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