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 }
103
104 fn add_summary(&mut self, _: &'a T, _: &T::Context) {}
105}
106
107#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
108pub struct Dimensions<D1, D2, D3 = ()>(pub D1, pub D2, pub D3);
109
110impl<'a, T: Summary, D1: Dimension<'a, T>, D2: Dimension<'a, T>, D3: Dimension<'a, T>>
111 Dimension<'a, T> for Dimensions<D1, D2, D3>
112{
113 fn zero(cx: &T::Context) -> Self {
114 Dimensions(D1::zero(cx), D2::zero(cx), D3::zero(cx))
115 }
116
117 fn add_summary(&mut self, summary: &'a T, cx: &T::Context) {
118 self.0.add_summary(summary, cx);
119 self.1.add_summary(summary, cx);
120 self.2.add_summary(summary, cx);
121 }
122}
123
124impl<'a, S, D1, D2, D3> SeekTarget<'a, S, Dimensions<D1, D2, D3>> for D1
125where
126 S: Summary,
127 D1: SeekTarget<'a, S, D1> + Dimension<'a, S>,
128 D2: Dimension<'a, S>,
129 D3: Dimension<'a, S>,
130{
131 fn cmp(&self, cursor_location: &Dimensions<D1, D2, D3>, cx: &S::Context) -> Ordering {
132 self.cmp(&cursor_location.0, cx)
133 }
134}
135
136/// Bias is used to settle ambiguities when determining positions in an ordered sequence.
137///
138/// The primary use case is for text, where Bias influences
139/// which character an offset or anchor is associated with.
140///
141/// # Examples
142/// Given the buffer `AˇBCD`:
143/// - The offset of the cursor is 1
144/// - [Bias::Left] would attach the cursor to the character `A`
145/// - [Bias::Right] would attach the cursor to the character `B`
146///
147/// Given the buffer `A«BCˇ»D`:
148/// - The offset of the cursor is 3, and the selection is from 1 to 3
149/// - The left anchor of the selection has [Bias::Right], attaching it to the character `B`
150/// - The right anchor of the selection has [Bias::Left], attaching it to the character `C`
151///
152/// Given the buffer `{ˇ<...>`, where `<...>` is a folded region:
153/// - The display offset of the cursor is 1, but the offset in the buffer is determined by the bias
154/// - [Bias::Left] would attach the cursor to the character `{`, with a buffer offset of 1
155/// - [Bias::Right] would attach the cursor to the first character of the folded region,
156/// and the buffer offset would be the offset of the first character of the folded region
157#[derive(Copy, Clone, Eq, PartialEq, PartialOrd, Ord, Debug, Hash, Default)]
158pub enum Bias {
159 /// Attach to the character on the left
160 #[default]
161 Left,
162 /// Attach to the character on the right
163 Right,
164}
165
166impl Bias {
167 pub fn invert(self) -> Self {
168 match self {
169 Self::Left => Self::Right,
170 Self::Right => Self::Left,
171 }
172 }
173}
174
175/// A B+ tree in which each leaf node contains `Item`s of type `T` and a `Summary`s for each `Item`.
176/// Each internal node contains a `Summary` of the items in its subtree.
177///
178/// The maximum number of items per node is `TREE_BASE * 2`.
179///
180/// Any [`Dimension`] supported by the [`Summary`] type can be used to seek to a specific location in the tree.
181#[derive(Clone)]
182pub struct SumTree<T: Item>(Arc<Node<T>>);
183
184impl<T> fmt::Debug for SumTree<T>
185where
186 T: fmt::Debug + Item,
187 T::Summary: fmt::Debug,
188{
189 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
190 f.debug_tuple("SumTree").field(&self.0).finish()
191 }
192}
193
194impl<T: Item> SumTree<T> {
195 pub fn new() -> Self {
196 SumTree(Arc::new(Node::Leaf {
197 items: ArrayVec::new(),
198 item_summaries: ArrayVec::new(),
199 }))
200 }
201
202 pub fn from_item(item: T, cx: &<T::Summary as Summary>::Context) -> Self {
203 let mut tree = Self::new();
204 tree.push(item, cx);
205 tree
206 }
207
208 pub fn from_iter<I: IntoIterator<Item = T>>(
209 iter: I,
210 cx: &<T::Summary as Summary>::Context,
211 ) -> Self {
212 let mut nodes = Vec::new();
213
214 let mut iter = iter.into_iter().fuse().peekable();
215 while iter.peek().is_some() {
216 let items: ArrayVec<T, { 2 * TREE_BASE }> = iter.by_ref().take(2 * TREE_BASE).collect();
217 let item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }> = items
218 .iter()
219 .scan(None, |previous_item, item| {
220 let summary = item.summary(cx);
221 let current_item = if let Some(mut base) = previous_item.take() {
222 <T::Summary as Summary>::add_summary(&mut base, &summary, cx);
223 base
224 } else {
225 summary
226 };
227 _ = previous_item.insert(current_item.clone());
228 Some(current_item)
229 })
230 .collect();
231 nodes.push(Node::Leaf {
232 items,
233 item_summaries,
234 });
235 }
236
237 let mut parent_nodes = Vec::new();
238 let mut height = 0;
239 while nodes.len() > 1 {
240 height += 1;
241 let mut current_parent_node = None;
242 for child_node in nodes.drain(..) {
243 let parent_node = current_parent_node.get_or_insert_with(|| Node::Internal {
244 height,
245 child_summaries: ArrayVec::new(),
246 child_trees: ArrayVec::new(),
247 });
248 let Node::Internal {
249 child_summaries,
250 child_trees,
251 ..
