libstdc++
stdio_sync_filebuf.h
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1 // Iostreams wrapper for stdio FILE* -*- C++ -*-
2 
3 // Copyright (C) 2003-2014 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 
39 #ifdef _GLIBCXX_USE_WCHAR_T
40 #include <cwchar>
41 #endif
42 
43 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
44 {
45 _GLIBCXX_BEGIN_NAMESPACE_VERSION
46 
47  /**
48  * @brief Provides a layer of compatibility for C.
49  * @ingroup io
50  *
51  * This GNU extension provides extensions for working with standard
52  * C FILE*'s. It must be instantiated by the user with the type of
53  * character used in the file stream, e.g., stdio_filebuf<char>.
54  */
55  template<typename _CharT, typename _Traits = std::char_traits<_CharT> >
56  class stdio_sync_filebuf : public std::basic_streambuf<_CharT, _Traits>
57  {
58  public:
59  // Types:
60  typedef _CharT char_type;
61  typedef _Traits traits_type;
62  typedef typename traits_type::int_type int_type;
63  typedef typename traits_type::pos_type pos_type;
64  typedef typename traits_type::off_type off_type;
65 
66  private:
67  // Underlying stdio FILE
68  std::__c_file* const _M_file;
69 
70  // Last character gotten. This is used when pbackfail is
71  // called from basic_streambuf::sungetc()
72  int_type _M_unget_buf;
73 
74  public:
75  explicit
76  stdio_sync_filebuf(std::__c_file* __f)
77  : _M_file(__f), _M_unget_buf(traits_type::eof())
78  { }
79 
80  /**
81  * @return The underlying FILE*.
82  *
83  * This function can be used to access the underlying C file pointer.
84  * Note that there is no way for the library to track what you do
85  * with the file, so be careful.
86  */
87  std::__c_file* const
88  file() { return this->_M_file; }
89 
90  protected:
91  int_type
92  syncgetc();
93 
94  int_type
95  syncungetc(int_type __c);
96 
97  int_type
98  syncputc(int_type __c);
99 
100  virtual int_type
101  underflow()
102  {
103  int_type __c = this->syncgetc();
104  return this->syncungetc(__c);
105  }
106 
107  virtual int_type
108  uflow()
109  {
110  // Store the gotten character in case we need to unget it.
111  _M_unget_buf = this->syncgetc();
112  return _M_unget_buf;
113  }
114 
115  virtual int_type
116  pbackfail(int_type __c = traits_type::eof())
117  {
118  int_type __ret;
119  const int_type __eof = traits_type::eof();
120 
121  // Check if the unget or putback was requested
122  if (traits_type::eq_int_type(__c, __eof)) // unget
123  {
124  if (!traits_type::eq_int_type(_M_unget_buf, __eof))
125  __ret = this->syncungetc(_M_unget_buf);
126  else // buffer invalid, fail.
127  __ret = __eof;
128  }
129  else // putback
130  __ret = this->syncungetc(__c);
131 
132  // The buffered character is no longer valid, discard it.
133  _M_unget_buf = __eof;
134  return __ret;
135  }
136 
137  virtual std::streamsize
138  xsgetn(char_type* __s, std::streamsize __n);
139 
140  virtual int_type
141  overflow(int_type __c = traits_type::eof())
142  {
143  int_type __ret;
144  if (traits_type::eq_int_type(__c, traits_type::eof()))
145  {
146  if (std::fflush(_M_file))
147  __ret = traits_type::eof();
148  else
149  __ret = traits_type::not_eof(__c);
150  }
151  else
152  __ret = this->syncputc(__c);
153  return __ret;
154  }
155 
156  virtual std::streamsize
157  xsputn(const char_type* __s, std::streamsize __n);
158 
159  virtual int
160  sync()
161  { return std::fflush(_M_file); }
162 
163  virtual std::streampos
164  seekoff(std::streamoff __off, std::ios_base::seekdir __dir,
165  std::ios_base::openmode = std::ios_base::in | std::ios_base::out)
166  {
167  std::streampos __ret(std::streamoff(-1));
168  int __whence;
169  if (__dir == std::ios_base::beg)
170  __whence = SEEK_SET;
171  else if (__dir == std::ios_base::cur)
172  __whence = SEEK_CUR;
173  else
174  __whence = SEEK_END;
175 #ifdef _GLIBCXX_USE_LFS
176  if (!fseeko64(_M_file, __off, __whence))
177  __ret = std::streampos(ftello64(_M_file));
178 #else
179  if (!fseek(_M_file, __off, __whence))
