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

   1 // Iostreams wrapper for stdio FILE* -*- C++ -*-
   2
   3 // Copyright (C) 2003-2017 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:
  68       typedef std::basic_streambuf<_CharT, _Traits> __streambuf_type;
  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
  92       stdio_sync_filebuf&
  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
 131       underflow()
 132       {
 133         int_type __c = this->syncgetc();
 134         return this->syncungetc(__c);
 135       }
 136
 137       virtual int_type
 138       uflow()
 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
 190       sync()
 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
 216       seekpos(std::streampos __pos,
 217               std::ios_base::openmode __mode =
 218               std::ios_base::in | std::ios_base::out)
 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