1 use core::borrow::Borrow;
2 use core::cmp::Ordering;
4 use core::hash::{Hash, Hasher};
5 use core::iter::{FromIterator, FusedIterator, Peekable};
6 use core::marker::PhantomData;
7 use core::ops::Bound::{Excluded, Included, Unbounded};
8 use core::ops::{Index, RangeBounds};
9 use core::{fmt, mem, ptr};
11 use super::node::{self, marker, ForceResult::*, Handle, InsertResult::*, NodeRef};
12 use super::search::{self, SearchResult::*};
13 use super::unwrap_unchecked;
16 use UnderflowResult::*;
18 /// A map based on a B-Tree.
20 /// B-Trees represent a fundamental compromise between cache-efficiency and actually minimizing
21 /// the amount of work performed in a search. In theory, a binary search tree (BST) is the optimal
22 /// choice for a sorted map, as a perfectly balanced BST performs the theoretical minimum amount of
23 /// comparisons necessary to find an element (log<sub>2</sub>n). However, in practice the way this
24 /// is done is *very* inefficient for modern computer architectures. In particular, every element
25 /// is stored in its own individually heap-allocated node. This means that every single insertion
26 /// triggers a heap-allocation, and every single comparison should be a cache-miss. Since these
27 /// are both notably expensive things to do in practice, we are forced to at very least reconsider
30 /// A B-Tree instead makes each node contain B-1 to 2B-1 elements in a contiguous array. By doing
31 /// this, we reduce the number of allocations by a factor of B, and improve cache efficiency in
32 /// searches. However, this does mean that searches will have to do *more* comparisons on average.
33 /// The precise number of comparisons depends on the node search strategy used. For optimal cache
34 /// efficiency, one could search the nodes linearly. For optimal comparisons, one could search
35 /// the node using binary search. As a compromise, one could also perform a linear search
36 /// that initially only checks every i<sup>th</sup> element for some choice of i.
38 /// Currently, our implementation simply performs naive linear search. This provides excellent
39 /// performance on *small* nodes of elements which are cheap to compare. However in the future we
40 /// would like to further explore choosing the optimal search strategy based on the choice of B,
41 /// and possibly other factors. Using linear search, searching for a random element is expected
42 /// to take O(B log<sub>B</sub>n) comparisons, which is generally worse than a BST. In practice,
43 /// however, performance is excellent.
45 /// It is a logic error for a key to be modified in such a way that the key's ordering relative to
46 /// any other key, as determined by the [`Ord`] trait, changes while it is in the map. This is
47 /// normally only possible through [`Cell`], [`RefCell`], global state, I/O, or unsafe code.
49 /// [`Ord`]: ../../std/cmp/trait.Ord.html
50 /// [`Cell`]: ../../std/cell/struct.Cell.html
51 /// [`RefCell`]: ../../std/cell/struct.RefCell.html
56 /// use std::collections::BTreeMap;
58 /// // type inference lets us omit an explicit type signature (which
59 /// // would be `BTreeMap<&str, &str>` in this example).
60 /// let mut movie_reviews = BTreeMap::new();
62 /// // review some movies.
63 /// movie_reviews.insert("Office Space", "Deals with real issues in the workplace.");
64 /// movie_reviews.insert("Pulp Fiction", "Masterpiece.");
65 /// movie_reviews.insert("The Godfather", "Very enjoyable.");
66 /// movie_reviews.insert("The Blues Brothers", "Eye lyked it a lot.");
68 /// // check for a specific one.
69 /// if !movie_reviews.contains_key("Les Misérables") {
70 /// println!("We've got {} reviews, but Les Misérables ain't one.",
71 /// movie_reviews.len());
74 /// // oops, this review has a lot of spelling mistakes, let's delete it.
75 /// movie_reviews.remove("The Blues Brothers");
77 /// // look up the values associated with some keys.
78 /// let to_find = ["Up!", "Office Space"];
79 /// for movie in &to_find {
80 /// match movie_reviews.get(movie) {
81 /// Some(review) => println!("{}: {}", movie, review),
82 /// None => println!("{} is unreviewed.", movie)
86 /// // Look up the value for a key (will panic if the key is not found).
87 /// println!("Movie review: {}", movie_reviews["Office Space"]);
89 /// // iterate over everything.
90 /// for (movie, review) in &movie_reviews {
91 /// println!("{}: \"{}\"", movie, review);
95 /// `BTreeMap` also implements an [`Entry API`](#method.entry), which allows
96 /// for more complex methods of getting, setting, updating and removing keys and
100 /// use std::collections::BTreeMap;
102 /// // type inference lets us omit an explicit type signature (which
103 /// // would be `BTreeMap<&str, u8>` in this example).
104 /// let mut player_stats = BTreeMap::new();
106 /// fn random_stat_buff() -> u8 {
107 /// // could actually return some random value here - let's just return
108 /// // some fixed value for now
112 /// // insert a key only if it doesn't already exist
113 /// player_stats.entry("health").or_insert(100);
115 /// // insert a key using a function that provides a new value only if it
116 /// // doesn't already exist
117 /// player_stats.entry("defence").or_insert_with(random_stat_buff);
119 /// // update a key, guarding against the key possibly not being set
120 /// let stat = player_stats.entry("attack").or_insert(100);
121 /// *stat += random_stat_buff();
123 #[stable(feature = "rust1", since = "1.0.0")]
124 pub struct BTreeMap<K, V> {
125 root: node::Root<K, V>,
129 #[stable(feature = "btree_drop", since = "1.7.0")]
130 unsafe impl<#[may_dangle] K, #[may_dangle] V> Drop for BTreeMap<K, V> {
133 drop(ptr::read(self).into_iter());
138 #[stable(feature = "rust1", since = "1.0.0")]
139 impl<K: Clone, V: Clone> Clone for BTreeMap<K, V> {
140 fn clone(&self) -> BTreeMap<K, V> {
141 fn clone_subtree<'a, K: Clone, V: Clone>(
142 node: node::NodeRef<marker::Immut<'a>, K, V, marker::LeafOrInternal>,
150 let mut out_tree = BTreeMap { root: node::Root::new_leaf(), length: 0 };
153 let mut out_node = match out_tree.root.as_mut().force() {
155 Internal(_) => unreachable!(),
158 let mut in_edge = leaf.first_edge();
159 while let Ok(kv) = in_edge.right_kv() {
160 let (k, v) = kv.into_kv();
161 in_edge = kv.right_edge();
163 out_node.push(k.clone(), v.clone());
164 out_tree.length += 1;
170 Internal(internal) => {
171 let mut out_tree = clone_subtree(internal.first_edge().descend());
174 let mut out_node = out_tree.root.push_level();
175 let mut in_edge = internal.first_edge();
176 while let Ok(kv) = in_edge.right_kv() {
177 let (k, v) = kv.into_kv();
178 in_edge = kv.right_edge();
180 let k = (*k).clone();
181 let v = (*v).clone();
182 let subtree = clone_subtree(in_edge.descend());
184 // We can't destructure subtree directly
185 // because BTreeMap implements Drop
186 let (subroot, sublength) = unsafe {
187 let root = ptr::read(&subtree.root);
188 let length = subtree.length;
189 mem::forget(subtree);
193 out_node.push(k, v, subroot);
194 out_tree.length += 1 + sublength;
204 // Ideally we'd call `BTreeMap::new` here, but that has the `K:
205 // Ord` constraint, which this method lacks.
206 BTreeMap { root: node::Root::shared_empty_root(), length: 0 }
208 clone_subtree(self.root.as_ref())
212 fn clone_from(&mut self, other: &Self) {
213 BTreeClone::clone_from(self, other);
218 fn clone_from(&mut self, other: &Self);
221 impl<K: Clone, V: Clone> BTreeClone for BTreeMap<K, V> {
222 default fn clone_from(&mut self, other: &Self) {
223 *self = other.clone();
227 impl<K: Clone + Ord, V: Clone> BTreeClone for BTreeMap<K, V> {
228 fn clone_from(&mut self, other: &Self) {
229 // This truncates `self` to `other.len()` by calling `split_off` on
230 // the first key after `other.len()` elements if it exists.
231 let split_off_key = if self.len() > other.len() {
232 let diff = self.len() - other.len();
233 if diff <= other.len() {
234 self.iter().nth_back(diff - 1).map(|pair| (*pair.0).clone())
236 self.iter().nth(other.len()).map(|pair| (*pair.0).clone())
241 if let Some(key) = split_off_key {
242 self.split_off(&key);
245 let mut siter = self.range_mut(..);
246 let mut oiter = other.iter();
247 // After truncation, `self` is at most as long as `other` so this loop
248 // replaces every key-value pair in `self`. Since `oiter` is in sorted
249 // order and the structure of the `BTreeMap` stays the same,
250 // the BTree invariants are maintained at the end of the loop.
251 while !siter.is_empty() {
252 if let Some((ok, ov)) = oiter.next() {
253 // SAFETY: This is safe because `siter` is nonempty.
254 let (sk, sv) = unsafe { siter.next_unchecked() };
261 // If `other` is longer than `self`, the remaining elements are inserted.
