Files
zed/crates/sum_tree/src/cursor.rs
T
Lukas Wirth 8f8a92ccf0 editor: Reduce amount of sumtree traversals in header_and_footer_blocks (#43709)
Introduces new "mapping point cursors" for the different display map
layers allowing one to map multiple points in increasing order more
efficiently than using the one shot operations.

This is used in the `BlockMap::sync` for `header_and_footer_blocks`
which spends a significant time in sumtree traversal due to repeatedly
transforming points between the different layers. This effectively turns
the complexity of those operations from quadratic in the number of
excerpts to linear, as we only go through the respective sumtrees once
instead of restarting from the start over and over again.

Release Notes:

- Improved performance for editors of large multibuffers with many
different files
2025-11-28 09:06:59 +01:00

824 lines
24 KiB
Rust

use super::*;
use arrayvec::ArrayVec;
use std::{cmp::Ordering, mem, sync::Arc};
#[derive(Clone)]
struct StackEntry<'a, T: Item, D> {
tree: &'a SumTree<T>,
index: u32,
position: D,
}
impl<'a, T: Item, D> StackEntry<'a, T, D> {
#[inline]
fn index(&self) -> usize {
self.index as usize
}
}
impl<T: Item + fmt::Debug, D: fmt::Debug> fmt::Debug for StackEntry<'_, T, D> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("StackEntry")
.field("index", &self.index)
.field("position", &self.position)
.finish()
}
}
#[derive(Clone)]
pub struct Cursor<'a, 'b, T: Item, D> {
tree: &'a SumTree<T>,
stack: ArrayVec<StackEntry<'a, T, D>, 16>,
position: D,
did_seek: bool,
at_end: bool,
cx: <T::Summary as Summary>::Context<'b>,
}
impl<T: Item + fmt::Debug, D: fmt::Debug> fmt::Debug for Cursor<'_, '_, T, D>
where
T::Summary: fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Cursor")
.field("tree", &self.tree)
.field("stack", &self.stack)
.field("position", &self.position)
.field("did_seek", &self.did_seek)
.field("at_end", &self.at_end)
.finish()
}
}
pub struct Iter<'a, T: Item> {
tree: &'a SumTree<T>,
stack: ArrayVec<StackEntry<'a, T, ()>, 16>,
}
impl<'a, 'b, T, D> Cursor<'a, 'b, T, D>
where
T: Item,
D: Dimension<'a, T::Summary>,
{
pub fn new(tree: &'a SumTree<T>, cx: <T::Summary as Summary>::Context<'b>) -> Self {
Self {
tree,
stack: ArrayVec::new(),
position: D::zero(cx),
did_seek: false,
at_end: tree.is_empty(),
cx,
}
}
fn reset(&mut self) {
self.did_seek = false;
self.at_end = self.tree.is_empty();
self.stack.truncate(0);
self.position = D::zero(self.cx);
}
pub fn start(&self) -> &D {
&self.position
}
#[track_caller]
pub fn end(&self) -> D {
if let Some(item_summary) = self.item_summary() {
let mut end = self.start().clone();
end.add_summary(item_summary, self.cx);
end
} else {
self.start().clone()
}
}
/// Item is None, when the list is empty, or this cursor is at the end of the list.
#[track_caller]
pub fn item(&self) -> Option<&'a T> {
self.assert_did_seek();
if let Some(entry) = self.stack.last() {
match *entry.tree.0 {
Node::Leaf { ref items, .. } => {
if entry.index() == items.len() {
None
} else {
Some(&items[entry.index()])
}
}
_ => unreachable!(),
}
} else {
None
}
}
#[track_caller]
pub fn item_summary(&self) -> Option<&'a T::Summary> {
self.assert_did_seek();
if let Some(entry) = self.stack.last() {
match *entry.tree.0 {
Node::Leaf {
ref item_summaries, ..
