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 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
00045 
00046   /**
00047    *  @brief Provides a layer of compatibility for C.
00048    *  @ingroup io
00049    *
00050    *  This GNU extension provides extensions for working with standard
00051    *  C FILE*'s.  It must be instantiated by the user with the type of
00052    *  character used in the file stream, e.g., stdio_filebuf<char>.
00053   */
00054   template<typename _CharT, typename _Traits = std::char_traits<_CharT> >
00055     class stdio_sync_filebuf : public std::basic_streambuf<_CharT, _Traits>
00056     {
00057     public:
00058       // Types:
00059       typedef _CharT                    char_type;
00060       typedef _Traits                   traits_type;
00061       typedef typename traits_type::int_type        int_type;
00062       typedef typename traits_type::pos_type        pos_type;
00063       typedef typename traits_type::off_type        off_type;
00064 
00065     private:
00066       // Underlying stdio FILE
00067       std::__c_file* const _M_file;
00068 
00069       // Last character gotten. This is used when pbackfail is
00070       // called from basic_streambuf::sungetc()
00071       int_type _M_unget_buf;
00072 
00073     public:
00074       explicit
00075       stdio_sync_filebuf(std::__c_file* __f)
00076       : _M_file(__f), _M_unget_buf(traits_type::eof())
00077       { }
00078 
00079       /**
00080        *  @return  The underlying FILE*.
00081        *
00082        *  This function can be used to access the underlying C file pointer.
00083        *  Note that there is no way for the library to track what you do
00084        *  with the file, so be careful.
00085        */
00086       std::__c_file* const
00087       file() { return this->_M_file; }
00088 
00089     protected:
00090       int_type
00091       syncgetc();
00092 
00093       int_type
00094       syncungetc(int_type __c);
00095 
00096       int_type
00097       syncputc(int_type __c);
00098 
00099       virtual int_type
00100       underflow()
00101       {
00102     int_type __c = this->syncgetc();
00103     return this->syncungetc(__c);
00104       }
00105 
00106       virtual int_type
00107       uflow()
00108       {
00109     // Store the gotten character in case we need to unget it.
00110     _M_unget_buf = this->syncgetc();
00111     return _M_unget_buf;
00112       }
00113 
00114       virtual int_type
00115       pbackfail(int_type __c = traits_type::eof())
00116       {
00117     int_type __ret;
00118     const int_type __eof = traits_type::eof();
00119 
00120     // Check if the unget or putback was requested
00121     if (traits_type::eq_int_type(__c, __eof)) // unget
00122       {
00123         if (!traits_type::eq_int_type(_M_unget_buf, __eof))
00124           __ret = this->syncungetc(_M_unget_buf);
00125         else // buffer invalid, fail.
00126           __ret = __eof;
00127       }
00128     else // putback
00129       __ret = this->syncungetc(__c);
00130 
00131     // The buffered character is no longer valid, discard it.
00132     _M_unget_buf = __eof;
00133     return __ret;
00134       }
00135 
00136       virtual std::streamsize
00137       xsgetn(char_type* __s, std::streamsize __n);
00138 
00139       virtual int_type
00140       overflow(int_type __c = traits_type::eof())
00141       {
00142     int_type __ret;
00143     if (traits_type::eq_int_type(__c, traits_type::eof()))
00144       {
00145         if (std::fflush(_M_file))
00146           __ret = traits_type::eof();
00147         else
00148           __ret = traits_type::not_eof(__c);
00149       }
00150     else
00151       __ret = this->syncputc(__c);
00152     return __ret;
00153       }
00154 
00155       virtual std::streamsize
00156       xsputn(const char_type* __s, std::streamsize __n);
00157 
00158       virtual int
00159       sync()
00160       { return std::fflush(_M_file); }
00161 
00162       virtual std::streampos
00163       seekoff(std::streamoff __off, std::ios_base::seekdir __dir,
00164           std::ios_base::openmode = std::ios_base::in | std::ios_base::out)