262 self.extend(oiter.map(|(k, v)| ((*k).clone(), (*v).clone())));
266 impl<K, Q: ?Sized> super::Recover<Q> for BTreeMap<K, ()>
273 fn get(&self, key: &Q) -> Option<&K> {
274 match search::search_tree(self.root.as_ref(), key) {
275 Found(handle) => Some(handle.into_kv().0),
280 fn take(&mut self, key: &Q) -> Option<K> {
281 match search::search_tree(self.root.as_mut(), key) {
282 Found(handle) => Some(
283 OccupiedEntry { handle, length: &mut self.length, _marker: PhantomData }
291 fn replace(&mut self, key: K) -> Option<K> {
292 self.ensure_root_is_owned();
293 match search::search_tree::<marker::Mut<'_>, K, (), K>(self.root.as_mut(), &key) {
294 Found(handle) => Some(mem::replace(handle.into_kv_mut().0, key)),
296 VacantEntry { key, handle, length: &mut self.length, _marker: PhantomData }
304 /// An iterator over the entries of a `BTreeMap`.
306 /// This `struct` is created by the [`iter`] method on [`BTreeMap`]. See its
307 /// documentation for more.
309 /// [`iter`]: struct.BTreeMap.html#method.iter
310 /// [`BTreeMap`]: struct.BTreeMap.html
311 #[stable(feature = "rust1", since = "1.0.0")]
312 pub struct Iter<'a, K: 'a, V: 'a> {
313 range: Range<'a, K, V>,
317 #[stable(feature = "collection_debug", since = "1.17.0")]
318 impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for Iter<'_, K, V> {
319 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
320 f.debug_list().entries(self.clone()).finish()
324 /// A mutable iterator over the entries of a `BTreeMap`.
326 /// This `struct` is created by the [`iter_mut`] method on [`BTreeMap`]. See its
327 /// documentation for more.
329 /// [`iter_mut`]: struct.BTreeMap.html#method.iter_mut
330 /// [`BTreeMap`]: struct.BTreeMap.html
331 #[stable(feature = "rust1", since = "1.0.0")]
333 pub struct IterMut<'a, K: 'a, V: 'a> {
334 range: RangeMut<'a, K, V>,
338 /// An owning iterator over the entries of a `BTreeMap`.
340 /// This `struct` is created by the [`into_iter`] method on [`BTreeMap`]
341 /// (provided by the `IntoIterator` trait). See its documentation for more.
343 /// [`into_iter`]: struct.BTreeMap.html#method.into_iter
344 /// [`BTreeMap`]: struct.BTreeMap.html
345 #[stable(feature = "rust1", since = "1.0.0")]
346 pub struct IntoIter<K, V> {
347 front: Handle<NodeRef<marker::Owned, K, V, marker::Leaf>, marker::Edge>,
348 back: Handle<NodeRef<marker::Owned, K, V, marker::Leaf>, marker::Edge>,
352 #[stable(feature = "collection_debug", since = "1.17.0")]
353 impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for IntoIter<K, V> {
354 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
355 let range = Range { front: self.front.reborrow(), back: self.back.reborrow() };
356 f.debug_list().entries(range).finish()
360 /// An iterator over the keys of a `BTreeMap`.
362 /// This `struct` is created by the [`keys`] method on [`BTreeMap`]. See its
363 /// documentation for more.
365 /// [`keys`]: struct.BTreeMap.html#method.keys
366 /// [`BTreeMap`]: struct.BTreeMap.html
367 #[stable(feature = "rust1", since = "1.0.0")]
368 pub struct Keys<'a, K: 'a, V: 'a> {
369 inner: Iter<'a, K, V>,
372 #[stable(feature = "collection_debug", since = "1.17.0")]
373 impl<K: fmt::Debug, V> fmt::Debug for Keys<'_, K, V> {
374 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
375 f.debug_list().entries(self.clone()).finish()
379 /// An iterator over the values of a `BTreeMap`.
381 /// This `struct` is created by the [`values`] method on [`BTreeMap`]. See its
382 /// documentation for more.
384 /// [`values`]: struct.BTreeMap.html#method.values
385 /// [`BTreeMap`]: struct.BTreeMap.html
386 #[stable(feature = "rust1", since = "1.0.0")]
387 pub struct Values<'a, K: 'a, V: 'a> {
388 inner: Iter<'a, K, V>,
391 #[stable(feature = "collection_debug", since = "1.17.0")]
392 impl<K, V: fmt::Debug> fmt::Debug for Values<'_, K, V> {
393 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
394 f.debug_list().entries(self.clone()).finish()
398 /// A mutable iterator over the values of a `BTreeMap`.
400 /// This `struct` is created by the [`values_mut`] method on [`BTreeMap`]. See its
401 /// documentation for more.
403 /// [`values_mut`]: struct.BTreeMap.html#method.values_mut
404 /// [`BTreeMap`]: struct.BTreeMap.html
405 #[stable(feature = "map_values_mut", since = "1.10.0")]
407 pub struct ValuesMut<'a, K: 'a, V: 'a> {
408 inner: IterMut<'a, K, V>,
411 /// An iterator over a sub-range of entries in a `BTreeMap`.
413 /// This `struct` is created by the [`range`] method on [`BTreeMap`]. See its
414 /// documentation for more.
416 /// [`range`]: struct.BTreeMap.html#method.range
417 /// [`BTreeMap`]: struct.BTreeMap.html
418 #[stable(feature = "btree_range", since = "1.17.0")]
419 pub struct Range<'a, K: 'a, V: 'a> {
420 front: Handle<NodeRef<marker::Immut<'a>, K, V, marker::Leaf>, marker::Edge>,
421 back: Handle<NodeRef<marker::Immut<'a>, K, V, marker::Leaf>, marker::Edge>,
424 #[stable(feature = "collection_debug", since = "1.17.0")]
425 impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for Range<'_, K, V> {
426 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
427 f.debug_list().entries(self.clone()).finish()
431 /// A mutable iterator over a sub-range of entries in a `BTreeMap`.
433 /// This `struct` is created by the [`range_mut`] method on [`BTreeMap`]. See its
434 /// documentation for more.
436 /// [`range_mut`]: struct.BTreeMap.html#method.range_mut
437 /// [`BTreeMap`]: struct.BTreeMap.html
438 #[stable(feature = "btree_range", since = "1.17.0")]
439 pub struct RangeMut<'a, K: 'a, V: 'a> {
440 front: Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>,
441 back: Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>,
443 // Be invariant in `K` and `V`
444 _marker: PhantomData<&'a mut (K, V)>,
447 #[stable(feature = "collection_debug", since = "1.17.0")]
448 impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for RangeMut<'_, K, V> {
449 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
450 let range = Range { front: self.front.reborrow(), back: self.back.reborrow() };
451 f.debug_list().entries(range).finish()
455 /// A view into a single entry in a map, which may either be vacant or occupied.
457 /// This `enum` is constructed from the [`entry`] method on [`BTreeMap`].
459 /// [`BTreeMap`]: struct.BTreeMap.html
460 /// [`entry`]: struct.BTreeMap.html#method.entry
461 #[stable(feature = "rust1", since = "1.0.0")]
462 pub enum Entry<'a, K: 'a, V: 'a> {
464 #[stable(feature = "rust1", since = "1.0.0")]
465 Vacant(#[stable(feature = "rust1", since = "1.0.0")] VacantEntry<'a, K, V>),
467 /// An occupied entry.
468 #[stable(feature = "rust1", since = "1.0.0")]
469 Occupied(#[stable(feature = "rust1", since = "1.0.0")] OccupiedEntry<'a, K, V>),
472 #[stable(feature = "debug_btree_map", since = "1.12.0")]
473 impl<K: Debug + Ord, V: Debug> Debug for Entry<'_, K, V> {
474 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
476 Vacant(ref v) => f.debug_tuple("Entry").field(v).finish(),
477 Occupied(ref o) => f.debug_tuple("Entry").field(o).finish(),
482 /// A view into a vacant entry in a `BTreeMap`.
483 /// It is part of the [`Entry`] enum.
485 /// [`Entry`]: enum.Entry.html
486 #[stable(feature = "rust1", since = "1.0.0")]
487 pub struct VacantEntry<'a, K: 'a, V: 'a> {
489 handle: Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>,
490 length: &'a mut usize,
492 // Be invariant in `K` and `V`
493 _marker: PhantomData<&'a mut (K, V)>,
496 #[stable(feature = "debug_btree_map", since = "1.12.0")]
497 impl<K: Debug + Ord, V> Debug for VacantEntry<'_, K, V> {
498 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
499 f.debug_tuple("VacantEntry").field(self.key()).finish()
503 /// A view into an occupied entry in a `BTreeMap`.
504 /// It is part of the [`Entry`] enum.
506 /// [`Entry`]: enum.Entry.html
507 #[stable(feature = "rust1", since = "1.0.0")]
508 pub struct OccupiedEntry<'a, K: 'a, V: 'a> {
509 handle: Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, marker::KV>,
511 length: &'a mut usize,
513 // Be invariant in `K` and `V`
514 _marker: PhantomData<&'a mut (K, V)>,
517 #[stable(feature = "debug_btree_map", since = "1.12.0")]
518 impl<K: Debug + Ord, V: Debug> Debug for OccupiedEntry<'_, K, V> {
519 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
520 f.debug_struct("OccupiedEntry").field("key", self.key()).field("value", self.get()).finish()
524 // An iterator for merging two sorted sequences into one
525 struct MergeIter<K, V, I: Iterator<Item = (K, V)>> {
530 impl<K: Ord, V> BTreeMap<K, V> {
531 /// Makes a new empty BTreeMap with a reasonable choice for B.
