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<'a>: Copy;
39 fn zero<'a>(cx: Self::Context<'a>) -> Self;
40 fn add_summary<'a>(&mut self, summary: &Self, cx: Self::Context<'a>);
41}
42
43pub trait ContextLessSummary: Clone {
44 fn zero() -> Self;
45 fn add_summary(&mut self, summary: &Self);
46}
47
48impl<T: ContextLessSummary> Summary for T {
49 type Context<'a> = ();
50
51 fn zero<'a>((): ()) -> Self {
52 T::zero()
53 }
54
55 fn add_summary<'a>(&mut self, summary: &Self, (): ()) {
56 T::add_summary(self, summary)
57 }
58}
59
60#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
61pub struct NoSummary;
62
63/// Catch-all implementation for when you need something that implements [`Summary`] without a specific type.
64/// We implement it on a `NoSummary` instead of re-using `()`, as that avoids blanket impl collisions with `impl<T: Summary> Dimension for T`
65/// (as we also need unit type to be a fill-in dimension)
66impl ContextLessSummary for NoSummary {
67 fn zero() -> Self {
68 NoSummary
69 }
70
71 fn add_summary(&mut self, _: &Self) {}
72}
73
74/// Each [`Summary`] type can have more than one [`Dimension`] type that it measures.
75///
76/// You can use dimensions to seek to a specific location in the [`SumTree`]
77///
78/// # Example:
79/// Zed's rope has a `TextSummary` type that summarizes lines, characters, and bytes.
80/// Each of these are different dimensions we may want to seek to
81pub trait Dimension<'a, S: Summary>: Clone {
82 fn zero(cx: S::Context<'_>) -> Self;
83
84 fn add_summary(&mut self, summary: &'a S, cx: S::Context<'_>);
85
86 fn from_summary(summary: &'a S, cx: S::Context<'_>) -> Self {
87 let mut dimension = Self::zero(cx);
88 dimension.add_summary(summary, cx);
89 dimension
90 }
91}
92
93impl<'a, T: Summary> Dimension<'a, T> for T {
94 fn zero(cx: T::Context<'_>) -> Self {
95 Summary::zero(cx)
96 }
97
98 fn add_summary(&mut self, summary: &'a T, cx: T::Context<'_>) {
99 Summary::add_summary(self, summary, cx);
100 }
101}
102
103pub trait SeekTarget<'a, S: Summary, D: Dimension<'a, S>> {
104 fn cmp(&self, cursor_location: &D, cx: S::Context<'_>) -> Ordering;
105}
106
107impl<'a, S: Summary, D: Dimension<'a, S> + Ord> SeekTarget<'a, S, D> for D {
108 fn cmp(&self, cursor_location: &Self, _: S::Context<'_>) -> Ordering {
109 Ord::cmp(self, cursor_location)
110 }
111}
112
113impl<'a, T: Summary> Dimension<'a, T> for () {
114 fn zero(_: T::Context<'_>) -> Self {}
115
116 fn add_summary(&mut self, _: &'a T, _: T::Context<'_>) {}
117}
118
119#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
120pub struct Dimensions<D1, D2, D3 = ()>(pub D1, pub D2, pub D3);
121
122impl<'a, T: Summary, D1: Dimension<'a, T>, D2: Dimension<'a, T>, D3: Dimension<'a, T>>
123 Dimension<'a, T> for Dimensions<D1, D2, D3>
124{
125 fn zero(cx: T::Context<'_>) -> Self {
126 Dimensions(D1::zero(cx), D2::zero(cx), D3::zero(cx))
127 }
128
129 fn add_summary(&mut self, summary: &'a T, cx: T::Context<'_>) {
130 self.0.add_summary(summary, cx);
131 self.1.add_summary(summary, cx);
132 self.2.add_summary(summary, cx);
133 }
134}
135
136impl<'a, S, D1, D2, D3> SeekTarget<'a, S, Dimensions<D1, D2, D3>> for D1
137where
138 S: Summary,
139 D1: SeekTarget<'a, S, D1> + Dimension<'a, S>,
140 D2: Dimension<'a, S>,
141 D3: Dimension<'a, S>,
142{
143 fn cmp(&self, cursor_location: &Dimensions<D1, D2, D3>, cx: S::Context<'_>) -> Ordering {
144 self.cmp(&cursor_location.0, cx)
145 }
146}
147
148/// Bias is used to settle ambiguities when determining positions in an ordered sequence.
149///
150/// The primary use case is for text, where Bias influences
151/// which character an offset or anchor is associated with.
152///
153/// # Examples
154/// Given the buffer `AˇBCD`:
155/// - The offset of the cursor is 1
156/// - [Bias::Left] would attach the cursor to the character `A`
157/// - [Bias::Right] would attach the cursor to the character `B`
158///
159/// Given the buffer `A«BCˇ»D`:
160/// - The offset of the cursor is 3, and the selection is from 1 to 3
161/// - The left anchor of the selection has [Bias::Right], attaching it to the character `B`
162/// - The right anchor of the selection has [Bias::Left], attaching it to the character `C`
163///
164/// Given the buffer `{ˇ<...>`, where `<...>` is a folded region:
165/// - The display offset of the cursor is 1, but the offset in the buffer is determined by the bias
166/// - [Bias::Left] would attach the cursor to the character `{`, with a buffer offset of 1
167/// - [Bias::Right] would attach the cursor to the first character of the folded region,
168/// and the buffer offset would be the offset of the first character of the folded region
169#[derive(Copy, Clone, Eq, PartialEq, PartialOrd, Ord, Debug, Hash, Default)]
170pub enum Bias {
171 /// Attach to the character on the left
172 #[default]
173 Left,
174 /// Attach to the character on the right
175 Right,
176}
177
178impl Bias {
179 pub const fn invert(self) -> Self {
180 match self {
181 Self::Left => Self::Right,
182 Self::Right => Self::Left,
183 }
184 }
185}
186
187/// A B+ tree in which each leaf node contains `Item`s of type `T` and a `Summary`s for each `Item`.
188/// Each internal node contains a `Summary` of the items in its subtree.
189///
190/// The maximum number of items per node is `TREE_BASE * 2`.
191///
192/// Any [`Dimension`] supported by the [`Summary`] type can be used to seek to a specific location in the tree.
