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Fix multiplication for uint256 (#88)

This commit is contained in:
Igor Aleksanov 2018-05-28 21:41:07 +03:00 committed by Tamás Blummer
parent feec1cae70
commit 881972b2a5
1 changed files with 43 additions and 4 deletions
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47
src/util/uint.rs
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@ -61,12 +61,17 @@ macro_rules! construct_uint {
let mut carry = [0u64; $n_words]; let mut carry = [0u64; $n_words];
let mut ret = [0u64; $n_words]; let mut ret = [0u64; $n_words];
for i in 0..$n_words { for i in 0..$n_words {
let not_last_word = i < $n_words - 1;
let upper = other as u64 * (arr[i] >> 32); let upper = other as u64 * (arr[i] >> 32);
let lower = other as u64 * (arr[i] & 0xFFFFFFFF); let lower = other as u64 * (arr[i] & 0xFFFFFFFF);
if i < 3 { if not_last_word {
carry[i + 1] += upper >> 32; carry[i + 1] += upper >> 32;
} }
ret[i] = lower + (upper << 32); let (sum, overflow) = lower.overflowing_add(upper << 32);
ret[i] = sum;
if overflow && not_last_word {
carry[i + 1] += 1;
}
} }
$name(ret) + $name(carry) $name(ret) + $name(carry)
} }
@ -118,10 +123,11 @@ macro_rules! construct_uint {
type Output = $name; type Output = $name;
fn mul(self, other: $name) -> $name { fn mul(self, other: $name) -> $name {
let mut me = self; let mut me = $name::zero();
// TODO: be more efficient about this // TODO: be more efficient about this
for i in 0..(2 * $n_words) { for i in 0..(2 * $n_words) {
me = (me + me.mul_u32((other >> (32 * i)).low_u32())) << (32 * i); let to_mul = (other >> (32 * i)).low_u32();
me = me + (self.mul_u32(to_mul) << (32 * i));
} }
me me
} }
@ -468,6 +474,39 @@ mod tests {
// TODO: bit inversion // TODO: bit inversion
} }
#[test]
pub fn mul_u32_test() {
let u64_val = Uint256::from_u64(0xDEADBEEFDEADBEEF).unwrap();
let u96_res = u64_val.mul_u32(0xFFFFFFFF);
let u128_res = u96_res.mul_u32(0xFFFFFFFF);
let u160_res = u128_res.mul_u32(0xFFFFFFFF);
let u192_res = u160_res.mul_u32(0xFFFFFFFF);
let u224_res = u192_res.mul_u32(0xFFFFFFFF);
let u256_res = u224_res.mul_u32(0xFFFFFFFF);
assert_eq!(u96_res, Uint256([0xffffffff21524111u64, 0xDEADBEEE, 0, 0]));
assert_eq!(u128_res, Uint256([0x21524111DEADBEEFu64, 0xDEADBEEE21524110, 0, 0]));
assert_eq!(u160_res, Uint256([0xBD5B7DDD21524111u64, 0x42A4822200000001, 0xDEADBEED, 0]));
assert_eq!(u192_res, Uint256([0x63F6C333DEADBEEFu64, 0xBD5B7DDFBD5B7DDB, 0xDEADBEEC63F6C334, 0]));
assert_eq!(u224_res, Uint256([0x7AB6FBBB21524111u64, 0xFFFFFFFBA69B4558, 0x854904485964BAAA, 0xDEADBEEB]));
assert_eq!(u256_res, Uint256([0xA69B4555DEADBEEFu64, 0xA69B455CD41BB662, 0xD41BB662A69B4550, 0xDEADBEEAA69B455C]));
}
#[test]
pub fn multiplication_test() {
let u64_val = Uint256::from_u64(0xDEADBEEFDEADBEEF).unwrap();
let u128_res = u64_val * u64_val;
assert_eq!(u128_res, Uint256([0x048D1354216DA321u64, 0xC1B1CD13A4D13D46, 0, 0]));
let u256_res = u128_res * u128_res;
assert_eq!(u256_res, Uint256([0xF4E166AAD40D0A41u64, 0xF5CF7F3618C2C886u64,
0x4AFCFF6F0375C608u64, 0x928D92B4D7F5DF33u64]));
}
#[test] #[test]
pub fn uint256_bitslice_test() { pub fn uint256_bitslice_test() {
let init = Uint256::from_u64(0xDEADBEEFDEADBEEF).unwrap(); let init = Uint256::from_u64(0xDEADBEEFDEADBEEF).unwrap();