dashu-int 0.6.0

Arbitrary-precision integer math library for Rust, balancing ergonomics and efficiency. Provides UBig and IBig (unsigned and signed), with small values inlined on the stack. Efficient arithmetic, modular arithmetic, and number theory (pow, ilog, gcd, gcd_ext); two's-complement bit operations; parsing and formatting in base 2-36; optional serde, rand, num-traits, rkyv, and zeroize.
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use crate::arch::word::Word;

/// Add a + b + carry.
///
/// Returns (result, overflow).
#[inline]
pub fn add_with_carry(a: Word, b: Word, carry: Word) -> (Word, Word) {
    let sum_nc = a.wrapping_add(b);
    let sum = sum_nc.wrapping_add(carry);
    let carry_out = Word::from(sum_nc < a) | Word::from(sum < sum_nc);
    (sum, carry_out)
}

/// Subtract a - b - borrow.
///
/// Returns (result, overflow).
#[inline]
pub fn sub_with_borrow(a: Word, b: Word, borrow: Word) -> (Word, Word) {
    let diff_nb = a.wrapping_sub(b);
    let diff = diff_nb.wrapping_sub(borrow);
    let borrow_out = Word::from(diff_nb > a) | Word::from(diff > diff_nb);
    (diff, borrow_out)
}