1mod cursor;
2mod tree_map;
3
4use arrayvec::ArrayVec;
5pub use cursor::{Cursor, FilterCursor, Iter};
6use rayon::prelude::*;
7use std::borrow::Cow;
8use std::fmt::Debug;
9use std::marker::PhantomData;
10use std::mem;
11use std::{cmp::Ordering, fmt, iter::FromIterator, sync::Arc};
12pub use tree_map::{MapSeekTarget, TreeMap, TreeSet};
13
14#[cfg(test)]
15pub const TREE_BASE: usize = 2;
16#[cfg(not(test))]
17pub const TREE_BASE: usize = 6;
18
19/// An item that can be stored in a [`SumTree`]
20///
21/// Must be summarized by a type that implements [`Summary`]
22pub trait Item: Clone {
23 type Summary: Summary;
24
25 fn summary(&self, cx: &<Self::Summary as Summary>::Context) -> Self::Summary;
26}
27
28/// An [`Item`] whose summary has a specific key that can be used to identify it
29pub trait KeyedItem: Item {
30 type Key: for<'a> Dimension<'a, Self::Summary> + Ord;
31
32 fn key(&self) -> Self::Key;
33}
34
35/// A type that describes the Sum of all [`Item`]s in a subtree of the [`SumTree`]
36///
37/// Each Summary type can have multiple [`Dimension`]s that it measures,
38/// which can be used to navigate the tree
39pub trait Summary: Clone {
40 type Context;
41
42 fn zero(cx: &Self::Context) -> Self;
43 fn add_summary(&mut self, summary: &Self, cx: &Self::Context);
44 fn sub_summary(&mut self, _: &Self, _: &Self::Context) {}
45}
46
47/// Catch-all implementation for when you need something that implements [`Summary`] without a specific type.
48/// We implement it on a &'static, as that avoids blanket impl collisions with `impl<T: Summary> Dimension for T`
49/// (as we also need unit type to be a fill-in dimension)
50impl Summary for &'static () {
51 type Context = ();
52
53 fn zero(_: &()) -> Self {
54 &()
55 }
56
57 fn add_summary(&mut self, _: &Self, _: &()) {}
58}
59
60/// Each [`Summary`] type can have more than one [`Dimension`] type that it measures.
61///
62/// You can use dimensions to seek to a specific location in the [`SumTree`]
63///
64/// # Example:
65/// Zed's rope has a `TextSummary` type that summarizes lines, characters, and bytes.
66/// Each of these are different dimensions we may want to seek to
67pub trait Dimension<'a, S: Summary>: Clone {
68 fn zero(cx: &S::Context) -> Self;
69
70 fn add_summary(&mut self, summary: &'a S, cx: &S::Context);
71
72 fn from_summary(summary: &'a S, cx: &S::Context) -> Self {
73 let mut dimension = Self::zero(cx);
74 dimension.add_summary(summary, cx);
75 dimension
76 }
77}
78
79impl<'a, T: Summary> Dimension<'a, T> for T {
80 fn zero(cx: &T::Context) -> Self {
81 Summary::zero(cx)
82 }
83
84 fn add_summary(&mut self, summary: &'a T, cx: &T::Context) {
85 Summary::add_summary(self, summary, cx);
86 }
87}
88
89pub trait SeekTarget<'a, S: Summary, D: Dimension<'a, S>> {
90 fn cmp(&self, cursor_location: &D, cx: &S::Context) -> Ordering;
91}
92
93impl<'a, S: Summary, D: Dimension<'a, S> + Ord> SeekTarget<'a, S, D> for D {
94 fn cmp(&self, cursor_location: &Self, _: &S::Context) -> Ordering {
95 Ord::cmp(self, cursor_location)
96 }
97}
98
99impl<'a, T: Summary> Dimension<'a, T> for () {
100 fn zero(_: &T::Context) -> Self {}
101
102 fn add_summary(&mut self, _: &'a T, _: &T::Context) {}
103}
104
105#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
106pub struct Dimensions<D1, D2, D3 = ()>(pub D1, pub D2, pub D3);
107
108impl<'a, T: Summary, D1: Dimension<'a, T>, D2: Dimension<'a, T>, D3: Dimension<'a, T>>
109 Dimension<'a, T> for Dimensions<D1, D2, D3>
110{
111 fn zero(cx: &T::Context) -> Self {
112 Dimensions(D1::zero(cx), D2::zero(cx), D3::zero(cx))
113 }
114
115 fn add_summary(&mut self, summary: &'a T, cx: &T::Context) {
116 self.0.add_summary(summary, cx);
117 self.1.add_summary(summary, cx);
118 self.2.add_summary(summary, cx);
119 }
120}
121
122impl<'a, S, D1, D2, D3> SeekTarget<'a, S, Dimensions<D1, D2, D3>> for D1
123where
124 S: Summary,
125 D1: SeekTarget<'a, S, D1> + Dimension<'a, S>,
126 D2: Dimension<'a, S>,
127 D3: Dimension<'a, S>,
128{
129 fn cmp(&self, cursor_location: &Dimensions<D1, D2, D3>, cx: &S::Context) -> Ordering {
130 self.cmp(&cursor_location.0, cx)
131 }
132}
133
134/// Bias is used to settle ambiguities when determining positions in an ordered sequence.
135///
136/// The primary use case is for text, where Bias influences
137/// which character an offset or anchor is associated with.
138///
139/// # Examples
140/// Given the buffer `AˇBCD`:
141/// - The offset of the cursor is 1
142/// - [Bias::Left] would attach the cursor to the character `A`
143/// - [Bias::Right] would attach the cursor to the character `B`
144///
145/// Given the buffer `A«BCˇ»D`:
146/// - The offset of the cursor is 3, and the selection is from 1 to 3
147/// - The left anchor of the selection has [Bias::Right], attaching it to the character `B`
148/// - The right anchor of the selection has [Bias::Left], attaching it to the character `C`
149///
150/// Given the buffer `{ˇ<...>`, where `<...>` is a folded region:
151/// - The display offset of the cursor is 1, but the offset in the buffer is determined by the bias
152/// - [Bias::Left] would attach the cursor to the character `{`, with a buffer offset of 1
153/// - [Bias::Right] would attach the cursor to the first character of the folded region,
154/// and the buffer offset would be the offset of the first character of the folded region
155#[derive(Copy, Clone, Eq, PartialEq, PartialOrd, Ord, Debug, Hash, Default)]
156pub enum Bias {
157 /// Attach to the character on the left
158 #[default]
159 Left,
160 /// Attach to the character on the right
161 Right,
162}
163
164impl Bias {
165 pub fn invert(self) -> Self {
166 match self {
167 Self::Left => Self::Right,
168 Self::Right => Self::Left,
169 }
170 }
171}
172
173/// A B+ tree in which each leaf node contains `Item`s of type `T` and a `Summary`s for each `Item`.
