59 lines
1.7 KiB
Rust
59 lines
1.7 KiB
Rust
// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
|
|
// file at the top-level directory of this distribution and at
|
|
// http://rust-lang.org/COPYRIGHT.
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
|
|
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
|
|
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
|
|
// option. This file may not be copied, modified, or distributed
|
|
// except according to those terms.
|
|
|
|
/// A vector type optimized for cases where this size is usually 0 (c.f. `SmallVector`).
|
|
/// The `Option<Box<..>>` wrapping allows us to represent a zero sized vector with `None`,
|
|
/// which uses only a single (null) pointer.
|
|
#[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, 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> 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(),
|
|
}
|
|
}
|
|
}
|