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::node::{self, marker, ForceResult::*, Handle, InsertResult::*, NodeRef};
12 use super::search::{self, SearchResult::*};
13 use super::unwrap_unchecked;
16 use UnderflowResult::*;
18 /// A map based on a B-Tree.
20 /// B-Trees represent a fundamental compromise between cache-efficiency and actually minimizing
21 /// the amount of work performed in a search. In theory, a binary search tree (BST) is the optimal
22 /// choice for a sorted map, as a perfectly balanced BST performs the theoretical minimum amount of
23 /// comparisons necessary to find an element (log<sub>2</sub>n). However, in practice the way this
24 /// is done is *very* inefficient for modern computer architectures. In particular, every element
25 /// is stored in its own individually heap-allocated node. This means that every single insertion
26 /// triggers a heap-allocation, and every single comparison should be a cache-miss. Since these
27 /// are both notably expensive things to do in practice, we are forced to at very least reconsider
30 /// A B-Tree instead makes each node contain B-1 to 2B-1 elements in a contiguous array. By doing
31 /// this, we reduce the number of allocations by a factor of B, and improve cache efficiency in
32 /// searches. However, this does mean that searches will have to do *more* comparisons on average.
33 /// The precise number of comparisons depends on the node search strategy used. For optimal cache
34 /// efficiency, one could search the nodes linearly. For optimal comparisons, one could search
35 /// the node using binary search. As a compromise, one could also perform a linear search
36 /// that initially only checks every i<sup>th</sup> element for some choice of i.
38 /// Currently, our implementation simply performs naive linear search. This provides excellent
39 /// performance on *small* nodes of elements which are cheap to compare. However in the future we
40 /// would like to further explore choosing the optimal search strategy based on the choice of B,
41 /// and possibly other factors. Using linear search, searching for a random element is expected
42 /// to take O(B * log(n)) comparisons, which is generally worse than a BST. In practice,
43 /// however, performance is excellent.
45 /// It is a logic error for a key to be modified in such a way that the key's ordering relative to
46 /// any other key, as determined by the [`Ord`] trait, changes while it is in the map. This is
47 /// normally only possible through [`Cell`], [`RefCell`], global state, I/O, or unsafe code.
49 /// [`Ord`]: core::cmp::Ord
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`](#method.entry), which allows
96 /// for more complex methods of getting, setting, updating and removing keys and
100 /// use std::collections::BTreeMap;
102 /// // type inference lets us omit an explicit type signature (which
103 /// // would be `BTreeMap<&str, u8>` in this example).
104 /// let mut player_stats = BTreeMap::new();
106 /// fn random_stat_buff() -> u8 {
107 /// // could actually return some random value here - let's just return
108 /// // some fixed value for now
112 /// // insert a key only if it doesn't already exist
113 /// player_stats.entry("health").or_insert(100);
115 /// // insert a key using a function that provides a new value only if it
116 /// // doesn't already exist
117 /// player_stats.entry("defence").or_insert_with(random_stat_buff);
119 /// // update a key, guarding against the key possibly not being set
120 /// let stat = player_stats.entry("attack").or_insert(100);
121 /// *stat += random_stat_buff();
123 #[stable(feature = "rust1", since = "1.0.0")]
124 pub struct BTreeMap<K, V> {
125 root: Option<node::Root<K, V>>,
129 #[stable(feature = "btree_drop", since = "1.7.0")]
130 unsafe impl<#[may_dangle] K, #[may_dangle] V> Drop for BTreeMap<K, V> {
133 drop(ptr::read(self).into_iter());
138 #[stable(feature = "rust1", since = "1.0.0")]
139 impl<K: Clone, V: Clone> Clone for BTreeMap<K, V> {
140 fn clone(&self) -> BTreeMap<K, V> {
141 fn clone_subtree<'a, K: Clone, V: Clone>(
142 node: node::NodeRef<marker::Immut<'a>, K, V, marker::LeafOrInternal>,
150 let mut out_tree = BTreeMap { root: Some(node::Root::new_leaf()), length: 0 };
153 let root = out_tree.root.as_mut().unwrap(); // unwrap succeeds because we just wrapped
154 let mut out_node = match root.node_as_mut().force() {
156 Internal(_) => unreachable!(),
159 let mut in_edge = leaf.first_edge();
160 while let Ok(kv) = in_edge.right_kv() {
161 let (k, v) = kv.into_kv();
162 in_edge = kv.right_edge();
164 out_node.push(k.clone(), v.clone());
165 out_tree.length += 1;
171 Internal(internal) => {
172 let mut out_tree = clone_subtree(internal.first_edge().descend());
175 let out_root = BTreeMap::ensure_is_owned(&mut out_tree.root);
176 let mut out_node = out_root.push_internal_level();
177 let mut in_edge = internal.first_edge();
178 while let Ok(kv) = in_edge.right_kv() {
179 let (k, v) = kv.into_kv();
180 in_edge = kv.right_edge();
182 let k = (*k).clone();
183 let v = (*v).clone();
184 let subtree = clone_subtree(in_edge.descend());
186 // We can't destructure subtree directly
187 // because BTreeMap implements Drop
188 let (subroot, sublength) = unsafe {
189 let subtree = ManuallyDrop::new(subtree);
190 let root = ptr::read(&subtree.root);
191 let length = subtree.length;
195 out_node.push(k, v, subroot.unwrap_or_else(node::Root::new_leaf));
196 out_tree.length += 1 + sublength;
206 // Ideally we'd call `BTreeMap::new` here, but that has the `K:
207 // Ord` constraint, which this method lacks.
208 BTreeMap { root: None, length: 0 }
210 clone_subtree(self.root.as_ref().unwrap().node_as_ref()) // unwrap succeeds because not empty
215 impl<K, Q: ?Sized> super::Recover<Q> for BTreeMap<K, ()>
222 fn get(&self, key: &Q) -> Option<&K> {
223 let root_node = self.root.as_ref()?.node_as_ref();
224 match search::search_tree(root_node, key) {
225 Found(handle) => Some(handle.into_kv().0),
230 fn take(&mut self, key: &Q) -> Option<K> {
231 let root_node = self.root.as_mut()?.node_as_mut();
232 match search::search_tree(root_node, key) {
233 Found(handle) => Some(
234 OccupiedEntry { handle, length: &mut self.length, _marker: PhantomData }
242 fn replace(&mut self, key: K) -> Option<K> {
243 let root = Self::ensure_is_owned(&mut self.root);
244 match search::search_tree::<marker::Mut<'_>, K, (), K>(root.node_as_mut(), &key) {
245 Found(handle) => Some(mem::replace(handle.into_key_mut(), key)),
247 VacantEntry { key, handle, length: &mut self.length, _marker: PhantomData }
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 length: &'a mut usize,
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>,
483 length: &'a mut usize,
485 // Be invariant in `K` and `V`
486 _marker: PhantomData<&'a mut (K, V)>,
489 #[stable(feature = "debug_btree_map", since = "1.12.0")]
490 impl<K: Debug + Ord, V: Debug> Debug for OccupiedEntry<'_, K, V> {
491 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
492 f.debug_struct("OccupiedEntry").field("key", self.key()).field("value", self.get()).finish()
496 // An iterator for merging two sorted sequences into one
497 struct MergeIter<K, V, I: Iterator<Item = (K, V)>> {
502 impl<K: Ord, V> BTreeMap<K, V> {
503 /// Makes a new empty BTreeMap.
505 /// Does not allocate anything on its own.
512 /// use std::collections::BTreeMap;
514 /// let mut map = BTreeMap::new();
516 /// // entries can now be inserted into the empty map
517 /// map.insert(1, "a");
519 #[stable(feature = "rust1", since = "1.0.0")]
520 #[rustc_const_unstable(feature = "const_btree_new", issue = "71835")]
521 pub const fn new() -> BTreeMap<K, V> {
522 BTreeMap { root: None, length: 0 }
525 /// Clears the map, removing all elements.
