glib/gcache.c

   1 /* GLIB - Library of useful routines for C programming
   2  * Copyright (C) 1995-1997  Peter Mattis, Spencer Kimball and Josh MacDonald
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Lesser General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Lesser General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public
  15  * License along with this library; if not, write to the
  16  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17  * Boston, MA 02111-1307, USA.
  18  */
  19
  20 /*
  21  * Modified by the GLib Team and others 1997-2000.  See the AUTHORS
  22  * file for a list of people on the GLib Team.  See the ChangeLog
  23  * files for a list of changes.  These files are distributed with
  24  * GLib at ftp://ftp.gtk.org/pub/gtk/.
  25  */
  26
  27 /*
  28  * MT safe
  29  */
  30
  31 #include "config.h"
  32
  33 #include "glib.h"
  34 #include "galias.h"
  35
  36 /**
  37  * SECTION: caches
  38  * @title: Caches
  39  * @short_description: caches allow sharing of complex data structures
  40  *                     to save resources
  41  *
  42  * A #GCache allows sharing of complex data structures, in order to
  43  * save system resources.
  44  *
  45  * GTK+ uses caches for #GtkStyles and #GdkGCs. These consume a lot of
  46  * resources, so a #GCache is used to see if a #GtkStyle or #GdkGC with
  47  * the required properties already exists. If it does, then the
  48  * existing object is used instead of creating a new one.
  49  *
  50  * #GCache uses keys and values. A #GCache key describes the properties
  51  * of a particular resource. A #GCache value is the actual resource.
  52  **/
  53
  54 typedef struct _GCacheNode  GCacheNode;
  55
  56 struct _GCacheNode
  57 {
  58   /* A reference counted node */
  59   gpointer value;
  60   gint ref_count;
  61 };
  62
  63 /**
  64  * GCache:
  65  *
  66  * The #GCache struct is an opaque data structure containing
  67  * information about a #GCache. It should only be accessed via the
  68  * following functions.
  69  **/
  70 struct _GCache
  71 {
  72   /* Called to create a value from a key */
  73   GCacheNewFunc value_new_func;
  74
  75   /* Called to destroy a value */
  76   GCacheDestroyFunc value_destroy_func;
  77
  78   /* Called to duplicate a key */
  79   GCacheDupFunc key_dup_func;
  80
  81   /* Called to destroy a key */
  82   GCacheDestroyFunc key_destroy_func;
  83
  84   /* Associates keys with nodes */
  85   GHashTable *key_table;
  86
  87   /* Associates nodes with keys */
  88   GHashTable *value_table;
  89 };
  90
  91 static inline GCacheNode*
  92 g_cache_node_new (gpointer value)
  93 {
  94   GCacheNode *node = g_slice_new (GCacheNode);
  95   node->value = value;
  96   node->ref_count = 1;
  97   return node;
  98 }
  99
 100 static inline void
 101 g_cache_node_destroy (GCacheNode *node)
 102 {
 103   g_slice_free (GCacheNode, node);
 104 }
 105
 106 /**
 107  * g_cache_new:
 108  * @value_new_func: a function to create a new object given a key.
 109  *                  This is called by g_cache_insert() if an object
 110  *                  with the given key does not already exist.
 111  * @value_destroy_func: a function to destroy an object. It is called
 112  *                      by g_cache_remove() when the object is no
 113  *                      longer needed (i.e. its reference count drops
 114  *                      to 0).
 115  * @key_dup_func: a function to copy a key. It is called by
 116  *                g_cache_insert() if the key does not already exist in
 117  *                the #GCache.
 118  * @key_destroy_func: a function to destroy a key. It is called by
 119  *                    g_cache_remove() when the object is no longer
 120  *                    needed (i.e. its reference count drops to 0).
 121  * @hash_key_func: a function to create a hash value from a key.
 122  * @hash_value_func: a function to create a hash value from a value.
