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Diffstat (limited to 'src/objcache.h')
-rw-r--r-- | src/objcache.h | 113 |
1 files changed, 113 insertions, 0 deletions
diff --git a/src/objcache.h b/src/objcache.h new file mode 100644 index 0000000..3516534 --- /dev/null +++ b/src/objcache.h @@ -0,0 +1,113 @@ +/****************************************************************************** + * + * + * + * 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 + |