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diff --git a/manual.html b/manual.html deleted file mode 100644 index f59427f..0000000 --- a/manual.html +++ /dev/null @@ -1,2540 +0,0 @@ -<html> -<head> -<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> -<title>bzip2 and libbzip2, version 1.0.6</title> -<meta name="generator" content="DocBook XSL Stylesheets V1.75.2"> -<style type="text/css" media="screen">/* Colours: -#74240f dark brown h1, h2, h3, h4 -#336699 medium blue links -#339999 turquoise link hover colour -#202020 almost black general text -#761596 purple md5sum text -#626262 dark gray pre border -#eeeeee very light gray pre background -#f2f2f9 very light blue nav table background -#3366cc medium blue nav table border -*/ - -a, a:link, a:visited, a:active { color: #336699; } -a:hover { color: #339999; } - -body { font: 80%/126% sans-serif; } -h1, h2, h3, h4 { color: #74240f; } - -dt { color: #336699; font-weight: bold } -dd { - margin-left: 1.5em; - padding-bottom: 0.8em; -} - -/* -- ruler -- */ -div.hr_blue { - height: 3px; - background:#ffffff url("/images/hr_blue.png") repeat-x; } -div.hr_blue hr { display:none; } - -/* release styles */ -#release p { margin-top: 0.4em; } -#release .md5sum { color: #761596; } - - -/* ------ styles for docs|manuals|howto ------ */ -/* -- lists -- */ -ul { - margin: 0px 4px 16px 16px; - padding: 0px; - list-style: url("/images/li-blue.png"); -} -ul li { - margin-bottom: 10px; -} -ul ul { - list-style-type: none; - list-style-image: none; - margin-left: 0px; -} - -/* header / footer nav tables */ -table.nav { - border: solid 1px #3366cc; - background: #f2f2f9; - background-color: #f2f2f9; - margin-bottom: 0.5em; -} -/* don't have underlined links in chunked nav menus */ -table.nav a { text-decoration: none; } -table.nav a:hover { text-decoration: underline; } -table.nav td { font-size: 85%; } - -code, tt, pre { font-size: 120%; } -code, tt { color: #761596; } - -div.literallayout, pre.programlisting, pre.screen { - color: #000000; - padding: 0.5em; - background: #eeeeee; - border: 1px solid #626262; - background-color: #eeeeee; - margin: 4px 0px 4px 0px; -} -</style> -</head> -<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div lang="en" class="book" title="bzip2 and libbzip2, version 1.0.6"> -<div class="titlepage"> -<div> -<div><h1 class="title"> -<a name="userman"></a>bzip2 and libbzip2, version 1.0.6</h1></div> -<div><h2 class="subtitle">A program and library for data compression</h2></div> -<div><div class="authorgroup"><div class="author"> -<h3 class="author"> -<span class="firstname">Julian</span> <span class="surname">Seward</span> -</h3> -<div class="affiliation"><span class="orgname">http://www.bzip.org<br></span></div> -</div></div></div> -<div><p class="releaseinfo">Version 1.0.6 of 6 September 2010</p></div> -<div><p class="copyright">Copyright © 1996-2010 Julian Seward</p></div> -<div><div class="legalnotice" title="Legal Notice"> -<a name="id537185"></a><p>This program, <code class="computeroutput">bzip2</code>, the - associated library <code class="computeroutput">libbzip2</code>, and - all documentation, are copyright © 1996-2010 Julian Seward. - All rights reserved.</p> -<p>Redistribution and use in source and binary forms, with - or without modification, are permitted provided that the - following conditions are met:</p> -<div class="itemizedlist"><ul class="itemizedlist" type="bullet"> -<li class="listitem" style="list-style-type: disc"><p>Redistributions of source code must retain the - above copyright notice, this list of conditions and the - following disclaimer.</p></li> -<li class="listitem" style="list-style-type: disc"><p>The origin of this software must not be - misrepresented; you must not claim that you wrote the original - software. If you use this software in a product, an - acknowledgment in the product documentation would be - appreciated but is not required.</p></li> -<li class="listitem" style="list-style-type: disc"><p>Altered source versions must be plainly marked - as such, and must not be misrepresented as being the original - software.</p></li> -<li class="listitem" style="list-style-type: disc"><p>The name of the author may not be used to - endorse or promote products derived from this software without - specific prior written permission.</p></li> -</ul></div> -<p>THIS SOFTWARE IS PROVIDED BY THE AUTHOR "AS IS" AND ANY - EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, - THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A - PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE - AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, - EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED - TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, - DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND - ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT - LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING - IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF - THE POSSIBILITY OF SUCH DAMAGE.</p> -<p>PATENTS: To the best of my knowledge, - <code class="computeroutput">bzip2</code> and - <code class="computeroutput">libbzip2</code> do not use any patented - algorithms. However, I do not have the resources to carry - out a patent search. Therefore I cannot give any guarantee of - the above statement. - </p> -</div></div> -</div> -<hr> -</div> -<div class="toc"> -<p><b>Table of Contents</b></p> -<dl> -<dt><span class="chapter"><a href="#intro">1. Introduction</a></span></dt> -<dt><span class="chapter"><a href="#using">2. How to use bzip2</a></span></dt> -<dd><dl> -<dt><span class="sect1"><a href="#name">2.1. NAME</a></span></dt> -<dt><span class="sect1"><a href="#synopsis">2.2. SYNOPSIS</a></span></dt> -<dt><span class="sect1"><a href="#description">2.3. DESCRIPTION</a></span></dt> -<dt><span class="sect1"><a href="#options">2.4. OPTIONS</a></span></dt> -<dt><span class="sect1"><a href="#memory-management">2.5. MEMORY MANAGEMENT</a></span></dt> -<dt><span class="sect1"><a href="#recovering">2.6. RECOVERING DATA FROM DAMAGED FILES</a></span></dt> -<dt><span class="sect1"><a href="#performance">2.7. PERFORMANCE NOTES</a></span></dt> -<dt><span class="sect1"><a href="#caveats">2.8. CAVEATS</a></span></dt> -<dt><span class="sect1"><a href="#author">2.9. AUTHOR</a></span></dt> -</dl></dd> -<dt><span class="chapter"><a href="#libprog">3. -Programming with <code class="computeroutput">libbzip2</code> -</a></span></dt> -<dd><dl> -<dt><span class="sect1"><a href="#top-level">3.1. Top-level structure</a></span></dt> -<dd><dl> -<dt><span class="sect2"><a href="#ll-summary">3.1.1. Low-level summary</a></span></dt> -<dt><span class="sect2"><a href="#hl-summary">3.1.2. High-level summary</a></span></dt> -<dt><span class="sect2"><a href="#util-fns-summary">3.1.3. Utility functions summary</a></span></dt> -</dl></dd> -<dt><span class="sect1"><a href="#err-handling">3.2. Error handling</a></span></dt> -<dt><span class="sect1"><a href="#low-level">3.3. Low-level interface</a></span></dt> -<dd><dl> -<dt><span class="sect2"><a href="#bzcompress-init">3.3.1. BZ2_bzCompressInit</a></span></dt> -<dt><span class="sect2"><a href="#bzCompress">3.3.2. BZ2_bzCompress</a></span></dt> -<dt><span class="sect2"><a href="#bzCompress-end">3.3.3. BZ2_bzCompressEnd</a></span></dt> -<dt><span class="sect2"><a href="#bzDecompress-init">3.3.4. BZ2_bzDecompressInit</a></span></dt> -<dt><span class="sect2"><a href="#bzDecompress">3.3.5. BZ2_bzDecompress</a></span></dt> -<dt><span class="sect2"><a href="#bzDecompress-end">3.3.6. BZ2_bzDecompressEnd</a></span></dt> -</dl></dd> -<dt><span class="sect1"><a href="#hl-interface">3.4. High-level interface</a></span></dt> -<dd><dl> -<dt><span class="sect2"><a href="#bzreadopen">3.4.1. BZ2_bzReadOpen</a></span></dt> -<dt><span class="sect2"><a href="#bzread">3.4.2. BZ2_bzRead</a></span></dt> -<dt><span class="sect2"><a href="#bzreadgetunused">3.4.3. BZ2_bzReadGetUnused</a></span></dt> -<dt><span class="sect2"><a href="#bzreadclose">3.4.4. BZ2_bzReadClose</a></span></dt> -<dt><span class="sect2"><a href="#bzwriteopen">3.4.5. BZ2_bzWriteOpen</a></span></dt> -<dt><span class="sect2"><a href="#bzwrite">3.4.6. BZ2_bzWrite</a></span></dt> -<dt><span class="sect2"><a href="#bzwriteclose">3.4.7. BZ2_bzWriteClose</a></span></dt> -<dt><span class="sect2"><a href="#embed">3.4.8. Handling embedded compressed data streams</a></span></dt> -<dt><span class="sect2"><a href="#std-rdwr">3.4.9. Standard file-reading/writing code</a></span></dt> -</dl></dd> -<dt><span class="sect1"><a href="#util-fns">3.5. Utility functions</a></span></dt> -<dd><dl> -<dt><span class="sect2"><a href="#bzbufftobuffcompress">3.5.1. BZ2_bzBuffToBuffCompress</a></span></dt> -<dt><span class="sect2"><a href="#bzbufftobuffdecompress">3.5.2. BZ2_bzBuffToBuffDecompress</a></span></dt> -</dl></dd> -<dt><span class="sect1"><a href="#zlib-compat">3.6. zlib compatibility functions</a></span></dt> -<dt><span class="sect1"><a href="#stdio-free">3.7. Using the library in a stdio-free environment</a></span></dt> -<dd><dl> -<dt><span class="sect2"><a href="#stdio-bye">3.7.1. Getting rid of stdio</a></span></dt> -<dt><span class="sect2"><a href="#critical-error">3.7.2. Critical error handling</a></span></dt> -</dl></dd> -<dt><span class="sect1"><a href="#win-dll">3.8. Making a Windows DLL</a></span></dt> -</dl></dd> -<dt><span class="chapter"><a href="#misc">4. Miscellanea</a></span></dt> -<dd><dl> -<dt><span class="sect1"><a href="#limits">4.1. Limitations of the compressed file format</a></span></dt> -<dt><span class="sect1"><a href="#port-issues">4.2. Portability issues</a></span></dt> -<dt><span class="sect1"><a href="#bugs">4.3. Reporting bugs</a></span></dt> -<dt><span class="sect1"><a href="#package">4.4. Did you get the right package?</a></span></dt> -<dt><span class="sect1"><a href="#reading">4.5. Further Reading</a></span></dt> -</dl></dd> -</dl> -</div> -<div class="chapter" title="1. Introduction"> -<div class="titlepage"><div><div><h2 class="title"> -<a name="intro"></a>1. Introduction</h2></div></div></div> -<p><code class="computeroutput">bzip2</code> compresses files -using the Burrows-Wheeler block-sorting text compression -algorithm, and Huffman coding. Compression is generally -considerably better than that achieved by more conventional -LZ77/LZ78-based compressors, and approaches the performance of -the PPM family of statistical compressors.</p> -<p><code class="computeroutput">bzip2</code> is built on top of -<code class="computeroutput">libbzip2</code>, a flexible library for -handling compressed data in the -<code class="computeroutput">bzip2</code> format. This manual -describes both how to use the program and how to work with the -library interface. Most of the manual is devoted to this -library, not the program, which is good news if your interest is -only in the program.</p> -<div class="itemizedlist"><ul class="itemizedlist" type="bullet"> -<li class="listitem" style="list-style-type: disc"><p><a class="xref" href="#using" title="2. How to use bzip2">How to use bzip2</a> describes how to use - <code class="computeroutput">bzip2</code>; this is the only part - you need to read if you just want to know how to operate the - program.</p></li> -<li class="listitem" style="list-style-type: disc"><p><a class="xref" href="#libprog" title="3. Programming with libbzip2">Programming with libbzip2</a> describes the - programming interfaces in detail, and</p></li> -<li class="listitem" style="list-style-type: disc"><p><a class="xref" href="#misc" title="4. Miscellanea">Miscellanea</a> records some - miscellaneous notes which I thought ought to be recorded - somewhere.</p></li> -</ul></div> -</div> -<div class="chapter" title="2. How to use bzip2"> -<div class="titlepage"><div><div><h2 class="title"> -<a name="using"></a>2. How to use bzip2</h2></div></div></div> -<div class="toc"> -<p><b>Table of Contents</b></p> -<dl> -<dt><span class="sect1"><a href="#name">2.1. NAME</a></span></dt> -<dt><span class="sect1"><a href="#synopsis">2.2. SYNOPSIS</a></span></dt> -<dt><span class="sect1"><a href="#description">2.3. DESCRIPTION</a></span></dt> -<dt><span class="sect1"><a href="#options">2.4. OPTIONS</a></span></dt> -<dt><span class="sect1"><a href="#memory-management">2.5. MEMORY MANAGEMENT</a></span></dt> -<dt><span class="sect1"><a href="#recovering">2.6. RECOVERING DATA FROM DAMAGED FILES</a></span></dt> -<dt><span class="sect1"><a href="#performance">2.7. PERFORMANCE NOTES</a></span></dt> -<dt><span class="sect1"><a href="#caveats">2.8. CAVEATS</a></span></dt> -<dt><span class="sect1"><a href="#author">2.9. AUTHOR</a></span></dt> -</dl> -</div> -<p>This chapter contains a copy of the -<code class="computeroutput">bzip2</code> man page, and nothing -else.</p> -<div class="sect1" title="2.1. NAME"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="name"></a>2.1. NAME</h2></div></div></div> -<div class="itemizedlist"><ul class="itemizedlist" type="bullet"> -<li class="listitem" style="list-style-type: disc"><p><code class="computeroutput">bzip2</code>, - <code class="computeroutput">bunzip2</code> - a block-sorting file - compressor, v1.0.6</p></li> -<li class="listitem" style="list-style-type: disc"><p><code class="computeroutput">bzcat</code> - - decompresses files to stdout</p></li> -<li class="listitem" style="list-style-type: disc"><p><code class="computeroutput">bzip2recover</code> - - recovers data from damaged bzip2 files</p></li> -</ul></div> -</div> -<div class="sect1" title="2.2. SYNOPSIS"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="synopsis"></a>2.2. SYNOPSIS</h2></div></div></div> -<div class="itemizedlist"><ul class="itemizedlist" type="bullet"> -<li class="listitem" style="list-style-type: disc"><p><code class="computeroutput">bzip2</code> [ - -cdfkqstvzVL123456789 ] [ filenames ... ]</p></li> -<li class="listitem" style="list-style-type: disc"><p><code class="computeroutput">bunzip2</code> [ - -fkvsVL ] [ filenames ... ]</p></li> -<li class="listitem" style="list-style-type: disc"><p><code class="computeroutput">bzcat</code> [ -s ] [ - filenames ... ]</p></li> -<li class="listitem" style="list-style-type: disc"><p><code class="computeroutput">bzip2recover</code> - filename</p></li> -</ul></div> -</div> -<div class="sect1" title="2.3. DESCRIPTION"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="description"></a>2.3. DESCRIPTION</h2></div></div></div> -<p><code class="computeroutput">bzip2</code> compresses files -using the Burrows-Wheeler block sorting text compression -algorithm, and Huffman coding. Compression is generally -considerably better than that achieved by more conventional -LZ77/LZ78-based compressors, and approaches the performance of -the PPM family of statistical compressors.</p> -<p>The command-line options are deliberately very similar to -those of GNU <code class="computeroutput">gzip</code>, but they are -not identical.</p> -<p><code class="computeroutput">bzip2</code> expects a list of -file names to accompany the command-line flags. Each file is -replaced by a compressed version of itself, with the name -<code class="computeroutput">original_name.bz2</code>. Each -compressed file has the same modification date, permissions, and, -when possible, ownership as the corresponding original, so that -these properties can be correctly restored at decompression time. -File name handling is naive in the sense that there is no -mechanism for preserving original file names, permissions, -ownerships or dates in filesystems which lack these concepts, or -have serious file name length restrictions, such as -MS-DOS.</p> -<p><code class="computeroutput">bzip2</code> and -<code class="computeroutput">bunzip2</code> will by default not -overwrite existing files. If you want this to happen, specify -the <code class="computeroutput">-f</code> flag.