 123  * @key_equal_func: a function to compare two keys. It should return
 124  *                  %TRUE if the two keys are equivalent.
 125  * @Returns: a new #GCache.
 126  *
 127  * Creates a new #GCache.
 128  **/
 129 /**
 130  * GCacheNewFunc:
 131  * @key: a #GCache key.
 132  * @Returns: a new #GCache value corresponding to the key.
 133  *
 134  * Specifies the type of the @value_new_func function passed to
 135  * g_cache_new(). It is passed a #GCache key and should create the
 136  * value corresponding to the key.
 137  **/
 138 /**
 139  * GCacheDestroyFunc:
 140  * @value: the #GCache value to destroy.
 141  *
 142  * Specifies the type of the @value_destroy_func and @key_destroy_func
 143  * functions passed to g_cache_new(). The functions are passed a
 144  * pointer to the #GCache key or #GCache value and should free any
 145  * memory and other resources associated with it.
 146  **/
 147 /**
 148  * GCacheDupFunc:
 149  * @value: the #GCache key to destroy (<emphasis>not</emphasis> a
 150  *         #GCache value as it seems).
 151  * @Returns: a copy of the #GCache key.
 152  *
 153  * Specifies the type of the @key_dup_func function passed to
 154  * g_cache_new(). The function is passed a key
 155  * (<emphasis>not</emphasis> a value as the prototype implies) and
 156  * should return a duplicate of the key.
 157  **/
 158 GCache*
 159 g_cache_new (GCacheNewFunc      value_new_func,
 160              GCacheDestroyFunc  value_destroy_func,
 161              GCacheDupFunc      key_dup_func,
 162              GCacheDestroyFunc  key_destroy_func,
 163              GHashFunc          hash_key_func,
 164              GHashFunc          hash_value_func,
 165              GEqualFunc         key_equal_func)
 166 {
 167   GCache *cache;
 168
 169   g_return_val_if_fail (value_new_func != NULL, NULL);
 170   g_return_val_if_fail (value_destroy_func != NULL, NULL);
 171   g_return_val_if_fail (key_dup_func != NULL, NULL);
 172   g_return_val_if_fail (key_destroy_func != NULL, NULL);
 173   g_return_val_if_fail (hash_key_func != NULL, NULL);
 174   g_return_val_if_fail (hash_value_func != NULL, NULL);
 175   g_return_val_if_fail (key_equal_func != NULL, NULL);
 176
 177   cache = g_slice_new (GCache);
 178   cache->value_new_func = value_new_func;
 179   cache->value_destroy_func = value_destroy_func;
 180   cache->key_dup_func = key_dup_func;
 181   cache->key_destroy_func = key_destroy_func;
 182   cache->key_table = g_hash_table_new (hash_key_func, key_equal_func);
 183   cache->value_table = g_hash_table_new (hash_value_func, NULL);
 184
 185   return cache;
 186 }
 187
 188 /**
 189  * g_cache_destroy:
 190  * @cache: a #GCache.
 191  *
 192  * Frees the memory allocated for the #GCache.
 193  *
 194  * Note that it does not destroy the keys and values which were
 195  * contained in the #GCache.
 196  **/
 197 void
 198 g_cache_destroy (GCache *cache)
 199 {
 200   g_return_if_fail (cache != NULL);
 201
 202   g_hash_table_destroy (cache->key_table);
 203   g_hash_table_destroy (cache->value_table);
 204   g_slice_free (GCache, cache);
 205 }
 206
 207 /**
 208  * g_cache_insert:
 209  * @cache: a #GCache.
 210  * @key: a key describing a #GCache object.
 211  * @Returns: a pointer to a #GCache value.
 212  *
 213  * Gets the value corresponding to the given key, creating it if
 214  * necessary. It first checks if the value already exists in the
 215  * #GCache, by using the @key_equal_func function passed to
 216  * g_cache_new(). If it does already exist it is returned, and its
 217  * reference count is increased by one. If the value does not currently
 218  * exist, if is created by calling the @value_new_func. The key is
 219  * duplicated by calling @key_dup_func and the duplicated key and value
 220  * are inserted into the #GCache.