174/// Each internal node contains a `Summary` of the items in its subtree.
175///
176/// The maximum number of items per node is `TREE_BASE * 2`.
177///
178/// Any [`Dimension`] supported by the [`Summary`] type can be used to seek to a specific location in the tree.
179#[derive(Clone)]
180pub struct SumTree<T: Item>(Arc<Node<T>>);
181
182impl<T> fmt::Debug for SumTree<T>
183where
184 T: fmt::Debug + Item,
185 T::Summary: fmt::Debug,
186{
187 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
188 f.debug_tuple("SumTree").field(&self.0).finish()
189 }
190}
191
192impl<T: Item> SumTree<T> {
193 pub fn new() -> Self {
194 SumTree(Arc::new(Node::Leaf {
195 items: ArrayVec::new(),
196 item_summaries: ArrayVec::new(),
197 }))
198 }
199
200 pub fn from_item(item: T, cx: &<T::Summary as Summary>::Context) -> Self {
201 let mut tree = Self::new();
202 tree.push(item, cx);
203 tree
204 }
205
206 pub fn from_iter<I: IntoIterator<Item = T>>(
207 iter: I,
208 cx: &<T::Summary as Summary>::Context,
209 ) -> Self {
210 let mut nodes = Vec::new();
211
212 let mut iter = iter.into_iter().fuse().peekable();
213 while iter.peek().is_some() {
214 let items: ArrayVec<T, { 2 * TREE_BASE }> = iter.by_ref().take(2 * TREE_BASE).collect();
215 let item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }> = items
216 .iter()
217 .scan(None, |previous_item, item| {
218 let summary = item.summary(cx);
219 let current_item = if let Some(mut base) = previous_item.take() {
220 <T::Summary as Summary>::add_summary(&mut base, &summary, cx);
221 base
222 } else {
223 summary
224 };
225 _ = previous_item.insert(current_item.clone());
226 Some(current_item)
227 })
228 .collect();
229 nodes.push(Node::Leaf {
230 items,
231 item_summaries,
232 });
233 }
234
235 let mut parent_nodes = Vec::new();
236 let mut height = 0;
237 while nodes.len() > 1 {
238 height += 1;
239 let mut current_parent_node = None;
240 for child_node in nodes.drain(..) {
241 let parent_node = current_parent_node.get_or_insert_with(|| Node::Internal {
242 height,
243 child_summaries: ArrayVec::new(),
244 child_trees: ArrayVec::new(),
245 });
246 let Node::Internal {
247 child_summaries,
248 child_trees,
249 ..
250 } = parent_node
251 else {
252 unreachable!()
253 };
254 let child_summary = child_node.summary_or_zero(cx);
255 let child_summary = if let Some(mut last) = child_summaries.last().cloned() {
256 <T::Summary as Summary>::add_summary(&mut last, &child_summary, cx);
257 last
258 } else {
259 child_summary.into_owned()
260 };
261
262 child_summaries.push(child_summary);
263 child_trees.push(Self(Arc::new(child_node)));
264
265 if child_trees.len() == 2 * TREE_BASE {
266 parent_nodes.extend(current_parent_node.take());
267 }
268 }
269 parent_nodes.extend(current_parent_node.take());
270 mem::swap(&mut nodes, &mut parent_nodes);
271 }
272
273 if nodes.is_empty() {
274 Self::new()
275 } else {
276 debug_assert_eq!(nodes.len(), 1);
277 Self(Arc::new(nodes.pop().unwrap()))
278 }
279 }
280
281 pub fn from_par_iter<I, Iter>(iter: I, cx: &<T::Summary as Summary>::Context) -> Self
282 where
283 I: IntoParallelIterator<Iter = Iter>,
284 Iter: IndexedParallelIterator<Item = T>,
285 T: Send + Sync,
286 T::Summary: Send + Sync,
287 <T::Summary as Summary>::Context: Sync,
288 {
289 let mut nodes = iter
290 .into_par_iter()
291 .chunks(2 * TREE_BASE)
292 .map(|items| {
293 let items: ArrayVec<T, { 2 * TREE_BASE }> = items.into_iter().collect();
294 let item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }> = items
295 .iter()
296 .scan(None, |previous_item, item| {
297 let summary = item.summary(cx);
298 let current_item = if let Some(mut base) = previous_item.take() {
299 <T::Summary as Summary>::add_summary(&mut base, &summary, cx);
300 base
301 } else {
302 summary
303 };
304 _ = previous_item.insert(current_item.clone());
305 Some(current_item)
306 })
307 .collect();
308
309 SumTree(Arc::new(Node::Leaf {
310 items,
311 item_summaries,
312 }))
313 })
314 .collect::<Vec<_>>();
315
316 let mut height = 0;
317 while nodes.len() > 1 {
318 height += 1;
319 nodes = nodes
320 .into_par_iter()
321 .chunks(2 * TREE_BASE)
322 .map(|child_nodes| {
323 let child_trees: ArrayVec<SumTree<T>, { 2 * TREE_BASE }> =
324 child_nodes.into_iter().collect();
325 let child_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }> = child_trees
326 .iter()
327 .map(|child_tree| child_tree.0.summary_or_zero(cx).into_owned())
328 .collect();
329 let mut summary = child_summaries[0].clone();
330 for child_summary in &child_summaries[1..] {
331 <T::Summary as Summary>::add_summary(&mut summary, child_summary, cx);
332 }
333 SumTree(Arc::new(Node::Internal {
334 height,
335
336 child_summaries,
337 child_trees,
338 }))
339 })
340 .collect::<Vec<_>>();
341 }
342
343 if nodes.is_empty() {
344 Self::new()
345 } else {
346 debug_assert_eq!(nodes.len(), 1);
347 nodes.pop().unwrap()
348 }
349 }
350
351 #[allow(unused)]
352 pub fn items(&self, cx: &<T::Summary as Summary>::Context) -> Vec<T> {
353 let mut items = Vec::new();
354 let mut cursor = self.cursor::<()>(cx);
355 cursor.next();
356 while let Some(item) = cursor.item() {
357 items.push(item.clone());
358 cursor.next();
359 }
360 items
361 }
362
363 pub fn iter(&self) -> Iter<'_, T> {
364 Iter::new(self)
365 }
366
367 pub fn cursor<'a, S>(&'a self, cx: &'a <T::Summary as Summary>::Context) -> Cursor<'a, T, S>
368 where
369 S: Dimension<'a, T::Summary>,
370 {
371 Cursor::new(self, cx)
372 }
373
374 /// Note: If the summary type requires a non `()` context, then the filter cursor
375 /// that is returned cannot be used with Rust's iterators.
