Adding SHA1 hashing for file keys instead of NSString's -hash method.

Author: lucianoks

JMImageCache.m

@@ -22,7 +22,7 @@
 	return [url absoluteString];
 }
 static inline NSString *cachePathForKey(NSString *key) {
-    NSString *fileName = [NSString stringWithFormat:@"JMImageCache-%u", [key hash]];
+    NSString *fileName = [NSString stringWithFormat:@"JMImageCache-%@", [JMImageCache SHA1FromString:key]];
 	return [JMImageCacheDirectory() stringByAppendingPathComponent:fileName];
 }
 
@@ -262,4 +262,25 @@ - (void) performDiskWriteOperation:(NSInvocation *)invoction {
 	[self.diskOperationQueue addOperation:operation];
 }
 
+#pragma mark - Hash methods
+
++ (NSString *)SHA1FromString:(NSString *)string
+{
+    unsigned char digest[CC_SHA1_DIGEST_LENGTH];
+    
+    NSData *stringBytes = [string dataUsingEncoding:NSUTF8StringEncoding];
+    
+    if (CC_SHA1([stringBytes bytes], (CC_LONG)[stringBytes length], digest)) {
+        
+        NSMutableString *output = [NSMutableString stringWithCapacity:CC_SHA1_DIGEST_LENGTH * 2];
+        
+        for (int i = 0; i < CC_SHA1_DIGEST_LENGTH; i++) {
+            [output appendFormat:@"%02x", digest[i]];
+        }
+        
+        return output;
+    }
+    return nil;
+}
+
 @end