text: /////////////////////////////////////////////////////////////////////////////
  //
  // (C) Copyright Olaf Krzikalla 2004-2006.
  // (C) Copyright Ion Gaztanaga  2006-2009
  //
  // 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/intrusive for documentation.
  //
  /////////////////////////////////////////////////////////////////////////////
  
  #ifndef BOOST_INTRUSIVE_LIST_NODE_HPP
  #define BOOST_INTRUSIVE_LIST_NODE_HPP
  
  #include <boost/intrusive/detail/config_begin.hpp>
  #include <iterator>
  #include <boost/intrusive/detail/assert.hpp>
  #include <boost/intrusive/detail/pointer_to_other.hpp>
  
  namespace boost {
  namespace intrusive {
  
  // list_node_traits can be used with circular_list_algorithms and supplies
  // a list_node holding the pointers needed for a double-linked list
  // it is used by list_derived_node and list_member_node
  
  template<class VoidPointer>
  struct list_node
  {
     typedef typename boost::pointer_to_other
        <VoidPointer, list_node>::type   node_ptr;
     node_ptr next_;
     node_ptr prev_;
  };
  
  template<class VoidPointer>
  struct list_node_traits
  {
     typedef list_node<VoidPointer> node;
     typedef typename boost::pointer_to_other
        <VoidPointer, node>::type          node_ptr;
     typedef typename boost::pointer_to_other
        <VoidPointer, const node>::type    const_node_ptr;
  
     static node_ptr get_previous(const_node_ptr n)
     {  return n->prev_;  }
  
     static void set_previous(node_ptr n, node_ptr prev)
     {  n->prev_ = prev;  }
  
     static node_ptr get_next(const_node_ptr n)
     {  return n->next_;  }
  
     static void set_next(node_ptr n, node_ptr next)
     {  n->next_ = next;  }
  };
  
  // list_iterator provides some basic functions for a 
  // node oriented bidirectional iterator:
  template<class Container, bool IsConst>
  class list_iterator
     :  public std::iterator
           < std::bidirectional_iterator_tag
           , typename Container::value_type
           , typename std::iterator_traits<typename Container::value_type*>::difference_type
           , typename detail::add_const_if_c
                       <typename Container::value_type, IsConst>::type *
           , typename detail::add_const_if_c
                       <typename Container::value_type, IsConst>::type &
           >
  {
     protected:
     typedef typename Container::real_value_traits   real_value_traits;
     typedef typename real_value_traits::node_traits node_traits;
     typedef typename node_traits::node              node;
     typedef typename node_traits::node_ptr          node_ptr;
     typedef typename boost::pointer_to_other
        <node_ptr, void>::type                       void_pointer;
     static const bool store_container_ptr = 
        detail::store_cont_ptr_on_it<Container>::value;
  
     public:
     typedef typename Container::value_type    value_type;
     typedef  typename detail::add_const_if_c
                       <typename Container::value_type, IsConst>::type *pointer;
     typedef typename detail::add_const_if_c
                       <typename Container::value_type, IsConst>::type &reference;
  
     list_iterator()
        : members_ (node_ptr(0), 0)
     {}
  
     explicit list_iterator(node_ptr node, const Container *cont_ptr)
        : members_ (node, cont_ptr)
     {}
  
     list_iterator(list_iterator<Container, false> const& other)
        :  members_(other.pointed_node(), other.get_container())
     {}
  
     const node_ptr &pointed_node() const
     { return members_.nodeptr_; }
  
     list_iterator &operator=(const node_ptr &node)
     {  members_.nodeptr_ = node;  return static_cast<list_iterator&>(*this);  }
  
     public:
     list_iterator& operator++() 
     { 
        members_.nodeptr_ = node_traits::get_next(members_.nodeptr_); 
        return static_cast<list_iterator&> (*this); 
     }
     
     list_iterator operator++(int)
     {
        list_iterator result (*this);
        members_.nodeptr_ = node_traits::get_next(members_.nodeptr_);
        return result;
     }
  
     list_iterator& operator--() 
     { 
        members_.nodeptr_ = node_traits::get_previous(members_.nodeptr_); 
        return static_cast<list_iterator&> (*this); 
     }
     
     list_iterator operator--(int)
     {
        list_iterator result (*this);
        members_.nodeptr_ = node_traits::get_previous(members_.nodeptr_);
        return result;
     }
  
     bool operator== (const list_iterator& i) const
     {  return members_.nodeptr_ == i.pointed_node();   }
  
     bool operator!= (const list_iterator& i) const
     {  return !operator== (i); }
  
     reference operator*() const
     {  return *operator->();   }
  
     pointer operator->() const
     { return detail::get_pointer(this->get_real_value_traits()->to_value_ptr(members_.nodeptr_)); }
  
     const Container *get_container() const
     {
        if(store_container_ptr){
           const Container* c = static_cast<const Container*>(members_.get_ptr());
           BOOST_INTRUSIVE_INVARIANT_ASSERT(c != 0);
           return c;
        }
        else{
           return 0;
        }
     }
  
     const real_value_traits *get_real_value_traits() const
     {
        if(store_container_ptr)
           return &this->get_container()->get_real_value_traits();
        else
           return 0;
     }
  
     list_iterator<Container, false> unconst() const
     {  return list_iterator<Container, false>(this->pointed_node(), this->get_container());   }
  
     private:
     struct members
        :  public detail::select_constptr
           <void_pointer, store_container_ptr>::type
     {
        typedef typename detail::select_constptr
           <void_pointer, store_container_ptr>::type Base;
  
        members(const node_ptr &n_ptr, const void *cont)
           :  Base(cont), nodeptr_(n_ptr)
        {}
  
        node_ptr nodeptr_;
     } members_;
  };
  
  } //namespace intrusive 
  } //namespace boost 
  
  #include <boost/intrusive/detail/config_end.hpp>
  
  #endif //BOOST_INTRUSIVE_LIST_NODE_HPP
  