Release-1.4.7-20060910

1 files changed, 113 insertions, 0 deletions

diff --git a/src/objcache.h b/src/objcache.h
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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
+