libstdc++-v3/include/ext/pb_ds/detail/list_update_policy/counter_lu_metadata.hpp

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2005, 2006, 2007 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 2, 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 // You should have received a copy of the GNU General Public License
  17 // along with this library; see the file COPYING.  If not, write to
  18 // the Free Software Foundation, 59 Temple Place - Suite 330, Boston,
  19 // MA 02111-1307, USA.
  20
  21 // As a special exception, you may use this file as part of a free
  22 // software library without restriction.  Specifically, if other files
  23 // instantiate templates or use macros or inline functions from this
  24 // file, or you compile this file and link it with other files to
  25 // produce an executable, this file does not by itself cause the
  26 // resulting executable to be covered by the GNU General Public
  27 // License.  This exception does not however invalidate any other
  28 // reasons why the executable file might be covered by the GNU General
  29 // Public License.
  30
  31 // Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
  32
  33 // Permission to use, copy, modify, sell, and distribute this software
  34 // is hereby granted without fee, provided that the above copyright
  35 // notice appears in all copies, and that both that copyright notice
  36 // and this permission notice appear in supporting documentation. None
  37 // of the above authors, nor IBM Haifa Research Laboratories, make any
  38 // representation about the suitability of this software for any
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  40 // warranty.
  41
  42 /**
  43  * @file counter_lu_metadata.hpp
  44  * Contains implementation of a lu counter policy's metadata.
  45  */
  46
  47 namespace pb_ds
  48 {
  49   namespace detail
  50   {
  51     template<typename Size_Type>
  52     class counter_lu_policy_base;
  53
  54     // A list-update metadata type that moves elements to the front of
  55     // the list based on the counter algorithm.
  56     template<typename Size_Type = size_t>
  57     class counter_lu_metadata
  58     {
  59     public:
  60       typedef Size_Type size_type;
  61
  62     private:
  63       counter_lu_metadata(size_type init_count) : m_count(init_count)
  64       { }
  65
  66       friend class counter_lu_policy_base<size_type>;
  67
  68       mutable size_type m_count;
  69     };
  70
  71     template<typename Size_Type>
  72     class counter_lu_policy_base
  73     {
  74     protected:
  75       typedef Size_Type size_type;
  76
  77       counter_lu_metadata<size_type>
  78       operator()(size_type max_size) const
  79       { return counter_lu_metadata<Size_Type>(std::rand() % max_size); }
  80
  81       template<typename Metadata_Reference>
  82       bool
  83       operator()(Metadata_Reference r_data, size_type m_max_count) const
  84       {
  85         if (++r_data.m_count != m_max_count)
  86           return false;
  87         r_data.m_count = 0;
  88         return true;
  89       }
  90     };
  91   } // namespace detail
  92 } // namespace pb_ds