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