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  11
  12     <H1 CLASS="title">Zlib Filters</H1>
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  15 <!-- End Banner -->
  16 <DL class="page-index">
  17   <DT><A href="#overview">Overview</A></DT>
  18   <DT><A href="#acknowledgments">Acknowledgments</A></DT>
  19   <DT><A href="#headers">Headers</A></DT>
  20   <DT><A href="#synopsis">Synopsis</A></DT>
  21   <DT><A HREF="#reference">Reference</A>
  22     <DL class="page-index">
  23       <DT><A HREF="#constants">namespace <CODE>boost::iostreams::zlib</CODE></A></DT>
  24       <DT><A HREF="#zlib_params">Class <CODE>zlib_params</CODE></A></DT>
  25       <DT><A HREF="#basic_zlib_compressor">Class template <CODE>zlib_compressor</CODE></A></DT>
  26       <DT><A HREF="#basic_zlib_decompressor">Class template <CODE>zlib_decompressor</CODE></A></DT>
  27       <DT><A HREF="#zlib_error">Class <CODE>zlib_error</CODE></A></DT>
  28     </DL>
  29   </DT>
  30   <DT><A href="#examples">Examples</A></DT>
  31   <DT><A href="#installation">Installation</A></DT>
  32 </DL>
  33
  34 <A NAME="overview"></A>
  35 <H2>Overview</H2>
  36
  37 <P>
  38     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>).
  39 </P>
  40 <P>
  41     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.
  42 </P>
  43
  44 <A NAME="acknowledgments"></A>
  45 <H2>Acknowledgments</H2>
  46
  47 <P>
  48     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>).
  49 </P>
  50
  51 Thanks to <A HREF="mailto:jloup@gailly.net">Jean-loup Gailly</A> and <A HREF="mailto:&#109;&#097;&#100;&#108;&#101;&#114;&#064;&#097;&#108;&#117;&#109;&#110;&#105;&#046;&#099;&#097;&#108;&#116;&#101;&#099;&#104;&#046;&#101;&#100;&#117;">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.
  52
  53 <A NAME="headers"></A>
  54 <H2>Headers</H2>
  55
  56 <DL>
  57   <DT><A CLASS="header" HREF="../../../../boost/iostreams/filter/zlib.hpp"><CODE>&lt;boost/iostreams/filter/zlib.hpp&gt;</CODE></A></DT>
  58 </DL>
  59
  60 <A NAME="synopsis"></A>
  61 <H2>Synopsis</H2>
  62
  63 <PRE CLASS="broken_ie"><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams {
  64
  65 <SPAN CLASS="keyword">namespace</SPAN> <A CLASS="documented" HREF="#constants">zlib</A> {
  66
  67     <SPAN CLASS="comment">// Compression levels</SPAN>
  68
  69 <SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#no_compression">no_compression</A>;
  70 <SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#best_speed">best_speed</A>;
  71 <SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#best_compression">best_compression</A>;
  72 <SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#default_compression">default_compression</A>;
  73
  74     <SPAN CLASS="comment">// Compression methods</SPAN>
  75
  76 <SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#deflated">deflated</A>;
  77
  78     <SPAN CLASS="comment">// Compression strategies</SPAN>
  79
  80 <SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#default_strategy">default_strategy</A>;
  81 <SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#filtered">filtered</A>;
  82 <SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#huffman_only">huffman_only</A>;
  83
  84     <SPAN CLASS="comment">// Status codes</SPAN>
  85
  86 <SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#stream_error">stream_error</A>;
  87 <SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#version_error">version_error</A>;
  88 <SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#data_error">data_error</A>;
  89 <SPAN CLASS="keyword">extern</SPAN> <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#buf_error">buf_error</A>;
  90
