1mod cursor;
2
3use crate::util::Bias;
4use arrayvec::ArrayVec;
5pub use cursor::Cursor;
6pub use cursor::FilterCursor;
7use std::{cmp::Ordering, fmt, iter::FromIterator, sync::Arc};
8
9#[cfg(test)]
10const TREE_BASE: usize = 2;
11#[cfg(not(test))]
12const TREE_BASE: usize = 6;
13
14pub trait Item: Clone + fmt::Debug {
15 type Summary: Summary;
16
17 fn summary(&self) -> Self::Summary;
18}
19
20pub trait KeyedItem: Item {
21 type Key: for<'a> Dimension<'a, Self::Summary> + Ord;
22
23 fn key(&self) -> Self::Key;
24}
25
26pub trait Summary: Default + Clone + fmt::Debug {
27 type Context;
28
29 fn add_summary(&mut self, summary: &Self, cx: &Self::Context);
30}
31
32pub trait Dimension<'a, S: Summary>: Clone + fmt::Debug + Default {
33 fn add_summary(&mut self, _summary: &'a S, _: &S::Context);
34}
35
36impl<'a, T: Summary> Dimension<'a, T> for () {
37 fn add_summary(&mut self, _: &'a T, _: &T::Context) {}
38}
39
40impl<'a, S, D1, D2> Dimension<'a, S> for (D1, D2)
41where
42 S: Summary,
43 D1: Dimension<'a, S>,
44 D2: Dimension<'a, S>,
45{
46 fn add_summary(&mut self, summary: &'a S, cx: &S::Context) {
47 self.0.add_summary(summary, cx);
48 self.1.add_summary(summary, cx);
49 }
50}
51
52pub trait SeekDimension<'a, T: Summary>: Dimension<'a, T> {
53 fn cmp(&self, other: &Self, cx: &T::Context) -> Ordering;
54}
55
56impl<'a, S: Summary, T: Dimension<'a, S> + Ord> SeekDimension<'a, S> for T {
57 fn cmp(&self, other: &Self, _ctx: &S::Context) -> Ordering {
58 Ord::cmp(self, other)
59 }
60}
61
62#[derive(Debug, Clone)]
63pub struct SumTree<T: Item>(Arc<Node<T>>);
64
65impl<T: Item> SumTree<T> {
66 pub fn new() -> Self {
67 SumTree(Arc::new(Node::Leaf {
68 summary: T::Summary::default(),
69 items: ArrayVec::new(),
70 item_summaries: ArrayVec::new(),
71 }))
72 }
73
74 pub fn from_item(item: T, cx: &<T::Summary as Summary>::Context) -> Self {
75 let mut tree = Self::new();
76 tree.push(item, cx);
77 tree
78 }
79
80 #[allow(unused)]
81 pub fn items(&self, cx: &<T::Summary as Summary>::Context) -> Vec<T> {
82 let mut items = Vec::new();
83 let mut cursor = self.cursor::<(), ()>();
84 cursor.next(cx);
85 while let Some(item) = cursor.item() {
86 items.push(item.clone());
87 cursor.next(cx);
88 }
89 items
90 }
91
92 pub fn cursor<'a, S, U>(&'a self) -> Cursor<T, S, U>
93 where
94 S: Dimension<'a, T::Summary>,
95 U: Dimension<'a, T::Summary>,
96 {
97 Cursor::new(self)
98 }
99
100 pub fn filter<'a, F, U>(
101 &'a self,
102 filter_node: F,
103 cx: &<T::Summary as Summary>::Context,
104 ) -> FilterCursor<F, T, U>
105 where
106 F: Fn(&T::Summary) -> bool,
107 U: Dimension<'a, T::Summary>,
108 {
109 FilterCursor::new(self, filter_node, cx)
110 }
111
112 #[allow(dead_code)]
113 pub fn first(&self) -> Option<&T> {
114 self.leftmost_leaf().0.items().first()
115 }
116
117 pub fn last(&self) -> Option<&T> {
118 self.rightmost_leaf().0.items().last()
119 }
120
121 pub fn update_last(&mut self, f: impl FnOnce(&mut T), cx: &<T::Summary as Summary>::Context) {
122 self.update_last_recursive(f, cx);
123 }
124
125 fn update_last_recursive(
126 &mut self,
127 f: impl FnOnce(&mut T),
128 cx: &<T::Summary as Summary>::Context,
129 ) -> Option<T::Summary> {
130 match Arc::make_mut(&mut self.0) {
131 Node::Internal {
132 summary,
133 child_summaries,
134 child_trees,
135 ..