193#[derive(Clone)]
194pub struct SumTree<T: Item>(Arc<Node<T>>);
195
196impl<T> fmt::Debug for SumTree<T>
197where
198 T: fmt::Debug + Item,
199 T::Summary: fmt::Debug,
200{
201 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
202 f.debug_tuple("SumTree").field(&self.0).finish()
203 }
204}
205
206impl<T: Item> SumTree<T> {
207 pub fn new(cx: <T::Summary as Summary>::Context<'_>) -> Self {
208 SumTree(Arc::new(Node::Leaf {
209 summary: <T::Summary as Summary>::zero(cx),
210 items: ArrayVec::new(),
211 item_summaries: ArrayVec::new(),
212 }))
213 }
214
215 /// 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.
216 pub fn from_summary(summary: T::Summary) -> Self {
217 SumTree(Arc::new(Node::Leaf {
218 summary,
219 items: ArrayVec::new(),
220 item_summaries: ArrayVec::new(),
221 }))
222 }
223
224 pub fn from_item(item: T, cx: <T::Summary as Summary>::Context<'_>) -> Self {
225 let mut tree = Self::new(cx);
226 tree.push(item, cx);
227 tree
228 }
229
230 pub fn from_iter<I: IntoIterator<Item = T>>(
231 iter: I,
232 cx: <T::Summary as Summary>::Context<'_>,
233 ) -> Self {
234 let mut nodes = Vec::new();
235
236 let mut iter = iter.into_iter().fuse().peekable();
237 while iter.peek().is_some() {
238 let items: ArrayVec<T, { 2 * TREE_BASE }> = iter.by_ref().take(2 * TREE_BASE).collect();
239 let item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }> =
240 items.iter().map(|item| item.summary(cx)).collect();
241
242 let mut summary = item_summaries[0].clone();
243 for item_summary in &item_summaries[1..] {
244 <T::Summary as Summary>::add_summary(&mut summary, item_summary, cx);
245 }
246
247 nodes.push(Node::Leaf {
248 summary,
249 items,
250 item_summaries,
251 });
252 }
253
254 let mut parent_nodes = Vec::new();
255 let mut height = 0;
256 while nodes.len() > 1 {
257 height += 1;
258 let mut current_parent_node = None;
259 for child_node in nodes.drain(..) {
260 let parent_node = current_parent_node.get_or_insert_with(|| Node::Internal {
261 summary: <T::Summary as Summary>::zero(cx),
262 height,
263 child_summaries: ArrayVec::new(),
264 child_trees: ArrayVec::new(),
265 });
266 let Node::Internal {
267 summary,
268 child_summaries,
269 child_trees,
270 ..
271 } = parent_node
272 else {
273 unreachable!()
274 };
275 let child_summary = child_node.summary();
276 <T::Summary as Summary>::add_summary(summary, child_summary, cx);
277 child_summaries.push(child_summary.clone());
278 child_trees.push(Self(Arc::new(child_node)));
279
280 if child_trees.len() == 2 * TREE_BASE {
281 parent_nodes.extend(current_parent_node.take());
282 }
283 }
284 parent_nodes.extend(current_parent_node.take());
285 mem::swap(&mut nodes, &mut parent_nodes);
286 }
287
288 if nodes.is_empty() {
289 Self::new(cx)
290 } else {
291 debug_assert_eq!(nodes.len(), 1);
292 Self(Arc::new(nodes.pop().unwrap()))
293 }
294 }
295
296 pub fn from_par_iter<I, Iter>(iter: I, cx: <T::Summary as Summary>::Context<'_>) -> Self
297 where
298 I: IntoParallelIterator<Iter = Iter>,
299 Iter: IndexedParallelIterator<Item = T>,
300 T: Send + Sync,
301 T::Summary: Send + Sync,
302 for<'a> <T::Summary as Summary>::Context<'a>: Sync,
303 {
304 let mut nodes = iter
305 .into_par_iter()
306 .chunks(2 * TREE_BASE)
307 .map(|items| {
308 let items: ArrayVec<T, { 2 * TREE_BASE }> = items.into_iter().collect();
309 let item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }> =
310 items.iter().map(|item| item.summary(cx)).collect();
311 let mut summary = item_summaries[0].clone();
312 for item_summary in &item_summaries[1..] {
313 <T::Summary as Summary>::add_summary(&mut summary, item_summary, cx);
314 }
315 SumTree(Arc::new(Node::Leaf {
316 summary,
317 items,
318 item_summaries,
319 }))
320 })
321 .collect::<Vec<_>>();
322
323 let mut height = 0;
324 while nodes.len() > 1 {
325 height += 1;
326 nodes = nodes
327 .into_par_iter()
328 .chunks(2 * TREE_BASE)
329 .map(|child_nodes| {
330 let child_trees: ArrayVec<SumTree<T>, { 2 * TREE_BASE }> =
331 child_nodes.into_iter().collect();
332 let child_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }> = child_trees
333 .iter()
334 .map(|child_tree| child_tree.summary().clone())
335 .collect();
336 let mut summary = child_summaries[0].clone();
337 for child_summary in &child_summaries[1..] {
338 <T::Summary as Summary>::add_summary(&mut summary, child_summary, cx);
339 }
340 SumTree(Arc::new(Node::Internal {
341 height,
342 summary,
343 child_summaries,
344 child_trees,
345 }))
346 })
347 .collect::<Vec<_>>();
348 }
349
350 if nodes.is_empty() {
351 Self::new(cx)
352 } else {
353 debug_assert_eq!(nodes.len(), 1);
354 nodes.pop().unwrap()
355 }
356 }
357
358 #[allow(unused)]
359 pub fn items<'a>(&'a self, cx: <T::Summary as Summary>::Context<'a>) -> Vec<T> {
360 let mut items = Vec::new();
361 let mut cursor = self.cursor::<()>(cx);
362 cursor.next();
363 while let Some(item) = cursor.item() {
364 items.push(item.clone());
365 cursor.next();
366 }
367 items
368 }
369
370 pub fn iter(&self) -> Iter<'_, T> {
371 Iter::new(self)
372 }
373
374 pub fn cursor<'a, 'b, S>(
375 &'a self,
376 cx: <T::Summary as Summary>::Context<'b>,
377 ) -> Cursor<'a, 'b, T, S>
378 where
379 S: Dimension<'a, T::Summary>,
380 {
381 Cursor::new(self, cx)
382 }
383
384 /// Note: If the summary type requires a non `()` context, then the filter cursor
385 /// that is returned cannot be used with Rust's iterators.