252 } = parent_node
253 else {
254 unreachable!()
255 };
256 let child_summary = child_node.summary_or_zero(cx);
257 let child_summary = if let Some(mut last) = child_summaries.last().cloned() {
258 <T::Summary as Summary>::add_summary(&mut last, &child_summary, cx);
259 last
260 } else {
261 child_summary.into_owned()
262 };
263
264 child_summaries.push(child_summary);
265 child_trees.push(Self(Arc::new(child_node)));
266
267 if child_trees.len() == 2 * TREE_BASE {
268 parent_nodes.extend(current_parent_node.take());
269 }
270 }
271 parent_nodes.extend(current_parent_node.take());
272 mem::swap(&mut nodes, &mut parent_nodes);
273 }
274
275 if nodes.is_empty() {
276 Self::new()
277 } else {
278 debug_assert_eq!(nodes.len(), 1);
279 Self(Arc::new(nodes.pop().unwrap()))
280 }
281 }
282
283 pub fn from_par_iter<I, Iter>(iter: I, cx: &<T::Summary as Summary>::Context) -> Self
284 where
285 I: IntoParallelIterator<Iter = Iter>,
286 Iter: IndexedParallelIterator<Item = T>,
287 T: Send + Sync,
288 T::Summary: Send + Sync,
289 <T::Summary as Summary>::Context: Sync,
290 {
291 let mut nodes = iter
292 .into_par_iter()
293 .chunks(2 * TREE_BASE)
294 .map(|items| {
295 let items: ArrayVec<T, { 2 * TREE_BASE }> = items.into_iter().collect();
296 let item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }> = items
297 .iter()
298 .scan(None, |previous_item, item| {
299 let summary = item.summary(cx);
300 let current_item = if let Some(mut base) = previous_item.take() {
301 <T::Summary as Summary>::add_summary(&mut base, &summary, cx);
302 base
303 } else {
304 summary
305 };
306 _ = previous_item.insert(current_item.clone());
307 Some(current_item)
308 })
309 .collect();
310
311 SumTree(Arc::new(Node::Leaf {
312 items,
313 item_summaries,
314 }))
315 })
316 .collect::<Vec<_>>();
317
318 let mut height = 0;
319 while nodes.len() > 1 {
320 height += 1;
321 nodes = nodes
322 .into_par_iter()
323 .chunks(2 * TREE_BASE)
324 .map(|child_nodes| {
325 let child_trees: ArrayVec<SumTree<T>, { 2 * TREE_BASE }> =
326 child_nodes.into_iter().collect();
327 let child_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }> = child_trees
328 .iter()
329 .map(|child_tree| child_tree.0.summary_or_zero(cx).into_owned())
330 .collect();
331 let mut summary = child_summaries[0].clone();
332 for child_summary in &child_summaries[1..] {
333 <T::Summary as Summary>::add_summary(&mut summary, child_summary, cx);
334 }
335 SumTree(Arc::new(Node::Internal {
336 height,
337
338 child_summaries,
339 child_trees,
340 }))
341 })
342 .collect::<Vec<_>>();
343 }
344
345 if nodes.is_empty() {
346 Self::new()
347 } else {
348 debug_assert_eq!(nodes.len(), 1);
349 nodes.pop().unwrap()
350 }
351 }
352
353 #[allow(unused)]
354 pub fn items(&self, cx: &<T::Summary as Summary>::Context) -> Vec<T> {
355 let mut items = Vec::new();
356 let mut cursor = self.cursor::<()>(cx);
357 cursor.next();
358 while let Some(item) = cursor.item() {
359 items.push(item.clone());
360 cursor.next();
361 }
362 items
363 }
364
365 pub fn iter(&self) -> Iter<'_, T> {
366 Iter::new(self)
367 }
368
369 pub fn cursor<'a, S>(&'a self, cx: &'a <T::Summary as Summary>::Context) -> Cursor<'a, T, S>
370 where
371 S: Dimension<'a, T::Summary>,
372 {
373 Cursor::new(self, cx)
374 }
375
376 /// Note: If the summary type requires a non `()` context, then the filter cursor
377 /// that is returned cannot be used with Rust's iterators.
378 pub fn filter<'a, F, U>(
379 &'a self,
380 cx: &'a <T::Summary as Summary>::Context,
381 filter_node: F,
382 ) -> FilterCursor<'a, F, T, U>
383 where
384 F: FnMut(&T::Summary) -> Ordering,
385 U: Dimension<'a, T::Summary>,
386 {
387 FilterCursor::new(self, cx, filter_node)
388 }
389
390 #[allow(dead_code)]
391 pub fn first(&self) -> Option<&T> {
392 self.leftmost_leaf().0.items().first()
393 }
394
395 pub fn last(&self) -> Option<&T> {
396 self.rightmost_leaf().0.items().last()
397 }
398
399 pub fn update_last(&mut self, f: impl FnOnce(&mut T), cx: &<T::Summary as Summary>::Context) {
400 self.update_last_recursive(f, cx);
401 }
402
403 fn update_last_recursive(
404 &mut self,
405 f: impl FnOnce(&mut T),
406 cx: &<T::Summary as Summary>::Context,
407 ) -> Option<T::Summary> {
408 match Arc::make_mut(&mut self.0) {
409 Node::Internal {
410 child_summaries,
411 child_trees,
412 ..
