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 fn push_tree_recursive(
520 &mut self,
521 other: SumTree<T>,
522 cx: &<T::Summary as Summary>::Context,
523 ) -> Option<SumTree<T>> {
524 match Arc::make_mut(&mut self.0) {
525 Node::Internal {
526 height,
527 summary,
528 child_summaries,
529 child_trees,
530 ..
531 } => {
532 let other_node = other.0.clone();
533 <T::Summary as Summary>::add_summary(summary, other_node.summary(), cx);
534
535 let height_delta = *height - other_node.height();
536 let mut summaries_to_append = ArrayVec::<T::Summary, { 2 * TREE_BASE }>::new();
537 let mut trees_to_append = ArrayVec::<SumTree<T>, { 2 * TREE_BASE }>::new();
538 if height_delta == 0 {
539 summaries_to_append.extend(other_node.child_summaries().iter().cloned());
540 trees_to_append.extend(other_node.child_trees().iter().cloned());
541 } else if height_delta == 1 && !other_node.is_underflowing() {
542 summaries_to_append.push(other_node.summary().clone());
543 trees_to_append.push(other)
544 } else {
545 let tree_to_append = child_trees
546 .last_mut()
547 .unwrap()
548 .push_tree_recursive(other, cx);
549 *child_summaries.last_mut().unwrap() =
550 child_trees.last().unwrap().0.summary().clone();
551
552 if let Some(split_tree) = tree_to_append {
553 summaries_to_append.push(split_tree.0.summary().clone());
554 trees_to_append.push(split_tree);
555 }
556 }
557
558 let child_count = child_trees.len() + trees_to_append.len();
559 if child_count > 2 * TREE_BASE {
560 let left_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
561 let right_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
562 let left_trees;
563 let right_trees;
564
565 let midpoint = (child_count + child_count % 2) / 2;
566 {
567 let mut all_summaries = child_summaries
568 .iter()
569 .chain(summaries_to_append.iter())
570 .cloned();
571 left_summaries = all_summaries.by_ref().take(midpoint).collect();
572 right_summaries = all_summaries.collect();
573 let mut all_trees =
574 child_trees.iter().chain(trees_to_append.iter()).cloned();
575 left_trees = all_trees.by_ref().take(midpoint).collect();
576 right_trees = all_trees.collect();
577 }
578 *summary = sum(left_summaries.iter(), cx);
579 *child_summaries = left_summaries;
580 *child_trees = left_trees;
581
582 Some(SumTree(Arc::new(Node::Internal {
583 height: *height,
584 summary: sum(right_summaries.iter(), cx),
585 child_summaries: right_summaries,
586 child_trees: right_trees,
587 })))
588 } else {
589 child_summaries.extend(summaries_to_append);
590 child_trees.extend(trees_to_append);
591 None
592 }
593 }
594 Node::Leaf {
595 summary,
596 items,
597 item_summaries,
598 } => {
599 let other_node = other.0;
600
601 let child_count = items.len() + other_node.items().len();
602 if child_count > 2 * TREE_BASE {
603 let left_items;
604 let right_items;
605 let left_summaries;
606 let right_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>;
607
608 let midpoint = (child_count + child_count % 2) / 2;
609 {
610 let mut all_items = items.iter().chain(other_node.items().iter()).cloned();
611 left_items = all_items.by_ref().take(midpoint).collect();
612 right_items = all_items.collect();
613
614 let mut all_summaries = item_summaries
615 .iter()
616 .chain(other_node.child_summaries())
617 .cloned();
618 left_summaries = all_summaries.by_ref().take(midpoint).collect();
619 right_summaries = all_summaries.collect();
620 }
621 *items = left_items;
622 *item_summaries = left_summaries;
623 *summary = sum(item_summaries.iter(), cx);
624 Some(SumTree(Arc::new(Node::Leaf {
625 items: right_items,
626 summary: sum(right_summaries.iter(), cx),
627 item_summaries: right_summaries,
628 })))
629 } else {
630 <T::Summary as Summary>::add_summary(summary, other_node.summary(), cx);
631 items.extend(other_node.items().iter().cloned());
632 item_summaries.extend(other_node.child_summaries().iter().cloned());
633 None
634 }
635 }
636 }
637 }
638
639 fn from_child_trees(
640 left: SumTree<T>,
641 right: SumTree<T>,
642 cx: &<T::Summary as Summary>::Context,
643 ) -> Self {
644 let height = left.0.height() + 1;
645 let mut child_summaries = ArrayVec::new();
646 child_summaries.push(left.0.summary().clone());
647 child_summaries.push(right.0.summary().clone());
648 let mut child_trees = ArrayVec::new();
649 child_trees.push(left);
650 child_trees.push(right);
651 SumTree(Arc::new(Node::Internal {
652 height,
653 summary: sum(child_summaries.iter(), cx),
654 child_summaries,
655 child_trees,
656 }))
657 }
658
659 fn leftmost_leaf(&self) -> &Self {
660 match *self.0 {
661 Node::Leaf { .. } => self,
662 Node::Internal {
663 ref child_trees, ..
