libs/iostreams/doc/classes/file_descriptor.html

   1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
   2 <HTML>
   3 <HEAD>
   4     <TITLE>File Descriptor Devices</TITLE>
   5     <LINK REL="stylesheet" HREF="../../../../boost.css">
   6     <LINK REL="stylesheet" HREF="../theme/iostreams.css">
   7     <STYLE> H3 CODE { font-size: 110% } </STYLE>
   8 </HEAD>
   9 <BODY>
  10
  11 <!-- Begin Banner -->
  12
  13     <H1 CLASS="title">File Descriptors</H1>
  14     <HR CLASS="banner">
  15
  16 <!-- End Banner -->
  17
  18 <DL class="page-index">
  19   <DT><A href="#overview">Overview</A></DT>
  20   <DT><A href="#acknowledgments">Acknowledments</A></DT>
  21   <DT><A href="#installation">Installation</A></DT>
  22   <DT><A href="#headers">Headers</A></DT>
  23   <DT><A href="#reference">Reference</A>
  24     <UL>
  25       <LI CLASS="square"><A href="#file_descriptor_source">Class <CODE>file_descriptor_source</CODE></A></LI>
  26       <LI CLASS="square"><A href="#file_descriptor_sink">Class <CODE>file_descriptor_sink</CODE></A></LI>
  27       <LI CLASS="square"><A href="#file_descriptor">Class <CODE>file_descriptor</CODE></A></LI>
  28     </UL>
  29   </DT>
  30 </DL>
  31
  32 <HR>
  33
  34 <A NAME="overview"></A>
  35 <H2>Overview</H2>
  36
  37 <P>
  38     The classes <CODE>file_descriptor_source</CODE>, <CODE>file_descriptor_sink</CODE> and <CODE>file_descriptor</CODE> provide file access via operating system file handles or file descriptors. These <A HREF="../guide/concepts.html#device_concepts">Devices</A> behave much like the <A HREF="file.html">File Wrappers</A> <CODE>basic_file_source</CODE>, <CODE>basic_file_sink</CODE> and <CODE>basic_file</CODE>, with the following important differences:
  39 </P>
  40 <UL>
  41     <LI CLASS="square">A file descriptor Device may be constructed from a file descriptor which is already open.
  42     <LI CLASS="square">The only <A HREF="../guide/buffering.html">buffering</A> is provded by the Boost Iostreams library.
  43     <LI CLASS="square">There is no automatic line-ending conversion.
  44     <LI CLASS="square">Wide-character streams are not supported.
  45 </UL>
  46
  47 <P>
  48     When a file descriptor Device is copied, the result represents the same underlying file descriptor. The underlying file descriptor is <I>not</I> duplicated.
  49 </P>
  50
  51 <P>
  52     The classes <CODE>file_descriptor</CODE> supports 64-bit seek offsets whenever they are supported by the underlying operating system or runtime library. Currently, file descriptor Devices may not work corectly with file descriptors opened in non-blocking mode.
  53 </P>
  54
  55 <P>
  56     Line-ending conversion can be provided, if desired, using the class <A HREF="newline_filter.html"><CODE>newline_filter</CODE></A>. Wide-character versions of the file descriptor Devices may be defined as follows, using the template <A HREF="code_converter.html"><CODE>code_converter</CODE></A>:
  57     <PRE CLASS="broken_ie">    <SPAN CLASS="preprocessor">#include</SPAN> <A CLASS="header" HREF="../../../../boost/iostreams/code_converter.hpp"><SPAN CLASS="literal">&lt;boost/iostreams/code_converter.hpp&gt;</SPAN></A>
  58     <SPAN CLASS="preprocessor">#include</SPAN> <A CLASS="header" HREF="../../../../boost/iostreams/device/file_descriptor.hpp"><SPAN CLASS="literal">&lt;boost/iostreams/maped_file.hpp&gt;</SPAN></A>
  59
  60     <SPAN CLASS='keyword'>typedef</SPAN> code_converter&lt;file_descriptor_source&gt;  wfile_descriptor_source;
  61     <SPAN CLASS='keyword'>typedef</SPAN> code_converter&lt;file_descriptor_sink&gt;    wfile_descriptor_sink;</PRE>
  62 </P>
  63
  64 <A NAME="acknowledgments"></A>
  65 <H2>Acknowledgments</H2>
  66
  67 <P>
  68     The file descriptor Devices are based on work of Nicolai Josuttis  (<A CLASS="bib_ref" HREF="../bibliography.html#josuttis1">[Josuttis1]</A> <I>pp.</I> 672-3 and <A CLASS="bib_ref" HREF="../bibliography.html#josuttis2">[Josuttis2]</A>).
