Fix BigInt => u128 conversion. (#352)

Fix BigInt => u128 conversion.

Author: oskin1

chain/rust/src/utils.rs

@@ -383,13 +383,13 @@ impl BigInteger {
  match *u32_digits {
  [] => Some(0),
  [a] => Some(u128::from(a)),
- [a, b] => Some(u128::from(b) | (u128::from(a) << 32)),
- [a, b, c] => Some(u128::from(c) | (u128::from(b) << 32) | (u128::from(a) << 64)),
+ [a, b] => Some(u128::from(a) | (u128::from(b) << 32)),
+ [a, b, c] => Some(u128::from(a) | (u128::from(b) << 32) | (u128::from(c) << 64)),
  [a, b, c, d] => Some(
- u128::from(d)
- | (u128::from(c) << 32)
- | (u128::from(b) << 64)
- | (u128::from(a) << 96),
+ u128::from(a)
+ | (u128::from(b) << 32)
+ | (u128::from(c) << 64)
+ | (u128::from(d) << 96),
  ),
  _ => None,
  }
@@ -1047,6 +1047,36 @@ mod tests {
  assert_eq!(x.to_string(), "18446744073709551615");
  }
 
+ #[test]
+ fn bigint_uint_u128_roundtrip() {
+ let int = 462_164_030_739_157_517;
+ let x = BigInteger::from_int(&Int::Uint {
+ value: int,
+ encoding: None,
+ });
+ assert_eq!(x.as_u128(), Some(int as u128))
+ }
+
+ #[test]
+ fn bigint_uint_u128_roundtrip_min() {
+ let int = u64::MIN;
+ let x = BigInteger::from_int(&Int::Uint {
+ value: int,
+ encoding: None,
+ });
+ assert_eq!(x.as_u128(), Some(int as u128))
+ }
+
+ #[test]
+ fn bigint_uint_u128_roundtrip_max() {
+ let int = u64::MAX;
+ let x = BigInteger::from_int(&Int::Uint {
+ value: int,
+ encoding: None,
+ });
+ assert_eq!(x.as_u128(), Some(int as u128))
+ }
+
  #[test]
  fn bigint_uint_u128_min() {
  let bytes = [0x00];