386 pub fn filter<'a, 'b, F, U>(
387 &'a self,
388 cx: <T::Summary as Summary>::Context<'b>,
389 filter_node: F,
390 ) -> FilterCursor<'a, 'b, F, T, U>
391 where
392 F: FnMut(&T::Summary) -> bool,
393 U: Dimension<'a, T::Summary>,
394 {
395 FilterCursor::new(self, cx, filter_node)
396 }
397
398 #[allow(dead_code)]
399 pub fn first(&self) -> Option<&T> {
400 self.leftmost_leaf().0.items().first()
401 }
402
403 pub fn last(&self) -> Option<&T> {
404 self.rightmost_leaf().0.items().last()
405 }
406
407 pub fn update_last(
408 &mut self,
409 f: impl FnOnce(&mut T),
410 cx: <T::Summary as Summary>::Context<'_>,
411 ) {
412 self.update_last_recursive(f, cx);
413 }
414
415 fn update_last_recursive(
416 &mut self,
417 f: impl FnOnce(&mut T),
418 cx: <T::Summary as Summary>::Context<'_>,
419 ) -> Option<T::Summary> {
420 match Arc::make_mut(&mut self.0) {
421 Node::Internal {
422 summary,
423 child_summaries,
424 child_trees,
425 ..
426 } => {
427 let last_summary = child_summaries.last_mut().unwrap();
428 let last_child = child_trees.last_mut().unwrap();
429 *last_summary = last_child.update_last_recursive(f, cx).unwrap();
430 *summary = sum(child_summaries.iter(), cx);
431 Some(summary.clone())
432 }
433 Node::Leaf {
434 summary,
435 items,
436 item_summaries,
437 } => {
438 if let Some((item, item_summary)) = items.last_mut().zip(item_summaries.last_mut())
439 {
440 (f)(item);
441 *item_summary = item.summary(cx);
442 *summary = sum(item_summaries.iter(), cx);
443 Some(summary.clone())
444 } else {
445 None
446 }
447 }
448 }
449 }
450
451 pub fn extent<'a, D: Dimension<'a, T::Summary>>(
452 &'a self,
453 cx: <T::Summary as Summary>::Context<'_>,
454 ) -> D {
455 let mut extent = D::zero(cx);
456 match self.0.as_ref() {
457 Node::Internal { summary, .. } | Node::Leaf { summary, .. } => {
458 extent.add_summary(summary, cx);
459 }
460 }
461 extent
462 }
463
464 pub fn summary(&self) -> &T::Summary {
465 match self.0.as_ref() {
466 Node::Internal { summary, .. } => summary,
467 Node::Leaf { summary, .. } => summary,
468 }
469 }
470
471 pub fn is_empty(&self) -> bool {
472 match self.0.as_ref() {
473 Node::Internal { .. } => false,
474 Node::Leaf { items, .. } => items.is_empty(),
475 }
476 }
477
478 pub fn extend<I>(&mut self, iter: I, cx: <T::Summary as Summary>::Context<'_>)
479 where
480 I: IntoIterator<Item = T>,
481 {
482 self.append(Self::from_iter(iter, cx), cx);
483 }
484
485 pub fn par_extend<I, Iter>(&mut self, iter: I, cx: <T::Summary as Summary>::Context<'_>)
486 where
487 I: IntoParallelIterator<Iter = Iter>,
488 Iter: IndexedParallelIterator<Item = T>,
489 T: Send + Sync,
490 T::Summary: Send + Sync,
491 for<'a> <T::Summary as Summary>::Context<'a>: Sync,
492 {
493 self.append(Self::from_par_iter(iter, cx), cx);
494 }
495
496 pub fn push(&mut self, item: T, cx: <T::Summary as Summary>::Context<'_>) {
497 let summary = item.summary(cx);
498 self.append(
499 SumTree(Arc::new(Node::Leaf {
500 summary: summary.clone(),
501 items: ArrayVec::from_iter(Some(item)),
502 item_summaries: ArrayVec::from_iter(Some(summary)),
503 })),
504 cx,
505 );
506 }
507
508 pub fn append(&mut self, other: Self, cx: <T::Summary as Summary>::Context<'_>) {
509 if self.is_empty() {
510 *self = other;
511 } else if !other.0.is_leaf() || !other.0.items().is_empty() {
512 if self.0.height() < other.0.height() {
513 for tree in other.0.child_trees() {
514 self.append(tree.clone(), cx);
515 }
516 } else if let Some(split_tree) = self.push_tree_recursive(other, cx) {
517 *self = Self::from_child_trees(self.clone(), split_tree, cx);
518 }
519 }
520 }
521
522 fn push_tree_recursive(
523 &mut self,
524 other: SumTree<T>,
525 cx: <T::Summary as Summary>::Context<'_>,
526 ) -> Option<SumTree<T>> {
527 match Arc::make_mut(&mut self.0) {
528 Node::Internal {
529 height,
530 summary,
531 child_summaries,
532 child_trees,
533 ..
