1 use core::borrow::Borrow;
2 use core::cmp::Ordering;
3 use core::fmt::{self, Debug};
4 use core::hash::{Hash, Hasher};
5 use core::iter::{FromIterator, FusedIterator, Peekable};
6 use core::marker::PhantomData;
7 use core::mem::{self, ManuallyDrop};
8 use core::ops::{Index, RangeBounds};
11 use super::borrow::DormantMutRef;
12 use super::node::{self, marker, ForceResult::*, Handle, InsertResult::*, NodeRef};
13 use super::search::{self, SearchResult::*};
14 use super::unwrap_unchecked;
17 use UnderflowResult::*;
19 /// A map based on a B-Tree.
21 /// B-Trees represent a fundamental compromise between cache-efficiency and actually minimizing
22 /// the amount of work performed in a search. In theory, a binary search tree (BST) is the optimal
23 /// choice for a sorted map, as a perfectly balanced BST performs the theoretical minimum amount of
24 /// comparisons necessary to find an element (log<sub>2</sub>n). However, in practice the way this
25 /// is done is *very* inefficient for modern computer architectures. In particular, every element
26 /// is stored in its own individually heap-allocated node. This means that every single insertion
27 /// triggers a heap-allocation, and every single comparison should be a cache-miss. Since these
28 /// are both notably expensive things to do in practice, we are forced to at very least reconsider
31 /// A B-Tree instead makes each node contain B-1 to 2B-1 elements in a contiguous array. By doing
32 /// this, we reduce the number of allocations by a factor of B, and improve cache efficiency in
33 /// searches. However, this does mean that searches will have to do *more* comparisons on average.
34 /// The precise number of comparisons depends on the node search strategy used. For optimal cache
35 /// efficiency, one could search the nodes linearly. For optimal comparisons, one could search
36 /// the node using binary search. As a compromise, one could also perform a linear search
37 /// that initially only checks every i<sup>th</sup> element for some choice of i.
39 /// Currently, our implementation simply performs naive linear search. This provides excellent
40 /// performance on *small* nodes of elements which are cheap to compare. However in the future we
41 /// would like to further explore choosing the optimal search strategy based on the choice of B,
42 /// and possibly other factors. Using linear search, searching for a random element is expected
43 /// to take O(B * log(n)) comparisons, which is generally worse than a BST. In practice,
44 /// however, performance is excellent.
46 /// It is a logic error for a key to be modified in such a way that the key's ordering relative to
47 /// any other key, as determined by the [`Ord`] trait, changes while it is in the map. This is
48 /// normally only possible through [`Cell`], [`RefCell`], global state, I/O, or unsafe code.
50 /// [`Ord`]: core::cmp::Ord
51 /// [`Cell`]: core::cell::Cell
52 /// [`RefCell`]: core::cell::RefCell
57 /// use std::collections::BTreeMap;
59 /// // type inference lets us omit an explicit type signature (which
60 /// // would be `BTreeMap<&str, &str>` in this example).
61 /// let mut movie_reviews = BTreeMap::new();
63 /// // review some movies.
64 /// movie_reviews.insert("Office Space", "Deals with real issues in the workplace.");
65 /// movie_reviews.insert("Pulp Fiction", "Masterpiece.");
66 /// movie_reviews.insert("The Godfather", "Very enjoyable.");
67 /// movie_reviews.insert("The Blues Brothers", "Eye lyked it a lot.");
69 /// // check for a specific one.
70 /// if !movie_reviews.contains_key("Les Misérables") {
71 /// println!("We've got {} reviews, but Les Misérables ain't one.",
72 /// movie_reviews.len());
75 /// // oops, this review has a lot of spelling mistakes, let's delete it.
76 /// movie_reviews.remove("The Blues Brothers");
78 /// // look up the values associated with some keys.
79 /// let to_find = ["Up!", "Office Space"];
80 /// for movie in &to_find {
81 /// match movie_reviews.get(movie) {
82 /// Some(review) => println!("{}: {}", movie, review),
83 /// None => println!("{} is unreviewed.", movie)
87 /// // Look up the value for a key (will panic if the key is not found).
88 /// println!("Movie review: {}", movie_reviews["Office Space"]);
90 /// // iterate over everything.
91 /// for (movie, review) in &movie_reviews {
92 /// println!("{}: \"{}\"", movie, review);
96 /// `BTreeMap` also implements an [`Entry API`](#method.entry), which allows
97 /// for more complex methods of getting, setting, updating and removing keys and
101 /// use std::collections::BTreeMap;
103 /// // type inference lets us omit an explicit type signature (which
104 /// // would be `BTreeMap<&str, u8>` in this example).
105 /// let mut player_stats = BTreeMap::new();
107 /// fn random_stat_buff() -> u8 {
108 /// // could actually return some random value here - let's just return
109 /// // some fixed value for now
113 /// // insert a key only if it doesn't already exist
114 /// player_stats.entry("health").or_insert(100);
116 /// // insert a key using a function that provides a new value only if it
117 /// // doesn't already exist
118 /// player_stats.entry("defence").or_insert_with(random_stat_buff);
120 /// // update a key, guarding against the key possibly not being set
121 /// let stat = player_stats.entry("attack").or_insert(100);
122 /// *stat += random_stat_buff();
124 #[stable(feature = "rust1", since = "1.0.0")]
125 pub struct BTreeMap<K, V> {
126 root: Option<node::Root<K, V>>,
130 #[stable(feature = "btree_drop", since = "1.7.0")]
131 unsafe impl<#[may_dangle] K, #[may_dangle] V> Drop for BTreeMap<K, V> {
134 drop(ptr::read(self).into_iter());
139 #[stable(feature = "rust1", since = "1.0.0")]
140 impl<K: Clone, V: Clone> Clone for BTreeMap<K, V> {
141 fn clone(&self) -> BTreeMap<K, V> {
142 fn clone_subtree<'a, K: Clone, V: Clone>(
143 node: node::NodeRef<marker::Immut<'a>, K, V, marker::LeafOrInternal>,
151 let mut out_tree = BTreeMap { root: Some(node::Root::new_leaf()), length: 0 };
154 let root = out_tree.root.as_mut().unwrap(); // unwrap succeeds because we just wrapped
155 let mut out_node = match root.node_as_mut().force() {
157 Internal(_) => unreachable!(),
160 let mut in_edge = leaf.first_edge();
161 while let Ok(kv) = in_edge.right_kv() {
162 let (k, v) = kv.into_kv();
163 in_edge = kv.right_edge();
165 out_node.push(k.clone(), v.clone());
166 out_tree.length += 1;
172 Internal(internal) => {
173 let mut out_tree = clone_subtree(internal.first_edge().descend());
176 let out_root = BTreeMap::ensure_is_owned(&mut out_tree.root);
177 let mut out_node = out_root.push_internal_level();
178 let mut in_edge = internal.first_edge();
179 while let Ok(kv) = in_edge.right_kv() {
180 let (k, v) = kv.into_kv();
181 in_edge = kv.right_edge();
183 let k = (*k).clone();
184 let v = (*v).clone();
185 let subtree = clone_subtree(in_edge.descend());
187 // We can't destructure subtree directly
188 // because BTreeMap implements Drop
189 let (subroot, sublength) = unsafe {
190 let subtree = ManuallyDrop::new(subtree);
191 let root = ptr::read(&subtree.root);
192 let length = subtree.length;
196 out_node.push(k, v, subroot.unwrap_or_else(node::Root::new_leaf));
197 out_tree.length += 1 + sublength;
207 // Ideally we'd call `BTreeMap::new` here, but that has the `K:
208 // Ord` constraint, which this method lacks.
209 BTreeMap { root: None, length: 0 }
211 clone_subtree(self.root.as_ref().unwrap().node_as_ref()) // unwrap succeeds because not empty
216 impl<K, Q: ?Sized> super::Recover<Q> for BTreeMap<K, ()>
223 fn get(&self, key: &Q) -> Option<&K> {
224 let root_node = self.root.as_ref()?.node_as_ref();
225 match search::search_tree(root_node, key) {
226 Found(handle) => Some(handle.into_kv().0),
231 fn take(&mut self, key: &Q) -> Option<K> {
232 let (map, dormant_map) = DormantMutRef::new(self);
233 let root_node = map.root.as_mut()?.node_as_mut();
234 match search::search_tree(root_node, key) {
236 Some(OccupiedEntry { handle, dormant_map, _marker: PhantomData }.remove_kv().0)
242 fn replace(&mut self, key: K) -> Option<K> {
243 let (map, dormant_map) = DormantMutRef::new(self);
244 let root_node = Self::ensure_is_owned(&mut map.root).node_as_mut();
245 match search::search_tree::<marker::Mut<'_>, K, (), K>(root_node, &key) {
246 Found(handle) => Some(mem::replace(handle.into_key_mut(), key)),
248 VacantEntry { key, handle, dormant_map, _marker: PhantomData }.insert(());
255 /// An iterator over the entries of a `BTreeMap`.
257 /// This `struct` is created by the [`iter`] method on [`BTreeMap`]. See its
258 /// documentation for more.
260 /// [`iter`]: BTreeMap::iter
261 #[stable(feature = "rust1", since = "1.0.0")]
262 pub struct Iter<'a, K: 'a, V: 'a> {
263 range: Range<'a, K, V>,
267 #[stable(feature = "collection_debug", since = "1.17.0")]
268 impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for Iter<'_, K, V> {
269 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
270 f.debug_list().entries(self.clone()).finish()
274 /// A mutable iterator over the entries of a `BTreeMap`.
276 /// This `struct` is created by the [`iter_mut`] method on [`BTreeMap`]. See its
277 /// documentation for more.
279 /// [`iter_mut`]: BTreeMap::iter_mut
280 #[stable(feature = "rust1", since = "1.0.0")]
282 pub struct IterMut<'a, K: 'a, V: 'a> {
283 range: RangeMut<'a, K, V>,
287 /// An owning iterator over the entries of a `BTreeMap`.
289 /// This `struct` is created by the [`into_iter`] method on [`BTreeMap`]
290 /// (provided by the `IntoIterator` trait). See its documentation for more.
292 /// [`into_iter`]: IntoIterator::into_iter
293 #[stable(feature = "rust1", since = "1.0.0")]
294 pub struct IntoIter<K, V> {
295 front: Option<Handle<NodeRef<marker::Owned, K, V, marker::Leaf>, marker::Edge>>,
296 back: Option<Handle<NodeRef<marker::Owned, K, V, marker::Leaf>, marker::Edge>>,
300 #[stable(feature = "collection_debug", since = "1.17.0")]
301 impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for IntoIter<K, V> {
302 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
304 front: self.front.as_ref().map(|f| f.reborrow()),
305 back: self.back.as_ref().map(|b| b.reborrow()),
307 f.debug_list().entries(range).finish()
311 /// An iterator over the keys of a `BTreeMap`.