  69 </P>
  70
  71 <A NAME="installation"></A>
  72 <H2>Installation</H2>
  73
  74 <P>
  75     The file descriptor Devices depends on the source file <A CLASS="header" HREF="../../src/file_descriptor.cpp"><CODE>&lt;libs/iostreams/src/file_descriptor.cpp&gt;</CODE></A>, which makes use of Windows or POSIX headers depending on the user's operating system. For installation instructions see <A HREF="../installation.html">Installation</A>.
  76 </P>
  77
  78 <A NAME="headers"></A>
  79 <H2>Headers</H2>
  80
  81 <DL class="page-index">
  82   <DT><A CLASS="header" HREF="../../../../boost/iostreams/device/file_descriptor.hpp"><CODE>&lt;boost/iostreams/device/file_descriptor.hpp&gt;</CODE></A></DT>
  83 </DL>
  84
  85
  86 <A NAME="reference"></A>
  87 <H2>Reference</H2>
  88
  89 <A NAME="file_descriptor_source"></A>
  90 <H3>Class <CODE>file_descriptor_source</CODE></H3>
  91
  92 <H4>Description</H4>
  93
  94 <P>Model of <A HREF="../concepts/device.html">SeekableSource</A> and <A HREF="../concepts/closable.html">Closable</A> providing read-only access to a file through an operating system file descriptor.</P>
  95
  96 <H4>Synopsis</H4>
  97
  98 <PRE CLASS="broken_ie"><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams {
  99
 100 <SPAN CLASS="keyword">enum</SPAN> file_descriptor_flags {
 101     never_close_handle,
 102     close_handle
 103 };
 104
 105 <SPAN CLASS="keyword">class</SPAN> file_descriptor_source {
 106 <SPAN CLASS="keyword">public</SPAN>:
 107     <SPAN CLASS='keyword'>typedef</SPAN> <SPAN CLASS='keyword'>char</SPAN>                      char_type;
 108     <SPAN CLASS='keyword'>typedef</SPAN> <SPAN CLASS='omitted'>[implementation-defined]</SPAN>  handle_type;
 109     <SPAN CLASS='keyword'>typedef</SPAN> <SPAN CLASS='omitted'>[implementation-defined]</SPAN>  category;
 110     <A CLASS="documented" HREF="#file_descriptor_source_ctor">file_descriptor_source</A>();
 111     <SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> Path&gt;
 112     <A CLASS="documented" HREF="#file_descriptor_source_ctor">file_descriptor_source</A>( <SPAN CLASS="keyword">const</SPAN> Path&amp; pathname,
 113                             std::ios_base::open_mode mode =
 114                                 std::ios_base::in );
 115     <A CLASS="documented" HREF="#file_descriptor_source_ctor">file_descriptor_source</A>( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 116
 117     <SPAN CLASS='comment'>// Windows-only</SPAN>
 118     <A CLASS="documented" HREF="#file_descriptor_source_ctor">file_descriptor_source</A>( HANDLE hFile, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 119
 120     <SPAN CLASS='comment'>// Deprecated</SPAN>
 121     <A CLASS="documented" HREF="#file_descriptor_source_ctor">file_descriptor_source</A>( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );
 122
 123     <SPAN CLASS='comment'>// Deprecated, Windows-only</SPAN>
 124     <A CLASS="documented" HREF="#file_descriptor_source_ctor">file_descriptor_source</A>( HANDLE hFile, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );
 125
 126     <SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> Path&gt;
 127     <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#file_descriptor_source_open">open</A>( <SPAN CLASS="keyword">const</SPAN> Path&amp; pathname,
 128                      std::ios_base::open_mode mode =
 129                          std::ios_base::in );
 130     <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#file_descriptor_source_open">open</A>( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 131
 132     <SPAN CLASS='comment'>// Windows-only</SPAN>