538 /// use std::collections::BTreeMap;
540 /// let mut map = BTreeMap::new();
542 /// // entries can now be inserted into the empty map
543 /// map.insert(1, "a");
545 #[stable(feature = "rust1", since = "1.0.0")]
546 pub fn new() -> BTreeMap<K, V> {
547 BTreeMap { root: node::Root::shared_empty_root(), length: 0 }
550 /// Clears the map, removing all elements.
557 /// use std::collections::BTreeMap;
559 /// let mut a = BTreeMap::new();
560 /// a.insert(1, "a");
562 /// assert!(a.is_empty());
564 #[stable(feature = "rust1", since = "1.0.0")]
565 pub fn clear(&mut self) {
566 *self = BTreeMap::new();
569 /// Returns a reference to the value corresponding to the key.
571 /// The key may be any borrowed form of the map's key type, but the ordering
572 /// on the borrowed form *must* match the ordering on the key type.
579 /// use std::collections::BTreeMap;
581 /// let mut map = BTreeMap::new();
582 /// map.insert(1, "a");
583 /// assert_eq!(map.get(&1), Some(&"a"));
584 /// assert_eq!(map.get(&2), None);
586 #[stable(feature = "rust1", since = "1.0.0")]
587 pub fn get<Q: ?Sized>(&self, key: &Q) -> Option<&V>
592 match search::search_tree(self.root.as_ref(), key) {
593 Found(handle) => Some(handle.into_kv().1),
598 /// Returns the key-value pair corresponding to the supplied key.
600 /// The supplied key may be any borrowed form of the map's key type, but the ordering
601 /// on the borrowed form *must* match the ordering on the key type.
606 /// use std::collections::BTreeMap;
608 /// let mut map = BTreeMap::new();
609 /// map.insert(1, "a");
610 /// assert_eq!(map.get_key_value(&1), Some((&1, &"a")));
611 /// assert_eq!(map.get_key_value(&2), None);
613 #[stable(feature = "map_get_key_value", since = "1.40.0")]
614 pub fn get_key_value<Q: ?Sized>(&self, k: &Q) -> Option<(&K, &V)>
619 match search::search_tree(self.root.as_ref(), k) {
620 Found(handle) => Some(handle.into_kv()),
625 /// Returns the first key-value pair in the map.
626 /// The key in this pair is the minimum key in the map.
633 /// #![feature(map_first_last)]
634 /// use std::collections::BTreeMap;
636 /// let mut map = BTreeMap::new();
637 /// assert_eq!(map.first_key_value(), None);
638 /// map.insert(1, "b");
639 /// map.insert(2, "a");
640 /// assert_eq!(map.first_key_value(), Some((&1, &"b")));
642 #[unstable(feature = "map_first_last", issue = "62924")]
643 pub fn first_key_value<T: ?Sized>(&self) -> Option<(&K, &V)>
648 let front = self.root.as_ref().first_leaf_edge();
649 front.right_kv().ok().map(Handle::into_kv)
652 /// Returns the first entry in the map for in-place manipulation.
653 /// The key of this entry is the minimum key in the map.
657 /// Contrived way to `clear` a map:
660 /// #![feature(map_first_last)]
661 /// use std::collections::BTreeMap;
663 /// let mut map = BTreeMap::new();
664 /// map.insert(1, "a");
665 /// map.insert(2, "b");
666 /// while let Some(entry) = map.first_entry() {
667 /// let (key, val) = entry.remove_entry();
668 /// assert!(!map.contains_key(&key));
671 #[unstable(feature = "map_first_last", issue = "62924")]
672 pub fn first_entry<T: ?Sized>(&mut self) -> Option<OccupiedEntry<'_, K, V>>
677 let front = self.root.as_mut().first_leaf_edge();
678 if let Ok(kv) = front.right_kv() {
680 handle: kv.forget_node_type(),
681 length: &mut self.length,
682 _marker: PhantomData,
689 /// Returns the last key-value pair in the map.
690 /// The key in this pair is the maximum key in the map.
697 /// #![feature(map_first_last)]
698 /// use std::collections::BTreeMap;
700 /// let mut map = BTreeMap::new();
701 /// map.insert(1, "b");
702 /// map.insert(2, "a");
703 /// assert_eq!(map.last_key_value(), Some((&2, &"a")));
705 #[unstable(feature = "map_first_last", issue = "62924")]
706 pub fn last_key_value<T: ?Sized>(&self) -> Option<(&K, &V)>
711 let back = self.root.as_ref().last_leaf_edge();
712 back.left_kv().ok().map(Handle::into_kv)
715 /// Returns the last entry in the map for in-place manipulation.
716 /// The key of this entry is the maximum key in the map.
720 /// Contrived way to `clear` a map:
723 /// #![feature(map_first_last)]
724 /// use std::collections::BTreeMap;
726 /// let mut map = BTreeMap::new();
727 /// map.insert(1, "a");
728 /// map.insert(2, "b");
729 /// while let Some(entry) = map.last_entry() {
730 /// let (key, val) = entry.remove_entry();
731 /// assert!(!map.contains_key(&key));
734 #[unstable(feature = "map_first_last", issue = "62924")]
735 pub fn last_entry<T: ?Sized>(&mut self) -> Option<OccupiedEntry<'_, K, V>>
740 let back = self.root.as_mut().last_leaf_edge();
741 if let Ok(kv) = back.left_kv() {
743 handle: kv.forget_node_type(),
744 length: &mut self.length,
745 _marker: PhantomData,
752 /// Returns `true` if the map contains a value for the specified key.
754 /// The key may be any borrowed form of the map's key type, but the ordering
755 /// on the borrowed form *must* match the ordering on the key type.
762 /// use std::collections::BTreeMap;
764 /// let mut map = BTreeMap::new();
765 /// map.insert(1, "a");
766 /// assert_eq!(map.contains_key(&1), true);
767 /// assert_eq!(map.contains_key(&2), false);
769 #[stable(feature = "rust1", since = "1.0.0")]
770 pub fn contains_key<Q: ?Sized>(&self, key: &Q) -> bool
775 self.get(key).is_some()
778 /// Returns a mutable reference to the value corresponding to the key.
780 /// The key may be any borrowed form of the map's key type, but the ordering
781 /// on the borrowed form *must* match the ordering on the key type.
788 /// use std::collections::BTreeMap;
790 /// let mut map = BTreeMap::new();
791 /// map.insert(1, "a");
792 /// if let Some(x) = map.get_mut(&1) {
795 /// assert_eq!(map[&1], "b");
797 // See `get` for implementation notes, this is basically a copy-paste with mut's added
798 #[stable(feature = "rust1", since = "1.0.0")]
799 pub fn get_mut<Q: ?Sized>(&mut self, key: &Q) -> Option<&mut V>
804 match search::search_tree(self.root.as_mut(), key) {
805 Found(handle) => Some(handle.into_kv_mut().1),
810 /// Inserts a key-value pair into the map.
812 /// If the map did not have this key present, `None` is returned.
814 /// If the map did have this key present, the value is updated, and the old
815 /// value is returned. The key is not updated, though; this matters for
816 /// types that can be `==` without being identical. See the [module-level
817 /// documentation] for more.
819 /// [module-level documentation]: index.html#insert-and-complex-keys
826 /// use std::collections::BTreeMap;
828 /// let mut map = BTreeMap::new();
829 /// assert_eq!(map.insert(37, "a"), None);
830 /// assert_eq!(map.is_empty(), false);
832 /// map.insert(37, "b");
833 /// assert_eq!(map.insert(37, "c"), Some("b"));
834 /// assert_eq!(map[&37], "c");
836 #[stable(feature = "rust1", since = "1.0.0")]
837 pub fn insert(&mut self, key: K, value: V) -> Option<V> {
838 match self.entry(key) {
839 Occupied(mut entry) => Some(entry.insert(value)),
847 /// Removes a key from the map, returning the value at the key if the key
848 /// was previously in the map.
850 /// The key may be any borrowed form of the map's key type, but the ordering
851 /// on the borrowed form *must* match the ordering on the key type.
858 /// use std::collections::BTreeMap;
860 /// let mut map = BTreeMap::new();
861 /// map.insert(1, "a");
862 /// assert_eq!(map.remove(&1), Some("a"));
863 /// assert_eq!(map.remove(&1), None);
865 #[stable(feature = "rust1", since = "1.0.0")]
866 pub fn remove<Q: ?Sized>(&mut self, key: &Q) -> Option<V>
871 self.remove_entry(key).map(|(_, v)| v)
874 /// Removes a key from the map, returning the stored key and value if the key
875 /// was previously in the map.
877 /// The key may be any borrowed form of the map's key type, but the ordering
878 /// on the borrowed form *must* match the ordering on the key type.