136 } => {
137 let last_summary = child_summaries.last_mut().unwrap();
138 let last_child = child_trees.last_mut().unwrap();
139 *last_summary = last_child.update_last_recursive(f, cx).unwrap();
140 *summary = sum(child_summaries.iter(), cx);
141 Some(summary.clone())
142 }
143 Node::Leaf {
144 summary,
145 items,
146 item_summaries,
147 } => {
148 if let Some((item, item_summary)) = items.last_mut().zip(item_summaries.last_mut())
149 {
150 (f)(item);
151 *item_summary = item.summary();
152 *summary = sum(item_summaries.iter(), cx);
153 Some(summary.clone())
154 } else {
155 None
156 }
157 }
158 }
159 }
160
161 pub fn extent<'a, D: Dimension<'a, T::Summary>>(
162 &'a self,
163 cx: &<T::Summary as Summary>::Context,
164 ) -> D {
165 let mut extent = D::default();
166 match self.0.as_ref() {
167 Node::Internal { summary, .. } | Node::Leaf { summary, .. } => {
168 extent.add_summary(summary, cx);
169 }
170 }
171 extent
172 }
173
174 pub fn summary(&self) -> T::Summary {
175 match self.0.as_ref() {
176 Node::Internal { summary, .. } => summary.clone(),
177 Node::Leaf { summary, .. } => summary.clone(),
178 }
179 }
180
181 pub fn is_empty(&self) -> bool {
182 match self.0.as_ref() {
183 Node::Internal { .. } => false,
184 Node::Leaf { items, .. } => items.is_empty(),
185 }
186 }
187
188 pub fn extend<I>(&mut self, iter: I, cx: &<T::Summary as Summary>::Context)
189 where
190 I: IntoIterator<Item = T>,
191 {
192 let mut leaf: Option<Node<T>> = None;
193
194 for item in iter {
195 if leaf.is_some() && leaf.as_ref().unwrap().items().len() == 2 * TREE_BASE {
196 self.push_tree(SumTree(Arc::new(leaf.take().unwrap())), cx);
197 }
198
199 if leaf.is_none() {
200 leaf = Some(Node::Leaf::<T> {
201 summary: T::Summary::default(),
202 items: ArrayVec::new(),
203 item_summaries: ArrayVec::new(),
204 });
205 }
206
207 if let Some(Node::Leaf {
208 summary,
209 items,
210 item_summaries,
211 }) = leaf.as_mut()
212 {
213 let item_summary = item.summary();
214 summary.add_summary(&item_summary, cx);
215 items.push(item);
216 item_summaries.push(item_summary);
217 } else {
218 unreachable!()
219 }
220 }
221
222 if leaf.is_some() {
223 self.push_tree(SumTree(Arc::new(leaf.take().unwrap())), cx);
224 }
225 }
226
227 pub fn push(&mut self, item: T, cx: &<T::Summary as Summary>::Context) {
228 let summary = item.summary();
229 self.push_tree(
230 SumTree(Arc::new(Node::Leaf {
231 summary: summary.clone(),
232 items: ArrayVec::from_iter(Some(item)),
233 item_summaries: ArrayVec::from_iter(Some(summary)),
234 })),
235 cx,
236 );
237 }
238
239 pub fn push_tree(&mut self, other: Self, cx: &<T::Summary as Summary>::Context) {
240 if !other.0.is_leaf() || other.0.items().len() > 0 {
241 if self.0.height() < other.0.height() {
242 for tree in other.0.child_trees() {
243 self.push_tree(tree.clone(), cx);
244 }
245 } else if let Some(split_tree) = self.push_tree_recursive(other, cx) {
246 *self = Self::from_child_trees(self.clone(), split_tree, cx);
247 }
248 }
249 }
250
251 fn push_tree_recursive(
252 &mut self,
253 other: SumTree<T>,
254 cx: &<T::Summary as Summary>::Context,
255 ) -> Option<SumTree<T>> {
256 match Arc::make_mut(&mut self.0) {
257 Node::Internal {
258 height,
259 summary,
260 child_summaries,
261 child_trees,
262 ..
