1mod cursor;
2
3use arrayvec::ArrayVec;
4pub use cursor::Cursor;
5pub use cursor::FilterCursor;
6use std::marker::PhantomData;
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 {
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 T {
37 fn add_summary(&mut self, summary: &'a T, cx: &T::Context) {
38 Summary::add_summary(self, summary, cx);
39 }
40}
41
42pub trait SeekTarget<'a, S: Summary, D: Dimension<'a, S>>: fmt::Debug {
43 fn cmp(&self, cursor_location: &D, cx: &S::Context) -> Ordering;
44}
45
46impl<'a, S: Summary, D: Dimension<'a, S> + Ord> SeekTarget<'a, S, D> for D {
47 fn cmp(&self, cursor_location: &Self, _: &S::Context) -> Ordering {
48 Ord::cmp(self, cursor_location)
49 }
50}
51
52impl<'a, T: Summary> Dimension<'a, T> for () {
53 fn add_summary(&mut self, _: &'a T, _: &T::Context) {}
54}
55
56impl<'a, T: Summary, D1: Dimension<'a, T>, D2: Dimension<'a, T>> Dimension<'a, T> for (D1, D2) {
57 fn add_summary(&mut self, summary: &'a T, cx: &T::Context) {
58 self.0.add_summary(summary, cx);
59 self.1.add_summary(summary, cx);
60 }
61}
62
63impl<'a, S: Summary, D1: SeekTarget<'a, S, D1> + Dimension<'a, S>, D2: Dimension<'a, S>>
64 SeekTarget<'a, S, (D1, D2)> for D1
65{
66 fn cmp(&self, cursor_location: &(D1, D2), cx: &S::Context) -> Ordering {
67 self.cmp(&cursor_location.0, cx)
68 }
69}
70
71struct End<D>(PhantomData<D>);
72
73impl<D> End<D> {
74 fn new() -> Self {
75 Self(PhantomData)
76 }
77}
78
79impl<'a, S: Summary, D: Dimension<'a, S>> SeekTarget<'a, S, D> for End<D> {
80 fn cmp(&self, _: &D, _: &S::Context) -> Ordering {
81 Ordering::Greater
82 }
83}
84
85impl<D> fmt::Debug for End<D> {
86 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
87 f.debug_tuple("End").finish()
88 }
89}
90
91#[derive(Copy, Clone, Eq, PartialEq, Debug, Hash)]
92pub enum Bias {
93 Left,
94 Right,
95}
96
97impl PartialOrd for Bias {
98 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
99 Some(self.cmp(other))
100 }
101}
102
103impl Ord for Bias {
104 fn cmp(&self, other: &Self) -> Ordering {
105 match (self, other) {
106 (Self::Left, Self::Left) => Ordering::Equal,
107 (Self::Left, Self::Right) => Ordering::Less,
108 (Self::Right, Self::Right) => Ordering::Equal,
109 (Self::Right, Self::Left) => Ordering::Greater,
110 }
111 }
112}
113
114#[derive(Debug, Clone)]
115pub struct SumTree<T: Item>(Arc<Node<T>>);
116
117impl<T: Item> SumTree<T> {
118 pub fn new() -> Self {
119 SumTree(Arc::new(Node::Leaf {
120 summary: T::Summary::default(),
121 items: ArrayVec::new(),
122 item_summaries: ArrayVec::new(),
123 }))
124 }
125
126 pub fn from_item(item: T, cx: &<T::Summary as Summary>::Context) -> Self {
127 let mut tree = Self::new();
128 tree.push(item, cx);
129 tree
130 }
131
132 pub fn from_iter<I: IntoIterator<Item = T>>(
133 iter: I,
134 cx: &<T::Summary as Summary>::Context,
135 ) -> Self {
136 let mut tree = Self::new();
137 tree.extend(iter, cx);
138 tree
139 }
140
141 #[allow(unused)]
142 pub fn items(&self, cx: &<T::Summary as Summary>::Context) -> Vec<T> {
143 let mut items = Vec::new();
144 let mut cursor = self.cursor::<()>();
145 cursor.next(cx);
146 while let Some(item) = cursor.item() {
147 items.push(item.clone());
148 cursor.next(cx);
149 }
150 items
151 }
152
153 pub fn cursor<'a, S>(&'a self) -> Cursor<T, S>
154 where
155 S: Dimension<'a, T::Summary>,
156 {
157 Cursor::new(self)
158 }
159
160 pub fn filter<'a, F, U>(
161 &'a self,
162 filter_node: F,
163 cx: &<T::Summary as Summary>::Context,
164 ) -> FilterCursor<F, T, U>
165 where
166 F: FnMut(&T::Summary) -> bool,
167 U: Dimension<'a, T::Summary>,
168 {
169 FilterCursor::new(self, filter_node, cx)
170 }
171
172 #[allow(dead_code)]
173 pub fn first(&self) -> Option<&T> {
174 self.leftmost_leaf().0.items().first()
175 }
176
177 pub fn last(&self) -> Option<&T> {
178 self.rightmost_leaf().0.items().last()
179 }
180
181 pub fn update_last(&mut self, f: impl FnOnce(&mut T), cx: &<T::Summary as Summary>::Context) {
182 self.update_last_recursive(f, cx);
183 }
184
185 fn update_last_recursive(
186 &mut self,
187 f: impl FnOnce(&mut T),
188 cx: &<T::Summary as Summary>::Context,
189 ) -> Option<T::Summary> {
190 match Arc::make_mut(&mut self.0) {
191 Node::Internal {
192 summary,
193 child_summaries,
194 child_trees,
195 ..