885 /// #![feature(btreemap_remove_entry)]
886 /// use std::collections::BTreeMap;
888 /// let mut map = BTreeMap::new();
889 /// map.insert(1, "a");
890 /// assert_eq!(map.remove_entry(&1), Some((1, "a")));
891 /// assert_eq!(map.remove_entry(&1), None);
893 #[unstable(feature = "btreemap_remove_entry", issue = "66714")]
894 pub fn remove_entry<Q: ?Sized>(&mut self, key: &Q) -> Option<(K, V)>
899 match search::search_tree(self.root.as_mut(), key) {
900 Found(handle) => Some(
901 OccupiedEntry { handle, length: &mut self.length, _marker: PhantomData }
908 /// Moves all elements from `other` into `Self`, leaving `other` empty.
913 /// use std::collections::BTreeMap;
915 /// let mut a = BTreeMap::new();
916 /// a.insert(1, "a");
917 /// a.insert(2, "b");
918 /// a.insert(3, "c");
920 /// let mut b = BTreeMap::new();
921 /// b.insert(3, "d");
922 /// b.insert(4, "e");
923 /// b.insert(5, "f");
925 /// a.append(&mut b);
927 /// assert_eq!(a.len(), 5);
928 /// assert_eq!(b.len(), 0);
930 /// assert_eq!(a[&1], "a");
931 /// assert_eq!(a[&2], "b");
932 /// assert_eq!(a[&3], "d");
933 /// assert_eq!(a[&4], "e");
934 /// assert_eq!(a[&5], "f");
936 #[stable(feature = "btree_append", since = "1.11.0")]
937 pub fn append(&mut self, other: &mut Self) {
938 // Do we have to append anything at all?
939 if other.is_empty() {
943 // We can just swap `self` and `other` if `self` is empty.
945 mem::swap(self, other);
949 // First, we merge `self` and `other` into a sorted sequence in linear time.
950 let self_iter = mem::take(self).into_iter();
951 let other_iter = mem::take(other).into_iter();
952 let iter = MergeIter { left: self_iter.peekable(), right: other_iter.peekable() };
954 // Second, we build a tree from the sorted sequence in linear time.
955 self.from_sorted_iter(iter);
956 self.fix_right_edge();
959 /// Constructs a double-ended iterator over a sub-range of elements in the map.
960 /// The simplest way is to use the range syntax `min..max`, thus `range(min..max)` will
961 /// yield elements from min (inclusive) to max (exclusive).
962 /// The range may also be entered as `(Bound<T>, Bound<T>)`, so for example
963 /// `range((Excluded(4), Included(10)))` will yield a left-exclusive, right-inclusive
964 /// range from 4 to 10.
968 /// Panics if range `start > end`.
969 /// Panics if range `start == end` and both bounds are `Excluded`.
976 /// use std::collections::BTreeMap;
977 /// use std::ops::Bound::Included;
979 /// let mut map = BTreeMap::new();
980 /// map.insert(3, "a");
981 /// map.insert(5, "b");
982 /// map.insert(8, "c");
983 /// for (&key, &value) in map.range((Included(&4), Included(&8))) {
984 /// println!("{}: {}", key, value);
986 /// assert_eq!(Some((&5, &"b")), map.range(4..).next());
988 #[stable(feature = "btree_range", since = "1.17.0")]
989 pub fn range<T: ?Sized, R>(&self, range: R) -> Range<'_, K, V>
995 let root1 = self.root.as_ref();
996 let root2 = self.root.as_ref();
997 let (f, b) = range_search(root1, root2, range);
999 Range { front: f, back: b }
1002 /// Constructs a mutable double-ended iterator over a sub-range of elements in the map.
1003 /// The simplest way is to use the range syntax `min..max`, thus `range(min..max)` will
1004 /// yield elements from min (inclusive) to max (exclusive).
1005 /// The range may also be entered as `(Bound<T>, Bound<T>)`, so for example
1006 /// `range((Excluded(4), Included(10)))` will yield a left-exclusive, right-inclusive
1007 /// range from 4 to 10.
1011 /// Panics if range `start > end`.
1012 /// Panics if range `start == end` and both bounds are `Excluded`.
1019 /// use std::collections::BTreeMap;
1021 /// let mut map: BTreeMap<&str, i32> = ["Alice", "Bob", "Carol", "Cheryl"]
1023 /// .map(|&s| (s, 0))
1025 /// for (_, balance) in map.range_mut("B".."Cheryl") {
1026 /// *balance += 100;
1028 /// for (name, balance) in &map {
1029 /// println!("{} => {}", name, balance);
1032 #[stable(feature = "btree_range", since = "1.17.0")]
1033 pub fn range_mut<T: ?Sized, R>(&mut self, range: R) -> RangeMut<'_, K, V>
1039 let root1 = self.root.as_mut();
1040 let root2 = unsafe { ptr::read(&root1) };
1041 let (f, b) = range_search(root1, root2, range);
1043 RangeMut { front: f, back: b, _marker: PhantomData }
1046 /// Gets the given key's corresponding entry in the map for in-place manipulation.
1053 /// use std::collections::BTreeMap;
1055 /// let mut count: BTreeMap<&str, usize> = BTreeMap::new();
1057 /// // count the number of occurrences of letters in the vec
1058 /// for x in vec!["a","b","a","c","a","b"] {
1059 /// *count.entry(x).or_insert(0) += 1;
1062 /// assert_eq!(count["a"], 3);
1064 #[stable(feature = "rust1", since = "1.0.0")]
1065 pub fn entry(&mut self, key: K) -> Entry<'_, K, V> {
1066 // FIXME(@porglezomp) Avoid allocating if we don't insert
1067 self.ensure_root_is_owned();
1068 match search::search_tree(self.root.as_mut(), &key) {
1070 Occupied(OccupiedEntry { handle, length: &mut self.length, _marker: PhantomData })
1073 Vacant(VacantEntry { key, handle, length: &mut self.length, _marker: PhantomData })
1078 fn from_sorted_iter<I: Iterator<Item = (K, V)>>(&mut self, iter: I) {
1079 self.ensure_root_is_owned();
1080 let mut cur_node = self.root.as_mut().last_leaf_edge().into_node();
1081 // Iterate through all key-value pairs, pushing them into nodes at the right level.
1082 for (key, value) in iter {
1083 // Try to push key-value pair into the current leaf node.
1084 if cur_node.len() < node::CAPACITY {
1085 cur_node.push(key, value);
1087 // No space left, go up and push there.
1089 let mut test_node = cur_node.forget_type();
1091 match test_node.ascend() {
1093 let parent = parent.into_node();
1094 if parent.len() < node::CAPACITY {
1095 // Found a node with space left, push here.
1100 test_node = parent.forget_type();
1104 // We are at the top, create a new root node and push there.
1105 open_node = node.into_root_mut().push_level();
1111 // Push key-value pair and new right subtree.
1112 let tree_height = open_node.height() - 1;
1113 let mut right_tree = node::Root::new_leaf();
1114 for _ in 0..tree_height {
1115 right_tree.push_level();
1117 open_node.push(key, value, right_tree);
1119 // Go down to the right-most leaf again.
1120 cur_node = open_node.forget_type().last_leaf_edge().into_node();
1127 fn fix_right_edge(&mut self) {
1128 // Handle underfull nodes, start from the top.
1129 let mut cur_node = self.root.as_mut();
1130 while let Internal(internal) = cur_node.force() {
1131 // Check if right-most child is underfull.
1132 let mut last_edge = internal.last_edge();
1133 let right_child_len = last_edge.reborrow().descend().len();
1134 if right_child_len < node::MIN_LEN {
1135 // We need to steal.
1136 let mut last_kv = match last_edge.left_kv() {
1138 Err(_) => unreachable!(),
1140 last_kv.bulk_steal_left(node::MIN_LEN - right_child_len);
1141 last_edge = last_kv.right_edge();
1145 cur_node = last_edge.descend();
1149 /// Splits the collection into two at the given key. Returns everything after the given key,
1150 /// including the key.
1157 /// use std::collections::BTreeMap;
1159 /// let mut a = BTreeMap::new();
1160 /// a.insert(1, "a");
1161 /// a.insert(2, "b");
1162 /// a.insert(3, "c");
1163 /// a.insert(17, "d");
1164 /// a.insert(41, "e");
1166 /// let b = a.split_off(&3);
1168 /// assert_eq!(a.len(), 2);
1169 /// assert_eq!(b.len(), 3);
1171 /// assert_eq!(a[&1], "a");
1172 /// assert_eq!(a[&2], "b");
1174 /// assert_eq!(b[&3], "c");
1175 /// assert_eq!(b[&17], "d");
1176 /// assert_eq!(b[&41], "e");
1178 #[stable(feature = "btree_split_off", since = "1.11.0")]
1179 pub fn split_off<Q: ?Sized + Ord>(&mut self, key: &Q) -> Self
1183 if self.is_empty() {
1187 let total_num = self.len();
1189 let mut right = Self::new();
1190 right.root = node::Root::new_leaf();
1191 for _ in 0..(self.root.as_ref().height()) {
1192 right.root.push_level();
1196 let mut left_node = self.root.as_mut();
1197 let mut right_node = right.root.as_mut();
1200 let mut split_edge = match search::search_node(left_node, key) {
1201 // key is going to the right tree
1202 Found(handle) => handle.left_edge(),
1203 GoDown(handle) => handle,
1206 split_edge.move_suffix(&mut right_node);
1208 match (split_edge.force(), right_node.force()) {
1209 (Internal(edge), Internal(node)) => {
1210 left_node = edge.descend();
1211 right_node = node.first_edge().descend();
1213 (Leaf(_), Leaf(_)) => {
1223 self.fix_right_border();
1224 right.fix_left_border();
1226 if self.root.as_ref().height() < right.root.as_ref().height() {
1227 self.recalc_length();
1228 right.length = total_num - self.len();
1230 right.recalc_length();
1231 self.length = total_num - right.len();
1237 /// Calculates the number of elements if it is incorrect.