 133     <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#file_descriptor_source_open">open</A>( HANDLE hFile, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 134
 135     <SPAN CLASS='comment'>// Deprecated</SPAN>
 136     <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#file_descriptor_source_open">open</A>( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );
 137
 138     <SPAN CLASS='comment'>// Deprecated, Windows-only</SPAN>
 139     <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#file_descriptor_source_open">open</A>( HANDLE hFile, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );
 140
 141     <SPAN CLASS="keyword">bool</SPAN> <A CLASS="documented" HREF="#file_descriptor_source_is_open">is_open</A>() <SPAN CLASS="keyword">const</SPAN>;
 142
 143     handle_type <A CLASS="documented" HREF="#file_descriptor_source_handle">handle</A>() <SPAN CLASS="keyword">const</SPAN>;
 144 };
 145
 146 } } <SPAN CLASS='comment'>// End namespace boost::io</SPAN></PRE>
 147
 148 <A NAME="file_descriptor_source_ctor"></A>
 149 <H4><CODE>file_descriptor_source::file_descriptor_source</CODE></H4>
 150
 151 <PRE CLASS="broken_ie">    file_descriptor_source();
 152     <SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> Path&gt;
 153     file_descriptor_source( <SPAN CLASS="keyword">const</SPAN> Path&amp; pathname,
 154                             std::ios_base::open_mode mode =
 155                                 std::ios_base::in );
 156     file_descriptor_source( <SPAN CLASS="keyword">int </SPAN>fd, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 157
 158     <SPAN CLASS='comment'>// Windows-only</SPAN>
 159     file_descriptor_source( HANDLE hFile, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 160
 161     <SPAN CLASS='comment'>// Deprecated</SPAN>
 162     file_descriptor_source( <SPAN CLASS="keyword">int </SPAN>fd, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );
 163
 164     <SPAN CLASS='comment'>// Deprecated, Windows-only</SPAN>
 165     file_descriptor_source( HANDLE hFile, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );</PRE>
 166 <P>
 167     The first member constructs an empty <CODE>file_descriptor_source</CODE>.
 168 </P>
 169
 170 <P>
 171     The second member constructs a <CODE>file_descriptor_source</CODE> to access the file with the given pathname. <CODE>Path</CODE> should be either a string or a Boost.Filesystem path. The parameter <CODE>mode</CODE> has the same interpretation as <CODE>(mode | std::ios_base::in)</CODE> in <CODE>std::basic_filebuf::open</CODE>.<A CLASS="footnote_ref" NAME="note_1_ref" HREF="#note_1"><SUP>[1]</SUP></A>
 172 </P>
 173
 174 <P>
 175     The third member constructs a <CODE>file_descriptor_source</CODE> to access the file with the given operating system or runtime-library file descriptor.
 176     If the second argument is <CODE>close_handle</CODE>, the file descriptor is closed when the <CODE>file_descriptor_source</CODE> being constructed &#8212; or one of its copies &#8212; is closed or destructed.
 177 </P>
 178
 179 <P>
 180     The fourth member is the same as the third, except that it accepts a Windows file handle instead of a file descriptor.
 181     If the second argument is <CODE>close_handle</CODE>, the file descriptor is closed when the <CODE>file_descriptor_source</CODE> being constructed &#8212; or one of its copies &#8212; is closed or destructed.
 182 </P>
 183
 184 <P>
 185     The deprecated members are there to provide backwards compatability with old versions.
 186     To use them you need to define <CODE>BOOST_IOSTREAMS_USE_DEPRECATED</CODE>.
 187     The descriptor is always closed by <CODE>close</CODE> but only closed in destructors if <CODE>close_on_exit</CODE> is <CODE>true</CODE>.
