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 #ifdef _GLIBCXX_STDIO_SYNC_FILEBUF_IMPL
00081       ~stdio_sync_filebuf() {}
00082 #endif
00083       /**
00084        *  @return  The underlying FILE*.
00085        *
00086        *  This function can be used to access the underlying C file pointer.
00087        *  Note that there is no way for the library to track what you do
00088        *  with the file, so be careful.
00089        */
00090       std::__c_file* const
00091       file() { return this->_M_file; }
00092 
00093     protected:
00094       int_type
00095       syncgetc();
00096 
00097       int_type
00098       syncungetc(int_type __c);
00099 
00100       int_type
00101       syncputc(int_type __c);
00102 
00103       virtual int_type
00104       underflow()
00105       {
00106     int_type __c = this->syncgetc();
00107     return this->syncungetc(__c);
00108       }
00109 
00110       virtual int_type
00111       uflow()
00112       {
00113     // Store the gotten character in case we need to unget it.
00114     _M_unget_buf = this->syncgetc();
00115     return _M_unget_buf;
00116       }
00117 
00118       virtual int_type
00119       pbackfail(int_type __c = traits_type::eof())
00120       {
00121     int_type __ret;
00122     const int_type __eof = traits_type::eof();
00123 
00124     // Check if the unget or putback was requested
00125     if (traits_type::eq_int_type(__c, __eof)) // unget
00126       {
00127         if (!traits_type::eq_int_type(_M_unget_buf, __eof))
00128           __ret = this->syncungetc(_M_unget_buf);
00129         else // buffer invalid, fail.
00130           __ret = __eof;
00131       }
00132     else // putback
00133       __ret = this->syncungetc(__c);
00134 
00135     // The buffered character is no longer valid, discard it.
00136     _M_unget_buf = __eof;
00137     return __ret;
00138       }
00139 
00140       virtual std::streamsize
00141       xsgetn(char_type* __s, std::streamsize __n);
00142 
00143       virtual int_type
00144       overflow(int_type __c = traits_type::eof())
00145       {
00146     int_type __ret;
00147     if (traits_type::eq_int_type(__c, traits_type::eof()))
00148       {
00149         if (std::fflush(_M_file))
00150           __ret = traits_type::eof();
00151         else
00152           __ret = traits_type::not_eof(__c);
00153       }
00154     else
00155       __ret = this->syncputc(__c);
00156     return __ret;
00157       }
00158 
00159       virtual std::streamsize
00160       xsputn(const char_type* __s, std::streamsize __n);
00161 
00162       virtual int
00163       sync()
00164       { return std::fflush(_M_file); }
00165 
00166       virtual std::streampos
00167       seekoff(std::streamoff __off, std::ios_base::seekdir __dir,
00168           std::ios_base::openmode = std::ios_base::in | std::ios_base::out)
00169       {
00170     std::streampos __ret(std::streamoff(-1));
00171     int __whence;
00172     if (__dir == std::ios_base::beg)
00173       __whence = SEEK_SET;
00174     else if (__dir == std::ios_base::cur)
00175       __whence = SEEK_CUR;
00176     else
00177       __whence = SEEK_END;
00178 #ifdef _GLIBCXX_USE_LFS
00179     if (!fseeko64(_M_file, __off, __whence))
00180       __ret = std::streampos(ftello64(_M_file));
00181 #else
00182     if (!fseek(_M_file, __off, __whence))
00183       __ret = std::streampos(std::ftell(_M_file));
00184 #endif
00185     return __ret;
00186       }
00187 
00188       virtual std::streampos
00189       seekpos(std::streampos __pos,
00190           std::ios_base::openmode __mode =
00191           std::ios_base::in | std::ios_base::out)
