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407 lines
23 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>Zlib Filters</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">Zlib Filters</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="#synopsis">Synopsis</A></DT>
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<DT><A HREF="#reference">Reference</A>
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<DL class="page-index">
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<DT><A HREF="#constants">namespace <CODE>boost::iostreams::zlib</CODE></A></DT>
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<DT><A HREF="#zlib_params">Class <CODE>zlib_params</CODE></A></DT>
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<DT><A HREF="#basic_zlib_compressor">Class template <CODE>zlib_compressor</CODE></A></DT>
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<DT><A HREF="#basic_zlib_decompressor">Class template <CODE>zlib_decompressor</CODE></A></DT>
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<DT><A HREF="#zlib_error">Class <CODE>zlib_error</CODE></A></DT>
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</DL>
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</DT>
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<DT><A href="#examples">Examples</A></DT>
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<DT><A href="#installation">Installation</A></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 class templates <A HREF="#basic_zlib_compressor"><CODE>basic_zlib_compressor</CODE></A> and <A HREF="#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>).
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</P>
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<P>
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The zlib Filters are <A HREF="../concepts/dual_use_filter.html">DualUseFilters</A> so that they may be used for either input or output. 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 zlib 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>).
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</P>
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Thanks to <A HREF="mailto:jloup@gailly.net">Jean-loup Gailly</A> and <A HREF="mailto:madler@alumni.caltech.edu">Mark Adler</A> for making their excellent library available to the public with a <A HREF="http://www.boost.org/more/lib_guide.htm#Requirements">Boost-compatible</A> license.
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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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</DL>
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<A NAME="synopsis">
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<H2>Synopsis</H2>
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<PRE CLASS="broken_ie"><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams {
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<SPAN CLASS="keyword">namespace</SPAN> <A CLASS="documented" HREF="#constants">zlib</A> {
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<SPAN CLASS="comment">// Compression levels</SPAN>
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<SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#no_compression">no_compression</A>;
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<SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#best_speed">best_speed</A>;
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<SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#best_compression">best_compression</A>;
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<SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#default_compression">default_compression</A>;
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<SPAN CLASS="comment">// Compression methods</SPAN>
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<SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#deflated">deflated</A>;
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<SPAN CLASS="comment">// Compression strategies</SPAN>
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<SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#default_strategy">default_strategy</A>;
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<SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#filtered">filtered</A>;
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<SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#huffman_only">huffman_only</A>;
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<SPAN CLASS="comment">// Status codes</SPAN>
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<SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#stream_error">stream_error</A>;
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<SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#version_error">version_error</A>;
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<SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#data_error">data_error</A>;
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<SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#buf_error">buf_error</A>;
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} <SPAN CLASS="comment">// End namespace boost::iostreams::zlib</SPAN>
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<SPAN CLASS="keyword">struct</SPAN> <A CLASS="documented" HREF="#zlib_params">zlib_params</A>;
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<SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> Alloc = std::allocator<<SPAN CLASS="keyword">char</SPAN>> >
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<SPAN CLASS="keyword">struc</SPAN>t <A CLASS="documented" HREF="#basic_zlib_compressor">basic_zlib_compressor</A>;
