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

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2005, 2006, 2007, 2009 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 <cstdlib>
  45 #include <ext/pb_ds/detail/list_update_policy/counter_lu_metadata.hpp>
  46
  47 namespace __gnu_pbds
  48 {
  49   // A null type that means that each link in a list-based container
  50   // does not actually need metadata.
  51   struct null_lu_metadata
  52   { };
  53
  54 #define PB_DS_CLASS_T_DEC template<typename Allocator>
  55 #define PB_DS_CLASS_C_DEC move_to_front_lu_policy<Allocator>
  56
  57   // A list-update policy that unconditionally moves elements to the
  58   // front of the list.
  59   template<typename Allocator = std::allocator<char> >
  60   class move_to_front_lu_policy
  61   {
  62   public:
  63     typedef Allocator allocator_type;
  64
  65     // Metadata on which this functor operates.
  66     typedef null_lu_metadata metadata_type;
  67
  68     // Reference to metadata on which this functor operates.
  69     typedef typename allocator_type::template rebind<metadata_type>::other metadata_rebind;
  70     typedef typename metadata_rebind::reference metadata_reference;
  71
  72     // Creates a metadata object.
  73     metadata_type
  74     operator()() const;
  75
  76     // Decides whether a metadata object should be moved to the front
  77     // of the list.
  78     inline bool
  79     operator()(metadata_reference r_metadata) const;
  80
  81   private:
  82     static null_lu_metadata s_metadata;
  83   };
  84
  85 #include <ext/pb_ds/detail/list_update_policy/mtf_lu_policy_imp.hpp>
  86
  87 #undef PB_DS_CLASS_T_DEC
  88 #undef PB_DS_CLASS_C_DEC
  89
  90 #define PB_DS_CLASS_T_DEC template<size_t Max_Count, class Allocator>
  91 #define PB_DS_CLASS_C_DEC counter_lu_policy<Max_Count, Allocator>
  92
  93   // A list-update policy that moves elements to the front of the list
  94   // based on the counter algorithm.
  95   template<size_t Max_Count = 5, typename Allocator = std::allocator<char> >
  96   class counter_lu_policy
  97   : private detail::counter_lu_policy_base<typename Allocator::size_type>
  98   {
  99   public:
 100     typedef Allocator allocator_type;
 101
 102     enum
 103       {
 104         max_count = Max_Count
 105       };
 106
 107     typedef typename allocator_type::size_type size_type;
 108
 109     // Metadata on which this functor operates.
 110     typedef detail::counter_lu_metadata<size_type> metadata_type;
 111
 112     // Reference to metadata on which this functor operates.
 113     typedef typename Allocator::template rebind<metadata_type>::other metadata_rebind;
 114     typedef typename metadata_rebind::reference metadata_reference;
 115
 116     // Creates a metadata object.
 117     metadata_type
 118     operator()() const;
 119
 120     // Decides whether a metadata object should be moved to the front
 121     // of the list.
 122     bool
 123     operator()(metadata_reference r_metadata) const;
 124
 125   private:
 126     typedef detail::counter_lu_policy_base<typename Allocator::size_type> base_type;
 127   };
 128
 129 #include <ext/pb_ds/detail/list_update_policy/counter_lu_policy_imp.hpp>
 130
 131 #undef PB_DS_CLASS_T_DEC
 132 #undef PB_DS_CLASS_C_DEC
 133
 134 } // namespace __gnu_pbds
 135
 136 #endif