413 } => {
414 let last_child = child_trees.last_mut().unwrap();
415
416 let mut bare_summary = last_child.update_last_recursive(f, cx).unwrap();
417
418 if let Some(mut second_to_last_summary) = child_summaries
419 .len()
420 .checked_sub(2)
421 .and_then(|ix| child_summaries.get(ix))
422 .cloned()
423 {
424 <T::Summary as Summary>::add_summary(
425 &mut second_to_last_summary,
426 &bare_summary,
427 cx,
428 );
429 bare_summary = second_to_last_summary;
430 }
431 let last_summary = child_summaries.last_mut().unwrap();
432 *last_summary = bare_summary;
433
434 Some(last_summary.clone())
435 }
436 Node::Leaf {
437 items,
438 item_summaries,
439 } => {
440 let preceding_summary = item_summaries
441 .len()
442 .checked_sub(2)
443 .and_then(|ix| item_summaries.get(ix))
444 .cloned();
445 if let Some((item, item_summary)) = items.last_mut().zip(item_summaries.last_mut())
446 {
447 (f)(item);
448 let mut bare_summary = item.summary(cx);
449
450 if let Some(mut second_to_last_summary) = preceding_summary {
451 <T::Summary as Summary>::add_summary(
452 &mut second_to_last_summary,
453 &bare_summary,
454 cx,
455 );
456 bare_summary = second_to_last_summary;
457 }
458 *item_summary = bare_summary.clone();
459
460 Some(item_summary.clone())
461 } else {
462 None
463 }
464 }
465 }
466 }
467
468 pub fn extent<'a, D: Dimension<'a, T::Summary>>(
469 &'a self,
470 cx: &<T::Summary as Summary>::Context,
471 ) -> D {
472 let mut extent = D::zero(cx);
473 if let Some(last) = self.0.child_summaries().last() {
474 extent.add_summary(last, cx);
475 }
476
477 extent
478 }
479
480 pub fn is_empty(&self) -> bool {
481 match self.0.as_ref() {
482 Node::Internal { .. } => false,
483 Node::Leaf { items, .. } => items.is_empty(),
484 }
485 }
486
487 pub fn extend<I>(&mut self, iter: I, cx: &<T::Summary as Summary>::Context)
488 where
489 I: IntoIterator<Item = T>,
490 {
491 self.append(Self::from_iter(iter, cx), cx);
492 }
493
494 pub fn par_extend<I, Iter>(&mut self, iter: I, cx: &<T::Summary as Summary>::Context)
495 where
496 I: IntoParallelIterator<Iter = Iter>,
497 Iter: IndexedParallelIterator<Item = T>,
498 T: Send + Sync,
499 T::Summary: Send + Sync,
500 <T::Summary as Summary>::Context: Sync,
501 {
502 self.append(Self::from_par_iter(iter, cx), cx);
503 }
504
505 pub fn push(&mut self, item: T, cx: &<T::Summary as Summary>::Context) {
506 let summary = item.summary(cx);
507 self.append(
508 SumTree(Arc::new(Node::Leaf {
509 items: ArrayVec::from_iter(Some(item)),
510 item_summaries: ArrayVec::from_iter(Some(summary)),
511 })),
512 cx,
513 );
514 }
515
516 pub fn append(&mut self, other: Self, cx: &<T::Summary as Summary>::Context) {
517 if self.is_empty() {
518 *self = other;
519 } else if !other.0.is_leaf() || !other.0.items().is_empty() {
520 if self.0.height() < other.0.height() {
521 for tree in other.0.child_trees() {
522 self.append(tree.clone(), cx);
523 }
524 } else if let Some(split_tree) = self.push_tree_recursive(other, cx) {
525 *self = Self::from_child_trees(self.clone(), split_tree, cx);
526 }
527 }
528 }
529
530 fn push_tree_recursive(
531 &mut self,
532 other: SumTree<T>,
533 cx: &<T::Summary as Summary>::Context,
534 ) -> Option<SumTree<T>> {
535 match Arc::make_mut(&mut self.0) {
536 Node::Internal {
537 height,
538 child_summaries,
539 child_trees,
540 ..
541 } => {
542 let other_node = other.0.clone();
543
544 let height_delta = *height - other_node.height();
545 let mut summaries_to_append = ArrayVec::<T::Summary, { 2 * TREE_BASE }>::new();
546 let mut trees_to_append = ArrayVec::<SumTree<T>, { 2 * TREE_BASE }>::new();
547 if height_delta == 0 {
548 summaries_to_append.extend(other_node.child_summaries().iter().cloned());
549 trees_to_append.extend(other_node.child_trees().iter().cloned());
550 } else if height_delta == 1 && !other_node.is_underflowing() {
551 summaries_to_append.push(other_node.summary_or_zero(cx).into_owned());
552 trees_to_append.push(other)
553 } else {
554 let tree_to_append = child_trees
555 .last_mut()
556 .unwrap()
557 .push_tree_recursive(other, cx);
558 *child_summaries.last_mut().unwrap() = child_trees
559 .last()
560 .unwrap()
561 .0
562 .summary_or_zero(cx)
563 .into_owned();
564
565 if let Some(split_tree) = tree_to_append {
566 summaries_to_append.push(split_tree.0.summary_or_zero(cx).into_owned());
567 trees_to_append.push(split_tree);
568 }
569 }
570
571 let child_count = child_trees.len() + trees_to_append.len();
572 if child_count > 2 * TREE_BASE {
573 let left_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
574 let right_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
575 let left_trees;
576 let right_trees;
577
578 let midpoint = (child_count + child_count % 2) / 2;
579 {
580 let mut all_summaries = child_summaries
581 .iter()
582 .chain(summaries_to_append.iter())
583 .cloned();
584 left_summaries = all_summaries.by_ref().take(midpoint).collect();
585 right_summaries = all_summaries.collect();
586 let mut all_trees =
587 child_trees.iter().chain(trees_to_append.iter()).cloned();
588 left_trees = all_trees.by_ref().take(midpoint).collect();