664 } => child_trees.first().unwrap().leftmost_leaf(),
665 }
666 }
667
668 fn rightmost_leaf(&self) -> &Self {
669 match *self.0 {
670 Node::Leaf { .. } => self,
671 Node::Internal {
672 ref child_trees, ..
673 } => child_trees.last().unwrap().rightmost_leaf(),
674 }
675 }
676
677 #[cfg(debug_assertions)]
678 pub fn _debug_entries(&self) -> Vec<&T> {
679 self.iter().collect::<Vec<_>>()
680 }
681}
682
683impl<T: Item + PartialEq> PartialEq for SumTree<T> {
684 fn eq(&self, other: &Self) -> bool {
685 self.iter().eq(other.iter())
686 }
687}
688
689impl<T: Item + Eq> Eq for SumTree<T> {}
690
691impl<T: KeyedItem> SumTree<T> {
692 pub fn insert_or_replace(
693 &mut self,
694 item: T,
695 cx: &<T::Summary as Summary>::Context,
696 ) -> Option<T> {
697 let mut replaced = None;
698 *self = {
699 let mut cursor = self.cursor::<T::Key>(cx);
700 let mut new_tree = cursor.slice(&item.key(), Bias::Left, cx);
701 if let Some(cursor_item) = cursor.item() {
702 if cursor_item.key() == item.key() {
703 replaced = Some(cursor_item.clone());
704 cursor.next(cx);
705 }
706 }
707 new_tree.push(item, cx);
708 new_tree.append(cursor.suffix(cx), cx);
709 new_tree
710 };
711 replaced
712 }
713
714 pub fn remove(&mut self, key: &T::Key, cx: &<T::Summary as Summary>::Context) -> Option<T> {
715 let mut removed = None;
716 *self = {
717 let mut cursor = self.cursor::<T::Key>(cx);
718 let mut new_tree = cursor.slice(key, Bias::Left, cx);
719 if let Some(item) = cursor.item() {
720 if item.key() == *key {
721 removed = Some(item.clone());
722 cursor.next(cx);
723 }
724 }
725 new_tree.append(cursor.suffix(cx), cx);
726 new_tree
727 };
728 removed
729 }
730
731 pub fn edit(
732 &mut self,
733 mut edits: Vec<Edit<T>>,
734 cx: &<T::Summary as Summary>::Context,
735 ) -> Vec<T> {
736 if edits.is_empty() {
737 return Vec::new();
738 }
739
740 let mut removed = Vec::new();
741 edits.sort_unstable_by_key(|item| item.key());
742
743 *self = {
744 let mut cursor = self.cursor::<T::Key>(cx);
745 let mut new_tree = SumTree::new(cx);
746 let mut buffered_items = Vec::new();
747
748 cursor.seek(&T::Key::zero(cx), Bias::Left, cx);
749 for edit in edits {
750 let new_key = edit.key();
751 let mut old_item = cursor.item();
752
753 if old_item
754 .as_ref()
755 .map_or(false, |old_item| old_item.key() < new_key)
756 {
757 new_tree.extend(buffered_items.drain(..), cx);
758 let slice = cursor.slice(&new_key, Bias::Left, cx);
759 new_tree.append(slice, cx);
760 old_item = cursor.item();
761 }
762
763 if let Some(old_item) = old_item {
764 if old_item.key() == new_key {
765 removed.push(old_item.clone());
766 cursor.next(cx);
767 }
768 }
769
770 match edit {
771 Edit::Insert(item) => {
772 buffered_items.push(item);
773 }
774 Edit::Remove(_) => {}
775 }
776 }
777
778 new_tree.extend(buffered_items, cx);
779 new_tree.append(cursor.suffix(cx), cx);
780 new_tree
781 };
782
783 removed
784 }
785
786 pub fn get(&self, key: &T::Key, cx: &<T::Summary as Summary>::Context) -> Option<&T> {
787 let mut cursor = self.cursor::<T::Key>(cx);
788 if cursor.seek(key, Bias::Left, cx) {