196 } => {
197 let last_summary = child_summaries.last_mut().unwrap();
198 let last_child = child_trees.last_mut().unwrap();
199 *last_summary = last_child.update_last_recursive(f, cx).unwrap();
200 *summary = sum(child_summaries.iter(), cx);
201 Some(summary.clone())
202 }
203 Node::Leaf {
204 summary,
205 items,
206 item_summaries,
207 } => {
208 if let Some((item, item_summary)) = items.last_mut().zip(item_summaries.last_mut())
209 {
210 (f)(item);
211 *item_summary = item.summary();
212 *summary = sum(item_summaries.iter(), cx);
213 Some(summary.clone())
214 } else {
215 None
216 }
217 }
218 }
219 }
220
221 pub fn extent<'a, D: Dimension<'a, T::Summary>>(
222 &'a self,
223 cx: &<T::Summary as Summary>::Context,
224 ) -> D {
225 let mut extent = D::default();
226 match self.0.as_ref() {
227 Node::Internal { summary, .. } | Node::Leaf { summary, .. } => {
228 extent.add_summary(summary, cx);
229 }
230 }
231 extent
232 }
233
234 pub fn summary(&self) -> T::Summary {
235 match self.0.as_ref() {
236 Node::Internal { summary, .. } => summary.clone(),
237 Node::Leaf { summary, .. } => summary.clone(),
238 }
239 }
240
241 pub fn is_empty(&self) -> bool {
242 match self.0.as_ref() {
243 Node::Internal { .. } => false,
244 Node::Leaf { items, .. } => items.is_empty(),
245 }
246 }
247
248 pub fn extend<I>(&mut self, iter: I, cx: &<T::Summary as Summary>::Context)
249 where
250 I: IntoIterator<Item = T>,
251 {
252 let mut leaf: Option<Node<T>> = None;
253
254 for item in iter {
255 if leaf.is_some() && leaf.as_ref().unwrap().items().len() == 2 * TREE_BASE {
256 self.push_tree(SumTree(Arc::new(leaf.take().unwrap())), cx);
257 }
258
259 if leaf.is_none() {
260 leaf = Some(Node::Leaf::<T> {
261 summary: T::Summary::default(),
262 items: ArrayVec::new(),
263 item_summaries: ArrayVec::new(),
264 });
265 }
266
267 if let Some(Node::Leaf {
268 summary,
269 items,
270 item_summaries,
271 }) = leaf.as_mut()
272 {
273 let item_summary = item.summary();
274 <T::Summary as Summary>::add_summary(summary, &item_summary, cx);
275 items.push(item);
276 item_summaries.push(item_summary);
277 } else {
278 unreachable!()
279 }
280 }
281
282 if leaf.is_some() {
283 self.push_tree(SumTree(Arc::new(leaf.take().unwrap())), cx);
284 }
285 }
286
287 pub fn push(&mut self, item: T, cx: &<T::Summary as Summary>::Context) {
288 let summary = item.summary();
289 self.push_tree(
290 SumTree(Arc::new(Node::Leaf {
291 summary: summary.clone(),
292 items: ArrayVec::from_iter(Some(item)),
293 item_summaries: ArrayVec::from_iter(Some(summary)),
294 })),
295 cx,
296 );
297 }
298
299 pub fn push_tree(&mut self, other: Self, cx: &<T::Summary as Summary>::Context) {
300 if !other.0.is_leaf() || other.0.items().len() > 0 {
301 if self.0.height() < other.0.height() {
302 for tree in other.0.child_trees() {
303 self.push_tree(tree.clone(), cx);
304 }
305 } else if let Some(split_tree) = self.push_tree_recursive(other, cx) {
306 *self = Self::from_child_trees(self.clone(), split_tree, cx);
307 }
308 }
309 }
310
311 fn push_tree_recursive(
312 &mut self,
313 other: SumTree<T>,
314 cx: &<T::Summary as Summary>::Context,
315 ) -> Option<SumTree<T>> {
316 match Arc::make_mut(&mut self.0) {
317 Node::Internal {
318 height,
319 summary,
320 child_summaries,
321 child_trees,
322 ..
