1mod cursor;
2#[cfg(any(test, feature = "test-support"))]
3pub mod property_test;
4mod tree_map;
5
6use arrayvec::ArrayVec;
7pub use cursor::{Cursor, FilterCursor, Iter};
8use rayon::iter::{IndexedParallelIterator, IntoParallelIterator, ParallelIterator as _};
9use std::marker::PhantomData;
10use std::mem;
11use std::{cmp::Ordering, fmt, iter::FromIterator, sync::Arc};
12pub use tree_map::{MapSeekTarget, TreeMap, TreeSet};
13use ztracing::instrument;
14
15#[cfg(test)]
16pub const TREE_BASE: usize = 2;
17#[cfg(not(test))]
18pub const TREE_BASE: usize = 6;
19
20/// An item that can be stored in a [`SumTree`]
21///
22/// Must be summarized by a type that implements [`Summary`]
23pub trait Item: Clone {
24 type Summary: Summary;
25
26 fn summary(&self, cx: <Self::Summary as Summary>::Context<'_>) -> Self::Summary;
27}
28
29/// An [`Item`] whose summary has a specific key that can be used to identify it
30pub trait KeyedItem: Item {
31 type Key: for<'a> Dimension<'a, Self::Summary> + Ord;
32
33 fn key(&self) -> Self::Key;
34}
35
36/// A type that describes the Sum of all [`Item`]s in a subtree of the [`SumTree`]
37///
38/// Each Summary type can have multiple [`Dimension`]s that it measures,
39/// which can be used to navigate the tree
40pub trait Summary: Clone {
41 type Context<'a>: Copy;
42 fn zero<'a>(cx: Self::Context<'a>) -> Self;
43 fn add_summary<'a>(&mut self, summary: &Self, cx: Self::Context<'a>);
44}
45
46pub trait ContextLessSummary: Clone {
47 fn zero() -> Self;
48 fn add_summary(&mut self, summary: &Self);
49}
50
51impl<T: ContextLessSummary> Summary for T {
52 type Context<'a> = ();
53
54 fn zero<'a>((): ()) -> Self {
55 T::zero()
56 }
57
58 fn add_summary<'a>(&mut self, summary: &Self, (): ()) {
59 T::add_summary(self, summary)
60 }
61}
62
63#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
64pub struct NoSummary;
65
66/// Catch-all implementation for when you need something that implements [`Summary`] without a specific type.
67/// We implement it on a `NoSummary` instead of re-using `()`, as that avoids blanket impl collisions with `impl<T: Summary> Dimension for T`
68/// (as we also need unit type to be a fill-in dimension)
69impl ContextLessSummary for NoSummary {
70 fn zero() -> Self {
71 NoSummary
72 }
73
74 fn add_summary(&mut self, _: &Self) {}
75}
76
77/// Each [`Summary`] type can have more than one [`Dimension`] type that it measures.
78///
79/// You can use dimensions to seek to a specific location in the [`SumTree`]
80///
81/// # Example:
82/// Zed's rope has a `TextSummary` type that summarizes lines, characters, and bytes.
83/// Each of these are different dimensions we may want to seek to
84pub trait Dimension<'a, S: Summary>: Clone {
85 fn zero(cx: S::Context<'_>) -> Self;
86
87 fn add_summary(&mut self, summary: &'a S, cx: S::Context<'_>);
88 #[must_use]
89 fn with_added_summary(mut self, summary: &'a S, cx: S::Context<'_>) -> Self {
90 self.add_summary(summary, cx);
91 self
92 }
93
94 fn from_summary(summary: &'a S, cx: S::Context<'_>) -> Self {
95 let mut dimension = Self::zero(cx);
96 dimension.add_summary(summary, cx);
97 dimension
98 }
99}
100
101impl<'a, T: Summary> Dimension<'a, T> for T {
102 fn zero(cx: T::Context<'_>) -> Self {
103 Summary::zero(cx)
104 }
105
106 fn add_summary(&mut self, summary: &'a T, cx: T::Context<'_>) {
107 Summary::add_summary(self, summary, cx);
108 }
109}
110
111pub trait SeekTarget<'a, S: Summary, D: Dimension<'a, S>> {
112 fn cmp(&self, cursor_location: &D, cx: S::Context<'_>) -> Ordering;
113}
114
115impl<'a, S: Summary, D: Dimension<'a, S> + Ord> SeekTarget<'a, S, D> for D {
116 fn cmp(&self, cursor_location: &Self, _: S::Context<'_>) -> Ordering {
117 Ord::cmp(self, cursor_location)
118 }
119}
120
121impl<'a, T: Summary> Dimension<'a, T> for () {
122 fn zero(_: T::Context<'_>) -> Self {}
123
124 fn add_summary(&mut self, _: &'a T, _: T::Context<'_>) {}
125}
126
127#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
128pub struct Dimensions<D1, D2, D3 = ()>(pub D1, pub D2, pub D3);
129
130impl<'a, T: Summary, D1: Dimension<'a, T>, D2: Dimension<'a, T>, D3: Dimension<'a, T>>
131 Dimension<'a, T> for Dimensions<D1, D2, D3>
132{
133 fn zero(cx: T::Context<'_>) -> Self {
134 Dimensions(D1::zero(cx), D2::zero(cx), D3::zero(cx))
135 }
136
137 fn add_summary(&mut self, summary: &'a T, cx: T::Context<'_>) {
138 self.0.add_summary(summary, cx);
139 self.1.add_summary(summary, cx);
140 self.2.add_summary(summary, cx);
141 }
142}
143
144impl<'a, S, D1, D2, D3> SeekTarget<'a, S, Dimensions<D1, D2, D3>> for D1
145where
146 S: Summary,
147 D1: SeekTarget<'a, S, D1> + Dimension<'a, S>,
148 D2: Dimension<'a, S>,
149 D3: Dimension<'a, S>,
150{
151 fn cmp(&self, cursor_location: &Dimensions<D1, D2, D3>, cx: S::Context<'_>) -> Ordering {
152 self.cmp(&cursor_location.0, cx)
153 }
154}
155
156/// Bias is used to settle ambiguities when determining positions in an ordered sequence.
157///
158/// The primary use case is for text, where Bias influences
159/// which character an offset or anchor is associated with.
160///
161/// # Examples
162/// Given the buffer `AˇBCD`:
163/// - The offset of the cursor is 1
164/// - [Bias::Left] would attach the cursor to the character `A`
165/// - [Bias::Right] would attach the cursor to the character `B`
166///
167/// Given the buffer `A«BCˇ»D`:
168/// - The offset of the cursor is 3, and the selection is from 1 to 3
169/// - The left anchor of the selection has [Bias::Right], attaching it to the character `B`
170/// - The right anchor of the selection has [Bias::Left], attaching it to the character `C`
171///
172/// Given the buffer `{ˇ<...>`, where `<...>` is a folded region:
173/// - The display offset of the cursor is 1, but the offset in the buffer is determined by the bias
174/// - [Bias::Left] would attach the cursor to the character `{`, with a buffer offset of 1
175/// - [Bias::Right] would attach the cursor to the first character of the folded region,
176/// and the buffer offset would be the offset of the first character of the folded region
177#[derive(Copy, Clone, Eq, PartialEq, PartialOrd, Ord, Debug, Hash, Default)]
178pub enum Bias {
179 /// Attach to the character on the left
180 #[default]
181 Left,
182 /// Attach to the character on the right
183 Right,
184}
185
186impl Bias {
187 pub fn invert(self) -> Self {
188 match self {
189 Self::Left => Self::Right,
190 Self::Right => Self::Left,
191 }
192 }
193}
194
195/// A B+ tree in which each leaf node contains `Item`s of type `T` and a `Summary`s for each `Item`.
196/// Each internal node contains a `Summary` of the items in its subtree.
197///
198/// The maximum number of items per node is `TREE_BASE * 2`.
199///
200/// Any [`Dimension`] supported by the [`Summary`] type can be used to seek to a specific location in the tree.
201#[derive(Clone)]
202pub struct SumTree<T: Item>(Arc<Node<T>>);
203
204impl<T> fmt::Debug for SumTree<T>
205where
206 T: fmt::Debug + Item,
207 T::Summary: fmt::Debug,
208{
209 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
210 f.debug_tuple("SumTree").field(&self.0).finish()
211 }
212}
213
214impl<T: Item> SumTree<T> {
215 pub fn new(cx: <T::Summary as Summary>::Context<'_>) -> Self {
216 SumTree(Arc::new(Node::Leaf {
217 summary: <T::Summary as Summary>::zero(cx),
218 items: ArrayVec::new(),
219 item_summaries: ArrayVec::new(),
220 }))
221 }
222
223 /// 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.
