libstdc++
stdio_filebuf.h
Go to the documentation of this file.
1 // File descriptor layer for filebuf -*- C++ -*-
2 
3 // Copyright (C) 2002-2023 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 <bits/requires_hosted.h> // GNU extensions are currently omitted
35 
36 #include <fstream>
37 
38 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
39 {
40 _GLIBCXX_BEGIN_NAMESPACE_VERSION
41 
42  /**
43  * @brief Provides a layer of compatibility for C/POSIX.
44  * @ingroup io
45  *
46  * This GNU extension provides extensions for working with standard C
47  * FILE*'s and POSIX file descriptors. It must be instantiated by the
48  * user with the type of character used in the file stream, e.g.,
49  * stdio_filebuf<char>.
50  */
51  template<typename _CharT, typename _Traits = std::char_traits<_CharT> >
52  class stdio_filebuf : public std::basic_filebuf<_CharT, _Traits>
53  {
54  public:
55  // Types:
56  typedef _CharT char_type;
57  typedef _Traits traits_type;
58  typedef typename traits_type::int_type int_type;
59  typedef typename traits_type::pos_type pos_type;
60  typedef typename traits_type::off_type off_type;
61  typedef std::size_t size_t;
62 
63  public:
64  /**
65  * deferred initialization
66  */
67  stdio_filebuf() : std::basic_filebuf<_CharT, _Traits>() {}
68 
69  /**
70  * @param __fd An open file descriptor.
71  * @param __mode Same meaning as in a standard filebuf.
72  * @param __size Optimal or preferred size of internal buffer,
73  * in chars.
74  *
75  * This constructor associates a file stream buffer with an open
76  * POSIX file descriptor. The file descriptor will be automatically
77  * closed when the stdio_filebuf is closed/destroyed.
78  */
79  stdio_filebuf(int __fd, std::ios_base::openmode __mode,
80  size_t __size = static_cast<size_t>(_GLIBCXX_BUFSIZ));
81 
82  /**
83  * @param __f An open @c FILE*.
84  * @param __mode Same meaning as in a standard filebuf.
85  * @param __size Optimal or preferred size of internal buffer,
86  * in chars. Defaults to system's @c BUFSIZ.
87  *
88  * This constructor associates a file stream buffer with an open
89  * C @c FILE*. The @c FILE* will not be automatically closed when the
90  * stdio_filebuf is closed/destroyed.
91  */
92  stdio_filebuf(std::__c_file* __f, std::ios_base::openmode __mode,
93  size_t __size = static_cast<size_t>(_GLIBCXX_BUFSIZ));
94 
95  /**
96  * Closes the external data stream if the file descriptor constructor
97  * was used.
98  */
99  virtual
100  ~stdio_filebuf();
101 
102 #if __cplusplus >= 201103L
103  stdio_filebuf(stdio_filebuf&&) = default;
104  stdio_filebuf& operator=(stdio_filebuf&&) = default;
105 
106  void
107  swap(stdio_filebuf& __fb)
109 #endif
110 
111  /**
112  * @return The underlying file descriptor.
113  *
114  * Once associated with an external data stream, this function can be
115  * used to access the underlying POSIX file descriptor. Note that
116  * there is no way for the library to track what you do with the
117  * descriptor, so be careful.
118  */
119  int
120  fd() { return this->_M_file.fd(); }
121 
122  /**
123  * @return The underlying FILE*.
124  *
125  * This function can be used to access the underlying "C" file pointer.
126  * Note that there is no way for the library to track what you do
127  * with the file, so be careful.
128  */
129  std::__c_file*
130  file() { return this->_M_file.file(); }
131  };
132 
133  template<typename _CharT, typename _Traits>
135  { }
136 
137  template<typename _CharT, typename _Traits>
139  stdio_filebuf(int __fd, std::ios_base::openmode __mode, size_t __size)
140  {
141  this->_M_file.sys_open(__fd, __mode);
142  if (this->is_open())
143  {
144  this->_M_mode = __mode;
145  this->_M_buf_size = __size;
146  this->_M_allocate_internal_buffer();
147  this->_M_reading = false;
148  this->_M_writing = false;
149  this->_M_set_buffer(-1);
150  }
151  }
152 
153  template<typename _CharT, typename _Traits>
155  stdio_filebuf(std::__c_file* __f, std::ios_base::openmode __mode,
156  size_t __size)
157  {
158  this->_M_file.sys_open(__f, __mode);
159  if (this->is_open())
160  {
161  this->_M_mode = __mode;
162  this->_M_buf_size = __size;
163  this->_M_allocate_internal_buffer();
164  this->_M_reading = false;
165  this->_M_writing = false;
166  this->_M_set_buffer(-1);
167  }
168  }
169 
170 _GLIBCXX_END_NAMESPACE_VERSION
171 } // namespace
172 
173 #endif
ISO C++ entities toplevel namespace is std.
GNU extensions for public use.
The actual work of input and output (for files).
Definition: fstream:88
Provides a layer of compatibility for C/POSIX.
Definition: stdio_filebuf.h:53
std::__c_file * file()