1mod cursor;
2mod tree_map;
3
4use arrayvec::ArrayVec;
5pub use cursor::{Cursor, FilterCursor, Iter};
6use rayon::iter::{IndexedParallelIterator, IntoParallelIterator, ParallelIterator as _};
7use std::marker::PhantomData;
8use std::mem;
9use std::{cmp::Ordering, fmt, iter::FromIterator, sync::Arc};
10pub use tree_map::{MapSeekTarget, TreeMap, TreeSet};
11use ztracing::instrument;
12
13#[cfg(test)]
14pub const TREE_BASE: usize = 2;
15#[cfg(not(test))]
16pub const TREE_BASE: usize = 6;
17
18/// An item that can be stored in a [`SumTree`]
19///
20/// Must be summarized by a type that implements [`Summary`]
21pub trait Item: Clone {
22 type Summary: Summary;
23
24 fn summary(&self, cx: <Self::Summary as Summary>::Context<'_>) -> Self::Summary;
25}
26
27/// An [`Item`] whose summary has a specific key that can be used to identify it
28pub trait KeyedItem: Item {
29 type Key: for<'a> Dimension<'a, Self::Summary> + Ord;
30
31 fn key(&self) -> Self::Key;
32}
33
34/// A type that describes the Sum of all [`Item`]s in a subtree of the [`SumTree`]
35///
36/// Each Summary type can have multiple [`Dimension`]s that it measures,
37/// which can be used to navigate the tree
38pub trait Summary: Clone {
39 type Context<'a>: Copy;
40 fn zero<'a>(cx: Self::Context<'a>) -> Self;
41 fn add_summary<'a>(&mut self, summary: &Self, cx: Self::Context<'a>);
42}
43
44pub trait ContextLessSummary: Clone {
45 fn zero() -> Self;
46 fn add_summary(&mut self, summary: &Self);
47}
48
49impl<T: ContextLessSummary> Summary for T {
50 type Context<'a> = ();
51
52 fn zero<'a>((): ()) -> Self {
53 T::zero()
54 }
55
56 fn add_summary<'a>(&mut self, summary: &Self, (): ()) {
57 T::add_summary(self, summary)
58 }
59}
60
61#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
62pub struct NoSummary;
63
64/// Catch-all implementation for when you need something that implements [`Summary`] without a specific type.
65/// We implement it on a `NoSummary` instead of re-using `()`, as that avoids blanket impl collisions with `impl<T: Summary> Dimension for T`
66/// (as we also need unit type to be a fill-in dimension)
67impl ContextLessSummary for NoSummary {
68 fn zero() -> Self {
69 NoSummary
70 }
71
72 fn add_summary(&mut self, _: &Self) {}
73}
74
75/// Each [`Summary`] type can have more than one [`Dimension`] type that it measures.
76///
77/// You can use dimensions to seek to a specific location in the [`SumTree`]
78///
79/// # Example:
80/// Zed's rope has a `TextSummary` type that summarizes lines, characters, and bytes.
81/// Each of these are different dimensions we may want to seek to
82pub trait Dimension<'a, S: Summary>: Clone {
83 fn zero(cx: S::Context<'_>) -> Self;
84
85 fn add_summary(&mut self, summary: &'a S, cx: S::Context<'_>);
86 #[must_use]
87 fn with_added_summary(mut self, summary: &'a S, cx: S::Context<'_>) -> Self {
88 self.add_summary(summary, cx);
89 self
90 }
91
92 fn from_summary(summary: &'a S, cx: S::Context<'_>) -> Self {
93 let mut dimension = Self::zero(cx);
94 dimension.add_summary(summary, cx);
95 dimension
96 }
97}
98
99impl<'a, T: Summary> Dimension<'a, T> for T {
100 fn zero(cx: T::Context<'_>) -> Self {
101 Summary::zero(cx)
102 }
103
104 fn add_summary(&mut self, summary: &'a T, cx: T::Context<'_>) {
105 Summary::add_summary(self, summary, cx);
106 }
107}
108
109pub trait SeekTarget<'a, S: Summary, D: Dimension<'a, S>> {
110 fn cmp(&self, cursor_location: &D, cx: S::Context<'_>) -> Ordering;
111}
112
113impl<'a, S: Summary, D: Dimension<'a, S> + Ord> SeekTarget<'a, S, D> for D {
114 fn cmp(&self, cursor_location: &Self, _: S::Context<'_>) -> Ordering {
115 Ord::cmp(self, cursor_location)
116 }
117}
118
119impl<'a, T: Summary> Dimension<'a, T> for () {
120 fn zero(_: T::Context<'_>) -> Self {}
121
122 fn add_summary(&mut self, _: &'a T, _: T::Context<'_>) {}
123}
124
125#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
126pub struct Dimensions<D1, D2, D3 = ()>(pub D1, pub D2, pub D3);
127
128impl<'a, T: Summary, D1: Dimension<'a, T>, D2: Dimension<'a, T>, D3: Dimension<'a, T>>
129 Dimension<'a, T> for Dimensions<D1, D2, D3>
130{
131 fn zero(cx: T::Context<'_>) -> Self {
132 Dimensions(D1::zero(cx), D2::zero(cx), D3::zero(cx))
133 }
134
135 fn add_summary(&mut self, summary: &'a T, cx: T::Context<'_>) {
136 self.0.add_summary(summary, cx);
137 self.1.add_summary(summary, cx);
138 self.2.add_summary(summary, cx);
139 }
140}
141
142impl<'a, S, D1, D2, D3> SeekTarget<'a, S, Dimensions<D1, D2, D3>> for D1
143where
144 S: Summary,
145 D1: SeekTarget<'a, S, D1> + Dimension<'a, S>,
146 D2: Dimension<'a, S>,
147 D3: Dimension<'a, S>,
148{
149 fn cmp(&self, cursor_location: &Dimensions<D1, D2, D3>, cx: S::Context<'_>) -> Ordering {
150 self.cmp(&cursor_location.0, cx)
151 }
152}
153
154/// Bias is used to settle ambiguities when determining positions in an ordered sequence.
155///
156/// The primary use case is for text, where Bias influences
157/// which character an offset or anchor is associated with.
158///
159/// # Examples
160/// Given the buffer `AˇBCD`:
161/// - The offset of the cursor is 1
162/// - [Bias::Left] would attach the cursor to the character `A`
163/// - [Bias::Right] would attach the cursor to the character `B`
164///
165/// Given the buffer `A«BCˇ»D`:
166/// - The offset of the cursor is 3, and the selection is from 1 to 3
167/// - The left anchor of the selection has [Bias::Right], attaching it to the character `B`
168/// - The right anchor of the selection has [Bias::Left], attaching it to the character `C`
169///
170/// Given the buffer `{ˇ<...>`, where `<...>` is a folded region:
171/// - The display offset of the cursor is 1, but the offset in the buffer is determined by the bias
172/// - [Bias::Left] would attach the cursor to the character `{`, with a buffer offset of 1
173/// - [Bias::Right] would attach the cursor to the first character of the folded region,
174/// and the buffer offset would be the offset of the first character of the folded region
175#[derive(Copy, Clone, Eq, PartialEq, PartialOrd, Ord, Debug, Hash, Default)]
176pub enum Bias {
177 /// Attach to the character on the left
178 #[default]
179 Left,
180 /// Attach to the character on the right
181 Right,
182}
183
184impl Bias {
185 pub fn invert(self) -> Self {
186 match self {
187 Self::Left => Self::Right,
188 Self::Right => Self::Left,
189 }
190 }
191}
192
193/// A B+ tree in which each leaf node contains `Item`s of type `T` and a `Summary`s for each `Item`.
194/// Each internal node contains a `Summary` of the items in its subtree.
195///
196/// The maximum number of items per node is `TREE_BASE * 2`.
197///
198/// Any [`Dimension`] supported by the [`Summary`] type can be used to seek to a specific location in the tree.
