One note: please don't use MD5; in fact, I don't see any reason why this would use any fixed hash function, rather than whatever is fastest with suitable guarantees on each platform, since this is data that never needs to move across systems.
MD5, in particular, is significantly slower than other options that we might use instead--this use case doesn't require a cryptographic hash function (and if it did require a cryptographic hash, MD5 is no longer considered safe to use, and is also slower than other options on many platforms)--it requires only a hash that is sufficient to detect if a file has changed, which is a much weaker requirement.