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<SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> Alloc = std::allocator<<SPAN CLASS="keyword">char</SPAN>> >
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<SPAN CLASS="keyword">struct</SPAN> <A CLASS="documented" HREF="#basic_zlib_decompressor">basic_zlib_decompressor</A>;
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<SPAN CLASS="keyword">typedef</SPAN> basic_zlib_compressor<> <SPAN CLASS="defined">zlib_compressor</SPAN>;
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<SPAN CLASS="keyword">typedef</SPAN> basic_zlib_decompressor<> <SPAN CLASS="defined">zlib_decompressor</SPAN>;
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<SPAN CLASS="keyword">class</SPAN> <A CLASS="documented" HREF="#zlib_error">zlib_error</A>;
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} } <SPAN CLASS="comment">// End namespace boost::io</SPAN></PRE>
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<A NAME="reference">
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<H2>Reference</H2>
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<A NAME="constants">
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<H3>Namespace <CODE>boost::iostreams::zlib</CODE></H3>
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<P>The namespace <CODE>boost::iostreams::zlib</CODE> contains integral constants used to configure zlib Filters and to report errors. The constants have the following interpretations. (<I>See</I> <A CLASS="bib_ref" HREF="../bibliography.html#gailly">[Gailly]</A> for additional details.)</P>
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<TABLE STYLE="margin-left:2em" BORDER=1 CELLPADDING=4>
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<TR><TH>Constant</TH><TH>Interpretation</TH></TR>
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<TR>
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<TD VALIGN="top"><A NAME="no_compression"></A><CODE>no_compression</CODE></TD>
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<TD>Compression-level constant specifying that no compression should be performed. Equal to <CODE>Z_NO_COMPRESSION</CODE>.</TD>
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</TR>
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<TR>
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<TD VALIGN="top"><A NAME="best_speed"></A><CODE>best_speed</CODE></TD>
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<TD>Compression-level constant requesting the fasted compression. Equal to <CODE>Z_BEST_SPEED</CODE>.</TD>
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</TR>
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<TR>
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<TD VALIGN="top"><A NAME="best_compression"></A><CODE>best_compression.</CODE></TD>
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<TD>Compression-level constant requesting the best compression ratio. Equal to <CODE>Z_BEST_COMPRESSION</CODE>.</TD>
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</TR>
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<TR>
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<TD VALIGN="top"><A NAME="default_compression"></A><CODE>default_compression</CODE></TD>
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<TD>Default compression level. Equal to <CODE>Z_DEFAULT_COMPRESSION</CODE>.</TD>
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</TR>
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<TR>
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<TD VALIGN="top"><A NAME="deflated"></A><CODE>deflated</CODE></TD>
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<TD>Compression method constant; currently the only supported method. Equal to <CODE>Z_DEFLATED</CODE>.</TD>
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</TR>
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<TR>
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<TD VALIGN="top"><A NAME="default_strategy"></A><CODE>default_strategy</CODE></TD>
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<TD>Compression strategy constant. Equal to <CODE>Z_DEFAULT_STRATEGY</CODE>.</TD>
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</TR>
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<TR>
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<TD VALIGN="top"><A NAME="filtered"></A><CODE>filtered</CODE></TD>
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<TD>Compression strategy constant. Equal to <CODE>Z_FILTERED</CODE>.</TD>
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</TR>
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<TR>
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<TD VALIGN="top"><A NAME="huffman_only"></A><CODE>huffman_only</CODE></TD>
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<TD>Compression strategy constant. Equal to <CODE>Z_HUFFMAN_ONLY</CODE>.</TD>
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</TR>
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<TR>
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<TD VALIGN="top"><A NAME="stream_error"></A><CODE>stream_error</CODE></TD>
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<TD>Error code used to indicate that one of the members of <CODE>zlib_params</CODE> is invalid; may also indicate an internal Iostreams Library error. Equal to <CODE>Z_STREAM_ERROR</CODE>.</TD>
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</TR>
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<TR>
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<TD VALIGN="top"><A NAME="version_error"></A><CODE>version_error</CODE></TD>
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<TD>
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Error code used to indicate that data was compressed with an incompatible version of zlib. Equal to <CODE>Z_VERSION_ERROR</CODE>.
