For the record, I changed my mind on integer representations. There's no real information in the size of the integer type, a program can represent it in memory however it wants. Using a u32 won't keep anyone from publishing a message with a u64 anyways. So if anyone (including future-me) wants to build on this, I'd recommend treating all integers as the same type rather than distinguishing by fixed-size representations.

(related stuff to think through: Integers vs naturals, integers vs floats, integers vs rationals, integers of a maximum size vs integers of arbitrary size)

@Dominic

Can you tell me more about how what you want relates to capnproto? Reinventing this properly would be a bunch of work, since there's stuff like padding and alignment issues. Capnproto has many features we wouldn't need, but maybe a somewhat simple scheme definition for hsdt could be sufficient for your use case.