+++ /dev/null
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-<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
- "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"[
-
-<!-- various strings, dates etc. common to all docs -->
-<!ENTITY % common-ents SYSTEM "entities.xml"> %common-ents;
-]>
-
-<book lang="en" id="userman" xreflabel="bzip2 Manual">
-
- <bookinfo>
- <title>bzip2 and libbzip2, version 1.0.6</title>
- <subtitle>A program and library for data compression</subtitle>
- <copyright>
- <year>&bz-lifespan;</year>
- <holder>Julian Seward</holder>
- </copyright>
- <releaseinfo>Version &bz-version; of &bz-date;</releaseinfo>
-
- <authorgroup>
- <author>
- <firstname>Julian</firstname>
- <surname>Seward</surname>
- <affiliation>
- <orgname>&bz-url;</orgname>
- </affiliation>
- </author>
- </authorgroup>
-
- <legalnotice>
-
- <para>This program, <computeroutput>bzip2</computeroutput>, the
- associated library <computeroutput>libbzip2</computeroutput>, and
- all documentation, are copyright © &bz-lifespan; Julian Seward.
- All rights reserved.</para>
-
- <para>Redistribution and use in source and binary forms, with
- or without modification, are permitted provided that the
- following conditions are met:</para>
-
- <itemizedlist mark='bullet'>
-
- <listitem><para>Redistributions of source code must retain the
- above copyright notice, this list of conditions and the
- following disclaimer.</para></listitem>
-
- <listitem><para>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.</para></listitem>
-
- <listitem><para>Altered source versions must be plainly marked
- as such, and must not be misrepresented as being the original
- software.</para></listitem>
-
- <listitem><para>The name of the author may not be used to
- endorse or promote products derived from this software without
- specific prior written permission.</para></listitem>
-
- </itemizedlist>
-
- <para>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.</para>
-
- <para>PATENTS: To the best of my knowledge,
- <computeroutput>bzip2</computeroutput> and
- <computeroutput>libbzip2</computeroutput> 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.
- </para>
-
-</legalnotice>
-
-</bookinfo>
-
-
-
-<chapter id="intro" xreflabel="Introduction">
-<title>Introduction</title>
-
-<para><computeroutput>bzip2</computeroutput> 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.</para>
-
-<para><computeroutput>bzip2</computeroutput> is built on top of
-<computeroutput>libbzip2</computeroutput>, a flexible library for
-handling compressed data in the
-<computeroutput>bzip2</computeroutput> 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.</para>
-
-<itemizedlist mark='bullet'>
-
- <listitem><para><xref linkend="using"/> describes how to use
- <computeroutput>bzip2</computeroutput>; this is the only part
- you need to read if you just want to know how to operate the
- program.</para></listitem>
-
- <listitem><para><xref linkend="libprog"/> describes the
- programming interfaces in detail, and</para></listitem>
-
- <listitem><para><xref linkend="misc"/> records some
- miscellaneous notes which I thought ought to be recorded
- somewhere.</para></listitem>
-
-</itemizedlist>
-
-</chapter>
-
-
-<chapter id="using" xreflabel="How to use bzip2">
-<title>How to use bzip2</title>
-
-<para>This chapter contains a copy of the
-<computeroutput>bzip2</computeroutput> man page, and nothing
-else.</para>
-
-<sect1 id="name" xreflabel="NAME">
-<title>NAME</title>
-
-<itemizedlist mark='bullet'>
-
- <listitem><para><computeroutput>bzip2</computeroutput>,
- <computeroutput>bunzip2</computeroutput> - a block-sorting file
- compressor, v1.0.6</para></listitem>
-
- <listitem><para><computeroutput>bzcat</computeroutput> -
- decompresses files to stdout</para></listitem>
-
- <listitem><para><computeroutput>bzip2recover</computeroutput> -
- recovers data from damaged bzip2 files</para></listitem>
-
-</itemizedlist>
-
-</sect1>
-
-
-<sect1 id="synopsis" xreflabel="SYNOPSIS">
-<title>SYNOPSIS</title>
-
-<itemizedlist mark='bullet'>
-
- <listitem><para><computeroutput>bzip2</computeroutput> [
- -cdfkqstvzVL123456789 ] [ filenames ... ]</para></listitem>
-
- <listitem><para><computeroutput>bunzip2</computeroutput> [
- -fkvsVL ] [ filenames ... ]</para></listitem>
-
- <listitem><para><computeroutput>bzcat</computeroutput> [ -s ] [
- filenames ... ]</para></listitem>
-
- <listitem><para><computeroutput>bzip2recover</computeroutput>
- filename</para></listitem>
-
-</itemizedlist>
-
-</sect1>
-
-
-<sect1 id="description" xreflabel="DESCRIPTION">
-<title>DESCRIPTION</title>
-
-<para><computeroutput>bzip2</computeroutput> 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.</para>
-
-<para>The command-line options are deliberately very similar to
-those of GNU <computeroutput>gzip</computeroutput>, but they are
-not identical.</para>
-
-<para><computeroutput>bzip2</computeroutput> 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
-<computeroutput>original_name.bz2</computeroutput>. 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.</para>
-
-<para><computeroutput>bzip2</computeroutput> and
-<computeroutput>bunzip2</computeroutput> will by default not
-overwrite existing files. If you want this to happen, specify
-the <computeroutput>-f</computeroutput> flag.</para>
-
-<para>If no file names are specified,
-<computeroutput>bzip2</computeroutput> compresses from standard
-input to standard output. In this case,
-<computeroutput>bzip2</computeroutput> will decline to write
-compressed output to a terminal, as this would be entirely
-incomprehensible and therefore pointless.</para>
-
-<para><computeroutput>bunzip2</computeroutput> (or
-<computeroutput>bzip2 -d</computeroutput>) decompresses all
-specified files. Files which were not created by
-<computeroutput>bzip2</computeroutput> will be detected and
-ignored, and a warning issued.
-<computeroutput>bzip2</computeroutput> attempts to guess the
-filename for the decompressed file from that of the compressed
-file as follows:</para>
-
-<itemizedlist mark='bullet'>
-
- <listitem><para><computeroutput>filename.bz2 </computeroutput>
- becomes
- <computeroutput>filename</computeroutput></para></listitem>
-
- <listitem><para><computeroutput>filename.bz </computeroutput>
- becomes
- <computeroutput>filename</computeroutput></para></listitem>
-
- <listitem><para><computeroutput>filename.tbz2</computeroutput>
- becomes
- <computeroutput>filename.tar</computeroutput></para></listitem>
-
- <listitem><para><computeroutput>filename.tbz </computeroutput>
- becomes
- <computeroutput>filename.tar</computeroutput></para></listitem>
-
- <listitem><para><computeroutput>anyothername </computeroutput>
- becomes
- <computeroutput>anyothername.out</computeroutput></para></listitem>
-
-</itemizedlist>
-
-<para>If the file does not end in one of the recognised endings,
-<computeroutput>.bz2</computeroutput>,
-<computeroutput>.bz</computeroutput>,
-<computeroutput>.tbz2</computeroutput> or
-<computeroutput>.tbz</computeroutput>,
-<computeroutput>bzip2</computeroutput> complains that it cannot
-guess the name of the original file, and uses the original name
-with <computeroutput>.out</computeroutput> appended.</para>
-
-<para>As with compression, supplying no filenames causes
-decompression from standard input to standard output.</para>
-
-<para><computeroutput>bunzip2</computeroutput> 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
-(<computeroutput>-t</computeroutput>) of concatenated compressed
-files is also supported.</para>
-
-<para>You can also compress or decompress files to the standard
-output by giving the <computeroutput>-c</computeroutput> 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
-<computeroutput>bzip2</computeroutput> version 0.9.0 or later.
-Earlier versions of <computeroutput>bzip2</computeroutput> will
-stop after decompressing the first file in the stream.</para>
-
-<para><computeroutput>bzcat</computeroutput> (or
-<computeroutput>bzip2 -dc</computeroutput>) decompresses all
-specified files to the standard output.</para>
-
-<para><computeroutput>bzip2</computeroutput> will read arguments
-from the environment variables
-<computeroutput>BZIP2</computeroutput> and
-<computeroutput>BZIP</computeroutput>, in that order, and will
-process them before any arguments read from the command line.
-This gives a convenient way to supply default arguments.</para>
-
-<para>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%.</para>
-
-<para>As a self-check for your protection,
-<computeroutput>bzip2</computeroutput> 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
-<computeroutput>bzip2</computeroutput> (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
-<computeroutput>bzip2recover</computeroutput> to try to recover
-data from damaged files.</para>
-
-<para>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
-<computeroutput>bzip2</computeroutput> to panic.</para>
-
-</sect1>
-
-
-<sect1 id="options" xreflabel="OPTIONS">
-<title>OPTIONS</title>
-
-<variablelist>
-
- <varlistentry>
- <term><computeroutput>-c --stdout</computeroutput></term>
- <listitem><para>Compress or decompress to standard
- output.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>-d --decompress</computeroutput></term>
- <listitem><para>Force decompression.
- <computeroutput>bzip2</computeroutput>,
- <computeroutput>bunzip2</computeroutput> and
- <computeroutput>bzcat</computeroutput> 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.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>-z --compress</computeroutput></term>
- <listitem><para>The complement to
- <computeroutput>-d</computeroutput>: forces compression,
- regardless of the invokation name.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>-t --test</computeroutput></term>
- <listitem><para>Check integrity of the specified file(s), but
- don't decompress them. This really performs a trial
- decompression and throws away the result.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>-f --force</computeroutput></term>
- <listitem><para>Force overwrite of output files. Normally,
- <computeroutput>bzip2</computeroutput> will not overwrite
- existing output files. Also forces
- <computeroutput>bzip2</computeroutput> to break hard links to
- files, which it otherwise wouldn't do.</para>
- <para><computeroutput>bzip2</computeroutput> normally declines
- to decompress files which don't have the correct magic header
- bytes. If forced (<computeroutput>-f</computeroutput>),
- however, it will pass such files through unmodified. This is
- how GNU <computeroutput>gzip</computeroutput> behaves.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>-k --keep</computeroutput></term>
- <listitem><para>Keep (don't delete) input files during
- compression or decompression.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>-s --small</computeroutput></term>
- <listitem><para>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.</para>
- <para>During compression, <computeroutput>-s</computeroutput>
- 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 <computeroutput>-s</computeroutput> for everything. See
- <xref linkend="memory-management"/> below.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>-q --quiet</computeroutput></term>
- <listitem><para>Suppress non-essential warning messages.
