gcc/libstdc++-v3/include/ext/enc_filebuf.h

// __enc_traits layer for filebuf -*- C++ -*-

// Copyright (C) 2002 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.

#include <fstream>
#include <locale>

namespace __gnu_cxx
{
  // Custom traits type with __enc_traits for state type, all other bits
  // equivalent to the required char_traits instantiations.
  template<typename _CharT>
    struct enc_char_traits: public std::char_traits<_CharT>
    {
      typedef std::__enc_traits	state_type;
    };

  template<typename _CharT>
    class enc_filebuf
    : public std::basic_filebuf<_CharT, enc_char_traits<_CharT> >
    {
    public:
      typedef typename enc_char_traits<_CharT>::state_type state_type;
      
      enc_filebuf(state_type& __state)
      : std::basic_filebuf<_CharT, enc_char_traits<_CharT> >()
      { 
	// Set state type to something useful.
	// Something more than copyconstructible is needed here, so
	// require copyconstructible + assignment operator.
	__glibcpp_class_requires(state_type, _SGIAssignableConcept);
	_M_state_cur = __state;
	_M_state_cur._M_init();
      };
    };
} // namespace __gnu_cxx