263 } => {
264 let other_node = other.0.clone();
265 summary.add_summary(other_node.summary(), cx);
266
267 let height_delta = *height - other_node.height();
268 let mut summaries_to_append = ArrayVec::<[T::Summary; 2 * TREE_BASE]>::new();
269 let mut trees_to_append = ArrayVec::<[SumTree<T>; 2 * TREE_BASE]>::new();
270 if height_delta == 0 {
271 summaries_to_append.extend(other_node.child_summaries().iter().cloned());
272 trees_to_append.extend(other_node.child_trees().iter().cloned());
273 } else if height_delta == 1 && !other_node.is_underflowing() {
274 summaries_to_append.push(other_node.summary().clone());
275 trees_to_append.push(other)
276 } else {
277 let tree_to_append = child_trees
278 .last_mut()
279 .unwrap()
280 .push_tree_recursive(other, cx);
281 *child_summaries.last_mut().unwrap() =
282 child_trees.last().unwrap().0.summary().clone();
283
284 if let Some(split_tree) = tree_to_append {
285 summaries_to_append.push(split_tree.0.summary().clone());
286 trees_to_append.push(split_tree);
287 }
288 }
289
290 let child_count = child_trees.len() + trees_to_append.len();
291 if child_count > 2 * TREE_BASE {
292 let left_summaries: ArrayVec<_>;
293 let right_summaries: ArrayVec<_>;
294 let left_trees;
295 let right_trees;
296
297 let midpoint = (child_count + child_count % 2) / 2;
298 {
299 let mut all_summaries = child_summaries
300 .iter()
301 .chain(summaries_to_append.iter())
302 .cloned();
303 left_summaries = all_summaries.by_ref().take(midpoint).collect();
304 right_summaries = all_summaries.collect();
305 let mut all_trees =
306 child_trees.iter().chain(trees_to_append.iter()).cloned();
307 left_trees = all_trees.by_ref().take(midpoint).collect();
308 right_trees = all_trees.collect();
309 }
310 *summary = sum(left_summaries.iter(), cx);
311 *child_summaries = left_summaries;
312 *child_trees = left_trees;
313
314 Some(SumTree(Arc::new(Node::Internal {
315 height: *height,
316 summary: sum(right_summaries.iter(), cx),
317 child_summaries: right_summaries,
318 child_trees: right_trees,
319 })))
320 } else {
321 child_summaries.extend(summaries_to_append);
322 child_trees.extend(trees_to_append);
323 None
324 }
325 }
326 Node::Leaf {
327 summary,
328 items,
329 item_summaries,
330 } => {
331 let other_node = other.0;
332
333 let child_count = items.len() + other_node.items().len();
334 if child_count > 2 * TREE_BASE {
335 let left_items;
336 let right_items;
337 let left_summaries;
338 let right_summaries: ArrayVec<[T::Summary; 2 * TREE_BASE]>;
339
340 let midpoint = (child_count + child_count % 2) / 2;
341 {
342 let mut all_items = items.iter().chain(other_node.items().iter()).cloned();
343 left_items = all_items.by_ref().take(midpoint).collect();
344 right_items = all_items.collect();
345
346 let mut all_summaries = item_summaries
347 .iter()
348 .chain(other_node.child_summaries())
349 .cloned();
350 left_summaries = all_summaries.by_ref().take(midpoint).collect();
351 right_summaries = all_summaries.collect();
352 }
353 *items = left_items;
354 *item_summaries = left_summaries;
355 *summary = sum(item_summaries.iter(), cx);
356 Some(SumTree(Arc::new(Node::Leaf {
357 items: right_items,
358 summary: sum(right_summaries.iter(), cx),
359 item_summaries: right_summaries,
360 })))
361 } else {
362 summary.add_summary(other_node.summary(), cx);
363 items.extend(other_node.items().iter().cloned());
364 item_summaries.extend(other_node.child_summaries().iter().cloned());
365 None
366 }
367 }
368 }
369 }
370
371 fn from_child_trees(
372 left: SumTree<T>,
373 right: SumTree<T>,
374 cx: &<T::Summary as Summary>::Context,
375 ) -> Self {
376 let height = left.0.height() + 1;
377 let mut child_summaries = ArrayVec::new();
378 child_summaries.push(left.0.summary().clone());
379 child_summaries.push(right.0.summary().clone());
380 let mut child_trees = ArrayVec::new();
381 child_trees.push(left);
382 child_trees.push(right);
383 SumTree(Arc::new(Node::Internal {
384 height,
385 summary: sum(child_summaries.iter(), cx),
386 child_summaries,
387 child_trees,
388 }))
389 }
390
391 fn leftmost_leaf(&self) -> &Self {
392 match *self.0 {
393 Node::Leaf { .. } => self,
394 Node::Internal {
395 ref child_trees, ..
