libstdc++

lu_counter_metadata.hpp
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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 lu_counter_metadata.hpp
38 * Contains implementation of a lu counter policy's metadata.
39 */
40
41 namespace __gnu_pbds
42 {
43 namespace detail
44 {
45 template<typename Size_Type>
46 class lu_counter_policy_base;
47
48 /// A list-update metadata type that moves elements to the front of
49 /// the list based on the counter algorithm.
50 template<typename Size_Type = std::size_t>
51 class lu_counter_metadata
52 {
53 public:
54 typedef Size_Type size_type;
55
56 private:
57 lu_counter_metadata(size_type init_count) : m_count(init_count)
58 { }
59
60 friend class lu_counter_policy_base<size_type>;
61
62 mutable size_type m_count;
63 };
64
65 /// Base class for list-update counter policy.
66 template<typename Size_Type>
67 class lu_counter_policy_base
68 {
69 protected:
70 typedef Size_Type size_type;
71
72 lu_counter_metadata<size_type>
73 operator()(size_type max_size) const
74 { return lu_counter_metadata<Size_Type>(std::rand() % max_size); }
75
76 template<typename Metadata_Reference>
77 bool
78 operator()(Metadata_Reference r_data, size_type m_max_count) const
79 {
80 if (++r_data.m_count != m_max_count)
81 return false;
82 r_data.m_count = 0;
83 return true;
84 }
85 };
86 } // namespace detail
87 } // namespace __gnu_pbds