1mod cursor;
2mod tree_map;
3
4use arrayvec::ArrayVec;
5pub use cursor::{Cursor, FilterCursor, Iter};
6use std::marker::PhantomData;
7use std::{cmp::Ordering, fmt, iter::FromIterator, sync::Arc};
8pub use tree_map::TreeMap;
9
10#[cfg(test)]
11const TREE_BASE: usize = 2;
12#[cfg(not(test))]
13const TREE_BASE: usize = 6;
14
15pub trait Item: Clone {
16 type Summary: Summary;
17
18 fn summary(&self) -> Self::Summary;
19}
20
21pub trait KeyedItem: Item {
22 type Key: for<'a> Dimension<'a, Self::Summary> + Ord;
23
24 fn key(&self) -> Self::Key;
25}
26
27pub trait Summary: Default + Clone + fmt::Debug {
28 type Context;
29
30 fn add_summary(&mut self, summary: &Self, cx: &Self::Context);
31}
32
33pub trait Dimension<'a, S: Summary>: Clone + fmt::Debug + Default {
34 fn add_summary(&mut self, _summary: &'a S, _: &S::Context);
35
36 fn from_summary(summary: &'a S, cx: &S::Context) -> Self {
37 let mut dimension = Self::default();
38 dimension.add_summary(summary, cx);
39 dimension
40 }
41}
42
43impl<'a, T: Summary> Dimension<'a, T> for T {
44 fn add_summary(&mut self, summary: &'a T, cx: &T::Context) {
45 Summary::add_summary(self, summary, cx);
46 }
47}
48
49pub trait SeekTarget<'a, S: Summary, D: Dimension<'a, S>>: fmt::Debug {
50 fn cmp(&self, cursor_location: &D, cx: &S::Context) -> Ordering;
51}
52
53impl<'a, S: Summary, D: Dimension<'a, S> + Ord> SeekTarget<'a, S, D> for D {
54 fn cmp(&self, cursor_location: &Self, _: &S::Context) -> Ordering {
55 Ord::cmp(self, cursor_location)
56 }
57}
58
59impl<'a, T: Summary> Dimension<'a, T> for () {
60 fn add_summary(&mut self, _: &'a T, _: &T::Context) {}
61}
62
63impl<'a, T: Summary, D1: Dimension<'a, T>, D2: Dimension<'a, T>> Dimension<'a, T> for (D1, D2) {
64 fn add_summary(&mut self, summary: &'a T, cx: &T::Context) {
65 self.0.add_summary(summary, cx);
66 self.1.add_summary(summary, cx);
67 }
68}
69
70impl<'a, S: Summary, D1: SeekTarget<'a, S, D1> + Dimension<'a, S>, D2: Dimension<'a, S>>
71 SeekTarget<'a, S, (D1, D2)> for D1
72{
73 fn cmp(&self, cursor_location: &(D1, D2), cx: &S::Context) -> Ordering {
74 self.cmp(&cursor_location.0, cx)
75 }
76}
77
78struct End<D>(PhantomData<D>);
79
80impl<D> End<D> {
81 fn new() -> Self {
82 Self(PhantomData)
83 }
84}
85
86impl<'a, S: Summary, D: Dimension<'a, S>> SeekTarget<'a, S, D> for End<D> {
87 fn cmp(&self, _: &D, _: &S::Context) -> Ordering {
88 Ordering::Greater
89 }
90}
91
92impl<D> fmt::Debug for End<D> {
93 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
94 f.debug_tuple("End").finish()
95 }
96}
97
98#[derive(Copy, Clone, Eq, PartialEq, Debug, Hash)]
99pub enum Bias {
100 Left,
101 Right,
102}
103
104impl PartialOrd for Bias {
105 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
106 Some(self.cmp(other))
107 }
108}
109
110impl Ord for Bias {
111 fn cmp(&self, other: &Self) -> Ordering {
112 match (self, other) {
113 (Self::Left, Self::Left) => Ordering::Equal,
114 (Self::Left, Self::Right) => Ordering::Less,
115 (Self::Right, Self::Right) => Ordering::Equal,
116 (Self::Right, Self::Left) => Ordering::Greater,
117 }
118 }
119}
120
121#[derive(Debug, Clone)]
122pub struct SumTree<T: Item>(Arc<Node<T>>);
123
124impl<T: Item> SumTree<T> {
125 pub fn new() -> Self {
126 SumTree(Arc::new(Node::Leaf {
127 summary: T::Summary::default(),
128 items: ArrayVec::new(),
129 item_summaries: ArrayVec::new(),
130 }))
131 }
132
133 pub fn from_item(item: T, cx: &<T::Summary as Summary>::Context) -> Self {
134 let mut tree = Self::new();
135 tree.push(item, cx);
136 tree
137 }
138
139 pub fn from_iter<I: IntoIterator<Item = T>>(
140 iter: I,
141 cx: &<T::Summary as Summary>::Context,
142 ) -> Self {
143 let mut tree = Self::new();
144 tree.extend(iter, cx);
145 tree
