streambuf

symbian上STL模板库的实现

// Stream buffer classes -*- C++ -*-

// Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004
// Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING.  If not, write to the Free
// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License.  This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.

//
// ISO C++ 14882: 27.5  Stream buffers
//

/** @file streambuf
 *  This is a Standard C++ Library header.  You should @c #include this header
 *  in your programs, rather than any of the "st[dl]_*.h" implementation files.
 */

#ifndef _CLIBXX_STREAMBUF
#define _CLIBXX_STREAMBUF 1

//#pragma GCC system_header

#include <bits/c++config.h>
#include <iosfwd>
#include <bits/localefwd.h>
#include <bits/ios_base.h>

namespace std
{
  /**
   *  @if maint
   *  Does stuff.
   *  @endif
  */
  template<typename _CharT, typename _Traits>
    streamsize
    __copy_streambufs(basic_streambuf<_CharT, _Traits>* __sbin,
		      basic_streambuf<_CharT, _Traits>* __sbout);
  
  /**
   *  @brief  The actual work of input and output (interface).
   *
   *  This is a base class.  Derived stream buffers each control a
   *  pair of character sequences:  one for input, and one for output.
   *
   *  Section [27.5.1] of the standard describes the requirements and
   *  behavior of stream buffer classes.  That section (three paragraphs)
   *  is reproduced here, for simplicity and accuracy.
   *
   *  -# Stream buffers can impose various constraints on the sequences
   *     they control.  Some constraints are:
   *     - The controlled input sequence can be not readable.
   *     - The controlled output sequence can be not writable.
   *     - The controlled sequences can be associated with the contents of
   *       other representations for character sequences, such as external
   *       files.
   *     - The controlled sequences can support operations @e directly to or
   *       from associated sequences.
   *     - The controlled sequences can impose limitations on how the
   *       program can read characters from a sequence, write characters to
   *       a sequence, put characters back into an input sequence, or alter
   *       the stream position.
   *     .
   *  -# Each sequence is characterized by three pointers which, if non-null,
   *     all point into the same @c charT array object.  The array object
   *     represents, at any moment, a (sub)sequence of characters from the
   *     sequence.  Operations performed on a sequence alter the values
   *     stored in these pointers, perform reads and writes directly to or
   *     from associated sequences, and alter "the stream position" and
   *     conversion state as needed to maintain this subsequence relationship.
   *     The three pointers are:
   *     - the <em>beginning pointer</em>, or lowest element address in the
   *       array (called @e xbeg here);
   *     - the <em>next pointer</em>, or next element address that is a
   *       current candidate for reading or writing (called @e xnext here);
   *     - the <em>end pointer</em>, or first element address beyond the
   *       end of the array (called @e xend here).
   *     .
   *  -# The following semantic constraints shall always apply for any set
   *     of three pointers for a sequence, using the pointer names given
   *     immediately above:
   *     - If @e xnext is not a null pointer, then @e xbeg and @e xend shall
   *       also be non-null pointers into the same @c charT array, as
   *       described above; otherwise, @e xbeg and @e xend shall also be null.
   *     - If @e xnext is not a null pointer and @e xnext < @e xend for an
   *       output sequence, then a <em>write position</em> is available.
   *       In this case, @e *xnext shall be assignable as the next element
   *       to write (to put, or to store a character value, into the sequence).
   *     - If @e xnext is not a null pointer and @e xbeg < @e xnext for an
   *       input sequence, then a <em>putback position</em> is available.
   *       In this case, @e xnext[-1] shall have a defined value and is the
   *       next (preceding) element to store a character that is put back
   *       into the input sequence.
   *     - If @e xnext is not a null pointer and @e xnext< @e xend for an
   *       input sequence, then a <em>read position</em> is available.
   *       In this case, @e *xnext shall have a defined value and is the
   *       next element to read (to get, or to obtain a character value,
   *       from the sequence).
  */
  template<typename _CharT, typename _Traits>
    class basic_streambuf 
    {
    public:
      //@{
      /**
       *  These are standard types.  They permit a standardized way of
       *  referring to names of (or names dependant on) the template
       *  parameters, which are specific to the implementation.
      */
      typedef _CharT 					char_type;
      typedef _Traits 					traits_type;
      typedef typename traits_type::int_type 		int_type;
      typedef typename traits_type::pos_type 		pos_type;
      typedef typename traits_type::off_type 		off_type;
      //@}

      //@{
      /**
       *  @if maint
       *  This is a non-standard type.
       *  @endif
      */
      typedef basic_streambuf<char_type, traits_type>  	__streambuf_type;
      //@}
      
      friend class basic_ios<char_type, traits_type>;
      friend class basic_istream<char_type, traits_type>;
      friend class basic_ostream<char_type, traits_type>;
      friend class istreambuf_iterator<char_type, traits_type>;
      friend class ostreambuf_iterator<char_type, traits_type>;

      friend streamsize
      __copy_streambufs<>(__streambuf_type* __sbin,
			  __streambuf_type* __sbout);
      
    protected:
      //@{
      /**
       *  @if maint
       *  This is based on _IO_FILE, just reordered to be more consistent,
       *  and is intended to be the most minimal abstraction for an
       *  internal buffer.
       *  -  get == input == read
       *  -  put == output == write
       *  @endif
      */
      char_type* 		_M_in_beg;     // Start of get area. 
      char_type* 		_M_in_cur;     // Current read area. 
      char_type* 		_M_in_end;     // End of get area. 
      char_type* 		_M_out_beg;    // Start of put area. 
      char_type* 		_M_out_cur;    // Current put area. 
      char_type* 		_M_out_end;    // End of put area.

      /**
       *  @if maint
       *  Current locale setting.
       *  @endif
      */
      locale 			_M_buf_locale;	

  public:
      /// Destructor deallocates no buffer space.
      virtual 
      ~basic_streambuf() 
      { }

      // [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() 
      { 
	const streamsize __ret = this->egptr() - this->gptr();
	return __ret ? __ret : this->showmanyc();
      }

      /**
       *  @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 __ret = traits_type::eof();
	if (__builtin_expect(!traits_type::eq_int_type(this->sbumpc(), 
						       __ret), true))
	  __ret = this->sgetc();
	return __ret;
      }

      /**
       *  @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()
      {
	int_type __ret;
	if (__builtin_expect(this->gptr() < this->egptr(), true))
	  {
	    __ret = traits_type::to_int_type(*this->gptr());
	    this->gbump(1);
	  }
	else 
	  __ret = this->uflow();
	return __ret;
      }

      /**
       *  @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 (__builtin_expect(this->gptr() < this->egptr(), true))
	  __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)
      {
	int_type __ret;
	const bool __testpos = this->eback() < this->gptr();
	if (__builtin_expect(!__testpos || 
			     !traits_type::eq(__c, this->gptr()[-1]), false))
	  __ret = this->pbackfail(traits_type::to_int_type(__c));
	else 
	  {
	    this->gbump(-1);
	    __ret = traits_type::to_int_type(*this->gptr());
	  }
	return __ret;
      }

      /**
       *  @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()
      {
	int_type __ret;
	if (__builtin_expect(this->eback() < this->gptr(), true))
	  {
	    this->gbump(-1);
	    __ret = traits_type::to_int_type(*this->gptr());
	  }
	else 
	  __ret = this->pbackfail();
	return __ret;
      }

      // [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