323 } => {
324 let other_node = other.0.clone();
325 <T::Summary as Summary>::add_summary(summary, other_node.summary(), cx);
326
327 let height_delta = *height - other_node.height();
328 let mut summaries_to_append = ArrayVec::<T::Summary, { 2 * TREE_BASE }>::new();
329 let mut trees_to_append = ArrayVec::<SumTree<T>, { 2 * TREE_BASE }>::new();
330 if height_delta == 0 {
331 summaries_to_append.extend(other_node.child_summaries().iter().cloned());
332 trees_to_append.extend(other_node.child_trees().iter().cloned());
333 } else if height_delta == 1 && !other_node.is_underflowing() {
334 summaries_to_append.push(other_node.summary().clone());
335 trees_to_append.push(other)
336 } else {
337 let tree_to_append = child_trees
338 .last_mut()
339 .unwrap()
340 .push_tree_recursive(other, cx);
341 *child_summaries.last_mut().unwrap() =
342 child_trees.last().unwrap().0.summary().clone();
343
344 if let Some(split_tree) = tree_to_append {
345 summaries_to_append.push(split_tree.0.summary().clone());
346 trees_to_append.push(split_tree);
347 }
348 }
349
350 let child_count = child_trees.len() + trees_to_append.len();
351 if child_count > 2 * TREE_BASE {
352 let left_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
353 let right_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
354 let left_trees;
355 let right_trees;
356
357 let midpoint = (child_count + child_count % 2) / 2;
358 {
359 let mut all_summaries = child_summaries
360 .iter()
361 .chain(summaries_to_append.iter())
362 .cloned();
363 left_summaries = all_summaries.by_ref().take(midpoint).collect();
364 right_summaries = all_summaries.collect();
365 let mut all_trees =
366 child_trees.iter().chain(trees_to_append.iter()).cloned();
367 left_trees = all_trees.by_ref().take(midpoint).collect();
368 right_trees = all_trees.collect();
369 }
370 *summary = sum(left_summaries.iter(), cx);
371 *child_summaries = left_summaries;
372 *child_trees = left_trees;
373
374 Some(SumTree(Arc::new(Node::Internal {
375 height: *height,
376 summary: sum(right_summaries.iter(), cx),
377 child_summaries: right_summaries,
378 child_trees: right_trees,
379 })))
380 } else {
381 child_summaries.extend(summaries_to_append);
382 child_trees.extend(trees_to_append);
383 None
384 }
385 }
386 Node::Leaf {
387 summary,
388 items,
389 item_summaries,
390 } => {
391 let other_node = other.0;
392
393 let child_count = items.len() + other_node.items().len();
394 if child_count > 2 * TREE_BASE {
395 let left_items;
396 let right_items;
397 let left_summaries;
398 let right_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>;
399
400 let midpoint = (child_count + child_count % 2) / 2;
401 {
402 let mut all_items = items.iter().chain(other_node.items().iter()).cloned();
403 left_items = all_items.by_ref().take(midpoint).collect();
404 right_items = all_items.collect();
405
406 let mut all_summaries = item_summaries
407 .iter()
408 .chain(other_node.child_summaries())
409 .cloned();
410 left_summaries = all_summaries.by_ref().take(midpoint).collect();
411 right_summaries = all_summaries.collect();
412 }
413 *items = left_items;
414 *item_summaries = left_summaries;
415 *summary = sum(item_summaries.iter(), cx);
416 Some(SumTree(Arc::new(Node::Leaf {
417 items: right_items,
418 summary: sum(right_summaries.iter(), cx),
419 item_summaries: right_summaries,
420 })))
421 } else {
422 <T::Summary as Summary>::add_summary(summary, other_node.summary(), cx);
423 items.extend(other_node.items().iter().cloned());