313 /// This `struct` is created by the [`keys`] method on [`BTreeMap`]. See its
314 /// documentation for more.
316 /// [`keys`]: BTreeMap::keys
317 #[stable(feature = "rust1", since = "1.0.0")]
318 pub struct Keys<'a, K: 'a, V: 'a> {
319 inner: Iter<'a, K, V>,
322 #[stable(feature = "collection_debug", since = "1.17.0")]
323 impl<K: fmt::Debug, V> fmt::Debug for Keys<'_, K, V> {
324 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
325 f.debug_list().entries(self.clone()).finish()
329 /// An iterator over the values of a `BTreeMap`.
331 /// This `struct` is created by the [`values`] method on [`BTreeMap`]. See its
332 /// documentation for more.
334 /// [`values`]: BTreeMap::values
335 #[stable(feature = "rust1", since = "1.0.0")]
336 pub struct Values<'a, K: 'a, V: 'a> {
337 inner: Iter<'a, K, V>,
340 #[stable(feature = "collection_debug", since = "1.17.0")]
341 impl<K, V: fmt::Debug> fmt::Debug for Values<'_, K, V> {
342 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
343 f.debug_list().entries(self.clone()).finish()
347 /// A mutable iterator over the values of a `BTreeMap`.
349 /// This `struct` is created by the [`values_mut`] method on [`BTreeMap`]. See its
350 /// documentation for more.
352 /// [`values_mut`]: BTreeMap::values_mut
353 #[stable(feature = "map_values_mut", since = "1.10.0")]
355 pub struct ValuesMut<'a, K: 'a, V: 'a> {
356 inner: IterMut<'a, K, V>,
359 /// An owning iterator over the keys of a `BTreeMap`.
361 /// This `struct` is created by the [`into_keys`] method on [`BTreeMap`].
362 /// See its documentation for more.
364 /// [`into_keys`]: BTreeMap::into_keys
365 #[unstable(feature = "map_into_keys_values", issue = "75294")]
367 pub struct IntoKeys<K, V> {
368 inner: IntoIter<K, V>,
371 /// An owning iterator over the values of a `BTreeMap`.
373 /// This `struct` is created by the [`into_values`] method on [`BTreeMap`].
374 /// See its documentation for more.
376 /// [`into_values`]: BTreeMap::into_values
377 #[unstable(feature = "map_into_keys_values", issue = "75294")]
379 pub struct IntoValues<K, V> {
380 inner: IntoIter<K, V>,
383 /// An iterator over a sub-range of entries in a `BTreeMap`.
385 /// This `struct` is created by the [`range`] method on [`BTreeMap`]. See its
386 /// documentation for more.
388 /// [`range`]: BTreeMap::range
389 #[stable(feature = "btree_range", since = "1.17.0")]
390 pub struct Range<'a, K: 'a, V: 'a> {
391 front: Option<Handle<NodeRef<marker::Immut<'a>, K, V, marker::Leaf>, marker::Edge>>,
392 back: Option<Handle<NodeRef<marker::Immut<'a>, K, V, marker::Leaf>, marker::Edge>>,
395 #[stable(feature = "collection_debug", since = "1.17.0")]
396 impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for Range<'_, K, V> {
397 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
398 f.debug_list().entries(self.clone()).finish()
402 /// A mutable iterator over a sub-range of entries in a `BTreeMap`.
404 /// This `struct` is created by the [`range_mut`] method on [`BTreeMap`]. See its
405 /// documentation for more.
407 /// [`range_mut`]: BTreeMap::range_mut
408 #[stable(feature = "btree_range", since = "1.17.0")]
409 pub struct RangeMut<'a, K: 'a, V: 'a> {
410 front: Option<Handle<NodeRef<marker::ValMut<'a>, K, V, marker::Leaf>, marker::Edge>>,
411 back: Option<Handle<NodeRef<marker::ValMut<'a>, K, V, marker::Leaf>, marker::Edge>>,
413 // Be invariant in `K` and `V`
414 _marker: PhantomData<&'a mut (K, V)>,
417 #[stable(feature = "collection_debug", since = "1.17.0")]
418 impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for RangeMut<'_, K, V> {
419 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
421 front: self.front.as_ref().map(|f| f.reborrow()),
422 back: self.back.as_ref().map(|b| b.reborrow()),
424 f.debug_list().entries(range).finish()
428 /// A view into a single entry in a map, which may either be vacant or occupied.
430 /// This `enum` is constructed from the [`entry`] method on [`BTreeMap`].
432 /// [`entry`]: BTreeMap::entry
433 #[stable(feature = "rust1", since = "1.0.0")]
434 pub enum Entry<'a, K: 'a, V: 'a> {
436 #[stable(feature = "rust1", since = "1.0.0")]
437 Vacant(#[stable(feature = "rust1", since = "1.0.0")] VacantEntry<'a, K, V>),
439 /// An occupied entry.
440 #[stable(feature = "rust1", since = "1.0.0")]
441 Occupied(#[stable(feature = "rust1", since = "1.0.0")] OccupiedEntry<'a, K, V>),
444 #[stable(feature = "debug_btree_map", since = "1.12.0")]
445 impl<K: Debug + Ord, V: Debug> Debug for Entry<'_, K, V> {
446 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
448 Vacant(ref v) => f.debug_tuple("Entry").field(v).finish(),
449 Occupied(ref o) => f.debug_tuple("Entry").field(o).finish(),
454 /// A view into a vacant entry in a `BTreeMap`.
455 /// It is part of the [`Entry`] enum.
457 /// [`Entry`]: enum.Entry.html
458 #[stable(feature = "rust1", since = "1.0.0")]
459 pub struct VacantEntry<'a, K: 'a, V: 'a> {
461 handle: Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>,
462 dormant_map: DormantMutRef<'a, BTreeMap<K, V>>,
464 // Be invariant in `K` and `V`
465 _marker: PhantomData<&'a mut (K, V)>,
468 #[stable(feature = "debug_btree_map", since = "1.12.0")]
469 impl<K: Debug + Ord, V> Debug for VacantEntry<'_, K, V> {
470 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
471 f.debug_tuple("VacantEntry").field(self.key()).finish()
475 /// A view into an occupied entry in a `BTreeMap`.
476 /// It is part of the [`Entry`] enum.
478 /// [`Entry`]: enum.Entry.html
479 #[stable(feature = "rust1", since = "1.0.0")]
480 pub struct OccupiedEntry<'a, K: 'a, V: 'a> {
481 handle: Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, marker::KV>,
482 dormant_map: DormantMutRef<'a, BTreeMap<K, V>>,
484 // Be invariant in `K` and `V`
485 _marker: PhantomData<&'a mut (K, V)>,
488 #[stable(feature = "debug_btree_map", since = "1.12.0")]
489 impl<K: Debug + Ord, V: Debug> Debug for OccupiedEntry<'_, K, V> {
490 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
491 f.debug_struct("OccupiedEntry").field("key", self.key()).field("value", self.get()).finish()
495 // An iterator for merging two sorted sequences into one
496 struct MergeIter<K, V, I: Iterator<Item = (K, V)>> {
501 impl<K: Ord, V> BTreeMap<K, V> {
502 /// Makes a new empty BTreeMap.
504 /// Does not allocate anything on its own.
511 /// use std::collections::BTreeMap;
513 /// let mut map = BTreeMap::new();
515 /// // entries can now be inserted into the empty map
516 /// map.insert(1, "a");
518 #[stable(feature = "rust1", since = "1.0.0")]
519 #[rustc_const_unstable(feature = "const_btree_new", issue = "71835")]
520 pub const fn new() -> BTreeMap<K, V> {
521 BTreeMap { root: None, length: 0 }
524 /// Clears the map, removing all elements.
531 /// use std::collections::BTreeMap;
533 /// let mut a = BTreeMap::new();
534 /// a.insert(1, "a");
536 /// assert!(a.is_empty());
538 #[stable(feature = "rust1", since = "1.0.0")]
539 pub fn clear(&mut self) {
540 *self = BTreeMap::new();
543 /// Returns a reference to the value corresponding to the key.
545 /// The key may be any borrowed form of the map's key type, but the ordering
546 /// on the borrowed form *must* match the ordering on the key type.
553 /// use std::collections::BTreeMap;
555 /// let mut map = BTreeMap::new();
556 /// map.insert(1, "a");
557 /// assert_eq!(map.get(&1), Some(&"a"));
558 /// assert_eq!(map.get(&2), None);
560 #[stable(feature = "rust1", since = "1.0.0")]
561 pub fn get<Q: ?Sized>(&self, key: &Q) -> Option<&V>
566 let root_node = self.root.as_ref()?.node_as_ref();
567 match search::search_tree(root_node, key) {
568 Found(handle) => Some(handle.into_kv().1),
573 /// Returns the key-value pair corresponding to the supplied key.
575 /// The supplied key may be any borrowed form of the map's key type, but the ordering
576 /// on the borrowed form *must* match the ordering on the key type.
581 /// use std::collections::BTreeMap;
583 /// let mut map = BTreeMap::new();
584 /// map.insert(1, "a");
585 /// assert_eq!(map.get_key_value(&1), Some((&1, &"a")));
586 /// assert_eq!(map.get_key_value(&2), None);
588 #[stable(feature = "map_get_key_value", since = "1.40.0")]
589 pub fn get_key_value<Q: ?Sized>(&self, k: &Q) -> Option<(&K, &V)>
594 let root_node = self.root.as_ref()?.node_as_ref();
595 match search::search_tree(root_node, k) {
596 Found(handle) => Some(handle.into_kv()),
601 /// Returns the first key-value pair in the map.
602 /// The key in this pair is the minimum key in the map.
609 /// #![feature(map_first_last)]
610 /// use std::collections::BTreeMap;
612 /// let mut map = BTreeMap::new();
613 /// assert_eq!(map.first_key_value(), None);
614 /// map.insert(1, "b");
615 /// map.insert(2, "a");
616 /// assert_eq!(map.first_key_value(), Some((&1, &"b")));
618 #[unstable(feature = "map_first_last", issue = "62924")]
619 pub fn first_key_value(&self) -> Option<(&K, &V)> {
620 let root_node = self.root.as_ref()?.node_as_ref();
621 root_node.first_leaf_edge().right_kv().ok().map(Handle::into_kv)
624 /// Returns the first entry in the map for in-place manipulation.