- Messages pertaining to I/O errors and other critical events
- will not be suppressed.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>-v --verbose</computeroutput></term>
- <listitem><para>Verbose mode -- show the compression ratio for
- each file processed. Further
- <computeroutput>-v</computeroutput>'s increase the verbosity
- level, spewing out lots of information which is primarily of
- interest for diagnostic purposes.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>-L --license -V --version</computeroutput></term>
- <listitem><para>Display the software version, license terms and
- conditions.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>-1</computeroutput> (or
- <computeroutput>--fast</computeroutput>) to
- <computeroutput>-9</computeroutput> (or
- <computeroutput>-best</computeroutput>)</term>
- <listitem><para>Set the block size to 100 k, 200 k ... 900 k
- when compressing. Has no effect when decompressing. See <xref
- linkend="memory-management" /> below. The
- <computeroutput>--fast</computeroutput> and
- <computeroutput>--best</computeroutput> aliases are primarily
- for GNU <computeroutput>gzip</computeroutput> compatibility.
- In particular, <computeroutput>--fast</computeroutput> doesn't
- make things significantly faster. And
- <computeroutput>--best</computeroutput> merely selects the
- default behaviour.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>--</computeroutput></term>
- <listitem><para>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:
- <computeroutput>bzip2 --
- -myfilename</computeroutput>.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>--repetitive-fast</computeroutput></term>
- <term><computeroutput>--repetitive-best</computeroutput></term>
- <listitem><para>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.</para></listitem>
- </varlistentry>
-
-</variablelist>
-
-</sect1>
-
-
-<sect1 id="memory-management" xreflabel="MEMORY MANAGEMENT">
-<title>MEMORY MANAGEMENT</title>
-
-<para><computeroutput>bzip2</computeroutput> 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 <computeroutput>-1</computeroutput>
-through <computeroutput>-9</computeroutput> 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
-<computeroutput>bunzip2</computeroutput> then allocates itself
-just enough memory to decompress the file. Since block sizes are
-stored in compressed files, it follows that the flags
-<computeroutput>-1</computeroutput> to
-<computeroutput>-9</computeroutput> are irrelevant to and so
-ignored during decompression.</para>
-
-<para>Compression and decompression requirements, in bytes, can be
-estimated as:</para>
-<programlisting>
-Compression: 400k + ( 8 x block size )
-
-Decompression: 100k + ( 4 x block size ), or
- 100k + ( 2.5 x block size )
-</programlisting>
-
-<para>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 <computeroutput>bzip2</computeroutput> 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.</para>
-
-<para>For files compressed with the default 900k block size,
-<computeroutput>bunzip2</computeroutput> will require about 3700
-kbytes to decompress. To support decompression of any file on a
-4 megabyte machine, <computeroutput>bunzip2</computeroutput> 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 <computeroutput>-s</computeroutput>.</para>
-
-<para>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.</para>
-
-<para>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 <computeroutput>-9</computeroutput> 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.</para>
-
-<para>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.</para>
-
-<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
-</programlisting>
-
-</sect1>
-
-
-<sect1 id="recovering" xreflabel="RECOVERING DATA FROM DAMAGED FILES">
-<title>RECOVERING DATA FROM DAMAGED FILES</title>
-
-<para><computeroutput>bzip2</computeroutput> compresses files in
-blocks, usually 900kbytes long. Each block is handled
-independently. If a media or transmission error causes a
-multi-block <computeroutput>.bz2</computeroutput> file to become
-damaged, it may be possible to recover data from the undamaged
-blocks in the file.</para>
-
-<para>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.</para>
-
-<para><computeroutput>bzip2recover</computeroutput> is a simple
-program whose purpose is to search for blocks in
-<computeroutput>.bz2</computeroutput> files, and write each block
-out into its own <computeroutput>.bz2</computeroutput> file. You
-can then use <computeroutput>bzip2 -t</computeroutput> to test
-the integrity of the resulting files, and decompress those which
-are undamaged.</para>
-
-<para><computeroutput>bzip2recover</computeroutput> takes a
-single argument, the name of the damaged file, and writes a
-number of files <computeroutput>rec0001file.bz2</computeroutput>,
-<computeroutput>rec0002file.bz2</computeroutput>, etc, containing
-the extracted blocks. The output filenames are designed so that
-the use of wildcards in subsequent processing -- for example,
-<computeroutput>bzip2 -dc rec*file.bz2 >
-recovered_data</computeroutput> -- lists the files in the correct
-order.</para>
-
-<para><computeroutput>bzip2recover</computeroutput> should be of
-most use dealing with large <computeroutput>.bz2</computeroutput>
-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.</para>
-
-</sect1>
-
-
-<sect1 id="performance" xreflabel="PERFORMANCE NOTES">
-<title>PERFORMANCE NOTES</title>
-
-<para>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
-<computeroutput>-vvvv</computeroutput> option to monitor progress
-in great detail, if you want.</para>
-
-<para>Decompression speed is unaffected by these
-phenomena.</para>
-
-<para><computeroutput>bzip2</computeroutput> 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
-<computeroutput>bzip2</computeroutput> will perform best on
-machines with very large caches.</para>
-
-</sect1>
-
-
-
-<sect1 id="caveats" xreflabel="CAVEATS">
-<title>CAVEATS</title>
-
-<para>I/O error messages are not as helpful as they could be.
-<computeroutput>bzip2</computeroutput> tries hard to detect I/O
-errors and exit cleanly, but the details of what the problem is
-sometimes seem rather misleading.</para>
-
-<para>This manual page pertains to version &bz-version; of
-<computeroutput>bzip2</computeroutput>. 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.</para>
-
-<para><computeroutput>bzip2recover</computeroutput> 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
-<computeroutput>bzip2recover</computeroutput> 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
-<computeroutput>MaybeUInt64</computeroutput> set to be an
-unsigned 64-bit integer.</para>
-
-</sect1>
-
-
-
-<sect1 id="author" xreflabel="AUTHOR">
-<title>AUTHOR</title>
-
-<para>Julian Seward,
-<computeroutput>&bz-email;</computeroutput></para>
-
-<para>The ideas embodied in
-<computeroutput>bzip2</computeroutput> 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 <computeroutput>bzip</computeroutput>, and many
-refinements), and Alistair Moffat, Radford Neal and Ian Witten
-(for the arithmetic coder in the original
-<computeroutput>bzip</computeroutput>). 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.</para>
-
-</sect1>
-
-</chapter>
-
-
-
-<chapter id="libprog" xreflabel="Programming with libbzip2">
-<title>
-Programming with <computeroutput>libbzip2</computeroutput>
-</title>
-
-<para>This chapter describes the programming interface to
-<computeroutput>libbzip2</computeroutput>.</para>
-
-<para>For general background information, particularly about
-memory use and performance aspects, you'd be well advised to read
-<xref linkend="using"/> as well.</para>
-
-
-<sect1 id="top-level" xreflabel="Top-level structure">
-<title>Top-level structure</title>
-
-<para><computeroutput>libbzip2</computeroutput> is a flexible
-library for compressing and decompressing data in the
-<computeroutput>bzip2</computeroutput> 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.</para>
-
-<para>The structure of
-<computeroutput>libbzip2</computeroutput>'s interfaces is similar
-to that of Jean-loup Gailly's and Mark Adler's excellent
-<computeroutput>zlib</computeroutput> library.</para>
-
-<para>All externally visible symbols have names beginning
-<computeroutput>BZ2_</computeroutput>. This is new in version
-1.0. The intention is to minimise pollution of the namespaces of
-library clients.</para>
-
-<para>To use any part of the library, you need to
-<computeroutput>#include <bzlib.h></computeroutput>
-into your sources.</para>
-
-
-
-<sect2 id="ll-summary" xreflabel="Low-level summary">
-<title>Low-level summary</title>
-
-<para>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
-<computeroutput>stdio.h</computeroutput>, which may be helpful
-for embedded applications.</para>
-
-<para>The low-level part of the library has no global variables
-and is therefore thread-safe.</para>
-
-<para>Six routines make up the low level interface:
-<computeroutput>BZ2_bzCompressInit</computeroutput>,
-<computeroutput>BZ2_bzCompress</computeroutput>, and
-<computeroutput>BZ2_bzCompressEnd</computeroutput> for
-compression, and a corresponding trio
-<computeroutput>BZ2_bzDecompressInit</computeroutput>,
-<computeroutput>BZ2_bzDecompress</computeroutput> and
-<computeroutput>BZ2_bzDecompressEnd</computeroutput> for
-decompression. The <computeroutput>*Init</computeroutput>
-functions allocate memory for compression/decompression and do
-other initialisations, whilst the
-<computeroutput>*End</computeroutput> functions close down
-operations and release memory.</para>
-
-<para>The real work is done by
-<computeroutput>BZ2_bzCompress</computeroutput> and
-<computeroutput>BZ2_bzDecompress</computeroutput>. 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.</para>
-
-</sect2>
-
-
-<sect2 id="hl-summary" xreflabel="High-level summary">
-<title>High-level summary</title>
-
-<para>This interface provides some handy wrappers around the
-low-level interface to facilitate reading and writing
-<computeroutput>bzip2</computeroutput> format files
-(<computeroutput>.bz2</computeroutput> files). The routines
-provide hooks to facilitate reading files in which the
-<computeroutput>bzip2</computeroutput> data stream is embedded
-within some larger-scale file structure, or where there are
-multiple <computeroutput>bzip2</computeroutput> data streams
-concatenated end-to-end.</para>
-
-<para>For reading files,
-<computeroutput>BZ2_bzReadOpen</computeroutput>,
-<computeroutput>BZ2_bzRead</computeroutput>,
-<computeroutput>BZ2_bzReadClose</computeroutput> and
-<computeroutput>BZ2_bzReadGetUnused</computeroutput> are
-supplied. For writing files,
-<computeroutput>BZ2_bzWriteOpen</computeroutput>,
-<computeroutput>BZ2_bzWrite</computeroutput> and
-<computeroutput>BZ2_bzWriteFinish</computeroutput> are
-available.</para>
-
-<para>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 <computeroutput>errno</computeroutput> to
-determine the cause of the error. In that case, you'd need a C
-library which correctly supports
-<computeroutput>errno</computeroutput> in a multithreaded
-environment.</para>
-
-<para>To make the library a little simpler and more portable,
-<computeroutput>BZ2_bzReadOpen</computeroutput> and
-<computeroutput>BZ2_bzWriteOpen</computeroutput> require you to
-pass them file handles (<computeroutput>FILE*</computeroutput>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.</para>
-
-</sect2>
-
-
-<sect2 id="util-fns-summary" xreflabel="Utility functions summary">
-<title>Utility functions summary</title>
-
-<para>For very simple needs,
-<computeroutput>BZ2_bzBuffToBuffCompress</computeroutput> and
-<computeroutput>BZ2_bzBuffToBuffDecompress</computeroutput> 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.</para>
-
-<para>Yoshioka Tsuneo
-(<computeroutput>tsuneo@rr.iij4u.or.jp</computeroutput>) has
-contributed some functions to give better
-<computeroutput>zlib</computeroutput> compatibility. These
-functions are <computeroutput>BZ2_bzopen</computeroutput>,
-<computeroutput>BZ2_bzread</computeroutput>,
-<computeroutput>BZ2_bzwrite</computeroutput>,
-<computeroutput>BZ2_bzflush</computeroutput>,
-<computeroutput>BZ2_bzclose</computeroutput>,
-<computeroutput>BZ2_bzerror</computeroutput> and
-<computeroutput>BZ2_bzlibVersion</computeroutput>. 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.</para>
-
-<para>Yoshioka also contributed modifications to allow the
-library to be built as a Windows DLL.</para>
-
-</sect2>
-
-</sect1>
-
-
-<sect1 id="err-handling" xreflabel="Error handling">
-<title>Error handling</title>
-
-<para>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.</para>
-
-<para>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.</para>
-
-<para>The file <computeroutput>bzlib.h</computeroutput> contains
-all definitions needed to use the library. In particular, you
-should definitely not include
-<computeroutput>bzlib_private.h</computeroutput>.</para>
-
-<para>In <computeroutput>bzlib.h</computeroutput>, 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.</para>
-
-<variablelist>
-
- <varlistentry>
- <term><computeroutput>BZ_OK</computeroutput></term>
- <listitem><para>The requested action was completed
- successfully.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>BZ_RUN_OK, BZ_FLUSH_OK,
- BZ_FINISH_OK</computeroutput></term>
- <listitem><para>In
- <computeroutput>BZ2_bzCompress</computeroutput>, the requested
- flush/finish/nothing-special action was completed
- successfully.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>BZ_STREAM_END</computeroutput></term>
- <listitem><para>Compression of data was completed, or the
- logical stream end was detected during
- decompression.</para></listitem>
- </varlistentry>
-
-</variablelist>
-
-<para>The following return values indicate an error of some
-kind.</para>
-
-<variablelist>
-
- <varlistentry>
- <term><computeroutput>BZ_CONFIG_ERROR</computeroutput></term>
- <listitem><para>Indicates that the library has been improperly
- compiled on your platform -- a major configuration error.
