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use crate::stable_hasher::{HashStable, StableHasher};
#[derive(Clone, Encodable, Decodable, Debug)]
pub struct ThinVec<T>(Option<Box<Vec<T>>>);
impl<T> ThinVec<T> {
pub fn new() -> Self {
ThinVec(None)
}
}
impl<T> From<Vec<T>> for ThinVec<T> {
fn from(vec: Vec<T>) -> Self {
if vec.is_empty() { ThinVec(None) } else { ThinVec(Some(Box::new(vec))) }
}
}
impl<T> Into<Vec<T>> for ThinVec<T> {
fn into(self) -> Vec<T> {
match self {
ThinVec(None) => Vec::new(),
ThinVec(Some(vec)) => *vec,
}
}
}
impl<T> ::std::ops::Deref for ThinVec<T> {
type Target = [T];
fn deref(&self) -> &[T] {
match *self {
ThinVec(None) => &[],
ThinVec(Some(ref vec)) => vec,
}
}
}
impl<T> ::std::ops::DerefMut for ThinVec<T> {
fn deref_mut(&mut self) -> &mut [T] {
match *self {
ThinVec(None) => &mut [],
ThinVec(Some(ref mut vec)) => vec,
}
}
}
impl<T> Extend<T> for ThinVec<T> {
fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
match *self {
ThinVec(Some(ref mut vec)) => vec.extend(iter),
ThinVec(None) => *self = iter.into_iter().collect::<Vec<_>>().into(),
}
}
fn extend_one(&mut self, item: T) {
match *self {
ThinVec(Some(ref mut vec)) => vec.push(item),
ThinVec(None) => *self = vec![item].into(),
}
}
fn extend_reserve(&mut self, additional: usize) {
match *self {
ThinVec(Some(ref mut vec)) => vec.reserve(additional),
ThinVec(None) => *self = Vec::with_capacity(additional).into(),
}
}
}
impl<T: HashStable<CTX>, CTX> HashStable<CTX> for ThinVec<T> {
fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
(**self).hash_stable(hcx, hasher)
}
}
impl<T> Default for ThinVec<T> {
fn default() -> Self {
Self(None)
}
}