istream.tcc

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

	    {
	      // Cannot compare int_type with streamsize generically.
	      streamsize __num = this->rdbuf()->in_avail();
	      if (__num >= 0)
		{
		  __num = min(__num, __n);
		  if (__num)
		    _M_gcount = this->rdbuf()->sgetn(__s, __num);
		}
	      else
		this->setstate(ios_base::eofbit);		    
	    }
	  catch(...)
	    {
	      // 27.6.1.3 paragraph 1
	      // Turn this on without causing an ios::failure to be thrown.
	      this->_M_setstate(ios_base::badbit);
	      if ((this->exceptions() & ios_base::badbit) != 0)
		__throw_exception_again;
	    }
	}
      else
	this->setstate(ios_base::failbit);
      return _M_gcount;
    }
      
  template<typename _CharT, typename _Traits>
    basic_istream<_CharT, _Traits>&
    basic_istream<_CharT, _Traits>::
    putback(char_type __c)
    {
#ifdef _GLIBCPP_RESOLVE_LIB_DEFECTS
// 60. What is a formatted input function?
      _M_gcount = 0;
#endif
      sentry __cerb(*this, true);
      if (__cerb) 
	{
	  try 
	    {
	      const int_type __eof = traits_type::eof();
	      __streambuf_type* __sb = this->rdbuf();
	      if (!__sb 
		  || traits_type::eq_int_type(__sb->sputbackc(__c), __eof))
		this->setstate(ios_base::badbit);		    
	    }
	  catch(...)
	    {
	      // 27.6.1.3 paragraph 1
	      // Turn this on without causing an ios::failure to be thrown.
	      this->_M_setstate(ios_base::badbit);
	      if ((this->exceptions() & ios_base::badbit) != 0)
		__throw_exception_again;
	    }
	}
      else
	this->setstate(ios_base::failbit);
      return *this;
    }
  
  template<typename _CharT, typename _Traits>
    basic_istream<_CharT, _Traits>&
    basic_istream<_CharT, _Traits>::
    unget(void)
    {
#ifdef _GLIBCPP_RESOLVE_LIB_DEFECTS
// 60. What is a formatted input function?
      _M_gcount = 0;
#endif
      sentry __cerb(*this, true);
      if (__cerb) 
	{
	  try 
	    {
	      const int_type __eof = traits_type::eof();
	      __streambuf_type* __sb = this->rdbuf();
	      if (!__sb 
		  || traits_type::eq_int_type(__sb->sungetc(), __eof))
		this->setstate(ios_base::badbit);		    
	    }
	  catch(...)
	    {
	      // 27.6.1.3 paragraph 1
	      // Turn this on without causing an ios::failure to be thrown.
	      this->_M_setstate(ios_base::badbit);
	      if ((this->exceptions() & ios_base::badbit) != 0)
		__throw_exception_again;
	    }
	}
      else
	this->setstate(ios_base::failbit);
      return *this;
    }
  
  template<typename _CharT, typename _Traits>
    int
    basic_istream<_CharT, _Traits>::
    sync(void)
    {
      // DR60.  Do not change _M_gcount.
      int __ret = -1;
      sentry __cerb(*this, true);
      if (__cerb) 
	{
	  try 
	    {
	      __streambuf_type* __sb = this->rdbuf();
	      if (__sb)
		{
		  if (__sb->pubsync() == -1)
		    this->setstate(ios_base::badbit);		    
		  else 
		    __ret = 0;
		}
	    }
	  catch(...)
	    {
	      // 27.6.1.3 paragraph 1
	      // Turn this on without causing an ios::failure to be thrown.
	      this->_M_setstate(ios_base::badbit);
	      if ((this->exceptions() & ios_base::badbit) != 0)
		__throw_exception_again;
	    }
	}
      return __ret;
    }
  
  template<typename _CharT, typename _Traits>
    typename basic_istream<_CharT, _Traits>::pos_type
    basic_istream<_CharT, _Traits>::
    tellg(void)
    {
      // DR60.  Do not change _M_gcount.
      pos_type __ret = pos_type(-1);
      if (!this->fail())
	__ret = this->rdbuf()->pubseekoff(0, ios_base::cur, ios_base::in);
      return __ret;
    }


  template<typename _CharT, typename _Traits>
    basic_istream<_CharT, _Traits>&
    basic_istream<_CharT, _Traits>::
    seekg(pos_type __pos)
    {
      // DR60.  Do not change _M_gcount.
      if (!this->fail())
	{
#ifdef _GLIBCPP_RESOLVE_LIB_DEFECTS
// 136.  seekp, seekg setting wrong streams?
	  pos_type __err = this->rdbuf()->pubseekpos(__pos, ios_base::in);

