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, _: &S::Context);
33}
34
35impl<'a, T: Summary> Dimension<'a, T> for () {
36 fn add_summary(&mut self, _: &'a T, _: &T::Context) {}
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, Debug, Hash)]
50pub enum Bias {
51 Left,
52 Right,
53}
54
55impl PartialOrd for Bias {
56 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
57 Some(self.cmp(other))
58 }
59}
60
61impl Ord for Bias {
62 fn cmp(&self, other: &Self) -> Ordering {
63 match (self, other) {
64 (Self::Left, Self::Left) => Ordering::Equal,
65 (Self::Left, Self::Right) => Ordering::Less,
66 (Self::Right, Self::Right) => Ordering::Equal,
67 (Self::Right, Self::Left) => Ordering::Greater,
68 }
69 }
70}
71
72#[derive(Debug, Clone)]
73pub struct SumTree<T: Item>(Arc<Node<T>>);
74
75impl<T: Item> SumTree<T> {
76 pub fn new() -> Self {
77 SumTree(Arc::new(Node::Leaf {
78 summary: T::Summary::default(),
79 items: ArrayVec::new(),
80 item_summaries: ArrayVec::new(),
81 }))
82 }
83
84 pub fn from_item(item: T, cx: &<T::Summary as Summary>::Context) -> Self {
85 let mut tree = Self::new();
86 tree.push(item, cx);
87 tree
88 }
89
90 #[allow(unused)]
91 pub fn items(&self, cx: &<T::Summary as Summary>::Context) -> Vec<T> {
92 let mut items = Vec::new();
93 let mut cursor = self.cursor::<(), ()>();
94 cursor.next(cx);
95 while let Some(item) = cursor.item() {
96 items.push(item.clone());
97 cursor.next(cx);
98 }
99 items
100 }
101
102 pub fn cursor<'a, S, U>(&'a self) -> Cursor<T, S, U>
103 where
104 S: Dimension<'a, T::Summary>,
105 U: Dimension<'a, T::Summary>,
106 {
107 Cursor::new(self)
108 }
109
110 pub fn filter<'a, F, U>(
111 &'a self,
112 filter_node: F,
113 cx: &<T::Summary as Summary>::Context,
114 ) -> FilterCursor<F, T, U>
115 where
116 F: Fn(&T::Summary) -> bool,
117 U: Dimension<'a, T::Summary>,
118 {
119 FilterCursor::new(self, filter_node, cx)
120 }
121
122 #[allow(dead_code)]
123 pub fn first(&self) -> Option<&T> {
124 self.leftmost_leaf().0.items().first()
125 }
126
127 pub fn last(&self) -> Option<&T> {
128 self.rightmost_leaf().0.items().last()
129 }
130
131 pub fn update_last(&mut self, f: impl FnOnce(&mut T), cx: &<T::Summary as Summary>::Context) {
132 self.update_last_recursive(f, cx);
133 }
134
135 fn update_last_recursive(
136 &mut self,
137 f: impl FnOnce(&mut T),
138 cx: &<T::Summary as Summary>::Context,
139 ) -> Option<T::Summary> {
140 match Arc::make_mut(&mut self.0) {
141 Node::Internal {
142 summary,
143 child_summaries,
144 child_trees,
145 ..