224 pub fn from_summary(summary: T::Summary) -> Self {
225 SumTree(Arc::new(Node::Leaf {
226 summary,
227 items: ArrayVec::new(),
228 item_summaries: ArrayVec::new(),
229 }))
230 }
231
232 pub fn from_item(item: T, cx: <T::Summary as Summary>::Context<'_>) -> Self {
233 let mut tree = Self::new(cx);
234 tree.push(item, cx);
235 tree
236 }
237
238 pub fn from_iter<I: IntoIterator<Item = T>>(
239 iter: I,
240 cx: <T::Summary as Summary>::Context<'_>,
241 ) -> Self {
242 let mut nodes = Vec::new();
243
244 let mut iter = iter.into_iter().fuse().peekable();
245 while iter.peek().is_some() {
246 let items: ArrayVec<T, { 2 * TREE_BASE }> = iter.by_ref().take(2 * TREE_BASE).collect();
247 let item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }> =
248 items.iter().map(|item| item.summary(cx)).collect();
249
250 let mut summary = item_summaries[0].clone();
251 for item_summary in &item_summaries[1..] {
252 <T::Summary as Summary>::add_summary(&mut summary, item_summary, cx);
253 }
254
255 nodes.push(SumTree(Arc::new(Node::Leaf {
256 summary,
257 items,
258 item_summaries,
259 })));
260 }
261
262 let mut parent_nodes = Vec::new();
263 let mut height = 0;
264 while nodes.len() > 1 {
265 height += 1;
266 let mut current_parent_node = None;
267 for child_node in nodes.drain(..) {
268 let parent_node = current_parent_node.get_or_insert_with(|| {
269 SumTree(Arc::new(Node::Internal {
270 summary: <T::Summary as Summary>::zero(cx),
271 height,
272 child_summaries: ArrayVec::new(),
273 child_trees: ArrayVec::new(),
274 }))
275 });
276 let Node::Internal {
277 summary,
278 child_summaries,
279 child_trees,
280 ..
281 } = Arc::get_mut(&mut parent_node.0).unwrap()
282 else {
283 unreachable!()
284 };
285 let child_summary = child_node.summary();
286 <T::Summary as Summary>::add_summary(summary, child_summary, cx);
287 child_summaries.push(child_summary.clone());
288 child_trees.push(child_node);
289
290 if child_trees.len() == 2 * TREE_BASE {
291 parent_nodes.extend(current_parent_node.take());
292 }
293 }
294 parent_nodes.extend(current_parent_node.take());
295 mem::swap(&mut nodes, &mut parent_nodes);
296 }
297
298 if nodes.is_empty() {
299 Self::new(cx)
300 } else {
301 debug_assert_eq!(nodes.len(), 1);
302 nodes.pop().unwrap()
303 }
304 }
305
306 pub fn from_par_iter<I, Iter>(iter: I, cx: <T::Summary as Summary>::Context<'_>) -> Self
307 where
308 I: IntoParallelIterator<Iter = Iter>,
309 Iter: IndexedParallelIterator<Item = T>,
310 T: Send + Sync,
311 T::Summary: Send + Sync,
312 for<'a> <T::Summary as Summary>::Context<'a>: Sync,
313 {
314 let mut nodes = iter
315 .into_par_iter()
316 .chunks(2 * TREE_BASE)
317 .map(|items| {
318 let items: ArrayVec<T, { 2 * TREE_BASE }> = items.into_iter().collect();
319 let item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }> =
320 items.iter().map(|item| item.summary(cx)).collect();
321 let mut summary = item_summaries[0].clone();
322 for item_summary in &item_summaries[1..] {
323 <T::Summary as Summary>::add_summary(&mut summary, item_summary, cx);
324 }
325 SumTree(Arc::new(Node::Leaf {
326 summary,
327 items,
328 item_summaries,
329 }))
330 })
331 .collect::<Vec<_>>();
332
333 let mut height = 0;
334 while nodes.len() > 1 {
335 height += 1;
336 nodes = nodes
337 .into_par_iter()
338 .chunks(2 * TREE_BASE)
339 .map(|child_nodes| {
340 let child_trees: ArrayVec<SumTree<T>, { 2 * TREE_BASE }> =
341 child_nodes.into_iter().collect();
342 let child_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }> = child_trees
343 .iter()
344 .map(|child_tree| child_tree.summary().clone())
345 .collect();
346 let mut summary = child_summaries[0].clone();
347 for child_summary in &child_summaries[1..] {
348 <T::Summary as Summary>::add_summary(&mut summary, child_summary, cx);
349 }
350 SumTree(Arc::new(Node::Internal {
351 height,
352 summary,
353 child_summaries,
354 child_trees,
355 }))
356 })
357 .collect::<Vec<_>>();
358 }
359
360 if nodes.is_empty() {
361 Self::new(cx)
362 } else {
363 debug_assert_eq!(nodes.len(), 1);
364 nodes.pop().unwrap()
365 }
366 }
367
368 #[allow(unused)]
369 pub fn items<'a>(&'a self, cx: <T::Summary as Summary>::Context<'a>) -> Vec<T> {
370 let mut items = Vec::new();
371 let mut cursor = self.cursor::<()>(cx);
372 cursor.next();
373 while let Some(item) = cursor.item() {
374 items.push(item.clone());
375 cursor.next();
376 }
377 items
378 }
379
380 pub fn iter(&self) -> Iter<'_, T> {
381 Iter::new(self)
382 }
383
384 /// A more efficient version of `Cursor::new()` + `Cursor::seek()` + `Cursor::item()`.
385 ///
386 /// Only returns the item that exactly has the target match.
387 #[instrument(skip_all)]
388 pub fn find_exact<'a, 'slf, D, Target>(
389 &'slf self,
390 cx: <T::Summary as Summary>::Context<'a>,
391 target: &Target,
392 bias: Bias,
393 ) -> (D, D, Option<&'slf T>)
394 where
395 D: Dimension<'slf, T::Summary>,
396 Target: SeekTarget<'slf, T::Summary, D>,
397 {
398 let tree_end = D::zero(cx).with_added_summary(self.summary(), cx);
399 let comparison = target.cmp(&tree_end, cx);
400 if comparison == Ordering::Greater || (comparison == Ordering::Equal && bias == Bias::Right)
401 {
402 return (tree_end.clone(), tree_end, None);
403 }
404
405 let mut pos = D::zero(cx);
406 return match Self::find_iterate::<_, _, true>(cx, target, bias, &mut pos, self) {
407 Some((item, end)) => (pos, end, Some(item)),
408 None => (pos.clone(), pos, None),
409 };
410 }
411
412 /// A more efficient version of `Cursor::new()` + `Cursor::seek()` + `Cursor::item()`
413 #[instrument(skip_all)]
414 pub fn find<'a, 'slf, D, Target>(
415 &'slf self,
416 cx: <T::Summary as Summary>::Context<'a>,
417 target: &Target,
418 bias: Bias,
419 ) -> (D, D, Option<&'slf T>)
420 where
421 D: Dimension<'slf, T::Summary>,
422 Target: SeekTarget<'slf, T::Summary, D>,
423 {
424 let tree_end = D::zero(cx).with_added_summary(self.summary(), cx);
425 let comparison = target.cmp(&tree_end, cx);
426 if comparison == Ordering::Greater || (comparison == Ordering::Equal && bias == Bias::Right)
427 {
428 return (tree_end.clone(), tree_end, None);
429 }
430
431 let mut pos = D::zero(cx);
432 return match Self::find_iterate::<_, _, false>(cx, target, bias, &mut pos, self) {
433 Some((item, end)) => (pos, end, Some(item)),
434 None => (pos.clone(), pos, None),
435 };
436 }
437
438 fn find_iterate<'tree, 'a, D, Target, const EXACT: bool>(
439 cx: <T::Summary as Summary>::Context<'a>,
440 target: &Target,
441 bias: Bias,
442 position: &mut D,
443 mut this: &'tree SumTree<T>,
444 ) -> Option<(&'tree T, D)>
445 where
446 D: Dimension<'tree, T::Summary>,
447 Target: SeekTarget<'tree, T::Summary, D>,
448 {
449 'iterate: loop {
450 match &*this.0 {
451 Node::Internal {
452 child_summaries,
453 child_trees,
454 ..