 188 </P>
 189
 190 <A NAME="file_descriptor_source_open"></A>
 191 <H4><CODE>file_descriptor_source::open</CODE></H4>
 192
 193 <PRE CLASS="broken_ie">    <SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> Path&gt;
 194     <SPAN CLASS="keyword">void</SPAN> open( <SPAN CLASS="keyword">const</SPAN> Path&amp; pathname,
 195                      std::ios_base::open_mode mode =
 196                          std::ios_base::in );
 197     <SPAN CLASS="keyword">void</SPAN> open( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 198
 199     <SPAN CLASS='comment'>// Windows-only</SPAN>
 200     <SPAN CLASS="keyword">void</SPAN> open( HANDLE hFile, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 201
 202     <SPAN CLASS='comment'>// Deprecated</SPAN>
 203     <SPAN CLASS="keyword">void</SPAN> open( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );
 204
 205     <SPAN CLASS='comment'>// Deprecated, Windows-only</SPAN>
 206     <SPAN CLASS="keyword">void</SPAN> open( HANDLE hFile, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );</PRE>
 207
 208 <P>
 209     The parameters of <CODE>open</CODE> the same as those of the corresponding constructors.
 210     If the file descriptor already holds a file, it'll be closed
 211     (unless opened or constructed with <CODE>never_close_handle</CODE>).
 212 </P>
 213
 214 <A NAME="file_descriptor_source_is_open"></A>
 215 <H4><CODE>file_descriptor_source::is_open</CODE></H4>
 216
 217 <PRE CLASS="broken_ie">    <SPAN CLASS="keyword">bool</SPAN> is_open() <SPAN CLASS="keyword">const</SPAN>;</PRE>
 218
 219 <P>Returns <CODE>true</CODE> if the underlying file was opened successfully.</P>
 220
 221 <A NAME="file_descriptor_source_handle"></A>
 222 <H4><CODE>file_descriptor_source::handle</CODE></H4>
 223
 224 <PRE CLASS="broken_ie">    handle_type handle() <SPAN CLASS="keyword">const</SPAN>;</PRE>
 225
 226 <P>Returns the underlying OS file descriptor.  On Windows, this is a <CODE>HANDLE</CODE>.  On other systems, it is an <CODE><SPAN CLASS="keyword">int</SPAN></CODE>.</P>
 227
 228 <A NAME="file_descriptor_sink"></A>
 229 <H3>Class <CODE>file_descriptor_sink</CODE></H3>
 230
 231 <H4>Description</H4>
 232
 233 <P>Model of <A HREF="../concepts/device.html">SeekableSink</A> and <A HREF="../concepts/closable.html">Closable</A> providing write-only access to a file through an operating system file descriptor.
 234
 235 <H4>Synopsis</H4>
 236
 237 <PRE CLASS="broken_ie"><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams {
 238
 239 <SPAN CLASS="keyword">enum</SPAN> file_descriptor_flags {
 240     never_close_handle,
 241     close_handle
 242 };
 243
 244 <SPAN CLASS="keyword">class</SPAN> file_descriptor_sink {
 245 <SPAN CLASS="keyword">public</SPAN>:
 246     <SPAN CLASS='keyword'>typedef</SPAN> <SPAN CLASS='keyword'>char</SPAN>                      char_type;
 247     <SPAN CLASS='keyword'>typedef</SPAN> <SPAN CLASS='omitted'>[implementation-defined]</SPAN>  handle_type;
 248     <SPAN CLASS='keyword'>typedef</SPAN> <SPAN CLASS='omitted'>[implementation-defined]</SPAN>  category;
 249     <A CLASS="documented" HREF="#file_descriptor_sink_ctor">file_descriptor_sink</A>();
 250     <SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> Path&gt;
 251     <A CLASS="documented" HREF="#file_descriptor_sink_ctor">file_descriptor_sink</A>( <SPAN CLASS="keyword">const</SPAN> Path&amp; pathname,
 252                           std::ios_base::open_mode mode =
 253                               std::ios_base::out );
 254     <A CLASS="documented" HREF="#file_descriptor_sink_ctor">file_descriptor_sink</A>( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 255
 256     <SPAN CLASS='comment'>// Windows-only</SPAN>
 257     <A CLASS="documented" HREF="#file_descriptor_sink_ctor">file_descriptor_sink</A>( HANDLE hFile, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 258
 259     <SPAN CLASS='comment'>// Deprecated</SPAN>
 260     <A CLASS="documented" HREF="#file_descriptor_sink_ctor">file_descriptor_sink</A>( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );
 261
