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 /// [`Cell`]: core::cell::Cell
51 /// [`RefCell`]: core::cell::RefCell
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`], which allows for more complex
96 /// methods of getting, setting, updating and removing keys and their values:
98 /// [`Entry API`]: BTreeMap::entry
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.
456 #[stable(feature = "rust1", since = "1.0.0")]
457 pub struct VacantEntry<'a, K: 'a, V: 'a> {
459 handle: Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>,
460 dormant_map: DormantMutRef<'a, BTreeMap<K, V>>,
462 // Be invariant in `K` and `V`
463 _marker: PhantomData<&'a mut (K, V)>,
466 #[stable(feature = "debug_btree_map", since = "1.12.0")]
467 impl<K: Debug + Ord, V> Debug for VacantEntry<'_, K, V> {
468 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
469 f.debug_tuple("VacantEntry").field(self.key()).finish()
473 /// A view into an occupied entry in a `BTreeMap`.
474 /// It is part of the [`Entry`] enum.
475 #[stable(feature = "rust1", since = "1.0.0")]
476 pub struct OccupiedEntry<'a, K: 'a, V: 'a> {
477 handle: Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, marker::KV>,
478 dormant_map: DormantMutRef<'a, BTreeMap<K, V>>,
480 // Be invariant in `K` and `V`
481 _marker: PhantomData<&'a mut (K, V)>,
484 #[stable(feature = "debug_btree_map", since = "1.12.0")]
485 impl<K: Debug + Ord, V: Debug> Debug for OccupiedEntry<'_, K, V> {
486 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
487 f.debug_struct("OccupiedEntry").field("key", self.key()).field("value", self.get()).finish()
491 // An iterator for merging two sorted sequences into one
492 struct MergeIter<K, V, I: Iterator<Item = (K, V)>> {
497 impl<K: Ord, V> BTreeMap<K, V> {
498 /// Makes a new empty BTreeMap.
500 /// Does not allocate anything on its own.
507 /// use std::collections::BTreeMap;
509 /// let mut map = BTreeMap::new();
511 /// // entries can now be inserted into the empty map
512 /// map.insert(1, "a");
514 #[stable(feature = "rust1", since = "1.0.0")]
515 #[rustc_const_unstable(feature = "const_btree_new", issue = "71835")]
516 pub const fn new() -> BTreeMap<K, V> {
517 BTreeMap { root: None, length: 0 }
520 /// Clears the map, removing all elements.
527 /// use std::collections::BTreeMap;
529 /// let mut a = BTreeMap::new();
530 /// a.insert(1, "a");
532 /// assert!(a.is_empty());
534 #[stable(feature = "rust1", since = "1.0.0")]
535 pub fn clear(&mut self) {
536 *self = BTreeMap::new();
539 /// Returns a reference to the value corresponding to the key.
541 /// The key may be any borrowed form of the map's key type, but the ordering
542 /// on the borrowed form *must* match the ordering on the key type.
549 /// use std::collections::BTreeMap;
551 /// let mut map = BTreeMap::new();
552 /// map.insert(1, "a");
553 /// assert_eq!(map.get(&1), Some(&"a"));
554 /// assert_eq!(map.get(&2), None);
556 #[stable(feature = "rust1", since = "1.0.0")]
557 pub fn get<Q: ?Sized>(&self, key: &Q) -> Option<&V>
562 let root_node = self.root.as_ref()?.node_as_ref();
563 match search::search_tree(root_node, key) {
564 Found(handle) => Some(handle.into_kv().1),
569 /// Returns the key-value pair corresponding to the supplied key.
571 /// The supplied 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.
577 /// use std::collections::BTreeMap;
579 /// let mut map = BTreeMap::new();
580 /// map.insert(1, "a");
581 /// assert_eq!(map.get_key_value(&1), Some((&1, &"a")));
582 /// assert_eq!(map.get_key_value(&2), None);
584 #[stable(feature = "map_get_key_value", since = "1.40.0")]
585 pub fn get_key_value<Q: ?Sized>(&self, k: &Q) -> Option<(&K, &V)>
590 let root_node = self.root.as_ref()?.node_as_ref();
591 match search::search_tree(root_node, k) {
592 Found(handle) => Some(handle.into_kv()),
597 /// Returns the first key-value pair in the map.
598 /// The key in this pair is the minimum key in the map.
605 /// #![feature(map_first_last)]
606 /// use std::collections::BTreeMap;
608 /// let mut map = BTreeMap::new();
609 /// assert_eq!(map.first_key_value(), None);
610 /// map.insert(1, "b");
611 /// map.insert(2, "a");
612 /// assert_eq!(map.first_key_value(), Some((&1, &"b")));
614 #[unstable(feature = "map_first_last", issue = "62924")]
615 pub fn first_key_value(&self) -> Option<(&K, &V)> {
616 let root_node = self.root.as_ref()?.node_as_ref();
617 root_node.first_leaf_edge().right_kv().ok().map(Handle::into_kv)
620 /// Returns the first entry in the map for in-place manipulation.
621 /// The key of this entry is the minimum key in the map.
626 /// #![feature(map_first_last)]
627 /// use std::collections::BTreeMap;
629 /// let mut map = BTreeMap::new();
630 /// map.insert(1, "a");
631 /// map.insert(2, "b");
632 /// if let Some(mut entry) = map.first_entry() {
633 /// if *entry.key() > 0 {
634 /// entry.insert("first");
637 /// assert_eq!(*map.get(&1).unwrap(), "first");
638 /// assert_eq!(*map.get(&2).unwrap(), "b");
640 #[unstable(feature = "map_first_last", issue = "62924")]
641 pub fn first_entry(&mut self) -> Option<OccupiedEntry<'_, K, V>> {
642 let (map, dormant_map) = DormantMutRef::new(self);
643 let root_node = map.root.as_mut()?.node_as_mut();
644 let kv = root_node.first_leaf_edge().right_kv().ok()?;
645 Some(OccupiedEntry { handle: kv.forget_node_type(), dormant_map, _marker: PhantomData })
648 /// Removes and returns the first element in the map.
649 /// The key of this element is the minimum key that was in the map.
653 /// Draining elements in ascending order, while keeping a usable map each iteration.
656 /// #![feature(map_first_last)]
657 /// use std::collections::BTreeMap;
659 /// let mut map = BTreeMap::new();
660 /// map.insert(1, "a");
661 /// map.insert(2, "b");
662 /// while let Some((key, _val)) = map.pop_first() {
663 /// assert!(map.iter().all(|(k, _v)| *k > key));
665 /// assert!(map.is_empty());
667 #[unstable(feature = "map_first_last", issue = "62924")]
668 pub fn pop_first(&mut self) -> Option<(K, V)> {
669 self.first_entry().map(|entry| entry.remove_entry())
672 /// Returns the last key-value pair in the map.
673 /// The key in this pair is the maximum key in the map.
680 /// #![feature(map_first_last)]
681 /// use std::collections::BTreeMap;
683 /// let mut map = BTreeMap::new();
684 /// map.insert(1, "b");
685 /// map.insert(2, "a");
686 /// assert_eq!(map.last_key_value(), Some((&2, &"a")));
688 #[unstable(feature = "map_first_last", issue = "62924")]
689 pub fn last_key_value(&self) -> Option<(&K, &V)> {
690 let root_node = self.root.as_ref()?.node_as_ref();
691 root_node.last_leaf_edge().left_kv().ok().map(Handle::into_kv)
694 /// Returns the last entry in the map for in-place manipulation.
695 /// The key of this entry is the maximum key in the map.
700 /// #![feature(map_first_last)]
701 /// use std::collections::BTreeMap;
703 /// let mut map = BTreeMap::new();
704 /// map.insert(1, "a");
705 /// map.insert(2, "b");
706 /// if let Some(mut entry) = map.last_entry() {
707 /// if *entry.key() > 0 {
708 /// entry.insert("last");
711 /// assert_eq!(*map.get(&1).unwrap(), "a");
712 /// assert_eq!(*map.get(&2).unwrap(), "last");
714 #[unstable(feature = "map_first_last", issue = "62924")]
715 pub fn last_entry(&mut self) -> Option<OccupiedEntry<'_, K, V>> {
716 let (map, dormant_map) = DormantMutRef::new(self);
717 let root_node = map.root.as_mut()?.node_as_mut();
718 let kv = root_node.last_leaf_edge().left_kv().ok()?;
719 Some(OccupiedEntry { handle: kv.forget_node_type(), dormant_map, _marker: PhantomData })
722 /// Removes and returns the last element in the map.
723 /// The key of this element is the maximum key that was in the map.
727 /// Draining elements in descending order, while keeping a usable map each iteration.