455 } => {
456 for (child_tree, child_summary) in child_trees.iter().zip(child_summaries) {
457 let child_end = position.clone().with_added_summary(child_summary, cx);
458
459 let comparison = target.cmp(&child_end, cx);
460 let target_in_child = comparison == Ordering::Less
461 || (comparison == Ordering::Equal && bias == Bias::Left);
462 if target_in_child {
463 this = child_tree;
464 continue 'iterate;
465 }
466 *position = child_end;
467 }
468 }
469 Node::Leaf {
470 items,
471 item_summaries,
472 ..
473 } => {
474 for (item, item_summary) in items.iter().zip(item_summaries) {
475 let mut child_end = position.clone();
476 child_end.add_summary(item_summary, cx);
477
478 let comparison = target.cmp(&child_end, cx);
479 let entry_found = if EXACT {
480 comparison == Ordering::Equal
481 } else {
482 comparison == Ordering::Less
483 || (comparison == Ordering::Equal && bias == Bias::Left)
484 };
485 if entry_found {
486 return Some((item, child_end));
487 }
488
489 *position = child_end;
490 }
491 }
492 }
493 return None;
494 }
495 }
496
497 /// A more efficient version of `Cursor::new()` + `Cursor::seek()` + `Cursor::item()`
498 #[instrument(skip_all)]
499 pub fn find_with_prev<'a, 'slf, D, Target>(
500 &'slf self,
501 cx: <T::Summary as Summary>::Context<'a>,
502 target: &Target,
503 bias: Bias,
504 ) -> (D, D, Option<(Option<&'slf T>, &'slf T)>)
505 where
506 D: Dimension<'slf, T::Summary>,
507 Target: SeekTarget<'slf, T::Summary, D>,
508 {
509 let tree_end = D::zero(cx).with_added_summary(self.summary(), cx);
510 let comparison = target.cmp(&tree_end, cx);
511 if comparison == Ordering::Greater || (comparison == Ordering::Equal && bias == Bias::Right)
512 {
513 return (tree_end.clone(), tree_end, None);
514 }
515
516 let mut pos = D::zero(cx);
517 return match Self::find_with_prev_iterate::<_, _, false>(cx, target, bias, &mut pos, self) {
518 Some((prev, item, end)) => (pos, end, Some((prev, item))),
519 None => (pos.clone(), pos, None),
520 };
521 }
522
523 fn find_with_prev_iterate<'tree, 'a, D, Target, const EXACT: bool>(
524 cx: <T::Summary as Summary>::Context<'a>,
525 target: &Target,
526 bias: Bias,
527 position: &mut D,
528 mut this: &'tree SumTree<T>,
529 ) -> Option<(Option<&'tree T>, &'tree T, D)>
530 where
531 D: Dimension<'tree, T::Summary>,
532 Target: SeekTarget<'tree, T::Summary, D>,
533 {
534 let mut prev = None;
535 'iterate: loop {
536 match &*this.0 {
537 Node::Internal {
538 child_summaries,
539 child_trees,
540 ..
541 } => {
542 for (child_tree, child_summary) in child_trees.iter().zip(child_summaries) {
543 let child_end = position.clone().with_added_summary(child_summary, cx);
544
545 let comparison = target.cmp(&child_end, cx);
546 let target_in_child = comparison == Ordering::Less
547 || (comparison == Ordering::Equal && bias == Bias::Left);
548 if target_in_child {
549 this = child_tree;
550 continue 'iterate;
551 }
552 prev = child_tree.last();
553 *position = child_end;
554 }
555 }
556 Node::Leaf {
557 items,
558 item_summaries,
559 ..
560 } => {
561 for (item, item_summary) in items.iter().zip(item_summaries) {
562 let mut child_end = position.clone();
563 child_end.add_summary(item_summary, cx);
564
565 let comparison = target.cmp(&child_end, cx);
566 let entry_found = if EXACT {
567 comparison == Ordering::Equal
568 } else {
569 comparison == Ordering::Less
570 || (comparison == Ordering::Equal && bias == Bias::Left)
571 };
572 if entry_found {
573 return Some((prev, item, child_end));
574 }
575
576 prev = Some(item);
577 *position = child_end;
578 }
579 }
580 }
581 return None;
582 }
583 }
584
585 pub fn cursor<'a, 'b, D>(
586 &'a self,
587 cx: <T::Summary as Summary>::Context<'b>,
588 ) -> Cursor<'a, 'b, T, D>
589 where
590 D: Dimension<'a, T::Summary>,
591 {
592 Cursor::new(self, cx)
593 }
594
595 /// Note: If the summary type requires a non `()` context, then the filter cursor
596 /// that is returned cannot be used with Rust's iterators.
597 pub fn filter<'a, 'b, F, U>(
598 &'a self,
599 cx: <T::Summary as Summary>::Context<'b>,
600 filter_node: F,
601 ) -> FilterCursor<'a, 'b, F, T, U>
602 where
603 F: FnMut(&T::Summary) -> bool,
604 U: Dimension<'a, T::Summary>,
605 {
606 FilterCursor::new(self, cx, filter_node)
607 }
608
609 #[allow(dead_code)]
610 pub fn first(&self) -> Option<&T> {
611 self.leftmost_leaf().0.items().first()
612 }
613
614 pub fn last(&self) -> Option<&T> {
615 self.rightmost_leaf().0.items().last()
616 }
617
618 pub fn last_summary(&self) -> Option<&T::Summary> {
619 self.rightmost_leaf().0.child_summaries().last()
620 }
621
622 pub fn update_last(
623 &mut self,
624 f: impl FnOnce(&mut T),
625 cx: <T::Summary as Summary>::Context<'_>,
626 ) {
627 self.update_last_recursive(f, cx);
628 }
629
630 fn update_last_recursive(
631 &mut self,
632 f: impl FnOnce(&mut T),
633 cx: <T::Summary as Summary>::Context<'_>,
634 ) -> Option<T::Summary> {
635 match Arc::make_mut(&mut self.0) {
636 Node::Internal {
637 summary,
638 child_summaries,
639 child_trees,
640 ..
641 } => {
642 let last_summary = child_summaries.last_mut().unwrap();
643 let last_child = child_trees.last_mut().unwrap();
644 *last_summary = last_child.update_last_recursive(f, cx).unwrap();
645 *summary = sum(child_summaries.iter(), cx);
646 Some(summary.clone())
647 }
648 Node::Leaf {
649 summary,
650 items,
651 item_summaries,
652 } => {
653 if let Some((item, item_summary)) = items.last_mut().zip(item_summaries.last_mut())
654 {
655 (f)(item);
656 *item_summary = item.summary(cx);
657 *summary = sum(item_summaries.iter(), cx);
658 Some(summary.clone())
659 } else {
660 None
661 }
662 }
663 }
664 }
665
666 pub fn update_first(
667 &mut self,
668 f: impl FnOnce(&mut T),
669 cx: <T::Summary as Summary>::Context<'_>,
670 ) {
671 self.update_first_recursive(f, cx);
672 }
673
674 fn update_first_recursive(
675 &mut self,
676 f: impl FnOnce(&mut T),
677 cx: <T::Summary as Summary>::Context<'_>,
678 ) -> Option<T::Summary> {
679 match Arc::make_mut(&mut self.0) {
680 Node::Internal {
681 summary,
682 child_summaries,
683 child_trees,
684 ..
