fn inv()

in math/src/field/f62/mod.rs [524:568]

• 39 lines of code
• 10 McCabe index (conditional complexity)

fn inv(x: u64) -> u64 {
    if x == 0 {
        return 0;
    };

    let mut a: u128 = 0;
    let mut u: u128 = if x & 1 == 1 {
        x as u128
    } else {
        (x as u128) + (M as u128)
    };
    let mut v: u128 = M as u128;
    let mut d = (M as u128) - 1;

    while v != 1 {
        while v < u {
            u -= v;
            d += a;
            while u & 1 == 0 {
                if d & 1 == 1 {
                    d += M as u128;
                }
                u >>= 1;
                d >>= 1;
            }
        }

        v -= u;
        a += d;

        while v & 1 == 0 {
            if a & 1 == 1 {
                a += M as u128;
            }
            v >>= 1;
            a >>= 1;
        }
    }

    while a > (M as u128) {
        a -= M as u128;
    }

    mul(a as u64, R3)
}