00165       {
00166     std::streampos __ret(std::streamoff(-1));
00167     int __whence;
00168     if (__dir == std::ios_base::beg)
00169       __whence = SEEK_SET;
00170     else if (__dir == std::ios_base::cur)
00171       __whence = SEEK_CUR;
00172     else
00173       __whence = SEEK_END;
00174 #ifdef _GLIBCXX_USE_LFS
00175     if (!fseeko64(_M_file, __off, __whence))
00176       __ret = std::streampos(ftello64(_M_file));
00177 #else
00178     if (!fseek(_M_file, __off, __whence))
00179       __ret = std::streampos(std::ftell(_M_file));
00180 #endif
00181     return __ret;
00182       }
00183 
00184       virtual std::streampos
00185       seekpos(std::streampos __pos,
00186           std::ios_base::openmode __mode =
00187           std::ios_base::in | std::ios_base::out)
00188       { return seekoff(std::streamoff(__pos), std::ios_base::beg, __mode); }
00189     };
00190 
00191   template<>
00192     inline stdio_sync_filebuf<char>::int_type
00193     stdio_sync_filebuf<char>::syncgetc()
00194     { return std::getc(_M_file); }
00195 
00196   template<>
00197     inline stdio_sync_filebuf<char>::int_type
00198     stdio_sync_filebuf<char>::syncungetc(int_type __c)
00199     { return std::ungetc(__c, _M_file); }
00200 
00201   template<>
00202     inline stdio_sync_filebuf<char>::int_type
00203     stdio_sync_filebuf<char>::syncputc(int_type __c)
00204     { return std::putc(__c, _M_file); }
00205 
00206   template<>
00207     inline std::streamsize
00208     stdio_sync_filebuf<char>::xsgetn(char* __s, std::streamsize __n)
00209     {
00210       std::streamsize __ret = std::fread(__s, 1, __n, _M_file);
00211       if (__ret > 0)
00212     _M_unget_buf = traits_type::to_int_type(__s[__ret - 1]);
00213       else
00214     _M_unget_buf = traits_type::eof();
00215       return __ret;
00216     }
00217 
00218   template<>
00219     inline std::streamsize
00220     stdio_sync_filebuf<char>::xsputn(const char* __s, std::streamsize __n)
00221     { return std::fwrite(__s, 1, __n, _M_file); }
00222 
00223 #ifdef _GLIBCXX_USE_WCHAR_T
00224   template<>
00225     inline stdio_sync_filebuf<wchar_t>::int_type
00226     stdio_sync_filebuf<wchar_t>::syncgetc()
00227     { return std::getwc(_M_file); }
00228 
00229   template<>
00230     inline stdio_sync_filebuf<wchar_t>::int_type
00231     stdio_sync_filebuf<wchar_t>::syncungetc(int_type __c)
00232     { return std::ungetwc(__c, _M_file); }
00233 
00234   template<>
00235     inline stdio_sync_filebuf<wchar_t>::int_type
00236     stdio_sync_filebuf<wchar_t>::syncputc(int_type __c)
00237     { return std::putwc(__c, _M_file); }
00238 
00239   template<>
00240     inline std::streamsize
00241     stdio_sync_filebuf<wchar_t>::xsgetn(wchar_t* __s, std::streamsize __n)
00242     {
00243       std::streamsize __ret = 0;
00244       const int_type __eof = traits_type::eof();
00245       while (__n--)
00246     {
00247       int_type __c = this->syncgetc();
00248       if (traits_type::eq_int_type(__c, __eof))
00249         break;
00250       __s[__ret] = traits_type::to_char_type(__c);
00251       ++__ret;
00252     }
00253 
00254       if (__ret > 0)
00255     _M_unget_buf = traits_type::to_int_type(__s[__ret - 1]);
00256       else
00257     _M_unget_buf = traits_type::eof();
00258       return __ret;
00259     }
00260 
00261   template<>
00262     inline std::streamsize
00263     stdio_sync_filebuf<wchar_t>::xsputn(const wchar_t* __s,
00264                     std::streamsize __n)
00265     {
00266       std::streamsize __ret = 0;
00267       const int_type __eof = traits_type::eof();
00268       while (__n--)
00269     {
00270       if (traits_type::eq_int_type(this->syncputc(*__s++), __eof))
00271         break;
00272       ++__ret;
00273     }
00274       return __ret;
00275     }
00276 #endif
00277 
00278 #if _GLIBCXX_EXTERN_TEMPLATE
00279   extern template class stdio_sync_filebuf<char>;
00280 #ifdef _GLIBCXX_USE_WCHAR_T
00281   extern template class stdio_sync_filebuf<wchar_t>;
00282 #endif
00283 #endif
00284 
00285 _GLIBCXX_END_NAMESPACE
00286 
00287 #endif