curv/arithmetic/
samplable.rs

1use rand::{rngs::OsRng, RngCore};
2
3use super::traits::{BitManipulation, Converter, Samplable, Zero};
4use super::BigInt;
5
6impl Samplable for BigInt {
7    fn sample_below(upper: &Self) -> Self {
8        assert!(*upper > Self::zero());
9
10        let bits = upper.bit_length();
11        loop {
12            let n = Self::sample(bits);
13            if n < *upper {
14                return n;
15            }
16        }
17    }
18
19    fn sample_range(lower: &Self, upper: &Self) -> Self {
20        assert!(upper > lower);
21        lower + Self::sample_below(&(upper - lower))
22    }
23
24    fn strict_sample_range(lower: &Self, upper: &Self) -> Self {
25        assert!(upper > lower);
26        loop {
27            let n = lower + Self::sample_below(&(upper - lower));
28            if n > *lower && n < *upper {
29                return n;
30            }
31        }
32    }
33
34    fn sample(bit_size: usize) -> Self {
35        if bit_size == 0 {
36            return BigInt::zero();
37        }
38        let mut rng = OsRng;
39        let bytes = (bit_size - 1) / 8 + 1;
40        let mut buf: Vec<u8> = vec![0; bytes];
41        rng.fill_bytes(&mut buf);
42        BigInt::from_bytes(&*buf) >> (bytes * 8 - bit_size)
43    }
44
45    fn strict_sample(bit_size: usize) -> Self {
46        if bit_size == 0 {
47            return BigInt::zero();
48        }
49        loop {
50            let n = Self::sample(bit_size);
51            if n.bit_length() == bit_size {
52                return n;
53            }
54        }
55    }
56}
curv/arithmetic/samplable.rs

curv/arithmetic/
samplable.rs
