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//! [`BoxedUint`] addition operations.
use crate::{BoxedUint, CheckedAdd, Limb, Zero};
use subtle::CtOption;
impl BoxedUint {
/// Computes `a + b + carry`, returning the result along with the new carry.
#[inline(always)]
pub fn adc(&self, rhs: &Self, carry: Limb) -> (Self, Limb) {
Self::chain(self, rhs, carry, |a, b, c| a.adc(b, c))
}
/// Perform wrapping addition, discarding overflow.
pub fn wrapping_add(&self, rhs: &Self) -> Self {
self.adc(rhs, Limb::ZERO).0
}
}
impl CheckedAdd<&BoxedUint> for BoxedUint {
type Output = Self;
fn checked_add(&self, rhs: &Self) -> CtOption<Self> {
let (result, carry) = self.adc(rhs, Limb::ZERO);
CtOption::new(result, carry.is_zero())
}
}
#[cfg(test)]
#[allow(clippy::unwrap_used)]
mod tests {
use super::{BoxedUint, CheckedAdd, Limb};
#[test]
fn adc_no_carry() {
let (res, carry) = BoxedUint::zero().adc(&BoxedUint::one(), Limb::ZERO);
assert_eq!(res, BoxedUint::one());
assert_eq!(carry, Limb::ZERO);
}
#[test]
fn adc_with_carry() {
let (res, carry) = BoxedUint::max(Limb::BITS)
.unwrap()
.adc(&BoxedUint::one(), Limb::ZERO);
assert_eq!(res, BoxedUint::zero());
assert_eq!(carry, Limb::ONE);
}
#[test]
fn checked_add_ok() {
let result = BoxedUint::zero().checked_add(&BoxedUint::one());
assert_eq!(result.unwrap(), BoxedUint::one());
}
#[test]
fn checked_add_overflow() {
let result = BoxedUint::max(Limb::BITS)
.unwrap()
.checked_add(&BoxedUint::one());
assert!(!bool::from(result.is_some()));
}
}
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