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</TD>
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</TR>
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<TR>
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<TD VALIGN="top"><A NAME="data_error"></A><CODE>data_error</CODE></TD>
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<TD>
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Error code used to indicate that a compressed datastream is corrupted. Equal to <CODE>Z_DATA_ERROR.</CODE>
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</TD>
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</TR>
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<TR>
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<TD VALIGN="top"><A NAME="buf_error"></A><CODE>buf_error</CODE></TD>
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<TD>Error code indicating an internal Iostreams Library error. Equal to <CODE>Z_BUF_ERROR.</CODE></TD>
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</TR>
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</TABLE>
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<A NAME="zlib_params">
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<H3>Class <CODE>zlib_params</CODE></H3>
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<H4>Description</H4>
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<P>Encapsulates the parameters used to configure <A HREF="#basic_zlib_compressor"><CODE>basic_zlib_compressor</CODE></A> and <A HREF="#basic_zlib_decompressor"><CODE>basic_zlib_decompressor</CODE></A>.</P>
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<H4>Synopsis</H4>
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<PRE CLASS="broken_ie"><SPAN CLASS="keyword">struct</SPAN> <SPAN CLASS="defined">zlib_params</SPAN> {
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<SPAN CLASS="comment">// Non-explicit constructor</SPAN>
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<A CLASS="documented" HREF="#zlib_params_constructors">zlib_params</A>( <SPAN CLASS="keyword">int</SPAN> level = zlib::default_compression,
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<SPAN CLASS="keyword">int</SPAN> method = zlib::deflated,
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<SPAN CLASS="keyword">int</SPAN> window_bits = default value,
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<SPAN CLASS="keyword">int</SPAN> mem_level = default value,
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<SPAN CLASS="keyword">int</SPAN> strategy = zlib::default_strategy,
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<SPAN CLASS="keyword">bool</SPAN> noheader = false );
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<SPAN CLASS="keyword">int</SPAN> level;
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<SPAN CLASS="keyword">int</SPAN> method;
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<SPAN CLASS="keyword">int</SPAN> window_bits;
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<SPAN CLASS="keyword">int</SPAN> mem_level;
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<SPAN CLASS="keyword">int</SPAN> strategy;
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<SPAN CLASS="keyword">bool</SPAN> noheader;
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};</PRE>
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<A NAME="zlib_params_constructors">
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<H4><CODE>zlib_params::zlib_params</CODE></H4>
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<PRE CLASS="broken_ie"> zlib_params( <SPAN CLASS="keyword">int</SPAN> level = zlib::default_compression,
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<SPAN CLASS="keyword">int</SPAN> method = zlib::deflated,
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<SPAN CLASS="keyword">int</SPAN> window_bits = default value,
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<SPAN CLASS="keyword">int</SPAN> mem_level = default value,
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<SPAN CLASS="keyword">int</SPAN> strategy = zlib::default_strategy,
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<SPAN CLASS="keyword">bool</SPAN> noheader = false );</PRE>
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<P>Constructs a <CODE>zlib_params</CODE> object, where the parameters have the following interpretations:</AP>
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<TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2>
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<TR>
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<TR>
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<TD VALIGN="top"><A NAME="level"></A><I>level</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
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<TD>Compression level. Must be equal to <CODE>zlib::default_compression</CODE> or a value in the range <CODE>0-9</CODE>. The value <CODE>0</CODE> yields no compression, while <CODE>9</CODE> yields the best compression ratio. Affects compression only.</TD>
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</TR>
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<TR>
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<TD VALIGN="top"><A NAME="method"></A><I>method</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
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<TD>Compression method. Must equal <A HREF="#deflated"><CODE>zlib::deflated</CODE></A>. Affects compression only.</TD>
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</TR>
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<TR>
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<TD VALIGN="top"><A NAME="window_bits"></A><I>window_bits</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
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<TD>The base two logarithm of the window size. Must be in the range 8-15; defaults to 15.</TD>
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</TR>
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<TR>
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<TD VALIGN="top"><A NAME="mem_level"></A><I>mem_level</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
