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FG		 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>
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528
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