199#[derive(Clone)]
200pub struct SumTree<T: Item>(Arc<Node<T>>);
201
202impl<T> fmt::Debug for SumTree<T>
203where
204 T: fmt::Debug + Item,
205 T::Summary: fmt::Debug,
206{
207 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
208 f.debug_tuple("SumTree").field(&self.0).finish()
209 }
210}
211
212impl<T: Item> SumTree<T> {
213 pub fn new(cx: <T::Summary as Summary>::Context<'_>) -> Self {
214 SumTree(Arc::new(Node::Leaf {
215 summary: <T::Summary as Summary>::zero(cx),
216 items: ArrayVec::new(),
217 item_summaries: ArrayVec::new(),
218 }))
219 }
220
221 /// 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.
222 pub fn from_summary(summary: T::Summary) -> Self {
223 SumTree(Arc::new(Node::Leaf {
224 summary,
225 items: ArrayVec::new(),
226 item_summaries: ArrayVec::new(),
227 }))
228 }
229
230 pub fn from_item(item: T, cx: <T::Summary as Summary>::Context<'_>) -> Self {
231 let mut tree = Self::new(cx);
232 tree.push(item, cx);
233 tree
234 }
235
236 pub fn from_iter<I: IntoIterator<Item = T>>(
237 iter: I,
238 cx: <T::Summary as Summary>::Context<'_>,
239 ) -> Self {
240 let mut nodes = Vec::new();
241
242 let mut iter = iter.into_iter().fuse().peekable();
243 while iter.peek().is_some() {
244 let items: ArrayVec<T, { 2 * TREE_BASE }> = iter.by_ref().take(2 * TREE_BASE).collect();
245 let item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }> =
246 items.iter().map(|item| item.summary(cx)).collect();
247
248 let mut summary = item_summaries[0].clone();
249 for item_summary in &item_summaries[1..] {
250 <T::Summary as Summary>::add_summary(&mut summary, item_summary, cx);
251 }
252
253 nodes.push(SumTree(Arc::new(Node::Leaf {
254 summary,
255 items,
256 item_summaries,
257 })));
258 }
259
260 let mut parent_nodes = Vec::new();
261 let mut height = 0;
262 while nodes.len() > 1 {
263 height += 1;
264 let mut current_parent_node = None;
265 for child_node in nodes.drain(..) {
266 let parent_node = current_parent_node.get_or_insert_with(|| {
267 SumTree(Arc::new(Node::Internal {
268 summary: <T::Summary as Summary>::zero(cx),
269 height,
270 child_summaries: ArrayVec::new(),
271 child_trees: ArrayVec::new(),
272 }))
273 });
274 let Node::Internal {
275 summary,
276 child_summaries,
277 child_trees,
278 ..
279 } = Arc::get_mut(&mut parent_node.0).unwrap()
280 else {
281 unreachable!()
282 };
283 let child_summary = child_node.summary();
284 <T::Summary as Summary>::add_summary(summary, child_summary, cx);
285 child_summaries.push(child_summary.clone());
286 child_trees.push(child_node);
287
288 if child_trees.len() == 2 * TREE_BASE {
289 parent_nodes.extend(current_parent_node.take());
290 }
291 }
292 parent_nodes.extend(current_parent_node.take());
293 mem::swap(&mut nodes, &mut parent_nodes);
294 }
295
296 if nodes.is_empty() {
297 Self::new(cx)
298 } else {
299 debug_assert_eq!(nodes.len(), 1);
300 nodes.pop().unwrap()
301 }
302 }
303
304 pub fn from_par_iter<I, Iter>(iter: I, cx: <T::Summary as Summary>::Context<'_>) -> Self
305 where
306 I: IntoParallelIterator<Iter = Iter>,
307 Iter: IndexedParallelIterator<Item = T>,
308 T: Send + Sync,
309 T::Summary: Send + Sync,
310 for<'a> <T::Summary as Summary>::Context<'a>: Sync,
311 {
312 let mut nodes = iter
313 .into_par_iter()
314 .chunks(2 * TREE_BASE)
315 .map(|items| {
316 let items: ArrayVec<T, { 2 * TREE_BASE }> = items.into_iter().collect();
317 let item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }> =
318 items.iter().map(|item| item.summary(cx)).collect();
319 let mut summary = item_summaries[0].clone();
320 for item_summary in &item_summaries[1..] {
321 <T::Summary as Summary>::add_summary(&mut summary, item_summary, cx);
322 }
323 SumTree(Arc::new(Node::Leaf {
324 summary,
325 items,
326 item_summaries,
327 }))
328 })
329 .collect::<Vec<_>>();
330
331 let mut height = 0;
332 while nodes.len() > 1 {
333 height += 1;
334 nodes = nodes
335 .into_par_iter()
336 .chunks(2 * TREE_BASE)
337 .map(|child_nodes| {
338 let child_trees: ArrayVec<SumTree<T>, { 2 * TREE_BASE }> =
339 child_nodes.into_iter().collect();
340 let child_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }> = child_trees
341 .iter()
342 .map(|child_tree| child_tree.summary().clone())
343 .collect();
344 let mut summary = child_summaries[0].clone();
345 for child_summary in &child_summaries[1..] {
346 <T::Summary as Summary>::add_summary(&mut summary, child_summary, cx);
347 }
348 SumTree(Arc::new(Node::Internal {
349 height,
350 summary,
351 child_summaries,
352 child_trees,
353 }))
354 })
355 .collect::<Vec<_>>();
356 }
357
358 if nodes.is_empty() {
359 Self::new(cx)
360 } else {
361 debug_assert_eq!(nodes.len(), 1);
362 nodes.pop().unwrap()
363 }
364 }
365
366 #[allow(unused)]
367 pub fn items<'a>(&'a self, cx: <T::Summary as Summary>::Context<'a>) -> Vec<T> {
368 let mut items = Vec::new();
369 let mut cursor = self.cursor::<()>(cx);
370 cursor.next();
371 while let Some(item) = cursor.item() {
372 items.push(item.clone());
373 cursor.next();
374 }
375 items
376 }
377
378 pub fn iter(&self) -> Iter<'_, T> {
379 Iter::new(self)
380 }
381
382 /// A more efficient version of `Cursor::new()` + `Cursor::seek()` + `Cursor::item()`.
383 ///
384 /// Only returns the item that exactly has the target match.
385 #[instrument(skip_all)]
386 pub fn find_exact<'a, 'slf, D, Target>(
387 &'slf self,
388 cx: <T::Summary as Summary>::Context<'a>,
389 target: &Target,
390 bias: Bias,
391 ) -> (D, D, Option<&'slf T>)
392 where
393 D: Dimension<'slf, T::Summary>,
394 Target: SeekTarget<'slf, T::Summary, D>,
395 {
396 let tree_end = D::zero(cx).with_added_summary(self.summary(), cx);
397 let comparison = target.cmp(&tree_end, cx);
398 if comparison == Ordering::Greater || (comparison == Ordering::Equal && bias == Bias::Right)
399 {
400 return (tree_end.clone(), tree_end, None);
401 }
402
403 let mut pos = D::zero(cx);
404 return match Self::find_recurse::<_, _, true>(cx, target, bias, &mut pos, self) {
405 Some((item, end)) => (pos, end, Some(item)),
406 None => (pos.clone(), pos, None),
407 };
408 }
409
410 /// A more efficient version of `Cursor::new()` + `Cursor::seek()` + `Cursor::item()`
411 #[instrument(skip_all)]
412 pub fn find<'a, 'slf, D, Target>(
413 &'slf self,
414 cx: <T::Summary as Summary>::Context<'a>,
415 target: &Target,
416 bias: Bias,
417 ) -> (D, D, Option<&'slf T>)
418 where
419 D: Dimension<'slf, T::Summary>,
420 Target: SeekTarget<'slf, T::Summary, D>,
421 {
422 let tree_end = D::zero(cx).with_added_summary(self.summary(), cx);
423 let comparison = target.cmp(&tree_end, cx);
424 if comparison == Ordering::Greater || (comparison == Ordering::Equal && bias == Bias::Right)
425 {
426 return (tree_end.clone(), tree_end, None);
427 }
428
429 let mut pos = D::zero(cx);
430 return match Self::find_recurse::<_, _, false>(cx, target, bias, &mut pos, self) {
431 Some((item, end)) => (pos, end, Some(item)),
432 None => (pos.clone(), pos, None),
433 };
434 }
435
436 fn find_recurse<'tree, 'a, D, Target, const EXACT: bool>(
437 cx: <T::Summary as Summary>::Context<'a>,
438 target: &Target,
439 bias: Bias,
440 position: &mut D,
441 this: &'tree SumTree<T>,
442 ) -> Option<(&'tree T, D)>
443 where
444 D: Dimension<'tree, T::Summary>,
445 Target: SeekTarget<'tree, T::Summary, D>,
446 {
447 match &*this.0 {
448 Node::Internal {
449 child_summaries,
450 child_trees,
451 ..
