic -fPIC, get rid of
127 the second one, leaving just "-fpic".
128
129
130That's the end of the currently known compilation problems.
diff --git a/README.XML.STUFF b/README.XML.STUFF
new file mode 100644
index 0000000..0ff209f
--- /dev/null
+++ b/README.XML.STUFF
@@ -0,0 +1,31 @@
1The script xmlproc.sh takes an xml file as input,
2and processes it to create .pdf, .html or .ps output.
3It uses format.pl, a perl script to format <pre> blocks nicely,
4 and add CDATA tags so writers do not have to use eg. &lt;
5
6The file "entities.xml" must be edited to reflect current
7version, year, etc.
8
9
10Usage:
11
12 xmlproc.sh -v manual.xml
13 Validates an xml file to ensure no dtd-compliance errors
14
15 xmlproc.sh -html manual.xml
16 Output: manual.html
17
18 xmlproc.sh -pdf manual.xml
19 Output: manual.pdf
20
21 xmlproc.sh -ps manual.xml
22 Output: manual.ps
23
24
25Notum bene:
26- pdfxmltex barfs if given a filename with an underscore in it
27
28- xmltex won't work yet - there's a bug in passivetex
29 which we are all waiting for Sebastian to fix.
30 So we are going the xml -> pdf -> ps route for the time being,
31 using pdfxmltex.
diff --git a/blocksort.c b/blocksort.c
index aba3efc..33ec9f5 100644
--- a/blocksort.c
+++ b/blocksort.c
@@ -8,7 +8,7 @@
8 This file is a part of bzip2 and/or libbzip2, a program and 8 This file is a part of bzip2 and/or libbzip2, a program and
9 library for lossless, block-sorting data compression. 9 library for lossless, block-sorting data compression.
10 10
11 Copyright (C) 1996-2002 Julian R Seward. All rights reserved. 11 Copyright (C) 1996-2005 Julian R Seward. All rights reserved.
12 12
13 Redistribution and use in source and binary forms, with or without 13 Redistribution and use in source and binary forms, with or without
14 modification, are permitted provided that the following conditions 14 modification, are permitted provided that the following conditions
@@ -42,7 +42,7 @@
42 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 42 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
43 43
44 Julian Seward, Cambridge, UK. 44 Julian Seward, Cambridge, UK.
45 jseward@acm.org 45 jseward@bzip.org
46 bzip2/libbzip2 version 1.0 of 21 March 2000 46 bzip2/libbzip2 version 1.0 of 21 March 2000
47 47
48 This program is based on (at least) the work of: 48 This program is based on (at least) the work of:
diff --git a/bz-common.xsl b/bz-common.xsl
new file mode 100644
index 0000000..66fcd6f
--- /dev/null
+++ b/bz-common.xsl
@@ -0,0 +1,39 @@
1<?xml version="1.0"?> <!-- -*- sgml -*- -->
2<xsl:stylesheet
3 xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
4
5<!-- we like '1.2 Title' -->
6<xsl:param name="section.autolabel" select="'1'"/>
7<xsl:param name="section.label.includes.component.label" select="'1'"/>
8
9<!-- Do not put 'Chapter' at the start of eg 'Chapter 1. Doing This' -->
10<xsl:param name="local.l10n.xml" select="document('')"/>
11<l:i18n xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0">
12 <l:l10n language="en">
13 <l:context name="title-numbered">
14 <l:template name="chapter" text="%n.&#160;%t"/>
15 </l:context>
16 </l:l10n>
17</l:i18n>
18
19<!-- don't generate sub-tocs for qanda sets -->
20<xsl:param name="generate.toc">
21set toc,title
22book toc,title,figure,table,example,equation
23chapter toc,title
24section toc
25sect1 toc
26sect2 toc
27sect3 toc
28sect4 nop
29sect5 nop
30qandaset toc
31qandadiv nop
32appendix toc,title
33article/appendix nop
34article toc,title
35preface toc,title
36reference toc,title
37</xsl:param>
38
39</xsl:stylesheet>
diff --git a/bz-fo.xsl b/bz-fo.xsl
new file mode 100644
index 0000000..7f2a767
--- /dev/null
+++ b/bz-fo.xsl
@@ -0,0 +1,257 @@
1<?xml version="1.0" encoding="UTF-8"?> <!-- -*- sgml -*- -->
2<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
3 xmlns:fo="http://www.w3.org/1999/XSL/Format" version="1.0">
4
5<xsl:import href="http://docbook.sourceforge.net/release/xsl/current/fo/docbook.xsl"/>
6<xsl:import href="bz-common.xsl"/>
7
8<!-- set indent = yes while debugging, then change to NO -->
9<xsl:output method="xml" indent="yes"/>
10
11<!-- ensure only passivetex extensions are on -->
12<xsl:param name="stylesheet.result.type" select="'fo'"/>
13<!-- fo extensions: PDF bookmarks and index terms -->
14<xsl:param name="use.extensions" select="'1'"/>
15<xsl:param name="xep.extensions" select="0"/>
16<xsl:param name="fop.extensions" select="0"/>
17<xsl:param name="saxon.extensions" select="0"/>
18<xsl:param name="passivetex.extensions" select="1"/>
19<xsl:param name="tablecolumns.extension" select="'1'"/>
20
21<!-- ensure we are using single sided -->
22<xsl:param name="double.sided" select="'0'"/>
23
24<!-- insert cross references to page numbers -->
25<xsl:param name="insert.xref.page.number" select="1"/>
26
27<!-- <?custom-pagebreak?> inserts a page break at this point -->
28<xsl:template match="processing-instruction('custom-pagebreak')">
29 <fo:block break-before='page'/>
30</xsl:template>
31
32<!-- show links in color -->
33<xsl:attribute-set name="xref.properties">
34 <xsl:attribute name="color">blue</xsl:attribute>
35</xsl:attribute-set>
36
37<!-- make pre listings indented a bit + a bg colour -->
38<xsl:template match="programlisting | screen">
39 <fo:block start-indent="0.25in" wrap-option="no-wrap"
40 white-space-collapse="false" text-align="start"
41 font-family="monospace" background-color="#f2f2f9"
42 linefeed-treatment="preserve"
43 xsl:use-attribute-sets="normal.para.spacing">
44 <xsl:apply-templates/>
45 </fo:block>
46</xsl:template>
47<!-- make verbatim output prettier -->
48<xsl:template match="literallayout">
49 <fo:block start-indent="0.25in" wrap-option="no-wrap"
50 white-space-collapse="false" text-align="start"
51 font-family="monospace" background-color="#edf7f4"
52 linefeed-treatment="preserve"
53 space-before="0em" space-after="0em">
54 <xsl:apply-templates/>
55 </fo:block>
56</xsl:template>
57
58<!-- workaround bug in passivetex fo output for itemizedlist -->
59<xsl:template match="itemizedlist/listitem">
60 <xsl:variable name="id">
61 <xsl:call-template name="object.id"/></xsl:variable>
62 <xsl:variable name="itemsymbol">
63 <xsl:call-template name="list.itemsymbol">
64 <xsl:with-param name="node" select="parent::itemizedlist"/>
65 </xsl:call-template>
66 </xsl:variable>
67 <xsl:variable name="item.contents">
68 <fo:list-item-label end-indent="label-end()">
69 <fo:block>
70 <xsl:choose>
71 <xsl:when test="$itemsymbol='disc'">&#x2022;</xsl:when>
72 <xsl:when test="$itemsymbol='bullet'">&#x2022;</xsl:when>
73 <xsl:otherwise>&#x2022;</xsl:otherwise>
74 </xsl:choose>
75 </fo:block>
76 </fo:list-item-label>
77 <fo:list-item-body start-indent="body-start()">
78 <xsl:apply-templates/> <!-- removed extra block wrapper -->
79 </fo:list-item-body>
80 </xsl:variable>
81 <xsl:choose>
82 <xsl:when test="parent::*/@spacing = 'compact'">
83 <fo:list-item id="{$id}"
84 xsl:use-attribute-sets="compact.list.item.spacing">
85 <xsl:copy-of select="$item.contents"/>
86 </fo:list-item>
87 </xsl:when>
88 <xsl:otherwise>
89 <fo:list-item id="{$id}" xsl:use-attribute-sets="list.item.spacing">
90 <xsl:copy-of select="$item.contents"/>
91 </fo:list-item>
92 </xsl:otherwise>
93 </xsl:choose>
94</xsl:template>
95
96<!-- workaround bug in passivetex fo output for orderedlist -->
97<xsl:template match="orderedlist/listitem">
98 <xsl:variable name="id">
99 <xsl:call-template name="object.id"/></xsl:variable>
100 <xsl:variable name="item.contents">
101 <fo:list-item-label end-indent="label-end()">
102 <fo:block>
103 <xsl:apply-templates select="." mode="item-number"/>
104 </fo:block>
105 </fo:list-item-label>
106 <fo:list-item-body start-indent="body-start()">
107 <xsl:apply-templates/> <!-- removed extra block wrapper -->
108 </fo:list-item-body>
109 </xsl:variable>
110 <xsl:choose>
111 <xsl:when test="parent::*/@spacing = 'compact'">
112 <fo:list-item id="{$id}"
113 xsl:use-attribute-sets="compact.list.item.spacing">
114 <xsl:copy-of select="$item.contents"/>
115 </fo:list-item>
116 </xsl:when>
117 <xsl:otherwise>
118 <fo:list-item id="{$id}" xsl:use-attribute-sets="list.item.spacing">
119 <xsl:copy-of select="$item.contents"/>
120 </fo:list-item>
121 </xsl:otherwise>
122 </xsl:choose>
123</xsl:template>
124
125<!-- workaround bug in passivetex fo output for variablelist -->
126<xsl:param name="variablelist.as.blocks" select="1"/>
127<xsl:template match="varlistentry" mode="vl.as.blocks">
128 <xsl:variable name="id">
129 <xsl:call-template name="object.id"/></xsl:variable>
130 <fo:block id="{$id}" xsl:use-attribute-sets="list.item.spacing"
131 keep-together.within-column="always"
132 keep-with-next.within-column="always">
133 <xsl:apply-templates select="term"/>
134 </fo:block>
135 <fo:block start-indent="0.5in" end-indent="0in"
136 space-after.minimum="0.2em"
137 space-after.optimum="0.4em"
138 space-after.maximum="0.6em">
139 <fo:block>
140 <xsl:apply-templates select="listitem"/>
141 </fo:block>
142 </fo:block>
143</xsl:template>
144
145
146<!-- workaround bug in footers: force right-align w/two 80|30 cols -->
147<xsl:template name="footer.table">
148 <xsl:param name="pageclass" select="''"/>
149 <xsl:param name="sequence" select="''"/>
150 <xsl:param name="gentext-key" select="''"/>
151 <xsl:choose>
152 <xsl:when test="$pageclass = 'index'">
153 <xsl:attribute name="margin-left">0pt</xsl:attribute>
154 </xsl:when>
155 </xsl:choose>
156 <xsl:variable name="candidate">
157 <fo:table table-layout="fixed" width="100%">
158 <fo:table-column column-number="1" column-width="80%"/>
159 <fo:table-column column-number="2" column-width="20%"/>
160 <fo:table-body>
161 <fo:table-row height="14pt">
162 <fo:table-cell text-align="left" display-align="after">
163 <xsl:attribute name="relative-align">baseline</xsl:attribute>
164 <fo:block>
165 <fo:block> </fo:block><!-- empty cell -->
166 </fo:block>
167 </fo:table-cell>
168 <fo:table-cell text-align="center" display-align="after">
169 <xsl:attribute name="relative-align">baseline</xsl:attribute>
170 <fo:block>
171 <xsl:call-template name="footer.content">
172 <xsl:with-param name="pageclass" select="$pageclass"/>
173 <xsl:with-param name="sequence" select="$sequence"/>
174 <xsl:with-param name="position" select="'center'"/>
175 <xsl:with-param name="gentext-key" select="$gentext-key"/>
176 </xsl:call-template>
177 </fo:block>
178 </fo:table-cell>
179 </fo:table-row>
180 </fo:table-body>
181 </fo:table>
182 </xsl:variable>
183 <!-- Really output a footer? -->
184 <xsl:choose>
185 <xsl:when test="$pageclass='titlepage' and $gentext-key='book'
186 and $sequence='first'">
187 <!-- no, book titlepages have no footers at all -->
188 </xsl:when>
189 <xsl:when test="$sequence = 'blank' and $footers.on.blank.pages = 0">
190 <!-- no output -->
191 </xsl:when>
192 <xsl:otherwise>
193 <xsl:copy-of select="$candidate"/>
194 </xsl:otherwise>
195 </xsl:choose>
196</xsl:template>
197
198
199<!-- fix bug in headers: force right-align w/two 40|60 cols -->
200<xsl:template name="header.table">
201 <xsl:param name="pageclass" select="''"/>
202 <xsl:param name="sequence" select="''"/>
203 <xsl:param name="gentext-key" select="''"/>
204 <xsl:choose>
205 <xsl:when test="$pageclass = 'index'">
206 <xsl:attribute name="margin-left">0pt</xsl:attribute>
207 </xsl:when>
208 </xsl:choose>
209 <xsl:variable name="candidate">
210 <fo:table table-layout="fixed" width="100%">
211 <xsl:call-template name="head.sep.rule">
212 <xsl:with-param name="pageclass" select="$pageclass"/>
213 <xsl:with-param name="sequence" select="$sequence"/>
214 <xsl:with-param name="gentext-key" select="$gentext-key"/>
215 </xsl:call-template>
216 <fo:table-column column-number="1" column-width="40%"/>
217 <fo:table-column column-number="2" column-width="60%"/>
218 <fo:table-body>
219 <fo:table-row height="14pt">
220 <fo:table-cell text-align="left" display-align="before">
221 <xsl:attribute name="relative-align">baseline</xsl:attribute>
222 <fo:block>
223 <fo:block> </fo:block><!-- empty cell -->
224 </fo:block>
225 </fo:table-cell>
226 <fo:table-cell text-align="center" display-align="before">
227 <xsl:attribute name="relative-align">baseline</xsl:attribute>
228 <fo:block>
229 <xsl:call-template name="header.content">
230 <xsl:with-param name="pageclass" select="$pageclass"/>
231 <xsl:with-param name="sequence" select="$sequence"/>
232 <xsl:with-param name="position" select="'center'"/>
233 <xsl:with-param name="gentext-key" select="$gentext-key"/>
234 </xsl:call-template>
235 </fo:block>
236 </fo:table-cell>
237 </fo:table-row>
238 </fo:table-body>
239 </fo:table>
240 </xsl:variable>
241 <!-- Really output a header? -->
242 <xsl:choose>
243 <xsl:when test="$pageclass = 'titlepage' and $gentext-key = 'book'
244 and $sequence='first'">
245 <!-- no, book titlepages have no headers at all -->
246 </xsl:when>
247 <xsl:when test="$sequence = 'blank' and $headers.on.blank.pages = 0">
248 <!-- no output -->
249 </xsl:when>
250 <xsl:otherwise>
251 <xsl:copy-of select="$candidate"/>
252 </xsl:otherwise>
253 </xsl:choose>
254</xsl:template>
255
256
257</xsl:stylesheet>
diff --git a/bz-html.xsl b/bz-html.xsl
new file mode 100644
index 0000000..1785fff
--- /dev/null
+++ b/bz-html.xsl
@@ -0,0 +1,20 @@
1<?xml version="1.0"?> <!-- -*- sgml -*- -->
2<!DOCTYPE xsl:stylesheet [ <!ENTITY bz-css SYSTEM "./bzip.css"> ]>
3
4<xsl:stylesheet
5 xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
6
7<xsl:import href="http://docbook.sourceforge.net/release/xsl/current/html/docbook.xsl"/>
8<xsl:import href="bz-common.xsl"/>
9
10<!-- use 8859-1 encoding -->
11<xsl:output method="html" encoding="ISO-8859-1" indent="yes"/>
12
13<!-- we include the css directly when generating one large file -->
14<xsl:template name="user.head.content">
15 <style type="text/css" media="screen">
16 <xsl:text>&bz-css;</xsl:text>
17 </style>
18</xsl:template>
19
20</xsl:stylesheet>
diff --git a/bzip.css b/bzip.css
new file mode 100644
index 0000000..43193d8
--- /dev/null
+++ b/bzip.css
@@ -0,0 +1,74 @@
1/* Colours:
2#74240f dark brown h1, h2, h3, h4
3#336699 medium blue links
4#339999 turquoise link hover colour
5#202020 almost black general text
6#761596 purple md5sum text
7#626262 dark gray pre border
8#eeeeee very light gray pre background
9#f2f2f9 very light blue nav table background
10#3366cc medium blue nav table border
11*/
12
13a, a:link, a:visited, a:active { color: #336699; }
14a:hover { color: #339999; }
15
16body { font: 80%/126% sans-serif; }
17h1, h2, h3, h4 { color: #74240f; }
18
19dt { color: #336699; font-weight: bold }
20dd {
21 margin-left: 1.5em;
22 padding-bottom: 0.8em;
23}
24
25/* -- ruler -- */
26div.hr_blue {
27 height: 3px;
28 background:#ffffff url("/images/hr_blue.png") repeat-x; }
29div.hr_blue hr { display:none; }
30
31/* release styles */
32#release p { margin-top: 0.4em; }
33#release .md5sum { color: #761596; }
34
35
36/* ------ styles for docs|manuals|howto ------ */
37/* -- lists -- */
38ul {
39 margin: 0px 4px 16px 16px;
40 padding: 0px;
41 list-style: url("/images/li-blue.png");
42}
43ul li {
44 margin-bottom: 10px;
45}
46ul ul {
47 list-style-type: none;
48 list-style-image: none;
49 margin-left: 0px;
50}
51
52/* header / footer nav tables */
53table.nav {
54 border: solid 1px #3366cc;
55 background: #f2f2f9;
56 background-color: #f2f2f9;
57 margin-bottom: 0.5em;
58}
59/* don't have underlined links in chunked nav menus */
60table.nav a { text-decoration: none; }
61table.nav a:hover { text-decoration: underline; }
62table.nav td { font-size: 85%; }
63
64code, tt, pre { font-size: 120%; }
65code, tt { color: #761596; }
66
67div.literallayout, pre.programlisting, pre.screen {
68 color: #000000;
69 padding: 0.5em;
70 background: #eeeeee;
71 border: 1px solid #626262;
72 background-color: #eeeeee;
73 margin: 4px 0px 4px 0px;
74}
diff --git a/bzip2.1 b/bzip2.1
index 623435c..d2c0661 100644
--- a/bzip2.1
+++ b/bzip2.1
@@ -1,7 +1,7 @@
1.PU 1.PU
2.TH bzip2 1 2.TH bzip2 1
3.SH NAME 3.SH NAME
4bzip2, bunzip2 \- a block-sorting file compressor, v1.0.2 4bzip2, bunzip2 \- a block-sorting file compressor, v1.0.3
5.br 5.br
6bzcat \- decompresses files to stdout 6bzcat \- decompresses files to stdout
7.br 7.br
@@ -405,19 +405,19 @@ I/O error messages are not as helpful as they could be.
405tries hard to detect I/O errors and exit cleanly, but the details of 405tries hard to detect I/O errors and exit cleanly, but the details of
406what the problem is sometimes seem rather misleading. 406what the problem is sometimes seem rather misleading.
407 407
408This manual page pertains to version 1.0.2 of 408This manual page pertains to version 1.0.3 of
409.I bzip2. 409.I bzip2.
410Compressed data created by this version is entirely forwards and 410Compressed data created by this version is entirely forwards and
411backwards compatible with the previous public releases, versions 411backwards compatible with the previous public releases, versions
4120.1pl2, 0.9.0, 0.9.5, 1.0.0 and 1.0.1, but with the following 4120.1pl2, 0.9.0, 0.9.5, 1.0.0, 1.0.1 and 1.0.2, but with the following
413exception: 0.9.0 and above can correctly decompress multiple 413exception: 0.9.0 and above can correctly decompress multiple
414concatenated compressed files. 0.1pl2 cannot do this; it will stop 414concatenated compressed files. 0.1pl2 cannot do this; it will stop
415after decompressing just the first file in the stream. 415after decompressing just the first file in the stream.
416 416
417.I bzip2recover 417.I bzip2recover
418versions prior to this one, 1.0.2, used 32-bit integers to represent 418versions prior to 1.0.2 used 32-bit integers to represent
419bit positions in compressed files, so it could not handle compressed 419bit positions in compressed files, so they could not handle compressed
420files more than 512 megabytes long. Version 1.0.2 and above uses 420files more than 512 megabytes long. Versions 1.0.2 and above use
42164-bit ints on some platforms which support them (GNU supported 42164-bit ints on some platforms which support them (GNU supported
422targets, and Windows). To establish whether or not bzip2recover was 422targets, and Windows). To establish whether or not bzip2recover was
423built with such a limitation, run it without arguments. In any event 423built with such a limitation, run it without arguments. In any event
@@ -427,9 +427,9 @@ with MaybeUInt64 set to be an unsigned 64-bit integer.
427 427
428 428
429.SH AUTHOR 429.SH AUTHOR
430Julian Seward, jseward@acm.org. 430Julian Seward, jsewardbzip.org.
431 431
432http://sources.redhat.com/bzip2 432http://www.bzip.org
433 433
434The ideas embodied in 434The ideas embodied in
435.I bzip2 435.I bzip2
@@ -447,6 +447,7 @@ source distribution for pointers to sources of documentation. Christian
447von Roques encouraged me to look for faster sorting algorithms, so as to 447von Roques encouraged me to look for faster sorting algorithms, so as to
448speed up compression. Bela Lubkin encouraged me to improve the 448speed up compression. Bela Lubkin encouraged me to improve the
449worst-case compression performance. 449worst-case compression performance.
450Donna Robinson XMLised the documentation.
450The bz* scripts are derived from those of GNU gzip. 451The bz* scripts are derived from those of GNU gzip.
451Many people sent patches, helped 452Many people sent patches, helped
452with portability problems, lent machines, gave advice and were generally 453with portability problems, lent machines, gave advice and were generally
diff --git a/bzip2.1.preformatted b/bzip2.1.preformatted
index 0f20cb5..129ca83 100644
--- a/bzip2.1.preformatted
+++ b/bzip2.1.preformatted
@@ -3,43 +3,43 @@ bzip2(1) bzip2(1)
3 3
4 4
5NNAAMMEE 5NNAAMMEE
6 bzip2, bunzip2 - a block-sorting file compressor, v1.0.2 6 bzip2, bunzip2 − a blockâ€sorting file compressor, v1.0.3
7 bzcat - decompresses files to stdout 7 bzcat − decompresses files to stdout
8 bzip2recover - recovers data from damaged bzip2 files 8 bzip2recover − recovers data from damaged bzip2 files
9 9
10 10
11SSYYNNOOPPSSIISS 11SSYYNNOOPPSSIISS
12 bbzziipp22 [ --ccddffkkqqssttvvzzVVLL112233445566778899 ] [ _f_i_l_e_n_a_m_e_s _._._. ] 12 bbzziipp22 [ −−ccddffkkqqssttvvzzVVLL112233445566778899 ] [ _f_i_l_e_n_a_m_e_s _._._. ]
13 bbuunnzziipp22 [ --ffkkvvssVVLL ] [ _f_i_l_e_n_a_m_e_s _._._. ] 13 bbuunnzziipp22 [ −−ffkkvvssVVLL ] [ _f_i_l_e_n_a_m_e_s _._._. ]
14 bbzzccaatt [ --ss ] [ _f_i_l_e_n_a_m_e_s _._._. ] 14 bbzzccaatt [ −−ss ] [ _f_i_l_e_n_a_m_e_s _._._. ]
15 bbzziipp22rreeccoovveerr _f_i_l_e_n_a_m_e 15 bbzziipp22rreeccoovveerr _f_i_l_e_n_a_m_e
16 16
17 17
18DDEESSCCRRIIPPTTIIOONN 18DDEESSCCRRIIPPTTIIOONN
19 _b_z_i_p_2 compresses files using the Burrows-Wheeler block 19 _b_z_i_p_2 compresses files using the Burrowsâ€Wheeler block
20 sorting text compression algorithm, and Huffman coding. 20 sorting text compression algorithm, and Huffman coding.
21 Compression is generally considerably better than that 21 Compression is generally considerably better than that
22 achieved by more conventional LZ77/LZ78-based compressors, 22 achieved by more conventional LZ77/LZ78â€based compressors,
23 and approaches the performance of the PPM family of sta­ 23 and approaches the performance of the PPM family of sta­
24 tistical compressors. 24 tistical compressors.
25 25
26 The command-line options are deliberately very similar to 26 The commandâ€line options are deliberately very similar to
27 those of _G_N_U _g_z_i_p_, but they are not identical. 27 those of _G_N_U _g_z_i_p_, but they are not identical.
28 28
29 _b_z_i_p_2 expects a list of file names to accompany the com­ 29 _b_z_i_p_2 expects a list of file names to accompany the com­
30 mand-line flags. Each file is replaced by a compressed 30 mandâ€line flags. Each file is replaced by a compressed
31 version of itself, with the name "original_name.bz2". 31 version of itself, with the name "original_name.bz2".
32 Each compressed file has the same modification date, per­ 32 Each compressed file has the same modification date, per­
33 missions, and, when possible, ownership as the correspond­ 33 missions, and, when possible, ownership as the correspond­
34 ing original, so that these properties can be correctly 34 ing original, so that these properties can be correctly
35 restored at decompression time. File name handling is 35 restored at decompression time. File name handling is
36 naive in the sense that there is no mechanism for preserv­ 36 naive in the sense that there is no mechanism for preserv­
37 ing original file names, permissions, ownerships or dates 37 ing original file names, permissions, ownerships or dates
38 in filesystems which lack these concepts, or have serious 38 in filesystems which lack these concepts, or have serious
39 file name length restrictions, such as MS-DOS. 39 file name length restrictions, such as MSâ€DOS.
40 40
41 _b_z_i_p_2 and _b_u_n_z_i_p_2 will by default not overwrite existing 41 _b_z_i_p_2 and _b_u_n_z_i_p_2 will by default not overwrite existing
42 files. If you want this to happen, specify the -f flag. 42 files. If you want this to happen, specify the −f flag.
43 43
44 If no file names are specified, _b_z_i_p_2 compresses from 44 If no file names are specified, _b_z_i_p_2 compresses from
45 standard input to standard output. In this case, _b_z_i_p_2 45 standard input to standard output. In this case, _b_z_i_p_2
@@ -47,7 +47,7 @@ DDEESSCCRRIIPPTTIIOONN
47 this would be entirely incomprehensible and therefore 47 this would be entirely incomprehensible and therefore
48 pointless. 48 pointless.
49 49
50 _b_u_n_z_i_p_2 (or _b_z_i_p_2 _-_d_) decompresses all specified files. 50 _b_u_n_z_i_p_2 (or _b_z_i_p_2 _−_d_) decompresses all specified files.
51 Files which were not created by _b_z_i_p_2 will be detected and 51 Files which were not created by _b_z_i_p_2 will be detected and
52 ignored, and a warning issued. _b_z_i_p_2 attempts to guess 52 ignored, and a warning issued. _b_z_i_p_2 attempts to guess
53 the filename for the decompressed file from that of the 53 the filename for the decompressed file from that of the
@@ -64,26 +64,26 @@ DDEESSCCRRIIPPTTIIOONN
64 guess the name of the original file, and uses the original 64 guess the name of the original file, and uses the original
65 name with _._o_u_t appended. 65 name with _._o_u_t appended.
66 66
67 As with compression, supplying no filenames causes decom­ 67 As with compression, supplying no filenames causes decom­
68 pression from standard input to standard output. 68 pression from standard input to standard output.
69 69
70 _b_u_n_z_i_p_2 will correctly decompress a file which is the con­ 70 _b_u_n_z_i_p_2 will correctly decompress a file which is the con­
71 catenation of two or more compressed files. The result is 71 catenation of two or more compressed files. The result is
72 the concatenation of the corresponding uncompressed files. 72 the concatenation of the corresponding uncompressed files.
73 Integrity testing (-t) of concatenated compressed files is 73 Integrity testing (−t) of concatenated compressed files is
74 also supported. 74 also supported.
75 75
76 You can also compress or decompress files to the standard 76 You can also compress or decompress files to the standard
77 output by giving the -c flag. Multiple files may be com­ 77 output by giving the −c flag. Multiple files may be com­
78 pressed and decompressed like this. The resulting outputs 78 pressed and decompressed like this. The resulting outputs
79 are fed sequentially to stdout. Compression of multiple 79 are fed sequentially to stdout. Compression of multiple
80 files in this manner generates a stream containing multi­ 80 files in this manner generates a stream containing multi­
81 ple compressed file representations. Such a stream can be 81 ple compressed file representations. Such a stream can be
82 decompressed correctly only by _b_z_i_p_2 version 0.9.0 or 82 decompressed correctly only by _b_z_i_p_2 version 0.9.0 or
83 later. Earlier versions of _b_z_i_p_2 will stop after decom­ 83 later. Earlier versions of _b_z_i_p_2 will stop after decom­
84 pressing the first file in the stream. 84 pressing the first file in the stream.
85 85
86 _b_z_c_a_t (or _b_z_i_p_2 _-_d_c_) decompresses all specified files to 86 _b_z_c_a_t (or _b_z_i_p_2 _â€_d_c_) decompresses all specified files to
87 the standard output. 87 the standard output.
88 88
89 _b_z_i_p_2 will read arguments from the environment variables 89 _b_z_i_p_2 will read arguments from the environment variables
@@ -99,15 +99,15 @@ DDEESSCCRRIIPPTTIIOONN
99 most file compressors) is coded at about 8.05 bits per 99 most file compressors) is coded at about 8.05 bits per
100 byte, giving an expansion of around 0.5%. 100 byte, giving an expansion of around 0.5%.
101 101
102 As a self-check for your protection, _b_z_i_p_2 uses 32-bit 102 As a selfâ€check for your protection, _b_z_i_p_2 uses 32â€bit
103 CRCs to make sure that the decompressed version of a file 103 CRCs to make sure that the decompressed version of a file
104 is identical to the original. This guards against corrup­ 104 is identical to the original. This guards against corrup­
105 tion of the compressed data, and against undetected bugs 105 tion of the compressed data, and against undetected bugs
106 in _b_z_i_p_2 (hopefully very unlikely). The chances of data 106 in _b_z_i_p_2 (hopefully very unlikely). The chances of data
107 corruption going undetected is microscopic, about one 107 corruption going undetected is microscopic, about one
108 chance in four billion for each file processed. Be aware, 108 chance in four billion for each file processed. Be aware,
109 though, that the check occurs upon decompression, so it 109 though, that the check occurs upon decompression, so it
110 can only tell you that something is wrong. It can't help 110 can only tell you that something is wrong. It can’t help
111 you recover the original uncompressed data. You can use 111 you recover the original uncompressed data. You can use
112 _b_z_i_p_2_r_e_c_o_v_e_r to try to recover data from damaged files. 112 _b_z_i_p_2_r_e_c_o_v_e_r to try to recover data from damaged files.
113 113
@@ -118,41 +118,41 @@ DDEESSCCRRIIPPTTIIOONN
118 118
119 119
120OOPPTTIIOONNSS 120OOPPTTIIOONNSS
121 --cc ----ssttddoouutt 121 −−cc â€â€â€â€ssttddoouutt
122 Compress or decompress to standard output. 122 Compress or decompress to standard output.
123 123
124 --dd ----ddeeccoommpprreessss 124 −−dd â€â€â€â€ddeeccoommpprreessss
125 Force decompression. _b_z_i_p_2_, _b_u_n_z_i_p_2 and _b_z_c_a_t are 125 Force decompression. _b_z_i_p_2_, _b_u_n_z_i_p_2 and _b_z_c_a_t are
126 really the same program, and the decision about 126 really the same program, and the decision about
127 what actions to take is done on the basis of which 127 what actions to take is done on the basis of which
128 name is used. This flag overrides that mechanism, 128 name is used. This flag overrides that mechanism,
129 and forces _b_z_i_p_2 to decompress. 129 and forces _b_z_i_p_2 to decompress.
130 130
131 --zz ----ccoommpprreessss 131 −−zz â€â€â€â€ccoommpprreessss
132 The complement to -d: forces compression, 132 The complement to −d: forces compression,
133 regardless of the invocation name. 133 regardless of the invocation name.
134 134
135 --tt ----tteesstt 135 −−tt â€â€â€â€tteesstt
136 Check integrity of the specified file(s), but don't 136 Check integrity of the specified file(s), but don’t
137 decompress them. This really performs a trial 137 decompress them. This really performs a trial
138 decompression and throws away the result. 138 decompression and throws away the result.
139 139
140 --ff ----ffoorrccee 140 −−ff â€â€â€â€ffoorrccee
141 Force overwrite of output files. Normally, _b_z_i_p_2 141 Force overwrite of output files. Normally, _b_z_i_p_2
142 will not overwrite existing output files. Also 142 will not overwrite existing output files. Also
143 forces _b_z_i_p_2 to break hard links to files, which it 143 forces _b_z_i_p_2 to break hard links to files, which it
144 otherwise wouldn't do. 144 otherwise wouldn’t do.
145 145
146 bzip2 normally declines to decompress files which 146 bzip2 normally declines to decompress files which
147 don't have the correct magic header bytes. If 147 don’t have the correct magic header bytes. If
148 forced (-f), however, it will pass such files 148 forced (â€f), however, it will pass such files
149 through unmodified. This is how GNU gzip behaves. 149 through unmodified. This is how GNU gzip behaves.
150 150
151 --kk ----kkeeeepp 151 −−kk â€â€â€â€kkeeeepp
152 Keep (don't delete) input files during compression 152 Keep (don’t delete) input files during compression
153 or decompression. 153 or decompression.
154 154
155 --ss ----ssmmaallll 155 −−ss â€â€â€â€ssmmaallll
156 Reduce memory usage, for compression, decompression 156 Reduce memory usage, for compression, decompression
157 and testing. Files are decompressed and tested 157 and testing. Files are decompressed and tested
158 using a modified algorithm which only requires 2.5 158 using a modified algorithm which only requires 2.5
@@ -160,46 +160,46 @@ OOPPTTIIOONNSS
160 decompressed in 2300k of memory, albeit at about 160 decompressed in 2300k of memory, albeit at about
161 half the normal speed. 161 half the normal speed.
162 162
163 During compression, -s selects a block size of 163 During compression, −s selects a block size of
164 200k, which limits memory use to around the same 164 200k, which limits memory use to around the same
165 figure, at the expense of your compression ratio. 165 figure, at the expense of your compression ratio.
166 In short, if your machine is low on memory (8 166 In short, if your machine is low on memory (8
167 megabytes or less), use -s for everything. See 167 megabytes or less), use −s for everything. See
168 MEMORY MANAGEMENT below. 168 MEMORY MANAGEMENT below.
169 169
170 --qq ----qquuiieett 170 −−qq â€â€â€â€qquuiieett
171 Suppress non-essential warning messages. Messages 171 Suppress nonâ€essential warning messages. Messages
172 pertaining to I/O errors and other critical events 172 pertaining to I/O errors and other critical events
173 will not be suppressed. 173 will not be suppressed.
174 174
175 --vv ----vveerrbboossee 175 −−vv â€â€â€â€vveerrbboossee
176 Verbose mode -- show the compression ratio for each 176 Verbose mode â€â€ show the compression ratio for each
177 file processed. Further -v's increase the ver­ 177 file processed. Further −v’s increase the ver­
178 bosity level, spewing out lots of information which 178 bosity level, spewing out lots of information which
179 is primarily of interest for diagnostic purposes. 179 is primarily of interest for diagnostic purposes.
180 180
181 --LL ----lliicceennssee --VV ----vveerrssiioonn 181 −−LL â€â€â€â€lliicceennssee â€â€VV â€â€â€â€vveerrssiioonn
182 Display the software version, license terms and 182 Display the software version, license terms and
183 conditions. 183 conditions.
184 184
185 --11 ((oorr ----ffaasstt)) ttoo --99 ((oorr ----bbeesstt)) 185 −−11 ((oorr −−−−ffaasstt)) ttoo −−99 ((oorr −−−−bbeesstt))
186 Set the block size to 100 k, 200 k .. 900 k when 186 Set the block size to 100 k, 200 k .. 900 k when
187 compressing. Has no effect when decompressing. 187 compressing. Has no effect when decompressing.
188 See MEMORY MANAGEMENT below. The --fast and --best 188 See MEMORY MANAGEMENT below. The −−fast and −−best
189 aliases are primarily for GNU gzip compatibility. 189 aliases are primarily for GNU gzip compatibility.
190 In particular, --fast doesn't make things signifi­ 190 In particular, −−fast doesn’t make things signifi­
191 cantly faster. And --best merely selects the 191 cantly faster. And −−best merely selects the
192 default behaviour. 192 default behaviour.
193 193
194 ---- Treats all subsequent arguments as file names, even 194 −− Treats all subsequent arguments as file names, even
195 if they start with a dash. This is so you can han­ 195 if they start with a dash. This is so you can han­
196 dle files with names beginning with a dash, for 196 dle files with names beginning with a dash, for
197 example: bzip2 -- -myfilename. 197 example: bzip2 −†−myfilename.
198 198
199 ----rreeppeettiittiivvee--ffaasstt ----rreeppeettiittiivvee--bbeesstt 199 −−â€â€rreeppeettiittiivveeâ€â€ffaasstt â€â€â€â€rreeppeettiittiivveeâ€â€bbeesstt
200 These flags are redundant in versions 0.9.5 and 200 These flags are redundant in versions 0.9.5 and
201 above. They provided some coarse control over the 201 above. They provided some coarse control over the
202 behaviour of the sorting algorithm in earlier ver­ 202 behaviour of the sorting algorithm in earlier ver­
203 sions, which was sometimes useful. 0.9.5 and above 203 sions, which was sometimes useful. 0.9.5 and above
204 have an improved algorithm which renders these 204 have an improved algorithm which renders these
205 flags irrelevant. 205 flags irrelevant.
@@ -209,13 +209,13 @@ MMEEMMOORRYY MMAANNAAGGEEMMEENNTT
209 _b_z_i_p_2 compresses large files in blocks. The block size 209 _b_z_i_p_2 compresses large files in blocks. The block size
210 affects both the compression ratio achieved, and the 210 affects both the compression ratio achieved, and the
211 amount of memory needed for compression and decompression. 211 amount of memory needed for compression and decompression.
212 The flags -1 through -9 specify the block size to be 212 The flags −1 through −9 specify the block size to be
213 100,000 bytes through 900,000 bytes (the default) respec­ 213 100,000 bytes through 900,000 bytes (the default) respec­
214 tively. At decompression time, the block size used for 214 tively. At decompression time, the block size used for
215 compression is read from the header of the compressed 215 compression is read from the header of the compressed
216 file, and _b_u_n_z_i_p_2 then allocates itself just enough memory 216 file, and _b_u_n_z_i_p_2 then allocates itself just enough memory
217 to decompress the file. Since block sizes are stored in 217 to decompress the file. Since block sizes are stored in
218 compressed files, it follows that the flags -1 to -9 are 218 compressed files, it follows that the flags −1 to −9 are
219 irrelevant to and so ignored during decompression. 219 irrelevant to and so ignored during decompression.
220 220
221 Compression and decompression requirements, in bytes, can 221 Compression and decompression requirements, in bytes, can
@@ -238,21 +238,21 @@ MMEEMMOORRYY MMAANNAAGGEEMMEENNTT
238 _b_u_n_z_i_p_2 will require about 3700 kbytes to decompress. To 238 _b_u_n_z_i_p_2 will require about 3700 kbytes to decompress. To
239 support decompression of any file on a 4 megabyte machine, 239 support decompression of any file on a 4 megabyte machine,
240 _b_u_n_z_i_p_2 has an option to decompress using approximately 240 _b_u_n_z_i_p_2 has an option to decompress using approximately
241 half this amount of memory, about 2300 kbytes. Decompres­ 241 half this amount of memory, about 2300 kbytes. Decompres­
242 sion speed is also halved, so you should use this option 242 sion speed is also halved, so you should use this option
243 only where necessary. The relevant flag is -s. 243 only where necessary. The relevant flag is â€s.
244 244
245 In general, try and use the largest block size memory con­ 245 In general, try and use the largest block size memory con­
246 straints allow, since that maximises the compression 246 straints allow, since that maximises the compression
247 achieved. Compression and decompression speed are virtu­ 247 achieved. Compression and decompression speed are virtu­
248 ally unaffected by block size. 248 ally unaffected by block size.