589 right_trees = all_trees.collect();
590 }
591
592 *child_summaries = left_summaries;
593 *child_trees = left_trees;
594
595 Some(SumTree(Arc::new(Node::Internal {
596 height: *height,
597 child_summaries: right_summaries,
598 child_trees: right_trees,
599 })))
600 } else {
601 child_summaries.extend(summaries_to_append);
602 child_trees.extend(trees_to_append);
603 None
604 }
605 }
606 Node::Leaf {
607 items,
608 item_summaries,
609 } => {
610 let other_node = other.0;
611
612 let child_count = items.len() + other_node.items().len();
613 if child_count > 2 * TREE_BASE {
614 let left_items;
615 let right_items;
616 let left_summaries;
617 let right_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>;
618
619 let midpoint = (child_count + child_count % 2) / 2;
620 {
621 let mut all_items = items.iter().chain(other_node.items().iter()).cloned();
622 left_items = all_items.by_ref().take(midpoint).collect();
623 right_items = all_items.collect();
624
625 let mut all_summaries = item_summaries
626 .iter()
627 .chain(other_node.child_summaries())
628 .cloned();
629 left_summaries = all_summaries.by_ref().take(midpoint).collect();
630 right_summaries = all_summaries.collect();
631 }
632 *items = left_items;
633 *item_summaries = left_summaries;
634
635 Some(SumTree(Arc::new(Node::Leaf {
636 items: right_items,
637
638 item_summaries: right_summaries,
639 })))
640 } else {
641 let baseline = item_summaries.last().cloned();
642
643 items.extend(other_node.items().iter().cloned());
644 item_summaries.extend(other_node.child_summaries().iter().map(|summary| {
645 if let Some(mut baseline) = baseline.clone() {
646 <T::Summary as Summary>::add_summary(&mut baseline, summary, cx);
647 baseline
648 } else {
649 summary.clone()
650 }
651 }));
652 None
653 }
654 }
655 }
656 }
657
658 fn from_child_trees(
659 left: SumTree<T>,
660 right: SumTree<T>,
661 cx: &<T::Summary as Summary>::Context,
662 ) -> Self {
663 let height = left.0.height() + 1;
664 let mut child_summaries = ArrayVec::new();
665 child_summaries.push(left.0.summary_or_zero(cx).into_owned());
666 child_summaries.push(right.0.summary_or_zero(cx).into_owned());
667 let mut child_trees = ArrayVec::new();
668 child_trees.push(left);
669 child_trees.push(right);
670 SumTree(Arc::new(Node::Internal {
671 height,
672
673 child_summaries,
674 child_trees,
675 }))
676 }
677
678 fn leftmost_leaf(&self) -> &Self {
679 match *self.0 {
680 Node::Leaf { .. } => self,
681 Node::Internal {
682 ref child_trees, ..
683 } => child_trees.first().unwrap().leftmost_leaf(),
684 }
685 }
686
687 fn rightmost_leaf(&self) -> &Self {
688 match *self.0 {
689 Node::Leaf { .. } => self,
690 Node::Internal {
691 ref child_trees, ..
692 } => child_trees.last().unwrap().rightmost_leaf(),
693 }
694 }
695}
696
697impl<T: Item + PartialEq> PartialEq for SumTree<T> {
698 fn eq(&self, other: &Self) -> bool {
699 self.iter().eq(other.iter())
700 }
701}
702
703impl<T: Item + Eq> Eq for SumTree<T> {}
704
705impl<T: KeyedItem> SumTree<T> {
706 pub fn insert_or_replace(
707 &mut self,
708 item: T,
709 cx: &<T::Summary as Summary>::Context,
710 ) -> Option<T> {
711 let mut replaced = None;
712 *self = {
713 let mut cursor = self.cursor::<T::Key>(cx);
714 let mut new_tree = cursor.slice(&item.key(), Bias::Left);
715 if let Some(cursor_item) = cursor.item() {
716 if cursor_item.key() == item.key() {
717 replaced = Some(cursor_item.clone());
718 cursor.next();
719 }
720 }
721 new_tree.push(item, cx);
722 new_tree.append(cursor.suffix(), cx);
723 new_tree
724 };
725 replaced
726 }
727
728 pub fn remove(&mut self, key: &T::Key, cx: &<T::Summary as Summary>::Context) -> Option<T> {
729 let mut removed = None;
730 *self = {
731 let mut cursor = self.cursor::<T::Key>(cx);
732 let mut new_tree = cursor.slice(key, Bias::Left);
733 if let Some(item) = cursor.item() {
734 if item.key() == *key {
735 removed = Some(item.clone());
736 cursor.next();
737 }
738 }
739 new_tree.append(cursor.suffix(), cx);
740 new_tree
741 };
742 removed
743 }
744
745 pub fn edit(
746 &mut self,
747 mut edits: Vec<Edit<T>>,
748 cx: &<T::Summary as Summary>::Context,
749 ) -> Vec<T> {
750 if edits.is_empty() {
751 return Vec::new();
752 }
753
754 let mut removed = Vec::new();
755 edits.sort_unstable_by_key(|item| item.key());
756
757 *self = {
758 let mut cursor = self.cursor::<T::Key>(cx);
759 let mut new_tree = SumTree::new();
760 let mut buffered_items = Vec::new();
761
762 cursor.seek(&T::Key::zero(cx), Bias::Left);
763 for edit in edits {
764 let new_key = edit.key();
765 let mut old_item = cursor.item();
766
767 if old_item
768 .as_ref()
769 .map_or(false, |old_item| old_item.key() < new_key)
770 {
771 new_tree.extend(buffered_items.drain(..), cx);
772 let slice = cursor.slice(&new_key, Bias::Left);
773 new_tree.append(slice, cx);
774 old_item = cursor.item();
775 }
776
777 if let Some(old_item) = old_item {
778 if old_item.key() == new_key {
779 removed.push(old_item.clone());
780 cursor.next();
781 }
782 }
783
784 match edit {
785 Edit::Insert(item) => {
786 buffered_items.push(item);
