1 // Iostreams wrapper for stdio FILE* -*- C++ -*-
2
3 // Copyright (C) 2003-2023 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_sync_filebuf.h
26 * This file is a GNU extension to the Standard C++ Library.
27 */
28
29 #ifndef _STDIO_SYNC_FILEBUF_H
30 #define _STDIO_SYNC_FILEBUF_H 1
31
32 #pragma GCC system_header
33
34 #include <bits/requires_hosted.h> // GNU extensions are currently omitted
35
36 #include <streambuf>
37 #include <cstdio>
38 #include <bits/c++io.h> // For __c_file
39 #include <bits/move.h> // For __exchange
40
41 #ifdef _GLIBCXX_USE_WCHAR_T
42 #include <cwchar>
43 #endif
44
45 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
46 {
47 _GLIBCXX_BEGIN_NAMESPACE_VERSION
48
49 /**
50 * @brief Provides a layer of compatibility for C.
51 * @ingroup io
52 *
53 * This GNU extension provides extensions for working with standard
54 * C FILE*'s. It must be instantiated by the user with the type of
55 * character used in the file stream, e.g., stdio_filebuf<char>.
56 */
57 template<typename _CharT, typename _Traits = std::char_traits<_CharT> >
58 class stdio_sync_filebuf : public std::basic_streambuf<_CharT, _Traits>
59 {
60 public:
61 // Types:
62 typedef _CharT char_type;
63 typedef _Traits traits_type;
64 typedef typename traits_type::int_type int_type;
65 typedef typename traits_type::pos_type pos_type;
66 typedef typename traits_type::off_type off_type;
67
68 private:
69 typedef std::basic_streambuf<_CharT, _Traits> __streambuf_type;
70
71 // Underlying stdio FILE
72 std::__c_file* _M_file;
73
74 // Last character gotten. This is used when pbackfail is
75 // called from basic_streambuf::sungetc()
76 int_type _M_unget_buf;
77
78 public:
79 explicit
80 stdio_sync_filebuf(std::__c_file* __f)
81 : _M_file(__f), _M_unget_buf(traits_type::eof())
82 { }
83
84 #if __cplusplus >= 201103L
85 stdio_sync_filebuf(stdio_sync_filebuf&& __fb) noexcept
86 : __streambuf_type(std::move(__fb)),
87 _M_file(__fb._M_file), _M_unget_buf(__fb._M_unget_buf)
88 {
89 __fb._M_file = nullptr;
90 __fb._M_unget_buf = traits_type::eof();
91 }
92
93 stdio_sync_filebuf&
94 operator=(stdio_sync_filebuf&& __fb) noexcept
95 {
96 __streambuf_type::operator=(__fb);
97 _M_file = std::__exchange(__fb._M_file, nullptr);
98 _M_unget_buf = std::__exchange(__fb._M_unget_buf, traits_type::eof());
99 return *this;
100 }
101
102 void
103 swap(stdio_sync_filebuf& __fb)
104 {
105 __streambuf_type::swap(__fb);
106 std::swap(_M_file, __fb._M_file);
107 std::swap(_M_unget_buf, __fb._M_unget_buf);
108 }
109 #endif
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; }
120
121 protected:
122 int_type
123 syncgetc();
124
125 int_type
126 syncungetc(int_type __c);
127
128 int_type
129 syncputc(int_type __c);
130
131 virtual int_type
132 underflow()
133 {
134 int_type __c = this->syncgetc();
135 return this->syncungetc(__c);
136 }
137
138 virtual int_type
139 uflow()
140 {
141 // Store the gotten character in case we need to unget it.
142 _M_unget_buf = this->syncgetc();
143 return _M_unget_buf;
144 }
145
146 virtual int_type
147 pbackfail(int_type __c = traits_type::eof())
148 {
149 int_type __ret;
150 const int_type __eof = traits_type::eof();
151
152 // Check if the unget or putback was requested
153 if (traits_type::eq_int_type(__c, __eof)) // unget
154 {
155 if (!traits_type::eq_int_type(_M_unget_buf, __eof))
156 __ret = this->syncungetc(_M_unget_buf);
157 else // buffer invalid, fail.
158 __ret = __eof;
159 }
160 else // putback
161 __ret = this->syncungetc(__c);
162
163 // The buffered character is no longer valid, discard it.