146 }
147
148 #[allow(unused)]
149 pub fn items(&self, cx: &<T::Summary as Summary>::Context) -> Vec<T> {
150 let mut items = Vec::new();
151 let mut cursor = self.cursor::<()>();
152 cursor.next(cx);
153 while let Some(item) = cursor.item() {
154 items.push(item.clone());
155 cursor.next(cx);
156 }
157 items
158 }
159
160 pub fn iter(&self) -> Iter<T> {
161 Iter::new(self)
162 }
163
164 pub fn cursor<'a, S>(&'a self) -> Cursor<T, S>
165 where
166 S: Dimension<'a, T::Summary>,
167 {
168 Cursor::new(self)
169 }
170
171 pub fn filter<'a, F, U>(
172 &'a self,
173 filter_node: F,
174 cx: &<T::Summary as Summary>::Context,
175 ) -> FilterCursor<F, T, U>
176 where
177 F: FnMut(&T::Summary) -> bool,
178 U: Dimension<'a, T::Summary>,
179 {
180 FilterCursor::new(self, filter_node, cx)
181 }
182
183 #[allow(dead_code)]
184 pub fn first(&self) -> Option<&T> {
185 self.leftmost_leaf().0.items().first()
186 }
187
188 pub fn last(&self) -> Option<&T> {
189 self.rightmost_leaf().0.items().last()
190 }
191
192 pub fn update_last(&mut self, f: impl FnOnce(&mut T), cx: &<T::Summary as Summary>::Context) {
193 self.update_last_recursive(f, cx);
194 }
195
196 fn update_last_recursive(
197 &mut self,
198 f: impl FnOnce(&mut T),
199 cx: &<T::Summary as Summary>::Context,
200 ) -> Option<T::Summary> {
201 match Arc::make_mut(&mut self.0) {
202 Node::Internal {
203 summary,
204 child_summaries,
205 child_trees,
206 ..
207 } => {
208 let last_summary = child_summaries.last_mut().unwrap();
209 let last_child = child_trees.last_mut().unwrap();
210 *last_summary = last_child.update_last_recursive(f, cx).unwrap();
211 *summary = sum(child_summaries.iter(), cx);
212 Some(summary.clone())
213 }
214 Node::Leaf {
215 summary,
216 items,
217 item_summaries,
218 } => {
219 if let Some((item, item_summary)) = items.last_mut().zip(item_summaries.last_mut())
220 {
221 (f)(item);
222 *item_summary = item.summary();
223 *summary = sum(item_summaries.iter(), cx);
224 Some(summary.clone())
225 } else {
226 None
227 }
228 }
229 }
230 }
231
232 pub fn extent<'a, D: Dimension<'a, T::Summary>>(
233 &'a self,
234 cx: &<T::Summary as Summary>::Context,
235 ) -> D {
236 let mut extent = D::default();
237 match self.0.as_ref() {
238 Node::Internal { summary, .. } | Node::Leaf { summary, .. } => {
239 extent.add_summary(summary, cx);
240 }
241 }
242 extent
243 }
244
245 pub fn summary(&self) -> T::Summary {
246 match self.0.as_ref() {
247 Node::Internal { summary, .. } => summary.clone(),
248 Node::Leaf { summary, .. } => summary.clone(),
249 }
250 }
251
252 pub fn is_empty(&self) -> bool {
253 match self.0.as_ref() {
254 Node::Internal { .. } => false,
255 Node::Leaf { items, .. } => items.is_empty(),
256 }
257 }
258
259 pub fn extend<I>(&mut self, iter: I, cx: &<T::Summary as Summary>::Context)
260 where
261 I: IntoIterator<Item = T>,
262 {
263 let mut leaf: Option<Node<T>> = None;
264
265 for item in iter {
266 if leaf.is_some() && leaf.as_ref().unwrap().items().len() == 2 * TREE_BASE {
267 self.push_tree(SumTree(Arc::new(leaf.take().unwrap())), cx);
268 }
269
270 if leaf.is_none() {
271 leaf = Some(Node::Leaf::<T> {
272 summary: T::Summary::default(),
273 items: ArrayVec::new(),
274 item_summaries: ArrayVec::new(),
275 });
276 }
277
278 if let Some(Node::Leaf {
279 summary,
280 items,
281 item_summaries,
282 }) = leaf.as_mut()
283 {
284 let item_summary = item.summary();
285 <T::Summary as Summary>::add_summary(summary, &item_summary, cx);
286 items.push(item);
287 item_summaries.push(item_summary);
288 } else {
289 unreachable!()
290 }
291 }
292
293 if leaf.is_some() {
294 self.push_tree(SumTree(Arc::new(leaf.take().unwrap())), cx);
295 }
296 }
297
298 pub fn push(&mut self, item: T, cx: &<T::Summary as Summary>::Context) {