532 /// use std::collections::BTreeMap;
534 /// let mut a = BTreeMap::new();
535 /// a.insert(1, "a");
537 /// assert!(a.is_empty());
539 #[stable(feature = "rust1", since = "1.0.0")]
540 pub fn clear(&mut self) {
541 *self = BTreeMap::new();
544 /// Returns a reference to the value corresponding to the key.
546 /// The key may be any borrowed form of the map's key type, but the ordering
547 /// on the borrowed form *must* match the ordering on the key type.
554 /// use std::collections::BTreeMap;
556 /// let mut map = BTreeMap::new();
557 /// map.insert(1, "a");
558 /// assert_eq!(map.get(&1), Some(&"a"));
559 /// assert_eq!(map.get(&2), None);
561 #[stable(feature = "rust1", since = "1.0.0")]
562 pub fn get<Q: ?Sized>(&self, key: &Q) -> Option<&V>
567 let root_node = self.root.as_ref()?.node_as_ref();
568 match search::search_tree(root_node, key) {
569 Found(handle) => Some(handle.into_kv().1),
574 /// Returns the key-value pair corresponding to the supplied key.
576 /// The supplied key may be any borrowed form of the map's key type, but the ordering
577 /// on the borrowed form *must* match the ordering on the key type.
582 /// use std::collections::BTreeMap;
584 /// let mut map = BTreeMap::new();
585 /// map.insert(1, "a");
586 /// assert_eq!(map.get_key_value(&1), Some((&1, &"a")));
587 /// assert_eq!(map.get_key_value(&2), None);
589 #[stable(feature = "map_get_key_value", since = "1.40.0")]
590 pub fn get_key_value<Q: ?Sized>(&self, k: &Q) -> Option<(&K, &V)>
595 let root_node = self.root.as_ref()?.node_as_ref();
596 match search::search_tree(root_node, k) {
597 Found(handle) => Some(handle.into_kv()),
602 /// Returns the first key-value pair in the map.
603 /// The key in this pair is the minimum key in the map.
610 /// #![feature(map_first_last)]
611 /// use std::collections::BTreeMap;
613 /// let mut map = BTreeMap::new();
614 /// assert_eq!(map.first_key_value(), None);
615 /// map.insert(1, "b");
616 /// map.insert(2, "a");
617 /// assert_eq!(map.first_key_value(), Some((&1, &"b")));
619 #[unstable(feature = "map_first_last", issue = "62924")]
620 pub fn first_key_value(&self) -> Option<(&K, &V)> {
621 let root_node = self.root.as_ref()?.node_as_ref();
622 root_node.first_leaf_edge().right_kv().ok().map(Handle::into_kv)
625 /// Returns the first entry in the map for in-place manipulation.
626 /// The key of this entry is the minimum key in the map.
631 /// #![feature(map_first_last)]
632 /// use std::collections::BTreeMap;
634 /// let mut map = BTreeMap::new();
635 /// map.insert(1, "a");
636 /// map.insert(2, "b");
637 /// if let Some(mut entry) = map.first_entry() {
638 /// if *entry.key() > 0 {
639 /// entry.insert("first");
642 /// assert_eq!(*map.get(&1).unwrap(), "first");
643 /// assert_eq!(*map.get(&2).unwrap(), "b");
645 #[unstable(feature = "map_first_last", issue = "62924")]
646 pub fn first_entry(&mut self) -> Option<OccupiedEntry<'_, K, V>> {
647 let root_node = self.root.as_mut()?.node_as_mut();
648 let kv = root_node.first_leaf_edge().right_kv().ok()?;
650 handle: kv.forget_node_type(),
651 length: &mut self.length,
652 _marker: PhantomData,
656 /// Removes and returns the first element in the map.
657 /// The key of this element is the minimum key that was in the map.
661 /// Draining elements in ascending order, while keeping a usable map each iteration.
664 /// #![feature(map_first_last)]
665 /// use std::collections::BTreeMap;
667 /// let mut map = BTreeMap::new();
668 /// map.insert(1, "a");
669 /// map.insert(2, "b");
670 /// while let Some((key, _val)) = map.pop_first() {
671 /// assert!(map.iter().all(|(k, _v)| *k > key));
673 /// assert!(map.is_empty());
675 #[unstable(feature = "map_first_last", issue = "62924")]
676 pub fn pop_first(&mut self) -> Option<(K, V)> {
677 self.first_entry().map(|entry| entry.remove_entry())
680 /// Returns the last key-value pair in the map.
681 /// The key in this pair is the maximum key in the map.
688 /// #![feature(map_first_last)]
689 /// use std::collections::BTreeMap;
691 /// let mut map = BTreeMap::new();
692 /// map.insert(1, "b");
693 /// map.insert(2, "a");
694 /// assert_eq!(map.last_key_value(), Some((&2, &"a")));
696 #[unstable(feature = "map_first_last", issue = "62924")]
697 pub fn last_key_value(&self) -> Option<(&K, &V)> {
698 let root_node = self.root.as_ref()?.node_as_ref();
699 root_node.last_leaf_edge().left_kv().ok().map(Handle::into_kv)
702 /// Returns the last entry in the map for in-place manipulation.
703 /// The key of this entry is the maximum key in the map.
708 /// #![feature(map_first_last)]
709 /// use std::collections::BTreeMap;
711 /// let mut map = BTreeMap::new();
712 /// map.insert(1, "a");
713 /// map.insert(2, "b");
714 /// if let Some(mut entry) = map.last_entry() {
715 /// if *entry.key() > 0 {
716 /// entry.insert("last");
719 /// assert_eq!(*map.get(&1).unwrap(), "a");
720 /// assert_eq!(*map.get(&2).unwrap(), "last");
722 #[unstable(feature = "map_first_last", issue = "62924")]
723 pub fn last_entry(&mut self) -> Option<OccupiedEntry<'_, K, V>> {
724 let root_node = self.root.as_mut()?.node_as_mut();
725 let kv = root_node.last_leaf_edge().left_kv().ok()?;
727 handle: kv.forget_node_type(),
728 length: &mut self.length,
729 _marker: PhantomData,
733 /// Removes and returns the last element in the map.
734 /// The key of this element is the maximum key that was in the map.
738 /// Draining elements in descending order, while keeping a usable map each iteration.
741 /// #![feature(map_first_last)]
742 /// use std::collections::BTreeMap;
744 /// let mut map = BTreeMap::new();
745 /// map.insert(1, "a");
746 /// map.insert(2, "b");
747 /// while let Some((key, _val)) = map.pop_last() {
748 /// assert!(map.iter().all(|(k, _v)| *k < key));
750 /// assert!(map.is_empty());
752 #[unstable(feature = "map_first_last", issue = "62924")]
753 pub fn pop_last(&mut self) -> Option<(K, V)> {
754 self.last_entry().map(|entry| entry.remove_entry())
757 /// Returns `true` if the map contains a value for the specified key.
759 /// The key may be any borrowed form of the map's key type, but the ordering
760 /// on the borrowed form *must* match the ordering on the key type.
767 /// use std::collections::BTreeMap;
769 /// let mut map = BTreeMap::new();
770 /// map.insert(1, "a");
771 /// assert_eq!(map.contains_key(&1), true);
772 /// assert_eq!(map.contains_key(&2), false);
774 #[stable(feature = "rust1", since = "1.0.0")]
775 pub fn contains_key<Q: ?Sized>(&self, key: &Q) -> bool
780 self.get(key).is_some()
783 /// Returns a mutable reference to the value corresponding to the key.
785 /// The key may be any borrowed form of the map's key type, but the ordering
786 /// on the borrowed form *must* match the ordering on the key type.
