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108 lines
6.8 KiB
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Executable File
108 lines
6.8 KiB
HTML
Executable File
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML>
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<HEAD>
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<TITLE>Compression/Decompression</TITLE>
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<LINK REL="stylesheet" HREF="../../../boost.css">
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<LINK REL="stylesheet" HREF="theme/iostreams.css">
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</HEAD>
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<BODY>
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<!-- Begin Banner -->
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<H1 CLASS="title">Compression/Decompression</H1>
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<HR CLASS="banner">
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<!-- End Banner -->
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<DL class="page-index">
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<DT><A href="#overview">Overview</A></DT>
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<DT><A href="#acknowledgments">Acknowledgments</A></DT>
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<DT><A href="#headers">Headers</A></DT>
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<DT><A href="#installation">Installation</A></DT>
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<DT>Reference
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<DL class="page-index">
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<DT><A HREF="classes/zlib.html">Zlib Filters</A></DT>
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<DT><A HREF="classes/gzip.html">Gzip Filters</A></DT>
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<DT><A HREF="classes/bzip2.html">Bzip2 Filters</A></DT>
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</DL>
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</DT>
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</DL>
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<A NAME="overview">
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<H2>Overview</H2>
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<P>
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The Boost Iostreams Library provides three pairs of Filters for compression/decompression. The class templates <A HREF="classes/zlib.html#basic_zlib_compressor"><CODE>basic_zlib_compressor</CODE></A> and <A HREF="classes/zlib.html#basic_zlib_decompressor"><CODE>basic_zlib_decompressor</CODE></A> perform compression and decompression in the Z<SPAN STYLE="font-size:80%">LIB</SPAN> format (<A CLASS="bib_ref" HREF="bibliography.html#deutsch1">[Deutsch1]</A>) using Jean-loup Gailly's and Mark Adler's zlib compression library (<A CLASS="bib_ref" HREF="bibliography.html#gailly">[Gailly]</A>). The class templates <A HREF="classes/gzip.html#basic_gzip_compressor"><CODE>basic_gzip_compressor</CODE></A> and <A HREF="classes/gzip.html#basic_gzip_decompressor"><CODE>basic_gzip_decompressor</CODE></A> perform compression and decompression in the G<SPAN STYLE="font-size:80%">ZIP</SPAN> format (<A CLASS="bib_ref" HREF="bibliography.html#deutsch3">[Deutsch3]</A>), also using zlib. The class templates <A HREF="classes/bzip2.html#basic_bzip2_compressor"><CODE>basic_bzip2_compressor</CODE></A> and <A HREF="classes/bzip2.html#basic_bzip2_decompressor"><CODE>basic_bzip2_decompressor</CODE></A> perform compression and decompression in the B<SPAN STYLE="font-size:80%">ZIP2</SPAN> format using Julian Seward' libbzip2 compression library (<A CLASS="bib_ref" HREF="bibliography.html#seward">[Seward]</A>).
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</P>
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<P>
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All the compression/decompression Filters are <A HREF="concepts/dual_use_filter.html">DualUseFilters</A> so that they may be used for either input or output.<A CLASS="footnote_ref" NAME="note_1_ref" HREF="#note_1"><SUP>[1]</SUP></A> Most commonly, however, the compression Filters will be used for output and the decompression Filters for input.
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</P>
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<A NAME="acknowledgments">
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<H2>Acknowledgments</H2>
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<P>
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The compression/decompression Filters were influences by the work of Jeff Garland (<A CLASS="bib_ref" HREF="bibliography.html#garland">[Garland]</A>) and Jonathan de Halleux (<A CLASS="bib_ref" HREF="bibliography.html#de_halleux">[de Halleux]</A>). Thanks also to <A HREF="mailto:jloup@gailly.net">Jean-loup Gailly</A> and <A HREF="mailto:madler@alumni.caltech.edu">Mark Adler</A> and to <A HREF="mailto:jseward@acm.org">Julian Seward</A> for making their excellent librarys available to the public with <A HREF="http://www.boost.org/more/lib_guide.htm#Requirements">Boost-compatible</A> licenses.