 221  **/
 222 gpointer
 223 g_cache_insert (GCache   *cache,
 224                 gpointer  key)
 225 {
 226   GCacheNode *node;
 227   gpointer value;
 228
 229   g_return_val_if_fail (cache != NULL, NULL);
 230
 231   node = g_hash_table_lookup (cache->key_table, key);
 232   if (node)
 233     {
 234       node->ref_count += 1;
 235       return node->value;
 236     }
 237
 238   key = (* cache->key_dup_func) (key);
 239   value = (* cache->value_new_func) (key);
 240   node = g_cache_node_new (value);
 241
 242   g_hash_table_insert (cache->key_table, key, node);
 243   g_hash_table_insert (cache->value_table, value, key);
 244
 245   return node->value;
 246 }
 247
 248 /**
 249  * g_cache_remove:
 250  * @cache: a #GCache.
 251  * @value: the value to remove.
 252  *
 253  * Decreases the reference count of the given value. If it drops to 0
 254  * then the value and its corresponding key are destroyed, using the
 255  * @value_destroy_func and @key_destroy_func passed to g_cache_new().
 256  **/
 257 void
 258 g_cache_remove (GCache        *cache,
 259                 gconstpointer  value)
 260 {
 261   GCacheNode *node;
 262   gpointer key;
 263
 264   g_return_if_fail (cache != NULL);
 265
 266   key = g_hash_table_lookup (cache->value_table, value);
 267   node = g_hash_table_lookup (cache->key_table, key);
 268
 269   g_return_if_fail (node != NULL);
 270
 271   node->ref_count -= 1;
 272   if (node->ref_count == 0)
 273     {
 274       g_hash_table_remove (cache->value_table, value);
 275       g_hash_table_remove (cache->key_table, key);
 276
 277       (* cache->key_destroy_func) (key);
 278       (* cache->value_destroy_func) (node->value);
 279       g_cache_node_destroy (node);
 280     }
 281 }
 282
 283 /**
 284  * g_cache_key_foreach:
 285  * @cache: a #GCache.
 286  * @func: the function to call with each #GCache key.
 287  * @user_data: user data to pass to the function.
 288  *
 289  * Calls the given function for each of the keys in the #GCache.
 290  *
 291  * NOTE @func is passed three parameters, the value and key of a cache
 292  * entry and the @user_data. The order of value and key is different
 293  * from the order in which g_hash_table_foreach() passes key-value
 294  * pairs to its callback function !
 295  **/
 296 void
 297 g_cache_key_foreach (GCache   *cache,
 298                      GHFunc    func,
 299                      gpointer  user_data)
 300 {
 301   g_return_if_fail (cache != NULL);
 302   g_return_if_fail (func != NULL);
 303
 304   g_hash_table_foreach (cache->value_table, func, user_data);
 305 }
 306
 307 /**
 308  * g_cache_value_foreach:
 309  * @cache: a #GCache.
 310  * @func: the function to call with each #GCache value.
 311  * @user_data: user data to pass to the function.
 312  *
 313  * Calls the given function for each of the values in the #GCache.
 314  *
 315  * Deprecated:2.10: The reason is that it passes pointers to internal
 316  *                  data structures to @func; use g_cache_key_foreach()
 317  *                  instead
 318  **/
 319 void
 320 g_cache_value_foreach (GCache   *cache,
 321                        GHFunc    func,
 322                        gpointer  user_data)
 323 {
 324   g_return_if_fail (cache != NULL);
 325   g_return_if_fail (func != NULL);
 326
 327   g_hash_table_foreach (cache->key_table, func, user_data);
 328 }
 329
 330 #define __G_CACHE_C__
 331 #include "galiasdef.c"