- Specifically, it means that
- <computeroutput>sizeof(char)</computeroutput>,
- <computeroutput>sizeof(short)</computeroutput> and
- <computeroutput>sizeof(int)</computeroutput> 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
- <computeroutput>sizeof(long)</computeroutput> and
- <computeroutput>sizeof(void*)</computeroutput> are 8. Under
- LP64, <computeroutput>sizeof(int)</computeroutput> is still 4,
- so <computeroutput>libbzip2</computeroutput>, which doesn't
- use the <computeroutput>long</computeroutput> type, is
- OK.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>BZ_SEQUENCE_ERROR</computeroutput></term>
- <listitem><para>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.
- <computeroutput>libbzip2</computeroutput> checks as much as it
- can to ensure this is happening, and returns
- <computeroutput>BZ_SEQUENCE_ERROR</computeroutput> 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.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>BZ_PARAM_ERROR</computeroutput></term>
- <listitem><para>Returned when a parameter to a function call is
- out of range or otherwise manifestly incorrect. As with
- <computeroutput>BZ_SEQUENCE_ERROR</computeroutput>, this
- denotes a bug in the client code. The distinction between
- <computeroutput>BZ_PARAM_ERROR</computeroutput> and
- <computeroutput>BZ_SEQUENCE_ERROR</computeroutput> is a bit
- hazy, but still worth making.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>BZ_MEM_ERROR</computeroutput></term>
- <listitem><para>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
- <computeroutput>BZ2_bzDecompress</computeroutput> and
- <computeroutput>BZ2_bzRead</computeroutput> may return
- <computeroutput>BZ_MEM_ERROR</computeroutput> even though some
- of the compressed data has been read. The same is not true
- for compression; once
- <computeroutput>BZ2_bzCompressInit</computeroutput> or
- <computeroutput>BZ2_bzWriteOpen</computeroutput> have
- successfully completed,
- <computeroutput>BZ_MEM_ERROR</computeroutput> cannot
- occur.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>BZ_DATA_ERROR</computeroutput></term>
- <listitem><para>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.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>BZ_DATA_ERROR_MAGIC</computeroutput></term>
- <listitem><para>As a special case of
- <computeroutput>BZ_DATA_ERROR</computeroutput>, it is
- sometimes useful to know when the compressed stream does not
- start with the correct magic bytes (<computeroutput>'B' 'Z'
- 'h'</computeroutput>).</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>BZ_IO_ERROR</computeroutput></term>
- <listitem><para>Returned by
- <computeroutput>BZ2_bzRead</computeroutput> and
- <computeroutput>BZ2_bzWrite</computeroutput> when there is an
- error reading or writing in the compressed file, and by
- <computeroutput>BZ2_bzReadOpen</computeroutput> and
- <computeroutput>BZ2_bzWriteOpen</computeroutput> for attempts
- to use a file for which the error indicator (viz,
- <computeroutput>ferror(f)</computeroutput>) is set. On
- receipt of <computeroutput>BZ_IO_ERROR</computeroutput>, the
- caller should consult <computeroutput>errno</computeroutput>
- and/or <computeroutput>perror</computeroutput> to acquire
- operating-system specific information about the
- problem.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>BZ_UNEXPECTED_EOF</computeroutput></term>
- <listitem><para>Returned by
- <computeroutput>BZ2_bzRead</computeroutput> when the
- compressed file finishes before the logical end of stream is
- detected.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><computeroutput>BZ_OUTBUFF_FULL</computeroutput></term>
- <listitem><para>Returned by
- <computeroutput>BZ2_bzBuffToBuffCompress</computeroutput> and
- <computeroutput>BZ2_bzBuffToBuffDecompress</computeroutput> to
- indicate that the output data will not fit into the output
- buffer provided.</para></listitem>
- </varlistentry>
-
-</variablelist>
-
-</sect1>
-
-
-
-<sect1 id="low-level" xreflabel=">Low-level interface">
-<title>Low-level interface</title>
-
-
-<sect2 id="bzcompress-init" xreflabel="BZ2_bzCompressInit">
-<title>BZ2_bzCompressInit</title>
-
-<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 );
-</programlisting>
-
-<para>Prepares for compression. The
-<computeroutput>bz_stream</computeroutput> structure holds all
-data pertaining to the compression activity. A
-<computeroutput>bz_stream</computeroutput> structure should be
-allocated and initialised prior to the call. The fields of
-<computeroutput>bz_stream</computeroutput> comprise the entirety
-of the user-visible data. <computeroutput>state</computeroutput>
-is a pointer to the private data structures required for
-compression.</para>
-
-<para>Custom memory allocators are supported, via fields
-<computeroutput>bzalloc</computeroutput>,
-<computeroutput>bzfree</computeroutput>, and
-<computeroutput>opaque</computeroutput>. The value
-<computeroutput>opaque</computeroutput> is passed to as the first
-argument to all calls to <computeroutput>bzalloc</computeroutput>
-and <computeroutput>bzfree</computeroutput>, but is otherwise
-ignored by the library. The call <computeroutput>bzalloc (
-opaque, n, m )</computeroutput> is expected to return a pointer
-<computeroutput>p</computeroutput> to <computeroutput>n *
-m</computeroutput> bytes of memory, and <computeroutput>bzfree (
-opaque, p )</computeroutput> should free that memory.</para>
-
-<para>If you don't want to use a custom memory allocator, set
-<computeroutput>bzalloc</computeroutput>,
-<computeroutput>bzfree</computeroutput> and
-<computeroutput>opaque</computeroutput> to
-<computeroutput>NULL</computeroutput>, and the library will then
-use the standard <computeroutput>malloc</computeroutput> /
-<computeroutput>free</computeroutput> routines.</para>
-
-<para>Before calling
-<computeroutput>BZ2_bzCompressInit</computeroutput>, fields
-<computeroutput>bzalloc</computeroutput>,
-<computeroutput>bzfree</computeroutput> and
-<computeroutput>opaque</computeroutput> should be filled
-appropriately, as just described. Upon return, the internal
-state will have been allocated and initialised, and
-<computeroutput>total_in_lo32</computeroutput>,
-<computeroutput>total_in_hi32</computeroutput>,
-<computeroutput>total_out_lo32</computeroutput> and
-<computeroutput>total_out_hi32</computeroutput> 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 <computeroutput>_hi32</computeroutput>
-fields to store the upper 32 bits of the count. So, for example,
-the total amount of data in is <computeroutput>(total_in_hi32
-<< 32) + total_in_lo32</computeroutput>.</para>
-
-<para>Parameter <computeroutput>blockSize100k</computeroutput>
-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.</para>
-
-<para>Parameter <computeroutput>verbosity</computeroutput> 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
-<computeroutput>-DBZ_NO_STDIO</computeroutput>, no such output
-will appear for any verbosity setting.</para>
-
-<para>Parameter <computeroutput>workFactor</computeroutput>
-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.</para>
-
-<para>Lower values of <computeroutput>workFactor</computeroutput>
-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.</para>
-
-<para>Allowable values range from 0 to 250 inclusive. 0 is a
-special case, equivalent to using the default value of 30.</para>
-
-<para>Note that the compressed output generated is the same
-regardless of whether or not the fallback algorithm is
-used.</para>
-
-<para>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.</para>
-
-<para>Possible return values:</para>
-
-<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
-</programlisting>
-
-<para>Allowable next actions:</para>
-
-<programlisting>
-BZ2_bzCompress
- if BZ_OK is returned
- no specific action needed in case of error
-</programlisting>
-
-</sect2>
-
-
-<sect2 id="bzCompress" xreflabel="BZ2_bzCompress">
-<title>BZ2_bzCompress</title>
-
-<programlisting>
-int BZ2_bzCompress ( bz_stream *strm, int action );
-</programlisting>
-
-<para>Provides more input and/or output buffer space for the
-library. The caller maintains input and output buffers, and
-calls <computeroutput>BZ2_bzCompress</computeroutput> to transfer
-data between them.</para>
-
-<para>Before each call to
-<computeroutput>BZ2_bzCompress</computeroutput>,
-<computeroutput>next_in</computeroutput> should point at the data
-to be compressed, and <computeroutput>avail_in</computeroutput>
-should indicate how many bytes the library may read.