376 pub fn filter<'a, F, U>(
377 &'a self,
378 cx: &'a <T::Summary as Summary>::Context,
379 filter_node: F,
380 ) -> FilterCursor<'a, F, T, U>
381 where
382 F: FnMut(&T::Summary) -> Ordering,
383 U: Dimension<'a, T::Summary>,
384 {
385 FilterCursor::new(self, cx, filter_node)
386 }
387
388 #[allow(dead_code)]
389 pub fn first(&self) -> Option<&T> {
390 self.leftmost_leaf().0.items().first()
391 }
392
393 pub fn last(&self) -> Option<&T> {
394 self.rightmost_leaf().0.items().last()
395 }
396
397 pub fn update_last(&mut self, f: impl FnOnce(&mut T), cx: &<T::Summary as Summary>::Context) {
398 self.update_last_recursive(f, cx);
399 }
400
401 fn update_last_recursive(
402 &mut self,
403 f: impl FnOnce(&mut T),
404 cx: &<T::Summary as Summary>::Context,
405 ) -> Option<T::Summary> {
406 match Arc::make_mut(&mut self.0) {
407 Node::Internal {
408 child_summaries,
409 child_trees,
410 ..
411 } => {
412 let last_child = child_trees.last_mut().unwrap();
413
414 let mut bare_summary = last_child.update_last_recursive(f, cx).unwrap();
415
416 if let Some(mut second_to_last_summary) = child_summaries
417 .len()
418 .checked_sub(2)
419 .and_then(|ix| child_summaries.get(ix))
420 .cloned()
421 {
422 <T::Summary as Summary>::add_summary(
423 &mut second_to_last_summary,
424 &bare_summary,
425 cx,
426 );
427 bare_summary = second_to_last_summary;
428 }
429 let last_summary = child_summaries.last_mut().unwrap();
430 *last_summary = bare_summary;
431
432 Some(last_summary.clone())
433 }
434 Node::Leaf {
435 items,
436 item_summaries,
437 } => {
438 let preceding_summary = item_summaries
439 .len()
440 .checked_sub(2)
441 .and_then(|ix| item_summaries.get(ix))
442 .cloned();
443 if let Some((item, item_summary)) = items.last_mut().zip(item_summaries.last_mut())
444 {
445 (f)(item);
446 let mut bare_summary = item.summary(cx);
447
448 if let Some(mut second_to_last_summary) = preceding_summary {
449 <T::Summary as Summary>::add_summary(
450 &mut second_to_last_summary,
451 &bare_summary,
452 cx,
453 );
454 bare_summary = second_to_last_summary;
455 }
456 *item_summary = bare_summary.clone();
457
458 Some(item_summary.clone())
459 } else {
460 None
461 }
462 }
463 }
464 }
465
466 pub fn extent<'a, D: Dimension<'a, T::Summary>>(
467 &'a self,
468 cx: &<T::Summary as Summary>::Context,
469 ) -> D {
470 let mut extent = D::zero(cx);
471 if let Some(last) = self.0.child_summaries().last() {
472 extent.add_summary(last, cx);
473 }
474
475 extent
476 }
477
478 pub fn is_empty(&self) -> bool {
479 match self.0.as_ref() {
480 Node::Internal { .. } => false,
481 Node::Leaf { items, .. } => items.is_empty(),
482 }
483 }
484
485 pub fn extend<I>(&mut self, iter: I, cx: &<T::Summary as Summary>::Context)
486 where
487 I: IntoIterator<Item = T>,
488 {
489 self.append(Self::from_iter(iter, cx), cx);
490 }
491
492 pub fn par_extend<I, Iter>(&mut self, iter: I, cx: &<T::Summary as Summary>::Context)
493 where
494 I: IntoParallelIterator<Iter = Iter>,
495 Iter: IndexedParallelIterator<Item = T>,
496 T: Send + Sync,
497 T::Summary: Send + Sync,
498 <T::Summary as Summary>::Context: Sync,
499 {
500 self.append(Self::from_par_iter(iter, cx), cx);
501 }
502
503 pub fn push(&mut self, item: T, cx: &<T::Summary as Summary>::Context) {
504 let summary = item.summary(cx);
505 self.append(
506 SumTree(Arc::new(Node::Leaf {
507 items: ArrayVec::from_iter(Some(item)),
508 item_summaries: ArrayVec::from_iter(Some(summary)),
509 })),
510 cx,
511 );
512 }
513
514 pub fn append(&mut self, other: Self, cx: &<T::Summary as Summary>::Context) {
515 if self.is_empty() {
516 *self = other;
517 } else if !other.0.is_leaf() || !other.0.items().is_empty() {
518 if self.0.height() < other.0.height() {
519 for tree in other.0.child_trees() {
520 self.append(tree.clone(), cx);
521 }
522 } else if let Some(split_tree) = self.push_tree_recursive(other, cx) {
523 *self = Self::from_child_trees(self.clone(), split_tree, cx);
524 }
525 }
526 }
527
528 fn push_tree_recursive(
529 &mut self,
530 other: SumTree<T>,
531 cx: &<T::Summary as Summary>::Context,
532 ) -> Option<SumTree<T>> {
533 match Arc::make_mut(&mut self.0) {
534 Node::Internal {
535 height,
536 child_summaries,
537 child_trees,
538 ..