452 } => {
453 for (child_tree, child_summary) in child_trees.iter().zip(child_summaries) {
454 let child_end = position.clone().with_added_summary(child_summary, cx);
455
456 let comparison = target.cmp(&child_end, cx);
457 let target_in_child = comparison == Ordering::Less
458 || (comparison == Ordering::Equal && bias == Bias::Left);
459 if target_in_child {
460 return Self::find_recurse::<D, Target, EXACT>(
461 cx, target, bias, position, child_tree,
462 );
463 }
464 *position = child_end;
465 }
466 }
467 Node::Leaf {
468 items,
469 item_summaries,
470 ..
471 } => {
472 for (item, item_summary) in items.iter().zip(item_summaries) {
473 let mut child_end = position.clone();
474 child_end.add_summary(item_summary, cx);
475
476 let comparison = target.cmp(&child_end, cx);
477 let entry_found = if EXACT {
478 comparison == Ordering::Equal
479 } else {
480 comparison == Ordering::Less
481 || (comparison == Ordering::Equal && bias == Bias::Left)
482 };
483 if entry_found {
484 return Some((item, child_end));
485 }
486
487 *position = child_end;
488 }
489 }
490 }
491 None
492 }
493
494 pub fn cursor<'a, 'b, D>(
495 &'a self,
496 cx: <T::Summary as Summary>::Context<'b>,
497 ) -> Cursor<'a, 'b, T, D>
498 where
499 D: Dimension<'a, T::Summary>,
500 {
501 Cursor::new(self, cx)
502 }
503
504 /// Note: If the summary type requires a non `()` context, then the filter cursor
505 /// that is returned cannot be used with Rust's iterators.
506 pub fn filter<'a, 'b, F, U>(
507 &'a self,
508 cx: <T::Summary as Summary>::Context<'b>,
509 filter_node: F,
510 ) -> FilterCursor<'a, 'b, F, T, U>
511 where
512 F: FnMut(&T::Summary) -> bool,
513 U: Dimension<'a, T::Summary>,
514 {
515 FilterCursor::new(self, cx, filter_node)
516 }
517
518 #[allow(dead_code)]
519 pub fn first(&self) -> Option<&T> {
520 self.leftmost_leaf().0.items().first()
521 }
522
523 pub fn last(&self) -> Option<&T> {
524 self.rightmost_leaf().0.items().last()
525 }
526
527 pub fn update_last(
528 &mut self,
529 f: impl FnOnce(&mut T),
530 cx: <T::Summary as Summary>::Context<'_>,
531 ) {
532 self.update_last_recursive(f, cx);
533 }
534
535 fn update_last_recursive(
536 &mut self,
537 f: impl FnOnce(&mut T),
538 cx: <T::Summary as Summary>::Context<'_>,
539 ) -> Option<T::Summary> {
540 match Arc::make_mut(&mut self.0) {
541 Node::Internal {
542 summary,
543 child_summaries,
544 child_trees,
545 ..
546 } => {
547 let last_summary = child_summaries.last_mut().unwrap();
548 let last_child = child_trees.last_mut().unwrap();
549 *last_summary = last_child.update_last_recursive(f, cx).unwrap();
550 *summary = sum(child_summaries.iter(), cx);
551 Some(summary.clone())
552 }
553 Node::Leaf {
554 summary,
555 items,
556 item_summaries,
557 } => {
558 if let Some((item, item_summary)) = items.last_mut().zip(item_summaries.last_mut())
559 {
560 (f)(item);
561 *item_summary = item.summary(cx);
562 *summary = sum(item_summaries.iter(), cx);
563 Some(summary.clone())
564 } else {
565 None
566 }
567 }
568 }
569 }
570
571 pub fn extent<'a, D: Dimension<'a, T::Summary>>(
572 &'a self,
573 cx: <T::Summary as Summary>::Context<'_>,
574 ) -> D {
575 let mut extent = D::zero(cx);
576 match self.0.as_ref() {
577 Node::Internal { summary, .. } | Node::Leaf { summary, .. } => {
578 extent.add_summary(summary, cx);
579 }
580 }
581 extent
582 }
583
584 pub fn summary(&self) -> &T::Summary {
585 match self.0.as_ref() {
586 Node::Internal { summary, .. } => summary,
587 Node::Leaf { summary, .. } => summary,
588 }
589 }
590
591 pub fn is_empty(&self) -> bool {
592 match self.0.as_ref() {
593 Node::Internal { .. } => false,
594 Node::Leaf { items, .. } => items.is_empty(),
595 }
596 }
597
598 pub fn extend<I>(&mut self, iter: I, cx: <T::Summary as Summary>::Context<'_>)
599 where
600 I: IntoIterator<Item = T>,
601 {
602 self.append(Self::from_iter(iter, cx), cx);
603 }
604
605 pub fn par_extend<I, Iter>(&mut self, iter: I, cx: <T::Summary as Summary>::Context<'_>)
606 where
607 I: IntoParallelIterator<Iter = Iter>,
608 Iter: IndexedParallelIterator<Item = T>,
609 T: Send + Sync,
610 T::Summary: Send + Sync,
611 for<'a> <T::Summary as Summary>::Context<'a>: Sync,
612 {
613 self.append(Self::from_par_iter(iter, cx), cx);
614 }
615
616 pub fn push(&mut self, item: T, cx: <T::Summary as Summary>::Context<'_>) {
617 let summary = item.summary(cx);
618 self.append(
619 SumTree(Arc::new(Node::Leaf {
620 summary: summary.clone(),
621 items: ArrayVec::from_iter(Some(item)),
622 item_summaries: ArrayVec::from_iter(Some(summary)),
623 })),
624 cx,
625 );
626 }
627
628 pub fn append(&mut self, mut other: Self, cx: <T::Summary as Summary>::Context<'_>) {
629 if self.is_empty() {
630 *self = other;
631 } else if !other.0.is_leaf() || !other.0.items().is_empty() {
632 if self.0.height() < other.0.height() {
633 if let Some(tree) = Self::append_large(self.clone(), &mut other, cx) {
634 *self = Self::from_child_trees(tree, other, cx);
635 } else {
636 *self = other;
637 }
638 } else if let Some(split_tree) = self.push_tree_recursive(other, cx) {
639 *self = Self::from_child_trees(self.clone(), split_tree, cx);
640 }
641 }
642 }
643
644 fn push_tree_recursive(
645 &mut self,
646 other: SumTree<T>,
647 cx: <T::Summary as Summary>::Context<'_>,
648 ) -> Option<SumTree<T>> {
649 match Arc::make_mut(&mut self.0) {
650 Node::Internal {
651 height,
652 summary,
653 child_summaries,
654 child_trees,
655 ..
