streambuf

symbian上STL模板库的实现

      sputc(char_type __c)
      {
	int_type __ret;
	if (__builtin_expect(this->pptr() < this->epptr(), true))
	  {
	    *this->pptr() = __c;
	    this->pbump(1);
	    __ret = traits_type::to_int_type(__c);
	  }
	else
	  __ret = this->overflow(traits_type::to_int_type(__c));
	return __ret;
      }

      /**
       *  @brief  Entry point for all single-character output functions.
       *  @param  s  A buffer read area.
       *  @param  n  A count.
       *
       *  One of two public output functions.
       *
       *
       *  Returns xsputn(s,n).  The effect is to write @a s[0] through
       *  @a s[n-1] to the output sequence, if possible.
      */
      streamsize 
      sputn(const char_type* __s, streamsize __n)
      { return this->xsputn(__s, __n); }

    protected:
      /**
       *  @brief  Base constructor.
       *
       *  Only called from derived constructors, and sets up all the
       *  buffer data to zero, including the pointers described in the
       *  basic_streambuf class description.  Note that, as a result,
       *  - the class starts with no read nor write positions available,
       *  - this is not an error
      */
      basic_streambuf()
      : _M_in_beg(0), _M_in_cur(0), _M_in_end(0), 
      _M_out_beg(0), _M_out_cur(0), _M_out_end(0),
      _M_buf_locale(locale()) 
      { }

      // [27.5.2.3.1] get area access
      //@{
      /**
       *  @brief  Access to the get area.
       *
       *  These functions are only available to other protected functions,
       *  including derived classes.
       *
       *  - eback() returns the beginning pointer for the input sequence
       *  - gptr() returns the next pointer for the input sequence
       *  - egptr() returns the end pointer for the input sequence
      */
      char_type* 
      eback() const { return _M_in_beg; }

      char_type* 
      gptr()  const { return _M_in_cur;  }

      char_type* 
      egptr() const { return _M_in_end; }
      //@}

      /**
       *  @brief  Moving the read position.
       *  @param  n  The delta by which to move.
       *
       *  This just advances the read position without returning any data.
      */
      void 
      gbump(int __n) { _M_in_cur += __n; }

      /**
       *  @brief  Setting the three read area pointers.
       *  @param  gbeg  A pointer.
       *  @param  gnext  A pointer.
       *  @param  gend  A pointer.
       *  @post  @a gbeg == @c eback(), @a gnext == @c gptr(), and
       *         @a gend == @c egptr()
      */
      void 
      setg(char_type* __gbeg, char_type* __gnext, char_type* __gend)
      {
	_M_in_beg = __gbeg;
	_M_in_cur = __gnext;
	_M_in_end = __gend;
      }

      // [27.5.2.3.2] put area access
      //@{
      /**
       *  @brief  Access to the put area.
       *
       *  These functions are only available to other protected functions,
       *  including derived classes.
       *
       *  - pbase() returns the beginning pointer for the output sequence
       *  - pptr() returns the next pointer for the output sequence
       *  - epptr() returns the end pointer for the output sequence
      */
      char_type* 
      pbase() const { return _M_out_beg; }

      char_type* 
      pptr() const { return _M_out_cur; }

      char_type* 
      epptr() const { return _M_out_end; }
      //@}

      /**
       *  @brief  Moving the write position.
       *  @param  n  The delta by which to move.
       *
       *  This just advances the write position without returning any data.
      */
      void 
      pbump(int __n) { _M_out_cur += __n; }

      /**
       *  @brief  Setting the three write area pointers.
       *  @param  pbeg  A pointer.
       *  @param  pend  A pointer.
       *  @post  @a pbeg == @c pbase(), @a pbeg == @c pptr(), and
       *         @a pend == @c epptr()
      */
      void 
      setp(char_type* __pbeg, char_type* __pend)
      { 
	_M_out_beg = _M_out_cur = __pbeg; 
	_M_out_end = __pend;
      }

      // [27.5.2.4] virtual functions
      // [27.5.2.4.1] locales
      /**
       *  @brief  Changes translations.
       *  @param  loc  A new locale.
       *
       *  Translations done during I/O which depend on the current locale
       *  are changed by this call.  The standard adds, "Between invocations
       *  of this function a class derived from streambuf can safely cache
       *  results of calls to locale functions and to members of facets
       *  so obtained."
       *
       *  @note  Base class version does nothing.
      */
      virtual void 
      imbue(const locale&) 
      { }

