libstdc++
list_update_policy.hpp
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1// -*- C++ -*-
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3// Copyright (C) 2005-2019 Free Software Foundation, Inc.
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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>
48
49namespace __gnu_pbds
50{
51 /**
52 * A list-update policy that unconditionally moves elements to the
53 * front of the list. A null type means that each link in a
54 * list-based container does not actually need metadata.
55 */
56 template<typename _Alloc = std::allocator<char> >
58 {
59 public:
60 typedef _Alloc allocator_type;
61
62 /// Metadata on which this functor operates.
64
65 private:
66 typedef typename _Alloc::template rebind<metadata_type> __rebind_m;
67
68 public:
69 /// Reference to metadata on which this functor operates.
70 typedef typename __rebind_m::other::reference metadata_reference;
71
72 /// Creates a metadata object.
74 operator()() const
75 { return s_metadata; }
76
77 /// Decides whether a metadata object should be moved to the front
78 /// of the list.
79 inline bool
81 { return true; }
82
83 private:
84 static null_type s_metadata;
85 };
86
87 /**
88 * A list-update policy that moves elements to the front of the
89 * list based on the counter algorithm.
90 */
91 template<std::size_t Max_Count = 5, typename _Alloc = std::allocator<char> >
93 : private detail::lu_counter_policy_base<typename _Alloc::size_type>
94 {
95 public:
96 typedef _Alloc allocator_type;
97 typedef typename allocator_type::size_type size_type;
98
99 enum
100 {
101 /// When some element is accessed this number of times, it
102 /// will be moved to the front of the list.
103 max_count = Max_Count
104 };
105
106 /// Metadata on which this functor operates.
108
109 private:
111 typedef typename _Alloc::template rebind<metadata_type> __rebind_m;
112
113 public:
114 /// Reference to metadata on which this functor operates.
115 typedef typename __rebind_m::other::reference metadata_reference;
116
117 /// Creates a metadata object.
120 { return base_type::operator()(max_count); }
121
122 /// Decides whether a metadata object should be moved to the front
123 /// of the list.
124 bool
126 { return base_type::operator()(r_data, max_count); }
127 };
128} // namespace __gnu_pbds
129
130#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.
__rebind_m::other::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.
__rebind_m::other::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...