534 } => {
535 let other_node = other.0.clone();
536 <T::Summary as Summary>::add_summary(summary, other_node.summary(), cx);
537
538 let height_delta = *height - other_node.height();
539 let mut summaries_to_append = ArrayVec::<T::Summary, { 2 * TREE_BASE }>::new();
540 let mut trees_to_append = ArrayVec::<SumTree<T>, { 2 * TREE_BASE }>::new();
541 if height_delta == 0 {
542 summaries_to_append.extend(other_node.child_summaries().iter().cloned());
543 trees_to_append.extend(other_node.child_trees().iter().cloned());
544 } else if height_delta == 1 && !other_node.is_underflowing() {
545 summaries_to_append.push(other_node.summary().clone());
546 trees_to_append.push(other)
547 } else {
548 let tree_to_append = child_trees
549 .last_mut()
550 .unwrap()
551 .push_tree_recursive(other, cx);
552 *child_summaries.last_mut().unwrap() =
553 child_trees.last().unwrap().0.summary().clone();
554
555 if let Some(split_tree) = tree_to_append {
556 summaries_to_append.push(split_tree.0.summary().clone());
557 trees_to_append.push(split_tree);
558 }
559 }
560
561 let child_count = child_trees.len() + trees_to_append.len();
562 if child_count > 2 * TREE_BASE {
563 let left_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
564 let right_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
565 let left_trees;
566 let right_trees;
567
568 let midpoint = (child_count + child_count % 2) / 2;
569 {
570 let mut all_summaries = child_summaries
571 .iter()
572 .chain(summaries_to_append.iter())
573 .cloned();
574 left_summaries = all_summaries.by_ref().take(midpoint).collect();
575 right_summaries = all_summaries.collect();
576 let mut all_trees =
577 child_trees.iter().chain(trees_to_append.iter()).cloned();
578 left_trees = all_trees.by_ref().take(midpoint).collect();
579 right_trees = all_trees.collect();
580 }
581 *summary = sum(left_summaries.iter(), cx);
582 *child_summaries = left_summaries;
583 *child_trees = left_trees;
584
585 Some(SumTree(Arc::new(Node::Internal {
586 height: *height,
587 summary: sum(right_summaries.iter(), cx),
588 child_summaries: right_summaries,
589 child_trees: right_trees,
590 })))
591 } else {
592 child_summaries.extend(summaries_to_append);
593 child_trees.extend(trees_to_append);
594 None
595 }
596 }
597 Node::Leaf {
598 summary,
599 items,
600 item_summaries,
601 } => {
602 let other_node = other.0;
603
604 let child_count = items.len() + other_node.items().len();
605 if child_count > 2 * TREE_BASE {
606 let left_items;
607 let right_items;
608 let left_summaries;
609 let right_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>;
610
611 let midpoint = (child_count + child_count % 2) / 2;
612 {
613 let mut all_items = items.iter().chain(other_node.items().iter()).cloned();
614 left_items = all_items.by_ref().take(midpoint).collect();
615 right_items = all_items.collect();
616
617 let mut all_summaries = item_summaries
618 .iter()
619 .chain(other_node.child_summaries())
620 .cloned();
621 left_summaries = all_summaries.by_ref().take(midpoint).collect();
622 right_summaries = all_summaries.collect();
623 }
624 *items = left_items;
625 *item_summaries = left_summaries;
626 *summary = sum(item_summaries.iter(), cx);
627 Some(SumTree(Arc::new(Node::Leaf {
628 items: right_items,
629 summary: sum(right_summaries.iter(), cx),
630 item_summaries: right_summaries,
631 })))
632 } else {
633 <T::Summary as Summary>::add_summary(summary, other_node.summary(), cx);
634 items.extend(other_node.items().iter().cloned());
635 item_summaries.extend(other_node.child_summaries().iter().cloned());
636 None
637 }
638 }
639 }
640 }
641
642 fn from_child_trees(
643 left: SumTree<T>,
644 right: SumTree<T>,
645 cx: <T::Summary as Summary>::Context<'_>,
646 ) -> Self {
647 let height = left.0.height() + 1;
648 let mut child_summaries = ArrayVec::new();
649 child_summaries.push(left.0.summary().clone());
650 child_summaries.push(right.0.summary().clone());
651 let mut child_trees = ArrayVec::new();
652 child_trees.push(left);
653 child_trees.push(right);
654 SumTree(Arc::new(Node::Internal {
655 height,
656 summary: sum(child_summaries.iter(), cx),
657 child_summaries,
658 child_trees,
659 }))
660 }
661
662 fn leftmost_leaf(&self) -> &Self {
663 match *self.0 {
664 Node::Leaf { .. } => self,
665 Node::Internal {
666 ref child_trees, ..
667 } => child_trees.first().unwrap().leftmost_leaf(),
668 }
669 }
670
671 fn rightmost_leaf(&self) -> &Self {
672 match *self.0 {
673 Node::Leaf { .. } => self,
674 Node::Internal {
675 ref child_trees, ..
676 } => child_trees.last().unwrap().rightmost_leaf(),
677 }
678 }
679}
680
681impl<T: Item + PartialEq> PartialEq for SumTree<T> {
682 fn eq(&self, other: &Self) -> bool {
683 self.iter().eq(other.iter())
684 }
685}
686
687impl<T: Item + Eq> Eq for SumTree<T> {}
688
689impl<T: KeyedItem> SumTree<T> {
690 pub fn insert_or_replace<'a, 'b>(
691 &'a mut self,
692 item: T,
693 cx: <T::Summary as Summary>::Context<'b>,
694 ) -> Option<T> {
695 let mut replaced = None;
696 {
697 let mut cursor = self.cursor::<T::Key>(cx);
698 let mut new_tree = cursor.slice(&item.key(), Bias::Left);
699 if let Some(cursor_item) = cursor.item()
700 && cursor_item.key() == item.key()
701 {
702 replaced = Some(cursor_item.clone());
703 cursor.next();
704 }
705 new_tree.push(item, cx);
706 new_tree.append(cursor.suffix(), cx);
707 drop(cursor);
708 *self = new_tree
709 };
710 replaced
711 }
712
713 pub fn remove(&mut self, key: &T::Key, cx: <T::Summary as Summary>::Context<'_>) -> Option<T> {
714 let mut removed = None;
715 *self = {
716 let mut cursor = self.cursor::<T::Key>(cx);
