fn optional_multiscalar_mul()

in src/edwards.rs [667:695]

• 20 lines of code
• 2 McCabe index (conditional complexity)

    fn optional_multiscalar_mul<I, J>(scalars: I, points: J) -> Option<EdwardsPoint>
    where
        I: IntoIterator,
        I::Item: Borrow<Scalar>,
        J: IntoIterator<Item = Option<EdwardsPoint>>,
    {
        // Sanity-check lengths of input iterators
        let mut scalars = scalars.into_iter();
        let mut points = points.into_iter();

        // Lower and upper bounds on iterators
        let (s_lo, s_hi) = scalars.by_ref().size_hint();
        let (p_lo, p_hi) = points.by_ref().size_hint();

        // They should all be equal
        assert_eq!(s_lo, p_lo);
        assert_eq!(s_hi, Some(s_lo));
        assert_eq!(p_hi, Some(p_lo));

        // Now we know there's a single size.
        // Use this as the hint to decide which algorithm to use.
        let size = s_lo;

        if size < 190 {
            scalar_mul::straus::Straus::optional_multiscalar_mul(scalars, points)
        } else {
            scalar_mul::pippenger::Pippenger::optional_multiscalar_mul(scalars, points)
        }
    }