libstdc++
stdio_sync_filebuf.h
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1 // Iostreams wrapper for stdio FILE* -*- C++ -*-
2 
3 // Copyright (C) 2003-2020 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 <streambuf>
35 #include <unistd.h>
36 #include <cstdio>
37 #include <bits/c++io.h> // For __c_file
38 #include <bits/move.h> // For __exchange
39 
40 #ifdef _GLIBCXX_USE_WCHAR_T
41 #include <cwchar>
42 #endif
43 
44 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
45 {
46 _GLIBCXX_BEGIN_NAMESPACE_VERSION
47 
48  /**
49  * @brief Provides a layer of compatibility for C.
50  * @ingroup io
51  *
52  * This GNU extension provides extensions for working with standard
53  * C FILE*'s. It must be instantiated by the user with the type of
54  * character used in the file stream, e.g., stdio_filebuf<char>.
55  */
56  template<typename _CharT, typename _Traits = std::char_traits<_CharT> >
57  class stdio_sync_filebuf : public std::basic_streambuf<_CharT, _Traits>
58  {
59  public:
60  // Types:
61  typedef _CharT char_type;
62  typedef _Traits traits_type;
63  typedef typename traits_type::int_type int_type;
64  typedef typename traits_type::pos_type pos_type;
65  typedef typename traits_type::off_type off_type;
66 
67  private:
69 
70  // Underlying stdio FILE
71  std::__c_file* _M_file;
72 
73  // Last character gotten. This is used when pbackfail is
74  // called from basic_streambuf::sungetc()
75  int_type _M_unget_buf;
76 
77  public:
78  explicit
79  stdio_sync_filebuf(std::__c_file* __f)
80  : _M_file(__f), _M_unget_buf(traits_type::eof())
81  { }
82 
83 #if __cplusplus >= 201103L
84  stdio_sync_filebuf(stdio_sync_filebuf&& __fb) noexcept
85  : __streambuf_type(std::move(__fb)),
86  _M_file(__fb._M_file), _M_unget_buf(__fb._M_unget_buf)
87  {
88  __fb._M_file = nullptr;
89  __fb._M_unget_buf = traits_type::eof();
90  }
91 
93  operator=(stdio_sync_filebuf&& __fb) noexcept
94  {
95  __streambuf_type::operator=(__fb);
96  _M_file = std::__exchange(__fb._M_file, nullptr);
97  _M_unget_buf = std::__exchange(__fb._M_unget_buf, traits_type::eof());
98  return *this;
99  }
100 
101  void
102  swap(stdio_sync_filebuf& __fb)
103  {
104  __streambuf_type::swap(__fb);
105  std::swap(_M_file, __fb._M_file);
106  std::swap(_M_unget_buf, __fb._M_unget_buf);
107  }
108 #endif
109 
110  /**
111  * @return The underlying FILE*.
112  *
113  * This function can be used to access the underlying C file pointer.
114  * Note that there is no way for the library to track what you do
115  * with the file, so be careful.
116  */
117  std::__c_file*
118  file() { return this->_M_file; }
119 
120  protected:
121  int_type
122  syncgetc();
123 
124  int_type
125  syncungetc(int_type __c);
126 
127  int_type
128  syncputc(int_type __c);
129 
130  virtual int_type
132  {
133  int_type __c = this->syncgetc();
134  return this->syncungetc(__c);
135  }
136 
137  virtual int_type
139  {
140  // Store the gotten character in case we need to unget it.
141  _M_unget_buf = this->syncgetc();
142  return _M_unget_buf;
143  }
144 
145  virtual int_type
146  pbackfail(int_type __c = traits_type::eof())
147  {
148  int_type __ret;
149  const int_type __eof = traits_type::eof();
150 
151  // Check if the unget or putback was requested
152  if (traits_type::eq_int_type(__c, __eof)) // unget
153  {
154  if (!traits_type::eq_int_type(_M_unget_buf, __eof))
155  __ret = this->syncungetc(_M_unget_buf);
156  else // buffer invalid, fail.
157  __ret = __eof;
158  }
159  else // putback
160  __ret = this->syncungetc(__c);
161 
162  // The buffered character is no longer valid, discard it.
