FEAT: Add ArrayVec.extend_from_slice

Author: Thomasdezeeuw

src/lib.rs

@@ -527,6 +527,39 @@ impl<A: Array> ArrayVec<A> {
         self.len = Index::from(length);
     }
 
+    /// Copy and appends all elements in a slice to the `ArrayVec`.
+    ///
+    /// ```
+    /// use arrayvec::ArrayVec;
+    ///
+    /// let mut vec: ArrayVec<[usize; 10]> = ArrayVec::new();
+    /// vec.push(1);
+    /// vec.extend_from_slice(&[2, 3]);
+    /// assert_eq!(&vec[..], &[1, 2, 3]);
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This method will panic if the capacity left (see [`capacity_left`]) is
+    /// smaller then the length of the provided slice.
+    ///
+    /// [`capacity_left`]: #method.capacity_left
+    pub fn extend_from_slice(&mut self, other: &[A::Item])
+        where A::Item: Copy,
+    {
+        if self.capacity_left() < other.len() {
+            panic!("ArrayVec::extend_from_slice: slice is larger then capacity left");
+        }
+
+        let self_len = self.len();
+        let other_len = other.len();
+
+        unsafe {
+            let dst = self.xs.as_mut_ptr().offset(self_len as isize);
+            ptr::copy_nonoverlapping(other.as_ptr(), dst, other_len);
+            self.set_len(self_len + other_len);
+        }
+    }
 
     /// Create a draining iterator that removes the specified range in the vector
     /// and yields the removed items from start to end. The element range is

tests/tests.rs

@@ -41,6 +41,17 @@ fn test_capacity_left() {
     assert_eq!(vec.capacity_left(), 0);
 }
 
+#[test]
+fn test_extend_from_slice() {
+    let mut vec: ArrayVec<[usize; 10]> = ArrayVec::new();
+
+    vec.extend_from_slice(&[1, 2, 3]);
+    assert_eq!(vec.len(), 3);
+    assert_eq!(&vec[..], &[1, 2, 3]);
+    assert_eq!(vec.pop(), Some(3));
+    assert_eq!(&vec[..], &[1, 2]);
+}
+
 #[test]
 fn test_u16_index() {
     const N: usize = 4096;