424 item_summaries.extend(other_node.child_summaries().iter().cloned());
425 None
426 }
427 }
428 }
429 }
430
431 fn from_child_trees(
432 left: SumTree<T>,
433 right: SumTree<T>,
434 cx: &<T::Summary as Summary>::Context,
435 ) -> Self {
436 let height = left.0.height() + 1;
437 let mut child_summaries = ArrayVec::new();
438 child_summaries.push(left.0.summary().clone());
439 child_summaries.push(right.0.summary().clone());
440 let mut child_trees = ArrayVec::new();
441 child_trees.push(left);
442 child_trees.push(right);
443 SumTree(Arc::new(Node::Internal {
444 height,
445 summary: sum(child_summaries.iter(), cx),
446 child_summaries,
447 child_trees,
448 }))
449 }
450
451 fn leftmost_leaf(&self) -> &Self {
452 match *self.0 {
453 Node::Leaf { .. } => self,
454 Node::Internal {
455 ref child_trees, ..
456 } => child_trees.first().unwrap().leftmost_leaf(),
457 }
458 }
459
460 fn rightmost_leaf(&self) -> &Self {
461 match *self.0 {
462 Node::Leaf { .. } => self,
463 Node::Internal {
464 ref child_trees, ..
465 } => child_trees.last().unwrap().rightmost_leaf(),
466 }
467 }
468}
469
470impl<T: KeyedItem> SumTree<T> {
471 pub fn insert_or_replace(&mut self, item: T, cx: &<T::Summary as Summary>::Context) -> bool {
472 let mut replaced = false;
473 *self = {
474 let mut cursor = self.cursor::<T::Key>();
475 let mut new_tree = cursor.slice(&item.key(), Bias::Left, cx);
476 if cursor
477 .item()
478 .map_or(false, |cursor_item| cursor_item.key() == item.key())
479 {
480 cursor.next(cx);
481 replaced = true;
482 }
483 new_tree.push(item, cx);
484 new_tree.push_tree(cursor.suffix(cx), cx);
485 new_tree
486 };
487 replaced
488 }
489
490 pub fn edit(
491 &mut self,
492 mut edits: Vec<Edit<T>>,
493 cx: &<T::Summary as Summary>::Context,
494 ) -> Vec<T> {
495 if edits.is_empty() {
496 return Vec::new();
497 }
498
499 let mut removed = Vec::new();
500 edits.sort_unstable_by_key(|item| item.key());
501
502 *self = {
503 let mut cursor = self.cursor::<T::Key>();
504 let mut new_tree = SumTree::new();
505 let mut buffered_items = Vec::new();
506
507 cursor.seek(&T::Key::default(), Bias::Left, cx);
508 for edit in edits {
509 let new_key = edit.key();
510 let mut old_item = cursor.item();
511
512 if old_item
513 .as_ref()
514 .map_or(false, |old_item| old_item.key() < new_key)
515 {
516 new_tree.extend(buffered_items.drain(..), cx);
517 let slice = cursor.slice(&new_key, Bias::Left, cx);
518 new_tree.push_tree(slice, cx);
519 old_item = cursor.item();
520 }
521
522 if let Some(old_item) = old_item {
523 if old_item.key() == new_key {
524 removed.push(old_item.clone());
525 cursor.next(cx);
526 }
527 }
528
529 match edit {
530 Edit::Insert(item) => {
531 buffered_items.push(item);
532 }
533 Edit::Remove(_) => {}
534 }
535 }
536
537 new_tree.extend(buffered_items, cx);
538 new_tree.push_tree(cursor.suffix(cx), cx);
539 new_tree
540 };
541
542 removed
543 }
544
545 pub fn get(&self, key: &T::Key, cx: &<T::Summary as Summary>::Context) -> Option<&T> {
546 let mut cursor = self.cursor::<T::Key>();
547 if cursor.seek(key, Bias::Left, cx) {
548 cursor.item()
549 } else {
550 None
551 }
552 }
553}
554
555impl<T: Item> Default for SumTree<T> {
556 fn default() -> Self {
557 Self::new()
558 }
559}
560
561#[derive(Clone, Debug)]
562pub enum Node<T: Item> {
563 Internal {
564 height: u8,
565 summary: T::Summary,
566 child_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
567 child_trees: ArrayVec<SumTree<T>, { 2 * TREE_BASE }>,
568 },
569 Leaf {
570 summary: T::Summary,