249 249
250 Another significant point applies to files which fit in a 250 Another significant point applies to files which fit in a
251 single block -- that means most files you'd encounter 251 single block â€â€ that means most files you’d encounter
252 using a large block size. The amount of real memory 252 using a large block size. The amount of real memory
253 touched is proportional to the size of the file, since the 253 touched is proportional to the size of the file, since the
254 file is smaller than a block. For example, compressing a 254 file is smaller than a block. For example, compressing a
255 file 20,000 bytes long with the flag -9 will cause the 255 file 20,000 bytes long with the flag â€9 will cause the
256 compressor to allocate around 7600k of memory, but only 256 compressor to allocate around 7600k of memory, but only
257 touch 400k + 20000 * 8 = 560 kbytes of it. Similarly, the 257 touch 400k + 20000 * 8 = 560 kbytes of it. Similarly, the
258 decompressor will allocate 3700k but only touch 100k + 258 decompressor will allocate 3700k but only touch 100k +
@@ -260,59 +260,59 @@ MMEEMMOORRYY MMAANNAAGGEEMMEENNTT
260 260
261 Here is a table which summarises the maximum memory usage 261 Here is a table which summarises the maximum memory usage
262 for different block sizes. Also recorded is the total 262 for different block sizes. Also recorded is the total
263 compressed size for 14 files of the Calgary Text Compres­ 263 compressed size for 14 files of the Calgary Text Compres­
264 sion Corpus totalling 3,141,622 bytes. This column gives 264 sion Corpus totalling 3,141,622 bytes. This column gives
265 some feel for how compression varies with block size. 265 some feel for how compression varies with block size.
266 These figures tend to understate the advantage of larger 266 These figures tend to understate the advantage of larger
267 block sizes for larger files, since the Corpus is domi­ 267 block sizes for larger files, since the Corpus is domi­
268 nated by smaller files. 268 nated by smaller files.
269 269
270 Compress Decompress Decompress Corpus 270 Compress Decompress Decompress Corpus
271 Flag usage usage -s usage Size 271 Flag usage usage â€s usage Size
272 272
273 -1 1200k 500k 350k 914704 273 â€1 1200k 500k 350k 914704
274 -2 2000k 900k 600k 877703 274 â€2 2000k 900k 600k 877703
275 -3 2800k 1300k 850k 860338 275 â€3 2800k 1300k 850k 860338
276 -4 3600k 1700k 1100k 846899 276 â€4 3600k 1700k 1100k 846899
277 -5 4400k 2100k 1350k 845160 277 â€5 4400k 2100k 1350k 845160
278 -6 5200k 2500k 1600k 838626 278 â€6 5200k 2500k 1600k 838626
279 -7 6100k 2900k 1850k 834096 279 â€7 6100k 2900k 1850k 834096
280 -8 6800k 3300k 2100k 828642 280 â€8 6800k 3300k 2100k 828642
281 -9 7600k 3700k 2350k 828642 281 â€9 7600k 3700k 2350k 828642
282 282
283 283
284RREECCOOVVEERRIINNGG DDAATTAA FFRROOMM DDAAMMAAGGEEDD FFIILLEESS 284RREECCOOVVEERRIINNGG DDAATTAA FFRROOMM DDAAMMAAGGEEDD FFIILLEESS
285 _b_z_i_p_2 compresses files in blocks, usually 900kbytes long. 285 _b_z_i_p_2 compresses files in blocks, usually 900kbytes long.
286 Each block is handled independently. If a media or trans­ 286 Each block is handled independently. If a media or trans­
287 mission error causes a multi-block .bz2 file to become 287 mission error causes a multiâ€block .bz2 file to become
288 damaged, it may be possible to recover data from the 288 damaged, it may be possible to recover data from the
289 undamaged blocks in the file. 289 undamaged blocks in the file.
290 290
291 The compressed representation of each block is delimited 291 The compressed representation of each block is delimited
292 by a 48-bit pattern, which makes it possible to find the 292 by a 48â€bit pattern, which makes it possible to find the
293 block boundaries with reasonable certainty. Each block 293 block boundaries with reasonable certainty. Each block
294 also carries its own 32-bit CRC, so damaged blocks can be 294 also carries its own 32â€bit CRC, so damaged blocks can be
295 distinguished from undamaged ones. 295 distinguished from undamaged ones.
296 296
297 _b_z_i_p_2_r_e_c_o_v_e_r is a simple program whose purpose is to 297 _b_z_i_p_2_r_e_c_o_v_e_r is a simple program whose purpose is to
298 search for blocks in .bz2 files, and write each block out 298 search for blocks in .bz2 files, and write each block out
299 into its own .bz2 file. You can then use _b_z_i_p_2 -t to test 299 into its own .bz2 file. You can then use _b_z_i_p_2 −t to test
300 the integrity of the resulting files, and decompress those 300 the integrity of the resulting files, and decompress those
301 which are undamaged. 301 which are undamaged.
302 302
303 _b_z_i_p_2_r_e_c_o_v_e_r takes a single argument, the name of the dam­ 303 _b_z_i_p_2_r_e_c_o_v_e_r takes a single argument, the name of the dam­
304 aged file, and writes a number of files 304 aged file, and writes a number of files
305 "rec00001file.bz2", "rec00002file.bz2", etc, containing 305 "rec00001file.bz2", "rec00002file.bz2", etc, containing
306 the extracted blocks. The output filenames are 306 the extracted blocks. The output filenames are
307 designed so that the use of wildcards in subsequent pro­ 307 designed so that the use of wildcards in subsequent pro­
308 cessing -- for example, "bzip2 -dc rec*file.bz2 > recov­ 308 cessing â€â€ for example, "bzip2 â€dc rec*file.bz2 > recov­
309 ered_data" -- processes the files in the correct order. 309 ered_data" â€â€ processes the files in the correct order.
310 310
311 _b_z_i_p_2_r_e_c_o_v_e_r should be of most use dealing with large .bz2 311 _b_z_i_p_2_r_e_c_o_v_e_r should be of most use dealing with large .bz2
312 files, as these will contain many blocks. It is clearly 312 files, as these will contain many blocks. It is clearly
313 futile to use it on damaged single-block files, since a 313 futile to use it on damaged singleâ€block files, since a
314 damaged block cannot be recovered. If you wish to min­ 314 damaged block cannot be recovered. If you wish to min­
315 imise any potential data loss through media or transmis­ 315 imise any potential data loss through media or transmis­
316 sion errors, you might consider compressing with a smaller 316 sion errors, you might consider compressing with a smaller
317 block size. 317 block size.
318 318
@@ -324,21 +324,21 @@ PPEERRFFOORRMMAANNCCEE NNOOTTEESS
324 ..." (repeated several hundred times) may compress more 324 ..." (repeated several hundred times) may compress more
325 slowly than normal. Versions 0.9.5 and above fare much 325 slowly than normal. Versions 0.9.5 and above fare much
326 better than previous versions in this respect. The ratio 326 better than previous versions in this respect. The ratio
327 between worst-case and average-case compression time is in 327 between worstâ€case and averageâ€case compression time is in
328 the region of 10:1. For previous versions, this figure 328 the region of 10:1. For previous versions, this figure
329 was more like 100:1. You can use the -vvvv option to mon­ 329 was more like 100:1. You can use the −vvvv option to mon­
330 itor progress in great detail, if you want. 330 itor progress in great detail, if you want.
331 331
332 Decompression speed is unaffected by these phenomena. 332 Decompression speed is unaffected by these phenomena.
333 333
334 _b_z_i_p_2 usually allocates several megabytes of memory to 334 _b_z_i_p_2 usually allocates several megabytes of memory to
335 operate in, and then charges all over it in a fairly ran­ 335 operate in, and then charges all over it in a fairly ran­
336 dom fashion. This means that performance, both for com­ 336 dom fashion. This means that performance, both for com­
337 pressing and decompressing, is largely determined by the 337 pressing and decompressing, is largely determined by the
338 speed at which your machine can service cache misses. 338 speed at which your machine can service cache misses.
339 Because of this, small changes to the code to reduce the 339 Because of this, small changes to the code to reduce the
340 miss rate have been observed to give disproportionately 340 miss rate have been observed to give disproportionately
341 large performance improvements. I imagine _b_z_i_p_2 will per­ 341 large performance improvements. I imagine _b_z_i_p_2 will per­
342 form best on machines with very large caches. 342 form best on machines with very large caches.
343 343
344 344
@@ -348,50 +348,51 @@ CCAAVVEEAATTSS
348 but the details of what the problem is sometimes seem 348 but the details of what the problem is sometimes seem
349 rather misleading. 349 rather misleading.
350 350
351 This manual page pertains to version 1.0.2 of _b_z_i_p_2_. Com­ 351 This manual page pertains to version 1.0.3 of _b_z_i_p_2_. Com­
352 pressed data created by this version is entirely forwards 352 pressed data created by this version is entirely forwards
353 and backwards compatible with the previous public 353 and backwards compatible with the previous public
354 releases, versions 0.1pl2, 0.9.0, 0.9.5, 1.0.0 and 1.0.1, 354 releases, versions 0.1pl2, 0.9.0, 0.9.5, 1.0.0, 1.0.1 and
355 but with the following exception: 0.9.0 and above can cor­ 355 1.0.2, but with the following exception: 0.9.0 and above
356 rectly decompress multiple concatenated compressed files. 356 can correctly decompress multiple concatenated compressed
357 0.1pl2 cannot do this; it will stop after decompressing 357 files. 0.1pl2 cannot do this; it will stop after decom­
358 just the first file in the stream. 358 pressing just the first file in the stream.
359 359
360 _b_z_i_p_2_r_e_c_o_v_e_r versions prior to this one, 1.0.2, used 360 _b_z_i_p_2_r_e_c_o_v_e_r versions prior to 1.0.2 used 32â€bit integers
361 32-bit integers to represent bit positions in compressed 361 to represent bit positions in compressed files, so they
362 files, so it could not handle compressed files more than 362 could not handle compressed files more than 512 megabytes
363 512 megabytes long. Version 1.0.2 and above uses 64-bit 363 long. Versions 1.0.2 and above use 64â€bit ints on some
364 ints on some platforms which support them (GNU supported 364 platforms which support them (GNU supported targets, and
365 targets, and Windows). To establish whether or not 365 Windows). To establish whether or not bzip2recover was
366 bzip2recover was built with such a limitation, run it 366 built with such a limitation, run it without arguments.
367 without arguments. In any event you can build yourself an 367 In any event you can build yourself an unlimited version
368 unlimited version if you can recompile it with MaybeUInt64 368 if you can recompile it with MaybeUInt64 set to be an
369 set to be an unsigned 64-bit integer. 369 unsigned 64â€bit integer.
370 370
371 371
372 372
373 373
374AAUUTTHHOORR 374AAUUTTHHOORR
375 Julian Seward, jseward@acm.org. 375 Julian Seward, jsewardbzip.org.
376 376
377 http://sources.redhat.com/bzip2 377 http://www.bzip.org
378 378
379 The ideas embodied in _b_z_i_p_2 are due to (at least) the fol­ 379 The ideas embodied in _b_z_i_p_2 are due to (at least) the fol­
380 lowing people: Michael Burrows and David Wheeler (for the 380 lowing people: Michael Burrows and David Wheeler (for the
381 block sorting transformation), David Wheeler (again, for 381 block sorting transformation), David Wheeler (again, for
382 the Huffman coder), Peter Fenwick (for the structured cod­ 382 the Huffman coder), Peter Fenwick (for the structured cod­
383 ing model in the original _b_z_i_p_, and many refinements), and 383 ing model in the original _b_z_i_p_, and many refinements), and
384 Alistair Moffat, Radford Neal and Ian Witten (for the 384 Alistair Moffat, Radford Neal and Ian Witten (for the
385 arithmetic coder in the original _b_z_i_p_)_. I am much 385 arithmetic coder in the original _b_z_i_p_)_. I am much
386 indebted for their help, support and advice. See the man­ 386 indebted for their help, support and advice. See the man­
387 ual in the source distribution for pointers to sources of 387 ual in the source distribution for pointers to sources of
388 documentation. Christian von Roques encouraged me to look 388 documentation. Christian von Roques encouraged me to look
389 for faster sorting algorithms, so as to speed up compres­ 389 for faster sorting algorithms, so as to speed up compres­
390 sion. Bela Lubkin encouraged me to improve the worst-case 390 sion. Bela Lubkin encouraged me to improve the worstâ€case
391 compression performance. The bz* scripts are derived from 391 compression performance. Donna Robinson XMLised the docu­
392 those of GNU gzip. Many people sent patches, helped with 392 mentation. The bz* scripts are derived from those of GNU
393 portability problems, lent machines, gave advice and were 393 gzip. Many people sent patches, helped with portability
394 generally helpful. 394 problems, lent machines, gave advice and were generally
395 helpful.
395 396
396 397
397 398
diff --git a/bzip2.c b/bzip2.c
index 807f420..79f87a5 100644
--- a/bzip2.c
+++ b/bzip2.c
@@ -7,7 +7,7 @@
7 This file is a part of bzip2 and/or libbzip2, a program and 7 This file is a part of bzip2 and/or libbzip2, a program and
8 library for lossless, block-sorting data compression. 8 library for lossless, block-sorting data compression.
9 9
10 Copyright (C) 1996-2002 Julian R Seward. All rights reserved. 10 Copyright (C) 1996-2005 Julian R Seward. All rights reserved.
11 11
12 Redistribution and use in source and binary forms, with or without 12 Redistribution and use in source and binary forms, with or without
13 modification, are permitted provided that the following conditions 13 modification, are permitted provided that the following conditions
@@ -41,7 +41,7 @@
41 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 41 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
42 42
43 Julian Seward, Cambridge, UK. 43 Julian Seward, Cambridge, UK.
44 jseward@acm.org 44 jseward@bzip.org
45 bzip2/libbzip2 version 1.0 of 21 March 2000 45 bzip2/libbzip2 version 1.0 of 21 March 2000
46 46
47 This program is based on (at least) the work of: 47 This program is based on (at least) the work of:
@@ -525,6 +525,7 @@ Bool uncompressStream ( FILE *zStream, FILE *stream )
525 UChar obuf[5000]; 525 UChar obuf[5000];
526 UChar unused[BZ_MAX_UNUSED]; 526 UChar unused[BZ_MAX_UNUSED];
527 Int32 nUnused; 527 Int32 nUnused;
528 void* unusedTmpV;
528 UChar* unusedTmp; 529 UChar* unusedTmp;
529 530
530 nUnused = 0; 531 nUnused = 0;
@@ -554,9 +555,10 @@ Bool uncompressStream ( FILE *zStream, FILE *stream )
554 } 555 }
555 if (bzerr != BZ_STREAM_END) goto errhandler; 556 if (bzerr != BZ_STREAM_END) goto errhandler;
556 557
557 BZ2_bzReadGetUnused ( &bzerr, bzf, (void**)(&unusedTmp), &nUnused ); 558 BZ2_bzReadGetUnused ( &bzerr, bzf, &unusedTmpV, &nUnused );
558 if (bzerr != BZ_OK) panic ( "decompress:bzReadGetUnused" ); 559 if (bzerr != BZ_OK) panic ( "decompress:bzReadGetUnused" );
559 560
561 unusedTmp = (UChar*)unusedTmpV;
560 for (i = 0; i < nUnused; i++) unused[i] = unusedTmp[i]; 562 for (i = 0; i < nUnused; i++) unused[i] = unusedTmp[i];
561 563
562 BZ2_bzReadClose ( &bzerr, bzf ); 564 BZ2_bzReadClose ( &bzerr, bzf );
@@ -639,6 +641,7 @@ Bool testStream ( FILE *zStream )
639 UChar obuf[5000]; 641 UChar obuf[5000];
640 UChar unused[BZ_MAX_UNUSED]; 642 UChar unused[BZ_MAX_UNUSED];
641 Int32 nUnused; 643 Int32 nUnused;
644 void* unusedTmpV;
642 UChar* unusedTmp; 645 UChar* unusedTmp;
643 646
644 nUnused = 0; 647 nUnused = 0;
@@ -662,9 +665,10 @@ Bool testStream ( FILE *zStream )
662 } 665 }
663 if (bzerr != BZ_STREAM_END) goto errhandler; 666 if (bzerr != BZ_STREAM_END) goto errhandler;
664 667
665 BZ2_bzReadGetUnused ( &bzerr, bzf, (void**)(&unusedTmp), &nUnused ); 668 BZ2_bzReadGetUnused ( &bzerr, bzf, &unusedTmpV, &nUnused );
666 if (bzerr != BZ_OK) panic ( "test:bzReadGetUnused" ); 669 if (bzerr != BZ_OK) panic ( "test:bzReadGetUnused" );
667 670
671 unusedTmp = (UChar*)unusedTmpV;
668 for (i = 0; i < nUnused; i++) unused[i] = unusedTmp[i]; 672 for (i = 0; i < nUnused; i++) unused[i] = unusedTmp[i];
669 673
670 BZ2_bzReadClose ( &bzerr, bzf ); 674 BZ2_bzReadClose ( &bzerr, bzf );
@@ -828,7 +832,7 @@ void panic ( Char* s )
828 "\n%s: PANIC -- internal consistency error:\n" 832 "\n%s: PANIC -- internal consistency error:\n"
829 "\t%s\n" 833 "\t%s\n"
830 "\tThis is a BUG. Please report it to me at:\n" 834 "\tThis is a BUG. Please report it to me at:\n"
831 "\tjseward@acm.org\n", 835 "\tjseward@bzip.org\n",
832 progName, s ); 836 progName, s );
833 showFileNames(); 837 showFileNames();
834 cleanUpAndFail( 3 ); 838 cleanUpAndFail( 3 );
@@ -908,7 +912,7 @@ void mySIGSEGVorSIGBUScatcher ( IntNative n )
908 " The user's manual, Section 4.3, has more info on (1) and (2).\n" 912 " The user's manual, Section 4.3, has more info on (1) and (2).\n"
909 " \n" 913 " \n"
910 " If you suspect this is a bug in bzip2, or are unsure about (1)\n" 914 " If you suspect this is a bug in bzip2, or are unsure about (1)\n"
911 " or (2), feel free to report it to me at: jseward@acm.org.\n" 915 " or (2), feel free to report it to me at: jseward@bzip.org.\n"
912 " Section 4.3 of the user's manual describes the info a useful\n" 916 " Section 4.3 of the user's manual describes the info a useful\n"
913 " bug report should have. If the manual is available on your\n" 917 " bug report should have. If the manual is available on your\n"
914 " system, please try and read it before mailing me. If you don't\n" 918 " system, please try and read it before mailing me. If you don't\n"
@@ -931,7 +935,7 @@ void mySIGSEGVorSIGBUScatcher ( IntNative n )
931 " The user's manual, Section 4.3, has more info on (2) and (3).\n" 935 " The user's manual, Section 4.3, has more info on (2) and (3).\n"
932 " \n" 936 " \n"
933 " If you suspect this is a bug in bzip2, or are unsure about (2)\n" 937 " If you suspect this is a bug in bzip2, or are unsure about (2)\n"
934 " or (3), feel free to report it to me at: jseward@acm.org.\n" 938 " or (3), feel free to report it to me at: jseward@bzip.org.\n"
935 " Section 4.3 of the user's manual describes the info a useful\n" 939 " Section 4.3 of the user's manual describes the info a useful\n"
936 " bug report should have. If the manual is available on your\n" 940 " bug report should have. If the manual is available on your\n"
937 " system, please try and read it before mailing me. If you don't\n" 941 " system, please try and read it before mailing me. If you don't\n"
@@ -1674,7 +1678,7 @@ void license ( void )
1674 "bzip2, a block-sorting file compressor. " 1678 "bzip2, a block-sorting file compressor. "
1675 "Version %s.\n" 1679 "Version %s.\n"
1676 " \n" 1680 " \n"
1677 " Copyright (C) 1996-2002 by Julian Seward.\n" 1681 " Copyright (C) 1996-2005 by Julian Seward.\n"
1678 " \n" 1682 " \n"
1679 " This program is free software; you can redistribute it and/or modify\n" 1683 " This program is free software; you can redistribute it and/or modify\n"
1680 " it under the terms set out in the LICENSE file, which is included\n" 1684 " it under the terms set out in the LICENSE file, which is included\n"
diff --git a/bzip2.txt b/bzip2.txt
index 6afe358..bf895b6 100644
--- a/bzip2.txt
+++ b/bzip2.txt
@@ -1,6 +1,6 @@
1 1
2NAME 2NAME
3 bzip2, bunzip2 - a block-sorting file compressor, v1.0.2 3 bzip2, bunzip2 - a block-sorting file compressor, v1.0.3
4 bzcat - decompresses files to stdout 4 bzcat - decompresses files to stdout
5 bzip2recover - recovers data from damaged bzip2 files 5 bzip2recover - recovers data from damaged bzip2 files
6 6
@@ -17,20 +17,20 @@ DESCRIPTION
17 sorting text compression algorithm, and Huffman coding. 17 sorting text compression algorithm, and Huffman coding.
18 Compression is generally considerably better than that 18 Compression is generally considerably better than that
19 achieved by more conventional LZ77/LZ78-based compressors, 19 achieved by more conventional LZ77/LZ78-based compressors,
20 and approaches the performance of the PPM family of sta­ 20 and approaches the performance of the PPM family of sta-
21 tistical compressors. 21 tistical compressors.
22 22
23 The command-line options are deliberately very similar to 23 The command-line options are deliberately very similar to
24 those of GNU gzip, but they are not identical. 24 those of GNU gzip, but they are not identical.
25 25
26 bzip2 expects a list of file names to accompany the com­ 26 bzip2 expects a list of file names to accompany the com-
27 mand-line flags. Each file is replaced by a compressed 27 mand-line flags. Each file is replaced by a compressed
28 version of itself, with the name "original_name.bz2". 28 version of itself, with the name "original_name.bz2".
29 Each compressed file has the same modification date, per­ 29 Each compressed file has the same modification date, per-
30 missions, and, when possible, ownership as the correspond­ 30 missions, and, when possible, ownership as the correspond-
31 ing original, so that these properties can be correctly 31 ing original, so that these properties can be correctly
32 restored at decompression time. File name handling is 32 restored at decompression time. File name handling is
33 naive in the sense that there is no mechanism for preserv­ 33 naive in the sense that there is no mechanism for preserv-
34 ing original file names, permissions, ownerships or dates 34 ing original file names, permissions, ownerships or dates
35 in filesystems which lack these concepts, or have serious 35 in filesystems which lack these concepts, or have serious
36 file name length restrictions, such as MS-DOS. 36 file name length restrictions, such as MS-DOS.
@@ -61,23 +61,23 @@ DESCRIPTION
61 guess the name of the original file, and uses the original 61 guess the name of the original file, and uses the original
62 name with .out appended. 62 name with .out appended.
63 63
64 As with compression, supplying no filenames causes decom­ 64 As with compression, supplying no filenames causes decom-
65 pression from standard input to standard output. 65 pression from standard input to standard output.
66 66
67 bunzip2 will correctly decompress a file which is the con­ 67 bunzip2 will correctly decompress a file which is the con-
68 catenation of two or more compressed files. The result is 68 catenation of two or more compressed files. The result is
69 the concatenation of the corresponding uncompressed files. 69 the concatenation of the corresponding uncompressed files.
70 Integrity testing (-t) of concatenated compressed files is 70 Integrity testing (-t) of concatenated compressed files is
71 also supported. 71 also supported.
72 72
73 You can also compress or decompress files to the standard 73 You can also compress or decompress files to the standard
74 output by giving the -c flag. Multiple files may be com­ 74 output by giving the -c flag. Multiple files may be com-
75 pressed and decompressed like this. The resulting outputs 75 pressed and decompressed like this. The resulting outputs
76 are fed sequentially to stdout. Compression of multiple 76 are fed sequentially to stdout. Compression of multiple
77 files in this manner generates a stream containing multi­ 77 files in this manner generates a stream containing multi-
78 ple compressed file representations. Such a stream can be 78 ple compressed file representations. Such a stream can be
79 decompressed correctly only by bzip2 version 0.9.0 or 79 decompressed correctly only by bzip2 version 0.9.0 or
80 later. Earlier versions of bzip2 will stop after decom­ 80 later. Earlier versions of bzip2 will stop after decom-
81 pressing the first file in the stream. 81 pressing the first file in the stream.
82 82
83 bzcat (or bzip2 -dc) decompresses all specified files to 83 bzcat (or bzip2 -dc) decompresses all specified files to
@@ -98,7 +98,7 @@ DESCRIPTION
98 98
99 As a self-check for your protection, bzip2 uses 32-bit 99 As a self-check for your protection, bzip2 uses 32-bit
100 CRCs to make sure that the decompressed version of a file 100 CRCs to make sure that the decompressed version of a file
101 is identical to the original. This guards against corrup­ 101 is identical to the original. This guards against corrup-
102 tion of the compressed data, and against undetected bugs 102 tion of the compressed data, and against undetected bugs
103 in bzip2 (hopefully very unlikely). The chances of data 103 in bzip2 (hopefully very unlikely). The chances of data
104 corruption going undetected is microscopic, about one 104 corruption going undetected is microscopic, about one
@@ -171,7 +171,7 @@ OPTIONS
171 171
172 -v --verbose 172 -v --verbose
173 Verbose mode -- show the compression ratio for each 173 Verbose mode -- show the compression ratio for each
174 file processed. Further -v's increase the ver­ 174 file processed. Further -v's increase the ver-
175 bosity level, spewing out lots of information which 175 bosity level, spewing out lots of information which
176 is primarily of interest for diagnostic purposes. 176 is primarily of interest for diagnostic purposes.
177 177
@@ -184,19 +184,19 @@ OPTIONS
184 compressing. Has no effect when decompressing. 184 compressing. Has no effect when decompressing.
185 See MEMORY MANAGEMENT below. The --fast and --best 185 See MEMORY MANAGEMENT below. The --fast and --best
186 aliases are primarily for GNU gzip compatibility. 186 aliases are primarily for GNU gzip compatibility.
187 In particular, --fast doesn't make things signifi­ 187 In particular, --fast doesn't make things signifi-
188 cantly faster. And --best merely selects the 188 cantly faster. And --best merely selects the
189 default behaviour. 189 default behaviour.
190 190
191 -- Treats all subsequent arguments as file names, even 191 -- Treats all subsequent arguments as file names, even
192 if they start with a dash. This is so you can han­ 192 if they start with a dash. This is so you can han-
193 dle files with names beginning with a dash, for 193 dle files with names beginning with a dash, for
194 example: bzip2 -- -myfilename. 194 example: bzip2 -- -myfilename.
195 195
196 --repetitive-fast --repetitive-best 196 --repetitive-fast --repetitive-best
197 These flags are redundant in versions 0.9.5 and 197 These flags are redundant in versions 0.9.5 and
198 above. They provided some coarse control over the 198 above. They provided some coarse control over the
199 behaviour of the sorting algorithm in earlier ver­ 199 behaviour of the sorting algorithm in earlier ver-
200 sions, which was sometimes useful. 0.9.5 and above 200 sions, which was sometimes useful. 0.9.5 and above
201 have an improved algorithm which renders these 201 have an improved algorithm which renders these
202 flags irrelevant. 202 flags irrelevant.
@@ -207,7 +207,7 @@ MEMORY MANAGEMENT
207 affects both the compression ratio achieved, and the 207 affects both the compression ratio achieved, and the
208 amount of memory needed for compression and decompression. 208 amount of memory needed for compression and decompression.
209 The flags -1 through -9 specify the block size to be 209 The flags -1 through -9 specify the block size to be
210 100,000 bytes through 900,000 bytes (the default) respec­ 210 100,000 bytes through 900,000 bytes (the default) respec-
211 tively. At decompression time, the block size used for 211 tively. At decompression time, the block size used for
212 compression is read from the header of the compressed 212 compression is read from the header of the compressed
213 file, and bunzip2 then allocates itself just enough memory 213 file, and bunzip2 then allocates itself just enough memory
@@ -235,13 +235,13 @@ MEMORY MANAGEMENT
235 bunzip2 will require about 3700 kbytes to decompress. To 235 bunzip2 will require about 3700 kbytes to decompress. To
236 support decompression of any file on a 4 megabyte machine, 236 support decompression of any file on a 4 megabyte machine,
237 bunzip2 has an option to decompress using approximately 237 bunzip2 has an option to decompress using approximately
238 half this amount of memory, about 2300 kbytes. Decompres­ 238 half this amount of memory, about 2300 kbytes. Decompres-
239 sion speed is also halved, so you should use this option 239 sion speed is also halved, so you should use this option
240 only where necessary. The relevant flag is -s. 240 only where necessary. The relevant flag is -s.
241 241
242 In general, try and use the largest block size memory con­ 242 In general, try and use the largest block size memory con-
243 straints allow, since that maximises the compression 243 straints allow, since that maximises the compression
244 achieved. Compression and decompression speed are virtu­ 244 achieved. Compression and decompression speed are virtu-
245 ally unaffected by block size. 245 ally unaffected by block size.
246 246
247 Another significant point applies to files which fit in a 247 Another significant point applies to files which fit in a
@@ -257,11 +257,11 @@ MEMORY MANAGEMENT
257 257
258 Here is a table which summarises the maximum memory usage 258 Here is a table which summarises the maximum memory usage
259 for different block sizes. Also recorded is the total 259 for different block sizes. Also recorded is the total
260 compressed size for 14 files of the Calgary Text Compres­ 260 compressed size for 14 files of the Calgary Text Compres-
261 sion Corpus totalling 3,141,622 bytes. This column gives 261 sion Corpus totalling 3,141,622 bytes. This column gives
262 some feel for how compression varies with block size. 262 some feel for how compression varies with block size.
263 These figures tend to understate the advantage of larger 263 These figures tend to understate the advantage of larger
264 block sizes for larger files, since the Corpus is domi­ 264 block sizes for larger files, since the Corpus is domi-
265 nated by smaller files. 265 nated by smaller files.
266 266
267 Compress Decompress Decompress Corpus 267 Compress Decompress Decompress Corpus
@@ -280,7 +280,7 @@ MEMORY MANAGEMENT
280 280
281RECOVERING DATA FROM DAMAGED FILES 281RECOVERING DATA FROM DAMAGED FILES
282 bzip2 compresses files in blocks, usually 900kbytes long. 282 bzip2 compresses files in blocks, usually 900kbytes long.
283 Each block is handled independently. If a media or trans­ 283 Each block is handled independently. If a media or trans-
284 mission error causes a multi-block .bz2 file to become 284 mission error causes a multi-block .bz2 file to become
285 damaged, it may be possible to recover data from the 285 damaged, it may be possible to recover data from the
286 undamaged blocks in the file. 286 undamaged blocks in the file.
@@ -297,19 +297,19 @@ RECOVERING DATA FROM DAMAGED FILES
297 the integrity of the resulting files, and decompress those 297 the integrity of the resulting files, and decompress those
298 which are undamaged. 298 which are undamaged.
299 299
300 bzip2recover takes a single argument, the name of the dam­ 300 bzip2recover takes a single argument, the name of the dam-
301 aged file, and writes a number of files 301 aged file, and writes a number of files
302 "rec00001file.bz2", "rec00002file.bz2", etc, containing 302 "rec00001file.bz2", "rec00002file.bz2", etc, containing
303 the extracted blocks. The output filenames are 303 the extracted blocks. The output filenames are
304 designed so that the use of wildcards in subsequent pro­ 304 designed so that the use of wildcards in subsequent pro-
305 cessing -- for example, "bzip2 -dc rec*file.bz2 > recov­ 305 cessing -- for example, "bzip2 -dc rec*file.bz2 > recov-
306 ered_data" -- processes the files in the correct order. 306 ered_data" -- processes the files in the correct order.
307 307
308 bzip2recover should be of most use dealing with large .bz2 308 bzip2recover should be of most use dealing with large .bz2
309 files, as these will contain many blocks. It is clearly 309 files, as these will contain many blocks. It is clearly
310 futile to use it on damaged single-block files, since a 310 futile to use it on damaged single-block files, since a
311 damaged block cannot be recovered. If you wish to min­ 311 damaged block cannot be recovered. If you wish to min-
312 imise any potential data loss through media or transmis­ 312 imise any potential data loss through media or transmis-
313 sion errors, you might consider compressing with a smaller 313 sion errors, you might consider compressing with a smaller
314 block size. 314 block size.
315 315
@@ -323,19 +323,19 @@ PERFORMANCE NOTES
323 better than previous versions in this respect. The ratio 323 better than previous versions in this respect. The ratio
324 between worst-case and average-case compression time is in 324 between worst-case and average-case compression time is in
325 the region of 10:1. For previous versions, this figure 325 the region of 10:1. For previous versions, this figure
326 was more like 100:1. You can use the -vvvv option to mon­ 326 was more like 100:1. You can use the -vvvv option to mon-
327 itor progress in great detail, if you want. 327 itor progress in great detail, if you want.
328 328
329 Decompression speed is unaffected by these phenomena. 329 Decompression speed is unaffected by these phenomena.
330 330
331 bzip2 usually allocates several megabytes of memory to 331 bzip2 usually allocates several megabytes of memory to
332 operate in, and then charges all over it in a fairly ran­ 332 operate in, and then charges all over it in a fairly ran-
333 dom fashion. This means that performance, both for com­ 333 dom fashion. This means that performance, both for com-
334 pressing and decompressing, is largely determined by the 334 pressing and decompressing, is largely determined by the
335 speed at which your machine can service cache misses. 335 speed at which your machine can service cache misses.
336 Because of this, small changes to the code to reduce the 336 Because of this, small changes to the code to reduce the
337 miss rate have been observed to give disproportionately 337 miss rate have been observed to give disproportionately
338 large performance improvements. I imagine bzip2 will per­ 338 large performance improvements. I imagine bzip2 will per-
339 form best on machines with very large caches. 339 form best on machines with very large caches.
340 340
341 341
@@ -345,46 +345,47 @@ CAVEATS
345 but the details of what the problem is sometimes seem 345 but the details of what the problem is sometimes seem
346 rather misleading. 346 rather misleading.
347 347
348 This manual page pertains to version 1.0.2 of bzip2. Com­ 348 This manual page pertains to version 1.0.3 of bzip2. Com-
349 pressed data created by this version is entirely forwards 349 pressed data created by this version is entirely forwards
350 and backwards compatible with the previous public 350 and backwards compatible with the previous public
351 releases, versions 0.1pl2, 0.9.0, 0.9.5, 1.0.0 and 1.0.1, 351 releases, versions 0.1pl2, 0.9.0, 0.9.5, 1.0.0, 1.0.1 and
352 but with the following exception: 0.9.0 and above can cor­ 352 1.0.2, but with the following exception: 0.9.0 and above
353 rectly decompress multiple concatenated compressed files. 353 can correctly decompress multiple concatenated compressed
354 0.1pl2 cannot do this; it will stop after decompressing 354 files. 0.1pl2 cannot do this; it will stop after decom-
355 just the first file in the stream. 355 pressing just the first file in the stream.
356 356
357 bzip2recover versions prior to this one, 1.0.2, used 357 bzip2recover versions prior to 1.0.2 used 32-bit integers
358 32-bit integers to represent bit positions in compressed 358 to represent bit positions in compressed files, so they
359 files, so it could not handle compressed files more than 359 could not handle compressed files more than 512 megabytes
360 512 megabytes long. Version 1.0.2 and above uses 64-bit 360 long. Versions 1.0.2 and above use 64-bit ints on some
361 ints on some platforms which support them (GNU supported 361 platforms which support them (GNU supported targets, and
362 targets, and Windows). To establish whether or not 362 Windows). To establish whether or not bzip2recover was
363 bzip2recover was built with such a limitation, run it 363 built with such a limitation, run it without arguments.
364 without arguments. In any event you can build yourself an 364 In any event you can build yourself an unlimited version
365 unlimited version if you can recompile it with MaybeUInt64 365 if you can recompile it with MaybeUInt64 set to be an
366 set to be an unsigned 64-bit integer. 366 unsigned 64-bit integer.
367 367
368 368
369AUTHOR 369AUTHOR
370 Julian Seward, jseward@acm.org. 370 Julian Seward, jsewardbzip.org.
371 371
372 http://sources.redhat.com/bzip2 372 http://www.bzip.org
373 373
374 The ideas embodied in bzip2 are due to (at least) the fol­ 374 The ideas embodied in bzip2 are due to (at least) the fol-
375 lowing people: Michael Burrows and David Wheeler (for the 375 lowing people: Michael Burrows and David Wheeler (for the
376 block sorting transformation), David Wheeler (again, for 376 block sorting transformation), David Wheeler (again, for
377 the Huffman coder), Peter Fenwick (for the structured cod­ 377 the Huffman coder), Peter Fenwick (for the structured cod-
378 ing model in the original bzip, and many refinements), and 378 ing model in the original bzip, and many refinements), and
379 Alistair Moffat, Radford Neal and Ian Witten (for the 379 Alistair Moffat, Radford Neal and Ian Witten (for the
380 arithmetic coder in the original bzip). I am much 380 arithmetic coder in the original bzip). I am much
381 indebted for their help, support and advice. See the man­ 381 indebted for their help, support and advice. See the man-
382 ual in the source distribution for pointers to sources of 382 ual in the source distribution for pointers to sources of
383 documentation. Christian von Roques encouraged me to look 383 documentation. Christian von Roques encouraged me to look
384 for faster sorting algorithms, so as to speed up compres­ 384 for faster sorting algorithms, so as to speed up compres-
385 sion. Bela Lubkin encouraged me to improve the worst-case 385 sion. Bela Lubkin encouraged me to improve the worst-case
386 compression performance. The bz* scripts are derived from 386 compression performance. Donna Robinson XMLised the docu-
387 those of GNU gzip. Many people sent patches, helped with 387 mentation. The bz* scripts are derived from those of GNU
388 portability problems, lent machines, gave advice and were 388 gzip. Many people sent patches, helped with portability
389 generally helpful. 389 problems, lent machines, gave advice and were generally
390 helpful.
390 391
diff --git a/bzip2recover.c b/bzip2recover.c
index 286873b..5cd405d 100644
--- a/bzip2recover.c
+++ b/bzip2recover.c
@@ -7,9 +7,9 @@
7/*-- 7/*--
8 This program is bzip2recover, a program to attempt data 8 This program is bzip2recover, a program to attempt data
9 salvage from damaged files created by the accompanying 9 salvage from damaged files created by the accompanying
10 bzip2-1.0 program. 10 bzip2-1.0.3 program.
11 11
12 Copyright (C) 1996-2002 Julian R Seward. All rights reserved. 12 Copyright (C) 1996-2005 Julian R Seward. All rights reserved.
13 13
14 Redistribution and use in source and binary forms, with or without 14 Redistribution and use in source and binary forms, with or without
15 modification, are permitted provided that the following conditions 15 modification, are permitted provided that the following conditions
@@ -43,8 +43,8 @@
43 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 43 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
44 44
45 Julian Seward, Cambridge, UK. 45 Julian Seward, Cambridge, UK.
46 jseward@acm.org 46 jseward@bzip.org
47 bzip2/libbzip2 version 1.0 of 21 March 2000 47 bzip2/libbzip2 version 1.0.3 of 15 February 2005
48--*/ 48--*/
49 49
50/*-- 50/*--
@@ -345,7 +345,7 @@ Int32 main ( Int32 argc, Char** argv )
345 inFileName[0] = outFileName[0] = 0; 345 inFileName[0] = outFileName[0] = 0;
346 346
347 fprintf ( stderr, 347 fprintf ( stderr,
348 "bzip2recover 1.0.2: extracts blocks from damaged .bz2 files.\n" ); 348 "bzip2recover 1.0.3: extracts blocks from damaged .bz2 files.\n" );
349 349
350 if (argc != 2) { 350 if (argc != 2) {
351 fprintf ( stderr, "%s: usage is `%s damaged_file_name'.\n", 351 fprintf ( stderr, "%s: usage is `%s damaged_file_name'.\n",
@@ -374,7 +374,7 @@ Int32 main ( Int32 argc, Char** argv )
374 if (strlen(argv[1]) >= BZ_MAX_FILENAME-20) { 374 if (strlen(argv[1]) >= BZ_MAX_FILENAME-20) {
375 fprintf ( stderr, 375 fprintf ( stderr,
376 "%s: supplied filename is suspiciously (>= %d chars) long. Bye!\n", 376 "%s: supplied filename is suspiciously (>= %d chars) long. Bye!\n",
377 progName, strlen(argv[1]) ); 377 progName, (int)strlen(argv[1]) );
378 exit(1); 378 exit(1);
379 } 379 }
380 380
diff --git a/bzlib.c b/bzlib.c
index 7d1cb27..e9c1e87 100644
--- a/bzlib.c
+++ b/bzlib.c
@@ -8,7 +8,7 @@
8 This file is a part of bzip2 and/or libbzip2, a program and 8 This file is a part of bzip2 and/or libbzip2, a program and
9 library for lossless, block-sorting data compression. 9 library for lossless, block-sorting data compression.
10 10
11 Copyright (C) 1996-2002 Julian R Seward. All rights reserved. 11 Copyright (C) 1996-2005 Julian R Seward. All rights reserved.
