A rather enthusiastic refactoring of [https://github.com/JanX2/google-diff-match-patch-Objective-C](Jan Weiß's Objective-C port) of Neil Fraser's [http://code.google.com/p/google-diff-match-patch/](Diff Match and Patch).
In the process of making it ARC friendly and tinkering to my internal Objective-C style I ended up reformatting to the extent that it's become a C interface which uses Objective-C objects. While I think it's rather streamlined as is, all the clever bits were done by others.
Source/DiffMatchPatch.h is the place to get started.