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