1mod cursor;
2mod tree_map;
3
4use arrayvec::ArrayVec;
5pub use cursor::{Cursor, FilterCursor, Iter};
6use rayon::prelude::*;
7use std::marker::PhantomData;
8use std::mem;
9use std::{cmp::Ordering, fmt, iter::FromIterator, sync::Arc};
10pub use tree_map::{MapSeekTarget, TreeMap, TreeSet};
11
12#[cfg(test)]
13pub const TREE_BASE: usize = 2;
14#[cfg(not(test))]
15pub const TREE_BASE: usize = 6;
16
17/// An item that can be stored in a [`SumTree`]
18///
19/// Must be summarized by a type that implements [`Summary`]
20pub trait Item: Clone {
21 type Summary: Summary;
22
23 fn summary(&self, cx: &<Self::Summary as Summary>::Context) -> Self::Summary;
24}
25
26/// An [`Item`] whose summary has a specific key that can be used to identify it
27pub trait KeyedItem: Item {
28 type Key: for<'a> Dimension<'a, Self::Summary> + Ord;
29
30 fn key(&self) -> Self::Key;
31}
32
33/// A type that describes the Sum of all [`Item`]s in a subtree of the [`SumTree`]
34///
35/// Each Summary type can have multiple [`Dimension`]s that it measures,
36/// which can be used to navigate the tree
37pub trait Summary: Clone {
38 type Context;
39
40 fn zero(cx: &Self::Context) -> Self;
41 fn add_summary(&mut self, summary: &Self, cx: &Self::Context);
42}
43
44/// This type exists because we can't implement Summary for () without causing
45/// type resolution errors
46#[derive(Copy, Clone, PartialEq, Eq, Debug)]
47pub struct Unit;
48
49impl Summary for Unit {
50 type Context = ();
51
52 fn zero(_: &()) -> Self {
53 Unit
54 }
55
56 fn add_summary(&mut self, _: &Self, _: &()) {}
57}
58
59/// Each [`Summary`] type can have more than one [`Dimension`] type that it measures.
60///
61/// You can use dimensions to seek to a specific location in the [`SumTree`]
62///
63/// # Example:
64/// Zed's rope has a `TextSummary` type that summarizes lines, characters, and bytes.
65/// Each of these are different dimensions we may want to seek to
66pub trait Dimension<'a, S: Summary>: Clone {
67 fn zero(cx: &S::Context) -> Self;
68
69 fn add_summary(&mut self, summary: &'a S, cx: &S::Context);
70
71 fn from_summary(summary: &'a S, cx: &S::Context) -> Self {
72 let mut dimension = Self::zero(cx);
73 dimension.add_summary(summary, cx);
74 dimension
75 }
76}
77
78impl<'a, T: Summary> Dimension<'a, T> for T {
79 fn zero(cx: &T::Context) -> Self {
80 Summary::zero(cx)
81 }
82
83 fn add_summary(&mut self, summary: &'a T, cx: &T::Context) {
84 Summary::add_summary(self, summary, cx);
85 }
86}
87
88pub trait SeekTarget<'a, S: Summary, D: Dimension<'a, S>> {
89 fn cmp(&self, cursor_location: &D, cx: &S::Context) -> Ordering;
90}
91
92impl<'a, S: Summary, D: Dimension<'a, S> + Ord> SeekTarget<'a, S, D> for D {
93 fn cmp(&self, cursor_location: &Self, _: &S::Context) -> Ordering {
94 Ord::cmp(self, cursor_location)
95 }
96}
97
98impl<'a, T: Summary> Dimension<'a, T> for () {
99 fn zero(_: &T::Context) -> Self {
100 ()
101 }
102
103 fn add_summary(&mut self, _: &'a T, _: &T::Context) {}
104}
105
106impl<'a, T: Summary, D1: Dimension<'a, T>, D2: Dimension<'a, T>> Dimension<'a, T> for (D1, D2) {
107 fn zero(cx: &T::Context) -> Self {
108 (D1::zero(cx), D2::zero(cx))
109 }
110
111 fn add_summary(&mut self, summary: &'a T, cx: &T::Context) {
112 self.0.add_summary(summary, cx);
113 self.1.add_summary(summary, cx);
114 }
115}
116
117impl<'a, S, D1, D2> SeekTarget<'a, S, (D1, D2)> for D1
118where
119 S: Summary,
120 D1: SeekTarget<'a, S, D1> + Dimension<'a, S>,
121 D2: Dimension<'a, S>,
122{
123 fn cmp(&self, cursor_location: &(D1, D2), cx: &S::Context) -> Ordering {
124 self.cmp(&cursor_location.0, cx)
125 }
126}
127
128impl<'a, S, D1, D2, D3> SeekTarget<'a, S, ((D1, D2), D3)> for D1
129where
130 S: Summary,
131 D1: SeekTarget<'a, S, D1> + Dimension<'a, S>,
132 D2: Dimension<'a, S>,
133 D3: Dimension<'a, S>,
134{
135 fn cmp(&self, cursor_location: &((D1, D2), D3), cx: &S::Context) -> Ordering {
136 self.cmp(&cursor_location.0.0, cx)
137 }
138}
139
140/// Bias is used to settle ambiguities when determining positions in an ordered sequence.
141///
142/// The primary use case is for text, where Bias influences
143/// which character an offset or anchor is associated with.
144///
145/// # Examples
146/// Given the buffer `AˇBCD`:
147/// - The offset of the cursor is 1
148/// - [Bias::Left] would attach the cursor to the character `A`
149/// - [Bias::Right] would attach the cursor to the character `B`
150///
151/// Given the buffer `A«BCˇ»D`:
152/// - The offset of the cursor is 3, and the selection is from 1 to 3
153/// - The left anchor of the selection has [Bias::Right], attaching it to the character `B`
154/// - The right anchor of the selection has [Bias::Left], attaching it to the character `C`
155///
156/// Given the buffer `{ˇ<...>`, where `<...>` is a folded region:
157/// - The display offset of the cursor is 1, but the offset in the buffer is determined by the bias
158/// - [Bias::Left] would attach the cursor to the character `{`, with a buffer offset of 1
159/// - [Bias::Right] would attach the cursor to the first character of the folded region,
160/// and the buffer offset would be the offset of the first character of the folded region
161#[derive(Copy, Clone, Eq, PartialEq, PartialOrd, Ord, Debug, Hash, Default)]
162pub enum Bias {
163 /// Attach to the character on the left
164 #[default]
165 Left,
166 /// Attach to the character on the right
167 Right,
168}
169
170impl Bias {
171 pub fn invert(self) -> Self {
172 match self {
173 Self::Left => Self::Right,
174 Self::Right => Self::Left,
175 }
176 }
177}
178
179/// A B+ tree in which each leaf node contains `Item`s of type `T` and a `Summary`s for each `Item`.
