libstdc++
stdio_sync_filebuf.h
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00001 // Iostreams wrapper for stdio FILE* -*- C++ -*-
00002 
00003 // Copyright (C) 2003, 2004, 2005, 2006, 2007, 2009, 2010
00004 // Free Software Foundation, Inc.
00005 //
00006 // This file is part of the GNU ISO C++ Library.  This library is free
00007 // software; you can redistribute it and/or modify it under the
00008 // terms of the GNU General Public License as published by the
00009 // Free Software Foundation; either version 3, or (at your option)
00010 // any later version.
00011 
00012 // This library is distributed in the hope that it will be useful,
00013 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00014 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00015 // GNU General Public License for more details.
00016 
00017 // Under Section 7 of GPL version 3, you are granted additional
00018 // permissions described in the GCC Runtime Library Exception, version
00019 // 3.1, as published by the Free Software Foundation.
00020 
00021 // You should have received a copy of the GNU General Public License and
00022 // a copy of the GCC Runtime Library Exception along with this program;
00023 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00024 // <http://www.gnu.org/licenses/>.
00025 
00026 /** @file ext/stdio_sync_filebuf.h
00027  *  This file is a GNU extension to the Standard C++ Library.
00028  */
00029 
00030 #ifndef _STDIO_SYNC_FILEBUF_H
00031 #define _STDIO_SYNC_FILEBUF_H 1
00032 
00033 #pragma GCC system_header
00034 
00035 #include <streambuf>
00036 #include <unistd.h>
00037 #include <cstdio>
00038 #include <bits/c++io.h>  // For __c_file
00039 
00040 #ifdef _GLIBCXX_USE_WCHAR_T
00041 #include <cwchar>
00042 #endif
00043 
00044 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
00045 {
00046 _GLIBCXX_BEGIN_NAMESPACE_VERSION
00047 
00048   /**
00049    *  @brief Provides a layer of compatibility for C.
00050    *  @ingroup io
00051    *
00052    *  This GNU extension provides extensions for working with standard
00053    *  C FILE*'s.  It must be instantiated by the user with the type of
00054    *  character used in the file stream, e.g., stdio_filebuf<char>.
00055   */
00056   template<typename _CharT, typename _Traits = std::char_traits<_CharT> >
00057     class stdio_sync_filebuf : public std::basic_streambuf<_CharT, _Traits>
00058     {
00059     public:
00060       // Types:
00061       typedef _CharT                    char_type;
00062       typedef _Traits                   traits_type;
00063       typedef typename traits_type::int_type        int_type;
00064       typedef typename traits_type::pos_type        pos_type;
00065       typedef typename traits_type::off_type        off_type;
00066 
00067     private:
00068       // Underlying stdio FILE
00069       std::__c_file* const _M_file;
00070 
00071       // Last character gotten. This is used when pbackfail is
00072       // called from basic_streambuf::sungetc()
00073       int_type _M_unget_buf;
00074 
00075     public:
00076       explicit
00077       stdio_sync_filebuf(std::__c_file* __f)
00078       : _M_file(__f), _M_unget_buf(traits_type::eof())
00079       { }
00080 
00081       /**
00082        *  @return  The underlying FILE*.
00083        *
00084        *  This function can be used to access the underlying C file pointer.
00085        *  Note that there is no way for the library to track what you do
00086        *  with the file, so be careful.
00087        */
00088       std::__c_file* const
00089       file() { return this->_M_file; }
00090 
00091     protected:
00092       int_type
00093       syncgetc();
00094 
00095       int_type
00096       syncungetc(int_type __c);
00097 
00098       int_type
00099       syncputc(int_type __c);
00100 
00101       virtual int_type
00102       underflow()
00103       {
00104     int_type __c = this->syncgetc();
00105     return this->syncungetc(__c);
00106       }
00107 
00108       virtual int_type
00109       uflow()
00110       {
00111     // Store the gotten character in case we need to unget it.
00112     _M_unget_buf = this->syncgetc();
00113     return _M_unget_buf;
00114       }
00115 
00116       virtual int_type
00117       pbackfail(int_type __c = traits_type::eof())
00118       {
00119     int_type __ret;
00120     const int_type __eof = traits_type::eof();
00121 
00122     // Check if the unget or putback was requested
00123     if (traits_type::eq_int_type(__c, __eof)) // unget
00124       {
00125         if (!traits_type::eq_int_type(_M_unget_buf, __eof))
00126           __ret = this->syncungetc(_M_unget_buf);
00127         else // buffer invalid, fail.
00128           __ret = __eof;
00129       }
00130     else // putback
00131       __ret = this->syncungetc(__c);
00132 
00133     // The buffered character is no longer valid, discard it.