299 let summary = item.summary();
300 self.push_tree(
301 SumTree(Arc::new(Node::Leaf {
302 summary: summary.clone(),
303 items: ArrayVec::from_iter(Some(item)),
304 item_summaries: ArrayVec::from_iter(Some(summary)),
305 })),
306 cx,
307 );
308 }
309
310 pub fn push_tree(&mut self, other: Self, cx: &<T::Summary as Summary>::Context) {
311 if !other.0.is_leaf() || other.0.items().len() > 0 {
312 if self.0.height() < other.0.height() {
313 for tree in other.0.child_trees() {
314 self.push_tree(tree.clone(), cx);
315 }
316 } else if let Some(split_tree) = self.push_tree_recursive(other, cx) {
317 *self = Self::from_child_trees(self.clone(), split_tree, cx);
318 }
319 }
320 }
321
322 fn push_tree_recursive(
323 &mut self,
324 other: SumTree<T>,
325 cx: &<T::Summary as Summary>::Context,
326 ) -> Option<SumTree<T>> {
327 match Arc::make_mut(&mut self.0) {
328 Node::Internal {
329 height,
330 summary,
331 child_summaries,
332 child_trees,
333 ..
334 } => {
335 let other_node = other.0.clone();
336 <T::Summary as Summary>::add_summary(summary, other_node.summary(), cx);
337
338 let height_delta = *height - other_node.height();
339 let mut summaries_to_append = ArrayVec::<T::Summary, { 2 * TREE_BASE }>::new();
340 let mut trees_to_append = ArrayVec::<SumTree<T>, { 2 * TREE_BASE }>::new();
341 if height_delta == 0 {
342 summaries_to_append.extend(other_node.child_summaries().iter().cloned());
343 trees_to_append.extend(other_node.child_trees().iter().cloned());
344 } else if height_delta == 1 && !other_node.is_underflowing() {
345 summaries_to_append.push(other_node.summary().clone());
346 trees_to_append.push(other)
347 } else {
348 let tree_to_append = child_trees
349 .last_mut()
350 .unwrap()
351 .push_tree_recursive(other, cx);
352 *child_summaries.last_mut().unwrap() =
353 child_trees.last().unwrap().0.summary().clone();
354
355 if let Some(split_tree) = tree_to_append {
356 summaries_to_append.push(split_tree.0.summary().clone());
357 trees_to_append.push(split_tree);
358 }
359 }
360
361 let child_count = child_trees.len() + trees_to_append.len();
362 if child_count > 2 * TREE_BASE {
363 let left_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
364 let right_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
365 let left_trees;
366 let right_trees;
367
368 let midpoint = (child_count + child_count % 2) / 2;
369 {
370 let mut all_summaries = child_summaries
371 .iter()
372 .chain(summaries_to_append.iter())
373 .cloned();
374 left_summaries = all_summaries.by_ref().take(midpoint).collect();
375 right_summaries = all_summaries.collect();
376 let mut all_trees =
377 child_trees.iter().chain(trees_to_append.iter()).cloned();
378 left_trees = all_trees.by_ref().take(midpoint).collect();
379 right_trees = all_trees.collect();
380 }
381 *summary = sum(left_summaries.iter(), cx);
382 *child_summaries = left_summaries;
383 *child_trees = left_trees;
384
385 Some(SumTree(Arc::new(Node::Internal {
386 height: *height,
387 summary: sum(right_summaries.iter(), cx),
388 child_summaries: right_summaries,
389 child_trees: right_trees,
390 })))
391 } else {
392 child_summaries.extend(summaries_to_append);
393 child_trees.extend(trees_to_append);
394 None
395 }
396 }
397 Node::Leaf {
398 summary,
399 items,
400 item_summaries,
401 } => {
402 let other_node = other.0;
403
404 let child_count = items.len() + other_node.items().len();
405 if child_count > 2 * TREE_BASE {
406 let left_items;
407 let right_items;
408 let left_summaries;
409 let right_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>;
410
411 let midpoint = (child_count + child_count % 2) / 2;
412 {
413 let mut all_items = items.iter().chain(other_node.items().iter()).cloned();
