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 <config.h>
  23 #include "types.h"
  24
  25 #include <time.h>
  26
  27 #include "hash.h"
  28 #include "mem.h"
  29 #include "log.h"
  30 #include "cache.h"
  31
  32 /** @brief The global cache */
  33 static hash *h;
  34
  35 /** @brief One cache entry */
  36 struct cache_entry {
  37   /** @brief What type of object this is */
  38   const struct cache_type *type;
  39
  40   /** @brief Pointer to object value */
  41   const void *value;
  42
  43   /** @brief Time that object was inserted into cache */
  44   time_t birth;
  45 };
  46
  47 /** @brief Return true if object @p c has expired */
  48 static int expired(const struct cache_entry *c, time_t now) {
  49   return now - c->birth > c->type->lifetime;
  50 }
  51
  52 /** @brief Insert an object into the cache
  53  * @param type Pointer to object type
  54  * @param key Unique key
  55  * @param value Pointer to value
  56  */
  57 void cache_put(const struct cache_type *type,
  58                const char *key, const void *value) {
  59   struct cache_entry *c;
  60
  61   if(!h)
  62     h = hash_new(sizeof (struct cache_entry));
  63   c = xmalloc(sizeof *c);
  64   c->type = type;
  65   c->value = value;
  66   time(&c->birth);
  67   hash_add(h, key, c,  HASH_INSERT_OR_REPLACE);
  68 }
  69
  70 /** @brief Look up an object in the cache
  71  * @param type Pointer to object type
  72  * @param key Unique key
  73  * @return Pointer to object value or NULL if not found
  74  */
  75 const void *cache_get(const struct cache_type *type, const char *key) {
  76   const struct cache_entry *c;
  77
  78   if(h
  79      && (c = hash_find(h, key))
  80      && c->type == type
  81      && !expired(c, time(0)))
  82     return c->value;
  83   else
  84     return 0;
  85 }
  86
  87 /** @brief Call used by from cache_expire() */
  88 static int expiry_callback(const char *key, void *value, void *u) {
  89   const struct cache_entry *c = value;
  90   const time_t *now = u;
  91
  92   if(expired(c, *now))
  93     hash_remove(h, key);
  94   return 0;
  95 }
  96
  97 /** @brief Expire the cache
  98  *
  99  * Called from time to time to expire cache entries. */
 100 void cache_expire(void) {
 101   time_t now;
 102
 103   if(h) {
 104     time(&now);
 105     hash_foreach(h, expiry_callback, &now);
 106   }
 107 }
 108
 109 /** @brief Callback used by cache_clean() */
 110 static int clean_callback(const char *key, void *value, void *u) {
 111   const struct cache_entry *c = value;
 112   const struct cache_type *type = u;
 113
 114   if(!type || c->type == type)
 115     hash_remove(h, key);
 116   return 0;
 117 }
 118
 119 /** @brief Clean the cache
 120  * @param type Pointer to type to clean
 121  *
 122  * Removes all entries of type @p type from the cache.
 123  */
 124 void cache_clean(const struct cache_type *type) {
 125   if(h)
 126     hash_foreach(h, clean_callback, (void *)type);
 127 }
 128
 129 /** @brief Report cache size
 130  *
 131  * Returns the number of objects in the cache
 132  */
 133 size_t cache_count(void) {
 134   return h ? hash_count(h) : 0;
 135 }
 136
 137 /*
 138 Local Variables:
 139 c-basic-offset:2
 140 comment-column:40
 141 fill-column:79
 142 indent-tabs-mode:nil
 143 End:
 144 */