list_update_policy.hpp
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// -*- C++ -*-
// Copyright (C) 2005-2013 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the terms
// of the GNU General Public License as published by the Free Software
// Foundation; either version 3, or (at your option) any later
// version.
// This library is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
// Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
// Permission to use, copy, modify, sell, and distribute this software
// is hereby granted without fee, provided that the above copyright
// notice appears in all copies, and that both that copyright notice
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/**
* @file list_update_policy.hpp
* Contains policies for list update containers.
*/
#ifndef PB_DS_LU_POLICY_HPP
#define PB_DS_LU_POLICY_HPP
#include <bits/c++config.h>
#include <cstdlib>
#include <ext/pb_ds/detail/list_update_policy/lu_counter_metadata.hpp>
#include <ext/pb_ds/tag_and_trait.hpp>
namespace __gnu_pbds
{
/**
* A list-update policy that unconditionally moves elements to the
* front of the list. A null type means that each link in a
* list-based container does not actually need metadata.
*/
template<typename _Alloc = std::allocator<char> >
class lu_move_to_front_policy
{
public:
typedef _Alloc allocator_type;
/// Metadata on which this functor operates.
typedef null_type metadata_type;
private:
typedef typename _Alloc::template rebind<metadata_type> __rebind_m;
public:
/// Reference to metadata on which this functor operates.
typedef typename __rebind_m::other::reference metadata_reference;
/// Creates a metadata object.
metadata_type
operator()() const
{ return s_metadata; }
/// Decides whether a metadata object should be moved to the front
/// of the list.
inline bool
operator()(metadata_reference r_metadata) const
{ return true; }
private:
static null_type s_metadata;
};
/**
* A list-update policy that moves elements to the front of the
* list based on the counter algorithm.
*/
template<std::size_t Max_Count = 5, typename _Alloc = std::allocator<char> >
class lu_counter_policy
: private detail::lu_counter_policy_base<typename _Alloc::size_type>
{
public:
typedef _Alloc allocator_type;
typedef typename allocator_type::size_type size_type;
enum
{
/// When some element is accessed this number of times, it
/// will be moved to the front of the list.
max_count = Max_Count
};
/// Metadata on which this functor operates.
typedef detail::lu_counter_metadata<size_type> metadata_type;
private:
typedef detail::lu_counter_policy_base<size_type> base_type;
typedef typename _Alloc::template rebind<metadata_type> __rebind_m;
public:
/// Reference to metadata on which this functor operates.
typedef typename __rebind_m::other::reference metadata_reference;
/// Creates a metadata object.
metadata_type
operator()() const
{ return base_type::operator()(max_count); }
/// Decides whether a metadata object should be moved to the front
/// of the list.
bool
operator()(metadata_reference r_data) const
{ return base_type::operator()(r_data, max_count); }
};
} // namespace __gnu_pbds
#endif