Committing GUID utility class.

JFGuidUtil.h

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+//
+// JFGuidUtil.h
+// JFCommon
+//
+// Created by Jason Fuerstenberg on 2012/04/02.
+// Copyright 2012 Jason Fuerstenberg
+//
+// http://www.jayfuerstenberg.com
+// jay@jayfuerstenberg.com
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+
+@interface JFGuidUtil : NSObject
+
++ (NSString *) maskedGuidWithOriginalGuid: (NSString *) originalGuid;
+
+@end

JFGuidUtil.m

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+//
+// JFGuidUtil.m
+// JFCommon
+//
+// Created by Jason Fuerstenberg on 2012/04/02.
+// Copyright 2012 Jason Fuerstenberg
+//
+// http://www.jayfuerstenberg.com
+// jay@jayfuerstenberg.com
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "JFGuidUtil.h"
+
+
+@implementation JFGuidUtil
+
+/*
+ * Returns a GUID with the last section masked with bullet marks (Japanese maru characters).
+ * If the original GUID is invalid nil is returned.
+ *
+ * This method is intended for logging GUIDs which may be sensitive/private in such a way
+ * that they can be compared with a reasonable degree of certainty by someone in possession
+ * of both the full GUID and the masked one.
+ *
+ * The masked GUID in and of itself cannot help an unauthorized person relearn the original
+ * GUID as the bulletized portion is lost information.
+ */
++ (NSString *) maskedGuidWithOriginalGuid: (NSString *) originalGuid {
+
+	NSUInteger length = [originalGuid length];
+	if (length != 36) {
+		// The length is not the expected 36 characters so this is an invalid GUID.
+		return nil;
+	}
+
+	NSRange rangeOfLastHyphen = [originalGuid rangeOfString: @"-"
+													options: NSBackwardsSearch];
+	if (rangeOfLastHyphen.location != length - 13) {
+		// This GUID has no hyphen in front of the last 12 digits, so it is invalid.
+		return nil;
+	}
+
+	// Replace all the characters after the last hyphen with a maru...
+	NSUInteger replacementIndex = rangeOfLastHyphen.location + 1;
+	NSRange replacementRange = NSMakeRange(replacementIndex, length - replacementIndex);
+	/*
+	 * NOTE: The below bullets may not display as expected if your log is not in UTF8.
+	 * You may change it to any character that suits your purpose though.
+	 */
+	NSString *maskedGuid = [originalGuid stringByReplacingCharactersInRange: replacementRange
+																 withString: @"●●●●●●●●●●●●"];
+
+	return maskedGuid;
+}
+
+@end