789 cursor.item()
790 } else {
791 None
792 }
793 }
794
795 #[inline]
796 pub fn contains(&self, key: &T::Key, cx: &<T::Summary as Summary>::Context) -> bool {
797 self.get(key, cx).is_some()
798 }
799
800 pub fn update<F, R>(
801 &mut self,
802 key: &T::Key,
803 cx: &<T::Summary as Summary>::Context,
804 f: F,
805 ) -> Option<R>
806 where
807 F: FnOnce(&mut T) -> R,
808 {
809 let mut cursor = self.cursor::<T::Key>(cx);
810 let mut new_tree = cursor.slice(key, Bias::Left, cx);
811 let mut result = None;
812 if Ord::cmp(key, &cursor.end(cx)) == Ordering::Equal {
813 let mut updated = cursor.item().unwrap().clone();
814 result = Some(f(&mut updated));
815 new_tree.push(updated, cx);
816 cursor.next(cx);
817 }
818 new_tree.append(cursor.suffix(cx), cx);
819 drop(cursor);
820 *self = new_tree;
821 result
822 }
823
824 pub fn retain<F: FnMut(&T) -> bool>(
825 &mut self,
826 cx: &<T::Summary as Summary>::Context,
827 mut predicate: F,
828 ) {
829 let mut new_map = SumTree::new(cx);
830
831 let mut cursor = self.cursor::<T::Key>(cx);
832 cursor.next(cx);
833 while let Some(item) = cursor.item() {
834 if predicate(&item) {
835 new_map.push(item.clone(), cx);
836 }
837 cursor.next(cx);
838 }
839 drop(cursor);
840
841 *self = new_map;
842 }
843}
844
845impl<T, S> Default for SumTree<T>
846where
847 T: Item<Summary = S>,
848 S: Summary<Context = ()>,
849{
850 fn default() -> Self {
851 Self::new(&())
852 }
853}
854
855#[derive(Clone)]
856pub enum Node<T: Item> {
857 Internal {
858 height: u8,
859 summary: T::Summary,
860 child_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
861 child_trees: ArrayVec<SumTree<T>, { 2 * TREE_BASE }>,
862 },
863 Leaf {
864 summary: T::Summary,
865 items: ArrayVec<T, { 2 * TREE_BASE }>,
866 item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
867 },
868}
869
870impl<T> fmt::Debug for Node<T>
871where
872 T: Item + fmt::Debug,
873 T::Summary: fmt::Debug,
874{
875 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
876 match self {
877 Node::Internal {
878 height,
879 summary,
880 child_summaries,
881 child_trees,
882 } => f
883 .debug_struct("Internal")
884 .field("height", height)
885 .field("summary", summary)
886 .field("child_summaries", child_summaries)
887 .field("child_trees", child_trees)
888 .finish(),
889 Node::Leaf {
890 summary,
891 items,
892 item_summaries,
893 } => f
894 .debug_struct("Leaf")
895 .field("summary", summary)
896 .field("items", items)
897 .field("item_summaries", item_summaries)
898 .finish(),
899 }
900 }
901}
902
903impl<T: Item> Node<T> {
904 fn is_leaf(&self) -> bool {
905 matches!(self, Node::Leaf { .. })
906 }
907
908 fn height(&self) -> u8 {
909 match self {
910 Node::Internal { height, .. } => *height,
911 Node::Leaf { .. } => 0,
912 }
913 }
914
915 fn summary(&self) -> &T::Summary {
916 match self {
917 Node::Internal { summary, .. } => summary,
918 Node::Leaf { summary, .. } => summary,
919 }
920 }
921
922 fn child_summaries(&self) -> &[T::Summary] {
923 match self {
924 Node::Internal {
925 child_summaries, ..