180/// Each internal node contains a `Summary` of the items in its subtree.
181///
182/// The maximum number of items per node is `TREE_BASE * 2`.
183///
184/// Any [`Dimension`] supported by the [`Summary`] type can be used to seek to a specific location in the tree.
185#[derive(Clone)]
186pub struct SumTree<T: Item>(Arc<Node<T>>);
187
188impl<T> fmt::Debug for SumTree<T>
189where
190 T: fmt::Debug + Item,
191 T::Summary: fmt::Debug,
192{
193 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
194 f.debug_tuple("SumTree").field(&self.0).finish()
195 }
196}
197
198impl<T: Item> SumTree<T> {
199 pub fn new(cx: &<T::Summary as Summary>::Context) -> Self {
200 SumTree(Arc::new(Node::Leaf {
201 summary: <T::Summary as Summary>::zero(cx),
202 items: ArrayVec::new(),
203 item_summaries: ArrayVec::new(),
204 }))
205 }
206
207 /// Useful in cases where the item type has a non-trivial context type, but the zero value of the summary type doesn't depend on that context.
208 pub fn from_summary(summary: T::Summary) -> Self {
209 SumTree(Arc::new(Node::Leaf {
210 summary,
211 items: ArrayVec::new(),
212 item_summaries: ArrayVec::new(),
213 }))
214 }
215
216 pub fn from_item(item: T, cx: &<T::Summary as Summary>::Context) -> Self {
217 let mut tree = Self::new(cx);
218 tree.push(item, cx);
219 tree
220 }
221
222 pub fn from_iter<I: IntoIterator<Item = T>>(
223 iter: I,
224 cx: &<T::Summary as Summary>::Context,
225 ) -> Self {
226 let mut nodes = Vec::new();
227
228 let mut iter = iter.into_iter().fuse().peekable();
229 while iter.peek().is_some() {
230 let items: ArrayVec<T, { 2 * TREE_BASE }> = iter.by_ref().take(2 * TREE_BASE).collect();
231 let item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }> =
232 items.iter().map(|item| item.summary(cx)).collect();
233
234 let mut summary = item_summaries[0].clone();
235 for item_summary in &item_summaries[1..] {
236 <T::Summary as Summary>::add_summary(&mut summary, item_summary, cx);
237 }
238
239 nodes.push(Node::Leaf {
240 summary,
241 items,
242 item_summaries,
243 });
244 }
245
246 let mut parent_nodes = Vec::new();
247 let mut height = 0;
248 while nodes.len() > 1 {
249 height += 1;
250 let mut current_parent_node = None;
251 for child_node in nodes.drain(..) {
252 let parent_node = current_parent_node.get_or_insert_with(|| Node::Internal {
253 summary: <T::Summary as Summary>::zero(cx),
254 height,
255 child_summaries: ArrayVec::new(),
256 child_trees: ArrayVec::new(),
257 });
258 let Node::Internal {
259 summary,
260 child_summaries,
261 child_trees,
262 ..
263 } = parent_node
264 else {
265 unreachable!()
266 };
267 let child_summary = child_node.summary();
268 <T::Summary as Summary>::add_summary(summary, child_summary, cx);
269 child_summaries.push(child_summary.clone());
270 child_trees.push(Self(Arc::new(child_node)));
271
272 if child_trees.len() == 2 * TREE_BASE {
273 parent_nodes.extend(current_parent_node.take());
274 }
275 }
276 parent_nodes.extend(current_parent_node.take());
277 mem::swap(&mut nodes, &mut parent_nodes);
278 }
279
280 if nodes.is_empty() {
281 Self::new(cx)
282 } else {
283 debug_assert_eq!(nodes.len(), 1);
284 Self(Arc::new(nodes.pop().unwrap()))
285 }
286 }
287
288 pub fn from_par_iter<I, Iter>(iter: I, cx: &<T::Summary as Summary>::Context) -> Self
289 where
290 I: IntoParallelIterator<Iter = Iter>,
291 Iter: IndexedParallelIterator<Item = T>,
292 T: Send + Sync,
293 T::Summary: Send + Sync,
294 <T::Summary as Summary>::Context: Sync,
295 {
296 let mut nodes = iter
297 .into_par_iter()
298 .chunks(2 * TREE_BASE)
299 .map(|items| {
300 let items: ArrayVec<T, { 2 * TREE_BASE }> = items.into_iter().collect();
301 let item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }> =
302 items.iter().map(|item| item.summary(cx)).collect();
303 let mut summary = item_summaries[0].clone();
304 for item_summary in &item_summaries[1..] {
305 <T::Summary as Summary>::add_summary(&mut summary, item_summary, cx);
306 }
307 SumTree(Arc::new(Node::Leaf {
308 summary,
309 items,
310 item_summaries,
311 }))
312 })
313 .collect::<Vec<_>>();
314
315 let mut height = 0;
316 while nodes.len() > 1 {
317 height += 1;
318 nodes = nodes
319 .into_par_iter()
320 .chunks(2 * TREE_BASE)
321 .map(|child_nodes| {
322 let child_trees: ArrayVec<SumTree<T>, { 2 * TREE_BASE }> =
323 child_nodes.into_iter().collect();
324 let child_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }> = child_trees
325 .iter()
326 .map(|child_tree| child_tree.summary().clone())
327 .collect();
328 let mut summary = child_summaries[0].clone();
329 for child_summary in &child_summaries[1..] {
330 <T::Summary as Summary>::add_summary(&mut summary, child_summary, cx);
331 }
332 SumTree(Arc::new(Node::Internal {
333 height,
334 summary,
335 child_summaries,
336 child_trees,
337 }))
338 })
339 .collect::<Vec<_>>();
340 }
341
342 if nodes.is_empty() {
343 Self::new(cx)
344 } else {
345 debug_assert_eq!(nodes.len(), 1);
346 nodes.pop().unwrap()
347 }
348 }
349
350 #[allow(unused)]
351 pub fn items(&self, cx: &<T::Summary as Summary>::Context) -> Vec<T> {
352 let mut items = Vec::new();
353 let mut cursor = self.cursor::<()>(cx);
354 cursor.next();
355 while let Some(item) = cursor.item() {
356 items.push(item.clone());
357 cursor.next();
358 }
359 items
360 }
361
362 pub fn iter(&self) -> Iter<'_, T> {
363 Iter::new(self)
364 }
365
366 pub fn cursor<'a, S>(&'a self, cx: &'a <T::Summary as Summary>::Context) -> Cursor<'a, T, S>
367 where
368 S: Dimension<'a, T::Summary>,
369 {
370 Cursor::new(self, cx)
371 }
372
373 /// Note: If the summary type requires a non `()` context, then the filter cursor
374 /// that is returned cannot be used with Rust's iterators.
