Instead of using an unsigned int as a parameter and expecting a user to always pass in the correct values, we can just convert the enum into an enum class and use that type as the parameter type instead, which makes the interface more type safe. We also get rid of the bookkeeping "NUM_" element in the enum by just using an unordered map. This function is generally low-frequency in terms of calls (and I'd hope so, considering otherwise would mean we're slamming the disk with IO all the time) so I'd consider this acceptable in this case.