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>
48 
49 namespace __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
80  operator()(metadata_reference r_metadata) const
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.
119  operator()() const
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
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.
Base class for list-update counter policy.
GNU extensions for policy-based data structures for public use.
__rebind_m::other::reference metadata_reference
Reference to metadata on which this functor operates.
__rebind_m::other::reference metadata_reference
Reference to metadata on which this functor operates.
When some element is accessed this number of times, it will be moved to the front of the list.
null_type metadata_type
Metadata on which this functor operates.
bool operator()(metadata_reference r_metadata) 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.
metadata_type operator()() const
Creates a metadata object.
A list-update metadata type that moves elements to the front of the list based on the counter algorit...
detail::lu_counter_metadata< size_type > metadata_type
Metadata on which this functor operates.