730 /// #![feature(map_first_last)]
731 /// use std::collections::BTreeMap;
733 /// let mut map = BTreeMap::new();
734 /// map.insert(1, "a");
735 /// map.insert(2, "b");
736 /// while let Some((key, _val)) = map.pop_last() {
737 /// assert!(map.iter().all(|(k, _v)| *k < key));
739 /// assert!(map.is_empty());
741 #[unstable(feature = "map_first_last", issue = "62924")]
742 pub fn pop_last(&mut self) -> Option<(K, V)> {
743 self.last_entry().map(|entry| entry.remove_entry())
746 /// Returns `true` if the map contains a value for the specified key.
748 /// The key may be any borrowed form of the map's key type, but the ordering
749 /// on the borrowed form *must* match the ordering on the key type.
756 /// use std::collections::BTreeMap;
758 /// let mut map = BTreeMap::new();
759 /// map.insert(1, "a");
760 /// assert_eq!(map.contains_key(&1), true);
761 /// assert_eq!(map.contains_key(&2), false);
763 #[stable(feature = "rust1", since = "1.0.0")]
764 pub fn contains_key<Q: ?Sized>(&self, key: &Q) -> bool
769 self.get(key).is_some()
772 /// Returns a mutable reference to the value corresponding to the key.
774 /// The key may be any borrowed form of the map's key type, but the ordering
775 /// on the borrowed form *must* match the ordering on the key type.
782 /// use std::collections::BTreeMap;
784 /// let mut map = BTreeMap::new();
785 /// map.insert(1, "a");
786 /// if let Some(x) = map.get_mut(&1) {
789 /// assert_eq!(map[&1], "b");
791 // See `get` for implementation notes, this is basically a copy-paste with mut's added
792 #[stable(feature = "rust1", since = "1.0.0")]
793 pub fn get_mut<Q: ?Sized>(&mut self, key: &Q) -> Option<&mut V>
798 let root_node = self.root.as_mut()?.node_as_mut();
799 match search::search_tree(root_node, key) {
800 Found(handle) => Some(handle.into_val_mut()),
805 /// Inserts a key-value pair into the map.
807 /// If the map did not have this key present, `None` is returned.
809 /// If the map did have this key present, the value is updated, and the old
810 /// value is returned. The key is not updated, though; this matters for
811 /// types that can be `==` without being identical. See the [module-level
812 /// documentation] for more.
814 /// [module-level documentation]: crate::collections#insert-and-complex-keys
821 /// use std::collections::BTreeMap;
823 /// let mut map = BTreeMap::new();
824 /// assert_eq!(map.insert(37, "a"), None);
825 /// assert_eq!(map.is_empty(), false);
827 /// map.insert(37, "b");
828 /// assert_eq!(map.insert(37, "c"), Some("b"));
829 /// assert_eq!(map[&37], "c");
831 #[stable(feature = "rust1", since = "1.0.0")]
832 pub fn insert(&mut self, key: K, value: V) -> Option<V> {
833 match self.entry(key) {
834 Occupied(mut entry) => Some(entry.insert(value)),
842 /// Removes a key from the map, returning the value at the key if the key
843 /// was previously in the map.
845 /// The key may be any borrowed form of the map's key type, but the ordering
846 /// on the borrowed form *must* match the ordering on the key type.
853 /// use std::collections::BTreeMap;
855 /// let mut map = BTreeMap::new();
856 /// map.insert(1, "a");
857 /// assert_eq!(map.remove(&1), Some("a"));
858 /// assert_eq!(map.remove(&1), None);
860 #[stable(feature = "rust1", since = "1.0.0")]
861 pub fn remove<Q: ?Sized>(&mut self, key: &Q) -> Option<V>
866 self.remove_entry(key).map(|(_, v)| v)
869 /// Removes a key from the map, returning the stored key and value if the key
870 /// was previously in the map.
872 /// The key may be any borrowed form of the map's key type, but the ordering
873 /// on the borrowed form *must* match the ordering on the key type.
880 /// use std::collections::BTreeMap;
882 /// let mut map = BTreeMap::new();
883 /// map.insert(1, "a");
884 /// assert_eq!(map.remove_entry(&1), Some((1, "a")));
885 /// assert_eq!(map.remove_entry(&1), None);
887 #[stable(feature = "btreemap_remove_entry", since = "1.45.0")]
888 pub fn remove_entry<Q: ?Sized>(&mut self, key: &Q) -> Option<(K, V)>
893 let (map, dormant_map) = DormantMutRef::new(self);
894 let root_node = map.root.as_mut()?.node_as_mut();
895 match search::search_tree(root_node, key) {
897 Some(OccupiedEntry { handle, dormant_map, _marker: PhantomData }.remove_entry())
903 /// Moves all elements from `other` into `Self`, leaving `other` empty.
908 /// use std::collections::BTreeMap;
910 /// let mut a = BTreeMap::new();
911 /// a.insert(1, "a");
912 /// a.insert(2, "b");
913 /// a.insert(3, "c");
915 /// let mut b = BTreeMap::new();
916 /// b.insert(3, "d");
917 /// b.insert(4, "e");
918 /// b.insert(5, "f");
920 /// a.append(&mut b);
922 /// assert_eq!(a.len(), 5);
923 /// assert_eq!(b.len(), 0);
925 /// assert_eq!(a[&1], "a");
926 /// assert_eq!(a[&2], "b");
927 /// assert_eq!(a[&3], "d");
928 /// assert_eq!(a[&4], "e");
929 /// assert_eq!(a[&5], "f");
931 #[stable(feature = "btree_append", since = "1.11.0")]
932 pub fn append(&mut self, other: &mut Self) {
933 // Do we have to append anything at all?
934 if other.is_empty() {
938 // We can just swap `self` and `other` if `self` is empty.
940 mem::swap(self, other);
944 // First, we merge `self` and `other` into a sorted sequence in linear time.
945 let self_iter = mem::take(self).into_iter();
946 let other_iter = mem::take(other).into_iter();
947 let iter = MergeIter { left: self_iter.peekable(), right: other_iter.peekable() };
949 // Second, we build a tree from the sorted sequence in linear time.
950 self.from_sorted_iter(iter);
953 /// Constructs a double-ended iterator over a sub-range of elements in the map.
954 /// The simplest way is to use the range syntax `min..max`, thus `range(min..max)` will
955 /// yield elements from min (inclusive) to max (exclusive).
956 /// The range may also be entered as `(Bound<T>, Bound<T>)`, so for example
957 /// `range((Excluded(4), Included(10)))` will yield a left-exclusive, right-inclusive
958 /// range from 4 to 10.
962 /// Panics if range `start > end`.
963 /// Panics if range `start == end` and both bounds are `Excluded`.
970 /// use std::collections::BTreeMap;
971 /// use std::ops::Bound::Included;
973 /// let mut map = BTreeMap::new();
974 /// map.insert(3, "a");
975 /// map.insert(5, "b");
976 /// map.insert(8, "c");
977 /// for (&key, &value) in map.range((Included(&4), Included(&8))) {
978 /// println!("{}: {}", key, value);
980 /// assert_eq!(Some((&5, &"b")), map.range(4..).next());
982 #[stable(feature = "btree_range", since = "1.17.0")]
983 pub fn range<T: ?Sized, R>(&self, range: R) -> Range<'_, K, V>
989 if let Some(root) = &self.root {
990 let (f, b) = root.node_as_ref().range_search(range);
992 Range { front: Some(f), back: Some(b) }
994 Range { front: None, back: None }
998 /// Constructs a mutable double-ended iterator over a sub-range of elements in the map.
999 /// The simplest way is to use the range syntax `min..max`, thus `range(min..max)` will
1000 /// yield elements from min (inclusive) to max (exclusive).
1001 /// The range may also be entered as `(Bound<T>, Bound<T>)`, so for example
1002 /// `range((Excluded(4), Included(10)))` will yield a left-exclusive, right-inclusive
1003 /// range from 4 to 10.
1007 /// Panics if range `start > end`.
1008 /// Panics if range `start == end` and both bounds are `Excluded`.
1015 /// use std::collections::BTreeMap;
1017 /// let mut map: BTreeMap<&str, i32> = ["Alice", "Bob", "Carol", "Cheryl"]
1019 /// .map(|&s| (s, 0))
1021 /// for (_, balance) in map.range_mut("B".."Cheryl") {
1022 /// *balance += 100;
1024 /// for (name, balance) in &map {
1025 /// println!("{} => {}", name, balance);
1028 #[stable(feature = "btree_range", since = "1.17.0")]
1029 pub fn range_mut<T: ?Sized, R>(&mut self, range: R) -> RangeMut<'_, K, V>
1035 if let Some(root) = &mut self.root {
1036 let (f, b) = root.node_as_valmut().range_search(range);
1038 RangeMut { front: Some(f), back: Some(b), _marker: PhantomData }
1040 RangeMut { front: None, back: None, _marker: PhantomData }
1044 /// Gets the given key's corresponding entry in the map for in-place manipulation.