</p> -<p>If no file names are specified, -<code class="computeroutput">bzip2</code> compresses from standard -input to standard output. In this case, -<code class="computeroutput">bzip2</code> will decline to write -compressed output to a terminal, as this would be entirely -incomprehensible and therefore pointless.</p> -<p><code class="computeroutput">bunzip2</code> (or -<code class="computeroutput">bzip2 -d</code>) decompresses all -specified files. Files which were not created by -<code class="computeroutput">bzip2</code> will be detected and -ignored, and a warning issued. -<code class="computeroutput">bzip2</code> attempts to guess the -filename for the decompressed file from that of the compressed -file as follows:</p> -<div class="itemizedlist"><ul class="itemizedlist" type="bullet"> -<li class="listitem" style="list-style-type: disc"><p><code class="computeroutput">filename.bz2 </code> - becomes - <code class="computeroutput">filename</code></p></li> -<li class="listitem" style="list-style-type: disc"><p><code class="computeroutput">filename.bz </code> - becomes - <code class="computeroutput">filename</code></p></li> -<li class="listitem" style="list-style-type: disc"><p><code class="computeroutput">filename.tbz2</code> - becomes - <code class="computeroutput">filename.tar</code></p></li> -<li class="listitem" style="list-style-type: disc"><p><code class="computeroutput">filename.tbz </code> - becomes - <code class="computeroutput">filename.tar</code></p></li> -<li class="listitem" style="list-style-type: disc"><p><code class="computeroutput">anyothername </code> - becomes - <code class="computeroutput">anyothername.out</code></p></li> -</ul></div> -<p>If the file does not end in one of the recognised endings, -<code class="computeroutput">.bz2</code>, -<code class="computeroutput">.bz</code>, -<code class="computeroutput">.tbz2</code> or -<code class="computeroutput">.tbz</code>, -<code class="computeroutput">bzip2</code> complains that it cannot -guess the name of the original file, and uses the original name -with <code class="computeroutput">.out</code> appended.</p> -<p>As with compression, supplying no filenames causes -decompression from standard input to standard output.</p> -<p><code class="computeroutput">bunzip2</code> will correctly -decompress a file which is the concatenation of two or more -compressed files. The result is the concatenation of the -corresponding uncompressed files. Integrity testing -(<code class="computeroutput">-t</code>) of concatenated compressed -files is also supported.</p> -<p>You can also compress or decompress files to the standard -output by giving the <code class="computeroutput">-c</code> flag. -Multiple files may be compressed and decompressed like this. The -resulting outputs are fed sequentially to stdout. Compression of -multiple files in this manner generates a stream containing -multiple compressed file representations. Such a stream can be -decompressed correctly only by -<code class="computeroutput">bzip2</code> version 0.9.0 or later. -Earlier versions of <code class="computeroutput">bzip2</code> will -stop after decompressing the first file in the stream.</p> -<p><code class="computeroutput">bzcat</code> (or -<code class="computeroutput">bzip2 -dc</code>) decompresses all -specified files to the standard output.</p> -<p><code class="computeroutput">bzip2</code> will read arguments -from the environment variables -<code class="computeroutput">BZIP2</code> and -<code class="computeroutput">BZIP</code>, in that order, and will -process them before any arguments read from the command line. -This gives a convenient way to supply default arguments.</p> -<p>Compression is always performed, even if the compressed -file is slightly larger than the original. Files of less than -about one hundred bytes tend to get larger, since the compression -mechanism has a constant overhead in the region of 50 bytes. -Random data (including the output of most file compressors) is -coded at about 8.05 bits per byte, giving an expansion of around -0.5%.</p> -<p>As a self-check for your protection, -<code class="computeroutput">bzip2</code> uses 32-bit CRCs to make -sure that the decompressed version of a file is identical to the -original. This guards against corruption of the compressed data, -and against undetected bugs in -<code class="computeroutput">bzip2</code> (hopefully very unlikely). -The chances of data corruption going undetected is microscopic, -about one chance in four billion for each file processed. Be -aware, though, that the check occurs upon decompression, so it -can only tell you that something is wrong. It can't help you -recover the original uncompressed data. You can use -<code class="computeroutput">bzip2recover</code> to try to recover -data from damaged files.</p> -<p>Return values: 0 for a normal exit, 1 for environmental -problems (file not found, invalid flags, I/O errors, etc.), 2 -to indicate a corrupt compressed file, 3 for an internal -consistency error (eg, bug) which caused -<code class="computeroutput">bzip2</code> to panic.</p> -</div> -<div class="sect1" title="2.4. OPTIONS"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="options"></a>2.4. OPTIONS</h2></div></div></div> -<div class="variablelist"><dl> -<dt><span class="term"><code class="computeroutput">-c --stdout</code></span></dt> -<dd><p>Compress or decompress to standard - output.</p></dd> -<dt><span class="term"><code class="computeroutput">-d --decompress</code></span></dt> -<dd><p>Force decompression. - <code class="computeroutput">bzip2</code>, - <code class="computeroutput">bunzip2</code> and - <code class="computeroutput">bzcat</code> are really the same - program, and the decision about what actions to take is done on - the basis of which name is used. This flag overrides that - mechanism, and forces bzip2 to decompress.</p></dd> -<dt><span class="term"><code class="computeroutput">-z --compress</code></span></dt> -<dd><p>The complement to - <code class="computeroutput">-d</code>: forces compression, - regardless of the invokation name.</p></dd> -<dt><span class="term"><code class="computeroutput">-t --test</code></span></dt> -<dd><p>Check integrity of the specified file(s), but - don't decompress them. This really performs a trial - decompression and throws away the result.</p></dd> -<dt><span class="term"><code class="computeroutput">-f --force</code></span></dt> -<dd> -<p>Force overwrite of output files. Normally, - <code class="computeroutput">bzip2</code> will not overwrite - existing output files. Also forces - <code class="computeroutput">bzip2</code> to break hard links to - files, which it otherwise wouldn't do.</p> -<p><code class="computeroutput">bzip2</code> normally declines - to decompress files which don't have the correct magic header - bytes. If forced (<code class="computeroutput">-f</code>), - however, it will pass such files through unmodified. This is - how GNU <code class="computeroutput">gzip</code> behaves.</p> -</dd> -<dt><span class="term"><code class="computeroutput">-k --keep</code></span></dt> -<dd><p>Keep (don't delete) input files during - compression or decompression.</p></dd> -<dt><span class="term"><code class="computeroutput">-s --small</code></span></dt> -<dd> -<p>Reduce memory usage, for compression, - decompression and testing. Files are decompressed and tested - using a modified algorithm which only requires 2.5 bytes per - block byte. This means any file can be decompressed in 2300k - of memory, albeit at about half the normal speed.</p> -<p>During compression, <code class="computeroutput">-s</code> - selects a block size of 200k, which limits memory use to around - the same figure, at the expense of your compression ratio. In - short, if your machine is low on memory (8 megabytes or less), - use <code class="computeroutput">-s</code> for everything. See - <a class="xref" href="#memory-management" title="2.5. MEMORY MANAGEMENT">MEMORY MANAGEMENT</a> below.</p> -</dd> -<dt><span class="term"><code class="computeroutput">-q --quiet</code></span></dt> -<dd><p>Suppress non-essential warning messages. - Messages pertaining to I/O errors and other critical events - will not be suppressed.</p></dd> -<dt><span class="term"><code class="computeroutput">-v --verbose</code></span></dt> -<dd><p>Verbose mode -- show the compression ratio for - each file processed. Further - <code class="computeroutput">-v</code>'s increase the verbosity - level, spewing out lots of information which is primarily of - interest for diagnostic purposes.</p></dd> -<dt><span class="term"><code class="computeroutput">-L --license -V --version</code></span></dt> -<dd><p>Display the software version, license terms and - conditions.</p></dd> -<dt><span class="term"><code class="computeroutput">-1</code> (or - <code class="computeroutput">--fast</code>) to - <code class="computeroutput">-9</code> (or - <code class="computeroutput">-best</code>)</span></dt> -<dd><p>Set the block size to 100 k, 200 k ... 900 k - when compressing. Has no effect when decompressing. See <a class="xref" href="#memory-management" title="2.5. MEMORY MANAGEMENT">MEMORY MANAGEMENT</a> below. The - <code class="computeroutput">--fast</code> and - <code class="computeroutput">--best</code> aliases are primarily - for GNU <code class="computeroutput">gzip</code> compatibility. - In particular, <code class="computeroutput">--fast</code> doesn't - make things significantly faster. And - <code class="computeroutput">--best</code> merely selects the - default behaviour.</p></dd> -<dt><span class="term"><code class="computeroutput">--</code></span></dt> -<dd><p>Treats all subsequent arguments as file names, - even if they start with a dash. This is so you can handle - files with names beginning with a dash, for example: - <code class="computeroutput">bzip2 -- - -myfilename</code>.</p></dd> -<dt> -<span class="term"><code class="computeroutput">--repetitive-fast</code>, </span><span class="term"><code class="computeroutput">--repetitive-best</code></span> -</dt> -<dd><p>These flags are redundant in versions 0.9.5 and - above. They provided some coarse control over the behaviour of - the sorting algorithm in earlier versions, which was sometimes - useful. 0.9.5 and above have an improved algorithm which - renders these flags irrelevant.</p></dd> -</dl></div> -</div> -<div class="sect1" title="2.5. MEMORY MANAGEMENT"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="memory-management"></a>2.5. MEMORY MANAGEMENT</h2></div></div></div> -<p><code class="computeroutput">bzip2</code> compresses large -files in blocks. The block size affects both the compression -ratio achieved, and the amount of memory needed for compression -and decompression. The flags <code class="computeroutput">-1</code> -through <code class="computeroutput">-9</code> specify the block -size to be 100,000 bytes through 900,000 bytes (the default) -respectively. At decompression time, the block size used for -compression is read from the header of the compressed file, and -<code class="computeroutput">bunzip2</code> then allocates itself -just enough memory to decompress the file. Since block sizes are -stored in compressed files, it follows that the flags -<code class="computeroutput">-1</code> to -<code class="computeroutput">-9</code> are irrelevant to and so -ignored during decompression.</p> -<p>Compression and decompression requirements, in bytes, can be -estimated as:</p> -<pre class="programlisting">Compression: 400k + ( 8 x block size ) - -Decompression: 100k + ( 4 x block size ), or - 100k + ( 2.5 x block size )</pre> -<p>Larger block sizes give rapidly diminishing marginal -returns. Most of the compression comes from the first two or -three hundred k of block size, a fact worth bearing in mind when -using <code class="computeroutput">bzip2</code> on small machines. -It is also important to appreciate that the decompression memory -requirement is set at compression time by the choice of block -size.</p> -<p>For files compressed with the default 900k block size, -<code class="computeroutput">bunzip2</code> will require about 3700 -kbytes to decompress. To support decompression of any file on a -4 megabyte machine, <code class="computeroutput">bunzip2</code> has -an option to decompress using approximately half this amount of -memory, about 2300 kbytes. Decompression speed is also halved, -so you should use this option only where necessary. The relevant -flag is <code class="computeroutput">-s</code>.</p> -<p>In general, try and use the largest block size memory -constraints allow, since that maximises the compression achieved. -Compression and decompression speed are virtually unaffected by -block size.</p> -<p>Another significant point applies to files which fit in a -single block -- that means most files you'd encounter using a -large block size. The amount of real memory touched is -proportional to the size of the file, since the file is smaller -than a block. For example, compressing a file 20,000 bytes long -with the flag <code class="computeroutput">-9</code> will cause the -compressor to allocate around 7600k of memory, but only touch -400k + 20000 * 8 = 560 kbytes of it. Similarly, the decompressor -will allocate 3700k but only touch 100k + 20000 * 4 = 180 -kbytes.</p> -<p>Here is a table which summarises the maximum memory usage -for different block sizes. Also recorded is the total compressed -size for 14 files of the Calgary Text Compression Corpus -totalling 3,141,622 bytes. This column gives some feel for how -compression varies with block size. These figures tend to -understate the advantage of larger block sizes for larger files, -since the Corpus is dominated by smaller files.</p> -<pre class="programlisting"> Compress Decompress Decompress Corpus -Flag usage usage -s usage Size - - -1 1200k 500k 350k 914704 - -2 2000k 900k 600k 877703 - -3 2800k 1300k 850k 860338 - -4 3600k 1700k 1100k 846899 - -5 4400k 2100k 1350k 845160 - -6 5200k 2500k 1600k 838626 - -7 6100k 2900k 1850k 834096 - -8 6800k 3300k 2100k 828642 - -9 7600k 3700k 2350k 828642</pre> -</div> -<div class="sect1" title="2.6. RECOVERING DATA FROM DAMAGED FILES"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="recovering"></a>2.6. RECOVERING DATA FROM DAMAGED FILES</h2></div></div></div> -<p><code class="computeroutput">bzip2</code> compresses files in -blocks, usually 900kbytes long. Each block is handled -independently. If a media or transmission error causes a -multi-block <code class="computeroutput">.bz2</code> file to become -damaged, it may be possible to recover data from the undamaged -blocks in the file.</p> -<p>The compressed representation of each block is delimited by -a 48-bit pattern, which makes it possible to find the block -boundaries with reasonable certainty. Each block also carries -its own 32-bit CRC, so damaged blocks can be distinguished from -undamaged ones.</p> -<p><code class="computeroutput">bzip2recover</code> is a simple -program whose purpose is to search for blocks in -<code class="computeroutput">.bz2</code> files, and write each block -out into its own <code class="computeroutput">.bz2</code> file. You -can then use <code class="computeroutput">bzip2 -t</code> to test -the integrity of the resulting files, and decompress those which -are undamaged.</p> -<p><code class="computeroutput">bzip2recover</code> takes a -single argument, the name of the damaged file, and writes a -number of files <code class="computeroutput">rec0001file.bz2</code>, -<code class="computeroutput">rec0002file.bz2</code>, etc, containing -the extracted blocks. The output filenames are designed so that -the use of wildcards in subsequent processing -- for example, -<code class="computeroutput">bzip2 -dc rec*file.bz2 > -recovered_data</code> -- lists the files in the correct -order.