793 /// use std::collections::BTreeMap;
795 /// let mut map = BTreeMap::new();
796 /// map.insert(1, "a");
797 /// if let Some(x) = map.get_mut(&1) {
800 /// assert_eq!(map[&1], "b");
802 // See `get` for implementation notes, this is basically a copy-paste with mut's added
803 #[stable(feature = "rust1", since = "1.0.0")]
804 pub fn get_mut<Q: ?Sized>(&mut self, key: &Q) -> Option<&mut V>
809 let root_node = self.root.as_mut()?.node_as_mut();
810 match search::search_tree(root_node, key) {
811 Found(handle) => Some(handle.into_val_mut()),
816 /// Inserts a key-value pair into the map.
818 /// If the map did not have this key present, `None` is returned.
820 /// If the map did have this key present, the value is updated, and the old
821 /// value is returned. The key is not updated, though; this matters for
822 /// types that can be `==` without being identical. See the [module-level
823 /// documentation] for more.
825 /// [module-level documentation]: index.html#insert-and-complex-keys
832 /// use std::collections::BTreeMap;
834 /// let mut map = BTreeMap::new();
835 /// assert_eq!(map.insert(37, "a"), None);
836 /// assert_eq!(map.is_empty(), false);
838 /// map.insert(37, "b");
839 /// assert_eq!(map.insert(37, "c"), Some("b"));
840 /// assert_eq!(map[&37], "c");
842 #[stable(feature = "rust1", since = "1.0.0")]
843 pub fn insert(&mut self, key: K, value: V) -> Option<V> {
844 match self.entry(key) {
845 Occupied(mut entry) => Some(entry.insert(value)),
853 /// Removes a key from the map, returning the value at the key if the key
854 /// was previously in the map.
856 /// The key may be any borrowed form of the map's key type, but the ordering
857 /// on the borrowed form *must* match the ordering on the key type.
864 /// use std::collections::BTreeMap;
866 /// let mut map = BTreeMap::new();
867 /// map.insert(1, "a");
868 /// assert_eq!(map.remove(&1), Some("a"));
869 /// assert_eq!(map.remove(&1), None);
871 #[stable(feature = "rust1", since = "1.0.0")]
872 pub fn remove<Q: ?Sized>(&mut self, key: &Q) -> Option<V>
877 self.remove_entry(key).map(|(_, v)| v)
880 /// Removes a key from the map, returning the stored key and value if the key
881 /// was previously in the map.
883 /// The key may be any borrowed form of the map's key type, but the ordering
884 /// on the borrowed form *must* match the ordering on the key type.
891 /// use std::collections::BTreeMap;
893 /// let mut map = BTreeMap::new();
894 /// map.insert(1, "a");
895 /// assert_eq!(map.remove_entry(&1), Some((1, "a")));
896 /// assert_eq!(map.remove_entry(&1), None);
898 #[stable(feature = "btreemap_remove_entry", since = "1.45.0")]
899 pub fn remove_entry<Q: ?Sized>(&mut self, key: &Q) -> Option<(K, V)>
904 let root_node = self.root.as_mut()?.node_as_mut();
905 match search::search_tree(root_node, key) {
906 Found(handle) => Some(
907 OccupiedEntry { handle, length: &mut self.length, _marker: PhantomData }
914 /// Moves all elements from `other` into `Self`, leaving `other` empty.
919 /// use std::collections::BTreeMap;
921 /// let mut a = BTreeMap::new();
922 /// a.insert(1, "a");
923 /// a.insert(2, "b");
924 /// a.insert(3, "c");
926 /// let mut b = BTreeMap::new();
927 /// b.insert(3, "d");
928 /// b.insert(4, "e");
929 /// b.insert(5, "f");
931 /// a.append(&mut b);
933 /// assert_eq!(a.len(), 5);
934 /// assert_eq!(b.len(), 0);
936 /// assert_eq!(a[&1], "a");
937 /// assert_eq!(a[&2], "b");
938 /// assert_eq!(a[&3], "d");
939 /// assert_eq!(a[&4], "e");
940 /// assert_eq!(a[&5], "f");
942 #[stable(feature = "btree_append", since = "1.11.0")]
943 pub fn append(&mut self, other: &mut Self) {
944 // Do we have to append anything at all?
945 if other.is_empty() {
949 // We can just swap `self` and `other` if `self` is empty.
951 mem::swap(self, other);
955 // First, we merge `self` and `other` into a sorted sequence in linear time.
956 let self_iter = mem::take(self).into_iter();
957 let other_iter = mem::take(other).into_iter();
958 let iter = MergeIter { left: self_iter.peekable(), right: other_iter.peekable() };
960 // Second, we build a tree from the sorted sequence in linear time.
961 self.from_sorted_iter(iter);
964 /// Constructs a double-ended iterator over a sub-range of elements in the map.
965 /// The simplest way is to use the range syntax `min..max`, thus `range(min..max)` will
966 /// yield elements from min (inclusive) to max (exclusive).
967 /// The range may also be entered as `(Bound<T>, Bound<T>)`, so for example
968 /// `range((Excluded(4), Included(10)))` will yield a left-exclusive, right-inclusive
969 /// range from 4 to 10.
973 /// Panics if range `start > end`.
974 /// Panics if range `start == end` and both bounds are `Excluded`.
981 /// use std::collections::BTreeMap;
982 /// use std::ops::Bound::Included;
984 /// let mut map = BTreeMap::new();
985 /// map.insert(3, "a");
986 /// map.insert(5, "b");
987 /// map.insert(8, "c");
988 /// for (&key, &value) in map.range((Included(&4), Included(&8))) {
989 /// println!("{}: {}", key, value);
991 /// assert_eq!(Some((&5, &"b")), map.range(4..).next());
993 #[stable(feature = "btree_range", since = "1.17.0")]
994 pub fn range<T: ?Sized, R>(&self, range: R) -> Range<'_, K, V>
1000 if let Some(root) = &self.root {
1001 let (f, b) = root.node_as_ref().range_search(range);
1003 Range { front: Some(f), back: Some(b) }
1005 Range { front: None, back: None }
1009 /// Constructs a mutable double-ended iterator over a sub-range of elements in the map.
1010 /// The simplest way is to use the range syntax `min..max`, thus `range(min..max)` will
1011 /// yield elements from min (inclusive) to max (exclusive).
1012 /// The range may also be entered as `(Bound<T>, Bound<T>)`, so for example
1013 /// `range((Excluded(4), Included(10)))` will yield a left-exclusive, right-inclusive
1014 /// range from 4 to 10.
1018 /// Panics if range `start > end`.
1019 /// Panics if range `start == end` and both bounds are `Excluded`.
1026 /// use std::collections::BTreeMap;
1028 /// let mut map: BTreeMap<&str, i32> = ["Alice", "Bob", "Carol", "Cheryl"]
1030 /// .map(|&s| (s, 0))
1032 /// for (_, balance) in map.range_mut("B".."Cheryl") {
1033 /// *balance += 100;
1035 /// for (name, balance) in &map {
1036 /// println!("{} => {}", name, balance);
1039 #[stable(feature = "btree_range", since = "1.17.0")]
1040 pub fn range_mut<T: ?Sized, R>(&mut self, range: R) -> RangeMut<'_, K, V>
1046 if let Some(root) = &mut self.root {
1047 let (f, b) = root.node_as_valmut().range_search(range);
1049 RangeMut { front: Some(f), back: Some(b), _marker: PhantomData }
1051 RangeMut { front: None, back: None, _marker: PhantomData }
1055 /// Gets the given key's corresponding entry in the map for in-place manipulation.
