libstdc++
stdio_sync_filebuf.h
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00001 // Iostreams wrapper for stdio FILE* -*- C++ -*-
00002 
00003 // Copyright (C) 2003-2013 Free Software Foundation, Inc.
00004 //
00005 // This file is part of the GNU ISO C++ Library.  This library is free
00006 // software; you can redistribute it and/or modify it under the
00007 // terms of the GNU General Public License as published by the
00008 // Free Software Foundation; either version 3, or (at your option)
00009 // any later version.
00010 
00011 // This library is distributed in the hope that it will be useful,
00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00014 // GNU General Public License for more details.
00015 
00016 // Under Section 7 of GPL version 3, you are granted additional
00017 // permissions described in the GCC Runtime Library Exception, version
00018 // 3.1, as published by the Free Software Foundation.
00019 
00020 // You should have received a copy of the GNU General Public License and
00021 // a copy of the GCC Runtime Library Exception along with this program;
00022 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00023 // <http://www.gnu.org/licenses/>.
00024 
00025 /** @file ext/stdio_sync_filebuf.h
00026  *  This file is a GNU extension to the Standard C++ Library.
00027  */
00028 
00029 #ifndef _STDIO_SYNC_FILEBUF_H
00030 #define _STDIO_SYNC_FILEBUF_H 1
00031 
00032 #pragma GCC system_header
00033 
00034 #include <streambuf>
00035 #include <unistd.h>
00036 #include <cstdio>
00037 #include <bits/c++io.h>  // For __c_file
00038 
00039 #ifdef _GLIBCXX_USE_WCHAR_T
00040 #include <cwchar>
00041 #endif
00042 
00043 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
00044 {
00045 _GLIBCXX_BEGIN_NAMESPACE_VERSION
00046 
00047   /**
00048    *  @brief Provides a layer of compatibility for C.
00049    *  @ingroup io
00050    *
00051    *  This GNU extension provides extensions for working with standard
00052    *  C FILE*'s.  It must be instantiated by the user with the type of
00053    *  character used in the file stream, e.g., stdio_filebuf<char>.
00054   */
00055   template<typename _CharT, typename _Traits = std::char_traits<_CharT> >
00056     class stdio_sync_filebuf : public std::basic_streambuf<_CharT, _Traits>
00057     {
00058     public:
00059       // Types:
00060       typedef _CharT                    char_type;
00061       typedef _Traits                   traits_type;
00062       typedef typename traits_type::int_type        int_type;
00063       typedef typename traits_type::pos_type        pos_type;
00064       typedef typename traits_type::off_type        off_type;
00065 
00066     private:
00067       // Underlying stdio FILE
00068       std::__c_file* const _M_file;
00069 
00070       // Last character gotten. This is used when pbackfail is
00071       // called from basic_streambuf::sungetc()
00072       int_type _M_unget_buf;
00073 
00074     public:
00075       explicit
00076       stdio_sync_filebuf(std::__c_file* __f)
00077       : _M_file(__f), _M_unget_buf(traits_type::eof())
00078       { }
00079 
00080       /**
00081        *  @return  The underlying FILE*.
00082        *
00083        *  This function can be used to access the underlying C file pointer.
00084        *  Note that there is no way for the library to track what you do
00085        *  with the file, so be careful.
00086        */
00087       std::__c_file* const
00088       file() { return this->_M_file; }
00089 
00090     protected:
00091       int_type
00092       syncgetc();
00093 
00094       int_type
00095       syncungetc(int_type __c);
00096 
00097       int_type
00098       syncputc(int_type __c);
00099 
00100       virtual int_type
00101       underflow()
00102       {
00103     int_type __c = this->syncgetc();
00104     return this->syncungetc(__c);
00105       }
00106 
00107       virtual int_type
00108       uflow()
00109       {
00110     // Store the gotten character in case we need to unget it.
00111     _M_unget_buf = this->syncgetc();
00112     return _M_unget_buf;
00113       }
00114 
00115       virtual int_type
00116       pbackfail(int_type __c = traits_type::eof())
00117       {
00118     int_type __ret;
00119     const int_type __eof = traits_type::eof();
00120 
00121     // Check if the unget or putback was requested
00122     if (traits_type::eq_int_type(__c, __eof)) // unget
00123       {
00124         if (!traits_type::eq_int_type(_M_unget_buf, __eof))
00125           __ret = this->syncungetc(_M_unget_buf);
00126         else // buffer invalid, fail.
00127           __ret = __eof;
00128       }
00129     else // putback
00130       __ret = this->syncungetc(__c);
00131 
00132     // The buffered character is no longer valid, discard it.