539 } => {
540 let other_node = other.0.clone();
541
542 let height_delta = *height - other_node.height();
543 let mut summaries_to_append = ArrayVec::<T::Summary, { 2 * TREE_BASE }>::new();
544 let mut trees_to_append = ArrayVec::<SumTree<T>, { 2 * TREE_BASE }>::new();
545 if height_delta == 0 {
546 summaries_to_append.extend(other_node.child_summaries().iter().cloned());
547 trees_to_append.extend(other_node.child_trees().iter().cloned());
548 } else if height_delta == 1 && !other_node.is_underflowing() {
549 summaries_to_append.push(other_node.summary_or_zero(cx).into_owned());
550 trees_to_append.push(other)
551 } else {
552 let tree_to_append = child_trees
553 .last_mut()
554 .unwrap()
555 .push_tree_recursive(other, cx);
556 *child_summaries.last_mut().unwrap() = child_trees
557 .last()
558 .unwrap()
559 .0
560 .summary_or_zero(cx)
561 .into_owned();
562
563 if let Some(split_tree) = tree_to_append {
564 summaries_to_append.push(split_tree.0.summary_or_zero(cx).into_owned());
565 trees_to_append.push(split_tree);
566 }
567 }
568
569 let child_count = child_trees.len() + trees_to_append.len();
570 if child_count > 2 * TREE_BASE {
571 let left_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
572 let right_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
573 let left_trees;
574 let right_trees;
575
576 let midpoint = (child_count + child_count % 2) / 2;
577 {
578 let mut all_summaries = child_summaries
579 .iter()
580 .chain(summaries_to_append.iter())
581 .cloned();
582 left_summaries = all_summaries.by_ref().take(midpoint).collect();
583 right_summaries = all_summaries.collect();
584 let mut all_trees =
585 child_trees.iter().chain(trees_to_append.iter()).cloned();
586 left_trees = all_trees.by_ref().take(midpoint).collect();
587 right_trees = all_trees.collect();
588 }
589
590 *child_summaries = left_summaries;
591 *child_trees = left_trees;
592
593 Some(SumTree(Arc::new(Node::Internal {
594 height: *height,
595 child_summaries: right_summaries,
596 child_trees: right_trees,
597 })))
598 } else {
599 child_summaries.extend(summaries_to_append);
600 child_trees.extend(trees_to_append);
601 None
602 }
603 }
604 Node::Leaf {
605 items,
606 item_summaries,
607 } => {
608 let other_node = other.0;
609
610 let child_count = items.len() + other_node.items().len();
611 if child_count > 2 * TREE_BASE {
612 let left_items;
613 let right_items;
614 let left_summaries;
615 let right_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>;
616
617 let midpoint = (child_count + child_count % 2) / 2;
618 {
619 let mut all_items = items.iter().chain(other_node.items().iter()).cloned();
620 left_items = all_items.by_ref().take(midpoint).collect();
621 right_items = all_items.collect();
622
623 let mut all_summaries = item_summaries
624 .iter()
625 .chain(other_node.child_summaries())
626 .cloned();
627 left_summaries = all_summaries.by_ref().take(midpoint).collect();
628 right_summaries = all_summaries.collect();
629 }
630 *items = left_items;
631 *item_summaries = left_summaries;
632
633 Some(SumTree(Arc::new(Node::Leaf {
634 items: right_items,
635
636 item_summaries: right_summaries,
637 })))
638 } else {
639 let baseline = item_summaries.last().cloned();
640
641 items.extend(other_node.items().iter().cloned());
642 item_summaries.extend(other_node.child_summaries().iter().map(|summary| {
643 if let Some(mut baseline) = baseline.clone() {
644 <T::Summary as Summary>::add_summary(&mut baseline, summary, cx);
645 baseline
646 } else {
647 summary.clone()
648 }
649 }));
650 None
651 }
652 }
653 }
654 }
655
656 fn from_child_trees(
657 left: SumTree<T>,
658 right: SumTree<T>,
659 cx: &<T::Summary as Summary>::Context,
660 ) -> Self {
661 let height = left.0.height() + 1;
662 let mut child_summaries = ArrayVec::new();
663 child_summaries.push(left.0.summary_or_zero(cx).into_owned());
664 child_summaries.push(right.0.summary_or_zero(cx).into_owned());
665 let mut child_trees = ArrayVec::new();
666 child_trees.push(left);
667 child_trees.push(right);
668 SumTree(Arc::new(Node::Internal {
669 height,
670
671 child_summaries,
672 child_trees,
673 }))
674 }
675
676 fn leftmost_leaf(&self) -> &Self {
677 match *self.0 {
678 Node::Leaf { .. } => self,
679 Node::Internal {
680 ref child_trees, ..
681 } => child_trees.first().unwrap().leftmost_leaf(),
682 }
683 }
684
685 fn rightmost_leaf(&self) -> &Self {
686 match *self.0 {
687 Node::Leaf { .. } => self,
688 Node::Internal {
689 ref child_trees, ..