926 } => child_summaries.as_slice(),
927 Node::Leaf { item_summaries, .. } => item_summaries.as_slice(),
928 }
929 }
930
931 fn child_trees(&self) -> &ArrayVec<SumTree<T>, { 2 * TREE_BASE }> {
932 match self {
933 Node::Internal { child_trees, .. } => child_trees,
934 Node::Leaf { .. } => panic!("Leaf nodes have no child trees"),
935 }
936 }
937
938 fn items(&self) -> &ArrayVec<T, { 2 * TREE_BASE }> {
939 match self {
940 Node::Leaf { items, .. } => items,
941 Node::Internal { .. } => panic!("Internal nodes have no items"),
942 }
943 }
944
945 fn is_underflowing(&self) -> bool {
946 match self {
947 Node::Internal { child_trees, .. } => child_trees.len() < TREE_BASE,
948 Node::Leaf { items, .. } => items.len() < TREE_BASE,
949 }
950 }
951}
952
953#[derive(Debug)]
954pub enum Edit<T: KeyedItem> {
955 Insert(T),
956 Remove(T::Key),
957}
958
959impl<T: KeyedItem> Edit<T> {
960 fn key(&self) -> T::Key {
961 match self {
962 Edit::Insert(item) => item.key(),
963 Edit::Remove(key) => key.clone(),
964 }
965 }
966}
967
968fn sum<'a, T, I>(iter: I, cx: &T::Context) -> T
969where
970 T: 'a + Summary,
971 I: Iterator<Item = &'a T>,
972{
973 let mut sum = T::zero(cx);
974 for value in iter {
975 sum.add_summary(value, cx);
976 }
977 sum
978}
979
980#[cfg(test)]
981mod tests {
982 use super::*;
983 use rand::{distributions, prelude::*};
984 use std::cmp;
985
986 #[ctor::ctor]
987 fn init_logger() {
988 if std::env::var("RUST_LOG").is_ok() {
989 env_logger::init();
990 }
991 }
992
993 #[test]
994 fn test_extend_and_push_tree() {
995 let mut tree1 = SumTree::default();
996 tree1.extend(0..20, &());
997
998 let mut tree2 = SumTree::default();
999 tree2.extend(50..100, &());
1000
1001 tree1.append(tree2, &());
1002 assert_eq!(
1003 tree1.items(&()),
1004 (0..20).chain(50..100).collect::<Vec<u8>>()
1005 );
1006 }
1007
1008 #[test]
1009 fn test_random() {
1010 let mut starting_seed = 0;
1011 if let Ok(value) = std::env::var("SEED") {
1012 starting_seed = value.parse().expect("invalid SEED variable");
1013 }
1014 let mut num_iterations = 100;
1015 if let Ok(value) = std::env::var("ITERATIONS") {
1016 num_iterations = value.parse().expect("invalid ITERATIONS variable");
1017 }
1018 let num_operations = std::env::var("OPERATIONS")
1019 .map_or(5, |o| o.parse().expect("invalid OPERATIONS variable"));
1020
1021 for seed in starting_seed..(starting_seed + num_iterations) {
1022 eprintln!("seed = {}", seed);
1023 let mut rng = StdRng::seed_from_u64(seed);
1024
1025 let rng = &mut rng;
1026 let mut tree = SumTree::<u8>::default();
1027 let count = rng.gen_range(0..10);
1028 if rng.gen() {
1029 tree.extend(rng.sample_iter(distributions::Standard).take(count), &());
1030 } else {
1031 let items = rng
1032 .sample_iter(distributions::Standard)
1033 .take(count)
1034 .collect::<Vec<_>>();
1035 tree.par_extend(items, &());
1036 }
1037
1038 for _ in 0..num_operations {
1039 let splice_end = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
1040 let splice_start = rng.gen_range(0..splice_end + 1);
1041 let count = rng.gen_range(0..10);
1042 let tree_end = tree.extent::<Count>(&());
1043 let new_items = rng
1044 .sample_iter(distributions::Standard)
1045 .take(count)
1046 .collect::<Vec<u8>>();
1047
1048 let mut reference_items = tree.items(&());
1049 reference_items.splice(splice_start..splice_end, new_items.clone());