414 left_items = all_items.by_ref().take(midpoint).collect();
415 right_items = all_items.collect();
416
417 let mut all_summaries = item_summaries
418 .iter()
419 .chain(other_node.child_summaries())
420 .cloned();
421 left_summaries = all_summaries.by_ref().take(midpoint).collect();
422 right_summaries = all_summaries.collect();
423 }
424 *items = left_items;
425 *item_summaries = left_summaries;
426 *summary = sum(item_summaries.iter(), cx);
427 Some(SumTree(Arc::new(Node::Leaf {
428 items: right_items,
429 summary: sum(right_summaries.iter(), cx),
430 item_summaries: right_summaries,
431 })))
432 } else {
433 <T::Summary as Summary>::add_summary(summary, other_node.summary(), cx);
434 items.extend(other_node.items().iter().cloned());
435 item_summaries.extend(other_node.child_summaries().iter().cloned());
436 None
437 }
438 }
439 }
440 }
441
442 fn from_child_trees(
443 left: SumTree<T>,
444 right: SumTree<T>,
445 cx: &<T::Summary as Summary>::Context,
446 ) -> Self {
447 let height = left.0.height() + 1;
448 let mut child_summaries = ArrayVec::new();
449 child_summaries.push(left.0.summary().clone());
450 child_summaries.push(right.0.summary().clone());
451 let mut child_trees = ArrayVec::new();
452 child_trees.push(left);
453 child_trees.push(right);
454 SumTree(Arc::new(Node::Internal {
455 height,
456 summary: sum(child_summaries.iter(), cx),
457 child_summaries,
458 child_trees,
459 }))
460 }
461
462 fn leftmost_leaf(&self) -> &Self {
463 match *self.0 {
464 Node::Leaf { .. } => self,
465 Node::Internal {
466 ref child_trees, ..
467 } => child_trees.first().unwrap().leftmost_leaf(),
468 }
469 }
470
471 fn rightmost_leaf(&self) -> &Self {
472 match *self.0 {
473 Node::Leaf { .. } => self,
474 Node::Internal {
475 ref child_trees, ..
476 } => child_trees.last().unwrap().rightmost_leaf(),
477 }
478 }
479}
480
481impl<T: KeyedItem> SumTree<T> {
482 pub fn insert_or_replace(&mut self, item: T, cx: &<T::Summary as Summary>::Context) -> bool {
483 let mut replaced = false;
484 *self = {
485 let mut cursor = self.cursor::<T::Key>();
486 let mut new_tree = cursor.slice(&item.key(), Bias::Left, cx);
487 if cursor
488 .item()
489 .map_or(false, |cursor_item| cursor_item.key() == item.key())
490 {
491 cursor.next(cx);
492 replaced = true;
493 }
494 new_tree.push(item, cx);
495 new_tree.push_tree(cursor.suffix(cx), cx);
496 new_tree
497 };
498 replaced
499 }
500
501 pub fn edit(
502 &mut self,
503 mut edits: Vec<Edit<T>>,
504 cx: &<T::Summary as Summary>::Context,
505 ) -> Vec<T> {
506 if edits.is_empty() {
507 return Vec::new();
508 }
509
510 let mut removed = Vec::new();
511 edits.sort_unstable_by_key(|item| item.key());
512
513 *self = {
514 let mut cursor = self.cursor::<T::Key>();
515 let mut new_tree = SumTree::new();
516 let mut buffered_items = Vec::new();
517
518 cursor.seek(&T::Key::default(), Bias::Left, cx);
519 for edit in edits {
520 let new_key = edit.key();
521 let mut old_item = cursor.item();
522
523 if old_item
524 .as_ref()
525 .map_or(false, |old_item| old_item.key() < new_key)
526 {
527 new_tree.extend(buffered_items.drain(..), cx);
528 let slice = cursor.slice(&new_key, Bias::Left, cx);
529 new_tree.push_tree(slice, cx);
530 old_item = cursor.item();
531 }
532
533 if let Some(old_item) = old_item {
534 if old_item.key() == new_key {
535 removed.push(old_item.clone());
536 cursor.next(cx);
537 }
538 }
539
540 match edit {
541 Edit::Insert(item) => {
542 buffered_items.push(item);
543 }
544 Edit::Remove(_) => {}
545 }
546 }
547
548 new_tree.extend(buffered_items, cx);
549 new_tree.push_tree(cursor.suffix(cx), cx);
550 new_tree
551 };
552
553 removed
554 }
555
556 pub fn get(&self, key: &T::Key, cx: &<T::Summary as Summary>::Context) -> Option<&T> {