} => {
if entry.index() == item_summaries.len() {
None
} else {
Some(&item_summaries[entry.index()])
}
}
_ => unreachable!(),
}
} else {
None
}
}
#[track_caller]
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()
}
}
#[track_caller]
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
}
#[track_caller]
pub fn prev_item(&self) -> Option<&'a T> {
self.assert_did_seek();
if let Some(entry) = self.stack.last() {
if entry.index() == 0 {
if let Some(prev_leaf) = self.prev_leaf() {
Some(prev_leaf.0.items().last().unwrap())
} else {
None
}
} else {
match *entry.tree.0 {
Node::Leaf { ref items, .. } => Some(&items[entry.index() - 1]),
_ => unreachable!(),
}
}
} else if self.at_end {
self.tree.last()
} else {
None
}
}
#[track_caller]
fn prev_leaf(&self) -> Option<&'a SumTree<T>> {
for entry in self.stack.iter().rev().skip(1) {
if entry.index() != 0 {
match *entry.tree.0 {
Node::Internal {
ref child_trees, ..
} => return Some(child_trees[entry.index() - 1].rightmost_leaf()),
Node::Leaf { .. } => unreachable!(),
};
}
}
None
}
#[track_caller]
pub fn prev(&mut self) {
self.search_backward(|_| true)
}
#[track_caller]
pub fn search_backward<F>(&mut self, mut filter_node: F)
where
F: FnMut(&T::Summary) -> bool,
{
if !self.did_seek {
self.did_seek = true;
self.at_end = true;
}
if self.at_end {
self.position = D::zero(self.cx);
self.at_end = self.tree.is_empty();
if !self.tree.is_empty() {
self.stack.push(StackEntry {
tree: self.tree,
index: self.tree.0.child_summaries().len() as u32,
position: D::from_summary(self.tree.summary(), self.cx),
});
}
}
let mut descending = false;
while !self.stack.is_empty() {
if let Some(StackEntry { position, .. }) = self.stack.iter().rev().nth(1) {
self.position = position.clone();
} else {
self.position = D::zero(self.cx);
}
let entry = self.stack.last_mut().unwrap();
if !descending {
if entry.index() == 0 {
self.stack.pop();
continue;
} else {
entry.index -= 1;
}
}
for summary in &entry.tree.0.child_summaries()[..entry.index()] {
self.position.add_summary(summary, self.cx);
}
entry.position = self.position.clone();
descending = filter_node(&entry.tree.0.child_summaries()[entry.index()]);
match entry.tree.0.as_ref() {
Node::Internal { child_trees, .. } => {
if descending {
let tree = &child_trees[entry.index()];
self.stack.push(StackEntry {
position: D::zero(self.cx),
tree,
index: tree.0.child_summaries().len() as u32 - 1,
})
}
}
Node::Leaf { .. } => {
if descending {
break;
}
}
}
}
}
#[track_caller]
pub fn next(&mut self) {
self.search_forward(|_| true)
}
#[track_caller]
pub fn search_forward<F>(&mut self, mut filter_node: F)
where
F: FnMut(&T::Summary) -> bool,
{
let mut descend = false;
if self.stack.is_empty() {
if !self.at_end {
self.stack.push(StackEntry {
tree: self.tree,
index: 0,
position: D::zero(self.cx),
});
descend = true;
}
self.did_seek = true;
}
while !self.stack.is_empty() {
let new_subtree = {
let entry = self.stack.last_mut().unwrap();
match entry.tree.0.as_ref() {
Node::Internal {
child_trees,
child_summaries,
..
