Function fnv 

pub fn fnv(h: u64, bytes: &[u8]) -> u64

FNV-1a over bytes, continuing from h. The one spelling of the mixer: a digest that must stay bit-stable across versions (a key, the access tree’s change detector, the corpus digest) is stable because it is this function and nothing else. A byte a round with a multiply on the chain — a nanosecond a byte — which is the right cost for a label and the wrong one for a megabyte of text: that goes through hash_bulk first.