Implement insert_slice for SmallVec

Author: nipunn1313

lib.rs

@@ -315,6 +315,16 @@ impl<A: Array> SmallVec<A> {
             self.set_len(len + 1);
         }
     }
+
+    fn insert_many<I: IntoIterator<Item=A::Item>>(&mut self, index: usize, iterable: I) {
+        let iter = iterable.into_iter();
+        let (lower_size_bound, _) = iter.size_hint();
+        self.reserve(lower_size_bound);
+
+        for (off, elem) in iter.enumerate() {
+            self.insert(index + off, elem);
+        }
+    }
 }
 
 impl<A: Array> ops::Deref for SmallVec<A> {
@@ -423,19 +433,10 @@ impl<A: Array> FromIterator<A::Item> for SmallVec<A> {
 }
 
 impl<A: Array> Extend<A::Item> for SmallVec<A> {
+    #[inline]
     fn extend<I: IntoIterator<Item=A::Item>>(&mut self, iterable: I) {
-        let iter = iterable.into_iter();
-        let (lower_size_bound, _) = iter.size_hint();
-
-        let target_len = self.len + lower_size_bound;
-
-        if target_len > self.capacity() {
-           self.grow(target_len);
-        }
-
-        for elem in iter {
-            self.push(elem);
-        }
+        let len = self.len();
+        self.insert_many(len, iterable);
     }
 }
 
@@ -869,6 +870,17 @@ pub mod tests {
         assert_eq!(&v.iter().map(|v| **v).collect::<Vec<_>>(), &[0, 3, 2]);
     }
 
+    #[test]
+    fn test_insert_many() {
+        let mut v: SmallVec<[u8; 8]> = SmallVec::new();
+        for x in 0..4 {
+            v.push(x);
+        }
+        assert_eq!(v.len(), 4);
+        v.insert_many(1, [5, 6].iter().cloned());
+        assert_eq!(&v.iter().map(|v| *v).collect::<Vec<_>>(), &[0, 5, 6, 1, 2, 3]);
+    }
+
     #[test]
     #[should_panic]
     fn test_drop_panic_smallvec() {