sbb static method
Implementation
static List<BigInt> sbb(BigInt a, BigInt b, BigInt borrow) {
final s = b + (borrow >> 63);
assert(s <= BinaryOps.maxU128);
BigInt diff = (a - s);
BigInt low = diff.toU64;
BigInt high = (diff >> 64).toU64;
return [low, high];
}