1 // -*- C++ -*-
2 
3 // Copyright (C) 2005-2022 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:
lu_counter_metadata(size_type init_count)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>
operator ()(size_type max_size) const73           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
operator ()(Metadata_Reference r_data,size_type m_max_count) const78           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
88