1062 /// use std::collections::BTreeMap;
1064 /// let mut count: BTreeMap<&str, usize> = BTreeMap::new();
1066 /// // count the number of occurrences of letters in the vec
1067 /// for x in vec!["a","b","a","c","a","b"] {
1068 /// *count.entry(x).or_insert(0) += 1;
1071 /// assert_eq!(count["a"], 3);
1073 #[stable(feature = "rust1", since = "1.0.0")]
1074 pub fn entry(&mut self, key: K) -> Entry<'_, K, V> {
1075 // FIXME(@porglezomp) Avoid allocating if we don't insert
1076 let root = Self::ensure_is_owned(&mut self.root);
1077 match search::search_tree(root.node_as_mut(), &key) {
1079 Occupied(OccupiedEntry { handle, length: &mut self.length, _marker: PhantomData })
1082 Vacant(VacantEntry { key, handle, length: &mut self.length, _marker: PhantomData })
1087 fn from_sorted_iter<I: Iterator<Item = (K, V)>>(&mut self, iter: I) {
1088 let root = Self::ensure_is_owned(&mut self.root);
1089 let mut cur_node = root.node_as_mut().last_leaf_edge().into_node();
1090 // Iterate through all key-value pairs, pushing them into nodes at the right level.
1091 for (key, value) in iter {
1092 // Try to push key-value pair into the current leaf node.
1093 if cur_node.len() < node::CAPACITY {
1094 cur_node.push(key, value);
1096 // No space left, go up and push there.
1098 let mut test_node = cur_node.forget_type();
1100 match test_node.ascend() {
1102 let parent = parent.into_node();
1103 if parent.len() < node::CAPACITY {
1104 // Found a node with space left, push here.
1109 test_node = parent.forget_type();
1113 // We are at the top, create a new root node and push there.
1114 open_node = root.push_internal_level();
1120 // Push key-value pair and new right subtree.
1121 let tree_height = open_node.height() - 1;
1122 let mut right_tree = node::Root::new_leaf();
1123 for _ in 0..tree_height {
1124 right_tree.push_internal_level();
1126 open_node.push(key, value, right_tree);
1128 // Go down to the right-most leaf again.
1129 cur_node = open_node.forget_type().last_leaf_edge().into_node();
1134 Self::fix_right_edge(root)
1137 fn fix_right_edge(root: &mut node::Root<K, V>) {
1138 // Handle underfull nodes, start from the top.
1139 let mut cur_node = root.node_as_mut();
1140 while let Internal(internal) = cur_node.force() {
1141 // Check if right-most child is underfull.
1142 let mut last_edge = internal.last_edge();
1143 let right_child_len = last_edge.reborrow().descend().len();
1144 if right_child_len < node::MIN_LEN {
1145 // We need to steal.
1146 let mut last_kv = match last_edge.left_kv() {
1148 Err(_) => unreachable!(),
1150 last_kv.bulk_steal_left(node::MIN_LEN - right_child_len);
1151 last_edge = last_kv.right_edge();
1155 cur_node = last_edge.descend();
1159 /// Splits the collection into two at the given key. Returns everything after the given key,
1160 /// including the key.
1167 /// use std::collections::BTreeMap;
1169 /// let mut a = BTreeMap::new();
1170 /// a.insert(1, "a");
1171 /// a.insert(2, "b");
1172 /// a.insert(3, "c");
1173 /// a.insert(17, "d");
1174 /// a.insert(41, "e");
1176 /// let b = a.split_off(&3);
1178 /// assert_eq!(a.len(), 2);
1179 /// assert_eq!(b.len(), 3);
1181 /// assert_eq!(a[&1], "a");
1182 /// assert_eq!(a[&2], "b");
1184 /// assert_eq!(b[&3], "c");
1185 /// assert_eq!(b[&17], "d");
1186 /// assert_eq!(b[&41], "e");
1188 #[stable(feature = "btree_split_off", since = "1.11.0")]
1189 pub fn split_off<Q: ?Sized + Ord>(&mut self, key: &Q) -> Self
1193 if self.is_empty() {
1197 let total_num = self.len();
1198 let left_root = self.root.as_mut().unwrap(); // unwrap succeeds because not empty
1200 let mut right = Self::new();
1201 let right_root = Self::ensure_is_owned(&mut right.root);
1202 for _ in 0..left_root.height() {
1203 right_root.push_internal_level();
1207 let mut left_node = left_root.node_as_mut();
1208 let mut right_node = right_root.node_as_mut();
1211 let mut split_edge = match search::search_node(left_node, key) {
1212 // key is going to the right tree
1213 Found(handle) => handle.left_edge(),
1214 GoDown(handle) => handle,
1217 split_edge.move_suffix(&mut right_node);
1219 match (split_edge.force(), right_node.force()) {
1220 (Internal(edge), Internal(node)) => {
1221 left_node = edge.descend();
1222 right_node = node.first_edge().descend();
1224 (Leaf(_), Leaf(_)) => {
1234 left_root.fix_right_border();
1235 right_root.fix_left_border();
1237 if left_root.height() < right_root.height() {
1238 self.length = left_root.node_as_ref().calc_length();
1239 right.length = total_num - self.len();
1241 right.length = right_root.node_as_ref().calc_length();
1242 self.length = total_num - right.len();
1248 /// Creates an iterator which uses a closure to determine if an element should be removed.
1250 /// If the closure returns true, the element is removed from the map and yielded.
1251 /// If the closure returns false, or panics, the element remains in the map and will not be
1254 /// Note that `drain_filter` lets you mutate every value in the filter closure, regardless of
1255 /// whether you choose to keep or remove it.
1257 /// If the iterator is only partially consumed or not consumed at all, each of the remaining
1258 /// elements will still be subjected to the closure and removed and dropped if it returns true.
1260 /// It is unspecified how many more elements will be subjected to the closure
1261 /// if a panic occurs in the closure, or a panic occurs while dropping an element,
1262 /// or if the `DrainFilter` value is leaked.
1266 /// Splitting a map into even and odd keys, reusing the original map:
1269 /// #![feature(btree_drain_filter)]
1270 /// use std::collections::BTreeMap;
1272 /// let mut map: BTreeMap<i32, i32> = (0..8).map(|x| (x, x)).collect();
1273 /// let evens: BTreeMap<_, _> = map.drain_filter(|k, _v| k % 2 == 0).collect();
1275 /// assert_eq!(evens.keys().copied().collect::<Vec<_>>(), vec![0, 2, 4, 6]);
1276 /// assert_eq!(odds.keys().copied().collect::<Vec<_>>(), vec![1, 3, 5, 7]);
1278 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1279 pub fn drain_filter<F>(&mut self, pred: F) -> DrainFilter<'_, K, V, F>
1281 F: FnMut(&K, &mut V) -> bool,
1283 DrainFilter { pred, inner: self.drain_filter_inner() }
1286 pub(super) fn drain_filter_inner(&mut self) -> DrainFilterInner<'_, K, V> {
1287 let root_node = self.root.as_mut().map(|r| r.node_as_mut());
1288 let front = root_node.map(|rn| rn.first_leaf_edge());
1289 DrainFilterInner { length: &mut self.length, cur_leaf_edge: front }
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 cur_leaf_edge: Option<Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>>,
1677 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1678 impl<K, V, F> Drop for DrainFilter<'_, K, V, F>
1680 F: FnMut(&K, &mut V) -> bool,
1682 fn drop(&mut self) {
1683 self.for_each(drop);
1687 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1688 impl<K, V, F> fmt::Debug for DrainFilter<'_, K, V, F>
1692 F: FnMut(&K, &mut V) -> bool,
1694 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1695 f.debug_tuple("DrainFilter").field(&self.inner.peek()).finish()
1699 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1700 impl<K, V, F> Iterator for DrainFilter<'_, K, V, F>
1702 F: FnMut(&K, &mut V) -> bool,
1706 fn next(&mut self) -> Option<(K, V)> {
1707 self.inner.next(&mut self.pred)
1710 fn size_hint(&self) -> (usize, Option<usize>) {
1711 self.inner.size_hint()
1715 impl<'a, K: 'a, V: 'a> DrainFilterInner<'a, K, V> {
1716 /// Allow Debug implementations to predict the next element.