146 } => {
147 let last_summary = child_summaries.last_mut().unwrap();
148 let last_child = child_trees.last_mut().unwrap();
149 *last_summary = last_child.update_last_recursive(f, cx).unwrap();
150 *summary = sum(child_summaries.iter(), cx);
151 Some(summary.clone())
152 }
153 Node::Leaf {
154 summary,
155 items,
156 item_summaries,
157 } => {
158 if let Some((item, item_summary)) = items.last_mut().zip(item_summaries.last_mut())
159 {
160 (f)(item);
161 *item_summary = item.summary();
162 *summary = sum(item_summaries.iter(), cx);
163 Some(summary.clone())
164 } else {
165 None
166 }
167 }
168 }
169 }
170
171 pub fn extent<'a, D: Dimension<'a, T::Summary>>(
172 &'a self,
173 cx: &<T::Summary as Summary>::Context,
174 ) -> D {
175 let mut extent = D::default();
176 match self.0.as_ref() {
177 Node::Internal { summary, .. } | Node::Leaf { summary, .. } => {
178 extent.add_summary(summary, cx);
179 }
180 }
181 extent
182 }
183
184 pub fn summary(&self) -> T::Summary {
185 match self.0.as_ref() {
186 Node::Internal { summary, .. } => summary.clone(),
187 Node::Leaf { summary, .. } => summary.clone(),
188 }
189 }
190
191 pub fn is_empty(&self) -> bool {
192 match self.0.as_ref() {
193 Node::Internal { .. } => false,
194 Node::Leaf { items, .. } => items.is_empty(),
195 }
196 }
197
198 pub fn extend<I>(&mut self, iter: I, cx: &<T::Summary as Summary>::Context)
199 where
200 I: IntoIterator<Item = T>,
201 {
202 let mut leaf: Option<Node<T>> = None;
203
204 for item in iter {
205 if leaf.is_some() && leaf.as_ref().unwrap().items().len() == 2 * TREE_BASE {
206 self.push_tree(SumTree(Arc::new(leaf.take().unwrap())), cx);
207 }
208
209 if leaf.is_none() {
210 leaf = Some(Node::Leaf::<T> {
211 summary: T::Summary::default(),
212 items: ArrayVec::new(),
213 item_summaries: ArrayVec::new(),
214 });
215 }
216
217 if let Some(Node::Leaf {
218 summary,
219 items,
220 item_summaries,
221 }) = leaf.as_mut()
222 {
223 let item_summary = item.summary();
224 summary.add_summary(&item_summary, cx);
225 items.push(item);
226 item_summaries.push(item_summary);
227 } else {
228 unreachable!()
229 }
230 }
231
232 if leaf.is_some() {
233 self.push_tree(SumTree(Arc::new(leaf.take().unwrap())), cx);
234 }
235 }
236
237 pub fn push(&mut self, item: T, cx: &<T::Summary as Summary>::Context) {
238 let summary = item.summary();
239 self.push_tree(
240 SumTree(Arc::new(Node::Leaf {
241 summary: summary.clone(),
242 items: ArrayVec::from_iter(Some(item)),
243 item_summaries: ArrayVec::from_iter(Some(summary)),
244 })),
245 cx,
246 );
247 }
248
249 pub fn push_tree(&mut self, other: Self, cx: &<T::Summary as Summary>::Context) {
250 if !other.0.is_leaf() || other.0.items().len() > 0 {
251 if self.0.height() < other.0.height() {
252 for tree in other.0.child_trees() {
253 self.push_tree(tree.clone(), cx);
254 }
255 } else if let Some(split_tree) = self.push_tree_recursive(other, cx) {
256 *self = Self::from_child_trees(self.clone(), split_tree, cx);
257 }
258 }
259 }
260
261 fn push_tree_recursive(
262 &mut self,
263 other: SumTree<T>,
264 cx: &<T::Summary as Summary>::Context,
265 ) -> Option<SumTree<T>> {
266 match Arc::make_mut(&mut self.0) {
267 Node::Internal {
268 height,
269 summary,
270 child_summaries,
271 child_trees,
272 ..
