1 use crate::big_digit::{BigDigit, DoubleBigDigit, BITS};
2
3 // Add with carry:
4 #[inline]
adc(a: BigDigit, b: BigDigit, acc: &mut DoubleBigDigit) -> BigDigit5 pub fn adc(a: BigDigit, b: BigDigit, acc: &mut DoubleBigDigit) -> BigDigit {
6 *acc += a as DoubleBigDigit;
7 *acc += b as DoubleBigDigit;
8 let lo = *acc as BigDigit;
9 *acc >>= BITS;
10 lo
11 }
12
13 // Only for the Add impl:
14 #[inline]
__add2(a: &mut [BigDigit], b: &[BigDigit]) -> BigDigit15 pub fn __add2(a: &mut [BigDigit], b: &[BigDigit]) -> BigDigit {
16 debug_assert!(a.len() >= b.len());
17
18 let mut carry = 0;
19 let (a_lo, a_hi) = a.split_at_mut(b.len());
20
21 for (a, b) in a_lo.iter_mut().zip(b) {
22 *a = adc(*a, *b, &mut carry);
23 }
24
25 if carry != 0 {
26 for a in a_hi {
27 *a = adc(*a, 0, &mut carry);
28 if carry == 0 {
29 break;
30 }
31 }
32 }
33
34 carry as BigDigit
35 }
36
37 /// /Two argument addition of raw slices:
38 /// a += b
39 ///
40 /// The caller _must_ ensure that a is big enough to store the result - typically this means
41 /// resizing a to max(a.len(), b.len()) + 1, to fit a possible carry.
add2(a: &mut [BigDigit], b: &[BigDigit])42 pub fn add2(a: &mut [BigDigit], b: &[BigDigit]) {
43 let carry = __add2(a, b);
44
45 debug_assert!(carry == 0);
46 }
47