396 } => child_trees.first().unwrap().leftmost_leaf(),
397 }
398 }
399
400 fn rightmost_leaf(&self) -> &Self {
401 match *self.0 {
402 Node::Leaf { .. } => self,
403 Node::Internal {
404 ref child_trees, ..
405 } => child_trees.last().unwrap().rightmost_leaf(),
406 }
407 }
408}
409
410impl<T: KeyedItem> SumTree<T> {
411 #[allow(unused)]
412 pub fn insert(&mut self, item: T, cx: &<T::Summary as Summary>::Context) {
413 *self = {
414 let mut cursor = self.cursor::<T::Key, ()>();
415 let mut new_tree = cursor.slice(&item.key(), Bias::Left, cx);
416 new_tree.push(item, cx);
417 new_tree.push_tree(cursor.suffix(cx), cx);
418 new_tree
419 };
420 }
421
422 pub fn edit(
423 &mut self,
424 mut edits: Vec<Edit<T>>,
425 cx: &<T::Summary as Summary>::Context,
426 ) -> Vec<T> {
427 if edits.is_empty() {
428 return Vec::new();
429 }
430
431 let mut removed = Vec::new();
432 edits.sort_unstable_by_key(|item| item.key());
433
434 *self = {
435 let mut cursor = self.cursor::<T::Key, ()>();
436 let mut new_tree = SumTree::new();
437 let mut buffered_items = Vec::new();
438
439 cursor.seek(&T::Key::default(), Bias::Left, cx);
440 for edit in edits {
441 let new_key = edit.key();
442 let mut old_item = cursor.item();
443
444 if old_item
445 .as_ref()
446 .map_or(false, |old_item| old_item.key() < new_key)
447 {
448 new_tree.extend(buffered_items.drain(..), cx);
449 let slice = cursor.slice(&new_key, Bias::Left, cx);
450 new_tree.push_tree(slice, cx);
451 old_item = cursor.item();
452 }
453
454 if let Some(old_item) = old_item {
455 if old_item.key() == new_key {
456 removed.push(old_item.clone());
457 cursor.next(cx);
458 }
459 }
460
461 match edit {
462 Edit::Insert(item) => {
463 buffered_items.push(item);
464 }
465 Edit::Remove(_) => {}
466 }
467 }
468
469 new_tree.extend(buffered_items, cx);
470 new_tree.push_tree(cursor.suffix(cx), cx);
471 new_tree
472 };
473
474 removed
475 }
476
477 pub fn get(&self, key: &T::Key, cx: &<T::Summary as Summary>::Context) -> Option<&T> {
478 let mut cursor = self.cursor::<T::Key, ()>();
479 if cursor.seek(key, Bias::Left, cx) {
480 cursor.item()
481 } else {
482 None
483 }
484 }
485}
486
487impl<T: Item> Default for SumTree<T> {
488 fn default() -> Self {
489 Self::new()
490 }
491}
492
493#[derive(Clone, Debug)]
494pub enum Node<T: Item> {
495 Internal {
496 height: u8,
497 summary: T::Summary,
498 child_summaries: ArrayVec<[T::Summary; 2 * TREE_BASE]>,
499 child_trees: ArrayVec<[SumTree<T>; 2 * TREE_BASE]>,
500 },
501 Leaf {
502 summary: T::Summary,
503 items: ArrayVec<[T; 2 * TREE_BASE]>,
504 item_summaries: ArrayVec<[T::Summary; 2 * TREE_BASE]>,
505 },
506}
507
508impl<T: Item> Node<T> {
509 fn is_leaf(&self) -> bool {
510 match self {
511 Node::Leaf { .. } => true,
512 _ => false,
513 }
514 }
515
516 fn height(&self) -> u8 {
517 match self {
518 Node::Internal { height, .. } => *height,
519 Node::Leaf { .. } => 0,
520 }
521 }
522
523 fn summary(&self) -> &T::Summary {
524 match self {
525 Node::Internal { summary, .. } => summary,
526 Node::Leaf { summary, .. } => summary,
527 }
528 }
529
530 fn child_summaries(&self) -> &[T::Summary] {
531 match self {
532 Node::Internal {
533 child_summaries, ..
