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 132
