// Stream buffer classes -*- C++ -*-
	
	// Copyright (C) 1997-2013 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 3, 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.
	
	// Under Section 7 of GPL version 3, you are granted additional
	// permissions described in the GCC Runtime Library Exception, version
	// 3.1, as published by the Free Software Foundation.
	
	// You should have received a copy of the GNU General Public License and
	// a copy of the GCC Runtime Library Exception along with this program;
	// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
	// <http://www.gnu.org/licenses/>.
	
	/** @file include/streambuf
	 *  This is a Standard C++ Library header.
	 */
	
	//
	// ISO C++ 14882: 27.5  Stream buffers
	//
	
	#ifndef _GLIBXX_STREAMBUF
	#define _GLIBXX_STREAMBUF 1
	
	#pragma GCC system_header
	
	#include <bits/c++config.h>
	#include <iosfwd>
	#include <bits/localefwd.h>
	#include <bits/ios_base.h>
	#include <bits/cpp_type_traits.h>
	#include <ext/type_traits.h>
	
	namespace std _GLIBCXX_VISIBILITY(default)
	{
	_GLIBCXX_BEGIN_NAMESPACE_VERSION
	
	  template<typename _CharT, typename _Traits>
	    streamsize
	    __copy_streambufs_eof(basic_streambuf<_CharT, _Traits>*,
				  basic_streambuf<_CharT, _Traits>*, bool&);
	
	  /**
	   *  @brief  The actual work of input and output (interface).
	   *  @ingroup io
	   *
	   *  @tparam _CharT  Type of character stream.
	   *  @tparam _Traits  Traits for character type, defaults to
	   *                   char_traits<_CharT>.
	   *
	   *  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 <em>the stream position</em> 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 dependent 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;
	      //@}
	
	      //@{
	      /// This is a non-standard type.
	      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_eof<>(basic_streambuf*, basic_streambuf*, bool&);
	
	      template<bool _IsMove, typename _CharT2>
	        friend typename __gnu_cxx::__enable_if<__is_char<_CharT2>::__value, 
						       _CharT2*>::__type
	        __copy_move_a2(istreambuf_iterator<_CharT2>,
			       istreambuf_iterator<_CharT2>, _CharT2*);
	
	      template<typename _CharT2>
	        friend typename __gnu_cxx::__enable_if<__is_char<_CharT2>::__value,
					  istreambuf_iterator<_CharT2> >::__type
	        find(istreambuf_iterator<_CharT2>, istreambuf_iterator<_CharT2>,
		     const _CharT2&);
	
	      template<typename _CharT2, typename _Traits2>
	        friend basic_istream<_CharT2, _Traits2>&
	        operator>>(basic_istream<_CharT2, _Traits2>&, _CharT2*);
	
	      template<typename _CharT2, typename _Traits2, typename _Alloc>
	        friend basic_istream<_CharT2, _Traits2>&
	        operator>>(basic_istream<_CharT2, _Traits2>&,
			   basic_string<_CharT2, _Traits2, _Alloc>&);
	
	      template<typename _CharT2, typename _Traits2, typename _Alloc>
	        friend basic_istream<_CharT2, _Traits2>&
	        getline(basic_istream<_CharT2, _Traits2>&,
			basic_string<_CharT2, _Traits2, _Alloc>&, _CharT2);
	
	    protected:
	      /*
	       *  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
	      */
	      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.
	
	      /// Current locale setting.
	      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.
	      */
	      basic_streambuf*
	      pubsetbuf(char_type* __s, streamsize __n) 
	      { return this->setbuf(__s, __n); }
	
	      /**
	       *  @brief  Alters the stream position.
	       *  @param  __off  Offset.
	       *  @param  __way  Value for ios_base::seekdir.
	       *  @param  __mode Value for ios_base::openmode.
	       *
	       *  Calls virtual seekoff function.
	      */
	      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); }
	
	      /**
	       *  @brief  Alters the stream position.
	       *  @param  __sp  Position
	       *  @param  __mode Value for ios_base::openmode.
	       *
	       *  Calls virtual seekpos function.
	      */
	      pos_type 
	      pubseekpos(pos_type __sp,
			 ios_base::openmode __mode = ios_base::in | ios_base::out)
	      { return this->seekpos(__sp, __mode); }
	
	      /**
	       *  @brief  Calls virtual sync function.
	      */
	      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 <em>the previous character.</em> 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 @a unget
	       *  the last character @a 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 
	      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,
	       *  <em>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.</em>
	       *
	       *  @note  Base class version does nothing.
	      */
	      virtual void 
	      imbue(const locale& __loc) 
	      { }
	
	      // [27.5.2.4.2] buffer management and positioning
	      /**
	       *  @brief  Manipulates the buffer.
	       *
	       *  Each derived class provides its own appropriate behavior.  See
	       *  the next-to-last paragraph of 
	       *  http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt11ch25s02.html
	       *  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 @a 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.
	       *
	       *  <em>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.</em> [27.5.2.4.3]/1
	       *
	       *  @note  Base class version does nothing, returns zero.
	       *  @note  The standard adds that <em>the intention is not only that the
	       *         calls [to underflow or uflow] will not return @c eof() but
	       *         that they will return immediately.</em>
	       *  @note  The standard adds that <em>the morphemes of @c showmanyc are
	       *         @b es-how-many-see, not @b show-manic.</em>
	      */
	      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 @a refilled.  In either case, the
	       *  next available character is returned, or @c traits::eof() to
	       *  indicate a null pending sequence.
	       *
	       *  For a formal definition 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++/manual/bk01pt11ch25.html
	       *
	       *  @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, <em>some other value</em> 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 @a consumed, with
	       *  <em>some effect</em> 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 definition 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(); }
	
	#if _GLIBCXX_USE_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
	       */
	      void 
	      stossc() 
	      {
		if (this->gptr() < this->egptr()) 
		  this->gbump(1);
		else 
		  this->uflow();
	      }
	#endif
	
	      // Also used by specializations for char and wchar_t in src.
	      void 
	      __safe_gbump(streamsize __n) { _M_in_cur += __n; }
	
	      void
	      __safe_pbump(streamsize __n) { _M_out_cur += __n; }
	
	    private:
	      // _GLIBCXX_RESOLVE_LIB_DEFECTS
	      // Side effect of DR 50. 
	      basic_streambuf(const basic_streambuf& __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) 
	      { }
	
	      basic_streambuf&
	      operator=(const basic_streambuf&) { return *this; };
	    };
	
	  // Explicit specialization declarations, defined in src/streambuf.cc.
	  template<>
	    streamsize
	    __copy_streambufs_eof(basic_streambuf<char>* __sbin,
				  basic_streambuf<char>* __sbout, bool& __ineof);
	#ifdef _GLIBCXX_USE_WCHAR_T
	  template<>
	    streamsize
	    __copy_streambufs_eof(basic_streambuf<wchar_t>* __sbin,
				  basic_streambuf<wchar_t>* __sbout, bool& __ineof);
	#endif
	
	_GLIBCXX_END_NAMESPACE_VERSION
	} // namespace
	
	#include <bits/streambuf.tcc>
	
	#endif /* _GLIBCXX_STREAMBUF */