fix add

src/lib.rs

@@ -19,6 +19,7 @@ use num_bigint::BigUint;
 use num_bigint::Sign;
 
 use core::mem::ManuallyDrop;
+use core::ops::Add;
 
 /// An error that occurred when processing a `SmallInt`.
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -77,6 +78,111 @@ impl core::fmt::Debug for SmallUint {
     }
 }
 
+fn add_two_slices(slice1: &[u32], slice2: &[u32]) -> Vec<u32> {
+
+    let s = slice1.len();
+    let j = slice2.len();
+
+    let larger = std::cmp::max(s, j);
+    let mut res = Vec::with_capacity(larger + 1);
+    let mut carry = false;
+
+    for t in 0..larger {
+
+        let value1 = if t < s {
+            slice1[t]
+        } else {
+            0
+        };
+
+        let value2 = if t < j {
+            slice2[t]
+        } else {
+            0
+        };
+
+        let (val, overflow) = value1.overflowing_add(value2);
+        let (cval, coverflow) = val.overflowing_add(carry as u32);
+        res.push(cval);
+        carry = overflow | coverflow;
+
+    }
+
+    if carry {
+        res.push(1);
+    }
+    while res[res.len() - 1] == 0 {
+        res.pop();
+    }
+    res
+}
+
+impl Add<SmallUint> for SmallUint {
+    type Output = SmallUint;
+
+    fn add(self, rhs: SmallUint) -> Self::Output {
+        match (&self.0, &rhs.0) {
+            (&SmallUintType::Inline(i), &SmallUintType::Inline(j)) => {
+                match i.overflowing_add(j) {
+                    (t, false) => Self(SmallUintType::Inline(t)),
+                    (t, true) => {
+                        let mut res = [0, 0, 0, 0, 1];
+
+                        let mut v = t;
+                        #[allow(clippy::needless_range_loop)]
+                        for r in 0..4 {
+                            res[r] = v as u32;
+
+                            v >>= 32;
+                        }
+
+                        let mut slice = ManuallyDrop::new(<Box<[u32]>>::from(res));
+
+                        Self(SmallUintType::Heap((slice.as_mut_ptr(), 5)))
+
+                    }
+                }
+            },
+            (&SmallUintType::Heap((r, s)), &SmallUintType::Inline(i)) | (&SmallUintType::Inline(i), &SmallUintType::Heap((r, s))) => {
+                let slice1 = unsafe { core::slice::from_raw_parts(r, s) };
+
+                let mut res = [0, 0, 0, 0];
+
+                let mut v = i;
+                #[allow(clippy::needless_range_loop)]
+                for r in 0..4 {
+                    res[r] = v as u32;
+
+                    v >>= 32;
+                }
+
+                let result = add_two_slices(slice1, &res[..]);
+                let size = result.len();
+
+                let mut slice = ManuallyDrop::new(result.into_boxed_slice());
+
+                Self(SmallUintType::Heap((slice.as_mut_ptr(), size)))
+
+
+            },
+            (&SmallUintType::Heap((r, s)), &SmallUintType::Heap((i, j))) => {
+
+                let slice1 = unsafe { core::slice::from_raw_parts(r, s) };
+                let slice2 = unsafe { core::slice::from_raw_parts(i, j) };
+
+                let res = add_two_slices(slice1, slice2);
+                let size = res.len();
+
+                let mut slice = ManuallyDrop::new(res.into_boxed_slice());
+
+                Self(SmallUintType::Heap((slice.as_mut_ptr(), size)))
+
+            }
+        }
+    }
+}
+
+
 impl Drop for SmallInt {
     fn drop(&mut self) {
         if let Self(SmallIntType::Heap((r, s))) = self {
@@ -322,9 +428,10 @@ impl From<&SmallUint> for BigUint {
 mod conversion_tests {
 
     use crate::SmallInt;
+    use crate::SmallUint;
 
     #[cfg(feature = "num-bigint")]
-    use num_bigint::{BigInt, Sign};
+    use num_bigint::{BigInt, Sign, BigUint};
 
     macro_rules! conversion_tests {
         ($t:ty, $i:ident) => {
@@ -352,6 +459,25 @@ mod conversion_tests {
     conversion_tests!(u128, test_u128);
     conversion_tests!(i128, test_i128);
 
+    #[test]
+    #[cfg(feature = "num-bigint")]
+    fn test_op_add_u_u() {
+        let i = SmallUint::from(u128::MAX);
+        let k = SmallUint::from(u128::MAX);
+        let q = i + k;
+        assert_eq!(BigUint::from(&q), BigUint::from(u128::MAX) + u128::MAX);
+
+        let i = SmallUint::from(u128::MAX);
+        let k = SmallUint::from(&BigUint::new(vec![5, 4, 9, 3, 1, 81]));
+        let q = i + k;
+        assert_eq!(BigUint::from(&q), BigUint::new(vec![5, 4, 9, 3, 1, 81]) + u128::MAX);
+
+        let i = SmallUint::from(&BigUint::new(vec![3, 9, 8]));
+        let k = SmallUint::from(&BigUint::new(vec![5, 4, 9, 3, 1, 81]));
+        let q = i + k;
+        assert_eq!(BigUint::from(&q), BigUint::new(vec![3, 9, 8]) + BigUint::new(vec![5, 4, 9, 3, 1, 81]));
+    }
+
     #[test]
     #[cfg(feature = "num-bigint")]
     fn test_bigint() {