787 }
788 Edit::Remove(_) => {}
789 }
790 }
791
792 new_tree.extend(buffered_items, cx);
793 new_tree.append(cursor.suffix(), cx);
794 new_tree
795 };
796
797 removed
798 }
799
800 pub fn get<'a>(
801 &'a self,
802 key: &T::Key,
803 cx: &'a <T::Summary as Summary>::Context,
804 ) -> Option<&'a T> {
805 let mut cursor = self.cursor::<T::Key>(cx);
806 if cursor.seek(key, Bias::Left) {
807 cursor.item()
808 } else {
809 None
810 }
811 }
812}
813
814impl<T: Item> Default for SumTree<T> {
815 fn default() -> Self {
816 Self::new()
817 }
818}
819
820#[derive(Clone)]
821pub enum Node<T: Item> {
822 Internal {
823 height: u8,
824 child_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
825 child_trees: ArrayVec<SumTree<T>, { 2 * TREE_BASE }>,
826 },
827 Leaf {
828 items: ArrayVec<T, { 2 * TREE_BASE }>,
829 item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
830 },
831}
832
833impl<T> fmt::Debug for Node<T>
834where
835 T: Item + fmt::Debug,
836 T::Summary: fmt::Debug,
837{
838 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
839 match self {
840 Node::Internal {
841 height,
842 child_summaries,
843 child_trees,
844 } => f
845 .debug_struct("Internal")
846 .field("height", height)
847 .field("child_summaries", child_summaries)
848 .field("child_trees", child_trees)
849 .finish(),
850 Node::Leaf {
851 items,
852 item_summaries,
853 } => f
854 .debug_struct("Leaf")
855 .field("items", items)
856 .field("item_summaries", item_summaries)
857 .finish(),
858 }
859 }
860}
861
862impl<T: Item> Node<T> {
863 fn is_leaf(&self) -> bool {
864 matches!(self, Node::Leaf { .. })
865 }
866
867 fn height(&self) -> u8 {
868 match self {
869 Node::Internal { height, .. } => *height,
870 Node::Leaf { .. } => 0,
871 }
872 }
873
874 fn summary<'a>(&'a self) -> Option<&'a T::Summary> {
875 let child_summaries = self.child_summaries();
876 child_summaries.last()
877 }
878
879 fn summary_or_zero<'a>(&'a self, cx: &<T::Summary as Summary>::Context) -> Cow<'a, T::Summary> {
880 self.summary().map_or_else(
881 || Cow::Owned(<T::Summary as Summary>::zero(cx)),
882 |last_summary| Cow::Borrowed(last_summary),
883 )
884 }
885
886 fn child_summaries(&self) -> &[T::Summary] {
887 match self {
888 Node::Internal {
889 child_summaries, ..
890 } => child_summaries.as_slice(),
891 Node::Leaf { item_summaries, .. } => item_summaries.as_slice(),
892 }
893 }
894
895 fn child_trees(&self) -> &ArrayVec<SumTree<T>, { 2 * TREE_BASE }> {
896 match self {
897 Node::Internal { child_trees, .. } => child_trees,
898 Node::Leaf { .. } => panic!("Leaf nodes have no child trees"),
899 }
900 }
901
902 fn items(&self) -> &ArrayVec<T, { 2 * TREE_BASE }> {
903 match self {
904 Node::Leaf { items, .. } => items,
905 Node::Internal { .. } => panic!("Internal nodes have no items"),
906 }
907 }
908
909 fn is_underflowing(&self) -> bool {
910 match self {
911 Node::Internal { child_trees, .. } => child_trees.len() < TREE_BASE,
912 Node::Leaf { items, .. } => items.len() < TREE_BASE,
913 }
914 }
915}
916
917#[derive(Debug)]
918pub enum Edit<T: KeyedItem> {
919 Insert(T),
920 Remove(T::Key),
921}
922
923impl<T: KeyedItem> Edit<T> {
924 fn key(&self) -> T::Key {
925 match self {
926 Edit::Insert(item) => item.key(),
927 Edit::Remove(key) => key.clone(),
928 }
929 }
930}
931
932#[cfg(test)]
933mod tests {
934 use super::*;
935 use rand::{distributions, prelude::*};
936 use std::cmp;
937
938 #[ctor::ctor]
939 fn init_logger() {
940 zlog::init_test();
941 }
942
943 #[test]
944 fn test_extend_and_push_tree() {
945 let mut tree1 = SumTree::default();
946 tree1.extend(0..20, &());
947
948 let mut tree2 = SumTree::default();
949 tree2.extend(50..100, &());
950
951 tree1.append(tree2, &());
952 assert_eq!(
953 tree1.items(&()),
954 (0..20).chain(50..100).collect::<Vec<u8>>()
955 );
956 }
957
958 #[test]
959 fn test_random() {
960 let mut starting_seed = 0;
961 if let Ok(value) = std::env::var("SEED") {
962 starting_seed = value.parse().expect("invalid SEED variable");
963 }
964 let mut num_iterations = 100;
965 if let Ok(value) = std::env::var("ITERATIONS") {
966 num_iterations = value.parse().expect("invalid ITERATIONS variable");
967 }
968 let num_operations = std::env::var("OPERATIONS")
969 .map_or(5, |o| o.parse().expect("invalid OPERATIONS variable"));
970
971 for seed in starting_seed..(starting_seed + num_iterations) {
972 eprintln!("seed = {}", seed);
973 let mut rng = StdRng::seed_from_u64(seed);
974
975 let rng = &mut rng;
976 let mut tree = SumTree::<u8>::default();
977 let count = rng.gen_range(0..10);
978 if rng.r#gen() {
979 tree.extend(rng.sample_iter(distributions::Standard).take(count), &());
980 } else {
981 let items = rng
982 .sample_iter(distributions::Standard)
983 .take(count)
984 .collect::<Vec<_>>();
985 tree.par_extend(items, &());
986 }
987
988 for _ in 0..num_operations {
989 let splice_end = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
990 let splice_start = rng.gen_range(0..splice_end + 1);
991 let count = rng.gen_range(0..10);
992 let tree_end = tree.extent::<Count>(&());
993 let new_items = rng