  91 }   <SPAN CLASS="comment">// End namespace boost::iostreams::zlib</SPAN>
  92
  93 <SPAN CLASS="keyword">struct</SPAN> <A CLASS="documented" HREF="#zlib_params">zlib_params</A>;
  94
  95 <SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> Alloc = std::allocator<<SPAN CLASS="keyword">char</SPAN>&gt; >
  96 <SPAN CLASS="keyword">struc</SPAN>t <A CLASS="documented" HREF="#basic_zlib_compressor">basic_zlib_compressor</A>;
  97
  98 <SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> Alloc = std::allocator<<SPAN CLASS="keyword">char</SPAN>&gt; >
  99 <SPAN CLASS="keyword">struct</SPAN> <A CLASS="documented" HREF="#basic_zlib_decompressor">basic_zlib_decompressor</A>;
 100
 101 <SPAN CLASS="keyword">typedef</SPAN> basic_zlib_compressor&lt;&gt;   <SPAN CLASS="defined">zlib_compressor</SPAN>;
 102 <SPAN CLASS="keyword">typedef</SPAN> basic_zlib_decompressor&lt;&gt; <SPAN CLASS="defined">zlib_decompressor</SPAN>;
 103
 104 <SPAN CLASS="keyword">class</SPAN> <A CLASS="documented" HREF="#zlib_error">zlib_error</A>;
 105
 106 } } <SPAN CLASS="comment">// End namespace boost::io</SPAN></PRE>
 107
 108 <A NAME="reference"></A>
 109 <H2>Reference</H2>
 110
 111 <A NAME="constants"></A>
 112 <H3>Namespace <CODE>boost::iostreams::zlib</CODE></H3>
 113
 114 <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>
 115
 116 <TABLE STYLE="margin-left:2em" BORDER=1 CELLPADDING=4>
 117 <TR><TH>Constant</TH><TH>Interpretation</TH></TR>
 118     <TR>
 119         <TD VALIGN="top"><A NAME="no_compression"></A><CODE>no_compression</CODE></TD>
 120         <TD>Compression-level constant specifying that no compression should be performed. Equal to <CODE>Z_NO_COMPRESSION</CODE>.</TD>
 121     </TR>
 122     <TR>
 123         <TD VALIGN="top"><A NAME="best_speed"></A><CODE>best_speed</CODE></TD>
 124         <TD>Compression-level constant requesting the fasted compression. Equal to <CODE>Z_BEST_SPEED</CODE>.</TD>
 125     </TR>
 126     <TR>
 127         <TD VALIGN="top"><A NAME="best_compression"></A><CODE>best_compression.</CODE></TD>
 128         <TD>Compression-level constant requesting the best compression ratio. Equal to <CODE>Z_BEST_COMPRESSION</CODE>.</TD>
 129     </TR>
 130     <TR>
 131         <TD VALIGN="top"><A NAME="default_compression"></A><CODE>default_compression</CODE></TD>
 132         <TD>Default compression level. Equal to <CODE>Z_DEFAULT_COMPRESSION</CODE>.</TD>
 133     </TR>
 134     <TR>
 135         <TD VALIGN="top"><A NAME="deflated"></A><CODE>deflated</CODE></TD>
 136         <TD>Compression method constant; currently the only supported method. Equal to <CODE>Z_DEFLATED</CODE>.</TD>
 137     </TR>
 138     <TR>
 139         <TD VALIGN="top"><A NAME="default_strategy"></A><CODE>default_strategy</CODE></TD>
 140         <TD>Compression strategy constant. Equal to <CODE>Z_DEFAULT_STRATEGY</CODE>.</TD>
 141     </TR>
 142     <TR>
 143         <TD VALIGN="top"><A NAME="filtered"></A><CODE>filtered</CODE></TD>
 144         <TD>Compression strategy constant. Equal to <CODE>Z_FILTERED</CODE>.</TD>
 145     </TR>
 146     <TR>
 147         <TD VALIGN="top"><A NAME="huffman_only"></A><CODE>huffman_only</CODE></TD>
 148         <TD>Compression strategy constant. Equal to <CODE>Z_HUFFMAN_ONLY</CODE>.</TD>
 149     </TR>
 150     <TR>
 151         <TD VALIGN="top"><A NAME="stream_error"></A><CODE>stream_error</CODE></TD>
 152         <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>
 153     </TR>
 154     <TR>
 155         <TD VALIGN="top"><A NAME="version_error"></A><CODE>version_error</CODE></TD>
 156         <TD>
 157             Error code used to indicate that data was compressed with an incompatible version of zlib. Equal to <CODE>Z_VERSION_ERROR</CODE>.
