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|
//! [`Uint`] addition operations.
use crate::{Checked, CheckedAdd, CtChoice, Limb, Uint, Wrapping, Zero};
use core::ops::{Add, AddAssign};
use subtle::CtOption;
impl<const LIMBS: usize> Uint<LIMBS> {
/// Computes `a + b + carry`, returning the result along with the new carry.
#[inline(always)]
pub const fn adc(&self, rhs: &Self, mut carry: Limb) -> (Self, Limb) {
let mut limbs = [Limb::ZERO; LIMBS];
let mut i = 0;
while i < LIMBS {
let (w, c) = self.limbs[i].adc(rhs.limbs[i], carry);
limbs[i] = w;
carry = c;
i += 1;
}
(Self { limbs }, carry)
}
/// Perform saturating addition, returning `MAX` on overflow.
pub const fn saturating_add(&self, rhs: &Self) -> Self {
let (res, overflow) = self.adc(rhs, Limb::ZERO);
Self::ct_select(&res, &Self::MAX, CtChoice::from_lsb(overflow.0))
}
/// Perform wrapping addition, discarding overflow.
pub const fn wrapping_add(&self, rhs: &Self) -> Self {
self.adc(rhs, Limb::ZERO).0
}
/// Perform wrapping addition, returning the truthy value as the second element of the tuple
/// if an overflow has occurred.
pub(crate) const fn conditional_wrapping_add(
&self,
rhs: &Self,
choice: CtChoice,
) -> (Self, CtChoice) {
let actual_rhs = Uint::ct_select(&Uint::ZERO, rhs, choice);
let (sum, carry) = self.adc(&actual_rhs, Limb::ZERO);
(sum, CtChoice::from_lsb(carry.0))
}
}
impl<const LIMBS: usize> CheckedAdd<&Uint<LIMBS>> for Uint<LIMBS> {
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())
}
}
impl<const LIMBS: usize> Add for Wrapping<Uint<LIMBS>> {
type Output = Self;
fn add(self, rhs: Self) -> Wrapping<Uint<LIMBS>> {
Wrapping(self.0.wrapping_add(&rhs.0))
}
}
impl<const LIMBS: usize> Add<&Wrapping<Uint<LIMBS>>> for Wrapping<Uint<LIMBS>> {
type Output = Wrapping<Uint<LIMBS>>;
fn add(self, rhs: &Wrapping<Uint<LIMBS>>) -> Wrapping<Uint<LIMBS>> {
Wrapping(self.0.wrapping_add(&rhs.0))
}
}
impl<const LIMBS: usize> Add<Wrapping<Uint<LIMBS>>> for &Wrapping<Uint<LIMBS>> {
type Output = Wrapping<Uint<LIMBS>>;
fn add(self, rhs: Wrapping<Uint<LIMBS>>) -> Wrapping<Uint<LIMBS>> {
Wrapping(self.0.wrapping_add(&rhs.0))
}
}
impl<const LIMBS: usize> Add<&Wrapping<Uint<LIMBS>>> for &Wrapping<Uint<LIMBS>> {
type Output = Wrapping<Uint<LIMBS>>;
fn add(self, rhs: &Wrapping<Uint<LIMBS>>) -> Wrapping<Uint<LIMBS>> {
Wrapping(self.0.wrapping_add(&rhs.0))
}
}
impl<const LIMBS: usize> AddAssign for Wrapping<Uint<LIMBS>> {
fn add_assign(&mut self, other: Self) {
*self = *self + other;
}
}
impl<const LIMBS: usize> AddAssign<&Wrapping<Uint<LIMBS>>> for Wrapping<Uint<LIMBS>> {
fn add_assign(&mut self, other: &Self) {
*self = *self + other;
}
}
impl<const LIMBS: usize> Add for Checked<Uint<LIMBS>> {
type Output = Self;
fn add(self, rhs: Self) -> Checked<Uint<LIMBS>> {
Checked(
self.0
.and_then(|lhs| rhs.0.and_then(|rhs| lhs.checked_add(&rhs))),
)
}
}
impl<const LIMBS: usize> Add<&Checked<Uint<LIMBS>>> for Checked<Uint<LIMBS>> {
type Output = Checked<Uint<LIMBS>>;
fn add(self, rhs: &Checked<Uint<LIMBS>>) -> Checked<Uint<LIMBS>> {
Checked(
self.0
.and_then(|lhs| rhs.0.and_then(|rhs| lhs.checked_add(&rhs))),
)
}
}
impl<const LIMBS: usize> Add<Checked<Uint<LIMBS>>> for &Checked<Uint<LIMBS>> {
type Output = Checked<Uint<LIMBS>>;
fn add(self, rhs: Checked<Uint<LIMBS>>) -> Checked<Uint<LIMBS>> {
Checked(
self.0
.and_then(|lhs| rhs.0.and_then(|rhs| lhs.checked_add(&rhs))),
)
}
}
impl<const LIMBS: usize> Add<&Checked<Uint<LIMBS>>> for &Checked<Uint<LIMBS>> {
type Output = Checked<Uint<LIMBS>>;
fn add(self, rhs: &Checked<Uint<LIMBS>>) -> Checked<Uint<LIMBS>> {
Checked(
self.0
.and_then(|lhs| rhs.0.and_then(|rhs| lhs.checked_add(&rhs))),
)
}
}
impl<const LIMBS: usize> AddAssign for Checked<Uint<LIMBS>> {
fn add_assign(&mut self, other: Self) {
*self = *self + other;
}
}
impl<const LIMBS: usize> AddAssign<&Checked<Uint<LIMBS>>> for Checked<Uint<LIMBS>> {
fn add_assign(&mut self, other: &Self) {
*self = *self + other;
}
}
#[cfg(test)]
mod tests {
use crate::{CheckedAdd, Limb, U128};
#[test]
fn adc_no_carry() {
let (res, carry) = U128::ZERO.adc(&U128::ONE, Limb::ZERO);
assert_eq!(res, U128::ONE);
assert_eq!(carry, Limb::ZERO);
}
#[test]
fn adc_with_carry() {
let (res, carry) = U128::MAX.adc(&U128::ONE, Limb::ZERO);
assert_eq!(res, U128::ZERO);
assert_eq!(carry, Limb::ONE);
}
#[test]
fn saturating_add_no_carry() {
assert_eq!(U128::ZERO.saturating_add(&U128::ONE), U128::ONE);
}
#[test]
fn saturating_add_with_carry() {
assert_eq!(U128::MAX.saturating_add(&U128::ONE), U128::MAX);
}
#[test]
fn wrapping_add_no_carry() {
assert_eq!(U128::ZERO.wrapping_add(&U128::ONE), U128::ONE);
}
#[test]
fn wrapping_add_with_carry() {
assert_eq!(U128::MAX.wrapping_add(&U128::ONE), U128::ZERO);
}
#[test]
fn checked_add_ok() {
let result = U128::ZERO.checked_add(&U128::ONE);
assert_eq!(result.unwrap(), U128::ONE);
}
#[test]
fn checked_add_overflow() {
let result = U128::MAX.checked_add(&U128::ONE);
assert!(!bool::from(result.is_some()));
}
}
|
