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Add Cursor::next_item

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This commit is contained in:
Antonio Scandurra 2023-06-23 18:25:27 +02:00 • committed by Kirill Bulatov
parent 5c21ed4263
commit 976edfedf7
2 changed files with 67 additions and 0 deletions
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36
crates/sum_tree/src/cursor.rs
View file

@ -97,6 +97,42 @@ where
}
}
pub fn next_item(&self) -> Option<&'a T> {
self.assert_did_seek();
if let Some(entry) = self.stack.last() {
if entry.index == entry.tree.0.items().len() - 1 {
if let Some(next_leaf) = self.next_leaf() {
Some(next_leaf.0.items().first().unwrap())
} else {
None
}
} else {
match *entry.tree.0 {
Node::Leaf { ref items, .. } => Some(&items[entry.index + 1]),
_ => unreachable!(),
}
}
} else if self.at_end {
None
} else {
self.tree.first()
}
}
fn next_leaf(&self) -> Option<&'a SumTree<T>> {
for entry in self.stack.iter().rev().skip(1) {
if entry.index < entry.tree.0.child_trees().len() - 1 {
match *entry.tree.0 {
Node::Internal {
ref child_trees, ..
} => return Some(child_trees[entry.index + 1].leftmost_leaf()),
Node::Leaf { .. } => unreachable!(),
};
}
}
None
}
pub fn prev_item(&self) -> Option<&'a T> {
self.assert_did_seek();
if let Some(entry) = self.stack.last() {

