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// -*- C++ -*-

// Copyright (C) 2005, 2006, 2007, 2009, 2010, 2011

// Free Software Foundation, Inc.

//

// This file is part of the GNU ISO C++ Library.  This library is free

// software; you can redistribute it and/or modify it under the terms

// of the GNU General Public License as published by the Free Software

// Foundation; either version 3, or (at your option) any later

// version.

// This library 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.

// Under Section 7 of GPL version 3, you are granted additional

// permissions described in the GCC Runtime Library Exception, version

// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and

// a copy of the GCC Runtime Library Exception along with this program;

// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see

// <http://www.gnu.org/licenses/>.

// Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.

// Permission to use, copy, modify, sell, and distribute this software

// is hereby granted without fee, provided that the above copyright

// notice appears in all copies, and that both that copyright notice

// and this permission notice appear in supporting documentation. None

// of the above authors, nor IBM Haifa Research Laboratories, make any

// representation about the suitability of this software for any

// purpose. It is provided "as is" without express or implied

// warranty.

/**

 * @file list_update_policy.hpp

 * Contains policies for list update containers.

 */

#ifndef PB_DS_LU_POLICY_HPP

#define PB_DS_LU_POLICY_HPP

#include <bits/c++config.h>

#include <cstdlib>

#include <ext/pb_ds/detail/list_update_policy/lu_counter_metadata.hpp>

#include <ext/pb_ds/tag_and_trait.hpp>

namespace __gnu_pbds

{

  /**

   *  A list-update policy that unconditionally moves elements to the

   *  front of the list. A null type means that each link in a

   *  list-based container does not actually need metadata.

   */

 template<typename _Alloc = std::allocator<char> >

   class lu_move_to_front_policy

   {

   public:

     typedef _Alloc                                     allocator_type;

     /// Metadata on which this functor operates.

     typedef null_type                                  metadata_type;

   private:

     typedef typename _Alloc::template rebind<metadata_type> __rebind_m;

   public:

     /// Reference to metadata on which this functor operates.

     typedef typename __rebind_m::other::reference      metadata_reference;

     /// Creates a metadata object.

     metadata_type

     operator()() const

     { return s_metadata; }

     /// Decides whether a metadata object should be moved to the front

     /// of the list.

     inline bool

     operator()(metadata_reference r_metadata) const

     { return true; }

   private:

     static null_type                                   s_metadata;

   };

  /**

   *  A list-update policy that moves elements to the front of the

   *  list based on the counter algorithm.

   */

  template<std::size_t Max_Count = 5, typename _Alloc = std::allocator<char> >

    class lu_counter_policy

    : private detail::lu_counter_policy_base<typename _Alloc::size_type>

    {

    public:

      typedef _Alloc                                    allocator_type;

      typedef typename allocator_type::size_type        size_type;

      enum

        {

          /// When some element is accessed this number of times, it

          /// will be moved to the front of the list.

          max_count = Max_Count

        };

      /// Metadata on which this functor operates.

      typedef detail::lu_counter_metadata<size_type>    metadata_type;

    private:

      typedef detail::lu_counter_policy_base<size_type>         base_type;

      typedef typename _Alloc::template rebind<metadata_type> __rebind_m;

    public:

      /// Reference to metadata on which this functor operates.

      typedef typename __rebind_m::other::reference     metadata_reference;

      /// Creates a metadata object.

      metadata_type

      operator()() const

      { return base_type::operator()(max_count); }

      /// Decides whether a metadata object should be moved to the front

      /// of the list.

      bool

      operator()(metadata_reference r_data) const

      { return base_type::operator()(r_data, max_count); }

    };

} // namespace __gnu_pbds

#endif