273 } => {
274 let other_node = other.0.clone();
275 summary.add_summary(other_node.summary(), cx);
276
277 let height_delta = *height - other_node.height();
278 let mut summaries_to_append = ArrayVec::<T::Summary, { 2 * TREE_BASE }>::new();
279 let mut trees_to_append = ArrayVec::<SumTree<T>, { 2 * TREE_BASE }>::new();
280 if height_delta == 0 {
281 summaries_to_append.extend(other_node.child_summaries().iter().cloned());
282 trees_to_append.extend(other_node.child_trees().iter().cloned());
283 } else if height_delta == 1 && !other_node.is_underflowing() {
284 summaries_to_append.push(other_node.summary().clone());
285 trees_to_append.push(other)
286 } else {
287 let tree_to_append = child_trees
288 .last_mut()
289 .unwrap()
290 .push_tree_recursive(other, cx);
291 *child_summaries.last_mut().unwrap() =
292 child_trees.last().unwrap().0.summary().clone();
293
294 if let Some(split_tree) = tree_to_append {
295 summaries_to_append.push(split_tree.0.summary().clone());
296 trees_to_append.push(split_tree);
297 }
298 }
299
300 let child_count = child_trees.len() + trees_to_append.len();
301 if child_count > 2 * TREE_BASE {
302 let left_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
303 let right_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
304 let left_trees;
305 let right_trees;
306
307 let midpoint = (child_count + child_count % 2) / 2;
308 {
309 let mut all_summaries = child_summaries
310 .iter()
311 .chain(summaries_to_append.iter())
312 .cloned();
313 left_summaries = all_summaries.by_ref().take(midpoint).collect();
314 right_summaries = all_summaries.collect();
315 let mut all_trees =
316 child_trees.iter().chain(trees_to_append.iter()).cloned();
317 left_trees = all_trees.by_ref().take(midpoint).collect();
318 right_trees = all_trees.collect();
319 }
320 *summary = sum(left_summaries.iter(), cx);
321 *child_summaries = left_summaries;
322 *child_trees = left_trees;
323
324 Some(SumTree(Arc::new(Node::Internal {
325 height: *height,
326 summary: sum(right_summaries.iter(), cx),
327 child_summaries: right_summaries,
328 child_trees: right_trees,
329 })))
330 } else {
331 child_summaries.extend(summaries_to_append);
332 child_trees.extend(trees_to_append);
333 None
334 }
335 }
336 Node::Leaf {
337 summary,
338 items,
339 item_summaries,
340 } => {
341 let other_node = other.0;
342
343 let child_count = items.len() + other_node.items().len();
344 if child_count > 2 * TREE_BASE {
345 let left_items;
346 let right_items;
347 let left_summaries;
348 let right_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>;
349
350 let midpoint = (child_count + child_count % 2) / 2;
351 {
352 let mut all_items = items.iter().chain(other_node.items().iter()).cloned();
353 left_items = all_items.by_ref().take(midpoint).collect();
354 right_items = all_items.collect();
355
356 let mut all_summaries = item_summaries
357 .iter()
358 .chain(other_node.child_summaries())
359 .cloned();
360 left_summaries = all_summaries.by_ref().take(midpoint).collect();
361 right_summaries = all_summaries.collect();
362 }
363 *items = left_items;
364 *item_summaries = left_summaries;
365 *summary = sum(item_summaries.iter(), cx);
366 Some(SumTree(Arc::new(Node::Leaf {
367 items: right_items,
368 summary: sum(right_summaries.iter(), cx),
369 item_summaries: right_summaries,
370 })))
371 } else {
372 summary.add_summary(other_node.summary(), cx);
373 items.extend(other_node.items().iter().cloned());
374 item_summaries.extend(other_node.child_summaries().iter().cloned());
375 None
376 }
377 }
378 }
379 }
380
381 fn from_child_trees(
382 left: SumTree<T>,
383 right: SumTree<T>,
384 cx: &<T::Summary as Summary>::Context,
385 ) -> Self {
386 let height = left.0.height() + 1;
387 let mut child_summaries = ArrayVec::new();
388 child_summaries.push(left.0.summary().clone());
389 child_summaries.push(right.0.summary().clone());
390 let mut child_trees = ArrayVec::new();
391 child_trees.push(left);
392 child_trees.push(right);
393 SumTree(Arc::new(Node::Internal {
394 height,
395 summary: sum(child_summaries.iter(), cx),
396 child_summaries,
397 child_trees,
398 }))
399 }
400
401 fn leftmost_leaf(&self) -> &Self {
402 match *self.0 {
403 Node::Leaf { .. } => self,
404 Node::Internal {
405 ref child_trees, ..
