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)
108 { std::basic_filebuf<_CharT, _Traits>::swap(__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>
134 stdio_filebuf<_CharT, _Traits>::~stdio_filebuf()
135 { }
136
137 template<typename _CharT, typename _Traits>
138 stdio_filebuf<_CharT, _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>
154 stdio_filebuf<_CharT, _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