00192       { return seekoff(std::streamoff(__pos), std::ios_base::beg, __mode); }
00193     };
00194 
00195   template<>
00196     inline stdio_sync_filebuf<char>::int_type
00197     stdio_sync_filebuf<char>::syncgetc()
00198     { return std::getc(_M_file); }
00199 
00200   template<>
00201     inline stdio_sync_filebuf<char>::int_type
00202     stdio_sync_filebuf<char>::syncungetc(int_type __c)
00203     { return std::ungetc(__c, _M_file); }
00204 
00205   template<>
00206     inline stdio_sync_filebuf<char>::int_type
00207     stdio_sync_filebuf<char>::syncputc(int_type __c)
00208     { return std::putc(__c, _M_file); }
00209 
00210   template<>
00211 #ifndef _GLIBCXX_STDIO_SYNC_FILEBUF_IMPL
00212     inline
00213 #endif
00214     std::streamsize
00215     stdio_sync_filebuf<char>::xsgetn(char* __s, std::streamsize __n)
00216     {
00217       std::streamsize __ret = std::fread(__s, 1, __n, _M_file);
00218       if (__ret > 0)
00219     _M_unget_buf = traits_type::to_int_type(__s[__ret - 1]);
00220       else
00221     _M_unget_buf = traits_type::eof();
00222       return __ret;
00223     }
00224 
00225   template<>
00226 #ifndef _GLIBCXX_STDIO_SYNC_FILEBUF_IMPL
00227     inline
00228 #endif
00229     std::streamsize
00230     stdio_sync_filebuf<char>::xsputn(const char* __s, std::streamsize __n)
00231     { return std::fwrite(__s, 1, __n, _M_file); }
00232 
00233 #ifdef _GLIBCXX_USE_WCHAR_T
00234   template<>
00235     inline stdio_sync_filebuf<wchar_t>::int_type
00236     stdio_sync_filebuf<wchar_t>::syncgetc()
00237     { return std::getwc(_M_file); }
00238 
00239   template<>
00240     inline stdio_sync_filebuf<wchar_t>::int_type
00241     stdio_sync_filebuf<wchar_t>::syncungetc(int_type __c)
00242     { return std::ungetwc(__c, _M_file); }
00243 
00244   template<>
00245     inline stdio_sync_filebuf<wchar_t>::int_type
00246     stdio_sync_filebuf<wchar_t>::syncputc(int_type __c)
00247     { return std::putwc(__c, _M_file); }
00248 
00249   template<>
00250 #ifndef _GLIBCXX_STDIO_SYNC_FILEBUF_IMPL
00251     inline
00252 #endif
00253     std::streamsize
00254     stdio_sync_filebuf<wchar_t>::xsgetn(wchar_t* __s, std::streamsize __n)
00255     {
00256       std::streamsize __ret = 0;
00257       const int_type __eof = traits_type::eof();
00258       while (__n--)
00259     {
00260       int_type __c = this->syncgetc();
00261       if (traits_type::eq_int_type(__c, __eof))
00262         break;
00263       __s[__ret] = traits_type::to_char_type(__c);
00264       ++__ret;
00265     }
00266 
00267       if (__ret > 0)
00268     _M_unget_buf = traits_type::to_int_type(__s[__ret - 1]);
00269       else
00270     _M_unget_buf = traits_type::eof();
00271       return __ret;
00272     }
00273 
00274   template<>
00275 #ifndef _GLIBCXX_STDIO_SYNC_FILEBUF_IMPL
00276     inline
00277 #endif
00278     std::streamsize
00279     stdio_sync_filebuf<wchar_t>::xsputn(const wchar_t* __s,
00280                     std::streamsize __n)
00281     {
00282       std::streamsize __ret = 0;
00283       const int_type __eof = traits_type::eof();
00284       while (__n--)
00285     {
00286       if (traits_type::eq_int_type(this->syncputc(*__s++), __eof))
00287         break;
00288       ++__ret;
00289     }
00290       return __ret;
00291     }
00292 #endif
00293 
00294 #if _GLIBCXX_EXTERN_TEMPLATE
00295   extern template class stdio_sync_filebuf<char>;
00296 #ifdef _GLIBCXX_USE_WCHAR_T
00297   extern template class stdio_sync_filebuf<wchar_t>;
00298 #endif
00299 #endif
00300 
00301 _GLIBCXX_END_NAMESPACE_VERSION
00302 } // namespace
00303 
00304 #endif