Add Overflowing trait

Closes issue #168

Author: Kamil Niski

src/ops/mod.rs

@@ -1,5 +1,6 @@
 pub mod checked;
 pub mod inv;
 pub mod mul_add;
+pub mod overflowing;
 pub mod saturating;
 pub mod wrapping;

src/ops/overflowing.rs

@@ -0,0 +1,97 @@
+use core::ops::{Add, Mul, Sub};
+
+macro_rules! overflowing_impl {
+    ($trait_name:ident, $method:ident, $t:ty) => {
+        impl $trait_name for $t {
+            #[inline]
+            fn $method(&self, v: &Self) -> (Self, bool) {
+                <$t>::$method(*self, *v)
+            }
+        }
+    };
+}
+
+/// If an overflow would have occurred then the wrapped value is returned.
+pub trait OverflowingAdd: Sized + Add<Self, Output = Self> {
+    /// Returns a tuple of the addition along with a boolean indicating whether an arithmetic overflow would occur.
+    fn overflowing_add(&self, v: &Self) -> (Self, bool);
+}
+
+overflowing_impl!(OverflowingAdd, overflowing_add, u8);
+overflowing_impl!(OverflowingAdd, overflowing_add, u16);
+overflowing_impl!(OverflowingAdd, overflowing_add, u32);
+overflowing_impl!(OverflowingAdd, overflowing_add, u64);
+overflowing_impl!(OverflowingAdd, overflowing_add, usize);
+#[cfg(has_i128)]
+overflowing_impl!(OverflowingAdd, overflowing_add, u128);
+
+overflowing_impl!(OverflowingAdd, overflowing_add, i8);
+overflowing_impl!(OverflowingAdd, overflowing_add, i16);
+overflowing_impl!(OverflowingAdd, overflowing_add, i32);
+overflowing_impl!(OverflowingAdd, overflowing_add, i64);
+overflowing_impl!(OverflowingAdd, overflowing_add, isize);
+#[cfg(has_i128)]
+overflowing_impl!(OverflowingAdd, overflowing_add, i128);
+
+/// If an overflow would have occurred then the wrapped value is returned.
+pub trait OverflowingSub: Sized + Sub<Self, Output = Self> {
+    /// Returns a tuple of the subtraction along with a boolean indicating whether an arithmetic overflow would occur.
+    fn overflowing_sub(&self, v: &Self) -> (Self, bool);
+}
+
+overflowing_impl!(OverflowingSub, overflowing_sub, u8);
+overflowing_impl!(OverflowingSub, overflowing_sub, u16);
+overflowing_impl!(OverflowingSub, overflowing_sub, u32);
+overflowing_impl!(OverflowingSub, overflowing_sub, u64);
+overflowing_impl!(OverflowingSub, overflowing_sub, usize);
+#[cfg(has_i128)]
+overflowing_impl!(OverflowingSub, overflowing_sub, u128);
+
+overflowing_impl!(OverflowingSub, overflowing_sub, i8);
+overflowing_impl!(OverflowingSub, overflowing_sub, i16);
+overflowing_impl!(OverflowingSub, overflowing_sub, i32);
+overflowing_impl!(OverflowingSub, overflowing_sub, i64);
+overflowing_impl!(OverflowingSub, overflowing_sub, isize);
+#[cfg(has_i128)]
+overflowing_impl!(OverflowingSub, overflowing_sub, i128);
+
+/// If an overflow would have occurred then the wrapped value is returned.
+pub trait OverflowingMul: Sized + Mul<Self, Output = Self> {
+    /// Returns a tuple of the subtraction along with a boolean indicating whether an arithmetic overflow would occur.
+    fn overflowing_mul(&self, v: &Self) -> (Self, bool);
+}
+
+overflowing_impl!(OverflowingMul, overflowing_mul, u8);
+overflowing_impl!(OverflowingMul, overflowing_mul, u16);
+overflowing_impl!(OverflowingMul, overflowing_mul, u32);
+overflowing_impl!(OverflowingMul, overflowing_mul, u64);
+overflowing_impl!(OverflowingMul, overflowing_mul, usize);
+#[cfg(has_i128)]
+overflowing_impl!(OverflowingMul, overflowing_mul, u128);
+
+overflowing_impl!(OverflowingMul, overflowing_mul, i8);
+overflowing_impl!(OverflowingMul, overflowing_mul, i16);
+overflowing_impl!(OverflowingMul, overflowing_mul, i32);
+overflowing_impl!(OverflowingMul, overflowing_mul, i64);
+overflowing_impl!(OverflowingMul, overflowing_mul, isize);
+#[cfg(has_i128)]
+overflowing_impl!(OverflowingMul, overflowing_mul, i128);
+
+#[test]
+fn test_overflowing_traits() {
+    fn overflowing_add<T: OverflowingAdd>(a: T, b: T) -> (T, bool) {
+        a.overflowing_add(&b)
+    }
+    fn overflowing_sub<T: OverflowingSub>(a: T, b: T) -> (T, bool) {
+        a.overflowing_sub(&b)
+    }
+    fn overflowing_mul<T: OverflowingMul>(a: T, b: T) -> (T, bool) {
+        a.overflowing_mul(&b)
+    }
+    assert_eq!(overflowing_add(5i16, 2), (7, false));
+    assert_eq!(overflowing_add(std::i16::MAX, 1), (std::i16::MIN, true));
+    assert_eq!(overflowing_sub(5i16, 2), (3, false));
+    assert_eq!(overflowing_sub(std::i16::MIN, 1), (std::i16::MAX, true));
+    assert_eq!(overflowing_mul(5i16, 2), (10, false));
+    assert_eq!(overflowing_mul(1_000_000_000i32, 10), (1410065408, true));
+}