header_holder.hpp

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/* Copyright 2003-2008 Joaquin M Lopez Munoz.
 * 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
 
#if defined(_MSC_VER)
#pragma once
#endif
 
#include <boost/noncopyable.hpp>
 
namespace boost{
 
namespace multi_index{
 
namespace detail{
 
/* A utility class 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 NodeTypePtr,typename Final>
struct header_holder:private noncopyable
{
  header_holder():member(final().allocate_node()){}
  ~header_holder(){final().deallocate_node(&*member);}
 
  NodeTypePtr member;
 
private:
  Final& final(){return *static_cast<Final*>(this);}
};
 
} /* namespace multi_index::detail */
 
} /* namespace multi_index */
 
} /* namespace boost */
 
#endif