406 } => child_trees.first().unwrap().leftmost_leaf(),
407 }
408 }
409
410 fn rightmost_leaf(&self) -> &Self {
411 match *self.0 {
412 Node::Leaf { .. } => self,
413 Node::Internal {
414 ref child_trees, ..
415 } => child_trees.last().unwrap().rightmost_leaf(),
416 }
417 }
418}
419
420impl<T: KeyedItem> SumTree<T> {
421 pub fn insert_or_replace(&mut self, item: T, cx: &<T::Summary as Summary>::Context) -> bool {
422 let mut replaced = false;
423 *self = {
424 let mut cursor = self.cursor::<T::Key, ()>();
425 let mut new_tree = cursor.slice(&item.key(), Bias::Left, cx);
426 if cursor
427 .item()
428 .map_or(false, |cursor_item| cursor_item.key() == item.key())
429 {
430 cursor.next(cx);
431 replaced = true;
432 }
433 new_tree.push(item, cx);
434 new_tree.push_tree(cursor.suffix(cx), cx);
435 new_tree
436 };
437 replaced
438 }
439
440 pub fn edit(
441 &mut self,
442 mut edits: Vec<Edit<T>>,
443 cx: &<T::Summary as Summary>::Context,
444 ) -> Vec<T> {
445 if edits.is_empty() {
446 return Vec::new();
447 }
448
449 let mut removed = Vec::new();
450 edits.sort_unstable_by_key(|item| item.key());
451
452 *self = {
453 let mut cursor = self.cursor::<T::Key, ()>();
454 let mut new_tree = SumTree::new();
455 let mut buffered_items = Vec::new();
456
457 cursor.seek(&T::Key::default(), Bias::Left, cx);
458 for edit in edits {
459 let new_key = edit.key();
460 let mut old_item = cursor.item();
461
462 if old_item
463 .as_ref()
464 .map_or(false, |old_item| old_item.key() < new_key)
465 {
466 new_tree.extend(buffered_items.drain(..), cx);
467 let slice = cursor.slice(&new_key, Bias::Left, cx);
468 new_tree.push_tree(slice, cx);
469 old_item = cursor.item();
470 }
471
472 if let Some(old_item) = old_item {
473 if old_item.key() == new_key {
474 removed.push(old_item.clone());
475 cursor.next(cx);
476 }
477 }
478
479 match edit {
480 Edit::Insert(item) => {
481 buffered_items.push(item);
482 }
483 Edit::Remove(_) => {}
484 }
485 }
486
487 new_tree.extend(buffered_items, cx);
488 new_tree.push_tree(cursor.suffix(cx), cx);
489 new_tree
490 };
491
492 removed
493 }
494
495 pub fn get(&self, key: &T::Key, cx: &<T::Summary as Summary>::Context) -> Option<&T> {
496 let mut cursor = self.cursor::<T::Key, ()>();
497 if cursor.seek(key, Bias::Left, cx) {
498 cursor.item()
499 } else {
500 None
501 }
502 }
503}
504
505impl<T: Item> Default for SumTree<T> {
506 fn default() -> Self {
507 Self::new()
508 }
509}
510
511#[derive(Clone, Debug)]
512pub enum Node<T: Item> {
513 Internal {
514 height: u8,
515 summary: T::Summary,
516 child_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
517 child_trees: ArrayVec<SumTree<T>, { 2 * TREE_BASE }>,
518 },
519 Leaf {
520 summary: T::Summary,
521 items: ArrayVec<T, { 2 * TREE_BASE }>,
522 item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
523 },
524}
525
526impl<T: Item> Node<T> {
527 fn is_leaf(&self) -> bool {
528 match self {
529 Node::Leaf { .. } => true,
530 _ => false,
531 }
532 }
533
534 fn height(&self) -> u8 {
535 match self {
536 Node::Internal { height, .. } => *height,
537 Node::Leaf { .. } => 0,
538 }
539 }
540
541 fn summary(&self) -> &T::Summary {
542 match self {
543 Node::Internal { summary, .. } => summary,
544 Node::Leaf { summary, .. } => summary,
545 }
546 }
547
548 fn child_summaries(&self) -> &[T::Summary] {
549 match self {
550 Node::Internal {
551 child_summaries, ..