1238 fn recalc_length(&mut self) {
1239 fn dfs<'a, K, V>(node: NodeRef<marker::Immut<'a>, K, V, marker::LeafOrInternal>) -> usize
1244 let mut res = node.len();
1246 if let Internal(node) = node.force() {
1247 let mut edge = node.first_edge();
1249 res += dfs(edge.reborrow().descend());
1250 match edge.right_kv() {
1252 edge = right_kv.right_edge();
1264 self.length = dfs(self.root.as_ref());
1267 /// Removes empty levels on the top.
1268 fn fix_top(&mut self) {
1271 let node = self.root.as_ref();
1272 if node.height() == 0 || node.len() > 0 {
1276 self.root.pop_level();
1280 fn fix_right_border(&mut self) {
1284 let mut cur_node = self.root.as_mut();
1286 while let Internal(node) = cur_node.force() {
1287 let mut last_kv = node.last_kv();
1289 if last_kv.can_merge() {
1290 cur_node = last_kv.merge().descend();
1292 let right_len = last_kv.reborrow().right_edge().descend().len();
1293 // `MINLEN + 1` to avoid readjust if merge happens on the next level.
1294 if right_len < node::MIN_LEN + 1 {
1295 last_kv.bulk_steal_left(node::MIN_LEN + 1 - right_len);
1297 cur_node = last_kv.right_edge().descend();
1305 /// The symmetric clone of `fix_right_border`.
1306 fn fix_left_border(&mut self) {
1310 let mut cur_node = self.root.as_mut();
1312 while let Internal(node) = cur_node.force() {
1313 let mut first_kv = node.first_kv();
1315 if first_kv.can_merge() {
1316 cur_node = first_kv.merge().descend();
1318 let left_len = first_kv.reborrow().left_edge().descend().len();
1319 if left_len < node::MIN_LEN + 1 {
1320 first_kv.bulk_steal_right(node::MIN_LEN + 1 - left_len);
1322 cur_node = first_kv.left_edge().descend();
1330 /// If the root node is the shared root node, allocate our own node.
1331 fn ensure_root_is_owned(&mut self) {
1332 if self.root.is_shared_root() {
1333 self.root = node::Root::new_leaf();
1338 #[stable(feature = "rust1", since = "1.0.0")]
1339 impl<'a, K: 'a, V: 'a> IntoIterator for &'a BTreeMap<K, V> {
1340 type Item = (&'a K, &'a V);
1341 type IntoIter = Iter<'a, K, V>;
1343 fn into_iter(self) -> Iter<'a, K, V> {
1348 #[stable(feature = "rust1", since = "1.0.0")]
1349 impl<'a, K: 'a, V: 'a> Iterator for Iter<'a, K, V> {
1350 type Item = (&'a K, &'a V);
1352 fn next(&mut self) -> Option<(&'a K, &'a V)> {
1353 if self.length == 0 {
1357 unsafe { Some(self.range.next_unchecked()) }
1361 fn size_hint(&self) -> (usize, Option<usize>) {
1362 (self.length, Some(self.length))
1365 fn last(mut self) -> Option<(&'a K, &'a V)> {
1370 #[stable(feature = "fused", since = "1.26.0")]
1371 impl<K, V> FusedIterator for Iter<'_, K, V> {}
1373 #[stable(feature = "rust1", since = "1.0.0")]
1374 impl<'a, K: 'a, V: 'a> DoubleEndedIterator for Iter<'a, K, V> {
1375 fn next_back(&mut self) -> Option<(&'a K, &'a V)> {
1376 if self.length == 0 {
1380 unsafe { Some(self.range.next_back_unchecked()) }
1385 #[stable(feature = "rust1", since = "1.0.0")]
1386 impl<K, V> ExactSizeIterator for Iter<'_, K, V> {
1387 fn len(&self) -> usize {
1392 #[stable(feature = "rust1", since = "1.0.0")]
1393 impl<K, V> Clone for Iter<'_, K, V> {
1394 fn clone(&self) -> Self {
1395 Iter { range: self.range.clone(), length: self.length }
1399 #[stable(feature = "rust1", since = "1.0.0")]
1400 impl<'a, K: 'a, V: 'a> IntoIterator for &'a mut BTreeMap<K, V> {
1401 type Item = (&'a K, &'a mut V);
1402 type IntoIter = IterMut<'a, K, V>;
1404 fn into_iter(self) -> IterMut<'a, K, V> {
1409 #[stable(feature = "rust1", since = "1.0.0")]
1410 impl<'a, K: 'a, V: 'a> Iterator for IterMut<'a, K, V> {
1411 type Item = (&'a K, &'a mut V);
1413 fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
1414 if self.length == 0 {
1418 let (k, v) = unsafe { self.range.next_unchecked() };
1419 Some((k, v)) // coerce k from `&mut K` to `&K`
1423 fn size_hint(&self) -> (usize, Option<usize>) {
1424 (self.length, Some(self.length))
1427 fn last(mut self) -> Option<(&'a K, &'a mut V)> {
1432 #[stable(feature = "rust1", since = "1.0.0")]
1433 impl<'a, K: 'a, V: 'a> DoubleEndedIterator for IterMut<'a, K, V> {
1434 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> {
1435 if self.length == 0 {
1439 let (k, v) = unsafe { self.range.next_back_unchecked() };
1440 Some((k, v)) // coerce k from `&mut K` to `&K`
1445 #[stable(feature = "rust1", since = "1.0.0")]
1446 impl<K, V> ExactSizeIterator for IterMut<'_, K, V> {
1447 fn len(&self) -> usize {
1452 #[stable(feature = "fused", since = "1.26.0")]
1453 impl<K, V> FusedIterator for IterMut<'_, K, V> {}
1455 #[stable(feature = "rust1", since = "1.0.0")]
1456 impl<K, V> IntoIterator for BTreeMap<K, V> {
1458 type IntoIter = IntoIter<K, V>;
1460 fn into_iter(self) -> IntoIter<K, V> {
1461 let root1 = unsafe { ptr::read(&self.root).into_ref() };
1462 let root2 = unsafe { ptr::read(&self.root).into_ref() };
1463 let len = self.length;
1466 IntoIter { front: root1.first_leaf_edge(), back: root2.last_leaf_edge(), length: len }
1470 #[stable(feature = "btree_drop", since = "1.7.0")]
1471 impl<K, V> Drop for IntoIter<K, V> {
1472 fn drop(&mut self) {
1473 struct DropGuard<'a, K, V>(&'a mut IntoIter<K, V>);
1475 impl<'a, K, V> Drop for DropGuard<'a, K, V> {
1476 fn drop(&mut self) {
1477 // Continue the same loop we perform below. This only runs when unwinding, so we
1478 // don't have to care about panics this time (they'll abort).
