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  1. // -*- C++ -*-
  2.  
  3. // Copyright (C) 2005-2015 Free Software Foundation, Inc.
  4. //
  5. // This file is part of the GNU ISO C++ Library.  This library is free
  6. // software; you can redistribute it and/or modify it under the terms
  7. // of the GNU General Public License as published by the Free Software
  8. // Foundation; either version 3, or (at your option) any later
  9. // version.
  10.  
  11. // This library is distributed in the hope that it will be useful, but
  12. // WITHOUT ANY WARRANTY; without even the implied warranty of
  13. // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14. // General Public License for more details.
  15.  
  16. // Under Section 7 of GPL version 3, you are granted additional
  17. // permissions described in the GCC Runtime Library Exception, version
  18. // 3.1, as published by the Free Software Foundation.
  19.  
  20. // You should have received a copy of the GNU General Public License and
  21. // a copy of the GCC Runtime Library Exception along with this program;
  22. // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23. // <http://www.gnu.org/licenses/>.
  24.  
  25. // Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
  26.  
  27. // Permission to use, copy, modify, sell, and distribute this software
  28. // is hereby granted without fee, provided that the above copyright
  29. // notice appears in all copies, and that both that copyright notice
  30. // and this permission notice appear in supporting documentation. None
  31. // of the above authors, nor IBM Haifa Research Laboratories, make any
  32. // representation about the suitability of this software for any
  33. // purpose. It is provided "as is" without express or implied
  34. // warranty.
  35.  
  36. /**
  37.  * @file list_update_policy.hpp
  38.  * Contains policies for list update containers.
  39.  */
  40.  
  41. #ifndef PB_DS_LU_POLICY_HPP
  42. #define PB_DS_LU_POLICY_HPP
  43.  
  44. #include <bits/c++config.h>
  45. #include <cstdlib>
  46. #include <ext/pb_ds/detail/list_update_policy/lu_counter_metadata.hpp>
  47. #include <ext/pb_ds/tag_and_trait.hpp>
  48.  
  49. namespace __gnu_pbds
  50. {
  51.   /**
  52.    *  A list-update policy that unconditionally moves elements to the
  53.    *  front of the list. A null type means that each link in a
  54.    *  list-based container does not actually need metadata.
  55.    */
  56.  template<typename _Alloc = std::allocator<char> >
  57.    class lu_move_to_front_policy
  58.    {
  59.    public:
  60.      typedef _Alloc                                     allocator_type;
  61.  
  62.      /// Metadata on which this functor operates.
  63.      typedef null_type                                  metadata_type;
  64.  
  65.    private:
  66.      typedef typename _Alloc::template rebind<metadata_type> __rebind_m;
  67.  
  68.    public:
  69.      /// Reference to metadata on which this functor operates.
  70.      typedef typename __rebind_m::other::reference      metadata_reference;
  71.  
  72.      /// Creates a metadata object.
  73.      metadata_type
  74.      operator()() const
  75.      { return s_metadata; }
  76.  
  77.      /// Decides whether a metadata object should be moved to the front
  78.      /// of the list.
  79.      inline bool
  80.      operator()(metadata_reference r_metadata) const
  81.      { return true; }
  82.  
  83.    private:
  84.      static null_type                                   s_metadata;
  85.    };
  86.  
  87.   /**
  88.    *  A list-update policy that moves elements to the front of the
  89.    *  list based on the counter algorithm.
  90.    */
  91.   template<std::size_t Max_Count = 5, typename _Alloc = std::allocator<char> >
  92.     class lu_counter_policy
  93.     : private detail::lu_counter_policy_base<typename _Alloc::size_type>
  94.     {
  95.     public:
  96.       typedef _Alloc                                    allocator_type;
  97.       typedef typename allocator_type::size_type        size_type;
  98.  
  99.       enum
  100.         {
  101.           /// When some element is accessed this number of times, it
  102.           /// will be moved to the front of the list.
  103.           max_count = Max_Count
  104.         };
  105.  
  106.       /// Metadata on which this functor operates.
  107.       typedef detail::lu_counter_metadata<size_type>    metadata_type;
  108.  
  109.     private:
  110.       typedef detail::lu_counter_policy_base<size_type>         base_type;
  111.       typedef typename _Alloc::template rebind<metadata_type> __rebind_m;
  112.  
  113.     public:
  114.       /// Reference to metadata on which this functor operates.
  115.       typedef typename __rebind_m::other::reference     metadata_reference;
  116.  
  117.       /// Creates a metadata object.
  118.       metadata_type
  119.       operator()() const
  120.       { return base_type::operator()(max_count); }
  121.  
  122.       /// Decides whether a metadata object should be moved to the front
  123.       /// of the list.
  124.       bool
  125.       operator()(metadata_reference r_data) const
  126.       { return base_type::operator()(r_data, max_count); }
  127.     };
  128. } // namespace __gnu_pbds
  129.  
  130. #endif
  131.