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1 | // -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*- |
2 | // vim: ts=8 sw=2 smarttab | |
3 | ||
4 | #pragma once | |
5 | ||
6 | #include <functional> | |
7 | #include <boost/intrusive/list.hpp> | |
8 | #include <boost/intrusive/unordered_set.hpp> | |
9 | #include "include/encoding.h" | |
10 | ||
11 | /// Combination of an LRU with fast hash-based membership lookup | |
12 | template<class T, int NUM_BUCKETS=128> | |
13 | class LRUSet { | |
14 | /// internal node | |
15 | struct Node | |
16 | : boost::intrusive::unordered_set_base_hook<> { | |
17 | // actual payload | |
18 | T value; | |
19 | ||
20 | // for the lru | |
21 | boost::intrusive::list_member_hook<> lru_item; | |
22 | ||
23 | Node(const T& v) : value(v) {} | |
24 | ||
25 | friend std::size_t hash_value(const Node &node) { | |
26 | return std::hash<T>{}(node.value); | |
27 | } | |
28 | friend bool operator<(const Node &a, const Node &b) { | |
29 | return a.value < b.value; | |
30 | } | |
31 | friend bool operator>(const Node &a, const Node &b) { | |
32 | return a.value > b.value; | |
33 | } | |
34 | friend bool operator==(const Node &a, const Node &b) { | |
35 | return a.value == b.value; | |
36 | } | |
37 | }; | |
38 | ||
39 | struct NodeDeleteDisposer { | |
40 | void operator()(Node *n) { delete n; } | |
41 | }; | |
42 | ||
43 | // lru | |
44 | boost::intrusive::list< | |
45 | Node, | |
46 | boost::intrusive::member_hook<Node, | |
47 | boost::intrusive::list_member_hook<>, | |
48 | &Node::lru_item> | |
49 | > lru; | |
50 | ||
51 | // hash-based set | |
52 | typename boost::intrusive::unordered_set<Node>::bucket_type base_buckets[NUM_BUCKETS]; | |
53 | boost::intrusive::unordered_set<Node> set; | |
54 | ||
55 | public: | |
56 | LRUSet() | |
57 | : set(typename boost::intrusive::unordered_set<Node>::bucket_traits(base_buckets, | |
58 | NUM_BUCKETS)) | |
59 | {} | |
60 | ~LRUSet() { | |
61 | clear(); | |
62 | } | |
63 | ||
64 | LRUSet(const LRUSet& other) | |
65 | : set(typename boost::intrusive::unordered_set<Node>::bucket_traits(base_buckets, | |
66 | NUM_BUCKETS)) { | |
67 | for (auto & i : other.lru) { | |
68 | insert(i.value); | |
69 | } | |
70 | } | |
71 | const LRUSet& operator=(const LRUSet& other) { | |
72 | clear(); | |
73 | for (auto& i : other.lru) { | |
74 | insert(i.value); | |
75 | } | |
76 | return *this; | |
77 | } | |
78 | ||
79 | size_t size() const { | |
80 | return set.size(); | |
81 | } | |
82 | ||
83 | bool empty() const { | |
84 | return set.empty(); | |
85 | } | |
86 | ||
87 | bool contains(const T& item) const { | |
88 | return set.count(item) > 0; | |
89 | } | |
90 | ||
91 | void clear() { | |
92 | prune(0); | |
93 | } | |
94 | ||
95 | void insert(const T& item) { | |
96 | erase(item); | |
97 | Node *n = new Node(item); | |
98 | lru.push_back(*n); | |
99 | set.insert(*n); | |
100 | } | |
101 | ||
102 | bool erase(const T& item) { | |
103 | auto p = set.find(item); | |
104 | if (p == set.end()) { | |
105 | return false; | |
106 | } | |
107 | lru.erase(lru.iterator_to(*p)); | |
108 | set.erase_and_dispose(p, NodeDeleteDisposer()); | |
109 | return true; | |
110 | } | |
111 | ||
112 | void prune(size_t max) { | |
113 | while (set.size() > max) { | |
114 | auto p = lru.begin(); | |
115 | set.erase(*p); | |
116 | lru.erase_and_dispose(p, NodeDeleteDisposer()); | |
117 | } | |
118 | } | |
119 | ||
120 | void encode(bufferlist& bl) const { | |
121 | using ceph::encode; | |
122 | ENCODE_START(1, 1, bl); | |
123 | uint32_t n = set.size(); | |
124 | encode(n, bl); | |
125 | auto p = set.begin(); | |
126 | while (n--) { | |
127 | encode(p->value, bl); | |
128 | ++p; | |
129 | } | |
130 | ENCODE_FINISH(bl); | |
131 | } | |
132 | ||
133 | void decode(bufferlist::const_iterator& p) { | |
134 | using ceph::decode; | |
135 | DECODE_START(1, p); | |
136 | uint32_t n; | |
137 | decode(n, p); | |
138 | while (n--) { | |
139 | T v; | |
140 | decode(v, p); | |
141 | insert(v); | |
142 | } | |
143 | DECODE_FINISH(p); | |
144 | } | |
145 | }; |