 158         </TD>
 159     </TR>
 160     <TR>
 161         <TD VALIGN="top"><A NAME="data_error"></A><CODE>data_error</CODE></TD>
 162         <TD>
 163             Error code used to indicate that a compressed datastream is corrupted. Equal to <CODE>Z_DATA_ERROR.</CODE>
 164         </TD>
 165     </TR>
 166     <TR>
 167         <TD VALIGN="top"><A NAME="buf_error"></A><CODE>buf_error</CODE></TD>
 168         <TD>Error code indicating an internal Iostreams library error. Equal to <CODE>Z_BUF_ERROR.</CODE></TD>
 169     </TR>
 170 </TABLE>
 171
 172 <A NAME="zlib_params"></A>
 173 <H3>Class <CODE>zlib_params</CODE></H3>
 174
 175 <H4>Description</H4>
 176
 177 <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>
 178
 179 <H4>Synopsis</H4>
 180
 181 <PRE CLASS="broken_ie"><SPAN CLASS="keyword">struct</SPAN> <SPAN CLASS="defined">zlib_params</SPAN> {
 182
 183     <SPAN CLASS="comment">// Non-explicit constructor</SPAN>
 184     <A CLASS="documented" HREF="#zlib_params_constructors">zlib_params</A>( <SPAN CLASS="keyword">int</SPAN> level           = zlib::default_compression,
 185                  <SPAN CLASS="keyword">int</SPAN> method          = zlib::deflated,
 186                  <SPAN CLASS="keyword">int</SPAN> window_bits     = default value,
 187                  <SPAN CLASS="keyword">int</SPAN> mem_level       = default value,
 188                  <SPAN CLASS="keyword">int</SPAN> strategy        = zlib::default_strategy,
 189                  <SPAN CLASS="keyword">bool</SPAN> noheader       = false );
 190     <SPAN CLASS="keyword">int</SPAN>  level;
 191     <SPAN CLASS="keyword">int</SPAN>  method;
 192     <SPAN CLASS="keyword">int</SPAN>  window_bits;
 193     <SPAN CLASS="keyword">int</SPAN>  mem_level;
 194     <SPAN CLASS="keyword">int</SPAN>  strategy;
 195     <SPAN CLASS="keyword">bool</SPAN> noheader;
 196 };</PRE>
 197
 198 <A NAME="zlib_params_constructors"></A>
 199 <H4><CODE>zlib_params::zlib_params</CODE></H4>
 200
 201 <PRE CLASS="broken_ie">    zlib_params( <SPAN CLASS="keyword">int</SPAN> level           = zlib::default_compression,
 202                  <SPAN CLASS="keyword">int</SPAN> method          = zlib::deflated,
 203                  <SPAN CLASS="keyword">int</SPAN> window_bits     = default value,
 204                  <SPAN CLASS="keyword">int</SPAN> mem_level       = default value,
 205                  <SPAN CLASS="keyword">int</SPAN> strategy        = zlib::default_strategy,
 206                  <SPAN CLASS="keyword">bool</SPAN> noheader       = false );</PRE>
 207
 208 <P>Constructs a <CODE>zlib_params</CODE> object, where the parameters have the following interpretations:</AP>
 209
 210 <TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2>
 211 <TR>
 212     <TR>
 213         <TD VALIGN="top"><A NAME="level"></A><I>level</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
 214         <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>
 215     </TR>
 216     <TR>
 217         <TD VALIGN="top"><A NAME="method"></A><I>method</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
 218         <TD>Compression method. Must equal <A HREF="#deflated"><CODE>zlib::deflated</CODE></A>. Affects compression only.</TD>
 219     </TR>
 220     <TR>
 221         <TD VALIGN="top"><A NAME="window_bits"></A><I>window_bits</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
 222         <TD>The base two logarithm of the window size. Must be in the range 8-15; defaults to 15.</TD>
 223     </TR>
 224     <TR>
 225         <TD VALIGN="top"><A NAME="mem_level"></A><I>mem_level</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
 226         <TD>Specifies the amount of memory to be used. Must be in the range 1-9; defaults to 8. Affects compression only.</TD>
 227     </TR>
 228     <TR>
 229         <TD VALIGN="top"><A NAME="strategy"></A><I>strategy</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
 230         <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>
 231     </TR>
 232     <TR>
 233         <TD VALIGN="top"><A NAME="noheader"></A><I>noheader</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
 234         <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>
 235     </TR>
 236 </TABLE>
 237
 238 <P>See <A CLASS="bib_ref" HREF="../bibliography.html#gailly">[Gailly]</A> for additional details.</P>
 239
 240 <A NAME="basic_zlib_compressor"></A>
 241 <H3>Class template <CODE>basic_zlib_compressor</CODE></H3>
 242
 243 <H4>Description</H4>
 244
 245 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>).
