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Add a secondary weak memory cache to improve speed and decrease memory usage when reusing previous images #791

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Add a secondary weak memory cache to improve speed and decrease memory usage when reusing previous images #791

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Add a weak NSMapTable-based memory cache. This allows the cache to re…
DimaVartanian Jul 4, 2014
f9dda42
user more concise initializer
DimaVartanian Jul 5, 2014
ba2ae43
Merge branch 'master' of https://github.com/rs/SDWebImage
DimaVartanian Jul 21, 2014
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31 changes: 23 additions & 8 deletions SDWebImage/SDImageCache.m
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,7 @@ BOOL ImageDataHasPNGPreffix(NSData *data) {
@interface SDImageCache ()

@property (strong, nonatomic) NSCache *memCache;
@property (strong, nonatomic) NSMapTable *weakMemCache;
@property (strong, nonatomic) NSString *diskCachePath;
@property (strong, nonatomic) NSMutableArray *customPaths;
@property (SDDispatchQueueSetterSementics, nonatomic) dispatch_queue_t ioQueue;
Expand Down Expand Up @@ -70,6 +71,9 @@ - (id)initWithNamespace:(NSString *)ns {
// Init the memory cache
_memCache = [[NSCache alloc] init];
_memCache.name = fullNamespace;

// Init the weak memory cache (to keep a weak reference to images cleared from our memory cache that are actually still alive)
_weakMemCache = [NSMapTable strongToWeakObjectsMapTable];

// Init the disk cache
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
Expand Down Expand Up @@ -146,8 +150,7 @@ - (void)storeImage:(UIImage *)image recalculateFromImage:(BOOL)recalculate image
if (!image || !key) {
return;
}

[self.memCache setObject:image forKey:key cost:image.size.height * image.size.width * image.scale];
[self addImageToMemoryCache:image forKey:key];

if (toDisk) {
dispatch_async(self.ioQueue, ^{
Expand Down Expand Up @@ -221,7 +224,21 @@ - (void)diskImageExistsWithKey:(NSString *)key completion:(SDWebImageCheckCacheC
}

- (UIImage *)imageFromMemoryCacheForKey:(NSString *)key {
return [self.memCache objectForKey:key];
UIImage *image = [self.memCache objectForKey:key];
// Check the weak memory cache to see if a previously cached image is still alive
if (!image) {
image = [self.weakMemCache objectForKey:key];
if (image) {
// re-add to memory cache
[self addImageToMemoryCache:image forKey:key];
}
}
return image;
}

- (void) addImageToMemoryCache:(UIImage *)image forKey:(NSString *)key {
[self.memCache setObject:image forKey:key cost:image.size.height * image.size.width * image.scale];
[self.weakMemCache setObject:image forKey:key];
}

- (UIImage *)imageFromDiskCacheForKey:(NSString *)key {
Expand All @@ -230,12 +247,11 @@ - (UIImage *)imageFromDiskCacheForKey:(NSString *)key {
if (image) {
return image;
}

// Second check the disk cache...
UIImage *diskImage = [self diskImageForKey:key];
if (diskImage) {
CGFloat cost = diskImage.size.height * diskImage.size.width * diskImage.scale;
[self.memCache setObject:diskImage forKey:key cost:cost];
[self addImageToMemoryCache:diskImage forKey:key];
}

return diskImage;
Expand Down Expand Up @@ -302,8 +318,7 @@ - (NSOperation *)queryDiskCacheForKey:(NSString *)key done:(SDWebImageQueryCompl
@autoreleasepool {
UIImage *diskImage = [self diskImageForKey:key];
if (diskImage) {
CGFloat cost = diskImage.size.height * diskImage.size.width * diskImage.scale;
[self.memCache setObject:diskImage forKey:key cost:cost];
[self addImageToMemoryCache:diskImage forKey:key];
}

dispatch_async(dispatch_get_main_queue(), ^{
Expand Down