1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
use std::borrow::Borrow;
use std::collections::hash_map::DefaultHasher;
use std::hash::{Hash, Hasher};
use std::marker::PhantomData;
#[derive(Debug)]
pub struct HashOf<T, H: Hasher = DefaultHasher> {
hash: u64,
_marker: PhantomData<*const (T, H)>,
}
impl<T, H: Hasher> PartialEq for HashOf<T, H> {
#[inline]
fn eq(&self, other: &Self) -> bool {
self.hash == other.hash
}
}
impl<T, H: Hasher> Eq for HashOf<T, H> {}
impl<T, H: Hasher> Hash for HashOf<T, H> {
#[inline]
fn hash<H2: Hasher>(&self, state: &mut H2) {
state.write_u64(self.hash)
}
}
impl<T> Clone for HashOf<T> {
#[inline]
fn clone(&self) -> Self {
*self
}
}
impl<T> Copy for HashOf<T> {}
impl<T> HashOf<T> {
#[inline]
pub fn to_inner(self) -> u64 {
self.hash
}
}
impl<T: Hash + ?Sized, Q: Borrow<T>, H: Hasher + Default> From<&T> for HashOf<Q, H> {
fn from(value: &T) -> Self {
let mut hasher = H::default();
value.hash(&mut hasher);
Self {
hash: hasher.finish(),
_marker: PhantomData,
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn borrow_hash_eq() {
let x = HashOf::<String>::from("test");
let s2 = String::new() + "test";
let y = HashOf::from(&s2);
assert_eq!(x, y);
}
#[test]
fn can_hash_non_borrow() {
let x = HashOf::<u32>::from(&0);
assert_ne!(x.to_inner(), 0);
}
}