717 let mut new_tree = cursor.slice(key, Bias::Left);
718 if let Some(item) = cursor.item()
719 && item.key() == *key
720 {
721 removed = Some(item.clone());
722 cursor.next();
723 }
724 new_tree.append(cursor.suffix(), cx);
725 new_tree
726 };
727 removed
728 }
729
730 pub fn edit(
731 &mut self,
732 mut edits: Vec<Edit<T>>,
733 cx: <T::Summary as Summary>::Context<'_>,
734 ) -> Vec<T> {
735 if edits.is_empty() {
736 return Vec::new();
737 }
738
739 let mut removed = Vec::new();
740 edits.sort_unstable_by_key(|item| item.key());
741
742 *self = {
743 let mut cursor = self.cursor::<T::Key>(cx);
744 let mut new_tree = SumTree::new(cx);
745 let mut buffered_items = Vec::new();
746
747 cursor.seek(&T::Key::zero(cx), Bias::Left);
748 for edit in edits {
749 let new_key = edit.key();
750 let mut old_item = cursor.item();
751
752 if old_item
753 .as_ref()
754 .is_some_and(|old_item| old_item.key() < new_key)
755 {
756 new_tree.extend(buffered_items.drain(..), cx);
757 let slice = cursor.slice(&new_key, Bias::Left);
758 new_tree.append(slice, cx);
759 old_item = cursor.item();
760 }
761
762 if let Some(old_item) = old_item
763 && old_item.key() == new_key
764 {
765 removed.push(old_item.clone());
766 cursor.next();
767 }
768
769 match edit {
770 Edit::Insert(item) => {
771 buffered_items.push(item);
772 }
773 Edit::Remove(_) => {}
774 }
775 }
776
777 new_tree.extend(buffered_items, cx);
778 new_tree.append(cursor.suffix(), cx);
779 new_tree
780 };
781
782 removed
783 }
784
785 pub fn get<'a>(
786 &'a self,
787 key: &T::Key,
788 cx: <T::Summary as Summary>::Context<'a>,
789 ) -> Option<&'a T> {
790 let mut cursor = self.cursor::<T::Key>(cx);
791 if cursor.seek(key, Bias::Left) {
792 cursor.item()
793 } else {
794 None
795 }
796 }
797}
798
799impl<T, S> Default for SumTree<T>
800where
801 T: Item<Summary = S>,
802 S: for<'a> Summary<Context<'a> = ()>,
803{
804 fn default() -> Self {
805 Self::new(())
806 }
807}
808
809#[derive(Clone)]
810pub enum Node<T: Item> {
811 Internal {
812 height: u8,
813 summary: T::Summary,
814 child_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
815 child_trees: ArrayVec<SumTree<T>, { 2 * TREE_BASE }>,
816 },
817 Leaf {
818 summary: T::Summary,
819 items: ArrayVec<T, { 2 * TREE_BASE }>,
820 item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
821 },
822}
823
824impl<T> fmt::Debug for Node<T>
825where
826 T: Item + fmt::Debug,
827 T::Summary: fmt::Debug,
828{
829 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
830 match self {
831 Node::Internal {
832 height,
833 summary,
834 child_summaries,
835 child_trees,
836 } => f
837 .debug_struct("Internal")
838 .field("height", height)
839 .field("summary", summary)
840 .field("child_summaries", child_summaries)
841 .field("child_trees", child_trees)
842 .finish(),
843 Node::Leaf {
844 summary,
845 items,
846 item_summaries,
847 } => f
848 .debug_struct("Leaf")
849 .field("summary", summary)
850 .field("items", items)
851 .field("item_summaries", item_summaries)
852 .finish(),
853 }
854 }
855}
856
857impl<T: Item> Node<T> {
858 const fn is_leaf(&self) -> bool {
859 matches!(self, Node::Leaf { .. })
860 }
861
862 const fn height(&self) -> u8 {
863 match self {
864 Node::Internal { height, .. } => *height,
865 Node::Leaf { .. } => 0,
866 }
867 }
868
869 const fn summary(&self) -> &T::Summary {
870 match self {
871 Node::Internal { summary, .. } => summary,
872 Node::Leaf { summary, .. } => summary,
873 }
874 }
875
876 fn child_summaries(&self) -> &[T::Summary] {
877 match self {
878 Node::Internal {
879 child_summaries, ..
880 } => child_summaries.as_slice(),
881 Node::Leaf { item_summaries, .. } => item_summaries.as_slice(),
882 }
883 }
884
885 fn child_trees(&self) -> &ArrayVec<SumTree<T>, { 2 * TREE_BASE }> {
886 match self {
887 Node::Internal { child_trees, .. } => child_trees,
888 Node::Leaf { .. } => panic!("Leaf nodes have no child trees"),
889 }
890 }
891
892 fn items(&self) -> &ArrayVec<T, { 2 * TREE_BASE }> {
893 match self {
894 Node::Leaf { items, .. } => items,
895 Node::Internal { .. } => panic!("Internal nodes have no items"),
896 }
897 }
898
899 const fn is_underflowing(&self) -> bool {
900 match self {
901 Node::Internal { child_trees, .. } => child_trees.len() < TREE_BASE,
902 Node::Leaf { items, .. } => items.len() < TREE_BASE,
903 }
904 }
905}
906
907#[derive(Debug)]
908pub enum Edit<T: KeyedItem> {
909 Insert(T),
910 Remove(T::Key),
911}
912
913impl<T: KeyedItem> Edit<T> {
914 fn key(&self) -> T::Key {
915 match self {
916 Edit::Insert(item) => item.key(),
917 Edit::Remove(key) => key.clone(),
918 }
919 }
920}
921
922fn sum<'a, T, I>(iter: I, cx: T::Context<'_>) -> T
923where
924 T: 'a + Summary,
925 I: Iterator<Item = &'a T>,
926{
927 let mut sum = T::zero(cx);
928 for value in iter {
929 sum.add_summary(value, cx);
930 }
931 sum
932}
933
934#[cfg(test)]
935mod tests {
936 use super::*;
937 use rand::{distr::StandardUniform, prelude::*};
938 use std::cmp;
939
940 #[ctor::ctor]
941 fn init_logger() {
942 zlog::init_test();
943 }
944
945 #[test]
946 fn test_extend_and_push_tree() {
947 let mut tree1 = SumTree::default();
948 tree1.extend(0..20, ());
949
950 let mut tree2 = SumTree::default();
951 tree2.extend(50..100, ());
952
953 tree1.append(tree2, ());
954 assert_eq!(tree1.items(()), (0..20).chain(50..100).collect::<Vec<u8>>());
955 }
956
957 #[test]
958 fn test_random() {
959 let mut starting_seed = 0;
960 if let Ok(value) = std::env::var("SEED") {
961 starting_seed = value.parse().expect("invalid SEED variable");
962 }
963 let mut num_iterations = 100;