 262     <SPAN CLASS='comment'>// Deprecated, Windows-only</SPAN>
 263     <A CLASS="documented" HREF="#file_descriptor_sink_ctor">file_descriptor_sink</A>( HANDLE hFile, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );
 264
 265     <SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> Path&gt;
 266     <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#file_descriptor_sink_open">open</A>( <SPAN CLASS="keyword">const</SPAN> Path&amp; pathname,
 267                      std::ios_base::open_mode mode =
 268                          std::ios_base::out );
 269     <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#file_descriptor_sink_open">open</A>( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 270
 271     <SPAN CLASS='comment'>// Windows-only</SPAN>
 272     <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#file_descriptor_sink_open">open</A>( HANDLE hFile, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 273
 274     <SPAN CLASS='comment'>// Deprecated</SPAN>
 275     <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#file_descriptor_sink_open">open</A>( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );
 276
 277     <SPAN CLASS='comment'>// Deprecated, Windows-only</SPAN>
 278     <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#file_descriptor_sink_open">open</A>( HANDLE hFile, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );
 279
 280     <SPAN CLASS="keyword">bool</SPAN> <A CLASS="documented" HREF="#file_descriptor_sink_is_open">is_open</A>() <SPAN CLASS="keyword">const</SPAN>;
 281
 282     handle_type <A CLASS="documented" HREF="#file_descriptor_sink_handle">handle</A>() <SPAN CLASS="keyword">const</SPAN>;
 283 };
 284
 285 } } <SPAN CLASS='comment'>// End namespace boost::io</SPAN></PRE>
 286
 287 <A NAME="file_descriptor_sink_ctor"></A>
 288 <H4><CODE>file_descriptor_sink::file_descriptor_sink</CODE></H4>
 289
 290 <PRE CLASS="broken_ie">    file_descriptor_sink();
 291     <SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> Path&gt;
 292     file_descriptor_sink( <SPAN CLASS="keyword">const</SPAN> Path&amp; pathname,
 293                           std::ios_base::open_mode mode =
 294                               std::ios_base::out );
 295     file_descriptor_sink( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 296
 297     <SPAN CLASS='comment'>// Windows-only</SPAN>
 298     file_descriptor_sink( HANDLE hFile, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 299
 300     <SPAN CLASS='comment'>// Deprecated</SPAN>
 301     file_descriptor_sink( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );
 302
 303     <SPAN CLASS='comment'>// Deprecated, Windows-only</SPAN>
 304     file_descriptor_sink( HANDLE hFile, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );</PRE>
 305
 306 <P>
 307     The first member constructs an empty <CODE>file_descriptor_sink</CODE>.
 308 </P>
 309
 310 <P>
 311     The second member constructs a <CODE>file_descriptor_sink</CODE> to access the file with the given pathname. <CODE>Path</CODE> should be either a string or a Boost.Filesystem path. The parameter <CODE>mode</CODE> has the same interpretation as <CODE>(mode | std::ios_base::out)</CODE> in <CODE>std::basic_filebuf::open</CODE>.<A CLASS="footnote_ref" NAME="note_1_ref2" HREF="#note_1"><SUP>[1]</SUP></A>
 312 </P>
 313
 314 <P>
 315     The third member constructs a <CODE>file_descriptor_sink</CODE> to access the file with the given operating system or runtime-library file descriptor.
 316     If the second argument is <CODE>close_handle</CODE>, the file descriptor is closed when the <CODE>file_descriptor_sink</CODE> being constructed &#8212; or one of its copies &#8212; is closed or destructed.
 317 </P>
 318
 319 <P>
 320     The fourth member is the same as the third, except that it accepts a Windows file handle instead of a file descriptor.
 321     If the second argument is <CODE>close_handle</CODE>, the file descriptor is closed when the <CODE>file_descriptor_sink</CODE> being constructed &#8212; or one of its copies &#8212; is closed or destructed.