1051 /// use std::collections::BTreeMap;
1053 /// let mut count: BTreeMap<&str, usize> = BTreeMap::new();
1055 /// // count the number of occurrences of letters in the vec
1056 /// for x in vec!["a","b","a","c","a","b"] {
1057 /// *count.entry(x).or_insert(0) += 1;
1060 /// assert_eq!(count["a"], 3);
1062 #[stable(feature = "rust1", since = "1.0.0")]
1063 pub fn entry(&mut self, key: K) -> Entry<'_, K, V> {
1064 // FIXME(@porglezomp) Avoid allocating if we don't insert
1065 let (map, dormant_map) = DormantMutRef::new(self);
1066 let root_node = Self::ensure_is_owned(&mut map.root).node_as_mut();
1067 match search::search_tree(root_node, &key) {
1068 Found(handle) => Occupied(OccupiedEntry { handle, dormant_map, _marker: PhantomData }),
1070 Vacant(VacantEntry { key, handle, dormant_map, _marker: PhantomData })
1075 fn from_sorted_iter<I: Iterator<Item = (K, V)>>(&mut self, iter: I) {
1076 let root = Self::ensure_is_owned(&mut self.root);
1077 let mut cur_node = root.node_as_mut().last_leaf_edge().into_node();
1078 // Iterate through all key-value pairs, pushing them into nodes at the right level.
1079 for (key, value) in iter {
1080 // Try to push key-value pair into the current leaf node.
1081 if cur_node.len() < node::CAPACITY {
1082 cur_node.push(key, value);
1084 // No space left, go up and push there.
1086 let mut test_node = cur_node.forget_type();
1088 match test_node.ascend() {
1090 let parent = parent.into_node();
1091 if parent.len() < node::CAPACITY {
1092 // Found a node with space left, push here.
1097 test_node = parent.forget_type();
1101 // We are at the top, create a new root node and push there.
1102 open_node = root.push_internal_level();
1108 // Push key-value pair and new right subtree.
1109 let tree_height = open_node.height() - 1;
1110 let mut right_tree = node::Root::new_leaf();
1111 for _ in 0..tree_height {
1112 right_tree.push_internal_level();
1114 open_node.push(key, value, right_tree);
1116 // Go down to the right-most leaf again.
1117 cur_node = open_node.forget_type().last_leaf_edge().into_node();
1122 Self::fix_right_edge(root)
1125 fn fix_right_edge(root: &mut node::Root<K, V>) {
1126 // Handle underfull nodes, start from the top.
1127 let mut cur_node = root.node_as_mut();
1128 while let Internal(internal) = cur_node.force() {
1129 // Check if right-most child is underfull.
1130 let mut last_edge = internal.last_edge();
1131 let right_child_len = last_edge.reborrow().descend().len();
1132 if right_child_len < node::MIN_LEN {
1133 // We need to steal.
1134 let mut last_kv = match last_edge.left_kv() {
1136 Err(_) => unreachable!(),
1138 last_kv.bulk_steal_left(node::MIN_LEN - right_child_len);
1139 last_edge = last_kv.right_edge();
1143 cur_node = last_edge.descend();
1147 /// Splits the collection into two at the given key. Returns everything after the given key,
1148 /// including the key.
1155 /// use std::collections::BTreeMap;
1157 /// let mut a = BTreeMap::new();
1158 /// a.insert(1, "a");
1159 /// a.insert(2, "b");
1160 /// a.insert(3, "c");
1161 /// a.insert(17, "d");
1162 /// a.insert(41, "e");
1164 /// let b = a.split_off(&3);
1166 /// assert_eq!(a.len(), 2);
1167 /// assert_eq!(b.len(), 3);
1169 /// assert_eq!(a[&1], "a");
1170 /// assert_eq!(a[&2], "b");
1172 /// assert_eq!(b[&3], "c");
1173 /// assert_eq!(b[&17], "d");
1174 /// assert_eq!(b[&41], "e");
1176 #[stable(feature = "btree_split_off", since = "1.11.0")]
1177 pub fn split_off<Q: ?Sized + Ord>(&mut self, key: &Q) -> Self
1181 if self.is_empty() {
1185 let total_num = self.len();
1186 let left_root = self.root.as_mut().unwrap(); // unwrap succeeds because not empty
1188 let mut right = Self::new();
1189 let right_root = Self::ensure_is_owned(&mut right.root);
1190 for _ in 0..left_root.height() {
1191 right_root.push_internal_level();
1195 let mut left_node = left_root.node_as_mut();
1196 let mut right_node = right_root.node_as_mut();
1199 let mut split_edge = match search::search_node(left_node, key) {
1200 // key is going to the right tree
1201 Found(handle) => handle.left_edge(),
1202 GoDown(handle) => handle,
1205 split_edge.move_suffix(&mut right_node);
1207 match (split_edge.force(), right_node.force()) {
1208 (Internal(edge), Internal(node)) => {
1209 left_node = edge.descend();
1210 right_node = node.first_edge().descend();
1212 (Leaf(_), Leaf(_)) => {
1222 left_root.fix_right_border();
1223 right_root.fix_left_border();
1225 if left_root.height() < right_root.height() {
1226 self.length = left_root.node_as_ref().calc_length();
1227 right.length = total_num - self.len();
1229 right.length = right_root.node_as_ref().calc_length();
1230 self.length = total_num - right.len();
1236 /// Creates an iterator which uses a closure to determine if an element should be removed.
1238 /// If the closure returns true, the element is removed from the map and yielded.
1239 /// If the closure returns false, or panics, the element remains in the map and will not be
1242 /// Note that `drain_filter` lets you mutate every value in the filter closure, regardless of
1243 /// whether you choose to keep or remove it.
1245 /// If the iterator is only partially consumed or not consumed at all, each of the remaining
1246 /// elements will still be subjected to the closure and removed and dropped if it returns true.
1248 /// It is unspecified how many more elements will be subjected to the closure
1249 /// if a panic occurs in the closure, or a panic occurs while dropping an element,
1250 /// or if the `DrainFilter` value is leaked.
1254 /// Splitting a map into even and odd keys, reusing the original map:
1257 /// #![feature(btree_drain_filter)]
1258 /// use std::collections::BTreeMap;
1260 /// let mut map: BTreeMap<i32, i32> = (0..8).map(|x| (x, x)).collect();
1261 /// let evens: BTreeMap<_, _> = map.drain_filter(|k, _v| k % 2 == 0).collect();
1263 /// assert_eq!(evens.keys().copied().collect::<Vec<_>>(), vec![0, 2, 4, 6]);
1264 /// assert_eq!(odds.keys().copied().collect::<Vec<_>>(), vec![1, 3, 5, 7]);
1266 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1267 pub fn drain_filter<F>(&mut self, pred: F) -> DrainFilter<'_, K, V, F>
1269 F: FnMut(&K, &mut V) -> bool,
1271 DrainFilter { pred, inner: self.drain_filter_inner() }
1274 pub(super) fn drain_filter_inner(&mut self) -> DrainFilterInner<'_, K, V> {
1275 if let Some(root) = self.root.as_mut() {
1276 let (root, dormant_root) = DormantMutRef::new(root);
1277 let front = root.node_as_mut().first_leaf_edge();
1279 length: &mut self.length,
1280 dormant_root: Some(dormant_root),
1281 cur_leaf_edge: Some(front),
1284 DrainFilterInner { length: &mut self.length, dormant_root: None, cur_leaf_edge: None }
1288 /// Creates a consuming iterator visiting all the keys, in sorted order.
1289 /// The map cannot be used after calling this.
1290 /// The iterator element type is `K`.
1295 /// #![feature(map_into_keys_values)]
1296 /// use std::collections::BTreeMap;
1298 /// let mut a = BTreeMap::new();
1299 /// a.insert(2, "b");
1300 /// a.insert(1, "a");
1302 /// let keys: Vec<i32> = a.into_keys().collect();
1303 /// assert_eq!(keys, [1, 2]);
1306 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1307 pub fn into_keys(self) -> IntoKeys<K, V> {
1308 IntoKeys { inner: self.into_iter() }
1311 /// Creates a consuming iterator visiting all the values, in order by key.
1312 /// The map cannot be used after calling this.
1313 /// The iterator element type is `V`.
