libstdc++
stdio_filebuf.h
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1 // File descriptor layer for filebuf -*- C++ -*-
2 
3 // Copyright (C) 2002-2014 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10 
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
15 
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19 
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24 
25 /** @file ext/stdio_filebuf.h
26  * This file is a GNU extension to the Standard C++ Library.
27  */
28 
29 #ifndef _STDIO_FILEBUF_H
30 #define _STDIO_FILEBUF_H 1
31 
32 #pragma GCC system_header
33 
34 #include <fstream>
35 
36 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
37 {
38 _GLIBCXX_BEGIN_NAMESPACE_VERSION
39 
40  /**
41  * @brief Provides a layer of compatibility for C/POSIX.
42  * @ingroup io
43  *
44  * This GNU extension provides extensions for working with standard C
45  * FILE*'s and POSIX file descriptors. It must be instantiated by the
46  * user with the type of character used in the file stream, e.g.,
47  * stdio_filebuf<char>.
48  */
49  template<typename _CharT, typename _Traits = std::char_traits<_CharT> >
50  class stdio_filebuf : public std::basic_filebuf<_CharT, _Traits>
51  {
52  public:
53  // Types:
54  typedef _CharT char_type;
55  typedef _Traits traits_type;
56  typedef typename traits_type::int_type int_type;
57  typedef typename traits_type::pos_type pos_type;
58  typedef typename traits_type::off_type off_type;
59  typedef std::size_t size_t;
60 
61  public:
62  /**
63  * deferred initialization
64  */
65  stdio_filebuf() : std::basic_filebuf<_CharT, _Traits>() {}
66 
67  /**
68  * @param __fd An open file descriptor.
69  * @param __mode Same meaning as in a standard filebuf.
70  * @param __size Optimal or preferred size of internal buffer,
71  * in chars.
72  *
73  * This constructor associates a file stream buffer with an open
74  * POSIX file descriptor. The file descriptor will be automatically
75  * closed when the stdio_filebuf is closed/destroyed.
76  */
77  stdio_filebuf(int __fd, std::ios_base::openmode __mode,
78  size_t __size = static_cast<size_t>(BUFSIZ));
79 
80  /**
81  * @param __f An open @c FILE*.
82  * @param __mode Same meaning as in a standard filebuf.
83  * @param __size Optimal or preferred size of internal buffer,
84  * in chars. Defaults to system's @c BUFSIZ.
85  *
86  * This constructor associates a file stream buffer with an open
87  * C @c FILE*. The @c FILE* will not be automatically closed when the
88  * stdio_filebuf is closed/destroyed.
89  */
90  stdio_filebuf(std::__c_file* __f, std::ios_base::openmode __mode,
91  size_t __size = static_cast<size_t>(BUFSIZ));
92 
93  /**
94  * Closes the external data stream if the file descriptor constructor
95  * was used.
96  */
97  virtual
99 
100  /**
101  * @return The underlying file descriptor.
102  *
103  * Once associated with an external data stream, this function can be
104  * used to access the underlying POSIX file descriptor. Note that
105  * there is no way for the library to track what you do with the
106  * descriptor, so be careful.
107  */
108  int
109  fd() { return this->_M_file.fd(); }
110 
111  /**
112  * @return The underlying FILE*.
113  *
114  * This function can be used to access the underlying "C" file pointer.
115  * Note that there is no way for the library to track what you do
116  * with the file, so be careful.
117  */
118  std::__c_file*
119  file() { return this->_M_file.file(); }
120  };
121 
122  template<typename _CharT, typename _Traits>
124  { }
125 
126  template<typename _CharT, typename _Traits>
128  stdio_filebuf(int __fd, std::ios_base::openmode __mode, size_t __size)
129  {
130  this->_M_file.sys_open(__fd, __mode);
131  if (this->is_open())
132  {
133  this->_M_mode = __mode;
134  this->_M_buf_size = __size;
135  this->_M_allocate_internal_buffer();
136  this->_M_reading = false;
137  this->_M_writing = false;
138  this->_M_set_buffer(-1);
139  }
140  }
141 
142  template<typename _CharT, typename _Traits>
144  stdio_filebuf(std::__c_file* __f, std::ios_base::openmode __mode,
145  size_t __size)
146  {
147  this->_M_file.sys_open(__f, __mode);
148  if (this->is_open())
149  {
150  this->_M_mode = __mode;
151  this->_M_buf_size = __size;
152  this->_M_allocate_internal_buffer();
153  this->_M_reading = false;
154  this->_M_writing = false;
155  this->_M_set_buffer(-1);
156  }
157  }
158 
159 _GLIBCXX_END_NAMESPACE_VERSION
160 } // namespace
161 
162 #endif
The actual work of input and output (for files).
Definition: fstream:72
Provides a layer of compatibility for C/POSIX.This GNU extension provides extensions for working with...
Definition: stdio_filebuf.h:50
std::__c_file * file()
basic_filebuf()
Does not open any files.
Definition: fstream.tcc:79