164 _M_unget_buf = __eof;
165 return __ret;
166 }
167
168 virtual std::streamsize
169 xsgetn(char_type* __s, std::streamsize __n);
170
171 virtual int_type
172 overflow(int_type __c = traits_type::eof())
173 {
174 int_type __ret;
175 if (traits_type::eq_int_type(__c, traits_type::eof()))
176 {
177 if (std::fflush(_M_file))
178 __ret = traits_type::eof();
179 else
180 __ret = traits_type::not_eof(__c);
181 }
182 else
183 __ret = this->syncputc(__c);
184 return __ret;
185 }
186
187 virtual std::streamsize
188 xsputn(const char_type* __s, std::streamsize __n);
189
190 virtual int
191 sync()
192 { return std::fflush(_M_file); }
193
194 virtual std::streampos
195 seekoff(std::streamoff __off, std::ios_base::seekdir __dir,
196 std::ios_base::openmode = std::ios_base::in | std::ios_base::out)
197 {
198 std::streampos __ret(std::streamoff(-1));
199 int __whence;
200 if (__dir == std::ios_base::beg)
201 __whence = SEEK_SET;
202 else if (__dir == std::ios_base::cur)
203 __whence = SEEK_CUR;
204 else
205 __whence = SEEK_END;
206 #ifdef _GLIBCXX_USE_LFS
207 if (!fseeko64(_M_file, __off, __whence))
208 __ret = std::streampos(ftello64(_M_file));
209 #else
210 if (!fseek(_M_file, __off, __whence))
211 __ret = std::streampos(std::ftell(_M_file));
212 #endif
213 return __ret;
214 }
215
216 virtual std::streampos
217 seekpos(std::streampos __pos,
218 std::ios_base::openmode __mode =
219 std::ios_base::in | std::ios_base::out)
220 { return seekoff(std::streamoff(__pos), std::ios_base::beg, __mode); }
221 };
222
223 template<>
224 inline stdio_sync_filebuf<char>::int_type
225 stdio_sync_filebuf<char>::syncgetc()
226 { return std::getc(_M_file); }
227
228 template<>
229 inline stdio_sync_filebuf<char>::int_type
230 stdio_sync_filebuf<char>::syncungetc(int_type __c)
231 { return std::ungetc(__c, _M_file); }
232
233 template<>
234 inline stdio_sync_filebuf<char>::int_type
235 stdio_sync_filebuf<char>::syncputc(int_type __c)
236 { return std::putc(__c, _M_file); }
237
238 template<>
239 inline std::streamsize
240 stdio_sync_filebuf<char>::xsgetn(char* __s, std::streamsize __n)
241 {
242 std::streamsize __ret = std::fread(__s, 1, __n, _M_file);
243 if (__ret > 0)
244 _M_unget_buf = traits_type::to_int_type(__s[__ret - 1]);
245 else
246 _M_unget_buf = traits_type::eof();
247 return __ret;
248 }
249
250 template<>
251 inline std::streamsize
252 stdio_sync_filebuf<char>::xsputn(const char* __s, std::streamsize __n)
253 { return std::fwrite(__s, 1, __n, _M_file); }
254
255 #ifdef _GLIBCXX_USE_WCHAR_T
256 template<>
257 inline stdio_sync_filebuf<wchar_t>::int_type
258 stdio_sync_filebuf<wchar_t>::syncgetc()
259 { return std::getwc(_M_file); }
260
261 template<>
262 inline stdio_sync_filebuf<wchar_t>::int_type
263 stdio_sync_filebuf<wchar_t>::syncungetc(int_type __c)
264 { return std::ungetwc(__c, _M_file); }
265
266 template<>
267 inline stdio_sync_filebuf<wchar_t>::int_type
268 stdio_sync_filebuf<wchar_t>::syncputc(int_type __c)
269 { return std::putwc(__c, _M_file); }
270
271 template<>
272 inline std::streamsize
273 stdio_sync_filebuf<wchar_t>::xsgetn(wchar_t* __s, std::streamsize __n)
274 {
275 std::streamsize __ret = 0;
276 const int_type __eof = traits_type::eof();
277 while (__n--)
278 {
279 int_type __c = this->syncgetc();
280 if (traits_type::eq_int_type(__c, __eof))
281 break;
282 __s[__ret] = traits_type::to_char_type(__c);
283 ++__ret;
284 }
285
286 if (__ret > 0)
287 _M_unget_buf = traits_type::to_int_type(__s[__ret - 1]);
288 else
289 _M_unget_buf = traits_type::eof();
290 return __ret;
291 }
292
293 template<>
294 inline std::streamsize
295 stdio_sync_filebuf<wchar_t>::xsputn(const wchar_t* __s,
296 std::streamsize __n)
297 {
298 std::streamsize __ret = 0;
299 const int_type __eof = traits_type::eof();
300 while (__n--)
301 {
302 if (traits_type::eq_int_type(this->syncputc(*__s++), __eof))
303 break;
304 ++__ret;
305 }
306 return __ret;
307 }
308 #endif
309
310 #if _GLIBCXX_EXTERN_TEMPLATE
311 extern template class stdio_sync_filebuf<char>;
312 #ifdef _GLIBCXX_USE_WCHAR_T
313 extern template class stdio_sync_filebuf<wchar_t>;
314 #endif
315 #endif
316
317 _GLIBCXX_END_NAMESPACE_VERSION
318 } // namespace
319
320 #endif