Interface CtSelect

ctutils/src/traits/ct_select.rs:24–39

Constant-time selection: choose between two values based on a given [`Choice`]. This crate provides built-in implementations for the following types: - [`i8`], [`i16`], [`i32`], [`i64`], [`i128`], [`isize`] - [`u8`], [`u16`], [`u32`], [`u64`], [`u128`], [`usize`] - [`NonZeroI8`], [`NonZeroI16`], [`NonZeroI32`], [`NonZeroI64`], [`NonZeroI128`], [`NonZeroI128`] - [`NonZeroU8`], [`NonZeroU16`], [`No

/// - `[T; N]` where `T` impls [`CtSelectArray`], which the previously mentioned types all do,
///   as well as any type which impls [`Clone`] + [`CtAssignSlice`] + [`CtSelect`].
pub trait CtSelect: Sized {
    /// Select between `self` and `other` based on `choice`, returning a copy of the value.
    ///
    /// # Returns
    /// - `self` if `choice` is [`Choice::FALSE`].
    /// - `other` if `choice` is [`Choice::TRUE`].
    #[must_use]
    fn ct_select(&self, other: &Self, choice: Choice) -> Self;

    /// Conditionally swap `self` and `other` if `choice` is [`Choice::TRUE`].
    fn ct_swap(&mut self, other: &mut Self, choice: Choice) {
        let tmp = self.ct_select(other, choice);
        *other = Self::ct_select(other, self, choice);
        *self = tmp;
    }
}

/// Implementing this trait enables use of the [`CtSelect`] trait to construct `[T; N]` where `T`
/// is the `Self` type implementing the trait, via a blanket impl.