} => {
if !descend {
entry.index += 1;
entry.position = self.position.clone();
}
while entry.index() < child_summaries.len() {
let next_summary = &child_summaries[entry.index()];
if filter_node(next_summary) {
break;
} else {
entry.index += 1;
entry.position.add_summary(next_summary, self.cx);
self.position.add_summary(next_summary, self.cx);
}
}
child_trees.get(entry.index())
}
Node::Leaf { item_summaries, .. } => {
if !descend {
let item_summary = &item_summaries[entry.index()];
entry.index += 1;
entry.position.add_summary(item_summary, self.cx);
self.position.add_summary(item_summary, self.cx);
}
loop {
if let Some(next_item_summary) = item_summaries.get(entry.index()) {
if filter_node(next_item_summary) {
return;
} else {
entry.index += 1;
entry.position.add_summary(next_item_summary, self.cx);
self.position.add_summary(next_item_summary, self.cx);
}
} else {
break None;
}
}
}
}
};
if let Some(subtree) = new_subtree {
descend = true;
self.stack.push(StackEntry {
tree: subtree,
index: 0,
position: self.position.clone(),
});
} else {
descend = false;
self.stack.pop();
}
}
self.at_end = self.stack.is_empty();
debug_assert!(self.stack.is_empty() || self.stack.last().unwrap().tree.0.is_leaf());
}
#[track_caller]
fn assert_did_seek(&self) {
assert!(
self.did_seek,
"Must call `seek`, `next` or `prev` before calling this method"
);
}
pub fn did_seek(&self) -> bool {
self.did_seek
}
}
impl<'a, 'b, T, D> Cursor<'a, 'b, T, D>
where
T: Item,
D: Dimension<'a, T::Summary>,
{
/// Returns whether we found the item you were seeking for.
#[track_caller]
pub fn seek<Target>(&mut self, pos: &Target, bias: Bias) -> bool
where
Target: SeekTarget<'a, T::Summary, D>,
{
self.reset();
self.seek_internal(pos, bias, &mut ())
}
/// Returns whether we found the item you were seeking for.
#[track_caller]
pub fn seek_forward<Target>(&mut self, pos: &Target, bias: Bias) -> bool
where
Target: SeekTarget<'a, T::Summary, D>,
{
self.seek_internal(pos, bias, &mut ())
}
/// Advances the cursor and returns traversed items as a tree.
#[track_caller]
pub fn slice<Target>(&mut self, end: &Target, bias: Bias) -> SumTree<T>
where
Target: SeekTarget<'a, T::Summary, D>,
{
let mut slice = SliceSeekAggregate {
tree: SumTree::new(self.cx),
leaf_items: ArrayVec::new(),
leaf_item_summaries: ArrayVec::new(),
leaf_summary: <T::Summary as Summary>::zero(self.cx),
};
self.seek_internal(end, bias, &mut slice);
slice.tree
}
#[track_caller]
pub fn suffix(&mut self) -> SumTree<T> {
self.slice(&End::new(), Bias::Right)
}
#[track_caller]
pub fn summary<Target, Output>(&mut self, end: &Target, bias: Bias) -> Output
where
Target: SeekTarget<'a, T::Summary, D>,
Output: Dimension<'a, T::Summary>,
{
let mut summary = SummarySeekAggregate(Output::zero(self.cx));
self.seek_internal(end, bias, &mut summary);
summary.0
}
/// Returns whether we found the item you were seeking for.
#[track_caller]
fn seek_internal(
&mut self,
target: &dyn SeekTarget<'a, T::Summary, D>,
bias: Bias,
aggregate: &mut dyn SeekAggregate<'a, T>,
) -> bool {
assert!(
target.cmp(&self.position, self.cx).is_ge(),
"cannot seek backward",
);
if !self.did_seek {
self.did_seek = true;
self.stack.push(StackEntry {
tree: self.tree,
index: 0,
position: D::zero(self.cx),
});
}
let mut ascending = false;
'outer: while let Some(entry) = self.stack.last_mut() {
match *entry.tree.0 {
Node::Internal {
ref child_summaries,
ref child_trees,
..
} => {
if ascending {
entry.index += 1;
entry.position = self.position.clone();
}
for (child_tree, child_summary) in child_trees[entry.index()..]
.iter()
.zip(&child_summaries[entry.index()..])
{
let mut child_end = self.position.clone();
child_end.add_summary(child_summary, self.cx);
let comparison = target.cmp(&child_end, self.cx);
if comparison == Ordering::Greater
|| (comparison == Ordering::Equal && bias == Bias::Right)
{
self.position = child_end;
aggregate.push_tree(child_tree, child_summary, self.cx);
entry.index += 1;
entry.position = self.position.clone();
} else {
self.stack.push(StackEntry {
tree: child_tree,
index: 0,
position: self.position.clone(),
});
ascending = false;
continue 'outer;
}
}
}
Node::Leaf {
ref items,
ref item_summaries,
..
