crypto_bigint/uint/
neg_mod.rs1use crate::{Limb, NegMod, Uint};
4
5impl<const LIMBS: usize> Uint<LIMBS> {
6 pub const fn neg_mod(&self, p: &Self) -> Self {
9 let z = self.is_nonzero();
10 let mut ret = p.sbb(self, Limb::ZERO).0;
11 let mut i = 0;
12 while i < LIMBS {
13 ret.limbs[i].0 = z.if_true_word(ret.limbs[i].0);
16 i += 1;
17 }
18 ret
19 }
20
21 pub const fn neg_mod_special(&self, c: Limb) -> Self {
24 Self::ZERO.sub_mod_special(self, c)
25 }
26}
27
28impl<const LIMBS: usize> NegMod for Uint<LIMBS> {
29 type Output = Self;
30
31 fn neg_mod(&self, p: &Self) -> Self {
32 debug_assert!(self < p);
33 self.neg_mod(p)
34 }
35}
36
37#[cfg(test)]
38mod tests {
39 use crate::U256;
40
41 #[test]
42 fn neg_mod_random() {
43 let x =
44 U256::from_be_hex("8d16e171674b4e6d8529edba4593802bf30b8cb161dd30aa8e550d41380007c2");
45 let p =
46 U256::from_be_hex("928334a4e4be0843ec225a4c9c61df34bdc7a81513e4b6f76f2bfa3148e2e1b5");
47
48 let actual = x.neg_mod(&p);
49 let expected =
50 U256::from_be_hex("056c53337d72b9d666f86c9256ce5f08cabc1b63b207864ce0d6ecf010e2d9f3");
51
52 assert_eq!(expected, actual);
53 }
54
55 #[test]
56 fn neg_mod_zero() {
57 let x =
58 U256::from_be_hex("0000000000000000000000000000000000000000000000000000000000000000");
59 let p =
60 U256::from_be_hex("928334a4e4be0843ec225a4c9c61df34bdc7a81513e4b6f76f2bfa3148e2e1b5");
61
62 let actual = x.neg_mod(&p);
63 let expected =
64 U256::from_be_hex("0000000000000000000000000000000000000000000000000000000000000000");
65
66 assert_eq!(expected, actual);
67 }
68}