656 } => {
657 let other_node = other.0.clone();
658 <T::Summary as Summary>::add_summary(summary, other_node.summary(), cx);
659
660 let height_delta = *height - other_node.height();
661 let mut summaries_to_append = ArrayVec::<T::Summary, { 2 * TREE_BASE }>::new();
662 let mut trees_to_append = ArrayVec::<SumTree<T>, { 2 * TREE_BASE }>::new();
663 if height_delta == 0 {
664 summaries_to_append.extend(other_node.child_summaries().iter().cloned());
665 trees_to_append.extend(other_node.child_trees().iter().cloned());
666 } else if height_delta == 1 && !other_node.is_underflowing() {
667 summaries_to_append.push(other_node.summary().clone());
668 trees_to_append.push(other)
669 } else {
670 let tree_to_append = child_trees
671 .last_mut()
672 .unwrap()
673 .push_tree_recursive(other, cx);
674 *child_summaries.last_mut().unwrap() =
675 child_trees.last().unwrap().0.summary().clone();
676
677 if let Some(split_tree) = tree_to_append {
678 summaries_to_append.push(split_tree.0.summary().clone());
679 trees_to_append.push(split_tree);
680 }
681 }
682
683 let child_count = child_trees.len() + trees_to_append.len();
684 if child_count > 2 * TREE_BASE {
685 let left_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
686 let right_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
687 let left_trees;
688 let right_trees;
689
690 let midpoint = (child_count + child_count % 2) / 2;
691 {
692 let mut all_summaries = child_summaries
693 .iter()
694 .chain(summaries_to_append.iter())
695 .cloned();
696 left_summaries = all_summaries.by_ref().take(midpoint).collect();
697 right_summaries = all_summaries.collect();
698 let mut all_trees =
699 child_trees.iter().chain(trees_to_append.iter()).cloned();
700 left_trees = all_trees.by_ref().take(midpoint).collect();
701 right_trees = all_trees.collect();
702 }
703 *summary = sum(left_summaries.iter(), cx);
704 *child_summaries = left_summaries;
705 *child_trees = left_trees;
706
707 Some(SumTree(Arc::new(Node::Internal {
708 height: *height,
709 summary: sum(right_summaries.iter(), cx),
710 child_summaries: right_summaries,
711 child_trees: right_trees,
712 })))
713 } else {
714 child_summaries.extend(summaries_to_append);
715 child_trees.extend(trees_to_append);
716 None
717 }
718 }
719 Node::Leaf {
720 summary,
721 items,
722 item_summaries,
723 } => {
724 let other_node = other.0;
725
726 let child_count = items.len() + other_node.items().len();
727 if child_count > 2 * TREE_BASE {
728 let left_items;
729 let right_items;
730 let left_summaries;
731 let right_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>;
732
733 let midpoint = (child_count + child_count % 2) / 2;
734 {
735 let mut all_items = items.iter().chain(other_node.items().iter()).cloned();
736 left_items = all_items.by_ref().take(midpoint).collect();
737 right_items = all_items.collect();
738
739 let mut all_summaries = item_summaries
740 .iter()
741 .chain(other_node.child_summaries())
742 .cloned();
743 left_summaries = all_summaries.by_ref().take(midpoint).collect();
744 right_summaries = all_summaries.collect();
745 }
746 *items = left_items;
747 *item_summaries = left_summaries;
748 *summary = sum(item_summaries.iter(), cx);
749 Some(SumTree(Arc::new(Node::Leaf {
750 items: right_items,
751 summary: sum(right_summaries.iter(), cx),
752 item_summaries: right_summaries,
753 })))
754 } else {
755 <T::Summary as Summary>::add_summary(summary, other_node.summary(), cx);
756 items.extend(other_node.items().iter().cloned());
757 item_summaries.extend(other_node.child_summaries().iter().cloned());
758 None
759 }
760 }
761 }
762 }
763
764 // appends the `large` tree to a `small` tree, assumes small.height() <= large.height()
765 fn append_large(
766 small: Self,
767 large: &mut Self,
768 cx: <T::Summary as Summary>::Context<'_>,
769 ) -> Option<Self> {
770 if small.0.height() == large.0.height() {
771 if !small.0.is_underflowing() {
772 Some(small)
773 } else {
774 Self::merge_into_right(small, large, cx)
775 }
776 } else {
777 debug_assert!(small.0.height() < large.0.height());
778 let Node::Internal {
779 height,
780 summary,
781 child_summaries,
782 child_trees,
783 } = Arc::make_mut(&mut large.0)
784 else {
785 unreachable!();
786 };
787 let mut full_summary = small.summary().clone();
788 Summary::add_summary(&mut full_summary, summary, cx);
789 *summary = full_summary;
790
791 let first = child_trees.first_mut().unwrap();
792 let res = Self::append_large(small, first, cx);
793 *child_summaries.first_mut().unwrap() = first.summary().clone();
794 if let Some(tree) = res {
795 if child_trees.len() < 2 * TREE_BASE {
796 child_summaries.insert(0, tree.summary().clone());
797 child_trees.insert(0, tree);
798 None
799 } else {
800 let new_child_summaries = {
801 let mut res = ArrayVec::from_iter([tree.summary().clone()]);
802 res.extend(child_summaries.drain(..TREE_BASE));
803 res
804 };
805 let tree = SumTree(Arc::new(Node::Internal {
806 height: *height,
807 summary: sum(new_child_summaries.iter(), cx),
808 child_summaries: new_child_summaries,
809 child_trees: {
810 let mut res = ArrayVec::from_iter([tree]);
811 res.extend(child_trees.drain(..TREE_BASE));
812 res
813 },
814 }));
815
816 *summary = sum(child_summaries.iter(), cx);
817 Some(tree)
818 }
819 } else {
820 None
821 }
822 }
823 }
824
825 // Merge two nodes into `large`.
826 //
827 // `large` will contain the contents of `small` followed by its own data.
828 // If the combined data exceed the node capacity, returns a new node that
829 // holds the first half of the merged items and `large` is left with the
830 // second half
831 //
832 // The nodes must be on the same height
833 // It only makes sense to call this when `small` is underflowing
834 fn merge_into_right(
835 small: Self,
836 large: &mut Self,
837 cx: <<T as Item>::Summary as Summary>::Context<'_>,
838 ) -> Option<SumTree<T>> {
839 debug_assert_eq!(small.0.height(), large.0.height());
840 match (small.0.as_ref(), Arc::make_mut(&mut large.0)) {
841 (
842 Node::Internal {
843 summary: small_summary,
844 child_summaries: small_child_summaries,
845 child_trees: small_child_trees,
846 ..
