libstdc++
stdio_sync_filebuf.h
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1 // Iostreams wrapper for stdio FILE* -*- C++ -*-
2 
3 // Copyright (C) 2003, 2004, 2005, 2006, 2007, 2009, 2010
4 // Free Software Foundation, Inc.
5 //
6 // This file is part of the GNU ISO C++ Library. This library is free
7 // software; you can redistribute it and/or modify it under the
8 // terms of the GNU General Public License as published by the
9 // Free Software Foundation; either version 3, or (at your option)
10 // any later version.
11 
12 // This library is distributed in the hope that it will be useful,
13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 // GNU General Public License for more details.
16 
17 // Under Section 7 of GPL version 3, you are granted additional
18 // permissions described in the GCC Runtime Library Exception, version
19 // 3.1, as published by the Free Software Foundation.
20 
21 // You should have received a copy of the GNU General Public License and
22 // a copy of the GCC Runtime Library Exception along with this program;
23 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
24 // <http://www.gnu.org/licenses/>.
25 
26 /** @file ext/stdio_sync_filebuf.h
27  * This file is a GNU extension to the Standard C++ Library.
28  */
29 
30 #ifndef _STDIO_SYNC_FILEBUF_H
31 #define _STDIO_SYNC_FILEBUF_H 1
32 
33 #pragma GCC system_header
34 
35 #include <streambuf>
36 #include <unistd.h>
37 #include <cstdio>
38 #include <bits/c++io.h> // For __c_file
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:
68  // Underlying stdio FILE
69  std::__c_file* const _M_file;
70 
71  // Last character gotten. This is used when pbackfail is
72  // called from basic_streambuf::sungetc()
73  int_type _M_unget_buf;
74 
75  public:
76  explicit
77  stdio_sync_filebuf(std::__c_file* __f)
78  : _M_file(__f), _M_unget_buf(traits_type::eof())
79  { }
80 
81  /**
82  * @return The underlying FILE*.
83  *
84  * This function can be used to access the underlying C file pointer.
85  * Note that there is no way for the library to track what you do
86  * with the file, so be careful.
87  */
88  std::__c_file* const
89  file() { return this->_M_file; }
90 
91  protected:
92  int_type
93  syncgetc();
94 
95  int_type
96  syncungetc(int_type __c);
97 
98  int_type
99  syncputc(int_type __c);
100 
101  virtual int_type
103  {
104  int_type __c = this->syncgetc();
105  return this->syncungetc(__c);
106  }
107 
108  virtual int_type
110  {
111  // Store the gotten character in case we need to unget it.
112  _M_unget_buf = this->syncgetc();
113  return _M_unget_buf;
114  }
115 
116  virtual int_type
117  pbackfail(int_type __c = traits_type::eof())
118  {
119  int_type __ret;
120  const int_type __eof = traits_type::eof();
121 
122  // Check if the unget or putback was requested
123  if (traits_type::eq_int_type(__c, __eof)) // unget
124  {
125  if (!traits_type::eq_int_type(_M_unget_buf, __eof))
126  __ret = this->syncungetc(_M_unget_buf);
127  else // buffer invalid, fail.
128  __ret = __eof;
129  }
130  else // putback
131  __ret = this->syncungetc(__c);
132 
133  // The buffered character is no longer valid, discard it.
134  _M_unget_buf = __eof;
135  return __ret;
136  }
137 
138  virtual std::streamsize
139  xsgetn(char_type* __s, std::streamsize __n);
140 
141  virtual int_type
142  overflow(int_type __c = traits_type::eof())
143  {
144  int_type __ret;
145  if (traits_type::eq_int_type(__c, traits_type::eof()))
146  {
147  if (std::fflush(_M_file))
148  __ret = traits_type::eof();
149  else
150  __ret = traits_type::not_eof(__c);
151  }
152  else
153  __ret = this->syncputc(__c);
154  return __ret;
155  }
156 
157  virtual std::streamsize
158  xsputn(const char_type* __s, std::streamsize __n);
159 
160  virtual int
162  { return std::fflush(_M_file); }
163 
164  virtual std::streampos
165  seekoff(std::streamoff __off, std::ios_base::seekdir __dir,
166  std::ios_base::openmode = std::ios_base::in | std::ios_base::out)
167  {
168  std::streampos __ret(std::streamoff(-1));
169  int __whence;
170  if (__dir == std::ios_base::beg)
171  __whence = SEEK_SET;
172  else if (__dir == std::ios_base::cur)
173  __whence = SEEK_CUR;
174  else
175  __whence = SEEK_END;
176 #ifdef _GLIBCXX_USE_LFS
177  if (!fseeko64(_M_file, __off, __whence))
178  __ret = std::streampos(ftello64(_M_file));
179 #else
180  if (!fseek(_M_file, __off, __whence))
181  __ret = std::streampos(std::ftell(_M_file));
182 #endif
183  return __ret;
184  }
185 
186  virtual std::streampos
187  seekpos(std::streampos __pos,
188  std::ios_base::openmode __mode =