1717 pub(super) fn peek(&self) -> Option<(&K, &V)> {
1718 let edge = self.cur_leaf_edge.as_ref()?;
1719 edge.reborrow().next_kv().ok().map(|kv| kv.into_kv())
1722 /// Implementation of a typical `DrainFilter::next` method, given the predicate.
1723 pub(super) fn next<F>(&mut self, pred: &mut F) -> Option<(K, V)>
1725 F: FnMut(&K, &mut V) -> bool,
1727 while let Ok(mut kv) = self.cur_leaf_edge.take()?.next_kv() {
1728 let (k, v) = kv.kv_mut();
1731 let (kv, pos) = kv.remove_kv_tracking();
1732 self.cur_leaf_edge = Some(pos);
1735 self.cur_leaf_edge = Some(kv.next_leaf_edge());
1740 /// Implementation of a typical `DrainFilter::size_hint` method.
1741 pub(super) fn size_hint(&self) -> (usize, Option<usize>) {
1742 (0, Some(*self.length))
1746 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1747 impl<K, V, F> FusedIterator for DrainFilter<'_, K, V, F> where F: FnMut(&K, &mut V) -> bool {}
1749 #[stable(feature = "btree_range", since = "1.17.0")]
1750 impl<'a, K, V> Iterator for Range<'a, K, V> {
1751 type Item = (&'a K, &'a V);
1753 fn next(&mut self) -> Option<(&'a K, &'a V)> {
1754 if self.is_empty() { None } else { unsafe { Some(self.next_unchecked()) } }
1757 fn last(mut self) -> Option<(&'a K, &'a V)> {
1761 fn min(mut self) -> Option<(&'a K, &'a V)> {
1765 fn max(mut self) -> Option<(&'a K, &'a V)> {
1770 #[stable(feature = "map_values_mut", since = "1.10.0")]
1771 impl<'a, K, V> Iterator for ValuesMut<'a, K, V> {
1772 type Item = &'a mut V;
1774 fn next(&mut self) -> Option<&'a mut V> {
1775 self.inner.next().map(|(_, v)| v)
1778 fn size_hint(&self) -> (usize, Option<usize>) {
1779 self.inner.size_hint()
1782 fn last(mut self) -> Option<&'a mut V> {
1787 #[stable(feature = "map_values_mut", since = "1.10.0")]
1788 impl<'a, K, V> DoubleEndedIterator for ValuesMut<'a, K, V> {
1789 fn next_back(&mut self) -> Option<&'a mut V> {
1790 self.inner.next_back().map(|(_, v)| v)
1794 #[stable(feature = "map_values_mut", since = "1.10.0")]
1795 impl<K, V> ExactSizeIterator for ValuesMut<'_, K, V> {
1796 fn len(&self) -> usize {
1801 #[stable(feature = "fused", since = "1.26.0")]
1802 impl<K, V> FusedIterator for ValuesMut<'_, K, V> {}
1804 impl<'a, K, V> Range<'a, K, V> {
1805 fn is_empty(&self) -> bool {
1806 self.front == self.back
1809 unsafe fn next_unchecked(&mut self) -> (&'a K, &'a V) {
1810 unsafe { unwrap_unchecked(self.front.as_mut()).next_unchecked() }
1814 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1815 impl<K, V> Iterator for IntoKeys<K, V> {
1818 fn next(&mut self) -> Option<K> {
1819 self.inner.next().map(|(k, _)| k)
1822 fn size_hint(&self) -> (usize, Option<usize>) {
1823 self.inner.size_hint()
1826 fn last(mut self) -> Option<K> {
1830 fn min(mut self) -> Option<K> {
1834 fn max(mut self) -> Option<K> {
1839 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1840 impl<K, V> DoubleEndedIterator for IntoKeys<K, V> {
1841 fn next_back(&mut self) -> Option<K> {
1842 self.inner.next_back().map(|(k, _)| k)
1846 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1847 impl<K, V> ExactSizeIterator for IntoKeys<K, V> {
1848 fn len(&self) -> usize {
1853 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1854 impl<K, V> FusedIterator for IntoKeys<K, V> {}
1856 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1857 impl<K, V> Iterator for IntoValues<K, V> {
1860 fn next(&mut self) -> Option<V> {
1861 self.inner.next().map(|(_, v)| v)
1864 fn size_hint(&self) -> (usize, Option<usize>) {
1865 self.inner.size_hint()
1868 fn last(mut self) -> Option<V> {
1873 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1874 impl<K, V> DoubleEndedIterator for IntoValues<K, V> {
1875 fn next_back(&mut self) -> Option<V> {
1876 self.inner.next_back().map(|(_, v)| v)
1880 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1881 impl<K, V> ExactSizeIterator for IntoValues<K, V> {
1882 fn len(&self) -> usize {
1887 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1888 impl<K, V> FusedIterator for IntoValues<K, V> {}
1890 #[stable(feature = "btree_range", since = "1.17.0")]
1891 impl<'a, K, V> DoubleEndedIterator for Range<'a, K, V> {
1892 fn next_back(&mut self) -> Option<(&'a K, &'a V)> {
1893 if self.is_empty() { None } else { Some(unsafe { self.next_back_unchecked() }) }
1897 impl<'a, K, V> Range<'a, K, V> {
1898 unsafe fn next_back_unchecked(&mut self) -> (&'a K, &'a V) {
1899 unsafe { unwrap_unchecked(self.back.as_mut()).next_back_unchecked() }
1903 #[stable(feature = "fused", since = "1.26.0")]
1904 impl<K, V> FusedIterator for Range<'_, K, V> {}
1906 #[stable(feature = "btree_range", since = "1.17.0")]
1907 impl<K, V> Clone for Range<'_, K, V> {
1908 fn clone(&self) -> Self {
1909 Range { front: self.front, back: self.back }
1913 #[stable(feature = "btree_range", since = "1.17.0")]
1914 impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
1915 type Item = (&'a K, &'a mut V);
1917 fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
1918 if self.is_empty() {
1921 let (k, v) = unsafe { self.next_unchecked() };
1922 Some((k, v)) // coerce k from `&mut K` to `&K`
1926 fn last(mut self) -> Option<(&'a K, &'a mut V)> {
1930 fn min(mut self) -> Option<(&'a K, &'a mut V)> {
1934 fn max(mut self) -> Option<(&'a K, &'a mut V)> {
1939 impl<'a, K, V> RangeMut<'a, K, V> {
1940 fn is_empty(&self) -> bool {
1941 self.front == self.back
1944 unsafe fn next_unchecked(&mut self) -> (&'a K, &'a mut V) {
1945 unsafe { unwrap_unchecked(self.front.as_mut()).next_unchecked() }
1949 #[stable(feature = "btree_range", since = "1.17.0")]
1950 impl<'a, K, V> DoubleEndedIterator for RangeMut<'a, K, V> {
1951 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> {
1952 if self.is_empty() {
1955 let (k, v) = unsafe { self.next_back_unchecked() };
1956 Some((k, v)) // coerce k from `&mut K` to `&K`
1961 #[stable(feature = "fused", since = "1.26.0")]
1962 impl<K, V> FusedIterator for RangeMut<'_, K, V> {}
1964 impl<'a, K, V> RangeMut<'a, K, V> {
1965 unsafe fn next_back_unchecked(&mut self) -> (&'a K, &'a mut V) {
1966 unsafe { unwrap_unchecked(self.back.as_mut()).next_back_unchecked() }
1970 #[stable(feature = "rust1", since = "1.0.0")]
1971 impl<K: Ord, V> FromIterator<(K, V)> for BTreeMap<K, V> {
1972 fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> BTreeMap<K, V> {
1973 let mut map = BTreeMap::new();
1979 #[stable(feature = "rust1", since = "1.0.0")]
1980 impl<K: Ord, V> Extend<(K, V)> for BTreeMap<K, V> {
1982 fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T) {
1983 iter.into_iter().for_each(move |(k, v)| {
1989 fn extend_one(&mut self, (k, v): (K, V)) {
1994 #[stable(feature = "extend_ref", since = "1.2.0")]
1995 impl<'a, K: Ord + Copy, V: Copy> Extend<(&'a K, &'a V)> for BTreeMap<K, V> {
1996 fn extend<I: IntoIterator<Item = (&'a K, &'a V)>>(&mut self, iter: I) {
1997 self.extend(iter.into_iter().map(|(&key, &value)| (key, value)));
2001 fn extend_one(&mut self, (&k, &v): (&'a K, &'a V)) {
2006 #[stable(feature = "rust1", since = "1.0.0")]
2007 impl<K: Hash, V: Hash> Hash for BTreeMap<K, V> {
2008 fn hash<H: Hasher>(&self, state: &mut H) {
2015 #[stable(feature = "rust1", since = "1.0.0")]
2016 impl<K: Ord, V> Default for BTreeMap<K, V> {
2017 /// Creates an empty `BTreeMap<K, V>`.