</p> -<p><code class="computeroutput">bzip2recover</code> should be of -most use dealing with large <code class="computeroutput">.bz2</code> -files, as these will contain many blocks. It is clearly futile -to use it on damaged single-block files, since a damaged block -cannot be recovered. If you wish to minimise any potential data -loss through media or transmission errors, you might consider -compressing with a smaller block size.</p> -</div> -<div class="sect1" title="2.7. PERFORMANCE NOTES"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="performance"></a>2.7. PERFORMANCE NOTES</h2></div></div></div> -<p>The sorting phase of compression gathers together similar -strings in the file. Because of this, files containing very long -runs of repeated symbols, like "aabaabaabaab ..." (repeated -several hundred times) may compress more slowly than normal. -Versions 0.9.5 and above fare much better than previous versions -in this respect. The ratio between worst-case and average-case -compression time is in the region of 10:1. For previous -versions, this figure was more like 100:1. You can use the -<code class="computeroutput">-vvvv</code> option to monitor progress -in great detail, if you want.</p> -<p>Decompression speed is unaffected by these -phenomena.</p> -<p><code class="computeroutput">bzip2</code> usually allocates -several megabytes of memory to operate in, and then charges all -over it in a fairly random fashion. This means that performance, -both for compressing and decompressing, is largely determined by -the speed at which your machine can service cache misses. -Because of this, small changes to the code to reduce the miss -rate have been observed to give disproportionately large -performance improvements. I imagine -<code class="computeroutput">bzip2</code> will perform best on -machines with very large caches.</p> -</div> -<div class="sect1" title="2.8. CAVEATS"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="caveats"></a>2.8. CAVEATS</h2></div></div></div> -<p>I/O error messages are not as helpful as they could be. -<code class="computeroutput">bzip2</code> tries hard to detect I/O -errors and exit cleanly, but the details of what the problem is -sometimes seem rather misleading.</p> -<p>This manual page pertains to version 1.0.6 of -<code class="computeroutput">bzip2</code>. Compressed data created by -this version is entirely forwards and backwards compatible with the -previous public releases, versions 0.1pl2, 0.9.0 and 0.9.5, 1.0.0, -1.0.1, 1.0.2 and 1.0.3, but with the following exception: 0.9.0 and -above can correctly decompress multiple concatenated compressed files. -0.1pl2 cannot do this; it will stop after decompressing just the first -file in the stream.</p> -<p><code class="computeroutput">bzip2recover</code> versions -prior to 1.0.2 used 32-bit integers to represent bit positions in -compressed files, so it could not handle compressed files more -than 512 megabytes long. Versions 1.0.2 and above use 64-bit ints -on some platforms which support them (GNU supported targets, and -Windows). To establish whether or not -<code class="computeroutput">bzip2recover</code> was built with such -a limitation, run it without arguments. In any event you can -build yourself an unlimited version if you can recompile it with -<code class="computeroutput">MaybeUInt64</code> set to be an -unsigned 64-bit integer.</p> -</div> -<div class="sect1" title="2.9. AUTHOR"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="author"></a>2.9. AUTHOR</h2></div></div></div> -<p>Julian Seward, -<code class="computeroutput">jseward@bzip.org</code></p> -<p>The ideas embodied in -<code class="computeroutput">bzip2</code> are due to (at least) the -following people: Michael Burrows and David Wheeler (for the -block sorting transformation), David Wheeler (again, for the -Huffman coder), Peter Fenwick (for the structured coding model in -the original <code class="computeroutput">bzip</code>, and many -refinements), and Alistair Moffat, Radford Neal and Ian Witten -(for the arithmetic coder in the original -<code class="computeroutput">bzip</code>). I am much indebted for -their help, support and advice. See the manual in the source -distribution for pointers to sources of documentation. Christian -von Roques encouraged me to look for faster sorting algorithms, -so as to speed up compression. Bela Lubkin encouraged me to -improve the worst-case compression performance. -Donna Robinson XMLised the documentation. -Many people sent -patches, helped with portability problems, lent machines, gave -advice and were generally helpful.</p> -</div> -</div> -<div class="chapter" title="3. Programming with libbzip2"> -<div class="titlepage"><div><div><h2 class="title"> -<a name="libprog"></a>3. -Programming with <code class="computeroutput">libbzip2</code> -</h2></div></div></div> -<div class="toc"> -<p><b>Table of Contents</b></p> -<dl> -<dt><span class="sect1"><a href="#top-level">3.1. Top-level structure</a></span></dt> -<dd><dl> -<dt><span class="sect2"><a href="#ll-summary">3.1.1. Low-level summary</a></span></dt> -<dt><span class="sect2"><a href="#hl-summary">3.1.2. High-level summary</a></span></dt> -<dt><span class="sect2"><a href="#util-fns-summary">3.1.3. Utility functions summary</a></span></dt> -</dl></dd> -<dt><span class="sect1"><a href="#err-handling">3.2. Error handling</a></span></dt> -<dt><span class="sect1"><a href="#low-level">3.3. Low-level interface</a></span></dt> -<dd><dl> -<dt><span class="sect2"><a href="#bzcompress-init">3.3.1. BZ2_bzCompressInit</a></span></dt> -<dt><span class="sect2"><a href="#bzCompress">3.3.2. BZ2_bzCompress</a></span></dt> -<dt><span class="sect2"><a href="#bzCompress-end">3.3.3. BZ2_bzCompressEnd</a></span></dt> -<dt><span class="sect2"><a href="#bzDecompress-init">3.3.4. BZ2_bzDecompressInit</a></span></dt> -<dt><span class="sect2"><a href="#bzDecompress">3.3.5. BZ2_bzDecompress</a></span></dt> -<dt><span class="sect2"><a href="#bzDecompress-end">3.3.6. BZ2_bzDecompressEnd</a></span></dt> -</dl></dd> -<dt><span class="sect1"><a href="#hl-interface">3.4. High-level interface</a></span></dt> -<dd><dl> -<dt><span class="sect2"><a href="#bzreadopen">3.4.1. BZ2_bzReadOpen</a></span></dt> -<dt><span class="sect2"><a href="#bzread">3.4.2. BZ2_bzRead</a></span></dt> -<dt><span class="sect2"><a href="#bzreadgetunused">3.4.3. BZ2_bzReadGetUnused</a></span></dt> -<dt><span class="sect2"><a href="#bzreadclose">3.4.4. BZ2_bzReadClose</a></span></dt> -<dt><span class="sect2"><a href="#bzwriteopen">3.4.5. BZ2_bzWriteOpen</a></span></dt> -<dt><span class="sect2"><a href="#bzwrite">3.4.6. BZ2_bzWrite</a></span></dt> -<dt><span class="sect2"><a href="#bzwriteclose">3.4.7. BZ2_bzWriteClose</a></span></dt> -<dt><span class="sect2"><a href="#embed">3.4.8. Handling embedded compressed data streams</a></span></dt> -<dt><span class="sect2"><a href="#std-rdwr">3.4.9. Standard file-reading/writing code</a></span></dt> -</dl></dd> -<dt><span class="sect1"><a href="#util-fns">3.5. Utility functions</a></span></dt> -<dd><dl> -<dt><span class="sect2"><a href="#bzbufftobuffcompress">3.5.1. BZ2_bzBuffToBuffCompress</a></span></dt> -<dt><span class="sect2"><a href="#bzbufftobuffdecompress">3.5.2. BZ2_bzBuffToBuffDecompress</a></span></dt> -</dl></dd> -<dt><span class="sect1"><a href="#zlib-compat">3.6. zlib compatibility functions</a></span></dt> -<dt><span class="sect1"><a href="#stdio-free">3.7. Using the library in a stdio-free environment</a></span></dt> -<dd><dl> -<dt><span class="sect2"><a href="#stdio-bye">3.7.1. Getting rid of stdio</a></span></dt> -<dt><span class="sect2"><a href="#critical-error">3.7.2. Critical error handling</a></span></dt> -</dl></dd> -<dt><span class="sect1"><a href="#win-dll">3.8. Making a Windows DLL</a></span></dt> -</dl> -</div> -<p>This chapter describes the programming interface to -<code class="computeroutput">libbzip2</code>.</p> -<p>For general background information, particularly about -memory use and performance aspects, you'd be well advised to read -<a class="xref" href="#using" title="2. How to use bzip2">How to use bzip2</a> as well.</p> -<div class="sect1" title="3.1. Top-level structure"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="top-level"></a>3.1. Top-level structure</h2></div></div></div> -<p><code class="computeroutput">libbzip2</code> is a flexible -library for compressing and decompressing data in the -<code class="computeroutput">bzip2</code> data format. Although -packaged as a single entity, it helps to regard the library as -three separate parts: the low level interface, and the high level -interface, and some utility functions.</p> -<p>The structure of -<code class="computeroutput">libbzip2</code>'s interfaces is similar -to that of Jean-loup Gailly's and Mark Adler's excellent -<code class="computeroutput">zlib</code> library.</p> -<p>All externally visible symbols have names beginning -<code class="computeroutput">BZ2_</code>. This is new in version -1.0. The intention is to minimise pollution of the namespaces of -library clients.</p> -<p>To use any part of the library, you need to -<code class="computeroutput">#include <bzlib.h></code> -into your sources.</p> -<div class="sect2" title="3.1.1. Low-level summary"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="ll-summary"></a>3.1.1. Low-level summary</h3></div></div></div> -<p>This interface provides services for compressing and -decompressing data in memory. There's no provision for dealing -with files, streams or any other I/O mechanisms, just straight -memory-to-memory work. In fact, this part of the library can be -compiled without inclusion of -<code class="computeroutput">stdio.h</code>, which may be helpful -for embedded applications.</p> -<p>The low-level part of the library has no global variables -and is therefore thread-safe.</p> -<p>Six routines make up the low level interface: -<code class="computeroutput">BZ2_bzCompressInit</code>, -<code class="computeroutput">BZ2_bzCompress</code>, and -<code class="computeroutput">BZ2_bzCompressEnd</code> for -compression, and a corresponding trio -<code class="computeroutput">BZ2_bzDecompressInit</code>, -<code class="computeroutput">BZ2_bzDecompress</code> and -<code class="computeroutput">BZ2_bzDecompressEnd</code> for -decompression. The <code class="computeroutput">*Init</code> -functions allocate memory for compression/decompression and do -other initialisations, whilst the -<code class="computeroutput">*End</code> functions close down -operations and release memory.</p> -<p>The real work is done by -<code class="computeroutput">BZ2_bzCompress</code> and -<code class="computeroutput">BZ2_bzDecompress</code>. These -compress and decompress data from a user-supplied input buffer to -a user-supplied output buffer. These buffers can be any size; -arbitrary quantities of data are handled by making repeated calls -to these functions. This is a flexible mechanism allowing a -consumer-pull style of activity, or producer-push, or a mixture -of both.</p> -</div> -<div class="sect2" title="3.1.2. High-level summary"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="hl-summary"></a>3.1.2. High-level summary</h3></div></div></div> -<p>This interface provides some handy wrappers around the -low-level interface to facilitate reading and writing -<code class="computeroutput">bzip2</code> format files -(<code class="computeroutput">.bz2</code> files). The routines -provide hooks to facilitate reading files in which the -<code class="computeroutput">bzip2</code> data stream is embedded -within some larger-scale file structure, or where there are -multiple <code class="computeroutput">bzip2</code> data streams -concatenated end-to-end.</p> -<p>For reading files, -<code class="computeroutput">BZ2_bzReadOpen</code>, -<code class="computeroutput">BZ2_bzRead</code>, -<code class="computeroutput">BZ2_bzReadClose</code> and -<code class="computeroutput">BZ2_bzReadGetUnused</code> are -supplied. For writing files, -<code class="computeroutput">BZ2_bzWriteOpen</code>, -<code class="computeroutput">BZ2_bzWrite</code> and -<code class="computeroutput">BZ2_bzWriteFinish</code> are -available.</p> -<p>As with the low-level library, no global variables are used -so the library is per se thread-safe. However, if I/O errors -occur whilst reading or writing the underlying compressed files, -you may have to consult <code class="computeroutput">errno</code> to -determine the cause of the error. In that case, you'd need a C -library which correctly supports -<code class="computeroutput">errno</code> in a multithreaded -environment.</p> -<p>To make the library a little simpler and more portable, -<code class="computeroutput">BZ2_bzReadOpen</code> and -<code class="computeroutput">BZ2_bzWriteOpen</code> require you to -pass them file handles (<code class="computeroutput">FILE*</code>s) -which have previously been opened for reading or writing -respectively. That avoids portability problems associated with -file operations and file attributes, whilst not being much of an -imposition on the programmer.</p> -</div> -<div class="sect2" title="3.1.3. Utility functions summary"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="util-fns-summary"></a>3.1.3. Utility functions summary</h3></div></div></div> -<p>For very simple needs, -<code class="computeroutput">BZ2_bzBuffToBuffCompress</code> and -<code class="computeroutput">BZ2_bzBuffToBuffDecompress</code> are -provided. These compress data in memory from one buffer to -another buffer in a single function call. You should assess -whether these functions fulfill your memory-to-memory -compression/decompression requirements before investing effort in -understanding the more general but more complex low-level -interface.</p> -<p>Yoshioka Tsuneo -(<code class="computeroutput">tsuneo@rr.iij4u.or.jp</code>) has -contributed some functions to give better -<code class="computeroutput">zlib</code> compatibility. These -functions are <code class="computeroutput">BZ2_bzopen</code>, -<code class="computeroutput">BZ2_bzread</code>, -<code class="computeroutput">BZ2_bzwrite</code>, -<code class="computeroutput">BZ2_bzflush</code>, -<code class="computeroutput">BZ2_bzclose</code>, -<code class="computeroutput">BZ2_bzerror</code> and -<code class="computeroutput">BZ2_bzlibVersion</code>. You may find -these functions more convenient for simple file reading and -writing, than those in the high-level interface. These functions -are not (yet) officially part of the library, and are minimally -documented here. If they break, you get to keep all the pieces. -I hope to document them properly when time permits.</p> -<p>Yoshioka also contributed modifications to allow the -library to be built as a Windows DLL.</p> -</div> -</div> -<div class="sect1" title="3.2. Error handling"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="err-handling"></a>3.2. Error handling</h2></div></div></div> -<p>The library is designed to recover cleanly in all -situations, including the worst-case situation of decompressing -random data. I'm not 100% sure that it can always do this, so -you might want to add a signal handler to catch segmentation -violations during decompression if you are feeling especially -paranoid. I would be interested in hearing more about the -robustness of the library to corrupted compressed data.</p> -<p>Version 1.0.3 more robust in this respect than any -previous version. Investigations with Valgrind (a tool for detecting -problems with memory management) indicate -that, at least for the few files I tested, all single-bit errors -in the decompressed data are caught properly, with no -segmentation faults, no uses of uninitialised data, no out of -range reads or writes, and no infinite looping in the decompressor. -So it's certainly pretty robust, although -I wouldn't claim it to be totally bombproof.</p> -<p>The file <code class="computeroutput">bzlib.h</code> contains -all definitions needed to use the library. In particular, you -should definitely not include -<code class="computeroutput">bzlib_private.h</code>.