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/*
* Copyright (C) 2005 Stefan Kleine Stegemann
*
* The sources from MissigKit are not released under any particular
* license. Do with them what ever you want to do. Include them in
* your projects, use MissingKit standalone or simply ignore it.
* Whatever you do, keep in mind the this piece of software may
* have errors and that it is distributed WITHOUT ANY WARRANTY;
* without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE.
*/
#ifndef _H_MKLRUCACHE
#define _H_MKLRUCACHE
#import "MKLinkedList.h"
#import <Foundation/Foundation.h>
/**
* A cache with a restricted size. When the sum of the sizes of the
* objects in the cache becomes bigger than the allowed size, objects
* are removed from the cache until the sum of the size of the remaining
* objects is smaller or equal than the allowed size. Objects are
* selected for removal from the cache using the least recently used
* strategy.
*
* Objects that are stored in an MKLRUCache must implement the formal
* protocol MKLRUCachable.
*
* Internally, the cache uses a linked list to keep track of the
* object usages. Whenever an object is fetched from the cache, it is
* put at the end of the list. When the cache needs to remove objects,
* it selects objects from the beginning of the list. The time required
* for the cache operations is the time for storing/retrieving objects
* from an NSDictionary plus a constant amount of time for maitaining
* the history list.
*/
@interface MKLRUCache : NSObject
{
unsigned long maxSize;
unsigned long size;
NSMutableDictionary* map;
MKLinkedList* history;
}
/** Intializes the receiver, a freshly allocated MKLRUCache with the
* specified maximum size. */
- (id) initWithMaxSize: (unsigned long)aMaxSize;
/** Add an object to the cache using the specified key. Neither key nor
* object may be nil. Adding an object to the cache marks the object as
* recently used. If another object is currently associated with the
* specified key this object is replaced by anObject. */
- (void) putObject: (id)anObject forKey: (id)aKey;
/** Fetch the object for the specified key from the cache. If the object
* was found, it is marked as recently used and returned. Returns nil
* if the cache doesn't have an object for the key. */
- (id) objectForKey: (id)aKey;
/** Check if the receiver contains an object that is associated with the
* specified key. */
- (BOOL) containsObjectForKey: (id)aKey;
/** Remove an object from the cache. Returns the object that has been removed
* or nil if no object is associated with the specified key. */
- (id) removeObjectForKey: (id)aKey;
/** Remove all objects from the cache. */
- (void) clear;
/** Set the maximum size for this cache. If necessary, objects are
* removed from the cache until the new maximum size is reached. */
- (void) setMaximumSize: (long)aMaxSize;
/** Get the maximum size for this cache */
- (unsigned long) maximumSize;
/** Get the number of objects in the cache. */
- (unsigned) countObjects;
/** Get the current size of the cache. This is the sum of the
* sizes of the objects in the receiver. */
- (unsigned long) size;
@end
/**
* Informal Protocol for objects that are stored in a MKLRUCache.
*/
@interface NSObject (MKLRUCachable)
/** Get the size for the receiver in bytes . This is the size that is
* considered by MKLRUCaches. */
- (unsigned long) sizeInLRUCache;
@end
/**
* Some methods to verify the state of an MKLRUCache.
*/
@interface MKLRUCache (Testing)
@end
#endif
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