mdw@git.distorted.org.uk Git - disorder/blob - lib/cache.c

   1 /*
   2  * This file is part of DisOrder
   3  * Copyright (C) 2006-2008 Richard Kettlewell
   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 3 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,
  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  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17  */
  18 /** @file lib/cache.c @brief Object caching */
  19
  20 #include "common.h"
  21
  22 #include <time.h>
  23
  24 #include "hash.h"
  25 #include "mem.h"
  26 #include "log.h"
  27 #include "cache.h"
  28
  29 /** @brief The global cache */
  30 static hash *h;
  31
  32 /** @brief One cache entry */
  33 struct cache_entry {
  34   /** @brief What type of object this is */
  35   const struct cache_type *type;
  36
  37   /** @brief Pointer to object value */
  38   const void *value;
  39
  40   /** @brief Time that object was inserted into cache */
  41   time_t birth;
  42 };
  43
  44 /** @brief Return true if object @p c has expired */
  45 static int expired(const struct cache_entry *c, time_t now) {
  46   return now - c->birth > c->type->lifetime;
  47 }
  48
  49 /** @brief Insert an object into the cache
  50  * @param type Pointer to object type
  51  * @param key Unique key
  52  * @param value Pointer to value
  53  */
  54 void cache_put(const struct cache_type *type,
  55                const char *key, const void *value) {
  56   struct cache_entry *c;
  57
  58   if(!h)
  59     h = hash_new(sizeof (struct cache_entry));
  60   c = xmalloc(sizeof *c);
  61   c->type = type;
  62   c->value = value;
  63   time(&c->birth);
  64   hash_add(h, key, c,  HASH_INSERT_OR_REPLACE);
  65 }
  66
  67 /** @brief Look up an object in the cache
  68  * @param type Pointer to object type
  69  * @param key Unique key
  70  * @return Pointer to object value or NULL if not found
  71  */
  72 const void *cache_get(const struct cache_type *type, const char *key) {
  73   const struct cache_entry *c;
  74
  75   if(h
  76      && (c = hash_find(h, key))
  77      && c->type == type
  78      && !expired(c, time(0)))
  79     return c->value;
  80   else
  81     return 0;
  82 }
  83
  84 /** @brief Call used by from cache_expire() */
  85 static int expiry_callback(const char *key, void *value, void *u) {
  86   const struct cache_entry *c = value;
  87   const time_t *now = u;
  88
  89   if(expired(c, *now))
  90     hash_remove(h, key);
  91   return 0;
  92 }
  93
  94 /** @brief Expire the cache
  95  *
  96  * Called from time to time to expire cache entries. */
  97 void cache_expire(void) {
  98   time_t now;
  99
 100   if(h) {
 101     time(&now);
 102     hash_foreach(h, expiry_callback, &now);
 103   }
 104 }
 105
 106 /** @brief Callback used by cache_clean() */
 107 static int clean_callback(const char *key, void *value, void *u) {
 108   const struct cache_entry *c = value;
 109   const struct cache_type *type = u;
 110
 111   if(!type || c->type == type)
 112     hash_remove(h, key);
 113   return 0;
 114 }
 115
 116 /** @brief Clean the cache
 117  * @param type Pointer to type to clean
 118  *
 119  * Removes all entries of type @p type from the cache.
 120  */
 121 void cache_clean(const struct cache_type *type) {
 122   if(h)
 123     hash_foreach(h, clean_callback, (void *)type);
 124 }
 125
 126 /** @brief Report cache size
 127  *
 128  * Returns the number of objects in the cache
 129  */
 130 size_t cache_count(void) {
 131   return h ? hash_count(h) : 0;
 132 }
 133
 134 /*
 135 Local Variables:
 136 c-basic-offset:2
 137 comment-column:40
 138 fill-column:79
 139 indent-tabs-mode:nil
 140 End:
 141 */