994 .sample_iter(distributions::Standard)
995 .take(count)
996 .collect::<Vec<u8>>();
997
998 let mut reference_items = tree.items(&());
999 reference_items.splice(splice_start..splice_end, new_items.clone());
1000
1001 tree = {
1002 let mut cursor = tree.cursor::<Count>(&());
1003 let mut new_tree = cursor.slice(&Count(splice_start), Bias::Right);
1004 if rng.r#gen() {
1005 new_tree.extend(new_items, &());
1006 } else {
1007 new_tree.par_extend(new_items, &());
1008 }
1009 cursor.seek(&Count(splice_end), Bias::Right);
1010 new_tree.append(cursor.slice(&tree_end, Bias::Right), &());
1011 new_tree
1012 };
1013
1014 assert_eq!(tree.items(&()), reference_items);
1015 assert_eq!(
1016 tree.iter().collect::<Vec<_>>(),
1017 tree.cursor::<()>(&()).collect::<Vec<_>>()
1018 );
1019
1020 log::info!("tree items: {:?}", tree.items(&()));
1021
1022 let mut filter_cursor =
1023 tree.filter::<_, Count>(&(), |summary| summary.contains_even.cmp(&false));
1024 let expected_filtered_items = tree
1025 .items(&())
1026 .into_iter()
1027 .enumerate()
1028 .filter(|(_, item)| (item & 1) == 0)
1029 .collect::<Vec<_>>();
1030
1031 let mut item_ix = if rng.r#gen() {
1032 filter_cursor.next();
1033 0
1034 } else {
1035 filter_cursor.prev();
1036 expected_filtered_items.len().saturating_sub(1)
1037 };
1038 while item_ix < expected_filtered_items.len() {
1039 log::info!("filter_cursor, item_ix: {}", item_ix);
1040 let actual_item = filter_cursor.item().unwrap();
1041 let (reference_index, reference_item) = expected_filtered_items[item_ix];
1042 assert_eq!(actual_item, &reference_item);
1043 assert_eq!(filter_cursor.start().0, reference_index);
1044 log::info!("next");
1045 filter_cursor.next();
1046 item_ix += 1;
1047
1048 while item_ix > 0 && rng.gen_bool(0.2) {
1049 log::info!("prev");
1050 filter_cursor.prev();
1051 item_ix -= 1;
1052
1053 if item_ix == 0 && rng.gen_bool(0.2) {
1054 filter_cursor.prev();
1055 assert_eq!(filter_cursor.item(), None);
1056 assert_eq!(filter_cursor.start().0, 0);
1057 filter_cursor.next();
1058 }
1059 }
1060 }
1061 assert_eq!(filter_cursor.item(), None);
1062
1063 let mut before_start = false;
1064 let mut cursor = tree.cursor::<Count>(&());
1065 let start_pos = rng.gen_range(0..=reference_items.len());
1066 cursor.seek(&Count(start_pos), Bias::Right);
1067 let mut pos = rng.gen_range(start_pos..=reference_items.len());
1068 cursor.seek_forward(&Count(pos), Bias::Right);
1069
1070 for i in 0..10 {
1071 assert_eq!(cursor.start().0, pos);
1072
1073 if pos > 0 {
1074 assert_eq!(cursor.prev_item().unwrap(), &reference_items[pos - 1]);
1075 } else {
1076 assert_eq!(cursor.prev_item(), None);
1077 }
1078
1079 if pos < reference_items.len() && !before_start {
1080 assert_eq!(cursor.item().unwrap(), &reference_items[pos]);
1081 } else {
1082 assert_eq!(cursor.item(), None);
1083 }
1084
1085 if before_start {
1086 assert_eq!(cursor.next_item(), reference_items.first());
1087 } else if pos + 1 < reference_items.len() {
1088 assert_eq!(cursor.next_item().unwrap(), &reference_items[pos + 1]);
1089 } else {
1090 assert_eq!(cursor.next_item(), None);
1091 }
1092
1093 if i < 5 {
1094 cursor.next();
1095 if pos < reference_items.len() {
1096 pos += 1;
1097 before_start = false;
1098 }
1099 } else {
1100 cursor.prev();
1101 if pos == 0 {
1102 before_start = true;
1103 }
1104 pos = pos.saturating_sub(1);
1105 }
1106 }
1107 }
1108
1109 for _ in 0..10 {
1110 let end = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
1111 let start = rng.gen_range(0..end + 1);
1112 let start_bias = if rng.r#gen() { Bias::Left } else { Bias::Right };
1113 let end_bias = if rng.r#gen() { Bias::Left } else { Bias::Right };
1114
1115 let mut cursor = tree.cursor::<Count>(&());
1116 cursor.seek(&Count(start), start_bias);
1117 let slice = cursor.slice(&Count(end), end_bias);
1118
1119 cursor.seek(&Count(start), start_bias);
1120 let summary = cursor.summary::<_, Sum>(&Count(end), end_bias);
1121
1122 assert_eq!(summary.0, slice.0.summary_or_zero(&()).sum);
1123 }
1124 }
1125 }
1126
1127 #[test]
1128 fn test_cursor() {
1129 // Empty tree
1130 let tree = SumTree::<u8>::default();
1131 let mut cursor = tree.cursor::<IntegersSummary>(&());
1132 assert_eq!(
1133 cursor.slice(&Count(0), Bias::Right).items(&()),
1134 Vec::<u8>::new()
1135 );
1136 assert_eq!(cursor.item(), None);
1137 assert_eq!(cursor.prev_item(), None);
1138 assert_eq!(cursor.next_item(), None);
1139 assert_eq!(cursor.start().sum, 0);
1140 cursor.prev();
1141 assert_eq!(cursor.item(), None);
1142 assert_eq!(cursor.prev_item(), None);
1143 assert_eq!(cursor.next_item(), None);
1144 assert_eq!(cursor.start().sum, 0);
1145 cursor.next();
1146 assert_eq!(cursor.item(), None);
1147 assert_eq!(cursor.prev_item(), None);
1148 assert_eq!(cursor.next_item(), None);
1149 assert_eq!(cursor.start().sum, 0);
1150
1151 // Single-element tree
1152 let mut tree = SumTree::<u8>::default();
1153 tree.extend(vec![1], &());
1154 let mut cursor = tree.cursor::<IntegersSummary>(&());
1155 assert_eq!(
1156 cursor.slice(&Count(0), Bias::Right).items(&()),
1157 Vec::<u8>::new()