375 pub fn filter<'a, F, U>(
376 &'a self,
377 cx: &'a <T::Summary as Summary>::Context,
378 filter_node: F,
379 ) -> FilterCursor<'a, F, T, U>
380 where
381 F: FnMut(&T::Summary) -> bool,
382 U: Dimension<'a, T::Summary>,
383 {
384 FilterCursor::new(self, cx, filter_node)
385 }
386
387 #[allow(dead_code)]
388 pub fn first(&self) -> Option<&T> {
389 self.leftmost_leaf().0.items().first()
390 }
391
392 pub fn last(&self) -> Option<&T> {
393 self.rightmost_leaf().0.items().last()
394 }
395
396 pub fn update_last(&mut self, f: impl FnOnce(&mut T), cx: &<T::Summary as Summary>::Context) {
397 self.update_last_recursive(f, cx);
398 }
399
400 fn update_last_recursive(
401 &mut self,
402 f: impl FnOnce(&mut T),
403 cx: &<T::Summary as Summary>::Context,
404 ) -> Option<T::Summary> {
405 match Arc::make_mut(&mut self.0) {
406 Node::Internal {
407 summary,
408 child_summaries,
409 child_trees,
410 ..
411 } => {
412 let last_summary = child_summaries.last_mut().unwrap();
413 let last_child = child_trees.last_mut().unwrap();
414 *last_summary = last_child.update_last_recursive(f, cx).unwrap();
415 *summary = sum(child_summaries.iter(), cx);
416 Some(summary.clone())
417 }
418 Node::Leaf {
419 summary,
420 items,
421 item_summaries,
422 } => {
423 if let Some((item, item_summary)) = items.last_mut().zip(item_summaries.last_mut())
424 {
425 (f)(item);
426 *item_summary = item.summary(cx);
427 *summary = sum(item_summaries.iter(), cx);
428 Some(summary.clone())
429 } else {
430 None
431 }
432 }
433 }
434 }
435
436 pub fn extent<'a, D: Dimension<'a, T::Summary>>(
437 &'a self,
438 cx: &<T::Summary as Summary>::Context,
439 ) -> D {
440 let mut extent = D::zero(cx);
441 match self.0.as_ref() {
442 Node::Internal { summary, .. } | Node::Leaf { summary, .. } => {
443 extent.add_summary(summary, cx);
444 }
445 }
446 extent
447 }
448
449 pub fn summary(&self) -> &T::Summary {
450 match self.0.as_ref() {
451 Node::Internal { summary, .. } => summary,
452 Node::Leaf { summary, .. } => summary,
453 }
454 }
455
456 pub fn is_empty(&self) -> bool {
457 match self.0.as_ref() {
458 Node::Internal { .. } => false,
459 Node::Leaf { items, .. } => items.is_empty(),
460 }
461 }
462
463 pub fn extend<I>(&mut self, iter: I, cx: &<T::Summary as Summary>::Context)
464 where
465 I: IntoIterator<Item = T>,
466 {
467 self.append(Self::from_iter(iter, cx), cx);
468 }
469
470 pub fn par_extend<I, Iter>(&mut self, iter: I, cx: &<T::Summary as Summary>::Context)
471 where
472 I: IntoParallelIterator<Iter = Iter>,
473 Iter: IndexedParallelIterator<Item = T>,
474 T: Send + Sync,
475 T::Summary: Send + Sync,
476 <T::Summary as Summary>::Context: Sync,
477 {
478 self.append(Self::from_par_iter(iter, cx), cx);
479 }
480
481 pub fn push(&mut self, item: T, cx: &<T::Summary as Summary>::Context) {
482 let summary = item.summary(cx);
483 self.append(
484 SumTree(Arc::new(Node::Leaf {
485 summary: summary.clone(),
486 items: ArrayVec::from_iter(Some(item)),
487 item_summaries: ArrayVec::from_iter(Some(summary)),
488 })),
489 cx,
490 );
491 }
492
493 pub fn append(&mut self, other: Self, cx: &<T::Summary as Summary>::Context) {
494 if self.is_empty() {
495 *self = other;
496 } else if !other.0.is_leaf() || !other.0.items().is_empty() {
497 if self.0.height() < other.0.height() {
498 for tree in other.0.child_trees() {
499 self.append(tree.clone(), cx);
500 }
501 } else if let Some(split_tree) = self.push_tree_recursive(other, cx) {
502 *self = Self::from_child_trees(self.clone(), split_tree, cx);
503 }
504 }
505 }
506
507 fn push_tree_recursive(
508 &mut self,
509 other: SumTree<T>,
510 cx: &<T::Summary as Summary>::Context,
511 ) -> Option<SumTree<T>> {
512 match Arc::make_mut(&mut self.0) {
513 Node::Internal {
514 height,
515 summary,
516 child_summaries,
517 child_trees,
518 ..