847 },
848 Node::Internal {
849 summary,
850 child_summaries,
851 child_trees,
852 height,
853 },
854 ) => {
855 let total_child_count = child_trees.len() + small_child_trees.len();
856 if total_child_count <= 2 * TREE_BASE {
857 let mut all_trees = small_child_trees.clone();
858 all_trees.extend(child_trees.drain(..));
859 *child_trees = all_trees;
860
861 let mut all_summaries = small_child_summaries.clone();
862 all_summaries.extend(child_summaries.drain(..));
863 *child_summaries = all_summaries;
864
865 let mut full_summary = small_summary.clone();
866 Summary::add_summary(&mut full_summary, summary, cx);
867 *summary = full_summary;
868 None
869 } else {
870 let midpoint = total_child_count.div_ceil(2);
871 let mut all_trees = small_child_trees.iter().chain(child_trees.iter()).cloned();
872 let left_trees = all_trees.by_ref().take(midpoint).collect();
873 *child_trees = all_trees.collect();
874
875 let mut all_summaries = small_child_summaries
876 .iter()
877 .chain(child_summaries.iter())
878 .cloned();
879 let left_summaries: ArrayVec<_, { 2 * TREE_BASE }> =
880 all_summaries.by_ref().take(midpoint).collect();
881 *child_summaries = all_summaries.collect();
882
883 *summary = sum(child_summaries.iter(), cx);
884 Some(SumTree(Arc::new(Node::Internal {
885 height: *height,
886 summary: sum(left_summaries.iter(), cx),
887 child_summaries: left_summaries,
888 child_trees: left_trees,
889 })))
890 }
891 }
892 (
893 Node::Leaf {
894 summary: small_summary,
895 items: small_items,
896 item_summaries: small_item_summaries,
897 },
898 Node::Leaf {
899 summary,
900 items,
901 item_summaries,
902 },
903 ) => {
904 let total_child_count = small_items.len() + items.len();
905 if total_child_count <= 2 * TREE_BASE {
906 let mut all_items = small_items.clone();
907 all_items.extend(items.drain(..));
908 *items = all_items;
909
910 let mut all_summaries = small_item_summaries.clone();
911 all_summaries.extend(item_summaries.drain(..));
912 *item_summaries = all_summaries;
913
914 let mut full_summary = small_summary.clone();
915 Summary::add_summary(&mut full_summary, summary, cx);
916 *summary = full_summary;
917 None
918 } else {
919 let midpoint = total_child_count.div_ceil(2);
920 let mut all_items = small_items.iter().chain(items.iter()).cloned();
921 let left_items = all_items.by_ref().take(midpoint).collect();
922 *items = all_items.collect();
923
924 let mut all_summaries = small_item_summaries
925 .iter()
926 .chain(item_summaries.iter())
927 .cloned();
928 let left_summaries: ArrayVec<_, { 2 * TREE_BASE }> =
929 all_summaries.by_ref().take(midpoint).collect();
930 *item_summaries = all_summaries.collect();
931
932 *summary = sum(item_summaries.iter(), cx);
933 Some(SumTree(Arc::new(Node::Leaf {
934 items: left_items,
935 summary: sum(left_summaries.iter(), cx),
936 item_summaries: left_summaries,
937 })))
938 }
939 }
940 _ => unreachable!(),
941 }
942 }
943
944 fn from_child_trees(
945 left: SumTree<T>,
946 right: SumTree<T>,
947 cx: <T::Summary as Summary>::Context<'_>,
948 ) -> Self {
949 let height = left.0.height() + 1;
950 let mut child_summaries = ArrayVec::new();
951 child_summaries.push(left.0.summary().clone());
952 child_summaries.push(right.0.summary().clone());
953 let mut child_trees = ArrayVec::new();
954 child_trees.push(left);
955 child_trees.push(right);
956 SumTree(Arc::new(Node::Internal {
957 height,
958 summary: sum(child_summaries.iter(), cx),
959 child_summaries,
960 child_trees,
961 }))
962 }
963
964 fn leftmost_leaf(&self) -> &Self {
965 match *self.0 {
966 Node::Leaf { .. } => self,
967 Node::Internal {
968 ref child_trees, ..
969 } => child_trees.first().unwrap().leftmost_leaf(),
970 }
971 }
972
973 fn rightmost_leaf(&self) -> &Self {
974 match *self.0 {
975 Node::Leaf { .. } => self,
976 Node::Internal {
977 ref child_trees, ..
978 } => child_trees.last().unwrap().rightmost_leaf(),
979 }
980 }
981}
982
983impl<T: Item + PartialEq> PartialEq for SumTree<T> {
984 fn eq(&self, other: &Self) -> bool {
985 self.iter().eq(other.iter())
986 }
987}
988
989impl<T: Item + Eq> Eq for SumTree<T> {}
990
991impl<T: KeyedItem> SumTree<T> {
992 pub fn insert_or_replace<'a, 'b>(
993 &'a mut self,
994 item: T,
995 cx: <T::Summary as Summary>::Context<'b>,
996 ) -> Option<T> {
997 let mut replaced = None;
998 {
999 let mut cursor = self.cursor::<T::Key>(cx);
1000 let mut new_tree = cursor.slice(&item.key(), Bias::Left);
1001 if let Some(cursor_item) = cursor.item()
1002 && cursor_item.key() == item.key()
1003 {
1004 replaced = Some(cursor_item.clone());
1005 cursor.next();
1006 }
1007 new_tree.push(item, cx);
1008 new_tree.append(cursor.suffix(), cx);
1009 drop(cursor);
1010 *self = new_tree
1011 };
1012 replaced
1013 }
1014
1015 pub fn remove(&mut self, key: &T::Key, cx: <T::Summary as Summary>::Context<'_>) -> Option<T> {
1016 let mut removed = None;
1017 *self = {
1018 let mut cursor = self.cursor::<T::Key>(cx);
1019 let mut new_tree = cursor.slice(key, Bias::Left);
1020 if let Some(item) = cursor.item()
1021 && item.key() == *key
1022 {
1023 removed = Some(item.clone());
1024 cursor.next();
1025 }
1026 new_tree.append(cursor.suffix(), cx);
1027 new_tree
1028 };
1029 removed
1030 }
1031
1032 pub fn edit(
1033 &mut self,
1034 mut edits: Vec<Edit<T>>,
1035 cx: <T::Summary as Summary>::Context<'_>,
1036 ) -> Vec<T> {
1037 if edits.is_empty() {
1038 return Vec::new();
1039 }
1040
1041 let mut removed = Vec::new();
1042 edits.sort_unstable_by_key(|item| item.key());
1043
1044 *self = {
1045 let mut cursor = self.cursor::<T::Key>(cx);
1046 let mut new_tree = SumTree::new(cx);
1047 let mut buffered_items = Vec::new();
1048
1049 cursor.seek(&T::Key::zero(cx), Bias::Left);
1050 for edit in edits {
1051 let new_key = edit.key();
1052 let mut old_item = cursor.item();
1053
1054 if old_item
1055 .as_ref()
1056 .is_some_and(|old_item| old_item.key() < new_key)
1057 {
1058 new_tree.extend(buffered_items.drain(..), cx);
1059 let slice = cursor.slice(&new_key, Bias::Left);
1060 new_tree.append(slice, cx);
1061 old_item = cursor.item();
1062 }
1063
1064 if let Some(old_item) = old_item
1065 && old_item.key() == new_key
1066 {
1067 removed.push(old_item.clone());
1068 cursor.next();
1069 }
1070
1071 match edit {
1072 Edit::Insert(item) => {
1073 buffered_items.push(item);
1074 }
1075 Edit::Remove(_) => {}
1076 }
1077 }
1078
1079 new_tree.extend(buffered_items, cx);
1080 new_tree.append(cursor.suffix(), cx);
1081 new_tree
1082 };
1083
1084 removed
1085 }
1086
1087 pub fn get<'a>(
1088 &'a self,
1089 key: &T::Key,
1090 cx: <T::Summary as Summary>::Context<'a>,
1091 ) -> Option<&'a T> {
1092 if let (_, _, Some(item)) = self.find_exact::<T::Key, _>(cx, key, Bias::Left) {
1093 Some(item)
1094 } else {
1095 None
1096 }
1097 }
1098}
1099
1100impl<T, S> Default for SumTree<T>
1101where
1102 T: Item<Summary = S>,
1103 S: for<'a> Summary<Context<'a> = ()>,
1104{
1105 fn default() -> Self {
1106 Self::new(())
1107 }
1108}
1109
1110#[derive(Clone)]
1111pub enum Node<T: Item> {
1112 Internal {
1113 height: u8,
1114 summary: T::Summary,
1115 child_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
1116 child_trees: ArrayVec<SumTree<T>, { 2 * TREE_BASE }>,
1117 },
1118 Leaf {
1119 summary: T::Summary,
1120 items: ArrayVec<T, { 2 * TREE_BASE }>,
1121 item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
1122 },
1123}
1124
1125impl<T> fmt::Debug for Node<T>
1126where
1127 T: Item + fmt::Debug,
1128 T::Summary: fmt::Debug,
1129{
1130 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1131 match self {
1132 Node::Internal {
1133 height,
1134 summary,
1135 child_summaries,
1136 child_trees,
1137 } => f
1138 .debug_struct("Internal")
1139 .field("height", height)
1140 .field("summary", summary)
1141 .field("child_summaries", child_summaries)
1142 .field("child_trees", child_trees)
1143 .finish(),
1144 Node::Leaf {
1145 summary,
1146 items,
1147 item_summaries,
1148 } => f
1149 .debug_struct("Leaf")
1150 .field("summary", summary)
1151 .field("items", items)
1152 .field("item_summaries", item_summaries)
1153 .finish(),
1154 }
1155 }
1156}
1157
1158impl<T: Item> Node<T> {
1159 fn is_leaf(&self) -> bool {
1160 matches!(self, Node::Leaf { .. })
1161 }
1162
1163 fn height(&self) -> u8 {
1164 match self {
1165 Node::Internal { height, .. } => *height,
1166 Node::Leaf { .. } => 0,
1167 }
1168 }
1169
1170 fn summary(&self) -> &T::Summary {
1171 match self {
1172 Node::Internal { summary, .. } => summary,
1173 Node::Leaf { summary, .. } => summary,
1174 }
1175 }
1176
1177 fn child_summaries(&self) -> &[T::Summary] {
1178 match self {
1179 Node::Internal {
1180 child_summaries, ..
