fstream.tcc

gcc-you can use this code to learn something about gcc, and inquire further into linux,

	}

      _M_last_overflowed = false;    // Set in _M_really_overflow, below.
      return __ret;
    }
  
  template<typename _CharT, typename _Traits>
    void
    basic_filebuf<_CharT, _Traits>::
    _M_convert_to_external(_CharT* __ibuf, streamsize __ilen,
			   streamsize& __elen, streamsize& __plen)
    {
      const locale __loc = this->getloc();
      const __codecvt_type& __cvt = use_facet<__codecvt_type>(__loc);
      
      if (__cvt.always_noconv() && __ilen)
	{
	  __elen += _M_file.xsputn(reinterpret_cast<char*>(__ibuf), __ilen);
	  __plen += __ilen;
	}
      else
	{
	  // Worst-case number of external bytes needed.
	  int __ext_multiplier = __cvt.encoding();
	  if (__ext_multiplier ==  -1 || __ext_multiplier == 0)
	    __ext_multiplier = sizeof(char_type);
	  streamsize __blen = __ilen * __ext_multiplier;
	  char* __buf = static_cast<char*>(__builtin_alloca(__blen));
	  char* __bend;
	  const char_type* __iend;
	  codecvt_base::result __r;
	  __r = __cvt.out(_M_state_cur, __ibuf, __ibuf + __ilen, 
			  __iend, __buf, __buf + __blen, __bend);

	  if (__r == codecvt_base::ok || __r == codecvt_base::partial)
	    __blen = __bend - __buf;
	  else if (__r == codecvt_base::noconv)
	    {
	      // Same as the always_noconv case above.
	      __buf = reinterpret_cast<char*>(__ibuf);
	      __blen = __ilen;
	    }
	  else
	    {
	      // Result == error 
	      __blen = 0;
	    }
	  
	  if (__blen)
	    {
	      __elen += _M_file.xsputn(__buf, __blen);
	      __plen += __blen;
	    }

	  // Try once more for partial conversions.
	  if (__r == codecvt_base::partial)
	    {
	      const char_type* __iresume = __iend;
	      streamsize __rlen = _M_out_end - __iend;
	      __r = __cvt.out(_M_state_cur, __iresume, __iresume + __rlen, 
			      __iend, __buf, __buf + __blen, __bend);
	      if (__r != codecvt_base::error)
		{
		  __rlen = __bend - __buf;
		  __elen += _M_file.xsputn(__buf, __rlen);
		  __plen += __rlen;
		}
	    }
	}
    }

  template<typename _CharT, typename _Traits>
    typename basic_filebuf<_CharT, _Traits>::int_type 
    basic_filebuf<_CharT, _Traits>::
    _M_really_overflow(int_type __c)
    {
      int_type __ret = traits_type::eof();
      bool __testput = _M_out_cur && _M_out_beg < _M_out_end;
      bool __testunbuffered = _M_file.is_open() && !_M_buf_size;

      if (__testput || __testunbuffered)
	{
	  // Sizes of external and pending output.
	  streamsize __elen = 0;
	  streamsize __plen = 0;

	  // Need to restore current position. The position of the external
	  // byte sequence (_M_file) corresponds to _M_filepos, and we need
	  // to move it to _M_out_beg for the write.
	  if (_M_filepos && _M_filepos != _M_out_beg)
	    {
	      off_type __off = _M_out_beg - _M_filepos;
	      _M_file.seekoff(__off, ios_base::cur);
	    }

	  // Convert internal buffer to external representation, output.
	  // NB: In the unbuffered case, no internal buffer exists. 
	  if (!__testunbuffered)
	    _M_convert_to_external(_M_out_beg,  _M_out_end - _M_out_beg, 
				   __elen, __plen);

	  // Checks for codecvt.out failures and _M_file.xsputn failures,
	  // respectively, inside _M_convert_to_external.
	  if (__testunbuffered || (__elen && __elen == __plen))
  	    {
	      // Convert pending sequence to external representation, output.
	      // If eof, then just attempt sync.
	      if (!traits_type::eq_int_type(__c, traits_type::eof()))
		{
		  char_type __pending = traits_type::to_char_type(__c);
		  _M_convert_to_external(&__pending, 1, __elen, __plen);
  
		  // User code must flush when switching modes (thus
		  // don't sync).
		  if (__elen == __plen && __elen)
		    {
		      _M_set_indeterminate();
		      __ret = traits_type::not_eof(__c);
		    }
		}
	      else if (!_M_file.sync())
		{
  		  _M_set_indeterminate();
  		  __ret = traits_type::not_eof(__c);
  		}
  	    }
	}
      _M_last_overflowed = true;	
      return __ret;
    }

  template<typename _CharT, typename _Traits>
    typename basic_filebuf<_CharT, _Traits>::__streambuf_type* 
    basic_filebuf<_CharT, _Traits>::
    setbuf(char_type* __s, streamsize __n)
    {
      if (!this->is_open() && __s == 0 && __n == 0)
	_M_buf_size_opt = 0;
      else if (__s && __n)
	{
	  // This is implementation-defined behavior, and assumes
	  // that an external char_type array of length (__s + __n)
	  // exists and has been pre-allocated. If this is not the
	  // case, things will quickly blow up.
	  // Step 1: Destroy the current internal array.
	  _M_destroy_internal_buffer();
	  
