utils/persistent-policy.h

/* -*-  Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2011 University of California, Los Angeles
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation;
 *
 * This program 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 program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Author: Alexander Afanasyev <alexander.afanasyev@ucla.edu>
 */

#ifndef PERSISTENT_POLICY_H_
#define PERSISTENT_POLICY_H_

#include <boost/intrusive/options.hpp>
#include <boost/intrusive/list.hpp>

namespace ndnSIM
{

/**
 * @brief Traits for persistent replacement policy
 *
 * In this policy entries are added until there is a space (controlled by set_max_size call).
 * If maximum is reached, new entries will not be added and nothing will be removed from the container
 */
struct persistent_policy_traits
{
  struct policy_hook_type : public boost::intrusive::list_member_hook<> {};

  template<class Container>
  struct container_hook
  {
    typedef boost::intrusive::member_hook< Container,
                                           policy_hook_type,
                                           &Container::policy_hook_ > type;
  };

  template<class Base,
           class Container,
           class Hook>
  struct policy 
  {
    typedef typename boost::intrusive::list< Container, Hook > policy_container;
    
    // could be just typedef
    class type : public policy_container
    {
    public:
      typedef Container parent_trie;
    
      type (Base &base)
        : base_ (base)
        , max_size_ (100) // when 0, policy is not enforced
      {
      }

      inline void
      update (typename parent_trie::iterator item)
      {
        // do nothing
      }
  
      inline bool
      insert (typename parent_trie::iterator item)
      {
        if (max_size_ != 0 && policy_container::size () >= max_size_)
          return false;
      
        policy_container::push_back (*item);
        return true;
      }
  
      inline void
      lookup (typename parent_trie::iterator item)
      {
        // do nothing
      }
  
      inline void
      erase (typename parent_trie::iterator item)
      {
        policy_container::erase (policy_container::s_iterator_to (*item));
      }

      inline void
      clear ()
      {
        policy_container::clear ();
      }

      inline void
      set_max_size (size_t max_size)
      {
        max_size_ = max_size;
      }

      inline size_t
      get_max_size () const
      {
        return max_size_;
      }

    private:
      // type () : base_(*((Base*)0)) { };

    private:
      Base &base_;
      size_t max_size_;
    };
  };
};

} // ndnSIM

#endif // PERSISTENT_POLICY_H_