1158 );
1159 assert_eq!(cursor.item(), Some(&1));
1160 assert_eq!(cursor.prev_item(), None);
1161 assert_eq!(cursor.next_item(), None);
1162 assert_eq!(cursor.start().sum, 0);
1163
1164 cursor.next();
1165 assert_eq!(cursor.item(), None);
1166 assert_eq!(cursor.prev_item(), Some(&1));
1167 assert_eq!(cursor.next_item(), None);
1168 assert_eq!(cursor.start().sum, 1);
1169
1170 cursor.prev();
1171 assert_eq!(cursor.item(), Some(&1));
1172 assert_eq!(cursor.prev_item(), None);
1173 assert_eq!(cursor.next_item(), None);
1174 assert_eq!(cursor.start().sum, 0);
1175
1176 let mut cursor = tree.cursor::<IntegersSummary>(&());
1177 assert_eq!(cursor.slice(&Count(1), Bias::Right).items(&()), [1]);
1178 assert_eq!(cursor.item(), None);
1179 assert_eq!(cursor.prev_item(), Some(&1));
1180 assert_eq!(cursor.next_item(), None);
1181 assert_eq!(cursor.start().sum, 1);
1182
1183 cursor.seek(&Count(0), Bias::Right);
1184 assert_eq!(
1185 cursor
1186 .slice(&tree.extent::<Count>(&()), Bias::Right)
1187 .items(&()),
1188 [1]
1189 );
1190 assert_eq!(cursor.item(), None);
1191 assert_eq!(cursor.prev_item(), Some(&1));
1192 assert_eq!(cursor.next_item(), None);
1193 assert_eq!(cursor.start().sum, 1);
1194
1195 // Multiple-element tree
1196 let mut tree = SumTree::default();
1197 tree.extend(vec![1, 2, 3, 4, 5, 6], &());
1198
1199 let mut cursor = tree.cursor::<IntegersSummary>(&());
1200
1201 let slice = cursor.slice(&Count(2), Bias::Right);
1202 assert_eq!(slice.items(&()), [1, 2]);
1203 assert_eq!(cursor.item(), Some(&3));
1204 assert_eq!(cursor.prev_item(), Some(&2));
1205 assert_eq!(cursor.next_item(), Some(&4));
1206 assert_eq!(cursor.start().sum, 3);
1207
1208 cursor.next();
1209 assert_eq!(cursor.item(), Some(&4));
1210 assert_eq!(cursor.prev_item(), Some(&3));
1211 assert_eq!(cursor.next_item(), Some(&5));
1212 assert_eq!(cursor.start().sum, 6);
1213
1214 cursor.next();
1215 assert_eq!(cursor.item(), Some(&5));
1216 assert_eq!(cursor.prev_item(), Some(&4));
1217 assert_eq!(cursor.next_item(), Some(&6));
1218 assert_eq!(cursor.start().sum, 10);
1219
1220 cursor.next();
1221 assert_eq!(cursor.item(), Some(&6));
1222 assert_eq!(cursor.prev_item(), Some(&5));
1223 assert_eq!(cursor.next_item(), None);
1224 assert_eq!(cursor.start().sum, 15);
1225
1226 cursor.next();
1227 cursor.next();
1228 assert_eq!(cursor.item(), None);
1229 assert_eq!(cursor.prev_item(), Some(&6));
1230 assert_eq!(cursor.next_item(), None);
1231 assert_eq!(cursor.start().sum, 21);
1232
1233 cursor.prev();
1234 assert_eq!(cursor.item(), Some(&6));
1235 assert_eq!(cursor.prev_item(), Some(&5));
1236 assert_eq!(cursor.next_item(), None);
1237 assert_eq!(cursor.start().sum, 15);
1238
1239 cursor.prev();
1240 assert_eq!(cursor.item(), Some(&5));
1241 assert_eq!(cursor.prev_item(), Some(&4));
1242 assert_eq!(cursor.next_item(), Some(&6));
1243 assert_eq!(cursor.start().sum, 10);
1244
1245 cursor.prev();
1246 assert_eq!(cursor.item(), Some(&4));
1247 assert_eq!(cursor.prev_item(), Some(&3));
1248 assert_eq!(cursor.next_item(), Some(&5));
1249 assert_eq!(cursor.start().sum, 6);
1250
1251 cursor.prev();
1252 assert_eq!(cursor.item(), Some(&3));
1253 assert_eq!(cursor.prev_item(), Some(&2));
1254 assert_eq!(cursor.next_item(), Some(&4));
1255 assert_eq!(cursor.start().sum, 3);
1256
1257 cursor.prev();
1258 assert_eq!(cursor.item(), Some(&2));
1259 assert_eq!(cursor.prev_item(), Some(&1));
1260 assert_eq!(cursor.next_item(), Some(&3));
1261 assert_eq!(cursor.start().sum, 1);
1262
1263 cursor.prev();
1264 assert_eq!(cursor.item(), Some(&1));
1265 assert_eq!(cursor.prev_item(), None);
1266 assert_eq!(cursor.next_item(), Some(&2));
1267 assert_eq!(cursor.start().sum, 0);
1268
1269 cursor.prev();
1270 assert_eq!(cursor.item(), None);
1271 assert_eq!(cursor.prev_item(), None);
1272 assert_eq!(cursor.next_item(), Some(&1));
1273 assert_eq!(cursor.start().sum, 0);
1274
1275 cursor.next();
1276 assert_eq!(cursor.item(), Some(&1));
1277 assert_eq!(cursor.prev_item(), None);
1278 assert_eq!(cursor.next_item(), Some(&2));
1279 assert_eq!(cursor.start().sum, 0);
1280
1281 let mut cursor = tree.cursor::<IntegersSummary>(&());
1282 assert_eq!(
1283 cursor
1284 .slice(&tree.extent::<Count>(&()), Bias::Right)
1285 .items(&()),
1286 tree.items(&())
1287 );
1288 assert_eq!(cursor.item(), None);
1289 assert_eq!(cursor.prev_item(), Some(&6));
1290 assert_eq!(cursor.next_item(), None);
1291 assert_eq!(cursor.start().sum, 21);
1292
1293 cursor.seek(&Count(3), Bias::Right);
1294 assert_eq!(
1295 cursor
1296 .slice(&tree.extent::<Count>(&()), Bias::Right)
1297 .items(&()),
1298 [4, 5, 6]
1299 );
1300 assert_eq!(cursor.item(), None);
1301 assert_eq!(cursor.prev_item(), Some(&6));
1302 assert_eq!(cursor.next_item(), None);
1303 assert_eq!(cursor.start().sum, 21);
1304
1305 // Seeking can bias left or right
1306 cursor.seek(&Count(1), Bias::Left);
1307 assert_eq!(cursor.item(), Some(&1));
1308 cursor.seek(&Count(1), Bias::Right);
1309 assert_eq!(cursor.item(), Some(&2));
1310
1311 // Slicing without resetting starts from where the cursor is parked at.