 322 </P>
 323
 324 <P>
 325     The deprecated members are there to provide backwards compatability with old versions.
 326     To use them you need to define <CODE>BOOST_IOSTREAMS_USE_DEPRECATED</CODE>.
 327     The descriptor is always closed by <CODE>close</CODE> but only closed in destructors if <CODE>close_on_exit</CODE> is <CODE>true</CODE>.
 328 </P>
 329
 330 <A NAME="file_descriptor_sink_open"></A>
 331 <H4><CODE>file_descriptor_sink::open</CODE></H4>
 332
 333 <PRE CLASS="broken_ie">    <SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> Path&gt;
 334     <SPAN CLASS="keyword">void</SPAN> open( <SPAN CLASS="keyword">const</SPAN> Path&amp; pathname,
 335                      std::ios_base::open_mode mode =
 336                          std::ios_base::out );
 337     <SPAN CLASS="keyword">void</SPAN> open( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 338
 339     <SPAN CLASS='comment'>// Windows-only</SPAN>
 340     <SPAN CLASS="keyword">void</SPAN> open( HANDLE hFile, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 341
 342     <SPAN CLASS='comment'>// Deprecated</SPAN>
 343     <SPAN CLASS="keyword">void</SPAN> open( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );
 344
 345     <SPAN CLASS='comment'>// Deprecated, Windows-only</SPAN>
 346     <SPAN CLASS="keyword">void</SPAN> open( HANDLE hFile, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );</PRE>
 347
 348 <P>
 349     The parameters of <CODE>open</CODE> the same as those of the corresponding constructors.
 350     If the file descriptor already holds a file, it'll be closed
 351     (unless opened or constructed with <CODE>never_close_handle</CODE>).
 352 </P>
 353
 354 <A NAME="file_descriptor_sink_is_open"></A>
 355 <H4><CODE>file_descriptor_sink::is_open</CODE></H4>
 356
 357 <PRE CLASS="broken_ie">    <SPAN CLASS="keyword">bool</SPAN> is_open() <SPAN CLASS="keyword">const</SPAN>;</PRE>
 358
 359 <P>Returns <CODE>true</CODE> if the underlying file was opened successfully.</P>
 360
 361 <A NAME="file_descriptor_sink_handle"></A>
 362 <H4><CODE>file_descriptor_sink::handle</CODE></H4>
 363
 364 <PRE CLASS="broken_ie">    handle_type handle() <SPAN CLASS="keyword">const</SPAN>;</PRE>
 365
 366 <P>Returns the underlying OS file descriptor.  On Windows, this is a <CODE>HANDLE</CODE>.  On other systems, it is an <CODE><SPAN CLASS="keyword">int</SPAN></CODE>.</P>
 367
 368 <A NAME="file_descriptor"></A>
 369 <H3>Class <CODE>file_descriptor</CODE></H3>
 370
 371 <H4>Description</H4>
 372
 373 <P>Model of <A HREF="../concepts/seekable_device.html">SeekableDevice</A> and <A HREF="../concepts/closable.html">Closable</A> providing read-write access to a file through an operating system file descriptor.
