std_streambuf.h

俄罗斯高人Mamaich的Pocket gcc编译器（运行在PocketPC上）的全部源代码。

      // Correctly sets the _M_out_cur pointer, and bumps the
      // appropriate _M_*_end pointers as well. Necessary for the
      // un-tied stringbufs, in in|out mode.
      // Invariant:
      // __n + _M_out_[cur, end] <= _M_buf + _M_buf_size
      // Assuming all _M_*_[beg, cur, end] pointers are operating on
      // the same range:
      // _M_buf <= _M_*_ <= _M_buf + _M_buf_size
      void 
      _M_out_cur_move(off_type __n) // argument needs to be +-
      {
	bool __testin = _M_in_cur;

	_M_out_cur += __n;
	if (__testin && _M_buf_unified)
	  _M_in_cur += __n;
	if (_M_out_cur > _M_out_end)
	  {
	    _M_out_end = _M_out_cur;
	    // NB: in | out buffers drag the _M_in_end pointer along...
	    if (__testin)
	      _M_in_end += __n;
	  }
      }

      // Return the size of the output buffer.  This depends on the
      // buffer in use: allocated buffers have a stored size in
      // _M_buf_size and setbuf() buffers don't.
      off_type
      _M_out_buf_size()
      {
	off_type __ret = 0;
	if (_M_out_cur)
	  {
	    // Using allocated buffer.
	    if (_M_out_beg == _M_buf)
	      __ret = _M_out_beg + _M_buf_size - _M_out_cur;
	    // Using non-allocated buffer.
	    else
	      __ret = _M_out_end - _M_out_cur;
	  }
	return __ret;
      }

  public:
      /// Destructor deallocates no buffer space.
      virtual 
      ~basic_streambuf() 
      {
	_M_buf_unified = false;
	_M_buf_size = 0;
	_M_buf_size_opt = 0;
	_M_mode = ios_base::openmode(0);
      }

      // [27.5.2.2.1] locales
      /**
       *  @brief  Entry point for imbue().
       *  @param  loc  The new locale.
       *  @return  The previous locale.
       *
       *  Calls the derived imbue(loc).
      */
      locale 
      pubimbue(const locale &__loc)
      {
	locale __tmp(this->getloc());
	this->imbue(__loc);
	_M_buf_locale = __loc;
	return __tmp;
      }

      /**
       *  @brief  Locale access.
       *  @return  The current locale in effect.
       *
       *  If pubimbue(loc) has been called, then the most recent @c loc
       *  is returned.  Otherwise the global locale in effect at the time
       *  of construction is returned.
      */
      locale   
      getloc() const
      { return _M_buf_locale; } 

      // [27.5.2.2.2] buffer management and positioning
      //@{
      /**
       *  @brief  Entry points for derived buffer functions.
       *
       *  The public versions of @c pubfoo dispatch to the protected
       *  derived @c foo member functions, passing the arguments (if any)
       *  and returning the result unchanged.
      */
      __streambuf_type* 
      pubsetbuf(char_type* __s, streamsize __n) 
      { return this->setbuf(__s, __n); }

      pos_type 
      pubseekoff(off_type __off, ios_base::seekdir __way, 
		 ios_base::openmode __mode = ios_base::in | ios_base::out)
      { return this->seekoff(__off, __way, __mode); }

      pos_type 
      pubseekpos(pos_type __sp,
		 ios_base::openmode __mode = ios_base::in | ios_base::out)
      { return this->seekpos(__sp, __mode); }

      int 
      pubsync() { return this->sync(); }
      //@}

      // [27.5.2.2.3] get area
      /**
       *  @brief  Looking ahead into the stream.
       *  @return  The number of characters available.
       *
       *  If a read position is available, returns the number of characters
       *  available for reading before the buffer must be refilled.
       *  Otherwise returns the derived @c showmanyc().
      */
      streamsize 
      in_avail() 
      { 
	streamsize __ret;
	if (_M_in_cur && _M_in_cur < _M_in_end)
	  {
	    if (_M_pback_init)
	      {
		size_t __save_len =  _M_pback_end_save - _M_pback_cur_save;
		size_t __pback_len = _M_in_cur - _M_pback;
		__ret = __save_len - __pback_len;
	      }
	    else
	      __ret = this->egptr() - this->gptr();
	  }
	else
	  __ret = this->showmanyc();
	return __ret;
      }

      /**
       *  @brief  Getting the next character.
       *  @return  The next character, or eof.
       *
       *  Calls @c sbumpc(), and if that function returns
       *  @c traits::eof(), so does this function.  Otherwise, @c sgetc().
      */
      int_type 
      snextc()
      {
	int_type __eof = traits_type::eof();
	return (traits_type::eq_int_type(this->sbumpc(), __eof) 
		? __eof : this->sgetc());
      }

      /**
       *  @brief  Getting the next character.
       *  @return  The next character, or eof.
       *
       *  If the input read position is available, returns that character
       *  and increments the read pointer, otherwise calls and returns
       *  @c uflow().
      */
      int_type 
      sbumpc();

      /**
       *  @brief  Getting the next character.
       *  @return  The next character, or eof.
       *
       *  If the input read position is available, returns that character,
       *  otherwise calls and returns @c underflow().  Does not move the 
       *  read position after fetching the character.
      */
      int_type 
      sgetc()
      {
	int_type __ret;
	if (_M_in_cur && _M_in_cur < _M_in_end)
	  __ret = traits_type::to_int_type(*(this->gptr()));
	else 
	  __ret = this->underflow();
	return __ret;
      }

      /**
       *  @brief  Entry point for xsgetn.
       *  @param  s  A buffer area.
       *  @param  n  A count.
       *
       *  Returns xsgetn(s,n).  The effect is to fill @a s[0] through
       *  @a s[n-1] with characters from the input sequence, if possible.
      */
      streamsize 
      sgetn(char_type* __s, streamsize __n)
      { return this->xsgetn(__s, __n); }

      // [27.5.2.2.4] putback
      /**
       *  @brief  Pushing characters back into the input stream.
       *  @param  c  The character to push back.
       *  @return  The previous character, if possible.
       *
       *  Similar to sungetc(), but @a c is pushed onto the stream instead
       *  of "the previous character".  If successful, the next character
       *  fetched from the input stream will be @a c.
      */
      int_type 
      sputbackc(char_type __c);

      /**
       *  @brief  Moving backwards in the input stream.
       *  @return  The previous character, if possible.
       *
       *  If a putback position is available, this function decrements the
       *  input pointer and returns that character.  Otherwise, calls and
       *  returns pbackfail().  The effect is to "unget" the last character
       *  "gotten".
      */
      int_type 
      sungetc();

      // [27.5.2.2.5] put area
      /**
       *  @brief  Entry point for all single-character output functions.
       *  @param  c  A character to output.
       *  @return  @a c, if possible.
       *
       *  One of two public output functions.
       *
       *  If a write position is available for the output sequence (i.e.,
       *  the buffer is not full), stores @a c in that position, increments
       *  the position, and returns @c traits::to_int_type(c).  If a write
       *  position is not available, returns @c overflow(c).
      */
      int_type 
      sputc(char_type __c);

      /**
       *  @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_buf(NULL), _M_buf_size(0), _M_buf_size_opt(BUFSIZ), 
      _M_buf_unified(false), _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_mode(ios_base::openmode(0)), _M_buf_locale(locale()), 
      _M_pback_cur_save(0), _M_pback_end_save(0), 
      _M_pback_init(false)
      { }

      // [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)