// 129. Need error indication from seekp() and seekg()
	  if (__err == pos_type(off_type(-1)))
	    this->setstate(ios_base::failbit);
#endif
	}
      return *this;
    }

  template<typename _CharT, typename _Traits>
    basic_istream<_CharT, _Traits>&
    basic_istream<_CharT, _Traits>::
    seekg(off_type __off, ios_base::seekdir __dir)
    {
      // DR60.  Do not change _M_gcount.
      if (!this->fail())
	{
#ifdef _GLIBCPP_RESOLVE_LIB_DEFECTS
// 136.  seekp, seekg setting wrong streams?
	  pos_type __err = this->rdbuf()->pubseekoff(__off, __dir, 
						     ios_base::in);

// 129. Need error indication from seekp() and seekg()
	  if (__err == pos_type(off_type(-1)))
	    this->setstate(ios_base::failbit);
#endif
	}
      return *this;
    }

  // 27.6.1.2.3 Character extraction templates
  template<typename _CharT, typename _Traits>
    basic_istream<_CharT, _Traits>&
    operator>>(basic_istream<_CharT, _Traits>& __in, _CharT& __c)
    {
      typedef basic_istream<_CharT, _Traits> 		__istream_type;
      typename __istream_type::sentry __cerb(__in, false);
      if (__cerb)
	{
	  try 
	    { __in.get(__c); }
	  catch(...)
	    {
	      // 27.6.1.2.1 Common requirements.
	      // Turn this on without causing an ios::failure to be thrown.
	      __in._M_setstate(ios_base::badbit);
	      if ((__in.exceptions() & ios_base::badbit) != 0)
		__throw_exception_again;
	    }
	}
      else
	__in.setstate(ios_base::failbit);
      return __in;
    }

  template<typename _CharT, typename _Traits>
    basic_istream<_CharT, _Traits>&
    operator>>(basic_istream<_CharT, _Traits>& __in, _CharT* __s)
    {
      typedef basic_istream<_CharT, _Traits> 		__istream_type;
      typedef typename __istream_type::__streambuf_type __streambuf_type;
      typedef typename _Traits::int_type 		int_type;
      typedef _CharT                     		char_type;
      typedef ctype<_CharT>     			__ctype_type;
      streamsize __extracted = 0;

      typename __istream_type::sentry __cerb(__in, false);
      if (__cerb)
	{
	  try 
	    {
	      // Figure out how many characters to extract.
	      streamsize __num = __in.width();
	      if (__num <= 0)
		__num = numeric_limits<streamsize>::max();
	      
	      const __ctype_type& __ctype = use_facet<__ctype_type>(__in.getloc());
	      const int_type __eof = _Traits::eof();
	      __streambuf_type* __sb = __in.rdbuf();
	      int_type __c = __sb->sgetc();
	      
	      while (__extracted < __num - 1 
		     && !_Traits::eq_int_type(__c, __eof)
		     && !__ctype.is(ctype_base::space, _Traits::to_char_type(__c)))
		{
		  *__s++ = _Traits::to_char_type(__c);
		  ++__extracted;
		  __c = __sb->snextc();
		}
	      if (_Traits::eq_int_type(__c, __eof))
		__in.setstate(ios_base::eofbit);

#ifdef _GLIBCPP_RESOLVE_LIB_DEFECTS
//68.  Extractors for char* should store null at end
	      *__s = char_type();
#endif
	      __in.width(0);
	    }
	  catch(...)
	    {
	      // 27.6.1.2.1 Common requirements.
	      // Turn this on without causing an ios::failure to be thrown.
	      __in._M_setstate(ios_base::badbit);
	      if ((__in.exceptions() & ios_base::badbit) != 0)
		__throw_exception_again;
	    }
	}
      if (!__extracted)
	__in.setstate(ios_base::failbit);
      return __in;
    }

  // 27.6.1.4 Standard basic_istream manipulators
  template<typename _CharT, typename _Traits>
    basic_istream<_CharT,_Traits>& 
    ws(basic_istream<_CharT,_Traits>& __in)
    {
      typedef basic_istream<_CharT, _Traits> 		__istream_type;
      typedef typename __istream_type::__streambuf_type __streambuf_type;
      typedef typename __istream_type::__ctype_type 	__ctype_type;
      typedef typename __istream_type::int_type 	__int_type;

      const __ctype_type& __ctype = use_facet<__ctype_type>(__in.getloc());
      const __int_type __eof = _Traits::eof();	      
      __streambuf_type* __sb = __in.rdbuf();
      __int_type __c = __sb->sgetc();

      while (!_Traits::eq_int_type(__c, __eof) 
	     && __ctype.is(ctype_base::space, _Traits::to_char_type(__c)))
	__c = __sb->snextc();

       if (_Traits::eq_int_type(__c, __eof))
	__in.setstate(ios_base::eofbit);