685 } => {
686 let first_summary = child_summaries.first_mut().unwrap();
687 let first_child = child_trees.first_mut().unwrap();
688 *first_summary = first_child.update_first_recursive(f, cx).unwrap();
689 *summary = sum(child_summaries.iter(), cx);
690 Some(summary.clone())
691 }
692 Node::Leaf {
693 summary,
694 items,
695 item_summaries,
696 } => {
697 if let Some((item, item_summary)) =
698 items.first_mut().zip(item_summaries.first_mut())
699 {
700 (f)(item);
701 *item_summary = item.summary(cx);
702 *summary = sum(item_summaries.iter(), cx);
703 Some(summary.clone())
704 } else {
705 None
706 }
707 }
708 }
709 }
710
711 pub fn extent<'a, D: Dimension<'a, T::Summary>>(
712 &'a self,
713 cx: <T::Summary as Summary>::Context<'_>,
714 ) -> D {
715 let mut extent = D::zero(cx);
716 match self.0.as_ref() {
717 Node::Internal { summary, .. } | Node::Leaf { summary, .. } => {
718 extent.add_summary(summary, cx);
719 }
720 }
721 extent
722 }
723
724 pub fn summary(&self) -> &T::Summary {
725 match self.0.as_ref() {
726 Node::Internal { summary, .. } => summary,
727 Node::Leaf { summary, .. } => summary,
728 }
729 }
730
731 pub fn is_empty(&self) -> bool {
732 match self.0.as_ref() {
733 Node::Internal { .. } => false,
734 Node::Leaf { items, .. } => items.is_empty(),
735 }
736 }
737
738 pub fn extend<I>(&mut self, iter: I, cx: <T::Summary as Summary>::Context<'_>)
739 where
740 I: IntoIterator<Item = T>,
741 {
742 self.append(Self::from_iter(iter, cx), cx);
743 }
744
745 pub fn par_extend<I, Iter>(&mut self, iter: I, cx: <T::Summary as Summary>::Context<'_>)
746 where
747 I: IntoParallelIterator<Iter = Iter>,
748 Iter: IndexedParallelIterator<Item = T>,
749 T: Send + Sync,
750 T::Summary: Send + Sync,
751 for<'a> <T::Summary as Summary>::Context<'a>: Sync,
752 {
753 self.append(Self::from_par_iter(iter, cx), cx);
754 }
755
756 pub fn push(&mut self, item: T, cx: <T::Summary as Summary>::Context<'_>) {
757 let summary = item.summary(cx);
758 self.append(
759 SumTree(Arc::new(Node::Leaf {
760 summary: summary.clone(),
761 items: ArrayVec::from_iter(Some(item)),
762 item_summaries: ArrayVec::from_iter(Some(summary)),
763 })),
764 cx,
765 );
766 }
767
768 pub fn append(&mut self, mut other: Self, cx: <T::Summary as Summary>::Context<'_>) {
769 if self.is_empty() {
770 *self = other;
771 } else if !other.0.is_leaf() || !other.0.items().is_empty() {
772 if self.0.height() < other.0.height() {
773 if let Some(tree) = Self::append_large(self.clone(), &mut other, cx) {
774 *self = Self::from_child_trees(tree, other, cx);
775 } else {
776 *self = other;
777 }
778 } else if let Some(split_tree) = self.push_tree_recursive(other, cx) {
779 *self = Self::from_child_trees(self.clone(), split_tree, cx);
780 }
781 }
782 }
783
784 fn push_tree_recursive(
785 &mut self,
786 other: SumTree<T>,
787 cx: <T::Summary as Summary>::Context<'_>,
788 ) -> Option<SumTree<T>> {
789 match Arc::make_mut(&mut self.0) {
790 Node::Internal {
791 height,
792 summary,
793 child_summaries,
794 child_trees,
795 ..
796 } => {
797 let other_node = other.0.clone();
798 <T::Summary as Summary>::add_summary(summary, other_node.summary(), cx);
799
800 let height_delta = *height - other_node.height();
801 let mut summaries_to_append = ArrayVec::<T::Summary, { 2 * TREE_BASE }>::new();
802 let mut trees_to_append = ArrayVec::<SumTree<T>, { 2 * TREE_BASE }>::new();
803 if height_delta == 0 {
804 summaries_to_append.extend(other_node.child_summaries().iter().cloned());
805 trees_to_append.extend(other_node.child_trees().iter().cloned());
806 } else if height_delta == 1 && !other_node.is_underflowing() {
807 summaries_to_append.push(other_node.summary().clone());
808 trees_to_append.push(other)
809 } else {
810 let tree_to_append = child_trees
811 .last_mut()
812 .unwrap()
813 .push_tree_recursive(other, cx);
814 *child_summaries.last_mut().unwrap() =
815 child_trees.last().unwrap().0.summary().clone();
816
817 if let Some(split_tree) = tree_to_append {
818 summaries_to_append.push(split_tree.0.summary().clone());
819 trees_to_append.push(split_tree);
820 }
821 }
822
823 let child_count = child_trees.len() + trees_to_append.len();
824 if child_count > 2 * TREE_BASE {
825 let left_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
826 let right_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
827 let left_trees;
828 let right_trees;
829
830 let midpoint = (child_count + child_count % 2) / 2;
831 {
832 let mut all_summaries = child_summaries
833 .iter()
834 .chain(summaries_to_append.iter())
835 .cloned();
836 left_summaries = all_summaries.by_ref().take(midpoint).collect();
837 right_summaries = all_summaries.collect();
838 let mut all_trees =
839 child_trees.iter().chain(trees_to_append.iter()).cloned();
840 left_trees = all_trees.by_ref().take(midpoint).collect();
841 right_trees = all_trees.collect();
842 }
843 *summary = sum(left_summaries.iter(), cx);
844 *child_summaries = left_summaries;
845 *child_trees = left_trees;
846
847 Some(SumTree(Arc::new(Node::Internal {
848 height: *height,
849 summary: sum(right_summaries.iter(), cx),
850 child_summaries: right_summaries,
851 child_trees: right_trees,
852 })))
853 } else {
854 child_summaries.extend(summaries_to_append);
855 child_trees.extend(trees_to_append);
856 None
857 }
858 }
859 Node::Leaf {
860 summary,
861 items,
862 item_summaries,
863 } => {
864 let other_node = other.0;
865
866 let child_count = items.len() + other_node.items().len();
867 if child_count > 2 * TREE_BASE {
868 let left_items;
869 let right_items;
870 let left_summaries;
871 let right_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>;
872
873 let midpoint = (child_count + child_count % 2) / 2;
874 {
875 let mut all_items = items.iter().chain(other_node.items().iter()).cloned();
876 left_items = all_items.by_ref().take(midpoint).collect();
877 right_items = all_items.collect();
878
879 let mut all_summaries = item_summaries
880 .iter()
881 .chain(other_node.child_summaries())
882 .cloned();
883 left_summaries = all_summaries.by_ref().take(midpoint).collect();
884 right_summaries = all_summaries.collect();
885 }
886 *items = left_items;
887 *item_summaries = left_summaries;
888 *summary = sum(item_summaries.iter(), cx);
889 Some(SumTree(Arc::new(Node::Leaf {
890 items: right_items,
891 summary: sum(right_summaries.iter(), cx),
892 item_summaries: right_summaries,
893 })))
894 } else {
895 <T::Summary as Summary>::add_summary(summary, other_node.summary(), cx);
896 items.extend(other_node.items().iter().cloned());
897 item_summaries.extend(other_node.child_summaries().iter().cloned());
898 None
899 }
900 }
901 }
902 }
903
904 // appends the `large` tree to a `small` tree, assumes small.height() <= large.height()
905 fn append_large(
906 small: Self,
907 large: &mut Self,
908 cx: <T::Summary as Summary>::Context<'_>,
909 ) -> Option<Self> {
910 if small.0.height() == large.0.height() {
911 if !small.0.is_underflowing() {
912 Some(small)
913 } else {
914 Self::merge_into_right(small, large, cx)
915 }
916 } else {
917 debug_assert!(small.0.height() < large.0.height());
918 let Node::Internal {
919 height,
920 summary,
921 child_summaries,
922 child_trees,
923 } = Arc::make_mut(&mut large.0)
924 else {
925 unreachable!();
926 };
927 let mut full_summary = small.summary().clone();
928 Summary::add_summary(&mut full_summary, summary, cx);
929 *summary = full_summary;
930
931 let first = child_trees.first_mut().unwrap();
932 let res = Self::append_large(small, first, cx);
933 *child_summaries.first_mut().unwrap() = first.summary().clone();
934 if let Some(tree) = res {
935 if child_trees.len() < 2 * TREE_BASE {
936 child_summaries.insert(0, tree.summary().clone());
937 child_trees.insert(0, tree);
938 None
939 } else {
940 let new_child_summaries = {
941 let mut res = ArrayVec::from_iter([tree.summary().clone()]);
942 res.extend(child_summaries.drain(..TREE_BASE));
943 res
944 };
945 let tree = SumTree(Arc::new(Node::Internal {
946 height: *height,
947 summary: sum(new_child_summaries.iter(), cx),
948 child_summaries: new_child_summaries,
949 child_trees: {
950 let mut res = ArrayVec::from_iter([tree]);
951 res.extend(child_trees.drain(..TREE_BASE));
952 res
953 },
954 }));
955
956 *summary = sum(child_summaries.iter(), cx);
957 Some(tree)
958 }
959 } else {
960 None
961 }
962 }
963 }
964
965 // Merge two nodes into `large`.