2018 fn default() -> BTreeMap<K, V> {
2023 #[stable(feature = "rust1", since = "1.0.0")]
2024 impl<K: PartialEq, V: PartialEq> PartialEq for BTreeMap<K, V> {
2025 fn eq(&self, other: &BTreeMap<K, V>) -> bool {
2026 self.len() == other.len() && self.iter().zip(other).all(|(a, b)| a == b)
2030 #[stable(feature = "rust1", since = "1.0.0")]
2031 impl<K: Eq, V: Eq> Eq for BTreeMap<K, V> {}
2033 #[stable(feature = "rust1", since = "1.0.0")]
2034 impl<K: PartialOrd, V: PartialOrd> PartialOrd for BTreeMap<K, V> {
2036 fn partial_cmp(&self, other: &BTreeMap<K, V>) -> Option<Ordering> {
2037 self.iter().partial_cmp(other.iter())
2041 #[stable(feature = "rust1", since = "1.0.0")]
2042 impl<K: Ord, V: Ord> Ord for BTreeMap<K, V> {
2044 fn cmp(&self, other: &BTreeMap<K, V>) -> Ordering {
2045 self.iter().cmp(other.iter())
2049 #[stable(feature = "rust1", since = "1.0.0")]
2050 impl<K: Debug, V: Debug> Debug for BTreeMap<K, V> {
2051 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2052 f.debug_map().entries(self.iter()).finish()
2056 #[stable(feature = "rust1", since = "1.0.0")]
2057 impl<K: Ord, Q: ?Sized, V> Index<&Q> for BTreeMap<K, V>
2064 /// Returns a reference to the value corresponding to the supplied key.
2068 /// Panics if the key is not present in the `BTreeMap`.
2070 fn index(&self, key: &Q) -> &V {
2071 self.get(key).expect("no entry found for key")
2075 impl<K, V> BTreeMap<K, V> {
2076 /// Gets an iterator over the entries of the map, sorted by key.
2083 /// use std::collections::BTreeMap;
2085 /// let mut map = BTreeMap::new();
2086 /// map.insert(3, "c");
2087 /// map.insert(2, "b");
2088 /// map.insert(1, "a");
2090 /// for (key, value) in map.iter() {
2091 /// println!("{}: {}", key, value);
2094 /// let (first_key, first_value) = map.iter().next().unwrap();
2095 /// assert_eq!((*first_key, *first_value), (1, "a"));
2097 #[stable(feature = "rust1", since = "1.0.0")]
2098 pub fn iter(&self) -> Iter<'_, K, V> {
2099 if let Some(root) = &self.root {
2100 let (f, b) = root.node_as_ref().full_range();
2102 Iter { range: Range { front: Some(f), back: Some(b) }, length: self.length }
2104 Iter { range: Range { front: None, back: None }, length: 0 }
2108 /// Gets a mutable iterator over the entries of the map, sorted by key.
2115 /// use std::collections::BTreeMap;
2117 /// let mut map = BTreeMap::new();
2118 /// map.insert("a", 1);
2119 /// map.insert("b", 2);
2120 /// map.insert("c", 3);
2122 /// // add 10 to the value if the key isn't "a"
2123 /// for (key, value) in map.iter_mut() {
2124 /// if key != &"a" {
2129 #[stable(feature = "rust1", since = "1.0.0")]
2130 pub fn iter_mut(&mut self) -> IterMut<'_, K, V> {
2131 if let Some(root) = &mut self.root {
2132 let (f, b) = root.node_as_valmut().full_range();
2135 range: RangeMut { front: Some(f), back: Some(b), _marker: PhantomData },
2136 length: self.length,
2139 IterMut { range: RangeMut { front: None, back: None, _marker: PhantomData }, length: 0 }
2143 /// Gets an iterator over the keys of the map, in sorted order.
2150 /// use std::collections::BTreeMap;
2152 /// let mut a = BTreeMap::new();
2153 /// a.insert(2, "b");
2154 /// a.insert(1, "a");
2156 /// let keys: Vec<_> = a.keys().cloned().collect();
2157 /// assert_eq!(keys, [1, 2]);
2159 #[stable(feature = "rust1", since = "1.0.0")]
2160 pub fn keys(&self) -> Keys<'_, K, V> {
2161 Keys { inner: self.iter() }
2164 /// Gets an iterator over the values of the map, in order by key.
2171 /// use std::collections::BTreeMap;
2173 /// let mut a = BTreeMap::new();
2174 /// a.insert(1, "hello");
2175 /// a.insert(2, "goodbye");
2177 /// let values: Vec<&str> = a.values().cloned().collect();
2178 /// assert_eq!(values, ["hello", "goodbye"]);
2180 #[stable(feature = "rust1", since = "1.0.0")]
2181 pub fn values(&self) -> Values<'_, K, V> {
2182 Values { inner: self.iter() }
2185 /// Gets a mutable iterator over the values of the map, in order by key.
2192 /// use std::collections::BTreeMap;
2194 /// let mut a = BTreeMap::new();
2195 /// a.insert(1, String::from("hello"));
2196 /// a.insert(2, String::from("goodbye"));
2198 /// for value in a.values_mut() {
2199 /// value.push_str("!");
2202 /// let values: Vec<String> = a.values().cloned().collect();
2203 /// assert_eq!(values, [String::from("hello!"),
2204 /// String::from("goodbye!")]);
2206 #[stable(feature = "map_values_mut", since = "1.10.0")]
2207 pub fn values_mut(&mut self) -> ValuesMut<'_, K, V> {
2208 ValuesMut { inner: self.iter_mut() }
2211 /// Returns the number of elements in the map.
2218 /// use std::collections::BTreeMap;
2220 /// let mut a = BTreeMap::new();
2221 /// assert_eq!(a.len(), 0);
2222 /// a.insert(1, "a");
2223 /// assert_eq!(a.len(), 1);
2225 #[stable(feature = "rust1", since = "1.0.0")]
2226 pub fn len(&self) -> usize {
2230 /// Returns `true` if the map contains no elements.
2237 /// use std::collections::BTreeMap;
2239 /// let mut a = BTreeMap::new();
2240 /// assert!(a.is_empty());
2241 /// a.insert(1, "a");
2242 /// assert!(!a.is_empty());
2244 #[stable(feature = "rust1", since = "1.0.0")]
2245 pub fn is_empty(&self) -> bool {
2249 /// If the root node is the empty (non-allocated) root node, allocate our
2250 /// own node. Is an associated function to avoid borrowing the entire BTreeMap.