1479 while let Some(_) = self.0.next() {}
1483 while let Some(pair) = self.next() {
1484 let guard = DropGuard(self);
1490 let leaf_node = ptr::read(&self.front).into_node();
1491 if leaf_node.is_shared_root() {
1495 if let Some(first_parent) = leaf_node.deallocate_and_ascend() {
1496 let mut cur_internal_node = first_parent.into_node();
1497 while let Some(parent) = cur_internal_node.deallocate_and_ascend() {
1498 cur_internal_node = parent.into_node()
1505 #[stable(feature = "rust1", since = "1.0.0")]
1506 impl<K, V> Iterator for IntoIter<K, V> {
1509 fn next(&mut self) -> Option<(K, V)> {
1510 if self.length == 0 {
1514 Some(unsafe { self.front.next_unchecked() })
1518 fn size_hint(&self) -> (usize, Option<usize>) {
1519 (self.length, Some(self.length))
1523 #[stable(feature = "rust1", since = "1.0.0")]
1524 impl<K, V> DoubleEndedIterator for IntoIter<K, V> {
1525 fn next_back(&mut self) -> Option<(K, V)> {
1526 if self.length == 0 {
1530 Some(unsafe { self.back.next_back_unchecked() })
1535 #[stable(feature = "rust1", since = "1.0.0")]
1536 impl<K, V> ExactSizeIterator for IntoIter<K, V> {
1537 fn len(&self) -> usize {
1542 #[stable(feature = "fused", since = "1.26.0")]
1543 impl<K, V> FusedIterator for IntoIter<K, V> {}
1545 #[stable(feature = "rust1", since = "1.0.0")]
1546 impl<'a, K, V> Iterator for Keys<'a, K, V> {
1549 fn next(&mut self) -> Option<&'a K> {
1550 self.inner.next().map(|(k, _)| k)
1553 fn size_hint(&self) -> (usize, Option<usize>) {
1554 self.inner.size_hint()
1557 fn last(mut self) -> Option<&'a K> {
1562 #[stable(feature = "rust1", since = "1.0.0")]
1563 impl<'a, K, V> DoubleEndedIterator for Keys<'a, K, V> {
1564 fn next_back(&mut self) -> Option<&'a K> {
1565 self.inner.next_back().map(|(k, _)| k)
1569 #[stable(feature = "rust1", since = "1.0.0")]
1570 impl<K, V> ExactSizeIterator for Keys<'_, K, V> {
1571 fn len(&self) -> usize {
1576 #[stable(feature = "fused", since = "1.26.0")]
1577 impl<K, V> FusedIterator for Keys<'_, K, V> {}
1579 #[stable(feature = "rust1", since = "1.0.0")]
1580 impl<K, V> Clone for Keys<'_, K, V> {
1581 fn clone(&self) -> Self {
1582 Keys { inner: self.inner.clone() }
1586 #[stable(feature = "rust1", since = "1.0.0")]
1587 impl<'a, K, V> Iterator for Values<'a, K, V> {
1590 fn next(&mut self) -> Option<&'a V> {
1591 self.inner.next().map(|(_, v)| v)
1594 fn size_hint(&self) -> (usize, Option<usize>) {
1595 self.inner.size_hint()
1598 fn last(mut self) -> Option<&'a V> {
1603 #[stable(feature = "rust1", since = "1.0.0")]
1604 impl<'a, K, V> DoubleEndedIterator for Values<'a, K, V> {
1605 fn next_back(&mut self) -> Option<&'a V> {
1606 self.inner.next_back().map(|(_, v)| v)
1610 #[stable(feature = "rust1", since = "1.0.0")]
1611 impl<K, V> ExactSizeIterator for Values<'_, K, V> {
1612 fn len(&self) -> usize {
1617 #[stable(feature = "fused", since = "1.26.0")]
1618 impl<K, V> FusedIterator for Values<'_, K, V> {}
1620 #[stable(feature = "rust1", since = "1.0.0")]
1621 impl<K, V> Clone for Values<'_, K, V> {
1622 fn clone(&self) -> Self {
1623 Values { inner: self.inner.clone() }
1627 #[stable(feature = "btree_range", since = "1.17.0")]
1628 impl<'a, K, V> Iterator for Range<'a, K, V> {
1629 type Item = (&'a K, &'a V);
1631 fn next(&mut self) -> Option<(&'a K, &'a V)> {
1632 if self.is_empty() { None } else { unsafe { Some(self.next_unchecked()) } }
1635 fn last(mut self) -> Option<(&'a K, &'a V)> {
1640 #[stable(feature = "map_values_mut", since = "1.10.0")]
1641 impl<'a, K, V> Iterator for ValuesMut<'a, K, V> {
1642 type Item = &'a mut V;
1644 fn next(&mut self) -> Option<&'a mut V> {
1645 self.inner.next().map(|(_, v)| v)
1648 fn size_hint(&self) -> (usize, Option<usize>) {
1649 self.inner.size_hint()
1652 fn last(mut self) -> Option<&'a mut V> {
1657 #[stable(feature = "map_values_mut", since = "1.10.0")]
1658 impl<'a, K, V> DoubleEndedIterator for ValuesMut<'a, K, V> {
1659 fn next_back(&mut self) -> Option<&'a mut V> {
1660 self.inner.next_back().map(|(_, v)| v)
1664 #[stable(feature = "map_values_mut", since = "1.10.0")]
1665 impl<K, V> ExactSizeIterator for ValuesMut<'_, K, V> {
1666 fn len(&self) -> usize {
1671 #[stable(feature = "fused", since = "1.26.0")]
1672 impl<K, V> FusedIterator for ValuesMut<'_, K, V> {}
1674 impl<'a, K, V> Range<'a, K, V> {
1675 fn is_empty(&self) -> bool {
1676 self.front == self.back
1679 unsafe fn next_unchecked(&mut self) -> (&'a K, &'a V) {
1680 self.front.next_unchecked()
1684 #[stable(feature = "btree_range", since = "1.17.0")]
1685 impl<'a, K, V> DoubleEndedIterator for Range<'a, K, V> {
1686 fn next_back(&mut self) -> Option<(&'a K, &'a V)> {
1687 if self.is_empty() { None } else { Some(unsafe { self.next_back_unchecked() }) }
1691 impl<'a, K, V> Range<'a, K, V> {
1692 unsafe fn next_back_unchecked(&mut self) -> (&'a K, &'a V) {
1693 self.back.next_back_unchecked()
1697 #[stable(feature = "fused", since = "1.26.0")]
1698 impl<K, V> FusedIterator for Range<'_, K, V> {}
1700 #[stable(feature = "btree_range", since = "1.17.0")]
1701 impl<K, V> Clone for Range<'_, K, V> {
1702 fn clone(&self) -> Self {
1703 Range { front: self.front, back: self.back }
1707 #[stable(feature = "btree_range", since = "1.17.0")]
1708 impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
1709 type Item = (&'a K, &'a mut V);
1711 fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
1712 if self.is_empty() {
1715 let (k, v) = unsafe { self.next_unchecked() };
1716 Some((k, v)) // coerce k from `&mut K` to `&K`
1720 fn last(mut self) -> Option<(&'a K, &'a mut V)> {
1725 impl<'a, K, V> RangeMut<'a, K, V> {
1726 fn is_empty(&self) -> bool {
1727 self.front == self.back
1730 unsafe fn next_unchecked(&mut self) -> (&'a mut K, &'a mut V) {
1731 self.front.next_unchecked()
1735 #[stable(feature = "btree_range", since = "1.17.0")]
1736 impl<'a, K, V> DoubleEndedIterator for RangeMut<'a, K, V> {
1737 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> {
1738 if self.is_empty() {
1741 let (k, v) = unsafe { self.next_back_unchecked() };
1742 Some((k, v)) // coerce k from `&mut K` to `&K`
1747 #[stable(feature = "fused", since = "1.26.0")]
1748 impl<K, V> FusedIterator for RangeMut<'_, K, V> {}
1750 impl<'a, K, V> RangeMut<'a, K, V> {
1751 unsafe fn next_back_unchecked(&mut self) -> (&'a mut K, &'a mut V) {
1752 self.back.next_back_unchecked()
1756 #[stable(feature = "rust1", since = "1.0.0")]
1757 impl<K: Ord, V> FromIterator<(K, V)> for BTreeMap<K, V> {
1758 fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> BTreeMap<K, V> {
1759 let mut map = BTreeMap::new();
1765 #[stable(feature = "rust1", since = "1.0.0")]
1766 impl<K: Ord, V> Extend<(K, V)> for BTreeMap<K, V> {
1768 fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T) {
1769 iter.into_iter().for_each(move |(k, v)| {
1775 #[stable(feature = "extend_ref", since = "1.2.0")]
1776 impl<'a, K: Ord + Copy, V: Copy> Extend<(&'a K, &'a V)> for BTreeMap<K, V> {
1777 fn extend<I: IntoIterator<Item = (&'a K, &'a V)>>(&mut self, iter: I) {
1778 self.extend(iter.into_iter().map(|(&key, &value)| (key, value)));
1782 #[stable(feature = "rust1", since = "1.0.0")]
1783 impl<K: Hash, V: Hash> Hash for BTreeMap<K, V> {
1784 fn hash<H: Hasher>(&self, state: &mut H) {
1791 #[stable(feature = "rust1", since = "1.0.0")]
1792 impl<K: Ord, V> Default for BTreeMap<K, V> {
1793 /// Creates an empty `BTreeMap<K, V>`.
1794 fn default() -> BTreeMap<K, V> {
1799 #[stable(feature = "rust1", since = "1.0.0")]
1800 impl<K: PartialEq, V: PartialEq> PartialEq for BTreeMap<K, V> {
1801 fn eq(&self, other: &BTreeMap<K, V>) -> bool {
1802 self.len() == other.len() && self.iter().zip(other).all(|(a, b)| a == b)
1806 #[stable(feature = "rust1", since = "1.0.0")]
1807 impl<K: Eq, V: Eq> Eq for BTreeMap<K, V> {}
1809 #[stable(feature = "rust1", since = "1.0.0")]
1810 impl<K: PartialOrd, V: PartialOrd> PartialOrd for BTreeMap<K, V> {
1812 fn partial_cmp(&self, other: &BTreeMap<K, V>) -> Option<Ordering> {
1813 self.iter().partial_cmp(other.iter())
1817 #[stable(feature = "rust1", since = "1.0.0")]
1818 impl<K: Ord, V: Ord> Ord for BTreeMap<K, V> {
1820 fn cmp(&self, other: &BTreeMap<K, V>) -> Ordering {
1821 self.iter().cmp(other.iter())
1825 #[stable(feature = "rust1", since = "1.0.0")]
1826 impl<K: Debug, V: Debug> Debug for BTreeMap<K, V> {
1827 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1828 f.debug_map().entries(self.iter()).finish()
1832 #[stable(feature = "rust1", since = "1.0.0")]
1833 impl<K: Ord, Q: ?Sized, V> Index<&Q> for BTreeMap<K, V>
1840 /// Returns a reference to the value corresponding to the supplied key.
1844 /// Panics if the key is not present in the `BTreeMap`.
