LRU Caching on Disk

MKNetworkKit/MKNetworkEngine.h

@@ -384,6 +384,18 @@
  */
 -(int) cacheMemoryCost;
 
+
+/*!
+ *  @abstract Cache Directory In Disk Size
+ *
+ *  @discussion
+ *	This method can be over-ridden by subclasses to provide an alternative in disk cache size.
+ *  By default, MKNetworkKit caches MKNETWORKCACHE_DEFAULT_DISK_SIZE bytes in disk cache
+ *  The default size is MKNETWORKCACHE_DEFAULT_DISK_SIZE
+ *  Overriding this method is optional
+ */
+-(unsigned long long int) cacheDiskSize;
+
 /*!
  *  @abstract Enable Caching
  *  

MKNetworkKit/MKNetworkEngine.m

@@ -618,6 +618,11 @@ -(int) cacheMemoryCost {
   return MKNETWORKCACHE_DEFAULT_COST;
 }
 
+-(unsigned long long int) cacheDiskSize{
+
+    return MKNETWORKCACHE_DEFAULT_DISK_SIZE;
+}
+
 -(void) saveCache {
 
   for(NSString *cacheKey in [self.memoryCache allKeys])
@@ -723,6 +728,12 @@ -(void) useCache {
   [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(saveCache)
                                                name:UIApplicationWillTerminateNotification
                                              object:nil];
+
+    //check for emptyCache whenever coming to app
+    [[NSNotificationCenter defaultCenter] addObserver:self
+                                             selector:@selector(emptyCache)
+                                                 name:UIApplicationDidBecomeActiveNotification
+                                               object:nil];
 
 #elif TARGET_OS_MAC
 
@@ -749,12 +760,37 @@ -(void) emptyCache {
                                 contentsOfDirectoryAtPath:[self cacheDirectoryName] error:&error];
   if(error) DLog(@"%@", error);
 
-  error = nil;
+    error = nil;
+
+    unsigned long long int folderSize = [self folderSize:[self cacheDirectoryName]];
+    unsigned long long int sizeToRemove = folderSize - [self cacheDiskSize];
+
+    if (folderSize <= 0) {
+        //return if we have not exceeded the limit
+        return;
+    }
+
+    unsigned long long int fileSize = 0;
+
   for(NSString *fileName in directoryContents) {
 
     NSString *path = [[self cacheDirectoryName] stringByAppendingPathComponent:fileName];
+
+      //calcualte size and add to count
+      NSDictionary *fileDictionary = [[NSFileManager defaultManager]
+                                      attributesOfItemAtPath:path
+                                      error:&error];
+
+      fileSize += [fileDictionary fileSize];
+
+      //remove file
     [[NSFileManager defaultManager] removeItemAtPath:path error:&error];
     if(error) DLog(@"%@", error);
+
+      //break if we are back in limit
+      if (fileSize > sizeToRemove) {
+          break;
+      }
   }
 
   error = nil;
@@ -763,4 +799,25 @@ -(void) emptyCache {
   if(error) DLog(@"%@", error);
 }
 
+- (unsigned long long int)folderSize:(NSString *)folderPath {
+    NSArray *filesArray = [[NSFileManager defaultManager] subpathsOfDirectoryAtPath:folderPath error:nil];
+    NSEnumerator *filesEnumerator = [filesArray objectEnumerator];
+    NSString *fileName;
+    unsigned long long int fileSize = 0;
+
+    while (fileName = [filesEnumerator nextObject]) {
+
+        NSString *path = [[self cacheDirectoryName] stringByAppendingPathComponent:fileName];
+        NSError *error = nil;
+
+        NSDictionary *fileDictionary = [[NSFileManager defaultManager]
+                                        attributesOfItemAtPath:path
+                                        error:&error];
+
+        fileSize += [fileDictionary fileSize];
+    }
+
+    return fileSize;
+}
+
 @end

MKNetworkKit/MKNetworkKit.h

@@ -82,6 +82,7 @@
 
 #define kMKNetworkEngineOperationCountChanged @"kMKNetworkEngineOperationCountChanged"
 #define MKNETWORKCACHE_DEFAULT_COST 10
+#define MKNETWORKCACHE_DEFAULT_DISK_SIZE 100*1024*1024 //100 MB
 #define MKNETWORKCACHE_DEFAULT_DIRECTORY @"MKNetworkKitCache"
 #define kMKNetworkKitDefaultCacheDuration 60 // 1 minute
 #define kMKNetworkKitDefaultImageHeadRequestDuration 3600*24*1 // 1 day (HEAD requests with eTag are sent only after expiry of this. Not that these are not RFC compliant, but needed for performance tuning)