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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 | * Ceph - scalable distributed file system | |
5 | * | |
6 | * Copyright (C) 2004-2006 Sage Weil <sage@newdream.net> | |
7 | * | |
8 | * This is free software; you can redistribute it and/or | |
9 | * modify it under the terms of the GNU Lesser General Public | |
10 | * License version 2.1, as published by the Free Software | |
11 | * Foundation. See file COPYING. | |
12 | * | |
13 | */ | |
14 | ||
15 | #ifndef CEPH_SIMPLECACHE_H | |
16 | #define CEPH_SIMPLECACHE_H | |
17 | ||
18 | #include <map> | |
19 | #include <list> | |
20 | #include <memory> | |
21 | #include "common/Mutex.h" | |
22 | #include "common/Cond.h" | |
23 | #include "include/unordered_map.h" | |
24 | ||
25 | template <class K, class V, class C = std::less<K>, class H = std::hash<K> > | |
26 | class SimpleLRU { | |
27 | Mutex lock; | |
28 | size_t max_size; | |
29 | ceph::unordered_map<K, typename list<pair<K, V> >::iterator, H> contents; | |
30 | list<pair<K, V> > lru; | |
31 | map<K, V, C> pinned; | |
32 | ||
33 | void trim_cache() { | |
34 | while (lru.size() > max_size) { | |
35 | contents.erase(lru.back().first); | |
36 | lru.pop_back(); | |
37 | } | |
38 | } | |
39 | ||
40 | void _add(K key, V&& value) { | |
41 | lru.emplace_front(key, std::move(value)); // can't move key because we access it below | |
42 | contents[key] = lru.begin(); | |
43 | trim_cache(); | |
44 | } | |
45 | ||
46 | public: | |
47 | SimpleLRU(size_t max_size) : lock("SimpleLRU::lock"), max_size(max_size) { | |
48 | contents.rehash(max_size); | |
49 | } | |
50 | ||
51 | void pin(K key, V val) { | |
52 | Mutex::Locker l(lock); | |
53 | pinned.emplace(std::move(key), std::move(val)); | |
54 | } | |
55 | ||
56 | void clear_pinned(K e) { | |
57 | Mutex::Locker l(lock); | |
58 | for (typename map<K, V, C>::iterator i = pinned.begin(); | |
59 | i != pinned.end() && i->first <= e; | |
60 | pinned.erase(i++)) { | |
61 | typename ceph::unordered_map<K, typename list<pair<K, V> >::iterator, H>::iterator iter = | |
62 | contents.find(i->first); | |
63 | if (iter == contents.end()) | |
64 | _add(i->first, std::move(i->second)); | |
65 | else | |
66 | lru.splice(lru.begin(), lru, iter->second); | |
67 | } | |
68 | } | |
69 | ||
70 | void clear(K key) { | |
71 | Mutex::Locker l(lock); | |
72 | typename ceph::unordered_map<K, typename list<pair<K, V> >::iterator, H>::iterator i = | |
73 | contents.find(key); | |
74 | if (i == contents.end()) | |
75 | return; | |
76 | lru.erase(i->second); | |
77 | contents.erase(i); | |
78 | } | |
79 | ||
80 | void set_size(size_t new_size) { | |
81 | Mutex::Locker l(lock); | |
82 | max_size = new_size; | |
83 | trim_cache(); | |
84 | } | |
85 | ||
86 | bool lookup(K key, V *out) { | |
87 | Mutex::Locker l(lock); | |
88 | typename ceph::unordered_map<K, typename list<pair<K, V> >::iterator, H>::iterator i = | |
89 | contents.find(key); | |
90 | if (i != contents.end()) { | |
91 | *out = i->second->second; | |
92 | lru.splice(lru.begin(), lru, i->second); | |
93 | return true; | |
94 | } | |
95 | typename map<K, V, C>::iterator i_pinned = pinned.find(key); | |
96 | if (i_pinned != pinned.end()) { | |
97 | *out = i_pinned->second; | |
98 | return true; | |
99 | } | |
100 | return false; | |
101 | } | |
102 | ||
103 | void add(K key, V value) { | |
104 | Mutex::Locker l(lock); | |
105 | _add(std::move(key), std::move(value)); | |
106 | } | |
107 | }; | |
108 | ||
109 | #endif |