966 //
967 // `large` will contain the contents of `small` followed by its own data.
968 // If the combined data exceed the node capacity, returns a new node that
969 // holds the first half of the merged items and `large` is left with the
970 // second half
971 //
972 // The nodes must be on the same height
973 // It only makes sense to call this when `small` is underflowing
974 fn merge_into_right(
975 small: Self,
976 large: &mut Self,
977 cx: <<T as Item>::Summary as Summary>::Context<'_>,
978 ) -> Option<SumTree<T>> {
979 debug_assert_eq!(small.0.height(), large.0.height());
980 match (small.0.as_ref(), Arc::make_mut(&mut large.0)) {
981 (
982 Node::Internal {
983 summary: small_summary,
984 child_summaries: small_child_summaries,
985 child_trees: small_child_trees,
986 ..
987 },
988 Node::Internal {
989 summary,
990 child_summaries,
991 child_trees,
992 height,
993 },
994 ) => {
995 let total_child_count = child_trees.len() + small_child_trees.len();
996 if total_child_count <= 2 * TREE_BASE {
997 let mut all_trees = small_child_trees.clone();
998 all_trees.extend(child_trees.drain(..));
999 *child_trees = all_trees;
1000
1001 let mut all_summaries = small_child_summaries.clone();
1002 all_summaries.extend(child_summaries.drain(..));
1003 *child_summaries = all_summaries;
1004
1005 let mut full_summary = small_summary.clone();
1006 Summary::add_summary(&mut full_summary, summary, cx);
1007 *summary = full_summary;
1008 None
1009 } else {
1010 let midpoint = total_child_count.div_ceil(2);
1011 let mut all_trees = small_child_trees.iter().chain(child_trees.iter()).cloned();
1012 let left_trees = all_trees.by_ref().take(midpoint).collect();
1013 *child_trees = all_trees.collect();
1014
1015 let mut all_summaries = small_child_summaries
1016 .iter()
1017 .chain(child_summaries.iter())
1018 .cloned();
1019 let left_summaries: ArrayVec<_, { 2 * TREE_BASE }> =
1020 all_summaries.by_ref().take(midpoint).collect();
1021 *child_summaries = all_summaries.collect();
1022
1023 *summary = sum(child_summaries.iter(), cx);
1024 Some(SumTree(Arc::new(Node::Internal {
1025 height: *height,
1026 summary: sum(left_summaries.iter(), cx),
1027 child_summaries: left_summaries,
1028 child_trees: left_trees,
1029 })))
1030 }
1031 }
1032 (
1033 Node::Leaf {
1034 summary: small_summary,
1035 items: small_items,
1036 item_summaries: small_item_summaries,
1037 },
1038 Node::Leaf {
1039 summary,
1040 items,
1041 item_summaries,
1042 },
1043 ) => {
1044 let total_child_count = small_items.len() + items.len();
1045 if total_child_count <= 2 * TREE_BASE {
1046 let mut all_items = small_items.clone();
1047 all_items.extend(items.drain(..));
1048 *items = all_items;
1049
1050 let mut all_summaries = small_item_summaries.clone();
1051 all_summaries.extend(item_summaries.drain(..));
1052 *item_summaries = all_summaries;
1053
1054 let mut full_summary = small_summary.clone();
1055 Summary::add_summary(&mut full_summary, summary, cx);
1056 *summary = full_summary;
1057 None
1058 } else {
1059 let midpoint = total_child_count.div_ceil(2);
1060 let mut all_items = small_items.iter().chain(items.iter()).cloned();
1061 let left_items = all_items.by_ref().take(midpoint).collect();
1062 *items = all_items.collect();
1063
1064 let mut all_summaries = small_item_summaries
1065 .iter()
1066 .chain(item_summaries.iter())
1067 .cloned();
1068 let left_summaries: ArrayVec<_, { 2 * TREE_BASE }> =
1069 all_summaries.by_ref().take(midpoint).collect();
1070 *item_summaries = all_summaries.collect();
1071
1072 *summary = sum(item_summaries.iter(), cx);
1073 Some(SumTree(Arc::new(Node::Leaf {
1074 items: left_items,
1075 summary: sum(left_summaries.iter(), cx),
1076 item_summaries: left_summaries,
1077 })))
1078 }
1079 }
1080 _ => unreachable!(),
1081 }
1082 }
1083
1084 fn from_child_trees(
1085 left: SumTree<T>,
1086 right: SumTree<T>,
1087 cx: <T::Summary as Summary>::Context<'_>,
1088 ) -> Self {
1089 let height = left.0.height() + 1;
1090 let mut child_summaries = ArrayVec::new();
1091 child_summaries.push(left.0.summary().clone());
1092 child_summaries.push(right.0.summary().clone());
1093 let mut child_trees = ArrayVec::new();
1094 child_trees.push(left);
1095 child_trees.push(right);
1096 SumTree(Arc::new(Node::Internal {
1097 height,
1098 summary: sum(child_summaries.iter(), cx),
1099 child_summaries,
1100 child_trees,
1101 }))
1102 }
1103
1104 fn leftmost_leaf(&self) -> &Self {
1105 match *self.0 {
1106 Node::Leaf { .. } => self,
1107 Node::Internal {
1108 ref child_trees, ..
1109 } => child_trees.first().unwrap().leftmost_leaf(),
1110 }
1111 }
1112
1113 fn rightmost_leaf(&self) -> &Self {
1114 match *self.0 {
1115 Node::Leaf { .. } => self,
1116 Node::Internal {
1117 ref child_trees, ..
1118 } => child_trees.last().unwrap().rightmost_leaf(),
1119 }
1120 }
1121}
1122
1123impl<T: Item + PartialEq> PartialEq for SumTree<T> {
1124 fn eq(&self, other: &Self) -> bool {
1125 self.iter().eq(other.iter())
1126 }
1127}
1128
1129impl<T: Item + Eq> Eq for SumTree<T> {}
1130
1131impl<T: KeyedItem> SumTree<T> {
1132 pub fn insert_or_replace<'a, 'b>(
1133 &'a mut self,
1134 item: T,
1135 cx: <T::Summary as Summary>::Context<'b>,
1136 ) -> Option<T> {
1137 let mut replaced = None;
1138 {
1139 let mut cursor = self.cursor::<T::Key>(cx);
1140 let mut new_tree = cursor.slice(&item.key(), Bias::Left);
1141 if let Some(cursor_item) = cursor.item()
1142 && cursor_item.key() == item.key()
1143 {
1144 replaced = Some(cursor_item.clone());
1145 cursor.next();
1146 }
1147 new_tree.push(item, cx);
1148 new_tree.append(cursor.suffix(), cx);
1149 drop(cursor);
1150 *self = new_tree
1151 };
1152 replaced
1153 }
1154
1155 pub fn remove(&mut self, key: &T::Key, cx: <T::Summary as Summary>::Context<'_>) -> Option<T> {
1156 let mut removed = None;
1157 *self = {
1158 let mut cursor = self.cursor::<T::Key>(cx);
1159 let mut new_tree = cursor.slice(key, Bias::Left);
1160 if let Some(item) = cursor.item()
1161 && item.key() == *key
1162 {
1163 removed = Some(item.clone());
1164 cursor.next();
1165 }
1166 new_tree.append(cursor.suffix(), cx);
1167 new_tree
1168 };
1169 removed
1170 }
1171
1172 pub fn edit(
1173 &mut self,
1174 mut edits: Vec<Edit<T>>,
1175 cx: <T::Summary as Summary>::Context<'_>,
1176 ) -> Vec<T> {
1177 if edits.is_empty() {
1178 return Vec::new();
1179 }
1180
1181 let mut removed = Vec::new();
1182 edits.sort_unstable_by_key(|item| item.key());
1183
1184 *self = {
1185 let mut cursor = self.cursor::<T::Key>(cx);
1186 let mut new_tree = SumTree::new(cx);
1187 let mut buffered_items = Vec::new();
1188
1189 cursor.seek(&T::Key::zero(cx), Bias::Left);