1318 /// #![feature(map_into_keys_values)]
1319 /// use std::collections::BTreeMap;
1321 /// let mut a = BTreeMap::new();
1322 /// a.insert(1, "hello");
1323 /// a.insert(2, "goodbye");
1325 /// let values: Vec<&str> = a.into_values().collect();
1326 /// assert_eq!(values, ["hello", "goodbye"]);
1329 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1330 pub fn into_values(self) -> IntoValues<K, V> {
1331 IntoValues { inner: self.into_iter() }
1335 #[stable(feature = "rust1", since = "1.0.0")]
1336 impl<'a, K, V> IntoIterator for &'a BTreeMap<K, V> {
1337 type Item = (&'a K, &'a V);
1338 type IntoIter = Iter<'a, K, V>;
1340 fn into_iter(self) -> Iter<'a, K, V> {
1345 #[stable(feature = "rust1", since = "1.0.0")]
1346 impl<'a, K: 'a, V: 'a> Iterator for Iter<'a, K, V> {
1347 type Item = (&'a K, &'a V);
1349 fn next(&mut self) -> Option<(&'a K, &'a V)> {
1350 if self.length == 0 {
1354 unsafe { Some(self.range.next_unchecked()) }
1358 fn size_hint(&self) -> (usize, Option<usize>) {
1359 (self.length, Some(self.length))
1362 fn last(mut self) -> Option<(&'a K, &'a V)> {
1366 fn min(mut self) -> Option<(&'a K, &'a V)> {
1370 fn max(mut self) -> Option<(&'a K, &'a V)> {
1375 #[stable(feature = "fused", since = "1.26.0")]
1376 impl<K, V> FusedIterator for Iter<'_, K, V> {}
1378 #[stable(feature = "rust1", since = "1.0.0")]
1379 impl<'a, K: 'a, V: 'a> DoubleEndedIterator for Iter<'a, K, V> {
1380 fn next_back(&mut self) -> Option<(&'a K, &'a V)> {
1381 if self.length == 0 {
1385 unsafe { Some(self.range.next_back_unchecked()) }
1390 #[stable(feature = "rust1", since = "1.0.0")]
1391 impl<K, V> ExactSizeIterator for Iter<'_, K, V> {
1392 fn len(&self) -> usize {
1397 #[stable(feature = "rust1", since = "1.0.0")]
1398 impl<K, V> Clone for Iter<'_, K, V> {
1399 fn clone(&self) -> Self {
1400 Iter { range: self.range.clone(), length: self.length }
1404 #[stable(feature = "rust1", since = "1.0.0")]
1405 impl<'a, K, V> IntoIterator for &'a mut BTreeMap<K, V> {
1406 type Item = (&'a K, &'a mut V);
1407 type IntoIter = IterMut<'a, K, V>;
1409 fn into_iter(self) -> IterMut<'a, K, V> {
1414 #[stable(feature = "rust1", since = "1.0.0")]
1415 impl<'a, K: 'a, V: 'a> Iterator for IterMut<'a, K, V> {
1416 type Item = (&'a K, &'a mut V);
1418 fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
1419 if self.length == 0 {
1423 let (k, v) = unsafe { self.range.next_unchecked() };
1424 Some((k, v)) // coerce k from `&mut K` to `&K`
1428 fn size_hint(&self) -> (usize, Option<usize>) {
1429 (self.length, Some(self.length))
1432 fn last(mut self) -> Option<(&'a K, &'a mut V)> {
1436 fn min(mut self) -> Option<(&'a K, &'a mut V)> {
1440 fn max(mut self) -> Option<(&'a K, &'a mut V)> {
1445 #[stable(feature = "rust1", since = "1.0.0")]
1446 impl<'a, K: 'a, V: 'a> DoubleEndedIterator for IterMut<'a, K, V> {
1447 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> {
1448 if self.length == 0 {
1452 let (k, v) = unsafe { self.range.next_back_unchecked() };
1453 Some((k, v)) // coerce k from `&mut K` to `&K`
1458 #[stable(feature = "rust1", since = "1.0.0")]
1459 impl<K, V> ExactSizeIterator for IterMut<'_, K, V> {
1460 fn len(&self) -> usize {
1465 #[stable(feature = "fused", since = "1.26.0")]
1466 impl<K, V> FusedIterator for IterMut<'_, K, V> {}
1468 #[stable(feature = "rust1", since = "1.0.0")]
1469 impl<K, V> IntoIterator for BTreeMap<K, V> {
1471 type IntoIter = IntoIter<K, V>;
1473 fn into_iter(self) -> IntoIter<K, V> {
1474 let mut me = ManuallyDrop::new(self);
1475 if let Some(root) = me.root.take() {
1476 let (f, b) = root.into_ref().full_range();
1478 IntoIter { front: Some(f), back: Some(b), length: me.length }
1480 IntoIter { front: None, back: None, length: 0 }
1485 #[stable(feature = "btree_drop", since = "1.7.0")]
1486 impl<K, V> Drop for IntoIter<K, V> {
1487 fn drop(&mut self) {
1488 struct DropGuard<'a, K, V>(&'a mut IntoIter<K, V>);
1490 impl<'a, K, V> Drop for DropGuard<'a, K, V> {
1491 fn drop(&mut self) {
1492 // Continue the same loop we perform below. This only runs when unwinding, so we
1493 // don't have to care about panics this time (they'll abort).
1494 while let Some(_) = self.0.next() {}
1498 unwrap_unchecked(ptr::read(&self.0.front)).into_node().forget_type();
1499 while let Some(parent) = node.deallocate_and_ascend() {
1500 node = parent.into_node().forget_type();
1506 while let Some(pair) = self.next() {
1507 let guard = DropGuard(self);
1513 if let Some(front) = ptr::read(&self.front) {
1514 let mut node = front.into_node().forget_type();
1515 // Most of the nodes have been deallocated while traversing
1516 // but one pile from a leaf up to the root is left standing.
1517 while let Some(parent) = node.deallocate_and_ascend() {
1518 node = parent.into_node().forget_type();
1525 #[stable(feature = "rust1", since = "1.0.0")]
1526 impl<K, V> Iterator for IntoIter<K, V> {
1529 fn next(&mut self) -> Option<(K, V)> {
1530 if self.length == 0 {
1534 Some(unsafe { self.front.as_mut().unwrap().next_unchecked() })
1538 fn size_hint(&self) -> (usize, Option<usize>) {
1539 (self.length, Some(self.length))
1543 #[stable(feature = "rust1", since = "1.0.0")]
1544 impl<K, V> DoubleEndedIterator for IntoIter<K, V> {
1545 fn next_back(&mut self) -> Option<(K, V)> {
1546 if self.length == 0 {
1550 Some(unsafe { self.back.as_mut().unwrap().next_back_unchecked() })
1555 #[stable(feature = "rust1", since = "1.0.0")]
1556 impl<K, V> ExactSizeIterator for IntoIter<K, V> {
1557 fn len(&self) -> usize {
1562 #[stable(feature = "fused", since = "1.26.0")]
1563 impl<K, V> FusedIterator for IntoIter<K, V> {}
1565 #[stable(feature = "rust1", since = "1.0.0")]
1566 impl<'a, K, V> Iterator for Keys<'a, K, V> {
1569 fn next(&mut self) -> Option<&'a K> {
1570 self.inner.next().map(|(k, _)| k)
1573 fn size_hint(&self) -> (usize, Option<usize>) {
1574 self.inner.size_hint()
1577 fn last(mut self) -> Option<&'a K> {
1581 fn min(mut self) -> Option<&'a K> {
1585 fn max(mut self) -> Option<&'a K> {
1590 #[stable(feature = "rust1", since = "1.0.0")]
1591 impl<'a, K, V> DoubleEndedIterator for Keys<'a, K, V> {
1592 fn next_back(&mut self) -> Option<&'a K> {
1593 self.inner.next_back().map(|(k, _)| k)
1597 #[stable(feature = "rust1", since = "1.0.0")]
1598 impl<K, V> ExactSizeIterator for Keys<'_, K, V> {
1599 fn len(&self) -> usize {
1604 #[stable(feature = "fused", since = "1.26.0")]
1605 impl<K, V> FusedIterator for Keys<'_, K, V> {}
1607 #[stable(feature = "rust1", since = "1.0.0")]
1608 impl<K, V> Clone for Keys<'_, K, V> {
1609 fn clone(&self) -> Self {
1610 Keys { inner: self.inner.clone() }
1614 #[stable(feature = "rust1", since = "1.0.0")]
1615 impl<'a, K, V> Iterator for Values<'a, K, V> {
1618 fn next(&mut self) -> Option<&'a V> {
1619 self.inner.next().map(|(_, v)| v)
1622 fn size_hint(&self) -> (usize, Option<usize>) {
1623 self.inner.size_hint()
1626 fn last(mut self) -> Option<&'a V> {
1631 #[stable(feature = "rust1", since = "1.0.0")]
1632 impl<'a, K, V> DoubleEndedIterator for Values<'a, K, V> {
1633 fn next_back(&mut self) -> Option<&'a V> {
1634 self.inner.next_back().map(|(_, v)| v)
1638 #[stable(feature = "rust1", since = "1.0.0")]
1639 impl<K, V> ExactSizeIterator for Values<'_, K, V> {
1640 fn len(&self) -> usize {
1645 #[stable(feature = "fused", since = "1.26.0")]
1646 impl<K, V> FusedIterator for Values<'_, K, V> {}
1648 #[stable(feature = "rust1", since = "1.0.0")]
1649 impl<K, V> Clone for Values<'_, K, V> {
1650 fn clone(&self) -> Self {
1651 Values { inner: self.inner.clone() }
1655 /// An iterator produced by calling `drain_filter` on BTreeMap.