12 12
13 Redistribution and use in source and binary forms, with or without 13 Redistribution and use in source and binary forms, with or without
14 modification, are permitted provided that the following conditions 14 modification, are permitted provided that the following conditions
@@ -42,7 +42,7 @@
42 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 42 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
43 43
44 Julian Seward, Cambridge, UK. 44 Julian Seward, Cambridge, UK.
45 jseward@acm.org 45 jseward@bzip.org
46 bzip2/libbzip2 version 1.0 of 21 March 2000 46 bzip2/libbzip2 version 1.0 of 21 March 2000
47 47
48 This program is based on (at least) the work of: 48 This program is based on (at least) the work of:
@@ -88,12 +88,12 @@ void BZ2_bz__AssertH__fail ( int errcode )
88 fprintf(stderr, 88 fprintf(stderr,
89 "\n\nbzip2/libbzip2: internal error number %d.\n" 89 "\n\nbzip2/libbzip2: internal error number %d.\n"
90 "This is a bug in bzip2/libbzip2, %s.\n" 90 "This is a bug in bzip2/libbzip2, %s.\n"
91 "Please report it to me at: jseward@acm.org. If this happened\n" 91 "Please report it to me at: jseward@bzip.org. If this happened\n"
92 "when you were using some program which uses libbzip2 as a\n" 92 "when you were using some program which uses libbzip2 as a\n"
93 "component, you should also report this bug to the author(s)\n" 93 "component, you should also report this bug to the author(s)\n"
94 "of that program. Please make an effort to report this bug;\n" 94 "of that program. Please make an effort to report this bug;\n"
95 "timely and accurate bug reports eventually lead to higher\n" 95 "timely and accurate bug reports eventually lead to higher\n"
96 "quality software. Thanks. Julian Seward, 30 December 2001.\n\n", 96 "quality software. Thanks. Julian Seward, 15 February 2005.\n\n",
97 errcode, 97 errcode,
98 BZ2_bzlibVersion() 98 BZ2_bzlibVersion()
99 ); 99 );
@@ -574,8 +574,11 @@ int BZ_API(BZ2_bzDecompressInit)
574 574
575 575
576/*---------------------------------------------------*/ 576/*---------------------------------------------------*/
577/* Return True iff data corruption is discovered.
578 Returns False if there is no problem.
579*/
577static 580static
578void unRLE_obuf_to_output_FAST ( DState* s ) 581Bool unRLE_obuf_to_output_FAST ( DState* s )
579{ 582{
580 UChar k1; 583 UChar k1;
581 584
@@ -584,7 +587,7 @@ void unRLE_obuf_to_output_FAST ( DState* s )
584 while (True) { 587 while (True) {
585 /* try to finish existing run */ 588 /* try to finish existing run */
586 while (True) { 589 while (True) {
587 if (s->strm->avail_out == 0) return; 590 if (s->strm->avail_out == 0) return False;
588 if (s->state_out_len == 0) break; 591 if (s->state_out_len == 0) break;
589 *( (UChar*)(s->strm->next_out) ) = s->state_out_ch; 592 *( (UChar*)(s->strm->next_out) ) = s->state_out_ch;
590 BZ_UPDATE_CRC ( s->calculatedBlockCRC, s->state_out_ch ); 593 BZ_UPDATE_CRC ( s->calculatedBlockCRC, s->state_out_ch );
@@ -594,10 +597,13 @@ void unRLE_obuf_to_output_FAST ( DState* s )
594 s->strm->total_out_lo32++; 597 s->strm->total_out_lo32++;
595 if (s->strm->total_out_lo32 == 0) s->strm->total_out_hi32++; 598 if (s->strm->total_out_lo32 == 0) s->strm->total_out_hi32++;
596 } 599 }
597 600
598 /* can a new run be started? */ 601 /* can a new run be started? */
599 if (s->nblock_used == s->save_nblock+1) return; 602 if (s->nblock_used == s->save_nblock+1) return False;
600 603
604 /* Only caused by corrupt data stream? */
605 if (s->nblock_used > s->save_nblock+1)
606 return True;
601 607
602 s->state_out_len = 1; 608 s->state_out_len = 1;
603 s->state_out_ch = s->k0; 609 s->state_out_ch = s->k0;
@@ -667,6 +673,10 @@ void unRLE_obuf_to_output_FAST ( DState* s )
667 cs_avail_out--; 673 cs_avail_out--;
668 } 674 }
669 } 675 }
676 /* Only caused by corrupt data stream? */
677 if (c_nblock_used > s_save_nblockPP)
678 return True;
679
670 /* can a new run be started? */ 680 /* can a new run be started? */
671 if (c_nblock_used == s_save_nblockPP) { 681 if (c_nblock_used == s_save_nblockPP) {
672 c_state_out_len = 0; goto return_notr; 682 c_state_out_len = 0; goto return_notr;
@@ -712,6 +722,7 @@ void unRLE_obuf_to_output_FAST ( DState* s )
712 s->strm->avail_out = cs_avail_out; 722 s->strm->avail_out = cs_avail_out;
713 /* end save */ 723 /* end save */
714 } 724 }
725 return False;
715} 726}
716 727
717 728
@@ -732,8 +743,11 @@ __inline__ Int32 BZ2_indexIntoF ( Int32 indx, Int32 *cftab )
732 743
733 744
734/*---------------------------------------------------*/ 745/*---------------------------------------------------*/
746/* Return True iff data corruption is discovered.
747 Returns False if there is no problem.
748*/
735static 749static
736void unRLE_obuf_to_output_SMALL ( DState* s ) 750Bool unRLE_obuf_to_output_SMALL ( DState* s )
737{ 751{
738 UChar k1; 752 UChar k1;
739 753
@@ -742,7 +756,7 @@ void unRLE_obuf_to_output_SMALL ( DState* s )
742 while (True) { 756 while (True) {
743 /* try to finish existing run */ 757 /* try to finish existing run */
744 while (True) { 758 while (True) {
745 if (s->strm->avail_out == 0) return; 759 if (s->strm->avail_out == 0) return False;
746 if (s->state_out_len == 0) break; 760 if (s->state_out_len == 0) break;
747 *( (UChar*)(s->strm->next_out) ) = s->state_out_ch; 761 *( (UChar*)(s->strm->next_out) ) = s->state_out_ch;
748 BZ_UPDATE_CRC ( s->calculatedBlockCRC, s->state_out_ch ); 762 BZ_UPDATE_CRC ( s->calculatedBlockCRC, s->state_out_ch );
@@ -754,8 +768,11 @@ void unRLE_obuf_to_output_SMALL ( DState* s )
754 } 768 }
755 769
756 /* can a new run be started? */ 770 /* can a new run be started? */
757 if (s->nblock_used == s->save_nblock+1) return; 771 if (s->nblock_used == s->save_nblock+1) return False;
758 772
773 /* Only caused by corrupt data stream? */
774 if (s->nblock_used > s->save_nblock+1)
775 return True;
759 776
760 s->state_out_len = 1; 777 s->state_out_len = 1;
761 s->state_out_ch = s->k0; 778 s->state_out_ch = s->k0;
@@ -788,7 +805,7 @@ void unRLE_obuf_to_output_SMALL ( DState* s )
788 while (True) { 805 while (True) {
789 /* try to finish existing run */ 806 /* try to finish existing run */
790 while (True) { 807 while (True) {
791 if (s->strm->avail_out == 0) return; 808 if (s->strm->avail_out == 0) return False;
792 if (s->state_out_len == 0) break; 809 if (s->state_out_len == 0) break;
793 *( (UChar*)(s->strm->next_out) ) = s->state_out_ch; 810 *( (UChar*)(s->strm->next_out) ) = s->state_out_ch;
794 BZ_UPDATE_CRC ( s->calculatedBlockCRC, s->state_out_ch ); 811 BZ_UPDATE_CRC ( s->calculatedBlockCRC, s->state_out_ch );
@@ -800,7 +817,11 @@ void unRLE_obuf_to_output_SMALL ( DState* s )
800 } 817 }
801 818
802 /* can a new run be started? */ 819 /* can a new run be started? */
803 if (s->nblock_used == s->save_nblock+1) return; 820 if (s->nblock_used == s->save_nblock+1) return False;
821
822 /* Only caused by corrupt data stream? */
823 if (s->nblock_used > s->save_nblock+1)
824 return True;
804 825
805 s->state_out_len = 1; 826 s->state_out_len = 1;
806 s->state_out_ch = s->k0; 827 s->state_out_ch = s->k0;
@@ -830,6 +851,7 @@ void unRLE_obuf_to_output_SMALL ( DState* s )
830/*---------------------------------------------------*/ 851/*---------------------------------------------------*/
831int BZ_API(BZ2_bzDecompress) ( bz_stream *strm ) 852int BZ_API(BZ2_bzDecompress) ( bz_stream *strm )
832{ 853{
854 Bool corrupt;
833 DState* s; 855 DState* s;
834 if (strm == NULL) return BZ_PARAM_ERROR; 856 if (strm == NULL) return BZ_PARAM_ERROR;
835 s = strm->state; 857 s = strm->state;
@@ -840,12 +862,13 @@ int BZ_API(BZ2_bzDecompress) ( bz_stream *strm )
840 if (s->state == BZ_X_IDLE) return BZ_SEQUENCE_ERROR; 862 if (s->state == BZ_X_IDLE) return BZ_SEQUENCE_ERROR;
841 if (s->state == BZ_X_OUTPUT) { 863 if (s->state == BZ_X_OUTPUT) {
842 if (s->smallDecompress) 864 if (s->smallDecompress)
843 unRLE_obuf_to_output_SMALL ( s ); else 865 corrupt = unRLE_obuf_to_output_SMALL ( s ); else
844 unRLE_obuf_to_output_FAST ( s ); 866 corrupt = unRLE_obuf_to_output_FAST ( s );
867 if (corrupt) return BZ_DATA_ERROR;
845 if (s->nblock_used == s->save_nblock+1 && s->state_out_len == 0) { 868 if (s->nblock_used == s->save_nblock+1 && s->state_out_len == 0) {
846 BZ_FINALISE_CRC ( s->calculatedBlockCRC ); 869 BZ_FINALISE_CRC ( s->calculatedBlockCRC );
847 if (s->verbosity >= 3) 870 if (s->verbosity >= 3)
848 VPrintf2 ( " {0x%x, 0x%x}", s->storedBlockCRC, 871 VPrintf2 ( " {0x%08x, 0x%08x}", s->storedBlockCRC,
849 s->calculatedBlockCRC ); 872 s->calculatedBlockCRC );
850 if (s->verbosity >= 2) VPrintf0 ( "]" ); 873 if (s->verbosity >= 2) VPrintf0 ( "]" );
851 if (s->calculatedBlockCRC != s->storedBlockCRC) 874 if (s->calculatedBlockCRC != s->storedBlockCRC)
@@ -863,7 +886,7 @@ int BZ_API(BZ2_bzDecompress) ( bz_stream *strm )
863 Int32 r = BZ2_decompress ( s ); 886 Int32 r = BZ2_decompress ( s );
864 if (r == BZ_STREAM_END) { 887 if (r == BZ_STREAM_END) {
865 if (s->verbosity >= 3) 888 if (s->verbosity >= 3)
866 VPrintf2 ( "\n combined CRCs: stored = 0x%x, computed = 0x%x", 889 VPrintf2 ( "\n combined CRCs: stored = 0x%08x, computed = 0x%08x",
867 s->storedCombinedCRC, s->calculatedCombinedCRC ); 890 s->storedCombinedCRC, s->calculatedCombinedCRC );
868 if (s->calculatedCombinedCRC != s->storedCombinedCRC) 891 if (s->calculatedCombinedCRC != s->storedCombinedCRC)
869 return BZ_DATA_ERROR; 892 return BZ_DATA_ERROR;
diff --git a/bzlib.h b/bzlib.h
index 9ac43a1..3237243 100644
--- a/bzlib.h
+++ b/bzlib.h
@@ -8,7 +8,7 @@
8 This file is a part of bzip2 and/or libbzip2, a program and 8 This file is a part of bzip2 and/or libbzip2, a program and
9 library for lossless, block-sorting data compression. 9 library for lossless, block-sorting data compression.
10 10
11 Copyright (C) 1996-2002 Julian R Seward. All rights reserved. 11 Copyright (C) 1996-2005 Julian R Seward. All rights reserved.
12 12
13 Redistribution and use in source and binary forms, with or without 13 Redistribution and use in source and binary forms, with or without
14 modification, are permitted provided that the following conditions 14 modification, are permitted provided that the following conditions
@@ -42,7 +42,7 @@
42 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 42 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
43 43
44 Julian Seward, Cambridge, UK. 44 Julian Seward, Cambridge, UK.
45 jseward@acm.org 45 jseward@bzip.org
46 bzip2/libbzip2 version 1.0 of 21 March 2000 46 bzip2/libbzip2 version 1.0 of 21 March 2000
47 47
48 This program is based on (at least) the work of: 48 This program is based on (at least) the work of:
@@ -110,8 +110,10 @@ typedef
110#define BZ_EXPORT 110#define BZ_EXPORT
111#endif 111#endif
112 112
113#ifndef BZ_NO_STDIO
113/* Need a definitition for FILE */ 114/* Need a definitition for FILE */
114#include <stdio.h> 115#include <stdio.h>
116#endif
115 117
116#ifdef _WIN32 118#ifdef _WIN32
117# include <windows.h> 119# include <windows.h>
diff --git a/bzlib_private.h b/bzlib_private.h
index ff973c3..ca76fe6 100644
--- a/bzlib_private.h
+++ b/bzlib_private.h
@@ -8,7 +8,7 @@
8 This file is a part of bzip2 and/or libbzip2, a program and 8 This file is a part of bzip2 and/or libbzip2, a program and
9 library for lossless, block-sorting data compression. 9 library for lossless, block-sorting data compression.
10 10
11 Copyright (C) 1996-2002 Julian R Seward. All rights reserved. 11 Copyright (C) 1996-2005 Julian R Seward. All rights reserved.
12 12
13 Redistribution and use in source and binary forms, with or without 13 Redistribution and use in source and binary forms, with or without
14 modification, are permitted provided that the following conditions 14 modification, are permitted provided that the following conditions
@@ -42,7 +42,7 @@
42 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 42 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
43 43
44 Julian Seward, Cambridge, UK. 44 Julian Seward, Cambridge, UK.
45 jseward@acm.org 45 jseward@bzip.org
46 bzip2/libbzip2 version 1.0 of 21 March 2000 46 bzip2/libbzip2 version 1.0 of 21 March 2000
47 47
48 This program is based on (at least) the work of: 48 This program is based on (at least) the work of:
@@ -76,7 +76,7 @@
76 76
77/*-- General stuff. --*/ 77/*-- General stuff. --*/
78 78
79#define BZ_VERSION "1.0.2, 30-Dec-2001" 79#define BZ_VERSION "1.0.3, 15-Feb-2005"
80 80
81typedef char Char; 81typedef char Char;
82typedef unsigned char Bool; 82typedef unsigned char Bool;
diff --git a/compress.c b/compress.c
index 56501c1..7e0c291 100644
--- a/compress.c
+++ b/compress.c
@@ -8,7 +8,7 @@
8 This file is a part of bzip2 and/or libbzip2, a program and 8 This file is a part of bzip2 and/or libbzip2, a program and
9 library for lossless, block-sorting data compression. 9 library for lossless, block-sorting data compression.
10 10
11 Copyright (C) 1996-2002 Julian R Seward. All rights reserved. 11 Copyright (C) 1996-2005 Julian R Seward. All rights reserved.
12 12
13 Redistribution and use in source and binary forms, with or without 13 Redistribution and use in source and binary forms, with or without
14 modification, are permitted provided that the following conditions 14 modification, are permitted provided that the following conditions
@@ -42,7 +42,7 @@
42 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 42 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
43 43
44 Julian Seward, Cambridge, UK. 44 Julian Seward, Cambridge, UK.
45 jseward@acm.org 45 jseward@bzip.org
46 bzip2/libbzip2 version 1.0 of 21 March 2000 46 bzip2/libbzip2 version 1.0 of 21 March 2000
47 47
48 This program is based on (at least) the work of: 48 This program is based on (at least) the work of:
@@ -488,9 +488,11 @@ void sendMTFValues ( EState* s )
488 /*-- 488 /*--
489 Recompute the tables based on the accumulated frequencies. 489 Recompute the tables based on the accumulated frequencies.
490 --*/ 490 --*/
491 /* maxLen was changed from 20 to 17 in bzip2-1.0.3. See
492 comment in huffman.c for details. */
491 for (t = 0; t < nGroups; t++) 493 for (t = 0; t < nGroups; t++)
492 BZ2_hbMakeCodeLengths ( &(s->len[t][0]), &(s->rfreq[t][0]), 494 BZ2_hbMakeCodeLengths ( &(s->len[t][0]), &(s->rfreq[t][0]),
493 alphaSize, 20 ); 495 alphaSize, 17 /*20*/ );
494 } 496 }
495 497
496 498
@@ -527,7 +529,7 @@ void sendMTFValues ( EState* s )
527 if (s->len[t][i] > maxLen) maxLen = s->len[t][i]; 529 if (s->len[t][i] > maxLen) maxLen = s->len[t][i];
528 if (s->len[t][i] < minLen) minLen = s->len[t][i]; 530 if (s->len[t][i] < minLen) minLen = s->len[t][i];
529 } 531 }
530 AssertH ( !(maxLen > 20), 3004 ); 532 AssertH ( !(maxLen > 17 /*20*/ ), 3004 );
531 AssertH ( !(minLen < 1), 3005 ); 533 AssertH ( !(minLen < 1), 3005 );
532 BZ2_hbAssignCodes ( &(s->code[t][0]), &(s->len[t][0]), 534 BZ2_hbAssignCodes ( &(s->code[t][0]), &(s->len[t][0]),
533 minLen, maxLen, alphaSize ); 535 minLen, maxLen, alphaSize );
@@ -651,8 +653,8 @@ void BZ2_compressBlock ( EState* s, Bool is_last_block )
651 if (s->blockNo > 1) s->numZ = 0; 653 if (s->blockNo > 1) s->numZ = 0;
652 654
653 if (s->verbosity >= 2) 655 if (s->verbosity >= 2)
654 VPrintf4( " block %d: crc = 0x%8x, " 656 VPrintf4( " block %d: crc = 0x%08x, "
655 "combined CRC = 0x%8x, size = %d\n", 657 "combined CRC = 0x%08x, size = %d\n",
656 s->blockNo, s->blockCRC, s->combinedCRC, s->nblock ); 658 s->blockNo, s->blockCRC, s->combinedCRC, s->nblock );
657 659
658 BZ2_blockSort ( s ); 660 BZ2_blockSort ( s );
@@ -703,7 +705,7 @@ void BZ2_compressBlock ( EState* s, Bool is_last_block )
703 bsPutUChar ( s, 0x50 ); bsPutUChar ( s, 0x90 ); 705 bsPutUChar ( s, 0x50 ); bsPutUChar ( s, 0x90 );
704 bsPutUInt32 ( s, s->combinedCRC ); 706 bsPutUInt32 ( s, s->combinedCRC );
705 if (s->verbosity >= 2) 707 if (s->verbosity >= 2)
706 VPrintf1( " final combined CRC = 0x%x\n ", s->combinedCRC ); 708 VPrintf1( " final combined CRC = 0x%08x\n ", s->combinedCRC );
707 bsFinishWrite ( s ); 709 bsFinishWrite ( s );
708 } 710 }
709} 711}
diff --git a/crctable.c b/crctable.c
index b16746a..b6dadfc 100644
--- a/crctable.c
+++ b/crctable.c
@@ -8,7 +8,7 @@
8 This file is a part of bzip2 and/or libbzip2, a program and 8 This file is a part of bzip2 and/or libbzip2, a program and
9 library for lossless, block-sorting data compression. 9 library for lossless, block-sorting data compression.
10 10
11 Copyright (C) 1996-2002 Julian R Seward. All rights reserved. 11 Copyright (C) 1996-2005 Julian R Seward. All rights reserved.
12 12
13 Redistribution and use in source and binary forms, with or without 13 Redistribution and use in source and binary forms, with or without
14 modification, are permitted provided that the following conditions 14 modification, are permitted provided that the following conditions
@@ -42,7 +42,7 @@
42 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 42 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
43 43
44 Julian Seward, Cambridge, UK. 44 Julian Seward, Cambridge, UK.
45 jseward@acm.org 45 jseward@bzip.org
46 bzip2/libbzip2 version 1.0 of 21 March 2000 46 bzip2/libbzip2 version 1.0 of 21 March 2000
47 47
48 This program is based on (at least) the work of: 48 This program is based on (at least) the work of:
diff --git a/decompress.c b/decompress.c
index e921347..81c3d2c 100644
--- a/decompress.c
+++ b/decompress.c
@@ -8,7 +8,7 @@
8 This file is a part of bzip2 and/or libbzip2, a program and 8 This file is a part of bzip2 and/or libbzip2, a program and
9 library for lossless, block-sorting data compression. 9 library for lossless, block-sorting data compression.
10 10
11 Copyright (C) 1996-2002 Julian R Seward. All rights reserved. 11 Copyright (C) 1996-2005 Julian R Seward. All rights reserved.
12 12
13 Redistribution and use in source and binary forms, with or without 13 Redistribution and use in source and binary forms, with or without
14 modification, are permitted provided that the following conditions 14 modification, are permitted provided that the following conditions
@@ -42,7 +42,7 @@
42 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 42 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
43 43
44 Julian Seward, Cambridge, UK. 44 Julian Seward, Cambridge, UK.
45 jseward@acm.org 45 jseward@bzip.org
46 bzip2/libbzip2 version 1.0 of 21 March 2000 46 bzip2/libbzip2 version 1.0 of 21 March 2000
47 47
48 This program is based on (at least) the work of: 48 This program is based on (at least) the work of:
@@ -524,17 +524,23 @@ Int32 BZ2_decompress ( DState* s )
524 if (s->origPtr < 0 || s->origPtr >= nblock) 524 if (s->origPtr < 0 || s->origPtr >= nblock)
525 RETURN(BZ_DATA_ERROR); 525 RETURN(BZ_DATA_ERROR);
526 526
527 /*-- Set up cftab to facilitate generation of T^(-1) --*/
528 s->cftab[0] = 0;
529 for (i = 1; i <= 256; i++) s->cftab[i] = s->unzftab[i-1];
530 for (i = 1; i <= 256; i++) s->cftab[i] += s->cftab[i-1];
531 for (i = 0; i <= 256; i++) {
532 if (s->cftab[i] < 0 || s->cftab[i] > nblock) {
533 /* s->cftab[i] can legitimately be == nblock */
534 RETURN(BZ_DATA_ERROR);
535 }
536 }
537
527 s->state_out_len = 0; 538 s->state_out_len = 0;
528 s->state_out_ch = 0; 539 s->state_out_ch = 0;
529 BZ_INITIALISE_CRC ( s->calculatedBlockCRC ); 540 BZ_INITIALISE_CRC ( s->calculatedBlockCRC );
530 s->state = BZ_X_OUTPUT; 541 s->state = BZ_X_OUTPUT;
531 if (s->verbosity >= 2) VPrintf0 ( "rt+rld" ); 542 if (s->verbosity >= 2) VPrintf0 ( "rt+rld" );
532 543
533 /*-- Set up cftab to facilitate generation of T^(-1) --*/
534 s->cftab[0] = 0;
535 for (i = 1; i <= 256; i++) s->cftab[i] = s->unzftab[i-1];
536 for (i = 1; i <= 256; i++) s->cftab[i] += s->cftab[i-1];
537
538 if (s->smallDecompress) { 544 if (s->smallDecompress) {
539 545
540 /*-- Make a copy of cftab, used in generation of T --*/ 546 /*-- Make a copy of cftab, used in generation of T --*/
diff --git a/entities.xml b/entities.xml
new file mode 100644
index 0000000..6d0975f
--- /dev/null
+++ b/entities.xml
@@ -0,0 +1,9 @@
1<!-- misc. strings -->
2<!ENTITY bz-url "http://www.bzip.org">
3<!ENTITY bz-email "jseward@bzip.org">
4<!ENTITY bz-lifespan "1996-2005">
5
6<!ENTITY bz-version "1.0.3">
7<!ENTITY bz-date "15 February 2005">
8
9<!ENTITY manual-title "bzip2 Manual">
diff --git a/format.pl b/format.pl
new file mode 100755
index 0000000..8ab47ac
--- /dev/null
+++ b/format.pl
@@ -0,0 +1,53 @@
1#!/usr/bin/perl -w
2use strict;
3
4# get command line values:
5if ( $#ARGV !=1 ) {
6 die "Usage: $0 xml_infile xml_outfile\n";
7}
8
9my $infile = shift;
10# check infile exists
11die "Can't find file \"$infile\""
12 unless -f $infile;
13# check we can read infile
14if (! -r $infile) {
15 die "Can't read input $infile\n";
16}
17# check we can open infile
18open( INFILE,"<$infile" ) or
19 die "Can't input $infile $!";
20
21#my $outfile = 'fmt-manual.xml';
22my $outfile = shift;
23#print "Infile: $infile, Outfile: $outfile\n";
24# check we can write to outfile
25open( OUTFILE,">$outfile" ) or
26 die "Can't output $outfile $! for writing";
27
28my ($prev, $curr, $str);
29$prev = ''; $curr = '';
30while ( <INFILE> ) {
31
32 print OUTFILE $prev;
33 $prev = $curr;
34 $curr = $_;
35 $str = '';
36
37 if ( $prev =~ /<programlisting>$|<screen>$/ ) {
38 chomp $prev;
39 $curr = join( '', $prev, "<![CDATA[", $curr );
40 $prev = '';
41 next;
42 }
43 elsif ( $curr =~ /<\/programlisting>|<\/screen>/ ) {
44 chomp $prev;
45 $curr = join( '', $prev, "]]>", $curr );
46 $prev = '';
47 next;
48 }
49}
50print OUTFILE $curr;
51close INFILE;
52close OUTFILE;
53exit;
diff --git a/huffman.c b/huffman.c
index 293095c..5bf190b 100644
--- a/huffman.c
+++ b/huffman.c
@@ -8,7 +8,7 @@
8 This file is a part of bzip2 and/or libbzip2, a program and 8 This file is a part of bzip2 and/or libbzip2, a program and
9 library for lossless, block-sorting data compression. 9 library for lossless, block-sorting data compression.
10 10
11 Copyright (C) 1996-2002 Julian R Seward. All rights reserved. 11 Copyright (C) 1996-2005 Julian R Seward. All rights reserved.
12 12
13 Redistribution and use in source and binary forms, with or without 13 Redistribution and use in source and binary forms, with or without
14 modification, are permitted provided that the following conditions 14 modification, are permitted provided that the following conditions
@@ -42,7 +42,7 @@
42 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 42 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
43 43
44 Julian Seward, Cambridge, UK. 44 Julian Seward, Cambridge, UK.
45 jseward@acm.org 45 jseward@bzip.org
46 bzip2/libbzip2 version 1.0 of 21 March 2000 46 bzip2/libbzip2 version 1.0 of 21 March 2000
47 47
48 This program is based on (at least) the work of: 48 This program is based on (at least) the work of:
@@ -162,7 +162,24 @@ void BZ2_hbMakeCodeLengths ( UChar *len,
162 162
163 if (! tooLong) break; 163 if (! tooLong) break;
164 164
165 for (i = 1; i < alphaSize; i++) { 165 /* 17 Oct 04: keep-going condition for the following loop used
166 to be 'i < alphaSize', which missed the last element,
167 theoretically leading to the possibility of the compressor
168 looping. However, this count-scaling step is only needed if
169 one of the generated Huffman code words is longer than
170 maxLen, which up to and including version 1.0.2 was 20 bits,
171 which is extremely unlikely. In version 1.0.3 maxLen was
172 changed to 17 bits, which has minimal effect on compression
173 ratio, but does mean this scaling step is used from time to
174 time, enough to verify that it works.
175
176 This means that bzip2-1.0.3 and later will only produce
177 Huffman codes with a maximum length of 17 bits. However, in
178 order to preserve backwards compatibility with bitstreams
179 produced by versions pre-1.0.3, the decompressor must still
180 handle lengths of up to 20. */
181
182 for (i = 1; i <= alphaSize; i++) {
166 j = weight[i] >> 8; 183 j = weight[i] >> 8;
167 j = 1 + (j / 2); 184 j = 1 + (j / 2);
168 weight[i] = j << 8; 185 weight[i] = j << 8;
diff --git a/manual.texi b/manual.texi
deleted file mode 100644
index 5bc27d5..0000000
--- a/manual.texi
+++ /dev/null
@@ -1,2243 +0,0 @@
1\input texinfo @c -*- Texinfo -*-
2@setfilename bzip2.info
3
4@ignore
5This file documents bzip2 version 1.0.2, and associated library
6libbzip2, written by Julian Seward (jseward@acm.org).
7
8Copyright (C) 1996-2002 Julian R Seward
9
10Permission is granted to make and distribute verbatim copies of
11this manual provided the copyright notice and this permission notice
12are preserved on all copies.
13
14Permission is granted to copy and distribute translations of this manual
15into another language, under the above conditions for verbatim copies.
16@end ignore
17
18@ifinfo
19@format
20START-INFO-DIR-ENTRY
21* Bzip2: (bzip2). A program and library for data compression.
22END-INFO-DIR-ENTRY
23@end format
24
25@end ifinfo
26
27@iftex
28@c @finalout
29@settitle bzip2 and libbzip2
30@titlepage
31@title bzip2 and libbzip2
32@subtitle a program and library for data compression
33@subtitle copyright (C) 1996-2002 Julian Seward
34@subtitle version 1.0.2 of 30 December 2001
35@author Julian Seward
36
37@end titlepage
38
39@parindent 0mm
40@parskip 2mm
41
42@end iftex
43@node Top,,, (dir)
44
45The following text is the License for this software. You should
46find it identical to that contained in the file LICENSE in the
47source distribution.
48
49@bf{------------------ START OF THE LICENSE ------------------}
50
51This program, @code{bzip2},
52and associated library @code{libbzip2}, are
53Copyright (C) 1996-2002 Julian R Seward. All rights reserved.
54
55Redistribution and use in source and binary forms, with or without
56modification, are permitted provided that the following conditions
57are met:
58@itemize @bullet
59@item
60 Redistributions of source code must retain the above copyright
61 notice, this list of conditions and the following disclaimer.
62@item
63 The origin of this software must not be misrepresented; you must
64 not claim that you wrote the original software. If you use this
65 software in a product, an acknowledgment in the product
66 documentation would be appreciated but is not required.
67@item
68 Altered source versions must be plainly marked as such, and must
69 not be misrepresented as being the original software.
70@item
71 The name of the author may not be used to endorse or promote
72 products derived from this software without specific prior written
73 permission.
74@end itemize
75THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
76OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
77WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
78ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
79DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
80DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
81GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
82INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
83WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
84NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
85SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
86
87Julian Seward, Cambridge, UK.
88
89@code{jseward@@acm.org}
90
91@code{bzip2}/@code{libbzip2} version 1.0.2 of 30 December 2001.
92
93@bf{------------------ END OF THE LICENSE ------------------}
94
95Web sites:
96
97@code{http://sources.redhat.com/bzip2}
98
99@code{http://www.cacheprof.org}
100
101PATENTS: To the best of my knowledge, @code{bzip2} does not use any patented
102algorithms. However, I do not have the resources available to carry out
103a full patent search. Therefore I cannot give any guarantee of the
104above statement.
105
106
107
108
109
110
111
112@chapter Introduction
113
114@code{bzip2} compresses files using the Burrows-Wheeler
115block-sorting text compression algorithm, and Huffman coding.
116Compression is generally considerably better than that
117achieved by more conventional LZ77/LZ78-based compressors,
118and approaches the performance of the PPM family of statistical compressors.
119
120@code{bzip2} is built on top of @code{libbzip2}, a flexible library
121for handling compressed data in the @code{bzip2} format. This manual
122describes both how to use the program and
123how to work with the library interface. Most of the
124manual is devoted to this library, not the program,
125which is good news if your interest is only in the program.
126
127Chapter 2 describes how to use @code{bzip2}; this is the only part
128you need to read if you just want to know how to operate the program.
129Chapter 3 describes the programming interfaces in detail, and
130Chapter 4 records some miscellaneous notes which I thought
131ought to be recorded somewhere.
132
133
134@chapter How to use @code{bzip2}
135
136This chapter contains a copy of the @code{bzip2} man page,
137and nothing else.
138
139@quotation
140
141@unnumberedsubsubsec NAME
142@itemize
143@item @code{bzip2}, @code{bunzip2}
144- a block-sorting file compressor, v1.0.2
145@item @code{bzcat}
146- decompresses files to stdout
147@item @code{bzip2recover}
148- recovers data from damaged bzip2 files
149@end itemize
150
151@unnumberedsubsubsec SYNOPSIS
152@itemize
153@item @code{bzip2} [ -cdfkqstvzVL123456789 ] [ filenames ... ]
154@item @code{bunzip2} [ -fkvsVL ] [ filenames ... ]
155@item @code{bzcat} [ -s ] [ filenames ... ]
156@item @code{bzip2recover} filename
157@end itemize
158
159@unnumberedsubsubsec DESCRIPTION
160
161@code{bzip2} compresses files using the Burrows-Wheeler block sorting
162text compression algorithm, and Huffman coding. Compression is
163generally considerably better than that achieved by more conventional
164LZ77/LZ78-based compressors, and approaches the performance of the PPM
165family of statistical compressors.
166
167The command-line options are deliberately very similar to those of GNU
168@code{gzip}, but they are not identical.
169
170@code{bzip2} expects a list of file names to accompany the command-line
171flags. Each file is replaced by a compressed version of itself, with
172the name @code{original_name.bz2}. Each compressed file has the same
173modification date, permissions, and, when possible, ownership as the
174corresponding original, so that these properties can be correctly
175restored at decompression time. File name handling is naive in the
176sense that there is no mechanism for preserving original file names,
177permissions, ownerships or dates in filesystems which lack these
178concepts, or have serious file name length restrictions, such as MS-DOS.
179
180@code{bzip2} and @code{bunzip2} will by default not overwrite existing
181files. If you want this to happen, specify the @code{-f} flag.
182
183If no file names are specified, @code{bzip2} compresses from standard
184input to standard output. In this case, @code{bzip2} will decline to
185write compressed output to a terminal, as this would be entirely
186incomprehensible and therefore pointless.
187
188@code{bunzip2} (or @code{bzip2 -d}) decompresses all
189specified files. Files which were not created by @code{bzip2}
190will be detected and ignored, and a warning issued.
191@code{bzip2} attempts to guess the filename for the decompressed file
192from that of the compressed file as follows:
193@itemize
194@item @code{filename.bz2 } becomes @code{filename}
195@item @code{filename.bz } becomes @code{filename}
196@item @code{filename.tbz2} becomes @code{filename.tar}
197@item @code{filename.tbz } becomes @code{filename.tar}
198@item @code{anyothername } becomes @code{anyothername.out}
199@end itemize
200If the file does not end in one of the recognised endings,
201@code{.bz2}, @code{.bz},
202@code{.tbz2} or @code{.tbz}, @code{bzip2} complains that it cannot
203guess the name of the original file, and uses the original name
204with @code{.out} appended.
205
206As with compression, supplying no
207filenames causes decompression from standard input to standard output.
208
209@code{bunzip2} will correctly decompress a file which is the
210concatenation of two or more compressed files. The result is the
211concatenation of the corresponding uncompressed files. Integrity
212testing (@code{-t}) of concatenated compressed files is also supported.
213
214You can also compress or decompress files to the standard output by
215giving the @code{-c} flag. Multiple files may be compressed and
216decompressed like this. The resulting outputs are fed sequentially to
217stdout. Compression of multiple files in this manner generates a stream
218containing multiple compressed file representations. Such a stream
219can be decompressed correctly only by @code{bzip2} version 0.9.0 or
220later. Earlier versions of @code{bzip2} will stop after decompressing
221the first file in the stream.
222
223@code{bzcat} (or @code{bzip2 -dc}) decompresses all specified files to
224the standard output.
225
226@code{bzip2} will read arguments from the environment variables
227@code{BZIP2} and @code{BZIP}, in that order, and will process them
228before any arguments read from the command line. This gives a
229convenient way to supply default arguments.
230
231Compression is always performed, even if the compressed file is slightly
232larger than the original. Files of less than about one hundred bytes
233tend to get larger, since the compression mechanism has a constant
234overhead in the region of 50 bytes. Random data (including the output
235of most file compressors) is coded at about 8.05 bits per byte, giving
236an expansion of around 0.5%.
237
238As a self-check for your protection, @code{bzip2} uses 32-bit CRCs to
239make sure that the decompressed version of a file is identical to the
240original. This guards against corruption of the compressed data, and
241against undetected bugs in @code{bzip2} (hopefully very unlikely). The
242chances of data corruption going undetected is microscopic, about one
243chance in four billion for each file processed. Be aware, though, that
244the check occurs upon decompression, so it can only tell you that
245something is wrong. It can't help you recover the original uncompressed
246data. You can use @code{bzip2recover} to try to recover data from
247damaged files.
248
249Return values: 0 for a normal exit, 1 for environmental problems (file
250not found, invalid flags, I/O errors, &c), 2 to indicate a corrupt
251compressed file, 3 for an internal consistency error (eg, bug) which
252caused @code{bzip2} to panic.
253
254
255@unnumberedsubsubsec OPTIONS
256@table @code
257@item -c --stdout
258Compress or decompress to standard output.
259@item -d --decompress
260Force decompression. @code{bzip2}, @code{bunzip2} and @code{bzcat} are
261really the same program, and the decision about what actions to take is
262done on the basis of which name is used. This flag overrides that
263mechanism, and forces bzip2 to decompress.
264@item -z --compress
265The complement to @code{-d}: forces compression, regardless of the
266invokation name.
267@item -t --test
268Check integrity of the specified file(s), but don't decompress them.
269This really performs a trial decompression and throws away the result.
270@item -f --force
271Force overwrite of output files. Normally, @code{bzip2} will not overwrite
272existing output files. Also forces @code{bzip2} to break hard links
273to files, which it otherwise wouldn't do.
274
275@code{bzip2} normally declines to decompress files which don't have the
276correct magic header bytes. If forced (@code{-f}), however, it will
277pass such files through unmodified. This is how GNU @code{gzip}
278behaves.
279@item -k --keep
280Keep (don't delete) input files during compression
281or decompression.
282@item -s --small
283Reduce memory usage, for compression, decompression and testing. Files
284are decompressed and tested using a modified algorithm which only
285requires 2.5 bytes per block byte. This means any file can be
286decompressed in 2300k of memory, albeit at about half the normal speed.
287
288During compression, @code{-s} selects a block size of 200k, which limits
289memory use to around the same figure, at the expense of your compression
290ratio. In short, if your machine is low on memory (8 megabytes or
291less), use -s for everything. See MEMORY MANAGEMENT below.
292@item -q --quiet
293Suppress non-essential warning messages. Messages pertaining to
294I/O errors and other critical events will not be suppressed.
295@item -v --verbose
296Verbose mode -- show the compression ratio for each file processed.
297Further @code{-v}'s increase the verbosity level, spewing out lots of
298information which is primarily of interest for diagnostic purposes.
299@item -L --license -V --version
300Display the software version, license terms and conditions.
301@item -1 (or --fast) to -9 (or --best)
302Set the block size to 100 k, 200 k .. 900 k when compressing. Has no
303effect when decompressing. See MEMORY MANAGEMENT below.
304The @code{--fast} and @code{--best} aliases are primarily for GNU
305@code{gzip} compatibility. In particular, @code{--fast} doesn't make
306things significantly faster. And @code{--best} merely selects the
307default behaviour.
308@item --
309Treats all subsequent arguments as file names, even if they start
310with a dash. This is so you can handle files with names beginning
311with a dash, for example: @code{bzip2 -- -myfilename}.
312@item --repetitive-fast
313@item --repetitive-best
314These flags are redundant in versions 0.9.5 and above. They provided
315some coarse control over the behaviour of the sorting algorithm in
316earlier versions, which was sometimes useful. 0.9.5 and above have an
317improved algorithm which renders these flags irrelevant.
318@end table
319
320
321@unnumberedsubsubsec MEMORY MANAGEMENT
322
323@code{bzip2} compresses large files in blocks. The block size affects
324both the compression ratio achieved, and the amount of memory needed for
325compression and decompression. The flags @code{-1} through @code{-9}
326specify the block size to be 100,000 bytes through 900,000 bytes (the
327default) respectively. At decompression time, the block size used for
328compression is read from the header of the compressed file, and
329@code{bunzip2} then allocates itself just enough memory to decompress
330the file. Since block sizes are stored in compressed files, it follows
331that the flags @code{-1} to @code{-9} are irrelevant to and so ignored
332during decompression.
333
334Compression and decompression requirements, in bytes, can be estimated
335as:
336@example
337 Compression: 400k + ( 8 x block size )
338
339 Decompression: 100k + ( 4 x block size ), or
340 100k + ( 2.5 x block size )
341@end example
342Larger block sizes give rapidly diminishing marginal returns. Most of
343the compression comes from the first two or three hundred k of block
344size, a fact worth bearing in mind when using @code{bzip2} on small machines.
345It is also important to appreciate that the decompression memory
346requirement is set at compression time by the choice of block size.
347
348For files compressed with the default 900k block size, @code{bunzip2}
349will require about 3700 kbytes to decompress. To support decompression
350of any file on a 4 megabyte machine, @code{bunzip2} has an option to
351decompress using approximately half this amount of memory, about 2300
352kbytes. Decompression speed is also halved, so you should use this
353option only where necessary. The relevant flag is @code{-s}.
