libstdc++
lu_counter_metadata.hpp
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00001 // -*- C++ -*-
00002 
00003 // Copyright (C) 2005-2015 Free Software Foundation, Inc.
00004 //
00005 // This file is part of the GNU ISO C++ Library.  This library is free
00006 // software; you can redistribute it and/or modify it under the terms
00007 // of the GNU General Public License as published by the Free Software
00008 // Foundation; either version 3, or (at your option) any later
00009 // version.
00010 
00011 // This library is distributed in the hope that it will be useful, but
00012 // WITHOUT ANY WARRANTY; without even the implied warranty of
00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00014 // General Public License for more details.
00015 
00016 // Under Section 7 of GPL version 3, you are granted additional
00017 // permissions described in the GCC Runtime Library Exception, version
00018 // 3.1, as published by the Free Software Foundation.
00019 
00020 // You should have received a copy of the GNU General Public License and
00021 // a copy of the GCC Runtime Library Exception along with this program;
00022 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00023 // <http://www.gnu.org/licenses/>.
00024 
00025 // Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
00026 
00027 // Permission to use, copy, modify, sell, and distribute this software
00028 // is hereby granted without fee, provided that the above copyright
00029 // notice appears in all copies, and that both that copyright notice
00030 // and this permission notice appear in supporting documentation. None
00031 // of the above authors, nor IBM Haifa Research Laboratories, make any
00032 // representation about the suitability of this software for any
00033 // purpose. It is provided "as is" without express or implied
00034 // warranty.
00035 
00036 /**
00037  * @file lu_counter_metadata.hpp
00038  * Contains implementation of a lu counter policy's metadata.
00039  */
00040 
00041 namespace __gnu_pbds
00042 {
00043   namespace detail
00044   {
00045     template<typename Size_Type>
00046       class lu_counter_policy_base;
00047 
00048     /// A list-update metadata type that moves elements to the front of
00049     /// the list based on the counter algorithm.
00050     template<typename Size_Type = std::size_t>
00051       class lu_counter_metadata
00052       {
00053       public:
00054         typedef Size_Type       size_type;
00055 
00056       private:
00057         lu_counter_metadata(size_type init_count) : m_count(init_count)
00058         { }
00059 
00060         friend class lu_counter_policy_base<size_type>;
00061 
00062         mutable size_type       m_count;
00063     };
00064 
00065     /// Base class for list-update counter policy.
00066     template<typename Size_Type>
00067       class lu_counter_policy_base
00068       {
00069       protected:
00070         typedef Size_Type       size_type;
00071 
00072         lu_counter_metadata<size_type>
00073         operator()(size_type max_size) const
00074         { return lu_counter_metadata<Size_Type>(std::rand() % max_size); }
00075 
00076         template<typename Metadata_Reference>
00077         bool
00078         operator()(Metadata_Reference r_data, size_type m_max_count) const
00079         {
00080           if (++r_data.m_count != m_max_count)
00081             return false;
00082           r_data.m_count = 0;
00083           return true;
00084         }
00085       };
00086   } // namespace detail
00087 } // namespace __gnu_pbds