625 /// The key of this entry is the minimum key in the map.
630 /// #![feature(map_first_last)]
631 /// use std::collections::BTreeMap;
633 /// let mut map = BTreeMap::new();
634 /// map.insert(1, "a");
635 /// map.insert(2, "b");
636 /// if let Some(mut entry) = map.first_entry() {
637 /// if *entry.key() > 0 {
638 /// entry.insert("first");
641 /// assert_eq!(*map.get(&1).unwrap(), "first");
642 /// assert_eq!(*map.get(&2).unwrap(), "b");
644 #[unstable(feature = "map_first_last", issue = "62924")]
645 pub fn first_entry(&mut self) -> Option<OccupiedEntry<'_, K, V>> {
646 let (map, dormant_map) = DormantMutRef::new(self);
647 let root_node = map.root.as_mut()?.node_as_mut();
648 let kv = root_node.first_leaf_edge().right_kv().ok()?;
649 Some(OccupiedEntry { handle: kv.forget_node_type(), dormant_map, _marker: PhantomData })
652 /// Removes and returns the first element in the map.
653 /// The key of this element is the minimum key that was in the map.
657 /// Draining elements in ascending order, while keeping a usable map each iteration.
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((key, _val)) = map.pop_first() {
667 /// assert!(map.iter().all(|(k, _v)| *k > key));
669 /// assert!(map.is_empty());
671 #[unstable(feature = "map_first_last", issue = "62924")]
672 pub fn pop_first(&mut self) -> Option<(K, V)> {
673 self.first_entry().map(|entry| entry.remove_entry())
676 /// Returns the last key-value pair in the map.
677 /// The key in this pair is the maximum key in the map.
684 /// #![feature(map_first_last)]
685 /// use std::collections::BTreeMap;
687 /// let mut map = BTreeMap::new();
688 /// map.insert(1, "b");
689 /// map.insert(2, "a");
690 /// assert_eq!(map.last_key_value(), Some((&2, &"a")));
692 #[unstable(feature = "map_first_last", issue = "62924")]
693 pub fn last_key_value(&self) -> Option<(&K, &V)> {
694 let root_node = self.root.as_ref()?.node_as_ref();
695 root_node.last_leaf_edge().left_kv().ok().map(Handle::into_kv)
698 /// Returns the last entry in the map for in-place manipulation.
699 /// The key of this entry is the maximum key in the map.
704 /// #![feature(map_first_last)]
705 /// use std::collections::BTreeMap;
707 /// let mut map = BTreeMap::new();
708 /// map.insert(1, "a");
709 /// map.insert(2, "b");
710 /// if let Some(mut entry) = map.last_entry() {
711 /// if *entry.key() > 0 {
712 /// entry.insert("last");
715 /// assert_eq!(*map.get(&1).unwrap(), "a");
716 /// assert_eq!(*map.get(&2).unwrap(), "last");
718 #[unstable(feature = "map_first_last", issue = "62924")]
719 pub fn last_entry(&mut self) -> Option<OccupiedEntry<'_, K, V>> {
720 let (map, dormant_map) = DormantMutRef::new(self);
721 let root_node = map.root.as_mut()?.node_as_mut();
722 let kv = root_node.last_leaf_edge().left_kv().ok()?;
723 Some(OccupiedEntry { handle: kv.forget_node_type(), dormant_map, _marker: PhantomData })
726 /// Removes and returns the last element in the map.
727 /// The key of this element is the maximum key that was in the map.
731 /// Draining elements in descending order, while keeping a usable map each iteration.
734 /// #![feature(map_first_last)]
735 /// use std::collections::BTreeMap;
737 /// let mut map = BTreeMap::new();
738 /// map.insert(1, "a");
739 /// map.insert(2, "b");
740 /// while let Some((key, _val)) = map.pop_last() {
741 /// assert!(map.iter().all(|(k, _v)| *k < key));
743 /// assert!(map.is_empty());
745 #[unstable(feature = "map_first_last", issue = "62924")]
746 pub fn pop_last(&mut self) -> Option<(K, V)> {
747 self.last_entry().map(|entry| entry.remove_entry())
750 /// Returns `true` if the map contains a value for the specified key.
752 /// The key may be any borrowed form of the map's key type, but the ordering
753 /// on the borrowed form *must* match the ordering on the key type.
760 /// use std::collections::BTreeMap;
762 /// let mut map = BTreeMap::new();
763 /// map.insert(1, "a");
764 /// assert_eq!(map.contains_key(&1), true);
765 /// assert_eq!(map.contains_key(&2), false);
767 #[stable(feature = "rust1", since = "1.0.0")]
768 pub fn contains_key<Q: ?Sized>(&self, key: &Q) -> bool
773 self.get(key).is_some()
776 /// Returns a mutable reference to the value corresponding to the key.
778 /// The key may be any borrowed form of the map's key type, but the ordering
779 /// on the borrowed form *must* match the ordering on the key type.
786 /// use std::collections::BTreeMap;
788 /// let mut map = BTreeMap::new();
789 /// map.insert(1, "a");
790 /// if let Some(x) = map.get_mut(&1) {
793 /// assert_eq!(map[&1], "b");
795 // See `get` for implementation notes, this is basically a copy-paste with mut's added
796 #[stable(feature = "rust1", since = "1.0.0")]
797 pub fn get_mut<Q: ?Sized>(&mut self, key: &Q) -> Option<&mut V>
802 let root_node = self.root.as_mut()?.node_as_mut();
803 match search::search_tree(root_node, key) {
804 Found(handle) => Some(handle.into_val_mut()),
809 /// Inserts a key-value pair into the map.
811 /// If the map did not have this key present, `None` is returned.
813 /// If the map did have this key present, the value is updated, and the old
814 /// value is returned. The key is not updated, though; this matters for
815 /// types that can be `==` without being identical. See the [module-level
816 /// documentation] for more.
818 /// [module-level documentation]: index.html#insert-and-complex-keys
825 /// use std::collections::BTreeMap;
827 /// let mut map = BTreeMap::new();
828 /// assert_eq!(map.insert(37, "a"), None);
829 /// assert_eq!(map.is_empty(), false);
831 /// map.insert(37, "b");
832 /// assert_eq!(map.insert(37, "c"), Some("b"));
833 /// assert_eq!(map[&37], "c");
835 #[stable(feature = "rust1", since = "1.0.0")]
836 pub fn insert(&mut self, key: K, value: V) -> Option<V> {
837 match self.entry(key) {
838 Occupied(mut entry) => Some(entry.insert(value)),
846 /// Removes a key from the map, returning the value at the key if the key
847 /// was previously in the map.
849 /// The key may be any borrowed form of the map's key type, but the ordering
850 /// on the borrowed form *must* match the ordering on the key type.
857 /// use std::collections::BTreeMap;
859 /// let mut map = BTreeMap::new();
860 /// map.insert(1, "a");
861 /// assert_eq!(map.remove(&1), Some("a"));
862 /// assert_eq!(map.remove(&1), None);
864 #[stable(feature = "rust1", since = "1.0.0")]
865 pub fn remove<Q: ?Sized>(&mut self, key: &Q) -> Option<V>
870 self.remove_entry(key).map(|(_, v)| v)
873 /// Removes a key from the map, returning the stored key and value if the key
874 /// was previously in the map.
876 /// The key may be any borrowed form of the map's key type, but the ordering
877 /// on the borrowed form *must* match the ordering on the key type.
884 /// use std::collections::BTreeMap;
886 /// let mut map = BTreeMap::new();
887 /// map.insert(1, "a");
888 /// assert_eq!(map.remove_entry(&1), Some((1, "a")));
889 /// assert_eq!(map.remove_entry(&1), None);
891 #[stable(feature = "btreemap_remove_entry", since = "1.45.0")]
892 pub fn remove_entry<Q: ?Sized>(&mut self, key: &Q) -> Option<(K, V)>
897 let (map, dormant_map) = DormantMutRef::new(self);
898 let root_node = map.root.as_mut()?.node_as_mut();
899 match search::search_tree(root_node, key) {
901 Some(OccupiedEntry { handle, dormant_map, _marker: PhantomData }.remove_entry())
907 /// Moves all elements from `other` into `Self`, leaving `other` empty.
912 /// use std::collections::BTreeMap;
914 /// let mut a = BTreeMap::new();
915 /// a.insert(1, "a");
916 /// a.insert(2, "b");
917 /// a.insert(3, "c");
919 /// let mut b = BTreeMap::new();
920 /// b.insert(3, "d");
921 /// b.insert(4, "e");
922 /// b.insert(5, "f");
924 /// a.append(&mut b);
926 /// assert_eq!(a.len(), 5);
927 /// assert_eq!(b.len(), 0);
929 /// assert_eq!(a[&1], "a");
930 /// assert_eq!(a[&2], "b");
931 /// assert_eq!(a[&3], "d");
932 /// assert_eq!(a[&4], "e");
933 /// assert_eq!(a[&5], "f");
935 #[stable(feature = "btree_append", since = "1.11.0")]
936 pub fn append(&mut self, other: &mut Self) {
937 // Do we have to append anything at all?
938 if other.is_empty() {
942 // We can just swap `self` and `other` if `self` is empty.
944 mem::swap(self, other);
948 // First, we merge `self` and `other` into a sorted sequence in linear time.
949 let self_iter = mem::take(self).into_iter();
950 let other_iter = mem::take(other).into_iter();
951 let iter = MergeIter { left: self_iter.peekable(), right: other_iter.peekable() };
953 // Second, we build a tree from the sorted sequence in linear time.
954 self.from_sorted_iter(iter);
957 /// Constructs a double-ended iterator over a sub-range of elements in the map.
958 /// The simplest way is to use the range syntax `min..max`, thus `range(min..max)` will
959 /// yield elements from min (inclusive) to max (exclusive).
960 /// The range may also be entered as `(Bound<T>, Bound<T>)`, so for example
961 /// `range((Excluded(4), Included(10)))` will yield a left-exclusive, right-inclusive
962 /// range from 4 to 10.
966 /// Panics if range `start > end`.
967 /// Panics if range `start == end` and both bounds are `Excluded`.
