1 files changed, 51 insertions, 0 deletions
diff --git a/vendor/crypto-bigint/src/uint/neg.rs b/vendor/crypto-bigint/src/uint/neg.rs
new file mode 100644
index 0000000..4881a27
--- /dev/null
+++ b/vendor/crypto-bigint/src/uint/neg.rs
@@ -0,0 +1,51 @@
+use core::ops::Neg;
+
+use crate::{CtChoice, Limb, Uint, WideWord, Word, Wrapping};
+
+impl<const LIMBS: usize> Neg for Wrapping<Uint<LIMBS>> {
+    type Output = Self;
+
+    fn neg(self) -> Self::Output {
+        Self(self.0.wrapping_neg())
+    }
+}
+
+impl<const LIMBS: usize> Uint<LIMBS> {
+    /// Negates based on `choice` by wrapping the integer.
+    pub(crate) const fn conditional_wrapping_neg(&self, choice: CtChoice) -> Uint<LIMBS> {
+        Uint::ct_select(self, &self.wrapping_neg(), choice)
+    }
+
+    /// Perform wrapping negation.
+    pub const fn wrapping_neg(&self) -> Self {
+        let mut ret = [Limb::ZERO; LIMBS];
+        let mut carry = 1;
+        let mut i = 0;
+        while i < LIMBS {
+            let r = (!self.limbs[i].0 as WideWord) + carry;
+            ret[i] = Limb(r as Word);
+            carry = r >> Limb::BITS;
+            i += 1;
+        }
+        Uint::new(ret)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::U256;
+
+    #[test]
+    fn wrapping_neg() {
+        assert_eq!(U256::ZERO.wrapping_neg(), U256::ZERO);
+        assert_eq!(U256::MAX.wrapping_neg(), U256::ONE);
+        assert_eq!(
+            U256::from_u64(13).wrapping_neg(),
+            U256::from_u64(13).not().saturating_add(&U256::ONE)
+        );
+        assert_eq!(
+            U256::from_u64(42).wrapping_neg(),
+            U256::from_u64(42).saturating_sub(&U256::ONE).not()
+        );
+    }
+}