552 } => child_summaries.as_slice(),
553 Node::Leaf { item_summaries, .. } => item_summaries.as_slice(),
554 }
555 }
556
557 fn child_trees(&self) -> &ArrayVec<SumTree<T>, { 2 * TREE_BASE }> {
558 match self {
559 Node::Internal { child_trees, .. } => child_trees,
560 Node::Leaf { .. } => panic!("Leaf nodes have no child trees"),
561 }
562 }
563
564 fn items(&self) -> &ArrayVec<T, { 2 * TREE_BASE }> {
565 match self {
566 Node::Leaf { items, .. } => items,
567 Node::Internal { .. } => panic!("Internal nodes have no items"),
568 }
569 }
570
571 fn is_underflowing(&self) -> bool {
572 match self {
573 Node::Internal { child_trees, .. } => child_trees.len() < TREE_BASE,
574 Node::Leaf { items, .. } => items.len() < TREE_BASE,
575 }
576 }
577}
578
579#[derive(Debug)]
580pub enum Edit<T: KeyedItem> {
581 Insert(T),
582 Remove(T::Key),
583}
584
585impl<T: KeyedItem> Edit<T> {
586 fn key(&self) -> T::Key {
587 match self {
588 Edit::Insert(item) => item.key(),
589 Edit::Remove(key) => key.clone(),
590 }
591 }
592}
593
594fn sum<'a, T, I>(iter: I, cx: &T::Context) -> T
595where
596 T: 'a + Summary,
597 I: Iterator<Item = &'a T>,
598{
599 let mut sum = T::default();
600 for value in iter {
601 sum.add_summary(value, cx);
602 }
603 sum
604}
605
606#[cfg(test)]
607mod tests {
608 use super::*;
609 use rand::{distributions, prelude::*};
610 use std::cmp;
611 use std::ops::Add;
612
613 #[test]
614 fn test_extend_and_push_tree() {
615 let mut tree1 = SumTree::new();
616 tree1.extend(0..20, &());
617
618 let mut tree2 = SumTree::new();
619 tree2.extend(50..100, &());
620
621 tree1.push_tree(tree2, &());
622 assert_eq!(
623 tree1.items(&()),
624 (0..20).chain(50..100).collect::<Vec<u8>>()
625 );
626 }
627
628 #[crate::test(self, iterations = 100)]
629 fn test_random(mut rng: StdRng) {
630 let rng = &mut rng;
631 let mut tree = SumTree::<u8>::new();
632 let count = rng.gen_range(0..10);
633 tree.extend(rng.sample_iter(distributions::Standard).take(count), &());
634
635 for _ in 0..5 {
636 let splice_end = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
637 let splice_start = rng.gen_range(0..splice_end + 1);
638 let count = rng.gen_range(0..3);
639 let tree_end = tree.extent::<Count>(&());
640 let new_items = rng
641 .sample_iter(distributions::Standard)
642 .take(count)
643 .collect::<Vec<u8>>();
644
645 let mut reference_items = tree.items(&());
646 reference_items.splice(splice_start..splice_end, new_items.clone());
647
648 tree = {
649 let mut cursor = tree.cursor::<Count, ()>();
650 let mut new_tree = cursor.slice(&Count(splice_start), Bias::Right, &());
651 new_tree.extend(new_items, &());
652 cursor.seek(&Count(splice_end), Bias::Right, &());
653 new_tree.push_tree(cursor.slice(&tree_end, Bias::Right, &()), &());
654 new_tree
655 };
656
657 assert_eq!(tree.items(&()), reference_items);
658
659 let mut filter_cursor = tree.filter::<_, Count>(|summary| summary.contains_even, &());
660 let mut reference_filter = tree
661 .items(&())
662 .into_iter()
663 .enumerate()
664 .filter(|(_, item)| (item & 1) == 0);
665 while let Some(actual_item) = filter_cursor.item() {
666 let (reference_index, reference_item) = reference_filter.next().unwrap();