31
crates/sum_tree/src/sum_tree.rs
View file

@ -816,6 +816,14 @@ mod tests {
assert_eq!(cursor.item(), None);
}
if before_start {
assert_eq!(cursor.next_item(), reference_items.get(0));
} else if pos + 1 < reference_items.len() {
assert_eq!(cursor.next_item().unwrap(), &reference_items[pos + 1]);
} else {
assert_eq!(cursor.next_item(), None);
}
if i < 5 {
cursor.next(&());
if pos < reference_items.len() {
@ -861,14 +869,17 @@ mod tests {
);
assert_eq!(cursor.item(), None);
assert_eq!(cursor.prev_item(), None);
assert_eq!(cursor.next_item(), None);
assert_eq!(cursor.start().sum, 0);
cursor.prev(&());
assert_eq!(cursor.item(), None);
assert_eq!(cursor.prev_item(), None);
assert_eq!(cursor.next_item(), None);
assert_eq!(cursor.start().sum, 0);
cursor.next(&());
assert_eq!(cursor.item(), None);
assert_eq!(cursor.prev_item(), None);
assert_eq!(cursor.next_item(), None);
assert_eq!(cursor.start().sum, 0);
// Single-element tree
@ -881,22 +892,26 @@ mod tests {
);
assert_eq!(cursor.item(), Some(&1));
assert_eq!(cursor.prev_item(), None);
assert_eq!(cursor.next_item(), None);
assert_eq!(cursor.start().sum, 0);
cursor.next(&());
assert_eq!(cursor.item(), None);
assert_eq!(cursor.prev_item(), Some(&1));
assert_eq!(cursor.next_item(), None);
assert_eq!(cursor.start().sum, 1);
cursor.prev(&());
assert_eq!(cursor.item(), Some(&1));
assert_eq!(cursor.prev_item(), None);
assert_eq!(cursor.next_item(), None);
assert_eq!(cursor.start().sum, 0);
let mut cursor = tree.cursor::<IntegersSummary>();
assert_eq!(cursor.slice(&Count(1), Bias::Right, &()).items(&()), [1]);
assert_eq!(cursor.item(), None);
assert_eq!(cursor.prev_item(), Some(&1));
assert_eq!(cursor.next_item(), None);
assert_eq!(cursor.start().sum, 1);
cursor.seek(&Count(0), Bias::Right, &());
@ -908,6 +923,7 @@ mod tests {
);
assert_eq!(cursor.item(), None);
assert_eq!(cursor.prev_item(), Some(&1));
assert_eq!(cursor.next_item(), None);
assert_eq!(cursor.start().sum, 1);
// Multiple-element tree
@ -918,67 +934,80 @@ mod tests {
assert_eq!(cursor.slice(&Count(2), Bias::Right, &()).items(&()), [1, 2]);
assert_eq!(cursor.item(), Some(&3));
assert_eq!(cursor.prev_item(), Some(&2));
assert_eq!(cursor.next_item(), Some(&4));
assert_eq!(cursor.start().sum, 3);
cursor.next(&());
assert_eq!(cursor.item(), Some(&4));
assert_eq!(cursor.prev_item(), Some(&3));
assert_eq!(cursor.next_item(), Some(&5));
assert_eq!(cursor.start().sum, 6);
cursor.next(&());
assert_eq!(cursor.item(), Some(&5));
assert_eq!(cursor.prev_item(), Some(&4));
assert_eq!(cursor.next_item(), Some(&6));
assert_eq!(cursor.start().sum, 10);
cursor.next(&());
assert_eq!(cursor.item(), Some(&6));
assert_eq!(cursor.prev_item(), Some(&5));
assert_eq!(cursor.next_item(), None);
assert_eq!(cursor.start().sum, 15);
cursor.next(&());
cursor.next(&());
assert_eq!(cursor.item(), None);
assert_eq!(cursor.prev_item(), Some(&6));
assert_eq!(cursor.next_item(), None);
assert_eq!(cursor.start().sum, 21);
cursor.prev(&());
assert_eq!(cursor.item(), Some(&6));
assert_eq!(cursor.prev_item(), Some(&5));
assert_eq!(cursor.next_item(), None);
assert_eq!(cursor.start().sum, 15);
cursor.prev(&());
assert_eq!(cursor.item(), Some(&5));
assert_eq!(cursor.prev_item(), Some(&4));
assert_eq!(cursor.next_item(), Some(&6));
assert_eq!(cursor.start().sum, 10);
cursor.prev(&());
assert_eq!(cursor.item(), Some(&4));
assert_eq!(cursor.prev_item(), Some(&3));
assert_eq!(cursor.next_item(), Some(&5));
assert_eq!(cursor.start().sum, 6);
cursor.prev(&());
assert_eq!(cursor.item(), Some(&3));
assert_eq!(cursor.prev_item(), Some(&2));
assert_eq!(cursor.next_item(), Some(&4));
assert_eq!(cursor.start().sum, 3);
cursor.prev(&());
assert_eq!(cursor.item(), Some(&2));
assert_eq!(cursor.prev_item(), Some(&1));
assert_eq!(cursor.next_item(), Some(&3));
assert_eq!(cursor.start().sum, 1);
cursor.prev(&());
assert_eq!(cursor.item(), Some(&1));
assert_eq!(cursor.prev_item(), None);
assert_eq!(cursor.next_item(), Some(&2));
assert_eq!(cursor.start().sum, 0);
cursor.prev(&());
assert_eq!(cursor.item(), None);
assert_eq!(cursor.prev_item(), None);
assert_eq!(cursor.next_item(), Some(&1));
assert_eq!(cursor.start().sum, 0);
cursor.next(&());
assert_eq!(cursor.item(), Some(&1));
assert_eq!(cursor.prev_item(), None);
assert_eq!(cursor.next_item(), Some(&2));
assert_eq!(cursor.start().sum, 0);
let mut cursor = tree.cursor::<IntegersSummary>();
@ -990,6 +1019,7 @@ mod tests {
);
assert_eq!(cursor.item(), None);
assert_eq!(cursor.prev_item(), Some(&6));
assert_eq!(cursor.next_item(), None);
assert_eq!(cursor.start().sum, 21);
cursor.seek(&Count(3), Bias::Right, &());
@ -1001,6 +1031,7 @@ mod tests {
);
assert_eq!(cursor.item(), None);
assert_eq!(cursor.prev_item(), Some(&6));
assert_eq!(cursor.next_item(), None);
assert_eq!(cursor.start().sum, 21);
// Seeking can bias left or right