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<TD>Specifies the amount of memory to be used. Must be in the range 1-9; defaults to 8. Affects compression only.</TD>
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</TR>
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<TR>
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<TD VALIGN="top"><A NAME="strategy"></A><I>strategy</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
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<TD>Must be <A HREF="#default_strategy"><CODE>zlib::default_strategy</CODE></A>, <A HREF="#filtered"><CODE>zlib::filtered</CODE></A> or <A HREF="#huffman_only"><CODE>zlib::huffman_only</CODE></A>. Affects compression only. </TD>
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</TR>
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<TR>
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<TD VALIGN="top"><A NAME="noheader"></A><I>noheader</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
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<TD>True if the Z<SPAN STYLE="font-size:80%">LIB</SPAN> header and trailing A<SPAN STYLE="font-size:80%">DLER</SPAN>-32 checksum should be omitted (see <A CLASS="bib_ref" HREF="../bibliography.html#deutsch1">[Deutsch1]</A>). This results in compression according to the <I>deflate</I> specification (see <A CLASS="bib_ref" HREF="../bibliography.html#deutsch2">[Deutsch2]</A>).</TD>
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</TR>
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</TABLE>
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<P>See <A CLASS="bib_ref" HREF="../bibliography.html#gailly">[Gailly]</A> for additional details.</P>
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<A NAME="basic_zlib_compressor">
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<H3>Class template <CODE>basic_zlib_compressor</CODE></H3>
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<H4>Description</H4>
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Model of <A HREF="../concepts/dual_use_filter.html">DualUseFilter</A> which performs compression using zlib (<A CLASS="bib_ref" HREF="../bibliography.html#gailly">[Gailly]</A>).
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<H4>Synopsis</H4>
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<PRE CLASS="broken_ie"><SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#basic_zlib_compressor_params">Alloc</A> = std::allocator<<SPAN CLASS="keyword">char</SPAN>> >
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<SPAN CLASS="keyword">struct</SPAN> <A CLASS="documented" HREF="#basic_zlib_compressor_params">basic_zlib_compressor</A> {
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<SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS="keyword">char</SPAN> char_type;
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<SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS="omitted">implementation-defined</SPAN> category;
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<A CLASS="documented" HREF="#basic_zlib_compressor_constructors">basic_zlib_compressor</A>( <SPAN CLASS="keyword">const</SPAN> <A CLASS="documented" HREF="#zlib_params">zlib_params</A>& = <SPAN CLASS="omitted">zlib::default_compression</SPAN>,
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std::streamsize buffer_size = <SPAN CLASS="omitted">default value</SPAN> );
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<SPAN CLASS="comment">// DualUseFilter members.</SPAN>
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};
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<SPAN CLASS="keyword">typedef</SPAN> <A CLASS="documented" HREF="#basic_zlib_compressor">basic_zlib_compressor</A><> <SPAN CLASS="defined">zlib_compressor</SPAN>;</PRE>
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<A NAME="basic_zlib_compressor_params"></A>
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<H4>Template Parameters</H4>
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<TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2>
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<TR>
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<TR>
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<TD VALIGN="top"><I>Alloc</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
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<TD>A C++ standard library allocator type (<A CLASS="bib_ref" HREF="../bibliography.html#iso">[ISO]</A>, 20.1.5), used to allocate a character buffer and to configure zlib.</TD>
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</TR>
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</TABLE>
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<A NAME="basic_zlib_compressor_constructors"></A>
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<H4><CODE>basic_zlib_compressor::basic_zlib_compressor</CODE></H4>
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<PRE CLASS="broken_ie"> <B>basic_zlib_compressor</B>( <SPAN CLASS="keyword">const</SPAN> <A CLASS="documented" HREF="#zlib_params">zlib_params</A>& = <SPAN CLASS="omitted">zlib::default_compression</SPAN>,
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std::streamsize buffer_size = <SPAN CLASS="omitted">default value</SPAN> );</PRE>
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<P>Constructs an instance of <CODE>basic_zlib_compressor</CODE> with the given parameters and buffer size. Since a <A CLASS="documented" HREF="#zlib_params"><CODE>zlib_params</CODE></A> object is implicitly constructible from an <CODE>int</CODE> representing a compression level, an <CODE>int</CODE> may be passed as the first constructor argument.</P>
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<A NAME="basic_zlib_decompressor">
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<H3>Class template <CODE>basic_zlib_decompressor</CODE></H3>
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<H4>Description</H4>
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Model of <A HREF="../concepts/dual_use_filter.html">DualUseFilter</A> which performs decompression using zlib (<A CLASS="bib_ref" HREF="../bibliography.html#gailly">[Gailly]</A>).