964 if let Ok(value) = std::env::var("ITERATIONS") {
965 num_iterations = value.parse().expect("invalid ITERATIONS variable");
966 }
967 let num_operations = std::env::var("OPERATIONS")
968 .map_or(5, |o| o.parse().expect("invalid OPERATIONS variable"));
969
970 for seed in starting_seed..(starting_seed + num_iterations) {
971 eprintln!("seed = {}", seed);
972 let mut rng = StdRng::seed_from_u64(seed);
973
974 let rng = &mut rng;
975 let mut tree = SumTree::<u8>::default();
976 let count = rng.random_range(0..10);
977 if rng.random() {
978 tree.extend(rng.sample_iter(StandardUniform).take(count), ());
979 } else {
980 let items = rng
981 .sample_iter(StandardUniform)
982 .take(count)
983 .collect::<Vec<_>>();
984 tree.par_extend(items, ());
985 }
986
987 for _ in 0..num_operations {
988 let splice_end = rng.random_range(0..tree.extent::<Count>(()).0 + 1);
989 let splice_start = rng.random_range(0..splice_end + 1);
990 let count = rng.random_range(0..10);
991 let tree_end = tree.extent::<Count>(());
992 let new_items = rng
993 .sample_iter(StandardUniform)
994 .take(count)
995 .collect::<Vec<u8>>();
996
997 let mut reference_items = tree.items(());
998 reference_items.splice(splice_start..splice_end, new_items.clone());
999
1000 tree = {
1001 let mut cursor = tree.cursor::<Count>(());
1002 let mut new_tree = cursor.slice(&Count(splice_start), Bias::Right);
1003 if rng.random() {
1004 new_tree.extend(new_items, ());
1005 } else {
1006 new_tree.par_extend(new_items, ());
1007 }
1008 cursor.seek(&Count(splice_end), Bias::Right);
1009 new_tree.append(cursor.slice(&tree_end, Bias::Right), ());
1010 new_tree
1011 };
1012
1013 assert_eq!(tree.items(()), reference_items);
1014 assert_eq!(
1015 tree.iter().collect::<Vec<_>>(),
1016 tree.cursor::<()>(()).collect::<Vec<_>>()
1017 );
1018
1019 log::info!("tree items: {:?}", tree.items(()));
1020
1021 let mut filter_cursor =
1022 tree.filter::<_, Count>((), |summary| summary.contains_even);
1023 let expected_filtered_items = tree
1024 .items(())
1025 .into_iter()
1026 .enumerate()
1027 .filter(|(_, item)| (item & 1) == 0)
1028 .collect::<Vec<_>>();
1029
1030 let mut item_ix = if rng.random() {
1031 filter_cursor.next();
1032 0
1033 } else {
1034 filter_cursor.prev();
1035 expected_filtered_items.len().saturating_sub(1)
1036 };
1037 while item_ix < expected_filtered_items.len() {
1038 log::info!("filter_cursor, item_ix: {}", item_ix);
1039 let actual_item = filter_cursor.item().unwrap();
1040 let (reference_index, reference_item) = expected_filtered_items[item_ix];
1041 assert_eq!(actual_item, &reference_item);
1042 assert_eq!(filter_cursor.start().0, reference_index);
1043 log::info!("next");
1044 filter_cursor.next();
1045 item_ix += 1;
1046
1047 while item_ix > 0 && rng.random_bool(0.2) {
1048 log::info!("prev");
1049 filter_cursor.prev();
1050 item_ix -= 1;
1051
1052 if item_ix == 0 && rng.random_bool(0.2) {
1053 filter_cursor.prev();
1054 assert_eq!(filter_cursor.item(), None);
1055 assert_eq!(filter_cursor.start().0, 0);
1056 filter_cursor.next();
1057 }
1058 }
1059 }
1060 assert_eq!(filter_cursor.item(), None);
1061
1062 let mut before_start = false;
1063 let mut cursor = tree.cursor::<Count>(());
1064 let start_pos = rng.random_range(0..=reference_items.len());
1065 cursor.seek(&Count(start_pos), Bias::Right);
1066 let mut pos = rng.random_range(start_pos..=reference_items.len());
1067 cursor.seek_forward(&Count(pos), Bias::Right);
1068
1069 for i in 0..10 {
1070 assert_eq!(cursor.start().0, pos);
1071
1072 if pos > 0 {
1073 assert_eq!(cursor.prev_item().unwrap(), &reference_items[pos - 1]);
1074 } else {
1075 assert_eq!(cursor.prev_item(), None);
1076 }
1077
1078 if pos < reference_items.len() && !before_start {
1079 assert_eq!(cursor.item().unwrap(), &reference_items[pos]);
1080 } else {
1081 assert_eq!(cursor.item(), None);
1082 }
1083
1084 if before_start {
1085 assert_eq!(cursor.next_item(), reference_items.first());
1086 } else if pos + 1 < reference_items.len() {
1087 assert_eq!(cursor.next_item().unwrap(), &reference_items[pos + 1]);
1088 } else {
1089 assert_eq!(cursor.next_item(), None);
1090 }
1091
1092 if i < 5 {
1093 cursor.next();
1094 if pos < reference_items.len() {
1095 pos += 1;
1096 before_start = false;
1097 }
1098 } else {
1099 cursor.prev();
1100 if pos == 0 {
1101 before_start = true;
1102 }
1103 pos = pos.saturating_sub(1);
1104 }
1105 }
1106 }
1107
1108 for _ in 0..10 {
1109 let end = rng.random_range(0..tree.extent::<Count>(()).0 + 1);
1110 let start = rng.random_range(0..end + 1);
1111 let start_bias = if rng.random() {
1112 Bias::Left
1113 } else {
1114 Bias::Right
1115 };
1116 let end_bias = if rng.random() {
1117 Bias::Left
1118 } else {
1119 Bias::Right
1120 };
1121
1122 let mut cursor = tree.cursor::<Count>(());
1123 cursor.seek(&Count(start), start_bias);
1124 let slice = cursor.slice(&Count(end), end_bias);
1125
1126 cursor.seek(&Count(start), start_bias);
1127 let summary = cursor.summary::<_, Sum>(&Count(end), end_bias);
1128
1129 assert_eq!(summary.0, slice.summary().sum);
1130 }
1131 }
1132 }
1133
1134 #[test]
1135 fn test_cursor() {
1136 // Empty tree
1137 let tree = SumTree::<u8>::default();
1138 let mut cursor = tree.cursor::<IntegersSummary>(());
1139 assert_eq!(
1140 cursor.slice(&Count(0), Bias::Right).items(()),
1141 Vec::<u8>::new()
1142 );
1143 assert_eq!(cursor.item(), None);
1144 assert_eq!(cursor.prev_item(), None);
1145 assert_eq!(cursor.next_item(), None);
1146 assert_eq!(cursor.start().sum, 0);
1147 cursor.prev();
1148 assert_eq!(cursor.item(), None);