690 } => child_trees.last().unwrap().rightmost_leaf(),
691 }
692 }
693}
694
695impl<T: Item + PartialEq> PartialEq for SumTree<T> {
696 fn eq(&self, other: &Self) -> bool {
697 self.iter().eq(other.iter())
698 }
699}
700
701impl<T: Item + Eq> Eq for SumTree<T> {}
702
703impl<T: KeyedItem> SumTree<T> {
704 pub fn insert_or_replace(
705 &mut self,
706 item: T,
707 cx: &<T::Summary as Summary>::Context,
708 ) -> Option<T> {
709 let mut replaced = None;
710 *self = {
711 let mut cursor = self.cursor::<T::Key>(cx);
712 let mut new_tree = cursor.slice(&item.key(), Bias::Left);
713 if let Some(cursor_item) = cursor.item()
714 && cursor_item.key() == item.key()
715 {
716 replaced = Some(cursor_item.clone());
717 cursor.next();
718 }
719 new_tree.push(item, cx);
720 new_tree.append(cursor.suffix(), cx);
721 new_tree
722 };
723 replaced
724 }
725
726 pub fn remove(&mut self, key: &T::Key, cx: &<T::Summary as Summary>::Context) -> Option<T> {
727 let mut removed = None;
728 *self = {
729 let mut cursor = self.cursor::<T::Key>(cx);
730 let mut new_tree = cursor.slice(key, Bias::Left);
731 if let Some(item) = cursor.item()
732 && item.key() == *key
733 {
734 removed = Some(item.clone());
735 cursor.next();
736 }
737 new_tree.append(cursor.suffix(), cx);
738 new_tree
739 };
740 removed
741 }
742
743 pub fn edit(
744 &mut self,
745 mut edits: Vec<Edit<T>>,
746 cx: &<T::Summary as Summary>::Context,
747 ) -> Vec<T> {
748 if edits.is_empty() {
749 return Vec::new();
750 }
751
752 let mut removed = Vec::new();
753 edits.sort_unstable_by_key(|item| item.key());
754
755 *self = {
756 let mut cursor = self.cursor::<T::Key>(cx);
757 let mut new_tree = SumTree::new();
758 let mut buffered_items = Vec::new();
759
760 cursor.seek(&T::Key::zero(cx), Bias::Left);
761 for edit in edits {
762 let new_key = edit.key();
763 let mut old_item = cursor.item();
764
765 if old_item
766 .as_ref()
767 .is_some_and(|old_item| old_item.key() < new_key)
768 {
769 new_tree.extend(buffered_items.drain(..), cx);
770 let slice = cursor.slice(&new_key, Bias::Left);
771 new_tree.append(slice, cx);
772 old_item = cursor.item();
773 }
774
775 if let Some(old_item) = old_item
776 && old_item.key() == new_key
777 {
778 removed.push(old_item.clone());
779 cursor.next();
780 }
781
782 match edit {
783 Edit::Insert(item) => {
784 buffered_items.push(item);
785 }
786 Edit::Remove(_) => {}
787 }
788 }
789
790 new_tree.extend(buffered_items, cx);
791 new_tree.append(cursor.suffix(), cx);
792 new_tree
793 };
794
795 removed
796 }
797
798 pub fn get<'a>(
799 &'a self,
800 key: &T::Key,
801 cx: &'a <T::Summary as Summary>::Context,
802 ) -> Option<&'a T> {
803 let mut cursor = self.cursor::<T::Key>(cx);
804 if cursor.seek(key, Bias::Left) {
805 cursor.item()
806 } else {
807 None
808 }
809 }
810}
811
812impl<T: Item> Default for SumTree<T> {
813 fn default() -> Self {
814 Self::new()
815 }
816}
817
818#[derive(Clone)]
819pub enum Node<T: Item> {
820 Internal {
821 height: u8,
822 child_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
823 child_trees: ArrayVec<SumTree<T>, { 2 * TREE_BASE }>,
824 },
825 Leaf {
826 items: ArrayVec<T, { 2 * TREE_BASE }>,
827 item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
828 },
829}
830
831impl<T> fmt::Debug for Node<T>
832where
833 T: Item + fmt::Debug,
834 T::Summary: fmt::Debug,
835{
836 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
837 match self {
838 Node::Internal {
839 height,
840 child_summaries,
841 child_trees,
842 } => f
843 .debug_struct("Internal")
844 .field("height", height)
845 .field("child_summaries", child_summaries)
846 .field("child_trees", child_trees)
847 .finish(),
848 Node::Leaf {
849 items,
850 item_summaries,
851 } => f
852 .debug_struct("Leaf")
853 .field("items", items)
854 .field("item_summaries", item_summaries)
855 .finish(),
856 }
857 }
858}
859
860impl<T: Item> Node<T> {
861 fn is_leaf(&self) -> bool {
862 matches!(self, Node::Leaf { .. })
863 }
864
865 fn height(&self) -> u8 {
866 match self {
867 Node::Internal { height, .. } => *height,
868 Node::Leaf { .. } => 0,
869 }
870 }
871
872 fn summary<'a>(&'a self) -> Option<&'a T::Summary> {
873 let child_summaries = self.child_summaries();
874 child_summaries.last()
875 }
876
877 fn summary_or_zero<'a>(&'a self, cx: &<T::Summary as Summary>::Context) -> Cow<'a, T::Summary> {
878 self.summary().map_or_else(
879 || Cow::Owned(<T::Summary as Summary>::zero(cx)),
880 |last_summary| Cow::Borrowed(last_summary),
881 )
882 }
883
884 fn child_summaries(&self) -> &[T::Summary] {
885 match self {
886 Node::Internal {
887 child_summaries, ..
888 } => child_summaries.as_slice(),
889 Node::Leaf { item_summaries, .. } => item_summaries.as_slice(),
890 }
891 }
892
893 fn child_trees(&self) -> &ArrayVec<SumTree<T>, { 2 * TREE_BASE }> {
894 match self {
895 Node::Internal { child_trees, .. } => child_trees,
896 Node::Leaf { .. } => panic!("Leaf nodes have no child trees"),
897 }
898 }
899
900 fn items(&self) -> &ArrayVec<T, { 2 * TREE_BASE }> {
901 match self {
902 Node::Leaf { items, .. } => items,
903 Node::Internal { .. } => panic!("Internal nodes have no items"),
904 }
905 }
906
907 fn is_underflowing(&self) -> bool {
908 match self {
909 Node::Internal { child_trees, .. } => child_trees.len() < TREE_BASE,
910 Node::Leaf { items, .. } => items.len() < TREE_BASE,
911 }
912 }
913}
914
915#[derive(Debug)]
916pub enum Edit<T: KeyedItem> {
917 Insert(T),
918 Remove(T::Key),
919}
920
921impl<T: KeyedItem> Edit<T> {
922 fn key(&self) -> T::Key {
923 match self {
924 Edit::Insert(item) => item.key(),
925 Edit::Remove(key) => key.clone(),
926 }
927 }
928}
929
930#[cfg(test)]
931mod tests {
932 use super::*;
933 use rand::{distributions, prelude::*};
934 use std::cmp;
935
936 #[ctor::ctor]
937 fn init_logger() {
938 zlog::init_test();
939 }
940
941 #[test]
942 fn test_extend_and_push_tree() {