 246
 247 <H4>Synopsis</H4>
 248
 249 <PRE CLASS="broken_ie"><SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#basic_zlib_compressor_params">Alloc</A> = std::allocator&lt;<SPAN CLASS="keyword">char</SPAN>&gt; &gt;
 250 <SPAN CLASS="keyword">struct</SPAN> <A CLASS="documented" HREF="#basic_zlib_compressor_params">basic_zlib_compressor</A> {
 251     <SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS="keyword">char</SPAN>                    char_type;
 252     <SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS="omitted">implementation-defined</SPAN>  category;
 253
 254     <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>&amp; = <SPAN CLASS="omitted">zlib::default_compression</SPAN>,
 255                            std::streamsize buffer_size = <SPAN CLASS="omitted">default value</SPAN> );
 256
 257     <SPAN CLASS="comment">// DualUseFilter members.</SPAN>
 258 };
 259
 260 <SPAN CLASS="keyword">typedef</SPAN> basic_zlib_compressor&lt;&gt; <SPAN CLASS="defined">zlib_compressor</SPAN>;</PRE>
 261
 262 <A NAME="basic_zlib_compressor_params"></A>
 263 <H4>Template Parameters</H4>
 264
 265 <TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2>
 266 <TR>
 267     <TR>
 268         <TD VALIGN="top"><I>Alloc</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
 269         <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>
 270     </TR>
 271 </TABLE>
 272
 273 <A NAME="basic_zlib_compressor_constructors"></A>
 274 <H4><CODE>basic_zlib_compressor::basic_zlib_compressor</CODE></H4>
 275
 276 <PRE CLASS="broken_ie">    basic_zlib_compressor( <SPAN CLASS="keyword">const</SPAN> <A CLASS="documented" HREF="#zlib_params">zlib_params</A>&amp; = <SPAN CLASS="omitted">zlib::default_compression</SPAN>,
 277                            std::streamsize buffer_size = <SPAN CLASS="omitted">default value</SPAN> );</PRE>
 278
 279 <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>
 280
 281 <A NAME="basic_zlib_decompressor"></A>
 282 <H3>Class template <CODE>basic_zlib_decompressor</CODE></H3>
 283
 284 <H4>Description</H4>
 285
 286 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>).
 287
 288 <H4>Synopsis</H4>
 289
 290 <PRE CLASS="broken_ie"><SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#basic_zlib_decompressor_params">Alloc</A> = std::allocator&lt;<SPAN CLASS="keyword">char</SPAN>&gt; &gt;
 291 <SPAN CLASS="keyword">struct</SPAN> <A CLASS="documented" HREF="#basic_zlib_decompressor_params">basic_zlib_decompressor</A> {
 292     <SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS="keyword">char</SPAN>                    char_type;
 293     <SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS="omitted">implementation-defined</SPAN>  category;
 294
 295     <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>,
 296                              std::streamsize buffer_size =
 297                                  <SPAN CLASS="omitted">default value</SPAN> );
 298     <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>&amp;,
 299                              std::streamsize buffer_size =
 300                                  <SPAN CLASS="omitted">default value</SPAN> );
 301
 302     <SPAN CLASS="comment">// DualUseFilter members.</SPAN>
 303 };
 304
 305 <SPAN CLASS="keyword">typedef</SPAN> basic_zlib_decompressor&lt;&gt; <SPAN CLASS="defined">zlib_decompressor</SPAN>;</PRE>
 306
 307 <A NAME="basic_zlib_decompressor_params"></A>
 308 <H4>Template Parameters</H4>
 309
 310 <TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2>
 311 <TR>
 312     <TR>
 313         <TD VALIGN="top"><I>Alloc</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
 314         <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>
 315     </TR>
 316 </TABLE>
 317
 318 <A NAME="basic_zlib_decompressor_constructors"></A>
 319 <H4><CODE>basic_zlib_decompressor::basic_zlib_decompressor</CODE></H4>
 320
 321 <PRE CLASS="broken_ie">    basic_zlib_decompressor( <SPAN CLASS="keyword">int</SPAN> window_bits = <SPAN CLASS="omitted">default value</SPAN>,
 322                              std::streamsize buffer_size =
 323                                  <SPAN CLASS="omitted">default value</SPAN> );
 324     basic_zlib_decompressor( <SPAN CLASS="keyword">const</SPAN> <A CLASS="documented" HREF="#zlib_params">zlib_params</A>&amp;,
 325                              std::streamsize buffer_size =
 326                                  <SPAN CLASS="omitted">default value</SPAN> );</PRE>
 327
 328 <P>The first member constructs an instance of <CODE>basic_zlib_decompressor</CODE> with the given parameters and buffer size.