534 } => child_summaries.as_slice(),
535 Node::Leaf { item_summaries, .. } => item_summaries.as_slice(),
536 }
537 }
538
539 fn child_trees(&self) -> &ArrayVec<[SumTree<T>; 2 * TREE_BASE]> {
540 match self {
541 Node::Internal { child_trees, .. } => child_trees,
542 Node::Leaf { .. } => panic!("Leaf nodes have no child trees"),
543 }
544 }
545
546 fn items(&self) -> &ArrayVec<[T; 2 * TREE_BASE]> {
547 match self {
548 Node::Leaf { items, .. } => items,
549 Node::Internal { .. } => panic!("Internal nodes have no items"),
550 }
551 }
552
553 fn is_underflowing(&self) -> bool {
554 match self {
555 Node::Internal { child_trees, .. } => child_trees.len() < TREE_BASE,
556 Node::Leaf { items, .. } => items.len() < TREE_BASE,
557 }
558 }
559}
560
561#[derive(Debug)]
562pub enum Edit<T: KeyedItem> {
563 Insert(T),
564 Remove(T::Key),
565}
566
567impl<T: KeyedItem> Edit<T> {
568 fn key(&self) -> T::Key {
569 match self {
570 Edit::Insert(item) => item.key(),
571 Edit::Remove(key) => key.clone(),
572 }
573 }
574}
575
576fn sum<'a, T, I>(iter: I, cx: &T::Context) -> T
577where
578 T: 'a + Summary,
579 I: Iterator<Item = &'a T>,
580{
581 let mut sum = T::default();
582 for value in iter {
583 sum.add_summary(value, cx);
584 }
585 sum
586}
587
588#[cfg(test)]
589mod tests {
590 use super::*;
591 use std::cmp;
592 use std::ops::Add;
593
594 #[test]
595 fn test_extend_and_push_tree() {
596 let mut tree1 = SumTree::new();
597 tree1.extend(0..20, &());
598
599 let mut tree2 = SumTree::new();
600 tree2.extend(50..100, &());
601
602 tree1.push_tree(tree2, &());
603 assert_eq!(
604 tree1.items(&()),
605 (0..20).chain(50..100).collect::<Vec<u8>>()
606 );
607 }
608
609 #[test]
610 fn test_random() {
611 for seed in 0..100 {
612 use rand::{distributions, prelude::*};
613
614 dbg!(seed);
615 let rng = &mut StdRng::seed_from_u64(seed);
616
617 let mut tree = SumTree::<u8>::new();
618 let count = rng.gen_range(0..10);
619 tree.extend(rng.sample_iter(distributions::Standard).take(count), &());
620
621 for _ in 0..5 {
622 let splice_end = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
623 let splice_start = rng.gen_range(0..splice_end + 1);
624 let count = rng.gen_range(0..3);
625 let tree_end = tree.extent::<Count>(&());
626 let new_items = rng
627 .sample_iter(distributions::Standard)
628 .take(count)
629 .collect::<Vec<u8>>();
630
631 let mut reference_items = tree.items(&());
632 reference_items.splice(splice_start..splice_end, new_items.clone());
633
634 tree = {
635 let mut cursor = tree.cursor::<Count, ()>();
636 let mut new_tree = cursor.slice(&Count(splice_start), Bias::Right, &());
637 new_tree.extend(new_items, &());
638 cursor.seek(&Count(splice_end), Bias::Right, &());
639 new_tree.push_tree(cursor.slice(&tree_end, Bias::Right, &()), &());
640 new_tree
641 };
642
643 assert_eq!(tree.items(&()), reference_items);
644
645 let mut filter_cursor =
646 tree.filter::<_, Count>(|summary| summary.contains_even, &());
647 let mut reference_filter = tree
648 .items(&())
649 .into_iter()
650 .enumerate()
651 .filter(|(_, item)| (item & 1) == 0);
652 while let Some(actual_item) = filter_cursor.item() {
653 let (reference_index, reference_item) = reference_filter.next().unwrap();
