/* Copyright 2003-2004 Joaquín M López Muñoz.
 * Distributed under the Boost Software License, Version 1.0.
 * (See accompanying file LICENSE_1_0.txt or copy at
 * http://www.boost.org/LICENSE_1_0.txt)
 *
 * See http://www.boost.org/libs/multi_index for library home page.
 */

#ifndef BOOST_MULTI_INDEX_DETAIL_HEADER_HOLDER_HPP
#define BOOST_MULTI_INDEX_DETAIL_HEADER_HOLDER_HPP

#include <boost/noncopyable.hpp>
#include <boost/utility/base_from_member.hpp>

namespace boost{

namespace multi_index{

namespace detail{

/* An utility class derived from base_from_member used to hold
 * a pointer to the header node. The base from member idiom is used
 * because index classes, which are superclasses of multi_index_container,
 * need this header in construction time.
 * The allocation is made by the allocator of the multi_index_container
 * class --hence, this allocator needs also be stored resorting
 * to the base from member trick.
 */

template<typename NodeType,typename Final>
struct header_holder:base_from_member<NodeType*>,private noncopyable
{
  header_holder():super(final().allocate_node()){}
  ~header_holder(){final().deallocate_node(super::member);}

private:
  typedef base_from_member<NodeType*> super;
  Final& final(){return *static_cast<Final*>(this);}
};

} /* namespace multi_index::detail */

} /* namespace multi_index */

} /* namespace boost */

#endif
