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Edit File: streambuf

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

// Copyright (C) 1997-2021 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

#define _IsUnused __attribute__ ((__unused__))

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 the stream position and
 * conversion state as needed to maintain this subsequence relationship.
 * The three pointers are:
 * - the beginning pointer, or lowest element address in the
 * array (called @e xbeg here);
 * - the next pointer, or next element address that is a
 * current candidate for reading or writing (called @e xnext here);
 * - the end pointer, 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 write position 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 putback position 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 read position 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 _Distance>
 friend typename __gnu_cxx::__enable_if<__is_char<_CharT2>::__value,
					 void>::__type
 advance(istreambuf_iterator<_CharT2>&, _Distance);

friend void __istream_extract(istream&, char*, streamsize);

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 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 @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,
 * 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& __loc _IsUnused)
 { }

// [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
 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.html#io.streambuf.buffering
 * 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.
 *
 * 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
 * @b es-how-many-see, not @b 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 pending sequence.
 *
 * 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
 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.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 pending sequence.
 *
 * 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 _IsUnused = 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
 * 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 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 _IsUnused = traits_type::eof())
 { return traits_type::eof(); }

#if _GLIBCXX_USE_DEPRECATED && __cplusplus <= 201402L
 // Annex D.6 (removed in C++17)
 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
 */
 _GLIBCXX_DEPRECATED_SUGGEST("std::basic_streambuf::sbumpc")
 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; }

#if __cplusplus < 201103L
 private:
#else
 protected:
#endif
 basic_streambuf(const basic_streambuf&);

basic_streambuf&
      operator=(const basic_streambuf&);

#if __cplusplus >= 201103L
      void
      swap(basic_streambuf& __sb)
      {
	std::swap(_M_in_beg, __sb._M_in_beg);
	std::swap(_M_in_cur, __sb._M_in_cur);
	std::swap(_M_in_end, __sb._M_in_end);
	std::swap(_M_out_beg, __sb._M_out_beg);
	std::swap(_M_out_cur, __sb._M_out_cur);
	std::swap(_M_out_end, __sb._M_out_end);
	std::swap(_M_buf_locale, __sb._M_buf_locale);
      }
#endif
    };

#if __cplusplus >= 201103L
 template<typename _CharT, typename _Traits>
 std::basic_streambuf<_CharT, _Traits>::
 basic_streambuf(const basic_streambuf&) = default;

template<typename _CharT, typename _Traits>
 std::basic_streambuf<_CharT, _Traits>&
 std::basic_streambuf<_CharT, _Traits>::
 operator=(const basic_streambuf&) = default;
#endif

// 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

#undef _IsUnused

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace

#include <bits/streambuf.tcc>

#endif /* _GLIBCXX_STREAMBUF */