ceph/src/boost/libs/intrusive/example/doc_stateful_value_traits.cpp

   1 /////////////////////////////////////////////////////////////////////////////
   2 //
   3 // (C) Copyright Ion Gaztanaga  2007-2013
   4 //
   5 // Distributed under the Boost Software License, Version 1.0.
   6 //    (See accompanying file LICENSE_1_0.txt or copy at
   7 //          http://www.boost.org/LICENSE_1_0.txt)
   8 //
   9 // See http://www.boost.org/libs/intrusive for documentation.
  10 //
  11 /////////////////////////////////////////////////////////////////////////////
  12 //[doc_stateful_value_traits
  13 #include <boost/intrusive/list.hpp>
  14
  15 using namespace boost::intrusive;
  16
  17 //This type is not modifiable so we can't store hooks or custom nodes
  18 typedef int identifier_t;
  19
  20 //This value traits will associate elements from an array of identifiers with
  21 //elements of an array of nodes. The element i of the value array will use the
  22 //node i of the node array:
  23 struct stateful_value_traits
  24 {
  25    typedef list_node_traits<void*>           node_traits;
  26    typedef node_traits::node                 node;
  27    typedef node *                            node_ptr;
  28    typedef const node *                      const_node_ptr;
  29    typedef identifier_t                      value_type;
  30    typedef identifier_t *                    pointer;
  31    typedef const identifier_t *              const_pointer;
  32    static const link_mode_type link_mode =   normal_link;
  33
  34    stateful_value_traits(pointer ids, node_ptr node_array)
  35       :  ids_(ids),  nodes_(node_array)
  36    {}
  37
  38    ///Note: non static functions!
  39    node_ptr to_node_ptr (value_type &value) const
  40       {  return this->nodes_ + (&value - this->ids_); }
  41    const_node_ptr to_node_ptr (const value_type &value) const
  42       {  return this->nodes_ + (&value - this->ids_); }
  43    pointer to_value_ptr(node_ptr n) const
  44       {  return this->ids_ + (n - this->nodes_); }
  45    const_pointer to_value_ptr(const_node_ptr n) const
  46       {  return this->ids_ + (n - this->nodes_); }
  47
  48    private:
  49    pointer  ids_;
  50    node_ptr nodes_;
  51 };
  52
  53 int main()
  54 {
  55    const int NumElements = 100;
  56
  57    //This is an array of ids that we want to "store"
  58    identifier_t                  ids   [NumElements];
  59
  60    //This is an array of nodes that is necessary to form the linked list
  61    list_node_traits<void*>::node nodes [NumElements];
  62
  63    //Initialize id objects, each one with a different number
  64    for(int i = 0; i != NumElements; ++i)   ids[i] = i;
  65
  66    //Define a list that will "link" identifiers using external nodes
  67    typedef list<identifier_t, value_traits<stateful_value_traits> > List;
  68
  69    //This list will store ids without modifying identifier_t instances
  70    //Stateful value traits must be explicitly passed in the constructor.
  71    List  my_list (stateful_value_traits (ids, nodes));
  72
  73    //Insert ids in reverse order in the list
  74    for(identifier_t * it(&ids[0]), *itend(&ids[NumElements]); it != itend; ++it)
  75       my_list.push_front(*it);
  76
  77    //Now test lists
  78    List::const_iterator   list_it (my_list.cbegin());
  79    identifier_t *it_val(&ids[NumElements]), *it_rbeg_val(&ids[0]);
  80
  81    //Test the objects inserted in the base hook list
  82    for(; it_val != it_rbeg_val; --it_val, ++list_it)
  83       if(&*list_it  != &it_val[-1])   return 1;
  84
  85    return 0;
  86 }
  87 //]