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 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  */
  20 /** @file lib/cache.c @brief Object caching */
  21
  22 #include "common.h"
  23
  24 #include <time.h>
  25
  26 #include "hash.h"
  27 #include "mem.h"
  28 #include "log.h"
  29 #include "cache.h"
  30
  31 /** @brief The global cache */
  32 static hash *h;
  33
  34 /** @brief One cache entry */
  35 struct cache_entry {
  36   /** @brief What type of object this is */
  37   const struct cache_type *type;
  38
  39   /** @brief Pointer to object value */
  40   const void *value;
  41
  42   /** @brief Time that object was inserted into cache */
  43   time_t birth;
  44 };
  45
  46 /** @brief Return true if object @p c has expired */
  47 static int expired(const struct cache_entry *c, time_t now) {
  48   return now - c->birth > c->type->lifetime;
  49 }
  50
  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  */
  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
  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  */
  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
  86 /** @brief Call used by from cache_expire() */
  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
  96 /** @brief Expire the cache
  97  *
  98  * Called from time to time to expire cache entries. */
  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
 108 /** @brief Callback used by cache_clean() */
 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
 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  */
 123 void cache_clean(const struct cache_type *type) {
 124   if(h)
 125     hash_foreach(h, clean_callback, (void *)type);
 126 }
 127
 128 /** @brief Report cache size
 129  *
 130  * Returns the number of objects in the cache
 131  */
 132 size_t cache_count(void) {
 133   return h ? hash_count(h) : 0;
 134 }
 135
 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 */