libstdc++
stdio_sync_filebuf.h
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00001 // Iostreams wrapper for stdio FILE* -*- C++ -*-
00002 
00003 // Copyright (C) 2003-2015 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 #include <bits/move.h>   // For __exchange
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       typedef std::basic_streambuf<_CharT, _Traits> __streambuf_type;
00069 
00070       // Underlying stdio FILE
00071       std::__c_file* _M_file;
00072 
00073       // Last character gotten. This is used when pbackfail is
00074       // called from basic_streambuf::sungetc()
00075       int_type _M_unget_buf;
00076 
00077     public:
00078       explicit
00079       stdio_sync_filebuf(std::__c_file* __f)
00080       : _M_file(__f), _M_unget_buf(traits_type::eof())
00081       { }
00082 
00083 #if __cplusplus >= 201103L
00084       stdio_sync_filebuf(stdio_sync_filebuf&& __fb) noexcept
00085       : __streambuf_type(std::move(__fb)),
00086       _M_file(__fb._M_file), _M_unget_buf(__fb._M_unget_buf)
00087       {
00088         __fb._M_file = nullptr;
00089         __fb._M_unget_buf = traits_type::eof();
00090       }
00091 
00092       stdio_sync_filebuf&
00093       operator=(stdio_sync_filebuf&& __fb) noexcept
00094       {
00095         __streambuf_type::operator=(__fb);
00096         _M_file = std::__exchange(__fb._M_file, nullptr);
00097         _M_unget_buf = std::__exchange(__fb._M_unget_buf, traits_type::eof());
00098         return *this;
00099       }
00100 
00101       void
00102       swap(stdio_sync_filebuf& __fb)
00103       {
00104         __streambuf_type::swap(__fb);
00105         std::swap(_M_file, __fb._M_file);
00106         std::swap(_M_unget_buf, __fb._M_unget_buf);
00107       }
00108 #endif
00109 
00110       /**
00111        *  @return  The underlying FILE*.
00112        *
00113        *  This function can be used to access the underlying C file pointer.
00114        *  Note that there is no way for the library to track what you do
00115        *  with the file, so be careful.
00116        */
00117       std::__c_file*
00118       file() { return this->_M_file; }
00119 
00120     protected:
00121       int_type
00122       syncgetc();
00123 
00124       int_type
00125       syncungetc(int_type __c);
00126 
00127       int_type
00128       syncputc(int_type __c);
00129 
00130       virtual int_type
00131       underflow()
00132       {
00133         int_type __c = this->syncgetc();
00134         return this->syncungetc(__c);
00135       }
00136 
00137       virtual int_type
00138       uflow()
00139       {
00140         // Store the gotten character in case we need to unget it.
00141         _M_unget_buf = this->syncgetc();
00142         return _M_unget_buf;
00143       }
00144 
00145       virtual int_type
00146       pbackfail(int_type __c = traits_type::eof())
00147       {
00148         int_type __ret;
00149         const int_type __eof = traits_type::eof();
00150 
00151         // Check if the unget or putback was requested
00152         if (traits_type::eq_int_type(__c, __eof)) // unget
00153           {
00154             if (!traits_type::eq_int_type(_M_unget_buf, __eof))
00155               __ret = this->syncungetc(_M_unget_buf);
00156             else // buffer invalid, fail.
00157               __ret = __eof;
00158           }
00159         else // putback
00160           __ret = this->syncungetc(__c);
00161 
00162         // The buffered character is no longer valid, discard it.