1656 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1657 pub struct DrainFilter<'a, K, V, F>
1661 F: 'a + FnMut(&K, &mut V) -> bool,
1664 inner: DrainFilterInner<'a, K, V>,
1666 /// Most of the implementation of DrainFilter, independent of the type
1667 /// of the predicate, thus also serving for BTreeSet::DrainFilter.
1668 pub(super) struct DrainFilterInner<'a, K: 'a, V: 'a> {
1669 length: &'a mut usize,
1670 // dormant_root is wrapped in an Option to be able to `take` it.
1671 dormant_root: Option<DormantMutRef<'a, node::Root<K, V>>>,
1672 // cur_leaf_edge is wrapped in an Option because maps without root lack a leaf edge.
1673 cur_leaf_edge: Option<Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>>,
1676 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1677 impl<K, V, F> Drop for DrainFilter<'_, K, V, F>
1679 F: FnMut(&K, &mut V) -> bool,
1681 fn drop(&mut self) {
1682 self.for_each(drop);
1686 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1687 impl<K, V, F> fmt::Debug for DrainFilter<'_, K, V, F>
1691 F: FnMut(&K, &mut V) -> bool,
1693 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1694 f.debug_tuple("DrainFilter").field(&self.inner.peek()).finish()
1698 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1699 impl<K, V, F> Iterator for DrainFilter<'_, K, V, F>
1701 F: FnMut(&K, &mut V) -> bool,
1705 fn next(&mut self) -> Option<(K, V)> {
1706 self.inner.next(&mut self.pred)
1709 fn size_hint(&self) -> (usize, Option<usize>) {
1710 self.inner.size_hint()
1714 impl<'a, K: 'a, V: 'a> DrainFilterInner<'a, K, V> {
1715 /// Allow Debug implementations to predict the next element.
1716 pub(super) fn peek(&self) -> Option<(&K, &V)> {
1717 let edge = self.cur_leaf_edge.as_ref()?;
1718 edge.reborrow().next_kv().ok().map(Handle::into_kv)
1721 /// Implementation of a typical `DrainFilter::next` method, given the predicate.
1722 pub(super) fn next<F>(&mut self, pred: &mut F) -> Option<(K, V)>
1724 F: FnMut(&K, &mut V) -> bool,
1726 while let Ok(mut kv) = self.cur_leaf_edge.take()?.next_kv() {
1727 let (k, v) = kv.kv_mut();
1730 let (kv, pos) = kv.remove_kv_tracking(|| {
1731 // SAFETY: we will touch the root in a way that will not
1732 // invalidate the position returned.
1733 let root = unsafe { self.dormant_root.take().unwrap().awaken() };
1734 root.pop_internal_level();
1735 self.dormant_root = Some(DormantMutRef::new(root).1);
1737 self.cur_leaf_edge = Some(pos);
1740 self.cur_leaf_edge = Some(kv.next_leaf_edge());
1745 /// Implementation of a typical `DrainFilter::size_hint` method.
1746 pub(super) fn size_hint(&self) -> (usize, Option<usize>) {
1747 (0, Some(*self.length))
1751 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1752 impl<K, V, F> FusedIterator for DrainFilter<'_, K, V, F> where F: FnMut(&K, &mut V) -> bool {}
1754 #[stable(feature = "btree_range", since = "1.17.0")]
1755 impl<'a, K, V> Iterator for Range<'a, K, V> {
1756 type Item = (&'a K, &'a V);
1758 fn next(&mut self) -> Option<(&'a K, &'a V)> {
1759 if self.is_empty() { None } else { unsafe { Some(self.next_unchecked()) } }
1762 fn last(mut self) -> Option<(&'a K, &'a V)> {
1766 fn min(mut self) -> Option<(&'a K, &'a V)> {
1770 fn max(mut self) -> Option<(&'a K, &'a V)> {
1775 #[stable(feature = "map_values_mut", since = "1.10.0")]
1776 impl<'a, K, V> Iterator for ValuesMut<'a, K, V> {
1777 type Item = &'a mut V;
1779 fn next(&mut self) -> Option<&'a mut V> {
1780 self.inner.next().map(|(_, v)| v)
1783 fn size_hint(&self) -> (usize, Option<usize>) {
1784 self.inner.size_hint()
1787 fn last(mut self) -> Option<&'a mut V> {
1792 #[stable(feature = "map_values_mut", since = "1.10.0")]
1793 impl<'a, K, V> DoubleEndedIterator for ValuesMut<'a, K, V> {
1794 fn next_back(&mut self) -> Option<&'a mut V> {
1795 self.inner.next_back().map(|(_, v)| v)
1799 #[stable(feature = "map_values_mut", since = "1.10.0")]
1800 impl<K, V> ExactSizeIterator for ValuesMut<'_, K, V> {
1801 fn len(&self) -> usize {
1806 #[stable(feature = "fused", since = "1.26.0")]
1807 impl<K, V> FusedIterator for ValuesMut<'_, K, V> {}
1809 impl<'a, K, V> Range<'a, K, V> {
1810 fn is_empty(&self) -> bool {
1811 self.front == self.back
1814 unsafe fn next_unchecked(&mut self) -> (&'a K, &'a V) {
1815 unsafe { unwrap_unchecked(self.front.as_mut()).next_unchecked() }
1819 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1820 impl<K, V> Iterator for IntoKeys<K, V> {
1823 fn next(&mut self) -> Option<K> {
1824 self.inner.next().map(|(k, _)| k)
1827 fn size_hint(&self) -> (usize, Option<usize>) {
1828 self.inner.size_hint()
1831 fn last(mut self) -> Option<K> {
1835 fn min(mut self) -> Option<K> {
1839 fn max(mut self) -> Option<K> {
1844 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1845 impl<K, V> DoubleEndedIterator for IntoKeys<K, V> {
1846 fn next_back(&mut self) -> Option<K> {
1847 self.inner.next_back().map(|(k, _)| k)
1851 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1852 impl<K, V> ExactSizeIterator for IntoKeys<K, V> {
1853 fn len(&self) -> usize {
1858 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1859 impl<K, V> FusedIterator for IntoKeys<K, V> {}
1861 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1862 impl<K, V> Iterator for IntoValues<K, V> {
1865 fn next(&mut self) -> Option<V> {
1866 self.inner.next().map(|(_, v)| v)
1869 fn size_hint(&self) -> (usize, Option<usize>) {
1870 self.inner.size_hint()
1873 fn last(mut self) -> Option<V> {
1878 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1879 impl<K, V> DoubleEndedIterator for IntoValues<K, V> {
1880 fn next_back(&mut self) -> Option<V> {
1881 self.inner.next_back().map(|(_, v)| v)
1885 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1886 impl<K, V> ExactSizeIterator for IntoValues<K, V> {
1887 fn len(&self) -> usize {
1892 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1893 impl<K, V> FusedIterator for IntoValues<K, V> {}
1895 #[stable(feature = "btree_range", since = "1.17.0")]
1896 impl<'a, K, V> DoubleEndedIterator for Range<'a, K, V> {
1897 fn next_back(&mut self) -> Option<(&'a K, &'a V)> {
1898 if self.is_empty() { None } else { Some(unsafe { self.next_back_unchecked() }) }
1902 impl<'a, K, V> Range<'a, K, V> {
1903 unsafe fn next_back_unchecked(&mut self) -> (&'a K, &'a V) {
1904 unsafe { unwrap_unchecked(self.back.as_mut()).next_back_unchecked() }
1908 #[stable(feature = "fused", since = "1.26.0")]
1909 impl<K, V> FusedIterator for Range<'_, K, V> {}
1911 #[stable(feature = "btree_range", since = "1.17.0")]
1912 impl<K, V> Clone for Range<'_, K, V> {
1913 fn clone(&self) -> Self {
1914 Range { front: self.front, back: self.back }
1918 #[stable(feature = "btree_range", since = "1.17.0")]
1919 impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
1920 type Item = (&'a K, &'a mut V);
1922 fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