} => {
aggregate.begin_leaf();
for (item, item_summary) in items[entry.index()..]
.iter()
.zip(&item_summaries[entry.index()..])
{
let mut child_end = self.position.clone();
child_end.add_summary(item_summary, self.cx);
let comparison = target.cmp(&child_end, self.cx);
if comparison == Ordering::Greater
|| (comparison == Ordering::Equal && bias == Bias::Right)
{
self.position = child_end;
aggregate.push_item(item, item_summary, self.cx);
entry.index += 1;
} else {
aggregate.end_leaf(self.cx);
break 'outer;
}
}
aggregate.end_leaf(self.cx);
}
}
self.stack.pop();
ascending = true;
}
self.at_end = self.stack.is_empty();
debug_assert!(self.stack.is_empty() || self.stack.last().unwrap().tree.0.is_leaf());
let mut end = self.position.clone();
if bias == Bias::Left
&& let Some(summary) = self.item_summary()
{
end.add_summary(summary, self.cx);
}
target.cmp(&end, self.cx) == Ordering::Equal
}
}
impl<'a, T: Item> Iter<'a, T> {
pub(crate) fn new(tree: &'a SumTree<T>) -> Self {
Self {
tree,
stack: Default::default(),
}
}
}
impl<'a, T: Item> Iterator for Iter<'a, T> {
type Item = &'a T;
fn next(&mut self) -> Option<Self::Item> {
let mut descend = false;
if self.stack.is_empty() {
self.stack.push(StackEntry {
tree: self.tree,
index: 0,
position: (),
});
descend = true;
}
while !self.stack.is_empty() {
let new_subtree = {
let entry = self.stack.last_mut().unwrap();
match entry.tree.0.as_ref() {
Node::Internal { child_trees, .. } => {
if !descend {
entry.index += 1;
}
child_trees.get(entry.index())
}
Node::Leaf { items, .. } => {
if !descend {
entry.index += 1;
}
if let Some(next_item) = items.get(entry.index()) {
return Some(next_item);
} else {
None
}
}
}
};
if let Some(subtree) = new_subtree {
descend = true;
self.stack.push(StackEntry {
tree: subtree,
index: 0,
position: (),
});
} else {
descend = false;
self.stack.pop();
}
}
None
}
}
impl<'a, 'b, T: Item, D> Iterator for Cursor<'a, 'b, T, D>
where
D: Dimension<'a, T::Summary>,
{
type Item = &'a T;
fn next(&mut self) -> Option<Self::Item> {
if !self.did_seek {
self.next();
}
if let Some(item) = self.item() {
self.next();
Some(item)
} else {
None
}
}
}
pub struct FilterCursor<'a, 'b, F, T: Item, D> {
cursor: Cursor<'a, 'b, T, D>,
filter_node: F,
}
impl<'a, 'b, F, T: Item, D> FilterCursor<'a, 'b, F, T, D>
where
F: FnMut(&T::Summary) -> bool,
T: Item,
D: Dimension<'a, T::Summary>,
{
pub fn new(
tree: &'a SumTree<T>,
cx: <T::Summary as Summary>::Context<'b>,
filter_node: F,
) -> Self {
let cursor = tree.cursor::<D>(cx);
Self {
cursor,
filter_node,
}
}
pub fn start(&self) -> &D {
self.cursor.start()
}
pub fn end(&self) -> D {
self.cursor.end()
}
pub fn item(&self) -> Option<&'a T> {
self.cursor.item()
}
pub fn item_summary(&self) -> Option<&'a T::Summary> {
self.cursor.item_summary()
}
pub fn next(&mut self) {
self.cursor.search_forward(&mut self.filter_node);
}
pub fn prev(&mut self) {
self.cursor.search_backward(&mut self.filter_node);