-<computeroutput>BZ2_bzCompress</computeroutput> updates
-<computeroutput>next_in</computeroutput>,
-<computeroutput>avail_in</computeroutput> and
-<computeroutput>total_in</computeroutput> to reflect the number
-of bytes it has read.</para>
-
-<para>Similarly, <computeroutput>next_out</computeroutput> should
-point to a buffer in which the compressed data is to be placed,
-with <computeroutput>avail_out</computeroutput> indicating how
-much output space is available.
-<computeroutput>BZ2_bzCompress</computeroutput> updates
-<computeroutput>next_out</computeroutput>,
-<computeroutput>avail_out</computeroutput> and
-<computeroutput>total_out</computeroutput> to reflect the number
-of bytes output.</para>
-
-<para>You may provide and remove as little or as much data as you
-like on each call of
-<computeroutput>BZ2_bzCompress</computeroutput>. 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.</para>
-
-<para>A second purpose of
-<computeroutput>BZ2_bzCompress</computeroutput> is to request a
-change of mode of the compressed stream.</para>
-
-<para>Conceptually, a compressed stream can be in one of four
-states: IDLE, RUNNING, FLUSHING and FINISHING. Before
-initialisation
-(<computeroutput>BZ2_bzCompressInit</computeroutput>) and after
-termination (<computeroutput>BZ2_bzCompressEnd</computeroutput>),
-a stream is regarded as IDLE.</para>
-
-<para>Upon initialisation
-(<computeroutput>BZ2_bzCompressInit</computeroutput>), the stream
-is placed in the RUNNING state. Subsequent calls to
-<computeroutput>BZ2_bzCompress</computeroutput> should pass
-<computeroutput>BZ_RUN</computeroutput> as the requested action;
-other actions are illegal and will result in
-<computeroutput>BZ_SEQUENCE_ERROR</computeroutput>.</para>
-
-<para>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,
-<computeroutput>BZ2_bzCompress</computeroutput> will no longer
-attempt to read data from
-<computeroutput>next_in</computeroutput>, but it will want to
-write data to <computeroutput>next_out</computeroutput>. 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
-<computeroutput>BZ2_bzCompress</computeroutput>.</para>
-
-<para>Instead, the calling program passes
-<computeroutput>BZ_FINISH</computeroutput> as an action to
-<computeroutput>BZ2_bzCompress</computeroutput>. This changes
-the stream's state to FINISHING. Any remaining input (ie,
-<computeroutput>next_in[0 .. avail_in-1]</computeroutput>) is
-compressed and transferred to the output buffer. To do this,
-<computeroutput>BZ2_bzCompress</computeroutput> must be called
-repeatedly until all the output has been consumed. At that
-point, <computeroutput>BZ2_bzCompress</computeroutput> returns
-<computeroutput>BZ_STREAM_END</computeroutput>, and the stream's
-state is set back to IDLE.
-<computeroutput>BZ2_bzCompressEnd</computeroutput> should then be
-called.</para>
-
-<para>Just to make sure the calling program does not cheat, the
-library makes a note of <computeroutput>avail_in</computeroutput>
-at the time of the first call to
-<computeroutput>BZ2_bzCompress</computeroutput> which has
-<computeroutput>BZ_FINISH</computeroutput> 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
-<computeroutput>avail_in</computeroutput> over subsequent calls
-to <computeroutput>BZ2_bzCompress</computeroutput>, the library
-can detect any attempts to slip in more data to compress. Any
-calls for which this is detected will return
-<computeroutput>BZ_SEQUENCE_ERROR</computeroutput>. This
-indicates a programming mistake which should be corrected.</para>
-
-<para>Instead of asking to finish, the calling program may ask
-<computeroutput>BZ2_bzCompress</computeroutput> 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 <computeroutput>BZ2_bzCompress</computeroutput>
-with an action of <computeroutput>BZ_FLUSH</computeroutput>,
-remove output data, and persist with the
-<computeroutput>BZ_FLUSH</computeroutput> action until the value
-<computeroutput>BZ_RUN</computeroutput> is returned. As with
-finishing, <computeroutput>BZ2_bzCompress</computeroutput>
-detects any attempt to provide more input data once the flush has
-begun.</para>
-
-<para>Once the flush is complete, the stream returns to the
-normal RUNNING state.</para>
-
-<para>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
-<computeroutput>BZ2_bzCompress</computeroutput>.</para>
-
-<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
-</programlisting>
-
-
-<para>That still looks complicated? Well, fair enough. The
-usual sequence of calls for compressing a load of data is:</para>
-
-<orderedlist>
-
- <listitem><para>Get started with
- <computeroutput>BZ2_bzCompressInit</computeroutput>.</para></listitem>
-
- <listitem><para>Shovel data in and shlurp out its compressed form
- using zero or more calls of
- <computeroutput>BZ2_bzCompress</computeroutput> with action =
- <computeroutput>BZ_RUN</computeroutput>.</para></listitem>
-
- <listitem><para>Finish up. Repeatedly call
- <computeroutput>BZ2_bzCompress</computeroutput> with action =
- <computeroutput>BZ_FINISH</computeroutput>, copying out the
- compressed output, until
- <computeroutput>BZ_STREAM_END</computeroutput> is
- returned.</para></listitem> <listitem><para>Close up and go home. Call
- <computeroutput>BZ2_bzCompressEnd</computeroutput>.</para></listitem>
-
-</orderedlist>
-
-<para>If the data you want to compress fits into your input
-buffer all at once, you can skip the calls of
-<computeroutput>BZ2_bzCompress ( ..., BZ_RUN )</computeroutput>
-and just do the <computeroutput>BZ2_bzCompress ( ..., BZ_FINISH
-)</computeroutput> calls.</para>
-
-<para>All required memory is allocated by
-<computeroutput>BZ2_bzCompressInit</computeroutput>. The
-compression library can accept any data at all (obviously). So
-you shouldn't get any error return values from the
-<computeroutput>BZ2_bzCompress</computeroutput> calls. If you
-do, they will be
-<computeroutput>BZ_SEQUENCE_ERROR</computeroutput>, and indicate
-a bug in your programming.</para>
-
-<para>Trivial other possible return values:</para>
-
-<programlisting>
-BZ_PARAM_ERROR
- if strm is NULL, or strm->s is NULL
-</programlisting>
-
-</sect2>
-
-
-<sect2 id="bzCompress-end" xreflabel="BZ2_bzCompressEnd">
-<title>BZ2_bzCompressEnd</title>
-
-<programlisting>
-int BZ2_bzCompressEnd ( bz_stream *strm );
-</programlisting>
-
-<para>Releases all memory associated with a compression
-stream.</para>
-
-<para>Possible return values:</para>
-
-<programlisting>
-BZ_PARAM_ERROR if strm is NULL or strm->s is NULL
-BZ_OK otherwise
-</programlisting>
-
-</sect2>
-
-
-<sect2 id="bzDecompress-init" xreflabel="BZ2_bzDecompressInit">
-<title>BZ2_bzDecompressInit</title>
-
-<programlisting>
-int BZ2_bzDecompressInit ( bz_stream *strm, int verbosity, int small );
-</programlisting>
-
-<para>Prepares for decompression. As with
-<computeroutput>BZ2_bzCompressInit</computeroutput>, a
-<computeroutput>bz_stream</computeroutput> record should be
-allocated and initialised before the call. Fields
-<computeroutput>bzalloc</computeroutput>,
-<computeroutput>bzfree</computeroutput> and
-<computeroutput>opaque</computeroutput> should be set if a custom
-memory allocator is required, or made
-<computeroutput>NULL</computeroutput> for the normal
-<computeroutput>malloc</computeroutput> /
-<computeroutput>free</computeroutput> routines. Upon return, the
-internal state will have been initialised, and
-<computeroutput>total_in</computeroutput> and
-<computeroutput>total_out</computeroutput> will be zero.</para>
-
-<para>For the meaning of parameter
-<computeroutput>verbosity</computeroutput>, see
-<computeroutput>BZ2_bzCompressInit</computeroutput>.</para>
-
-<para>If <computeroutput>small</computeroutput> 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 <xref linkend="using"/>
-for more information on memory management.</para>
-
-<para>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
-<computeroutput>BZ2_bzDecompressInit</computeroutput> succeeds, a
-subsequent <computeroutput>BZ2_bzDecompress</computeroutput>
-could fail with
-<computeroutput>BZ_MEM_ERROR</computeroutput>.</para>
-
-<para>Possible return values:</para>
-
-<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
-</programlisting>
-
-<para>Allowable next actions:</para>
-
-<programlisting>
-BZ2_bzDecompress
- if BZ_OK was returned
- no specific action required in case of error
-</programlisting>
-
-</sect2>
-
-
-<sect2 id="bzDecompress" xreflabel="BZ2_bzDecompress">
-<title>BZ2_bzDecompress</title>
-
-<programlisting>
-int BZ2_bzDecompress ( bz_stream *strm );
-</programlisting>
-
-<para>Provides more input and/out output buffer space for the
-library. The caller maintains input and output buffers, and uses
-<computeroutput>BZ2_bzDecompress</computeroutput> to transfer
-data between them.</para>
-
-<para>Before each call to
-<computeroutput>BZ2_bzDecompress</computeroutput>,
-<computeroutput>next_in</computeroutput> should point at the
-compressed data, and <computeroutput>avail_in</computeroutput>
-should indicate how many bytes the library may read.
-<computeroutput>BZ2_bzDecompress</computeroutput> updates
-<computeroutput>next_in</computeroutput>,
-<computeroutput>avail_in</computeroutput> and
-<computeroutput>total_in</computeroutput> to reflect the number
-of bytes it has read.</para>
-
-<para>Similarly, <computeroutput>next_out</computeroutput> should
-point to a buffer in which the uncompressed output is to be
-placed, with <computeroutput>avail_out</computeroutput>
-indicating how much output space is available.
