[pdkl95]

> What's the query interface like for the bit array?

I don't see any request for a query interface in the list of requirements.

The point of the packed-bit array is that you don't need any kind of query interface other than a few accessor macros. It's a memory-mapped array of 64-bit integers; you just index into the array and use a macro to mask out the bits you're interested in.

The "old-timer" solution - which actually solves the stated problem instead of a hypothetical future problem with lots of extra requirements - can be written in a few pages of C. It shouldn't take more than an hour, perhaps two (plus some time for testing).

If and only if the requirements change0 to something significantly more complex would something like a query interface make sense (YAGNI). The task as stated just isn't very hard.