519 } => {
520 let other_node = other.0.clone();
521 <T::Summary as Summary>::add_summary(summary, other_node.summary(), cx);
522
523 let height_delta = *height - other_node.height();
524 let mut summaries_to_append = ArrayVec::<T::Summary, { 2 * TREE_BASE }>::new();
525 let mut trees_to_append = ArrayVec::<SumTree<T>, { 2 * TREE_BASE }>::new();
526 if height_delta == 0 {
527 summaries_to_append.extend(other_node.child_summaries().iter().cloned());
528 trees_to_append.extend(other_node.child_trees().iter().cloned());
529 } else if height_delta == 1 && !other_node.is_underflowing() {
530 summaries_to_append.push(other_node.summary().clone());
531 trees_to_append.push(other)
532 } else {
533 let tree_to_append = child_trees
534 .last_mut()
535 .unwrap()
536 .push_tree_recursive(other, cx);
537 *child_summaries.last_mut().unwrap() =
538 child_trees.last().unwrap().0.summary().clone();
539
540 if let Some(split_tree) = tree_to_append {
541 summaries_to_append.push(split_tree.0.summary().clone());
542 trees_to_append.push(split_tree);
543 }
544 }
545
546 let child_count = child_trees.len() + trees_to_append.len();
547 if child_count > 2 * TREE_BASE {
548 let left_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
549 let right_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
550 let left_trees;
551 let right_trees;
552
553 let midpoint = (child_count + child_count % 2) / 2;
554 {
555 let mut all_summaries = child_summaries
556 .iter()
557 .chain(summaries_to_append.iter())
558 .cloned();
559 left_summaries = all_summaries.by_ref().take(midpoint).collect();
560 right_summaries = all_summaries.collect();
561 let mut all_trees =
562 child_trees.iter().chain(trees_to_append.iter()).cloned();
563 left_trees = all_trees.by_ref().take(midpoint).collect();
564 right_trees = all_trees.collect();
565 }
566 *summary = sum(left_summaries.iter(), cx);
567 *child_summaries = left_summaries;
568 *child_trees = left_trees;
569
570 Some(SumTree(Arc::new(Node::Internal {
571 height: *height,
572 summary: sum(right_summaries.iter(), cx),
573 child_summaries: right_summaries,
574 child_trees: right_trees,
575 })))
576 } else {
577 child_summaries.extend(summaries_to_append);
578 child_trees.extend(trees_to_append);
579 None
580 }
581 }
582 Node::Leaf {
583 summary,
584 items,
585 item_summaries,
586 } => {
587 let other_node = other.0;
588
589 let child_count = items.len() + other_node.items().len();
590 if child_count > 2 * TREE_BASE {
591 let left_items;
592 let right_items;
593 let left_summaries;
594 let right_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>;
595
596 let midpoint = (child_count + child_count % 2) / 2;
597 {
598 let mut all_items = items.iter().chain(other_node.items().iter()).cloned();
599 left_items = all_items.by_ref().take(midpoint).collect();
600 right_items = all_items.collect();
601
602 let mut all_summaries = item_summaries
603 .iter()
604 .chain(other_node.child_summaries())
605 .cloned();
606 left_summaries = all_summaries.by_ref().take(midpoint).collect();
607 right_summaries = all_summaries.collect();
608 }
609 *items = left_items;
610 *item_summaries = left_summaries;
611 *summary = sum(item_summaries.iter(), cx);
612 Some(SumTree(Arc::new(Node::Leaf {
613 items: right_items,
614 summary: sum(right_summaries.iter(), cx),
615 item_summaries: right_summaries,
616 })))
617 } else {
618 <T::Summary as Summary>::add_summary(summary, other_node.summary(), cx);
619 items.extend(other_node.items().iter().cloned());
620 item_summaries.extend(other_node.child_summaries().iter().cloned());
621 None
622 }
623 }
624 }
625 }
626
627 fn from_child_trees(
628 left: SumTree<T>,
629 right: SumTree<T>,
630 cx: &<T::Summary as Summary>::Context,
631 ) -> Self {
632 let height = left.0.height() + 1;
633 let mut child_summaries = ArrayVec::new();
634 child_summaries.push(left.0.summary().clone());
635 child_summaries.push(right.0.summary().clone());
636 let mut child_trees = ArrayVec::new();
637 child_trees.push(left);
638 child_trees.push(right);
639 SumTree(Arc::new(Node::Internal {
640 height,
641 summary: sum(child_summaries.iter(), cx),
642 child_summaries,
643 child_trees,
644 }))
645 }
646
647 fn leftmost_leaf(&self) -> &Self {
648 match *self.0 {
649 Node::Leaf { .. } => self,
650 Node::Internal {
651 ref child_trees, ..
652 } => child_trees.first().unwrap().leftmost_leaf(),
653 }
654 }
655
656 fn rightmost_leaf(&self) -> &Self {
657 match *self.0 {
658 Node::Leaf { .. } => self,
659 Node::Internal {
660 ref child_trees, ..
