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use std::{collections::HashSet, future::Future, hash::Hash, pin::Pin, task::Poll};
pub fn _race_pop<'a, T: 'a, F: Future<Output = T> + Unpin>(
futures: &'a mut Vec<F>,
) -> impl Future<Output = Option<T>> + 'a {
_FutureRacePop { futures }
}
struct _FutureRacePop<'a, T, F: Future<Output = T> + Unpin> {
futures: &'a mut Vec<F>,
}
impl<T, F: Future<Output = T> + Unpin> Future for _FutureRacePop<'_, T, F> {
type Output = Option<T>;
fn poll(mut self: Pin<&mut Self>, cx: &mut std::task::Context<'_>) -> Poll<Self::Output> {
if self.futures.is_empty() {
return Poll::Ready(None);
}
match self.futures.iter_mut().enumerate().find_map(|(i, future)| {
match Pin::new(future).poll(cx) {
Poll::Ready(res) => Some((i, res)),
Poll::Pending => None,
}
}) {
Some((i, res)) => {
self.futures.swap_remove(i);
Poll::Ready(Some(res))
}
None => Poll::Pending,
}
}
}
pub async fn _visit<N, V, F, R, L, G, T>(node: N, visit: V, get_referenced_nodes: R) -> Vec<T>
where
N: Clone + Hash + PartialEq + Eq,
V: Fn(N) -> F,
F: Future<Output = T>,
R: Fn(N) -> G,
L: IntoIterator<Item = N>,
G: Future<Output = L>,
{
let mut visited = HashSet::new();
let mut results = Vec::new();
visited.insert(node.clone());
let mut queue = vec![node];
let mut futures_queue = Vec::new();
loop {
match queue.pop() {
Some(node) => {
results.push(visit(node.clone()).await);
futures_queue.push(Box::pin(get_referenced_nodes(node)));
}
None => match _race_pop(&mut futures_queue).await {
Some(iter) => {
for node in iter {
if !visited.contains(&node) {
visited.insert(node.clone());
queue.push(node.clone());
}
}
}
None => break,
},
}
}
assert!(futures_queue.is_empty());
results
}
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