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1 | /* |
2 | * This file is part of DisOrder |
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3 | * Copyright (C) 2006-2008 Richard Kettlewell |
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4 | * |
5 | * This program is free software; you can redistribute it and/or modify |
6 | * it under the terms of the GNU General Public License as published by |
7 | * the Free Software Foundation; either version 2 of the License, or |
8 | * (at your option) any later version. |
9 | * |
10 | * This program is distributed in the hope that it will be useful, but |
11 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
13 | * General Public License for more details. |
14 | * |
15 | * You should have received a copy of the GNU General Public License |
16 | * along with this program; if not, write to the Free Software |
17 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 |
18 | * USA |
19 | */ |
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20 | /** @file lib/cache.c @brief Object caching */ |
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21 | |
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22 | #include "common.h" |
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23 | |
24 | #include <time.h> |
25 | |
26 | #include "hash.h" |
27 | #include "mem.h" |
28 | #include "log.h" |
29 | #include "cache.h" |
30 | |
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31 | /** @brief The global cache */ |
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32 | static hash *h; |
33 | |
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34 | /** @brief One cache entry */ |
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35 | struct cache_entry { |
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36 | /** @brief What type of object this is */ |
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37 | const struct cache_type *type; |
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38 | |
39 | /** @brief Pointer to object value */ |
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40 | const void *value; |
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41 | |
42 | /** @brief Time that object was inserted into cache */ |
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43 | time_t birth; |
44 | }; |
45 | |
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46 | /** @brief Return true if object @p c has expired */ |
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47 | static int expired(const struct cache_entry *c, time_t now) { |
48 | return now - c->birth > c->type->lifetime; |
49 | } |
50 | |
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51 | /** @brief Insert an object into the cache |
52 | * @param type Pointer to object type |
53 | * @param key Unique key |
54 | * @param value Pointer to value |
55 | */ |
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56 | void cache_put(const struct cache_type *type, |
57 | const char *key, const void *value) { |
58 | struct cache_entry *c; |
59 | |
60 | if(!h) |
61 | h = hash_new(sizeof (struct cache_entry)); |
62 | c = xmalloc(sizeof *c); |
63 | c->type = type; |
64 | c->value = value; |
65 | time(&c->birth); |
66 | hash_add(h, key, c, HASH_INSERT_OR_REPLACE); |
67 | } |
68 | |
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69 | /** @brief Look up an object in the cache |
70 | * @param type Pointer to object type |
71 | * @param key Unique key |
72 | * @return Pointer to object value or NULL if not found |
73 | */ |
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74 | const void *cache_get(const struct cache_type *type, const char *key) { |
75 | const struct cache_entry *c; |
76 | |
77 | if(h |
78 | && (c = hash_find(h, key)) |
79 | && c->type == type |
80 | && !expired(c, time(0))) |
81 | return c->value; |
82 | else |
83 | return 0; |
84 | } |
85 | |
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86 | /** @brief Call used by from cache_expire() */ |
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87 | static int expiry_callback(const char *key, void *value, void *u) { |
88 | const struct cache_entry *c = value; |
89 | const time_t *now = u; |
90 | |
91 | if(expired(c, *now)) |
92 | hash_remove(h, key); |
93 | return 0; |
94 | } |
95 | |
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96 | /** @brief Expire the cache |
97 | * |
98 | * Called from time to time to expire cache entries. */ |
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99 | void cache_expire(void) { |
100 | time_t now; |
101 | |
102 | if(h) { |
103 | time(&now); |
104 | hash_foreach(h, expiry_callback, &now); |
105 | } |
106 | } |
107 | |
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108 | /** @brief Callback used by cache_clean() */ |
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109 | static int clean_callback(const char *key, void *value, void *u) { |
110 | const struct cache_entry *c = value; |
111 | const struct cache_type *type = u; |
112 | |
113 | if(!type || c->type == type) |
114 | hash_remove(h, key); |
115 | return 0; |
116 | } |
117 | |
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118 | /** @brief Clean the cache |
119 | * @param type Pointer to type to clean |
120 | * |
121 | * Removes all entries of type @p type from the cache. |
122 | */ |
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123 | void cache_clean(const struct cache_type *type) { |
124 | if(h) |
125 | hash_foreach(h, clean_callback, (void *)type); |
126 | } |
127 | |
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128 | /** @brief Report cache size |
129 | * |
130 | * Returns the number of objects in the cache |
131 | */ |
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132 | size_t cache_count(void) { |
133 | return h ? hash_count(h) : 0; |
134 | } |
135 | |
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136 | /* |
137 | Local Variables: |
138 | c-basic-offset:2 |
139 | comment-column:40 |
140 | fill-column:79 |
141 | indent-tabs-mode:nil |
142 | End: |
143 | */ |