00133     _M_unget_buf = __eof;
00134     return __ret;
00135       }
00136 
00137       virtual std::streamsize
00138       xsgetn(char_type* __s, std::streamsize __n);
00139 
00140       virtual int_type
00141       overflow(int_type __c = traits_type::eof())
00142       {
00143     int_type __ret;
00144     if (traits_type::eq_int_type(__c, traits_type::eof()))
00145       {
00146         if (std::fflush(_M_file))
00147           __ret = traits_type::eof();
00148         else
00149           __ret = traits_type::not_eof(__c);
00150       }
00151     else
00152       __ret = this->syncputc(__c);
00153     return __ret;
00154       }
00155 
00156       virtual std::streamsize
00157       xsputn(const char_type* __s, std::streamsize __n);
00158 
00159       virtual int
00160       sync()
00161       { return std::fflush(_M_file); }
00162 
00163       virtual std::streampos
00164       seekoff(std::streamoff __off, std::ios_base::seekdir __dir,
00165           std::ios_base::openmode = std::ios_base::in | std::ios_base::out)
00166       {
00167     std::streampos __ret(std::streamoff(-1));
00168     int __whence;
00169     if (__dir == std::ios_base::beg)
00170       __whence = SEEK_SET;
00171     else if (__dir == std::ios_base::cur)
00172       __whence = SEEK_CUR;
00173     else
00174       __whence = SEEK_END;
00175 #ifdef _GLIBCXX_USE_LFS
00176     if (!fseeko64(_M_file, __off, __whence))
00177       __ret = std::streampos(ftello64(_M_file));
00178 #else
00179     if (!fseek(_M_file, __off, __whence))
00180       __ret = std::streampos(std::ftell(_M_file));
00181 #endif
00182     return __ret;
00183       }
00184 
00185       virtual std::streampos
00186       seekpos(std::streampos __pos,
00187           std::ios_base::openmode __mode =
00188           std::ios_base::in | std::ios_base::out)
00189       { return seekoff(std::streamoff(__pos), std::ios_base::beg, __mode); }
00190     };
00191 
00192   template<>
00193     inline stdio_sync_filebuf<char>::int_type
00194     stdio_sync_filebuf<char>::syncgetc()
00195     { return std::getc(_M_file); }
00196 
00197   template<>
00198     inline stdio_sync_filebuf<char>::int_type
00199     stdio_sync_filebuf<char>::syncungetc(int_type __c)
00200     { return std::ungetc(__c, _M_file); }
00201 
00202   template<>
00203     inline stdio_sync_filebuf<char>::int_type
00204     stdio_sync_filebuf<char>::syncputc(int_type __c)
00205     { return std::putc(__c, _M_file); }
00206 
00207   template<>
00208     inline std::streamsize
00209     stdio_sync_filebuf<char>::xsgetn(char* __s, std::streamsize __n)
00210     {
00211       std::streamsize __ret = std::fread(__s, 1, __n, _M_file);
00212       if (__ret > 0)
00213     _M_unget_buf = traits_type::to_int_type(__s[__ret - 1]);
00214       else
00215     _M_unget_buf = traits_type::eof();
00216       return __ret;
00217     }
00218 
00219   template<>
00220     inline std::streamsize
00221     stdio_sync_filebuf<char>::xsputn(const char* __s, std::streamsize __n)
00222     { return std::fwrite(__s, 1, __n, _M_file); }
00223 
00224 #ifdef _GLIBCXX_USE_WCHAR_T
00225   template<>
00226     inline stdio_sync_filebuf<wchar_t>::int_type
00227     stdio_sync_filebuf<wchar_t>::syncgetc()
00228     { return std::getwc(_M_file); }
00229 
00230   template<>
00231     inline stdio_sync_filebuf<wchar_t>::int_type
00232     stdio_sync_filebuf<wchar_t>::syncungetc(int_type __c)
00233     { return std::ungetwc(__c, _M_file); }
00234 
00235   template<>
00236     inline stdio_sync_filebuf<wchar_t>::int_type
00237     stdio_sync_filebuf<wchar_t>::syncputc(int_type __c)
00238     { return std::putwc(__c, _M_file); }
00239 
00240   template<>
00241     inline std::streamsize
00242     stdio_sync_filebuf<wchar_t>::xsgetn(wchar_t* __s, std::streamsize __n)
00243     {
00244       std::streamsize __ret = 0;
00245       const int_type __eof = traits_type::eof();
00246       while (__n--)
00247     {
00248       int_type __c = this->syncgetc();
00249       if (traits_type::eq_int_type(__c, __eof))
00250         break;
00251       __s[__ret] = traits_type::to_char_type(__c);
00252       ++__ret;
00253     }
00254 
00255       if (__ret > 0)
00256     _M_unget_buf = traits_type::to_int_type(__s[__ret - 1]);
00257       else
00258     _M_unget_buf = traits_type::eof();
00259       return __ret;
00260     }
00261 
00262   template<>
00263     inline std::streamsize
00264     stdio_sync_filebuf<wchar_t>::xsputn(const wchar_t* __s,
00265                     std::streamsize __n)
00266     {
00267       std::streamsize __ret = 0;
00268       const int_type __eof = traits_type::eof();
00269       while (__n--)
00270     {
00271       if (traits_type::eq_int_type(this->syncputc(*__s++), __eof))
00272         break;
00273       ++__ret;
00274     }
00275       return __ret;
00276     }
00277 #endif
00278 
00279 #if _GLIBCXX_EXTERN_TEMPLATE
00280   extern template class stdio_sync_filebuf<char>;
00281 #ifdef _GLIBCXX_USE_WCHAR_T
00282   extern template class stdio_sync_filebuf<wchar_t>;
00283 #endif
00284 #endif
00285 
00286 _GLIBCXX_END_NAMESPACE_VERSION
00287 } // namespace
00288 
00289 #endif