974 /// use std::collections::BTreeMap;
975 /// use std::ops::Bound::Included;
977 /// let mut map = BTreeMap::new();
978 /// map.insert(3, "a");
979 /// map.insert(5, "b");
980 /// map.insert(8, "c");
981 /// for (&key, &value) in map.range((Included(&4), Included(&8))) {
982 /// println!("{}: {}", key, value);
984 /// assert_eq!(Some((&5, &"b")), map.range(4..).next());
986 #[stable(feature = "btree_range", since = "1.17.0")]
987 pub fn range<T: ?Sized, R>(&self, range: R) -> Range<'_, K, V>
993 if let Some(root) = &self.root {
994 let (f, b) = root.node_as_ref().range_search(range);
996 Range { front: Some(f), back: Some(b) }
998 Range { front: None, back: None }
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 if let Some(root) = &mut self.root {
1040 let (f, b) = root.node_as_valmut().range_search(range);
1042 RangeMut { front: Some(f), back: Some(b), _marker: PhantomData }
1044 RangeMut { front: None, back: None, _marker: PhantomData }
1048 /// Gets the given key's corresponding entry in the map for in-place manipulation.
1055 /// use std::collections::BTreeMap;
1057 /// let mut count: BTreeMap<&str, usize> = BTreeMap::new();
1059 /// // count the number of occurrences of letters in the vec
1060 /// for x in vec!["a","b","a","c","a","b"] {
1061 /// *count.entry(x).or_insert(0) += 1;
1064 /// assert_eq!(count["a"], 3);
1066 #[stable(feature = "rust1", since = "1.0.0")]
1067 pub fn entry(&mut self, key: K) -> Entry<'_, K, V> {
1068 // FIXME(@porglezomp) Avoid allocating if we don't insert
1069 let (map, dormant_map) = DormantMutRef::new(self);
1070 let root_node = Self::ensure_is_owned(&mut map.root).node_as_mut();
1071 match search::search_tree(root_node, &key) {
1072 Found(handle) => Occupied(OccupiedEntry { handle, dormant_map, _marker: PhantomData }),
1074 Vacant(VacantEntry { key, handle, dormant_map, _marker: PhantomData })
1079 fn from_sorted_iter<I: Iterator<Item = (K, V)>>(&mut self, iter: I) {
1080 let root = Self::ensure_is_owned(&mut self.root);
1081 let mut cur_node = root.node_as_mut().last_leaf_edge().into_node();
1082 // Iterate through all key-value pairs, pushing them into nodes at the right level.
1083 for (key, value) in iter {
1084 // Try to push key-value pair into the current leaf node.
1085 if cur_node.len() < node::CAPACITY {
1086 cur_node.push(key, value);
1088 // No space left, go up and push there.
1090 let mut test_node = cur_node.forget_type();
1092 match test_node.ascend() {
1094 let parent = parent.into_node();
1095 if parent.len() < node::CAPACITY {
1096 // Found a node with space left, push here.
1101 test_node = parent.forget_type();
1105 // We are at the top, create a new root node and push there.
1106 open_node = root.push_internal_level();
1112 // Push key-value pair and new right subtree.
1113 let tree_height = open_node.height() - 1;
1114 let mut right_tree = node::Root::new_leaf();
1115 for _ in 0..tree_height {
1116 right_tree.push_internal_level();
1118 open_node.push(key, value, right_tree);
1120 // Go down to the right-most leaf again.
1121 cur_node = open_node.forget_type().last_leaf_edge().into_node();
1126 Self::fix_right_edge(root)
1129 fn fix_right_edge(root: &mut node::Root<K, V>) {
1130 // Handle underfull nodes, start from the top.
1131 let mut cur_node = root.node_as_mut();
1132 while let Internal(internal) = cur_node.force() {
1133 // Check if right-most child is underfull.
1134 let mut last_edge = internal.last_edge();
1135 let right_child_len = last_edge.reborrow().descend().len();
1136 if right_child_len < node::MIN_LEN {
1137 // We need to steal.
1138 let mut last_kv = match last_edge.left_kv() {
1140 Err(_) => unreachable!(),
1142 last_kv.bulk_steal_left(node::MIN_LEN - right_child_len);
1143 last_edge = last_kv.right_edge();
1147 cur_node = last_edge.descend();
1151 /// Splits the collection into two at the given key. Returns everything after the given key,
1152 /// including the key.
1159 /// use std::collections::BTreeMap;
1161 /// let mut a = BTreeMap::new();
1162 /// a.insert(1, "a");
1163 /// a.insert(2, "b");
1164 /// a.insert(3, "c");
1165 /// a.insert(17, "d");
1166 /// a.insert(41, "e");
1168 /// let b = a.split_off(&3);
1170 /// assert_eq!(a.len(), 2);
1171 /// assert_eq!(b.len(), 3);
1173 /// assert_eq!(a[&1], "a");
1174 /// assert_eq!(a[&2], "b");
1176 /// assert_eq!(b[&3], "c");
1177 /// assert_eq!(b[&17], "d");
1178 /// assert_eq!(b[&41], "e");
1180 #[stable(feature = "btree_split_off", since = "1.11.0")]
1181 pub fn split_off<Q: ?Sized + Ord>(&mut self, key: &Q) -> Self
1185 if self.is_empty() {
1189 let total_num = self.len();
1190 let left_root = self.root.as_mut().unwrap(); // unwrap succeeds because not empty
1192 let mut right = Self::new();
1193 let right_root = Self::ensure_is_owned(&mut right.root);
1194 for _ in 0..left_root.height() {
1195 right_root.push_internal_level();
1199 let mut left_node = left_root.node_as_mut();
1200 let mut right_node = right_root.node_as_mut();
1203 let mut split_edge = match search::search_node(left_node, key) {
1204 // key is going to the right tree
1205 Found(handle) => handle.left_edge(),
1206 GoDown(handle) => handle,
1209 split_edge.move_suffix(&mut right_node);
1211 match (split_edge.force(), right_node.force()) {
1212 (Internal(edge), Internal(node)) => {
1213 left_node = edge.descend();
1214 right_node = node.first_edge().descend();
1216 (Leaf(_), Leaf(_)) => {
1226 left_root.fix_right_border();
1227 right_root.fix_left_border();
1229 if left_root.height() < right_root.height() {
1230 self.length = left_root.node_as_ref().calc_length();
1231 right.length = total_num - self.len();
1233 right.length = right_root.node_as_ref().calc_length();
1234 self.length = total_num - right.len();
1240 /// Creates an iterator which uses a closure to determine if an element should be removed.
1242 /// If the closure returns true, the element is removed from the map and yielded.
1243 /// If the closure returns false, or panics, the element remains in the map and will not be
1246 /// Note that `drain_filter` lets you mutate every value in the filter closure, regardless of
1247 /// whether you choose to keep or remove it.
1249 /// If the iterator is only partially consumed or not consumed at all, each of the remaining
1250 /// elements will still be subjected to the closure and removed and dropped if it returns true.
1252 /// It is unspecified how many more elements will be subjected to the closure
1253 /// if a panic occurs in the closure, or a panic occurs while dropping an element,
1254 /// or if the `DrainFilter` value is leaked.
1258 /// Splitting a map into even and odd keys, reusing the original map:
1261 /// #![feature(btree_drain_filter)]
1262 /// use std::collections::BTreeMap;
1264 /// let mut map: BTreeMap<i32, i32> = (0..8).map(|x| (x, x)).collect();
1265 /// let evens: BTreeMap<_, _> = map.drain_filter(|k, _v| k % 2 == 0).collect();
1267 /// assert_eq!(evens.keys().copied().collect::<Vec<_>>(), vec![0, 2, 4, 6]);
1268 /// assert_eq!(odds.keys().copied().collect::<Vec<_>>(), vec![1, 3, 5, 7]);
1270 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1271 pub fn drain_filter<F>(&mut self, pred: F) -> DrainFilter<'_, K, V, F>
1273 F: FnMut(&K, &mut V) -> bool,
1275 DrainFilter { pred, inner: self.drain_filter_inner() }
1278 pub(super) fn drain_filter_inner(&mut self) -> DrainFilterInner<'_, K, V> {
1279 if let Some(root) = self.root.as_mut() {
1280 let (root, dormant_root) = DormantMutRef::new(root);
1281 let front = root.node_as_mut().first_leaf_edge();
1283 length: &mut self.length,
1284 dormant_root: Some(dormant_root),
1285 cur_leaf_edge: Some(front),
1288 DrainFilterInner { length: &mut self.length, dormant_root: None, cur_leaf_edge: None }
1292 /// Creates a consuming iterator visiting all the keys, in sorted order.
1293 /// The map cannot be used after calling this.
1294 /// The iterator element type is `K`.
1299 /// #![feature(map_into_keys_values)]
1300 /// use std::collections::BTreeMap;
1302 /// let mut a = BTreeMap::new();
1303 /// a.insert(2, "b");
1304 /// a.insert(1, "a");
1306 /// let keys: Vec<i32> = a.into_keys().collect();
1307 /// assert_eq!(keys, [1, 2]);
1310 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1311 pub fn into_keys(self) -> IntoKeys<K, V> {
1312 IntoKeys { inner: self.into_iter() }
1315 /// Creates a consuming iterator visiting all the values, in order by key.
1316 /// The map cannot be used after calling this.
1317 /// The iterator element type is `V`.