654 assert_eq!(actual_item, &reference_item);
655 assert_eq!(filter_cursor.start().0, reference_index);
656 filter_cursor.next(&());
657 }
658 assert!(reference_filter.next().is_none());
659
660 let mut pos = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
661 let mut before_start = false;
662 let mut cursor = tree.cursor::<Count, Count>();
663 cursor.seek(&Count(pos), Bias::Right, &());
664
665 for i in 0..10 {
666 assert_eq!(cursor.start().0, pos);
667
668 if pos > 0 {
669 assert_eq!(cursor.prev_item().unwrap(), &reference_items[pos - 1]);
670 } else {
671 assert_eq!(cursor.prev_item(), None);
672 }
673
674 if pos < reference_items.len() && !before_start {
675 assert_eq!(cursor.item().unwrap(), &reference_items[pos]);
676 } else {
677 assert_eq!(cursor.item(), None);
678 }
679
680 if i < 5 {
681 cursor.next(&());
682 if pos < reference_items.len() {
683 pos += 1;
684 before_start = false;
685 }
686 } else {
687 cursor.prev(&());
688 if pos == 0 {
689 before_start = true;
690 }
691 pos = pos.saturating_sub(1);
692 }
693 }
694 }
695
696 for _ in 0..10 {
697 let end = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
698 let start = rng.gen_range(0..end + 1);
699 let start_bias = if rng.gen() { Bias::Left } else { Bias::Right };
700 let end_bias = if rng.gen() { Bias::Left } else { Bias::Right };
701
702 let mut cursor = tree.cursor::<Count, ()>();
703 cursor.seek(&Count(start), start_bias, &());
704 let slice = cursor.slice(&Count(end), end_bias, &());
705
706 cursor.seek(&Count(start), start_bias, &());
707 let summary = cursor.summary::<Sum>(&Count(end), end_bias, &());
708
709 assert_eq!(summary, slice.summary().sum);
710 }
711 }
712 }
713
714 #[test]
715 fn test_cursor() {
716 // Empty tree
717 let tree = SumTree::<u8>::new();
718 let mut cursor = tree.cursor::<Count, Sum>();
719 assert_eq!(
720 cursor.slice(&Count(0), Bias::Right, &()).items(&()),
721 Vec::<u8>::new()
722 );
723 assert_eq!(cursor.item(), None);
724 assert_eq!(cursor.prev_item(), None);
725 assert_eq!(cursor.start(), &Sum(0));
726
727 // Single-element tree
728 let mut tree = SumTree::<u8>::new();
729 tree.extend(vec![1], &());
730 let mut cursor = tree.cursor::<Count, Sum>();
731 assert_eq!(
732 cursor.slice(&Count(0), Bias::Right, &()).items(&()),
733 Vec::<u8>::new()
734 );
735 assert_eq!(cursor.item(), Some(&1));
736 assert_eq!(cursor.prev_item(), None);
737 assert_eq!(cursor.start(), &Sum(0));
738
739 cursor.next(&());
740 assert_eq!(cursor.item(), None);
741 assert_eq!(cursor.prev_item(), Some(&1));
742 assert_eq!(cursor.start(), &Sum(1));
743
744 cursor.prev(&());
745 assert_eq!(cursor.item(), Some(&1));
746 assert_eq!(cursor.prev_item(), None);
747 assert_eq!(cursor.start(), &Sum(0));
748
749 let mut cursor = tree.cursor::<Count, Sum>();
750 assert_eq!(cursor.slice(&Count(1), Bias::Right, &()).items(&()), [1]);
751 assert_eq!(cursor.item(), None);
752 assert_eq!(cursor.prev_item(), Some(&1));
753 assert_eq!(cursor.start(), &Sum(1));
754
755 cursor.seek(&Count(0), Bias::Right, &());
756 assert_eq!(
757 cursor
758 .slice(&tree.extent::<Count>(&()), Bias::Right, &())
759 .items(&()),
760 [1]
761 );
762 assert_eq!(cursor.item(), None);