</p> -<p>In <code class="computeroutput">bzlib.h</code>, the various -return values are defined. The following list is not intended as -an exhaustive description of the circumstances in which a given -value may be returned -- those descriptions are given later. -Rather, it is intended to convey the rough meaning of each return -value. The first five actions are normal and not intended to -denote an error situation.</p> -<div class="variablelist"><dl> -<dt><span class="term"><code class="computeroutput">BZ_OK</code></span></dt> -<dd><p>The requested action was completed - successfully.</p></dd> -<dt><span class="term"><code class="computeroutput">BZ_RUN_OK, BZ_FLUSH_OK, - BZ_FINISH_OK</code></span></dt> -<dd><p>In - <code class="computeroutput">BZ2_bzCompress</code>, the requested - flush/finish/nothing-special action was completed - successfully.</p></dd> -<dt><span class="term"><code class="computeroutput">BZ_STREAM_END</code></span></dt> -<dd><p>Compression of data was completed, or the - logical stream end was detected during - decompression.</p></dd> -</dl></div> -<p>The following return values indicate an error of some -kind.</p> -<div class="variablelist"><dl> -<dt><span class="term"><code class="computeroutput">BZ_CONFIG_ERROR</code></span></dt> -<dd><p>Indicates that the library has been improperly - compiled on your platform -- a major configuration error. - Specifically, it means that - <code class="computeroutput">sizeof(char)</code>, - <code class="computeroutput">sizeof(short)</code> and - <code class="computeroutput">sizeof(int)</code> are not 1, 2 and - 4 respectively, as they should be. Note that the library - should still work properly on 64-bit platforms which follow - the LP64 programming model -- that is, where - <code class="computeroutput">sizeof(long)</code> and - <code class="computeroutput">sizeof(void*)</code> are 8. Under - LP64, <code class="computeroutput">sizeof(int)</code> is still 4, - so <code class="computeroutput">libbzip2</code>, which doesn't - use the <code class="computeroutput">long</code> type, is - OK.</p></dd> -<dt><span class="term"><code class="computeroutput">BZ_SEQUENCE_ERROR</code></span></dt> -<dd><p>When using the library, it is important to call - the functions in the correct sequence and with data structures - (buffers etc) in the correct states. - <code class="computeroutput">libbzip2</code> checks as much as it - can to ensure this is happening, and returns - <code class="computeroutput">BZ_SEQUENCE_ERROR</code> if not. - Code which complies precisely with the function semantics, as - detailed below, should never receive this value; such an event - denotes buggy code which you should - investigate.</p></dd> -<dt><span class="term"><code class="computeroutput">BZ_PARAM_ERROR</code></span></dt> -<dd><p>Returned when a parameter to a function call is - out of range or otherwise manifestly incorrect. As with - <code class="computeroutput">BZ_SEQUENCE_ERROR</code>, this - denotes a bug in the client code. The distinction between - <code class="computeroutput">BZ_PARAM_ERROR</code> and - <code class="computeroutput">BZ_SEQUENCE_ERROR</code> is a bit - hazy, but still worth making.</p></dd> -<dt><span class="term"><code class="computeroutput">BZ_MEM_ERROR</code></span></dt> -<dd><p>Returned when a request to allocate memory - failed. Note that the quantity of memory needed to decompress - a stream cannot be determined until the stream's header has - been read. So - <code class="computeroutput">BZ2_bzDecompress</code> and - <code class="computeroutput">BZ2_bzRead</code> may return - <code class="computeroutput">BZ_MEM_ERROR</code> even though some - of the compressed data has been read. The same is not true - for compression; once - <code class="computeroutput">BZ2_bzCompressInit</code> or - <code class="computeroutput">BZ2_bzWriteOpen</code> have - successfully completed, - <code class="computeroutput">BZ_MEM_ERROR</code> cannot - occur.</p></dd> -<dt><span class="term"><code class="computeroutput">BZ_DATA_ERROR</code></span></dt> -<dd><p>Returned when a data integrity error is - detected during decompression. Most importantly, this means - when stored and computed CRCs for the data do not match. This - value is also returned upon detection of any other anomaly in - the compressed data.</p></dd> -<dt><span class="term"><code class="computeroutput">BZ_DATA_ERROR_MAGIC</code></span></dt> -<dd><p>As a special case of - <code class="computeroutput">BZ_DATA_ERROR</code>, it is - sometimes useful to know when the compressed stream does not - start with the correct magic bytes (<code class="computeroutput">'B' 'Z' - 'h'</code>).</p></dd> -<dt><span class="term"><code class="computeroutput">BZ_IO_ERROR</code></span></dt> -<dd><p>Returned by - <code class="computeroutput">BZ2_bzRead</code> and - <code class="computeroutput">BZ2_bzWrite</code> when there is an - error reading or writing in the compressed file, and by - <code class="computeroutput">BZ2_bzReadOpen</code> and - <code class="computeroutput">BZ2_bzWriteOpen</code> for attempts - to use a file for which the error indicator (viz, - <code class="computeroutput">ferror(f)</code>) is set. On - receipt of <code class="computeroutput">BZ_IO_ERROR</code>, the - caller should consult <code class="computeroutput">errno</code> - and/or <code class="computeroutput">perror</code> to acquire - operating-system specific information about the - problem.</p></dd> -<dt><span class="term"><code class="computeroutput">BZ_UNEXPECTED_EOF</code></span></dt> -<dd><p>Returned by - <code class="computeroutput">BZ2_bzRead</code> when the - compressed file finishes before the logical end of stream is - detected.</p></dd> -<dt><span class="term"><code class="computeroutput">BZ_OUTBUFF_FULL</code></span></dt> -<dd><p>Returned by - <code class="computeroutput">BZ2_bzBuffToBuffCompress</code> and - <code class="computeroutput">BZ2_bzBuffToBuffDecompress</code> to - indicate that the output data will not fit into the output - buffer provided.</p></dd> -</dl></div> -</div> -<div class="sect1" title="3.3. Low-level interface"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="low-level"></a>3.3. Low-level interface</h2></div></div></div> -<div class="sect2" title="3.3.1. BZ2_bzCompressInit"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="bzcompress-init"></a>3.3.1. BZ2_bzCompressInit</h3></div></div></div> -<pre class="programlisting">typedef struct { - char *next_in; - unsigned int avail_in; - unsigned int total_in_lo32; - unsigned int total_in_hi32; - - char *next_out; - unsigned int avail_out; - unsigned int total_out_lo32; - unsigned int total_out_hi32; - - void *state; - - void *(*bzalloc)(void *,int,int); - void (*bzfree)(void *,void *); - void *opaque; -} bz_stream; - -int BZ2_bzCompressInit ( bz_stream *strm, - int blockSize100k, - int verbosity, - int workFactor );</pre> -<p>Prepares for compression. The -<code class="computeroutput">bz_stream</code> structure holds all -data pertaining to the compression activity. A -<code class="computeroutput">bz_stream</code> structure should be -allocated and initialised prior to the call. The fields of -<code class="computeroutput">bz_stream</code> comprise the entirety -of the user-visible data. <code class="computeroutput">state</code> -is a pointer to the private data structures required for -compression.</p> -<p>Custom memory allocators are supported, via fields -<code class="computeroutput">bzalloc</code>, -<code class="computeroutput">bzfree</code>, and -<code class="computeroutput">opaque</code>. The value -<code class="computeroutput">opaque</code> is passed to as the first -argument to all calls to <code class="computeroutput">bzalloc</code> -and <code class="computeroutput">bzfree</code>, but is otherwise -ignored by the library. The call <code class="computeroutput">bzalloc ( -opaque, n, m )</code> is expected to return a pointer -<code class="computeroutput">p</code> to <code class="computeroutput">n * -m</code> bytes of memory, and <code class="computeroutput">bzfree ( -opaque, p )</code> should free that memory.</p> -<p>If you don't want to use a custom memory allocator, set -<code class="computeroutput">bzalloc</code>, -<code class="computeroutput">bzfree</code> and -<code class="computeroutput">opaque</code> to -<code class="computeroutput">NULL</code>, and the library will then -use the standard <code class="computeroutput">malloc</code> / -<code class="computeroutput">free</code> routines.</p> -<p>Before calling -<code class="computeroutput">BZ2_bzCompressInit</code>, fields -<code class="computeroutput">bzalloc</code>, -<code class="computeroutput">bzfree</code> and -<code class="computeroutput">opaque</code> should be filled -appropriately, as just described. Upon return, the internal -state will have been allocated and initialised, and -<code class="computeroutput">total_in_lo32</code>, -<code class="computeroutput">total_in_hi32</code>, -<code class="computeroutput">total_out_lo32</code> and -<code class="computeroutput">total_out_hi32</code> will have been -set to zero. These four fields are used by the library to inform -the caller of the total amount of data passed into and out of the -library, respectively. You should not try to change them. As of -version 1.0, 64-bit counts are maintained, even on 32-bit -platforms, using the <code class="computeroutput">_hi32</code> -fields to store the upper 32 bits of the count. So, for example, -the total amount of data in is <code class="computeroutput">(total_in_hi32 -<< 32) + total_in_lo32</code>.</p> -<p>Parameter <code class="computeroutput">blockSize100k</code> -specifies the block size to be used for compression. It should -be a value between 1 and 9 inclusive, and the actual block size -used is 100000 x this figure. 9 gives the best compression but -takes most memory.</p> -<p>Parameter <code class="computeroutput">verbosity</code> should -be set to a number between 0 and 4 inclusive. 0 is silent, and -greater numbers give increasingly verbose monitoring/debugging -output. If the library has been compiled with -<code class="computeroutput">-DBZ_NO_STDIO</code>, no such output -will appear for any verbosity setting.</p> -<p>Parameter <code class="computeroutput">workFactor</code> -controls how the compression phase behaves when presented with -worst case, highly repetitive, input data. If compression runs -into difficulties caused by repetitive data, the library switches -from the standard sorting algorithm to a fallback algorithm. The -fallback is slower than the standard algorithm by perhaps a -factor of three, but always behaves reasonably, no matter how bad -the input.</p> -<p>Lower values of <code class="computeroutput">workFactor</code> -reduce the amount of effort the standard algorithm will expend -before resorting to the fallback. You should set this parameter -carefully; too low, and many inputs will be handled by the -fallback algorithm and so compress rather slowly, too high, and -your average-to-worst case compression times can become very -large. The default value of 30 gives reasonable behaviour over a -wide range of circumstances.</p> -<p>Allowable values range from 0 to 250 inclusive. 0 is a -special case, equivalent to using the default value of 30.</p> -<p>Note that the compressed output generated is the same -regardless of whether or not the fallback algorithm is -used.</p> -<p>Be aware also that this parameter may disappear entirely in -future versions of the library. In principle it should be -possible to devise a good way to automatically choose which -algorithm to use. Such a mechanism would render the parameter -obsolete.</p> -<p>Possible return values:</p> -<pre class="programlisting">BZ_CONFIG_ERROR - if the library has been mis-compiled -BZ_PARAM_ERROR - if strm is NULL - or blockSize < 1 or blockSize > 9 - or verbosity < 0 or verbosity > 4 - or workFactor < 0 or workFactor > 250 -BZ_MEM_ERROR - if not enough memory is available -BZ_OK - otherwise</pre> -<p>Allowable next actions:</p> -<pre class="programlisting">BZ2_bzCompress - if BZ_OK is returned - no specific action needed in case of error</pre> -</div> -<div class="sect2" title="3.3.2. BZ2_bzCompress"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="bzCompress"></a>3.3.2. BZ2_bzCompress</h3></div></div></div> -<pre class="programlisting">int BZ2_bzCompress ( bz_stream *strm, int action );</pre> -<p>Provides more input and/or output buffer space for the -library. The caller maintains input and output buffers, and -calls <code class="computeroutput">BZ2_bzCompress</code> to transfer -data between them.</p> -<p>Before each call to -<code class="computeroutput">BZ2_bzCompress</code>, -<code class="computeroutput">next_in</code> should point at the data -to be compressed, and <code class="computeroutput">avail_in</code> -should indicate how many bytes the library may read. -<code class="computeroutput">BZ2_bzCompress</code> updates -<code class="computeroutput">next_in</code>, -<code class="computeroutput">avail_in</code> and -<code class="computeroutput">total_in</code> to reflect the number -of bytes it has read.</p> -<p>Similarly, <code class="computeroutput">next_out</code> should -point to a buffer in which the compressed data is to be placed, -with <code class="computeroutput">avail_out</code> indicating how -much output space is available. -<code class="computeroutput">BZ2_bzCompress</code> updates -<code class="computeroutput">next_out</code>, -<code class="computeroutput">avail_out</code> and -<code class="computeroutput">total_out</code> to reflect the number -of bytes output.</p> -<p>You may provide and remove as little or as much data as you -like on each call of -<code class="computeroutput">BZ2_bzCompress</code>. In the limit, -it is acceptable to supply and remove data one byte at a time, -although this would be terribly inefficient. You should always -ensure that at least one byte of output space is available at -each call.</p> -<p>A second purpose of -<code class="computeroutput">BZ2_bzCompress</code> is to request a -change of mode of the compressed stream.</p> -<p>Conceptually, a compressed stream can be in one of four -states: IDLE, RUNNING, FLUSHING and FINISHING. Before -initialisation -(<code class="computeroutput">BZ2_bzCompressInit</code>) and after -termination (<code class="computeroutput">BZ2_bzCompressEnd</code>), -a stream is regarded as IDLE.</p> -<p>Upon initialisation -(<code class="computeroutput">BZ2_bzCompressInit</code>), the stream -is placed in the RUNNING state. Subsequent calls to -<code class="computeroutput">BZ2_bzCompress</code> should pass -<code class="computeroutput">BZ_RUN</code> as the requested action; -other actions are illegal and will result in -<code class="computeroutput">BZ_SEQUENCE_ERROR</code>.</p> -<p>At some point, the calling program will have provided all -the input data it wants to. It will then want to finish up -- in -effect, asking the library to process any data it might have -buffered internally. In this state, -<code class="computeroutput">BZ2_bzCompress</code> will no longer -attempt to read data from -<code class="computeroutput">next_in</code>, but it will want to -write data to <code class="computeroutput">next_out</code>. Because -the output buffer supplied by the user can be arbitrarily small, -the finishing-up operation cannot necessarily be done with a -single call of -<code class="computeroutput">BZ2_bzCompress</code>.</p> -<p>Instead, the calling program passes -<code class="computeroutput">BZ_FINISH</code> as an action to -<code class="computeroutput">BZ2_bzCompress</code>. This changes -the stream's state to FINISHING. Any remaining input (ie, -<code class="computeroutput">next_in[0 .. avail_in-1]</code>) is -compressed and transferred to the output buffer. To do this, -<code class="computeroutput">BZ2_bzCompress</code> must be called -repeatedly until all the output has been consumed. At that -point, <code class="computeroutput">BZ2_bzCompress</code> returns -<code class="computeroutput">BZ_STREAM_END</code>, and the stream's -state is set back to IDLE. -<code class="computeroutput">BZ2_bzCompressEnd</code> should then be -called.