1050
1051 tree = {
1052 let mut cursor = tree.cursor::<Count>(&());
1053 let mut new_tree = cursor.slice(&Count(splice_start), Bias::Right, &());
1054 if rng.gen() {
1055 new_tree.extend(new_items, &());
1056 } else {
1057 new_tree.par_extend(new_items, &());
1058 }
1059 cursor.seek(&Count(splice_end), Bias::Right, &());
1060 new_tree.append(cursor.slice(&tree_end, Bias::Right, &()), &());
1061 new_tree
1062 };
1063
1064 assert_eq!(tree.items(&()), reference_items);
1065 assert_eq!(
1066 tree.iter().collect::<Vec<_>>(),
1067 tree.cursor::<()>(&()).collect::<Vec<_>>()
1068 );
1069
1070 log::info!("tree items: {:?}", tree.items(&()));
1071
1072 let mut filter_cursor =
1073 tree.filter::<_, Count>(&(), |summary| summary.contains_even);
1074 let expected_filtered_items = tree
1075 .items(&())
1076 .into_iter()
1077 .enumerate()
1078 .filter(|(_, item)| (item & 1) == 0)
1079 .collect::<Vec<_>>();
1080
1081 let mut item_ix = if rng.gen() {
1082 filter_cursor.next(&());
1083 0
1084 } else {
1085 filter_cursor.prev(&());
1086 expected_filtered_items.len().saturating_sub(1)
1087 };
1088 while item_ix < expected_filtered_items.len() {
1089 log::info!("filter_cursor, item_ix: {}", item_ix);
1090 let actual_item = filter_cursor.item().unwrap();
1091 let (reference_index, reference_item) = expected_filtered_items[item_ix];
1092 assert_eq!(actual_item, &reference_item);
1093 assert_eq!(filter_cursor.start().0, reference_index);
1094 log::info!("next");
1095 filter_cursor.next(&());
1096 item_ix += 1;
1097
1098 while item_ix > 0 && rng.gen_bool(0.2) {
1099 log::info!("prev");
1100 filter_cursor.prev(&());
1101 item_ix -= 1;
1102
1103 if item_ix == 0 && rng.gen_bool(0.2) {
1104 filter_cursor.prev(&());
1105 assert_eq!(filter_cursor.item(), None);
1106 assert_eq!(filter_cursor.start().0, 0);
1107 filter_cursor.next(&());
1108 }
1109 }
1110 }
1111 assert_eq!(filter_cursor.item(), None);
1112
1113 let mut before_start = false;
1114 let mut cursor = tree.cursor::<Count>(&());
1115 let start_pos = rng.gen_range(0..=reference_items.len());
1116 cursor.seek(&Count(start_pos), Bias::Right, &());
1117 let mut pos = rng.gen_range(start_pos..=reference_items.len());
1118 cursor.seek_forward(&Count(pos), Bias::Right, &());
1119
1120 for i in 0..10 {
1121 assert_eq!(cursor.start().0, pos);
1122
1123 if pos > 0 {
1124 assert_eq!(cursor.prev_item().unwrap(), &reference_items[pos - 1]);
1125 } else {
1126 assert_eq!(cursor.prev_item(), None);
1127 }
1128
1129 if pos < reference_items.len() && !before_start {
1130 assert_eq!(cursor.item().unwrap(), &reference_items[pos]);
1131 } else {
1132 assert_eq!(cursor.item(), None);
1133 }
1134
1135 if before_start {
1136 assert_eq!(cursor.next_item(), reference_items.first());
1137 } else if pos + 1 < reference_items.len() {
1138 assert_eq!(cursor.next_item().unwrap(), &reference_items[pos + 1]);
1139 } else {
1140 assert_eq!(cursor.next_item(), None);
1141 }
1142
1143 if i < 5 {
1144 cursor.next(&());
1145 if pos < reference_items.len() {
1146 pos += 1;
1147 before_start = false;
1148 }
1149 } else {
1150 cursor.prev(&());
1151 if pos == 0 {
1152 before_start = true;
1153 }
1154 pos = pos.saturating_sub(1);
1155 }
1156 }
1157 }
1158
1159 for _ in 0..10 {
1160 let end = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
1161 let start = rng.gen_range(0..end + 1);