190  { return seekoff(std::streamoff(__pos), std::ios_base::beg, __mode); }
191  };
192 
193  template<>
194  inline stdio_sync_filebuf<char>::int_type
195  stdio_sync_filebuf<char>::syncgetc()
196  { return std::getc(_M_file); }
197 
198  template<>
199  inline stdio_sync_filebuf<char>::int_type
200  stdio_sync_filebuf<char>::syncungetc(int_type __c)
201  { return std::ungetc(__c, _M_file); }
202 
203  template<>
204  inline stdio_sync_filebuf<char>::int_type
205  stdio_sync_filebuf<char>::syncputc(int_type __c)
206  { return std::putc(__c, _M_file); }
207 
208  template<>
209  inline std::streamsize
210  stdio_sync_filebuf<char>::xsgetn(char* __s, std::streamsize __n)
211  {
212  std::streamsize __ret = std::fread(__s, 1, __n, _M_file);
213  if (__ret > 0)
214  _M_unget_buf = traits_type::to_int_type(__s[__ret - 1]);
215  else
216  _M_unget_buf = traits_type::eof();
217  return __ret;
218  }
219 
220  template<>
221  inline std::streamsize
222  stdio_sync_filebuf<char>::xsputn(const char* __s, std::streamsize __n)
223  { return std::fwrite(__s, 1, __n, _M_file); }
224 
225 #ifdef _GLIBCXX_USE_WCHAR_T
226  template<>
227  inline stdio_sync_filebuf<wchar_t>::int_type
228  stdio_sync_filebuf<wchar_t>::syncgetc()
229  { return std::getwc(_M_file); }
230 
231  template<>
232  inline stdio_sync_filebuf<wchar_t>::int_type
233  stdio_sync_filebuf<wchar_t>::syncungetc(int_type __c)
234  { return std::ungetwc(__c, _M_file); }
235 
236  template<>
237  inline stdio_sync_filebuf<wchar_t>::int_type
238  stdio_sync_filebuf<wchar_t>::syncputc(int_type __c)
239  { return std::putwc(__c, _M_file); }
240 
241  template<>
242  inline std::streamsize
243  stdio_sync_filebuf<wchar_t>::xsgetn(wchar_t* __s, std::streamsize __n)
244  {
245  std::streamsize __ret = 0;
246  const int_type __eof = traits_type::eof();
247  while (__n--)
248  {
249  int_type __c = this->syncgetc();
250  if (traits_type::eq_int_type(__c, __eof))
251  break;
252  __s[__ret] = traits_type::to_char_type(__c);
253  ++__ret;
254  }
255 
256  if (__ret > 0)
257  _M_unget_buf = traits_type::to_int_type(__s[__ret - 1]);
258  else
259  _M_unget_buf = traits_type::eof();
260  return __ret;
261  }
262 
263  template<>
264  inline std::streamsize
265  stdio_sync_filebuf<wchar_t>::xsputn(const wchar_t* __s,
266  std::streamsize __n)
267  {
268  std::streamsize __ret = 0;
269  const int_type __eof = traits_type::eof();
270  while (__n--)
271  {
272  if (traits_type::eq_int_type(this->syncputc(*__s++), __eof))
273  break;
274  ++__ret;
275  }
276  return __ret;
277  }
278 #endif
279 
280 #if _GLIBCXX_EXTERN_TEMPLATE
281  extern template class stdio_sync_filebuf<char>;
282 #ifdef _GLIBCXX_USE_WCHAR_T
283  extern template class stdio_sync_filebuf<wchar_t>;
284 #endif
285 #endif
286 
287 _GLIBCXX_END_NAMESPACE_VERSION
288 } // namespace
289 
290 #endif
_Traits traits_type
Definition: streambuf:127
std::__c_file *const file()
Class representing stream positions.
Definition: postypes.h:114
static const seekdir beg
Request a seek relative to the beginning of the stream.
Definition: ios_base.h:398
traits_type::int_type int_type
Definition: streambuf:128
static const openmode out
Open for output. Default for ofstream and fstream.
Definition: ios_base.h:380
virtual int_type underflow()
Fetches more data from the controlled sequence.
fpos< mbstate_t > streampos
File position for char streams.
Definition: postypes.h:230
virtual int_type uflow()
Fetches more data from the controlled sequence.
ptrdiff_t streamsize
Integral type for I/O operation counts and buffer sizes.
Definition: postypes.h:100
static const openmode in
Open for input. Default for ifstream and fstream.
Definition: ios_base.h:377
virtual int sync()
Synchronizes the buffer arrays with the controlled sequences.
traits_type::pos_type pos_type
Definition: streambuf:129
The actual work of input and output (interface).This is a base class. Derived stream buffers each con...
Definition: iosfwd:82
traits_type::off_type off_type
Definition: streambuf:130
static const seekdir cur
Request a seek relative to the current position within the sequence.
Definition: ios_base.h:401
long long streamoff
Type used by fpos, char_traits<char>, and char_traits<wchar_t>.
Definition: postypes.h:96
virtual int_type overflow(int_type __c=traits_type::eof())
Consumes data from the buffer; writes to the controlled sequence.
Provides a layer of compatibility for C.This GNU extension provides extensions for working with stand...
virtual int_type pbackfail(int_type __c=traits_type::eof())
Tries to back up the input sequence.