571 items: ArrayVec<T, { 2 * TREE_BASE }>,
572 item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
573 },
574}
575
576impl<T: Item> Node<T> {
577 fn is_leaf(&self) -> bool {
578 match self {
579 Node::Leaf { .. } => true,
580 _ => false,
581 }
582 }
583
584 fn height(&self) -> u8 {
585 match self {
586 Node::Internal { height, .. } => *height,
587 Node::Leaf { .. } => 0,
588 }
589 }
590
591 fn summary(&self) -> &T::Summary {
592 match self {
593 Node::Internal { summary, .. } => summary,
594 Node::Leaf { summary, .. } => summary,
595 }
596 }
597
598 fn child_summaries(&self) -> &[T::Summary] {
599 match self {
600 Node::Internal {
601 child_summaries, ..
602 } => child_summaries.as_slice(),
603 Node::Leaf { item_summaries, .. } => item_summaries.as_slice(),
604 }
605 }
606
607 fn child_trees(&self) -> &ArrayVec<SumTree<T>, { 2 * TREE_BASE }> {
608 match self {
609 Node::Internal { child_trees, .. } => child_trees,
610 Node::Leaf { .. } => panic!("Leaf nodes have no child trees"),
611 }
612 }
613
614 fn items(&self) -> &ArrayVec<T, { 2 * TREE_BASE }> {
615 match self {
616 Node::Leaf { items, .. } => items,
617 Node::Internal { .. } => panic!("Internal nodes have no items"),
618 }
619 }
620
621 fn is_underflowing(&self) -> bool {
622 match self {
623 Node::Internal { child_trees, .. } => child_trees.len() < TREE_BASE,
624 Node::Leaf { items, .. } => items.len() < TREE_BASE,
625 }
626 }
627}
628
629#[derive(Debug)]
630pub enum Edit<T: KeyedItem> {
631 Insert(T),
632 Remove(T::Key),
633}
634
635impl<T: KeyedItem> Edit<T> {
636 fn key(&self) -> T::Key {
637 match self {
638 Edit::Insert(item) => item.key(),
639 Edit::Remove(key) => key.clone(),
640 }
641 }
642}
643
644fn sum<'a, T, I>(iter: I, cx: &T::Context) -> T
645where
646 T: 'a + Summary,
647 I: Iterator<Item = &'a T>,
648{
649 let mut sum = T::default();
650 for value in iter {
651 sum.add_summary(value, cx);
652 }
653 sum
654}
655
656#[cfg(test)]
657mod tests {
658 use super::*;
659 use rand::{distributions, prelude::*};
660 use std::cmp;
661
662 #[test]
663 fn test_extend_and_push_tree() {
664 let mut tree1 = SumTree::new();
665 tree1.extend(0..20, &());
666
667 let mut tree2 = SumTree::new();
668 tree2.extend(50..100, &());
669
670 tree1.push_tree(tree2, &());
671 assert_eq!(
672 tree1.items(&()),
673 (0..20).chain(50..100).collect::<Vec<u8>>()
674 );
675 }
676
677 #[test]
678 fn test_random() {
679 let mut starting_seed = 0;
680 if let Ok(value) = std::env::var("SEED") {
681 starting_seed = value.parse().expect("invalid SEED variable");
682 }
683 let mut num_iterations = 100;
684 if let Ok(value) = std::env::var("ITERATIONS") {
685 num_iterations = value.parse().expect("invalid ITERATIONS variable");
686 }
687
688 for seed in starting_seed..(starting_seed + num_iterations) {
689 let mut rng = StdRng::seed_from_u64(seed);
690
691 let rng = &mut rng;
692 let mut tree = SumTree::<u8>::new();
693 let count = rng.gen_range(0..10);
694 tree.extend(rng.sample_iter(distributions::Standard).take(count), &());
695
696 for _ in 0..5 {
697 let splice_end = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
698 let splice_start = rng.gen_range(0..splice_end + 1);
699 let count = rng.gen_range(0..3);
700 let tree_end = tree.extent::<Count>(&());
701 let new_items = rng
702 .sample_iter(distributions::Standard)
703 .take(count)
704 .collect::<Vec<u8>>();
705
706 let mut reference_items = tree.items(&());
707 reference_items.splice(splice_start..splice_end, new_items.clone());
708
