Merge pull request #430 from cuviper/split_at_checked

Add `Slice::split_at_checked` and `split_at_mut_checked`

Author: cuviper

src/map/slice.rs

@@ -124,6 +124,7 @@ impl<K, V> Slice<K, V> {
     /// Divides one slice into two at an index.
     ///
     /// ***Panics*** if `index > len`.
+    /// For a non-panicking alternative see [`split_at_checked`][Self::split_at_checked].
     #[track_caller]
     pub fn split_at(&self, index: usize) -> (&Self, &Self) {
         let (first, second) = self.entries.split_at(index);
@@ -133,12 +134,29 @@ impl<K, V> Slice<K, V> {
     /// Divides one mutable slice into two at an index.
     ///
     /// ***Panics*** if `index > len`.
+    /// For a non-panicking alternative see [`split_at_mut_checked`][Self::split_at_mut_checked].
     #[track_caller]
     pub fn split_at_mut(&mut self, index: usize) -> (&mut Self, &mut Self) {
         let (first, second) = self.entries.split_at_mut(index);
         (Self::from_mut_slice(first), Self::from_mut_slice(second))
     }
 
+    /// Divides one slice into two at an index.
+    ///
+    /// Returns `None` if `index > len`.
+    pub fn split_at_checked(&self, index: usize) -> Option<(&Self, &Self)> {
+        let (first, second) = self.entries.split_at_checked(index)?;
+        Some((Self::from_slice(first), Self::from_slice(second)))
+    }
+
+    /// Divides one mutable slice into two at an index.
+    ///
+    /// Returns `None` if `index > len`.
+    pub fn split_at_mut_checked(&mut self, index: usize) -> Option<(&mut Self, &mut Self)> {
+        let (first, second) = self.entries.split_at_mut_checked(index)?;
+        Some((Self::from_mut_slice(first), Self::from_mut_slice(second)))
+    }
+
     /// Returns the first key-value pair and the rest of the slice,
     /// or `None` if it is empty.
     pub fn split_first(&self) -> Option<((&K, &V), &Self)> {

src/set/slice.rs

@@ -85,12 +85,21 @@ impl<T> Slice<T> {
     /// Divides one slice into two at an index.
     ///
     /// ***Panics*** if `index > len`.
+    /// For a non-panicking alternative see [`split_at_checked`][Self::split_at_checked].
     #[track_caller]
     pub fn split_at(&self, index: usize) -> (&Self, &Self) {
         let (first, second) = self.entries.split_at(index);
         (Self::from_slice(first), Self::from_slice(second))
     }
 
+    /// Divides one slice into two at an index.
+    ///
+    /// Returns `None` if `index > len`.
+    pub fn split_at_checked(&self, index: usize) -> Option<(&Self, &Self)> {
+        let (first, second) = self.entries.split_at_checked(index)?;
+        Some((Self::from_slice(first), Self::from_slice(second)))
+    }
+
     /// Returns the first value and the rest of the slice,
     /// or `None` if it is empty.
     pub fn split_first(&self) -> Option<(&T, &Self)> {