943 let mut tree1 = SumTree::default();
944 tree1.extend(0..20, &());
945
946 let mut tree2 = SumTree::default();
947 tree2.extend(50..100, &());
948
949 tree1.append(tree2, &());
950 assert_eq!(
951 tree1.items(&()),
952 (0..20).chain(50..100).collect::<Vec<u8>>()
953 );
954 }
955
956 #[test]
957 fn test_random() {
958 let mut starting_seed = 0;
959 if let Ok(value) = std::env::var("SEED") {
960 starting_seed = value.parse().expect("invalid SEED variable");
961 }
962 let mut num_iterations = 100;
963 if let Ok(value) = std::env::var("ITERATIONS") {
964 num_iterations = value.parse().expect("invalid ITERATIONS variable");
965 }
966 let num_operations = std::env::var("OPERATIONS")
967 .map_or(5, |o| o.parse().expect("invalid OPERATIONS variable"));
968
969 for seed in starting_seed..(starting_seed + num_iterations) {
970 eprintln!("seed = {}", seed);
971 let mut rng = StdRng::seed_from_u64(seed);
972
973 let rng = &mut rng;
974 let mut tree = SumTree::<u8>::default();
975 let count = rng.gen_range(0..10);
976 if rng.r#gen() {
977 tree.extend(rng.sample_iter(distributions::Standard).take(count), &());
978 } else {
979 let items = rng
980 .sample_iter(distributions::Standard)
981 .take(count)
982 .collect::<Vec<_>>();
983 tree.par_extend(items, &());
984 }
985
986 for _ in 0..num_operations {
987 let splice_end = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
988 let splice_start = rng.gen_range(0..splice_end + 1);
989 let count = rng.gen_range(0..10);
990 let tree_end = tree.extent::<Count>(&());
991 let new_items = rng
992 .sample_iter(distributions::Standard)
993 .take(count)
994 .collect::<Vec<u8>>();
995
996 let mut reference_items = tree.items(&());
997 reference_items.splice(splice_start..splice_end, new_items.clone());
998
999 tree = {
1000 let mut cursor = tree.cursor::<Count>(&());
1001 let mut new_tree = cursor.slice(&Count(splice_start), Bias::Right);
1002 if rng.r#gen() {
1003 new_tree.extend(new_items, &());
1004 } else {
1005 new_tree.par_extend(new_items, &());
1006 }
1007 cursor.seek(&Count(splice_end), Bias::Right);
1008 new_tree.append(cursor.slice(&tree_end, Bias::Right), &());
1009 new_tree
1010 };
1011
1012 assert_eq!(tree.items(&()), reference_items);
1013 assert_eq!(
1014 tree.iter().collect::<Vec<_>>(),
1015 tree.cursor::<()>(&()).collect::<Vec<_>>()
1016 );
1017
1018 log::info!("tree items: {:?}", tree.items(&()));
1019
1020 let mut filter_cursor =
1021 tree.filter::<_, Count>(&(), |summary| summary.contains_even.cmp(&false));
1022 let expected_filtered_items = tree
1023 .items(&())
1024 .into_iter()
1025 .enumerate()
1026 .filter(|(_, item)| (item & 1) == 0)
1027 .collect::<Vec<_>>();
1028
1029 let mut item_ix = if rng.r#gen() {
1030 filter_cursor.next();
1031 0
1032 } else {
1033 filter_cursor.prev();
1034 expected_filtered_items.len().saturating_sub(1)
1035 };
1036 while item_ix < expected_filtered_items.len() {
1037 log::info!("filter_cursor, item_ix: {}", item_ix);
1038 let actual_item = filter_cursor.item().unwrap();
1039 let (reference_index, reference_item) = expected_filtered_items[item_ix];
1040 assert_eq!(actual_item, &reference_item);
1041 assert_eq!(filter_cursor.start().0, reference_index);
1042 log::info!("next");
1043 filter_cursor.next();
1044 item_ix += 1;
1045
1046 while item_ix > 0 && rng.gen_bool(0.2) {
1047 log::info!("prev");
1048 filter_cursor.prev();
1049 item_ix -= 1;
1050
1051 if item_ix == 0 && rng.gen_bool(0.2) {
1052 filter_cursor.prev();
1053 assert_eq!(filter_cursor.item(), None);
1054 assert_eq!(filter_cursor.start().0, 0);
1055 filter_cursor.next();
1056 }
1057 }
1058 }
1059 assert_eq!(filter_cursor.item(), None);
1060
1061 let mut before_start = false;
1062 let mut cursor = tree.cursor::<Count>(&());
1063 let start_pos = rng.gen_range(0..=reference_items.len());
1064 cursor.seek(&Count(start_pos), Bias::Right);
1065 let mut pos = rng.gen_range(start_pos..=reference_items.len());
1066 cursor.seek_forward(&Count(pos), Bias::Right);
1067
1068 for i in 0..10 {
1069 assert_eq!(cursor.start().0, pos);
1070
1071 if pos > 0 {
1072 assert_eq!(cursor.prev_item().unwrap(), &reference_items[pos - 1]);
1073 } else {
1074 assert_eq!(cursor.prev_item(), None);
1075 }
1076
1077 if pos < reference_items.len() && !before_start {
1078 assert_eq!(cursor.item().unwrap(), &reference_items[pos]);
1079 } else {
1080 assert_eq!(cursor.item(), None);
1081 }
1082
1083 if before_start {
1084 assert_eq!(cursor.next_item(), reference_items.first());
1085 } else if pos + 1 < reference_items.len() {
1086 assert_eq!(cursor.next_item().unwrap(), &reference_items[pos + 1]);
1087 } else {
1088 assert_eq!(cursor.next_item(), None);
1089 }
1090
1091 if i < 5 {
1092 cursor.next();
1093 if pos < reference_items.len() {
1094 pos += 1;
1095 before_start = false;
1096 }
1097 } else {
1098 cursor.prev();
1099 if pos == 0 {
1100 before_start = true;
1101 }
1102 pos = pos.saturating_sub(1);
1103 }
1104 }
1105 }
1106
1107 for _ in 0..10 {
1108 let end = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
1109 let start = rng.gen_range(0..end + 1);
1110 let start_bias = if rng.r#gen() { Bias::Left } else { Bias::Right };
1111 let end_bias = if rng.r#gen() { Bias::Left } else { Bias::Right };
1112
1113 let mut cursor = tree.cursor::<Count>(&());
1114 cursor.seek(&Count(start), start_bias);
1115 let slice = cursor.slice(&Count(end), end_bias);
1116
1117 cursor.seek(&Count(start), start_bias);
1118 let summary = cursor.summary::<_, Sum>(&Count(end), end_bias);
1119
1120 assert_eq!(summary.0, slice.0.summary_or_zero(&()).sum);
1121 }
1122 }
1123 }
1124
1125 #[test]
1126 fn test_cursor() {
1127 // Empty tree
1128 let tree = SumTree::<u8>::default();
1129 let mut cursor = tree.cursor::<IntegersSummary>(&());
1130 assert_eq!(
1131 cursor.slice(&Count(0), Bias::Right).items(&()),
1132 Vec::<u8>::new()
1133 );