2251 fn ensure_is_owned(root: &mut Option<node::Root<K, V>>) -> &mut node::Root<K, V> {
2252 root.get_or_insert_with(node::Root::new_leaf)
2256 impl<'a, K: Ord, V> Entry<'a, K, V> {
2257 /// Ensures a value is in the entry by inserting the default if empty, and returns
2258 /// a mutable reference to the value in the entry.
2263 /// use std::collections::BTreeMap;
2265 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2266 /// map.entry("poneyland").or_insert(12);
2268 /// assert_eq!(map["poneyland"], 12);
2270 #[stable(feature = "rust1", since = "1.0.0")]
2271 pub fn or_insert(self, default: V) -> &'a mut V {
2273 Occupied(entry) => entry.into_mut(),
2274 Vacant(entry) => entry.insert(default),
2278 /// Ensures a value is in the entry by inserting the result of the default function if empty,
2279 /// and returns a mutable reference to the value in the entry.
2284 /// use std::collections::BTreeMap;
2286 /// let mut map: BTreeMap<&str, String> = BTreeMap::new();
2287 /// let s = "hoho".to_string();
2289 /// map.entry("poneyland").or_insert_with(|| s);
2291 /// assert_eq!(map["poneyland"], "hoho".to_string());
2293 #[stable(feature = "rust1", since = "1.0.0")]
2294 pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V {
2296 Occupied(entry) => entry.into_mut(),
2297 Vacant(entry) => entry.insert(default()),
2301 #[unstable(feature = "or_insert_with_key", issue = "71024")]
2302 /// Ensures a value is in the entry by inserting, if empty, the result of the default function,
2303 /// which takes the key as its argument, and returns a mutable reference to the value in the
2309 /// #![feature(or_insert_with_key)]
2310 /// use std::collections::BTreeMap;
2312 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2314 /// map.entry("poneyland").or_insert_with_key(|key| key.chars().count());
2316 /// assert_eq!(map["poneyland"], 9);
2319 pub fn or_insert_with_key<F: FnOnce(&K) -> V>(self, default: F) -> &'a mut V {
2321 Occupied(entry) => entry.into_mut(),
2323 let value = default(entry.key());
2329 /// Returns a reference to this entry's key.
2334 /// use std::collections::BTreeMap;
2336 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2337 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2339 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2340 pub fn key(&self) -> &K {
2342 Occupied(ref entry) => entry.key(),
2343 Vacant(ref entry) => entry.key(),
2347 /// Provides in-place mutable access to an occupied entry before any
2348 /// potential inserts into the map.
2353 /// use std::collections::BTreeMap;
2355 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2357 /// map.entry("poneyland")
2358 /// .and_modify(|e| { *e += 1 })
2360 /// assert_eq!(map["poneyland"], 42);
2362 /// map.entry("poneyland")
2363 /// .and_modify(|e| { *e += 1 })
2365 /// assert_eq!(map["poneyland"], 43);
2367 #[stable(feature = "entry_and_modify", since = "1.26.0")]
2368 pub fn and_modify<F>(self, f: F) -> Self
2373 Occupied(mut entry) => {
2377 Vacant(entry) => Vacant(entry),
2382 impl<'a, K: Ord, V: Default> Entry<'a, K, V> {
2383 #[stable(feature = "entry_or_default", since = "1.28.0")]
2384 /// Ensures a value is in the entry by inserting the default value if empty,
2385 /// and returns a mutable reference to the value in the entry.
2390 /// use std::collections::BTreeMap;
2392 /// let mut map: BTreeMap<&str, Option<usize>> = BTreeMap::new();
2393 /// map.entry("poneyland").or_default();
2395 /// assert_eq!(map["poneyland"], None);
2397 pub fn or_default(self) -> &'a mut V {
2399 Occupied(entry) => entry.into_mut(),
2400 Vacant(entry) => entry.insert(Default::default()),
2405 impl<'a, K: Ord, V> VacantEntry<'a, K, V> {
2406 /// Gets a reference to the key that would be used when inserting a value
2407 /// through the VacantEntry.
2412 /// use std::collections::BTreeMap;
2414 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2415 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2417 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2418 pub fn key(&self) -> &K {
2422 /// Take ownership of the key.
2427 /// use std::collections::BTreeMap;
2428 /// use std::collections::btree_map::Entry;
2430 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2432 /// if let Entry::Vacant(v) = map.entry("poneyland") {
2436 #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
2437 pub fn into_key(self) -> K {
2441 /// Sets the value of the entry with the `VacantEntry`'s key,
2442 /// and returns a mutable reference to it.
2447 /// use std::collections::BTreeMap;
2448 /// use std::collections::btree_map::Entry;
2450 /// let mut map: BTreeMap<&str, u32> = BTreeMap::new();
2452 /// if let Entry::Vacant(o) = map.entry("poneyland") {
2455 /// assert_eq!(map["poneyland"], 37);
2457 #[stable(feature = "rust1", since = "1.0.0")]
2458 pub fn insert(self, value: V) -> &'a mut V {
2461 let out_ptr = match self.handle.insert_recursing(self.key, value) {
2462 (Fit(_), val_ptr) => val_ptr,
2463 (Split(ins), val_ptr) => {
2464 let root = ins.left.into_root_mut();
2465 root.push_internal_level().push(ins.k, ins.v, ins.right);
2469 // Now that we have finished growing the tree using borrowed references,
2470 // dereference the pointer to a part of it, that we picked up along the way.
2471 unsafe { &mut *out_ptr }
2475 impl<'a, K: Ord, V> OccupiedEntry<'a, K, V> {
2476 /// Gets a reference to the key in the entry.
2481 /// use std::collections::BTreeMap;
2483 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2484 /// map.entry("poneyland").or_insert(12);
2485 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2487 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2488 pub fn key(&self) -> &K {
2489 self.handle.reborrow().into_kv().0
2492 /// Take ownership of the key and value from the map.
2497 /// use std::collections::BTreeMap;
2498 /// use std::collections::btree_map::Entry;
2500 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2501 /// map.entry("poneyland").or_insert(12);
2503 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2504 /// // We delete the entry from the map.
2505 /// o.remove_entry();
2508 /// // If now try to get the value, it will panic:
2509 /// // println!("{}", map["poneyland"]);
2511 #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
2512 pub fn remove_entry(self) -> (K, V) {
2516 /// Gets a reference to the value in the entry.
2521 /// use std::collections::BTreeMap;
2522 /// use std::collections::btree_map::Entry;
2524 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2525 /// map.entry("poneyland").or_insert(12);
2527 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2528 /// assert_eq!(o.get(), &12);
2531 #[stable(feature = "rust1", since = "1.0.0")]
2532 pub fn get(&self) -> &V {
2533 self.handle.reborrow().into_kv().1
2536 /// Gets a mutable reference to the value in the entry.
2538 /// If you need a reference to the `OccupiedEntry` that may outlive the
2539 /// destruction of the `Entry` value, see [`into_mut`].
2541 /// [`into_mut`]: #method.into_mut
2546 /// use std::collections::BTreeMap;
2547 /// use std::collections::btree_map::Entry;
2549 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2550 /// map.entry("poneyland").or_insert(12);
2552 /// assert_eq!(map["poneyland"], 12);
2553 /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
2554 /// *o.get_mut() += 10;
2555 /// assert_eq!(*o.get(), 22);
2557 /// // We can use the same Entry multiple times.
2558 /// *o.get_mut() += 2;
2560 /// assert_eq!(map["poneyland"], 24);
2562 #[stable(feature = "rust1", since = "1.0.0")]
2563 pub fn get_mut(&mut self) -> &mut V {
2564 self.handle.kv_mut().1
2567 /// Converts the entry into a mutable reference to its value.
2569 /// If you need multiple references to the `OccupiedEntry`, see [`get_mut`].