 374
 375 <H4>Synopsis</H4>
 376
 377 <PRE CLASS="broken_ie"><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams {
 378
 379 <SPAN CLASS="keyword">enum</SPAN> file_descriptor_flags {
 380     never_close_handle,
 381     close_handle
 382 };
 383
 384 <SPAN CLASS="keyword">class</SPAN> file_descriptor {
 385 <SPAN CLASS="keyword">public</SPAN>:
 386     <SPAN CLASS='keyword'>typedef</SPAN> <SPAN CLASS='keyword'>char</SPAN>                      char_type;
 387     <SPAN CLASS='keyword'>typedef</SPAN> <SPAN CLASS='omitted'>[implementation-defined]</SPAN>  handle_type;
 388     <SPAN CLASS='keyword'>typedef</SPAN> <SPAN CLASS='omitted'>[implementation-defined]</SPAN>  category;
 389     <A CLASS="documented" HREF="#file_descriptor_constructor">file_descriptor</A>();
 390     <SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> Path&gt;
 391     <A CLASS="documented" HREF="#file_descriptor_constructor">file_descriptor</A>( <SPAN CLASS="keyword">const</SPAN> Path&amp; pathname,
 392                      std::ios_base::open_mode mode =
 393                          std::ios_base::in | std::ios_base::out );
 394     <A CLASS="documented" HREF="#file_descriptor_constructor">file_descriptor</A>( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 395
 396     <SPAN CLASS='comment'>// Windows-only</SPAN>
 397     <A CLASS="documented" HREF="#file_descriptor_constructor">file_descriptor</A>( HANDLE hFile, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 398
 399     <SPAN CLASS='comment'>// Deprecated</SPAN>
 400     <A CLASS="documented" HREF="#file_descriptor_constructor">file_descriptor</A>( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );
 401
 402     <SPAN CLASS='comment'>// Deprecated, Windows-only</SPAN>
 403     <A CLASS="documented" HREF="#file_descriptor_constructor">file_descriptor</A>( HANDLE hFile, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );
 404
 405     <SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> Path&gt;
 406     <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#file_descriptor_open">open</A>( <SPAN CLASS="keyword">const</SPAN> Path&amp; pathname,
 407                      std::ios_base::open_mode mode =
 408                          std::ios_base::in | std::ios_base::out );
 409     <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#file_descriptor_open">open</A>( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 410
 411     <SPAN CLASS='comment'>// Windows-only</SPAN>
 412     <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#file_descriptor_open">open</A>( HANDLE hFile, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 413
 414     <SPAN CLASS='comment'>// Deprecated</SPAN>
 415     <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#file_descriptor_open">open</A>( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );
 416
 417     <SPAN CLASS='comment'>// Deprecated, Windows-only</SPAN>
 418     <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#file_descriptor_open">open</A>( HANDLE hFile, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );
 419
 420     <SPAN CLASS="keyword">bool</SPAN> <A CLASS="documented" HREF="#file_descriptor_is_open">is_open</A>() <SPAN CLASS="keyword">const</SPAN>;
 421
 422     handle_type <A CLASS="documented" HREF="#file_descriptor_handle">handle</A>() <SPAN CLASS="keyword">const</SPAN>;
 423 };
 424
 425 } } <SPAN CLASS='comment'>// End namespace boost::io</SPAN></PRE>
 426
 427 <A NAME="file_descriptor_constructor"></A>
 428 <H4><CODE>file_descriptor::file_descriptor</CODE></H4>
 429
 430 <PRE CLASS="broken_ie">    file_descriptor();
 431     <SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> Path&gt;
 432     file_descriptor( <SPAN CLASS="keyword">const</SPAN> Path&amp; pathname,
 433                      std::ios_base::open_mode mode =
 434                          std::ios_base::in | std::ios_base::out );
 435     file_descriptor( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 436
 437     <SPAN CLASS='comment'>// Windows-only</SPAN>
 438     file_descriptor( HANDLE hFile, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 439
 440     <SPAN CLASS='comment'>// Deprecated</SPAN>
 441     file_descriptor( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );
 442
 443     <SPAN CLASS='comment'>// Deprecated, Windows-only</SPAN>
 444     file_descriptor( HANDLE hFile, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );</PRE>
 445
 446 <P>
 447     The first member constructs an empty <CODE>file_descriptor</CODE>.
 448 </P>
 449
 450 <P>
 451     The second member constructs a <CODE>file_descriptor</CODE> to access the file with the given pathname. <CODE>Path</CODE> should be either a string or a Boost.Filesystem path. The parameter <CODE>mode</CODE> has the same interpretation as in <CODE>std::basic_filebuf::open</CODE>.<A CLASS="footnote_ref" NAME="note_1_ref3" HREF="#note_1"><SUP>[1]</SUP></A>
 452 </P>
 453
 454 <P>
 455     The third member constructs a <CODE>file_descriptor</CODE> to access the file with the given operating system or runtime-library file descriptor.
