libstdc++-v3/include/ext/stdio_sync_filebuf.h

   1 // Iostreams wrapper for stdio FILE* -*- C++ -*-
   2
   3 // Copyright (C) 2003-2024 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