00134     _M_unget_buf = __eof;
00135     return __ret;
00136       }
00137 
00138       virtual std::streamsize
00139       xsgetn(char_type* __s, std::streamsize __n);
00140 
00141       virtual int_type
00142       overflow(int_type __c = traits_type::eof())
00143       {
00144     int_type __ret;
00145     if (traits_type::eq_int_type(__c, traits_type::eof()))
00146       {
00147         if (std::fflush(_M_file))
00148           __ret = traits_type::eof();
00149         else
00150           __ret = traits_type::not_eof(__c);
00151       }
00152     else
00153       __ret = this->syncputc(__c);
00154     return __ret;
00155       }
00156 
00157       virtual std::streamsize
00158       xsputn(const char_type* __s, std::streamsize __n);
00159 
00160       virtual int
00161       sync()
00162       { return std::fflush(_M_file); }
00163 
00164       virtual std::streampos
00165       seekoff(std::streamoff __off, std::ios_base::seekdir __dir,
00166           std::ios_base::openmode = std::ios_base::in | std::ios_base::out)
00167       {
00168     std::streampos __ret(std::streamoff(-1));
00169     int __whence;
00170     if (__dir == std::ios_base::beg)
00171       __whence = SEEK_SET;
00172     else if (__dir == std::ios_base::cur)
00173       __whence = SEEK_CUR;
00174     else
00175       __whence = SEEK_END;
00176 #ifdef _GLIBCXX_USE_LFS
00177     if (!fseeko64(_M_file, __off, __whence))
00178       __ret = std::streampos(ftello64(_M_file));
00179 #else
00180     if (!fseek(_M_file, __off, __whence))
00181       __ret = std::streampos(std::ftell(_M_file));
00182 #endif
00183     return __ret;
00184       }
00185 
00186       virtual std::streampos
00187       seekpos(std::streampos __pos,
00188           std::ios_base::openmode __mode =
00189           std::ios_base::in | std::ios_base::out)
00190       { return seekoff(std::streamoff(__pos), std::ios_base::beg, __mode); }
00191     };
00192 
00193   template<>
00194     inline stdio_sync_filebuf<char>::int_type
00195     stdio_sync_filebuf<char>::syncgetc()
00196     { return std::getc(_M_file); }
00197 
00198   template<>
00199     inline stdio_sync_filebuf<char>::int_type
00200     stdio_sync_filebuf<char>::syncungetc(int_type __c)
00201     { return std::ungetc(__c, _M_file); }
00202 
00203   template<>
00204     inline stdio_sync_filebuf<char>::int_type
00205     stdio_sync_filebuf<char>::syncputc(int_type __c)
00206     { return std::putc(__c, _M_file); }
00207 
00208   template<>
00209     inline std::streamsize
00210     stdio_sync_filebuf<char>::xsgetn(char* __s, std::streamsize __n)
00211     {
00212       std::streamsize __ret = std::fread(__s, 1, __n, _M_file);
00213       if (__ret > 0)
00214     _M_unget_buf = traits_type::to_int_type(__s[__ret - 1]);
00215       else
00216     _M_unget_buf = traits_type::eof();
00217       return __ret;
00218     }
00219 
00220   template<>
00221     inline std::streamsize
00222     stdio_sync_filebuf<char>::xsputn(const char* __s, std::streamsize __n)
00223     { return std::fwrite(__s, 1, __n, _M_file); }
00224 
00225 #ifdef _GLIBCXX_USE_WCHAR_T
00226   template<>
00227     inline stdio_sync_filebuf<wchar_t>::int_type
00228     stdio_sync_filebuf<wchar_t>::syncgetc()
00229     { return std::getwc(_M_file); }
00230 
00231   template<>
00232     inline stdio_sync_filebuf<wchar_t>::int_type
00233     stdio_sync_filebuf<wchar_t>::syncungetc(int_type __c)
00234     { return std::ungetwc(__c, _M_file); }
00235 
00236   template<>
00237     inline stdio_sync_filebuf<wchar_t>::int_type
00238     stdio_sync_filebuf<wchar_t>::syncputc(int_type __c)
00239     { return std::putwc(__c, _M_file); }
00240 
00241   template<>
00242     inline std::streamsize
00243     stdio_sync_filebuf<wchar_t>::xsgetn(wchar_t* __s, std::streamsize __n)
00244     {
00245       std::streamsize __ret = 0;
00246       const int_type __eof = traits_type::eof();
00247       while (__n--)
00248     {
00249       int_type __c = this->syncgetc();
00250       if (traits_type::eq_int_type(__c, __eof))
00251         break;
00252       __s[__ret] = traits_type::to_char_type(__c);
00253       ++__ret;
00254     }
00255 
00256       if (__ret > 0)
00257     _M_unget_buf = traits_type::to_int_type(__s[__ret - 1]);
00258       else
00259     _M_unget_buf = traits_type::eof();
00260       return __ret;
00261     }
00262 
00263   template<>
00264     inline std::streamsize
00265     stdio_sync_filebuf<wchar_t>::xsputn(const wchar_t* __s,
00266                     std::streamsize __n)
00267     {
00268       std::streamsize __ret = 0;
00269       const int_type __eof = traits_type::eof();
00270       while (__n--)
00271     {
00272       if (traits_type::eq_int_type(this->syncputc(*__s++), __eof))
00273         break;
00274       ++__ret;
00275     }
00276       return __ret;
00277     }
00278 #endif
00279 
00280 #if _GLIBCXX_EXTERN_TEMPLATE
00281   extern template class stdio_sync_filebuf<char>;
00282 #ifdef _GLIBCXX_USE_WCHAR_T
00283   extern template class stdio_sync_filebuf<wchar_t>;
00284 #endif
00285 #endif
00286 
00287 _GLIBCXX_END_NAMESPACE_VERSION
00288 } // namespace
00289 
00290 #endif