1162 let start_bias = if rng.gen() { Bias::Left } else { Bias::Right };
1163 let end_bias = if rng.gen() { Bias::Left } else { Bias::Right };
1164
1165 let mut cursor = tree.cursor::<Count>(&());
1166 cursor.seek(&Count(start), start_bias, &());
1167 let slice = cursor.slice(&Count(end), end_bias, &());
1168
1169 cursor.seek(&Count(start), start_bias, &());
1170 let summary = cursor.summary::<_, Sum>(&Count(end), end_bias, &());
1171
1172 assert_eq!(summary.0, slice.summary().sum);
1173 }
1174 }
1175 }
1176
1177 #[test]
1178 fn test_cursor() {
1179 // Empty tree
1180 let tree = SumTree::<u8>::default();
1181 let mut cursor = tree.cursor::<IntegersSummary>(&());
1182 assert_eq!(
1183 cursor.slice(&Count(0), Bias::Right, &()).items(&()),
1184 Vec::<u8>::new()
1185 );
1186 assert_eq!(cursor.item(), None);
1187 assert_eq!(cursor.prev_item(), None);
1188 assert_eq!(cursor.next_item(), None);
1189 assert_eq!(cursor.start().sum, 0);
1190 cursor.prev(&());
1191 assert_eq!(cursor.item(), None);
1192 assert_eq!(cursor.prev_item(), None);
1193 assert_eq!(cursor.next_item(), None);
1194 assert_eq!(cursor.start().sum, 0);
1195 cursor.next(&());
1196 assert_eq!(cursor.item(), None);
1197 assert_eq!(cursor.prev_item(), None);
1198 assert_eq!(cursor.next_item(), None);
1199 assert_eq!(cursor.start().sum, 0);
1200
1201 // Single-element tree
1202 let mut tree = SumTree::<u8>::default();
1203 tree.extend(vec![1], &());
1204 let mut cursor = tree.cursor::<IntegersSummary>(&());
1205 assert_eq!(
1206 cursor.slice(&Count(0), Bias::Right, &()).items(&()),
1207 Vec::<u8>::new()
1208 );
1209 assert_eq!(cursor.item(), Some(&1));
1210 assert_eq!(cursor.prev_item(), None);
1211 assert_eq!(cursor.next_item(), None);
1212 assert_eq!(cursor.start().sum, 0);
1213
1214 cursor.next(&());
1215 assert_eq!(cursor.item(), None);
1216 assert_eq!(cursor.prev_item(), Some(&1));
1217 assert_eq!(cursor.next_item(), None);
1218 assert_eq!(cursor.start().sum, 1);
1219
1220 cursor.prev(&());
1221 assert_eq!(cursor.item(), Some(&1));
1222 assert_eq!(cursor.prev_item(), None);
1223 assert_eq!(cursor.next_item(), None);
1224 assert_eq!(cursor.start().sum, 0);
1225
1226 let mut cursor = tree.cursor::<IntegersSummary>(&());
1227 assert_eq!(cursor.slice(&Count(1), Bias::Right, &()).items(&()), [1]);
1228 assert_eq!(cursor.item(), None);
1229 assert_eq!(cursor.prev_item(), Some(&1));
1230 assert_eq!(cursor.next_item(), None);
1231 assert_eq!(cursor.start().sum, 1);
1232
1233 cursor.seek(&Count(0), Bias::Right, &());
1234 assert_eq!(
1235 cursor
1236 .slice(&tree.extent::<Count>(&()), Bias::Right, &())
1237 .items(&()),
1238 [1]
1239 );
1240 assert_eq!(cursor.item(), None);
1241 assert_eq!(cursor.prev_item(), Some(&1));
1242 assert_eq!(cursor.next_item(), None);
1243 assert_eq!(cursor.start().sum, 1);
1244
1245 // Multiple-element tree
1246 let mut tree = SumTree::default();
1247 tree.extend(vec![1, 2, 3, 4, 5, 6], &());
1248 let mut cursor = tree.cursor::<IntegersSummary>(&());
1249
1250 assert_eq!(cursor.slice(&Count(2), Bias::Right, &()).items(&()), [1, 2]);
1251 assert_eq!(cursor.item(), Some(&3));
1252 assert_eq!(cursor.prev_item(), Some(&2));
1253 assert_eq!(cursor.next_item(), Some(&4));
1254 assert_eq!(cursor.start().sum, 3);
1255
1256 cursor.next(&());
1257 assert_eq!(cursor.item(), Some(&4));
1258 assert_eq!(cursor.prev_item(), Some(&3));