1190 for edit in edits {
1191 let new_key = edit.key();
1192 let mut old_item = cursor.item();
1193
1194 if old_item
1195 .as_ref()
1196 .is_some_and(|old_item| old_item.key() < new_key)
1197 {
1198 new_tree.extend(buffered_items.drain(..), cx);
1199 let slice = cursor.slice(&new_key, Bias::Left);
1200 new_tree.append(slice, cx);
1201 old_item = cursor.item();
1202 }
1203
1204 if let Some(old_item) = old_item
1205 && old_item.key() == new_key
1206 {
1207 removed.push(old_item.clone());
1208 cursor.next();
1209 }
1210
1211 match edit {
1212 Edit::Insert(item) => {
1213 buffered_items.push(item);
1214 }
1215 Edit::Remove(_) => {}
1216 }
1217 }
1218
1219 new_tree.extend(buffered_items, cx);
1220 new_tree.append(cursor.suffix(), cx);
1221 new_tree
1222 };
1223
1224 removed
1225 }
1226
1227 pub fn get<'a>(
1228 &'a self,
1229 key: &T::Key,
1230 cx: <T::Summary as Summary>::Context<'a>,
1231 ) -> Option<&'a T> {
1232 if let (_, _, Some(item)) = self.find_exact::<T::Key, _>(cx, key, Bias::Left) {
1233 Some(item)
1234 } else {
1235 None
1236 }
1237 }
1238}
1239
1240impl<T, S> Default for SumTree<T>
1241where
1242 T: Item<Summary = S>,
1243 S: for<'a> Summary<Context<'a> = ()>,
1244{
1245 fn default() -> Self {
1246 Self::new(())
1247 }
1248}
1249
1250#[derive(Clone)]
1251pub enum Node<T: Item> {
1252 Internal {
1253 height: u8,
1254 summary: T::Summary,
1255 child_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
1256 child_trees: ArrayVec<SumTree<T>, { 2 * TREE_BASE }>,
1257 },
1258 Leaf {
1259 summary: T::Summary,
1260 items: ArrayVec<T, { 2 * TREE_BASE }>,
1261 item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
1262 },
1263}
1264
1265impl<T> fmt::Debug for Node<T>
1266where
1267 T: Item + fmt::Debug,
1268 T::Summary: fmt::Debug,
1269{
1270 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1271 match self {
1272 Node::Internal {
1273 height,
1274 summary,
1275 child_summaries,
1276 child_trees,
1277 } => f
1278 .debug_struct("Internal")
1279 .field("height", height)
1280 .field("summary", summary)
1281 .field("child_summaries", child_summaries)
1282 .field("child_trees", child_trees)
1283 .finish(),
1284 Node::Leaf {
1285 summary,
1286 items,
1287 item_summaries,
1288 } => f
1289 .debug_struct("Leaf")
1290 .field("summary", summary)
1291 .field("items", items)
1292 .field("item_summaries", item_summaries)
1293 .finish(),
1294 }
1295 }
1296}
1297
1298impl<T: Item> Node<T> {
1299 fn is_leaf(&self) -> bool {
1300 matches!(self, Node::Leaf { .. })
1301 }
1302
1303 fn height(&self) -> u8 {
1304 match self {
1305 Node::Internal { height, .. } => *height,
1306 Node::Leaf { .. } => 0,
1307 }
1308 }
1309
1310 fn summary(&self) -> &T::Summary {
1311 match self {
1312 Node::Internal { summary, .. } => summary,
1313 Node::Leaf { summary, .. } => summary,
1314 }
1315 }
1316
1317 fn child_summaries(&self) -> &[T::Summary] {
1318 match self {
1319 Node::Internal {
1320 child_summaries, ..
1321 } => child_summaries.as_slice(),
1322 Node::Leaf { item_summaries, .. } => item_summaries.as_slice(),
1323 }
1324 }
1325
1326 fn child_trees(&self) -> &ArrayVec<SumTree<T>, { 2 * TREE_BASE }> {
1327 match self {
1328 Node::Internal { child_trees, .. } => child_trees,
1329 Node::Leaf { .. } => panic!("Leaf nodes have no child trees"),
1330 }
1331 }
1332
1333 fn items(&self) -> &ArrayVec<T, { 2 * TREE_BASE }> {
1334 match self {
1335 Node::Leaf { items, .. } => items,
1336 Node::Internal { .. } => panic!("Internal nodes have no items"),
1337 }
1338 }
1339
1340 fn is_underflowing(&self) -> bool {
1341 match self {
1342 Node::Internal { child_trees, .. } => child_trees.len() < TREE_BASE,
1343 Node::Leaf { items, .. } => items.len() < TREE_BASE,
1344 }
1345 }
1346}
1347
1348#[derive(Debug)]
1349pub enum Edit<T: KeyedItem> {
1350 Insert(T),
1351 Remove(T::Key),
1352}
1353
1354impl<T: KeyedItem> Edit<T> {
1355 fn key(&self) -> T::Key {
1356 match self {
1357 Edit::Insert(item) => item.key(),
1358 Edit::Remove(key) => key.clone(),
1359 }
1360 }
1361}
1362
1363fn sum<'a, T, I>(iter: I, cx: T::Context<'_>) -> T
1364where
1365 T: 'a + Summary,
1366 I: Iterator<Item = &'a T>,
1367{
1368 let mut sum = T::zero(cx);
1369 for value in iter {
1370 sum.add_summary(value, cx);
1371 }
1372 sum
1373}
1374
1375#[cfg(test)]
1376mod tests {
1377 use super::*;
1378 use rand::{distr::StandardUniform, prelude::*};
1379 use std::cmp;
1380
1381 #[ctor::ctor]
1382 fn init_logger() {
1383 zlog::init_test();
1384 }
1385
1386 #[test]
1387 fn test_extend_and_push_tree() {
1388 let mut tree1 = SumTree::default();
1389 tree1.extend(0..20, ());
1390
1391 let mut tree2 = SumTree::default();
1392 tree2.extend(50..100, ());
1393
1394 tree1.append(tree2, ());
1395 assert_eq!(tree1.items(()), (0..20).chain(50..100).collect::<Vec<u8>>());
1396 }
1397
1398 #[test]
1399 fn test_random() {
1400 let mut starting_seed = 0;
1401 if let Ok(value) = std::env::var("SEED") {
1402 starting_seed = value.parse().expect("invalid SEED variable");
1403 }
1404 let mut num_iterations = 100;
1405 if let Ok(value) = std::env::var("ITERATIONS") {
1406 num_iterations = value.parse().expect("invalid ITERATIONS variable");
1407 }
1408 let num_operations = std::env::var("OPERATIONS")
1409 .map_or(5, |o| o.parse().expect("invalid OPERATIONS variable"));
1410
1411 for seed in starting_seed..(starting_seed + num_iterations) {
1412 eprintln!("seed = {}", seed);
1413 let mut rng = StdRng::seed_from_u64(seed);
1414
1415 let rng = &mut rng;
1416 let mut tree = SumTree::<u8>::default();
1417 let count = rng.random_range(0..10);
1418 if rng.random() {
1419 tree.extend(rng.sample_iter(StandardUniform).take(count), ());
1420 } else {
1421 let items = rng
1422 .sample_iter(StandardUniform)
1423 .take(count)
1424 .collect::<Vec<_>>();
1425 tree.par_extend(items, ());
1426 }
1427
1428 for _ in 0..num_operations {
1429 let splice_end = rng.random_range(0..tree.extent::<Count>(()).0 + 1);
1430 let splice_start = rng.random_range(0..splice_end + 1);
1431 let count = rng.random_range(0..10);
1432 let tree_end = tree.extent::<Count>(());
1433 let new_items = rng
1434 .sample_iter(StandardUniform)
1435 .take(count)
1436 .collect::<Vec<u8>>();
1437
1438 let mut reference_items = tree.items(());
1439 reference_items.splice(splice_start..splice_end, new_items.clone());
1440
1441 tree = {
1442 let mut cursor = tree.cursor::<Count>(());
1443 let mut new_tree = cursor.slice(&Count(splice_start), Bias::Right);
1444 if rng.random() {
1445 new_tree.extend(new_items, ());
1446 } else {
1447 new_tree.par_extend(new_items, ());
1448 }