667 assert_eq!(actual_item, &reference_item);
668 assert_eq!(filter_cursor.start().0, reference_index);
669 filter_cursor.next(&());
670 }
671 assert!(reference_filter.next().is_none());
672
673 let mut pos = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
674 let mut before_start = false;
675 let mut cursor = tree.cursor::<Count, Count>();
676 cursor.seek(&Count(pos), Bias::Right, &());
677
678 for i in 0..10 {
679 assert_eq!(cursor.sum_start().0, pos);
680
681 if pos > 0 {
682 assert_eq!(cursor.prev_item().unwrap(), &reference_items[pos - 1]);
683 } else {
684 assert_eq!(cursor.prev_item(), None);
685 }
686
687 if pos < reference_items.len() && !before_start {
688 assert_eq!(cursor.item().unwrap(), &reference_items[pos]);
689 } else {
690 assert_eq!(cursor.item(), None);
691 }
692
693 if i < 5 {
694 cursor.next(&());
695 if pos < reference_items.len() {
696 pos += 1;
697 before_start = false;
698 }
699 } else {
700 cursor.prev(&());
701 if pos == 0 {
702 before_start = true;
703 }
704 pos = pos.saturating_sub(1);
705 }
706 }
707 }
708
709 for _ in 0..10 {
710 let end = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
711 let start = rng.gen_range(0..end + 1);
712 let start_bias = if rng.gen() { Bias::Left } else { Bias::Right };
713 let end_bias = if rng.gen() { Bias::Left } else { Bias::Right };
714
715 let mut cursor = tree.cursor::<Count, ()>();
716 cursor.seek(&Count(start), start_bias, &());
717 let slice = cursor.slice(&Count(end), end_bias, &());
718
719 cursor.seek(&Count(start), start_bias, &());
720 let summary = cursor.summary::<Sum>(&Count(end), end_bias, &());
721
722 assert_eq!(summary, slice.summary().sum);
723 }
724 }
725
726 #[test]
727 fn test_cursor() {
728 // Empty tree
729 let tree = SumTree::<u8>::new();
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(), None);
736 assert_eq!(cursor.prev_item(), None);
737 assert_eq!(cursor.sum_start(), &Sum(0));
738
739 // Single-element tree
740 let mut tree = SumTree::<u8>::new();
741 tree.extend(vec![1], &());
742 let mut cursor = tree.cursor::<Count, Sum>();
743 assert_eq!(
744 cursor.slice(&Count(0), Bias::Right, &()).items(&()),
745 Vec::<u8>::new()
746 );
747 assert_eq!(cursor.item(), Some(&1));
748 assert_eq!(cursor.prev_item(), None);
749 assert_eq!(cursor.sum_start(), &Sum(0));
750
751 cursor.next(&());
752 assert_eq!(cursor.item(), None);
753 assert_eq!(cursor.prev_item(), Some(&1));
754 assert_eq!(cursor.sum_start(), &Sum(1));
755
756 cursor.prev(&());
757 assert_eq!(cursor.item(), Some(&1));
758 assert_eq!(cursor.prev_item(), None);
759 assert_eq!(cursor.sum_start(), &Sum(0));
760
761 let mut cursor = tree.cursor::<Count, Sum>();
762 assert_eq!(cursor.slice(&Count(1), Bias::Right, &()).items(&()), [1]);
763 assert_eq!(cursor.item(), None);
764 assert_eq!(cursor.prev_item(), Some(&1));
765 assert_eq!(cursor.sum_start(), &Sum(1));
766
767 cursor.seek(&Count(0), Bias::Right, &());
768 assert_eq!(
769 cursor
770 .slice(&tree.extent::<Count>(&()), Bias::Right, &())
771 .items(&()),
772 [1]
773 );
774 assert_eq!(cursor.item(), None);
775 assert_eq!(cursor.prev_item(), Some(&1));
776 assert_eq!(cursor.sum_start(), &Sum(1));
777