354
355In general, try and use the largest block size memory constraints allow,
356since that maximises the compression achieved. Compression and
357decompression speed are virtually unaffected by block size.
358
359Another significant point applies to files which fit in a single block
360-- that means most files you'd encounter using a large block size. The
361amount of real memory touched is proportional to the size of the file,
362since the file is smaller than a block. For example, compressing a file
36320,000 bytes long with the flag @code{-9} will cause the compressor to
364allocate around 7600k of memory, but only touch 400k + 20000 * 8 = 560
365kbytes of it. Similarly, the decompressor will allocate 3700k but only
366touch 100k + 20000 * 4 = 180 kbytes.
367
368Here is a table which summarises the maximum memory usage for different
369block sizes. Also recorded is the total compressed size for 14 files of
370the Calgary Text Compression Corpus totalling 3,141,622 bytes. This
371column gives some feel for how compression varies with block size.
372These figures tend to understate the advantage of larger block sizes for
373larger files, since the Corpus is dominated by smaller files.
374@example
375 Compress Decompress Decompress Corpus
376 Flag usage usage -s usage Size
377
378 -1 1200k 500k 350k 914704
379 -2 2000k 900k 600k 877703
380 -3 2800k 1300k 850k 860338
381 -4 3600k 1700k 1100k 846899
382 -5 4400k 2100k 1350k 845160
383 -6 5200k 2500k 1600k 838626
384 -7 6100k 2900k 1850k 834096
385 -8 6800k 3300k 2100k 828642
386 -9 7600k 3700k 2350k 828642
387@end example
388
389@unnumberedsubsubsec RECOVERING DATA FROM DAMAGED FILES
390
391@code{bzip2} compresses files in blocks, usually 900kbytes long. Each
392block is handled independently. If a media or transmission error causes
393a multi-block @code{.bz2} file to become damaged, it may be possible to
394recover data from the undamaged blocks in the file.
395
396The compressed representation of each block is delimited by a 48-bit
397pattern, which makes it possible to find the block boundaries with
398reasonable certainty. Each block also carries its own 32-bit CRC, so
399damaged blocks can be distinguished from undamaged ones.
400
401@code{bzip2recover} is a simple program whose purpose is to search for
402blocks in @code{.bz2} files, and write each block out into its own
403@code{.bz2} file. You can then use @code{bzip2 -t} to test the
404integrity of the resulting files, and decompress those which are
405undamaged.
406
407@code{bzip2recover}
408takes a single argument, the name of the damaged file, and writes a
409number of files @code{rec00001file.bz2}, @code{rec00002file.bz2}, etc,
410containing the extracted blocks. The output filenames are designed so
411that the use of wildcards in subsequent processing -- for example,
412@code{bzip2 -dc rec*file.bz2 > recovered_data} -- processes the files in
413the correct order.
414
415@code{bzip2recover} should be of most use dealing with large @code{.bz2}
416files, as these will contain many blocks. It is clearly futile to use
417it on damaged single-block files, since a damaged block cannot be
418recovered. If you wish to minimise any potential data loss through
419media or transmission errors, you might consider compressing with a
420smaller block size.
421
422
423@unnumberedsubsubsec PERFORMANCE NOTES
424
425The sorting phase of compression gathers together similar strings in the
426file. Because of this, files containing very long runs of repeated
427symbols, like "aabaabaabaab ..." (repeated several hundred times) may
428compress more slowly than normal. Versions 0.9.5 and above fare much
429better than previous versions in this respect. The ratio between
430worst-case and average-case compression time is in the region of 10:1.
431For previous versions, this figure was more like 100:1. You can use the
432@code{-vvvv} option to monitor progress in great detail, if you want.
433
434Decompression speed is unaffected by these phenomena.
435
436@code{bzip2} usually allocates several megabytes of memory to operate
437in, and then charges all over it in a fairly random fashion. This means
438that performance, both for compressing and decompressing, is largely
439determined by the speed at which your machine can service cache misses.
440Because of this, small changes to the code to reduce the miss rate have
441been observed to give disproportionately large performance improvements.
442I imagine @code{bzip2} will perform best on machines with very large
443caches.
444
445
446@unnumberedsubsubsec CAVEATS
447
448I/O error messages are not as helpful as they could be. @code{bzip2}
449tries hard to detect I/O errors and exit cleanly, but the details of
450what the problem is sometimes seem rather misleading.
451
452This manual page pertains to version 1.0.2 of @code{bzip2}. Compressed
453data created by this version is entirely forwards and backwards
454compatible with the previous public releases, versions 0.1pl2, 0.9.0,
4550.9.5, 1.0.0 and 1.0.1, but with the following exception: 0.9.0 and
456above can correctly decompress multiple concatenated compressed files.
4570.1pl2 cannot do this; it will stop after decompressing just the first
458file in the stream.
459
460@code{bzip2recover} versions prior to this one, 1.0.2, used 32-bit
461integers to represent bit positions in compressed files, so it could not
462handle compressed files more than 512 megabytes long. Version 1.0.2 and
463above uses 64-bit ints on some platforms which support them (GNU
464supported targets, and Windows). To establish whether or not
465@code{bzip2recover} was built with such a limitation, run it without
466arguments. In any event you can build yourself an unlimited version if
467you can recompile it with @code{MaybeUInt64} set to be an unsigned
46864-bit integer.
469
470
471
472@unnumberedsubsubsec AUTHOR
473Julian Seward, @code{jseward@@acm.org}.
474
475@code{http://sources.redhat.com/bzip2}
476
477The ideas embodied in @code{bzip2} are due to (at least) the following
478people: Michael Burrows and David Wheeler (for the block sorting
479transformation), David Wheeler (again, for the Huffman coder), Peter
480Fenwick (for the structured coding model in the original @code{bzip},
481and many refinements), and Alistair Moffat, Radford Neal and Ian Witten
482(for the arithmetic coder in the original @code{bzip}). I am much
483indebted for their help, support and advice. See the manual in the
484source distribution for pointers to sources of documentation. Christian
485von Roques encouraged me to look for faster sorting algorithms, so as to
486speed up compression. Bela Lubkin encouraged me to improve the
487worst-case compression performance. The @code{bz*} scripts are derived
488from those of GNU @code{gzip}. Many people sent patches, helped with
489portability problems, lent machines, gave advice and were generally
490helpful.
491
492@end quotation
493
494
495
496
497@chapter Programming with @code{libbzip2}
498
499This chapter describes the programming interface to @code{libbzip2}.
500
501For general background information, particularly about memory
502use and performance aspects, you'd be well advised to read Chapter 2
503as well.
504
505@section Top-level structure
506
507@code{libbzip2} is a flexible library for compressing and decompressing
508data in the @code{bzip2} data format. Although packaged as a single
509entity, it helps to regard the library as three separate parts: the low
510level interface, and the high level interface, and some utility
511functions.
512
513The structure of @code{libbzip2}'s interfaces is similar to
514that of Jean-loup Gailly's and Mark Adler's excellent @code{zlib}
515library.
516
517All externally visible symbols have names beginning @code{BZ2_}.
518This is new in version 1.0. The intention is to minimise pollution
519of the namespaces of library clients.
520
521@subsection Low-level summary
522
523This interface provides services for compressing and decompressing
524data in memory. There's no provision for dealing with files, streams
525or any other I/O mechanisms, just straight memory-to-memory work.
526In fact, this part of the library can be compiled without inclusion
527of @code{stdio.h}, which may be helpful for embedded applications.
528
529The low-level part of the library has no global variables and
530is therefore thread-safe.
531
532Six routines make up the low level interface:
533@code{BZ2_bzCompressInit}, @code{BZ2_bzCompress}, and @* @code{BZ2_bzCompressEnd}
534for compression,
535and a corresponding trio @code{BZ2_bzDecompressInit}, @* @code{BZ2_bzDecompress}
536and @code{BZ2_bzDecompressEnd} for decompression.
537The @code{*Init} functions allocate
538memory for compression/decompression and do other
539initialisations, whilst the @code{*End} functions close down operations
540and release memory.
541
542The real work is done by @code{BZ2_bzCompress} and @code{BZ2_bzDecompress}.
543These compress and decompress data from a user-supplied input buffer
544to a user-supplied output buffer. These buffers can be any size;
545arbitrary quantities of data are handled by making repeated calls
546to these functions. This is a flexible mechanism allowing a
547consumer-pull style of activity, or producer-push, or a mixture of
548both.
549
550
551
552@subsection High-level summary
553
554This interface provides some handy wrappers around the low-level
555interface to facilitate reading and writing @code{bzip2} format
556files (@code{.bz2} files). The routines provide hooks to facilitate
557reading files in which the @code{bzip2} data stream is embedded
558within some larger-scale file structure, or where there are
559multiple @code{bzip2} data streams concatenated end-to-end.
560
561For reading files, @code{BZ2_bzReadOpen}, @code{BZ2_bzRead},
562@code{BZ2_bzReadClose} and @* @code{BZ2_bzReadGetUnused} are supplied. For
563writing files, @code{BZ2_bzWriteOpen}, @code{BZ2_bzWrite} and
564@code{BZ2_bzWriteFinish} are available.
565
566As with the low-level library, no global variables are used
567so the library is per se thread-safe. However, if I/O errors
568occur whilst reading or writing the underlying compressed files,
569you may have to consult @code{errno} to determine the cause of
570the error. In that case, you'd need a C library which correctly
571supports @code{errno} in a multithreaded environment.
572
573To make the library a little simpler and more portable,
574@code{BZ2_bzReadOpen} and @code{BZ2_bzWriteOpen} require you to pass them file
575handles (@code{FILE*}s) which have previously been opened for reading or
576writing respectively. That avoids portability problems associated with
577file operations and file attributes, whilst not being much of an
578imposition on the programmer.
579
580
581
582@subsection Utility functions summary
583For very simple needs, @code{BZ2_bzBuffToBuffCompress} and
584@code{BZ2_bzBuffToBuffDecompress} are provided. These compress
585data in memory from one buffer to another buffer in a single
586function call. You should assess whether these functions
587fulfill your memory-to-memory compression/decompression
588requirements before investing effort in understanding the more
589general but more complex low-level interface.
590
591Yoshioka Tsuneo (@code{QWF00133@@niftyserve.or.jp} /
592@code{tsuneo-y@@is.aist-nara.ac.jp}) has contributed some functions to
593give better @code{zlib} compatibility. These functions are
594@code{BZ2_bzopen}, @code{BZ2_bzread}, @code{BZ2_bzwrite}, @code{BZ2_bzflush},
595@code{BZ2_bzclose},
596@code{BZ2_bzerror} and @code{BZ2_bzlibVersion}. You may find these functions
597more convenient for simple file reading and writing, than those in the
598high-level interface. These functions are not (yet) officially part of
599the library, and are minimally documented here. If they break, you
600get to keep all the pieces. I hope to document them properly when time
601permits.
602
603Yoshioka also contributed modifications to allow the library to be
604built as a Windows DLL.
605
606
607@section Error handling
608
609The library is designed to recover cleanly in all situations, including
610the worst-case situation of decompressing random data. I'm not
611100% sure that it can always do this, so you might want to add
612a signal handler to catch segmentation violations during decompression
613if you are feeling especially paranoid. I would be interested in
614hearing more about the robustness of the library to corrupted
615compressed data.
616
617Version 1.0 is much more robust in this respect than
6180.9.0 or 0.9.5. Investigations with Checker (a tool for
619detecting problems with memory management, similar to Purify)
620indicate that, at least for the few files I tested, all single-bit
621errors in the decompressed data are caught properly, with no
622segmentation faults, no reads of uninitialised data and no
623out of range reads or writes. So it's certainly much improved,
624although I wouldn't claim it to be totally bombproof.
625
626The file @code{bzlib.h} contains all definitions needed to use
627the library. In particular, you should definitely not include
628@code{bzlib_private.h}.
629
630In @code{bzlib.h}, the various return values are defined. The following
631list is not intended as an exhaustive description of the circumstances
632in which a given value may be returned -- those descriptions are given
633later. Rather, it is intended to convey the rough meaning of each
634return value. The first five actions are normal and not intended to
635denote an error situation.
636@table @code
637@item BZ_OK
638The requested action was completed successfully.
639@item BZ_RUN_OK
640@itemx BZ_FLUSH_OK
641@itemx BZ_FINISH_OK
642In @code{BZ2_bzCompress}, the requested flush/finish/nothing-special action
643was completed successfully.
644@item BZ_STREAM_END
645Compression of data was completed, or the logical stream end was
646detected during decompression.
647@end table
648
649The following return values indicate an error of some kind.
650@table @code
651@item BZ_CONFIG_ERROR
652Indicates that the library has been improperly compiled on your
653platform -- a major configuration error. Specifically, it means
654that @code{sizeof(char)}, @code{sizeof(short)} and @code{sizeof(int)}
655are not 1, 2 and 4 respectively, as they should be. Note that the
656library should still work properly on 64-bit platforms which follow
657the LP64 programming model -- that is, where @code{sizeof(long)}
658and @code{sizeof(void*)} are 8. Under LP64, @code{sizeof(int)} is
659still 4, so @code{libbzip2}, which doesn't use the @code{long} type,
660is OK.
661@item BZ_SEQUENCE_ERROR
662When using the library, it is important to call the functions in the
663correct sequence and with data structures (buffers etc) in the correct
664states. @code{libbzip2} checks as much as it can to ensure this is
665happening, and returns @code{BZ_SEQUENCE_ERROR} if not. Code which
666complies precisely with the function semantics, as detailed below,
667should never receive this value; such an event denotes buggy code
668which you should investigate.
669@item BZ_PARAM_ERROR
670Returned when a parameter to a function call is out of range
671or otherwise manifestly incorrect. As with @code{BZ_SEQUENCE_ERROR},
672this denotes a bug in the client code. The distinction between
673@code{BZ_PARAM_ERROR} and @code{BZ_SEQUENCE_ERROR} is a bit hazy, but still worth
674making.
675@item BZ_MEM_ERROR
676Returned when a request to allocate memory failed. Note that the
677quantity of memory needed to decompress a stream cannot be determined
678until the stream's header has been read. So @code{BZ2_bzDecompress} and
679@code{BZ2_bzRead} may return @code{BZ_MEM_ERROR} even though some of
680the compressed data has been read. The same is not true for
681compression; once @code{BZ2_bzCompressInit} or @code{BZ2_bzWriteOpen} have
682successfully completed, @code{BZ_MEM_ERROR} cannot occur.
683@item BZ_DATA_ERROR
684Returned when a data integrity error is detected during decompression.
685Most importantly, this means when stored and computed CRCs for the
686data do not match. This value is also returned upon detection of any
687other anomaly in the compressed data.
688@item BZ_DATA_ERROR_MAGIC
689As a special case of @code{BZ_DATA_ERROR}, it is sometimes useful to
690know when the compressed stream does not start with the correct
691magic bytes (@code{'B' 'Z' 'h'}).
692@item BZ_IO_ERROR
693Returned by @code{BZ2_bzRead} and @code{BZ2_bzWrite} when there is an error
694reading or writing in the compressed file, and by @code{BZ2_bzReadOpen}
695and @code{BZ2_bzWriteOpen} for attempts to use a file for which the
696error indicator (viz, @code{ferror(f)}) is set.
697On receipt of @code{BZ_IO_ERROR}, the caller should consult
698@code{errno} and/or @code{perror} to acquire operating-system
699specific information about the problem.
700@item BZ_UNEXPECTED_EOF
701Returned by @code{BZ2_bzRead} when the compressed file finishes
702before the logical end of stream is detected.
703@item BZ_OUTBUFF_FULL
704Returned by @code{BZ2_bzBuffToBuffCompress} and
705@code{BZ2_bzBuffToBuffDecompress} to indicate that the output data
706will not fit into the output buffer provided.
707@end table
708
709
710
711@section Low-level interface
712
713@subsection @code{BZ2_bzCompressInit}
714@example
715typedef
716 struct @{
717 char *next_in;
718 unsigned int avail_in;
719 unsigned int total_in_lo32;
720 unsigned int total_in_hi32;
721
722 char *next_out;
723 unsigned int avail_out;
724 unsigned int total_out_lo32;
725 unsigned int total_out_hi32;
726
727 void *state;
728
729 void *(*bzalloc)(void *,int,int);
730 void (*bzfree)(void *,void *);
731 void *opaque;
732 @}
733 bz_stream;
734
735int BZ2_bzCompressInit ( bz_stream *strm,
736 int blockSize100k,
737 int verbosity,
738 int workFactor );
739
740@end example
741
742Prepares for compression. The @code{bz_stream} structure
743holds all data pertaining to the compression activity.
744A @code{bz_stream} structure should be allocated and initialised
745prior to the call.
746The fields of @code{bz_stream}
747comprise the entirety of the user-visible data. @code{state}
748is a pointer to the private data structures required for compression.
749
750Custom memory allocators are supported, via fields @code{bzalloc},
751@code{bzfree},
752and @code{opaque}. The value
753@code{opaque} is passed to as the first argument to
754all calls to @code{bzalloc} and @code{bzfree}, but is
755otherwise ignored by the library.
756The call @code{bzalloc ( opaque, n, m )} is expected to return a
757pointer @code{p} to
758@code{n * m} bytes of memory, and @code{bzfree ( opaque, p )}
759should free
760that memory.
761
762If you don't want to use a custom memory allocator, set @code{bzalloc},
763@code{bzfree} and
764@code{opaque} to @code{NULL},
765and the library will then use the standard @code{malloc}/@code{free}
766routines.
767
768Before calling @code{BZ2_bzCompressInit}, fields @code{bzalloc},
769@code{bzfree} and @code{opaque} should
770be filled appropriately, as just described. Upon return, the internal
771state will have been allocated and initialised, and @code{total_in_lo32},
772@code{total_in_hi32}, @code{total_out_lo32} and
773@code{total_out_hi32} will have been set to zero.
774These four fields are used by the library
775to inform the caller of the total amount of data passed into and out of
776the library, respectively. You should not try to change them.
777As of version 1.0, 64-bit counts are maintained, even on 32-bit
778platforms, using the @code{_hi32} fields to store the upper 32 bits
779of the count. So, for example, the total amount of data in
780is @code{(total_in_hi32 << 32) + total_in_lo32}.
781
782Parameter @code{blockSize100k} specifies the block size to be used for
783compression. It should be a value between 1 and 9 inclusive, and the
784actual block size used is 100000 x this figure. 9 gives the best
785compression but takes most memory.
786
787Parameter @code{verbosity} should be set to a number between 0 and 4
788inclusive. 0 is silent, and greater numbers give increasingly verbose
789monitoring/debugging output. If the library has been compiled with
790@code{-DBZ_NO_STDIO}, no such output will appear for any verbosity
791setting.
792
793Parameter @code{workFactor} controls how the compression phase behaves
794when presented with worst case, highly repetitive, input data. If
795compression runs into difficulties caused by repetitive data, the
796library switches from the standard sorting algorithm to a fallback
797algorithm. The fallback is slower than the standard algorithm by
798perhaps a factor of three, but always behaves reasonably, no matter how
799bad the input.
800
801Lower values of @code{workFactor} reduce the amount of effort the
802standard algorithm will expend before resorting to the fallback. You
803should set this parameter carefully; too low, and many inputs will be
804handled by the fallback algorithm and so compress rather slowly, too
805high, and your average-to-worst case compression times can become very
806large. The default value of 30 gives reasonable behaviour over a wide
807range of circumstances.
808
809Allowable values range from 0 to 250 inclusive. 0 is a special case,
810equivalent to using the default value of 30.
811
812Note that the compressed output generated is the same regardless of
813whether or not the fallback algorithm is used.
814
815Be aware also that this parameter may disappear entirely in future
816versions of the library. In principle it should be possible to devise a
817good way to automatically choose which algorithm to use. Such a
818mechanism would render the parameter obsolete.
819
820Possible return values:
821@display
822 @code{BZ_CONFIG_ERROR}
823 if the library has been mis-compiled
824 @code{BZ_PARAM_ERROR}
825 if @code{strm} is @code{NULL}
826 or @code{blockSize} < 1 or @code{blockSize} > 9
827 or @code{verbosity} < 0 or @code{verbosity} > 4
828 or @code{workFactor} < 0 or @code{workFactor} > 250
829 @code{BZ_MEM_ERROR}
830 if not enough memory is available
831 @code{BZ_OK}
832 otherwise
833@end display
834Allowable next actions:
835@display
836 @code{BZ2_bzCompress}
837 if @code{BZ_OK} is returned
838 no specific action needed in case of error
839@end display
840
841@subsection @code{BZ2_bzCompress}
842@example
843 int BZ2_bzCompress ( bz_stream *strm, int action );
844@end example
845Provides more input and/or output buffer space for the library. The
846caller maintains input and output buffers, and calls @code{BZ2_bzCompress} to
847transfer data between them.
848
849Before each call to @code{BZ2_bzCompress}, @code{next_in} should point at
850the data to be compressed, and @code{avail_in} should indicate how many
851bytes the library may read. @code{BZ2_bzCompress} updates @code{next_in},
852@code{avail_in} and @code{total_in} to reflect the number of bytes it
853has read.
854
855Similarly, @code{next_out} should point to a buffer in which the
856compressed data is to be placed, with @code{avail_out} indicating how
857much output space is available. @code{BZ2_bzCompress} updates
858@code{next_out}, @code{avail_out} and @code{total_out} to reflect the
859number of bytes output.
860
861You may provide and remove as little or as much data as you like on each
862call of @code{BZ2_bzCompress}. In the limit, it is acceptable to supply and
863remove data one byte at a time, although this would be terribly
864inefficient. You should always ensure that at least one byte of output
865space is available at each call.
866
867A second purpose of @code{BZ2_bzCompress} is to request a change of mode of the
868compressed stream.
869
870Conceptually, a compressed stream can be in one of four states: IDLE,
871RUNNING, FLUSHING and FINISHING. Before initialisation
872(@code{BZ2_bzCompressInit}) and after termination (@code{BZ2_bzCompressEnd}), a
873stream is regarded as IDLE.
874
875Upon initialisation (@code{BZ2_bzCompressInit}), the stream is placed in the
876RUNNING state. Subsequent calls to @code{BZ2_bzCompress} should pass
877@code{BZ_RUN} as the requested action; other actions are illegal and
878will result in @code{BZ_SEQUENCE_ERROR}.
879
880At some point, the calling program will have provided all the input data
881it wants to. It will then want to finish up -- in effect, asking the
882library to process any data it might have buffered internally. In this
883state, @code{BZ2_bzCompress} will no longer attempt to read data from
884@code{next_in}, but it will want to write data to @code{next_out}.
885Because the output buffer supplied by the user can be arbitrarily small,
886the finishing-up operation cannot necessarily be done with a single call
887of @code{BZ2_bzCompress}.
888
889Instead, the calling program passes @code{BZ_FINISH} as an action to
890@code{BZ2_bzCompress}. This changes the stream's state to FINISHING. Any
891remaining input (ie, @code{next_in[0 .. avail_in-1]}) is compressed and
892transferred to the output buffer. To do this, @code{BZ2_bzCompress} must be
893called repeatedly until all the output has been consumed. At that
894point, @code{BZ2_bzCompress} returns @code{BZ_STREAM_END}, and the stream's
895state is set back to IDLE. @code{BZ2_bzCompressEnd} should then be
896called.
897
898Just to make sure the calling program does not cheat, the library makes
899a note of @code{avail_in} at the time of the first call to
900@code{BZ2_bzCompress} which has @code{BZ_FINISH} as an action (ie, at the
901time the program has announced its intention to not supply any more
902input). By comparing this value with that of @code{avail_in} over
903subsequent calls to @code{BZ2_bzCompress}, the library can detect any
904attempts to slip in more data to compress. Any calls for which this is
905detected will return @code{BZ_SEQUENCE_ERROR}. This indicates a
906programming mistake which should be corrected.
907
908Instead of asking to finish, the calling program may ask
909@code{BZ2_bzCompress} to take all the remaining input, compress it and
910terminate the current (Burrows-Wheeler) compression block. This could
911be useful for error control purposes. The mechanism is analogous to
912that for finishing: call @code{BZ2_bzCompress} with an action of
913@code{BZ_FLUSH}, remove output data, and persist with the
914@code{BZ_FLUSH} action until the value @code{BZ_RUN} is returned. As
915with finishing, @code{BZ2_bzCompress} detects any attempt to provide more
916input data once the flush has begun.
917
918Once the flush is complete, the stream returns to the normal RUNNING
919state.
920
921This all sounds pretty complex, but isn't really. Here's a table
922which shows which actions are allowable in each state, what action
923will be taken, what the next state is, and what the non-error return
924values are. Note that you can't explicitly ask what state the
925stream is in, but nor do you need to -- it can be inferred from the
926values returned by @code{BZ2_bzCompress}.
927@display
928IDLE/@code{any}
929 Illegal. IDLE state only exists after @code{BZ2_bzCompressEnd} or
930 before @code{BZ2_bzCompressInit}.
931 Return value = @code{BZ_SEQUENCE_ERROR}
932
933RUNNING/@code{BZ_RUN}
934 Compress from @code{next_in} to @code{next_out} as much as possible.
935 Next state = RUNNING
936 Return value = @code{BZ_RUN_OK}
937
938RUNNING/@code{BZ_FLUSH}
939 Remember current value of @code{next_in}. Compress from @code{next_in}
940 to @code{next_out} as much as possible, but do not accept any more input.
941 Next state = FLUSHING
942 Return value = @code{BZ_FLUSH_OK}
943
944RUNNING/@code{BZ_FINISH}
945 Remember current value of @code{next_in}. Compress from @code{next_in}
946 to @code{next_out} as much as possible, but do not accept any more input.
947 Next state = FINISHING
948 Return value = @code{BZ_FINISH_OK}
949
950FLUSHING/@code{BZ_FLUSH}
951 Compress from @code{next_in} to @code{next_out} as much as possible,
952 but do not accept any more input.
953 If all the existing input has been used up and all compressed
954 output has been removed
955 Next state = RUNNING; Return value = @code{BZ_RUN_OK}
956 else
957 Next state = FLUSHING; Return value = @code{BZ_FLUSH_OK}
958
959FLUSHING/other
960 Illegal.
961 Return value = @code{BZ_SEQUENCE_ERROR}
962
963FINISHING/@code{BZ_FINISH}
964 Compress from @code{next_in} to @code{next_out} as much as possible,
965 but to not accept any more input.
966 If all the existing input has been used up and all compressed
967 output has been removed
968 Next state = IDLE; Return value = @code{BZ_STREAM_END}
969 else
970 Next state = FINISHING; Return value = @code{BZ_FINISHING}
971
972FINISHING/other
973 Illegal.
974 Return value = @code{BZ_SEQUENCE_ERROR}
975@end display
976
977That still looks complicated? Well, fair enough. The usual sequence
978of calls for compressing a load of data is:
979@itemize @bullet
980@item Get started with @code{BZ2_bzCompressInit}.
981@item Shovel data in and shlurp out its compressed form using zero or more
982calls of @code{BZ2_bzCompress} with action = @code{BZ_RUN}.
983@item Finish up.
984Repeatedly call @code{BZ2_bzCompress} with action = @code{BZ_FINISH},
985copying out the compressed output, until @code{BZ_STREAM_END} is returned.
986@item Close up and go home. Call @code{BZ2_bzCompressEnd}.
987@end itemize
988If the data you want to compress fits into your input buffer all
989at once, you can skip the calls of @code{BZ2_bzCompress ( ..., BZ_RUN )} and
990just do the @code{BZ2_bzCompress ( ..., BZ_FINISH )} calls.
991
992All required memory is allocated by @code{BZ2_bzCompressInit}. The
993compression library can accept any data at all (obviously). So you
994shouldn't get any error return values from the @code{BZ2_bzCompress} calls.
995If you do, they will be @code{BZ_SEQUENCE_ERROR}, and indicate a bug in
996your programming.
997
998Trivial other possible return values:
999@display
1000 @code{BZ_PARAM_ERROR}
1001 if @code{strm} is @code{NULL}, or @code{strm->s} is @code{NULL}
1002@end display
1003
1004@subsection @code{BZ2_bzCompressEnd}
1005@example
1006int BZ2_bzCompressEnd ( bz_stream *strm );
1007@end example
1008Releases all memory associated with a compression stream.
1009
1010Possible return values:
1011@display
1012 @code{BZ_PARAM_ERROR} if @code{strm} is @code{NULL} or @code{strm->s} is @code{NULL}
1013 @code{BZ_OK} otherwise
1014@end display
1015
1016
1017@subsection @code{BZ2_bzDecompressInit}
1018@example
1019int BZ2_bzDecompressInit ( bz_stream *strm, int verbosity, int small );
1020@end example
1021Prepares for decompression. As with @code{BZ2_bzCompressInit}, a
1022@code{bz_stream} record should be allocated and initialised before the
1023call. Fields @code{bzalloc}, @code{bzfree} and @code{opaque} should be
1024set if a custom memory allocator is required, or made @code{NULL} for
1025the normal @code{malloc}/@code{free} routines. Upon return, the internal
1026state will have been initialised, and @code{total_in} and
1027@code{total_out} will be zero.
1028
1029For the meaning of parameter @code{verbosity}, see @code{BZ2_bzCompressInit}.
1030
1031If @code{small} is nonzero, the library will use an alternative
1032decompression algorithm which uses less memory but at the cost of
1033decompressing more slowly (roughly speaking, half the speed, but the
1034maximum memory requirement drops to around 2300k). See Chapter 2 for
1035more information on memory management.
1036
1037Note that the amount of memory needed to decompress
1038a stream cannot be determined until the stream's header has been read,
1039so even if @code{BZ2_bzDecompressInit} succeeds, a subsequent
1040@code{BZ2_bzDecompress} could fail with @code{BZ_MEM_ERROR}.
1041
1042Possible return values:
1043@display
1044 @code{BZ_CONFIG_ERROR}
1045 if the library has been mis-compiled
1046 @code{BZ_PARAM_ERROR}
1047 if @code{(small != 0 && small != 1)}
1048 or @code{(verbosity < 0 || verbosity > 4)}
1049 @code{BZ_MEM_ERROR}
1050 if insufficient memory is available
1051@end display
1052
1053Allowable next actions:
1054@display
1055 @code{BZ2_bzDecompress}
1056 if @code{BZ_OK} was returned
1057 no specific action required in case of error
1058@end display
1059
1060
1061
1062@subsection @code{BZ2_bzDecompress}
1063@example
1064int BZ2_bzDecompress ( bz_stream *strm );
1065@end example
1066Provides more input and/out output buffer space for the library. The
1067caller maintains input and output buffers, and uses @code{BZ2_bzDecompress}
1068to transfer data between them.
1069
1070Before each call to @code{BZ2_bzDecompress}, @code{next_in}
1071should point at the compressed data,
1072and @code{avail_in} should indicate how many bytes the library
1073may read. @code{BZ2_bzDecompress} updates @code{next_in}, @code{avail_in}
1074and @code{total_in}
1075to reflect the number of bytes it has read.
1076
1077Similarly, @code{next_out} should point to a buffer in which the uncompressed
1078output is to be placed, with @code{avail_out} indicating how much output space
1079is available. @code{BZ2_bzCompress} updates @code{next_out},
1080@code{avail_out} and @code{total_out} to reflect
1081the number of bytes output.
1082
1083You may provide and remove as little or as much data as you like on
1084each call of @code{BZ2_bzDecompress}.
1085In the limit, it is acceptable to
1086supply and remove data one byte at a time, although this would be
1087terribly inefficient. You should always ensure that at least one
1088byte of output space is available at each call.
1089
1090Use of @code{BZ2_bzDecompress} is simpler than @code{BZ2_bzCompress}.
1091
1092You should provide input and remove output as described above, and
1093repeatedly call @code{BZ2_bzDecompress} until @code{BZ_STREAM_END} is
1094returned. Appearance of @code{BZ_STREAM_END} denotes that
1095@code{BZ2_bzDecompress} has detected the logical end of the compressed
1096stream. @code{BZ2_bzDecompress} will not produce @code{BZ_STREAM_END} until
1097all output data has been placed into the output buffer, so once
1098@code{BZ_STREAM_END} appears, you are guaranteed to have available all
1099the decompressed output, and @code{BZ2_bzDecompressEnd} can safely be
1100called.
1101
1102If case of an error return value, you should call @code{BZ2_bzDecompressEnd}
1103to clean up and release memory.
1104
1105Possible return values:
1106@display
1107 @code{BZ_PARAM_ERROR}
1108 if @code{strm} is @code{NULL} or @code{strm->s} is @code{NULL}
1109 or @code{strm->avail_out < 1}
1110 @code{BZ_DATA_ERROR}
1111 if a data integrity error is detected in the compressed stream
1112 @code{BZ_DATA_ERROR_MAGIC}
1113 if the compressed stream doesn't begin with the right magic bytes
1114 @code{BZ_MEM_ERROR}
1115 if there wasn't enough memory available
1116 @code{BZ_STREAM_END}
1117 if the logical end of the data stream was detected and all
1118 output in has been consumed, eg @code{s->avail_out > 0}
1119 @code{BZ_OK}
1120 otherwise
1121@end display
1122Allowable next actions:
1123@display
1124 @code{BZ2_bzDecompress}
1125 if @code{BZ_OK} was returned
1126 @code{BZ2_bzDecompressEnd}
1127 otherwise
1128@end display
1129
1130
1131@subsection @code{BZ2_bzDecompressEnd}
1132@example
1133int BZ2_bzDecompressEnd ( bz_stream *strm );
1134@end example
1135Releases all memory associated with a decompression stream.
1136
1137Possible return values:
1138@display
1139 @code{BZ_PARAM_ERROR}
1140 if @code{strm} is @code{NULL} or @code{strm->s} is @code{NULL}
1141 @code{BZ_OK}
1142 otherwise
1143@end display
1144
1145Allowable next actions:
1146@display
1147 None.
1148@end display
1149
1150
1151@section High-level interface
1152
1153This interface provides functions for reading and writing
1154@code{bzip2} format files. First, some general points.
1155
1156@itemize @bullet
1157@item All of the functions take an @code{int*} first argument,
1158 @code{bzerror}.
1159 After each call, @code{bzerror} should be consulted first to determine
1160 the outcome of the call. If @code{bzerror} is @code{BZ_OK},
1161 the call completed
1162 successfully, and only then should the return value of the function
1163 (if any) be consulted. If @code{bzerror} is @code{BZ_IO_ERROR},
1164 there was an error
1165 reading/writing the underlying compressed file, and you should
1166 then consult @code{errno}/@code{perror} to determine the
1167 cause of the difficulty.
1168 @code{bzerror} may also be set to various other values; precise details are
1169 given on a per-function basis below.
1170@item If @code{bzerror} indicates an error
1171 (ie, anything except @code{BZ_OK} and @code{BZ_STREAM_END}),
1172 you should immediately call @code{BZ2_bzReadClose} (or @code{BZ2_bzWriteClose},
1173 depending on whether you are attempting to read or to write)
1174 to free up all resources associated
1175 with the stream. Once an error has been indicated, behaviour of all calls
1176 except @code{BZ2_bzReadClose} (@code{BZ2_bzWriteClose}) is undefined.
1177 The implication is that (1) @code{bzerror} should
1178 be checked after each call, and (2) if @code{bzerror} indicates an error,
1179 @code{BZ2_bzReadClose} (@code{BZ2_bzWriteClose}) should then be called to clean up.
1180@item The @code{FILE*} arguments passed to
1181 @code{BZ2_bzReadOpen}/@code{BZ2_bzWriteOpen}
1182 should be set to binary mode.
1183 Most Unix systems will do this by default, but other platforms,
1184 including Windows and Mac, will not. If you omit this, you may
1185 encounter problems when moving code to new platforms.
1186@item Memory allocation requests are handled by
1187 @code{malloc}/@code{free}.
1188 At present
1189 there is no facility for user-defined memory allocators in the file I/O
1190 functions (could easily be added, though).
1191@end itemize
1192
1193
1194
1195@subsection @code{BZ2_bzReadOpen}
1196@example
1197 typedef void BZFILE;
1198
1199 BZFILE *BZ2_bzReadOpen ( int *bzerror, FILE *f,
1200 int small, int verbosity,
1201 void *unused, int nUnused );
1202@end example
1203Prepare to read compressed data from file handle @code{f}. @code{f}
1204should refer to a file which has been opened for reading, and for which
1205the error indicator (@code{ferror(f)})is not set. If @code{small} is 1,
1206the library will try to decompress using less memory, at the expense of
1207speed.
1208
1209For reasons explained below, @code{BZ2_bzRead} will decompress the
1210@code{nUnused} bytes starting at @code{unused}, before starting to read
1211from the file @code{f}. At most @code{BZ_MAX_UNUSED} bytes may be
1212supplied like this. If this facility is not required, you should pass
1213@code{NULL} and @code{0} for @code{unused} and n@code{Unused}
1214respectively.
1215
1216For the meaning of parameters @code{small} and @code{verbosity},
1217see @code{BZ2_bzDecompressInit}.
1218
1219The amount of memory needed to decompress a file cannot be determined
1220until the file's header has been read. So it is possible that
1221@code{BZ2_bzReadOpen} returns @code{BZ_OK} but a subsequent call of
1222@code{BZ2_bzRead} will return @code{BZ_MEM_ERROR}.
1223
1224Possible assignments to @code{bzerror}:
1225@display
1226 @code{BZ_CONFIG_ERROR}
1227 if the library has been mis-compiled
1228 @code{BZ_PARAM_ERROR}
1229 if @code{f} is @code{NULL}
1230 or @code{small} is neither @code{0} nor @code{1}
1231 or @code{(unused == NULL && nUnused != 0)}
1232 or @code{(unused != NULL && !(0 <= nUnused <= BZ_MAX_UNUSED))}
1233 @code{BZ_IO_ERROR}
1234 if @code{ferror(f)} is nonzero
1235 @code{BZ_MEM_ERROR}
1236 if insufficient memory is available
1237 @code{BZ_OK}
1238 otherwise.
1239@end display
1240
1241Possible return values:
1242@display
1243 Pointer to an abstract @code{BZFILE}
1244 if @code{bzerror} is @code{BZ_OK}
1245 @code{NULL}
1246 otherwise
1247@end display
1248
1249Allowable next actions:
1250@display
1251 @code{BZ2_bzRead}
1252 if @code{bzerror} is @code{BZ_OK}
1253 @code{BZ2_bzClose}
1254 otherwise
1255@end display
1256
1257
1258@subsection @code{BZ2_bzRead}
1259@example
1260 int BZ2_bzRead ( int *bzerror, BZFILE *b, void *buf, int len );
1261@end example
1262Reads up to @code{len} (uncompressed) bytes from the compressed file
1263@code{b} into
1264the buffer @code{buf}. If the read was successful,
1265@code{bzerror} is set to @code{BZ_OK}
1266and the number of bytes read is returned. If the logical end-of-stream
1267was detected, @code{bzerror} will be set to @code{BZ_STREAM_END},
1268and the number
1269of bytes read is returned. All other @code{bzerror} values denote an error.
1270
1271@code{BZ2_bzRead} will supply @code{len} bytes,
1272unless the logical stream end is detected
1273or an error occurs. Because of this, it is possible to detect the
1274stream end by observing when the number of bytes returned is
1275less than the number
1276requested. Nevertheless, this is regarded as inadvisable; you should
1277instead check @code{bzerror} after every call and watch out for
1278@code{BZ_STREAM_END}.
1279
1280Internally, @code{BZ2_bzRead} copies data from the compressed file in chunks
1281of size @code{BZ_MAX_UNUSED} bytes
1282before decompressing it. If the file contains more bytes than strictly
1283needed to reach the logical end-of-stream, @code{BZ2_bzRead} will almost certainly
1284read some of the trailing data before signalling @code{BZ_SEQUENCE_END}.
1285To collect the read but unused data once @code{BZ_SEQUENCE_END} has
1286appeared, call @code{BZ2_bzReadGetUnused} immediately before @code{BZ2_bzReadClose}.
1287
1288Possible assignments to @code{bzerror}:
1289@display
1290 @code{BZ_PARAM_ERROR}
1291 if @code{b} is @code{NULL} or @code{buf} is @code{NULL} or @code{len < 0}
1292 @code{BZ_SEQUENCE_ERROR}
1293 if @code{b} was opened with @code{BZ2_bzWriteOpen}
1294 @code{BZ_IO_ERROR}
1295 if there is an error reading from the compressed file
1296 @code{BZ_UNEXPECTED_EOF}
1297 if the compressed file ended before the logical end-of-stream was detected
1298 @code{BZ_DATA_ERROR}
1299 if a data integrity error was detected in the compressed stream
1300 @code{BZ_DATA_ERROR_MAGIC}
1301 if the stream does not begin with the requisite header bytes (ie, is not
1302 a @code{bzip2} data file). This is really a special case of @code{BZ_DATA_ERROR}.
1303 @code{BZ_MEM_ERROR}
1304 if insufficient memory was available
1305 @code{BZ_STREAM_END}
1306 if the logical end of stream was detected.
1307 @code{BZ_OK}
1308 otherwise.