1449 cursor.seek(&Count(splice_end), Bias::Right);
1450 new_tree.append(cursor.slice(&tree_end, Bias::Right), ());
1451 new_tree
1452 };
1453
1454 assert_eq!(tree.items(()), reference_items);
1455 assert_eq!(
1456 tree.iter().collect::<Vec<_>>(),
1457 tree.cursor::<()>(()).collect::<Vec<_>>()
1458 );
1459
1460 log::info!("tree items: {:?}", tree.items(()));
1461
1462 let mut filter_cursor =
1463 tree.filter::<_, Count>((), |summary| summary.contains_even);
1464 let expected_filtered_items = tree
1465 .items(())
1466 .into_iter()
1467 .enumerate()
1468 .filter(|(_, item)| (item & 1) == 0)
1469 .collect::<Vec<_>>();
1470
1471 let mut item_ix = if rng.random() {
1472 filter_cursor.next();
1473 0
1474 } else {
1475 filter_cursor.prev();
1476 expected_filtered_items.len().saturating_sub(1)
1477 };
1478 while item_ix < expected_filtered_items.len() {
1479 log::info!("filter_cursor, item_ix: {}", item_ix);
1480 let actual_item = filter_cursor.item().unwrap();
1481 let (reference_index, reference_item) = expected_filtered_items[item_ix];
1482 assert_eq!(actual_item, &reference_item);
1483 assert_eq!(filter_cursor.start().0, reference_index);
1484 log::info!("next");
1485 filter_cursor.next();
1486 item_ix += 1;
1487
1488 while item_ix > 0 && rng.random_bool(0.2) {
1489 log::info!("prev");
1490 filter_cursor.prev();
1491 item_ix -= 1;
1492
1493 if item_ix == 0 && rng.random_bool(0.2) {
1494 filter_cursor.prev();
1495 assert_eq!(filter_cursor.item(), None);
1496 assert_eq!(filter_cursor.start().0, 0);
1497 filter_cursor.next();
1498 }
1499 }
1500 }
1501 assert_eq!(filter_cursor.item(), None);
1502
1503 let mut before_start = false;
1504 let mut cursor = tree.cursor::<Count>(());
1505 let start_pos = rng.random_range(0..=reference_items.len());
1506 cursor.seek(&Count(start_pos), Bias::Right);
1507 let mut pos = rng.random_range(start_pos..=reference_items.len());
1508 cursor.seek_forward(&Count(pos), Bias::Right);
1509
1510 for i in 0..10 {
1511 assert_eq!(cursor.start().0, pos);
1512
1513 if pos > 0 {
1514 assert_eq!(cursor.prev_item().unwrap(), &reference_items[pos - 1]);
1515 } else {
1516 assert_eq!(cursor.prev_item(), None);
1517 }
1518
1519 if pos < reference_items.len() && !before_start {
1520 assert_eq!(cursor.item().unwrap(), &reference_items[pos]);
1521 } else {
1522 assert_eq!(cursor.item(), None);
1523 }
1524
1525 if before_start {
1526 assert_eq!(cursor.next_item(), reference_items.first());
1527 } else if pos + 1 < reference_items.len() {
1528 assert_eq!(cursor.next_item().unwrap(), &reference_items[pos + 1]);
1529 } else {
1530 assert_eq!(cursor.next_item(), None);
1531 }
1532
1533 if i < 5 {
1534 cursor.next();
1535 if pos < reference_items.len() {
1536 pos += 1;
1537 before_start = false;
1538 }
1539 } else {
1540 cursor.prev();
1541 if pos == 0 {
1542 before_start = true;
1543 }
1544 pos = pos.saturating_sub(1);
1545 }
1546 }
1547 }
1548
1549 for _ in 0..10 {
1550 let end = rng.random_range(0..tree.extent::<Count>(()).0 + 1);
1551 let start = rng.random_range(0..end + 1);
1552 let start_bias = if rng.random() {
1553 Bias::Left
1554 } else {
1555 Bias::Right
1556 };
1557 let end_bias = if rng.random() {
1558 Bias::Left
1559 } else {
1560 Bias::Right
1561 };
1562
1563 let mut cursor = tree.cursor::<Count>(());
1564 cursor.seek(&Count(start), start_bias);
1565 let slice = cursor.slice(&Count(end), end_bias);
1566
1567 cursor.seek(&Count(start), start_bias);
1568 let summary = cursor.summary::<_, Sum>(&Count(end), end_bias);
1569
1570 assert_eq!(summary.0, slice.summary().sum);
1571 }
1572 }
1573 }
1574
1575 #[test]
1576 fn test_cursor() {
1577 // Empty tree
1578 let tree = SumTree::<u8>::default();
1579 let mut cursor = tree.cursor::<IntegersSummary>(());
1580 assert_eq!(
1581 cursor.slice(&Count(0), Bias::Right).items(()),
1582 Vec::<u8>::new()
1583 );
1584 assert_eq!(cursor.item(), None);
1585 assert_eq!(cursor.prev_item(), None);
1586 assert_eq!(cursor.next_item(), None);
1587 assert_eq!(cursor.start().sum, 0);
1588 cursor.prev();
1589 assert_eq!(cursor.item(), None);
1590 assert_eq!(cursor.prev_item(), None);
1591 assert_eq!(cursor.next_item(), None);
1592 assert_eq!(cursor.start().sum, 0);
1593 cursor.next();
1594 assert_eq!(cursor.item(), None);
1595 assert_eq!(cursor.prev_item(), None);
1596 assert_eq!(cursor.next_item(), None);
1597 assert_eq!(cursor.start().sum, 0);
1598
1599 // Single-element tree
1600 let mut tree = SumTree::<u8>::default();
1601 tree.extend(vec![1], ());
1602 let mut cursor = tree.cursor::<IntegersSummary>(());
1603 assert_eq!(
1604 cursor.slice(&Count(0), Bias::Right).items(()),
1605 Vec::<u8>::new()
1606 );
1607 assert_eq!(cursor.item(), Some(&1));
1608 assert_eq!(cursor.prev_item(), None);
1609 assert_eq!(cursor.next_item(), None);
1610 assert_eq!(cursor.start().sum, 0);
1611
1612 cursor.next();
1613 assert_eq!(cursor.item(), None);
1614 assert_eq!(cursor.prev_item(), Some(&1));
1615 assert_eq!(cursor.next_item(), None);
1616 assert_eq!(cursor.start().sum, 1);
1617
1618 cursor.prev();
1619 assert_eq!(cursor.item(), Some(&1));
1620 assert_eq!(cursor.prev_item(), None);
1621 assert_eq!(cursor.next_item(), None);
1622 assert_eq!(cursor.start().sum, 0);
1623
1624 let mut cursor = tree.cursor::<IntegersSummary>(());
1625 assert_eq!(cursor.slice(&Count(1), Bias::Right).items(()), [1]);
1626 assert_eq!(cursor.item(), None);
1627 assert_eq!(cursor.prev_item(), Some(&1));
1628 assert_eq!(cursor.next_item(), None);
1629 assert_eq!(cursor.start().sum, 1);
1630
1631 cursor.seek(&Count(0), Bias::Right);
1632 assert_eq!(
1633 cursor
1634 .slice(&tree.extent::<Count>(()), Bias::Right)
1635 .items(()),
1636 [1]
1637 );
1638 assert_eq!(cursor.item(), None);
1639 assert_eq!(cursor.prev_item(), Some(&1));
1640 assert_eq!(cursor.next_item(), None);
1641 assert_eq!(cursor.start().sum, 1);
1642
1643 // Multiple-element tree
1644 let mut tree = SumTree::default();
1645 tree.extend(vec![1, 2, 3, 4, 5, 6], ());
1646 let mut cursor = tree.cursor::<IntegersSummary>(());
1647
1648 assert_eq!(cursor.slice(&Count(2), Bias::Right).items(()), [1, 2]);
1649 assert_eq!(cursor.item(), Some(&3));
1650 assert_eq!(cursor.prev_item(), Some(&2));
1651 assert_eq!(cursor.next_item(), Some(&4));
1652 assert_eq!(cursor.start().sum, 3);
1653
1654 cursor.next();
1655 assert_eq!(cursor.item(), Some(&4));
1656 assert_eq!(cursor.prev_item(), Some(&3));
1657 assert_eq!(cursor.next_item(), Some(&5));
1658 assert_eq!(cursor.start().sum, 6);
1659
1660 cursor.next();
1661 assert_eq!(cursor.item(), Some(&5));
1662 assert_eq!(cursor.prev_item(), Some(&4));
1663 assert_eq!(cursor.next_item(), Some(&6));
