// -*- C++ -*-
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// Copyright (C) 2005-2020 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the terms
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// of the GNU General Public License as published by the Free Software
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// Foundation; either version 3, or (at your option) any later
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// version.
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// This library is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// General Public License for more details.
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// Under Section 7 of GPL version 3, you are granted additional
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// permissions described in the GCC Runtime Library Exception, version
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// 3.1, as published by the Free Software Foundation.
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// You should have received a copy of the GNU General Public License and
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// a copy of the GCC Runtime Library Exception along with this program;
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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// <http://www.gnu.org/licenses/>.
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// Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
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// Permission to use, copy, modify, sell, and distribute this software
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// is hereby granted without fee, provided that the above copyright
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// notice appears in all copies, and that both that copyright notice
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// and this permission notice appear in supporting documentation. None
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// of the above authors, nor IBM Haifa Research Laboratories, make any
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// representation about the suitability of this software for any
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// purpose. It is provided "as is" without express or implied
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// warranty.
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/**
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* @file list_update_policy.hpp
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* Contains policies for list update containers.
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*/
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#ifndef PB_DS_LU_POLICY_HPP
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#define PB_DS_LU_POLICY_HPP
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#include <bits/c++config.h>
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#include <cstdlib>
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#include <ext/pb_ds/detail/types_traits.hpp>
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#include <ext/pb_ds/detail/list_update_policy/lu_counter_metadata.hpp>
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#include <ext/pb_ds/tag_and_trait.hpp>
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namespace __gnu_pbds
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{
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/**
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* A list-update policy that unconditionally moves elements to the
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* front of the list. A null type means that each link in a
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* list-based container does not actually need metadata.
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*/
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template<typename _Alloc = std::allocator<char> >
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class lu_move_to_front_policy
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{
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public:
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typedef _Alloc allocator_type;
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/// Metadata on which this functor operates.
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typedef null_type metadata_type;
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public:
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/// Reference to metadata on which this functor operates.
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typedef typename detail::rebind_traits<_Alloc, metadata_type>::reference
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metadata_reference;
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/// Creates a metadata object.
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metadata_type
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operator()() const
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{ return s_metadata; }
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/// Decides whether a metadata object should be moved to the front
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/// of the list.
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inline bool
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operator()(metadata_reference r_metadata) const
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{ return true; }
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private:
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static null_type s_metadata;
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};
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/**
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* A list-update policy that moves elements to the front of the
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* list based on the counter algorithm.
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*/
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template<std::size_t Max_Count = 5, typename _Alloc = std::allocator<char> >
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class lu_counter_policy
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: private detail::lu_counter_policy_base<typename _Alloc::size_type>
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{
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public:
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typedef _Alloc allocator_type;
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typedef typename allocator_type::size_type size_type;
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enum
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{
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/// When some element is accessed this number of times, it
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/// will be moved to the front of the list.
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max_count = Max_Count
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};
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/// Metadata on which this functor operates.
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typedef detail::lu_counter_metadata<size_type> metadata_type;
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private:
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typedef detail::lu_counter_policy_base<size_type> base_type;
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public:
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/// Reference to metadata on which this functor operates.
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typedef typename detail::rebind_traits<_Alloc, metadata_type>::reference
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metadata_reference;
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/// Creates a metadata object.
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metadata_type
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operator()() const
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{ return base_type::operator()(max_count); }
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/// Decides whether a metadata object should be moved to the front
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/// of the list.
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bool
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operator()(metadata_reference r_data) const
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{ return base_type::operator()(r_data, max_count); }
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};
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} // namespace __gnu_pbds
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#endif
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