557 let mut cursor = self.cursor::<T::Key>();
558 if cursor.seek(key, Bias::Left, cx) {
559 cursor.item()
560 } else {
561 None
562 }
563 }
564}
565
566impl<T: Item> Default for SumTree<T> {
567 fn default() -> Self {
568 Self::new()
569 }
570}
571
572#[derive(Clone, Debug)]
573pub enum Node<T: Item> {
574 Internal {
575 height: u8,
576 summary: T::Summary,
577 child_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
578 child_trees: ArrayVec<SumTree<T>, { 2 * TREE_BASE }>,
579 },
580 Leaf {
581 summary: T::Summary,
582 items: ArrayVec<T, { 2 * TREE_BASE }>,
583 item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
584 },
585}
586
587impl<T: Item> Node<T> {
588 fn is_leaf(&self) -> bool {
589 match self {
590 Node::Leaf { .. } => true,
591 _ => false,
592 }
593 }
594
595 fn height(&self) -> u8 {
596 match self {
597 Node::Internal { height, .. } => *height,
598 Node::Leaf { .. } => 0,
599 }
600 }
601
602 fn summary(&self) -> &T::Summary {
603 match self {
604 Node::Internal { summary, .. } => summary,
605 Node::Leaf { summary, .. } => summary,
606 }
607 }
608
609 fn child_summaries(&self) -> &[T::Summary] {
610 match self {
611 Node::Internal {
612 child_summaries, ..
613 } => child_summaries.as_slice(),
614 Node::Leaf { item_summaries, .. } => item_summaries.as_slice(),
615 }
616 }
617
618 fn child_trees(&self) -> &ArrayVec<SumTree<T>, { 2 * TREE_BASE }> {
619 match self {
620 Node::Internal { child_trees, .. } => child_trees,
621 Node::Leaf { .. } => panic!("Leaf nodes have no child trees"),
622 }
623 }
624
625 fn items(&self) -> &ArrayVec<T, { 2 * TREE_BASE }> {
626 match self {
627 Node::Leaf { items, .. } => items,
628 Node::Internal { .. } => panic!("Internal nodes have no items"),
629 }
630 }
631
632 fn is_underflowing(&self) -> bool {
633 match self {
634 Node::Internal { child_trees, .. } => child_trees.len() < TREE_BASE,
635 Node::Leaf { items, .. } => items.len() < TREE_BASE,
636 }
637 }
638}
639
640#[derive(Debug)]
641pub enum Edit<T: KeyedItem> {
642 Insert(T),
643 Remove(T::Key),
644}
645
646impl<T: KeyedItem> Edit<T> {
647 fn key(&self) -> T::Key {
648 match self {
649 Edit::Insert(item) => item.key(),
650 Edit::Remove(key) => key.clone(),
651 }
652 }
653}
654
655fn sum<'a, T, I>(iter: I, cx: &T::Context) -> T
656where
657 T: 'a + Summary,
658 I: Iterator<Item = &'a T>,
659{
660 let mut sum = T::default();
661 for value in iter {
662 sum.add_summary(value, cx);
663 }
664 sum
665}
666
667#[cfg(test)]
668mod tests {
669 use super::*;
670 use rand::{distributions, prelude::*};
671 use std::cmp;
672
673 #[test]
674 fn test_extend_and_push_tree() {
675 let mut tree1 = SumTree::new();
676 tree1.extend(0..20, &());
677
678 let mut tree2 = SumTree::new();
679 tree2.extend(50..100, &());
680
681 tree1.push_tree(tree2, &());
682 assert_eq!(
683 tree1.items(&()),
684 (0..20).chain(50..100).collect::<Vec<u8>>()
685 );
686 }
687
688 #[test]
689 fn test_random() {
690 let mut starting_seed = 0;
691 if let Ok(value) = std::env::var("SEED") {
692 starting_seed = value.parse().expect("invalid SEED variable");
693 }
694 let mut num_iterations = 100;
695 if let Ok(value) = std::env::var("ITERATIONS") {
696 num_iterations = value.parse().expect("invalid ITERATIONS variable");
697 }
698
699 for seed in starting_seed..(starting_seed + num_iterations) {
700 let mut rng = StdRng::seed_from_u64(seed);
701
702 let rng = &mut rng;
703 let mut tree = SumTree::<u8>::new();
704 let count = rng.gen_range(0..10);
705 tree.extend(rng.sample_iter(distributions::Standard).take(count), &());
706
707 for _ in 0..5 {
708 let splice_end = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
709 let splice_start = rng.gen_range(0..splice_end + 1);