1664 assert_eq!(cursor.start().sum, 10);
1665
1666 cursor.next();
1667 assert_eq!(cursor.item(), Some(&6));
1668 assert_eq!(cursor.prev_item(), Some(&5));
1669 assert_eq!(cursor.next_item(), None);
1670 assert_eq!(cursor.start().sum, 15);
1671
1672 cursor.next();
1673 cursor.next();
1674 assert_eq!(cursor.item(), None);
1675 assert_eq!(cursor.prev_item(), Some(&6));
1676 assert_eq!(cursor.next_item(), None);
1677 assert_eq!(cursor.start().sum, 21);
1678
1679 cursor.prev();
1680 assert_eq!(cursor.item(), Some(&6));
1681 assert_eq!(cursor.prev_item(), Some(&5));
1682 assert_eq!(cursor.next_item(), None);
1683 assert_eq!(cursor.start().sum, 15);
1684
1685 cursor.prev();
1686 assert_eq!(cursor.item(), Some(&5));
1687 assert_eq!(cursor.prev_item(), Some(&4));
1688 assert_eq!(cursor.next_item(), Some(&6));
1689 assert_eq!(cursor.start().sum, 10);
1690
1691 cursor.prev();
1692 assert_eq!(cursor.item(), Some(&4));
1693 assert_eq!(cursor.prev_item(), Some(&3));
1694 assert_eq!(cursor.next_item(), Some(&5));
1695 assert_eq!(cursor.start().sum, 6);
1696
1697 cursor.prev();
1698 assert_eq!(cursor.item(), Some(&3));
1699 assert_eq!(cursor.prev_item(), Some(&2));
1700 assert_eq!(cursor.next_item(), Some(&4));
1701 assert_eq!(cursor.start().sum, 3);
1702
1703 cursor.prev();
1704 assert_eq!(cursor.item(), Some(&2));
1705 assert_eq!(cursor.prev_item(), Some(&1));
1706 assert_eq!(cursor.next_item(), Some(&3));
1707 assert_eq!(cursor.start().sum, 1);
1708
1709 cursor.prev();
1710 assert_eq!(cursor.item(), Some(&1));
1711 assert_eq!(cursor.prev_item(), None);
1712 assert_eq!(cursor.next_item(), Some(&2));
1713 assert_eq!(cursor.start().sum, 0);
1714
1715 cursor.prev();
1716 assert_eq!(cursor.item(), None);
1717 assert_eq!(cursor.prev_item(), None);
1718 assert_eq!(cursor.next_item(), Some(&1));
1719 assert_eq!(cursor.start().sum, 0);
1720
1721 cursor.next();
1722 assert_eq!(cursor.item(), Some(&1));
1723 assert_eq!(cursor.prev_item(), None);
1724 assert_eq!(cursor.next_item(), Some(&2));
1725 assert_eq!(cursor.start().sum, 0);
1726
1727 let mut cursor = tree.cursor::<IntegersSummary>(());
1728 assert_eq!(
1729 cursor
1730 .slice(&tree.extent::<Count>(()), Bias::Right)
1731 .items(()),
1732 tree.items(())
1733 );
1734 assert_eq!(cursor.item(), None);
1735 assert_eq!(cursor.prev_item(), Some(&6));
1736 assert_eq!(cursor.next_item(), None);
1737 assert_eq!(cursor.start().sum, 21);
1738
1739 cursor.seek(&Count(3), Bias::Right);
1740 assert_eq!(
1741 cursor
1742 .slice(&tree.extent::<Count>(()), Bias::Right)
1743 .items(()),
1744 [4, 5, 6]
1745 );
1746 assert_eq!(cursor.item(), None);
1747 assert_eq!(cursor.prev_item(), Some(&6));
1748 assert_eq!(cursor.next_item(), None);
1749 assert_eq!(cursor.start().sum, 21);
1750
1751 // Seeking can bias left or right
1752 cursor.seek(&Count(1), Bias::Left);
1753 assert_eq!(cursor.item(), Some(&1));
1754 cursor.seek(&Count(1), Bias::Right);
1755 assert_eq!(cursor.item(), Some(&2));
1756
1757 // Slicing without resetting starts from where the cursor is parked at.
1758 cursor.seek(&Count(1), Bias::Right);
1759 assert_eq!(cursor.slice(&Count(3), Bias::Right).items(()), vec![2, 3]);
1760 assert_eq!(cursor.slice(&Count(6), Bias::Left).items(()), vec![4, 5]);
1761 assert_eq!(cursor.slice(&Count(6), Bias::Right).items(()), vec![6]);
1762 }
1763
1764 #[test]
1765 fn test_edit() {
1766 let mut tree = SumTree::<u8>::default();
1767
1768 let removed = tree.edit(vec![Edit::Insert(1), Edit::Insert(2), Edit::Insert(0)], ());
1769 assert_eq!(tree.items(()), vec![0, 1, 2]);
1770 assert_eq!(removed, Vec::<u8>::new());
1771 assert_eq!(tree.get(&0, ()), Some(&0));
1772 assert_eq!(tree.get(&1, ()), Some(&1));
1773 assert_eq!(tree.get(&2, ()), Some(&2));
1774 assert_eq!(tree.get(&4, ()), None);
1775
1776 let removed = tree.edit(vec![Edit::Insert(2), Edit::Insert(4), Edit::Remove(0)], ());
1777 assert_eq!(tree.items(()), vec![1, 2, 4]);
1778 assert_eq!(removed, vec![0, 2]);
1779 assert_eq!(tree.get(&0, ()), None);
1780 assert_eq!(tree.get(&1, ()), Some(&1));
1781 assert_eq!(tree.get(&2, ()), Some(&2));
1782 assert_eq!(tree.get(&4, ()), Some(&4));
1783 }
1784
1785 #[test]
1786 fn test_from_iter() {
1787 assert_eq!(
1788 SumTree::from_iter(0..100, ()).items(()),
1789 (0..100).collect::<Vec<_>>()
1790 );
1791
1792 // Ensure `from_iter` works correctly when the given iterator restarts
1793 // after calling `next` if `None` was already returned.
1794 let mut ix = 0;
1795 let iterator = std::iter::from_fn(|| {
1796 ix = (ix + 1) % 2;
1797 if ix == 1 { Some(1) } else { None }
1798 });
1799 assert_eq!(SumTree::from_iter(iterator, ()).items(()), vec![1]);
1800 }
1801
1802 #[derive(Clone, Default, Debug)]
1803 pub struct IntegersSummary {
1804 count: usize,
1805 sum: usize,
1806 contains_even: bool,
1807 max: u8,
1808 }
1809
1810 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
1811 struct Count(usize);
1812
1813 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
1814 struct Sum(usize);
1815
1816 impl Item for u8 {
1817 type Summary = IntegersSummary;
1818
1819 fn summary(&self, _cx: ()) -> Self::Summary {
1820 IntegersSummary {
1821 count: 1,
1822 sum: *self as usize,
1823 contains_even: (*self & 1) == 0,
1824 max: *self,
1825 }
1826 }
1827 }
1828
1829 impl KeyedItem for u8 {
1830 type Key = u8;
1831
1832 fn key(&self) -> Self::Key {
1833 *self
1834 }
1835 }
1836
1837 impl ContextLessSummary for IntegersSummary {
1838 fn zero() -> Self {
1839 Default::default()
1840 }
1841
1842 fn add_summary(&mut self, other: &Self) {
1843 self.count += other.count;
1844 self.sum += other.sum;
1845 self.contains_even |= other.contains_even;
1846 self.max = cmp::max(self.max, other.max);
1847 }
1848 }
1849
1850 impl Dimension<'_, IntegersSummary> for u8 {
1851 fn zero(_cx: ()) -> Self {
1852 Default::default()
1853 }
1854
1855 fn add_summary(&mut self, summary: &IntegersSummary, _: ()) {
1856 *self = summary.max;
1857 }
1858 }
1859
1860 impl Dimension<'_, IntegersSummary> for Count {
1861 fn zero(_cx: ()) -> Self {
1862 Default::default()
1863 }
1864
1865 fn add_summary(&mut self, summary: &IntegersSummary, _: ()) {
1866 self.0 += summary.count;
1867 }
1868 }
1869
1870 impl SeekTarget<'_, IntegersSummary, IntegersSummary> for Count {
1871 fn cmp(&self, cursor_location: &IntegersSummary, _: ()) -> Ordering {
1872 self.0.cmp(&cursor_location.count)
1873 }
1874 }
1875
1876 impl Dimension<'_, IntegersSummary> for Sum {
1877 fn zero(_cx: ()) -> Self {
1878 Default::default()
1879 }
1880
1881 fn add_summary(&mut self, summary: &IntegersSummary, _: ()) {
1882 self.0 += summary.sum;
1883 }
1884 }
1885}