</p> -<p>Just to make sure the calling program does not cheat, the -library makes a note of <code class="computeroutput">avail_in</code> -at the time of the first call to -<code class="computeroutput">BZ2_bzCompress</code> which has -<code class="computeroutput">BZ_FINISH</code> as an action (ie, at -the time the program has announced its intention to not supply -any more input). By comparing this value with that of -<code class="computeroutput">avail_in</code> over subsequent calls -to <code class="computeroutput">BZ2_bzCompress</code>, the library -can detect any attempts to slip in more data to compress. Any -calls for which this is detected will return -<code class="computeroutput">BZ_SEQUENCE_ERROR</code>. This -indicates a programming mistake which should be corrected.</p> -<p>Instead of asking to finish, the calling program may ask -<code class="computeroutput">BZ2_bzCompress</code> to take all the -remaining input, compress it and terminate the current -(Burrows-Wheeler) compression block. This could be useful for -error control purposes. The mechanism is analogous to that for -finishing: call <code class="computeroutput">BZ2_bzCompress</code> -with an action of <code class="computeroutput">BZ_FLUSH</code>, -remove output data, and persist with the -<code class="computeroutput">BZ_FLUSH</code> action until the value -<code class="computeroutput">BZ_RUN</code> is returned. As with -finishing, <code class="computeroutput">BZ2_bzCompress</code> -detects any attempt to provide more input data once the flush has -begun.</p> -<p>Once the flush is complete, the stream returns to the -normal RUNNING state.</p> -<p>This all sounds pretty complex, but isn't really. Here's a -table which shows which actions are allowable in each state, what -action will be taken, what the next state is, and what the -non-error return values are. Note that you can't explicitly ask -what state the stream is in, but nor do you need to -- it can be -inferred from the values returned by -<code class="computeroutput">BZ2_bzCompress</code>.</p> -<pre class="programlisting">IDLE/any - Illegal. IDLE state only exists after BZ2_bzCompressEnd or - before BZ2_bzCompressInit. - Return value = BZ_SEQUENCE_ERROR - -RUNNING/BZ_RUN - Compress from next_in to next_out as much as possible. - Next state = RUNNING - Return value = BZ_RUN_OK - -RUNNING/BZ_FLUSH - Remember current value of next_in. Compress from next_in - to next_out as much as possible, but do not accept any more input. - Next state = FLUSHING - Return value = BZ_FLUSH_OK - -RUNNING/BZ_FINISH - Remember current value of next_in. Compress from next_in - to next_out as much as possible, but do not accept any more input. - Next state = FINISHING - Return value = BZ_FINISH_OK - -FLUSHING/BZ_FLUSH - Compress from next_in to next_out as much as possible, - but do not accept any more input. - If all the existing input has been used up and all compressed - output has been removed - Next state = RUNNING; Return value = BZ_RUN_OK - else - Next state = FLUSHING; Return value = BZ_FLUSH_OK - -FLUSHING/other - Illegal. - Return value = BZ_SEQUENCE_ERROR - -FINISHING/BZ_FINISH - Compress from next_in to next_out as much as possible, - but to not accept any more input. - If all the existing input has been used up and all compressed - output has been removed - Next state = IDLE; Return value = BZ_STREAM_END - else - Next state = FINISHING; Return value = BZ_FINISH_OK - -FINISHING/other - Illegal. - Return value = BZ_SEQUENCE_ERROR</pre> -<p>That still looks complicated? Well, fair enough. The -usual sequence of calls for compressing a load of data is:</p> -<div class="orderedlist"><ol class="orderedlist" type="1"> -<li class="listitem"><p>Get started with - <code class="computeroutput">BZ2_bzCompressInit</code>.</p></li> -<li class="listitem"><p>Shovel data in and shlurp out its compressed form - using zero or more calls of - <code class="computeroutput">BZ2_bzCompress</code> with action = - <code class="computeroutput">BZ_RUN</code>.</p></li> -<li class="listitem"><p>Finish up. Repeatedly call - <code class="computeroutput">BZ2_bzCompress</code> with action = - <code class="computeroutput">BZ_FINISH</code>, copying out the - compressed output, until - <code class="computeroutput">BZ_STREAM_END</code> is - returned.</p></li> -<li class="listitem"><p>Close up and go home. Call - <code class="computeroutput">BZ2_bzCompressEnd</code>.</p></li> -</ol></div> -<p>If the data you want to compress fits into your input -buffer all at once, you can skip the calls of -<code class="computeroutput">BZ2_bzCompress ( ..., BZ_RUN )</code> -and just do the <code class="computeroutput">BZ2_bzCompress ( ..., BZ_FINISH -)</code> calls.</p> -<p>All required memory is allocated by -<code class="computeroutput">BZ2_bzCompressInit</code>. The -compression library can accept any data at all (obviously). So -you shouldn't get any error return values from the -<code class="computeroutput">BZ2_bzCompress</code> calls. If you -do, they will be -<code class="computeroutput">BZ_SEQUENCE_ERROR</code>, and indicate -a bug in your programming.</p> -<p>Trivial other possible return values:</p> -<pre class="programlisting">BZ_PARAM_ERROR - if strm is NULL, or strm->s is NULL</pre> -</div> -<div class="sect2" title="3.3.3. BZ2_bzCompressEnd"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="bzCompress-end"></a>3.3.3. BZ2_bzCompressEnd</h3></div></div></div> -<pre class="programlisting">int BZ2_bzCompressEnd ( bz_stream *strm );</pre> -<p>Releases all memory associated with a compression -stream.</p> -<p>Possible return values:</p> -<pre class="programlisting">BZ_PARAM_ERROR if strm is NULL or strm->s is NULL -BZ_OK otherwise</pre> -</div> -<div class="sect2" title="3.3.4. BZ2_bzDecompressInit"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="bzDecompress-init"></a>3.3.4. BZ2_bzDecompressInit</h3></div></div></div> -<pre class="programlisting">int BZ2_bzDecompressInit ( bz_stream *strm, int verbosity, int small );</pre> -<p>Prepares for decompression. As with -<code class="computeroutput">BZ2_bzCompressInit</code>, a -<code class="computeroutput">bz_stream</code> record should be -allocated and initialised before the call. Fields -<code class="computeroutput">bzalloc</code>, -<code class="computeroutput">bzfree</code> and -<code class="computeroutput">opaque</code> should be set if a custom -memory allocator is required, or made -<code class="computeroutput">NULL</code> for the normal -<code class="computeroutput">malloc</code> / -<code class="computeroutput">free</code> routines. Upon return, the -internal state will have been initialised, and -<code class="computeroutput">total_in</code> and -<code class="computeroutput">total_out</code> will be zero.</p> -<p>For the meaning of parameter -<code class="computeroutput">verbosity</code>, see -<code class="computeroutput">BZ2_bzCompressInit</code>.</p> -<p>If <code class="computeroutput">small</code> is nonzero, the -library will use an alternative decompression algorithm which -uses less memory but at the cost of decompressing more slowly -(roughly speaking, half the speed, but the maximum memory -requirement drops to around 2300k). See <a class="xref" href="#using" title="2. How to use bzip2">How to use bzip2</a> -for more information on memory management.</p> -<p>Note that the amount of memory needed to decompress a -stream cannot be determined until the stream's header has been -read, so even if -<code class="computeroutput">BZ2_bzDecompressInit</code> succeeds, a -subsequent <code class="computeroutput">BZ2_bzDecompress</code> -could fail with -<code class="computeroutput">BZ_MEM_ERROR</code>.</p> -<p>Possible return values:</p> -<pre class="programlisting">BZ_CONFIG_ERROR - if the library has been mis-compiled -BZ_PARAM_ERROR - if ( small != 0 && small != 1 ) - or (verbosity <; 0 || verbosity > 4) -BZ_MEM_ERROR - if insufficient memory is available</pre> -<p>Allowable next actions:</p> -<pre class="programlisting">BZ2_bzDecompress - if BZ_OK was returned - no specific action required in case of error</pre> -</div> -<div class="sect2" title="3.3.5. BZ2_bzDecompress"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="bzDecompress"></a>3.3.5. BZ2_bzDecompress</h3></div></div></div> -<pre class="programlisting">int BZ2_bzDecompress ( bz_stream *strm );</pre> -<p>Provides more input and/out output buffer space for the -library. The caller maintains input and output buffers, and uses -<code class="computeroutput">BZ2_bzDecompress</code> to transfer -data between them.</p> -<p>Before each call to -<code class="computeroutput">BZ2_bzDecompress</code>, -<code class="computeroutput">next_in</code> should point at the -compressed data, and <code class="computeroutput">avail_in</code> -should indicate how many bytes the library may read. -<code class="computeroutput">BZ2_bzDecompress</code> updates -<code class="computeroutput">next_in</code>, -<code class="computeroutput">avail_in</code> and -<code class="computeroutput">total_in</code> to reflect the number -of bytes it has read.</p> -<p>Similarly, <code class="computeroutput">next_out</code> should -point to a buffer in which the uncompressed output is to be -placed, with <code class="computeroutput">avail_out</code> -indicating how much output space is available. -<code class="computeroutput">BZ2_bzCompress</code> updates -<code class="computeroutput">next_out</code>, -<code class="computeroutput">avail_out</code> and -<code class="computeroutput">total_out</code> to reflect the number -of bytes output.</p> -<p>You may provide and remove as little or as much data as you -like on each call of -<code class="computeroutput">BZ2_bzDecompress</code>. In the limit, -it is acceptable to supply and remove data one byte at a time, -although this would be terribly inefficient. You should always -ensure that at least one byte of output space is available at -each call.</p> -<p>Use of <code class="computeroutput">BZ2_bzDecompress</code> is -simpler than -<code class="computeroutput">BZ2_bzCompress</code>.</p> -<p>You should provide input and remove output as described -above, and repeatedly call -<code class="computeroutput">BZ2_bzDecompress</code> until -<code class="computeroutput">BZ_STREAM_END</code> is returned. -Appearance of <code class="computeroutput">BZ_STREAM_END</code> -denotes that <code class="computeroutput">BZ2_bzDecompress</code> -has detected the logical end of the compressed stream. -<code class="computeroutput">BZ2_bzDecompress</code> will not -produce <code class="computeroutput">BZ_STREAM_END</code> until all -output data has been placed into the output buffer, so once -<code class="computeroutput">BZ_STREAM_END</code> appears, you are -guaranteed to have available all the decompressed output, and -<code class="computeroutput">BZ2_bzDecompressEnd</code> can safely -be called.</p> -<p>If case of an error return value, you should call -<code class="computeroutput">BZ2_bzDecompressEnd</code> to clean up -and release memory.</p> -<p>Possible return values:</p> -<pre class="programlisting">BZ_PARAM_ERROR - if strm is NULL or strm->s is NULL - or strm->avail_out < 1 -BZ_DATA_ERROR - if a data integrity error is detected in the compressed stream -BZ_DATA_ERROR_MAGIC - if the compressed stream doesn't begin with the right magic bytes -BZ_MEM_ERROR - if there wasn't enough memory available -BZ_STREAM_END - if the logical end of the data stream was detected and all - output in has been consumed, eg s-->avail_out > 0 -BZ_OK - otherwise</pre> -<p>Allowable next actions:</p> -<pre class="programlisting">BZ2_bzDecompress - if BZ_OK was returned -BZ2_bzDecompressEnd - otherwise</pre> -</div> -<div class="sect2" title="3.3.6. BZ2_bzDecompressEnd"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="bzDecompress-end"></a>3.3.6. BZ2_bzDecompressEnd</h3></div></div></div> -<pre class="programlisting">int BZ2_bzDecompressEnd ( bz_stream *strm );</pre> -<p>Releases all memory associated with a decompression -stream.</p> -<p>Possible return values:</p> -<pre class="programlisting">BZ_PARAM_ERROR - if strm is NULL or strm->s is NULL -BZ_OK - otherwise</pre> -<p>Allowable next actions:</p> -<pre class="programlisting"> None.</pre> -</div> -</div> -<div class="sect1" title="3.4. High-level interface"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="hl-interface"></a>3.4. High-level interface</h2></div></div></div> -<p>This interface provides functions for reading and writing -<code class="computeroutput">bzip2</code> format files. First, some -general points.</p> -<div class="itemizedlist"><ul class="itemizedlist" type="bullet"> -<li class="listitem" style="list-style-type: disc"><p>All of the functions take an - <code class="computeroutput">int*</code> first argument, - <code class="computeroutput">bzerror</code>. After each call, - <code class="computeroutput">bzerror</code> should be consulted - first to determine the outcome of the call. If - <code class="computeroutput">bzerror</code> is - <code class="computeroutput">BZ_OK</code>, the call completed - successfully, and only then should the return value of the - function (if any) be consulted. If - <code class="computeroutput">bzerror</code> is - <code class="computeroutput">BZ_IO_ERROR</code>, there was an - error reading/writing the underlying compressed file, and you - should then consult <code class="computeroutput">errno</code> / - <code class="computeroutput">perror</code> to determine the cause - of the difficulty. <code class="computeroutput">bzerror</code> - may also be set to various other values; precise details are - given on a per-function basis below.</p></li> -<li class="listitem" style="list-style-type: disc"><p>If <code class="computeroutput">bzerror</code> indicates - an error (ie, anything except - <code class="computeroutput">BZ_OK</code> and - <code class="computeroutput">BZ_STREAM_END</code>), you should - immediately call - <code class="computeroutput">BZ2_bzReadClose</code> (or - <code class="computeroutput">BZ2_bzWriteClose</code>, depending on - whether you are attempting to read or to write) to free up all - resources associated with the stream. Once an error has been - indicated, behaviour of all calls except - <code class="computeroutput">BZ2_bzReadClose</code> - (<code class="computeroutput">BZ2_bzWriteClose</code>) is - undefined. The implication is that (1) - <code class="computeroutput">bzerror</code> should be checked - after each call, and (2) if - <code class="computeroutput">bzerror</code> indicates an error, - <code class="computeroutput">BZ2_bzReadClose</code> - (<code class="computeroutput">BZ2_bzWriteClose</code>) should then - be called to clean up.</p></li> -<li class="listitem" style="list-style-type: disc"><p>The <code class="computeroutput">FILE*</code> arguments - passed to <code class="computeroutput">BZ2_bzReadOpen</code> / - <code class="computeroutput">BZ2_bzWriteOpen</code> should be set - to binary mode. Most Unix systems will do this by default, but - other platforms, including Windows and Mac, will not. If you - omit this, you may encounter problems when moving code to new - platforms.</p></li> -<li class="listitem" style="list-style-type: disc"><p>Memory allocation requests are handled by - <code class="computeroutput">malloc</code> / - <code class="computeroutput">free</code>. At present there is no - facility for user-defined memory allocators in the file I/O - functions (could easily be added, though).