ps_ecc/polynomial/implementations/
hash.rs

1use std::hash::{Hash, Hasher};
2
3use crate::Polynomial;
4
5impl Hash for Polynomial {
6    fn hash<H: Hasher>(&self, state: &mut H) {
7        self.degree.hash(state);
8        self.coefficients[..=self.degree as usize].hash(state);
9    }
10}
11
12#[cfg(test)]
13#[allow(clippy::expect_used)]
14mod tests {
15    use std::collections::hash_map::DefaultHasher;
16    use std::hash::{Hash, Hasher};
17
18    use crate::Polynomial;
19
20    fn hash_of<T: Hash>(value: &T) -> u64 {
21        let mut hasher = DefaultHasher::new();
22
23        value.hash(&mut hasher);
24        hasher.finish()
25    }
26
27    #[test]
28    fn equal_polynomials_same_hash() {
29        let a = Polynomial::try_from(&[1u8, 2, 3][..]).expect("valid");
30        let b = Polynomial::try_from(&[1u8, 2, 3][..]).expect("valid");
31
32        assert_eq!(hash_of(&a), hash_of(&b));
33    }
34
35    #[test]
36    fn trailing_zeros_same_hash() {
37        let a = Polynomial::try_from(&[1u8, 2, 3][..]).expect("valid");
38        let b = Polynomial::try_from(&[1u8, 2, 3, 0, 0][..]).expect("valid");
39
40        assert_eq!(a, b);
41        assert_eq!(hash_of(&a), hash_of(&b));
42    }
43
44    #[test]
45    fn different_polynomials_likely_different_hash() {
46        let a = Polynomial::try_from(&[1u8, 2, 3][..]).expect("valid");
47        let b = Polynomial::try_from(&[1u8, 2, 4][..]).expect("valid");
48
49        // Not guaranteed, but extremely likely with a good hasher
50        assert_ne!(hash_of(&a), hash_of(&b));
51    }
52
53    #[test]
54    fn zero_polynomial_consistent_hash() {
55        let a = Polynomial::default();
56        let b = Polynomial::default();
57
58        assert_eq!(hash_of(&a), hash_of(&b));
59    }
60
61    #[test]
62    fn different_degrees_different_hash() {
63        let a = Polynomial::try_from(&[1u8][..]).expect("valid");
64        let b = Polynomial::try_from(&[1u8, 0, 1][..]).expect("valid");
65
66        assert_ne!(hash_of(&a), hash_of(&b));
67    }
68}
ps_ecc/polynomial/implementations/hash.rs

ps_ecc/polynomial/implementations/
hash.rs