661 } => child_trees.last().unwrap().rightmost_leaf(),
662 }
663 }
664}
665
666impl<T: Item + PartialEq> PartialEq for SumTree<T> {
667 fn eq(&self, other: &Self) -> bool {
668 self.iter().eq(other.iter())
669 }
670}
671
672impl<T: Item + Eq> Eq for SumTree<T> {}
673
674impl<T: KeyedItem> SumTree<T> {
675 pub fn insert_or_replace(
676 &mut self,
677 item: T,
678 cx: &<T::Summary as Summary>::Context,
679 ) -> Option<T> {
680 let mut replaced = None;
681 *self = {
682 let mut cursor = self.cursor::<T::Key>(cx);
683 let mut new_tree = cursor.slice(&item.key(), Bias::Left);
684 if let Some(cursor_item) = cursor.item() {
685 if cursor_item.key() == item.key() {
686 replaced = Some(cursor_item.clone());
687 cursor.next();
688 }
689 }
690 new_tree.push(item, cx);
691 new_tree.append(cursor.suffix(), cx);
692 new_tree
693 };
694 replaced
695 }
696
697 pub fn remove(&mut self, key: &T::Key, cx: &<T::Summary as Summary>::Context) -> Option<T> {
698 let mut removed = None;
699 *self = {
700 let mut cursor = self.cursor::<T::Key>(cx);
701 let mut new_tree = cursor.slice(key, Bias::Left);
702 if let Some(item) = cursor.item() {
703 if item.key() == *key {
704 removed = Some(item.clone());
705 cursor.next();
706 }
707 }
708 new_tree.append(cursor.suffix(), cx);
709 new_tree
710 };
711 removed
712 }
713
714 pub fn edit(
715 &mut self,
716 mut edits: Vec<Edit<T>>,
717 cx: &<T::Summary as Summary>::Context,
718 ) -> Vec<T> {
719 if edits.is_empty() {
720 return Vec::new();
721 }
722
723 let mut removed = Vec::new();
724 edits.sort_unstable_by_key(|item| item.key());
725
726 *self = {
727 let mut cursor = self.cursor::<T::Key>(cx);
728 let mut new_tree = SumTree::new(cx);
729 let mut buffered_items = Vec::new();
730
731 cursor.seek(&T::Key::zero(cx), Bias::Left);
732 for edit in edits {
733 let new_key = edit.key();
734 let mut old_item = cursor.item();
735
736 if old_item
737 .as_ref()
738 .map_or(false, |old_item| old_item.key() < new_key)
739 {
740 new_tree.extend(buffered_items.drain(..), cx);
741 let slice = cursor.slice(&new_key, Bias::Left);
742 new_tree.append(slice, cx);
743 old_item = cursor.item();
744 }
745
746 if let Some(old_item) = old_item {
747 if old_item.key() == new_key {
748 removed.push(old_item.clone());
749 cursor.next();
750 }
751 }
752
753 match edit {
754 Edit::Insert(item) => {
755 buffered_items.push(item);
756 }
757 Edit::Remove(_) => {}
758 }
759 }
760
761 new_tree.extend(buffered_items, cx);
762 new_tree.append(cursor.suffix(), cx);
763 new_tree
764 };
765
766 removed
767 }
768
769 pub fn get<'a>(
770 &'a self,
771 key: &T::Key,
772 cx: &'a <T::Summary as Summary>::Context,
773 ) -> Option<&'a T> {
774 let mut cursor = self.cursor::<T::Key>(cx);
775 if cursor.seek(key, Bias::Left) {
776 cursor.item()
777 } else {
778 None
779 }
780 }
781}
782
783impl<T, S> Default for SumTree<T>
784where
785 T: Item<Summary = S>,
786 S: Summary<Context = ()>,
787{
788 fn default() -> Self {
789 Self::new(&())
790 }
791}
792
793#[derive(Clone)]
794pub enum Node<T: Item> {
795 Internal {
796 height: u8,
797 summary: T::Summary,
798 child_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
799 child_trees: ArrayVec<SumTree<T>, { 2 * TREE_BASE }>,
800 },
801 Leaf {
802 summary: T::Summary,
803 items: ArrayVec<T, { 2 * TREE_BASE }>,
804 item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
805 },
806}
807
808impl<T> fmt::Debug for Node<T>
809where
810 T: Item + fmt::Debug,
811 T::Summary: fmt::Debug,
812{
813 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
814 match self {
815 Node::Internal {
816 height,
817 summary,
818 child_summaries,
819 child_trees,
820 } => f
821 .debug_struct("Internal")
822 .field("height", height)
823 .field("summary", summary)
824 .field("child_summaries", child_summaries)
825 .field("child_trees", child_trees)
826 .finish(),
827 Node::Leaf {
828 summary,
829 items,
830 item_summaries,
831 } => f
832 .debug_struct("Leaf")
833 .field("summary", summary)
834 .field("items", items)
835 .field("item_summaries", item_summaries)
836 .finish(),
837 }
838 }
839}
840
841impl<T: Item> Node<T> {
842 fn is_leaf(&self) -> bool {
843 matches!(self, Node::Leaf { .. })
844 }
845
846 fn height(&self) -> u8 {
847 match self {
848 Node::Internal { height, .. } => *height,
849 Node::Leaf { .. } => 0,
850 }
851 }
852
853 fn summary(&self) -> &T::Summary {
854 match self {
855 Node::Internal { summary, .. } => summary,
856 Node::Leaf { summary, .. } => summary,
857 }
858 }
859
860 fn child_summaries(&self) -> &[T::Summary] {
861 match self {
862 Node::Internal {
863 child_summaries, ..
864 } => child_summaries.as_slice(),
865 Node::Leaf { item_summaries, .. } => item_summaries.as_slice(),
866 }
867 }
868
869 fn child_trees(&self) -> &ArrayVec<SumTree<T>, { 2 * TREE_BASE }> {
870 match self {
871 Node::Internal { child_trees, .. } => child_trees,
872 Node::Leaf { .. } => panic!("Leaf nodes have no child trees"),
873 }
874 }
875
876 fn items(&self) -> &ArrayVec<T, { 2 * TREE_BASE }> {
877 match self {
878 Node::Leaf { items, .. } => items,
879 Node::Internal { .. } => panic!("Internal nodes have no items"),
880 }
881 }
882
883 fn is_underflowing(&self) -> bool {
884 match self {
885 Node::Internal { child_trees, .. } => child_trees.len() < TREE_BASE,
886 Node::Leaf { items, .. } => items.len() < TREE_BASE,
887 }
888 }
889}
890
891#[derive(Debug)]
892pub enum Edit<T: KeyedItem> {
893 Insert(T),
894 Remove(T::Key),
895}
896
897impl<T: KeyedItem> Edit<T> {
898 fn key(&self) -> T::Key {
899 match self {
900 Edit::Insert(item) => item.key(),
901 Edit::Remove(key) => key.clone(),
902 }
903 }
904}
905
906fn sum<'a, T, I>(iter: I, cx: &T::Context) -> T
907where
908 T: 'a + Summary,
909 I: Iterator<Item = &'a T>,
910{
911 let mut sum = T::zero(cx);
912 for value in iter {
913 sum.add_summary(value, cx);
