libstdc++
list_update_policy.hpp
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3 // Copyright (C) 2005, 2006, 2007, 2009 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 <cstdlib>
45 #include <ext/pb_ds/detail/list_update_policy/counter_lu_metadata.hpp>
46 
47 namespace __gnu_pbds
48 {
49  // A null type that means that each link in a list-based container
50  // does not actually need metadata.
51  struct null_lu_metadata
52  { };
53 
54 #define PB_DS_CLASS_T_DEC template<typename Allocator>
55 #define PB_DS_CLASS_C_DEC move_to_front_lu_policy<Allocator>
56 
57  // A list-update policy that unconditionally moves elements to the
58  // front of the list.
59  template<typename Allocator = std::allocator<char> >
60  class move_to_front_lu_policy
61  {
62  public:
63  typedef Allocator allocator_type;
64 
65  // Metadata on which this functor operates.
66  typedef null_lu_metadata metadata_type;
67 
68  // Reference to metadata on which this functor operates.
69  typedef typename allocator_type::template rebind<metadata_type>::other metadata_rebind;
70  typedef typename metadata_rebind::reference metadata_reference;
71 
72  // Creates a metadata object.
73  metadata_type
74  operator()() const;
75 
76  // Decides whether a metadata object should be moved to the front
77  // of the list.
78  inline bool
79  operator()(metadata_reference r_metadata) const;
80 
81  private:
82  static null_lu_metadata s_metadata;
83  };
84 
85 #include <ext/pb_ds/detail/list_update_policy/mtf_lu_policy_imp.hpp>
86 
87 #undef PB_DS_CLASS_T_DEC
88 #undef PB_DS_CLASS_C_DEC
89 
90 #define PB_DS_CLASS_T_DEC template<size_t Max_Count, class Allocator>
91 #define PB_DS_CLASS_C_DEC counter_lu_policy<Max_Count, Allocator>
92 
93  // A list-update policy that moves elements to the front of the list
94  // based on the counter algorithm.
95  template<size_t Max_Count = 5, typename Allocator = std::allocator<char> >
96  class counter_lu_policy
97  : private detail::counter_lu_policy_base<typename Allocator::size_type>
98  {
99  public:
100  typedef Allocator allocator_type;
101 
102  enum
103  {
104  max_count = Max_Count
105  };
106 
107  typedef typename allocator_type::size_type size_type;
108 
109  // Metadata on which this functor operates.
110  typedef detail::counter_lu_metadata<size_type> metadata_type;
111 
112  // Reference to metadata on which this functor operates.
113  typedef typename Allocator::template rebind<metadata_type>::other metadata_rebind;
114  typedef typename metadata_rebind::reference metadata_reference;
115 
116  // Creates a metadata object.
117  metadata_type
118  operator()() const;
119 
120  // Decides whether a metadata object should be moved to the front
121  // of the list.
122  bool
123  operator()(metadata_reference r_metadata) const;
124 
125  private:
126  typedef detail::counter_lu_policy_base<typename Allocator::size_type> base_type;
127  };
128 
129 #include <ext/pb_ds/detail/list_update_policy/counter_lu_policy_imp.hpp>
130 
131 #undef PB_DS_CLASS_T_DEC
132 #undef PB_DS_CLASS_C_DEC
133 
134 } // namespace __gnu_pbds
135 
136 #endif