</p></li> -</ul></div> -<div class="sect2" title="3.4.1. BZ2_bzReadOpen"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="bzreadopen"></a>3.4.1. BZ2_bzReadOpen</h3></div></div></div> -<pre class="programlisting">typedef void BZFILE; - -BZFILE *BZ2_bzReadOpen( int *bzerror, FILE *f, - int verbosity, int small, - void *unused, int nUnused );</pre> -<p>Prepare to read compressed data from file handle -<code class="computeroutput">f</code>. -<code class="computeroutput">f</code> should refer to a file which -has been opened for reading, and for which the error indicator -(<code class="computeroutput">ferror(f)</code>)is not set. If -<code class="computeroutput">small</code> is 1, the library will try -to decompress using less memory, at the expense of speed.</p> -<p>For reasons explained below, -<code class="computeroutput">BZ2_bzRead</code> will decompress the -<code class="computeroutput">nUnused</code> bytes starting at -<code class="computeroutput">unused</code>, before starting to read -from the file <code class="computeroutput">f</code>. At most -<code class="computeroutput">BZ_MAX_UNUSED</code> bytes may be -supplied like this. If this facility is not required, you should -pass <code class="computeroutput">NULL</code> and -<code class="computeroutput">0</code> for -<code class="computeroutput">unused</code> and -n<code class="computeroutput">Unused</code> respectively.</p> -<p>For the meaning of parameters -<code class="computeroutput">small</code> and -<code class="computeroutput">verbosity</code>, see -<code class="computeroutput">BZ2_bzDecompressInit</code>.</p> -<p>The amount of memory needed to decompress a file cannot be -determined until the file's header has been read. So it is -possible that <code class="computeroutput">BZ2_bzReadOpen</code> -returns <code class="computeroutput">BZ_OK</code> but a subsequent -call of <code class="computeroutput">BZ2_bzRead</code> will return -<code class="computeroutput">BZ_MEM_ERROR</code>.</p> -<p>Possible assignments to -<code class="computeroutput">bzerror</code>:</p> -<pre class="programlisting">BZ_CONFIG_ERROR - if the library has been mis-compiled -BZ_PARAM_ERROR - if f is NULL - or small is neither 0 nor 1 - or ( unused == NULL && nUnused != 0 ) - or ( unused != NULL && !(0 <= nUnused <= BZ_MAX_UNUSED) ) -BZ_IO_ERROR - if ferror(f) is nonzero -BZ_MEM_ERROR - if insufficient memory is available -BZ_OK - otherwise.</pre> -<p>Possible return values:</p> -<pre class="programlisting">Pointer to an abstract BZFILE - if bzerror is BZ_OK -NULL - otherwise</pre> -<p>Allowable next actions:</p> -<pre class="programlisting">BZ2_bzRead - if bzerror is BZ_OK -BZ2_bzClose - otherwise</pre> -</div> -<div class="sect2" title="3.4.2. BZ2_bzRead"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="bzread"></a>3.4.2. BZ2_bzRead</h3></div></div></div> -<pre class="programlisting">int BZ2_bzRead ( int *bzerror, BZFILE *b, void *buf, int len );</pre> -<p>Reads up to <code class="computeroutput">len</code> -(uncompressed) bytes from the compressed file -<code class="computeroutput">b</code> into the buffer -<code class="computeroutput">buf</code>. If the read was -successful, <code class="computeroutput">bzerror</code> is set to -<code class="computeroutput">BZ_OK</code> and the number of bytes -read is returned. If the logical end-of-stream was detected, -<code class="computeroutput">bzerror</code> will be set to -<code class="computeroutput">BZ_STREAM_END</code>, and the number of -bytes read is returned. All other -<code class="computeroutput">bzerror</code> values denote an -error.</p> -<p><code class="computeroutput">BZ2_bzRead</code> will supply -<code class="computeroutput">len</code> bytes, unless the logical -stream end is detected or an error occurs. Because of this, it -is possible to detect the stream end by observing when the number -of bytes returned is less than the number requested. -Nevertheless, this is regarded as inadvisable; you should instead -check <code class="computeroutput">bzerror</code> after every call -and watch out for -<code class="computeroutput">BZ_STREAM_END</code>.</p> -<p>Internally, <code class="computeroutput">BZ2_bzRead</code> -copies data from the compressed file in chunks of size -<code class="computeroutput">BZ_MAX_UNUSED</code> bytes before -decompressing it. If the file contains more bytes than strictly -needed to reach the logical end-of-stream, -<code class="computeroutput">BZ2_bzRead</code> will almost certainly -read some of the trailing data before signalling -<code class="computeroutput">BZ_SEQUENCE_END</code>. To collect the -read but unused data once -<code class="computeroutput">BZ_SEQUENCE_END</code> has appeared, -call <code class="computeroutput">BZ2_bzReadGetUnused</code> -immediately before -<code class="computeroutput">BZ2_bzReadClose</code>.</p> -<p>Possible assignments to -<code class="computeroutput">bzerror</code>:</p> -<pre class="programlisting">BZ_PARAM_ERROR - if b is NULL or buf is NULL or len < 0 -BZ_SEQUENCE_ERROR - if b was opened with BZ2_bzWriteOpen -BZ_IO_ERROR - if there is an error reading from the compressed file -BZ_UNEXPECTED_EOF - if the compressed file ended before - the logical end-of-stream was detected -BZ_DATA_ERROR - if a data integrity error was detected in the compressed stream -BZ_DATA_ERROR_MAGIC - if the stream does not begin with the requisite header bytes - (ie, is not a bzip2 data file). This is really - a special case of BZ_DATA_ERROR. -BZ_MEM_ERROR - if insufficient memory was available -BZ_STREAM_END - if the logical end of stream was detected. -BZ_OK - otherwise.</pre> -<p>Possible return values:</p> -<pre class="programlisting">number of bytes read - if bzerror is BZ_OK or BZ_STREAM_END -undefined - otherwise</pre> -<p>Allowable next actions:</p> -<pre class="programlisting">collect data from buf, then BZ2_bzRead or BZ2_bzReadClose - if bzerror is BZ_OK -collect data from buf, then BZ2_bzReadClose or BZ2_bzReadGetUnused - if bzerror is BZ_SEQUENCE_END -BZ2_bzReadClose - otherwise</pre> -</div> -<div class="sect2" title="3.4.3. BZ2_bzReadGetUnused"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="bzreadgetunused"></a>3.4.3. BZ2_bzReadGetUnused</h3></div></div></div> -<pre class="programlisting">void BZ2_bzReadGetUnused( int* bzerror, BZFILE *b, - void** unused, int* nUnused );</pre> -<p>Returns data which was read from the compressed file but -was not needed to get to the logical end-of-stream. -<code class="computeroutput">*unused</code> is set to the address of -the data, and <code class="computeroutput">*nUnused</code> to the -number of bytes. <code class="computeroutput">*nUnused</code> will -be set to a value between <code class="computeroutput">0</code> and -<code class="computeroutput">BZ_MAX_UNUSED</code> inclusive.</p> -<p>This function may only be called once -<code class="computeroutput">BZ2_bzRead</code> has signalled -<code class="computeroutput">BZ_STREAM_END</code> but before -<code class="computeroutput">BZ2_bzReadClose</code>.</p> -<p>Possible assignments to -<code class="computeroutput">bzerror</code>:</p> -<pre class="programlisting">BZ_PARAM_ERROR - if b is NULL - or unused is NULL or nUnused is NULL -BZ_SEQUENCE_ERROR - if BZ_STREAM_END has not been signalled - or if b was opened with BZ2_bzWriteOpen -BZ_OK - otherwise</pre> -<p>Allowable next actions:</p> -<pre class="programlisting">BZ2_bzReadClose</pre> -</div> -<div class="sect2" title="3.4.4. BZ2_bzReadClose"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="bzreadclose"></a>3.4.4. BZ2_bzReadClose</h3></div></div></div> -<pre class="programlisting">void BZ2_bzReadClose ( int *bzerror, BZFILE *b );</pre> -<p>Releases all memory pertaining to the compressed file -<code class="computeroutput">b</code>. -<code class="computeroutput">BZ2_bzReadClose</code> does not call -<code class="computeroutput">fclose</code> on the underlying file -handle, so you should do that yourself if appropriate. -<code class="computeroutput">BZ2_bzReadClose</code> should be called -to clean up after all error situations.</p> -<p>Possible assignments to -<code class="computeroutput">bzerror</code>:</p> -<pre class="programlisting">BZ_SEQUENCE_ERROR - if b was opened with BZ2_bzOpenWrite -BZ_OK - otherwise</pre> -<p>Allowable next actions:</p> -<pre class="programlisting">none</pre> -</div> -<div class="sect2" title="3.4.5. BZ2_bzWriteOpen"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="bzwriteopen"></a>3.4.5. BZ2_bzWriteOpen</h3></div></div></div> -<pre class="programlisting">BZFILE *BZ2_bzWriteOpen( int *bzerror, FILE *f, - int blockSize100k, int verbosity, - int workFactor );</pre> -<p>Prepare to write compressed data to file handle -<code class="computeroutput">f</code>. -<code class="computeroutput">f</code> should refer to a file which -has been opened for writing, and for which the error indicator -(<code class="computeroutput">ferror(f)</code>)is not set.</p> -<p>For the meaning of parameters -<code class="computeroutput">blockSize100k</code>, -<code class="computeroutput">verbosity</code> and -<code class="computeroutput">workFactor</code>, see -<code class="computeroutput">BZ2_bzCompressInit</code>.</p> -<p>All required memory is allocated at this stage, so if the -call completes successfully, -<code class="computeroutput">BZ_MEM_ERROR</code> cannot be signalled -by a subsequent call to -<code class="computeroutput">BZ2_bzWrite</code>.</p> -<p>Possible assignments to -<code class="computeroutput">bzerror</code>:</p> -<pre class="programlisting">BZ_CONFIG_ERROR - if the library has been mis-compiled -BZ_PARAM_ERROR - if f is NULL - or blockSize100k < 1 or blockSize100k > 9 -BZ_IO_ERROR - if ferror(f) is nonzero -BZ_MEM_ERROR - if insufficient memory is available -BZ_OK - otherwise</pre> -<p>Possible return values:</p> -<pre class="programlisting">Pointer to an abstract BZFILE - if bzerror is BZ_OK -NULL - otherwise</pre> -<p>Allowable next actions:</p> -<pre class="programlisting">BZ2_bzWrite - if bzerror is BZ_OK - (you could go directly to BZ2_bzWriteClose, but this would be pretty pointless) -BZ2_bzWriteClose - otherwise</pre> -</div> -<div class="sect2" title="3.4.6. BZ2_bzWrite"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="bzwrite"></a>3.4.6. BZ2_bzWrite</h3></div></div></div> -<pre class="programlisting">void BZ2_bzWrite ( int *bzerror, BZFILE *b, void *buf, int len );</pre> -<p>Absorbs <code class="computeroutput">len</code> bytes from the -buffer <code class="computeroutput">buf</code>, eventually to be -compressed and written to the file.</p> -<p>Possible assignments to -<code class="computeroutput">bzerror</code>:</p> -<pre class="programlisting">BZ_PARAM_ERROR - if b is NULL or buf is NULL or len < 0 -BZ_SEQUENCE_ERROR - if b was opened with BZ2_bzReadOpen -BZ_IO_ERROR - if there is an error writing the compressed file. -BZ_OK - otherwise</pre> -</div> -<div class="sect2" title="3.4.7. BZ2_bzWriteClose"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="bzwriteclose"></a>3.4.7. BZ2_bzWriteClose</h3></div></div></div> -<pre class="programlisting">void BZ2_bzWriteClose( int *bzerror, BZFILE* f, - int abandon, - unsigned int* nbytes_in, - unsigned int* nbytes_out ); - -void BZ2_bzWriteClose64( int *bzerror, BZFILE* f, - int abandon, - unsigned int* nbytes_in_lo32, - unsigned int* nbytes_in_hi32, - unsigned int* nbytes_out_lo32, - unsigned int* nbytes_out_hi32 );</pre> -<p>Compresses and flushes to the compressed file all data so -far supplied by <code class="computeroutput">BZ2_bzWrite</code>. -The logical end-of-stream markers are also written, so subsequent -calls to <code class="computeroutput">BZ2_bzWrite</code> are -illegal. All memory associated with the compressed file -<code class="computeroutput">b</code> is released. -<code class="computeroutput">fflush</code> is called on the -compressed file, but it is not -<code class="computeroutput">fclose</code>'d.</p> -<p>If <code class="computeroutput">BZ2_bzWriteClose</code> is -called to clean up after an error, the only action is to release -the memory. The library records the error codes issued by -previous calls, so this situation will be detected automatically. -There is no attempt to complete the compression operation, nor to -<code class="computeroutput">fflush</code> the compressed file. You -can force this behaviour to happen even in the case of no error, -by passing a nonzero value to -<code class="computeroutput">abandon</code>.</p> -<p>If <code class="computeroutput">nbytes_in</code> is non-null, -<code class="computeroutput">*nbytes_in</code> will be set to be the -total volume of uncompressed data handled. Similarly, -<code class="computeroutput">nbytes_out</code> will be set to the -total volume of compressed data written. For compatibility with -older versions of the library, -<code class="computeroutput">BZ2_bzWriteClose</code> only yields the -lower 32 bits of these counts. Use -<code class="computeroutput">BZ2_bzWriteClose64</code> if you want -the full 64 bit counts. These two functions are otherwise -absolutely identical.</p> -<p>Possible assignments to -<code class="computeroutput">bzerror</code>:</p> -<pre class="programlisting">BZ_SEQUENCE_ERROR - if b was opened with BZ2_bzReadOpen -BZ_IO_ERROR - if there is an error writing the compressed file -BZ_OK - otherwise</pre> -</div> -<div class="sect2" title="3.4.8. Handling embedded compressed data streams"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="embed"></a>3.4.8. Handling embedded compressed data streams</h3></div></div></div> -<p>The high-level library facilitates use of -<code class="computeroutput">bzip2</code> data streams which form -some part of a surrounding, larger data stream.</p> -<div class="itemizedlist"><ul class="itemizedlist" type="bullet"> -<li class="listitem" style="list-style-type: disc"><p>For writing, the library takes an open file handle, - writes compressed data to it, - <code class="computeroutput">fflush</code>es it but does not - <code class="computeroutput">fclose</code> it. The calling - application can write its own data before and after the - compressed data stream, using that same file handle.</p></li> -<li class="listitem" style="list-style-type: disc"><p>Reading is more complex, and the facilities are not as - general as they could be since generality is hard to reconcile - with efficiency. <code class="computeroutput">BZ2_bzRead</code> - reads from the compressed file in blocks of size - <code class="computeroutput">BZ_MAX_UNUSED</code> bytes, and in - doing so probably will overshoot the logical end of compressed - stream. To recover this data once decompression has ended, - call <code class="computeroutput">BZ2_bzReadGetUnused</code> after - the last call of <code class="computeroutput">BZ2_bzRead</code> - (the one returning - <code class="computeroutput">BZ_STREAM_END</code>) but before - calling - <code class="computeroutput">BZ2_bzReadClose</code>.</p></li> -</ul></div> -<p>This mechanism makes it easy to decompress multiple -<code class="computeroutput">bzip2</code> streams placed end-to-end. -As the end of one stream, when -<code class="computeroutput">BZ2_bzRead</code> returns -<code class="computeroutput">BZ_STREAM_END</code>, call -<code class="computeroutput">BZ2_bzReadGetUnused</code> to collect -the unused data (copy it into your own buffer somewhere). That -data forms the start of the next compressed stream. To start -uncompressing that next stream, call -<code class="computeroutput">BZ2_bzReadOpen</code> again, feeding in -the unused data via the <code class="computeroutput">unused</code> / -<code class="computeroutput">nUnused</code> parameters. Keep doing -this until <code class="computeroutput">BZ_STREAM_END</code> return -coincides with the physical end of file -(<code class="computeroutput">feof(f)</code>). In this situation -<code class="computeroutput">BZ2_bzReadGetUnused</code> will of -course return no data.</p> -<p>This should give some feel for how the high-level interface -can be used. If you require extra flexibility, you'll have to -bite the bullet and get to grips with the low-level -interface.