Add push_many_from_slice method

src/arrayvec.rs

@@ -579,6 +579,35 @@ impl<T, const CAP: usize> ArrayVec<T, CAP> {
         Ok(())
     }
 
+    /// Copy as many elements as we can from the slice and append to the `ArrayVec`.
+    ///
+    /// ```
+    /// use arrayvec::ArrayVec;
+    ///
+    /// let mut vec: ArrayVec<usize, 2> = ArrayVec::new();
+    /// vec.push(1);
+    /// let rest = vec.push_many_from_slice(&[2, 3]);
+    /// assert_eq!(&vec[..], &[1, 2]);
+    /// assert_eq!(rest, &[3]);
+    /// ```
+    ///
+    /// Can be thought of as a variation of [try_extend_from_slice] where
+    /// instead of failing, it does the "best it can" (extends the `ArrayVec`
+    /// with some but not all of the elements).
+    pub fn push_many_from_slice<'a, 'b>(&'a mut self, other: &'b [T]) -> &'b [T]
+        where T: Copy,
+    {
+        let self_len = self.len();
+        let take = usize::min(self.remaining_capacity(), other.len());
+
+        unsafe {
+            let dst = self.get_unchecked_ptr(self_len);
+            ptr::copy_nonoverlapping(other.as_ptr(), dst, take);
+            self.set_len(self_len + take);
+        }
+        &other[take..]
+    }
+
     /// 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
     /// removed even if the iterator is not consumed until the end.

tests/tests.rs

@@ -74,6 +74,21 @@ fn test_try_from_slice_error() {
     assert_matches!(res, Err(_));
 }
 
+#[test]
+fn test_push_many_from_slice() {
+    let mut vec: ArrayVec<usize,  4> = ArrayVec::new();
+
+    let ret = vec.push_many_from_slice(&[1, 2, 3]);
+    assert_eq!(ret, &[]);
+    assert_eq!(vec.len(), 3);
+    assert_eq!(&vec[..], &[1, 2, 3]);
+    assert_eq!(vec.pop(), Some(3));
+    assert_eq!(&vec[..], &[1, 2]);
+    let ret = vec.push_many_from_slice(&[3, 4, 5, 6]);
+    assert_eq!(&vec[..], &[1, 2, 3, 4]);
+    assert_eq!(ret, &[5, 6]);
+}
+
 #[test]
 fn test_u16_index() {
     const N: usize = 4096;
@@ -790,4 +805,4 @@ fn test_arraystring_zero_filled_has_some_sanity_checks() {
     let string = ArrayString::<4>::zero_filled();
     assert_eq!(string.as_str(), "\0\0\0\0");
     assert_eq!(string.len(), 4);
-}
+}