}
}
impl<'a, 'b, F, T: Item, U> Iterator for FilterCursor<'a, 'b, F, T, U>
where
F: FnMut(&T::Summary) -> bool,
U: Dimension<'a, T::Summary>,
{
type Item = &'a T;
fn next(&mut self) -> Option<Self::Item> {
if !self.cursor.did_seek {
self.next();
}
if let Some(item) = self.item() {
self.cursor.search_forward(&mut self.filter_node);
Some(item)
} else {
None
}
}
}
trait SeekAggregate<'a, T: Item> {
fn begin_leaf(&mut self);
fn end_leaf(&mut self, cx: <T::Summary as Summary>::Context<'_>);
fn push_item(
&mut self,
item: &'a T,
summary: &'a T::Summary,
cx: <T::Summary as Summary>::Context<'_>,
);
fn push_tree(
&mut self,
tree: &'a SumTree<T>,
summary: &'a T::Summary,
cx: <T::Summary as Summary>::Context<'_>,
);
}
struct SliceSeekAggregate<T: Item> {
tree: SumTree<T>,
leaf_items: ArrayVec<T, { 2 * TREE_BASE }>,
leaf_item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
leaf_summary: T::Summary,
}
struct SummarySeekAggregate<D>(D);
impl<T: Item> SeekAggregate<'_, T> for () {
fn begin_leaf(&mut self) {}
fn end_leaf(&mut self, _: <T::Summary as Summary>::Context<'_>) {}
fn push_item(&mut self, _: &T, _: &T::Summary, _: <T::Summary as Summary>::Context<'_>) {}
fn push_tree(
&mut self,
_: &SumTree<T>,
_: &T::Summary,
_: <T::Summary as Summary>::Context<'_>,
) {
}
}
impl<T: Item> SeekAggregate<'_, T> for SliceSeekAggregate<T> {
fn begin_leaf(&mut self) {}
fn end_leaf(&mut self, cx: <T::Summary as Summary>::Context<'_>) {
self.tree.append(
SumTree(Arc::new(Node::Leaf {
summary: mem::replace(&mut self.leaf_summary, <T::Summary as Summary>::zero(cx)),
items: mem::take(&mut self.leaf_items),
item_summaries: mem::take(&mut self.leaf_item_summaries),
})),
cx,
);
}
fn push_item(
&mut self,
item: &T,
summary: &T::Summary,
cx: <T::Summary as Summary>::Context<'_>,
) {
self.leaf_items.push(item.clone());
self.leaf_item_summaries.push(summary.clone());
Summary::add_summary(&mut self.leaf_summary, summary, cx);
}
fn push_tree(
&mut self,
tree: &SumTree<T>,
_: &T::Summary,
cx: <T::Summary as Summary>::Context<'_>,
) {
self.tree.append(tree.clone(), cx);
}
}
impl<'a, T: Item, D> SeekAggregate<'a, T> for SummarySeekAggregate<D>
where
D: Dimension<'a, T::Summary>,
{
fn begin_leaf(&mut self) {}
fn end_leaf(&mut self, _: <T::Summary as Summary>::Context<'_>) {}
fn push_item(
&mut self,
_: &T,
summary: &'a T::Summary,
cx: <T::Summary as Summary>::Context<'_>,
) {
self.0.add_summary(summary, cx);
}
fn push_tree(
&mut self,
_: &SumTree<T>,
summary: &'a T::Summary,
cx: <T::Summary as Summary>::Context<'_>,
) {
self.0.add_summary(summary, cx);
}
}
struct End<D>(PhantomData<D>);
impl<D> End<D> {
fn new() -> Self {
Self(PhantomData)
}
}
impl<'a, S: Summary, D: Dimension<'a, S>> SeekTarget<'a, S, D> for End<D> {
fn cmp(&self, _: &D, _: S::Context<'_>) -> Ordering {
Ordering::Greater
}
}
impl<D> fmt::Debug for End<D> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_tuple("End").finish()
}
}