contrib/gcc-8.0/libstdc++-v3/include/ext/pb_ds/detail/list_update_policy/lu_counter_metadata.hpp

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2005-2018 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