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"><boost/iostreams/code_converter.hpp></SPAN></A> 58 <SPAN CLASS="preprocessor">#include</SPAN> <A CLASS="header" HREF="../../../../boost/iostreams/device/file_descriptor.hpp"><SPAN CLASS="literal"><boost/iostreams/maped_file.hpp></SPAN></A> 59 60 <SPAN CLASS='keyword'>typedef</SPAN> code_converter<file_descriptor_source> wfile_descriptor_source; 61 <SPAN CLASS='keyword'>typedef</SPAN> code_converter<file_descriptor_sink> 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><libs/iostreams/src/file_descriptor.cpp></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><boost/iostreams/device/file_descriptor.hpp></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><<SPAN CLASS="keyword">typename</SPAN> Path> 112 <A CLASS="documented" HREF="#file_descriptor_source_ctor">file_descriptor_source</A>( <SPAN CLASS="keyword">const</SPAN> Path& 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><<SPAN CLASS="keyword">typename</SPAN> Path> 127 <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#file_descriptor_source_open">open</A>( <SPAN CLASS="keyword">const</SPAN> Path& 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><<SPAN CLASS="keyword">typename</SPAN> Path> 153 file_descriptor_source( <SPAN CLASS="keyword">const</SPAN> Path& 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 — or one of its copies — 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 — or one of its copies — 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><<SPAN CLASS="keyword">typename</SPAN> Path> 194 <SPAN CLASS="keyword">void</SPAN> open( <SPAN CLASS="keyword">const</SPAN> Path& 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><<SPAN CLASS="keyword">typename</SPAN> Path> 251 <A CLASS="documented" HREF="#file_descriptor_sink_ctor">file_descriptor_sink</A>( <SPAN CLASS="keyword">const</SPAN> Path& 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><<SPAN CLASS="keyword">typename</SPAN> Path> 266 <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#file_descriptor_sink_open">open</A>( <SPAN CLASS="keyword">const</SPAN> Path& 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><<SPAN CLASS="keyword">typename</SPAN> Path> 292 file_descriptor_sink( <SPAN CLASS="keyword">const</SPAN> Path& 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 — or one of its copies — 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 — or one of its copies — 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><<SPAN CLASS="keyword">typename</SPAN> Path> 334 <SPAN CLASS="keyword">void</SPAN> open( <SPAN CLASS="keyword">const</SPAN> Path& 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><<SPAN CLASS="keyword">typename</SPAN> Path> 391 <A CLASS="documented" HREF="#file_descriptor_constructor">file_descriptor</A>( <SPAN CLASS="keyword">const</SPAN> Path& 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><<SPAN CLASS="keyword">typename</SPAN> Path> 406 <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#file_descriptor_open">open</A>( <SPAN CLASS="keyword">const</SPAN> Path& 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><<SPAN CLASS="keyword">typename</SPAN> Path> 432 file_descriptor( <SPAN CLASS="keyword">const</SPAN> Path& 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 — or one of its copies — 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> — or one of its copies — 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><<SPAN CLASS="keyword">typename</SPAN> Path> 474 <SPAN CLASS="keyword">void</SPAN> open( <SPAN CLASS="keyword">const</SPAN> Path& 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">© Copyright 2008 <a href="http://www.coderage.com/" target="_top">CodeRage, LLC</a><br/>© Copyright 2004-2007 <a href="https://www.boost.org/users/people/jonathan_turkanis.html" 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>