1322 /// #![feature(map_into_keys_values)]
1323 /// use std::collections::BTreeMap;
1325 /// let mut a = BTreeMap::new();
1326 /// a.insert(1, "hello");
1327 /// a.insert(2, "goodbye");
1329 /// let values: Vec<&str> = a.into_values().collect();
1330 /// assert_eq!(values, ["hello", "goodbye"]);
1333 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1334 pub fn into_values(self) -> IntoValues<K, V> {
1335 IntoValues { inner: self.into_iter() }
1339 #[stable(feature = "rust1", since = "1.0.0")]
1340 impl<'a, K, V> IntoIterator for &'a BTreeMap<K, V> {
1341 type Item = (&'a K, &'a V);
1342 type IntoIter = Iter<'a, K, V>;
1344 fn into_iter(self) -> Iter<'a, K, V> {
1349 #[stable(feature = "rust1", since = "1.0.0")]
1350 impl<'a, K: 'a, V: 'a> Iterator for Iter<'a, K, V> {
1351 type Item = (&'a K, &'a V);
1353 fn next(&mut self) -> Option<(&'a K, &'a V)> {
1354 if self.length == 0 {
1358 unsafe { Some(self.range.next_unchecked()) }
1362 fn size_hint(&self) -> (usize, Option<usize>) {
1363 (self.length, Some(self.length))
1366 fn last(mut self) -> Option<(&'a K, &'a V)> {
1370 fn min(mut self) -> Option<(&'a K, &'a V)> {
1374 fn max(mut self) -> Option<(&'a K, &'a V)> {
1379 #[stable(feature = "fused", since = "1.26.0")]
1380 impl<K, V> FusedIterator for Iter<'_, K, V> {}
1382 #[stable(feature = "rust1", since = "1.0.0")]
1383 impl<'a, K: 'a, V: 'a> DoubleEndedIterator for Iter<'a, K, V> {
1384 fn next_back(&mut self) -> Option<(&'a K, &'a V)> {
1385 if self.length == 0 {
1389 unsafe { Some(self.range.next_back_unchecked()) }
1394 #[stable(feature = "rust1", since = "1.0.0")]
1395 impl<K, V> ExactSizeIterator for Iter<'_, K, V> {
1396 fn len(&self) -> usize {
1401 #[stable(feature = "rust1", since = "1.0.0")]
1402 impl<K, V> Clone for Iter<'_, K, V> {
1403 fn clone(&self) -> Self {
1404 Iter { range: self.range.clone(), length: self.length }
1408 #[stable(feature = "rust1", since = "1.0.0")]
1409 impl<'a, K, V> IntoIterator for &'a mut BTreeMap<K, V> {
1410 type Item = (&'a K, &'a mut V);
1411 type IntoIter = IterMut<'a, K, V>;
1413 fn into_iter(self) -> IterMut<'a, K, V> {
1418 #[stable(feature = "rust1", since = "1.0.0")]
1419 impl<'a, K: 'a, V: 'a> Iterator for IterMut<'a, K, V> {
1420 type Item = (&'a K, &'a mut V);
1422 fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
1423 if self.length == 0 {
1427 let (k, v) = unsafe { self.range.next_unchecked() };
1428 Some((k, v)) // coerce k from `&mut K` to `&K`
1432 fn size_hint(&self) -> (usize, Option<usize>) {
1433 (self.length, Some(self.length))
1436 fn last(mut self) -> Option<(&'a K, &'a mut V)> {
1440 fn min(mut self) -> Option<(&'a K, &'a mut V)> {
1444 fn max(mut self) -> Option<(&'a K, &'a mut V)> {
1449 #[stable(feature = "rust1", since = "1.0.0")]
1450 impl<'a, K: 'a, V: 'a> DoubleEndedIterator for IterMut<'a, K, V> {
1451 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> {
1452 if self.length == 0 {
1456 let (k, v) = unsafe { self.range.next_back_unchecked() };
1457 Some((k, v)) // coerce k from `&mut K` to `&K`
1462 #[stable(feature = "rust1", since = "1.0.0")]
1463 impl<K, V> ExactSizeIterator for IterMut<'_, K, V> {
1464 fn len(&self) -> usize {
1469 #[stable(feature = "fused", since = "1.26.0")]
1470 impl<K, V> FusedIterator for IterMut<'_, K, V> {}
1472 #[stable(feature = "rust1", since = "1.0.0")]
1473 impl<K, V> IntoIterator for BTreeMap<K, V> {
1475 type IntoIter = IntoIter<K, V>;
1477 fn into_iter(self) -> IntoIter<K, V> {
1478 let mut me = ManuallyDrop::new(self);
1479 if let Some(root) = me.root.take() {
1480 let (f, b) = root.into_ref().full_range();
1482 IntoIter { front: Some(f), back: Some(b), length: me.length }
1484 IntoIter { front: None, back: None, length: 0 }
1489 #[stable(feature = "btree_drop", since = "1.7.0")]
1490 impl<K, V> Drop for IntoIter<K, V> {
1491 fn drop(&mut self) {
1492 struct DropGuard<'a, K, V>(&'a mut IntoIter<K, V>);
1494 impl<'a, K, V> Drop for DropGuard<'a, K, V> {
1495 fn drop(&mut self) {
1496 // Continue the same loop we perform below. This only runs when unwinding, so we
1497 // don't have to care about panics this time (they'll abort).
1498 while let Some(_) = self.0.next() {}
1502 unwrap_unchecked(ptr::read(&self.0.front)).into_node().forget_type();
1503 while let Some(parent) = node.deallocate_and_ascend() {
1504 node = parent.into_node().forget_type();
1510 while let Some(pair) = self.next() {
1511 let guard = DropGuard(self);
1517 if let Some(front) = ptr::read(&self.front) {
1518 let mut node = front.into_node().forget_type();
1519 // Most of the nodes have been deallocated while traversing
1520 // but one pile from a leaf up to the root is left standing.
1521 while let Some(parent) = node.deallocate_and_ascend() {
1522 node = parent.into_node().forget_type();
1529 #[stable(feature = "rust1", since = "1.0.0")]
1530 impl<K, V> Iterator for IntoIter<K, V> {
1533 fn next(&mut self) -> Option<(K, V)> {
1534 if self.length == 0 {
1538 Some(unsafe { self.front.as_mut().unwrap().next_unchecked() })
1542 fn size_hint(&self) -> (usize, Option<usize>) {
1543 (self.length, Some(self.length))
1547 #[stable(feature = "rust1", since = "1.0.0")]
1548 impl<K, V> DoubleEndedIterator for IntoIter<K, V> {
1549 fn next_back(&mut self) -> Option<(K, V)> {
1550 if self.length == 0 {
1554 Some(unsafe { self.back.as_mut().unwrap().next_back_unchecked() })
1559 #[stable(feature = "rust1", since = "1.0.0")]
1560 impl<K, V> ExactSizeIterator for IntoIter<K, V> {
1561 fn len(&self) -> usize {
1566 #[stable(feature = "fused", since = "1.26.0")]
1567 impl<K, V> FusedIterator for IntoIter<K, V> {}
1569 #[stable(feature = "rust1", since = "1.0.0")]
1570 impl<'a, K, V> Iterator for Keys<'a, K, V> {
1573 fn next(&mut self) -> Option<&'a K> {
1574 self.inner.next().map(|(k, _)| k)
1577 fn size_hint(&self) -> (usize, Option<usize>) {
1578 self.inner.size_hint()
1581 fn last(mut self) -> Option<&'a K> {
1585 fn min(mut self) -> Option<&'a K> {
1589 fn max(mut self) -> Option<&'a K> {
1594 #[stable(feature = "rust1", since = "1.0.0")]
1595 impl<'a, K, V> DoubleEndedIterator for Keys<'a, K, V> {
1596 fn next_back(&mut self) -> Option<&'a K> {
1597 self.inner.next_back().map(|(k, _)| k)
1601 #[stable(feature = "rust1", since = "1.0.0")]
1602 impl<K, V> ExactSizeIterator for Keys<'_, K, V> {
1603 fn len(&self) -> usize {
1608 #[stable(feature = "fused", since = "1.26.0")]
1609 impl<K, V> FusedIterator for Keys<'_, K, V> {}
1611 #[stable(feature = "rust1", since = "1.0.0")]
1612 impl<K, V> Clone for Keys<'_, K, V> {
1613 fn clone(&self) -> Self {
1614 Keys { inner: self.inner.clone() }
1618 #[stable(feature = "rust1", since = "1.0.0")]
1619 impl<'a, K, V> Iterator for Values<'a, K, V> {
1622 fn next(&mut self) -> Option<&'a V> {
1623 self.inner.next().map(|(_, v)| v)
1626 fn size_hint(&self) -> (usize, Option<usize>) {
1627 self.inner.size_hint()
1630 fn last(mut self) -> Option<&'a V> {
1635 #[stable(feature = "rust1", since = "1.0.0")]
1636 impl<'a, K, V> DoubleEndedIterator for Values<'a, K, V> {
1637 fn next_back(&mut self) -> Option<&'a V> {
1638 self.inner.next_back().map(|(_, v)| v)
1642 #[stable(feature = "rust1", since = "1.0.0")]
1643 impl<K, V> ExactSizeIterator for Values<'_, K, V> {
1644 fn len(&self) -> usize {
1649 #[stable(feature = "fused", since = "1.26.0")]
1650 impl<K, V> FusedIterator for Values<'_, K, V> {}
1652 #[stable(feature = "rust1", since = "1.0.0")]
1653 impl<K, V> Clone for Values<'_, K, V> {
1654 fn clone(&self) -> Self {
1655 Values { inner: self.inner.clone() }
1659 /// An iterator produced by calling `drain_filter` on BTreeMap.
1660 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1661 pub struct DrainFilter<'a, K, V, F>
1665 F: 'a + FnMut(&K, &mut V) -> bool,
1668 inner: DrainFilterInner<'a, K, V>,
1670 /// Most of the implementation of DrainFilter, independent of the type
1671 /// of the predicate, thus also serving for BTreeSet::DrainFilter.
1672 pub(super) struct DrainFilterInner<'a, K: 'a, V: 'a> {
1673 length: &'a mut usize,
1674 // dormant_root is wrapped in an Option to be able to `take` it.
1675 dormant_root: Option<DormantMutRef<'a, node::Root<K, V>>>,
1676 // cur_leaf_edge is wrapped in an Option because maps without root lack a leaf edge.
1677 cur_leaf_edge: Option<Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>>,
1680 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1681 impl<K, V, F> Drop for DrainFilter<'_, K, V, F>
1683 F: FnMut(&K, &mut V) -> bool,
1685 fn drop(&mut self) {
1686 self.for_each(drop);
1690 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1691 impl<K, V, F> fmt::Debug for DrainFilter<'_, K, V, F>
1695 F: FnMut(&K, &mut V) -> bool,
1697 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1698 f.debug_tuple("DrainFilter").field(&self.inner.peek()).finish()
1702 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1703 impl<K, V, F> Iterator for DrainFilter<'_, K, V, F>
1705 F: FnMut(&K, &mut V) -> bool,
1709 fn next(&mut self) -> Option<(K, V)> {
1710 self.inner.next(&mut self.pred)
1713 fn size_hint(&self) -> (usize, Option<usize>) {
1714 self.inner.size_hint()
1718 impl<'a, K: 'a, V: 'a> DrainFilterInner<'a, K, V> {
1719 /// Allow Debug implementations to predict the next element.
1720 pub(super) fn peek(&self) -> Option<(&K, &V)> {
1721 let edge = self.cur_leaf_edge.as_ref()?;
1722 edge.reborrow().next_kv().ok().map(|kv| kv.into_kv())
1725 /// Implementation of a typical `DrainFilter::next` method, given the predicate.