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<H4>Synopsis</H4>
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<PRE CLASS="broken_ie"><SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#basic_zlib_decompressor_params">Alloc</A> = std::allocator<<SPAN CLASS="keyword">char</SPAN>> >
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<SPAN CLASS="keyword">struct</SPAN> <A CLASS="documented" HREF="#basic_zlib_decompressor_params">basic_zlib_decompressor</A> {
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<SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS="keyword">char</SPAN> char_type;
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<SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS="omitted">implementation-defined</SPAN> category;
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<A CLASS="documented" HREF="#basic_zlib_decompressor_constructors">basic_zlib_decompressor</A>( <SPAN CLASS="keyword">int</SPAN> window_bits = <SPAN CLASS="omitted">default value</SPAN>,
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std::streamsize buffer_size =
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<SPAN CLASS="omitted">default value</SPAN> );
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<A CLASS="documented" HREF="#basic_zlib_decompressor_constructors">basic_zlib_decompressor</A>( <SPAN CLASS="keyword">const</SPAN> <A CLASS="documented" HREF="#zlib_params">zlib_params</A>&,
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std::streamsize buffer_size =
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<SPAN CLASS="omitted">default value</SPAN> );
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<SPAN CLASS="comment">// DualUseFilter members.</SPAN>
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};
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<SPAN CLASS="keyword">typedef</SPAN> <A CLASS="documented" HREF="#basic_zlib_decompressor">basic_zlib_decompressor</A><> <SPAN CLASS="defined">zlib_decompressor</SPAN>;</PRE>
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<A NAME="basic_zlib_decompressor_params"></A>
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<H4>Template Parameters</H4>
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<TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2>
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<TR>
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<TR>
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<TD VALIGN="top"><I>Alloc</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
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<TD>A C++ standard library allocator type (<A CLASS="bib_ref" HREF="../bibliography.html#iso">[ISO]</A>, 20.1.5), used to allocate a character buffer and to configure zlib.</TD>
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</TR>
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</TABLE>
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<A NAME="basic_zlib_decompressor_constructors"></A>
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<H4><CODE>basic_zlib_decompressor::basic_zlib_decompressor</CODE></H4>
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<PRE CLASS="broken_ie"> <A CLASS="documented" HREF="#basic_zlib_decompressor_constructors">basic_zlib_decompressor</A>( <SPAN CLASS="keyword">int</SPAN> window_bits = <SPAN CLASS="omitted">default value</SPAN>,
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std::streamsize buffer_size =
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<SPAN CLASS="omitted">default value</SPAN> );
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<A CLASS="documented" HREF="#basic_zlib_decompressor_constructors">basic_zlib_decompressor</A>( <SPAN CLASS="keyword">const</SPAN> <A CLASS="documented" HREF="#zlib_params">zlib_params</A>&,
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std::streamsize buffer_size =
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<SPAN CLASS="omitted">default value</SPAN> );</PRE>
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<P>The first member constructs an instance of <CODE>basic_zlib_decompressor</CODE> with the given parameters and buffer size.
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The second member constructs an instance of <CODE>basic_zlib_decompressor</CODE> with the given <A HREF="#window_bits">window bits</A> value and buffer size. Other parameters affecting decompression are set to default values.</P>
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<A NAME="zlib_error">
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<H3>Class <CODE>zlib_error</CODE></H3>
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<H4>Description</H4>
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Used by the zlib Filters to report errors.
