1 /// A vector type optimized for cases where this size is usually 0 (cf. `SmallVector`).
2 /// The `Option<Box<..>>` wrapping allows us to represent a zero sized vector with `None`,
3 /// which uses only a single (null) pointer.
4 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
5 pub struct ThinVec<T>(Option<Box<Vec<T>>>);
13 impl<T> From<Vec<T>> for ThinVec<T> {
14 fn from(vec: Vec<T>) -> Self {
18 ThinVec(Some(Box::new(vec)))
23 impl<T> Into<Vec<T>> for ThinVec<T> {
24 fn into(self) -> Vec<T> {
26 ThinVec(None) => Vec::new(),
27 ThinVec(Some(vec)) => *vec,
32 impl<T> ::std::ops::Deref for ThinVec<T> {
34 fn deref(&self) -> &[T] {
37 ThinVec(Some(ref vec)) => vec,
42 impl<T> ::std::ops::DerefMut for ThinVec<T> {
43 fn deref_mut(&mut self) -> &mut [T] {
45 ThinVec(None) => &mut [],
46 ThinVec(Some(ref mut vec)) => vec,
51 impl<T> Extend<T> for ThinVec<T> {
52 fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
54 ThinVec(Some(ref mut vec)) => vec.extend(iter),
55 ThinVec(None) => *self = iter.into_iter().collect::<Vec<_>>().into(),