-<computeroutput>BZ2_bzCompress</computeroutput> updates
-<computeroutput>next_out</computeroutput>,
-<computeroutput>avail_out</computeroutput> and
-<computeroutput>total_out</computeroutput> to reflect the number
-of bytes output.</para>
-
-<para>You may provide and remove as little or as much data as you
-like on each call of
-<computeroutput>BZ2_bzDecompress</computeroutput>. 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.</para>
-
-<para>Use of <computeroutput>BZ2_bzDecompress</computeroutput> is
-simpler than
-<computeroutput>BZ2_bzCompress</computeroutput>.</para>
-
-<para>You should provide input and remove output as described
-above, and repeatedly call
-<computeroutput>BZ2_bzDecompress</computeroutput> until
-<computeroutput>BZ_STREAM_END</computeroutput> is returned.
-Appearance of <computeroutput>BZ_STREAM_END</computeroutput>
-denotes that <computeroutput>BZ2_bzDecompress</computeroutput>
-has detected the logical end of the compressed stream.
-<computeroutput>BZ2_bzDecompress</computeroutput> will not
-produce <computeroutput>BZ_STREAM_END</computeroutput> until all
-output data has been placed into the output buffer, so once
-<computeroutput>BZ_STREAM_END</computeroutput> appears, you are
-guaranteed to have available all the decompressed output, and
-<computeroutput>BZ2_bzDecompressEnd</computeroutput> can safely
-be called.</para>
-
-<para>If case of an error return value, you should call
-<computeroutput>BZ2_bzDecompressEnd</computeroutput> to clean up
-and release memory.</para>
-
-<para>Possible return values:</para>
-
-<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
-</programlisting>
-
-<para>Allowable next actions:</para>
-
-<programlisting>
-BZ2_bzDecompress
- if BZ_OK was returned
-BZ2_bzDecompressEnd
- otherwise
-</programlisting>
-
-</sect2>
-
-
-<sect2 id="bzDecompress-end" xreflabel="BZ2_bzDecompressEnd">
-<title>BZ2_bzDecompressEnd</title>
-
-<programlisting>
-int BZ2_bzDecompressEnd ( bz_stream *strm );
-</programlisting>
-
-<para>Releases all memory associated with a decompression
-stream.</para>
-
-<para>Possible return values:</para>
-
-<programlisting>
-BZ_PARAM_ERROR
- if strm is NULL or strm->s is NULL
-BZ_OK
- otherwise
-</programlisting>
-
-<para>Allowable next actions:</para>
-
-<programlisting>
- None.
-</programlisting>
-
-</sect2>
-
-</sect1>
-
-
-<sect1 id="hl-interface" xreflabel="High-level interface">
-<title>High-level interface</title>
-
-<para>This interface provides functions for reading and writing
-<computeroutput>bzip2</computeroutput> format files. First, some
-general points.</para>
-
-<itemizedlist mark='bullet'>
-
- <listitem><para>All of the functions take an
- <computeroutput>int*</computeroutput> first argument,
- <computeroutput>bzerror</computeroutput>. After each call,
- <computeroutput>bzerror</computeroutput> should be consulted
- first to determine the outcome of the call. If
- <computeroutput>bzerror</computeroutput> is
- <computeroutput>BZ_OK</computeroutput>, the call completed
- successfully, and only then should the return value of the
- function (if any) be consulted. If
- <computeroutput>bzerror</computeroutput> is
- <computeroutput>BZ_IO_ERROR</computeroutput>, there was an
- error reading/writing the underlying compressed file, and you
- should then consult <computeroutput>errno</computeroutput> /
- <computeroutput>perror</computeroutput> to determine the cause
- of the difficulty. <computeroutput>bzerror</computeroutput>
- may also be set to various other values; precise details are
- given on a per-function basis below.</para></listitem>
-
- <listitem><para>If <computeroutput>bzerror</computeroutput> indicates
- an error (ie, anything except
- <computeroutput>BZ_OK</computeroutput> and
- <computeroutput>BZ_STREAM_END</computeroutput>), you should
- immediately call
- <computeroutput>BZ2_bzReadClose</computeroutput> (or
- <computeroutput>BZ2_bzWriteClose</computeroutput>, 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
- <computeroutput>BZ2_bzReadClose</computeroutput>
- (<computeroutput>BZ2_bzWriteClose</computeroutput>) is
- undefined. The implication is that (1)
- <computeroutput>bzerror</computeroutput> should be checked
- after each call, and (2) if
- <computeroutput>bzerror</computeroutput> indicates an error,
- <computeroutput>BZ2_bzReadClose</computeroutput>
- (<computeroutput>BZ2_bzWriteClose</computeroutput>) should then
- be called to clean up.</para></listitem>
-
- <listitem><para>The <computeroutput>FILE*</computeroutput> arguments
- passed to <computeroutput>BZ2_bzReadOpen</computeroutput> /
- <computeroutput>BZ2_bzWriteOpen</computeroutput> 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.</para></listitem>
-
- <listitem><para>Memory allocation requests are handled by
- <computeroutput>malloc</computeroutput> /
- <computeroutput>free</computeroutput>. At present there is no
- facility for user-defined memory allocators in the file I/O
- functions (could easily be added, though).</para></listitem>
-
-</itemizedlist>
-
-
-
-<sect2 id="bzreadopen" xreflabel="BZ2_bzReadOpen">
-<title>BZ2_bzReadOpen</title>
-
-<programlisting>
-typedef void BZFILE;
-
-BZFILE *BZ2_bzReadOpen( int *bzerror, FILE *f,
- int verbosity, int small,
- void *unused, int nUnused );
-</programlisting>
-
-<para>Prepare to read compressed data from file handle
-<computeroutput>f</computeroutput>.
-<computeroutput>f</computeroutput> should refer to a file which
-has been opened for reading, and for which the error indicator
-(<computeroutput>ferror(f)</computeroutput>)is not set. If
-<computeroutput>small</computeroutput> is 1, the library will try
-to decompress using less memory, at the expense of speed.</para>
-
-<para>For reasons explained below,
-<computeroutput>BZ2_bzRead</computeroutput> will decompress the
-<computeroutput>nUnused</computeroutput> bytes starting at
-<computeroutput>unused</computeroutput>, before starting to read
-from the file <computeroutput>f</computeroutput>. At most
-<computeroutput>BZ_MAX_UNUSED</computeroutput> bytes may be
-supplied like this. If this facility is not required, you should
-pass <computeroutput>NULL</computeroutput> and
-<computeroutput>0</computeroutput> for
-<computeroutput>unused</computeroutput> and
-n<computeroutput>Unused</computeroutput> respectively.</para>
-
-<para>For the meaning of parameters
-<computeroutput>small</computeroutput> and
-<computeroutput>verbosity</computeroutput>, see
-<computeroutput>BZ2_bzDecompressInit</computeroutput>.</para>
-
-<para>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 <computeroutput>BZ2_bzReadOpen</computeroutput>
-returns <computeroutput>BZ_OK</computeroutput> but a subsequent
-call of <computeroutput>BZ2_bzRead</computeroutput> will return
-<computeroutput>BZ_MEM_ERROR</computeroutput>.</para>
-
-<para>Possible assignments to
-<computeroutput>bzerror</computeroutput>:</para>
-
-<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.
-</programlisting>
-
-<para>Possible return values:</para>
-
-<programlisting>
-Pointer to an abstract BZFILE
- if bzerror is BZ_OK
-NULL
- otherwise
-</programlisting>
-
-<para>Allowable next actions:</para>
-
-<programlisting>
-BZ2_bzRead
- if bzerror is BZ_OK
-BZ2_bzClose
- otherwise
-</programlisting>
-
-</sect2>
-
-
-<sect2 id="bzread" xreflabel="BZ2_bzRead">
-<title>BZ2_bzRead</title>
-
-<programlisting>
-int BZ2_bzRead ( int *bzerror, BZFILE *b, void *buf, int len );
-</programlisting>
-
-<para>Reads up to <computeroutput>len</computeroutput>
-(uncompressed) bytes from the compressed file
-<computeroutput>b</computeroutput> into the buffer
-<computeroutput>buf</computeroutput>. If the read was
-successful, <computeroutput>bzerror</computeroutput> is set to
-<computeroutput>BZ_OK</computeroutput> and the number of bytes
-read is returned. If the logical end-of-stream was detected,
-<computeroutput>bzerror</computeroutput> will be set to
-<computeroutput>BZ_STREAM_END</computeroutput>, and the number of
-bytes read is returned. All other
-<computeroutput>bzerror</computeroutput> values denote an
-error.</para>
-
-<para><computeroutput>BZ2_bzRead</computeroutput> will supply
-<computeroutput>len</computeroutput> 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 <computeroutput>bzerror</computeroutput> after every call
-and watch out for
-<computeroutput>BZ_STREAM_END</computeroutput>.</para>
-
-<para>Internally, <computeroutput>BZ2_bzRead</computeroutput>
-copies data from the compressed file in chunks of size
-<computeroutput>BZ_MAX_UNUSED</computeroutput> bytes before
-decompressing it. If the file contains more bytes than strictly
-needed to reach the logical end-of-stream,
-<computeroutput>BZ2_bzRead</computeroutput> will almost certainly
-read some of the trailing data before signalling
-<computeroutput>BZ_SEQUENCE_END</computeroutput>. To collect the
-read but unused data once
-<computeroutput>BZ_SEQUENCE_END</computeroutput> has appeared,
-call <computeroutput>BZ2_bzReadGetUnused</computeroutput>
-immediately before
-<computeroutput>BZ2_bzReadClose</computeroutput>.</para>
-
-<para>Possible assignments to
-<computeroutput>bzerror</computeroutput>:</para>
-
-<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.
-</programlisting>
-
-<para>Possible return values:</para>
-
-<programlisting>
-number of bytes read
- if bzerror is BZ_OK or BZ_STREAM_END
-undefined
- otherwise
-</programlisting>
-
-<para>Allowable next actions:</para>
-
-<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
-</programlisting>
-
-</sect2>
-
-
-<sect2 id="bzreadgetunused" xreflabel="BZ2_bzReadGetUnused">
-<title>BZ2_bzReadGetUnused</title>
-
-<programlisting>
-void BZ2_bzReadGetUnused( int* bzerror, BZFILE *b,
- void** unused, int* nUnused );
-</programlisting>
-
-<para>Returns data which was read from the compressed file but
-was not needed to get to the logical end-of-stream.