1846 fn index(&self, key: &Q) -> &V {
1847 self.get(key).expect("no entry found for key")
1851 fn range_search<BorrowType, K, V, Q: ?Sized, R: RangeBounds<Q>>(
1852 root1: NodeRef<BorrowType, K, V, marker::LeafOrInternal>,
1853 root2: NodeRef<BorrowType, K, V, marker::LeafOrInternal>,
1856 Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge>,
1857 Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge>,
1863 match (range.start_bound(), range.end_bound()) {
1864 (Excluded(s), Excluded(e)) if s == e => {
1865 panic!("range start and end are equal and excluded in BTreeMap")
1867 (Included(s), Included(e))
1868 | (Included(s), Excluded(e))
1869 | (Excluded(s), Included(e))
1870 | (Excluded(s), Excluded(e))
1873 panic!("range start is greater than range end in BTreeMap")
1878 let mut min_node = root1;
1879 let mut max_node = root2;
1880 let mut min_found = false;
1881 let mut max_found = false;
1884 let front = match (min_found, range.start_bound()) {
1885 (false, Included(key)) => match search::search_node(min_node, key) {
1890 GoDown(edge) => edge,
1892 (false, Excluded(key)) => match search::search_node(min_node, key) {
1897 GoDown(edge) => edge,
1899 (true, Included(_)) => min_node.last_edge(),
1900 (true, Excluded(_)) => min_node.first_edge(),
1901 (_, Unbounded) => min_node.first_edge(),
1904 let back = match (max_found, range.end_bound()) {
1905 (false, Included(key)) => match search::search_node(max_node, key) {
1910 GoDown(edge) => edge,
1912 (false, Excluded(key)) => match search::search_node(max_node, key) {
1917 GoDown(edge) => edge,
1919 (true, Included(_)) => max_node.first_edge(),
1920 (true, Excluded(_)) => max_node.last_edge(),
1921 (_, Unbounded) => max_node.last_edge(),
1924 if front.partial_cmp(&back) == Some(Ordering::Greater) {
1925 panic!("Ord is ill-defined in BTreeMap range");
1927 match (front.force(), back.force()) {
1928 (Leaf(f), Leaf(b)) => {
1931 (Internal(min_int), Internal(max_int)) => {
1932 min_node = min_int.descend();
1933 max_node = max_int.descend();
1935 _ => unreachable!("BTreeMap has different depths"),
1940 impl<K, V> BTreeMap<K, V> {
1941 /// Gets an iterator over the entries of the map, sorted by key.
1948 /// use std::collections::BTreeMap;
1950 /// let mut map = BTreeMap::new();
1951 /// map.insert(3, "c");
1952 /// map.insert(2, "b");
1953 /// map.insert(1, "a");
1955 /// for (key, value) in map.iter() {
1956 /// println!("{}: {}", key, value);
1959 /// let (first_key, first_value) = map.iter().next().unwrap();
1960 /// assert_eq!((*first_key, *first_value), (1, "a"));
1962 #[stable(feature = "rust1", since = "1.0.0")]
1963 pub fn iter(&self) -> Iter<'_, K, V> {
1966 front: self.root.as_ref().first_leaf_edge(),
1967 back: self.root.as_ref().last_leaf_edge(),
1969 length: self.length,
1973 /// Gets a mutable iterator over the entries of the map, sorted by key.
1980 /// use std::collections::BTreeMap;
1982 /// let mut map = BTreeMap::new();
1983 /// map.insert("a", 1);
1984 /// map.insert("b", 2);
1985 /// map.insert("c", 3);
1987 /// // add 10 to the value if the key isn't "a"
1988 /// for (key, value) in map.iter_mut() {
1989 /// if key != &"a" {
1994 #[stable(feature = "rust1", since = "1.0.0")]
1995 pub fn iter_mut(&mut self) -> IterMut<'_, K, V> {
1996 let root1 = self.root.as_mut();
1997 let root2 = unsafe { ptr::read(&root1) };
2000 front: root1.first_leaf_edge(),
2001 back: root2.last_leaf_edge(),
2002 _marker: PhantomData,
2004 length: self.length,
2008 /// Gets an iterator over the keys of the map, in sorted order.
2015 /// use std::collections::BTreeMap;
2017 /// let mut a = BTreeMap::new();
2018 /// a.insert(2, "b");
2019 /// a.insert(1, "a");
2021 /// let keys: Vec<_> = a.keys().cloned().collect();
2022 /// assert_eq!(keys, [1, 2]);
2024 #[stable(feature = "rust1", since = "1.0.0")]
2025 pub fn keys(&self) -> Keys<'_, K, V> {
2026 Keys { inner: self.iter() }
2029 /// Gets an iterator over the values of the map, in order by key.
2036 /// use std::collections::BTreeMap;
2038 /// let mut a = BTreeMap::new();
2039 /// a.insert(1, "hello");
2040 /// a.insert(2, "goodbye");
2042 /// let values: Vec<&str> = a.values().cloned().collect();
2043 /// assert_eq!(values, ["hello", "goodbye"]);
2045 #[stable(feature = "rust1", since = "1.0.0")]
2046 pub fn values(&self) -> Values<'_, K, V> {
2047 Values { inner: self.iter() }
2050 /// Gets a mutable iterator over the values of the map, in order by key.
2057 /// use std::collections::BTreeMap;
2059 /// let mut a = BTreeMap::new();
2060 /// a.insert(1, String::from("hello"));
2061 /// a.insert(2, String::from("goodbye"));
2063 /// for value in a.values_mut() {
2064 /// value.push_str("!");
2067 /// let values: Vec<String> = a.values().cloned().collect();
2068 /// assert_eq!(values, [String::from("hello!"),
2069 /// String::from("goodbye!")]);
2071 #[stable(feature = "map_values_mut", since = "1.10.0")]
2072 pub fn values_mut(&mut self) -> ValuesMut<'_, K, V> {
2073 ValuesMut { inner: self.iter_mut() }
2076 /// Returns the number of elements in the map.
2083 /// use std::collections::BTreeMap;
2085 /// let mut a = BTreeMap::new();
2086 /// assert_eq!(a.len(), 0);
2087 /// a.insert(1, "a");
2088 /// assert_eq!(a.len(), 1);
2090 #[stable(feature = "rust1", since = "1.0.0")]
2091 pub fn len(&self) -> usize {
2095 /// Returns `true` if the map contains no elements.
2102 /// use std::collections::BTreeMap;
2104 /// let mut a = BTreeMap::new();
2105 /// assert!(a.is_empty());
2106 /// a.insert(1, "a");
2107 /// assert!(!a.is_empty());
2109 #[stable(feature = "rust1", since = "1.0.0")]
2110 pub fn is_empty(&self) -> bool {
2115 impl<'a, K: Ord, V> Entry<'a, K, V> {
2116 /// Ensures a value is in the entry by inserting the default if empty, and returns
2117 /// a mutable reference to the value in the entry.
2122 /// use std::collections::BTreeMap;
2124 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2125 /// map.entry("poneyland").or_insert(12);
2127 /// assert_eq!(map["poneyland"], 12);
2129 #[stable(feature = "rust1", since = "1.0.0")]
2130 pub fn or_insert(self, default: V) -> &'a mut V {
2132 Occupied(entry) => entry.into_mut(),
2133 Vacant(entry) => entry.insert(default),
2137 /// Ensures a value is in the entry by inserting the result of the default function if empty,
2138 /// and returns a mutable reference to the value in the entry.
2143 /// use std::collections::BTreeMap;
2145 /// let mut map: BTreeMap<&str, String> = BTreeMap::new();
2146 /// let s = "hoho".to_string();
2148 /// map.entry("poneyland").or_insert_with(|| s);
2150 /// assert_eq!(map["poneyland"], "hoho".to_string());
2152 #[stable(feature = "rust1", since = "1.0.0")]
2153 pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V {
2155 Occupied(entry) => entry.into_mut(),
2156 Vacant(entry) => entry.insert(default()),
2160 /// Returns a reference to this entry's key.
2165 /// use std::collections::BTreeMap;
2167 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2168 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2170 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2171 pub fn key(&self) -> &K {
2173 Occupied(ref entry) => entry.key(),
2174 Vacant(ref entry) => entry.key(),
2178 /// Provides in-place mutable access to an occupied entry before any
2179 /// potential inserts into the map.
2184 /// use std::collections::BTreeMap;
2186 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2188 /// map.entry("poneyland")
2189 /// .and_modify(|e| { *e += 1 })
2191 /// assert_eq!(map["poneyland"], 42);
2193 /// map.entry("poneyland")
2194 /// .and_modify(|e| { *e += 1 })
2196 /// assert_eq!(map["poneyland"], 43);
2198 #[stable(feature = "entry_and_modify", since = "1.26.0")]
2199 pub fn and_modify<F>(self, f: F) -> Self
2204 Occupied(mut entry) => {
2208 Vacant(entry) => Vacant(entry),
2213 impl<'a, K: Ord, V: Default> Entry<'a, K, V> {
2214 #[stable(feature = "entry_or_default", since = "1.28.0")]
2215 /// Ensures a value is in the entry by inserting the default value if empty,
2216 /// and returns a mutable reference to the value in the entry.
