libstdc++
list_update_policy.hpp
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25// Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
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35
36/**
37 * @file list_update_policy.hpp
38 * Contains policies for list update containers.
39 */
40
41#ifndef PB_DS_LU_POLICY_HPP
42#define PB_DS_LU_POLICY_HPP
43
44#include <bits/c++config.h>
45#include <cstdlib>
49
50namespace __gnu_pbds
51{
52 /**
53 * A list-update policy that unconditionally moves elements to the
54 * front of the list. A null type means that each link in a
55 * list-based container does not actually need metadata.
56 */
57 template<typename _Alloc = std::allocator<char> >
59 {
60 public:
61 typedef _Alloc allocator_type;
62
63 /// Metadata on which this functor operates.
65
66 public:
67 /// Reference to metadata on which this functor operates.
68 typedef typename detail::rebind_traits<_Alloc, metadata_type>::reference
70
71 /// Creates a metadata object.
73 operator()() const
74 { return s_metadata; }
75
76 /// Decides whether a metadata object should be moved to the front
77 /// of the list.
78 inline bool
80 { return true; }
81
82 private:
83 static null_type s_metadata;
84 };
85
86 /**
87 * A list-update policy that moves elements to the front of the
88 * list based on the counter algorithm.
89 */
90 template<std::size_t Max_Count = 5, typename _Alloc = std::allocator<char> >
92 : private detail::lu_counter_policy_base<typename _Alloc::size_type>
93 {
94 public:
95 typedef _Alloc allocator_type;
96 typedef typename allocator_type::size_type size_type;
97
98 enum
99 {
100 /// When some element is accessed this number of times, it
101 /// will be moved to the front of the list.
102 max_count = Max_Count
103 };
104
105 /// Metadata on which this functor operates.
107
108 private:
110
111 public:
112 /// Reference to metadata on which this functor operates.
113 typedef typename detail::rebind_traits<_Alloc, metadata_type>::reference
115
116 /// Creates a metadata object.
119 { return base_type::operator()(max_count); }
120
121 /// Decides whether a metadata object should be moved to the front
122 /// of the list.
123 bool
125 { return base_type::operator()(r_data, max_count); }
126 };
127} // namespace __gnu_pbds
128
129#endif
GNU extensions for policy-based data structures for public use.
bool operator()(metadata_reference r_metadata) const
Decides whether a metadata object should be moved to the front of the list.
detail::rebind_traits< _Alloc, metadata_type >::reference metadata_reference
Reference to metadata on which this functor operates.
null_type metadata_type
Metadata on which this functor operates.
metadata_type operator()() const
Creates a metadata object.
detail::rebind_traits< _Alloc, metadata_type >::reference metadata_reference
Reference to metadata on which this functor operates.
@ max_count
When some element is accessed this number of times, it will be moved to the front of the list.
detail::lu_counter_metadata< size_type > metadata_type
Metadata on which this functor operates.
metadata_type operator()() const
Creates a metadata object.
bool operator()(metadata_reference r_data) const
Decides whether a metadata object should be moved to the front of the list.
Represents no type, or absence of type, for template tricks.
Base class for list-update counter policy.
A list-update metadata type that moves elements to the front of the list based on the counter algorit...