1726 pub(super) fn next<F>(&mut self, pred: &mut F) -> Option<(K, V)>
1728 F: FnMut(&K, &mut V) -> bool,
1730 while let Ok(mut kv) = self.cur_leaf_edge.take()?.next_kv() {
1731 let (k, v) = kv.kv_mut();
1734 let (kv, pos) = kv.remove_kv_tracking(|| {
1735 // SAFETY: we will touch the root in a way that will not
1736 // invalidate the position returned.
1737 let root = unsafe { self.dormant_root.take().unwrap().awaken() };
1738 root.pop_internal_level();
1739 self.dormant_root = Some(DormantMutRef::new(root).1);
1741 self.cur_leaf_edge = Some(pos);
1744 self.cur_leaf_edge = Some(kv.next_leaf_edge());
1749 /// Implementation of a typical `DrainFilter::size_hint` method.
1750 pub(super) fn size_hint(&self) -> (usize, Option<usize>) {
1751 (0, Some(*self.length))
1755 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1756 impl<K, V, F> FusedIterator for DrainFilter<'_, K, V, F> where F: FnMut(&K, &mut V) -> bool {}
1758 #[stable(feature = "btree_range", since = "1.17.0")]
1759 impl<'a, K, V> Iterator for Range<'a, K, V> {
1760 type Item = (&'a K, &'a V);
1762 fn next(&mut self) -> Option<(&'a K, &'a V)> {
1763 if self.is_empty() { None } else { unsafe { Some(self.next_unchecked()) } }
1766 fn last(mut self) -> Option<(&'a K, &'a V)> {
1770 fn min(mut self) -> Option<(&'a K, &'a V)> {
1774 fn max(mut self) -> Option<(&'a K, &'a V)> {
1779 #[stable(feature = "map_values_mut", since = "1.10.0")]
1780 impl<'a, K, V> Iterator for ValuesMut<'a, K, V> {
1781 type Item = &'a mut V;
1783 fn next(&mut self) -> Option<&'a mut V> {
1784 self.inner.next().map(|(_, v)| v)
1787 fn size_hint(&self) -> (usize, Option<usize>) {
1788 self.inner.size_hint()
1791 fn last(mut self) -> Option<&'a mut V> {
1796 #[stable(feature = "map_values_mut", since = "1.10.0")]
1797 impl<'a, K, V> DoubleEndedIterator for ValuesMut<'a, K, V> {
1798 fn next_back(&mut self) -> Option<&'a mut V> {
1799 self.inner.next_back().map(|(_, v)| v)
1803 #[stable(feature = "map_values_mut", since = "1.10.0")]
1804 impl<K, V> ExactSizeIterator for ValuesMut<'_, K, V> {
1805 fn len(&self) -> usize {
1810 #[stable(feature = "fused", since = "1.26.0")]
1811 impl<K, V> FusedIterator for ValuesMut<'_, K, V> {}
1813 impl<'a, K, V> Range<'a, K, V> {
1814 fn is_empty(&self) -> bool {
1815 self.front == self.back
1818 unsafe fn next_unchecked(&mut self) -> (&'a K, &'a V) {
1819 unsafe { unwrap_unchecked(self.front.as_mut()).next_unchecked() }
1823 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1824 impl<K, V> Iterator for IntoKeys<K, V> {
1827 fn next(&mut self) -> Option<K> {
1828 self.inner.next().map(|(k, _)| k)
1831 fn size_hint(&self) -> (usize, Option<usize>) {
1832 self.inner.size_hint()
1835 fn last(mut self) -> Option<K> {
1839 fn min(mut self) -> Option<K> {
1843 fn max(mut self) -> Option<K> {
1848 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1849 impl<K, V> DoubleEndedIterator for IntoKeys<K, V> {
1850 fn next_back(&mut self) -> Option<K> {
1851 self.inner.next_back().map(|(k, _)| k)
1855 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1856 impl<K, V> ExactSizeIterator for IntoKeys<K, V> {
1857 fn len(&self) -> usize {
1862 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1863 impl<K, V> FusedIterator for IntoKeys<K, V> {}
1865 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1866 impl<K, V> Iterator for IntoValues<K, V> {
1869 fn next(&mut self) -> Option<V> {
1870 self.inner.next().map(|(_, v)| v)
1873 fn size_hint(&self) -> (usize, Option<usize>) {
1874 self.inner.size_hint()
1877 fn last(mut self) -> Option<V> {
1882 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1883 impl<K, V> DoubleEndedIterator for IntoValues<K, V> {
1884 fn next_back(&mut self) -> Option<V> {
1885 self.inner.next_back().map(|(_, v)| v)
1889 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1890 impl<K, V> ExactSizeIterator for IntoValues<K, V> {
1891 fn len(&self) -> usize {
1896 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1897 impl<K, V> FusedIterator for IntoValues<K, V> {}
1899 #[stable(feature = "btree_range", since = "1.17.0")]
1900 impl<'a, K, V> DoubleEndedIterator for Range<'a, K, V> {
1901 fn next_back(&mut self) -> Option<(&'a K, &'a V)> {
1902 if self.is_empty() { None } else { Some(unsafe { self.next_back_unchecked() }) }
1906 impl<'a, K, V> Range<'a, K, V> {
1907 unsafe fn next_back_unchecked(&mut self) -> (&'a K, &'a V) {
1908 unsafe { unwrap_unchecked(self.back.as_mut()).next_back_unchecked() }
1912 #[stable(feature = "fused", since = "1.26.0")]
1913 impl<K, V> FusedIterator for Range<'_, K, V> {}
1915 #[stable(feature = "btree_range", since = "1.17.0")]
1916 impl<K, V> Clone for Range<'_, K, V> {
1917 fn clone(&self) -> Self {
1918 Range { front: self.front, back: self.back }
1922 #[stable(feature = "btree_range", since = "1.17.0")]
1923 impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
1924 type Item = (&'a K, &'a mut V);
1926 fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
1927 if self.is_empty() {
1930 let (k, v) = unsafe { self.next_unchecked() };
1931 Some((k, v)) // coerce k from `&mut K` to `&K`
1935 fn last(mut self) -> Option<(&'a K, &'a mut V)> {
1939 fn min(mut self) -> Option<(&'a K, &'a mut V)> {
1943 fn max(mut self) -> Option<(&'a K, &'a mut V)> {
1948 impl<'a, K, V> RangeMut<'a, K, V> {
1949 fn is_empty(&self) -> bool {
1950 self.front == self.back
1953 unsafe fn next_unchecked(&mut self) -> (&'a K, &'a mut V) {
1954 unsafe { unwrap_unchecked(self.front.as_mut()).next_unchecked() }
1958 #[stable(feature = "btree_range", since = "1.17.0")]
1959 impl<'a, K, V> DoubleEndedIterator for RangeMut<'a, K, V> {
1960 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> {
1961 if self.is_empty() {
1964 let (k, v) = unsafe { self.next_back_unchecked() };
1965 Some((k, v)) // coerce k from `&mut K` to `&K`
1970 #[stable(feature = "fused", since = "1.26.0")]
1971 impl<K, V> FusedIterator for RangeMut<'_, K, V> {}
1973 impl<'a, K, V> RangeMut<'a, K, V> {
1974 unsafe fn next_back_unchecked(&mut self) -> (&'a K, &'a mut V) {
1975 unsafe { unwrap_unchecked(self.back.as_mut()).next_back_unchecked() }
1979 #[stable(feature = "rust1", since = "1.0.0")]
1980 impl<K: Ord, V> FromIterator<(K, V)> for BTreeMap<K, V> {
1981 fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> BTreeMap<K, V> {
1982 let mut map = BTreeMap::new();
1988 #[stable(feature = "rust1", since = "1.0.0")]
1989 impl<K: Ord, V> Extend<(K, V)> for BTreeMap<K, V> {
1991 fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T) {
1992 iter.into_iter().for_each(move |(k, v)| {
1998 fn extend_one(&mut self, (k, v): (K, V)) {
2003 #[stable(feature = "extend_ref", since = "1.2.0")]
2004 impl<'a, K: Ord + Copy, V: Copy> Extend<(&'a K, &'a V)> for BTreeMap<K, V> {
2005 fn extend<I: IntoIterator<Item = (&'a K, &'a V)>>(&mut self, iter: I) {
2006 self.extend(iter.into_iter().map(|(&key, &value)| (key, value)));
2010 fn extend_one(&mut self, (&k, &v): (&'a K, &'a V)) {
2015 #[stable(feature = "rust1", since = "1.0.0")]
2016 impl<K: Hash, V: Hash> Hash for BTreeMap<K, V> {
2017 fn hash<H: Hasher>(&self, state: &mut H) {
2024 #[stable(feature = "rust1", since = "1.0.0")]
2025 impl<K: Ord, V> Default for BTreeMap<K, V> {
2026 /// Creates an empty `BTreeMap<K, V>`.
2027 fn default() -> BTreeMap<K, V> {
2032 #[stable(feature = "rust1", since = "1.0.0")]
2033 impl<K: PartialEq, V: PartialEq> PartialEq for BTreeMap<K, V> {
2034 fn eq(&self, other: &BTreeMap<K, V>) -> bool {
2035 self.len() == other.len() && self.iter().zip(other).all(|(a, b)| a == b)
2039 #[stable(feature = "rust1", since = "1.0.0")]
2040 impl<K: Eq, V: Eq> Eq for BTreeMap<K, V> {}
2042 #[stable(feature = "rust1", since = "1.0.0")]
2043 impl<K: PartialOrd, V: PartialOrd> PartialOrd for BTreeMap<K, V> {
2045 fn partial_cmp(&self, other: &BTreeMap<K, V>) -> Option<Ordering> {
2046 self.iter().partial_cmp(other.iter())
2050 #[stable(feature = "rust1", since = "1.0.0")]
2051 impl<K: Ord, V: Ord> Ord for BTreeMap<K, V> {
2053 fn cmp(&self, other: &BTreeMap<K, V>) -> Ordering {
2054 self.iter().cmp(other.iter())
2058 #[stable(feature = "rust1", since = "1.0.0")]
2059 impl<K: Debug, V: Debug> Debug for BTreeMap<K, V> {
2060 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2061 f.debug_map().entries(self.iter()).finish()
2065 #[stable(feature = "rust1", since = "1.0.0")]
2066 impl<K: Ord, Q: ?Sized, V> Index<&Q> for BTreeMap<K, V>
2073 /// Returns a reference to the value corresponding to the supplied key.
2077 /// Panics if the key is not present in the `BTreeMap`.