1923 if self.is_empty() {
1926 let (k, v) = unsafe { self.next_unchecked() };
1927 Some((k, v)) // coerce k from `&mut K` to `&K`
1931 fn last(mut self) -> Option<(&'a K, &'a mut V)> {
1935 fn min(mut self) -> Option<(&'a K, &'a mut V)> {
1939 fn max(mut self) -> Option<(&'a K, &'a mut V)> {
1944 impl<'a, K, V> RangeMut<'a, K, V> {
1945 fn is_empty(&self) -> bool {
1946 self.front == self.back
1949 unsafe fn next_unchecked(&mut self) -> (&'a K, &'a mut V) {
1950 unsafe { unwrap_unchecked(self.front.as_mut()).next_unchecked() }
1954 #[stable(feature = "btree_range", since = "1.17.0")]
1955 impl<'a, K, V> DoubleEndedIterator for RangeMut<'a, K, V> {
1956 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> {
1957 if self.is_empty() {
1960 let (k, v) = unsafe { self.next_back_unchecked() };
1961 Some((k, v)) // coerce k from `&mut K` to `&K`
1966 #[stable(feature = "fused", since = "1.26.0")]
1967 impl<K, V> FusedIterator for RangeMut<'_, K, V> {}
1969 impl<'a, K, V> RangeMut<'a, K, V> {
1970 unsafe fn next_back_unchecked(&mut self) -> (&'a K, &'a mut V) {
1971 unsafe { unwrap_unchecked(self.back.as_mut()).next_back_unchecked() }
1975 #[stable(feature = "rust1", since = "1.0.0")]
1976 impl<K: Ord, V> FromIterator<(K, V)> for BTreeMap<K, V> {
1977 fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> BTreeMap<K, V> {
1978 let mut map = BTreeMap::new();
1984 #[stable(feature = "rust1", since = "1.0.0")]
1985 impl<K: Ord, V> Extend<(K, V)> for BTreeMap<K, V> {
1987 fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T) {
1988 iter.into_iter().for_each(move |(k, v)| {
1994 fn extend_one(&mut self, (k, v): (K, V)) {
1999 #[stable(feature = "extend_ref", since = "1.2.0")]
2000 impl<'a, K: Ord + Copy, V: Copy> Extend<(&'a K, &'a V)> for BTreeMap<K, V> {
2001 fn extend<I: IntoIterator<Item = (&'a K, &'a V)>>(&mut self, iter: I) {
2002 self.extend(iter.into_iter().map(|(&key, &value)| (key, value)));
2006 fn extend_one(&mut self, (&k, &v): (&'a K, &'a V)) {
2011 #[stable(feature = "rust1", since = "1.0.0")]
2012 impl<K: Hash, V: Hash> Hash for BTreeMap<K, V> {
2013 fn hash<H: Hasher>(&self, state: &mut H) {
2020 #[stable(feature = "rust1", since = "1.0.0")]
2021 impl<K: Ord, V> Default for BTreeMap<K, V> {
2022 /// Creates an empty `BTreeMap<K, V>`.
2023 fn default() -> BTreeMap<K, V> {
2028 #[stable(feature = "rust1", since = "1.0.0")]
2029 impl<K: PartialEq, V: PartialEq> PartialEq for BTreeMap<K, V> {
2030 fn eq(&self, other: &BTreeMap<K, V>) -> bool {
2031 self.len() == other.len() && self.iter().zip(other).all(|(a, b)| a == b)
2035 #[stable(feature = "rust1", since = "1.0.0")]
2036 impl<K: Eq, V: Eq> Eq for BTreeMap<K, V> {}
2038 #[stable(feature = "rust1", since = "1.0.0")]
2039 impl<K: PartialOrd, V: PartialOrd> PartialOrd for BTreeMap<K, V> {
2041 fn partial_cmp(&self, other: &BTreeMap<K, V>) -> Option<Ordering> {
2042 self.iter().partial_cmp(other.iter())
2046 #[stable(feature = "rust1", since = "1.0.0")]
2047 impl<K: Ord, V: Ord> Ord for BTreeMap<K, V> {
2049 fn cmp(&self, other: &BTreeMap<K, V>) -> Ordering {
2050 self.iter().cmp(other.iter())
2054 #[stable(feature = "rust1", since = "1.0.0")]
2055 impl<K: Debug, V: Debug> Debug for BTreeMap<K, V> {
2056 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2057 f.debug_map().entries(self.iter()).finish()
2061 #[stable(feature = "rust1", since = "1.0.0")]
2062 impl<K: Ord, Q: ?Sized, V> Index<&Q> for BTreeMap<K, V>
2069 /// Returns a reference to the value corresponding to the supplied key.
2073 /// Panics if the key is not present in the `BTreeMap`.
2075 fn index(&self, key: &Q) -> &V {
2076 self.get(key).expect("no entry found for key")
2080 impl<K, V> BTreeMap<K, V> {
2081 /// Gets an iterator over the entries of the map, sorted by key.
2088 /// use std::collections::BTreeMap;
2090 /// let mut map = BTreeMap::new();
2091 /// map.insert(3, "c");
2092 /// map.insert(2, "b");
2093 /// map.insert(1, "a");
2095 /// for (key, value) in map.iter() {
2096 /// println!("{}: {}", key, value);
2099 /// let (first_key, first_value) = map.iter().next().unwrap();
2100 /// assert_eq!((*first_key, *first_value), (1, "a"));
2102 #[stable(feature = "rust1", since = "1.0.0")]
2103 pub fn iter(&self) -> Iter<'_, K, V> {
2104 if let Some(root) = &self.root {
2105 let (f, b) = root.node_as_ref().full_range();
2107 Iter { range: Range { front: Some(f), back: Some(b) }, length: self.length }
2109 Iter { range: Range { front: None, back: None }, length: 0 }
2113 /// Gets a mutable iterator over the entries of the map, sorted by key.
2120 /// use std::collections::BTreeMap;
2122 /// let mut map = BTreeMap::new();
2123 /// map.insert("a", 1);
2124 /// map.insert("b", 2);
2125 /// map.insert("c", 3);
2127 /// // add 10 to the value if the key isn't "a"
2128 /// for (key, value) in map.iter_mut() {
2129 /// if key != &"a" {
2134 #[stable(feature = "rust1", since = "1.0.0")]
2135 pub fn iter_mut(&mut self) -> IterMut<'_, K, V> {
2136 if let Some(root) = &mut self.root {
2137 let (f, b) = root.node_as_valmut().full_range();
2140 range: RangeMut { front: Some(f), back: Some(b), _marker: PhantomData },
2141 length: self.length,
2144 IterMut { range: RangeMut { front: None, back: None, _marker: PhantomData }, length: 0 }
2148 /// Gets an iterator over the keys of the map, in sorted order.
2155 /// use std::collections::BTreeMap;
2157 /// let mut a = BTreeMap::new();
2158 /// a.insert(2, "b");
2159 /// a.insert(1, "a");
2161 /// let keys: Vec<_> = a.keys().cloned().collect();
2162 /// assert_eq!(keys, [1, 2]);
2164 #[stable(feature = "rust1", since = "1.0.0")]
2165 pub fn keys(&self) -> Keys<'_, K, V> {
2166 Keys { inner: self.iter() }
2169 /// Gets an iterator over the values of the map, in order by key.
2176 /// use std::collections::BTreeMap;
2178 /// let mut a = BTreeMap::new();
2179 /// a.insert(1, "hello");
2180 /// a.insert(2, "goodbye");
2182 /// let values: Vec<&str> = a.values().cloned().collect();
2183 /// assert_eq!(values, ["hello", "goodbye"]);
2185 #[stable(feature = "rust1", since = "1.0.0")]
2186 pub fn values(&self) -> Values<'_, K, V> {
2187 Values { inner: self.iter() }
2190 /// Gets a mutable iterator over the values of the map, in order by key.
2197 /// use std::collections::BTreeMap;
2199 /// let mut a = BTreeMap::new();
2200 /// a.insert(1, String::from("hello"));
2201 /// a.insert(2, String::from("goodbye"));
2203 /// for value in a.values_mut() {
2204 /// value.push_str("!");
2207 /// let values: Vec<String> = a.values().cloned().collect();
2208 /// assert_eq!(values, [String::from("hello!"),
2209 /// String::from("goodbye!")]);
2211 #[stable(feature = "map_values_mut", since = "1.10.0")]
2212 pub fn values_mut(&mut self) -> ValuesMut<'_, K, V> {
2213 ValuesMut { inner: self.iter_mut() }
2216 /// Returns the number of elements in the map.