1259 assert_eq!(cursor.next_item(), Some(&5));
1260 assert_eq!(cursor.start().sum, 6);
1261
1262 cursor.next(&());
1263 assert_eq!(cursor.item(), Some(&5));
1264 assert_eq!(cursor.prev_item(), Some(&4));
1265 assert_eq!(cursor.next_item(), Some(&6));
1266 assert_eq!(cursor.start().sum, 10);
1267
1268 cursor.next(&());
1269 assert_eq!(cursor.item(), Some(&6));
1270 assert_eq!(cursor.prev_item(), Some(&5));
1271 assert_eq!(cursor.next_item(), None);
1272 assert_eq!(cursor.start().sum, 15);
1273
1274 cursor.next(&());
1275 cursor.next(&());
1276 assert_eq!(cursor.item(), None);
1277 assert_eq!(cursor.prev_item(), Some(&6));
1278 assert_eq!(cursor.next_item(), None);
1279 assert_eq!(cursor.start().sum, 21);
1280
1281 cursor.prev(&());
1282 assert_eq!(cursor.item(), Some(&6));
1283 assert_eq!(cursor.prev_item(), Some(&5));
1284 assert_eq!(cursor.next_item(), None);
1285 assert_eq!(cursor.start().sum, 15);
1286
1287 cursor.prev(&());
1288 assert_eq!(cursor.item(), Some(&5));
1289 assert_eq!(cursor.prev_item(), Some(&4));
1290 assert_eq!(cursor.next_item(), Some(&6));
1291 assert_eq!(cursor.start().sum, 10);
1292
1293 cursor.prev(&());
1294 assert_eq!(cursor.item(), Some(&4));
1295 assert_eq!(cursor.prev_item(), Some(&3));
1296 assert_eq!(cursor.next_item(), Some(&5));
1297 assert_eq!(cursor.start().sum, 6);
1298
1299 cursor.prev(&());
1300 assert_eq!(cursor.item(), Some(&3));
1301 assert_eq!(cursor.prev_item(), Some(&2));
1302 assert_eq!(cursor.next_item(), Some(&4));
1303 assert_eq!(cursor.start().sum, 3);
1304
1305 cursor.prev(&());
1306 assert_eq!(cursor.item(), Some(&2));
1307 assert_eq!(cursor.prev_item(), Some(&1));
1308 assert_eq!(cursor.next_item(), Some(&3));
1309 assert_eq!(cursor.start().sum, 1);
1310
1311 cursor.prev(&());
1312 assert_eq!(cursor.item(), Some(&1));
1313 assert_eq!(cursor.prev_item(), None);
1314 assert_eq!(cursor.next_item(), Some(&2));
1315 assert_eq!(cursor.start().sum, 0);
1316
1317 cursor.prev(&());
1318 assert_eq!(cursor.item(), None);
1319 assert_eq!(cursor.prev_item(), None);
1320 assert_eq!(cursor.next_item(), Some(&1));
1321 assert_eq!(cursor.start().sum, 0);
1322
1323 cursor.next(&());
1324 assert_eq!(cursor.item(), Some(&1));
1325 assert_eq!(cursor.prev_item(), None);
1326 assert_eq!(cursor.next_item(), Some(&2));
1327 assert_eq!(cursor.start().sum, 0);
1328
1329 let mut cursor = tree.cursor::<IntegersSummary>(&());
1330 assert_eq!(
1331 cursor
1332 .slice(&tree.extent::<Count>(&()), Bias::Right, &())
1333 .items(&()),
1334 tree.items(&())
1335 );
1336 assert_eq!(cursor.item(), None);
1337 assert_eq!(cursor.prev_item(), Some(&6));
1338 assert_eq!(cursor.next_item(), None);
1339 assert_eq!(cursor.start().sum, 21);
1340
1341 cursor.seek(&Count(3), Bias::Right, &());
1342 assert_eq!(
1343 cursor
1344 .slice(&tree.extent::<Count>(&()), Bias::Right, &())
1345 .items(&()),
1346 [4, 5, 6]
1347 );
1348 assert_eq!(cursor.item(), None);
1349 assert_eq!(cursor.prev_item(), Some(&6));
1350 assert_eq!(cursor.next_item(), None);
1351 assert_eq!(cursor.start().sum, 21);
1352
1353 // Seeking can bias left or right
1354 cursor.seek(&Count(1), Bias::Left, &());
1355 assert_eq!(cursor.item(), Some(&1));
1356 cursor.seek(&Count(1), Bias::Right, &());
1357 assert_eq!(cursor.item(), Some(&2));
1358
1359 // Slicing without resetting starts from where the cursor is parked at.
