1 // -*- C++ -*- 2 3 // Copyright (C) 2005-2013 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