778 // Multiple-element tree
779 let mut tree = SumTree::new();
780 tree.extend(vec![1, 2, 3, 4, 5, 6], &());
781 let mut cursor = tree.cursor::<Count, Sum>();
782
783 assert_eq!(cursor.slice(&Count(2), Bias::Right, &()).items(&()), [1, 2]);
784 assert_eq!(cursor.item(), Some(&3));
785 assert_eq!(cursor.prev_item(), Some(&2));
786 assert_eq!(cursor.sum_start(), &Sum(3));
787
788 cursor.next(&());
789 assert_eq!(cursor.item(), Some(&4));
790 assert_eq!(cursor.prev_item(), Some(&3));
791 assert_eq!(cursor.sum_start(), &Sum(6));
792
793 cursor.next(&());
794 assert_eq!(cursor.item(), Some(&5));
795 assert_eq!(cursor.prev_item(), Some(&4));
796 assert_eq!(cursor.sum_start(), &Sum(10));
797
798 cursor.next(&());
799 assert_eq!(cursor.item(), Some(&6));
800 assert_eq!(cursor.prev_item(), Some(&5));
801 assert_eq!(cursor.sum_start(), &Sum(15));
802
803 cursor.next(&());
804 cursor.next(&());
805 assert_eq!(cursor.item(), None);
806 assert_eq!(cursor.prev_item(), Some(&6));
807 assert_eq!(cursor.sum_start(), &Sum(21));
808
809 cursor.prev(&());
810 assert_eq!(cursor.item(), Some(&6));
811 assert_eq!(cursor.prev_item(), Some(&5));
812 assert_eq!(cursor.sum_start(), &Sum(15));
813
814 cursor.prev(&());
815 assert_eq!(cursor.item(), Some(&5));
816 assert_eq!(cursor.prev_item(), Some(&4));
817 assert_eq!(cursor.sum_start(), &Sum(10));
818
819 cursor.prev(&());
820 assert_eq!(cursor.item(), Some(&4));
821 assert_eq!(cursor.prev_item(), Some(&3));
822 assert_eq!(cursor.sum_start(), &Sum(6));
823
824 cursor.prev(&());
825 assert_eq!(cursor.item(), Some(&3));
826 assert_eq!(cursor.prev_item(), Some(&2));
827 assert_eq!(cursor.sum_start(), &Sum(3));
828
829 cursor.prev(&());
830 assert_eq!(cursor.item(), Some(&2));
831 assert_eq!(cursor.prev_item(), Some(&1));
832 assert_eq!(cursor.sum_start(), &Sum(1));
833
834 cursor.prev(&());
835 assert_eq!(cursor.item(), Some(&1));
836 assert_eq!(cursor.prev_item(), None);
837 assert_eq!(cursor.sum_start(), &Sum(0));
838
839 cursor.prev(&());
840 assert_eq!(cursor.item(), None);
841 assert_eq!(cursor.prev_item(), None);
842 assert_eq!(cursor.sum_start(), &Sum(0));
843
844 cursor.next(&());
845 assert_eq!(cursor.item(), Some(&1));
846 assert_eq!(cursor.prev_item(), None);
847 assert_eq!(cursor.sum_start(), &Sum(0));
848
849 let mut cursor = tree.cursor::<Count, Sum>();
850 assert_eq!(
851 cursor
852 .slice(&tree.extent::<Count>(&()), Bias::Right, &())
853 .items(&()),
854 tree.items(&())
855 );
856 assert_eq!(cursor.item(), None);
857 assert_eq!(cursor.prev_item(), Some(&6));
858 assert_eq!(cursor.sum_start(), &Sum(21));
859
860 cursor.seek(&Count(3), Bias::Right, &());
861 assert_eq!(
862 cursor
863 .slice(&tree.extent::<Count>(&()), Bias::Right, &())
864 .items(&()),
865 [4, 5, 6]
866 );
867 assert_eq!(cursor.item(), None);
868 assert_eq!(cursor.prev_item(), Some(&6));
869 assert_eq!(cursor.sum_start(), &Sum(21));
870
871 // Seeking can bias left or right
872 cursor.seek(&Count(1), Bias::Left, &());
873 assert_eq!(cursor.item(), Some(&1));
874 cursor.seek(&Count(1), Bias::Right, &());
875 assert_eq!(cursor.item(), Some(&2));
876
877 // Slicing without resetting starts from where the cursor is parked at.