	  // Step 2: Use the external array.
	  _M_buf = __s;
	  _M_buf_size_opt = _M_buf_size = __n;
	  _M_set_indeterminate();
	}
      _M_last_overflowed = false;	
      return this; 
    }
  
  template<typename _CharT, typename _Traits>
    typename basic_filebuf<_CharT, _Traits>::pos_type
    basic_filebuf<_CharT, _Traits>::
    seekoff(off_type __off, ios_base::seekdir __way, ios_base::openmode __mode)
    {
      pos_type __ret =  pos_type(off_type(-1)); 
      bool __testin = (ios_base::in & _M_mode & __mode) != 0;
      bool __testout = (ios_base::out & _M_mode & __mode) != 0;

      int __width = 0;
      if (has_facet<__codecvt_type>(this->_M_buf_locale))
	  __width = use_facet<__codecvt_type>(this->_M_buf_locale).encoding();
      if (__width < 0)
	__width = 0;

      bool __testfail = __off != 0 && __width <= 0;      
      if (this->is_open() && !__testfail && (__testin || __testout)) 
	{
	  // Ditch any pback buffers to avoid confusion.
	  _M_pback_destroy();

	  if (__way != ios_base::cur || __off != 0)
	    { 
	      off_type __computed_off = __width * __off;
	      
	      bool __testget = _M_in_cur && _M_in_beg < _M_in_end;
	      bool __testput = _M_out_cur && _M_out_beg < _M_out_end;
	      // Sync the internal and external streams.
	      // out
	      if (__testput || _M_last_overflowed)
		{
		  // Part one: update the output sequence.
		  this->sync();
		  // Part two: output unshift sequence.
		  _M_output_unshift();
		}
	      //in
	      else if (__testget && __way == ios_base::cur)
		__computed_off += _M_in_cur - _M_filepos;

	      // Return pos_type(off_type(-1)) in case of failure.	  
	      __ret = _M_file.seekoff(__computed_off, __way, __mode);
	      _M_set_indeterminate();
	    }
	  // NB: Need to do this in case _M_file in indeterminate
	  // state, ie _M_file._offset == -1
	  else
	    {
 	      pos_type __tmp =
 		_M_file.seekoff(__off, ios_base::cur, __mode);
 	      if (__tmp >= 0)
		{
		  // Seek successful.
		  __ret = __tmp;
		  __ret += max(_M_out_cur, _M_in_cur) - _M_filepos;
		}
	    }
	}
      _M_last_overflowed = false;	
      return __ret;
    }

  template<typename _CharT, typename _Traits>
    typename basic_filebuf<_CharT, _Traits>::pos_type
    basic_filebuf<_CharT, _Traits>::
    seekpos(pos_type __pos, ios_base::openmode __mode)
    {
#ifdef _GLIBCPP_RESOLVE_LIB_DEFECTS
// 171. Strange seekpos() semantics due to joint position
      return this->seekoff(off_type(__pos), ios_base::beg, __mode);
#endif
    }

  template<typename _CharT, typename _Traits>
    void 
    basic_filebuf<_CharT, _Traits>::
    _M_output_unshift()
    { }

  template<typename _CharT, typename _Traits>
    void
    basic_filebuf<_CharT, _Traits>::
    imbue(const locale& __loc)
    {
      bool __testbeg = gptr() == eback() && pptr() == pbase();

      if (__testbeg && _M_buf_locale != __loc)
	_M_buf_locale = __loc;

      // NB this may require the reconversion of previously
      // converted chars. This in turn may cause the reconstruction
      // of the original file. YIKES!!
      // XXX The part in the above comment is not done.
      _M_last_overflowed = false;	
    }

  // Inhibit implicit instantiations for required instantiations,
  // which are defined via explicit instantiations elsewhere.  
  // NB:  This syntax is a GNU extension.
#if _GLIBCPP_EXTERN_TEMPLATE
  extern template class basic_filebuf<char>;
  extern template class basic_ifstream<char>;
  extern template class basic_ofstream<char>;
  extern template class basic_fstream<char>;

#ifdef _GLIBCPP_USE_WCHAR_T
  extern template class basic_filebuf<wchar_t>;
  extern template class basic_ifstream<wchar_t>;
  extern template class basic_ofstream<wchar_t>;
  extern template class basic_fstream<wchar_t>;
#endif
#endif
} // namespace std

#endif