      // [27.5.2.4.2] buffer management and positioning
      /**
       *  @brief  Maniuplates the buffer.
       *
       *  Each derived class provides its own appropriate behavior.  See
       *  the next-to-last paragraph of 
       *  http://gcc.gnu.org/onlinedocs/libstdc++/27_io/howto.html#2 for
       *  more on this function.
       *
       *  @note  Base class version does nothing, returns @c this.
      */
      virtual basic_streambuf<char_type,_Traits>* 
      setbuf(char_type*, streamsize)
      {	return this; }
      
      /**
       *  @brief  Alters the stream positions.
       *
       *  Each derived class provides its own appropriate behavior.
       *  @note  Base class version does nothing, returns a @c pos_type
       *         that represents an invalid stream position.
      */
      virtual pos_type 
      seekoff(off_type, ios_base::seekdir,
	      ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out)
      { return pos_type(off_type(-1)); } 

      /**
       *  @brief  Alters the stream positions.
       *
       *  Each derived class provides its own appropriate behavior.
       *  @note  Base class version does nothing, returns a @c pos_type
       *         that represents an invalid stream position.
      */
      virtual pos_type 
      seekpos(pos_type, 
	      ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out)
      { return pos_type(off_type(-1)); } 

      /**
       *  @brief  Synchronizes the buffer arrays with the controlled sequences.
       *  @return  -1 on failure.
       *
       *  Each derived class provides its own appropriate behavior,
       *  including the definition of "failure".
       *  @note  Base class version does nothing, returns zero.
      */
      virtual int 
      sync() { return 0; }

      // [27.5.2.4.3] get area
      /**
       *  @brief  Investigating the data available.
       *  @return  An estimate of the number of characters available in the
       *           input sequence, or -1.
       *
       *  "If it returns a positive value, then successive calls to
       *  @c underflow() will not return @c traits::eof() until at least that
       *  number of characters have been supplied.  If @c showmanyc()
       *  returns -1, then calls to @c underflow() or @c uflow() will fail."
       *  [27.5.2.4.3]/1
       *
       *  @note  Base class version does nothing, returns zero.
       *  @note  The standard adds that "the intention is not only that the
       *         calls [to underflow or uflow] will not return @c eof() but
       *         that they will return "immediately".
       *  @note  The standard adds that "the morphemes of @c showmanyc are
       *         "es-how-many-see", not "show-manic".
      */
      virtual streamsize 
      showmanyc() { return 0; }

      /**
       *  @brief  Multiple character extraction.
       *  @param  s  A buffer area.
       *  @param  n  Maximum number of characters to assign.
       *  @return  The number of characters assigned.
       *
       *  Fills @a s[0] through @a s[n-1] with characters from the input
       *  sequence, as if by @c sbumpc().  Stops when either @a n characters
       *  have been copied, or when @c traits::eof() would be copied.
       *
       *  It is expected that derived classes provide a more efficient
       *  implementation by overriding this definition.
      */
      virtual streamsize 
      xsgetn(char_type* __s, streamsize __n);

      /**
       *  @brief  Fetches more data from the controlled sequence.
       *  @return  The first character from the <em>pending sequence</em>.
       *
       *  Informally, this function is called when the input buffer is
       *  exhausted (or does not exist, as buffering need not actually be
       *  done).  If a buffer exists, it is "refilled".  In either case, the
       *  next available character is returned, or @c traits::eof() to
       *  indicate a null pending sequence.
       *
       *  For a formal definiton of the pending sequence, see a good text
       *  such as Langer & Kreft, or [27.5.2.4.3]/7-14.
       *
       *  A functioning input streambuf can be created by overriding only
       *  this function (no buffer area will be used).  For an example, see
       *  http://gcc.gnu.org/onlinedocs/libstdc++/27_io/howto.html#6
       *
       *  @note  Base class version does nothing, returns eof().
      */
      virtual int_type 
      underflow()
      { return traits_type::eof(); }