2079 fn index(&self, key: &Q) -> &V {
2080 self.get(key).expect("no entry found for key")
2084 impl<K, V> BTreeMap<K, V> {
2085 /// Gets an iterator over the entries of the map, sorted by key.
2092 /// use std::collections::BTreeMap;
2094 /// let mut map = BTreeMap::new();
2095 /// map.insert(3, "c");
2096 /// map.insert(2, "b");
2097 /// map.insert(1, "a");
2099 /// for (key, value) in map.iter() {
2100 /// println!("{}: {}", key, value);
2103 /// let (first_key, first_value) = map.iter().next().unwrap();
2104 /// assert_eq!((*first_key, *first_value), (1, "a"));
2106 #[stable(feature = "rust1", since = "1.0.0")]
2107 pub fn iter(&self) -> Iter<'_, K, V> {
2108 if let Some(root) = &self.root {
2109 let (f, b) = root.node_as_ref().full_range();
2111 Iter { range: Range { front: Some(f), back: Some(b) }, length: self.length }
2113 Iter { range: Range { front: None, back: None }, length: 0 }
2117 /// Gets a mutable iterator over the entries of the map, sorted by key.
2124 /// use std::collections::BTreeMap;
2126 /// let mut map = BTreeMap::new();
2127 /// map.insert("a", 1);
2128 /// map.insert("b", 2);
2129 /// map.insert("c", 3);
2131 /// // add 10 to the value if the key isn't "a"
2132 /// for (key, value) in map.iter_mut() {
2133 /// if key != &"a" {
2138 #[stable(feature = "rust1", since = "1.0.0")]
2139 pub fn iter_mut(&mut self) -> IterMut<'_, K, V> {
2140 if let Some(root) = &mut self.root {
2141 let (f, b) = root.node_as_valmut().full_range();
2144 range: RangeMut { front: Some(f), back: Some(b), _marker: PhantomData },
2145 length: self.length,
2148 IterMut { range: RangeMut { front: None, back: None, _marker: PhantomData }, length: 0 }
2152 /// Gets an iterator over the keys of the map, in sorted order.
2159 /// use std::collections::BTreeMap;
2161 /// let mut a = BTreeMap::new();
2162 /// a.insert(2, "b");
2163 /// a.insert(1, "a");
2165 /// let keys: Vec<_> = a.keys().cloned().collect();
2166 /// assert_eq!(keys, [1, 2]);
2168 #[stable(feature = "rust1", since = "1.0.0")]
2169 pub fn keys(&self) -> Keys<'_, K, V> {
2170 Keys { inner: self.iter() }
2173 /// Gets an iterator over the values of the map, in order by key.
2180 /// use std::collections::BTreeMap;
2182 /// let mut a = BTreeMap::new();
2183 /// a.insert(1, "hello");
2184 /// a.insert(2, "goodbye");
2186 /// let values: Vec<&str> = a.values().cloned().collect();
2187 /// assert_eq!(values, ["hello", "goodbye"]);
2189 #[stable(feature = "rust1", since = "1.0.0")]
2190 pub fn values(&self) -> Values<'_, K, V> {
2191 Values { inner: self.iter() }
2194 /// Gets a mutable iterator over the values of the map, in order by key.
2201 /// use std::collections::BTreeMap;
2203 /// let mut a = BTreeMap::new();
2204 /// a.insert(1, String::from("hello"));
2205 /// a.insert(2, String::from("goodbye"));
2207 /// for value in a.values_mut() {
2208 /// value.push_str("!");
2211 /// let values: Vec<String> = a.values().cloned().collect();
2212 /// assert_eq!(values, [String::from("hello!"),
2213 /// String::from("goodbye!")]);
2215 #[stable(feature = "map_values_mut", since = "1.10.0")]
2216 pub fn values_mut(&mut self) -> ValuesMut<'_, K, V> {
2217 ValuesMut { inner: self.iter_mut() }
2220 /// Returns the number of elements in the map.
2227 /// use std::collections::BTreeMap;
2229 /// let mut a = BTreeMap::new();
2230 /// assert_eq!(a.len(), 0);
2231 /// a.insert(1, "a");
2232 /// assert_eq!(a.len(), 1);
2234 #[stable(feature = "rust1", since = "1.0.0")]
2235 pub fn len(&self) -> usize {
2239 /// Returns `true` if the map contains no elements.
2246 /// use std::collections::BTreeMap;
2248 /// let mut a = BTreeMap::new();
2249 /// assert!(a.is_empty());
2250 /// a.insert(1, "a");
2251 /// assert!(!a.is_empty());
2253 #[stable(feature = "rust1", since = "1.0.0")]
2254 pub fn is_empty(&self) -> bool {
2258 /// If the root node is the empty (non-allocated) root node, allocate our
2259 /// own node. Is an associated function to avoid borrowing the entire BTreeMap.
2260 fn ensure_is_owned(root: &mut Option<node::Root<K, V>>) -> &mut node::Root<K, V> {
2261 root.get_or_insert_with(node::Root::new_leaf)
2265 impl<'a, K: Ord, V> Entry<'a, K, V> {
2266 /// Ensures a value is in the entry by inserting the default if empty, and returns
2267 /// a mutable reference to the value in the entry.
2272 /// use std::collections::BTreeMap;
2274 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2275 /// map.entry("poneyland").or_insert(12);
2277 /// assert_eq!(map["poneyland"], 12);
2279 #[stable(feature = "rust1", since = "1.0.0")]
2280 pub fn or_insert(self, default: V) -> &'a mut V {
2282 Occupied(entry) => entry.into_mut(),
2283 Vacant(entry) => entry.insert(default),
2287 /// Ensures a value is in the entry by inserting the result of the default function if empty,
2288 /// and returns a mutable reference to the value in the entry.
2293 /// use std::collections::BTreeMap;
2295 /// let mut map: BTreeMap<&str, String> = BTreeMap::new();
2296 /// let s = "hoho".to_string();
2298 /// map.entry("poneyland").or_insert_with(|| s);
2300 /// assert_eq!(map["poneyland"], "hoho".to_string());
2302 #[stable(feature = "rust1", since = "1.0.0")]
2303 pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V {
2305 Occupied(entry) => entry.into_mut(),
2306 Vacant(entry) => entry.insert(default()),
2310 #[unstable(feature = "or_insert_with_key", issue = "71024")]
2311 /// Ensures a value is in the entry by inserting, if empty, the result of the default function,
2312 /// which takes the key as its argument, and returns a mutable reference to the value in the
2318 /// #![feature(or_insert_with_key)]
2319 /// use std::collections::BTreeMap;
2321 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2323 /// map.entry("poneyland").or_insert_with_key(|key| key.chars().count());
2325 /// assert_eq!(map["poneyland"], 9);
2328 pub fn or_insert_with_key<F: FnOnce(&K) -> V>(self, default: F) -> &'a mut V {
2330 Occupied(entry) => entry.into_mut(),
2332 let value = default(entry.key());
2338 /// Returns a reference to this entry's key.
2343 /// use std::collections::BTreeMap;
2345 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2346 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2348 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2349 pub fn key(&self) -> &K {
2351 Occupied(ref entry) => entry.key(),
2352 Vacant(ref entry) => entry.key(),
2356 /// Provides in-place mutable access to an occupied entry before any
2357 /// potential inserts into the map.
2362 /// use std::collections::BTreeMap;
2364 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2366 /// map.entry("poneyland")
2367 /// .and_modify(|e| { *e += 1 })
2369 /// assert_eq!(map["poneyland"], 42);
2371 /// map.entry("poneyland")
2372 /// .and_modify(|e| { *e += 1 })
2374 /// assert_eq!(map["poneyland"], 43);
2376 #[stable(feature = "entry_and_modify", since = "1.26.0")]
2377 pub fn and_modify<F>(self, f: F) -> Self
2382 Occupied(mut entry) => {
2386 Vacant(entry) => Vacant(entry),
2391 impl<'a, K: Ord, V: Default> Entry<'a, K, V> {
2392 #[stable(feature = "entry_or_default", since = "1.28.0")]
2393 /// Ensures a value is in the entry by inserting the default value if empty,
2394 /// and returns a mutable reference to the value in the entry.
2399 /// use std::collections::BTreeMap;
2401 /// let mut map: BTreeMap<&str, Option<usize>> = BTreeMap::new();
2402 /// map.entry("poneyland").or_default();
2404 /// assert_eq!(map["poneyland"], None);
2406 pub fn or_default(self) -> &'a mut V {
2408 Occupied(entry) => entry.into_mut(),
2409 Vacant(entry) => entry.insert(Default::default()),
2414 impl<'a, K: Ord, V> VacantEntry<'a, K, V> {
2415 /// Gets a reference to the key that would be used when inserting a value
2416 /// through the VacantEntry.
2421 /// use std::collections::BTreeMap;
2423 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2424 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2426 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2427 pub fn key(&self) -> &K {
2431 /// Take ownership of the key.
2436 /// use std::collections::BTreeMap;
2437 /// use std::collections::btree_map::Entry;
2439 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2441 /// if let Entry::Vacant(v) = map.entry("poneyland") {
2445 #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
2446 pub fn into_key(self) -> K {
2450 /// Sets the value of the entry with the `VacantEntry`'s key,
2451 /// and returns a mutable reference to it.
2456 /// use std::collections::BTreeMap;
2457 /// use std::collections::btree_map::Entry;
2459 /// let mut map: BTreeMap<&str, u32> = BTreeMap::new();
2461 /// if let Entry::Vacant(o) = map.entry("poneyland") {
2464 /// assert_eq!(map["poneyland"], 37);
2466 #[stable(feature = "rust1", since = "1.0.0")]
2467 pub fn insert(self, value: V) -> &'a mut V {
2468 let out_ptr = match self.handle.insert_recursing(self.key, value) {
2469 (Fit(_), val_ptr) => {
2470 // Safety: We have consumed self.handle and the handle returned.
2471 let map = unsafe { self.dormant_map.awaken() };
2475 (Split(ins), val_ptr) => {
2477 // Safety: We have consumed self.handle and the reference returned.
2478 let map = unsafe { self.dormant_map.awaken() };
2479 let root = map.root.as_mut().unwrap();
2480 root.push_internal_level().push(ins.k, ins.v, ins.right);
2485 // Now that we have finished growing the tree using borrowed references,
2486 // dereference the pointer to a part of it, that we picked up along the way.
2487 unsafe { &mut *out_ptr }
2491 impl<'a, K: Ord, V> OccupiedEntry<'a, K, V> {
2492 /// Gets a reference to the key in the entry.
