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Memory management for hands-off reader
[disorder] / lib / cache.c
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460b9539 1/*
2 * This file is part of DisOrder
5aff007d 3 * Copyright (C) 2006-2008 Richard Kettlewell
460b9539 4 *
e7eb3a27 5 * This program is free software: you can redistribute it and/or modify
460b9539 6 * it under the terms of the GNU General Public License as published by
e7eb3a27 7 * the Free Software Foundation, either version 3 of the License, or
460b9539 8 * (at your option) any later version.
e7eb3a27
RK
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
460b9539 15 * You should have received a copy of the GNU General Public License
e7eb3a27 16 * along with this program. If not, see <http://www.gnu.org/licenses/>.
460b9539 17 */
14ad73b9 18/** @file lib/cache.c @brief Object caching */
460b9539 19
05b75f8d 20#include "common.h"
460b9539 21
22#include <time.h>
23
24#include "hash.h"
25#include "mem.h"
26#include "log.h"
4265e5d3 27#include "syscalls.h"
460b9539 28#include "cache.h"
29
d7b6f0d1 30/** @brief The global cache */
460b9539 31static hash *h;
32
d7b6f0d1 33/** @brief One cache entry */
460b9539 34struct cache_entry {
d7b6f0d1 35 /** @brief What type of object this is */
460b9539 36 const struct cache_type *type;
d7b6f0d1 37
38 /** @brief Pointer to object value */
460b9539 39 const void *value;
d7b6f0d1 40
41 /** @brief Time that object was inserted into cache */
460b9539 42 time_t birth;
43};
44
d7b6f0d1 45/** @brief Return true if object @p c has expired */
460b9539 46static int expired(const struct cache_entry *c, time_t now) {
47 return now - c->birth > c->type->lifetime;
48}
49
d7b6f0d1 50/** @brief Insert an object into the cache
51 * @param type Pointer to object type
52 * @param key Unique key
53 * @param value Pointer to value
54 */
460b9539 55void cache_put(const struct cache_type *type,
56 const char *key, const void *value) {
57 struct cache_entry *c;
58
59 if(!h)
60 h = hash_new(sizeof (struct cache_entry));
61 c = xmalloc(sizeof *c);
62 c->type = type;
63 c->value = value;
4265e5d3 64 xtime(&c->birth);
460b9539 65 hash_add(h, key, c, HASH_INSERT_OR_REPLACE);
66}
67
d7b6f0d1 68/** @brief Look up an object in the cache
69 * @param type Pointer to object type
70 * @param key Unique key
71 * @return Pointer to object value or NULL if not found
72 */
460b9539 73const void *cache_get(const struct cache_type *type, const char *key) {
74 const struct cache_entry *c;
75
76 if(h
77 && (c = hash_find(h, key))
78 && c->type == type
4265e5d3 79 && !expired(c, xtime(0)))
460b9539 80 return c->value;
81 else
82 return 0;
83}
84
0e4472a0 85/** @brief Call used by from cache_expire() */
460b9539 86static int expiry_callback(const char *key, void *value, void *u) {
87 const struct cache_entry *c = value;
88 const time_t *now = u;
89
90 if(expired(c, *now))
91 hash_remove(h, key);
92 return 0;
93}
94
d7b6f0d1 95/** @brief Expire the cache
96 *
97 * Called from time to time to expire cache entries. */
460b9539 98void cache_expire(void) {
99 time_t now;
100
101 if(h) {
4265e5d3 102 xtime(&now);
460b9539 103 hash_foreach(h, expiry_callback, &now);
104 }
105}
106
0e4472a0 107/** @brief Callback used by cache_clean() */
460b9539 108static int clean_callback(const char *key, void *value, void *u) {
109 const struct cache_entry *c = value;
110 const struct cache_type *type = u;
111
112 if(!type || c->type == type)
113 hash_remove(h, key);
114 return 0;
115}
116
d7b6f0d1 117/** @brief Clean the cache
118 * @param type Pointer to type to clean
119 *
120 * Removes all entries of type @p type from the cache.
121 */
460b9539 122void cache_clean(const struct cache_type *type) {
123 if(h)
124 hash_foreach(h, clean_callback, (void *)type);
125}
126
d7b6f0d1 127/** @brief Report cache size
128 *
129 * Returns the number of objects in the cache
130 */
0b7c8909 131size_t cache_count(void) {
132 return h ? hash_count(h) : 0;
133}
134
460b9539 135/*
136Local Variables:
137c-basic-offset:2
138comment-column:40
139fill-column:79
140indent-tabs-mode:nil
141End:
142*/