1134 assert_eq!(cursor.item(), None);
1135 assert_eq!(cursor.prev_item(), None);
1136 assert_eq!(cursor.next_item(), None);
1137 assert_eq!(cursor.start().sum, 0);
1138 cursor.prev();
1139 assert_eq!(cursor.item(), None);
1140 assert_eq!(cursor.prev_item(), None);
1141 assert_eq!(cursor.next_item(), None);
1142 assert_eq!(cursor.start().sum, 0);
1143 cursor.next();
1144 assert_eq!(cursor.item(), None);
1145 assert_eq!(cursor.prev_item(), None);
1146 assert_eq!(cursor.next_item(), None);
1147 assert_eq!(cursor.start().sum, 0);
1148
1149 // Single-element tree
1150 let mut tree = SumTree::<u8>::default();
1151 tree.extend(vec![1], &());
1152 let mut cursor = tree.cursor::<IntegersSummary>(&());
1153 assert_eq!(
1154 cursor.slice(&Count(0), Bias::Right).items(&()),
1155 Vec::<u8>::new()
1156 );
1157 assert_eq!(cursor.item(), Some(&1));
1158 assert_eq!(cursor.prev_item(), None);
1159 assert_eq!(cursor.next_item(), None);
1160 assert_eq!(cursor.start().sum, 0);
1161
1162 cursor.next();
1163 assert_eq!(cursor.item(), None);
1164 assert_eq!(cursor.prev_item(), Some(&1));
1165 assert_eq!(cursor.next_item(), None);
1166 assert_eq!(cursor.start().sum, 1);
1167
1168 cursor.prev();
1169 assert_eq!(cursor.item(), Some(&1));
1170 assert_eq!(cursor.prev_item(), None);
1171 assert_eq!(cursor.next_item(), None);
1172 assert_eq!(cursor.start().sum, 0);
1173
1174 let mut cursor = tree.cursor::<IntegersSummary>(&());
1175 assert_eq!(cursor.slice(&Count(1), Bias::Right).items(&()), [1]);
1176 assert_eq!(cursor.item(), None);
1177 assert_eq!(cursor.prev_item(), Some(&1));
1178 assert_eq!(cursor.next_item(), None);
1179 assert_eq!(cursor.start().sum, 1);
1180
1181 cursor.seek(&Count(0), Bias::Right);
1182 assert_eq!(
1183 cursor
1184 .slice(&tree.extent::<Count>(&()), Bias::Right)
1185 .items(&()),
1186 [1]
1187 );
1188 assert_eq!(cursor.item(), None);
1189 assert_eq!(cursor.prev_item(), Some(&1));
1190 assert_eq!(cursor.next_item(), None);
1191 assert_eq!(cursor.start().sum, 1);
1192
1193 // Multiple-element tree
1194 let mut tree = SumTree::default();
1195 tree.extend(vec![1, 2, 3, 4, 5, 6], &());
1196
1197 let mut cursor = tree.cursor::<IntegersSummary>(&());
1198
1199 let slice = cursor.slice(&Count(2), Bias::Right);
1200 assert_eq!(slice.items(&()), [1, 2]);
1201 assert_eq!(cursor.item(), Some(&3));
1202 assert_eq!(cursor.prev_item(), Some(&2));
1203 assert_eq!(cursor.next_item(), Some(&4));
1204 assert_eq!(cursor.start().sum, 3);
1205
1206 cursor.next();
1207 assert_eq!(cursor.item(), Some(&4));
1208 assert_eq!(cursor.prev_item(), Some(&3));
1209 assert_eq!(cursor.next_item(), Some(&5));
1210 assert_eq!(cursor.start().sum, 6);
1211
1212 cursor.next();
1213 assert_eq!(cursor.item(), Some(&5));
1214 assert_eq!(cursor.prev_item(), Some(&4));
1215 assert_eq!(cursor.next_item(), Some(&6));
1216 assert_eq!(cursor.start().sum, 10);
1217
1218 cursor.next();
1219 assert_eq!(cursor.item(), Some(&6));
1220 assert_eq!(cursor.prev_item(), Some(&5));
1221 assert_eq!(cursor.next_item(), None);
1222 assert_eq!(cursor.start().sum, 15);
1223
1224 cursor.next();
1225 cursor.next();
1226 assert_eq!(cursor.item(), None);
1227 assert_eq!(cursor.prev_item(), Some(&6));
1228 assert_eq!(cursor.next_item(), None);
1229 assert_eq!(cursor.start().sum, 21);
1230
1231 cursor.prev();
1232 assert_eq!(cursor.item(), Some(&6));
1233 assert_eq!(cursor.prev_item(), Some(&5));
1234 assert_eq!(cursor.next_item(), None);
1235 assert_eq!(cursor.start().sum, 15);
1236
1237 cursor.prev();
1238 assert_eq!(cursor.item(), Some(&5));
1239 assert_eq!(cursor.prev_item(), Some(&4));
1240 assert_eq!(cursor.next_item(), Some(&6));
1241 assert_eq!(cursor.start().sum, 10);
1242
1243 cursor.prev();
1244 assert_eq!(cursor.item(), Some(&4));
1245 assert_eq!(cursor.prev_item(), Some(&3));
1246 assert_eq!(cursor.next_item(), Some(&5));
1247 assert_eq!(cursor.start().sum, 6);
1248
1249 cursor.prev();
1250 assert_eq!(cursor.item(), Some(&3));
1251 assert_eq!(cursor.prev_item(), Some(&2));
1252 assert_eq!(cursor.next_item(), Some(&4));
1253 assert_eq!(cursor.start().sum, 3);
1254
1255 cursor.prev();
1256 assert_eq!(cursor.item(), Some(&2));
1257 assert_eq!(cursor.prev_item(), Some(&1));
1258 assert_eq!(cursor.next_item(), Some(&3));
1259 assert_eq!(cursor.start().sum, 1);
1260
1261 cursor.prev();
1262 assert_eq!(cursor.item(), Some(&1));
1263 assert_eq!(cursor.prev_item(), None);
1264 assert_eq!(cursor.next_item(), Some(&2));
1265 assert_eq!(cursor.start().sum, 0);
1266
1267 cursor.prev();
1268 assert_eq!(cursor.item(), None);
1269 assert_eq!(cursor.prev_item(), None);
1270 assert_eq!(cursor.next_item(), Some(&1));
1271 assert_eq!(cursor.start().sum, 0);
1272
1273 cursor.next();
1274 assert_eq!(cursor.item(), Some(&1));
1275 assert_eq!(cursor.prev_item(), None);
1276 assert_eq!(cursor.next_item(), Some(&2));
1277 assert_eq!(cursor.start().sum, 0);
1278
1279 let mut cursor = tree.cursor::<IntegersSummary>(&());
1280 assert_eq!(
1281 cursor
1282 .slice(&tree.extent::<Count>(&()), Bias::Right)
1283 .items(&()),
1284 tree.items(&())
1285 );
1286 assert_eq!(cursor.item(), None);
1287 assert_eq!(cursor.prev_item(), Some(&6));
1288 assert_eq!(cursor.next_item(), None);
1289 assert_eq!(cursor.start().sum, 21);
1290
1291 cursor.seek(&Count(3), Bias::Right);
1292 assert_eq!(
1293 cursor
1294 .slice(&tree.extent::<Count>(&()), Bias::Right)
1295 .items(&()),
1296 [4, 5, 6]
1297 );
1298 assert_eq!(cursor.item(), None);
1299 assert_eq!(cursor.prev_item(), Some(&6));
1300 assert_eq!(cursor.next_item(), None);
1301 assert_eq!(cursor.start().sum, 21);
1302
1303 // Seeking can bias left or right
1304 cursor.seek(&Count(1), Bias::Left);
1305 assert_eq!(cursor.item(), Some(&1));
1306 cursor.seek(&Count(1), Bias::Right);
1307 assert_eq!(cursor.item(), Some(&2));
1308
1309 // Slicing without resetting starts from where the cursor is parked at.