-<computeroutput>*unused</computeroutput> is set to the address of
-the data, and <computeroutput>*nUnused</computeroutput> to the
-number of bytes. <computeroutput>*nUnused</computeroutput> will
-be set to a value between <computeroutput>0</computeroutput> and
-<computeroutput>BZ_MAX_UNUSED</computeroutput> inclusive.</para>
-
-<para>This function may only be called once
-<computeroutput>BZ2_bzRead</computeroutput> has signalled
-<computeroutput>BZ_STREAM_END</computeroutput> but before
-<computeroutput>BZ2_bzReadClose</computeroutput>.</para>
-
-<para>Possible assignments to
-<computeroutput>bzerror</computeroutput>:</para>
-
-<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
-</programlisting>
-
-<para>Allowable next actions:</para>
-
-<programlisting>
-BZ2_bzReadClose
-</programlisting>
-
-</sect2>
-
-
-<sect2 id="bzreadclose" xreflabel="BZ2_bzReadClose">
-<title>BZ2_bzReadClose</title>
-
-<programlisting>
-void BZ2_bzReadClose ( int *bzerror, BZFILE *b );
-</programlisting>
-
-<para>Releases all memory pertaining to the compressed file
-<computeroutput>b</computeroutput>.
-<computeroutput>BZ2_bzReadClose</computeroutput> does not call
-<computeroutput>fclose</computeroutput> on the underlying file
-handle, so you should do that yourself if appropriate.
-<computeroutput>BZ2_bzReadClose</computeroutput> should be called
-to clean up after all error situations.</para>
-
-<para>Possible assignments to
-<computeroutput>bzerror</computeroutput>:</para>
-
-<programlisting>
-BZ_SEQUENCE_ERROR
- if b was opened with BZ2_bzOpenWrite
-BZ_OK
- otherwise
-</programlisting>
-
-<para>Allowable next actions:</para>
-
-<programlisting>
-none
-</programlisting>
-
-</sect2>
-
-
-<sect2 id="bzwriteopen" xreflabel="BZ2_bzWriteOpen">
-<title>BZ2_bzWriteOpen</title>
-
-<programlisting>
-BZFILE *BZ2_bzWriteOpen( int *bzerror, FILE *f,
- int blockSize100k, int verbosity,
- int workFactor );
-</programlisting>
-
-<para>Prepare to write compressed data to file handle
-<computeroutput>f</computeroutput>.
-<computeroutput>f</computeroutput> should refer to a file which
-has been opened for writing, and for which the error indicator
-(<computeroutput>ferror(f)</computeroutput>)is not set.</para>
-
-<para>For the meaning of parameters
-<computeroutput>blockSize100k</computeroutput>,
-<computeroutput>verbosity</computeroutput> and
-<computeroutput>workFactor</computeroutput>, see
-<computeroutput>BZ2_bzCompressInit</computeroutput>.</para>
-
-<para>All required memory is allocated at this stage, so if the
-call completes successfully,
-<computeroutput>BZ_MEM_ERROR</computeroutput> cannot be signalled
-by a subsequent call to
-<computeroutput>BZ2_bzWrite</computeroutput>.</para>
-
-<para>Possible assignments to
-<computeroutput>bzerror</computeroutput>:</para>
-
-<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
-</programlisting>
-
-<para>Possible return values:</para>
-
-<programlisting>
-Pointer to an abstract BZFILE
- if bzerror is BZ_OK
-NULL
- otherwise
-</programlisting>
-
-<para>Allowable next actions:</para>
-
-<programlisting>
-BZ2_bzWrite
- if bzerror is BZ_OK
- (you could go directly to BZ2_bzWriteClose, but this would be pretty pointless)
-BZ2_bzWriteClose
- otherwise
-</programlisting>
-
-</sect2>
-
-
-<sect2 id="bzwrite" xreflabel="BZ2_bzWrite">
-<title>BZ2_bzWrite</title>
-
-<programlisting>
-void BZ2_bzWrite ( int *bzerror, BZFILE *b, void *buf, int len );
-</programlisting>
-
-<para>Absorbs <computeroutput>len</computeroutput> bytes from the
-buffer <computeroutput>buf</computeroutput>, eventually to be
-compressed and written to the file.</para>
-
-<para>Possible assignments to
-<computeroutput>bzerror</computeroutput>:</para>
-
-<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
-</programlisting>
-
-</sect2>
-
-
-<sect2 id="bzwriteclose" xreflabel="BZ2_bzWriteClose">
-<title>BZ2_bzWriteClose</title>
-
-<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 );
-</programlisting>
-
-<para>Compresses and flushes to the compressed file all data so
-far supplied by <computeroutput>BZ2_bzWrite</computeroutput>.
-The logical end-of-stream markers are also written, so subsequent
-calls to <computeroutput>BZ2_bzWrite</computeroutput> are
-illegal. All memory associated with the compressed file
-<computeroutput>b</computeroutput> is released.
-<computeroutput>fflush</computeroutput> is called on the
-compressed file, but it is not
-<computeroutput>fclose</computeroutput>'d.</para>
-
-<para>If <computeroutput>BZ2_bzWriteClose</computeroutput> 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
-<computeroutput>fflush</computeroutput> the compressed file. You
-can force this behaviour to happen even in the case of no error,
-by passing a nonzero value to
-<computeroutput>abandon</computeroutput>.</para>
-
-<para>If <computeroutput>nbytes_in</computeroutput> is non-null,
-<computeroutput>*nbytes_in</computeroutput> will be set to be the
-total volume of uncompressed data handled. Similarly,
-<computeroutput>nbytes_out</computeroutput> will be set to the
-total volume of compressed data written. For compatibility with
-older versions of the library,
-<computeroutput>BZ2_bzWriteClose</computeroutput> only yields the
-lower 32 bits of these counts. Use
-<computeroutput>BZ2_bzWriteClose64</computeroutput> if you want
-the full 64 bit counts. These two functions are otherwise
-absolutely identical.</para>
-
-<para>Possible assignments to
-<computeroutput>bzerror</computeroutput>:</para>
-
-<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
-</programlisting>
-
-</sect2>
-
-
-<sect2 id="embed" xreflabel="Handling embedded compressed data streams">
-<title>Handling embedded compressed data streams</title>
-
-<para>The high-level library facilitates use of
-<computeroutput>bzip2</computeroutput> data streams which form
-some part of a surrounding, larger data stream.</para>
-
-<itemizedlist mark='bullet'>
-
- <listitem><para>For writing, the library takes an open file handle,
- writes compressed data to it,
- <computeroutput>fflush</computeroutput>es it but does not
- <computeroutput>fclose</computeroutput> it. The calling
- application can write its own data before and after the
- compressed data stream, using that same file handle.</para></listitem>
-
- <listitem><para>Reading is more complex, and the facilities are not as
- general as they could be since generality is hard to reconcile
- with efficiency. <computeroutput>BZ2_bzRead</computeroutput>
- reads from the compressed file in blocks of size
- <computeroutput>BZ_MAX_UNUSED</computeroutput> bytes, and in
- doing so probably will overshoot the logical end of compressed
- stream. To recover this data once decompression has ended,
- call <computeroutput>BZ2_bzReadGetUnused</computeroutput> after
- the last call of <computeroutput>BZ2_bzRead</computeroutput>
- (the one returning
- <computeroutput>BZ_STREAM_END</computeroutput>) but before
- calling
- <computeroutput>BZ2_bzReadClose</computeroutput>.</para></listitem>
-
-</itemizedlist>
-
-<para>This mechanism makes it easy to decompress multiple
-<computeroutput>bzip2</computeroutput> streams placed end-to-end.
-As the end of one stream, when
-<computeroutput>BZ2_bzRead</computeroutput> returns
-<computeroutput>BZ_STREAM_END</computeroutput>, call
-<computeroutput>BZ2_bzReadGetUnused</computeroutput> 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
-<computeroutput>BZ2_bzReadOpen</computeroutput> again, feeding in
-the unused data via the <computeroutput>unused</computeroutput> /
-<computeroutput>nUnused</computeroutput> parameters. Keep doing
-this until <computeroutput>BZ_STREAM_END</computeroutput> return
-coincides with the physical end of file
-(<computeroutput>feof(f)</computeroutput>). In this situation
-<computeroutput>BZ2_bzReadGetUnused</computeroutput> will of
-course return no data.</para>
-
-<para>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.</para>
-
-</sect2>
-
-
-<sect2 id="std-rdwr" xreflabel="Standard file-reading/writing code">
-<title>Standard file-reading/writing code</title>
-
-<para>Here's how you'd write data to a compressed file:</para>
-
-<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 */
-}
-</programlisting>
-
-<para>And to read from a compressed file:</para>
-
-<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 );
-}
-</programlisting>
-
-</sect2>
-
-</sect1>
-
-
-<sect1 id="util-fns" xreflabel="Utility functions">
-<title>Utility functions</title>
-
-
-<sect2 id="bzbufftobuffcompress" xreflabel="BZ2_bzBuffToBuffCompress">
-<title>BZ2_bzBuffToBuffCompress</title>
-
-<programlisting>
-int BZ2_bzBuffToBuffCompress( char* dest,
- unsigned int* destLen,
- char* source,
- unsigned int sourceLen,
- int blockSize100k,
- int verbosity,
- int workFactor );
-</programlisting>
-
-<para>Attempts to compress the data in <computeroutput>source[0
-.. sourceLen-1]</computeroutput> into the destination buffer,
-<computeroutput>dest[0 .. *destLen-1]</computeroutput>. If the
-destination buffer is big enough,
-<computeroutput>*destLen</computeroutput> is set to the size of
-the compressed data, and <computeroutput>BZ_OK</computeroutput>
-is returned. If the compressed data won't fit,
-<computeroutput>*destLen</computeroutput> is unchanged, and
-<computeroutput>BZ_OUTBUFF_FULL</computeroutput> is
-returned.</para>
-
-<para>Compression in this manner is a one-shot event, done with a
-single call to this function. The resulting compressed data is a
-complete <computeroutput>bzip2</computeroutput> 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.</para>
-
-<para>For the meaning of parameters
-<computeroutput>blockSize100k</computeroutput>,
-<computeroutput>verbosity</computeroutput> and
-<computeroutput>workFactor</computeroutput>, see
-<computeroutput>BZ2_bzCompressInit</computeroutput>.</para>
-
-<para>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.</para>
-
-<para><computeroutput>BZ2_bzBuffToBuffDecompress</computeroutput>
-will not write data at or beyond
-<computeroutput>dest[*destLen]</computeroutput>, even in case of
-buffer overflow.</para>
-
-<para>Possible return values:</para>
-
-<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
-</programlisting>
-
-</sect2>
-
-
-<sect2 id="bzbufftobuffdecompress" xreflabel="BZ2_bzBuffToBuffDecompress">
-<title>BZ2_bzBuffToBuffDecompress</title>
-
-<programlisting>
-int BZ2_bzBuffToBuffDecompress( char* dest,
- unsigned int* destLen,
- char* source,
- unsigned int sourceLen,
- int small,
- int verbosity );
-</programlisting>
-
-<para>Attempts to decompress the data in <computeroutput>source[0
-.. sourceLen-1]</computeroutput> into the destination buffer,
-<computeroutput>dest[0 .. *destLen-1]</computeroutput>. If the
-destination buffer is big enough,
-<computeroutput>*destLen</computeroutput> is set to the size of
-the uncompressed data, and <computeroutput>BZ_OK</computeroutput>
-is returned. If the compressed data won't fit,
-<computeroutput>*destLen</computeroutput> is unchanged, and
-<computeroutput>BZ_OUTBUFF_FULL</computeroutput> is
-returned.</para>
-
-<para><computeroutput>source</computeroutput> is assumed to hold
-a complete <computeroutput>bzip2</computeroutput> format data
-stream.
