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