1181 } => child_summaries.as_slice(),
1182 Node::Leaf { item_summaries, .. } => item_summaries.as_slice(),
1183 }
1184 }
1185
1186 fn child_trees(&self) -> &ArrayVec<SumTree<T>, { 2 * TREE_BASE }> {
1187 match self {
1188 Node::Internal { child_trees, .. } => child_trees,
1189 Node::Leaf { .. } => panic!("Leaf nodes have no child trees"),
1190 }
1191 }
1192
1193 fn items(&self) -> &ArrayVec<T, { 2 * TREE_BASE }> {
1194 match self {
1195 Node::Leaf { items, .. } => items,
1196 Node::Internal { .. } => panic!("Internal nodes have no items"),
1197 }
1198 }
1199
1200 fn is_underflowing(&self) -> bool {
1201 match self {
1202 Node::Internal { child_trees, .. } => child_trees.len() < TREE_BASE,
1203 Node::Leaf { items, .. } => items.len() < TREE_BASE,
1204 }
1205 }
1206}
1207
1208#[derive(Debug)]
1209pub enum Edit<T: KeyedItem> {
1210 Insert(T),
1211 Remove(T::Key),
1212}
1213
1214impl<T: KeyedItem> Edit<T> {
1215 fn key(&self) -> T::Key {
1216 match self {
1217 Edit::Insert(item) => item.key(),
1218 Edit::Remove(key) => key.clone(),
1219 }
1220 }
1221}
1222
1223fn sum<'a, T, I>(iter: I, cx: T::Context<'_>) -> T
1224where
1225 T: 'a + Summary,
1226 I: Iterator<Item = &'a T>,
1227{
1228 let mut sum = T::zero(cx);
1229 for value in iter {
1230 sum.add_summary(value, cx);
1231 }
1232 sum
1233}
1234
1235#[cfg(test)]
1236mod tests {
1237 use super::*;
1238 use rand::{distr::StandardUniform, prelude::*};
1239 use std::cmp;
1240
1241 #[ctor::ctor]
1242 fn init_logger() {
1243 zlog::init_test();
1244 }
1245
1246 #[test]
1247 fn test_extend_and_push_tree() {
1248 let mut tree1 = SumTree::default();
1249 tree1.extend(0..20, ());
1250
1251 let mut tree2 = SumTree::default();
1252 tree2.extend(50..100, ());
1253
1254 tree1.append(tree2, ());
1255 assert_eq!(tree1.items(()), (0..20).chain(50..100).collect::<Vec<u8>>());
1256 }
1257
1258 #[test]
1259 fn test_random() {
1260 let mut starting_seed = 0;
1261 if let Ok(value) = std::env::var("SEED") {
1262 starting_seed = value.parse().expect("invalid SEED variable");
1263 }
1264 let mut num_iterations = 100;
1265 if let Ok(value) = std::env::var("ITERATIONS") {
1266 num_iterations = value.parse().expect("invalid ITERATIONS variable");
1267 }
1268 let num_operations = std::env::var("OPERATIONS")
1269 .map_or(5, |o| o.parse().expect("invalid OPERATIONS variable"));
1270
1271 for seed in starting_seed..(starting_seed + num_iterations) {
1272 eprintln!("seed = {}", seed);
1273 let mut rng = StdRng::seed_from_u64(seed);
1274
1275 let rng = &mut rng;
1276 let mut tree = SumTree::<u8>::default();
1277 let count = rng.random_range(0..10);
1278 if rng.random() {
1279 tree.extend(rng.sample_iter(StandardUniform).take(count), ());
1280 } else {
1281 let items = rng
1282 .sample_iter(StandardUniform)
1283 .take(count)
1284 .collect::<Vec<_>>();
1285 tree.par_extend(items, ());
1286 }
1287
1288 for _ in 0..num_operations {
1289 let splice_end = rng.random_range(0..tree.extent::<Count>(()).0 + 1);
1290 let splice_start = rng.random_range(0..splice_end + 1);
1291 let count = rng.random_range(0..10);
1292 let tree_end = tree.extent::<Count>(());
1293 let new_items = rng
1294 .sample_iter(StandardUniform)
1295 .take(count)
1296 .collect::<Vec<u8>>();
1297
1298 let mut reference_items = tree.items(());
1299 reference_items.splice(splice_start..splice_end, new_items.clone());
1300
1301 tree = {
1302 let mut cursor = tree.cursor::<Count>(());
1303 let mut new_tree = cursor.slice(&Count(splice_start), Bias::Right);
1304 if rng.random() {
1305 new_tree.extend(new_items, ());
1306 } else {
1307 new_tree.par_extend(new_items, ());
1308 }
1309 cursor.seek(&Count(splice_end), Bias::Right);
1310 new_tree.append(cursor.slice(&tree_end, Bias::Right), ());
1311 new_tree
1312 };
1313
1314 assert_eq!(tree.items(()), reference_items);
1315 assert_eq!(
1316 tree.iter().collect::<Vec<_>>(),
1317 tree.cursor::<()>(()).collect::<Vec<_>>()
1318 );
1319
1320 log::info!("tree items: {:?}", tree.items(()));
1321
1322 let mut filter_cursor =
1323 tree.filter::<_, Count>((), |summary| summary.contains_even);
1324 let expected_filtered_items = tree
1325 .items(())
1326 .into_iter()
1327 .enumerate()
1328 .filter(|(_, item)| (item & 1) == 0)
1329 .collect::<Vec<_>>();
1330
1331 let mut item_ix = if rng.random() {
1332 filter_cursor.next();
1333 0
1334 } else {
1335 filter_cursor.prev();
1336 expected_filtered_items.len().saturating_sub(1)
1337 };
1338 while item_ix < expected_filtered_items.len() {
1339 log::info!("filter_cursor, item_ix: {}", item_ix);
1340 let actual_item = filter_cursor.item().unwrap();
1341 let (reference_index, reference_item) = expected_filtered_items[item_ix];
1342 assert_eq!(actual_item, &reference_item);
1343 assert_eq!(filter_cursor.start().0, reference_index);
1344 log::info!("next");
1345 filter_cursor.next();
1346 item_ix += 1;
1347
1348 while item_ix > 0 && rng.random_bool(0.2) {
1349 log::info!("prev");
1350 filter_cursor.prev();
1351 item_ix -= 1;
1352
1353 if item_ix == 0 && rng.random_bool(0.2) {
1354 filter_cursor.prev();
1355 assert_eq!(filter_cursor.item(), None);
1356 assert_eq!(filter_cursor.start().0, 0);
1357 filter_cursor.next();
1358 }
1359 }
1360 }
1361 assert_eq!(filter_cursor.item(), None);
1362
1363 let mut before_start = false;
1364 let mut cursor = tree.cursor::<Count>(());
1365 let start_pos = rng.random_range(0..=reference_items.len());
1366 cursor.seek(&Count(start_pos), Bias::Right);
1367 let mut pos = rng.random_range(start_pos..=reference_items.len());
1368 cursor.seek_forward(&Count(pos), Bias::Right);
1369
1370 for i in 0..10 {
1371 assert_eq!(cursor.start().0, pos);
