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+/******************************************************************************
+ *
+ *
+ *
+ * Copyright (C) 1997-2006 by Dimitri van Heesch.
+ *
+ * Permission to use, copy, modify, and distribute this software and its
+ * documentation under the terms of the GNU General Public License is hereby
+ * granted. No representations are made about the suitability of this software
+ * for any purpose. It is provided "as is" without express or implied warranty.
+ * See the GNU General Public License for more details.
+ *
+ * Documents produced by Doxygen are derivative works derived from the
+ * input used in their production; they are not affected by this license.
+ *
+ */
+
+#ifndef OBJCACHE_H
+#define OBJCACHE_H
+
+//#define CACHE_TEST
+//#define CACHE_DEBUG
+#define CACHE_STATS
+
+/** @brief Cache for objects.
+ *
+ * This cache is used to decide which objects should remain in
+ * memory. It uses a least recently used policy (LRU) to decide
+ * which object should make room for a new object when the cache
+ * is full. An object should be added using add(), and then use()
+ * should be called when the object is used.
+ */
+class ObjCache
+{
+ private:
+ struct CacheNode
+ {
+ CacheNode() : next(-1), prev(-1), obj(0) {}
+ int next;
+ int prev;
+ void *obj;
+ };
+ struct HashNode
+ {
+ HashNode() : head(-1), nextHash(-1), index(-1), obj(0) {}
+ int head;
+ int nextHash;
+ int index;
+ void *obj;
+ };
+
+ public:
+ /*! Creates the cache. The number of elements in the cache is 2 to
+ * the power of \a logSize.
+ */
+ ObjCache(unsigned int logSize);
+
+ /*! Deletes the cache and free all internal data-structures used. */
+ ~ObjCache();
+
+ /*! Adds \a obj to the cache. When victim is not null, this object is
+ * removed from the cache to make room for \a obj.
+ * Returns a handle to the object, which can be used by the use()
+ * function, each time the object is used.
+ */
+ int add(void *obj,void **victim);
+
+ /*! Indicates that this object is used. This will move the object
+ * to the front of the internal LRU list to make sure it is removed last.
+ * The parameter \a handle is returned when called add().
+ */
+ void use(int handle)
+ {
+ hits++;
+ if (handle==m_lastHandle) return;
+ m_lastHandle = handle;
+ moveToFront(handle);
+ }
+
+ /*! Removes the item identified by \a handle from the cache.
+ * @see add()
+ */
+ void del(int handle);
+
+ /*! Debug function. Prints the LRU list */
+ void printLRU();
+ /*! Print miss/hits statistics */
+ void printStats();
+
+ private:
+ void moveToFront(int index);
+ unsigned int hash(void *addr);
+ HashNode *hashFind(void *obj);
+ HashNode *hashInsert(void *obj);
+ void hashRemove(void *obj);
+
+ CacheNode *m_cache;
+ HashNode *m_hash;
+ int m_head;
+ int m_tail;
+ int m_size;
+ int m_freeHashNodes;
+ int m_freeCacheNodes;
+ int m_lastHandle;
+
+#ifdef CACHE_STATS
+ static int misses;
+ static int hits;
+#endif
+};
+
+#endif // OBJCACHE_H
+