180  __ret = std::streampos(std::ftell(_M_file));
181 #endif
182  return __ret;
183  }
184 
185  virtual std::streampos
186  seekpos(std::streampos __pos,
187  std::ios_base::openmode __mode =
189  { return seekoff(std::streamoff(__pos), std::ios_base::beg, __mode); }
190  };
191 
192  template<>
193  inline stdio_sync_filebuf<char>::int_type
194  stdio_sync_filebuf<char>::syncgetc()
195  { return std::getc(_M_file); }
196 
197  template<>
198  inline stdio_sync_filebuf<char>::int_type
199  stdio_sync_filebuf<char>::syncungetc(int_type __c)
200  { return std::ungetc(__c, _M_file); }
201 
202  template<>
203  inline stdio_sync_filebuf<char>::int_type
204  stdio_sync_filebuf<char>::syncputc(int_type __c)
205  { return std::putc(__c, _M_file); }
206 
207  template<>
208  inline std::streamsize
209  stdio_sync_filebuf<char>::xsgetn(char* __s, std::streamsize __n)
210  {
211  std::streamsize __ret = std::fread(__s, 1, __n, _M_file);
212  if (__ret > 0)
213  _M_unget_buf = traits_type::to_int_type(__s[__ret - 1]);
214  else
215  _M_unget_buf = traits_type::eof();
216  return __ret;
217  }
218 
219  template<>
220  inline std::streamsize
221  stdio_sync_filebuf<char>::xsputn(const char* __s, std::streamsize __n)
222  { return std::fwrite(__s, 1, __n, _M_file); }
223 
224 #ifdef _GLIBCXX_USE_WCHAR_T
225  template<>
226  inline stdio_sync_filebuf<wchar_t>::int_type
227  stdio_sync_filebuf<wchar_t>::syncgetc()
228  { return std::getwc(_M_file); }
229 
230  template<>
231  inline stdio_sync_filebuf<wchar_t>::int_type
232  stdio_sync_filebuf<wchar_t>::syncungetc(int_type __c)
233  { return std::ungetwc(__c, _M_file); }
234 
235  template<>
236  inline stdio_sync_filebuf<wchar_t>::int_type
237  stdio_sync_filebuf<wchar_t>::syncputc(int_type __c)
238  { return std::putwc(__c, _M_file); }
239 
240  template<>
241  inline std::streamsize
242  stdio_sync_filebuf<wchar_t>::xsgetn(wchar_t* __s, std::streamsize __n)
243  {
244  std::streamsize __ret = 0;
245  const int_type __eof = traits_type::eof();
246  while (__n--)
247  {
248  int_type __c = this->syncgetc();
249  if (traits_type::eq_int_type(__c, __eof))
250  break;
251  __s[__ret] = traits_type::to_char_type(__c);
252  ++__ret;
253  }
254 
255  if (__ret > 0)
256  _M_unget_buf = traits_type::to_int_type(__s[__ret - 1]);
257  else
258  _M_unget_buf = traits_type::eof();
259  return __ret;
260  }
261 
262  template<>
263  inline std::streamsize
264  stdio_sync_filebuf<wchar_t>::xsputn(const wchar_t* __s,
265  std::streamsize __n)
266  {
267  std::streamsize __ret = 0;
268  const int_type __eof = traits_type::eof();
269  while (__n--)
270  {
271  if (traits_type::eq_int_type(this->syncputc(*__s++), __eof))
272  break;
273  ++__ret;
274  }
275  return __ret;
276  }
277 #endif
278 
279 #if _GLIBCXX_EXTERN_TEMPLATE
280  extern template class stdio_sync_filebuf<char>;
281 #ifdef _GLIBCXX_USE_WCHAR_T
282  extern template class stdio_sync_filebuf<wchar_t>;
283 #endif
284 #endif
285 
286 _GLIBCXX_END_NAMESPACE_VERSION
287 } // namespace
288 
289 #endif
static const seekdir cur
Request a seek relative to the current position within the sequence.
Definition: ios_base.h:399
GNU extensions for public use.
Provides a layer of compatibility for C.This GNU extension provides extensions for working with stand...
long long streamoff
Type used by fpos, char_traits, and char_traits.
Definition: postypes.h:94
static const openmode in
Open for input. Default for ifstream and fstream.
Definition: ios_base.h:375
ptrdiff_t streamsize
Integral type for I/O operation counts and buffer sizes.
Definition: postypes.h:98
fpos< mbstate_t > streampos
File position for char streams.
Definition: postypes.h:228
static const seekdir beg
Request a seek relative to the beginning of the stream.
Definition: ios_base.h:396
static const openmode out
Open for output. Default for ofstream and fstream.
Definition: ios_base.h:378
Class representing stream positions.
Definition: postypes.h:112
std::__c_file *const file()