MemoryCache.m
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//
// MemoryCache.m
// Images
//
// Created by Joseph Gentle on 30/08/08.
// Copyright 2008 __MyCompanyName__. All rights reserved.
//
#import "MemoryCache.h"
#import "TileImage.h"
@implementation MemoryCache
-(id)initWithCapacity: (NSUInteger) _capacity
{
if (![super init])
return nil;
cache = [[NSMutableDictionary alloc] initWithCapacity:_capacity];
if (_capacity < 1)
_capacity = 1;
capacity = _capacity;
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(imageLoadingCancelled:)
name:MapImageLoadingCancelledNotification
object:nil];
return self;
}
-(id)init
{
return [self initWithCapacity:5];
}
-(void) dealloc
{
[[NSNotificationCenter defaultCenter] removeObserver:self];
[cache release];
[super dealloc];
}
-(void) removeTile: (Tile) tile
{
NSLog(@"tile %d %d %d removed from cache", tile.x, tile.y, tile.zoom);
[cache removeObjectForKey:[TileCache tileHash: tile]];
}
-(void) imageLoadingCancelled: (NSNotification*)notification
{
[self removeTile: [[notification object] tile]];
}
-(TileImage*) cachedImage:(Tile)tile
{
NSNumber *key = [TileCache tileHash: tile];
TileImage *image = [cache objectForKey:key];
/* if (image == nil)
NSLog(@"cache miss %@", key);
else
NSLog(@"cache hit %@", key);
*/
return image;
}
-(void)makeSpaceInCache
{
while ([cache count] >= capacity)
{
// Rather than scanning I would really like to be using a priority queue
// backed by a heap here.
NSEnumerator *enumerator = [cache objectEnumerator];
TileImage *image;
NSDate *oldestDate = nil;
TileImage *oldestImage = nil;
while ((image = (TileImage*)[enumerator nextObject]))
{
if (oldestDate == nil
|| ([oldestDate timeIntervalSinceReferenceDate] > [[image lastUsedTime] timeIntervalSinceReferenceDate]))
{
oldestDate = [image lastUsedTime];
oldestImage = image;
}
}
[self removeTile:[oldestImage tile]];
}
}
-(void)addTile: (Tile)tile WithImage: (TileImage*)image
{
if (TileIsDummy(tile))
return;
// NSLog(@"cache add %@", key);
[self makeSpaceInCache];
NSNumber *key = [TileCache tileHash: tile];
[cache setObject:image forKey:key];
}
@end