763 assert_eq!(cursor.prev_item(), Some(&1));
764 assert_eq!(cursor.start(), &Sum(1));
765
766 // Multiple-element tree
767 let mut tree = SumTree::new();
768 tree.extend(vec![1, 2, 3, 4, 5, 6], &());
769 let mut cursor = tree.cursor::<Count, Sum>();
770
771 assert_eq!(cursor.slice(&Count(2), Bias::Right, &()).items(&()), [1, 2]);
772 assert_eq!(cursor.item(), Some(&3));
773 assert_eq!(cursor.prev_item(), Some(&2));
774 assert_eq!(cursor.start(), &Sum(3));
775
776 cursor.next(&());
777 assert_eq!(cursor.item(), Some(&4));
778 assert_eq!(cursor.prev_item(), Some(&3));
779 assert_eq!(cursor.start(), &Sum(6));
780
781 cursor.next(&());
782 assert_eq!(cursor.item(), Some(&5));
783 assert_eq!(cursor.prev_item(), Some(&4));
784 assert_eq!(cursor.start(), &Sum(10));
785
786 cursor.next(&());
787 assert_eq!(cursor.item(), Some(&6));
788 assert_eq!(cursor.prev_item(), Some(&5));
789 assert_eq!(cursor.start(), &Sum(15));
790
791 cursor.next(&());
792 cursor.next(&());
793 assert_eq!(cursor.item(), None);
794 assert_eq!(cursor.prev_item(), Some(&6));
795 assert_eq!(cursor.start(), &Sum(21));
796
797 cursor.prev(&());
798 assert_eq!(cursor.item(), Some(&6));
799 assert_eq!(cursor.prev_item(), Some(&5));
800 assert_eq!(cursor.start(), &Sum(15));
801
802 cursor.prev(&());
803 assert_eq!(cursor.item(), Some(&5));
804 assert_eq!(cursor.prev_item(), Some(&4));
805 assert_eq!(cursor.start(), &Sum(10));
806
807 cursor.prev(&());
808 assert_eq!(cursor.item(), Some(&4));
809 assert_eq!(cursor.prev_item(), Some(&3));
810 assert_eq!(cursor.start(), &Sum(6));
811
812 cursor.prev(&());
813 assert_eq!(cursor.item(), Some(&3));
814 assert_eq!(cursor.prev_item(), Some(&2));
815 assert_eq!(cursor.start(), &Sum(3));
816
817 cursor.prev(&());
818 assert_eq!(cursor.item(), Some(&2));
819 assert_eq!(cursor.prev_item(), Some(&1));
820 assert_eq!(cursor.start(), &Sum(1));
821
822 cursor.prev(&());
823 assert_eq!(cursor.item(), Some(&1));
824 assert_eq!(cursor.prev_item(), None);
825 assert_eq!(cursor.start(), &Sum(0));
826
827 cursor.prev(&());
828 assert_eq!(cursor.item(), None);
829 assert_eq!(cursor.prev_item(), None);
830 assert_eq!(cursor.start(), &Sum(0));
831
832 cursor.next(&());
833 assert_eq!(cursor.item(), Some(&1));
834 assert_eq!(cursor.prev_item(), None);
835 assert_eq!(cursor.start(), &Sum(0));
836
837 let mut cursor = tree.cursor::<Count, Sum>();
838 assert_eq!(
839 cursor
840 .slice(&tree.extent::<Count>(&()), Bias::Right, &())
841 .items(&()),
842 tree.items(&())
843 );
844 assert_eq!(cursor.item(), None);
845 assert_eq!(cursor.prev_item(), Some(&6));
846 assert_eq!(cursor.start(), &Sum(21));
847
848 cursor.seek(&Count(3), Bias::Right, &());
849 assert_eq!(
850 cursor
851 .slice(&tree.extent::<Count>(&()), Bias::Right, &())
852 .items(&()),
853 [4, 5, 6]
854 );
855 assert_eq!(cursor.item(), None);
856 assert_eq!(cursor.prev_item(), Some(&6));
857 assert_eq!(cursor.start(), &Sum(21));
858
859 // Seeking can bias left or right
860 cursor.seek(&Count(1), Bias::Left, &());
861 assert_eq!(cursor.item(), Some(&1));
862 cursor.seek(&Count(1), Bias::Right, &());
863 assert_eq!(cursor.item(), Some(&2));
864
865 // Slicing without resetting starts from where the cursor is parked at.
