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lru: Stop mixed iteration when cursors meet #1121

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36 changes: 34 additions & 2 deletions pingora-lru/src/linked_list.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -469,7 +469,7 @@ impl<'a, K: Default + Clone> Iterator for LinkedListIter<'a, K> {

fn next(&mut self) -> Option<Self::Item> {
let next_index = self.list.next_compact(self.head);
if next_index == TAIL || next_index == NULL {
if next_index == self.tail || next_index == NULL {
None
} else {
self.head = next_index;
Expand All @@ -486,7 +486,7 @@ impl<'a, K: Default + Clone> Iterator for LinkedListIter<'a, K> {
impl<K: Default + Clone> DoubleEndedIterator for LinkedListIter<'_, K> {
fn next_back(&mut self) -> Option<Self::Item> {
let prev_index = self.list.prev_compact(self.tail);
if prev_index == HEAD || prev_index == NULL {
if prev_index == self.head || prev_index == NULL {
None
} else {
self.tail = prev_index;
Expand All @@ -511,6 +511,38 @@ mod test {
assert_eq!(values, &list_values)
}

#[test]
fn test_iter_front_after_back() {
let mut list = LinkedList::with_capacity(3);
for value in 0..3u64 {
list.push_tail(value);
}
let mut iter = list.iter();
assert_eq!(iter.next_back(), Some(&2));
assert_eq!(iter.next(), Some(&0));
assert_eq!(iter.next_back(), Some(&1));
assert_eq!(iter.size_hint(), (0, Some(0)));
assert_eq!(iter.next(), None);
assert_eq!(iter.next_back(), None);
assert_eq!(iter.size_hint(), (0, Some(0)));
}

#[test]
fn test_iter_back_after_front() {
let mut list = LinkedList::with_capacity(3);
for value in 0..3u64 {
list.push_tail(value);
}
let mut iter = list.iter();
assert_eq!(iter.next(), Some(&0));
assert_eq!(iter.next_back(), Some(&2));
assert_eq!(iter.next(), Some(&1));
assert_eq!(iter.size_hint(), (0, Some(0)));
assert_eq!(iter.next_back(), None);
assert_eq!(iter.next(), None);
assert_eq!(iter.size_hint(), (0, Some(0)));
}

#[test]
fn test_insert() {
let mut list = LinkedList::with_capacity(10);
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