710 let count = rng.gen_range(0..3);
711 let tree_end = tree.extent::<Count>(&());
712 let new_items = rng
713 .sample_iter(distributions::Standard)
714 .take(count)
715 .collect::<Vec<u8>>();
716
717 let mut reference_items = tree.items(&());
718 reference_items.splice(splice_start..splice_end, new_items.clone());
719
720 tree = {
721 let mut cursor = tree.cursor::<Count>();
722 let mut new_tree = cursor.slice(&Count(splice_start), Bias::Right, &());
723 new_tree.extend(new_items, &());
724 cursor.seek(&Count(splice_end), Bias::Right, &());
725 new_tree.push_tree(cursor.slice(&tree_end, Bias::Right, &()), &());
726 new_tree
727 };
728
729 assert_eq!(tree.items(&()), reference_items);
730 assert_eq!(
731 tree.iter().collect::<Vec<_>>(),
732 tree.cursor::<()>().collect::<Vec<_>>()
733 );
734
735 let mut filter_cursor =
736 tree.filter::<_, Count>(|summary| summary.contains_even, &());
737 let mut reference_filter = tree
738 .items(&())
739 .into_iter()
740 .enumerate()
741 .filter(|(_, item)| (item & 1) == 0);
742 while let Some(actual_item) = filter_cursor.item() {
743 let (reference_index, reference_item) = reference_filter.next().unwrap();
744 assert_eq!(actual_item, &reference_item);
745 assert_eq!(filter_cursor.start().0, reference_index);
746 filter_cursor.next(&());
747 }
748 assert!(reference_filter.next().is_none());
749
750 let mut pos = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
751 let mut before_start = false;
752 let mut cursor = tree.cursor::<Count>();
753 cursor.seek(&Count(pos), Bias::Right, &());
754
755 for i in 0..10 {
756 assert_eq!(cursor.start().0, pos);
757
758 if pos > 0 {
759 assert_eq!(cursor.prev_item().unwrap(), &reference_items[pos - 1]);
760 } else {
761 assert_eq!(cursor.prev_item(), None);
762 }
763
764 if pos < reference_items.len() && !before_start {
765 assert_eq!(cursor.item().unwrap(), &reference_items[pos]);
766 } else {
767 assert_eq!(cursor.item(), None);
768 }
769
770 if i < 5 {
771 cursor.next(&());
772 if pos < reference_items.len() {
773 pos += 1;
774 before_start = false;
775 }
776 } else {
777 cursor.prev(&());
778 if pos == 0 {
779 before_start = true;
780 }
781 pos = pos.saturating_sub(1);
782 }
783 }
784 }
785
786 for _ in 0..10 {
787 let end = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
788 let start = rng.gen_range(0..end + 1);
789 let start_bias = if rng.gen() { Bias::Left } else { Bias::Right };
790 let end_bias = if rng.gen() { Bias::Left } else { Bias::Right };
791
792 let mut cursor = tree.cursor::<Count>();
793 cursor.seek(&Count(start), start_bias, &());
794 let slice = cursor.slice(&Count(end), end_bias, &());
795
796 cursor.seek(&Count(start), start_bias, &());
797 let summary = cursor.summary::<_, Sum>(&Count(end), end_bias, &());
798
799 assert_eq!(summary.0, slice.summary().sum);
800 }
801 }
802 }
803
804 #[test]
805 fn test_cursor() {
806 // Empty tree
807 let tree = SumTree::<u8>::new();
808 let mut cursor = tree.cursor::<IntegersSummary>();
809 assert_eq!(
810 cursor.slice(&Count(0), Bias::Right, &()).items(&()),
811 Vec::<u8>::new()
812 );
813 assert_eq!(cursor.item(), None);
814 assert_eq!(cursor.prev_item(), None);
815 assert_eq!(cursor.start().sum, 0);
816
817 // Single-element tree
818 let mut tree = SumTree::<u8>::new();
819 tree.extend(vec![1], &());
820 let mut cursor = tree.cursor::<IntegersSummary>();
821 assert_eq!(
822 cursor.slice(&Count(0), Bias::Right, &()).items(&()),
823 Vec::<u8>::new()
824 );
825 assert_eq!(cursor.item(), Some(&1));
826 assert_eq!(cursor.prev_item(), None);
827 assert_eq!(cursor.start().sum, 0);
828
829 cursor.next(&());
830 assert_eq!(cursor.item(), None);
831 assert_eq!(cursor.prev_item(), Some(&1));
