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

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2005, 2006, 2007, 2009, 2010
   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/counter_lu_metadata.hpp>
  48
  49 namespace __gnu_pbds
  50 {
  51   // A null type that means that each link in a list-based container
  52   // does not actually need metadata.
  53   struct null_lu_metadata
  54   { };
  55
  56 #define PB_DS_CLASS_T_DEC template<typename Allocator>
  57 #define PB_DS_CLASS_C_DEC move_to_front_lu_policy<Allocator>
  58
  59   // A list-update policy that unconditionally moves elements to the
  60   // front of the list.
  61   template<typename Allocator = std::allocator<char> >
  62   class move_to_front_lu_policy
  63   {
  64   public:
  65     typedef Allocator allocator_type;
  66
  67     // Metadata on which this functor operates.
  68     typedef null_lu_metadata metadata_type;
  69
  70     // Reference to metadata on which this functor operates.
  71     typedef typename allocator_type::template rebind<metadata_type>::other metadata_rebind;
  72     typedef typename metadata_rebind::reference metadata_reference;
  73
  74     // Creates a metadata object.
  75     metadata_type
  76     operator()() const;
  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
  83   private:
  84     static null_lu_metadata s_metadata;
  85   };
  86
  87 #include <ext/pb_ds/detail/list_update_policy/mtf_lu_policy_imp.hpp>
  88
  89 #undef PB_DS_CLASS_T_DEC
  90 #undef PB_DS_CLASS_C_DEC
  91
  92 #define PB_DS_CLASS_T_DEC template<std::size_t Max_Count, class Allocator>
  93 #define PB_DS_CLASS_C_DEC counter_lu_policy<Max_Count, Allocator>
  94
  95   // A list-update policy that moves elements to the front of the list
  96   // based on the counter algorithm.
  97   template<std::size_t Max_Count = 5,
  98            typename Allocator = std::allocator<char> >
  99   class counter_lu_policy
 100   : private detail::counter_lu_policy_base<typename Allocator::size_type>
 101   {
 102   public:
 103     typedef Allocator allocator_type;
 104
 105     enum
 106       {
 107         max_count = Max_Count
 108       };
 109
 110     typedef typename allocator_type::size_type size_type;
 111
 112     // Metadata on which this functor operates.
 113     typedef detail::counter_lu_metadata<size_type> metadata_type;
 114
 115     // Reference to metadata on which this functor operates.
 116     typedef typename Allocator::template rebind<metadata_type>::other metadata_rebind;
 117     typedef typename metadata_rebind::reference metadata_reference;
 118
 119     // Creates a metadata object.
 120     metadata_type
 121     operator()() const;
 122
 123     // Decides whether a metadata object should be moved to the front
 124     // of the list.
 125     bool
 126     operator()(metadata_reference r_metadata) const;
 127
 128   private:
 129     typedef detail::counter_lu_policy_base<typename Allocator::size_type> base_type;
 130   };
 131
 132 #include <ext/pb_ds/detail/list_update_policy/counter_lu_policy_imp.hpp>
 133
 134 #undef PB_DS_CLASS_T_DEC
 135 #undef PB_DS_CLASS_C_DEC
 136
 137 } // namespace __gnu_pbds
 138
 139 #endif