1312 cursor.seek(&Count(1), Bias::Right);
1313 assert_eq!(cursor.slice(&Count(3), Bias::Right).items(&()), vec![2, 3]);
1314 assert_eq!(cursor.slice(&Count(6), Bias::Left).items(&()), vec![4, 5]);
1315 assert_eq!(cursor.slice(&Count(6), Bias::Right).items(&()), vec![6]);
1316 }
1317
1318 #[test]
1319 fn test_edit() {
1320 let mut tree = SumTree::<u8>::default();
1321
1322 let removed = tree.edit(vec![Edit::Insert(1), Edit::Insert(2), Edit::Insert(0)], &());
1323 assert_eq!(tree.items(&()), vec![0, 1, 2]);
1324 assert_eq!(removed, Vec::<u8>::new());
1325 assert_eq!(tree.get(&0, &()), Some(&0));
1326 assert_eq!(tree.get(&1, &()), Some(&1));
1327 assert_eq!(tree.get(&2, &()), Some(&2));
1328 assert_eq!(tree.get(&4, &()), None);
1329
1330 let removed = tree.edit(vec![Edit::Insert(2), Edit::Insert(4), Edit::Remove(0)], &());
1331 assert_eq!(tree.items(&()), vec![1, 2, 4]);
1332 assert_eq!(removed, vec![0, 2]);
1333 assert_eq!(tree.get(&0, &()), None);
1334 assert_eq!(tree.get(&1, &()), Some(&1));
1335 assert_eq!(tree.get(&2, &()), Some(&2));
1336 assert_eq!(tree.get(&4, &()), Some(&4));
1337 }
1338
1339 #[test]
1340 fn test_from_iter() {
1341 assert_eq!(
1342 SumTree::from_iter(0..100, &()).items(&()),
1343 (0..100).collect::<Vec<_>>()
1344 );
1345
1346 // Ensure `from_iter` works correctly when the given iterator restarts
1347 // after calling `next` if `None` was already returned.
1348 let mut ix = 0;
1349 let iterator = std::iter::from_fn(|| {
1350 ix = (ix + 1) % 2;
1351 if ix == 1 { Some(1) } else { None }
1352 });
1353 assert_eq!(SumTree::from_iter(iterator, &()).items(&()), vec![1]);
1354 }
1355
1356 #[derive(Clone, Default, Debug)]
1357 pub struct IntegersSummary {
1358 count: usize,
1359 sum: usize,
1360 contains_even: bool,
1361 max: u8,
1362 }
1363
1364 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
1365 struct Count(usize);
1366
1367 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
1368 struct Sum(usize);
1369
1370 impl Item for u8 {
1371 type Summary = IntegersSummary;
1372
1373 fn summary(&self, _cx: &()) -> Self::Summary {
1374 IntegersSummary {
1375 count: 1,
1376 sum: *self as usize,
1377 contains_even: (*self & 1) == 0,
1378 max: *self,
1379 }
1380 }
1381 }
1382
1383 impl KeyedItem for u8 {
1384 type Key = u8;
1385
1386 fn key(&self) -> Self::Key {
1387 *self
1388 }
1389 }
1390
1391 impl Summary for IntegersSummary {
1392 type Context = ();
1393
1394 fn zero(_cx: &()) -> Self {
1395 Default::default()
1396 }
1397
1398 fn add_summary(&mut self, other: &Self, _: &()) {
1399 self.count += other.count;
1400 self.sum += other.sum;
1401 self.contains_even |= other.contains_even;
1402 self.max = cmp::max(self.max, other.max);
1403 }
1404 }
1405
1406 impl Dimension<'_, IntegersSummary> for u8 {
1407 fn zero(_cx: &()) -> Self {
1408 Default::default()
1409 }
1410
1411 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
1412 *self = summary.max;
1413 }
1414 }
1415
1416 impl Dimension<'_, IntegersSummary> for Count {
1417 fn zero(_cx: &()) -> Self {
1418 Default::default()
1419 }
1420
1421 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
1422 self.0 += summary.count;
1423 }
1424 }
1425
1426 impl SeekTarget<'_, IntegersSummary, IntegersSummary> for Count {
1427 fn cmp(&self, cursor_location: &IntegersSummary, _: &()) -> Ordering {
1428 self.0.cmp(&cursor_location.count)
1429 }
1430 }
1431
1432 impl Dimension<'_, IntegersSummary> for Sum {
1433 fn zero(_cx: &()) -> Self {
1434 Default::default()
1435 }
1436
1437 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
1438 self.0 += summary.sum;
1439 }
1440 }
1441}