1372
1373 if pos > 0 {
1374 assert_eq!(cursor.prev_item().unwrap(), &reference_items[pos - 1]);
1375 } else {
1376 assert_eq!(cursor.prev_item(), None);
1377 }
1378
1379 if pos < reference_items.len() && !before_start {
1380 assert_eq!(cursor.item().unwrap(), &reference_items[pos]);
1381 } else {
1382 assert_eq!(cursor.item(), None);
1383 }
1384
1385 if before_start {
1386 assert_eq!(cursor.next_item(), reference_items.first());
1387 } else if pos + 1 < reference_items.len() {
1388 assert_eq!(cursor.next_item().unwrap(), &reference_items[pos + 1]);
1389 } else {
1390 assert_eq!(cursor.next_item(), None);
1391 }
1392
1393 if i < 5 {
1394 cursor.next();
1395 if pos < reference_items.len() {
1396 pos += 1;
1397 before_start = false;
1398 }
1399 } else {
1400 cursor.prev();
1401 if pos == 0 {
1402 before_start = true;
1403 }
1404 pos = pos.saturating_sub(1);
1405 }
1406 }
1407 }
1408
1409 for _ in 0..10 {
1410 let end = rng.random_range(0..tree.extent::<Count>(()).0 + 1);
1411 let start = rng.random_range(0..end + 1);
1412 let start_bias = if rng.random() {
1413 Bias::Left
1414 } else {
1415 Bias::Right
1416 };
1417 let end_bias = if rng.random() {
1418 Bias::Left
1419 } else {
1420 Bias::Right
1421 };
1422
1423 let mut cursor = tree.cursor::<Count>(());
1424 cursor.seek(&Count(start), start_bias);
1425 let slice = cursor.slice(&Count(end), end_bias);
1426
1427 cursor.seek(&Count(start), start_bias);
1428 let summary = cursor.summary::<_, Sum>(&Count(end), end_bias);
1429
1430 assert_eq!(summary.0, slice.summary().sum);
1431 }
1432 }
1433 }
1434
1435 #[test]
1436 fn test_cursor() {
1437 // Empty tree
1438 let tree = SumTree::<u8>::default();
1439 let mut cursor = tree.cursor::<IntegersSummary>(());
1440 assert_eq!(
1441 cursor.slice(&Count(0), Bias::Right).items(()),
1442 Vec::<u8>::new()
1443 );
1444 assert_eq!(cursor.item(), None);
1445 assert_eq!(cursor.prev_item(), None);
1446 assert_eq!(cursor.next_item(), None);
1447 assert_eq!(cursor.start().sum, 0);
1448 cursor.prev();
1449 assert_eq!(cursor.item(), None);
1450 assert_eq!(cursor.prev_item(), None);
1451 assert_eq!(cursor.next_item(), None);
1452 assert_eq!(cursor.start().sum, 0);
1453 cursor.next();
1454 assert_eq!(cursor.item(), None);
1455 assert_eq!(cursor.prev_item(), None);
1456 assert_eq!(cursor.next_item(), None);
1457 assert_eq!(cursor.start().sum, 0);
1458
1459 // Single-element tree
1460 let mut tree = SumTree::<u8>::default();
1461 tree.extend(vec![1], ());
1462 let mut cursor = tree.cursor::<IntegersSummary>(());
1463 assert_eq!(
1464 cursor.slice(&Count(0), Bias::Right).items(()),
1465 Vec::<u8>::new()
1466 );
1467 assert_eq!(cursor.item(), Some(&1));
1468 assert_eq!(cursor.prev_item(), None);
1469 assert_eq!(cursor.next_item(), None);
1470 assert_eq!(cursor.start().sum, 0);
1471
1472 cursor.next();
1473 assert_eq!(cursor.item(), None);
1474 assert_eq!(cursor.prev_item(), Some(&1));
1475 assert_eq!(cursor.next_item(), None);
1476 assert_eq!(cursor.start().sum, 1);
1477
1478 cursor.prev();
1479 assert_eq!(cursor.item(), Some(&1));
1480 assert_eq!(cursor.prev_item(), None);
1481 assert_eq!(cursor.next_item(), None);
1482 assert_eq!(cursor.start().sum, 0);
1483
1484 let mut cursor = tree.cursor::<IntegersSummary>(());
1485 assert_eq!(cursor.slice(&Count(1), Bias::Right).items(()), [1]);
1486 assert_eq!(cursor.item(), None);
1487 assert_eq!(cursor.prev_item(), Some(&1));
1488 assert_eq!(cursor.next_item(), None);
1489 assert_eq!(cursor.start().sum, 1);
1490
1491 cursor.seek(&Count(0), Bias::Right);
1492 assert_eq!(
1493 cursor
1494 .slice(&tree.extent::<Count>(()), Bias::Right)
1495 .items(()),
1496 [1]
1497 );
1498 assert_eq!(cursor.item(), None);
1499 assert_eq!(cursor.prev_item(), Some(&1));
1500 assert_eq!(cursor.next_item(), None);
1501 assert_eq!(cursor.start().sum, 1);
1502
1503 // Multiple-element tree
1504 let mut tree = SumTree::default();
1505 tree.extend(vec![1, 2, 3, 4, 5, 6], ());
1506 let mut cursor = tree.cursor::<IntegersSummary>(());
1507
1508 assert_eq!(cursor.slice(&Count(2), Bias::Right).items(()), [1, 2]);
1509 assert_eq!(cursor.item(), Some(&3));
1510 assert_eq!(cursor.prev_item(), Some(&2));
1511 assert_eq!(cursor.next_item(), Some(&4));
1512 assert_eq!(cursor.start().sum, 3);
1513
1514 cursor.next();
1515 assert_eq!(cursor.item(), Some(&4));
1516 assert_eq!(cursor.prev_item(), Some(&3));
1517 assert_eq!(cursor.next_item(), Some(&5));
1518 assert_eq!(cursor.start().sum, 6);
1519
1520 cursor.next();
1521 assert_eq!(cursor.item(), Some(&5));
1522 assert_eq!(cursor.prev_item(), Some(&4));
1523 assert_eq!(cursor.next_item(), Some(&6));
1524 assert_eq!(cursor.start().sum, 10);
1525
1526 cursor.next();
1527 assert_eq!(cursor.item(), Some(&6));
1528 assert_eq!(cursor.prev_item(), Some(&5));
1529 assert_eq!(cursor.next_item(), None);
1530 assert_eq!(cursor.start().sum, 15);
1531
1532 cursor.next();
1533 cursor.next();
1534 assert_eq!(cursor.item(), None);
1535 assert_eq!(cursor.prev_item(), Some(&6));
1536 assert_eq!(cursor.next_item(), None);
1537 assert_eq!(cursor.start().sum, 21);
1538
1539 cursor.prev();
1540 assert_eq!(cursor.item(), Some(&6));
1541 assert_eq!(cursor.prev_item(), Some(&5));
1542 assert_eq!(cursor.next_item(), None);
1543 assert_eq!(cursor.start().sum, 15);
1544
1545 cursor.prev();
1546 assert_eq!(cursor.item(), Some(&5));
1547 assert_eq!(cursor.prev_item(), Some(&4));
1548 assert_eq!(cursor.next_item(), Some(&6));
1549 assert_eq!(cursor.start().sum, 10);
1550
1551 cursor.prev();
1552 assert_eq!(cursor.item(), Some(&4));
1553 assert_eq!(cursor.prev_item(), Some(&3));
