libstdc++-v3/include/ext/pb_ds/list_update_policy.hpp

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2005, 2006, 2007, 2009, 2010, 2011
   4 // Free Software Foundation, Inc.
   5 //
   6 // This file is part of the GNU ISO C++ Library.  This library is free
   7 // software; you can redistribute it and/or modify it under the terms
   8 // of the GNU General Public License as published by the Free Software
   9 // Foundation; either version 3, or (at your option) any later
  10 // version.
  11
  12 // This library is distributed in the hope that it will be useful, but
  13 // WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15 // General Public License for more details.
  16
  17 // Under Section 7 of GPL version 3, you are granted additional
  18 // permissions described in the GCC Runtime Library Exception, version
  19 // 3.1, as published by the Free Software Foundation.
  20
  21 // You should have received a copy of the GNU General Public License and
  22 // a copy of the GCC Runtime Library Exception along with this program;
  23 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  24 // <http://www.gnu.org/licenses/>.
  25
  26 // Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
  27
  28 // Permission to use, copy, modify, sell, and distribute this software
  29 // is hereby granted without fee, provided that the above copyright
  30 // notice appears in all copies, and that both that copyright notice
  31 // and this permission notice appear in supporting documentation. None
  32 // of the above authors, nor IBM Haifa Research Laboratories, make any
  33 // representation about the suitability of this software for any
  34 // purpose. It is provided "as is" without express or implied
  35 // warranty.
  36
  37 /**
  38  * @file list_update_policy.hpp
  39  * Contains policies for list update containers.
  40  */
  41
  42 #ifndef PB_DS_LU_POLICY_HPP
  43 #define PB_DS_LU_POLICY_HPP
  44
  45 #include <bits/c++config.h>
  46 #include <cstdlib>
  47 #include <ext/pb_ds/detail/list_update_policy/lu_counter_metadata.hpp>
  48 #include <ext/pb_ds/tag_and_trait.hpp>
  49
  50 namespace __gnu_pbds
  51 {
  52   /**
  53    *  A list-update policy that unconditionally moves elements to the
  54    *  front of the list. A null type means that each link in a
  55    *  list-based container does not actually need metadata.
  56    */
  57  template<typename _Alloc = std::allocator<char> >
  58    class lu_move_to_front_policy
  59    {
  60    public:
  61      typedef _Alloc                                     allocator_type;
  62
  63      /// Metadata on which this functor operates.
  64      typedef null_type                                  metadata_type;
  65
  66    private:
  67      typedef typename _Alloc::template rebind<metadata_type> __rebind_m;
  68
  69    public:
  70      /// Reference to metadata on which this functor operates.
  71      typedef typename __rebind_m::other::reference      metadata_reference;
  72
  73      /// Creates a metadata object.
  74      metadata_type
  75      operator()() const
  76      { return s_metadata; }
  77
  78      /// Decides whether a metadata object should be moved to the front
  79      /// of the list.
  80      inline bool
  81      operator()(metadata_reference r_metadata) const
  82      { return true; }
  83
  84    private:
  85      static null_type                                   s_metadata;
  86    };
  87
  88   /**
  89    *  A list-update policy that moves elements to the front of the
  90    *  list based on the counter algorithm.
  91    */
  92   template<std::size_t Max_Count = 5, typename _Alloc = std::allocator<char> >
  93     class lu_counter_policy
  94     : private detail::lu_counter_policy_base<typename _Alloc::size_type>
  95     {
  96     public:
  97       typedef _Alloc                                    allocator_type;
  98       typedef typename allocator_type::size_type        size_type;
  99
 100       enum
 101         {
 102           /// When some element is accessed this number of times, it
 103           /// will be moved to the front of the list.
 104           max_count = Max_Count
 105         };
 106
 107       /// Metadata on which this functor operates.
 108       typedef detail::lu_counter_metadata<size_type>    metadata_type;
 109
 110     private:
 111       typedef detail::lu_counter_policy_base<size_type>         base_type;
 112       typedef typename _Alloc::template rebind<metadata_type> __rebind_m;
 113
 114     public:
 115       /// Reference to metadata on which this functor operates.
 116       typedef typename __rebind_m::other::reference     metadata_reference;
 117
 118       /// Creates a metadata object.
 119       metadata_type
 120       operator()() const
 121       { return base_type::operator()(max_count); }
 122
 123       /// Decides whether a metadata object should be moved to the front
 124       /// of the list.
 125       bool
 126       operator()(metadata_reference r_data) const
 127       { return base_type::operator()(r_data, max_count); }
 128     };
 129 } // namespace __gnu_pbds
 130
 131 #endif