914 }
915 sum
916}
917
918#[cfg(test)]
919mod tests {
920 use super::*;
921 use rand::{distributions, prelude::*};
922 use std::cmp;
923
924 #[ctor::ctor]
925 fn init_logger() {
926 zlog::init_test();
927 }
928
929 #[test]
930 fn test_extend_and_push_tree() {
931 let mut tree1 = SumTree::default();
932 tree1.extend(0..20, &());
933
934 let mut tree2 = SumTree::default();
935 tree2.extend(50..100, &());
936
937 tree1.append(tree2, &());
938 assert_eq!(
939 tree1.items(&()),
940 (0..20).chain(50..100).collect::<Vec<u8>>()
941 );
942 }
943
944 #[test]
945 fn test_random() {
946 let mut starting_seed = 0;
947 if let Ok(value) = std::env::var("SEED") {
948 starting_seed = value.parse().expect("invalid SEED variable");
949 }
950 let mut num_iterations = 100;
951 if let Ok(value) = std::env::var("ITERATIONS") {
952 num_iterations = value.parse().expect("invalid ITERATIONS variable");
953 }
954 let num_operations = std::env::var("OPERATIONS")
955 .map_or(5, |o| o.parse().expect("invalid OPERATIONS variable"));
956
957 for seed in starting_seed..(starting_seed + num_iterations) {
958 eprintln!("seed = {}", seed);
959 let mut rng = StdRng::seed_from_u64(seed);
960
961 let rng = &mut rng;
962 let mut tree = SumTree::<u8>::default();
963 let count = rng.gen_range(0..10);
964 if rng.r#gen() {
965 tree.extend(rng.sample_iter(distributions::Standard).take(count), &());
966 } else {
967 let items = rng
968 .sample_iter(distributions::Standard)
969 .take(count)
970 .collect::<Vec<_>>();
971 tree.par_extend(items, &());
972 }
973
974 for _ in 0..num_operations {
975 let splice_end = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
976 let splice_start = rng.gen_range(0..splice_end + 1);
977 let count = rng.gen_range(0..10);
978 let tree_end = tree.extent::<Count>(&());
979 let new_items = rng
980 .sample_iter(distributions::Standard)
981 .take(count)
982 .collect::<Vec<u8>>();
983
984 let mut reference_items = tree.items(&());
985 reference_items.splice(splice_start..splice_end, new_items.clone());
986
987 tree = {
988 let mut cursor = tree.cursor::<Count>(&());
989 let mut new_tree = cursor.slice(&Count(splice_start), Bias::Right);
990 if rng.r#gen() {
991 new_tree.extend(new_items, &());
992 } else {
993 new_tree.par_extend(new_items, &());
994 }
995 cursor.seek(&Count(splice_end), Bias::Right);
996 new_tree.append(cursor.slice(&tree_end, Bias::Right), &());
997 new_tree
998 };
999
1000 assert_eq!(tree.items(&()), reference_items);
1001 assert_eq!(
1002 tree.iter().collect::<Vec<_>>(),
1003 tree.cursor::<()>(&()).collect::<Vec<_>>()
1004 );
1005
1006 log::info!("tree items: {:?}", tree.items(&()));
1007
1008 let mut filter_cursor =
1009 tree.filter::<_, Count>(&(), |summary| summary.contains_even);
1010 let expected_filtered_items = tree
1011 .items(&())
1012 .into_iter()
1013 .enumerate()
1014 .filter(|(_, item)| (item & 1) == 0)
1015 .collect::<Vec<_>>();
1016
1017 let mut item_ix = if rng.r#gen() {
1018 filter_cursor.next();
1019 0
1020 } else {
1021 filter_cursor.prev();
1022 expected_filtered_items.len().saturating_sub(1)
1023 };
1024 while item_ix < expected_filtered_items.len() {
1025 log::info!("filter_cursor, item_ix: {}", item_ix);
1026 let actual_item = filter_cursor.item().unwrap();
1027 let (reference_index, reference_item) = expected_filtered_items[item_ix];
1028 assert_eq!(actual_item, &reference_item);
1029 assert_eq!(filter_cursor.start().0, reference_index);
1030 log::info!("next");
1031 filter_cursor.next();
1032 item_ix += 1;
1033
1034 while item_ix > 0 && rng.gen_bool(0.2) {
1035 log::info!("prev");
1036 filter_cursor.prev();
1037 item_ix -= 1;
1038
1039 if item_ix == 0 && rng.gen_bool(0.2) {
1040 filter_cursor.prev();
1041 assert_eq!(filter_cursor.item(), None);
1042 assert_eq!(filter_cursor.start().0, 0);
1043 filter_cursor.next();
1044 }
1045 }
1046 }
1047 assert_eq!(filter_cursor.item(), None);
1048
1049 let mut before_start = false;
1050 let mut cursor = tree.cursor::<Count>(&());
1051 let start_pos = rng.gen_range(0..=reference_items.len());
1052 cursor.seek(&Count(start_pos), Bias::Right);
1053 let mut pos = rng.gen_range(start_pos..=reference_items.len());
1054 cursor.seek_forward(&Count(pos), Bias::Right);
1055
1056 for i in 0..10 {
1057 assert_eq!(cursor.start().0, pos);
1058
1059 if pos > 0 {
1060 assert_eq!(cursor.prev_item().unwrap(), &reference_items[pos - 1]);
1061 } else {
1062 assert_eq!(cursor.prev_item(), None);
1063 }
1064
1065 if pos < reference_items.len() && !before_start {
1066 assert_eq!(cursor.item().unwrap(), &reference_items[pos]);
1067 } else {
1068 assert_eq!(cursor.item(), None);
1069 }
1070
1071 if before_start {
1072 assert_eq!(cursor.next_item(), reference_items.first());
1073 } else if pos + 1 < reference_items.len() {
1074 assert_eq!(cursor.next_item().unwrap(), &reference_items[pos + 1]);
1075 } else {
1076 assert_eq!(cursor.next_item(), None);
1077 }
1078
1079 if i < 5 {
1080 cursor.next();
1081 if pos < reference_items.len() {
1082 pos += 1;
1083 before_start = false;
1084 }
1085 } else {
1086 cursor.prev();
1087 if pos == 0 {
1088 before_start = true;
1089 }
1090 pos = pos.saturating_sub(1);
1091 }
1092 }
1093 }
1094
1095 for _ in 0..10 {
1096 let end = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
1097 let start = rng.gen_range(0..end + 1);
1098 let start_bias = if rng.r#gen() { Bias::Left } else { Bias::Right };
1099 let end_bias = if rng.r#gen() { Bias::Left } else { Bias::Right };
1100
1101 let mut cursor = tree.cursor::<Count>(&());
1102 cursor.seek(&Count(start), start_bias);
1103 let slice = cursor.slice(&Count(end), end_bias);
1104
1105 cursor.seek(&Count(start), start_bias);
1106 let summary = cursor.summary::<_, Sum>(&Count(end), end_bias);
1107
1108 assert_eq!(summary.0, slice.summary().sum);
1109 }
1110 }
1111 }
1112
1113 #[test]
