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