-<computeroutput>BZ2_bzBuffToBuffDecompress</computeroutput> tries
-to decompress the entirety of the stream into the output
-buffer.</para>
-
-<para>For the meaning of parameters
-<computeroutput>small</computeroutput> and
-<computeroutput>verbosity</computeroutput>, see
-<computeroutput>BZ2_bzDecompressInit</computeroutput>.</para>
-
-<para>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.</para>
-
-<para><computeroutput>BZ2_bzBuffToBuffDecompress</computeroutput>
-will not write data at or beyond
-<computeroutput>dest[*destLen]</computeroutput>, even in case of
-buffer overflow.</para>
-
-<para>Possible return values:</para>
-
-<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
-</programlisting>
-
-</sect2>
-
-</sect1>
-
-
-<sect1 id="zlib-compat" xreflabel="zlib compatibility functions">
-<title>zlib compatibility functions</title>
-
-<para>Yoshioka Tsuneo has contributed some functions to give
-better <computeroutput>zlib</computeroutput> compatibility.
-These functions are <computeroutput>BZ2_bzopen</computeroutput>,
-<computeroutput>BZ2_bzread</computeroutput>,
-<computeroutput>BZ2_bzwrite</computeroutput>,
-<computeroutput>BZ2_bzflush</computeroutput>,
-<computeroutput>BZ2_bzclose</computeroutput>,
-<computeroutput>BZ2_bzerror</computeroutput> and
-<computeroutput>BZ2_bzlibVersion</computeroutput>. 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.</para>
-
-<programlisting>
-typedef void BZFILE;
-
-const char * BZ2_bzlibVersion ( void );
-</programlisting>
-
-<para>Returns a string indicating the library version.</para>
-
-<programlisting>
-BZFILE * BZ2_bzopen ( const char *path, const char *mode );
-BZFILE * BZ2_bzdopen ( int fd, const char *mode );
-</programlisting>
-
-<para>Opens a <computeroutput>.bz2</computeroutput> file for
-reading or writing, using either its name or a pre-existing file
-descriptor. Analogous to <computeroutput>fopen</computeroutput>
-and <computeroutput>fdopen</computeroutput>.</para>
-
-<programlisting>
-int BZ2_bzread ( BZFILE* b, void* buf, int len );
-int BZ2_bzwrite ( BZFILE* b, void* buf, int len );
-</programlisting>
-
-<para>Reads/writes data from/to a previously opened
-<computeroutput>BZFILE</computeroutput>. Analogous to
-<computeroutput>fread</computeroutput> and
-<computeroutput>fwrite</computeroutput>.</para>
-
-<programlisting>
-int BZ2_bzflush ( BZFILE* b );
-void BZ2_bzclose ( BZFILE* b );
-</programlisting>
-
-<para>Flushes/closes a <computeroutput>BZFILE</computeroutput>.
-<computeroutput>BZ2_bzflush</computeroutput> doesn't actually do
-anything. Analogous to <computeroutput>fflush</computeroutput>
-and <computeroutput>fclose</computeroutput>.</para>
-
-<programlisting>
-const char * BZ2_bzerror ( BZFILE *b, int *errnum )
-</programlisting>
-
-<para>Returns a string describing the more recent error status of
-<computeroutput>b</computeroutput>, and also sets
-<computeroutput>*errnum</computeroutput> to its numerical
-value.</para>
-
-</sect1>
-
-
-<sect1 id="stdio-free"
- xreflabel="Using the library in a stdio-free environment">
-<title>Using the library in a stdio-free environment</title>
-
-
-<sect2 id="stdio-bye" xreflabel="Getting rid of stdio">
-<title>Getting rid of stdio</title>
-
-<para>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
-<computeroutput>BZ_NO_STDIO</computeroutput> defined. Doing this
-gives you a library containing only the following eight
-functions:</para>
-
-<para><computeroutput>BZ2_bzCompressInit</computeroutput>,
-<computeroutput>BZ2_bzCompress</computeroutput>,
-<computeroutput>BZ2_bzCompressEnd</computeroutput>
-<computeroutput>BZ2_bzDecompressInit</computeroutput>,
-<computeroutput>BZ2_bzDecompress</computeroutput>,
-<computeroutput>BZ2_bzDecompressEnd</computeroutput>
-<computeroutput>BZ2_bzBuffToBuffCompress</computeroutput>,
-<computeroutput>BZ2_bzBuffToBuffDecompress</computeroutput></para>
-
-<para>When compiled like this, all functions will ignore
-<computeroutput>verbosity</computeroutput> settings.</para>
-
-</sect2>
-
-
-<sect2 id="critical-error" xreflabel="Critical error handling">
-<title>Critical error handling</title>
-
-<para><computeroutput>libbzip2</computeroutput> 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
-<computeroutput>BZ_NO_STDIO</computeroutput> set.</para>
-
-<para>For a normal compile, an assertion failure yields the
-message:</para>
-
-<blockquote>
-<para>bzip2/libbzip2: internal error number N.</para>
-<para>This is a bug in bzip2/libbzip2, &bz-version; of &bz-date;.
-Please report it to me at: &bz-email;. 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, &bz-date;.
-</para></blockquote>
-
-<para>where <computeroutput>N</computeroutput> is some error code
-number. If <computeroutput>N == 1007</computeroutput>, 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).</para>
-
-<para><computeroutput>exit(3)</computeroutput> is then
-called.</para>
-
-<para>For a <computeroutput>stdio</computeroutput>-free library,
-assertion failures result in a call to a function declared
-as:</para>
-
-<programlisting>
-extern void bz_internal_error ( int errcode );
-</programlisting>
-
-<para>The relevant code is passed as a parameter. You should
-supply such a function.</para>
-
-<para>In either case, once an assertion failure has occurred, any
-<computeroutput>bz_stream</computeroutput> records involved can
-be regarded as invalid. You should not attempt to resume normal
-operation with them.</para>
-
-<para>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.</para>
-
-</sect2>
-
-</sect1>
-
-
-<sect1 id="win-dll" xreflabel="Making a Windows DLL">
-<title>Making a Windows DLL</title>
-
-<para>Everything related to Windows has been contributed by
-Yoshioka Tsuneo
-(<computeroutput>tsuneo@rr.iij4u.or.jp</computeroutput>), so
-you should send your queries to him (but perhaps Cc: me,
-<computeroutput>&bz-email;</computeroutput>).</para>
-
-<para>My vague understanding of what to do is: using Visual C++
-5.0, open the project file
-<computeroutput>libbz2.dsp</computeroutput>, and build. That's
-all.</para>
-
-<para>If you can't open the project file for some reason, make a
-new one, naming these files:
-<computeroutput>blocksort.c</computeroutput>,
-<computeroutput>bzlib.c</computeroutput>,
-<computeroutput>compress.c</computeroutput>,
-<computeroutput>crctable.c</computeroutput>,
-<computeroutput>decompress.c</computeroutput>,
-<computeroutput>huffman.c</computeroutput>,
-<computeroutput>randtable.c</computeroutput> and
-<computeroutput>libbz2.def</computeroutput>. You will also need
-to name the header files <computeroutput>bzlib.h</computeroutput>
-and <computeroutput>bzlib_private.h</computeroutput>.</para>
-
-<para>If you don't use VC++, you may need to define the
-proprocessor symbol
-<computeroutput>_WIN32</computeroutput>.</para>
-
-<para>Finally, <computeroutput>dlltest.c</computeroutput> is a
-sample program using the DLL. It has a project file,
-<computeroutput>dlltest.dsp</computeroutput>.</para>
-
-<para>If you just want a makefile for Visual C, have a look at
-<computeroutput>makefile.msc</computeroutput>.</para>
-
-<para>Be aware that if you compile
-<computeroutput>bzip2</computeroutput> itself on Win32, you must
-set <computeroutput>BZ_UNIX</computeroutput> to 0 and
-<computeroutput>BZ_LCCWIN32</computeroutput> to 1, in the file
-<computeroutput>bzip2.c</computeroutput>, before compiling.