1114 fn test_cursor() {
1115 // Empty tree
1116 let tree = SumTree::<u8>::default();
1117 let mut cursor = tree.cursor::<IntegersSummary>(&());
1118 assert_eq!(
1119 cursor.slice(&Count(0), Bias::Right).items(&()),
1120 Vec::<u8>::new()
1121 );
1122 assert_eq!(cursor.item(), None);
1123 assert_eq!(cursor.prev_item(), None);
1124 assert_eq!(cursor.next_item(), None);
1125 assert_eq!(cursor.start().sum, 0);
1126 cursor.prev();
1127 assert_eq!(cursor.item(), None);
1128 assert_eq!(cursor.prev_item(), None);
1129 assert_eq!(cursor.next_item(), None);
1130 assert_eq!(cursor.start().sum, 0);
1131 cursor.next();
1132 assert_eq!(cursor.item(), None);
1133 assert_eq!(cursor.prev_item(), None);
1134 assert_eq!(cursor.next_item(), None);
1135 assert_eq!(cursor.start().sum, 0);
1136
1137 // Single-element tree
1138 let mut tree = SumTree::<u8>::default();
1139 tree.extend(vec![1], &());
1140 let mut cursor = tree.cursor::<IntegersSummary>(&());
1141 assert_eq!(
1142 cursor.slice(&Count(0), Bias::Right).items(&()),
1143 Vec::<u8>::new()
1144 );
1145 assert_eq!(cursor.item(), Some(&1));
1146 assert_eq!(cursor.prev_item(), None);
1147 assert_eq!(cursor.next_item(), None);
1148 assert_eq!(cursor.start().sum, 0);
1149
1150 cursor.next();
1151 assert_eq!(cursor.item(), None);
1152 assert_eq!(cursor.prev_item(), Some(&1));
1153 assert_eq!(cursor.next_item(), None);
1154 assert_eq!(cursor.start().sum, 1);
1155
1156 cursor.prev();
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 let mut cursor = tree.cursor::<IntegersSummary>(&());
1163 assert_eq!(cursor.slice(&Count(1), Bias::Right).items(&()), [1]);
1164 assert_eq!(cursor.item(), None);
1165 assert_eq!(cursor.prev_item(), Some(&1));
1166 assert_eq!(cursor.next_item(), None);
1167 assert_eq!(cursor.start().sum, 1);
1168
1169 cursor.seek(&Count(0), Bias::Right);
1170 assert_eq!(
1171 cursor
1172 .slice(&tree.extent::<Count>(&()), Bias::Right)
1173 .items(&()),
1174 [1]
1175 );
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 // Multiple-element tree
1182 let mut tree = SumTree::default();
1183 tree.extend(vec![1, 2, 3, 4, 5, 6], &());
1184 let mut cursor = tree.cursor::<IntegersSummary>(&());
1185
1186 assert_eq!(cursor.slice(&Count(2), Bias::Right).items(&()), [1, 2]);
1187 assert_eq!(cursor.item(), Some(&3));
1188 assert_eq!(cursor.prev_item(), Some(&2));
1189 assert_eq!(cursor.next_item(), Some(&4));
1190 assert_eq!(cursor.start().sum, 3);
1191
1192 cursor.next();
1193 assert_eq!(cursor.item(), Some(&4));
1194 assert_eq!(cursor.prev_item(), Some(&3));
1195 assert_eq!(cursor.next_item(), Some(&5));
1196 assert_eq!(cursor.start().sum, 6);
1197
1198 cursor.next();
1199 assert_eq!(cursor.item(), Some(&5));
1200 assert_eq!(cursor.prev_item(), Some(&4));
1201 assert_eq!(cursor.next_item(), Some(&6));
1202 assert_eq!(cursor.start().sum, 10);
1203
1204 cursor.next();
1205 assert_eq!(cursor.item(), Some(&6));
1206 assert_eq!(cursor.prev_item(), Some(&5));
1207 assert_eq!(cursor.next_item(), None);
1208 assert_eq!(cursor.start().sum, 15);
1209
1210 cursor.next();
1211 cursor.next();
1212 assert_eq!(cursor.item(), None);
1213 assert_eq!(cursor.prev_item(), Some(&6));
1214 assert_eq!(cursor.next_item(), None);
1215 assert_eq!(cursor.start().sum, 21);
1216
1217 cursor.prev();
1218 assert_eq!(cursor.item(), Some(&6));
1219 assert_eq!(cursor.prev_item(), Some(&5));
1220 assert_eq!(cursor.next_item(), None);
1221 assert_eq!(cursor.start().sum, 15);
1222
1223 cursor.prev();
1224 assert_eq!(cursor.item(), Some(&5));
1225 assert_eq!(cursor.prev_item(), Some(&4));
1226 assert_eq!(cursor.next_item(), Some(&6));
1227 assert_eq!(cursor.start().sum, 10);
1228
1229 cursor.prev();
1230 assert_eq!(cursor.item(), Some(&4));
1231 assert_eq!(cursor.prev_item(), Some(&3));
1232 assert_eq!(cursor.next_item(), Some(&5));
1233 assert_eq!(cursor.start().sum, 6);
1234
1235 cursor.prev();
1236 assert_eq!(cursor.item(), Some(&3));
1237 assert_eq!(cursor.prev_item(), Some(&2));
1238 assert_eq!(cursor.next_item(), Some(&4));
1239 assert_eq!(cursor.start().sum, 3);
1240
1241 cursor.prev();
1242 assert_eq!(cursor.item(), Some(&2));
1243 assert_eq!(cursor.prev_item(), Some(&1));
1244 assert_eq!(cursor.next_item(), Some(&3));
1245 assert_eq!(cursor.start().sum, 1);
1246
1247 cursor.prev();
1248 assert_eq!(cursor.item(), Some(&1));
1249 assert_eq!(cursor.prev_item(), None);
1250 assert_eq!(cursor.next_item(), Some(&2));
1251 assert_eq!(cursor.start().sum, 0);
1252
1253 cursor.prev();
1254 assert_eq!(cursor.item(), None);
1255 assert_eq!(cursor.prev_item(), None);
1256 assert_eq!(cursor.next_item(), Some(&1));
1257 assert_eq!(cursor.start().sum, 0);
1258
1259 cursor.next();
1260 assert_eq!(cursor.item(), Some(&1));
1261 assert_eq!(cursor.prev_item(), None);
1262 assert_eq!(cursor.next_item(), Some(&2));
1263 assert_eq!(cursor.start().sum, 0);
1264
1265 let mut cursor = tree.cursor::<IntegersSummary>(&());
1266 assert_eq!(
1267 cursor
1268 .slice(&tree.extent::<Count>(&()), Bias::Right)
1269 .items(&()),
1270 tree.items(&())
1271 );
1272 assert_eq!(cursor.item(), None);
1273 assert_eq!(cursor.prev_item(), Some(&6));
1274 assert_eq!(cursor.next_item(), None);
1275 assert_eq!(cursor.start().sum, 21);
1276
1277 cursor.seek(&Count(3), Bias::Right);
1278 assert_eq!(
1279 cursor
1280 .slice(&tree.extent::<Count>(&()), Bias::Right)
1281 .items(&()),
1282 [4, 5, 6]
1283 );
1284 assert_eq!(cursor.item(), None);
1285 assert_eq!(cursor.prev_item(), Some(&6));
1286 assert_eq!(cursor.next_item(), None);
1287 assert_eq!(cursor.start().sum, 21);
1288
1289 // Seeking can bias left or right
1290 cursor.seek(&Count(1), Bias::Left);
1291 assert_eq!(cursor.item(), Some(&1));
1292 cursor.seek(&Count(1), Bias::Right);
1293 assert_eq!(cursor.item(), Some(&2));
1294
1295 // Slicing without resetting starts from where the cursor is parked at.