163  _M_unget_buf = __eof;
164  return __ret;
165  }
166 
167  virtual std::streamsize
168  xsgetn(char_type* __s, std::streamsize __n);
169 
170  virtual int_type
171  overflow(int_type __c = traits_type::eof())
172  {
173  int_type __ret;
174  if (traits_type::eq_int_type(__c, traits_type::eof()))
175  {
176  if (std::fflush(_M_file))
177  __ret = traits_type::eof();
178  else
179  __ret = traits_type::not_eof(__c);
180  }
181  else
182  __ret = this->syncputc(__c);
183  return __ret;
184  }
185 
186  virtual std::streamsize
187  xsputn(const char_type* __s, std::streamsize __n);
188 
189  virtual int
191  { return std::fflush(_M_file); }
192 
193  virtual std::streampos
194  seekoff(std::streamoff __off, std::ios_base::seekdir __dir,
195  std::ios_base::openmode = std::ios_base::in | std::ios_base::out)
196  {
197  std::streampos __ret(std::streamoff(-1));
198  int __whence;
199  if (__dir == std::ios_base::beg)
200  __whence = SEEK_SET;
201  else if (__dir == std::ios_base::cur)
202  __whence = SEEK_CUR;
203  else
204  __whence = SEEK_END;
205 #ifdef _GLIBCXX_USE_LFS
206  if (!fseeko64(_M_file, __off, __whence))
207  __ret = std::streampos(ftello64(_M_file));
208 #else
209  if (!fseek(_M_file, __off, __whence))
210  __ret = std::streampos(std::ftell(_M_file));
211 #endif
212  return __ret;
213  }
214 
215  virtual std::streampos
217  std::ios_base::openmode __mode =
219  { return seekoff(std::streamoff(__pos), std::ios_base::beg, __mode); }
220  };
221 
222  template<>
223  inline stdio_sync_filebuf<char>::int_type
224  stdio_sync_filebuf<char>::syncgetc()
225  { return std::getc(_M_file); }
226 
227  template<>
228  inline stdio_sync_filebuf<char>::int_type
229  stdio_sync_filebuf<char>::syncungetc(int_type __c)
230  { return std::ungetc(__c, _M_file); }
231 
232  template<>
233  inline stdio_sync_filebuf<char>::int_type
234  stdio_sync_filebuf<char>::syncputc(int_type __c)
235  { return std::putc(__c, _M_file); }
236 
237  template<>
238  inline std::streamsize
239  stdio_sync_filebuf<char>::xsgetn(char* __s, std::streamsize __n)
240  {
241  std::streamsize __ret = std::fread(__s, 1, __n, _M_file);
242  if (__ret > 0)
243  _M_unget_buf = traits_type::to_int_type(__s[__ret - 1]);
244  else
245  _M_unget_buf = traits_type::eof();
246  return __ret;
247  }
248 
249  template<>
250  inline std::streamsize
251  stdio_sync_filebuf<char>::xsputn(const char* __s, std::streamsize __n)
252  { return std::fwrite(__s, 1, __n, _M_file); }
253 
254 #ifdef _GLIBCXX_USE_WCHAR_T
255  template<>
256  inline stdio_sync_filebuf<wchar_t>::int_type
257  stdio_sync_filebuf<wchar_t>::syncgetc()
258  { return std::getwc(_M_file); }
259 
260  template<>
261  inline stdio_sync_filebuf<wchar_t>::int_type
262  stdio_sync_filebuf<wchar_t>::syncungetc(int_type __c)
263  { return std::ungetwc(__c, _M_file); }
264 
265  template<>
266  inline stdio_sync_filebuf<wchar_t>::int_type
267  stdio_sync_filebuf<wchar_t>::syncputc(int_type __c)
268  { return std::putwc(__c, _M_file); }
269 
270  template<>
271  inline std::streamsize
272  stdio_sync_filebuf<wchar_t>::xsgetn(wchar_t* __s, std::streamsize __n)
273  {
274  std::streamsize __ret = 0;
275  const int_type __eof = traits_type::eof();
276  while (__n--)
277  {
278  int_type __c = this->syncgetc();
279  if (traits_type::eq_int_type(__c, __eof))
280  break;
281  __s[__ret] = traits_type::to_char_type(__c);
282  ++__ret;
283  }
284 
285  if (__ret > 0)
286  _M_unget_buf = traits_type::to_int_type(__s[__ret - 1]);
287  else
288  _M_unget_buf = traits_type::eof();
289  return __ret;
290  }
291 
292  template<>
293  inline std::streamsize
294  stdio_sync_filebuf<wchar_t>::xsputn(const wchar_t* __s,
295  std::streamsize __n)
296  {
297  std::streamsize __ret = 0;
298  const int_type __eof = traits_type::eof();
299  while (__n--)
300  {
301  if (traits_type::eq_int_type(this->syncputc(*__s++), __eof))
302  break;
303  ++__ret;
304  }
305  return __ret;
306  }
307 #endif
308 
309 #if _GLIBCXX_EXTERN_TEMPLATE
310  extern template class stdio_sync_filebuf<char>;
311 #ifdef _GLIBCXX_USE_WCHAR_T
312  extern template class stdio_sync_filebuf<wchar_t>;
313 #endif
314 #endif
315 
316 _GLIBCXX_END_NAMESPACE_VERSION
317 } // namespace
318 
319 #endif
constexpr std::remove_reference< _Tp >::type && move(_Tp &&__t) noexcept
Convert a value to an rvalue.
Definition: move.h:101
ptrdiff_t streamsize
Integral type for I/O operation counts and buffer sizes.
Definition: postypes.h:98
long long streamoff
Type used by fpos, char_traits<char>, and char_traits<wchar_t>.
Definition: postypes.h:94
fpos< mbstate_t > streampos
File position for char streams.
Definition: postypes.h:234
GNU extensions for public use.
The actual work of input and output (interface).
Definition: streambuf:123
static const seekdir cur
Request a seek relative to the current position within the sequence.
Definition: ios_base.h:485
static const seekdir beg
Request a seek relative to the beginning of the stream.
Definition: ios_base.h:482
static const openmode in
Open for input. Default for ifstream and fstream.
Definition: ios_base.h:461
static const openmode out
Open for output. Default for ofstream and fstream.
Definition: ios_base.h:464
Class representing stream positions.
Definition: postypes.h:113
Provides a layer of compatibility for C.
virtual std::streampos seekpos(std::streampos __pos, std::ios_base::openmode __mode=std::ios_base::in|std::ios_base::out)
Alters the stream positions.
virtual int_type underflow()
Fetches more data from the controlled sequence.
virtual int sync()
Synchronizes the buffer arrays with the controlled sequences.
virtual int_type uflow()
Fetches more data from the controlled sequence.