878 cursor.seek(&Count(1), Bias::Right, &());
879 assert_eq!(
880 cursor.slice(&Count(3), Bias::Right, &()).items(&()),
881 vec![2, 3]
882 );
883 assert_eq!(
884 cursor.slice(&Count(6), Bias::Left, &()).items(&()),
885 vec![4, 5]
886 );
887 assert_eq!(
888 cursor.slice(&Count(6), Bias::Right, &()).items(&()),
889 vec![6]
890 );
891 }
892
893 #[test]
894 fn test_edit() {
895 let mut tree = SumTree::<u8>::new();
896
897 let removed = tree.edit(vec![Edit::Insert(1), Edit::Insert(2), Edit::Insert(0)], &());
898 assert_eq!(tree.items(&()), vec![0, 1, 2]);
899 assert_eq!(removed, Vec::<u8>::new());
900 assert_eq!(tree.get(&0, &()), Some(&0));
901 assert_eq!(tree.get(&1, &()), Some(&1));
902 assert_eq!(tree.get(&2, &()), Some(&2));
903 assert_eq!(tree.get(&4, &()), None);
904
905 let removed = tree.edit(vec![Edit::Insert(2), Edit::Insert(4), Edit::Remove(0)], &());
906 assert_eq!(tree.items(&()), vec![1, 2, 4]);
907 assert_eq!(removed, vec![0, 2]);
908 assert_eq!(tree.get(&0, &()), None);
909 assert_eq!(tree.get(&1, &()), Some(&1));
910 assert_eq!(tree.get(&2, &()), Some(&2));
911 assert_eq!(tree.get(&4, &()), Some(&4));
912 }
913
914 #[derive(Clone, Default, Debug)]
915 pub struct IntegersSummary {
916 count: Count,
917 sum: Sum,
918 contains_even: bool,
919 max: u8,
920 }
921
922 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
923 struct Count(usize);
924
925 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
926 struct Sum(usize);
927
928 impl Item for u8 {
929 type Summary = IntegersSummary;
930
931 fn summary(&self) -> Self::Summary {
932 IntegersSummary {
933 count: Count(1),
934 sum: Sum(*self as usize),
935 contains_even: (*self & 1) == 0,
936 max: *self,
937 }
938 }
939 }
940
941 impl KeyedItem for u8 {
942 type Key = u8;
943
944 fn key(&self) -> Self::Key {
945 *self
946 }
947 }
948
949 impl Summary for IntegersSummary {
950 type Context = ();
951
952 fn add_summary(&mut self, other: &Self, _: &()) {
953 self.count.0 += &other.count.0;
954 self.sum.0 += &other.sum.0;
955 self.contains_even |= other.contains_even;
956 self.max = cmp::max(self.max, other.max);
957 }
958 }
959
960 impl<'a> Dimension<'a, IntegersSummary> for u8 {
961 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
962 *self = summary.max;
963 }
964 }
965
966 impl<'a> Dimension<'a, IntegersSummary> for Count {
967 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
968 self.0 += summary.count.0;
969 }
970 }
971
972 impl<'a> Dimension<'a, IntegersSummary> for Sum {
973 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
974 self.0 += summary.sum.0;
975 }
976 }
977
978 impl<'a> Add<&'a Self> for Sum {
979 type Output = Self;
980
981 fn add(mut self, other: &Self) -> Self {
982 self.0 += other.0;
983 self
984 }
985 }
986}