1360 cursor.seek(&Count(1), Bias::Right, &());
1361 assert_eq!(
1362 cursor.slice(&Count(3), Bias::Right, &()).items(&()),
1363 vec![2, 3]
1364 );
1365 assert_eq!(
1366 cursor.slice(&Count(6), Bias::Left, &()).items(&()),
1367 vec![4, 5]
1368 );
1369 assert_eq!(
1370 cursor.slice(&Count(6), Bias::Right, &()).items(&()),
1371 vec![6]
1372 );
1373 }
1374
1375 #[test]
1376 fn test_edit() {
1377 let mut tree = SumTree::<u8>::default();
1378
1379 let removed = tree.edit(vec![Edit::Insert(1), Edit::Insert(2), Edit::Insert(0)], &());
1380 assert_eq!(tree.items(&()), vec![0, 1, 2]);
1381 assert_eq!(removed, Vec::<u8>::new());
1382 assert_eq!(tree.get(&0, &()), Some(&0));
1383 assert_eq!(tree.get(&1, &()), Some(&1));
1384 assert_eq!(tree.get(&2, &()), Some(&2));
1385 assert_eq!(tree.get(&4, &()), None);
1386
1387 let removed = tree.edit(vec![Edit::Insert(2), Edit::Insert(4), Edit::Remove(0)], &());
1388 assert_eq!(tree.items(&()), vec![1, 2, 4]);
1389 assert_eq!(removed, vec![0, 2]);
1390 assert_eq!(tree.get(&0, &()), None);
1391 assert_eq!(tree.get(&1, &()), Some(&1));
1392 assert_eq!(tree.get(&2, &()), Some(&2));
1393 assert_eq!(tree.get(&4, &()), Some(&4));
1394 }
1395
1396 #[test]
1397 fn test_from_iter() {
1398 assert_eq!(
1399 SumTree::from_iter(0..100, &()).items(&()),
1400 (0..100).collect::<Vec<_>>()
1401 );
1402
1403 // Ensure `from_iter` works correctly when the given iterator restarts
1404 // after calling `next` if `None` was already returned.
1405 let mut ix = 0;
1406 let iterator = std::iter::from_fn(|| {
1407 ix = (ix + 1) % 2;
1408 if ix == 1 {
1409 Some(1)
1410 } else {
1411 None
1412 }
1413 });
1414 assert_eq!(SumTree::from_iter(iterator, &()).items(&()), vec![1]);
1415 }
1416
1417 #[derive(Clone, Default, Debug)]
1418 pub struct IntegersSummary {
1419 count: usize,
1420 sum: usize,
1421 contains_even: bool,
1422 max: u8,
1423 }
1424
1425 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
1426 struct Count(usize);
1427
1428 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
1429 struct Sum(usize);
1430
1431 impl Item for u8 {
1432 type Summary = IntegersSummary;
1433
1434 fn summary(&self, _cx: &()) -> Self::Summary {
1435 IntegersSummary {
1436 count: 1,
1437 sum: *self as usize,
1438 contains_even: (*self & 1) == 0,
1439 max: *self,
1440 }
1441 }
1442 }
1443
1444 impl KeyedItem for u8 {
1445 type Key = u8;
1446
1447 fn key(&self) -> Self::Key {
1448 *self
1449 }
1450 }
1451
1452 impl Summary for IntegersSummary {
1453 type Context = ();
1454
1455 fn zero(_cx: &()) -> Self {
1456 Default::default()
1457 }
1458
1459 fn add_summary(&mut self, other: &Self, _: &()) {
1460 self.count += other.count;
1461 self.sum += other.sum;
1462 self.contains_even |= other.contains_even;
1463 self.max = cmp::max(self.max, other.max);
1464 }
1465 }
1466
1467 impl<'a> Dimension<'a, IntegersSummary> for u8 {
1468 fn zero(_cx: &()) -> Self {
1469 Default::default()
1470 }
1471
1472 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
1473 *self = summary.max;
1474 }
1475 }
1476
1477 impl<'a> Dimension<'a, IntegersSummary> for Count {
1478 fn zero(_cx: &()) -> Self {
1479 Default::default()
1480 }
1481
1482 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
1483 self.0 += summary.count;
1484 }
1485 }
1486
1487 impl<'a> SeekTarget<'a, IntegersSummary, IntegersSummary> for Count {
1488 fn cmp(&self, cursor_location: &IntegersSummary, _: &()) -> Ordering {
1489 self.0.cmp(&cursor_location.count)
1490 }
1491 }
1492
1493 impl<'a> Dimension<'a, IntegersSummary> for Sum {
1494 fn zero(_cx: &()) -> Self {
1495 Default::default()
1496 }
1497
1498 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
1499 self.0 += summary.sum;
1500 }
1501 }
1502}