rune/
hash.rs

1//! Utilities for working with hashes.
2
3use crate::alloc::HashMap;
4
5use core::hash::{BuildHasher, Hasher};
6
7const SEED: u64 = 18446744073709551557u64;
8
9#[doc(inline)]
10pub use rune_core::hash::{Hash, IntoHash, ParametersBuilder, ToTypeHash, TooManyParameters};
11
12/// A hash map suitable for storing values with hash keys.
13pub(crate) type Map<T> = HashMap<Hash, T, HashBuildHasher>;
14
15#[derive(Default, Clone, Copy)]
16pub(crate) struct HashBuildHasher;
17
18impl BuildHasher for HashBuildHasher {
19    type Hasher = HashHasher;
20
21    #[inline]
22    fn build_hasher(&self) -> Self::Hasher {
23        HashHasher(SEED)
24    }
25}
26
27pub(crate) struct HashHasher(u64);
28
29impl Hasher for HashHasher {
30    #[inline]
31    fn finish(&self) -> u64 {
32        self.0
33    }
34
35    #[inline]
36    fn write(&mut self, _: &[u8]) {
37        panic!("Hash hashers assume that 64-bit hashes are already random")
38    }
39
40    #[inline]
41    fn write_u64(&mut self, hash: u64) {
42        self.0 ^= hash;
43    }
44}