1149 assert_eq!(cursor.prev_item(), None);
1150 assert_eq!(cursor.next_item(), None);
1151 assert_eq!(cursor.start().sum, 0);
1152 cursor.next();
1153 assert_eq!(cursor.item(), None);
1154 assert_eq!(cursor.prev_item(), None);
1155 assert_eq!(cursor.next_item(), None);
1156 assert_eq!(cursor.start().sum, 0);
1157
1158 // Single-element tree
1159 let mut tree = SumTree::<u8>::default();
1160 tree.extend(vec![1], ());
1161 let mut cursor = tree.cursor::<IntegersSummary>(());
1162 assert_eq!(
1163 cursor.slice(&Count(0), Bias::Right).items(()),
1164 Vec::<u8>::new()
1165 );
1166 assert_eq!(cursor.item(), Some(&1));
1167 assert_eq!(cursor.prev_item(), None);
1168 assert_eq!(cursor.next_item(), None);
1169 assert_eq!(cursor.start().sum, 0);
1170
1171 cursor.next();
1172 assert_eq!(cursor.item(), None);
1173 assert_eq!(cursor.prev_item(), Some(&1));
1174 assert_eq!(cursor.next_item(), None);
1175 assert_eq!(cursor.start().sum, 1);
1176
1177 cursor.prev();
1178 assert_eq!(cursor.item(), Some(&1));
1179 assert_eq!(cursor.prev_item(), None);
1180 assert_eq!(cursor.next_item(), None);
1181 assert_eq!(cursor.start().sum, 0);
1182
1183 let mut cursor = tree.cursor::<IntegersSummary>(());
1184 assert_eq!(cursor.slice(&Count(1), Bias::Right).items(()), [1]);
1185 assert_eq!(cursor.item(), None);
1186 assert_eq!(cursor.prev_item(), Some(&1));
1187 assert_eq!(cursor.next_item(), None);
1188 assert_eq!(cursor.start().sum, 1);
1189
1190 cursor.seek(&Count(0), Bias::Right);
1191 assert_eq!(
1192 cursor
1193 .slice(&tree.extent::<Count>(()), Bias::Right)
1194 .items(()),
1195 [1]
1196 );
1197 assert_eq!(cursor.item(), None);
1198 assert_eq!(cursor.prev_item(), Some(&1));
1199 assert_eq!(cursor.next_item(), None);
1200 assert_eq!(cursor.start().sum, 1);
1201
1202 // Multiple-element tree
1203 let mut tree = SumTree::default();
1204 tree.extend(vec![1, 2, 3, 4, 5, 6], ());
1205 let mut cursor = tree.cursor::<IntegersSummary>(());
1206
1207 assert_eq!(cursor.slice(&Count(2), Bias::Right).items(()), [1, 2]);
1208 assert_eq!(cursor.item(), Some(&3));
1209 assert_eq!(cursor.prev_item(), Some(&2));
1210 assert_eq!(cursor.next_item(), Some(&4));
1211 assert_eq!(cursor.start().sum, 3);
1212
1213 cursor.next();
1214 assert_eq!(cursor.item(), Some(&4));
1215 assert_eq!(cursor.prev_item(), Some(&3));
1216 assert_eq!(cursor.next_item(), Some(&5));
1217 assert_eq!(cursor.start().sum, 6);
1218
1219 cursor.next();
1220 assert_eq!(cursor.item(), Some(&5));
1221 assert_eq!(cursor.prev_item(), Some(&4));
1222 assert_eq!(cursor.next_item(), Some(&6));
1223 assert_eq!(cursor.start().sum, 10);
1224
1225 cursor.next();
1226 assert_eq!(cursor.item(), Some(&6));
1227 assert_eq!(cursor.prev_item(), Some(&5));
1228 assert_eq!(cursor.next_item(), None);
1229 assert_eq!(cursor.start().sum, 15);
1230
1231 cursor.next();
1232 cursor.next();
1233 assert_eq!(cursor.item(), None);
1234 assert_eq!(cursor.prev_item(), Some(&6));
1235 assert_eq!(cursor.next_item(), None);
1236 assert_eq!(cursor.start().sum, 21);
1237
1238 cursor.prev();
1239 assert_eq!(cursor.item(), Some(&6));
1240 assert_eq!(cursor.prev_item(), Some(&5));
1241 assert_eq!(cursor.next_item(), None);
1242 assert_eq!(cursor.start().sum, 15);
1243
1244 cursor.prev();
1245 assert_eq!(cursor.item(), Some(&5));
1246 assert_eq!(cursor.prev_item(), Some(&4));
1247 assert_eq!(cursor.next_item(), Some(&6));
1248 assert_eq!(cursor.start().sum, 10);
1249
1250 cursor.prev();
1251 assert_eq!(cursor.item(), Some(&4));
1252 assert_eq!(cursor.prev_item(), Some(&3));
1253 assert_eq!(cursor.next_item(), Some(&5));
1254 assert_eq!(cursor.start().sum, 6);
1255
1256 cursor.prev();
1257 assert_eq!(cursor.item(), Some(&3));
1258 assert_eq!(cursor.prev_item(), Some(&2));
1259 assert_eq!(cursor.next_item(), Some(&4));
1260 assert_eq!(cursor.start().sum, 3);
1261
1262 cursor.prev();
1263 assert_eq!(cursor.item(), Some(&2));
1264 assert_eq!(cursor.prev_item(), Some(&1));
1265 assert_eq!(cursor.next_item(), Some(&3));
1266 assert_eq!(cursor.start().sum, 1);
1267
1268 cursor.prev();
1269 assert_eq!(cursor.item(), Some(&1));
1270 assert_eq!(cursor.prev_item(), None);
1271 assert_eq!(cursor.next_item(), Some(&2));
1272 assert_eq!(cursor.start().sum, 0);
1273
1274 cursor.prev();
1275 assert_eq!(cursor.item(), None);
1276 assert_eq!(cursor.prev_item(), None);
1277 assert_eq!(cursor.next_item(), Some(&1));
1278 assert_eq!(cursor.start().sum, 0);
1279
1280 cursor.next();
1281 assert_eq!(cursor.item(), Some(&1));
1282 assert_eq!(cursor.prev_item(), None);
1283 assert_eq!(cursor.next_item(), Some(&2));
1284 assert_eq!(cursor.start().sum, 0);
1285
1286 let mut cursor = tree.cursor::<IntegersSummary>(());
1287 assert_eq!(
1288 cursor
1289 .slice(&tree.extent::<Count>(()), Bias::Right)
1290 .items(()),
1291 tree.items(())
1292 );
1293 assert_eq!(cursor.item(), None);
1294 assert_eq!(cursor.prev_item(), Some(&6));
1295 assert_eq!(cursor.next_item(), None);
1296 assert_eq!(cursor.start().sum, 21);
1297
1298 cursor.seek(&Count(3), Bias::Right);
1299 assert_eq!(
1300 cursor
1301 .slice(&tree.extent::<Count>(()), Bias::Right)
1302 .items(()),
1303 [4, 5, 6]
1304 );
1305 assert_eq!(cursor.item(), None);
1306 assert_eq!(cursor.prev_item(), Some(&6));
1307 assert_eq!(cursor.next_item(), None);
1308 assert_eq!(cursor.start().sum, 21);
1309
1310 // Seeking can bias left or right
1311 cursor.seek(&Count(1), Bias::Left);
1312 assert_eq!(cursor.item(), Some(&1));
1313 cursor.seek(&Count(1), Bias::Right);
1314 assert_eq!(cursor.item(), Some(&2));
1315
1316 // Slicing without resetting starts from where the cursor is parked at.
