Merge pull request SDWebImage#434 from jparise/calculate-size

Add -calculateSizeWithCompletionBlock:.

Author: Olivier Poitrey

SDWebImage/SDImageCache.h

@@ -154,4 +154,9 @@ typedef enum SDImageCacheType SDImageCacheType;
  */
 - (int)getDiskCount;
 
+/**
+ * Asynchronously calculate the disk cache's size.
+ */
+- (void)calculateSizeWithCompletionBlock:(void (^)(NSUInteger fileCount, unsigned long long totalSize))completionBlock;
+
 @end

SDWebImage/SDImageCache.m

@@ -423,4 +423,37 @@ - (int)getDiskCount
     return count;
 }
 
+- (void)calculateSizeWithCompletionBlock:(void (^)(NSUInteger fileCount, unsigned long long totalSize))completionBlock
+{
+    NSURL *diskCacheURL = [NSURL fileURLWithPath:self.diskCachePath isDirectory:YES];
+
+    dispatch_async(self.ioQueue, ^
+    {
+        NSUInteger fileCount = 0;
+        unsigned long long totalSize = 0;
+
+        NSFileManager *fileManager = [NSFileManager defaultManager];
+        NSDirectoryEnumerator *fileEnumerator = [fileManager enumeratorAtURL:diskCacheURL
+                                                  includingPropertiesForKeys:@[ NSFileSize ]
+                                                                     options:NSDirectoryEnumerationSkipsHiddenFiles
+                                                                errorHandler:NULL];
+
+        for (NSURL *fileURL in fileEnumerator)
+        {
+            NSNumber *fileSize;
+            [fileURL getResourceValue:&fileSize forKey:NSURLFileSizeKey error:NULL];
+            totalSize += [fileSize unsignedLongLongValue];
+            fileCount += 1;
+        }
+
+        if (completionBlock)
+        {
+            dispatch_async(dispatch_get_main_queue(), ^
+            {
+                completionBlock(fileCount, totalSize);
+            });
+        }
+    });
+}
+
 @end