1310 cursor.seek(&Count(1), Bias::Right);
1311 assert_eq!(cursor.slice(&Count(3), Bias::Right).items(&()), vec![2, 3]);
1312 assert_eq!(cursor.slice(&Count(6), Bias::Left).items(&()), vec![4, 5]);
1313 assert_eq!(cursor.slice(&Count(6), Bias::Right).items(&()), vec![6]);
1314 }
1315
1316 #[test]
1317 fn test_edit() {
1318 let mut tree = SumTree::<u8>::default();
1319
1320 let removed = tree.edit(vec![Edit::Insert(1), Edit::Insert(2), Edit::Insert(0)], &());
1321 assert_eq!(tree.items(&()), vec![0, 1, 2]);
1322 assert_eq!(removed, Vec::<u8>::new());
1323 assert_eq!(tree.get(&0, &()), Some(&0));
1324 assert_eq!(tree.get(&1, &()), Some(&1));
1325 assert_eq!(tree.get(&2, &()), Some(&2));
1326 assert_eq!(tree.get(&4, &()), None);
1327
1328 let removed = tree.edit(vec![Edit::Insert(2), Edit::Insert(4), Edit::Remove(0)], &());
1329 assert_eq!(tree.items(&()), vec![1, 2, 4]);
1330 assert_eq!(removed, vec![0, 2]);
1331 assert_eq!(tree.get(&0, &()), None);
1332 assert_eq!(tree.get(&1, &()), Some(&1));
1333 assert_eq!(tree.get(&2, &()), Some(&2));
1334 assert_eq!(tree.get(&4, &()), Some(&4));
1335 }
1336
1337 #[test]
1338 fn test_from_iter() {
1339 assert_eq!(
1340 SumTree::from_iter(0..100, &()).items(&()),
1341 (0..100).collect::<Vec<_>>()
1342 );
1343
1344 // Ensure `from_iter` works correctly when the given iterator restarts
1345 // after calling `next` if `None` was already returned.
1346 let mut ix = 0;
1347 let iterator = std::iter::from_fn(|| {
1348 ix = (ix + 1) % 2;
1349 if ix == 1 { Some(1) } else { None }
1350 });
1351 assert_eq!(SumTree::from_iter(iterator, &()).items(&()), vec![1]);
1352 }
1353
1354 #[derive(Clone, Default, Debug)]
1355 pub struct IntegersSummary {
1356 count: usize,
1357 sum: usize,
1358 contains_even: bool,
1359 max: u8,
1360 }
1361
1362 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
1363 struct Count(usize);
1364
1365 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
1366 struct Sum(usize);
1367
1368 impl Item for u8 {
1369 type Summary = IntegersSummary;
1370
1371 fn summary(&self, _cx: &()) -> Self::Summary {
1372 IntegersSummary {
1373 count: 1,
1374 sum: *self as usize,
1375 contains_even: (*self & 1) == 0,
1376 max: *self,
1377 }
1378 }
1379 }
1380
1381 impl KeyedItem for u8 {
1382 type Key = u8;
1383
1384 fn key(&self) -> Self::Key {
1385 *self
1386 }
1387 }
1388
1389 impl Summary for IntegersSummary {
1390 type Context = ();
1391
1392 fn zero(_cx: &()) -> Self {
1393 Default::default()
1394 }
1395
1396 fn add_summary(&mut self, other: &Self, _: &()) {
1397 self.count += other.count;
1398 self.sum += other.sum;
1399 self.contains_even |= other.contains_even;
1400 self.max = cmp::max(self.max, other.max);
1401 }
1402 }
1403
1404 impl Dimension<'_, IntegersSummary> for u8 {
1405 fn zero(_cx: &()) -> Self {
1406 Default::default()
1407 }
1408
1409 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
1410 *self = summary.max;
1411 }
1412 }
1413
1414 impl Dimension<'_, IntegersSummary> for Count {
1415 fn zero(_cx: &()) -> Self {
1416 Default::default()
1417 }
1418
1419 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
1420 self.0 += summary.count;
1421 }
1422 }
1423
1424 impl SeekTarget<'_, IntegersSummary, IntegersSummary> for Count {
1425 fn cmp(&self, cursor_location: &IntegersSummary, _: &()) -> Ordering {
1426 self.0.cmp(&cursor_location.count)
1427 }
1428 }
1429
1430 impl Dimension<'_, IntegersSummary> for Sum {
1431 fn zero(_cx: &()) -> Self {
1432 Default::default()
1433 }
1434
1435 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
1436 self.0 += summary.sum;
1437 }
1438 }
1439}