1309@end display
1310
1311Possible return values:
1312@display
1313 number of bytes read
1314 if @code{bzerror} is @code{BZ_OK} or @code{BZ_STREAM_END}
1315 undefined
1316 otherwise
1317@end display
1318
1319Allowable next actions:
1320@display
1321 collect data from @code{buf}, then @code{BZ2_bzRead} or @code{BZ2_bzReadClose}
1322 if @code{bzerror} is @code{BZ_OK}
1323 collect data from @code{buf}, then @code{BZ2_bzReadClose} or @code{BZ2_bzReadGetUnused}
1324 if @code{bzerror} is @code{BZ_SEQUENCE_END}
1325 @code{BZ2_bzReadClose}
1326 otherwise
1327@end display
1328
1329
1330
1331@subsection @code{BZ2_bzReadGetUnused}
1332@example
1333 void BZ2_bzReadGetUnused ( int* bzerror, BZFILE *b,
1334 void** unused, int* nUnused );
1335@end example
1336Returns data which was read from the compressed file but was not needed
1337to get to the logical end-of-stream. @code{*unused} is set to the address
1338of the data, and @code{*nUnused} to the number of bytes. @code{*nUnused} will
1339be set to a value between @code{0} and @code{BZ_MAX_UNUSED} inclusive.
1340
1341This function may only be called once @code{BZ2_bzRead} has signalled
1342@code{BZ_STREAM_END} but before @code{BZ2_bzReadClose}.
1343
1344Possible assignments to @code{bzerror}:
1345@display
1346 @code{BZ_PARAM_ERROR}
1347 if @code{b} is @code{NULL}
1348 or @code{unused} is @code{NULL} or @code{nUnused} is @code{NULL}
1349 @code{BZ_SEQUENCE_ERROR}
1350 if @code{BZ_STREAM_END} has not been signalled
1351 or if @code{b} was opened with @code{BZ2_bzWriteOpen}
1352 @code{BZ_OK}
1353 otherwise
1354@end display
1355
1356Allowable next actions:
1357@display
1358 @code{BZ2_bzReadClose}
1359@end display
1360
1361
1362@subsection @code{BZ2_bzReadClose}
1363@example
1364 void BZ2_bzReadClose ( int *bzerror, BZFILE *b );
1365@end example
1366Releases all memory pertaining to the compressed file @code{b}.
1367@code{BZ2_bzReadClose} does not call @code{fclose} on the underlying file
1368handle, so you should do that yourself if appropriate.
1369@code{BZ2_bzReadClose} should be called to clean up after all error
1370situations.
1371
1372Possible assignments to @code{bzerror}:
1373@display
1374 @code{BZ_SEQUENCE_ERROR}
1375 if @code{b} was opened with @code{BZ2_bzOpenWrite}
1376 @code{BZ_OK}
1377 otherwise
1378@end display
1379
1380Allowable next actions:
1381@display
1382 none
1383@end display
1384
1385
1386
1387@subsection @code{BZ2_bzWriteOpen}
1388@example
1389 BZFILE *BZ2_bzWriteOpen ( int *bzerror, FILE *f,
1390 int blockSize100k, int verbosity,
1391 int workFactor );
1392@end example
1393Prepare to write compressed data to file handle @code{f}.
1394@code{f} should refer to
1395a file which has been opened for writing, and for which the error
1396indicator (@code{ferror(f)})is not set.
1397
1398For the meaning of parameters @code{blockSize100k},
1399@code{verbosity} and @code{workFactor}, see
1400@* @code{BZ2_bzCompressInit}.
1401
1402All required memory is allocated at this stage, so if the call
1403completes successfully, @code{BZ_MEM_ERROR} cannot be signalled by a
1404subsequent call to @code{BZ2_bzWrite}.
1405
1406Possible assignments to @code{bzerror}:
1407@display
1408 @code{BZ_CONFIG_ERROR}
1409 if the library has been mis-compiled
1410 @code{BZ_PARAM_ERROR}
1411 if @code{f} is @code{NULL}
1412 or @code{blockSize100k < 1} or @code{blockSize100k > 9}
1413 @code{BZ_IO_ERROR}
1414 if @code{ferror(f)} is nonzero
1415 @code{BZ_MEM_ERROR}
1416 if insufficient memory is available
1417 @code{BZ_OK}
1418 otherwise
1419@end display
1420
1421Possible return values:
1422@display
1423 Pointer to an abstract @code{BZFILE}
1424 if @code{bzerror} is @code{BZ_OK}
1425 @code{NULL}
1426 otherwise
1427@end display
1428
1429Allowable next actions:
1430@display
1431 @code{BZ2_bzWrite}
1432 if @code{bzerror} is @code{BZ_OK}
1433 (you could go directly to @code{BZ2_bzWriteClose}, but this would be pretty pointless)
1434 @code{BZ2_bzWriteClose}
1435 otherwise
1436@end display
1437
1438
1439
1440@subsection @code{BZ2_bzWrite}
1441@example
1442 void BZ2_bzWrite ( int *bzerror, BZFILE *b, void *buf, int len );
1443@end example
1444Absorbs @code{len} bytes from the buffer @code{buf}, eventually to be
1445compressed and written to the file.
1446
1447Possible assignments to @code{bzerror}:
1448@display
1449 @code{BZ_PARAM_ERROR}
1450 if @code{b} is @code{NULL} or @code{buf} is @code{NULL} or @code{len < 0}
1451 @code{BZ_SEQUENCE_ERROR}
1452 if b was opened with @code{BZ2_bzReadOpen}
1453 @code{BZ_IO_ERROR}
1454 if there is an error writing the compressed file.
1455 @code{BZ_OK}
1456 otherwise
1457@end display
1458
1459
1460
1461
1462@subsection @code{BZ2_bzWriteClose}
1463@example
1464 void BZ2_bzWriteClose ( int *bzerror, BZFILE* f,
1465 int abandon,
1466 unsigned int* nbytes_in,
1467 unsigned int* nbytes_out );
1468
1469 void BZ2_bzWriteClose64 ( int *bzerror, BZFILE* f,
1470 int abandon,
1471 unsigned int* nbytes_in_lo32,
1472 unsigned int* nbytes_in_hi32,
1473 unsigned int* nbytes_out_lo32,
1474 unsigned int* nbytes_out_hi32 );
1475@end example
1476
1477Compresses and flushes to the compressed file all data so far supplied
1478by @code{BZ2_bzWrite}. The logical end-of-stream markers are also written, so
1479subsequent calls to @code{BZ2_bzWrite} are illegal. All memory associated
1480with the compressed file @code{b} is released.
1481@code{fflush} is called on the
1482compressed file, but it is not @code{fclose}'d.
1483
1484If @code{BZ2_bzWriteClose} is called to clean up after an error, the only
1485action is to release the memory. The library records the error codes
1486issued by previous calls, so this situation will be detected
1487automatically. There is no attempt to complete the compression
1488operation, nor to @code{fflush} the compressed file. You can force this
1489behaviour to happen even in the case of no error, by passing a nonzero
1490value to @code{abandon}.
1491
1492If @code{nbytes_in} is non-null, @code{*nbytes_in} will be set to be the
1493total volume of uncompressed data handled. Similarly, @code{nbytes_out}
1494will be set to the total volume of compressed data written. For
1495compatibility with older versions of the library, @code{BZ2_bzWriteClose}
1496only yields the lower 32 bits of these counts. Use
1497@code{BZ2_bzWriteClose64} if you want the full 64 bit counts. These
1498two functions are otherwise absolutely identical.
1499
1500
1501Possible assignments to @code{bzerror}:
1502@display
1503 @code{BZ_SEQUENCE_ERROR}
1504 if @code{b} was opened with @code{BZ2_bzReadOpen}
1505 @code{BZ_IO_ERROR}
1506 if there is an error writing the compressed file
1507 @code{BZ_OK}
1508 otherwise
1509@end display
1510
1511@subsection Handling embedded compressed data streams
1512
1513The high-level library facilitates use of
1514@code{bzip2} data streams which form some part of a surrounding, larger
1515data stream.
1516@itemize @bullet
1517@item For writing, the library takes an open file handle, writes
1518compressed data to it, @code{fflush}es it but does not @code{fclose} it.
1519The calling application can write its own data before and after the
1520compressed data stream, using that same file handle.
1521@item Reading is more complex, and the facilities are not as general
1522as they could be since generality is hard to reconcile with efficiency.
1523@code{BZ2_bzRead} reads from the compressed file in blocks of size
1524@code{BZ_MAX_UNUSED} bytes, and in doing so probably will overshoot
1525the logical end of compressed stream.
1526To recover this data once decompression has
1527ended, call @code{BZ2_bzReadGetUnused} after the last call of @code{BZ2_bzRead}
1528(the one returning @code{BZ_STREAM_END}) but before calling
1529@code{BZ2_bzReadClose}.
1530@end itemize
1531
1532This mechanism makes it easy to decompress multiple @code{bzip2}
1533streams placed end-to-end. As the end of one stream, when @code{BZ2_bzRead}
1534returns @code{BZ_STREAM_END}, call @code{BZ2_bzReadGetUnused} to collect the
1535unused data (copy it into your own buffer somewhere).
1536That data forms the start of the next compressed stream.
1537To start uncompressing that next stream, call @code{BZ2_bzReadOpen} again,
1538feeding in the unused data via the @code{unused}/@code{nUnused}
1539parameters.
1540Keep doing this until @code{BZ_STREAM_END} return coincides with the
1541physical end of file (@code{feof(f)}). In this situation
1542@code{BZ2_bzReadGetUnused}
1543will of course return no data.
1544
1545This should give some feel for how the high-level interface can be used.
1546If you require extra flexibility, you'll have to bite the bullet and get
1547to grips with the low-level interface.
1548
1549@subsection Standard file-reading/writing code
1550Here's how you'd write data to a compressed file:
1551@example @code
1552FILE* f;
1553BZFILE* b;
1554int nBuf;
1555char buf[ /* whatever size you like */ ];
1556int bzerror;
1557int nWritten;
1558
1559f = fopen ( "myfile.bz2", "w" );
1560if (!f) @{
1561 /* handle error */
1562@}
1563b = BZ2_bzWriteOpen ( &bzerror, f, 9 );
1564if (bzerror != BZ_OK) @{
1565 BZ2_bzWriteClose ( b );
1566 /* handle error */
1567@}
1568
1569while ( /* condition */ ) @{
1570 /* get data to write into buf, and set nBuf appropriately */
1571 nWritten = BZ2_bzWrite ( &bzerror, b, buf, nBuf );
1572 if (bzerror == BZ_IO_ERROR) @{
1573 BZ2_bzWriteClose ( &bzerror, b );
1574 /* handle error */
1575 @}
1576@}
1577
1578BZ2_bzWriteClose ( &bzerror, b );
1579if (bzerror == BZ_IO_ERROR) @{
1580 /* handle error */
1581@}
1582@end example
1583And to read from a compressed file:
1584@example
1585FILE* f;
1586BZFILE* b;
1587int nBuf;
1588char buf[ /* whatever size you like */ ];
1589int bzerror;
1590int nWritten;
1591
1592f = fopen ( "myfile.bz2", "r" );
1593if (!f) @{
1594 /* handle error */
1595@}
1596b = BZ2_bzReadOpen ( &bzerror, f, 0, NULL, 0 );
1597if (bzerror != BZ_OK) @{
1598 BZ2_bzReadClose ( &bzerror, b );
1599 /* handle error */
1600@}
1601
1602bzerror = BZ_OK;
1603while (bzerror == BZ_OK && /* arbitrary other conditions */) @{
1604 nBuf = BZ2_bzRead ( &bzerror, b, buf, /* size of buf */ );
1605 if (bzerror == BZ_OK) @{
1606 /* do something with buf[0 .. nBuf-1] */
1607 @}
1608@}
1609if (bzerror != BZ_STREAM_END) @{
1610 BZ2_bzReadClose ( &bzerror, b );
1611 /* handle error */
1612@} else @{
1613 BZ2_bzReadClose ( &bzerror );
1614@}
1615@end example
1616
1617
1618
1619@section Utility functions
1620@subsection @code{BZ2_bzBuffToBuffCompress}
1621@example
1622 int BZ2_bzBuffToBuffCompress( char* dest,
1623 unsigned int* destLen,
1624 char* source,
1625 unsigned int sourceLen,
1626 int blockSize100k,
1627 int verbosity,
1628 int workFactor );
1629@end example
1630Attempts to compress the data in @code{source[0 .. sourceLen-1]}
1631into the destination buffer, @code{dest[0 .. *destLen-1]}.
1632If the destination buffer is big enough, @code{*destLen} is
1633set to the size of the compressed data, and @code{BZ_OK} is
1634returned. If the compressed data won't fit, @code{*destLen}
1635is unchanged, and @code{BZ_OUTBUFF_FULL} is returned.
1636
1637Compression in this manner is a one-shot event, done with a single call
1638to this function. The resulting compressed data is a complete
1639@code{bzip2} format data stream. There is no mechanism for making
1640additional calls to provide extra input data. If you want that kind of
1641mechanism, use the low-level interface.
1642
1643For the meaning of parameters @code{blockSize100k}, @code{verbosity}
1644and @code{workFactor}, @* see @code{BZ2_bzCompressInit}.
1645
1646To guarantee that the compressed data will fit in its buffer, allocate
1647an output buffer of size 1% larger than the uncompressed data, plus
1648six hundred extra bytes.
1649
1650@code{BZ2_bzBuffToBuffDecompress} will not write data at or
1651beyond @code{dest[*destLen]}, even in case of buffer overflow.
1652
1653Possible return values:
1654@display
1655 @code{BZ_CONFIG_ERROR}
1656 if the library has been mis-compiled
1657 @code{BZ_PARAM_ERROR}
1658 if @code{dest} is @code{NULL} or @code{destLen} is @code{NULL}
1659 or @code{blockSize100k < 1} or @code{blockSize100k > 9}
1660 or @code{verbosity < 0} or @code{verbosity > 4}
1661 or @code{workFactor < 0} or @code{workFactor > 250}
1662 @code{BZ_MEM_ERROR}
1663 if insufficient memory is available
1664 @code{BZ_OUTBUFF_FULL}
1665 if the size of the compressed data exceeds @code{*destLen}
1666 @code{BZ_OK}
1667 otherwise
1668@end display
1669
1670
1671
1672@subsection @code{BZ2_bzBuffToBuffDecompress}
1673@example
1674 int BZ2_bzBuffToBuffDecompress ( char* dest,
1675 unsigned int* destLen,
1676 char* source,
1677 unsigned int sourceLen,
1678 int small,
1679 int verbosity );
1680@end example
1681Attempts to decompress the data in @code{source[0 .. sourceLen-1]}
1682into the destination buffer, @code{dest[0 .. *destLen-1]}.
1683If the destination buffer is big enough, @code{*destLen} is
1684set to the size of the uncompressed data, and @code{BZ_OK} is
1685returned. If the compressed data won't fit, @code{*destLen}
1686is unchanged, and @code{BZ_OUTBUFF_FULL} is returned.
1687
1688@code{source} is assumed to hold a complete @code{bzip2} format
1689data stream. @* @code{BZ2_bzBuffToBuffDecompress} tries to decompress
1690the entirety of the stream into the output buffer.
1691
1692For the meaning of parameters @code{small} and @code{verbosity},
1693see @code{BZ2_bzDecompressInit}.
1694
1695Because the compression ratio of the compressed data cannot be known in
1696advance, there is no easy way to guarantee that the output buffer will
1697be big enough. You may of course make arrangements in your code to
1698record the size of the uncompressed data, but such a mechanism is beyond
1699the scope of this library.
1700
1701@code{BZ2_bzBuffToBuffDecompress} will not write data at or
1702beyond @code{dest[*destLen]}, even in case of buffer overflow.
1703
1704Possible return values:
1705@display
1706 @code{BZ_CONFIG_ERROR}
1707 if the library has been mis-compiled
1708 @code{BZ_PARAM_ERROR}
1709 if @code{dest} is @code{NULL} or @code{destLen} is @code{NULL}
1710 or @code{small != 0 && small != 1}
1711 or @code{verbosity < 0} or @code{verbosity > 4}
1712 @code{BZ_MEM_ERROR}
1713 if insufficient memory is available
1714 @code{BZ_OUTBUFF_FULL}
1715 if the size of the compressed data exceeds @code{*destLen}
1716 @code{BZ_DATA_ERROR}
1717 if a data integrity error was detected in the compressed data
1718 @code{BZ_DATA_ERROR_MAGIC}
1719 if the compressed data doesn't begin with the right magic bytes
1720 @code{BZ_UNEXPECTED_EOF}
1721 if the compressed data ends unexpectedly
1722 @code{BZ_OK}
1723 otherwise
1724@end display
1725
1726
1727
1728@section @code{zlib} compatibility functions
1729Yoshioka Tsuneo has contributed some functions to
1730give better @code{zlib} compatibility. These functions are
1731@code{BZ2_bzopen}, @code{BZ2_bzread}, @code{BZ2_bzwrite}, @code{BZ2_bzflush},
1732@code{BZ2_bzclose},
1733@code{BZ2_bzerror} and @code{BZ2_bzlibVersion}.
1734These functions are not (yet) officially part of
1735the library. If they break, you get to keep all the pieces.
1736Nevertheless, I think they work ok.
1737@example
1738typedef void BZFILE;
1739
1740const char * BZ2_bzlibVersion ( void );
1741@end example
1742Returns a string indicating the library version.
1743@example
1744BZFILE * BZ2_bzopen ( const char *path, const char *mode );
1745BZFILE * BZ2_bzdopen ( int fd, const char *mode );
1746@end example
1747Opens a @code{.bz2} file for reading or writing, using either its name
1748or a pre-existing file descriptor.
1749Analogous to @code{fopen} and @code{fdopen}.
1750@example
1751int BZ2_bzread ( BZFILE* b, void* buf, int len );
1752int BZ2_bzwrite ( BZFILE* b, void* buf, int len );
1753@end example
1754Reads/writes data from/to a previously opened @code{BZFILE}.
1755Analogous to @code{fread} and @code{fwrite}.
1756@example
1757int BZ2_bzflush ( BZFILE* b );
1758void BZ2_bzclose ( BZFILE* b );
1759@end example
1760Flushes/closes a @code{BZFILE}. @code{BZ2_bzflush} doesn't actually do
1761anything. Analogous to @code{fflush} and @code{fclose}.
1762
1763@example
1764const char * BZ2_bzerror ( BZFILE *b, int *errnum )
1765@end example
1766Returns a string describing the more recent error status of
1767@code{b}, and also sets @code{*errnum} to its numerical value.
1768
1769
1770@section Using the library in a @code{stdio}-free environment
1771
1772@subsection Getting rid of @code{stdio}
1773
1774In a deeply embedded application, you might want to use just
1775the memory-to-memory functions. You can do this conveniently
1776by compiling the library with preprocessor symbol @code{BZ_NO_STDIO}
1777defined. Doing this gives you a library containing only the following
1778eight functions:
1779
1780@code{BZ2_bzCompressInit}, @code{BZ2_bzCompress}, @code{BZ2_bzCompressEnd} @*
1781@code{BZ2_bzDecompressInit}, @code{BZ2_bzDecompress}, @code{BZ2_bzDecompressEnd} @*
1782@code{BZ2_bzBuffToBuffCompress}, @code{BZ2_bzBuffToBuffDecompress}
1783
1784When compiled like this, all functions will ignore @code{verbosity}
1785settings.
1786
1787@subsection Critical error handling
1788@code{libbzip2} contains a number of internal assertion checks which
1789should, needless to say, never be activated. Nevertheless, if an
1790assertion should fail, behaviour depends on whether or not the library
1791was compiled with @code{BZ_NO_STDIO} set.
1792
1793For a normal compile, an assertion failure yields the message
1794@example
1795 bzip2/libbzip2: internal error number N.
1796 This is a bug in bzip2/libbzip2, 1.0.2, 30-Dec-2001.
1797 Please report it to me at: jseward@@acm.org. If this happened
1798 when you were using some program which uses libbzip2 as a
1799 component, you should also report this bug to the author(s)
1800 of that program. Please make an effort to report this bug;
1801 timely and accurate bug reports eventually lead to higher
1802 quality software. Thanks. Julian Seward, 30 December 2001.
1803@end example
1804where @code{N} is some error code number. If @code{N == 1007}, it also
1805prints some extra text advising the reader that unreliable memory is
1806often associated with internal error 1007. (This is a
1807frequently-observed-phenomenon with versions 1.0.0/1.0.1).
1808
1809@code{exit(3)} is then called.
1810
1811For a @code{stdio}-free library, assertion failures result
1812in a call to a function declared as:
1813@example
1814 extern void bz_internal_error ( int errcode );
1815@end example
1816The relevant code is passed as a parameter. You should supply
1817such a function.
1818
1819In either case, once an assertion failure has occurred, any
1820@code{bz_stream} records involved can be regarded as invalid.
1821You should not attempt to resume normal operation with them.
1822
1823You may, of course, change critical error handling to suit
1824your needs. As I said above, critical errors indicate bugs
1825in the library and should not occur. All "normal" error
1826situations are indicated via error return codes from functions,
1827and can be recovered from.
1828
1829
1830@section Making a Windows DLL
1831Everything related to Windows has been contributed by Yoshioka Tsuneo
1832@* (@code{QWF00133@@niftyserve.or.jp} /
1833@code{tsuneo-y@@is.aist-nara.ac.jp}), so you should send your queries to
1834him (but perhaps Cc: me, @code{jseward@@acm.org}).
1835
1836My vague understanding of what to do is: using Visual C++ 5.0,
1837open the project file @code{libbz2.dsp}, and build. That's all.
1838
1839If you can't
1840open the project file for some reason, make a new one, naming these files:
1841@code{blocksort.c}, @code{bzlib.c}, @code{compress.c},
1842@code{crctable.c}, @code{decompress.c}, @code{huffman.c}, @*
1843@code{randtable.c} and @code{libbz2.def}. You will also need
1844to name the header files @code{bzlib.h} and @code{bzlib_private.h}.
1845
1846If you don't use VC++, you may need to define the proprocessor symbol
1847@code{_WIN32}.
1848
1849Finally, @code{dlltest.c} is a sample program using the DLL. It has a
1850project file, @code{dlltest.dsp}.
1851
1852If you just want a makefile for Visual C, have a look at
1853@code{makefile.msc}.
1854
1855Be aware that if you compile @code{bzip2} itself on Win32, you must set
1856@code{BZ_UNIX} to 0 and @code{BZ_LCCWIN32} to 1, in the file
1857@code{bzip2.c}, before compiling. Otherwise the resulting binary won't
1858work correctly.
1859
1860I haven't tried any of this stuff myself, but it all looks plausible.
1861
1862
1863
1864@chapter Miscellanea
1865
1866These are just some random thoughts of mine. Your mileage may
1867vary.
1868
1869@section Limitations of the compressed file format
1870@code{bzip2-1.0}, @code{0.9.5} and @code{0.9.0}
1871use exactly the same file format as the previous
1872version, @code{bzip2-0.1}. This decision was made in the interests of
1873stability. Creating yet another incompatible compressed file format
1874would create further confusion and disruption for users.
1875
1876Nevertheless, this is not a painless decision. Development
1877work since the release of @code{bzip2-0.1} in August 1997
1878has shown complexities in the file format which slow down
1879decompression and, in retrospect, are unnecessary. These are:
1880@itemize @bullet
1881@item The run-length encoder, which is the first of the
1882 compression transformations, is entirely irrelevant.
1883 The original purpose was to protect the sorting algorithm
1884 from the very worst case input: a string of repeated
1885 symbols. But algorithm steps Q6a and Q6b in the original
1886 Burrows-Wheeler technical report (SRC-124) show how
1887 repeats can be handled without difficulty in block
1888 sorting.
1889@item The randomisation mechanism doesn't really need to be
1890 there. Udi Manber and Gene Myers published a suffix
1891 array construction algorithm a few years back, which
1892 can be employed to sort any block, no matter how
1893 repetitive, in O(N log N) time. Subsequent work by
1894 Kunihiko Sadakane has produced a derivative O(N (log N)^2)
1895 algorithm which usually outperforms the Manber-Myers
1896 algorithm.
1897
1898 I could have changed to Sadakane's algorithm, but I find
1899 it to be slower than @code{bzip2}'s existing algorithm for
1900 most inputs, and the randomisation mechanism protects
1901 adequately against bad cases. I didn't think it was
1902 a good tradeoff to make. Partly this is due to the fact
1903 that I was not flooded with email complaints about
1904 @code{bzip2-0.1}'s performance on repetitive data, so
1905 perhaps it isn't a problem for real inputs.
1906
1907 Probably the best long-term solution,
1908 and the one I have incorporated into 0.9.5 and above,
1909 is to use the existing sorting
1910 algorithm initially, and fall back to a O(N (log N)^2)
1911 algorithm if the standard algorithm gets into difficulties.
1912@item The compressed file format was never designed to be
1913 handled by a library, and I have had to jump though
1914 some hoops to produce an efficient implementation of
1915 decompression. It's a bit hairy. Try passing
1916 @code{decompress.c} through the C preprocessor
1917 and you'll see what I mean. Much of this complexity
1918 could have been avoided if the compressed size of
1919 each block of data was recorded in the data stream.
1920@item An Adler-32 checksum, rather than a CRC32 checksum,
1921 would be faster to compute.
1922@end itemize
1923It would be fair to say that the @code{bzip2} format was frozen
1924before I properly and fully understood the performance
1925consequences of doing so.
1926
1927Improvements which I was able to incorporate into
19280.9.0, despite using the same file format, are:
1929@itemize @bullet
1930@item Single array implementation of the inverse BWT. This
1931 significantly speeds up decompression, presumably
1932 because it reduces the number of cache misses.
1933@item Faster inverse MTF transform for large MTF values. The
1934 new implementation is based on the notion of sliding blocks
1935 of values.
1936@item @code{bzip2-0.9.0} now reads and writes files with @code{fread}
1937 and @code{fwrite}; version 0.1 used @code{putc} and @code{getc}.
1938 Duh! Well, you live and learn.
1939
1940@end itemize
1941Further ahead, it would be nice
1942to be able to do random access into files. This will
1943require some careful design of compressed file formats.
1944
1945
1946
1947@section Portability issues
1948After some consideration, I have decided not to use
1949GNU @code{autoconf} to configure 0.9.5 or 1.0.
1950
1951@code{autoconf}, admirable and wonderful though it is,
1952mainly assists with portability problems between Unix-like
1953platforms. But @code{bzip2} doesn't have much in the way
1954of portability problems on Unix; most of the difficulties appear
1955when porting to the Mac, or to Microsoft's operating systems.
1956@code{autoconf} doesn't help in those cases, and brings in a
1957whole load of new complexity.
1958
1959Most people should be able to compile the library and program
1960under Unix straight out-of-the-box, so to speak, especially
1961if you have a version of GNU C available.
1962
1963There are a couple of @code{__inline__} directives in the code. GNU C
1964(@code{gcc}) should be able to handle them. If you're not using
1965GNU C, your C compiler shouldn't see them at all.
1966If your compiler does, for some reason, see them and doesn't
1967like them, just @code{#define} @code{__inline__} to be @code{/* */}. One
1968easy way to do this is to compile with the flag @code{-D__inline__=},
1969which should be understood by most Unix compilers.
1970
1971If you still have difficulties, try compiling with the macro
1972@code{BZ_STRICT_ANSI} defined. This should enable you to build the
1973library in a strictly ANSI compliant environment. Building the program
1974itself like this is dangerous and not supported, since you remove
1975@code{bzip2}'s checks against compressing directories, symbolic links,
1976devices, and other not-really-a-file entities. This could cause
1977filesystem corruption!
1978
1979One other thing: if you create a @code{bzip2} binary for public
1980distribution, please try and link it statically (@code{gcc -s}). This
1981avoids all sorts of library-version issues that others may encounter
1982later on.
1983
1984If you build @code{bzip2} on Win32, you must set @code{BZ_UNIX} to 0 and
1985@code{BZ_LCCWIN32} to 1, in the file @code{bzip2.c}, before compiling.
1986Otherwise the resulting binary won't work correctly.
1987
1988
1989
1990@section Reporting bugs
1991I tried pretty hard to make sure @code{bzip2} is
1992bug free, both by design and by testing. Hopefully
1993you'll never need to read this section for real.
1994
1995Nevertheless, if @code{bzip2} dies with a segmentation
1996fault, a bus error or an internal assertion failure, it
1997will ask you to email me a bug report. Experience with
1998version 0.1 shows that almost all these problems can
1999be traced to either compiler bugs or hardware problems.
2000@itemize @bullet
2001@item
2002Recompile the program with no optimisation, and see if it
2003works. And/or try a different compiler.
2004I heard all sorts of stories about various flavours
2005of GNU C (and other compilers) generating bad code for
2006@code{bzip2}, and I've run across two such examples myself.
2007
20082.7.X versions of GNU C are known to generate bad code from
2009time to time, at high optimisation levels.
2010If you get problems, try using the flags
2011@code{-O2} @code{-fomit-frame-pointer} @code{-fno-strength-reduce}.
2012You should specifically @emph{not} use @code{-funroll-loops}.
2013
2014You may notice that the Makefile runs six tests as part of
2015the build process. If the program passes all of these, it's
2016a pretty good (but not 100%) indication that the compiler has
2017done its job correctly.
2018@item
2019If @code{bzip2} crashes randomly, and the crashes are not
2020repeatable, you may have a flaky memory subsystem. @code{bzip2}
2021really hammers your memory hierarchy, and if it's a bit marginal,
2022you may get these problems. Ditto if your disk or I/O subsystem
2023is slowly failing. Yup, this really does happen.
2024
2025Try using a different machine of the same type, and see if
2026you can repeat the problem.
2027@item This isn't really a bug, but ... If @code{bzip2} tells
2028you your file is corrupted on decompression, and you
2029obtained the file via FTP, there is a possibility that you
2030forgot to tell FTP to do a binary mode transfer. That absolutely
2031will cause the file to be non-decompressible. You'll have to transfer
2032it again.
2033@end itemize
2034
2035If you've incorporated @code{libbzip2} into your own program
2036and are getting problems, please, please, please, check that the
2037parameters you are passing in calls to the library, are
2038correct, and in accordance with what the documentation says
2039is allowable. I have tried to make the library robust against
2040such problems, but I'm sure I haven't succeeded.
2041
2042Finally, if the above comments don't help, you'll have to send
2043me a bug report. Now, it's just amazing how many people will
2044send me a bug report saying something like
2045@display
2046 bzip2 crashed with segmentation fault on my machine
2047@end display
2048and absolutely nothing else. Needless to say, a such a report
2049is @emph{totally, utterly, completely and comprehensively 100% useless;
2050a waste of your time, my time, and net bandwidth}.
2051With no details at all, there's no way I can possibly begin
2052to figure out what the problem is.
2053
2054The rules of the game are: facts, facts, facts. Don't omit
2055them because "oh, they won't be relevant". At the bare
2056minimum:
2057@display
2058 Machine type. Operating system version.
2059 Exact version of @code{bzip2} (do @code{bzip2 -V}).
2060 Exact version of the compiler used.
2061 Flags passed to the compiler.
2062@end display
2063However, the most important single thing that will help me is
2064the file that you were trying to compress or decompress at the
2065time the problem happened. Without that, my ability to do anything
2066more than speculate about the cause, is limited.
2067
2068Please remember that I connect to the Internet with a modem, so
2069you should contact me before mailing me huge files.
2070
2071
2072@section Did you get the right package?
2073
2074@code{bzip2} is a resource hog. It soaks up large amounts of CPU cycles
2075and memory. Also, it gives very large latencies. In the worst case, you
2076can feed many megabytes of uncompressed data into the library before
2077getting any compressed output, so this probably rules out applications
2078requiring interactive behaviour.
2079
2080These aren't faults of my implementation, I hope, but more
2081an intrinsic property of the Burrows-Wheeler transform (unfortunately).
2082Maybe this isn't what you want.
2083
2084If you want a compressor and/or library which is faster, uses less
2085memory but gets pretty good compression, and has minimal latency,
2086consider Jean-loup
2087Gailly's and Mark Adler's work, @code{zlib-1.1.3} and
2088@code{gzip-1.2.4}. Look for them at
2089
2090@code{http://www.zlib.org} and
2091@code{http://www.gzip.org} respectively.
2092
2093For something faster and lighter still, you might try Markus F X J
2094Oberhumer's @code{LZO} real-time compression/decompression library, at
2095@* @code{http://wildsau.idv.uni-linz.ac.at/mfx/lzo.html}.
2096
2097If you want to use the @code{bzip2} algorithms to compress small blocks
2098of data, 64k bytes or smaller, for example on an on-the-fly disk
2099compressor, you'd be well advised not to use this library. Instead,
2100I've made a special library tuned for that kind of use. It's part of
2101@code{e2compr-0.40}, an on-the-fly disk compressor for the Linux
2102@code{ext2} filesystem. Look at
2103@code{http://www.netspace.net.au/~reiter/e2compr}.
2104
2105
2106
2107@section Testing
2108
2109A record of the tests I've done.
2110
2111First, some data sets:
2112@itemize @bullet
2113@item B: a directory containing 6001 files, one for every length in the
2114 range 0 to 6000 bytes. The files contain random lowercase
2115 letters. 18.7 megabytes.
2116@item H: my home directory tree. Documents, source code, mail files,
2117 compressed data. H contains B, and also a directory of
2118 files designed as boundary cases for the sorting; mostly very
2119 repetitive, nasty files. 565 megabytes.
2120@item A: directory tree holding various applications built from source:
2121 @code{egcs}, @code{gcc-2.8.1}, KDE, GTK, Octave, etc.
2122 2200 megabytes.
2123@end itemize
2124The tests conducted are as follows. Each test means compressing
2125(a copy of) each file in the data set, decompressing it and
2126comparing it against the original.
2127
2128First, a bunch of tests with block sizes and internal buffer
2129sizes set very small,
2130to detect any problems with the
2131blocking and buffering mechanisms.
2132This required modifying the source code so as to try to
2133break it.
2134@enumerate
2135@item Data set H, with
2136 buffer size of 1 byte, and block size of 23 bytes.
2137@item Data set B, buffer sizes 1 byte, block size 1 byte.
2138@item As (2) but small-mode decompression.
2139@item As (2) with block size 2 bytes.
2140@item As (2) with block size 3 bytes.
2141@item As (2) with block size 4 bytes.
2142@item As (2) with block size 5 bytes.
2143@item As (2) with block size 6 bytes and small-mode decompression.
2144@item H with buffer size of 1 byte, but normal block
2145 size (up to 900000 bytes).
2146@end enumerate
2147Then some tests with unmodified source code.
2148@enumerate
2149@item H, all settings normal.
2150@item As (1), with small-mode decompress.
2151@item H, compress with flag @code{-1}.
2152@item H, compress with flag @code{-s}, decompress with flag @code{-s}.
2153@item Forwards compatibility: H, @code{bzip2-0.1pl2} compressing,
2154 @code{bzip2-0.9.5} decompressing, all settings normal.
2155@item Backwards compatibility: H, @code{bzip2-0.9.5} compressing,
2156 @code{bzip2-0.1pl2} decompressing, all settings normal.
2157@item Bigger tests: A, all settings normal.
2158@item As (7), using the fallback (Sadakane-like) sorting algorithm.
2159@item As (8), compress with flag @code{-1}, decompress with flag
2160 @code{-s}.
2161@item H, using the fallback sorting algorithm.
2162@item Forwards compatibility: A, @code{bzip2-0.1pl2} compressing,
2163 @code{bzip2-0.9.5} decompressing, all settings normal.
2164@item Backwards compatibility: A, @code{bzip2-0.9.5} compressing,
2165 @code{bzip2-0.1pl2} decompressing, all settings normal.
2166@item Misc test: about 400 megabytes of @code{.tar} files with
2167 @code{bzip2} compiled with Checker (a memory access error
2168 detector, like Purify).
2169@item Misc tests to make sure it builds and runs ok on non-Linux/x86
2170 platforms.
2171@end enumerate
2172These tests were conducted on a 225 MHz IDT WinChip machine, running
2173Linux 2.0.36. They represent nearly a week of continuous computation.
2174All tests completed successfully.
2175
2176
2177@section Further reading
2178@code{bzip2} is not research work, in the sense that it doesn't present
2179any new ideas. Rather, it's an engineering exercise based on existing
2180ideas.
2181
2182Four documents describe essentially all the ideas behind @code{bzip2}:
2183@example
2184Michael Burrows and D. J. Wheeler:
2185 "A block-sorting lossless data compression algorithm"
2186 10th May 1994.
2187 Digital SRC Research Report 124.
2188 ftp://ftp.digital.com/pub/DEC/SRC/research-reports/SRC-124.ps.gz
2189 If you have trouble finding it, try searching at the
2190 New Zealand Digital Library, http://www.nzdl.org.
2191
2192Daniel S. Hirschberg and Debra A. LeLewer
2193 "Efficient Decoding of Prefix Codes"
2194 Communications of the ACM, April 1990, Vol 33, Number 4.
2195 You might be able to get an electronic copy of this
2196 from the ACM Digital Library.
2197
2198David J. Wheeler
2199 Program bred3.c and accompanying document bred3.ps.
2200 This contains the idea behind the multi-table Huffman
2201 coding scheme.
2202 ftp://ftp.cl.cam.ac.uk/users/djw3/
2203
2204Jon L. Bentley and Robert Sedgewick
2205 "Fast Algorithms for Sorting and Searching Strings"
2206 Available from Sedgewick's web page,
2207 www.cs.princeton.edu/~rs
2208@end example
2209The following paper gives valuable additional insights into the
2210algorithm, but is not immediately the basis of any code
2211used in bzip2.
2212@example
2213Peter Fenwick:
2214 Block Sorting Text Compression
2215 Proceedings of the 19th Australasian Computer Science Conference,
2216 Melbourne, Australia. Jan 31 - Feb 2, 1996.
2217 ftp://ftp.cs.auckland.ac.nz/pub/peter-f/ACSC96paper.ps
2218@end example
2219Kunihiko Sadakane's sorting algorithm, mentioned above,
2220is available from:
2221@example
2222http://naomi.is.s.u-tokyo.ac.jp/~sada/papers/Sada98b.ps.gz
2223@end example
2224The Manber-Myers suffix array construction
2225algorithm is described in a paper
2226available from:
2227@example
2228http://www.cs.arizona.edu/people/gene/PAPERS/suffix.ps
2229@end example
2230Finally, the following paper documents some recent investigations
2231I made into the performance of sorting algorithms:
2232@example
2233Julian Seward:
2234 On the Performance of BWT Sorting Algorithms
2235 Proceedings of the IEEE Data Compression Conference 2000
2236 Snowbird, Utah. 28-30 March 2000.
2237@end example
2238
2239
2240@contents
2241
2242@bye
2243
diff --git a/manual.xml b/manual.xml
new file mode 100644
index 0000000..1ab5bd7
--- /dev/null
+++ b/manual.xml
@@ -0,0 +1,2966 @@
1<?xml version="1.0"?> <!-- -*- sgml -*- -->
2<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"[
4
5<!-- various strings, dates etc. common to all docs -->
6<!ENTITY % common-ents SYSTEM "entities.xml"> %common-ents;
7]>
8
9<book lang="en" id="userman" xreflabel="bzip2 Manual">
10
11 <bookinfo>
12 <title>bzip2 and libbzip2, version 1.0.3</title>
13 <subtitle>A program and library for data compression</subtitle>
14 <copyright>
15 <year>&bz-lifespan;</year>
16 <holder>Julian Seward</holder>
17 </copyright>
18 <releaseinfo>Version &bz-version; of &bz-date;</releaseinfo>
19
20 <authorgroup>
21 <author>
22 <firstname>Julian</firstname>
23 <surname>Seward</surname>
24 <affiliation>
25 <orgname>&bz-url;</orgname>
26 </affiliation>
27 </author>
28 </authorgroup>
29
30 <legalnotice>
31
32 <para>This program, <computeroutput>bzip2</computeroutput>, the
33 associated library <computeroutput>libbzip2</computeroutput>, and
34 all documentation, are copyright &copy; &bz-lifespan; Julian Seward.
35 All rights reserved.</para>
36
37 <para>Redistribution and use in source and binary forms, with
38 or without modification, are permitted provided that the
39 following conditions are met:</para>
40
41 <itemizedlist mark='bullet'>
42
43 <listitem><para>Redistributions of source code must retain the
44 above copyright notice, this list of conditions and the
45 following disclaimer.</para></listitem>
46
47 <listitem><para>The origin of this software must not be
48 misrepresented; you must not claim that you wrote the original
49 software. If you use this software in a product, an
50 acknowledgment in the product documentation would be
51 appreciated but is not required.</para></listitem>
52
53 <listitem><para>Altered source versions must be plainly marked
54 as such, and must not be misrepresented as being the original
55 software.</para></listitem>
56
57 <listitem><para>The name of the author may not be used to
58 endorse or promote products derived from this software without
59 specific prior written permission.</para></listitem>
60
61 </itemizedlist>
62
63 <para>THIS SOFTWARE IS PROVIDED BY THE AUTHOR "AS IS" AND ANY
64 EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
65 THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
66 PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
67 AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
68 EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
69 TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
70 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
71 ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
72 LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
73 IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
74 THE POSSIBILITY OF SUCH DAMAGE.</para>
75
76 <para>PATENTS: To the best of my knowledge,
77 <computeroutput>bzip2</computeroutput> and
78 <computeroutput>libbzip2</computeroutput> do not use any patented
79 algorithms. However, I do not have the resources to carry
80 out a patent search. Therefore I cannot give any guarantee of
81 the above statement.
