Some(tail)
}
}
+
+ #[inline]
+ fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
+ let len = self.len();
+ if n >= len {
+ self.v = &mut [];
+ None
+ } else {
+ let start = (len - 1 - n) * self.chunk_size;
+ let end = match start.checked_add(self.chunk_size) {
+ Some(res) => cmp::min(res, self.v.len()),
+ None => self.v.len(),
+ };
+ let (temp, _tail) = mem::replace(&mut self.v, &mut []).split_at_mut(end);
+ let (head, nth_back) = temp.split_at_mut(start);
+ self.v = head;
+ Some(nth_back)
+ }
+ }
}
#[stable(feature = "rust1", since = "1.0.0")]
assert_eq!(c2.next(), None);
}
+#[test]
+fn test_chunks_mut_nth_back() {
+ let v: &mut [i32] = &mut [0, 1, 2, 3, 4, 5];
+ let mut c = v.chunks_mut(2);
+ assert_eq!(c.nth_back(1).unwrap(), &[2, 3]);
+ assert_eq!(c.next().unwrap(), &[0, 1]);
+
+ let v1: &mut [i32] = &mut [0, 1, 2, 3, 4];
+ let mut c1 = v1.chunks_mut(3);
+ assert_eq!(c1.nth_back(1).unwrap(), &[0, 1, 2]);
+ assert_eq!(c1.next(), None);
+
+ let v3: &mut [i32] = &mut [0, 1, 2, 3, 4];
+ let mut c3 = v3.chunks_mut(10);
+ assert_eq!(c3.nth_back(0).unwrap(), &[0, 1, 2, 3, 4]);
+ assert_eq!(c3.next(), None);
+
+ let v4: &mut [i32] = &mut [0, 1, 2];
+ let mut c4 = v4.chunks_mut(10);
+ assert_eq!(c4.nth_back(1_000_000_000usize), None);
+}
+
#[test]
fn test_chunks_mut_last() {
let v: &mut [i32] = &mut [0, 1, 2, 3, 4, 5];