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</P>
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<!-- Adler's obfuscated address is copied from his homepage -->
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<A NAME="headers">
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<H2>Headers</H2>
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<DL>
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<DT><A CLASS="header" HREF="../../../boost/iostreams/filter/zlib.hpp"><CODE><boost/iostreams/filter/zlib.hpp></CODE></A></DT>
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<DT><A CLASS="header" HREF="../../../boost/iostreams/filter/gzip.hpp"><CODE><boost/iostreams/filter/gzip.hpp></CODE></A></DT>
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<DT><A CLASS="header" HREF="../../../boost/iostreams/filter/bzip2.hpp"><CODE><boost/iostreams/filter/bzip2.hpp></CODE></A></DT>
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</DL>
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<A NAME="installation">
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<H2>Installation</H2>
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<P>
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The zlib and gzip Filters depend on the source file <A CLASS="header" HREF="../src/zlib.cpp"><CODE><libs/src/zlib.cpp></CODE></A>. The bzip2 Filters depend on the source file <A CLASS="header" HREF="../src/bzip2.cpp"><CODE><libs/src/bzip2.cpp></CODE></A>. These source files use several headers from the zlib and gzip libraries, included with the Iostreams Library distribution in the directories <A CLASS="header" HREF="../src/zlib"><CODE><libs/iostreams/src/zlib></CODE></A> and <A CLASS="header" HREF="../src/bzip2"><CODE><libs/iostreams/src/bzip2></CODE></A>. Code using these filters must be linked against the zlib or libbzip2 binaries, which are available on most UNIX systems and which can be obtained for Windows systems here:
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<UL>
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<LI CLASS="square"><A HREF="http://www.gzip.org/zlib/contrib/index.html" TARGET="_top">zlib binaries (unofficial)</A>
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<LI CLASS="square"><!-- <A HREF=""> -->libbzip2 binaries (currently broken)<!-- </A> -->
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</UL>
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Alternatively, the binaries can be build from the source code (<A CLASS="bib_ref" HREF="bibliography.html#gailly">[Gailly]</A>, <A CLASS="bib_ref" HREF="bibliography.html#deutsch2">[Seward]</A>).
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</P>
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<A NAME="other">
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<H2>Other Compression Methods</H2>
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<P>
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It is easy to write Filters based on compression algorithms from other libraries, such as <A HREF="http://www.oberhumer.com/opensource/lzo/lzodoc.php" TARGET="_top">L<SPAN STYLE="font-size:80%">ZO</SPAN></A>, <A HREF="http://www.openssl.org" TARGET="_top">OpenSSL</A> and <A HREF="http://www.eskimo.com/~weidai/cryptlib.html" TARGET="_top">Crypto++</A>. No Filters using L<SPAN STYLE="font-size:80%">ZO</SPAN> or OpenSSL are supplied since their licenses are not <A HREF="http://www.boost.org/more/lib_guide.htm#Requirements" TARGET="_top">>Boost-compatible</A>. Most of Crypto++ is public domain, but providing Crypto++ filters would require including too many additional headers in the Iostreams Library distribution.
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</P>
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<P>
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In the future, additional compression methods may be added to the Iostreams Library.
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</P>
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<!-- Begin Footnotes -->
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<HR>
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<P>
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<A CLASS="footnote_ref" NAME="note_1" HREF="#note_1_ref"><SUP>[1]</SUP></A>Currently, <CODE>basic_gzip_decompressor</CODE> only models <A HREF="concepts/input_filter.html">InputFilter</A>, but this will be fixed soon.
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</P>
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<!-- End Footnotes -->
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<!-- Begin Footer -->
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<HR>
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<P CLASS="copyright">Revised
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<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
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20 May, 2004
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<!--webbot bot="Timestamp" endspan i-checksum="38504" -->
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</P>
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<P CLASS="copyright">© Copyright Jonathan Turkanis, 2004</P>
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<P CLASS="copyright">
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Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at <A HREF="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</A>)
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</P>
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