2571 /// [`get_mut`]: #method.get_mut
2576 /// use std::collections::BTreeMap;
2577 /// use std::collections::btree_map::Entry;
2579 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2580 /// map.entry("poneyland").or_insert(12);
2582 /// assert_eq!(map["poneyland"], 12);
2583 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2584 /// *o.into_mut() += 10;
2586 /// assert_eq!(map["poneyland"], 22);
2588 #[stable(feature = "rust1", since = "1.0.0")]
2589 pub fn into_mut(self) -> &'a mut V {
2590 self.handle.into_val_mut()
2593 /// Sets the value of the entry with the `OccupiedEntry`'s key,
2594 /// and returns the entry's old value.
2599 /// use std::collections::BTreeMap;
2600 /// use std::collections::btree_map::Entry;
2602 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2603 /// map.entry("poneyland").or_insert(12);
2605 /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
2606 /// assert_eq!(o.insert(15), 12);
2608 /// assert_eq!(map["poneyland"], 15);
2610 #[stable(feature = "rust1", since = "1.0.0")]
2611 pub fn insert(&mut self, value: V) -> V {
2612 mem::replace(self.get_mut(), value)
2615 /// Takes the value of the entry out of the map, and returns it.
2620 /// use std::collections::BTreeMap;
2621 /// use std::collections::btree_map::Entry;
2623 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2624 /// map.entry("poneyland").or_insert(12);
2626 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2627 /// assert_eq!(o.remove(), 12);
2629 /// // If we try to get "poneyland"'s value, it'll panic:
2630 /// // println!("{}", map["poneyland"]);
2632 #[stable(feature = "rust1", since = "1.0.0")]
2633 pub fn remove(self) -> V {
2637 // Body of `remove_entry`, separate to keep the above implementations short.
2638 fn remove_kv(self) -> (K, V) {
2641 let (old_kv, _) = self.handle.remove_kv_tracking();
2646 impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, marker::KV> {
2647 /// Removes a key/value-pair from the map, and returns that pair, as well as
2648 /// the leaf edge corresponding to that former pair.
2649 fn remove_kv_tracking(
2651 ) -> ((K, V), Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>) {
2652 let (old_kv, mut pos, was_internal) = match self.force() {
2654 let (old_kv, pos) = leaf.remove();
2655 (old_kv, pos, false)
2657 Internal(mut internal) => {
2658 // Replace the location freed in the internal node with an
2659 // adjacent KV, and remove that adjacent KV from its leaf.
2660 // Always choose the adjacent KV on the left side because
2661 // it is typically faster to pop an element from the end
2662 // of the KV arrays without needing to shift other elements.
2664 let key_loc = internal.kv_mut().0 as *mut K;
2665 let val_loc = internal.kv_mut().1 as *mut V;
2667 let to_remove = internal.left_edge().descend().last_leaf_edge().left_kv().ok();
2668 let to_remove = unsafe { unwrap_unchecked(to_remove) };
2670 let (kv, pos) = to_remove.remove();
2672 let old_key = unsafe { mem::replace(&mut *key_loc, kv.0) };
2673 let old_val = unsafe { mem::replace(&mut *val_loc, kv.1) };
2675 ((old_key, old_val), pos, true)
2680 let mut cur_node = unsafe { ptr::read(&pos).into_node().forget_type() };
2681 let mut at_leaf = true;
2682 while cur_node.len() < node::MIN_LEN {
2683 match handle_underfull_node(cur_node) {
2685 Merged(edge, merged_with_left, offset) => {
2686 // If we merged with our right sibling then our tracked
2687 // position has not changed. However if we merged with our
2688 // left sibling then our tracked position is now dangling.
2689 if at_leaf && merged_with_left {
2690 let idx = pos.idx() + offset;
2691 let node = match unsafe { ptr::read(&edge).descend().force() } {
2693 Internal(_) => unreachable!(),
2695 pos = unsafe { Handle::new_edge(node, idx) };
2698 let parent = edge.into_node();
2699 if parent.len() == 0 {
2700 // The parent that was just emptied must be the root,
2701 // because nodes on a lower level would not have been
2702 // left with a single child.
2703 parent.into_root_mut().pop_internal_level();
2706 cur_node = parent.forget_type();
2710 Stole(stole_from_left) => {
2711 // Adjust the tracked position if we stole from a left sibling
2712 if stole_from_left && at_leaf {
2713 // SAFETY: This is safe since we just added an element to our node.
2715 pos.move_next_unchecked();
2723 // If we deleted from an internal node then we need to compensate for
2724 // the earlier swap and adjust the tracked position to point to the
2727 pos = unsafe { unwrap_unchecked(pos.next_kv().ok()).next_leaf_edge() };
2734 impl<K, V> node::Root<K, V> {
2735 /// Removes empty levels on the top, but keep an empty leaf if the entire tree is empty.
2736 fn fix_top(&mut self) {
2737 while self.height() > 0 && self.node_as_ref().len() == 0 {
2738 self.pop_internal_level();
2742 fn fix_right_border(&mut self) {
2746 let mut cur_node = self.node_as_mut();
2748 while let Internal(node) = cur_node.force() {
2749 let mut last_kv = node.last_kv();
2751 if last_kv.can_merge() {
2752 cur_node = last_kv.merge().descend();
2754 let right_len = last_kv.reborrow().right_edge().descend().len();
2755 // `MINLEN + 1` to avoid readjust if merge happens on the next level.
2756 if right_len < node::MIN_LEN + 1 {
2757 last_kv.bulk_steal_left(node::MIN_LEN + 1 - right_len);
2759 cur_node = last_kv.right_edge().descend();
2767 /// The symmetric clone of `fix_right_border`.
2768 fn fix_left_border(&mut self) {
2772 let mut cur_node = self.node_as_mut();
2774 while let Internal(node) = cur_node.force() {
2775 let mut first_kv = node.first_kv();
2777 if first_kv.can_merge() {
2778 cur_node = first_kv.merge().descend();
2780 let left_len = first_kv.reborrow().left_edge().descend().len();
2781 if left_len < node::MIN_LEN + 1 {
2782 first_kv.bulk_steal_right(node::MIN_LEN + 1 - left_len);
2784 cur_node = first_kv.left_edge().descend();
2793 enum UnderflowResult<'a, K, V> {
2795 Merged(Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::Edge>, bool, usize),
2799 fn handle_underfull_node<'a, K: 'a, V: 'a>(
2800 node: NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>,
2801 ) -> UnderflowResult<'_, K, V> {
2802 let parent = match node.ascend() {
2803 Ok(parent) => parent,
2804 Err(_) => return AtRoot,
2807 // Prefer the left KV if it exists. Merging with the left side is faster,
2808 // since merging happens towards the left and `node` has fewer elements.
2809 // Stealing from the left side is faster, since we can pop from the end of
2811 let (is_left, mut handle) = match parent.left_kv() {
2812 Ok(left) => (true, left),
2814 let right = unsafe { unwrap_unchecked(parent.right_kv().ok()) };
2819 if handle.can_merge() {
2820 let offset = if is_left { handle.reborrow().left_edge().descend().len() + 1 } else { 0 };
2821 Merged(handle.merge(), is_left, offset)
2824 handle.steal_left();
2826 handle.steal_right();
2832 impl<K: Ord, V, I: Iterator<Item = (K, V)>> Iterator for MergeIter<K, V, I> {
2835 fn next(&mut self) -> Option<(K, V)> {
2836 let res = match (self.left.peek(), self.right.peek()) {
2837 (Some(&(ref left_key, _)), Some(&(ref right_key, _))) => left_key.cmp(right_key),
2838 (Some(_), None) => Ordering::Less,
2839 (None, Some(_)) => Ordering::Greater,
2840 (None, None) => return None,
2843 // Check which elements comes first and only advance the corresponding iterator.
2844 // If two keys are equal, take the value from `right`.
2846 Ordering::Less => self.left.next(),
2847 Ordering::Greater => self.right.next(),
2848 Ordering::Equal => {