list_update_policy.hpp
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// -*- C++ -*-
// Copyright (C) 2005-2025 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
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// of the GNU General Public License as published by the Free Software
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// version.
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// Under Section 7 of GPL version 3, you are granted additional
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// 3.1, as published by the Free Software Foundation.
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// a copy of the GCC Runtime Library Exception along with this program;
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// Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
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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/types_traits.hpp>
#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;
public:
/// Reference to metadata on which this functor operates.
typedef typename detail::rebind_traits<_Alloc, metadata_type>::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;
public:
/// Reference to metadata on which this functor operates.
typedef typename detail::rebind_traits<_Alloc, metadata_type>::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
cstdlib
c++config.h
tag_and_trait.hpp
types_traits.hpp
lu_counter_metadata.hpp
__gnu_pbds
GNU extensions for policy-based data structures for public use.
Definition assoc_container.hpp:52
__gnu_pbds::lu_move_to_front_policy
Definition list_update_policy.hpp:59
__gnu_pbds::lu_move_to_front_policy::operator()
bool operator()(metadata_reference r_metadata) const
Decides whether a metadata object should be moved to the front of the list.
Definition list_update_policy.hpp:79
__gnu_pbds::lu_move_to_front_policy::metadata_reference
detail::rebind_traits< _Alloc, metadata_type >::reference metadata_reference
Reference to metadata on which this functor operates.
Definition list_update_policy.hpp:69
__gnu_pbds::lu_move_to_front_policy::metadata_type
null_type metadata_type
Metadata on which this functor operates.
Definition list_update_policy.hpp:64
__gnu_pbds::lu_move_to_front_policy::operator()
metadata_type operator()() const
Creates a metadata object.
Definition list_update_policy.hpp:73
__gnu_pbds::lu_counter_policy
Definition list_update_policy.hpp:93
__gnu_pbds::lu_counter_policy::metadata_reference
detail::rebind_traits< _Alloc, metadata_type >::reference metadata_reference
Reference to metadata on which this functor operates.
Definition list_update_policy.hpp:114
__gnu_pbds::lu_counter_policy::max_count
@ max_count
When some element is accessed this number of times, it will be moved to the front of the list.
Definition list_update_policy.hpp:102
__gnu_pbds::lu_counter_policy::metadata_type
detail::lu_counter_metadata< size_type > metadata_type
Metadata on which this functor operates.
Definition list_update_policy.hpp:106
__gnu_pbds::lu_counter_policy::operator()
metadata_type operator()() const
Creates a metadata object.
Definition list_update_policy.hpp:118
__gnu_pbds::lu_counter_policy::operator()
bool operator()(metadata_reference r_data) const
Decides whether a metadata object should be moved to the front of the list.
Definition list_update_policy.hpp:124
__gnu_pbds::null_type
Represents no type, or absence of type, for template tricks.
Definition tag_and_trait.hpp:210
__gnu_pbds::detail::lu_counter_policy_base
Base class for list-update counter policy.
Definition lu_counter_metadata.hpp:68
__gnu_pbds::detail::lu_counter_metadata
A list-update metadata type that moves elements to the front of the list based on the counter algorit...
Definition lu_counter_metadata.hpp:52