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//! Module containing the [`WeakVec`] API.
use std::sync::Weak;
/// An optimized container for `Weak` references of `T` that minimizes reallocations by
/// dropping older elements that no longer have strong references to them.
#[derive(Debug)]
pub(crate) struct WeakVec<T> {
inner: Vec<Weak<T>>,
}
impl<T> Default for WeakVec<T> {
fn default() -> Self {
Self {
inner: Default::default(),
}
}
}
impl<T> WeakVec<T> {
pub(crate) fn new() -> Self {
Self { inner: Vec::new() }
}
/// Pushes a new element to this collection.
///
/// If the inner Vec needs to be reallocated, we will first drop older elements that
/// no longer have strong references to them.
pub(crate) fn push(&mut self, value: Weak<T>) {
if self.inner.len() == self.inner.capacity() {
// Iterating backwards has the advantage that we don't do more work than we have to.
for i in (0..self.inner.len()).rev() {
if self.inner[i].strong_count() == 0 {
self.inner.swap_remove(i);
}
}
// Make sure our capacity is twice the number of live elements.
// Leaving some spare capacity ensures that we won't re-scan immediately.
self.inner.reserve_exact(self.inner.len());
}
self.inner.push(value);
}
}
pub(crate) struct WeakVecIter<T> {
inner: std::vec::IntoIter<Weak<T>>,
}
impl<T> Iterator for WeakVecIter<T> {
type Item = Weak<T>;
fn next(&mut self) -> Option<Self::Item> {
self.inner.next()
}
}
impl<T> IntoIterator for WeakVec<T> {
type Item = Weak<T>;
type IntoIter = WeakVecIter<T>;
fn into_iter(self) -> Self::IntoIter {
WeakVecIter {
inner: self.inner.into_iter(),
}
}
}