 456     If the second argument is <CODE>close_handle</CODE>, the file descriptor is closed when the <CODE>file_descriptor</CODE> being constructed &#8212; or one of its copies &#8212; is closed or destructed.
 457 </P>
 458
 459 <P>
 460     The fourth member is the same as the third, except that it accepts a Windows file handle instead of a file descriptor.
 461     If the second argument is <CODE>close_handle</CODE>, the file descriptor is closed when the new <CODE>file_descriptor</CODE> &#8212; or one of its copies &#8212; is closed or destructed.
 462 </P>
 463
 464 <P>
 465     The deprecated members are there to provide backwards compatability with old versions.
 466     To use them you need to define <CODE>BOOST_IOSTREAMS_USE_DEPRECATED</CODE>.
 467     The descriptor is always closed by <CODE>close</CODE> but only closed in destructors if <CODE>close_on_exit</CODE> is <CODE>true</CODE>.
 468 </P>
 469
 470 <A NAME="file_descriptor_open"></A>
 471 <H4><CODE>file_descriptor::open</CODE></H4>
 472
 473 <PRE CLASS="broken_ie">    <SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> Path&gt;
 474     <SPAN CLASS="keyword">void</SPAN> open( <SPAN CLASS="keyword">const</SPAN> Path&amp; pathname,
 475                      std::ios_base::open_mode mode =
 476                          std::ios_base::in | std::ios_base::out );
 477     <SPAN CLASS="keyword">void</SPAN> open( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 478
 479     <SPAN CLASS='comment'>// Windows-only</SPAN>
 480     <SPAN CLASS="keyword">void</SPAN> open( HANDLE hFile, <SPAN CLASS="keyword">file_descriptor_flags</SPAN> );
 481
 482     <SPAN CLASS='comment'>// Deprecated</SPAN>
 483     <SPAN CLASS="keyword">void</SPAN> open( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );
 484
 485     <SPAN CLASS='comment'>// Deprecated, Windows-only</SPAN>
 486     <SPAN CLASS="keyword">void</SPAN> open( HANDLE hFile, <SPAN CLASS="keyword">bool</SPAN> close_on_exit = <SPAN CLASS="keyword">false</SPAN> );</PRE>
 487
 488 <P>
 489     The parameters of <CODE>open</CODE> the same as those of the corresponding constructors.
 490     If the file descriptor already holds a file, it'll be closed
 491     (unless opened or constructed with <CODE>never_close_handle</CODE>).
 492 </P>
 493
 494 <A NAME="file_descriptor_is_open"></A>
 495 <H4><CODE>file_descriptor::is_open</CODE></H4>
 496
 497 <PRE CLASS="broken_ie">    <SPAN CLASS="keyword">bool</SPAN> is_open() <SPAN CLASS="keyword">const</SPAN>;</PRE>
 498
 499 <P>Returns <CODE><SPAN CLASS="keyword">true</SPAN></CODE> if the underlying file was opened successfully.</P>
 500
 501 <A NAME="file_descriptor_handle"></A>
 502 <H4><CODE>file_descriptor::handle</CODE></H4>
 503
 504 <PRE CLASS="broken_ie">    handle_type handle() <SPAN CLASS="keyword">const</SPAN>;</PRE>
 505
 506 <P>Returns the underlying OS file descriptor.  On Windows, this is a <CODE>HANDLE</CODE>.  On other systems, it is an <CODE><SPAN CLASS="keyword">int</SPAN></CODE>.</P>
 507
 508 <!-- Begin Footnotes -->
 509
 510 <HR>
 511
 512 <P>
 513     <A CLASS="footnote_ref" NAME="note_1" HREF="#note_1_ref"><SUP>[1]</SUP></A><A CLASS="bib_ref" HREF="../bibliography.html#iso">[I<SPAN STYLE="font-size:80%">SO</SPAN>]</A>, Table 92.
 514 </P>
 515
 516 <!-- End Footnotes -->
 517
 518 <!-- Begin Footer -->
 519
 520 <HR>
 521
 522 <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>
 523 <P CLASS="copyright">
 524     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>)
 525 </P>
 526
 527 <!-- End Footer -->
 528
 529 </BODY>