1317 cursor.seek(&Count(1), Bias::Right);
1318 assert_eq!(cursor.slice(&Count(3), Bias::Right).items(()), vec![2, 3]);
1319 assert_eq!(cursor.slice(&Count(6), Bias::Left).items(()), vec![4, 5]);
1320 assert_eq!(cursor.slice(&Count(6), Bias::Right).items(()), vec![6]);
1321 }
1322
1323 #[test]
1324 fn test_edit() {
1325 let mut tree = SumTree::<u8>::default();
1326
1327 let removed = tree.edit(vec![Edit::Insert(1), Edit::Insert(2), Edit::Insert(0)], ());
1328 assert_eq!(tree.items(()), vec![0, 1, 2]);
1329 assert_eq!(removed, Vec::<u8>::new());
1330 assert_eq!(tree.get(&0, ()), Some(&0));
1331 assert_eq!(tree.get(&1, ()), Some(&1));
1332 assert_eq!(tree.get(&2, ()), Some(&2));
1333 assert_eq!(tree.get(&4, ()), None);
1334
1335 let removed = tree.edit(vec![Edit::Insert(2), Edit::Insert(4), Edit::Remove(0)], ());
1336 assert_eq!(tree.items(()), vec![1, 2, 4]);
1337 assert_eq!(removed, vec![0, 2]);
1338 assert_eq!(tree.get(&0, ()), None);
1339 assert_eq!(tree.get(&1, ()), Some(&1));
1340 assert_eq!(tree.get(&2, ()), Some(&2));
1341 assert_eq!(tree.get(&4, ()), Some(&4));
1342 }
1343
1344 #[test]
1345 fn test_from_iter() {
1346 assert_eq!(
1347 SumTree::from_iter(0..100, ()).items(()),
1348 (0..100).collect::<Vec<_>>()
1349 );
1350
1351 // Ensure `from_iter` works correctly when the given iterator restarts
1352 // after calling `next` if `None` was already returned.
1353 let mut ix = 0;
1354 let iterator = std::iter::from_fn(|| {
1355 ix = (ix + 1) % 2;
1356 if ix == 1 { Some(1) } else { None }
1357 });
1358 assert_eq!(SumTree::from_iter(iterator, ()).items(()), vec![1]);
1359 }
1360
1361 #[derive(Clone, Default, Debug)]
1362 pub struct IntegersSummary {
1363 count: usize,
1364 sum: usize,
1365 contains_even: bool,
1366 max: u8,
1367 }
1368
1369 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
1370 struct Count(usize);
1371
1372 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
1373 struct Sum(usize);
1374
1375 impl Item for u8 {
1376 type Summary = IntegersSummary;
1377
1378 fn summary(&self, _cx: ()) -> Self::Summary {
1379 IntegersSummary {
1380 count: 1,
1381 sum: *self as usize,
1382 contains_even: (*self & 1) == 0,
1383 max: *self,
1384 }
1385 }
1386 }
1387
1388 impl KeyedItem for u8 {
1389 type Key = u8;
1390
1391 fn key(&self) -> Self::Key {
1392 *self
1393 }
1394 }
1395
1396 impl ContextLessSummary for IntegersSummary {
1397 fn zero() -> Self {
1398 Default::default()
1399 }
1400
1401 fn add_summary(&mut self, other: &Self) {
1402 self.count += other.count;
1403 self.sum += other.sum;
1404 self.contains_even |= other.contains_even;
1405 self.max = cmp::max(self.max, other.max);
1406 }
1407 }
1408
1409 impl Dimension<'_, IntegersSummary> for u8 {
1410 fn zero(_cx: ()) -> Self {
1411 Default::default()
1412 }
1413
1414 fn add_summary(&mut self, summary: &IntegersSummary, _: ()) {
1415 *self = summary.max;
1416 }
1417 }
1418
1419 impl Dimension<'_, IntegersSummary> for Count {
1420 fn zero(_cx: ()) -> Self {
1421 Default::default()
1422 }
1423
1424 fn add_summary(&mut self, summary: &IntegersSummary, _: ()) {
1425 self.0 += summary.count;
1426 }
1427 }
1428
1429 impl SeekTarget<'_, IntegersSummary, IntegersSummary> for Count {
1430 fn cmp(&self, cursor_location: &IntegersSummary, _: ()) -> Ordering {
1431 self.0.cmp(&cursor_location.count)
1432 }
1433 }
1434
1435 impl Dimension<'_, IntegersSummary> for Sum {
1436 fn zero(_cx: ()) -> Self {
1437 Default::default()
1438 }
1439
1440 fn add_summary(&mut self, summary: &IntegersSummary, _: ()) {
1441 self.0 += summary.sum;
1442 }
1443 }
1444}