832 assert_eq!(cursor.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.start().sum, 0);
838
839 let mut cursor = tree.cursor::<IntegersSummary>();
840 assert_eq!(cursor.slice(&Count(1), Bias::Right, &()).items(&()), [1]);
841 assert_eq!(cursor.item(), None);
842 assert_eq!(cursor.prev_item(), Some(&1));
843 assert_eq!(cursor.start().sum, 1);
844
845 cursor.seek(&Count(0), Bias::Right, &());
846 assert_eq!(
847 cursor
848 .slice(&tree.extent::<Count>(&()), Bias::Right, &())
849 .items(&()),
850 [1]
851 );
852 assert_eq!(cursor.item(), None);
853 assert_eq!(cursor.prev_item(), Some(&1));
854 assert_eq!(cursor.start().sum, 1);
855
856 // Multiple-element tree
857 let mut tree = SumTree::new();
858 tree.extend(vec![1, 2, 3, 4, 5, 6], &());
859 let mut cursor = tree.cursor::<IntegersSummary>();
860
861 assert_eq!(cursor.slice(&Count(2), Bias::Right, &()).items(&()), [1, 2]);
862 assert_eq!(cursor.item(), Some(&3));
863 assert_eq!(cursor.prev_item(), Some(&2));
864 assert_eq!(cursor.start().sum, 3);
865
866 cursor.next(&());
867 assert_eq!(cursor.item(), Some(&4));
868 assert_eq!(cursor.prev_item(), Some(&3));
869 assert_eq!(cursor.start().sum, 6);
870
871 cursor.next(&());
872 assert_eq!(cursor.item(), Some(&5));
873 assert_eq!(cursor.prev_item(), Some(&4));
874 assert_eq!(cursor.start().sum, 10);
875
876 cursor.next(&());
877 assert_eq!(cursor.item(), Some(&6));
878 assert_eq!(cursor.prev_item(), Some(&5));
879 assert_eq!(cursor.start().sum, 15);
880
881 cursor.next(&());
882 cursor.next(&());
883 assert_eq!(cursor.item(), None);
884 assert_eq!(cursor.prev_item(), Some(&6));
885 assert_eq!(cursor.start().sum, 21);
886
887 cursor.prev(&());
888 assert_eq!(cursor.item(), Some(&6));
889 assert_eq!(cursor.prev_item(), Some(&5));
890 assert_eq!(cursor.start().sum, 15);
891
892 cursor.prev(&());
893 assert_eq!(cursor.item(), Some(&5));
894 assert_eq!(cursor.prev_item(), Some(&4));
895 assert_eq!(cursor.start().sum, 10);
896
897 cursor.prev(&());
898 assert_eq!(cursor.item(), Some(&4));
899 assert_eq!(cursor.prev_item(), Some(&3));
900 assert_eq!(cursor.start().sum, 6);
901
902 cursor.prev(&());
903 assert_eq!(cursor.item(), Some(&3));
904 assert_eq!(cursor.prev_item(), Some(&2));
905 assert_eq!(cursor.start().sum, 3);
906
907 cursor.prev(&());
908 assert_eq!(cursor.item(), Some(&2));
909 assert_eq!(cursor.prev_item(), Some(&1));
910 assert_eq!(cursor.start().sum, 1);
911
912 cursor.prev(&());
913 assert_eq!(cursor.item(), Some(&1));
914 assert_eq!(cursor.prev_item(), None);
915 assert_eq!(cursor.start().sum, 0);
916
917 cursor.prev(&());
918 assert_eq!(cursor.item(), None);
919 assert_eq!(cursor.prev_item(), None);
920 assert_eq!(cursor.start().sum, 0);
921
922 cursor.next(&());
923 assert_eq!(cursor.item(), Some(&1));
924 assert_eq!(cursor.prev_item(), None);
925 assert_eq!(cursor.start().sum, 0);
926
927 let mut cursor = tree.cursor::<IntegersSummary>();
928 assert_eq!(
929 cursor
930 .slice(&tree.extent::<Count>(&()), Bias::Right, &())
931 .items(&()),
932 tree.items(&())
933 );
934 assert_eq!(cursor.item(), None);
935 assert_eq!(cursor.prev_item(), Some(&6));
936 assert_eq!(cursor.start().sum, 21);
937
938 cursor.seek(&Count(3), Bias::Right, &());
939 assert_eq!(
940 cursor
941 .slice(&tree.extent::<Count>(&()), Bias::Right, &())
942 .items(&()),
943 [4, 5, 6]
944 );
945 assert_eq!(cursor.item(), None);
946 assert_eq!(cursor.prev_item(), Some(&6));
947 assert_eq!(cursor.start().sum, 21);
948
949 // Seeking can bias left or right
950 cursor.seek(&Count(1), Bias::Left, &());
951 assert_eq!(cursor.item(), Some(&1));
952 cursor.seek(&Count(1), Bias::Right, &());
953 assert_eq!(cursor.item(), Some(&2));
954
955 // Slicing without resetting starts from where the cursor is parked at.