1554 assert_eq!(cursor.next_item(), Some(&5));
1555 assert_eq!(cursor.start().sum, 6);
1556
1557 cursor.prev();
1558 assert_eq!(cursor.item(), Some(&3));
1559 assert_eq!(cursor.prev_item(), Some(&2));
1560 assert_eq!(cursor.next_item(), Some(&4));
1561 assert_eq!(cursor.start().sum, 3);
1562
1563 cursor.prev();
1564 assert_eq!(cursor.item(), Some(&2));
1565 assert_eq!(cursor.prev_item(), Some(&1));
1566 assert_eq!(cursor.next_item(), Some(&3));
1567 assert_eq!(cursor.start().sum, 1);
1568
1569 cursor.prev();
1570 assert_eq!(cursor.item(), Some(&1));
1571 assert_eq!(cursor.prev_item(), None);
1572 assert_eq!(cursor.next_item(), Some(&2));
1573 assert_eq!(cursor.start().sum, 0);
1574
1575 cursor.prev();
1576 assert_eq!(cursor.item(), None);
1577 assert_eq!(cursor.prev_item(), None);
1578 assert_eq!(cursor.next_item(), Some(&1));
1579 assert_eq!(cursor.start().sum, 0);
1580
1581 cursor.next();
1582 assert_eq!(cursor.item(), Some(&1));
1583 assert_eq!(cursor.prev_item(), None);
1584 assert_eq!(cursor.next_item(), Some(&2));
1585 assert_eq!(cursor.start().sum, 0);
1586
1587 let mut cursor = tree.cursor::<IntegersSummary>(());
1588 assert_eq!(
1589 cursor
1590 .slice(&tree.extent::<Count>(()), Bias::Right)
1591 .items(()),
1592 tree.items(())
1593 );
1594 assert_eq!(cursor.item(), None);
1595 assert_eq!(cursor.prev_item(), Some(&6));
1596 assert_eq!(cursor.next_item(), None);
1597 assert_eq!(cursor.start().sum, 21);
1598
1599 cursor.seek(&Count(3), Bias::Right);
1600 assert_eq!(
1601 cursor
1602 .slice(&tree.extent::<Count>(()), Bias::Right)
1603 .items(()),
1604 [4, 5, 6]
1605 );
1606 assert_eq!(cursor.item(), None);
1607 assert_eq!(cursor.prev_item(), Some(&6));
1608 assert_eq!(cursor.next_item(), None);
1609 assert_eq!(cursor.start().sum, 21);
1610
1611 // Seeking can bias left or right
1612 cursor.seek(&Count(1), Bias::Left);
1613 assert_eq!(cursor.item(), Some(&1));
1614 cursor.seek(&Count(1), Bias::Right);
1615 assert_eq!(cursor.item(), Some(&2));
1616
1617 // Slicing without resetting starts from where the cursor is parked at.
1618 cursor.seek(&Count(1), Bias::Right);
1619 assert_eq!(cursor.slice(&Count(3), Bias::Right).items(()), vec![2, 3]);
1620 assert_eq!(cursor.slice(&Count(6), Bias::Left).items(()), vec![4, 5]);
1621 assert_eq!(cursor.slice(&Count(6), Bias::Right).items(()), vec![6]);
1622 }
1623
1624 #[test]
1625 fn test_edit() {
1626 let mut tree = SumTree::<u8>::default();
1627
1628 let removed = tree.edit(vec![Edit::Insert(1), Edit::Insert(2), Edit::Insert(0)], ());
1629 assert_eq!(tree.items(()), vec![0, 1, 2]);
1630 assert_eq!(removed, Vec::<u8>::new());
1631 assert_eq!(tree.get(&0, ()), Some(&0));
1632 assert_eq!(tree.get(&1, ()), Some(&1));
1633 assert_eq!(tree.get(&2, ()), Some(&2));
1634 assert_eq!(tree.get(&4, ()), None);
1635
1636 let removed = tree.edit(vec![Edit::Insert(2), Edit::Insert(4), Edit::Remove(0)], ());
1637 assert_eq!(tree.items(()), vec![1, 2, 4]);
1638 assert_eq!(removed, vec![0, 2]);
1639 assert_eq!(tree.get(&0, ()), None);
1640 assert_eq!(tree.get(&1, ()), Some(&1));
1641 assert_eq!(tree.get(&2, ()), Some(&2));
1642 assert_eq!(tree.get(&4, ()), Some(&4));
1643 }
1644
1645 #[test]
1646 fn test_from_iter() {
1647 assert_eq!(
1648 SumTree::from_iter(0..100, ()).items(()),
1649 (0..100).collect::<Vec<_>>()
1650 );
1651
1652 // Ensure `from_iter` works correctly when the given iterator restarts
1653 // after calling `next` if `None` was already returned.
1654 let mut ix = 0;
1655 let iterator = std::iter::from_fn(|| {
1656 ix = (ix + 1) % 2;
1657 if ix == 1 { Some(1) } else { None }
1658 });
1659 assert_eq!(SumTree::from_iter(iterator, ()).items(()), vec![1]);
1660 }
1661
1662 #[derive(Clone, Default, Debug)]
1663 pub struct IntegersSummary {
1664 count: usize,
1665 sum: usize,
1666 contains_even: bool,
1667 max: u8,
1668 }
1669
1670 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
1671 struct Count(usize);
1672
1673 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
1674 struct Sum(usize);
1675
1676 impl Item for u8 {
1677 type Summary = IntegersSummary;
1678
1679 fn summary(&self, _cx: ()) -> Self::Summary {
1680 IntegersSummary {
1681 count: 1,
1682 sum: *self as usize,
1683 contains_even: (*self & 1) == 0,
1684 max: *self,
1685 }
1686 }
1687 }
1688
1689 impl KeyedItem for u8 {
1690 type Key = u8;
1691
1692 fn key(&self) -> Self::Key {
1693 *self
1694 }
1695 }
1696
1697 impl ContextLessSummary for IntegersSummary {
1698 fn zero() -> Self {
1699 Default::default()
1700 }
1701
1702 fn add_summary(&mut self, other: &Self) {
1703 self.count += other.count;
1704 self.sum += other.sum;
1705 self.contains_even |= other.contains_even;
1706 self.max = cmp::max(self.max, other.max);
1707 }
1708 }
1709
1710 impl Dimension<'_, IntegersSummary> for u8 {
1711 fn zero(_cx: ()) -> Self {
1712 Default::default()
1713 }
1714
1715 fn add_summary(&mut self, summary: &IntegersSummary, _: ()) {
1716 *self = summary.max;
1717 }
1718 }
1719
1720 impl Dimension<'_, IntegersSummary> for Count {
1721 fn zero(_cx: ()) -> Self {
1722 Default::default()
1723 }
1724
1725 fn add_summary(&mut self, summary: &IntegersSummary, _: ()) {
1726 self.0 += summary.count;
1727 }
1728 }
1729
1730 impl SeekTarget<'_, IntegersSummary, IntegersSummary> for Count {
1731 fn cmp(&self, cursor_location: &IntegersSummary, _: ()) -> Ordering {
1732 self.0.cmp(&cursor_location.count)
1733 }
1734 }
1735
1736 impl Dimension<'_, IntegersSummary> for Sum {
1737 fn zero(_cx: ()) -> Self {
1738 Default::default()
1739 }
1740
1741 fn add_summary(&mut self, summary: &IntegersSummary, _: ()) {
1742 self.0 += summary.sum;
1743 }
1744 }
1745}