fuzzy_regex/engine/
hash.rs

1//! Fast hash utilities for internal use.
2//!
3//! `FxHash` is a fast, non-cryptographic hash function that provides
4//! ~2x speedup over the default hasher for small keys.
5
6use std::collections::{HashMap, HashSet};
7use std::hash::{BuildHasherDefault, Hasher};
8
9/// A fast hasher using the `FxHash` algorithm - optimized for small keys.
10/// This provides ~2x speedup over the default hasher for state lookups.
11#[derive(Default)]
12pub struct FxHasher {
13    hash: u64,
14}
15
16impl Hasher for FxHasher {
17    #[inline]
18    fn write(&mut self, bytes: &[u8]) {
19        const K: u64 = 0x517c_c1b7_2722_0a95;
20        for &byte in bytes {
21            self.hash = (self.hash.rotate_left(5) ^ u64::from(byte)).wrapping_mul(K);
22        }
23    }
24
25    #[inline]
26    fn finish(&self) -> u64 {
27        self.hash
28    }
29}
30
31/// `HashMap` with `FxHasher` for fast lookups.
32pub type FxHashMap<K, V> = HashMap<K, V, BuildHasherDefault<FxHasher>>;
33
34/// `HashSet` with `FxHasher` for fast lookups.
35pub type FxHashSet<K> = HashSet<K, BuildHasherDefault<FxHasher>>;
fuzzy_regex/engine/hash.rs

fuzzy_regex/engine/
hash.rs
