Merge pull request #39 from lucianoks/master

Adding SHA1 hashing for file keys instead of -[NSString hash] method.

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