709 tree = {
710 let mut cursor = tree.cursor::<Count>();
711 let mut new_tree = cursor.slice(&Count(splice_start), Bias::Right, &());
712 new_tree.extend(new_items, &());
713 cursor.seek(&Count(splice_end), Bias::Right, &());
714 new_tree.push_tree(cursor.slice(&tree_end, Bias::Right, &()), &());
715 new_tree
716 };
717
718 assert_eq!(tree.items(&()), reference_items);
719
720 let mut filter_cursor =
721 tree.filter::<_, Count>(|summary| summary.contains_even, &());
722 let mut reference_filter = tree
723 .items(&())
724 .into_iter()
725 .enumerate()
726 .filter(|(_, item)| (item & 1) == 0);
727 while let Some(actual_item) = filter_cursor.item() {
728 let (reference_index, reference_item) = reference_filter.next().unwrap();
729 assert_eq!(actual_item, &reference_item);
730 assert_eq!(filter_cursor.start().0, reference_index);
731 filter_cursor.next(&());
732 }
733 assert!(reference_filter.next().is_none());
734
735 let mut pos = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
736 let mut before_start = false;
737 let mut cursor = tree.cursor::<Count>();
738 cursor.seek(&Count(pos), Bias::Right, &());
739
740 for i in 0..10 {
741 assert_eq!(cursor.start().0, pos);
742
743 if pos > 0 {
744 assert_eq!(cursor.prev_item().unwrap(), &reference_items[pos - 1]);
745 } else {
746 assert_eq!(cursor.prev_item(), None);
747 }
748
749 if pos < reference_items.len() && !before_start {
750 assert_eq!(cursor.item().unwrap(), &reference_items[pos]);
751 } else {
752 assert_eq!(cursor.item(), None);
753 }
754
755 if i < 5 {
756 cursor.next(&());
757 if pos < reference_items.len() {
758 pos += 1;
759 before_start = false;
760 }
761 } else {
762 cursor.prev(&());
763 if pos == 0 {
764 before_start = true;
765 }
766 pos = pos.saturating_sub(1);
767 }
768 }
769 }
770
771 for _ in 0..10 {
772 let end = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
773 let start = rng.gen_range(0..end + 1);
774 let start_bias = if rng.gen() { Bias::Left } else { Bias::Right };
775 let end_bias = if rng.gen() { Bias::Left } else { Bias::Right };
776
777 let mut cursor = tree.cursor::<Count>();
778 cursor.seek(&Count(start), start_bias, &());
779 let slice = cursor.slice(&Count(end), end_bias, &());
780
781 cursor.seek(&Count(start), start_bias, &());
782 let summary = cursor.summary::<_, Sum>(&Count(end), end_bias, &());
783
784 assert_eq!(summary.0, slice.summary().sum);
785 }
786 }
787 }
788
789 #[test]
790 fn test_cursor() {
791 // Empty tree
792 let tree = SumTree::<u8>::new();
793 let mut cursor = tree.cursor::<IntegersSummary>();
794 assert_eq!(
795 cursor.slice(&Count(0), Bias::Right, &()).items(&()),
796 Vec::<u8>::new()
797 );
798 assert_eq!(cursor.item(), None);
799 assert_eq!(cursor.prev_item(), None);
800 assert_eq!(cursor.start().sum, 0);
801
802 // Single-element tree
803 let mut tree = SumTree::<u8>::new();
804 tree.extend(vec![1], &());
805 let mut cursor = tree.cursor::<IntegersSummary>();
806 assert_eq!(
807 cursor.slice(&Count(0), Bias::Right, &()).items(&()),
808 Vec::<u8>::new()
809 );
810 assert_eq!(cursor.item(), Some(&1));
811 assert_eq!(cursor.prev_item(), None);
812 assert_eq!(cursor.start().sum, 0);
813
814 cursor.next(&());
815 assert_eq!(cursor.item(), None);
816 assert_eq!(cursor.prev_item(), Some(&1));
817 assert_eq!(cursor.start().sum, 1);
818
819 cursor.prev(&());
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::<IntegersSummary>();
825 assert_eq!(cursor.slice(&Count(1), Bias::Right, &()).items(&()), [1]);
826 assert_eq!(cursor.item(), None);