956 cursor.seek(&Count(1), Bias::Right, &());
957 assert_eq!(
958 cursor.slice(&Count(3), Bias::Right, &()).items(&()),
959 vec![2, 3]
960 );
961 assert_eq!(
962 cursor.slice(&Count(6), Bias::Left, &()).items(&()),
963 vec![4, 5]
964 );
965 assert_eq!(
966 cursor.slice(&Count(6), Bias::Right, &()).items(&()),
967 vec![6]
968 );
969 }
970
971 #[test]
972 fn test_edit() {
973 let mut tree = SumTree::<u8>::new();
974
975 let removed = tree.edit(vec![Edit::Insert(1), Edit::Insert(2), Edit::Insert(0)], &());
976 assert_eq!(tree.items(&()), vec![0, 1, 2]);
977 assert_eq!(removed, Vec::<u8>::new());
978 assert_eq!(tree.get(&0, &()), Some(&0));
979 assert_eq!(tree.get(&1, &()), Some(&1));
980 assert_eq!(tree.get(&2, &()), Some(&2));
981 assert_eq!(tree.get(&4, &()), None);
982
983 let removed = tree.edit(vec![Edit::Insert(2), Edit::Insert(4), Edit::Remove(0)], &());
984 assert_eq!(tree.items(&()), vec![1, 2, 4]);
985 assert_eq!(removed, vec![0, 2]);
986 assert_eq!(tree.get(&0, &()), None);
987 assert_eq!(tree.get(&1, &()), Some(&1));
988 assert_eq!(tree.get(&2, &()), Some(&2));
989 assert_eq!(tree.get(&4, &()), Some(&4));
990 }
991
992 #[derive(Clone, Default, Debug)]
993 pub struct IntegersSummary {
994 count: usize,
995 sum: usize,
996 contains_even: bool,
997 max: u8,
998 }
999
1000 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
1001 struct Count(usize);
1002
1003 #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
1004 struct Sum(usize);
1005
1006 impl Item for u8 {
1007 type Summary = IntegersSummary;
1008
1009 fn summary(&self) -> Self::Summary {
1010 IntegersSummary {
1011 count: 1,
1012 sum: *self as usize,
1013 contains_even: (*self & 1) == 0,
1014 max: *self,
1015 }
1016 }
1017 }
1018
1019 impl KeyedItem for u8 {
1020 type Key = u8;
1021
1022 fn key(&self) -> Self::Key {
1023 *self
1024 }
1025 }
1026
1027 impl Summary for IntegersSummary {
1028 type Context = ();
1029
1030 fn add_summary(&mut self, other: &Self, _: &()) {
1031 self.count += other.count;
1032 self.sum += other.sum;
1033 self.contains_even |= other.contains_even;
1034 self.max = cmp::max(self.max, other.max);
1035 }
1036 }
1037
1038 impl<'a> Dimension<'a, IntegersSummary> for u8 {
1039 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
1040 *self = summary.max;
1041 }
1042 }
1043
1044 impl<'a> Dimension<'a, IntegersSummary> for Count {
1045 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
1046 self.0 += summary.count;
1047 }
1048 }
1049
1050 impl<'a> SeekTarget<'a, IntegersSummary, IntegersSummary> for Count {
1051 fn cmp(&self, cursor_location: &IntegersSummary, _: &()) -> Ordering {
1052 self.0.cmp(&cursor_location.count)
1053 }
1054 }
1055
1056 impl<'a> Dimension<'a, IntegersSummary> for Sum {
1057 fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
1058 self.0 += summary.sum;
1059 }
1060 }
1061}