 329 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>
 330
 331 <A NAME="zlib_error"></A>
 332 <H3>Class <CODE>zlib_error</CODE></H3>
 333
 334 <H4>Description</H4>
 335
 336 Used by the zlib Filters to report errors.
 337
 338 <H4>Synopsis</H4>
 339
 340 <PRE CLASS="broken_ie"><SPAN CLASS="keyword">class</SPAN> <SPAN CLASS="defined">zlib_error</SPAN> : <SPAN CLASS="keyword">public</SPAN> std::ios_base::failure {
 341 <SPAN CLASS="keyword">public:</SPAN>
 342     <A CLASS="documented" HREF="#zlib_error_constructor">zlib_error</A>(<SPAN CLASS="keyword">int</SPAN> error);
 343     <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#zlib_error_error">error</A>() const;
 344 };</PRE>
 345
 346 <A NAME="zlib_error_constructor"></A>
 347 <H4><CODE>zlib_error::zlib_error</CODE></H4>
 348
 349 <PRE CLASS="broken_ie">    zlib_error(<SPAN CLASS="keyword">int</SPAN> error);</PRE>
 350
 351 <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>
 352
 353 <A NAME="zlib_error_error"></A>
 354 <H4><CODE>zlib_error::error</CODE></H4>
 355
 356 <PRE CLASS="broken_ie">    <SPAN CLASS="keyword">void</SPAN> error() <SPAN CLASS="keyword">const</SPAN>;</PRE>
 357
 358 <P>Returns an error code from the namespace <A HREF="#constants"><CODE>boost::iostreams::zlib</CODE></A>.</P>
 359
 360 <A NAME="examples"></A>
 361 <H2>Examples</H2>
 362
 363 The following code decompresses data from a file and writes it to standard output.
 364
 365 <PRE CLASS="broken_ie"><SPAN CLASS="preprocessor">#include</SPAN> <SPAN CLASS="literal">&lt;fstream&gt;</SPAN>
 366 <SPAN CLASS="preprocessor">#include</SPAN> <SPAN CLASS="literal">&lt;iostream&gt;</SPAN>
 367 <SPAN CLASS="preprocessor">#include</SPAN> <A CLASS="header" HREF="../../../../boost/iostreams/filtering_streambuf.hpp"><SPAN CLASS="literal">&lt;boost/iostreams/filtering_streambuf.hpp&gt;</SPAN></A>
 368 <SPAN CLASS="preprocessor">#include</SPAN> <A CLASS="header" HREF="../../../../boost/iostreams/copy.hpp"><SPAN CLASS="literal">&lt;boost/iostreams/copy.hpp&gt;</SPAN></A>
 369 <SPAN CLASS="preprocessor">#include</SPAN> <A CLASS="header" HREF="../../../../boost/iostreams/filter/zlib.hpp"><SPAN CLASS="literal">&lt;boost/iostreams/filter/zlib.hpp&gt;</SPAN></A>
 370
 371 int main()
 372 {
 373     <SPAN CLASS="keyword">using</SPAN> <SPAN CLASS="keyword">namespace</SPAN> std;
 374
 375     ifstream file(<SPAN CLASS="literal">"hello.z"</SPAN>, ios_base::in | ios_base::binary);
 376     filtering_streambuf&lt;input&gt; in;
 377     in.push(zlib_decompressor());
 378     in.push(file);
 379     boost::iostreams::copy(in, cout);
 380 }</PRE>
 381
 382 <A NAME="installation"></A>
 383 <H3>Installation</H3>
 384
 385 <P>
 386      The zlib Filters depend on the third-party zlib library, which is <I>not</I> included in the Boost distribution. Prebuilt zlib binaries are available on most UNIX and UNIX-like systems, and will be found automatically by the Boost build system. Windows users can obtain prebuilt binaries at the <A HREF="http://www.gzip.org/zlib/" TARGET="_top">zlib homepage</A>. Users can also configure the Boost Iostream library to build zlib from the source code, which is available at the zlib homepage. For details on configuring the build system to find your zlib installation, please see <A HREF="../installation.html">Installation</A>.
 387 </P>
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 394
 395 <P CLASS="copyright">&copy; Copyright 2008 <a href="http://www.coderage.com/" target="_top">CodeRage, LLC</a><br/>&copy; Copyright 2004-2007 <a href="http://www.coderage.com/turkanis/" target="_top">Jonathan Turkanis</a></P>
 396 <P CLASS="copyright">
 397     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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