827 assert_eq!(cursor.prev_item(), Some(&1));
828 assert_eq!(cursor.start().sum, 1);
829
830 cursor.seek(&Count(0), Bias::Right, &());
831 assert_eq!(
832 cursor
833 .slice(&tree.extent::<Count>(&()), Bias::Right, &())
834 .items(&()),
835 [1]
836 );
837 assert_eq!(cursor.item(), None);
838 assert_eq!(cursor.prev_item(), Some(&1));
839 assert_eq!(cursor.start().sum, 1);
840
841 // Multiple-element tree
842 let mut tree = SumTree::new();
843 tree.extend(vec![1, 2, 3, 4, 5, 6], &());
844 let mut cursor = tree.cursor::<IntegersSummary>();
845
846 assert_eq!(cursor.slice(&Count(2), Bias::Right, &()).items(&()), [1, 2]);
847 assert_eq!(cursor.item(), Some(&3));
848 assert_eq!(cursor.prev_item(), Some(&2));
849 assert_eq!(cursor.start().sum, 3);
850
851 cursor.next(&());
852 assert_eq!(cursor.item(), Some(&4));
853 assert_eq!(cursor.prev_item(), Some(&3));
854 assert_eq!(cursor.start().sum, 6);
855
856 cursor.next(&());
857 assert_eq!(cursor.item(), Some(&5));
858 assert_eq!(cursor.prev_item(), Some(&4));
859 assert_eq!(cursor.start().sum, 10);
860
861 cursor.next(&());
862 assert_eq!(cursor.item(), Some(&6));
863 assert_eq!(cursor.prev_item(), Some(&5));
864 assert_eq!(cursor.start().sum, 15);
865
866 cursor.next(&());
867 cursor.next(&());
868 assert_eq!(cursor.item(), None);
869 assert_eq!(cursor.prev_item(), Some(&6));
870 assert_eq!(cursor.start().sum, 21);
871
872 cursor.prev(&());
873 assert_eq!(cursor.item(), Some(&6));
874 assert_eq!(cursor.prev_item(), Some(&5));
875 assert_eq!(cursor.start().sum, 15);
876
877 cursor.prev(&());
878 assert_eq!(cursor.item(), Some(&5));
879 assert_eq!(cursor.prev_item(), Some(&4));
880 assert_eq!(cursor.start().sum, 10);
881
882 cursor.prev(&());
883 assert_eq!(cursor.item(), Some(&4));
884 assert_eq!(cursor.prev_item(), Some(&3));
885 assert_eq!(cursor.start().sum, 6);
886
887 cursor.prev(&());
888 assert_eq!(cursor.item(), Some(&3));
889 assert_eq!(cursor.prev_item(), Some(&2));
890 assert_eq!(cursor.start().sum, 3);
891
892 cursor.prev(&());
893 assert_eq!(cursor.item(), Some(&2));
894 assert_eq!(cursor.prev_item(), Some(&1));
895 assert_eq!(cursor.start().sum, 1);
896
897 cursor.prev(&());
898 assert_eq!(cursor.item(), Some(&1));
899 assert_eq!(cursor.prev_item(), None);
900 assert_eq!(cursor.start().sum, 0);
901
902 cursor.prev(&());
903 assert_eq!(cursor.item(), None);
904 assert_eq!(cursor.prev_item(), None);
905 assert_eq!(cursor.start().sum, 0);
906
907 cursor.next(&());
908 assert_eq!(cursor.item(), Some(&1));
909 assert_eq!(cursor.prev_item(), None);
910 assert_eq!(cursor.start().sum, 0);
911
912 let mut cursor = tree.cursor::<IntegersSummary>();
913 assert_eq!(
914 cursor
915 .slice(&tree.extent::<Count>(&()), Bias::Right, &())
916 .items(&()),
917 tree.items(&())
918 );
919 assert_eq!(cursor.item(), None);
920 assert_eq!(cursor.prev_item(), Some(&6));
921 assert_eq!(cursor.start().sum, 21);
922
923 cursor.seek(&Count(3), Bias::Right, &());
924 assert_eq!(
925 cursor
926 .slice(&tree.extent::<Count>(&()), Bias::Right, &())
927 .items(&()),
928 [4, 5, 6]
929 );
930 assert_eq!(cursor.item(), None);
931 assert_eq!(cursor.prev_item(), Some(&6));
932 assert_eq!(cursor.start().sum, 21);
933
934 // Seeking can bias left or right
935 cursor.seek(&Count(1), Bias::Left, &());
936 assert_eq!(cursor.item(), Some(&1));
937 cursor.seek(&Count(1), Bias::Right, &());
938 assert_eq!(cursor.item(), Some(&2));
939
940 // Slicing without resetting starts from where the cursor is parked at.
