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