1296 cursor.seek(&Count(1), Bias::Right);
1297 assert_eq!(cursor.slice(&Count(3), Bias::Right).items(&()), vec![2, 3]);
1298 assert_eq!(cursor.slice(&Count(6), Bias::Left).items(&()), vec![4, 5]);
1299 assert_eq!(cursor.slice(&Count(6), Bias::Right).items(&()), vec![6]);
1300 }
1301
1302 #[test]
1303 fn test_edit() {
1304 let mut tree = SumTree::<u8>::default();
1305
1306 let removed = tree.edit(vec![Edit::Insert(1), Edit::Insert(2), Edit::Insert(0)], &());
1307 assert_eq!(tree.items(&()), vec![0, 1, 2]);
1308 assert_eq!(removed, Vec::<u8>::new());
1309 assert_eq!(tree.get(&0, &()), Some(&0));
1310 assert_eq!(tree.get(&1, &()), Some(&1));
1311 assert_eq!(tree.get(&2, &()), Some(&2));
1312 assert_eq!(tree.get(&4, &()), None);
1313
1314 let removed = tree.edit(vec![Edit::Insert(2), Edit::Insert(4), Edit::Remove(0)], &());
1315 assert_eq!(tree.items(&()), vec![1, 2, 4]);
1316 assert_eq!(removed, vec![0, 2]);
1317 assert_eq!(tree.get(&0, &()), None);
1318 assert_eq!(tree.get(&1, &()), Some(&1));
1319 assert_eq!(tree.get(&2, &()), Some(&2));
1320 assert_eq!(tree.get(&4, &()), Some(&4));
1321 }
1322
1323 #[test]
1324 fn test_from_iter() {
1325 assert_eq!(
1326 SumTree::from_iter(0..100, &()).items(&()),
1327 (0..100).collect::<Vec<_>>()
1328 );
1329
1330 // Ensure `from_iter` works correctly when the given iterator restarts
1331 // after calling `next` if `None` was already returned.
1332 let mut ix = 0;
1333 let iterator = std::iter::from_fn(|| {
1334 ix = (ix + 1) % 2;
1335 if ix == 1 { Some(1) } else { None }
1336 });
1337 assert_eq!(SumTree::from_iter(iterator, &()).items(&()), vec![1]);
1338 }
1339
1340 #[derive(Clone, Default, Debug)]
1341 pub struct IntegersSummary {
1342 count: usize,
1343 sum: usize,
1344 contains_even: bool,
1345 max: u8,
1346 }
1347
1348 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
1349 struct Count(usize);
1350
1351 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
1352 struct Sum(usize);
1353
1354 impl Item for u8 {
1355 type Summary = IntegersSummary;
1356
1357 fn summary(&self, _cx: &()) -> Self::Summary {
1358 IntegersSummary {
1359 count: 1,
1360 sum: *self as usize,
1361 contains_even: (*self & 1) == 0,
1362 max: *self,
1363 }
1364 }
1365 }
1366
1367 impl KeyedItem for u8 {
1368 type Key = u8;
1369
1370 fn key(&self) -> Self::Key {
1371 *self
1372 }
1373 }
1374
1375 impl Summary for IntegersSummary {
1376 type Context = ();
1377
1378 fn zero(_cx: &()) -> Self {
1379 Default::default()
1380 }
1381
1382 fn add_summary(&mut self, other: &Self, _: &()) {
1383 self.count += other.count;
1384 self.sum += other.sum;
1385 self.contains_even |= other.contains_even;
1386 self.max = cmp::max(self.max, other.max);
1387 }
1388 }
1389
1390 impl Dimension<'_, IntegersSummary> for u8 {
1391 fn zero(_cx: &()) -> Self {
1392 Default::default()
1393 }
1394
1395 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
1396 *self = summary.max;
1397 }
1398 }
1399
1400 impl Dimension<'_, IntegersSummary> for Count {
1401 fn zero(_cx: &()) -> Self {
1402 Default::default()
1403 }
1404
1405 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
1406 self.0 += summary.count;
1407 }
1408 }
1409
1410 impl SeekTarget<'_, IntegersSummary, IntegersSummary> for Count {
1411 fn cmp(&self, cursor_location: &IntegersSummary, _: &()) -> Ordering {
1412 self.0.cmp(&cursor_location.count)
1413 }
1414 }
1415
1416 impl Dimension<'_, IntegersSummary> for Sum {
1417 fn zero(_cx: &()) -> Self {
1418 Default::default()
1419 }
1420
1421 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
1422 self.0 += summary.sum;
1423 }
1424 }
1425}