</p> -</div> -<div class="sect2" title="3.4.9. Standard file-reading/writing code"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="std-rdwr"></a>3.4.9. Standard file-reading/writing code</h3></div></div></div> -<p>Here's how you'd write data to a compressed file:</p> -<pre class="programlisting">FILE* f; -BZFILE* b; -int nBuf; -char buf[ /* whatever size you like */ ]; -int bzerror; -int nWritten; - -f = fopen ( "myfile.bz2", "w" ); -if ( !f ) { - /* handle error */ -} -b = BZ2_bzWriteOpen( &bzerror, f, 9 ); -if (bzerror != BZ_OK) { - BZ2_bzWriteClose ( b ); - /* handle error */ -} - -while ( /* condition */ ) { - /* get data to write into buf, and set nBuf appropriately */ - nWritten = BZ2_bzWrite ( &bzerror, b, buf, nBuf ); - if (bzerror == BZ_IO_ERROR) { - BZ2_bzWriteClose ( &bzerror, b ); - /* handle error */ - } -} - -BZ2_bzWriteClose( &bzerror, b ); -if (bzerror == BZ_IO_ERROR) { - /* handle error */ -}</pre> -<p>And to read from a compressed file:</p> -<pre class="programlisting">FILE* f; -BZFILE* b; -int nBuf; -char buf[ /* whatever size you like */ ]; -int bzerror; -int nWritten; - -f = fopen ( "myfile.bz2", "r" ); -if ( !f ) { - /* handle error */ -} -b = BZ2_bzReadOpen ( &bzerror, f, 0, NULL, 0 ); -if ( bzerror != BZ_OK ) { - BZ2_bzReadClose ( &bzerror, b ); - /* handle error */ -} - -bzerror = BZ_OK; -while ( bzerror == BZ_OK && /* arbitrary other conditions */) { - nBuf = BZ2_bzRead ( &bzerror, b, buf, /* size of buf */ ); - if ( bzerror == BZ_OK ) { - /* do something with buf[0 .. nBuf-1] */ - } -} -if ( bzerror != BZ_STREAM_END ) { - BZ2_bzReadClose ( &bzerror, b ); - /* handle error */ -} else { - BZ2_bzReadClose ( &bzerror, b ); -}</pre> -</div> -</div> -<div class="sect1" title="3.5. Utility functions"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="util-fns"></a>3.5. Utility functions</h2></div></div></div> -<div class="sect2" title="3.5.1. BZ2_bzBuffToBuffCompress"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="bzbufftobuffcompress"></a>3.5.1. BZ2_bzBuffToBuffCompress</h3></div></div></div> -<pre class="programlisting">int BZ2_bzBuffToBuffCompress( char* dest, - unsigned int* destLen, - char* source, - unsigned int sourceLen, - int blockSize100k, - int verbosity, - int workFactor );</pre> -<p>Attempts to compress the data in <code class="computeroutput">source[0 -.. sourceLen-1]</code> into the destination buffer, -<code class="computeroutput">dest[0 .. *destLen-1]</code>. If the -destination buffer is big enough, -<code class="computeroutput">*destLen</code> is set to the size of -the compressed data, and <code class="computeroutput">BZ_OK</code> -is returned. If the compressed data won't fit, -<code class="computeroutput">*destLen</code> is unchanged, and -<code class="computeroutput">BZ_OUTBUFF_FULL</code> is -returned.</p> -<p>Compression in this manner is a one-shot event, done with a -single call to this function. The resulting compressed data is a -complete <code class="computeroutput">bzip2</code> format data -stream. There is no mechanism for making additional calls to -provide extra input data. If you want that kind of mechanism, -use the low-level interface.</p> -<p>For the meaning of parameters -<code class="computeroutput">blockSize100k</code>, -<code class="computeroutput">verbosity</code> and -<code class="computeroutput">workFactor</code>, see -<code class="computeroutput">BZ2_bzCompressInit</code>.</p> -<p>To guarantee that the compressed data will fit in its -buffer, allocate an output buffer of size 1% larger than the -uncompressed data, plus six hundred extra bytes.</p> -<p><code class="computeroutput">BZ2_bzBuffToBuffDecompress</code> -will not write data at or beyond -<code class="computeroutput">dest[*destLen]</code>, even in case of -buffer overflow.</p> -<p>Possible return values:</p> -<pre class="programlisting">BZ_CONFIG_ERROR - if the library has been mis-compiled -BZ_PARAM_ERROR - if dest is NULL or destLen is NULL - or blockSize100k < 1 or blockSize100k > 9 - or verbosity < 0 or verbosity > 4 - or workFactor < 0 or workFactor > 250 -BZ_MEM_ERROR - if insufficient memory is available -BZ_OUTBUFF_FULL - if the size of the compressed data exceeds *destLen -BZ_OK - otherwise</pre> -</div> -<div class="sect2" title="3.5.2. BZ2_bzBuffToBuffDecompress"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="bzbufftobuffdecompress"></a>3.5.2. BZ2_bzBuffToBuffDecompress</h3></div></div></div> -<pre class="programlisting">int BZ2_bzBuffToBuffDecompress( char* dest, - unsigned int* destLen, - char* source, - unsigned int sourceLen, - int small, - int verbosity );</pre> -<p>Attempts to decompress the data in <code class="computeroutput">source[0 -.. sourceLen-1]</code> into the destination buffer, -<code class="computeroutput">dest[0 .. *destLen-1]</code>. If the -destination buffer is big enough, -<code class="computeroutput">*destLen</code> is set to the size of -the uncompressed data, and <code class="computeroutput">BZ_OK</code> -is returned. If the compressed data won't fit, -<code class="computeroutput">*destLen</code> is unchanged, and -<code class="computeroutput">BZ_OUTBUFF_FULL</code> is -returned.</p> -<p><code class="computeroutput">source</code> is assumed to hold -a complete <code class="computeroutput">bzip2</code> format data -stream. -<code class="computeroutput">BZ2_bzBuffToBuffDecompress</code> tries -to decompress the entirety of the stream into the output -buffer.</p> -<p>For the meaning of parameters -<code class="computeroutput">small</code> and -<code class="computeroutput">verbosity</code>, see -<code class="computeroutput">BZ2_bzDecompressInit</code>.</p> -<p>Because the compression ratio of the compressed data cannot -be known in advance, there is no easy way to guarantee that the -output buffer will be big enough. You may of course make -arrangements in your code to record the size of the uncompressed -data, but such a mechanism is beyond the scope of this -library.</p> -<p><code class="computeroutput">BZ2_bzBuffToBuffDecompress</code> -will not write data at or beyond -<code class="computeroutput">dest[*destLen]</code>, even in case of -buffer overflow.</p> -<p>Possible return values:</p> -<pre class="programlisting">BZ_CONFIG_ERROR - if the library has been mis-compiled -BZ_PARAM_ERROR - if dest is NULL or destLen is NULL - or small != 0 && small != 1 - or verbosity < 0 or verbosity > 4 -BZ_MEM_ERROR - if insufficient memory is available -BZ_OUTBUFF_FULL - if the size of the compressed data exceeds *destLen -BZ_DATA_ERROR - if a data integrity error was detected in the compressed data -BZ_DATA_ERROR_MAGIC - if the compressed data doesn't begin with the right magic bytes -BZ_UNEXPECTED_EOF - if the compressed data ends unexpectedly -BZ_OK - otherwise</pre> -</div> -</div> -<div class="sect1" title="3.6. zlib compatibility functions"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="zlib-compat"></a>3.6. zlib compatibility functions</h2></div></div></div> -<p>Yoshioka Tsuneo has contributed some functions to give -better <code class="computeroutput">zlib</code> compatibility. -These functions are <code class="computeroutput">BZ2_bzopen</code>, -<code class="computeroutput">BZ2_bzread</code>, -<code class="computeroutput">BZ2_bzwrite</code>, -<code class="computeroutput">BZ2_bzflush</code>, -<code class="computeroutput">BZ2_bzclose</code>, -<code class="computeroutput">BZ2_bzerror</code> and -<code class="computeroutput">BZ2_bzlibVersion</code>. These -functions are not (yet) officially part of the library. If they -break, you get to keep all the pieces. Nevertheless, I think -they work ok.</p> -<pre class="programlisting">typedef void BZFILE; - -const char * BZ2_bzlibVersion ( void );</pre> -<p>Returns a string indicating the library version.</p> -<pre class="programlisting">BZFILE * BZ2_bzopen ( const char *path, const char *mode ); -BZFILE * BZ2_bzdopen ( int fd, const char *mode );</pre> -<p>Opens a <code class="computeroutput">.bz2</code> file for -reading or writing, using either its name or a pre-existing file -descriptor. Analogous to <code class="computeroutput">fopen</code> -and <code class="computeroutput">fdopen</code>.</p> -<pre class="programlisting">int BZ2_bzread ( BZFILE* b, void* buf, int len ); -int BZ2_bzwrite ( BZFILE* b, void* buf, int len );</pre> -<p>Reads/writes data from/to a previously opened -<code class="computeroutput">BZFILE</code>. Analogous to -<code class="computeroutput">fread</code> and -<code class="computeroutput">fwrite</code>.</p> -<pre class="programlisting">int BZ2_bzflush ( BZFILE* b ); -void BZ2_bzclose ( BZFILE* b );</pre> -<p>Flushes/closes a <code class="computeroutput">BZFILE</code>. -<code class="computeroutput">BZ2_bzflush</code> doesn't actually do -anything. Analogous to <code class="computeroutput">fflush</code> -and <code class="computeroutput">fclose</code>.</p> -<pre class="programlisting">const char * BZ2_bzerror ( BZFILE *b, int *errnum )</pre> -<p>Returns a string describing the more recent error status of -<code class="computeroutput">b</code>, and also sets -<code class="computeroutput">*errnum</code> to its numerical -value.</p> -</div> -<div class="sect1" title="3.7. Using the library in a stdio-free environment"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="stdio-free"></a>3.7. Using the library in a stdio-free environment</h2></div></div></div> -<div class="sect2" title="3.7.1. Getting rid of stdio"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="stdio-bye"></a>3.7.1. Getting rid of stdio</h3></div></div></div> -<p>In a deeply embedded application, you might want to use -just the memory-to-memory functions. You can do this -conveniently by compiling the library with preprocessor symbol -<code class="computeroutput">BZ_NO_STDIO</code> defined. Doing this -gives you a library containing only the following eight -functions:</p> -<p><code class="computeroutput">BZ2_bzCompressInit</code>, -<code class="computeroutput">BZ2_bzCompress</code>, -<code class="computeroutput">BZ2_bzCompressEnd</code> -<code class="computeroutput">BZ2_bzDecompressInit</code>, -<code class="computeroutput">BZ2_bzDecompress</code>, -<code class="computeroutput">BZ2_bzDecompressEnd</code> -<code class="computeroutput">BZ2_bzBuffToBuffCompress</code>, -<code class="computeroutput">BZ2_bzBuffToBuffDecompress</code></p> -<p>When compiled like this, all functions will ignore -<code class="computeroutput">verbosity</code> settings.</p> -</div> -<div class="sect2" title="3.7.2. Critical error handling"> -<div class="titlepage"><div><div><h3 class="title"> -<a name="critical-error"></a>3.7.2. Critical error handling</h3></div></div></div> -<p><code class="computeroutput">libbzip2</code> contains a number -of internal assertion checks which should, needless to say, never -be activated. Nevertheless, if an assertion should fail, -behaviour depends on whether or not the library was compiled with -<code class="computeroutput">BZ_NO_STDIO</code> set.</p> -<p>For a normal compile, an assertion failure yields the -message:</p> -<div class="blockquote"><blockquote class="blockquote"> -<p>bzip2/libbzip2: internal error number N.</p> -<p>This is a bug in bzip2/libbzip2, 1.0.6 of 6 September 2010. -Please report it to me at: jseward@bzip.org. If this happened -when you were using some program which uses libbzip2 as a -component, you should also report this bug to the author(s) -of that program. Please make an effort to report this bug; -timely and accurate bug reports eventually lead to higher -quality software. Thanks. Julian Seward, 6 September 2010. -</p> -</blockquote></div> -<p>where <code class="computeroutput">N</code> is some error code -number. If <code class="computeroutput">N == 1007</code>, it also -prints some extra text advising the reader that unreliable memory -is often associated with internal error 1007. (This is a -frequently-observed-phenomenon with versions 1.0.0/1.0.1).</p> -<p><code class="computeroutput">exit(3)</code> is then -called.</p> -<p>For a <code class="computeroutput">stdio</code>-free library, -assertion failures result in a call to a function declared -as:</p> -<pre class="programlisting">extern void bz_internal_error ( int errcode );</pre> -<p>The relevant code is passed as a parameter. You should -supply such a function.</p> -<p>In either case, once an assertion failure has occurred, any -<code class="computeroutput">bz_stream</code> records involved can -be regarded as invalid. You should not attempt to resume normal -operation with them.</p> -<p>You may, of course, change critical error handling to suit -your needs. As I said above, critical errors indicate bugs in -the library and should not occur. All "normal" error situations -are indicated via error return codes from functions, and can be -recovered from.</p> -</div> -</div> -<div class="sect1" title="3.8. Making a Windows DLL"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="win-dll"></a>3.8. Making a Windows DLL</h2></div></div></div> -<p>Everything related to Windows has been contributed by -Yoshioka Tsuneo -(<code class="computeroutput">tsuneo@rr.iij4u.or.jp</code>), so -you should send your queries to him (but perhaps Cc: me, -<code class="computeroutput">jseward@bzip.org</code>).</p> -<p>My vague understanding of what to do is: using Visual C++ -5.0, open the project file -<code class="computeroutput">libbz2.dsp</code>, and build. That's -all.</p> -<p>If you can't open the project file for some reason, make a -new one, naming these files: -<code class="computeroutput">blocksort.c</code>, -<code class="computeroutput">bzlib.c</code>, -<code class="computeroutput">compress.c</code>, -<code class="computeroutput">crctable.c</code>, -<code class="computeroutput">decompress.c</code>, -<code class="computeroutput">huffman.c</code>, -<code class="computeroutput">randtable.c</code> and -<code class="computeroutput">libbz2.def</code>. You will also need -to name the header files <code class="computeroutput">bzlib.h</code> -and <code class="computeroutput">bzlib_private.h</code>.</p> -<p>If you don't use VC++, you may need to define the -proprocessor symbol -<code class="computeroutput">_WIN32</code>.</p> -<p>Finally, <code class="computeroutput">dlltest.c</code> is a -sample program using the DLL. It has a project file, -<code class="computeroutput">dlltest.dsp</code>.</p> -<p>If you just want a makefile for Visual C, have a look at -<code class="computeroutput">makefile.msc</code>.</p> -<p>Be aware that if you compile -<code class="computeroutput">bzip2</code> itself on Win32, you must -set <code class="computeroutput">BZ_UNIX</code> to 0 and -<code class="computeroutput">BZ_LCCWIN32</code> to 1, in the file -<code class="computeroutput">bzip2.c</code>, before compiling. -Otherwise the resulting binary won't work correctly.</p> -<p>I haven't tried any of this stuff myself, but it all looks -plausible.</p> -</div> -</div> -<div class="chapter" title="4. Miscellanea"> -<div class="titlepage"><div><div><h2 class="title"> -<a name="misc"></a>4. Miscellanea</h2></div></div></div> -<div class="toc"> -<p><b>Table of Contents</b></p> -<dl> -<dt><span class="sect1"><a href="#limits">4.1. Limitations of the compressed file format</a></span></dt> -<dt><span class="sect1"><a href="#port-issues">4.2. Portability issues</a></span></dt> -<dt><span class="sect1"><a href="#bugs">4.3. Reporting bugs</a></span></dt> -<dt><span class="sect1"><a href="#package">4.4. Did you get the right package?</a></span></dt> -<dt><span class="sect1"><a href="#reading">4.5. Further Reading</a></span></dt> -</dl> -</div> -<p>These are just some random thoughts of mine. Your mileage -may vary.