2497 /// use std::collections::BTreeMap;
2499 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2500 /// map.entry("poneyland").or_insert(12);
2501 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2503 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2504 pub fn key(&self) -> &K {
2505 self.handle.reborrow().into_kv().0
2508 /// Take ownership of the key and value from the map.
2513 /// use std::collections::BTreeMap;
2514 /// use std::collections::btree_map::Entry;
2516 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2517 /// map.entry("poneyland").or_insert(12);
2519 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2520 /// // We delete the entry from the map.
2521 /// o.remove_entry();
2524 /// // If now try to get the value, it will panic:
2525 /// // println!("{}", map["poneyland"]);
2527 #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
2528 pub fn remove_entry(self) -> (K, V) {
2532 /// Gets a reference to the value in the entry.
2537 /// use std::collections::BTreeMap;
2538 /// use std::collections::btree_map::Entry;
2540 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2541 /// map.entry("poneyland").or_insert(12);
2543 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2544 /// assert_eq!(o.get(), &12);
2547 #[stable(feature = "rust1", since = "1.0.0")]
2548 pub fn get(&self) -> &V {
2549 self.handle.reborrow().into_kv().1
2552 /// Gets a mutable reference to the value in the entry.
2554 /// If you need a reference to the `OccupiedEntry` that may outlive the
2555 /// destruction of the `Entry` value, see [`into_mut`].
2557 /// [`into_mut`]: #method.into_mut
2562 /// use std::collections::BTreeMap;
2563 /// use std::collections::btree_map::Entry;
2565 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2566 /// map.entry("poneyland").or_insert(12);
2568 /// assert_eq!(map["poneyland"], 12);
2569 /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
2570 /// *o.get_mut() += 10;
2571 /// assert_eq!(*o.get(), 22);
2573 /// // We can use the same Entry multiple times.
2574 /// *o.get_mut() += 2;
2576 /// assert_eq!(map["poneyland"], 24);
2578 #[stable(feature = "rust1", since = "1.0.0")]
2579 pub fn get_mut(&mut self) -> &mut V {
2580 self.handle.kv_mut().1
2583 /// Converts the entry into a mutable reference to its value.
2585 /// If you need multiple references to the `OccupiedEntry`, see [`get_mut`].
2587 /// [`get_mut`]: #method.get_mut
2592 /// use std::collections::BTreeMap;
2593 /// use std::collections::btree_map::Entry;
2595 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2596 /// map.entry("poneyland").or_insert(12);
2598 /// assert_eq!(map["poneyland"], 12);
2599 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2600 /// *o.into_mut() += 10;
2602 /// assert_eq!(map["poneyland"], 22);
2604 #[stable(feature = "rust1", since = "1.0.0")]
2605 pub fn into_mut(self) -> &'a mut V {
2606 self.handle.into_val_mut()
2609 /// Sets the value of the entry with the `OccupiedEntry`'s key,
2610 /// and returns the entry's old value.
2615 /// use std::collections::BTreeMap;
2616 /// use std::collections::btree_map::Entry;
2618 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2619 /// map.entry("poneyland").or_insert(12);
2621 /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
2622 /// assert_eq!(o.insert(15), 12);
2624 /// assert_eq!(map["poneyland"], 15);
2626 #[stable(feature = "rust1", since = "1.0.0")]
2627 pub fn insert(&mut self, value: V) -> V {
2628 mem::replace(self.get_mut(), value)
2631 /// Takes the value of the entry out of the map, and returns it.
2636 /// use std::collections::BTreeMap;
2637 /// use std::collections::btree_map::Entry;
2639 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2640 /// map.entry("poneyland").or_insert(12);
2642 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2643 /// assert_eq!(o.remove(), 12);
2645 /// // If we try to get "poneyland"'s value, it'll panic:
2646 /// // println!("{}", map["poneyland"]);
2648 #[stable(feature = "rust1", since = "1.0.0")]
2649 pub fn remove(self) -> V {
2653 // Body of `remove_entry`, separate to keep the above implementations short.
2654 fn remove_kv(self) -> (K, V) {
2655 let mut emptied_internal_root = false;
2656 let (old_kv, _) = self.handle.remove_kv_tracking(|| emptied_internal_root = true);
2657 // SAFETY: we consumed the intermediate root borrow, `self.handle`.
2658 let map = unsafe { self.dormant_map.awaken() };
2660 if emptied_internal_root {
2661 let root = map.root.as_mut().unwrap();
2662 root.pop_internal_level();
2668 impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, marker::KV> {
2669 /// Removes a key/value-pair from the map, and returns that pair, as well as
2670 /// the leaf edge corresponding to that former pair.
2671 fn remove_kv_tracking<F: FnOnce()>(
2673 handle_emptied_internal_root: F,
2674 ) -> ((K, V), Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>) {
2675 let (old_kv, mut pos, was_internal) = match self.force() {
2677 let (old_kv, pos) = leaf.remove();
2678 (old_kv, pos, false)
2680 Internal(mut internal) => {
2681 // Replace the location freed in the internal node with an
2682 // adjacent KV, and remove that adjacent KV from its leaf.
2683 // Always choose the adjacent KV on the left side because
2684 // it is typically faster to pop an element from the end
2685 // of the KV arrays without needing to shift other elements.
2687 let key_loc = internal.kv_mut().0 as *mut K;
2688 let val_loc = internal.kv_mut().1 as *mut V;
2690 let to_remove = internal.left_edge().descend().last_leaf_edge().left_kv().ok();
2691 let to_remove = unsafe { unwrap_unchecked(to_remove) };
2693 let (kv, pos) = to_remove.remove();
2695 let old_key = unsafe { mem::replace(&mut *key_loc, kv.0) };
2696 let old_val = unsafe { mem::replace(&mut *val_loc, kv.1) };
2698 ((old_key, old_val), pos, true)
2703 let mut cur_node = unsafe { ptr::read(&pos).into_node().forget_type() };
2704 let mut at_leaf = true;
2705 while cur_node.len() < node::MIN_LEN {
2706 match handle_underfull_node(cur_node) {
2708 Merged(edge, merged_with_left, offset) => {
2709 // If we merged with our right sibling then our tracked
2710 // position has not changed. However if we merged with our
2711 // left sibling then our tracked position is now dangling.
2712 if at_leaf && merged_with_left {
2713 let idx = pos.idx() + offset;
2714 let node = match unsafe { ptr::read(&edge).descend().force() } {
2716 Internal(_) => unreachable!(),
2718 pos = unsafe { Handle::new_edge(node, idx) };
2721 let parent = edge.into_node();
2722 if parent.len() == 0 {
2723 // The parent that was just emptied must be the root,
2724 // because nodes on a lower level would not have been
2725 // left with a single child.
2726 handle_emptied_internal_root();
2729 cur_node = parent.forget_type();
2733 Stole(stole_from_left) => {
2734 // Adjust the tracked position if we stole from a left sibling
2735 if stole_from_left && at_leaf {
2736 // SAFETY: This is safe since we just added an element to our node.
2738 pos.move_next_unchecked();
2746 // If we deleted from an internal node then we need to compensate for
2747 // the earlier swap and adjust the tracked position to point to the
2750 pos = unsafe { unwrap_unchecked(pos.next_kv().ok()).next_leaf_edge() };
2757 impl<K, V> node::Root<K, V> {
2758 /// Removes empty levels on the top, but keep an empty leaf if the entire tree is empty.
2759 fn fix_top(&mut self) {
2760 while self.height() > 0 && self.node_as_ref().len() == 0 {
2761 self.pop_internal_level();
2765 fn fix_right_border(&mut self) {
2769 let mut cur_node = self.node_as_mut();
2771 while let Internal(node) = cur_node.force() {
2772 let mut last_kv = node.last_kv();
2774 if last_kv.can_merge() {
2775 cur_node = last_kv.merge().descend();
2777 let right_len = last_kv.reborrow().right_edge().descend().len();
2778 // `MINLEN + 1` to avoid readjust if merge happens on the next level.
2779 if right_len < node::MIN_LEN + 1 {
2780 last_kv.bulk_steal_left(node::MIN_LEN + 1 - right_len);
2782 cur_node = last_kv.right_edge().descend();
2790 /// The symmetric clone of `fix_right_border`.
2791 fn fix_left_border(&mut self) {
2795 let mut cur_node = self.node_as_mut();
2797 while let Internal(node) = cur_node.force() {
2798 let mut first_kv = node.first_kv();
2800 if first_kv.can_merge() {
2801 cur_node = first_kv.merge().descend();
2803 let left_len = first_kv.reborrow().left_edge().descend().len();
2804 if left_len < node::MIN_LEN + 1 {
2805 first_kv.bulk_steal_right(node::MIN_LEN + 1 - left_len);
2807 cur_node = first_kv.left_edge().descend();
2816 enum UnderflowResult<'a, K, V> {
2818 Merged(Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::Edge>, bool, usize),
2822 fn handle_underfull_node<'a, K: 'a, V: 'a>(
2823 node: NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>,
2824 ) -> UnderflowResult<'_, K, V> {
2825 let parent = match node.ascend() {
2826 Ok(parent) => parent,
2827 Err(_) => return AtRoot,
2830 // Prefer the left KV if it exists. Merging with the left side is faster,
2831 // since merging happens towards the left and `node` has fewer elements.
2832 // Stealing from the left side is faster, since we can pop from the end of
2834 let (is_left, mut handle) = match parent.left_kv() {
2835 Ok(left) => (true, left),
2837 let right = unsafe { unwrap_unchecked(parent.right_kv().ok()) };
2842 if handle.can_merge() {
2843 let offset = if is_left { handle.reborrow().left_edge().descend().len() + 1 } else { 0 };
2844 Merged(handle.merge(), is_left, offset)
2847 handle.steal_left();
2849 handle.steal_right();
2855 impl<K: Ord, V, I: Iterator<Item = (K, V)>> Iterator for MergeIter<K, V, I> {
2858 fn next(&mut self) -> Option<(K, V)> {
2859 let res = match (self.left.peek(), self.right.peek()) {
2860 (Some(&(ref left_key, _)), Some(&(ref right_key, _))) => left_key.cmp(right_key),
2861 (Some(_), None) => Ordering::Less,
2862 (None, Some(_)) => Ordering::Greater,
2863 (None, None) => return None,
2866 // Check which elements comes first and only advance the corresponding iterator.
2867 // If two keys are equal, take the value from `right`.
2869 Ordering::Less => self.left.next(),
2870 Ordering::Greater => self.right.next(),
2871 Ordering::Equal => {