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<H4>Synopsis</H4>
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<PRE CLASS="broken_ie"><SPAN CLASS="keyword">class</SPAN> <SPAN CLASS="defined">zlib_error</SPAN> : <SPAN CLASS="keyword">public</SPAN> std::ios_base::failure {
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<SPAN CLASS="keyword">public:</SPAN>
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<A CLASS="documented" HREF="#zlib_error_constructor">zlib_error</A>(<SPAN CLASS="keyword">int</SPAN> error);
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<SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#zlib_error_error">error</A>() const;
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};</PRE>
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<A NAME="zlib_error_constructor"></A>
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<H4><CODE>zlib_error::zlib_error</CODE></H4>
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<PRE CLASS="broken_ie"> <B>zlib_error</B>(<SPAN CLASS="keyword">int</SPAN> error);</PRE>
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<P>Constructs an instance of <CODE>zlib_error</CODE> with the given error code from the namespace <A HREF="#constants"><CODE>boost::iostreams::zlib</CODE></A>.</P>
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<A NAME="zlib_error_error"></A>
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<H4><CODE>zlib_error::error</CODE></H4>
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<PRE CLASS="broken_ie"> <SPAN CLASS="keyword">void</SPAN> <B>error</B>() <SPAN CLASS="keyword">const</SPAN>;</PRE>
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<P>Returns an error code from the namespace <A HREF="#constants"><CODE>boost::iostreams::zlib</CODE></A>.</P>
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<A NAME="examples">
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<H2>Examples</H2>
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The following code decompresses data from a file and writes it to standard output.
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<PRE CLASS="broken_ie"><SPAN CLASS="preprocessor">#include</SPAN> <SPAN CLASS="literal"><fstream></SPAN>
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<SPAN CLASS="preprocessor">#include</SPAN> <SPAN CLASS="literal"><iostream></SPAN>
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<SPAN CLASS="preprocessor">#include</SPAN> <A CLASS="header" HREF="../../../../boost/iostreams/filtering_streambuf.hpp"><SPAN CLASS="literal"><boost/iostreams/filtering_streambuf.hpp></SPAN></A>
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<SPAN CLASS="preprocessor">#include</SPAN> <A CLASS="header" HREF="../../../../boost/iostreams/copy.hpp"><SPAN CLASS="literal"><boost/iostreams/copy.hpp></SPAN></A>
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<SPAN CLASS="preprocessor">#include</SPAN> <A CLASS="header" HREF="../../../../boost/iostreams/filter/zlib.hpp"><SPAN CLASS="literal"><boost/iostreams/filter/zlib.hpp></SPAN></A>
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int main()
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{
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<SPAN CLASS="keyword">using</SPAN> <SPAN CLASS="keyword">namespace</SPAN> std;
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ifstream file(<SPAN CLASS="literal">"hello.z"</SPAN>, ios_base::in | ios_base::binary);
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filtering_streambuf<input> in;
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in.push(zlib_decompressor());
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in.push(file);
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boost::iostreams::copy(in, cout);
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}</PRE>
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<A NAME="installation">
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<H3>Installation</H3>
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<P>
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The zlib Filters depend on the source file <A CLASS="header" HREF="../../src/zlib.cpp"><CODE><libs/src/zlib.cpp></CODE></A>. This source file uses several headers from the zlib library, included with the Iostreams Library distribution in the directory <A CLASS="header" HREF="../../src/zlib"><CODE><libs/iostreams/src/zlib></CODE></A>. Code using these Filters must be linked against zlib binaries, which are available on most UNIX systems and which can be obtained for Windows systems <A HREF="http://www.gzip.org/zlib/contrib/index.html">here</A>. Alternatively, binaries can be build from the source code (<A CLASS="bib_ref" HREF="../bibliography.html#gailly">[Gailly]</A>).
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</P>
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<!-- Adler's obfuscated address is copied from his homepage -->
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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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