-Otherwise the resulting binary won't work correctly.</para>
-
-<para>I haven't tried any of this stuff myself, but it all looks
-plausible.</para>
-
-</sect1>
-
-</chapter>
-
-
-
-<chapter id="misc" xreflabel="Miscellanea">
-<title>Miscellanea</title>
-
-<para>These are just some random thoughts of mine. Your mileage
-may vary.</para>
-
-
-<sect1 id="limits" xreflabel="Limitations of the compressed file format">
-<title>Limitations of the compressed file format</title>
-
-<para><computeroutput>bzip2-1.0.X</computeroutput>,
-<computeroutput>0.9.5</computeroutput> and
-<computeroutput>0.9.0</computeroutput> use exactly the same file
-format as the original version,
-<computeroutput>bzip2-0.1</computeroutput>. This decision was
-made in the interests of stability. Creating yet another
-incompatible compressed file format would create further
-confusion and disruption for users.</para>
-
-<para>Nevertheless, this is not a painless decision. Development
-work since the release of
-<computeroutput>bzip2-0.1</computeroutput> in August 1997 has
-shown complexities in the file format which slow down
-decompression and, in retrospect, are unnecessary. These
-are:</para>
-
-<itemizedlist mark='bullet'>
-
- <listitem><para>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.</para></listitem>
-
- <listitem><para>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.</para>
-
- <para>I could have changed to Sadakane's algorithm, but I find
- it to be slower than <computeroutput>bzip2</computeroutput>'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
- <computeroutput>bzip2-0.1</computeroutput>'s performance on
- repetitive data, so perhaps it isn't a problem for real
- inputs.</para>
-
- <para>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.</para></listitem>
-
- <listitem><para>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
- <computeroutput>decompress.c</computeroutput> 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.</para></listitem>
-
- <listitem><para>An Adler-32 checksum, rather than a CRC32 checksum,
- would be faster to compute.</para></listitem>
-
-</itemizedlist>
-
-<para>It would be fair to say that the
-<computeroutput>bzip2</computeroutput> format was frozen before I
-properly and fully understood the performance consequences of
-doing so.</para>
-
-<para>Improvements which I was able to incorporate into 0.9.0,
-despite using the same file format, are:</para>
-
-<itemizedlist mark='bullet'>
-
- <listitem><para>Single array implementation of the inverse BWT. This
- significantly speeds up decompression, presumably because it
- reduces the number of cache misses.</para></listitem>
-
- <listitem><para>Faster inverse MTF transform for large MTF values.
- The new implementation is based on the notion of sliding blocks
- of values.</para></listitem>
-
- <listitem><para><computeroutput>bzip2-0.9.0</computeroutput> now reads
- and writes files with <computeroutput>fread</computeroutput>
- and <computeroutput>fwrite</computeroutput>; version 0.1 used
- <computeroutput>putc</computeroutput> and
- <computeroutput>getc</computeroutput>. Duh! Well, you live
- and learn.</para></listitem>
-
-</itemizedlist>
-
-<para>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.</para>
-
-</sect1>
-
-
-<sect1 id="port-issues" xreflabel="Portability issues">
-<title>Portability issues</title>
-
-<para>After some consideration, I have decided not to use GNU
-<computeroutput>autoconf</computeroutput> to configure 0.9.5 or
-1.0.</para>
-
-<para><computeroutput>autoconf</computeroutput>, admirable and
-wonderful though it is, mainly assists with portability problems
-between Unix-like platforms. But
-<computeroutput>bzip2</computeroutput> 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. <computeroutput>autoconf</computeroutput> doesn't help
-in those cases, and brings in a whole load of new
-complexity.</para>
-
-<para>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.</para>
-
-<para>There are a couple of
-<computeroutput>__inline__</computeroutput> directives in the
-code. GNU C (<computeroutput>gcc</computeroutput>) 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
-<computeroutput>#define</computeroutput>
-<computeroutput>__inline__</computeroutput> to be
-<computeroutput>/* */</computeroutput>. One easy way to do this
-is to compile with the flag
-<computeroutput>-D__inline__=</computeroutput>, which should be
-understood by most Unix compilers.</para>
-
-<para>If you still have difficulties, try compiling with the
-macro <computeroutput>BZ_STRICT_ANSI</computeroutput> 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
-<computeroutput>bzip2</computeroutput>'s checks against
-compressing directories, symbolic links, devices, and other
-not-really-a-file entities. This could cause filesystem
-corruption!</para>
-
-<para>One other thing: if you create a
-<computeroutput>bzip2</computeroutput> binary for public distribution,
-please consider linking it statically (<computeroutput>gcc
--static</computeroutput>). This avoids all sorts of library-version
-issues that others may encounter later on.</para>
-
-<para>If you build <computeroutput>bzip2</computeroutput> on
-Win32, you must set <computeroutput>BZ_UNIX</computeroutput> to 0
-and <computeroutput>BZ_LCCWIN32</computeroutput> to 1, in the
-file <computeroutput>bzip2.c</computeroutput>, before compiling.
-Otherwise the resulting binary won't work correctly.</para>
-
-</sect1>
-
-
-<sect1 id="bugs" xreflabel="Reporting bugs">
-<title>Reporting bugs</title>
-
-<para>I tried pretty hard to make sure
-<computeroutput>bzip2</computeroutput> is bug free, both by
-design and by testing. Hopefully you'll never need to read this
-section for real.</para>
-
-<para>Nevertheless, if <computeroutput>bzip2</computeroutput> 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.</para>
-
-<itemizedlist mark='bullet'>
-
- <listitem><para>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
- <computeroutput>bzip2</computeroutput>, and I've run across two
- such examples myself.</para>
-
- <para>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
- <computeroutput>-O2</computeroutput>
- <computeroutput>-fomit-frame-pointer</computeroutput>
- <computeroutput>-fno-strength-reduce</computeroutput>. You
- should specifically <emphasis>not</emphasis> use
- <computeroutput>-funroll-loops</computeroutput>.</para>
-
- <para>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.</para></listitem>
-
- <listitem><para>If <computeroutput>bzip2</computeroutput>
- crashes randomly, and the crashes are not repeatable, you may
- have a flaky memory subsystem.
- <computeroutput>bzip2</computeroutput> 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.</para>
-
- <para>Try using a different machine of the same type, and see
- if you can repeat the problem.</para></listitem>
-
- <listitem><para>This isn't really a bug, but ... If
- <computeroutput>bzip2</computeroutput> 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.</para></listitem>
-
-</itemizedlist>
-
-<para>If you've incorporated
-<computeroutput>libbzip2</computeroutput> 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.</para>
-
-<para>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:</para>
-
-<programlisting>
-bzip2 crashed with segmentation fault on my machine
-</programlisting>
-
-<para>and absolutely nothing else. Needless to say, a such a
-report is <emphasis>totally, utterly, completely and
-comprehensively 100% useless; a waste of your time, my time, and
-net bandwidth</emphasis>. With no details at all, there's no way
-I can possibly begin to figure out what the problem is.</para>
-
-<para>The rules of the game are: facts, facts, facts. Don't omit
-them because "oh, they won't be relevant". At the bare
-minimum:</para>
-
-<programlisting>
-Machine type. Operating system version.
-Exact version of bzip2 (do bzip2 -V).
-Exact version of the compiler used.
-Flags passed to the compiler.
-</programlisting>
-
-<para>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.</para>
-
-</sect1>
-
-
-<sect1 id="package" xreflabel="Did you get the right package?">
-<title>Did you get the right package?</title>
-
-<para><computeroutput>bzip2</computeroutput> 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.</para>
-
-<para>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.</para>
-
-<para>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, <computeroutput>zlib-1.2.1</computeroutput> and
-<computeroutput>gzip-1.2.4</computeroutput>. Look for them at
-<ulink url="http://www.zlib.org">http://www.zlib.org</ulink> and
-<ulink url="http://www.gzip.org">http://www.gzip.org</ulink>
-respectively.</para>
-
-<para>For something faster and lighter still, you might try Markus F
-X J Oberhumer's <computeroutput>LZO</computeroutput> real-time
-compression/decompression library, at
-<ulink url="http://www.oberhumer.com/opensource">http://www.oberhumer.com/opensource</ulink>.</para>
-
-</sect1>
-
-
-
-<sect1 id="reading" xreflabel="Further Reading">
-<title>Further Reading</title>
-
-<para><computeroutput>bzip2</computeroutput> 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.</para>
-
-<para>Four documents describe essentially all the ideas behind
-<computeroutput>bzip2</computeroutput>:</para>
-
-<literallayout>Michael Burrows and D. J. Wheeler:
- "A block-sorting lossless data compression algorithm"
- 10th May 1994.
- Digital SRC Research Report 124.
- ftp://ftp.digital.com/pub/DEC/SRC/research-reports/SRC-124.ps.gz
- If you have trouble finding it, try searching at the
- New Zealand Digital Library, http://www.nzdl.org.
-
-Daniel S. Hirschberg and Debra A. LeLewer
- "Efficient Decoding of Prefix Codes"
- Communications of the ACM, April 1990, Vol 33, Number 4.
- You might be able to get an electronic copy of this
- from the ACM Digital Library.
-
-David J. Wheeler
- Program bred3.c and accompanying document bred3.ps.
- This contains the idea behind the multi-table Huffman coding scheme.
- ftp://ftp.cl.cam.ac.uk/users/djw3/
-
-Jon L. Bentley and Robert Sedgewick
- "Fast Algorithms for Sorting and Searching Strings"
- Available from Sedgewick's web page,
- www.cs.princeton.edu/~rs
-</literallayout>
-
-<para>The following paper gives valuable additional insights into
-the algorithm, but is not immediately the basis of any code used
-in bzip2.</para>
-
-<literallayout>Peter Fenwick:
- Block Sorting Text Compression
- Proceedings of the 19th Australasian Computer Science Conference,
- Melbourne, Australia. Jan 31 - Feb 2, 1996.
- ftp://ftp.cs.auckland.ac.nz/pub/peter-f/ACSC96paper.ps</literallayout>
-
-<para>Kunihiko Sadakane's sorting algorithm, mentioned above, is
-available from:</para>
-
-<literallayout>http://naomi.is.s.u-tokyo.ac.jp/~sada/papers/Sada98b.ps.gz
-</literallayout>
-
-<para>The Manber-Myers suffix array construction algorithm is
-described in a paper available from:</para>
-
-<literallayout>http://www.cs.arizona.edu/people/gene/PAPERS/suffix.ps
-</literallayout>
-
-<para>Finally, the following papers document some
-investigations I made into the performance of sorting
-and decompression algorithms:</para>
-
-<literallayout>Julian Seward
- On the Performance of BWT Sorting Algorithms
- Proceedings of the IEEE Data Compression Conference 2000
- Snowbird, Utah. 28-30 March 2000.
-
-Julian Seward
- Space-time Tradeoffs in the Inverse B-W Transform
- Proceedings of the IEEE Data Compression Conference 2001
- Snowbird, Utah. 27-29 March 2001.
-</literallayout>
-
-</sect1>
-
-</chapter>
-
-</book>
projects / ceph.git / blobdiff