82 </para>
83
84</legalnotice>
85
86</bookinfo>
87
88
89
90<chapter id="intro" xreflabel="Introduction">
91<title>Introduction</title>
92
93<para><computeroutput>bzip2</computeroutput> compresses files
94using the Burrows-Wheeler block-sorting text compression
95algorithm, and Huffman coding. Compression is generally
96considerably better than that achieved by more conventional
97LZ77/LZ78-based compressors, and approaches the performance of
98the PPM family of statistical compressors.</para>
99
100<para><computeroutput>bzip2</computeroutput> is built on top of
101<computeroutput>libbzip2</computeroutput>, a flexible library for
102handling compressed data in the
103<computeroutput>bzip2</computeroutput> format. This manual
104describes both how to use the program and how to work with the
105library interface. Most of the manual is devoted to this
106library, not the program, which is good news if your interest is
107only in the program.</para>
108
109<itemizedlist mark='bullet'>
110
111 <listitem><para><xref linkend="using"/> describes how to use
112 <computeroutput>bzip2</computeroutput>; this is the only part
113 you need to read if you just want to know how to operate the
114 program.</para></listitem>
115
116 <listitem><para><xref linkend="libprog"/> describes the
117 programming interfaces in detail, and</para></listitem>
118
119 <listitem><para><xref linkend="misc"/> records some
120 miscellaneous notes which I thought ought to be recorded
121 somewhere.</para></listitem>
122
123</itemizedlist>
124
125</chapter>
126
127
128<chapter id="using" xreflabel="How to use bzip2">
129<title>How to use bzip2</title>
130
131<para>This chapter contains a copy of the
132<computeroutput>bzip2</computeroutput> man page, and nothing
133else.</para>
134
135<sect1 id="name" xreflabel="NAME">
136<title>NAME</title>
137
138<itemizedlist mark='bullet'>
139
140 <listitem><para><computeroutput>bzip2</computeroutput>,
141 <computeroutput>bunzip2</computeroutput> - a block-sorting file
142 compressor, v1.0.3</para></listitem>
143
144 <listitem><para><computeroutput>bzcat</computeroutput> -
145 decompresses files to stdout</para></listitem>
146
147 <listitem><para><computeroutput>bzip2recover</computeroutput> -
148 recovers data from damaged bzip2 files</para></listitem>
149
150</itemizedlist>
151
152</sect1>
153
154
155<sect1 id="synopsis" xreflabel="SYNOPSIS">
156<title>SYNOPSIS</title>
157
158<itemizedlist mark='bullet'>
159
160 <listitem><para><computeroutput>bzip2</computeroutput> [
161 -cdfkqstvzVL123456789 ] [ filenames ... ]</para></listitem>
162
163 <listitem><para><computeroutput>bunzip2</computeroutput> [
164 -fkvsVL ] [ filenames ... ]</para></listitem>
165
166 <listitem><para><computeroutput>bzcat</computeroutput> [ -s ] [
167 filenames ... ]</para></listitem>
168
169 <listitem><para><computeroutput>bzip2recover</computeroutput>
170 filename</para></listitem>
171
172</itemizedlist>
173
174</sect1>
175
176
177<sect1 id="description" xreflabel="DESCRIPTION">
178<title>DESCRIPTION</title>
179
180<para><computeroutput>bzip2</computeroutput> compresses files
181using the Burrows-Wheeler block sorting text compression
182algorithm, and Huffman coding. Compression is generally
183considerably better than that achieved by more conventional
184LZ77/LZ78-based compressors, and approaches the performance of
185the PPM family of statistical compressors.</para>
186
187<para>The command-line options are deliberately very similar to
188those of GNU <computeroutput>gzip</computeroutput>, but they are
189not identical.</para>
190
191<para><computeroutput>bzip2</computeroutput> expects a list of
192file names to accompany the command-line flags. Each file is
193replaced by a compressed version of itself, with the name
194<computeroutput>original_name.bz2</computeroutput>. Each
195compressed file has the same modification date, permissions, and,
196when possible, ownership as the corresponding original, so that
197these properties can be correctly restored at decompression time.
198File name handling is naive in the sense that there is no
199mechanism for preserving original file names, permissions,
200ownerships or dates in filesystems which lack these concepts, or
201have serious file name length restrictions, such as
202MS-DOS.</para>
203
204<para><computeroutput>bzip2</computeroutput> and
205<computeroutput>bunzip2</computeroutput> will by default not
206overwrite existing files. If you want this to happen, specify
207the <computeroutput>-f</computeroutput> flag.</para>
208
209<para>If no file names are specified,
210<computeroutput>bzip2</computeroutput> compresses from standard
211input to standard output. In this case,
212<computeroutput>bzip2</computeroutput> will decline to write
213compressed output to a terminal, as this would be entirely
214incomprehensible and therefore pointless.</para>
215
216<para><computeroutput>bunzip2</computeroutput> (or
217<computeroutput>bzip2 -d</computeroutput>) decompresses all
218specified files. Files which were not created by
219<computeroutput>bzip2</computeroutput> will be detected and
220ignored, and a warning issued.
221<computeroutput>bzip2</computeroutput> attempts to guess the
222filename for the decompressed file from that of the compressed
223file as follows:</para>
224
225<itemizedlist mark='bullet'>
226
227 <listitem><para><computeroutput>filename.bz2 </computeroutput>
228 becomes
229 <computeroutput>filename</computeroutput></para></listitem>
230
231 <listitem><para><computeroutput>filename.bz </computeroutput>
232 becomes
233 <computeroutput>filename</computeroutput></para></listitem>
234
235 <listitem><para><computeroutput>filename.tbz2</computeroutput>
236 becomes
237 <computeroutput>filename.tar</computeroutput></para></listitem>
238
239 <listitem><para><computeroutput>filename.tbz </computeroutput>
240 becomes
241 <computeroutput>filename.tar</computeroutput></para></listitem>
242
243 <listitem><para><computeroutput>anyothername </computeroutput>
244 becomes
245 <computeroutput>anyothername.out</computeroutput></para></listitem>
246
247</itemizedlist>
248
249<para>If the file does not end in one of the recognised endings,
250<computeroutput>.bz2</computeroutput>,
251<computeroutput>.bz</computeroutput>,
252<computeroutput>.tbz2</computeroutput> or
253<computeroutput>.tbz</computeroutput>,
254<computeroutput>bzip2</computeroutput> complains that it cannot
255guess the name of the original file, and uses the original name
256with <computeroutput>.out</computeroutput> appended.</para>
257
258<para>As with compression, supplying no filenames causes
259decompression from standard input to standard output.</para>
260
261<para><computeroutput>bunzip2</computeroutput> will correctly
262decompress a file which is the concatenation of two or more
263compressed files. The result is the concatenation of the
264corresponding uncompressed files. Integrity testing
265(<computeroutput>-t</computeroutput>) of concatenated compressed
266files is also supported.</para>
267
268<para>You can also compress or decompress files to the standard
269output by giving the <computeroutput>-c</computeroutput> flag.
270Multiple files may be compressed and decompressed like this. The
271resulting outputs are fed sequentially to stdout. Compression of
272multiple files in this manner generates a stream containing
273multiple compressed file representations. Such a stream can be
274decompressed correctly only by
275<computeroutput>bzip2</computeroutput> version 0.9.0 or later.
276Earlier versions of <computeroutput>bzip2</computeroutput> will
277stop after decompressing the first file in the stream.</para>
278
279<para><computeroutput>bzcat</computeroutput> (or
280<computeroutput>bzip2 -dc</computeroutput>) decompresses all
281specified files to the standard output.</para>
282
283<para><computeroutput>bzip2</computeroutput> will read arguments
284from the environment variables
285<computeroutput>BZIP2</computeroutput> and
286<computeroutput>BZIP</computeroutput>, in that order, and will
287process them before any arguments read from the command line.
288This gives a convenient way to supply default arguments.</para>
289
290<para>Compression is always performed, even if the compressed
291file is slightly larger than the original. Files of less than
292about one hundred bytes tend to get larger, since the compression
293mechanism has a constant overhead in the region of 50 bytes.
294Random data (including the output of most file compressors) is
295coded at about 8.05 bits per byte, giving an expansion of around
2960.5%.</para>
297
298<para>As a self-check for your protection,
299<computeroutput>bzip2</computeroutput> uses 32-bit CRCs to make
300sure that the decompressed version of a file is identical to the
301original. This guards against corruption of the compressed data,
302and against undetected bugs in
303<computeroutput>bzip2</computeroutput> (hopefully very unlikely).
304The chances of data corruption going undetected is microscopic,
305about one chance in four billion for each file processed. Be
306aware, though, that the check occurs upon decompression, so it
307can only tell you that something is wrong. It can't help you
308recover the original uncompressed data. You can use
309<computeroutput>bzip2recover</computeroutput> to try to recover
310data from damaged files.</para>
311
312<para>Return values: 0 for a normal exit, 1 for environmental
313problems (file not found, invalid flags, I/O errors, etc.), 2
314to indicate a corrupt compressed file, 3 for an internal
315consistency error (eg, bug) which caused
316<computeroutput>bzip2</computeroutput> to panic.</para>
317
318</sect1>
319
320
321<sect1 id="options" xreflabel="OPTIONS">
322<title>OPTIONS</title>
323
324<variablelist>
325
326 <varlistentry>
327 <term><computeroutput>-c --stdout</computeroutput></term>
328 <listitem><para>Compress or decompress to standard
329 output.</para></listitem>
330 </varlistentry>
331
332 <varlistentry>
333 <term><computeroutput>-d --decompress</computeroutput></term>
334 <listitem><para>Force decompression.
335 <computeroutput>bzip2</computeroutput>,
336 <computeroutput>bunzip2</computeroutput> and
337 <computeroutput>bzcat</computeroutput> are really the same
338 program, and the decision about what actions to take is done on
339 the basis of which name is used. This flag overrides that
340 mechanism, and forces bzip2 to decompress.</para></listitem>
341 </varlistentry>
342
343 <varlistentry>
344 <term><computeroutput>-z --compress</computeroutput></term>
345 <listitem><para>The complement to
346 <computeroutput>-d</computeroutput>: forces compression,
347 regardless of the invokation name.</para></listitem>
348 </varlistentry>
349
350 <varlistentry>
351 <term><computeroutput>-t --test</computeroutput></term>
352 <listitem><para>Check integrity of the specified file(s), but
353 don't decompress them. This really performs a trial
354 decompression and throws away the result.</para></listitem>
355 </varlistentry>
356
357 <varlistentry>
358 <term><computeroutput>-f --force</computeroutput></term>
359 <listitem><para>Force overwrite of output files. Normally,
360 <computeroutput>bzip2</computeroutput> will not overwrite
361 existing output files. Also forces
362 <computeroutput>bzip2</computeroutput> to break hard links to
363 files, which it otherwise wouldn't do.</para>
364 <para><computeroutput>bzip2</computeroutput> normally declines
365 to decompress files which don't have the correct magic header
366 bytes. If forced (<computeroutput>-f</computeroutput>),
367 however, it will pass such files through unmodified. This is
368 how GNU <computeroutput>gzip</computeroutput> behaves.</para>
369 </listitem>
370 </varlistentry>
371
372 <varlistentry>
373 <term><computeroutput>-k --keep</computeroutput></term>
374 <listitem><para>Keep (don't delete) input files during
375 compression or decompression.</para></listitem>
376 </varlistentry>
377
378 <varlistentry>
379 <term><computeroutput>-s --small</computeroutput></term>
380 <listitem><para>Reduce memory usage, for compression,
381 decompression and testing. Files are decompressed and tested
382 using a modified algorithm which only requires 2.5 bytes per
383 block byte. This means any file can be decompressed in 2300k
384 of memory, albeit at about half the normal speed.</para>
385 <para>During compression, <computeroutput>-s</computeroutput>
386 selects a block size of 200k, which limits memory use to around
387 the same figure, at the expense of your compression ratio. In
388 short, if your machine is low on memory (8 megabytes or less),
389 use <computeroutput>-s</computeroutput> for everything. See
390 <xref linkend="memory-management"/> below.</para></listitem>
391 </varlistentry>
392
393 <varlistentry>
394 <term><computeroutput>-q --quiet</computeroutput></term>
395 <listitem><para>Suppress non-essential warning messages.
396 Messages pertaining to I/O errors and other critical events
397 will not be suppressed.</para></listitem>
398 </varlistentry>
399
400 <varlistentry>
401 <term><computeroutput>-v --verbose</computeroutput></term>
402 <listitem><para>Verbose mode -- show the compression ratio for
403 each file processed. Further
404 <computeroutput>-v</computeroutput>'s increase the verbosity
405 level, spewing out lots of information which is primarily of
406 interest for diagnostic purposes.</para></listitem>
407 </varlistentry>
408
409 <varlistentry>
410 <term><computeroutput>-L --license -V --version</computeroutput></term>
411 <listitem><para>Display the software version, license terms and
412 conditions.</para></listitem>
413 </varlistentry>
414
415 <varlistentry>
416 <term><computeroutput>-1</computeroutput> (or
417 <computeroutput>--fast</computeroutput>) to
418 <computeroutput>-9</computeroutput> (or
419 <computeroutput>-best</computeroutput>)</term>
420 <listitem><para>Set the block size to 100 k, 200 k ... 900 k
421 when compressing. Has no effect when decompressing. See <xref
422 linkend="memory-management" /> below. The
423 <computeroutput>--fast</computeroutput> and
424 <computeroutput>--best</computeroutput> aliases are primarily
425 for GNU <computeroutput>gzip</computeroutput> compatibility.
426 In particular, <computeroutput>--fast</computeroutput> doesn't
427 make things significantly faster. And
428 <computeroutput>--best</computeroutput> merely selects the
429 default behaviour.</para></listitem>
430 </varlistentry>
431
432 <varlistentry>
433 <term><computeroutput>--</computeroutput></term>
434 <listitem><para>Treats all subsequent arguments as file names,
435 even if they start with a dash. This is so you can handle
436 files with names beginning with a dash, for example:
437 <computeroutput>bzip2 --
438 -myfilename</computeroutput>.</para></listitem>
439 </varlistentry>
440
441 <varlistentry>
442 <term><computeroutput>--repetitive-fast</computeroutput></term>
443 <term><computeroutput>--repetitive-best</computeroutput></term>
444 <listitem><para>These flags are redundant in versions 0.9.5 and
445 above. They provided some coarse control over the behaviour of
446 the sorting algorithm in earlier versions, which was sometimes
447 useful. 0.9.5 and above have an improved algorithm which
448 renders these flags irrelevant.</para></listitem>
449 </varlistentry>
450
451</variablelist>
452
453</sect1>
454
455
456<sect1 id="memory-management" xreflabel="MEMORY MANAGEMENT">
457<title>MEMORY MANAGEMENT</title>
458
459<para><computeroutput>bzip2</computeroutput> compresses large
460files in blocks. The block size affects both the compression
461ratio achieved, and the amount of memory needed for compression
462and decompression. The flags <computeroutput>-1</computeroutput>
463through <computeroutput>-9</computeroutput> specify the block
464size to be 100,000 bytes through 900,000 bytes (the default)
465respectively. At decompression time, the block size used for
466compression is read from the header of the compressed file, and
467<computeroutput>bunzip2</computeroutput> then allocates itself
468just enough memory to decompress the file. Since block sizes are
469stored in compressed files, it follows that the flags
470<computeroutput>-1</computeroutput> to
471<computeroutput>-9</computeroutput> are irrelevant to and so
472ignored during decompression.</para>
473
474<para>Compression and decompression requirements, in bytes, can be
475estimated as:</para>
476<programlisting>
477Compression: 400k + ( 8 x block size )
478
479Decompression: 100k + ( 4 x block size ), or
480 100k + ( 2.5 x block size )
481</programlisting>
482
483<para>Larger block sizes give rapidly diminishing marginal
484returns. Most of the compression comes from the first two or
485three hundred k of block size, a fact worth bearing in mind when
486using <computeroutput>bzip2</computeroutput> on small machines.
487It is also important to appreciate that the decompression memory
488requirement is set at compression time by the choice of block
489size.</para>
490
491<para>For files compressed with the default 900k block size,
492<computeroutput>bunzip2</computeroutput> will require about 3700
493kbytes to decompress. To support decompression of any file on a
4944 megabyte machine, <computeroutput>bunzip2</computeroutput> has
495an option to decompress using approximately half this amount of
496memory, about 2300 kbytes. Decompression speed is also halved,
497so you should use this option only where necessary. The relevant
498flag is <computeroutput>-s</computeroutput>.</para>
499
500<para>In general, try and use the largest block size memory
501constraints allow, since that maximises the compression achieved.
502Compression and decompression speed are virtually unaffected by
503block size.</para>
504
505<para>Another significant point applies to files which fit in a
506single block -- that means most files you'd encounter using a
507large block size. The amount of real memory touched is
508proportional to the size of the file, since the file is smaller
509than a block. For example, compressing a file 20,000 bytes long
510with the flag <computeroutput>-9</computeroutput> will cause the
511compressor to allocate around 7600k of memory, but only touch
512400k + 20000 * 8 = 560 kbytes of it. Similarly, the decompressor
513will allocate 3700k but only touch 100k + 20000 * 4 = 180
514kbytes.</para>
515
516<para>Here is a table which summarises the maximum memory usage
517for different block sizes. Also recorded is the total compressed
518size for 14 files of the Calgary Text Compression Corpus
519totalling 3,141,622 bytes. This column gives some feel for how
520compression varies with block size. These figures tend to
521understate the advantage of larger block sizes for larger files,
522since the Corpus is dominated by smaller files.</para>
523
524<programlisting>
525 Compress Decompress Decompress Corpus
526Flag usage usage -s usage Size
527
528 -1 1200k 500k 350k 914704
529 -2 2000k 900k 600k 877703
530 -3 2800k 1300k 850k 860338
531 -4 3600k 1700k 1100k 846899
532 -5 4400k 2100k 1350k 845160
533 -6 5200k 2500k 1600k 838626
534 -7 6100k 2900k 1850k 834096
535 -8 6800k 3300k 2100k 828642
536 -9 7600k 3700k 2350k 828642
537</programlisting>
538
539</sect1>
540
541
542<sect1 id="recovering" xreflabel="RECOVERING DATA FROM DAMAGED FILES">
543<title>RECOVERING DATA FROM DAMAGED FILES</title>
544
545<para><computeroutput>bzip2</computeroutput> compresses files in
546blocks, usually 900kbytes long. Each block is handled
547independently. If a media or transmission error causes a
548multi-block <computeroutput>.bz2</computeroutput> file to become
549damaged, it may be possible to recover data from the undamaged
550blocks in the file.</para>
551
552<para>The compressed representation of each block is delimited by
553a 48-bit pattern, which makes it possible to find the block
554boundaries with reasonable certainty. Each block also carries
555its own 32-bit CRC, so damaged blocks can be distinguished from
556undamaged ones.</para>
557
558<para><computeroutput>bzip2recover</computeroutput> is a simple
559program whose purpose is to search for blocks in
560<computeroutput>.bz2</computeroutput> files, and write each block
561out into its own <computeroutput>.bz2</computeroutput> file. You
562can then use <computeroutput>bzip2 -t</computeroutput> to test
563the integrity of the resulting files, and decompress those which
564are undamaged.</para>
565
566<para><computeroutput>bzip2recover</computeroutput> takes a
567single argument, the name of the damaged file, and writes a
568number of files <computeroutput>rec0001file.bz2</computeroutput>,
569<computeroutput>rec0002file.bz2</computeroutput>, etc, containing
570the extracted blocks. The output filenames are designed so that
571the use of wildcards in subsequent processing -- for example,
572<computeroutput>bzip2 -dc rec*file.bz2 &#62;
573recovered_data</computeroutput> -- lists the files in the correct
574order.</para>
575
576<para><computeroutput>bzip2recover</computeroutput> should be of
577most use dealing with large <computeroutput>.bz2</computeroutput>
578files, as these will contain many blocks. It is clearly futile
579to use it on damaged single-block files, since a damaged block
580cannot be recovered. If you wish to minimise any potential data
581loss through media or transmission errors, you might consider
582compressing with a smaller block size.</para>
583
584</sect1>
585
586
587<sect1 id="performance" xreflabel="PERFORMANCE NOTES">
588<title>PERFORMANCE NOTES</title>
589
590<para>The sorting phase of compression gathers together similar
591strings in the file. Because of this, files containing very long
592runs of repeated symbols, like "aabaabaabaab ..." (repeated
593several hundred times) may compress more slowly than normal.
594Versions 0.9.5 and above fare much better than previous versions
595in this respect. The ratio between worst-case and average-case
596compression time is in the region of 10:1. For previous
597versions, this figure was more like 100:1. You can use the
598<computeroutput>-vvvv</computeroutput> option to monitor progress
599in great detail, if you want.</para>
600
601<para>Decompression speed is unaffected by these
602phenomena.</para>
603
604<para><computeroutput>bzip2</computeroutput> usually allocates
605several megabytes of memory to operate in, and then charges all
606over it in a fairly random fashion. This means that performance,
607both for compressing and decompressing, is largely determined by
608the speed at which your machine can service cache misses.
609Because of this, small changes to the code to reduce the miss
610rate have been observed to give disproportionately large
611performance improvements. I imagine
612<computeroutput>bzip2</computeroutput> will perform best on
613machines with very large caches.</para>
614
615</sect1>
616
617
618
619<sect1 id="caveats" xreflabel="CAVEATS">
620<title>CAVEATS</title>
621
622<para>I/O error messages are not as helpful as they could be.
623<computeroutput>bzip2</computeroutput> tries hard to detect I/O
624errors and exit cleanly, but the details of what the problem is
625sometimes seem rather misleading.</para>
626
627<para>This manual page pertains to version &bz-version; of
628<computeroutput>bzip2</computeroutput>. Compressed data created
629by this version is entirely forwards and backwards compatible
630with the previous public releases, versions 0.1pl2, 0.9.0 and
6310.9.5, 1.0.0, 1.0.1 and 1.0.2, but with the following exception: 0.9.0
632and above can correctly decompress multiple concatenated
633compressed files. 0.1pl2 cannot do this; it will stop after
634decompressing just the first file in the stream.</para>
635
636<para><computeroutput>bzip2recover</computeroutput> versions
637prior to 1.0.2 used 32-bit integers to represent bit positions in
638compressed files, so it could not handle compressed files more
639than 512 megabytes long. Versions 1.0.2 and above use 64-bit ints
640on some platforms which support them (GNU supported targets, and
641Windows). To establish whether or not
642<computeroutput>bzip2recover</computeroutput> was built with such
643a limitation, run it without arguments. In any event you can
644build yourself an unlimited version if you can recompile it with
645<computeroutput>MaybeUInt64</computeroutput> set to be an
646unsigned 64-bit integer.</para>
647
648</sect1>
649
650
651
652<sect1 id="author" xreflabel="AUTHOR">
653<title>AUTHOR</title>
654
655<para>Julian Seward,
656<computeroutput>&bz-email;</computeroutput></para>
657
658<para>The ideas embodied in
659<computeroutput>bzip2</computeroutput> are due to (at least) the
660following people: Michael Burrows and David Wheeler (for the
661block sorting transformation), David Wheeler (again, for the
662Huffman coder), Peter Fenwick (for the structured coding model in
663the original <computeroutput>bzip</computeroutput>, and many
664refinements), and Alistair Moffat, Radford Neal and Ian Witten
665(for the arithmetic coder in the original
666<computeroutput>bzip</computeroutput>). I am much indebted for
667their help, support and advice. See the manual in the source
668distribution for pointers to sources of documentation. Christian
669von Roques encouraged me to look for faster sorting algorithms,
670so as to speed up compression. Bela Lubkin encouraged me to
671improve the worst-case compression performance.
672Donna Robinson XMLised the documentation.
673Many people sent
674patches, helped with portability problems, lent machines, gave
675advice and were generally helpful.</para>
676
677</sect1>
678
679</chapter>
680
681
682
683<chapter id="libprog" xreflabel="Programming with libbzip2">
684<title>
685Programming with <computeroutput>libbzip2</computeroutput>
686</title>
687
688<para>This chapter describes the programming interface to
689<computeroutput>libbzip2</computeroutput>.</para>
690
691<para>For general background information, particularly about
692memory use and performance aspects, you'd be well advised to read
693<xref linkend="using"/> as well.</para>
694
695
696<sect1 id="top-level" xreflabel="Top-level structure">
697<title>Top-level structure</title>
698
699<para><computeroutput>libbzip2</computeroutput> is a flexible
700library for compressing and decompressing data in the
701<computeroutput>bzip2</computeroutput> data format. Although
702packaged as a single entity, it helps to regard the library as
703three separate parts: the low level interface, and the high level
704interface, and some utility functions.</para>
705
706<para>The structure of
707<computeroutput>libbzip2</computeroutput>'s interfaces is similar
708to that of Jean-loup Gailly's and Mark Adler's excellent
709<computeroutput>zlib</computeroutput> library.</para>
710
711<para>All externally visible symbols have names beginning
712<computeroutput>BZ2_</computeroutput>. This is new in version
7131.0. The intention is to minimise pollution of the namespaces of
714library clients.</para>
715
716<para>To use any part of the library, you need to
717<computeroutput>#include &lt;bzlib.h&gt;</computeroutput>
718into your sources.</para>
719
720
721
722<sect2 id="ll-summary" xreflabel="Low-level summary">
723<title>Low-level summary</title>
724
725<para>This interface provides services for compressing and
726decompressing data in memory. There's no provision for dealing
727with files, streams or any other I/O mechanisms, just straight
728memory-to-memory work. In fact, this part of the library can be
729compiled without inclusion of
730<computeroutput>stdio.h</computeroutput>, which may be helpful
731for embedded applications.</para>
732
733<para>The low-level part of the library has no global variables
734and is therefore thread-safe.</para>
735
736<para>Six routines make up the low level interface:
737<computeroutput>BZ2_bzCompressInit</computeroutput>,
738<computeroutput>BZ2_bzCompress</computeroutput>, and
739<computeroutput>BZ2_bzCompressEnd</computeroutput> for
740compression, and a corresponding trio
741<computeroutput>BZ2_bzDecompressInit</computeroutput>,
742<computeroutput>BZ2_bzDecompress</computeroutput> and
743<computeroutput>BZ2_bzDecompressEnd</computeroutput> for
744decompression. The <computeroutput>*Init</computeroutput>
745functions allocate memory for compression/decompression and do
746other initialisations, whilst the
747<computeroutput>*End</computeroutput> functions close down
748operations and release memory.</para>
749
750<para>The real work is done by
751<computeroutput>BZ2_bzCompress</computeroutput> and
752<computeroutput>BZ2_bzDecompress</computeroutput>. These
753compress and decompress data from a user-supplied input buffer to
754a user-supplied output buffer. These buffers can be any size;
755arbitrary quantities of data are handled by making repeated calls
756to these functions. This is a flexible mechanism allowing a
757consumer-pull style of activity, or producer-push, or a mixture
758of both.</para>
759
760</sect2>
761
762
763<sect2 id="hl-summary" xreflabel="High-level summary">
764<title>High-level summary</title>
765
766<para>This interface provides some handy wrappers around the
767low-level interface to facilitate reading and writing
768<computeroutput>bzip2</computeroutput> format files
769(<computeroutput>.bz2</computeroutput> files). The routines
770provide hooks to facilitate reading files in which the
771<computeroutput>bzip2</computeroutput> data stream is embedded
772within some larger-scale file structure, or where there are
773multiple <computeroutput>bzip2</computeroutput> data streams
774concatenated end-to-end.</para>
775
776<para>For reading files,
777<computeroutput>BZ2_bzReadOpen</computeroutput>,
778<computeroutput>BZ2_bzRead</computeroutput>,
779<computeroutput>BZ2_bzReadClose</computeroutput> and
780<computeroutput>BZ2_bzReadGetUnused</computeroutput> are
781supplied. For writing files,
782<computeroutput>BZ2_bzWriteOpen</computeroutput>,
783<computeroutput>BZ2_bzWrite</computeroutput> and
784<computeroutput>BZ2_bzWriteFinish</computeroutput> are
785available.</para>
786
787<para>As with the low-level library, no global variables are used
788so the library is per se thread-safe. However, if I/O errors
789occur whilst reading or writing the underlying compressed files,
790you may have to consult <computeroutput>errno</computeroutput> to
791determine the cause of the error. In that case, you'd need a C
792library which correctly supports
793<computeroutput>errno</computeroutput> in a multithreaded
794environment.</para>
795
796<para>To make the library a little simpler and more portable,
797<computeroutput>BZ2_bzReadOpen</computeroutput> and
798<computeroutput>BZ2_bzWriteOpen</computeroutput> require you to
799pass them file handles (<computeroutput>FILE*</computeroutput>s)
800which have previously been opened for reading or writing
801respectively. That avoids portability problems associated with
802file operations and file attributes, whilst not being much of an
803imposition on the programmer.</para>
804
805</sect2>
806
807
808<sect2 id="util-fns-summary" xreflabel="Utility functions summary">
809<title>Utility functions summary</title>
810
811<para>For very simple needs,
812<computeroutput>BZ2_bzBuffToBuffCompress</computeroutput> and
813<computeroutput>BZ2_bzBuffToBuffDecompress</computeroutput> are
814provided. These compress data in memory from one buffer to
815another buffer in a single function call. You should assess
816whether these functions fulfill your memory-to-memory
817compression/decompression requirements before investing effort in
818understanding the more general but more complex low-level
819interface.</para>
820
821<para>Yoshioka Tsuneo
822(<computeroutput>QWF00133@niftyserve.or.jp</computeroutput> /
823<computeroutput>tsuneo-y@is.aist-nara.ac.jp</computeroutput>) has
824contributed some functions to give better
825<computeroutput>zlib</computeroutput> compatibility. These
826functions are <computeroutput>BZ2_bzopen</computeroutput>,
827<computeroutput>BZ2_bzread</computeroutput>,
828<computeroutput>BZ2_bzwrite</computeroutput>,
829<computeroutput>BZ2_bzflush</computeroutput>,
830<computeroutput>BZ2_bzclose</computeroutput>,
831<computeroutput>BZ2_bzerror</computeroutput> and
832<computeroutput>BZ2_bzlibVersion</computeroutput>. You may find
833these functions more convenient for simple file reading and
834writing, than those in the high-level interface. These functions
835are not (yet) officially part of the library, and are minimally
836documented here. If they break, you get to keep all the pieces.
837I hope to document them properly when time permits.</para>
838
839<para>Yoshioka also contributed modifications to allow the
840library to be built as a Windows DLL.</para>
841
842</sect2>
843
844</sect1>
845
846
847<sect1 id="err-handling" xreflabel="Error handling">
848<title>Error handling</title>
849
850<para>The library is designed to recover cleanly in all
851situations, including the worst-case situation of decompressing
852random data. I'm not 100% sure that it can always do this, so
853you might want to add a signal handler to catch segmentation
854violations during decompression if you are feeling especially
855paranoid. I would be interested in hearing more about the
856robustness of the library to corrupted compressed data.</para>
857
858<para>Version 1.0.3 more robust in this respect than any
859previous version. Investigations with Valgrind (a tool for detecting
860problems with memory management) indicate
861that, at least for the few files I tested, all single-bit errors
862in the decompressed data are caught properly, with no
863segmentation faults, no uses of uninitialised data, no out of
864range reads or writes, and no infinite looping in the decompressor.
865So it's certainly pretty robust, although
866I wouldn't claim it to be totally bombproof.</para>
867
868<para>The file <computeroutput>bzlib.h</computeroutput> contains
869all definitions needed to use the library. In particular, you
870should definitely not include
871<computeroutput>bzlib_private.h</computeroutput>.</para>
872
873<para>In <computeroutput>bzlib.h</computeroutput>, the various
874return values are defined. The following list is not intended as
875an exhaustive description of the circumstances in which a given
876value may be returned -- those descriptions are given later.
877Rather, it is intended to convey the rough meaning of each return
878value. The first five actions are normal and not intended to
879denote an error situation.</para>
880
881<variablelist>
882
883 <varlistentry>
884 <term><computeroutput>BZ_OK</computeroutput></term>
885 <listitem><para>The requested action was completed
886 successfully.</para></listitem>
887 </varlistentry>
888
889 <varlistentry>
890 <term><computeroutput>BZ_RUN_OK, BZ_FLUSH_OK,
891 BZ_FINISH_OK</computeroutput></term>
892 <listitem><para>In
893 <computeroutput>BZ2_bzCompress</computeroutput>, the requested
894 flush/finish/nothing-special action was completed
895 successfully.</para></listitem>
896 </varlistentry>
897
898 <varlistentry>
899 <term><computeroutput>BZ_STREAM_END</computeroutput></term>
900 <listitem><para>Compression of data was completed, or the
901 logical stream end was detected during
902 decompression.</para></listitem>
903 </varlistentry>
904
905</variablelist>
906
907<para>The following return values indicate an error of some
908kind.</para>
909
910<variablelist>
911
912 <varlistentry>
913 <term><computeroutput>BZ_CONFIG_ERROR</computeroutput></term>
914 <listitem><para>Indicates that the library has been improperly
915 compiled on your platform -- a major configuration error.
916 Specifically, it means that
917 <computeroutput>sizeof(char)</computeroutput>,
918 <computeroutput>sizeof(short)</computeroutput> and
919 <computeroutput>sizeof(int)</computeroutput> are not 1, 2 and
920 4 respectively, as they should be. Note that the library
921 should still work properly on 64-bit platforms which follow
922 the LP64 programming model -- that is, where
923 <computeroutput>sizeof(long)</computeroutput> and
924 <computeroutput>sizeof(void*)</computeroutput> are 8. Under
925 LP64, <computeroutput>sizeof(int)</computeroutput> is still 4,
926 so <computeroutput>libbzip2</computeroutput>, which doesn't
927 use the <computeroutput>long</computeroutput> type, is
928 OK.</para></listitem>
929 </varlistentry>
930
931 <varlistentry>
932 <term><computeroutput>BZ_SEQUENCE_ERROR</computeroutput></term>
933 <listitem><para>When using the library, it is important to call
934 the functions in the correct sequence and with data structures
935 (buffers etc) in the correct states.
936 <computeroutput>libbzip2</computeroutput> checks as much as it
937 can to ensure this is happening, and returns
938 <computeroutput>BZ_SEQUENCE_ERROR</computeroutput> if not.
939 Code which complies precisely with the function semantics, as
940 detailed below, should never receive this value; such an event
941 denotes buggy code which you should
942 investigate.</para></listitem>
943 </varlistentry>
944
945 <varlistentry>
946 <term><computeroutput>BZ_PARAM_ERROR</computeroutput></term>
947 <listitem><para>Returned when a parameter to a function call is
948 out of range or otherwise manifestly incorrect. As with
949 <computeroutput>BZ_SEQUENCE_ERROR</computeroutput>, this
950 denotes a bug in the client code. The distinction between
951 <computeroutput>BZ_PARAM_ERROR</computeroutput> and
952 <computeroutput>BZ_SEQUENCE_ERROR</computeroutput> is a bit
953 hazy, but still worth making.</para></listitem>
954 </varlistentry>
955
956 <varlistentry>
957 <term><computeroutput>BZ_MEM_ERROR</computeroutput></term>
958 <listitem><para>Returned when a request to allocate memory
959 failed. Note that the quantity of memory needed to decompress
960 a stream cannot be determined until the stream's header has
961 been read. So
962 <computeroutput>BZ2_bzDecompress</computeroutput> and
963 <computeroutput>BZ2_bzRead</computeroutput> may return
964 <computeroutput>BZ_MEM_ERROR</computeroutput> even though some
965 of the compressed data has been read. The same is not true
966 for compression; once
967 <computeroutput>BZ2_bzCompressInit</computeroutput> or
968 <computeroutput>BZ2_bzWriteOpen</computeroutput> have
969 successfully completed,
970 <computeroutput>BZ_MEM_ERROR</computeroutput> cannot
971 occur.</para></listitem>
972 </varlistentry>
973
974 <varlistentry>
975 <term><computeroutput>BZ_DATA_ERROR</computeroutput></term>
976 <listitem><para>Returned when a data integrity error is
977 detected during decompression. Most importantly, this means
978 when stored and computed CRCs for the data do not match. This
979 value is also returned upon detection of any other anomaly in
980 the compressed data.</para></listitem>
981 </varlistentry>
982
983 <varlistentry>
984 <term><computeroutput>BZ_DATA_ERROR_MAGIC</computeroutput></term>
985 <listitem><para>As a special case of
986 <computeroutput>BZ_DATA_ERROR</computeroutput>, it is
987 sometimes useful to know when the compressed stream does not
988 start with the correct magic bytes (<computeroutput>'B' 'Z'
989 'h'</computeroutput>).</para></listitem>
990 </varlistentry>
991
992 <varlistentry>
993 <term><computeroutput>BZ_IO_ERROR</computeroutput></term>
994 <listitem><para>Returned by
995 <computeroutput>BZ2_bzRead</computeroutput> and
996 <computeroutput>BZ2_bzWrite</computeroutput> when there is an
997 error reading or writing in the compressed file, and by
998 <computeroutput>BZ2_bzReadOpen</computeroutput> and
999 <computeroutput>BZ2_bzWriteOpen</computeroutput> for attempts
1000 to use a file for which the error indicator (viz,
1001 <computeroutput>ferror(f)</computeroutput>) is set. On
1002 receipt of <computeroutput>BZ_IO_ERROR</computeroutput>, the
1003 caller should consult <computeroutput>errno</computeroutput>
1004 and/or <computeroutput>perror</computeroutput> to acquire
1005 operating-system specific information about the
1006 problem.</para></listitem>
1007 </varlistentry>
1008
1009 <varlistentry>
1010 <term><computeroutput>BZ_UNEXPECTED_EOF</computeroutput></term>
1011 <listitem><para>Returned by
1012 <computeroutput>BZ2_bzRead</computeroutput> when the
1013 compressed file finishes before the logical end of stream is
1014 detected.</para></listitem>
1015 </varlistentry>
1016
1017 <varlistentry>
1018 <term><computeroutput>BZ_OUTBUFF_FULL</computeroutput></term>
1019 <listitem><para>Returned by
1020 <computeroutput>BZ2_bzBuffToBuffCompress</computeroutput> and
1021 <computeroutput>BZ2_bzBuffToBuffDecompress</computeroutput> to
1022 indicate that the output data will not fit into the output
1023 buffer provided.</para></listitem>
1024 </varlistentry>
1025
1026</variablelist>
1027
1028</sect1>
1029
1030
1031
1032<sect1 id="low-level" xreflabel=">Low-level interface">
1033<title>Low-level interface</title>
1034
1035
1036<sect2 id="bzcompress-init" xreflabel="BZ2_bzCompressInit">
1037<title><computeroutput>BZ2_bzCompressInit</computeroutput></title>
1038
1039<programlisting>
1040typedef struct {
1041 char *next_in;
1042 unsigned int avail_in;
1043 unsigned int total_in_lo32;
1044 unsigned int total_in_hi32;
1045
1046 char *next_out;
1047 unsigned int avail_out;
1048 unsigned int total_out_lo32;
1049 unsigned int total_out_hi32;
1050
1051 void *state;
1052
1053 void *(*bzalloc)(void *,int,int);
1054 void (*bzfree)(void *,void *);
1055 void *opaque;
1056} bz_stream;
1057
1058int BZ2_bzCompressInit ( bz_stream *strm,
1059 int blockSize100k,
1060 int verbosity,
1061 int workFactor );
1062</programlisting>
1063
1064<para>Prepares for compression. The
1065<computeroutput>bz_stream</computeroutput> structure holds all
1066data pertaining to the compression activity. A
1067<computeroutput>bz_stream</computeroutput> structure should be
1068allocated and initialised prior to the call. The fields of
1069<computeroutput>bz_stream</computeroutput> comprise the entirety
1070of the user-visible data. <computeroutput>state</computeroutput>
1071is a pointer to the private data structures required for
1072compression.</para>
1073
1074<para>Custom memory allocators are supported, via fields
1075<computeroutput>bzalloc</computeroutput>,
1076<computeroutput>bzfree</computeroutput>, and
1077<computeroutput>opaque</computeroutput>. The value
1078<computeroutput>opaque</computeroutput> is passed to as the first
1079argument to all calls to <computeroutput>bzalloc</computeroutput>
1080and <computeroutput>bzfree</computeroutput>, but is otherwise
1081ignored by the library. The call <computeroutput>bzalloc (
1082opaque, n, m )</computeroutput> is expected to return a pointer
1083<computeroutput>p</computeroutput> to <computeroutput>n *
1084m</computeroutput> bytes of memory, and <computeroutput>bzfree (
1085opaque, p )</computeroutput> should free that memory.</para>
1086
1087<para>If you don't want to use a custom memory allocator, set
1088<computeroutput>bzalloc</computeroutput>,
1089<computeroutput>bzfree</computeroutput> and
1090<computeroutput>opaque</computeroutput> to
1091<computeroutput>NULL</computeroutput>, and the library will then
1092use the standard <computeroutput>malloc</computeroutput> /
1093<computeroutput>free</computeroutput> routines.</para>
1094
1095<para>Before calling
1096<computeroutput>BZ2_bzCompressInit</computeroutput>, fields
1097<computeroutput>bzalloc</computeroutput>,
1098<computeroutput>bzfree</computeroutput> and
1099<computeroutput>opaque</computeroutput> should be filled
1100appropriately, as just described. Upon return, the internal
1101state will have been allocated and initialised, and
1102<computeroutput>total_in_lo32</computeroutput>,
1103<computeroutput>total_in_hi32</computeroutput>,
1104<computeroutput>total_out_lo32</computeroutput> and
1105<computeroutput>total_out_hi32</computeroutput> will have been
1106set to zero. These four fields are used by the library to inform
1107the caller of the total amount of data passed into and out of the
1108library, respectively. You should not try to change them. As of
1109version 1.0, 64-bit counts are maintained, even on 32-bit
1110platforms, using the <computeroutput>_hi32</computeroutput>
1111fields to store the upper 32 bits of the count. So, for example,
1112the total amount of data in is <computeroutput>(total_in_hi32
1113&#60;&#60; 32) + total_in_lo32</computeroutput>.</para>
1114
1115<para>Parameter <computeroutput>blockSize100k</computeroutput>
1116specifies the block size to be used for compression. It should
1117be a value between 1 and 9 inclusive, and the actual block size
1118used is 100000 x this figure. 9 gives the best compression but
1119takes most memory.</para>
1120
1121<para>Parameter <computeroutput>verbosity</computeroutput> should
1122be set to a number between 0 and 4 inclusive. 0 is silent, and
1123greater numbers give increasingly verbose monitoring/debugging
1124output. If the library has been compiled with
1125<computeroutput>-DBZ_NO_STDIO</computeroutput>, no such output
1126will appear for any verbosity setting.</para>
1127
1128<para>Parameter <computeroutput>workFactor</computeroutput>
1129controls how the compression phase behaves when presented with
1130worst case, highly repetitive, input data. If compression runs
1131into difficulties caused by repetitive data, the library switches
1132from the standard sorting algorithm to a fallback algorithm. The
1133fallback is slower than the standard algorithm by perhaps a
1134factor of three, but always behaves reasonably, no matter how bad
1135the input.</para>
1136
1137<para>Lower values of <computeroutput>workFactor</computeroutput>
1138reduce the amount of effort the standard algorithm will expend
1139before resorting to the fallback. You should set this parameter
1140carefully; too low, and many inputs will be handled by the
1141fallback algorithm and so compress rather slowly, too high, and
1142your average-to-worst case compression times can become very
1143large. The default value of 30 gives reasonable behaviour over a
1144wide range of circumstances.</para>
1145
1146<para>Allowable values range from 0 to 250 inclusive. 0 is a
1147special case, equivalent to using the default value of 30.</para>
1148
1149<para>Note that the compressed output generated is the same
1150regardless of whether or not the fallback algorithm is
1151used.</para>
1152
1153<para>Be aware also that this parameter may disappear entirely in
1154future versions of the library. In principle it should be
1155possible to devise a good way to automatically choose which
1156algorithm to use. Such a mechanism would render the parameter
1157obsolete.</para>
1158
1159<para>Possible return values:</para>
1160
1161<programlisting>
1162BZ_CONFIG_ERROR
1163 if the library has been mis-compiled
1164BZ_PARAM_ERROR
1165 if strm is NULL
1166 or blockSize < 1 or blockSize > 9
1167 or verbosity < 0 or verbosity > 4
1168 or workFactor < 0 or workFactor > 250
1169BZ_MEM_ERROR
1170 if not enough memory is available
1171BZ_OK
1172 otherwise
1173</programlisting>
1174
1175<para>Allowable next actions:</para>
1176
1177<programlisting>
1178BZ2_bzCompress
1179 if BZ_OK is returned
1180 no specific action needed in case of error
1181</programlisting>
1182
1183</sect2>
1184
1185
1186<sect2 id="bzCompress" xreflabel="BZ2_bzCompress">
1187<title><computeroutput>BZ2_bzCompress</computeroutput></title>
1188
1189<programlisting>
1190int BZ2_bzCompress ( bz_stream *strm, int action );
1191</programlisting>
1192
1193<para>Provides more input and/or output buffer space for the
1194library. The caller maintains input and output buffers, and
1195calls <computeroutput>BZ2_bzCompress</computeroutput> to transfer
1196data between them.</para>
1197
1198<para>Before each call to
1199<computeroutput>BZ2_bzCompress</computeroutput>,
1200<computeroutput>next_in</computeroutput> should point at the data
1201to be compressed, and <computeroutput>avail_in</computeroutput>
1202should indicate how many bytes the library may read.