2223 /// use std::collections::BTreeMap;
2225 /// let mut a = BTreeMap::new();
2226 /// assert_eq!(a.len(), 0);
2227 /// a.insert(1, "a");
2228 /// assert_eq!(a.len(), 1);
2230 #[stable(feature = "rust1", since = "1.0.0")]
2231 pub fn len(&self) -> usize {
2235 /// Returns `true` if the map contains no elements.
2242 /// use std::collections::BTreeMap;
2244 /// let mut a = BTreeMap::new();
2245 /// assert!(a.is_empty());
2246 /// a.insert(1, "a");
2247 /// assert!(!a.is_empty());
2249 #[stable(feature = "rust1", since = "1.0.0")]
2250 pub fn is_empty(&self) -> bool {
2254 /// If the root node is the empty (non-allocated) root node, allocate our
2255 /// own node. Is an associated function to avoid borrowing the entire BTreeMap.
2256 fn ensure_is_owned(root: &mut Option<node::Root<K, V>>) -> &mut node::Root<K, V> {
2257 root.get_or_insert_with(node::Root::new_leaf)
2261 impl<'a, K: Ord, V> Entry<'a, K, V> {
2262 /// Ensures a value is in the entry by inserting the default if empty, and returns
2263 /// a mutable reference to the value in the entry.
2268 /// use std::collections::BTreeMap;
2270 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2271 /// map.entry("poneyland").or_insert(12);
2273 /// assert_eq!(map["poneyland"], 12);
2275 #[stable(feature = "rust1", since = "1.0.0")]
2276 pub fn or_insert(self, default: V) -> &'a mut V {
2278 Occupied(entry) => entry.into_mut(),
2279 Vacant(entry) => entry.insert(default),
2283 /// Ensures a value is in the entry by inserting the result of the default function if empty,
2284 /// and returns a mutable reference to the value in the entry.
2289 /// use std::collections::BTreeMap;
2291 /// let mut map: BTreeMap<&str, String> = BTreeMap::new();
2292 /// let s = "hoho".to_string();
2294 /// map.entry("poneyland").or_insert_with(|| s);
2296 /// assert_eq!(map["poneyland"], "hoho".to_string());
2298 #[stable(feature = "rust1", since = "1.0.0")]
2299 pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V {
2301 Occupied(entry) => entry.into_mut(),
2302 Vacant(entry) => entry.insert(default()),
2306 #[unstable(feature = "or_insert_with_key", issue = "71024")]
2307 /// Ensures a value is in the entry by inserting, if empty, the result of the default function,
2308 /// which takes the key as its argument, and returns a mutable reference to the value in the
2314 /// #![feature(or_insert_with_key)]
2315 /// use std::collections::BTreeMap;
2317 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2319 /// map.entry("poneyland").or_insert_with_key(|key| key.chars().count());
2321 /// assert_eq!(map["poneyland"], 9);
2324 pub fn or_insert_with_key<F: FnOnce(&K) -> V>(self, default: F) -> &'a mut V {
2326 Occupied(entry) => entry.into_mut(),
2328 let value = default(entry.key());
2334 /// Returns a reference to this entry's key.
2339 /// use std::collections::BTreeMap;
2341 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2342 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2344 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2345 pub fn key(&self) -> &K {
2347 Occupied(ref entry) => entry.key(),
2348 Vacant(ref entry) => entry.key(),
2352 /// Provides in-place mutable access to an occupied entry before any
2353 /// potential inserts into the map.
2358 /// use std::collections::BTreeMap;
2360 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2362 /// map.entry("poneyland")
2363 /// .and_modify(|e| { *e += 1 })
2365 /// assert_eq!(map["poneyland"], 42);
2367 /// map.entry("poneyland")
2368 /// .and_modify(|e| { *e += 1 })
2370 /// assert_eq!(map["poneyland"], 43);
2372 #[stable(feature = "entry_and_modify", since = "1.26.0")]
2373 pub fn and_modify<F>(self, f: F) -> Self
2378 Occupied(mut entry) => {
2382 Vacant(entry) => Vacant(entry),
2387 impl<'a, K: Ord, V: Default> Entry<'a, K, V> {
2388 #[stable(feature = "entry_or_default", since = "1.28.0")]
2389 /// Ensures a value is in the entry by inserting the default value if empty,
2390 /// and returns a mutable reference to the value in the entry.
2395 /// use std::collections::BTreeMap;
2397 /// let mut map: BTreeMap<&str, Option<usize>> = BTreeMap::new();
2398 /// map.entry("poneyland").or_default();
2400 /// assert_eq!(map["poneyland"], None);
2402 pub fn or_default(self) -> &'a mut V {
2404 Occupied(entry) => entry.into_mut(),
2405 Vacant(entry) => entry.insert(Default::default()),
2410 impl<'a, K: Ord, V> VacantEntry<'a, K, V> {
2411 /// Gets a reference to the key that would be used when inserting a value
2412 /// through the VacantEntry.
2417 /// use std::collections::BTreeMap;
2419 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2420 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2422 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2423 pub fn key(&self) -> &K {
2427 /// Take ownership of the key.
2432 /// use std::collections::BTreeMap;
2433 /// use std::collections::btree_map::Entry;
2435 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2437 /// if let Entry::Vacant(v) = map.entry("poneyland") {
2441 #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
2442 pub fn into_key(self) -> K {
2446 /// Sets the value of the entry with the `VacantEntry`'s key,
2447 /// and returns a mutable reference to it.
2452 /// use std::collections::BTreeMap;
2453 /// use std::collections::btree_map::Entry;
2455 /// let mut map: BTreeMap<&str, u32> = BTreeMap::new();
2457 /// if let Entry::Vacant(o) = map.entry("poneyland") {
2460 /// assert_eq!(map["poneyland"], 37);
2462 #[stable(feature = "rust1", since = "1.0.0")]
2463 pub fn insert(self, value: V) -> &'a mut V {
2464 let out_ptr = match self.handle.insert_recursing(self.key, value) {
2465 (Fit(_), val_ptr) => {
2466 // Safety: We have consumed self.handle and the handle returned.
2467 let map = unsafe { self.dormant_map.awaken() };
2471 (Split(ins), val_ptr) => {
2473 // Safety: We have consumed self.handle and the reference returned.
2474 let map = unsafe { self.dormant_map.awaken() };
2475 let root = map.root.as_mut().unwrap();
2476 root.push_internal_level().push(ins.k, ins.v, ins.right);
2481 // Now that we have finished growing the tree using borrowed references,
2482 // dereference the pointer to a part of it, that we picked up along the way.
2483 unsafe { &mut *out_ptr }
2487 impl<'a, K: Ord, V> OccupiedEntry<'a, K, V> {
2488 /// Gets a reference to the key in the entry.
2493 /// use std::collections::BTreeMap;
2495 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2496 /// map.entry("poneyland").or_insert(12);
2497 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2499 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2500 pub fn key(&self) -> &K {
2501 self.handle.reborrow().into_kv().0
2504 /// Take ownership of the key and value from the map.
2509 /// use std::collections::BTreeMap;
2510 /// use std::collections::btree_map::Entry;
2512 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2513 /// map.entry("poneyland").or_insert(12);
2515 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2516 /// // We delete the entry from the map.
2517 /// o.remove_entry();
2520 /// // If now try to get the value, it will panic:
2521 /// // println!("{}", map["poneyland"]);
2523 #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
2524 pub fn remove_entry(self) -> (K, V) {
2528 /// Gets a reference to the value in the entry.
2533 /// use std::collections::BTreeMap;
2534 /// use std::collections::btree_map::Entry;
2536 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2537 /// map.entry("poneyland").or_insert(12);
2539 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2540 /// assert_eq!(o.get(), &12);
2543 #[stable(feature = "rust1", since = "1.0.0")]
2544 pub fn get(&self) -> &V {
2545 self.handle.reborrow().into_kv().1
2548 /// Gets a mutable reference to the value in the entry.
2550 /// If you need a reference to the `OccupiedEntry` that may outlive the
2551 /// destruction of the `Entry` value, see [`into_mut`].
2553 /// [`into_mut`]: OccupiedEntry::into_mut
2558 /// use std::collections::BTreeMap;
2559 /// use std::collections::btree_map::Entry;
2561 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2562 /// map.entry("poneyland").or_insert(12);
2564 /// assert_eq!(map["poneyland"], 12);
2565 /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
2566 /// *o.get_mut() += 10;
2567 /// assert_eq!(*o.get(), 22);
2569 /// // We can use the same Entry multiple times.