941 cursor.seek(&Count(1), Bias::Right, &());
942 assert_eq!(
943 cursor.slice(&Count(3), Bias::Right, &()).items(&()),
944 vec![2, 3]
945 );
946 assert_eq!(
947 cursor.slice(&Count(6), Bias::Left, &()).items(&()),
948 vec![4, 5]
949 );
950 assert_eq!(
951 cursor.slice(&Count(6), Bias::Right, &()).items(&()),
952 vec![6]
953 );
954 }
955
956 #[test]
957 fn test_edit() {
958 let mut tree = SumTree::<u8>::new();
959
960 let removed = tree.edit(vec![Edit::Insert(1), Edit::Insert(2), Edit::Insert(0)], &());
961 assert_eq!(tree.items(&()), vec![0, 1, 2]);
962 assert_eq!(removed, Vec::<u8>::new());
963 assert_eq!(tree.get(&0, &()), Some(&0));
964 assert_eq!(tree.get(&1, &()), Some(&1));
965 assert_eq!(tree.get(&2, &()), Some(&2));
966 assert_eq!(tree.get(&4, &()), None);
967
968 let removed = tree.edit(vec![Edit::Insert(2), Edit::Insert(4), Edit::Remove(0)], &());
969 assert_eq!(tree.items(&()), vec![1, 2, 4]);
970 assert_eq!(removed, vec![0, 2]);
971 assert_eq!(tree.get(&0, &()), None);
972 assert_eq!(tree.get(&1, &()), Some(&1));
973 assert_eq!(tree.get(&2, &()), Some(&2));
974 assert_eq!(tree.get(&4, &()), Some(&4));
975 }
976
977 #[derive(Clone, Default, Debug)]
978 pub struct IntegersSummary {
979 count: usize,
980 sum: usize,
981 contains_even: bool,
982 max: u8,
983 }
984
985 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
986 struct Count(usize);
987
988 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
989 struct Sum(usize);
990
991 impl Item for u8 {
992 type Summary = IntegersSummary;
993
994 fn summary(&self) -> Self::Summary {
995 IntegersSummary {
996 count: 1,
997 sum: *self as usize,
998 contains_even: (*self & 1) == 0,
999 max: *self,
1000 }
1001 }
1002 }
1003
1004 impl KeyedItem for u8 {
1005 type Key = u8;
1006
1007 fn key(&self) -> Self::Key {
1008 *self
1009 }
1010 }
1011
1012 impl Summary for IntegersSummary {
1013 type Context = ();
1014
1015 fn add_summary(&mut self, other: &Self, _: &()) {
1016 self.count += other.count;
1017 self.sum += other.sum;
1018 self.contains_even |= other.contains_even;
1019 self.max = cmp::max(self.max, other.max);
1020 }
1021 }
1022
1023 impl<'a> Dimension<'a, IntegersSummary> for u8 {
1024 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
1025 *self = summary.max;
1026 }
1027 }
1028
1029 impl<'a> Dimension<'a, IntegersSummary> for Count {
1030 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
1031 self.0 += summary.count;
1032 }
1033 }
1034
1035 impl<'a> SeekTarget<'a, IntegersSummary, IntegersSummary> for Count {
1036 fn cmp(&self, cursor_location: &IntegersSummary, _: &()) -> Ordering {
1037 self.0.cmp(&cursor_location.count)
1038 }
1039 }
1040
1041 impl<'a> Dimension<'a, IntegersSummary> for Sum {
1042 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
1043 self.0 += summary.sum;
1044 }
1045 }
1046}