1203<computeroutput>BZ2_bzCompress</computeroutput> updates
1204<computeroutput>next_in</computeroutput>,
1205<computeroutput>avail_in</computeroutput> and
1206<computeroutput>total_in</computeroutput> to reflect the number
1207of bytes it has read.</para>
1208
1209<para>Similarly, <computeroutput>next_out</computeroutput> should
1210point to a buffer in which the compressed data is to be placed,
1211with <computeroutput>avail_out</computeroutput> indicating how
1212much output space is available.
1213<computeroutput>BZ2_bzCompress</computeroutput> updates
1214<computeroutput>next_out</computeroutput>,
1215<computeroutput>avail_out</computeroutput> and
1216<computeroutput>total_out</computeroutput> to reflect the number
1217of bytes output.</para>
1218
1219<para>You may provide and remove as little or as much data as you
1220like on each call of
1221<computeroutput>BZ2_bzCompress</computeroutput>. In the limit,
1222it is acceptable to supply and remove data one byte at a time,
1223although this would be terribly inefficient. You should always
1224ensure that at least one byte of output space is available at
1225each call.</para>
1226
1227<para>A second purpose of
1228<computeroutput>BZ2_bzCompress</computeroutput> is to request a
1229change of mode of the compressed stream.</para>
1230
1231<para>Conceptually, a compressed stream can be in one of four
1232states: IDLE, RUNNING, FLUSHING and FINISHING. Before
1233initialisation
1234(<computeroutput>BZ2_bzCompressInit</computeroutput>) and after
1235termination (<computeroutput>BZ2_bzCompressEnd</computeroutput>),
1236a stream is regarded as IDLE.</para>
1237
1238<para>Upon initialisation
1239(<computeroutput>BZ2_bzCompressInit</computeroutput>), the stream
1240is placed in the RUNNING state. Subsequent calls to
1241<computeroutput>BZ2_bzCompress</computeroutput> should pass
1242<computeroutput>BZ_RUN</computeroutput> as the requested action;
1243other actions are illegal and will result in
1244<computeroutput>BZ_SEQUENCE_ERROR</computeroutput>.</para>
1245
1246<para>At some point, the calling program will have provided all
1247the input data it wants to. It will then want to finish up -- in
1248effect, asking the library to process any data it might have
1249buffered internally. In this state,
1250<computeroutput>BZ2_bzCompress</computeroutput> will no longer
1251attempt to read data from
1252<computeroutput>next_in</computeroutput>, but it will want to
1253write data to <computeroutput>next_out</computeroutput>. Because
1254the output buffer supplied by the user can be arbitrarily small,
1255the finishing-up operation cannot necessarily be done with a
1256single call of
1257<computeroutput>BZ2_bzCompress</computeroutput>.</para>
1258
1259<para>Instead, the calling program passes
1260<computeroutput>BZ_FINISH</computeroutput> as an action to
1261<computeroutput>BZ2_bzCompress</computeroutput>. This changes
1262the stream's state to FINISHING. Any remaining input (ie,
1263<computeroutput>next_in[0 .. avail_in-1]</computeroutput>) is
1264compressed and transferred to the output buffer. To do this,
1265<computeroutput>BZ2_bzCompress</computeroutput> must be called
1266repeatedly until all the output has been consumed. At that
1267point, <computeroutput>BZ2_bzCompress</computeroutput> returns
1268<computeroutput>BZ_STREAM_END</computeroutput>, and the stream's
1269state is set back to IDLE.
1270<computeroutput>BZ2_bzCompressEnd</computeroutput> should then be
1271called.</para>
1272
1273<para>Just to make sure the calling program does not cheat, the
1274library makes a note of <computeroutput>avail_in</computeroutput>
1275at the time of the first call to
1276<computeroutput>BZ2_bzCompress</computeroutput> which has
1277<computeroutput>BZ_FINISH</computeroutput> as an action (ie, at
1278the time the program has announced its intention to not supply
1279any more input). By comparing this value with that of
1280<computeroutput>avail_in</computeroutput> over subsequent calls
1281to <computeroutput>BZ2_bzCompress</computeroutput>, the library
1282can detect any attempts to slip in more data to compress. Any
1283calls for which this is detected will return
1284<computeroutput>BZ_SEQUENCE_ERROR</computeroutput>. This
1285indicates a programming mistake which should be corrected.</para>
1286
1287<para>Instead of asking to finish, the calling program may ask
1288<computeroutput>BZ2_bzCompress</computeroutput> to take all the
1289remaining input, compress it and terminate the current
1290(Burrows-Wheeler) compression block. This could be useful for
1291error control purposes. The mechanism is analogous to that for
1292finishing: call <computeroutput>BZ2_bzCompress</computeroutput>
1293with an action of <computeroutput>BZ_FLUSH</computeroutput>,
1294remove output data, and persist with the
1295<computeroutput>BZ_FLUSH</computeroutput> action until the value
1296<computeroutput>BZ_RUN</computeroutput> is returned. As with
1297finishing, <computeroutput>BZ2_bzCompress</computeroutput>
1298detects any attempt to provide more input data once the flush has
1299begun.</para>
1300
1301<para>Once the flush is complete, the stream returns to the
1302normal RUNNING state.</para>
1303
1304<para>This all sounds pretty complex, but isn't really. Here's a
1305table which shows which actions are allowable in each state, what
1306action will be taken, what the next state is, and what the
1307non-error return values are. Note that you can't explicitly ask
1308what state the stream is in, but nor do you need to -- it can be
1309inferred from the values returned by
1310<computeroutput>BZ2_bzCompress</computeroutput>.</para>
1311
1312<programlisting>
1313IDLE/any
1314 Illegal. IDLE state only exists after BZ2_bzCompressEnd or
1315 before BZ2_bzCompressInit.
1316 Return value = BZ_SEQUENCE_ERROR
1317
1318RUNNING/BZ_RUN
1319 Compress from next_in to next_out as much as possible.
1320 Next state = RUNNING
1321 Return value = BZ_RUN_OK
1322
1323RUNNING/BZ_FLUSH
1324 Remember current value of next_in. Compress from next_in
1325 to next_out as much as possible, but do not accept any more input.
1326 Next state = FLUSHING
1327 Return value = BZ_FLUSH_OK
1328
1329RUNNING/BZ_FINISH
1330 Remember current value of next_in. Compress from next_in
1331 to next_out as much as possible, but do not accept any more input.
1332 Next state = FINISHING
1333 Return value = BZ_FINISH_OK
1334
1335FLUSHING/BZ_FLUSH
1336 Compress from next_in to next_out as much as possible,
1337 but do not accept any more input.
1338 If all the existing input has been used up and all compressed
1339 output has been removed
1340 Next state = RUNNING; Return value = BZ_RUN_OK
1341 else
1342 Next state = FLUSHING; Return value = BZ_FLUSH_OK
1343
1344FLUSHING/other
1345 Illegal.
1346 Return value = BZ_SEQUENCE_ERROR
1347
1348FINISHING/BZ_FINISH
1349 Compress from next_in to next_out as much as possible,
1350 but to not accept any more input.
1351 If all the existing input has been used up and all compressed
1352 output has been removed
1353 Next state = IDLE; Return value = BZ_STREAM_END
1354 else
1355 Next state = FINISHING; Return value = BZ_FINISHING
1356
1357FINISHING/other
1358 Illegal.
1359 Return value = BZ_SEQUENCE_ERROR
1360</programlisting>
1361
1362
1363<para>That still looks complicated? Well, fair enough. The
1364usual sequence of calls for compressing a load of data is:</para>
1365
1366<orderedlist>
1367
1368 <listitem><para>Get started with
1369 <computeroutput>BZ2_bzCompressInit</computeroutput>.</para></listitem>
1370
1371 <listitem><para>Shovel data in and shlurp out its compressed form
1372 using zero or more calls of
1373 <computeroutput>BZ2_bzCompress</computeroutput> with action =
1374 <computeroutput>BZ_RUN</computeroutput>.</para></listitem>
1375
1376 <listitem><para>Finish up. Repeatedly call
1377 <computeroutput>BZ2_bzCompress</computeroutput> with action =
1378 <computeroutput>BZ_FINISH</computeroutput>, copying out the
1379 compressed output, until
1380 <computeroutput>BZ_STREAM_END</computeroutput> is
1381 returned.</para></listitem> <listitem><para>Close up and go home. Call
1382 <computeroutput>BZ2_bzCompressEnd</computeroutput>.</para></listitem>
1383
1384</orderedlist>
1385
1386<para>If the data you want to compress fits into your input
1387buffer all at once, you can skip the calls of
1388<computeroutput>BZ2_bzCompress ( ..., BZ_RUN )</computeroutput>
1389and just do the <computeroutput>BZ2_bzCompress ( ..., BZ_FINISH
1390)</computeroutput> calls.</para>
1391
1392<para>All required memory is allocated by
1393<computeroutput>BZ2_bzCompressInit</computeroutput>. The
1394compression library can accept any data at all (obviously). So
1395you shouldn't get any error return values from the
1396<computeroutput>BZ2_bzCompress</computeroutput> calls. If you
1397do, they will be
1398<computeroutput>BZ_SEQUENCE_ERROR</computeroutput>, and indicate
1399a bug in your programming.</para>
1400
1401<para>Trivial other possible return values:</para>
1402
1403<programlisting>
1404BZ_PARAM_ERROR
1405 if strm is NULL, or strm->s is NULL
1406</programlisting>
1407
1408</sect2>
1409
1410
1411<sect2 id="bzCompress-end" xreflabel="BZ2_bzCompressEnd">
1412<title><computeroutput>BZ2_bzCompressEnd</computeroutput></title>
1413
1414<programlisting>
1415int BZ2_bzCompressEnd ( bz_stream *strm );
1416</programlisting>
1417
1418<para>Releases all memory associated with a compression
1419stream.</para>
1420
1421<para>Possible return values:</para>
1422
1423<programlisting>
1424BZ_PARAM_ERROR if strm is NULL or strm->s is NULL
1425BZ_OK otherwise
1426</programlisting>
1427
1428</sect2>
1429
1430
1431<sect2 id="bzDecompress-init" xreflabel="BZ2_bzDecompressInit">
1432<title><computeroutput>BZ2_bzDecompressInit</computeroutput></title>
1433
1434<programlisting>
1435int BZ2_bzDecompressInit ( bz_stream *strm, int verbosity, int small );
1436</programlisting>
1437
1438<para>Prepares for decompression. As with
1439<computeroutput>BZ2_bzCompressInit</computeroutput>, a
1440<computeroutput>bz_stream</computeroutput> record should be
1441allocated and initialised before the call. Fields
1442<computeroutput>bzalloc</computeroutput>,
1443<computeroutput>bzfree</computeroutput> and
1444<computeroutput>opaque</computeroutput> should be set if a custom
1445memory allocator is required, or made
1446<computeroutput>NULL</computeroutput> for the normal
1447<computeroutput>malloc</computeroutput> /
1448<computeroutput>free</computeroutput> routines. Upon return, the
1449internal state will have been initialised, and
1450<computeroutput>total_in</computeroutput> and
1451<computeroutput>total_out</computeroutput> will be zero.</para>
1452
1453<para>For the meaning of parameter
1454<computeroutput>verbosity</computeroutput>, see
1455<computeroutput>BZ2_bzCompressInit</computeroutput>.</para>
1456
1457<para>If <computeroutput>small</computeroutput> is nonzero, the
1458library will use an alternative decompression algorithm which
1459uses less memory but at the cost of decompressing more slowly
1460(roughly speaking, half the speed, but the maximum memory
1461requirement drops to around 2300k). See <xref linkend="using"/>
1462for more information on memory management.</para>
1463
1464<para>Note that the amount of memory needed to decompress a
1465stream cannot be determined until the stream's header has been
1466read, so even if
1467<computeroutput>BZ2_bzDecompressInit</computeroutput> succeeds, a
1468subsequent <computeroutput>BZ2_bzDecompress</computeroutput>
1469could fail with
1470<computeroutput>BZ_MEM_ERROR</computeroutput>.</para>
1471
1472<para>Possible return values:</para>
1473
1474<programlisting>
1475BZ_CONFIG_ERROR
1476 if the library has been mis-compiled
1477BZ_PARAM_ERROR
1478 if ( small != 0 && small != 1 )
1479 or (verbosity <; 0 || verbosity > 4)
1480BZ_MEM_ERROR
1481 if insufficient memory is available
1482</programlisting>
1483
1484<para>Allowable next actions:</para>
1485
1486<programlisting>
1487BZ2_bzDecompress
1488 if BZ_OK was returned
1489 no specific action required in case of error
1490</programlisting>
1491
1492</sect2>
1493
1494
1495<sect2 id="bzDecompress" xreflabel="BZ2_bzDecompress">
1496<title><computeroutput>BZ2_bzDecompress</computeroutput></title>
1497
1498<programlisting>
1499int BZ2_bzDecompress ( bz_stream *strm );
1500</programlisting>
1501
1502<para>Provides more input and/out output buffer space for the
1503library. The caller maintains input and output buffers, and uses
1504<computeroutput>BZ2_bzDecompress</computeroutput> to transfer
1505data between them.</para>
1506
1507<para>Before each call to
1508<computeroutput>BZ2_bzDecompress</computeroutput>,
1509<computeroutput>next_in</computeroutput> should point at the
1510compressed data, and <computeroutput>avail_in</computeroutput>
1511should indicate how many bytes the library may read.
1512<computeroutput>BZ2_bzDecompress</computeroutput> updates
1513<computeroutput>next_in</computeroutput>,
1514<computeroutput>avail_in</computeroutput> and
1515<computeroutput>total_in</computeroutput> to reflect the number
1516of bytes it has read.</para>
1517
1518<para>Similarly, <computeroutput>next_out</computeroutput> should
1519point to a buffer in which the uncompressed output is to be
1520placed, with <computeroutput>avail_out</computeroutput>
1521indicating how much output space is available.
1522<computeroutput>BZ2_bzCompress</computeroutput> updates
1523<computeroutput>next_out</computeroutput>,
1524<computeroutput>avail_out</computeroutput> and
1525<computeroutput>total_out</computeroutput> to reflect the number
1526of bytes output.</para>
1527
1528<para>You may provide and remove as little or as much data as you
1529like on each call of
1530<computeroutput>BZ2_bzDecompress</computeroutput>. In the limit,
1531it is acceptable to supply and remove data one byte at a time,
1532although this would be terribly inefficient. You should always
1533ensure that at least one byte of output space is available at
1534each call.</para>
1535
1536<para>Use of <computeroutput>BZ2_bzDecompress</computeroutput> is
1537simpler than
1538<computeroutput>BZ2_bzCompress</computeroutput>.</para>
1539
1540<para>You should provide input and remove output as described
1541above, and repeatedly call
1542<computeroutput>BZ2_bzDecompress</computeroutput> until
1543<computeroutput>BZ_STREAM_END</computeroutput> is returned.
1544Appearance of <computeroutput>BZ_STREAM_END</computeroutput>
1545denotes that <computeroutput>BZ2_bzDecompress</computeroutput>
1546has detected the logical end of the compressed stream.
1547<computeroutput>BZ2_bzDecompress</computeroutput> will not
1548produce <computeroutput>BZ_STREAM_END</computeroutput> until all
1549output data has been placed into the output buffer, so once
1550<computeroutput>BZ_STREAM_END</computeroutput> appears, you are
1551guaranteed to have available all the decompressed output, and
1552<computeroutput>BZ2_bzDecompressEnd</computeroutput> can safely
1553be called.</para>
1554
1555<para>If case of an error return value, you should call
1556<computeroutput>BZ2_bzDecompressEnd</computeroutput> to clean up
1557and release memory.</para>
1558
1559<para>Possible return values:</para>
1560
1561<programlisting>
1562BZ_PARAM_ERROR
1563 if strm is NULL or strm->s is NULL
1564 or strm->avail_out < 1
1565BZ_DATA_ERROR
1566 if a data integrity error is detected in the compressed stream
1567BZ_DATA_ERROR_MAGIC
1568 if the compressed stream doesn't begin with the right magic bytes
1569BZ_MEM_ERROR
1570 if there wasn't enough memory available
1571BZ_STREAM_END
1572 if the logical end of the data stream was detected and all
1573 output in has been consumed, eg s-->avail_out > 0
1574BZ_OK
1575 otherwise
1576</programlisting>
1577
1578<para>Allowable next actions:</para>
1579
1580<programlisting>
1581BZ2_bzDecompress
1582 if BZ_OK was returned
1583BZ2_bzDecompressEnd
1584 otherwise
1585</programlisting>
1586
1587</sect2>
1588
1589
1590<sect2 id="bzDecompress-end" xreflabel="BZ2_bzDecompressEnd">
1591<title><computeroutput>BZ2_bzDecompressEnd</computeroutput></title>
1592
1593<programlisting>
1594int BZ2_bzDecompressEnd ( bz_stream *strm );
1595</programlisting>
1596
1597<para>Releases all memory associated with a decompression
1598stream.</para>
1599
1600<para>Possible return values:</para>
1601
1602<programlisting>
1603BZ_PARAM_ERROR
1604 if strm is NULL or strm->s is NULL
1605BZ_OK
1606 otherwise
1607</programlisting>
1608
1609<para>Allowable next actions:</para>
1610
1611<programlisting>
1612 None.
1613</programlisting>
1614
1615</sect2>
1616
1617</sect1>
1618
1619
1620<sect1 id="hl-interface" xreflabel="High-level interface">
1621<title>High-level interface</title>
1622
1623<para>This interface provides functions for reading and writing
1624<computeroutput>bzip2</computeroutput> format files. First, some
1625general points.</para>
1626
1627<itemizedlist mark='bullet'>
1628
1629 <listitem><para>All of the functions take an
1630 <computeroutput>int*</computeroutput> first argument,
1631 <computeroutput>bzerror</computeroutput>. After each call,
1632 <computeroutput>bzerror</computeroutput> should be consulted
1633 first to determine the outcome of the call. If
1634 <computeroutput>bzerror</computeroutput> is
1635 <computeroutput>BZ_OK</computeroutput>, the call completed
1636 successfully, and only then should the return value of the
1637 function (if any) be consulted. If
1638 <computeroutput>bzerror</computeroutput> is
1639 <computeroutput>BZ_IO_ERROR</computeroutput>, there was an
1640 error reading/writing the underlying compressed file, and you
1641 should then consult <computeroutput>errno</computeroutput> /
1642 <computeroutput>perror</computeroutput> to determine the cause
1643 of the difficulty. <computeroutput>bzerror</computeroutput>
1644 may also be set to various other values; precise details are
1645 given on a per-function basis below.</para></listitem>
1646
1647 <listitem><para>If <computeroutput>bzerror</computeroutput> indicates
1648 an error (ie, anything except
1649 <computeroutput>BZ_OK</computeroutput> and
1650 <computeroutput>BZ_STREAM_END</computeroutput>), you should
1651 immediately call
1652 <computeroutput>BZ2_bzReadClose</computeroutput> (or
1653 <computeroutput>BZ2_bzWriteClose</computeroutput>, depending on
1654 whether you are attempting to read or to write) to free up all
1655 resources associated with the stream. Once an error has been
1656 indicated, behaviour of all calls except
1657 <computeroutput>BZ2_bzReadClose</computeroutput>
1658 (<computeroutput>BZ2_bzWriteClose</computeroutput>) is
1659 undefined. The implication is that (1)
1660 <computeroutput>bzerror</computeroutput> should be checked
1661 after each call, and (2) if
1662 <computeroutput>bzerror</computeroutput> indicates an error,
1663 <computeroutput>BZ2_bzReadClose</computeroutput>
1664 (<computeroutput>BZ2_bzWriteClose</computeroutput>) should then
1665 be called to clean up.</para></listitem>
1666
1667 <listitem><para>The <computeroutput>FILE*</computeroutput> arguments
1668 passed to <computeroutput>BZ2_bzReadOpen</computeroutput> /
1669 <computeroutput>BZ2_bzWriteOpen</computeroutput> should be set
1670 to binary mode. Most Unix systems will do this by default, but
1671 other platforms, including Windows and Mac, will not. If you
1672 omit this, you may encounter problems when moving code to new
1673 platforms.</para></listitem>
1674
1675 <listitem><para>Memory allocation requests are handled by
1676 <computeroutput>malloc</computeroutput> /
1677 <computeroutput>free</computeroutput>. At present there is no
1678 facility for user-defined memory allocators in the file I/O
1679 functions (could easily be added, though).</para></listitem>
1680
1681</itemizedlist>
1682
1683
1684
1685<sect2 id="bzreadopen" xreflabel="BZ2_bzReadOpen">
1686<title><computeroutput>BZ2_bzReadOpen</computeroutput></title>
1687
1688<programlisting>
1689typedef void BZFILE;
1690
1691BZFILE *BZ2_bzReadOpen( int *bzerror, FILE *f,
1692 int verbosity, int small,
1693 void *unused, int nUnused );
1694</programlisting>
1695
1696<para>Prepare to read compressed data from file handle
1697<computeroutput>f</computeroutput>.
1698<computeroutput>f</computeroutput> should refer to a file which
1699has been opened for reading, and for which the error indicator
1700(<computeroutput>ferror(f)</computeroutput>)is not set. If
1701<computeroutput>small</computeroutput> is 1, the library will try
1702to decompress using less memory, at the expense of speed.</para>
1703
1704<para>For reasons explained below,
1705<computeroutput>BZ2_bzRead</computeroutput> will decompress the
1706<computeroutput>nUnused</computeroutput> bytes starting at
1707<computeroutput>unused</computeroutput>, before starting to read
1708from the file <computeroutput>f</computeroutput>. At most
1709<computeroutput>BZ_MAX_UNUSED</computeroutput> bytes may be
1710supplied like this. If this facility is not required, you should
1711pass <computeroutput>NULL</computeroutput> and
1712<computeroutput>0</computeroutput> for
1713<computeroutput>unused</computeroutput> and
1714n<computeroutput>Unused</computeroutput> respectively.</para>
1715
1716<para>For the meaning of parameters
1717<computeroutput>small</computeroutput> and
1718<computeroutput>verbosity</computeroutput>, see
1719<computeroutput>BZ2_bzDecompressInit</computeroutput>.</para>
1720
1721<para>The amount of memory needed to decompress a file cannot be
1722determined until the file's header has been read. So it is
1723possible that <computeroutput>BZ2_bzReadOpen</computeroutput>
1724returns <computeroutput>BZ_OK</computeroutput> but a subsequent
1725call of <computeroutput>BZ2_bzRead</computeroutput> will return
1726<computeroutput>BZ_MEM_ERROR</computeroutput>.</para>
1727
1728<para>Possible assignments to
1729<computeroutput>bzerror</computeroutput>:</para>
1730
1731<programlisting>
1732BZ_CONFIG_ERROR
1733 if the library has been mis-compiled
1734BZ_PARAM_ERROR
1735 if f is NULL
1736 or small is neither 0 nor 1
1737 or ( unused == NULL && nUnused != 0 )
1738 or ( unused != NULL && !(0 <= nUnused <= BZ_MAX_UNUSED) )
1739BZ_IO_ERROR
1740 if ferror(f) is nonzero
1741BZ_MEM_ERROR
1742 if insufficient memory is available
1743BZ_OK
1744 otherwise.
1745</programlisting>
1746
1747<para>Possible return values:</para>
1748
1749<programlisting>
1750Pointer to an abstract BZFILE
1751 if bzerror is BZ_OK
1752NULL
1753 otherwise
1754</programlisting>
1755
1756<para>Allowable next actions:</para>
1757
1758<programlisting>
1759BZ2_bzRead
1760 if bzerror is BZ_OK
1761BZ2_bzClose
1762 otherwise
1763</programlisting>
1764
1765</sect2>
1766
1767
1768<sect2 id="bzread" xreflabel="BZ2_bzRead">
1769<title><computeroutput>BZ2_bzRead</computeroutput></title>
1770
1771<programlisting>
1772int BZ2_bzRead ( int *bzerror, BZFILE *b, void *buf, int len );
1773</programlisting>
1774
1775<para>Reads up to <computeroutput>len</computeroutput>
1776(uncompressed) bytes from the compressed file
1777<computeroutput>b</computeroutput> into the buffer
1778<computeroutput>buf</computeroutput>. If the read was
1779successful, <computeroutput>bzerror</computeroutput> is set to
1780<computeroutput>BZ_OK</computeroutput> and the number of bytes
1781read is returned. If the logical end-of-stream was detected,
1782<computeroutput>bzerror</computeroutput> will be set to
1783<computeroutput>BZ_STREAM_END</computeroutput>, and the number of
1784bytes read is returned. All other
1785<computeroutput>bzerror</computeroutput> values denote an
1786error.</para>
1787
1788<para><computeroutput>BZ2_bzRead</computeroutput> will supply
1789<computeroutput>len</computeroutput> bytes, unless the logical
1790stream end is detected or an error occurs. Because of this, it
1791is possible to detect the stream end by observing when the number
1792of bytes returned is less than the number requested.
1793Nevertheless, this is regarded as inadvisable; you should instead
1794check <computeroutput>bzerror</computeroutput> after every call
1795and watch out for
1796<computeroutput>BZ_STREAM_END</computeroutput>.</para>
1797
1798<para>Internally, <computeroutput>BZ2_bzRead</computeroutput>
1799copies data from the compressed file in chunks of size
1800<computeroutput>BZ_MAX_UNUSED</computeroutput> bytes before
1801decompressing it. If the file contains more bytes than strictly
1802needed to reach the logical end-of-stream,
1803<computeroutput>BZ2_bzRead</computeroutput> will almost certainly
1804read some of the trailing data before signalling
1805<computeroutput>BZ_SEQUENCE_END</computeroutput>. To collect the
1806read but unused data once
1807<computeroutput>BZ_SEQUENCE_END</computeroutput> has appeared,
1808call <computeroutput>BZ2_bzReadGetUnused</computeroutput>
1809immediately before
1810<computeroutput>BZ2_bzReadClose</computeroutput>.</para>
1811
1812<para>Possible assignments to
1813<computeroutput>bzerror</computeroutput>:</para>
1814
1815<programlisting>
1816BZ_PARAM_ERROR
1817 if b is NULL or buf is NULL or len < 0
1818BZ_SEQUENCE_ERROR
1819 if b was opened with BZ2_bzWriteOpen
1820BZ_IO_ERROR
1821 if there is an error reading from the compressed file
1822BZ_UNEXPECTED_EOF
1823 if the compressed file ended before
1824 the logical end-of-stream was detected
1825BZ_DATA_ERROR
1826 if a data integrity error was detected in the compressed stream
1827BZ_DATA_ERROR_MAGIC
1828 if the stream does not begin with the requisite header bytes
1829 (ie, is not a bzip2 data file). This is really
1830 a special case of BZ_DATA_ERROR.
1831BZ_MEM_ERROR
1832 if insufficient memory was available
1833BZ_STREAM_END
1834 if the logical end of stream was detected.
1835BZ_OK
1836 otherwise.
1837</programlisting>
1838
1839<para>Possible return values:</para>
1840
1841<programlisting>
1842number of bytes read
1843 if bzerror is BZ_OK or BZ_STREAM_END
1844undefined
1845 otherwise
1846</programlisting>
1847
1848<para>Allowable next actions:</para>
1849
1850<programlisting>
1851collect data from buf, then BZ2_bzRead or BZ2_bzReadClose
1852 if bzerror is BZ_OK
1853collect data from buf, then BZ2_bzReadClose or BZ2_bzReadGetUnused
1854 if bzerror is BZ_SEQUENCE_END
1855BZ2_bzReadClose
1856 otherwise
1857</programlisting>
1858
1859</sect2>
1860
1861
1862<sect2 id="bzreadgetunused" xreflabel="BZ2_bzReadGetUnused">
1863<title><computeroutput>BZ2_bzReadGetUnused</computeroutput></title>
1864
1865<programlisting>
1866void BZ2_bzReadGetUnused( int* bzerror, BZFILE *b,
1867 void** unused, int* nUnused );
1868</programlisting>
1869
1870<para>Returns data which was read from the compressed file but
1871was not needed to get to the logical end-of-stream.
1872<computeroutput>*unused</computeroutput> is set to the address of
1873the data, and <computeroutput>*nUnused</computeroutput> to the
1874number of bytes. <computeroutput>*nUnused</computeroutput> will
1875be set to a value between <computeroutput>0</computeroutput> and
1876<computeroutput>BZ_MAX_UNUSED</computeroutput> inclusive.</para>
1877
1878<para>This function may only be called once
1879<computeroutput>BZ2_bzRead</computeroutput> has signalled
1880<computeroutput>BZ_STREAM_END</computeroutput> but before
1881<computeroutput>BZ2_bzReadClose</computeroutput>.</para>
1882
1883<para>Possible assignments to
1884<computeroutput>bzerror</computeroutput>:</para>
1885
1886<programlisting>
1887BZ_PARAM_ERROR
1888 if b is NULL
1889 or unused is NULL or nUnused is NULL
1890BZ_SEQUENCE_ERROR
1891 if BZ_STREAM_END has not been signalled
1892 or if b was opened with BZ2_bzWriteOpen
1893BZ_OK
1894 otherwise
1895</programlisting>
1896
1897<para>Allowable next actions:</para>
1898
1899<programlisting>
1900BZ2_bzReadClose
1901</programlisting>
1902
1903</sect2>
1904
1905
1906<sect2 id="bzreadclose" xreflabel="BZ2_bzReadClose">
1907<title><computeroutput>BZ2_bzReadClose</computeroutput></title>
1908
1909<programlisting>
1910void BZ2_bzReadClose ( int *bzerror, BZFILE *b );
1911</programlisting>
1912
1913<para>Releases all memory pertaining to the compressed file
1914<computeroutput>b</computeroutput>.
1915<computeroutput>BZ2_bzReadClose</computeroutput> does not call
1916<computeroutput>fclose</computeroutput> on the underlying file
1917handle, so you should do that yourself if appropriate.
1918<computeroutput>BZ2_bzReadClose</computeroutput> should be called
1919to clean up after all error situations.</para>
1920
1921<para>Possible assignments to
1922<computeroutput>bzerror</computeroutput>:</para>
1923
1924<programlisting>
1925BZ_SEQUENCE_ERROR
1926 if b was opened with BZ2_bzOpenWrite
1927BZ_OK
1928 otherwise
1929</programlisting>
1930
1931<para>Allowable next actions:</para>
1932
1933<programlisting>
1934none
1935</programlisting>
1936
1937</sect2>
1938
1939
1940<sect2 id="bzwriteopen" xreflabel="BZ2_bzWriteOpen">
1941<title><computeroutput>BZ2_bzWriteOpen</computeroutput></title>
1942
1943<programlisting>
1944BZFILE *BZ2_bzWriteOpen( int *bzerror, FILE *f,
1945 int blockSize100k, int verbosity,
1946 int workFactor );
1947</programlisting>
1948
1949<para>Prepare to write compressed data to file handle
1950<computeroutput>f</computeroutput>.
1951<computeroutput>f</computeroutput> should refer to a file which
1952has been opened for writing, and for which the error indicator
1953(<computeroutput>ferror(f)</computeroutput>)is not set.</para>
1954
1955<para>For the meaning of parameters
1956<computeroutput>blockSize100k</computeroutput>,
1957<computeroutput>verbosity</computeroutput> and
1958<computeroutput>workFactor</computeroutput>, see
1959<computeroutput>BZ2_bzCompressInit</computeroutput>.</para>
1960
1961<para>All required memory is allocated at this stage, so if the
1962call completes successfully,
1963<computeroutput>BZ_MEM_ERROR</computeroutput> cannot be signalled
1964by a subsequent call to
1965<computeroutput>BZ2_bzWrite</computeroutput>.</para>
1966
1967<para>Possible assignments to
1968<computeroutput>bzerror</computeroutput>:</para>
1969
1970<programlisting>
1971BZ_CONFIG_ERROR
1972 if the library has been mis-compiled
1973BZ_PARAM_ERROR
1974 if f is NULL
1975 or blockSize100k < 1 or blockSize100k > 9
1976BZ_IO_ERROR
1977 if ferror(f) is nonzero
1978BZ_MEM_ERROR
1979 if insufficient memory is available
1980BZ_OK
1981 otherwise
1982</programlisting>
1983
1984<para>Possible return values:</para>
1985
1986<programlisting>
1987Pointer to an abstract BZFILE
1988 if bzerror is BZ_OK
1989NULL
1990 otherwise
1991</programlisting>
1992
1993<para>Allowable next actions:</para>
1994
1995<programlisting>
1996BZ2_bzWrite
1997 if bzerror is BZ_OK
1998 (you could go directly to BZ2_bzWriteClose, but this would be pretty pointless)
1999BZ2_bzWriteClose
2000 otherwise
2001</programlisting>
2002
2003</sect2>
2004
2005
2006<sect2 id="bzwrite" xreflabel="BZ2_bzWrite">
2007<title><computeroutput>BZ2_bzWrite</computeroutput></title>
2008
2009<programlisting>
2010void BZ2_bzWrite ( int *bzerror, BZFILE *b, void *buf, int len );
2011</programlisting>
2012
2013<para>Absorbs <computeroutput>len</computeroutput> bytes from the
2014buffer <computeroutput>buf</computeroutput>, eventually to be
2015compressed and written to the file.</para>
2016
2017<para>Possible assignments to
2018<computeroutput>bzerror</computeroutput>:</para>
2019
2020<programlisting>
2021BZ_PARAM_ERROR
2022 if b is NULL or buf is NULL or len < 0
2023BZ_SEQUENCE_ERROR
2024 if b was opened with BZ2_bzReadOpen
2025BZ_IO_ERROR
2026 if there is an error writing the compressed file.
2027BZ_OK
2028 otherwise
2029</programlisting>
2030
2031</sect2>
2032
2033
2034<sect2 id="bzwriteclose" xreflabel="BZ2_bzWriteClose">
2035<title><computeroutput>BZ2_bzWriteClose</computeroutput></title>
2036
2037<programlisting>
2038void BZ2_bzWriteClose( int *bzerror, BZFILE* f,
2039 int abandon,
2040 unsigned int* nbytes_in,
2041 unsigned int* nbytes_out );
2042
2043void BZ2_bzWriteClose64( int *bzerror, BZFILE* f,
2044 int abandon,
2045 unsigned int* nbytes_in_lo32,
2046 unsigned int* nbytes_in_hi32,
2047 unsigned int* nbytes_out_lo32,
2048 unsigned int* nbytes_out_hi32 );
2049</programlisting>
2050
2051<para>Compresses and flushes to the compressed file all data so
2052far supplied by <computeroutput>BZ2_bzWrite</computeroutput>.
2053The logical end-of-stream markers are also written, so subsequent
2054calls to <computeroutput>BZ2_bzWrite</computeroutput> are
2055illegal. All memory associated with the compressed file
2056<computeroutput>b</computeroutput> is released.
2057<computeroutput>fflush</computeroutput> is called on the
2058compressed file, but it is not
2059<computeroutput>fclose</computeroutput>'d.</para>
2060
2061<para>If <computeroutput>BZ2_bzWriteClose</computeroutput> is
2062called to clean up after an error, the only action is to release
2063the memory. The library records the error codes issued by
2064previous calls, so this situation will be detected automatically.