2570 /// *o.get_mut() += 2;
2572 /// assert_eq!(map["poneyland"], 24);
2574 #[stable(feature = "rust1", since = "1.0.0")]
2575 pub fn get_mut(&mut self) -> &mut V {
2576 self.handle.kv_mut().1
2579 /// Converts the entry into a mutable reference to its value.
2581 /// If you need multiple references to the `OccupiedEntry`, see [`get_mut`].
2583 /// [`get_mut`]: OccupiedEntry::get_mut
2588 /// use std::collections::BTreeMap;
2589 /// use std::collections::btree_map::Entry;
2591 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2592 /// map.entry("poneyland").or_insert(12);
2594 /// assert_eq!(map["poneyland"], 12);
2595 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2596 /// *o.into_mut() += 10;
2598 /// assert_eq!(map["poneyland"], 22);
2600 #[stable(feature = "rust1", since = "1.0.0")]
2601 pub fn into_mut(self) -> &'a mut V {
2602 self.handle.into_val_mut()
2605 /// Sets the value of the entry with the `OccupiedEntry`'s key,
2606 /// and returns the entry's old value.
2611 /// use std::collections::BTreeMap;
2612 /// use std::collections::btree_map::Entry;
2614 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2615 /// map.entry("poneyland").or_insert(12);
2617 /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
2618 /// assert_eq!(o.insert(15), 12);
2620 /// assert_eq!(map["poneyland"], 15);
2622 #[stable(feature = "rust1", since = "1.0.0")]
2623 pub fn insert(&mut self, value: V) -> V {
2624 mem::replace(self.get_mut(), value)
2627 /// Takes the value of the entry out of the map, and returns it.
2632 /// use std::collections::BTreeMap;
2633 /// use std::collections::btree_map::Entry;
2635 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2636 /// map.entry("poneyland").or_insert(12);
2638 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2639 /// assert_eq!(o.remove(), 12);
2641 /// // If we try to get "poneyland"'s value, it'll panic:
2642 /// // println!("{}", map["poneyland"]);
2644 #[stable(feature = "rust1", since = "1.0.0")]
2645 pub fn remove(self) -> V {
2649 // Body of `remove_entry`, separate to keep the above implementations short.
2650 fn remove_kv(self) -> (K, V) {
2651 let mut emptied_internal_root = false;
2652 let (old_kv, _) = self.handle.remove_kv_tracking(|| emptied_internal_root = true);
2653 // SAFETY: we consumed the intermediate root borrow, `self.handle`.
2654 let map = unsafe { self.dormant_map.awaken() };
2656 if emptied_internal_root {
2657 let root = map.root.as_mut().unwrap();
2658 root.pop_internal_level();
2664 impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, marker::KV> {
2665 /// Removes a key/value-pair from the map, and returns that pair, as well as
2666 /// the leaf edge corresponding to that former pair.
2667 fn remove_kv_tracking<F: FnOnce()>(
2669 handle_emptied_internal_root: F,
2670 ) -> ((K, V), Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>) {
2671 let (old_kv, mut pos, was_internal) = match self.force() {
2673 let (old_kv, pos) = leaf.remove();
2674 (old_kv, pos, false)
2676 Internal(mut internal) => {
2677 // Replace the location freed in the internal node with an
2678 // adjacent KV, and remove that adjacent KV from its leaf.
2679 // Always choose the adjacent KV on the left side because
2680 // it is typically faster to pop an element from the end
2681 // of the KV arrays without needing to shift other elements.
2683 let key_loc = internal.kv_mut().0 as *mut K;
2684 let val_loc = internal.kv_mut().1 as *mut V;
2686 let to_remove = internal.left_edge().descend().last_leaf_edge().left_kv().ok();
2687 let to_remove = unsafe { unwrap_unchecked(to_remove) };
2689 let (kv, pos) = to_remove.remove();
2691 let old_key = unsafe { mem::replace(&mut *key_loc, kv.0) };
2692 let old_val = unsafe { mem::replace(&mut *val_loc, kv.1) };
2694 ((old_key, old_val), pos, true)
2699 let mut cur_node = unsafe { ptr::read(&pos).into_node().forget_type() };
2700 let mut at_leaf = true;
2701 while cur_node.len() < node::MIN_LEN {
2702 match handle_underfull_node(cur_node) {
2704 Merged(edge, merged_with_left, offset) => {
2705 // If we merged with our right sibling then our tracked
2706 // position has not changed. However if we merged with our
2707 // left sibling then our tracked position is now dangling.
2708 if at_leaf && merged_with_left {
2709 let idx = pos.idx() + offset;
2710 let node = match unsafe { ptr::read(&edge).descend().force() } {
2712 Internal(_) => unreachable!(),
2714 pos = unsafe { Handle::new_edge(node, idx) };
2717 let parent = edge.into_node();
2718 if parent.len() == 0 {
2719 // The parent that was just emptied must be the root,
2720 // because nodes on a lower level would not have been
2721 // left with a single child.
2722 handle_emptied_internal_root();
2725 cur_node = parent.forget_type();
2729 Stole(stole_from_left) => {
2730 // Adjust the tracked position if we stole from a left sibling
2731 if stole_from_left && at_leaf {
2732 // SAFETY: This is safe since we just added an element to our node.
2734 pos.move_next_unchecked();
2742 // If we deleted from an internal node then we need to compensate for
2743 // the earlier swap and adjust the tracked position to point to the
2746 pos = unsafe { unwrap_unchecked(pos.next_kv().ok()).next_leaf_edge() };
2753 impl<K, V> node::Root<K, V> {
2754 /// Removes empty levels on the top, but keep an empty leaf if the entire tree is empty.
2755 fn fix_top(&mut self) {
2756 while self.height() > 0 && self.node_as_ref().len() == 0 {
2757 self.pop_internal_level();
2761 fn fix_right_border(&mut self) {
2765 let mut cur_node = self.node_as_mut();
2767 while let Internal(node) = cur_node.force() {
2768 let mut last_kv = node.last_kv();
2770 if last_kv.can_merge() {
2771 cur_node = last_kv.merge().descend();
2773 let right_len = last_kv.reborrow().right_edge().descend().len();
2774 // `MINLEN + 1` to avoid readjust if merge happens on the next level.
2775 if right_len < node::MIN_LEN + 1 {
2776 last_kv.bulk_steal_left(node::MIN_LEN + 1 - right_len);
2778 cur_node = last_kv.right_edge().descend();
2786 /// The symmetric clone of `fix_right_border`.
2787 fn fix_left_border(&mut self) {
2791 let mut cur_node = self.node_as_mut();
2793 while let Internal(node) = cur_node.force() {
2794 let mut first_kv = node.first_kv();
2796 if first_kv.can_merge() {
2797 cur_node = first_kv.merge().descend();
2799 let left_len = first_kv.reborrow().left_edge().descend().len();
2800 if left_len < node::MIN_LEN + 1 {
2801 first_kv.bulk_steal_right(node::MIN_LEN + 1 - left_len);
2803 cur_node = first_kv.left_edge().descend();
2812 enum UnderflowResult<'a, K, V> {
2814 Merged(Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::Edge>, bool, usize),
2818 fn handle_underfull_node<'a, K: 'a, V: 'a>(
2819 node: NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>,
2820 ) -> UnderflowResult<'_, K, V> {
2821 let parent = match node.ascend() {
2822 Ok(parent) => parent,
2823 Err(_) => return AtRoot,
2826 // Prefer the left KV if it exists. Merging with the left side is faster,
2827 // since merging happens towards the left and `node` has fewer elements.
2828 // Stealing from the left side is faster, since we can pop from the end of
2830 let (is_left, mut handle) = match parent.left_kv() {
2831 Ok(left) => (true, left),
2833 let right = unsafe { unwrap_unchecked(parent.right_kv().ok()) };
2838 if handle.can_merge() {
2839 let offset = if is_left { handle.reborrow().left_edge().descend().len() + 1 } else { 0 };
2840 Merged(handle.merge(), is_left, offset)
2843 handle.steal_left();
2845 handle.steal_right();
2851 impl<K: Ord, V, I: Iterator<Item = (K, V)>> Iterator for MergeIter<K, V, I> {
2854 fn next(&mut self) -> Option<(K, V)> {
2855 let res = match (self.left.peek(), self.right.peek()) {
2856 (Some(&(ref left_key, _)), Some(&(ref right_key, _))) => left_key.cmp(right_key),
2857 (Some(_), None) => Ordering::Less,
2858 (None, Some(_)) => Ordering::Greater,
2859 (None, None) => return None,
2862 // Check which elements comes first and only advance the corresponding iterator.
2863 // If two keys are equal, take the value from `right`.
2865 Ordering::Less => self.left.next(),
2866 Ordering::Greater => self.right.next(),
2867 Ordering::Equal => {