00163         _M_unget_buf = __eof;
00164         return __ret;
00165       }
00166 
00167       virtual std::streamsize
00168       xsgetn(char_type* __s, std::streamsize __n);
00169 
00170       virtual int_type
00171       overflow(int_type __c = traits_type::eof())
00172       {
00173         int_type __ret;
00174         if (traits_type::eq_int_type(__c, traits_type::eof()))
00175           {
00176             if (std::fflush(_M_file))
00177               __ret = traits_type::eof();
00178             else
00179               __ret = traits_type::not_eof(__c);
00180           }
00181         else
00182           __ret = this->syncputc(__c);
00183         return __ret;
00184       }
00185 
00186       virtual std::streamsize
00187       xsputn(const char_type* __s, std::streamsize __n);
00188 
00189       virtual int
00190       sync()
00191       { return std::fflush(_M_file); }
00192 
00193       virtual std::streampos
00194       seekoff(std::streamoff __off, std::ios_base::seekdir __dir,
00195               std::ios_base::openmode = std::ios_base::in | std::ios_base::out)
00196       {
00197         std::streampos __ret(std::streamoff(-1));
00198         int __whence;
00199         if (__dir == std::ios_base::beg)
00200           __whence = SEEK_SET;
00201         else if (__dir == std::ios_base::cur)
00202           __whence = SEEK_CUR;
00203         else
00204           __whence = SEEK_END;
00205 #ifdef _GLIBCXX_USE_LFS
00206         if (!fseeko64(_M_file, __off, __whence))
00207           __ret = std::streampos(ftello64(_M_file));
00208 #else
00209         if (!fseek(_M_file, __off, __whence))
00210           __ret = std::streampos(std::ftell(_M_file));
00211 #endif
00212         return __ret;
00213       }
00214 
00215       virtual std::streampos
00216       seekpos(std::streampos __pos,
00217               std::ios_base::openmode __mode =
00218               std::ios_base::in | std::ios_base::out)
00219       { return seekoff(std::streamoff(__pos), std::ios_base::beg, __mode); }
00220     };
00221 
00222   template<>
00223     inline stdio_sync_filebuf<char>::int_type
00224     stdio_sync_filebuf<char>::syncgetc()
00225     { return std::getc(_M_file); }
00226 
00227   template<>
00228     inline stdio_sync_filebuf<char>::int_type
00229     stdio_sync_filebuf<char>::syncungetc(int_type __c)
00230     { return std::ungetc(__c, _M_file); }
00231 
00232   template<>
00233     inline stdio_sync_filebuf<char>::int_type
00234     stdio_sync_filebuf<char>::syncputc(int_type __c)
00235     { return std::putc(__c, _M_file); }
00236 
00237   template<>
00238     inline std::streamsize
00239     stdio_sync_filebuf<char>::xsgetn(char* __s, std::streamsize __n)
00240     {
00241       std::streamsize __ret = std::fread(__s, 1, __n, _M_file);
00242       if (__ret > 0)
00243         _M_unget_buf = traits_type::to_int_type(__s[__ret - 1]);
00244       else
00245         _M_unget_buf = traits_type::eof();
00246       return __ret;
00247     }
00248 
00249   template<>
00250     inline std::streamsize
00251     stdio_sync_filebuf<char>::xsputn(const char* __s, std::streamsize __n)
00252     { return std::fwrite(__s, 1, __n, _M_file); }
00253 
00254 #ifdef _GLIBCXX_USE_WCHAR_T
00255   template<>
00256     inline stdio_sync_filebuf<wchar_t>::int_type
00257     stdio_sync_filebuf<wchar_t>::syncgetc()
00258     { return std::getwc(_M_file); }
00259 
00260   template<>
00261     inline stdio_sync_filebuf<wchar_t>::int_type
00262     stdio_sync_filebuf<wchar_t>::syncungetc(int_type __c)
00263     { return std::ungetwc(__c, _M_file); }
00264 
00265   template<>
00266     inline stdio_sync_filebuf<wchar_t>::int_type
00267     stdio_sync_filebuf<wchar_t>::syncputc(int_type __c)
00268     { return std::putwc(__c, _M_file); }
00269 
00270   template<>
00271     inline std::streamsize
00272     stdio_sync_filebuf<wchar_t>::xsgetn(wchar_t* __s, std::streamsize __n)
00273     {
00274       std::streamsize __ret = 0;
00275       const int_type __eof = traits_type::eof();
00276       while (__n--)
00277         {
00278           int_type __c = this->syncgetc();
00279           if (traits_type::eq_int_type(__c, __eof))
00280             break;
00281           __s[__ret] = traits_type::to_char_type(__c);
00282           ++__ret;
00283         }
00284 
00285       if (__ret > 0)
00286         _M_unget_buf = traits_type::to_int_type(__s[__ret - 1]);
00287       else
00288         _M_unget_buf = traits_type::eof();
00289       return __ret;
00290     }
00291 
00292   template<>
00293     inline std::streamsize
00294     stdio_sync_filebuf<wchar_t>::xsputn(const wchar_t* __s,
00295                                         std::streamsize __n)
00296     {
00297       std::streamsize __ret = 0;
00298       const int_type __eof = traits_type::eof();
00299       while (__n--)
00300         {
00301           if (traits_type::eq_int_type(this->syncputc(*__s++), __eof))
00302             break;
00303           ++__ret;
00304         }
00305       return __ret;
00306     }
00307 #endif
00308 
00309 #if _GLIBCXX_EXTERN_TEMPLATE
00310   extern template class stdio_sync_filebuf<char>;
00311 #ifdef _GLIBCXX_USE_WCHAR_T
00312   extern template class stdio_sync_filebuf<wchar_t>;
00313 #endif
00314 #endif
00315 
00316 _GLIBCXX_END_NAMESPACE_VERSION
00317 } // namespace
00318 
00319 #endif