2065There is no attempt to complete the compression operation, nor to
2066<computeroutput>fflush</computeroutput> the compressed file. You
2067can force this behaviour to happen even in the case of no error,
2068by passing a nonzero value to
2069<computeroutput>abandon</computeroutput>.</para>
2070
2071<para>If <computeroutput>nbytes_in</computeroutput> is non-null,
2072<computeroutput>*nbytes_in</computeroutput> will be set to be the
2073total volume of uncompressed data handled. Similarly,
2074<computeroutput>nbytes_out</computeroutput> will be set to the
2075total volume of compressed data written. For compatibility with
2076older versions of the library,
2077<computeroutput>BZ2_bzWriteClose</computeroutput> only yields the
2078lower 32 bits of these counts. Use
2079<computeroutput>BZ2_bzWriteClose64</computeroutput> if you want
2080the full 64 bit counts. These two functions are otherwise
2081absolutely identical.</para>
2082
2083<para>Possible assignments to
2084<computeroutput>bzerror</computeroutput>:</para>
2085
2086<programlisting>
2087BZ_SEQUENCE_ERROR
2088 if b was opened with BZ2_bzReadOpen
2089BZ_IO_ERROR
2090 if there is an error writing the compressed file
2091BZ_OK
2092 otherwise
2093</programlisting>
2094
2095</sect2>
2096
2097
2098<sect2 id="embed" xreflabel="Handling embedded compressed data streams">
2099<title>Handling embedded compressed data streams</title>
2100
2101<para>The high-level library facilitates use of
2102<computeroutput>bzip2</computeroutput> data streams which form
2103some part of a surrounding, larger data stream.</para>
2104
2105<itemizedlist mark='bullet'>
2106
2107 <listitem><para>For writing, the library takes an open file handle,
2108 writes compressed data to it,
2109 <computeroutput>fflush</computeroutput>es it but does not
2110 <computeroutput>fclose</computeroutput> it. The calling
2111 application can write its own data before and after the
2112 compressed data stream, using that same file handle.</para></listitem>
2113
2114 <listitem><para>Reading is more complex, and the facilities are not as
2115 general as they could be since generality is hard to reconcile
2116 with efficiency. <computeroutput>BZ2_bzRead</computeroutput>
2117 reads from the compressed file in blocks of size
2118 <computeroutput>BZ_MAX_UNUSED</computeroutput> bytes, and in
2119 doing so probably will overshoot the logical end of compressed
2120 stream. To recover this data once decompression has ended,
2121 call <computeroutput>BZ2_bzReadGetUnused</computeroutput> after
2122 the last call of <computeroutput>BZ2_bzRead</computeroutput>
2123 (the one returning
2124 <computeroutput>BZ_STREAM_END</computeroutput>) but before
2125 calling
2126 <computeroutput>BZ2_bzReadClose</computeroutput>.</para></listitem>
2127
2128</itemizedlist>
2129
2130<para>This mechanism makes it easy to decompress multiple
2131<computeroutput>bzip2</computeroutput> streams placed end-to-end.
2132As the end of one stream, when
2133<computeroutput>BZ2_bzRead</computeroutput> returns
2134<computeroutput>BZ_STREAM_END</computeroutput>, call
2135<computeroutput>BZ2_bzReadGetUnused</computeroutput> to collect
2136the unused data (copy it into your own buffer somewhere). That
2137data forms the start of the next compressed stream. To start
2138uncompressing that next stream, call
2139<computeroutput>BZ2_bzReadOpen</computeroutput> again, feeding in
2140the unused data via the <computeroutput>unused</computeroutput> /
2141<computeroutput>nUnused</computeroutput> parameters. Keep doing
2142this until <computeroutput>BZ_STREAM_END</computeroutput> return
2143coincides with the physical end of file
2144(<computeroutput>feof(f)</computeroutput>). In this situation
2145<computeroutput>BZ2_bzReadGetUnused</computeroutput> will of
2146course return no data.</para>
2147
2148<para>This should give some feel for how the high-level interface
2149can be used. If you require extra flexibility, you'll have to
2150bite the bullet and get to grips with the low-level
2151interface.</para>
2152
2153</sect2>
2154
2155
2156<sect2 id="std-rdwr" xreflabel="Standard file-reading/writing code">
2157<title>Standard file-reading/writing code</title>
2158
2159<para>Here's how you'd write data to a compressed file:</para>
2160
2161<programlisting>
2162FILE* f;
2163BZFILE* b;
2164int nBuf;
2165char buf[ /* whatever size you like */ ];
2166int bzerror;
2167int nWritten;
2168
2169f = fopen ( "myfile.bz2", "w" );
2170if ( !f ) {
2171 /* handle error */
2172}
2173b = BZ2_bzWriteOpen( &bzerror, f, 9 );
2174if (bzerror != BZ_OK) {
2175 BZ2_bzWriteClose ( b );
2176 /* handle error */
2177}
2178
2179while ( /* condition */ ) {
2180 /* get data to write into buf, and set nBuf appropriately */
2181 nWritten = BZ2_bzWrite ( &bzerror, b, buf, nBuf );
2182 if (bzerror == BZ_IO_ERROR) {
2183 BZ2_bzWriteClose ( &bzerror, b );
2184 /* handle error */
2185 }
2186}
2187
2188BZ2_bzWriteClose( &bzerror, b );
2189if (bzerror == BZ_IO_ERROR) {
2190 /* handle error */
2191}
2192</programlisting>
2193
2194<para>And to read from a compressed file:</para>
2195
2196<programlisting>
2197FILE* f;
2198BZFILE* b;
2199int nBuf;
2200char buf[ /* whatever size you like */ ];
2201int bzerror;
2202int nWritten;
2203
2204f = fopen ( "myfile.bz2", "r" );
2205if ( !f ) {
2206 /* handle error */
2207}
2208b = BZ2_bzReadOpen ( &bzerror, f, 0, NULL, 0 );
2209if ( bzerror != BZ_OK ) {
2210 BZ2_bzReadClose ( &bzerror, b );
2211 /* handle error */
2212}
2213
2214bzerror = BZ_OK;
2215while ( bzerror == BZ_OK && /* arbitrary other conditions */) {
2216 nBuf = BZ2_bzRead ( &bzerror, b, buf, /* size of buf */ );
2217 if ( bzerror == BZ_OK ) {
2218 /* do something with buf[0 .. nBuf-1] */
2219 }
2220}
2221if ( bzerror != BZ_STREAM_END ) {
2222 BZ2_bzReadClose ( &bzerror, b );
2223 /* handle error */
2224} else {
2225 BZ2_bzReadClose ( &bzerror );
2226}
2227</programlisting>
2228
2229</sect2>
2230
2231</sect1>
2232
2233
2234<sect1 id="util-fns" xreflabel="Utility functions">
2235<title>Utility functions</title>
2236
2237
2238<sect2 id="bzbufftobuffcompress" xreflabel="BZ2_bzBuffToBuffCompress">
2239<title><computeroutput>BZ2_bzBuffToBuffCompress</computeroutput></title>
2240
2241<programlisting>
2242int BZ2_bzBuffToBuffCompress( char* dest,
2243 unsigned int* destLen,
2244 char* source,
2245 unsigned int sourceLen,
2246 int blockSize100k,
2247 int verbosity,
2248 int workFactor );
2249</programlisting>
2250
2251<para>Attempts to compress the data in <computeroutput>source[0
2252.. sourceLen-1]</computeroutput> into the destination buffer,
2253<computeroutput>dest[0 .. *destLen-1]</computeroutput>. If the
2254destination buffer is big enough,
2255<computeroutput>*destLen</computeroutput> is set to the size of
2256the compressed data, and <computeroutput>BZ_OK</computeroutput>
2257is returned. If the compressed data won't fit,
2258<computeroutput>*destLen</computeroutput> is unchanged, and
2259<computeroutput>BZ_OUTBUFF_FULL</computeroutput> is
2260returned.</para>
2261
2262<para>Compression in this manner is a one-shot event, done with a
2263single call to this function. The resulting compressed data is a
2264complete <computeroutput>bzip2</computeroutput> format data
2265stream. There is no mechanism for making additional calls to
2266provide extra input data. If you want that kind of mechanism,
2267use the low-level interface.</para>
2268
2269<para>For the meaning of parameters
2270<computeroutput>blockSize100k</computeroutput>,
2271<computeroutput>verbosity</computeroutput> and
2272<computeroutput>workFactor</computeroutput>, see
2273<computeroutput>BZ2_bzCompressInit</computeroutput>.</para>
2274
2275<para>To guarantee that the compressed data will fit in its
2276buffer, allocate an output buffer of size 1% larger than the
2277uncompressed data, plus six hundred extra bytes.</para>
2278
2279<para><computeroutput>BZ2_bzBuffToBuffDecompress</computeroutput>
2280will not write data at or beyond
2281<computeroutput>dest[*destLen]</computeroutput>, even in case of
2282buffer overflow.</para>
2283
2284<para>Possible return values:</para>
2285
2286<programlisting>
2287BZ_CONFIG_ERROR
2288 if the library has been mis-compiled
2289BZ_PARAM_ERROR
2290 if dest is NULL or destLen is NULL
2291 or blockSize100k < 1 or blockSize100k > 9
2292 or verbosity < 0 or verbosity > 4
2293 or workFactor < 0 or workFactor > 250
2294BZ_MEM_ERROR
2295 if insufficient memory is available
2296BZ_OUTBUFF_FULL
2297 if the size of the compressed data exceeds *destLen
2298BZ_OK
2299 otherwise
2300</programlisting>
2301
2302</sect2>
2303
2304
2305<sect2 id="bzbufftobuffdecompress" xreflabel="BZ2_bzBuffToBuffDecompress">
2306<title><computeroutput>BZ2_bzBuffToBuffDecompress</computeroutput></title>
2307
2308<programlisting>
2309int BZ2_bzBuffToBuffDecompress( char* dest,
2310 unsigned int* destLen,
2311 char* source,
2312 unsigned int sourceLen,
2313 int small,
2314 int verbosity );
2315</programlisting>
2316
2317<para>Attempts to decompress the data in <computeroutput>source[0
2318.. sourceLen-1]</computeroutput> into the destination buffer,
2319<computeroutput>dest[0 .. *destLen-1]</computeroutput>. If the
2320destination buffer is big enough,
2321<computeroutput>*destLen</computeroutput> is set to the size of
2322the uncompressed data, and <computeroutput>BZ_OK</computeroutput>
2323is returned. If the compressed data won't fit,
2324<computeroutput>*destLen</computeroutput> is unchanged, and
2325<computeroutput>BZ_OUTBUFF_FULL</computeroutput> is
2326returned.</para>
2327
2328<para><computeroutput>source</computeroutput> is assumed to hold
2329a complete <computeroutput>bzip2</computeroutput> format data
2330stream.
2331<computeroutput>BZ2_bzBuffToBuffDecompress</computeroutput> tries
2332to decompress the entirety of the stream into the output
2333buffer.</para>
2334
2335<para>For the meaning of parameters
2336<computeroutput>small</computeroutput> and
2337<computeroutput>verbosity</computeroutput>, see
2338<computeroutput>BZ2_bzDecompressInit</computeroutput>.</para>
2339
2340<para>Because the compression ratio of the compressed data cannot
2341be known in advance, there is no easy way to guarantee that the
2342output buffer will be big enough. You may of course make
2343arrangements in your code to record the size of the uncompressed
2344data, but such a mechanism is beyond the scope of this
2345library.</para>
2346
2347<para><computeroutput>BZ2_bzBuffToBuffDecompress</computeroutput>
2348will not write data at or beyond
2349<computeroutput>dest[*destLen]</computeroutput>, even in case of
2350buffer overflow.</para>
2351
2352<para>Possible return values:</para>
2353
2354<programlisting>
2355BZ_CONFIG_ERROR
2356 if the library has been mis-compiled
2357BZ_PARAM_ERROR
2358 if dest is NULL or destLen is NULL
2359 or small != 0 && small != 1
2360 or verbosity < 0 or verbosity > 4
2361BZ_MEM_ERROR
2362 if insufficient memory is available
2363BZ_OUTBUFF_FULL
2364 if the size of the compressed data exceeds *destLen
2365BZ_DATA_ERROR
2366 if a data integrity error was detected in the compressed data
2367BZ_DATA_ERROR_MAGIC
2368 if the compressed data doesn't begin with the right magic bytes
2369BZ_UNEXPECTED_EOF
2370 if the compressed data ends unexpectedly
2371BZ_OK
2372 otherwise
2373</programlisting>
2374
2375</sect2>
2376
2377</sect1>
2378
2379
2380<sect1 id="zlib-compat" xreflabel="zlib compatibility functions">
2381<title><computeroutput>zlib</computeroutput> compatibility functions</title>
2382
2383<para>Yoshioka Tsuneo has contributed some functions to give
2384better <computeroutput>zlib</computeroutput> compatibility.
2385These functions are <computeroutput>BZ2_bzopen</computeroutput>,
2386<computeroutput>BZ2_bzread</computeroutput>,
2387<computeroutput>BZ2_bzwrite</computeroutput>,
2388<computeroutput>BZ2_bzflush</computeroutput>,
2389<computeroutput>BZ2_bzclose</computeroutput>,
2390<computeroutput>BZ2_bzerror</computeroutput> and
2391<computeroutput>BZ2_bzlibVersion</computeroutput>. These
2392functions are not (yet) officially part of the library. If they
2393break, you get to keep all the pieces. Nevertheless, I think
2394they work ok.</para>
2395
2396<programlisting>
2397typedef void BZFILE;
2398
2399const char * BZ2_bzlibVersion ( void );
2400</programlisting>
2401
2402<para>Returns a string indicating the library version.</para>
2403
2404<programlisting>
2405BZFILE * BZ2_bzopen ( const char *path, const char *mode );
2406BZFILE * BZ2_bzdopen ( int fd, const char *mode );
2407</programlisting>
2408
2409<para>Opens a <computeroutput>.bz2</computeroutput> file for
2410reading or writing, using either its name or a pre-existing file
2411descriptor. Analogous to <computeroutput>fopen</computeroutput>
2412and <computeroutput>fdopen</computeroutput>.</para>
2413
2414<programlisting>
2415int BZ2_bzread ( BZFILE* b, void* buf, int len );
2416int BZ2_bzwrite ( BZFILE* b, void* buf, int len );
2417</programlisting>
2418
2419<para>Reads/writes data from/to a previously opened
2420<computeroutput>BZFILE</computeroutput>. Analogous to
2421<computeroutput>fread</computeroutput> and
2422<computeroutput>fwrite</computeroutput>.</para>
2423
2424<programlisting>
2425int BZ2_bzflush ( BZFILE* b );
2426void BZ2_bzclose ( BZFILE* b );
2427</programlisting>
2428
2429<para>Flushes/closes a <computeroutput>BZFILE</computeroutput>.
2430<computeroutput>BZ2_bzflush</computeroutput> doesn't actually do
2431anything. Analogous to <computeroutput>fflush</computeroutput>
2432and <computeroutput>fclose</computeroutput>.</para>
2433
2434<programlisting>
2435const char * BZ2_bzerror ( BZFILE *b, int *errnum )
2436</programlisting>
2437
2438<para>Returns a string describing the more recent error status of
2439<computeroutput>b</computeroutput>, and also sets
2440<computeroutput>*errnum</computeroutput> to its numerical
2441value.</para>
2442
2443</sect1>
2444
2445
2446<sect1 id="stdio-free"
2447 xreflabel="Using the library in a stdio-free environment">
2448<title>Using the library in a <computeroutput>stdio</computeroutput>-free environment</title>
2449
2450
2451<sect2 id="stdio-bye" xreflabel="Getting rid of stdio">
2452<title>Getting rid of <computeroutput>stdio</computeroutput></title>
2453
2454<para>In a deeply embedded application, you might want to use
2455just the memory-to-memory functions. You can do this
2456conveniently by compiling the library with preprocessor symbol
2457<computeroutput>BZ_NO_STDIO</computeroutput> defined. Doing this
2458gives you a library containing only the following eight
2459functions:</para>
2460
2461<para><computeroutput>BZ2_bzCompressInit</computeroutput>,
2462<computeroutput>BZ2_bzCompress</computeroutput>,
2463<computeroutput>BZ2_bzCompressEnd</computeroutput>
2464<computeroutput>BZ2_bzDecompressInit</computeroutput>,
2465<computeroutput>BZ2_bzDecompress</computeroutput>,
2466<computeroutput>BZ2_bzDecompressEnd</computeroutput>
2467<computeroutput>BZ2_bzBuffToBuffCompress</computeroutput>,
2468<computeroutput>BZ2_bzBuffToBuffDecompress</computeroutput></para>
2469
2470<para>When compiled like this, all functions will ignore
2471<computeroutput>verbosity</computeroutput> settings.</para>
2472
2473</sect2>
2474
2475
2476<sect2 id="critical-error" xreflabel="Critical error handling">
2477<title>Critical error handling</title>
2478
2479<para><computeroutput>libbzip2</computeroutput> contains a number
2480of internal assertion checks which should, needless to say, never
2481be activated. Nevertheless, if an assertion should fail,
2482behaviour depends on whether or not the library was compiled with
2483<computeroutput>BZ_NO_STDIO</computeroutput> set.</para>
2484
2485<para>For a normal compile, an assertion failure yields the
2486message:</para>
2487
2488<blockquote>
2489<para>bzip2/libbzip2: internal error number N.</para>
2490<para>This is a bug in bzip2/libbzip2, &bz-version; of &bz-date;.
2491Please report it to me at: &bz-email;. If this happened
2492when you were using some program which uses libbzip2 as a
2493component, you should also report this bug to the author(s)
2494of that program. Please make an effort to report this bug;
2495timely and accurate bug reports eventually lead to higher
2496quality software. Thanks. Julian Seward, &bz-date;.
2497</para></blockquote>
2498
2499<para>where <computeroutput>N</computeroutput> is some error code
2500number. If <computeroutput>N == 1007</computeroutput>, it also
2501prints some extra text advising the reader that unreliable memory
2502is often associated with internal error 1007. (This is a
2503frequently-observed-phenomenon with versions 1.0.0/1.0.1).</para>
2504
2505<para><computeroutput>exit(3)</computeroutput> is then
2506called.</para>
2507
2508<para>For a <computeroutput>stdio</computeroutput>-free library,
2509assertion failures result in a call to a function declared
2510as:</para>
2511
2512<programlisting>
2513extern void bz_internal_error ( int errcode );
2514</programlisting>
2515
2516<para>The relevant code is passed as a parameter. You should
2517supply such a function.</para>
2518
2519<para>In either case, once an assertion failure has occurred, any
2520<computeroutput>bz_stream</computeroutput> records involved can
2521be regarded as invalid. You should not attempt to resume normal
2522operation with them.</para>
2523
2524<para>You may, of course, change critical error handling to suit
2525your needs. As I said above, critical errors indicate bugs in
2526the library and should not occur. All "normal" error situations
2527are indicated via error return codes from functions, and can be
2528recovered from.</para>
2529
2530</sect2>
2531
2532</sect1>
2533
2534
2535<sect1 id="win-dll" xreflabel="Making a Windows DLL">
2536<title>Making a Windows DLL</title>
2537
2538<para>Everything related to Windows has been contributed by
2539Yoshioka Tsuneo
2540(<computeroutput>QWF00133@niftyserve.or.jp</computeroutput> /
2541<computeroutput>tsuneo-y@is.aist-nara.ac.jp</computeroutput>), so
2542you should send your queries to him (but perhaps Cc: me,
2543<computeroutput>&bz-email;</computeroutput>).</para>
2544
2545<para>My vague understanding of what to do is: using Visual C++
25465.0, open the project file
2547<computeroutput>libbz2.dsp</computeroutput>, and build. That's
2548all.</para>
2549
2550<para>If you can't open the project file for some reason, make a
2551new one, naming these files:
2552<computeroutput>blocksort.c</computeroutput>,
2553<computeroutput>bzlib.c</computeroutput>,
2554<computeroutput>compress.c</computeroutput>,
2555<computeroutput>crctable.c</computeroutput>,
2556<computeroutput>decompress.c</computeroutput>,
2557<computeroutput>huffman.c</computeroutput>,
2558<computeroutput>randtable.c</computeroutput> and
2559<computeroutput>libbz2.def</computeroutput>. You will also need
2560to name the header files <computeroutput>bzlib.h</computeroutput>
2561and <computeroutput>bzlib_private.h</computeroutput>.</para>
2562
2563<para>If you don't use VC++, you may need to define the
2564proprocessor symbol
2565<computeroutput>_WIN32</computeroutput>.</para>
2566
2567<para>Finally, <computeroutput>dlltest.c</computeroutput> is a
2568sample program using the DLL. It has a project file,
2569<computeroutput>dlltest.dsp</computeroutput>.</para>
2570
2571<para>If you just want a makefile for Visual C, have a look at
2572<computeroutput>makefile.msc</computeroutput>.</para>
2573
2574<para>Be aware that if you compile
2575<computeroutput>bzip2</computeroutput> itself on Win32, you must
2576set <computeroutput>BZ_UNIX</computeroutput> to 0 and
2577<computeroutput>BZ_LCCWIN32</computeroutput> to 1, in the file
2578<computeroutput>bzip2.c</computeroutput>, before compiling.
2579Otherwise the resulting binary won't work correctly.</para>
2580
2581<para>I haven't tried any of this stuff myself, but it all looks
2582plausible.</para>
2583
2584</sect1>
2585
2586</chapter>
2587
2588
2589
2590<chapter id="misc" xreflabel="Miscellanea">
2591<title>Miscellanea</title>
2592
2593<para>These are just some random thoughts of mine. Your mileage
2594may vary.</para>
2595
2596
2597<sect1 id="limits" xreflabel="Limitations of the compressed file format">
2598<title>Limitations of the compressed file format</title>
2599
2600<para><computeroutput>bzip2-1.0.X</computeroutput>,
2601<computeroutput>0.9.5</computeroutput> and
2602<computeroutput>0.9.0</computeroutput> use exactly the same file
2603format as the original version,
2604<computeroutput>bzip2-0.1</computeroutput>. This decision was
2605made in the interests of stability. Creating yet another
2606incompatible compressed file format would create further
2607confusion and disruption for users.</para>
2608
2609<para>Nevertheless, this is not a painless decision. Development
2610work since the release of
2611<computeroutput>bzip2-0.1</computeroutput> in August 1997 has
2612shown complexities in the file format which slow down
2613decompression and, in retrospect, are unnecessary. These
2614are:</para>
2615
2616<itemizedlist mark='bullet'>
2617
2618 <listitem><para>The run-length encoder, which is the first of the
2619 compression transformations, is entirely irrelevant. The
2620 original purpose was to protect the sorting algorithm from the
2621 very worst case input: a string of repeated symbols. But
2622 algorithm steps Q6a and Q6b in the original Burrows-Wheeler
2623 technical report (SRC-124) show how repeats can be handled
2624 without difficulty in block sorting.</para></listitem>
2625
2626 <listitem><para>The randomisation mechanism doesn't really need to be
2627 there. Udi Manber and Gene Myers published a suffix array
2628 construction algorithm a few years back, which can be employed
2629 to sort any block, no matter how repetitive, in O(N log N)
2630 time. Subsequent work by Kunihiko Sadakane has produced a
2631 derivative O(N (log N)^2) algorithm which usually outperforms
2632 the Manber-Myers algorithm.</para>
2633
2634 <para>I could have changed to Sadakane's algorithm, but I find
2635 it to be slower than <computeroutput>bzip2</computeroutput>'s
2636 existing algorithm for most inputs, and the randomisation
2637 mechanism protects adequately against bad cases. I didn't
2638 think it was a good tradeoff to make. Partly this is due to
2639 the fact that I was not flooded with email complaints about
2640 <computeroutput>bzip2-0.1</computeroutput>'s performance on
2641 repetitive data, so perhaps it isn't a problem for real
2642 inputs.</para>
2643
2644 <para>Probably the best long-term solution, and the one I have
2645 incorporated into 0.9.5 and above, is to use the existing
2646 sorting algorithm initially, and fall back to a O(N (log N)^2)
2647 algorithm if the standard algorithm gets into
2648 difficulties.</para></listitem>
2649
2650 <listitem><para>The compressed file format was never designed to be
2651 handled by a library, and I have had to jump though some hoops
2652 to produce an efficient implementation of decompression. It's
2653 a bit hairy. Try passing
2654 <computeroutput>decompress.c</computeroutput> through the C
2655 preprocessor and you'll see what I mean. Much of this
2656 complexity could have been avoided if the compressed size of
2657 each block of data was recorded in the data stream.</para></listitem>
2658
2659 <listitem><para>An Adler-32 checksum, rather than a CRC32 checksum,
2660 would be faster to compute.</para></listitem>
2661
2662</itemizedlist>
2663
2664<para>It would be fair to say that the
2665<computeroutput>bzip2</computeroutput> format was frozen before I
2666properly and fully understood the performance consequences of
2667doing so.</para>
2668
2669<para>Improvements which I was able to incorporate into 0.9.0,
2670despite using the same file format, are:</para>
2671
2672<itemizedlist mark='bullet'>
2673
2674 <listitem><para>Single array implementation of the inverse BWT. This
2675 significantly speeds up decompression, presumably because it
2676 reduces the number of cache misses.</para></listitem>
2677
2678 <listitem><para>Faster inverse MTF transform for large MTF values.
2679 The new implementation is based on the notion of sliding blocks
2680 of values.</para></listitem>
2681
2682 <listitem><para><computeroutput>bzip2-0.9.0</computeroutput> now reads
2683 and writes files with <computeroutput>fread</computeroutput>
2684 and <computeroutput>fwrite</computeroutput>; version 0.1 used
2685 <computeroutput>putc</computeroutput> and
2686 <computeroutput>getc</computeroutput>. Duh! Well, you live
2687 and learn.</para></listitem>
2688
2689</itemizedlist>
2690
2691<para>Further ahead, it would be nice to be able to do random
2692access into files. This will require some careful design of
2693compressed file formats.</para>
2694
2695</sect1>
2696
2697
2698<sect1 id="port-issues" xreflabel="Portability issues">
2699<title>Portability issues</title>
2700
2701<para>After some consideration, I have decided not to use GNU
2702<computeroutput>autoconf</computeroutput> to configure 0.9.5 or
27031.0.</para>
2704
2705<para><computeroutput>autoconf</computeroutput>, admirable and
2706wonderful though it is, mainly assists with portability problems
2707between Unix-like platforms. But
2708<computeroutput>bzip2</computeroutput> doesn't have much in the
2709way of portability problems on Unix; most of the difficulties
2710appear when porting to the Mac, or to Microsoft's operating
2711systems. <computeroutput>autoconf</computeroutput> doesn't help
2712in those cases, and brings in a whole load of new
2713complexity.</para>
2714
2715<para>Most people should be able to compile the library and
2716program under Unix straight out-of-the-box, so to speak,
2717especially if you have a version of GNU C available.</para>
2718
2719<para>There are a couple of
2720<computeroutput>__inline__</computeroutput> directives in the
2721code. GNU C (<computeroutput>gcc</computeroutput>) should be
2722able to handle them. If you're not using GNU C, your C compiler
2723shouldn't see them at all. If your compiler does, for some
2724reason, see them and doesn't like them, just
2725<computeroutput>#define</computeroutput>
2726<computeroutput>__inline__</computeroutput> to be
2727<computeroutput>/* */</computeroutput>. One easy way to do this
2728is to compile with the flag
2729<computeroutput>-D__inline__=</computeroutput>, which should be
2730understood by most Unix compilers.</para>
2731
2732<para>If you still have difficulties, try compiling with the
2733macro <computeroutput>BZ_STRICT_ANSI</computeroutput> defined.
2734This should enable you to build the library in a strictly ANSI
2735compliant environment. Building the program itself like this is
2736dangerous and not supported, since you remove
2737<computeroutput>bzip2</computeroutput>'s checks against
2738compressing directories, symbolic links, devices, and other
2739not-really-a-file entities. This could cause filesystem
2740corruption!</para>
2741
2742<para>One other thing: if you create a
2743<computeroutput>bzip2</computeroutput> binary for public distribution,
2744please consider linking it statically (<computeroutput>gcc
2745-static</computeroutput>). This avoids all sorts of library-version
2746issues that others may encounter later on.</para>
2747
2748<para>If you build <computeroutput>bzip2</computeroutput> on
2749Win32, you must set <computeroutput>BZ_UNIX</computeroutput> to 0
2750and <computeroutput>BZ_LCCWIN32</computeroutput> to 1, in the
2751file <computeroutput>bzip2.c</computeroutput>, before compiling.
2752Otherwise the resulting binary won't work correctly.</para>
2753
2754</sect1>
2755
2756
2757<sect1 id="bugs" xreflabel="Reporting bugs">
2758<title>Reporting bugs</title>
2759
2760<para>I tried pretty hard to make sure
2761<computeroutput>bzip2</computeroutput> is bug free, both by
2762design and by testing. Hopefully you'll never need to read this
2763section for real.</para>
2764
2765<para>Nevertheless, if <computeroutput>bzip2</computeroutput> dies
2766with a segmentation fault, a bus error or an internal assertion
2767failure, it will ask you to email me a bug report. Experience from
2768years of feedback of bzip2 users indicates that almost all these
2769problems can be traced to either compiler bugs or hardware
2770problems.</para>
2771
2772<itemizedlist mark='bullet'>
2773
2774 <listitem><para>Recompile the program with no optimisation, and
2775 see if it works. And/or try a different compiler. I heard all
2776 sorts of stories about various flavours of GNU C (and other
2777 compilers) generating bad code for
2778 <computeroutput>bzip2</computeroutput>, and I've run across two
2779 such examples myself.</para>
2780
2781 <para>2.7.X versions of GNU C are known to generate bad code
2782 from time to time, at high optimisation levels. If you get
2783 problems, try using the flags
2784 <computeroutput>-O2</computeroutput>
2785 <computeroutput>-fomit-frame-pointer</computeroutput>
2786 <computeroutput>-fno-strength-reduce</computeroutput>. You
2787 should specifically <emphasis>not</emphasis> use
2788 <computeroutput>-funroll-loops</computeroutput>.</para>
2789
2790 <para>You may notice that the Makefile runs six tests as part
2791 of the build process. If the program passes all of these, it's
2792 a pretty good (but not 100%) indication that the compiler has
2793 done its job correctly.</para></listitem>
2794
2795 <listitem><para>If <computeroutput>bzip2</computeroutput>
2796 crashes randomly, and the crashes are not repeatable, you may
2797 have a flaky memory subsystem.
2798 <computeroutput>bzip2</computeroutput> really hammers your
2799 memory hierarchy, and if it's a bit marginal, you may get these
2800 problems. Ditto if your disk or I/O subsystem is slowly
2801 failing. Yup, this really does happen.</para>
2802
2803 <para>Try using a different machine of the same type, and see
2804 if you can repeat the problem.</para></listitem>
2805
2806 <listitem><para>This isn't really a bug, but ... If
2807 <computeroutput>bzip2</computeroutput> tells you your file is
2808 corrupted on decompression, and you obtained the file via FTP,
2809 there is a possibility that you forgot to tell FTP to do a
2810 binary mode transfer. That absolutely will cause the file to
2811 be non-decompressible. You'll have to transfer it
2812 again.</para></listitem>
2813
2814</itemizedlist>
2815
2816<para>If you've incorporated
2817<computeroutput>libbzip2</computeroutput> into your own program
2818and are getting problems, please, please, please, check that the
2819parameters you are passing in calls to the library, are correct,
2820and in accordance with what the documentation says is allowable.
2821I have tried to make the library robust against such problems,
2822but I'm sure I haven't succeeded.</para>
2823
2824<para>Finally, if the above comments don't help, you'll have to
2825send me a bug report. Now, it's just amazing how many people
2826will send me a bug report saying something like:</para>
2827
2828<programlisting>
2829bzip2 crashed with segmentation fault on my machine
2830</programlisting>
2831
2832<para>and absolutely nothing else. Needless to say, a such a
2833report is <emphasis>totally, utterly, completely and
2834comprehensively 100% useless; a waste of your time, my time, and
2835net bandwidth</emphasis>. With no details at all, there's no way
2836I can possibly begin to figure out what the problem is.</para>
2837
2838<para>The rules of the game are: facts, facts, facts. Don't omit
2839them because "oh, they won't be relevant". At the bare
2840minimum:</para>
2841
2842<programlisting>
2843Machine type. Operating system version.
2844Exact version of bzip2 (do bzip2 -V).
2845Exact version of the compiler used.
2846Flags passed to the compiler.
2847</programlisting>
2848
2849<para>However, the most important single thing that will help me
2850is the file that you were trying to compress or decompress at the
2851time the problem happened. Without that, my ability to do
2852anything more than speculate about the cause, is limited.</para>
2853
2854</sect1>
2855
2856
2857<sect1 id="package" xreflabel="Did you get the right package?">
2858<title>Did you get the right package?</title>
2859
2860<para><computeroutput>bzip2</computeroutput> is a resource hog.
2861It soaks up large amounts of CPU cycles and memory. Also, it
2862gives very large latencies. In the worst case, you can feed many
2863megabytes of uncompressed data into the library before getting
2864any compressed output, so this probably rules out applications
2865requiring interactive behaviour.</para>
2866
2867<para>These aren't faults of my implementation, I hope, but more
2868an intrinsic property of the Burrows-Wheeler transform
2869(unfortunately). Maybe this isn't what you want.</para>
2870
2871<para>If you want a compressor and/or library which is faster,
2872uses less memory but gets pretty good compression, and has
2873minimal latency, consider Jean-loup Gailly's and Mark Adler's
2874work, <computeroutput>zlib-1.2.1</computeroutput> and
2875<computeroutput>gzip-1.2.4</computeroutput>. Look for them at
2876<ulink url="http://www.zlib.org">http://www.zlib.org</ulink> and
2877<ulink url="http://www.gzip.org">http://www.gzip.org</ulink>
2878respectively.</para>
2879
2880<para>For something faster and lighter still, you might try Markus F
2881X J Oberhumer's <computeroutput>LZO</computeroutput> real-time
2882compression/decompression library, at
2883<ulink url="http://www.oberhumer.com/opensource">http://www.oberhumer.com/opensource</ulink>.</para>
2884
2885</sect1>
2886
2887
2888
2889<sect1 id="reading" xreflabel="Further Reading">
2890<title>Further Reading</title>
2891
2892<para><computeroutput>bzip2</computeroutput> is not research
2893work, in the sense that it doesn't present any new ideas.
2894Rather, it's an engineering exercise based on existing
2895ideas.</para>
2896
2897<para>Four documents describe essentially all the ideas behind
2898<computeroutput>bzip2</computeroutput>:</para>
2899
2900<literallayout>Michael Burrows and D. J. Wheeler:
2901 "A block-sorting lossless data compression algorithm"
2902 10th May 1994.
2903 Digital SRC Research Report 124.
2904 ftp://ftp.digital.com/pub/DEC/SRC/research-reports/SRC-124.ps.gz
2905 If you have trouble finding it, try searching at the
2906 New Zealand Digital Library, http://www.nzdl.org.
2907
2908Daniel S. Hirschberg and Debra A. LeLewer
2909 "Efficient Decoding of Prefix Codes"
2910 Communications of the ACM, April 1990, Vol 33, Number 4.
2911 You might be able to get an electronic copy of this
2912 from the ACM Digital Library.
2913
2914David J. Wheeler
2915 Program bred3.c and accompanying document bred3.ps.
2916 This contains the idea behind the multi-table Huffman coding scheme.
2917 ftp://ftp.cl.cam.ac.uk/users/djw3/
2918
2919Jon L. Bentley and Robert Sedgewick
2920 "Fast Algorithms for Sorting and Searching Strings"
2921 Available from Sedgewick's web page,
2922 www.cs.princeton.edu/~rs
2923</literallayout>
2924
2925<para>The following paper gives valuable additional insights into
2926the algorithm, but is not immediately the basis of any code used
2927in bzip2.</para>
2928
2929<literallayout>Peter Fenwick:
2930 Block Sorting Text Compression
2931 Proceedings of the 19th Australasian Computer Science Conference,
2932 Melbourne, Australia. Jan 31 - Feb 2, 1996.
2933 ftp://ftp.cs.auckland.ac.nz/pub/peter-f/ACSC96paper.ps</literallayout>
2934
2935<para>Kunihiko Sadakane's sorting algorithm, mentioned above, is
2936available from:</para>
2937
2938<literallayout>http://naomi.is.s.u-tokyo.ac.jp/~sada/papers/Sada98b.ps.gz
2939</literallayout>
2940
2941<para>The Manber-Myers suffix array construction algorithm is
2942described in a paper available from:</para>
2943
2944<literallayout>http://www.cs.arizona.edu/people/gene/PAPERS/suffix.ps
2945</literallayout>
2946
2947<para>Finally, the following papers document some
2948investigations I made into the performance of sorting
2949and decompression algorithms:</para>
2950
2951<literallayout>Julian Seward
2952 On the Performance of BWT Sorting Algorithms
2953 Proceedings of the IEEE Data Compression Conference 2000
2954 Snowbird, Utah. 28-30 March 2000.
2955
2956Julian Seward
2957 Space-time Tradeoffs in the Inverse B-W Transform
2958 Proceedings of the IEEE Data Compression Conference 2001
2959 Snowbird, Utah. 27-29 March 2001.
2960</literallayout>
2961
2962</sect1>
2963
2964</chapter>
2965
2966</book>
diff --git a/randtable.c b/randtable.c
index 5c922e9..940462d 100644
--- a/randtable.c
+++ b/randtable.c
@@ -8,7 +8,7 @@
8 This file is a part of bzip2 and/or libbzip2, a program and 8 This file is a part of bzip2 and/or libbzip2, a program and
9 library for lossless, block-sorting data compression. 9 library for lossless, block-sorting data compression.
10 10
11 Copyright (C) 1996-2002 Julian R Seward. All rights reserved. 11 Copyright (C) 1996-2005 Julian R Seward. All rights reserved.
12 12
13 Redistribution and use in source and binary forms, with or without 13 Redistribution and use in source and binary forms, with or without
14 modification, are permitted provided that the following conditions 14 modification, are permitted provided that the following conditions
@@ -42,7 +42,7 @@
42 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 42 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
43 43
44 Julian Seward, Cambridge, UK. 44 Julian Seward, Cambridge, UK.
45 jseward@acm.org 45 jseward@bzip.org
46 bzip2/libbzip2 version 1.0 of 21 March 2000 46 bzip2/libbzip2 version 1.0 of 21 March 2000
47 47
48 This program is based on (at least) the work of: 48 This program is based on (at least) the work of:
diff --git a/xmlproc.sh b/xmlproc.sh
new file mode 100755
index 0000000..6fe4d57
--- /dev/null
+++ b/xmlproc.sh
@@ -0,0 +1,99 @@
1#!/bin/bash
2# see the README in this directory for usage etc.
3
4usage() {
5 echo '';
6 echo 'Usage: xmlproc.sh -[option] <filename.xml>';
7 echo 'Specify a target from:';
8 echo '-v verify xml file conforms to dtd';
9 echo '-html output in html format (single file)';
10 echo '-ps output in postscript format';
11 echo '-pdf output in pdf format';
12 exit;
13}
14
15if test $# -ne 2; then
16 usage
17fi
18# assign the variable for the output type
19action=$1; shift
20# assign the output filename
21xmlfile=$1; shift
22# and check user input it correct
23if !(test -f $xmlfile); then
24 echo "No such file: $xmlfile";
25 exit;
26fi
27# some other stuff we will use
28OUT=output
29xsl_fo=bz-fo.xsl
30xsl_html=bz-html.xsl
31
32basename=$xmlfile
33basename=${basename//'.xml'/''}
34
35fofile="${basename}.fo"
36htmlfile="${basename}.html"
37pdffile="${basename}.pdf"
38psfile="${basename}.ps"
39xmlfmtfile="${basename}.fmt"
40
41# first process the xmlfile with CDATA tags
42./format.pl $xmlfile $xmlfmtfile
43# so the shell knows where the catalogs live
44export XML_CATALOG_FILES=/etc/xml/catalog
45
46# post-processing tidy up
47cleanup() {
48 echo "Cleaning up: # $@"
49 while [ $# != 0 ]
50 do
51 arg=$1; shift;
52 echo " deleting $arg";
53 rm $arg
54 done
55}
56
57case $action in
58 -v)
59 flags='--noout --xinclude --noblanks --postvalid'
60 dtd='--dtdvalid http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd'
61 xmllint $flags $dtd $xmlfmtfile 2> $OUT
62 egrep 'error' $OUT
63 rm $OUT
64 ;;
65
66 -html)
67 echo "Creating $htmlfile ..."
68 xsltproc --nonet --xinclude -o $htmlfile $xsl_html $xmlfmtfile
69 cleanup $xmlfmtfile
70 ;;
71
72 -pdf)
73 echo "Creating $pdffile ..."
74 xsltproc --nonet --xinclude -o $fofile $xsl_fo $xmlfmtfile
75 pdfxmltex $fofile >$OUT </dev/null
76 pdfxmltex $fofile >$OUT </dev/null
77 pdfxmltex $fofile >$OUT </dev/null
78 cleanup $OUT $xmlfmtfile *.aux *.fo *.log *.out
79 ;;
80
81 -ps)
82 echo "Creating $psfile ..."
83 xsltproc --nonet --xinclude -o $fofile $xsl_fo $xmlfmtfile
84 pdfxmltex $fofile >$OUT </dev/null
85 pdfxmltex $fofile >$OUT </dev/null
86 pdfxmltex $fofile >$OUT </dev/null
87 pdftops $pdffile $psfile
88 cleanup $OUT $xmlfmtfile $pdffile *.aux *.fo *.log *.out
89# passivetex is broken, so we can't go this route yet.
90# xmltex $fofile >$OUT </dev/null
91# xmltex $fofile >$OUT </dev/null
92# xmltex $fofile >$OUT </dev/null
93# dvips -R -q -o bzip-manual.ps *.dvi
94 ;;
95
96 *)
97 usage
98 ;;
99esac