      /**
       *  @brief  Fetches more data from the controlled sequence.
       *  @return  The first character from the <em>pending sequence</em>.
       *
       *  Informally, this function does the same thing as @c underflow(),
       *  and in fact is required to call that function.  It also returns
       *  the new character, like @c underflow() does.  However, this
       *  function also moves the read position forward by one.
      */
      virtual int_type 
      uflow() 
      {
	int_type __ret = traits_type::eof();
	const bool __testeof = traits_type::eq_int_type(this->underflow(), 
							__ret);
	if (!__testeof)
	  {
	    __ret = traits_type::to_int_type(*this->gptr());
	    this->gbump(1);
	  }
	return __ret;    
      }

      // [27.5.2.4.4] putback
      /**
       *  @brief  Tries to back up the input sequence.
       *  @param  c  The character to be inserted back into the sequence.
       *  @return  eof() on failure, "some other value" on success
       *  @post  The constraints of @c gptr(), @c eback(), and @c pptr()
       *         are the same as for @c underflow().
       *
       *  @note  Base class version does nothing, returns eof().
      */
      virtual int_type 
      pbackfail(int_type /* __c */  = traits_type::eof())
      { return traits_type::eof(); }

      // Put area:
      /**
       *  @brief  Multiple character insertion.
       *  @param  s  A buffer area.
       *  @param  n  Maximum number of characters to write.
       *  @return  The number of characters written.
       *
       *  Writes @a s[0] through @a s[n-1] to the output sequence, as if
       *  by @c sputc().  Stops when either @a n characters have been
       *  copied, or when @c sputc() would return @c traits::eof().
       *
       *  It is expected that derived classes provide a more efficient
       *  implementation by overriding this definition.
      */
      virtual streamsize 
      xsputn(const char_type* __s, streamsize __n);

      /**
       *  @brief  Consumes data from the buffer; writes to the
       *          controlled sequence.
       *  @param  c  An additional character to consume.
       *  @return  eof() to indicate failure, something else (usually
       *           @a c, or not_eof())
       *
       *  Informally, this function is called when the output buffer is full
       *  (or does not exist, as buffering need not actually be done).  If a
       *  buffer exists, it is "consumed", with "some effect" on the
       *  controlled sequence.  (Typically, the buffer is written out to the
       *  sequence verbatim.)  In either case, the character @a c is also
       *  written out, if @a c is not @c eof().
       *
       *  For a formal definiton of this function, see a good text
       *  such as Langer & Kreft, or [27.5.2.4.5]/3-7.
       *
       *  A functioning output streambuf can be created by overriding only
       *  this function (no buffer area will be used).
       *
       *  @note  Base class version does nothing, returns eof().
      */
      virtual int_type 
      overflow(int_type /* __c */ = traits_type::eof())
      { return traits_type::eof(); }

#ifdef _GLIBCXX_DEPRECATED
    // Annex D.6
    public:
      /**
       *  @brief  Tosses a character.
       *
       *  Advances the read pointer, ignoring the character that would have
       *  been read.
       *
       *  See http://gcc.gnu.org/ml/libstdc++/2002-05/msg00168.html
       *
       *  @note  This function has been deprecated by the standard.  You
       *         must define @c _GLIBCXX_DEPRECATED to make this visible; see
       *         c++config.h.
      */
      void 
      stossc() 
      {
	if (this->gptr() < this->egptr()) 
	  this->gbump(1);
	else 
	  this->uflow();
      }
#endif

    private:
      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // Side effect of DR 50. 
      basic_streambuf(const __streambuf_type& __sb)
      : _M_in_beg(__sb._M_in_beg), _M_in_cur(__sb._M_in_cur), 
      _M_in_end(__sb._M_in_end), _M_out_beg(__sb._M_out_beg), 
      _M_out_cur(__sb._M_out_cur), _M_out_end(__sb._M_out_cur),
      _M_buf_locale(__sb._M_buf_locale) 
      { }

      __streambuf_type& 
      operator=(const __streambuf_type&) { return *this; };
    };
} // namespace std

#ifndef _GLIBCXX_EXPORT_TEMPLATE
# include <bits/streambuf.tcc>
#endif

#endif /* _GLIBCXX_STREAMBUF */