libstdc++
stdio_filebuf.h
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1 // File descriptor layer for filebuf -*- C++ -*-
2 
3 // Copyright (C) 2002-2025 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 #ifdef _GLIBCXX_SYSHDR
33 #pragma GCC system_header
34 #endif
35 
36 #include <bits/requires_hosted.h> // GNU extensions are currently omitted
37 
38 #include <fstream>
39 
40 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
41 {
42 _GLIBCXX_BEGIN_NAMESPACE_VERSION
43 
44  /**
45  * @brief Provides a layer of compatibility for C/POSIX.
46  * @ingroup io
47  *
48  * This GNU extension provides extensions for working with standard C
49  * FILE*'s and POSIX file descriptors. It must be instantiated by the
50  * user with the type of character used in the file stream, e.g.,
51  * stdio_filebuf<char>.
52  */
53  template<typename _CharT, typename _Traits = std::char_traits<_CharT> >
54  class stdio_filebuf : public std::basic_filebuf<_CharT, _Traits>
55  {
56  public:
57  // Types:
58  typedef _CharT char_type;
59  typedef _Traits traits_type;
60  typedef typename traits_type::int_type int_type;
61  typedef typename traits_type::pos_type pos_type;
62  typedef typename traits_type::off_type off_type;
63  typedef std::size_t size_t;
64 
65  public:
66  /**
67  * deferred initialization
68  */
69  stdio_filebuf() : std::basic_filebuf<_CharT, _Traits>() {}
70 
71  /**
72  * @param __fd An open file descriptor.
73  * @param __mode Same meaning as in a standard filebuf.
74  * @param __size Optimal or preferred size of internal buffer,
75  * in chars.
76  *
77  * This constructor associates a file stream buffer with an open
78  * POSIX file descriptor. The file descriptor will be automatically
79  * closed when the stdio_filebuf is closed/destroyed.
80  */
81  stdio_filebuf(int __fd, std::ios_base::openmode __mode,
82  size_t __size = static_cast<size_t>(_GLIBCXX_BUFSIZ));
83 
84  /**
85  * @param __f An open @c FILE*.
86  * @param __mode Same meaning as in a standard filebuf.
87  * @param __size Optimal or preferred size of internal buffer,
88  * in chars. Defaults to system's @c BUFSIZ.
89  *
90  * This constructor associates a file stream buffer with an open
91  * C @c FILE*. The @c FILE* will not be automatically closed when the
92  * stdio_filebuf is closed/destroyed.
93  */
94  stdio_filebuf(std::__c_file* __f, std::ios_base::openmode __mode,
95  size_t __size = static_cast<size_t>(_GLIBCXX_BUFSIZ));
96 
97  /**
98  * Closes the external data stream if the file descriptor constructor
99  * was used.
100  */
101  virtual
102  ~stdio_filebuf();
103 
104 #if __cplusplus >= 201103L
105  stdio_filebuf(stdio_filebuf&&) = default;
106  stdio_filebuf& operator=(stdio_filebuf&&) = default;
107 
108  void
109  swap(stdio_filebuf& __fb)
111 #endif
112 
113  /**
114  * @return The underlying file descriptor.
115  *
116  * Once associated with an external data stream, this function can be
117  * used to access the underlying POSIX file descriptor. Note that
118  * there is no way for the library to track what you do with the
119  * descriptor, so be careful.
120  */
121  int
122  fd() { return this->_M_file.fd(); }
123 
124  /**
125  * @return The underlying FILE*.
126  *
127  * This function can be used to access the underlying "C" file pointer.
128  * Note that there is no way for the library to track what you do
129  * with the file, so be careful.
130  */
131  std::__c_file*
132  file() { return this->_M_file.file(); }
133  };
134 
135  template<typename _CharT, typename _Traits>
137  { }
138 
139  template<typename _CharT, typename _Traits>
141  stdio_filebuf(int __fd, std::ios_base::openmode __mode, size_t __size)
142  {
143  this->_M_file.sys_open(__fd, __mode);
144  if (this->is_open())
145  {
146  this->_M_mode = __mode;
147  this->_M_buf_size = __size;
148  this->_M_allocate_internal_buffer();
149  this->_M_reading = false;
150  this->_M_writing = false;
151  this->_M_set_buffer(-1);
152  }
153  }
154 
155  template<typename _CharT, typename _Traits>
157  stdio_filebuf(std::__c_file* __f, std::ios_base::openmode __mode,
158  size_t __size)
159  {
160  this->_M_file.sys_open(__f, __mode);
161  if (this->is_open())
162  {
163  this->_M_mode = __mode;
164  this->_M_buf_size = __size;
165  this->_M_allocate_internal_buffer();
166  this->_M_reading = false;
167  this->_M_writing = false;
168  this->_M_set_buffer(-1);
169  }
170  }
171 
172 _GLIBCXX_END_NAMESPACE_VERSION
173 } // namespace
174 
175 #endif
ISO C++ entities toplevel namespace is std.
GNU extensions for public use.
The actual work of input and output (for files).
Definition: fstream:93
Provides a layer of compatibility for C/POSIX.
Definition: stdio_filebuf.h:55
std::__c_file * file()