866 cursor.seek(&Count(1), Bias::Right, &());
867 assert_eq!(
868 cursor.slice(&Count(3), Bias::Right, &()).items(&()),
869 vec![2, 3]
870 );
871 assert_eq!(
872 cursor.slice(&Count(6), Bias::Left, &()).items(&()),
873 vec![4, 5]
874 );
875 assert_eq!(
876 cursor.slice(&Count(6), Bias::Right, &()).items(&()),
877 vec![6]
878 );
879 }
880
881 #[test]
882 fn test_edit() {
883 let mut tree = SumTree::<u8>::new();
884
885 let removed = tree.edit(vec![Edit::Insert(1), Edit::Insert(2), Edit::Insert(0)], &());
886 assert_eq!(tree.items(&()), vec![0, 1, 2]);
887 assert_eq!(removed, Vec::<u8>::new());
888 assert_eq!(tree.get(&0, &()), Some(&0));
889 assert_eq!(tree.get(&1, &()), Some(&1));
890 assert_eq!(tree.get(&2, &()), Some(&2));
891 assert_eq!(tree.get(&4, &()), None);
892
893 let removed = tree.edit(vec![Edit::Insert(2), Edit::Insert(4), Edit::Remove(0)], &());
894 assert_eq!(tree.items(&()), vec![1, 2, 4]);
895 assert_eq!(removed, vec![0, 2]);
896 assert_eq!(tree.get(&0, &()), None);
897 assert_eq!(tree.get(&1, &()), Some(&1));
898 assert_eq!(tree.get(&2, &()), Some(&2));
899 assert_eq!(tree.get(&4, &()), Some(&4));
900 }
901
902 #[derive(Clone, Default, Debug)]
903 pub struct IntegersSummary {
904 count: Count,
905 sum: Sum,
906 contains_even: bool,
907 max: u8,
908 }
909
910 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
911 struct Count(usize);
912
913 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
914 struct Sum(usize);
915
916 impl Item for u8 {
917 type Summary = IntegersSummary;
918
919 fn summary(&self) -> Self::Summary {
920 IntegersSummary {
921 count: Count(1),
922 sum: Sum(*self as usize),
923 contains_even: (*self & 1) == 0,
924 max: *self,
925 }
926 }
927 }
928
929 impl KeyedItem for u8 {
930 type Key = u8;
931
932 fn key(&self) -> Self::Key {
933 *self
934 }
935 }
936
937 impl Summary for IntegersSummary {
938 type Context = ();
939
940 fn add_summary(&mut self, other: &Self, _: &()) {
941 self.count.0 += &other.count.0;
942 self.sum.0 += &other.sum.0;
943 self.contains_even |= other.contains_even;
944 self.max = cmp::max(self.max, other.max);
945 }
946 }
947
948 impl<'a> Dimension<'a, IntegersSummary> for u8 {
949 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
950 *self = summary.max;
951 }
952 }
953
954 impl<'a> Dimension<'a, IntegersSummary> for Count {
955 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
956 self.0 += summary.count.0;
957 }
958 }
959
960 impl<'a> Dimension<'a, IntegersSummary> for Sum {
961 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
962 self.0 += summary.sum.0;
963 }
964 }
965
966 impl<'a> Add<&'a Self> for Sum {
967 type Output = Self;
968
969 fn add(mut self, other: &Self) -> Self {
970 self.0 += other.0;
971 self
972 }
973 }
974}