      return __in;
    }

  // 21.3.7.9 basic_string::getline and operators
  template<typename _CharT, typename _Traits, typename _Alloc>
    basic_istream<_CharT, _Traits>&
    operator>>(basic_istream<_CharT, _Traits>& __in,
	       basic_string<_CharT, _Traits, _Alloc>& __str)
    {
      typedef basic_istream<_CharT, _Traits> 		__istream_type;
      typedef typename __istream_type::int_type 	__int_type;
      typedef typename __istream_type::__streambuf_type __streambuf_type;
      typedef typename __istream_type::__ctype_type 	__ctype_type;
      typedef basic_string<_CharT, _Traits, _Alloc> 	__string_type;
      typedef typename __string_type::size_type		__size_type;
      __size_type __extracted = 0;

      typename __istream_type::sentry __cerb(__in, false);
      if (__cerb) 
	{
	  __str.erase();
	  streamsize __w = __in.width();
	  __size_type __n;
	  __n = __w > 0 ? static_cast<__size_type>(__w) : __str.max_size();

	  const __ctype_type& __ctype = use_facet<__ctype_type>(__in.getloc());
	  const __int_type __eof = _Traits::eof();
	  __streambuf_type* __sb = __in.rdbuf();
	  __int_type __c = __sb->sgetc();
	  
	  while (__extracted < __n 
		 && !_Traits::eq_int_type(__c, __eof)
		 && !__ctype.is(ctype_base::space, _Traits::to_char_type(__c)))
	    {
	      __str += _Traits::to_char_type(__c);
	      ++__extracted;
	      __c = __sb->snextc();
	    }
	  if (_Traits::eq_int_type(__c, __eof))
	    __in.setstate(ios_base::eofbit);
	  __in.width(0);
	}
#ifdef _GLIBCPP_RESOLVE_LIB_DEFECTS
//211.  operator>>(istream&, string&) doesn't set failbit
      if (!__extracted)
	__in.setstate (ios_base::failbit);
#endif
      return __in;
    }

  template<typename _CharT, typename _Traits, typename _Alloc>
    basic_istream<_CharT, _Traits>&
    getline(basic_istream<_CharT, _Traits>& __in,
	    basic_string<_CharT, _Traits, _Alloc>& __str, _CharT __delim)
    {
      typedef basic_istream<_CharT, _Traits> 		__istream_type;
      typedef typename __istream_type::int_type 	__int_type;
      typedef typename __istream_type::__streambuf_type __streambuf_type;
      typedef typename __istream_type::__ctype_type 	__ctype_type;
      typedef basic_string<_CharT, _Traits, _Alloc> 	__string_type;
      typedef typename __string_type::size_type		__size_type;

      __size_type __extracted = 0;
      bool __testdelim = false;
      typename __istream_type::sentry __cerb(__in, true);
      if (__cerb) 
	{
	  __str.erase();
	  __size_type __n = __str.max_size();

	  __int_type __idelim = _Traits::to_int_type(__delim);
	  __streambuf_type* __sb = __in.rdbuf();
	  __int_type __c = __sb->sbumpc();
	  const __int_type __eof = _Traits::eof();
	  __testdelim = _Traits::eq_int_type(__c, __idelim);

	  while (__extracted <= __n 
		 && !_Traits::eq_int_type(__c, __eof)
		 && !__testdelim)
	    {
	      __str += _Traits::to_char_type(__c);
	      ++__extracted;
	      __c = __sb->sbumpc();
	      __testdelim = _Traits::eq_int_type(__c, __idelim);
	    }
	  if (_Traits::eq_int_type(__c, __eof))
	    __in.setstate(ios_base::eofbit);
	}
      if (!__extracted && !__testdelim)
	__in.setstate(ios_base::failbit);
      return __in;
    }

  template<class _CharT, class _Traits, class _Alloc>
    inline basic_istream<_CharT,_Traits>&
    getline(basic_istream<_CharT, _Traits>& __in, 
	    basic_string<_CharT,_Traits,_Alloc>& __str)
    { return getline(__in, __str, __in.widen('\n')); }

  // 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_istream<char>;
  extern template istream& ws(istream&);
  extern template istream& operator>>(istream&, char&);
  extern template istream& operator>>(istream&, char*);
  extern template istream& operator>>(istream&, unsigned char&);
  extern template istream& operator>>(istream&, signed char&);
  extern template istream& operator>>(istream&, unsigned char*);
  extern template istream& operator>>(istream&, signed char*);

#ifdef _GLIBCPP_USE_WCHAR_T
  extern template class basic_istream<wchar_t>;
  extern template wistream& ws(wistream&);
  extern template wistream& operator>>(wistream&, wchar_t&);
  extern template wistream& operator>>(wistream&, wchar_t*);
#endif
#endif
} // namespace std