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