1/// A convenience alias for creating a hash map with an FNV hasher.
2pub(crate) type HashMap<K, V> =
3 std::collections::HashMap<K, V, std::hash::BuildHasherDefault<Hasher>>;
4
5/// A hasher that implements the Fowler–Noll–Vo (FNV) hash.
6pub(crate) struct Hasher(u64);
7
8impl Hasher {
9 const OFFSET_BASIS: u64 = 0xcbf29ce484222325;
10 const PRIME: u64 = 0x100000001b3;
11}
12
13impl Default for Hasher {
14 fn default() -> Hasher {
15 Hasher(Hasher::OFFSET_BASIS)
16 }
17}
18
19impl std::hash::Hasher for Hasher {
20 fn finish(&self) -> u64 {
21 self.0
22 }
23
24 fn write(&mut self, bytes: &[u8]) {
25 for &byte: u8 in bytes.iter() {
26 self.0 = self.0 ^ u64::from(byte);
27 self.0 = self.0.wrapping_mul(Hasher::PRIME);
28 }
29 }
30}
31