2221 /// use std::collections::BTreeMap;
2223 /// let mut map: BTreeMap<&str, Option<usize>> = BTreeMap::new();
2224 /// map.entry("poneyland").or_default();
2226 /// assert_eq!(map["poneyland"], None);
2228 pub fn or_default(self) -> &'a mut V {
2230 Occupied(entry) => entry.into_mut(),
2231 Vacant(entry) => entry.insert(Default::default()),
2236 impl<'a, K: Ord, V> VacantEntry<'a, K, V> {
2237 /// Gets a reference to the key that would be used when inserting a value
2238 /// through the VacantEntry.
2243 /// use std::collections::BTreeMap;
2245 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2246 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2248 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2249 pub fn key(&self) -> &K {
2253 /// Take ownership of the key.
2258 /// use std::collections::BTreeMap;
2259 /// use std::collections::btree_map::Entry;
2261 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2263 /// if let Entry::Vacant(v) = map.entry("poneyland") {
2267 #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
2268 pub fn into_key(self) -> K {
2272 /// Sets the value of the entry with the `VacantEntry`'s key,
2273 /// and returns a mutable reference to it.
2278 /// use std::collections::BTreeMap;
2280 /// let mut count: BTreeMap<&str, usize> = BTreeMap::new();
2282 /// // count the number of occurrences of letters in the vec
2283 /// for x in vec!["a","b","a","c","a","b"] {
2284 /// *count.entry(x).or_insert(0) += 1;
2287 /// assert_eq!(count["a"], 3);
2289 #[stable(feature = "rust1", since = "1.0.0")]
2290 pub fn insert(self, value: V) -> &'a mut V {
2299 let mut cur_parent = match self.handle.insert(self.key, value) {
2300 (Fit(handle), _) => return handle.into_kv_mut().1,
2301 (Split(left, k, v, right), ptr) => {
2306 left.ascend().map_err(|n| n.into_root_mut())
2312 Ok(parent) => match parent.insert(ins_k, ins_v, ins_edge) {
2313 Fit(_) => return unsafe { &mut *out_ptr },
2314 Split(left, k, v, right) => {
2318 cur_parent = left.ascend().map_err(|n| n.into_root_mut());
2322 root.push_level().push(ins_k, ins_v, ins_edge);
2323 return unsafe { &mut *out_ptr };
2330 impl<'a, K: Ord, V> OccupiedEntry<'a, K, V> {
2331 /// Gets a reference to the key in the entry.
2336 /// use std::collections::BTreeMap;
2338 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2339 /// map.entry("poneyland").or_insert(12);
2340 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2342 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2343 pub fn key(&self) -> &K {
2344 self.handle.reborrow().into_kv().0
2347 /// Take ownership of the key and value from the map.
2352 /// use std::collections::BTreeMap;
2353 /// use std::collections::btree_map::Entry;
2355 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2356 /// map.entry("poneyland").or_insert(12);
2358 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2359 /// // We delete the entry from the map.
2360 /// o.remove_entry();
2363 /// // If now try to get the value, it will panic:
2364 /// // println!("{}", map["poneyland"]);
2366 #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
2367 pub fn remove_entry(self) -> (K, V) {
2371 /// Gets a reference to the value in the entry.
2376 /// use std::collections::BTreeMap;
2377 /// use std::collections::btree_map::Entry;
2379 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2380 /// map.entry("poneyland").or_insert(12);
2382 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2383 /// assert_eq!(o.get(), &12);
2386 #[stable(feature = "rust1", since = "1.0.0")]
2387 pub fn get(&self) -> &V {
2388 self.handle.reborrow().into_kv().1
2391 /// Gets a mutable reference to the value in the entry.
2393 /// If you need a reference to the `OccupiedEntry` that may outlive the
2394 /// destruction of the `Entry` value, see [`into_mut`].
2396 /// [`into_mut`]: #method.into_mut
2401 /// use std::collections::BTreeMap;
2402 /// use std::collections::btree_map::Entry;
2404 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2405 /// map.entry("poneyland").or_insert(12);
2407 /// assert_eq!(map["poneyland"], 12);
2408 /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
2409 /// *o.get_mut() += 10;
2410 /// assert_eq!(*o.get(), 22);
2412 /// // We can use the same Entry multiple times.
2413 /// *o.get_mut() += 2;
2415 /// assert_eq!(map["poneyland"], 24);
2417 #[stable(feature = "rust1", since = "1.0.0")]
2418 pub fn get_mut(&mut self) -> &mut V {
2419 self.handle.kv_mut().1
2422 /// Converts the entry into a mutable reference to its value.
2424 /// If you need multiple references to the `OccupiedEntry`, see [`get_mut`].
2426 /// [`get_mut`]: #method.get_mut
2431 /// use std::collections::BTreeMap;
2432 /// use std::collections::btree_map::Entry;
2434 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2435 /// map.entry("poneyland").or_insert(12);
2437 /// assert_eq!(map["poneyland"], 12);
2438 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2439 /// *o.into_mut() += 10;
2441 /// assert_eq!(map["poneyland"], 22);
2443 #[stable(feature = "rust1", since = "1.0.0")]
2444 pub fn into_mut(self) -> &'a mut V {
2445 self.handle.into_kv_mut().1
2448 /// Sets the value of the entry with the `OccupiedEntry`'s key,
2449 /// and returns the entry's old value.
2454 /// use std::collections::BTreeMap;
2455 /// use std::collections::btree_map::Entry;
2457 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2458 /// map.entry("poneyland").or_insert(12);
2460 /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
2461 /// assert_eq!(o.insert(15), 12);
2463 /// assert_eq!(map["poneyland"], 15);
2465 #[stable(feature = "rust1", since = "1.0.0")]
2466 pub fn insert(&mut self, value: V) -> V {
2467 mem::replace(self.get_mut(), value)
2470 /// Takes the value of the entry out of the map, and returns it.
2475 /// use std::collections::BTreeMap;
2476 /// use std::collections::btree_map::Entry;
2478 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2479 /// map.entry("poneyland").or_insert(12);
2481 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2482 /// assert_eq!(o.remove(), 12);
2484 /// // If we try to get "poneyland"'s value, it'll panic:
2485 /// // println!("{}", map["poneyland"]);
2487 #[stable(feature = "rust1", since = "1.0.0")]
2488 pub fn remove(self) -> V {
2492 fn remove_kv(self) -> (K, V) {
2495 let (small_leaf, old_key, old_val) = match self.handle.force() {
2497 let (hole, old_key, old_val) = leaf.remove();
2498 (hole.into_node(), old_key, old_val)
2500 Internal(mut internal) => {
2501 let key_loc = internal.kv_mut().0 as *mut K;
2502 let val_loc = internal.kv_mut().1 as *mut V;
2504 let to_remove = internal.right_edge().descend().first_leaf_edge().right_kv().ok();
2505 let to_remove = unsafe { unwrap_unchecked(to_remove) };
2507 let (hole, key, val) = to_remove.remove();
2509 let old_key = unsafe { mem::replace(&mut *key_loc, key) };
2510 let old_val = unsafe { mem::replace(&mut *val_loc, val) };
2512 (hole.into_node(), old_key, old_val)
2517 let mut cur_node = small_leaf.forget_type();
2518 while cur_node.len() < node::MIN_LEN {
2519 match handle_underfull_node(cur_node) {
2521 EmptyParent(_) => unreachable!(),
2523 if parent.len() == 0 {
2524 // We must be at the root
2525 parent.into_root_mut().pop_level();
2528 cur_node = parent.forget_type();
2539 enum UnderflowResult<'a, K, V> {
2541 EmptyParent(NodeRef<marker::Mut<'a>, K, V, marker::Internal>),
2542 Merged(NodeRef<marker::Mut<'a>, K, V, marker::Internal>),
2543 Stole(NodeRef<marker::Mut<'a>, K, V, marker::Internal>),
2546 fn handle_underfull_node<K, V>(
2547 node: NodeRef<marker::Mut<'_>, K, V, marker::LeafOrInternal>,
2548 ) -> UnderflowResult<'_, K, V> {
2549 let parent = if let Ok(parent) = node.ascend() {
2555 let (is_left, mut handle) = match parent.left_kv() {
2556 Ok(left) => (true, left),
2557 Err(parent) => match parent.right_kv() {
2558 Ok(right) => (false, right),
2560 return EmptyParent(parent.into_node());
2565 if handle.can_merge() {
2566 Merged(handle.merge().into_node())
2569 handle.steal_left();
2571 handle.steal_right();
2573 Stole(handle.into_node())
2577 impl<K: Ord, V, I: Iterator<Item = (K, V)>> Iterator for MergeIter<K, V, I> {
2580 fn next(&mut self) -> Option<(K, V)> {
2581 let res = match (self.left.peek(), self.right.peek()) {
2582 (Some(&(ref left_key, _)), Some(&(ref right_key, _))) => left_key.cmp(right_key),
2583 (Some(_), None) => Ordering::Less,
2584 (None, Some(_)) => Ordering::Greater,
2585 (None, None) => return None,
2588 // Check which elements comes first and only advance the corresponding iterator.
2589 // If two keys are equal, take the value from `right`.
2591 Ordering::Less => self.left.next(),
2592 Ordering::Greater => self.right.next(),
2593 Ordering::Equal => {