</p> -<div class="sect1" title="4.1. Limitations of the compressed file format"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="limits"></a>4.1. Limitations of the compressed file format</h2></div></div></div> -<p><code class="computeroutput">bzip2-1.0.X</code>, -<code class="computeroutput">0.9.5</code> and -<code class="computeroutput">0.9.0</code> use exactly the same file -format as the original version, -<code class="computeroutput">bzip2-0.1</code>. This decision was -made in the interests of stability. Creating yet another -incompatible compressed file format would create further -confusion and disruption for users.</p> -<p>Nevertheless, this is not a painless decision. Development -work since the release of -<code class="computeroutput">bzip2-0.1</code> in August 1997 has -shown complexities in the file format which slow down -decompression and, in retrospect, are unnecessary. These -are:</p> -<div class="itemizedlist"><ul class="itemizedlist" type="bullet"> -<li class="listitem" style="list-style-type: disc"><p>The run-length encoder, which is the first of the - compression transformations, is entirely irrelevant. The - original purpose was to protect the sorting algorithm from the - very worst case input: a string of repeated symbols. But - algorithm steps Q6a and Q6b in the original Burrows-Wheeler - technical report (SRC-124) show how repeats can be handled - without difficulty in block sorting.</p></li> -<li class="listitem" style="list-style-type: disc"> -<p>The randomisation mechanism doesn't really need to be - there. Udi Manber and Gene Myers published a suffix array - construction algorithm a few years back, which can be employed - to sort any block, no matter how repetitive, in O(N log N) - time. Subsequent work by Kunihiko Sadakane has produced a - derivative O(N (log N)^2) algorithm which usually outperforms - the Manber-Myers algorithm.</p> -<p>I could have changed to Sadakane's algorithm, but I find - it to be slower than <code class="computeroutput">bzip2</code>'s - existing algorithm for most inputs, and the randomisation - mechanism protects adequately against bad cases. I didn't - think it was a good tradeoff to make. Partly this is due to - the fact that I was not flooded with email complaints about - <code class="computeroutput">bzip2-0.1</code>'s performance on - repetitive data, so perhaps it isn't a problem for real - inputs.</p> -<p>Probably the best long-term solution, and the one I have - incorporated into 0.9.5 and above, is to use the existing - sorting algorithm initially, and fall back to a O(N (log N)^2) - algorithm if the standard algorithm gets into - difficulties.</p> -</li> -<li class="listitem" style="list-style-type: disc"><p>The compressed file format was never designed to be - handled by a library, and I have had to jump though some hoops - to produce an efficient implementation of decompression. It's - a bit hairy. Try passing - <code class="computeroutput">decompress.c</code> through the C - preprocessor and you'll see what I mean. Much of this - complexity could have been avoided if the compressed size of - each block of data was recorded in the data stream.</p></li> -<li class="listitem" style="list-style-type: disc"><p>An Adler-32 checksum, rather than a CRC32 checksum, - would be faster to compute.</p></li> -</ul></div> -<p>It would be fair to say that the -<code class="computeroutput">bzip2</code> format was frozen before I -properly and fully understood the performance consequences of -doing so.</p> -<p>Improvements which I was able to incorporate into 0.9.0, -despite using the same file format, are:</p> -<div class="itemizedlist"><ul class="itemizedlist" type="bullet"> -<li class="listitem" style="list-style-type: disc"><p>Single array implementation of the inverse BWT. This - significantly speeds up decompression, presumably because it - reduces the number of cache misses.</p></li> -<li class="listitem" style="list-style-type: disc"><p>Faster inverse MTF transform for large MTF values. - The new implementation is based on the notion of sliding blocks - of values.</p></li> -<li class="listitem" style="list-style-type: disc"><p><code class="computeroutput">bzip2-0.9.0</code> now reads - and writes files with <code class="computeroutput">fread</code> - and <code class="computeroutput">fwrite</code>; version 0.1 used - <code class="computeroutput">putc</code> and - <code class="computeroutput">getc</code>. Duh! Well, you live - and learn.</p></li> -</ul></div> -<p>Further ahead, it would be nice to be able to do random -access into files. This will require some careful design of -compressed file formats.</p> -</div> -<div class="sect1" title="4.2. Portability issues"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="port-issues"></a>4.2. Portability issues</h2></div></div></div> -<p>After some consideration, I have decided not to use GNU -<code class="computeroutput">autoconf</code> to configure 0.9.5 or -1.0.</p> -<p><code class="computeroutput">autoconf</code>, admirable and -wonderful though it is, mainly assists with portability problems -between Unix-like platforms. But -<code class="computeroutput">bzip2</code> doesn't have much in the -way of portability problems on Unix; most of the difficulties -appear when porting to the Mac, or to Microsoft's operating -systems. <code class="computeroutput">autoconf</code> doesn't help -in those cases, and brings in a whole load of new -complexity.</p> -<p>Most people should be able to compile the library and -program under Unix straight out-of-the-box, so to speak, -especially if you have a version of GNU C available.</p> -<p>There are a couple of -<code class="computeroutput">__inline__</code> directives in the -code. GNU C (<code class="computeroutput">gcc</code>) should be -able to handle them. If you're not using GNU C, your C compiler -shouldn't see them at all. If your compiler does, for some -reason, see them and doesn't like them, just -<code class="computeroutput">#define</code> -<code class="computeroutput">__inline__</code> to be -<code class="computeroutput">/* */</code>. One easy way to do this -is to compile with the flag -<code class="computeroutput">-D__inline__=</code>, which should be -understood by most Unix compilers.</p> -<p>If you still have difficulties, try compiling with the -macro <code class="computeroutput">BZ_STRICT_ANSI</code> defined. -This should enable you to build the library in a strictly ANSI -compliant environment. Building the program itself like this is -dangerous and not supported, since you remove -<code class="computeroutput">bzip2</code>'s checks against -compressing directories, symbolic links, devices, and other -not-really-a-file entities. This could cause filesystem -corruption!</p> -<p>One other thing: if you create a -<code class="computeroutput">bzip2</code> binary for public distribution, -please consider linking it statically (<code class="computeroutput">gcc --static</code>). This avoids all sorts of library-version -issues that others may encounter later on.</p> -<p>If you build <code class="computeroutput">bzip2</code> on -Win32, you must set <code class="computeroutput">BZ_UNIX</code> to 0 -and <code class="computeroutput">BZ_LCCWIN32</code> to 1, in the -file <code class="computeroutput">bzip2.c</code>, before compiling. -Otherwise the resulting binary won't work correctly.</p> -</div> -<div class="sect1" title="4.3. Reporting bugs"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="bugs"></a>4.3. Reporting bugs</h2></div></div></div> -<p>I tried pretty hard to make sure -<code class="computeroutput">bzip2</code> is bug free, both by -design and by testing. Hopefully you'll never need to read this -section for real.</p> -<p>Nevertheless, if <code class="computeroutput">bzip2</code> dies -with a segmentation fault, a bus error or an internal assertion -failure, it will ask you to email me a bug report. Experience from -years of feedback of bzip2 users indicates that almost all these -problems can be traced to either compiler bugs or hardware -problems.</p> -<div class="itemizedlist"><ul class="itemizedlist" type="bullet"> -<li class="listitem" style="list-style-type: disc"> -<p>Recompile the program with no optimisation, and - see if it works. And/or try a different compiler. I heard all - sorts of stories about various flavours of GNU C (and other - compilers) generating bad code for - <code class="computeroutput">bzip2</code>, and I've run across two - such examples myself.</p> -<p>2.7.X versions of GNU C are known to generate bad code - from time to time, at high optimisation levels. If you get - problems, try using the flags - <code class="computeroutput">-O2</code> - <code class="computeroutput">-fomit-frame-pointer</code> - <code class="computeroutput">-fno-strength-reduce</code>. You - should specifically <span class="emphasis"><em>not</em></span> use - <code class="computeroutput">-funroll-loops</code>.</p> -<p>You may notice that the Makefile runs six tests as part - of the build process. If the program passes all of these, it's - a pretty good (but not 100%) indication that the compiler has - done its job correctly.</p> -</li> -<li class="listitem" style="list-style-type: disc"> -<p>If <code class="computeroutput">bzip2</code> - crashes randomly, and the crashes are not repeatable, you may - have a flaky memory subsystem. - <code class="computeroutput">bzip2</code> really hammers your - memory hierarchy, and if it's a bit marginal, you may get these - problems. Ditto if your disk or I/O subsystem is slowly - failing. Yup, this really does happen.</p> -<p>Try using a different machine of the same type, and see - if you can repeat the problem.</p> -</li> -<li class="listitem" style="list-style-type: disc"><p>This isn't really a bug, but ... If - <code class="computeroutput">bzip2</code> tells you your file is - corrupted on decompression, and you obtained the file via FTP, - there is a possibility that you forgot to tell FTP to do a - binary mode transfer. That absolutely will cause the file to - be non-decompressible. You'll have to transfer it - again.</p></li> -</ul></div> -<p>If you've incorporated -<code class="computeroutput">libbzip2</code> into your own program -and are getting problems, please, please, please, check that the -parameters you are passing in calls to the library, are correct, -and in accordance with what the documentation says is allowable. -I have tried to make the library robust against such problems, -but I'm sure I haven't succeeded.</p> -<p>Finally, if the above comments don't help, you'll have to -send me a bug report. Now, it's just amazing how many people -will send me a bug report saying something like:</p> -<pre class="programlisting">bzip2 crashed with segmentation fault on my machine</pre> -<p>and absolutely nothing else. Needless to say, a such a -report is <span class="emphasis"><em>totally, utterly, completely and -comprehensively 100% useless; a waste of your time, my time, and -net bandwidth</em></span>. With no details at all, there's no way -I can possibly begin to figure out what the problem is.</p> -<p>The rules of the game are: facts, facts, facts. Don't omit -them because "oh, they won't be relevant". At the bare -minimum:</p> -<pre class="programlisting">Machine type. Operating system version. -Exact version of bzip2 (do bzip2 -V). -Exact version of the compiler used. -Flags passed to the compiler.</pre> -<p>However, the most important single thing that will help me -is the file that you were trying to compress or decompress at the -time the problem happened. Without that, my ability to do -anything more than speculate about the cause, is limited.</p> -</div> -<div class="sect1" title="4.4. Did you get the right package?"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="package"></a>4.4. Did you get the right package?</h2></div></div></div> -<p><code class="computeroutput">bzip2</code> is a resource hog. -It soaks up large amounts of CPU cycles and memory. Also, it -gives very large latencies. In the worst case, you can feed many -megabytes of uncompressed data into the library before getting -any compressed output, so this probably rules out applications -requiring interactive behaviour.</p> -<p>These aren't faults of my implementation, I hope, but more -an intrinsic property of the Burrows-Wheeler transform -(unfortunately). Maybe this isn't what you want.</p> -<p>If you want a compressor and/or library which is faster, -uses less memory but gets pretty good compression, and has -minimal latency, consider Jean-loup Gailly's and Mark Adler's -work, <code class="computeroutput">zlib-1.2.1</code> and -<code class="computeroutput">gzip-1.2.4</code>. Look for them at -<a class="ulink" href="http://www.zlib.org" target="_top">http://www.zlib.org</a> and -<a class="ulink" href="http://www.gzip.org" target="_top">http://www.gzip.org</a> -respectively.</p> -<p>For something faster and lighter still, you might try Markus F -X J Oberhumer's <code class="computeroutput">LZO</code> real-time -compression/decompression library, at -<a class="ulink" href="http://www.oberhumer.com/opensource" target="_top">http://www.oberhumer.com/opensource</a>.</p> -</div> -<div class="sect1" title="4.5. Further Reading"> -<div class="titlepage"><div><div><h2 class="title" style="clear: both"> -<a name="reading"></a>4.5. Further Reading</h2></div></div></div> -<p><code class="computeroutput">bzip2</code> is not research -work, in the sense that it doesn't present any new ideas. -Rather, it's an engineering exercise based on existing -ideas.</p> -<p>Four documents describe essentially all the ideas behind -<code class="computeroutput">bzip2</code>:</p> -<div class="literallayout"><p>Michael Burrows and D. J. Wheeler:<br> - "A block-sorting lossless data compression algorithm"<br> - 10th May 1994. <br> - Digital SRC Research Report 124.<br> - ftp://ftp.digital.com/pub/DEC/SRC/research-reports/SRC-124.ps.gz<br> - If you have trouble finding it, try searching at the<br> - New Zealand Digital Library, http://www.nzdl.org.<br> -<br> -Daniel S. Hirschberg and Debra A. LeLewer<br> - "Efficient Decoding of Prefix Codes"<br> - Communications of the ACM, April 1990, Vol 33, Number 4.<br> - You might be able to get an electronic copy of this<br> - from the ACM Digital Library.<br> -<br> -David J. Wheeler<br> - Program bred3.c and accompanying document bred3.ps.<br> - This contains the idea behind the multi-table Huffman coding scheme.<br> - ftp://ftp.cl.cam.ac.uk/users/djw3/<br> -<br> -Jon L. Bentley and Robert Sedgewick<br> - "Fast Algorithms for Sorting and Searching Strings"<br> - Available from Sedgewick's web page,<br> - www.cs.princeton.edu/~rs<br> -</p></div> -<p>The following paper gives valuable additional insights into -the algorithm, but is not immediately the basis of any code used -in bzip2.</p> -<div class="literallayout"><p>Peter Fenwick:<br> - Block Sorting Text Compression<br> - Proceedings of the 19th Australasian Computer Science Conference,<br> - Melbourne, Australia. Jan 31 - Feb 2, 1996.<br> - ftp://ftp.cs.auckland.ac.nz/pub/peter-f/ACSC96paper.ps</p></div> -<p>Kunihiko Sadakane's sorting algorithm, mentioned above, is -available from:</p> -<div class="literallayout"><p>http://naomi.is.s.u-tokyo.ac.jp/~sada/papers/Sada98b.ps.gz<br> -</p></div> -<p>The Manber-Myers suffix array construction algorithm is -described in a paper available from:</p> -<div class="literallayout"><p>http://www.cs.arizona.edu/people/gene/PAPERS/suffix.ps<br> -</p></div> -<p>Finally, the following papers document some -investigations I made into the performance of sorting -and decompression algorithms:</p> -<div class="literallayout"><p>Julian Seward<br> - On the Performance of BWT Sorting Algorithms<br> - Proceedings of the IEEE Data Compression Conference 2000<br> - Snowbird, Utah. 28-30 March 2000.<br> -<br> -Julian Seward<br> - Space-time Tradeoffs in the Inverse B-W Transform<br> - Proceedings of the IEEE Data Compression Conference 2001<br> - Snowbird, Utah. 27-29 March 2001.<br> -</p></div> -</div> -</div> -</div></body> -</html> |