1 use core::borrow::Borrow;
2 use core::cmp::Ordering;
4 use core::hash::{Hash, Hasher};
5 use core::iter::{FromIterator, FusedIterator, Peekable};
6 use core::marker::PhantomData;
7 use core::mem::{self, ManuallyDrop};
8 use core::ops::Bound::{Excluded, Included, Unbounded};
9 use core::ops::{Index, RangeBounds};
12 use super::node::{self, marker, ForceResult::*, Handle, InsertResult::*, NodeRef};
13 use super::search::{self, SearchResult::*};
14 use super::unwrap_unchecked;
17 use UnderflowResult::*;
19 /// A map based on a B-Tree.
21 /// B-Trees represent a fundamental compromise between cache-efficiency and actually minimizing
22 /// the amount of work performed in a search. In theory, a binary search tree (BST) is the optimal
23 /// choice for a sorted map, as a perfectly balanced BST performs the theoretical minimum amount of
24 /// comparisons necessary to find an element (log<sub>2</sub>n). However, in practice the way this
25 /// is done is *very* inefficient for modern computer architectures. In particular, every element
26 /// is stored in its own individually heap-allocated node. This means that every single insertion
27 /// triggers a heap-allocation, and every single comparison should be a cache-miss. Since these
28 /// are both notably expensive things to do in practice, we are forced to at very least reconsider
31 /// A B-Tree instead makes each node contain B-1 to 2B-1 elements in a contiguous array. By doing
32 /// this, we reduce the number of allocations by a factor of B, and improve cache efficiency in
33 /// searches. However, this does mean that searches will have to do *more* comparisons on average.
34 /// The precise number of comparisons depends on the node search strategy used. For optimal cache
35 /// efficiency, one could search the nodes linearly. For optimal comparisons, one could search
36 /// the node using binary search. As a compromise, one could also perform a linear search
37 /// that initially only checks every i<sup>th</sup> element for some choice of i.
39 /// Currently, our implementation simply performs naive linear search. This provides excellent
40 /// performance on *small* nodes of elements which are cheap to compare. However in the future we
41 /// would like to further explore choosing the optimal search strategy based on the choice of B,
42 /// and possibly other factors. Using linear search, searching for a random element is expected
43 /// to take O(B * log(n)) comparisons, which is generally worse than a BST. In practice,
44 /// however, performance is excellent.
46 /// It is a logic error for a key to be modified in such a way that the key's ordering relative to
47 /// any other key, as determined by the [`Ord`] trait, changes while it is in the map. This is
48 /// normally only possible through [`Cell`], [`RefCell`], global state, I/O, or unsafe code.
50 /// [`Ord`]: ../../std/cmp/trait.Ord.html
51 /// [`Cell`]: ../../std/cell/struct.Cell.html
52 /// [`RefCell`]: ../../std/cell/struct.RefCell.html
57 /// use std::collections::BTreeMap;
59 /// // type inference lets us omit an explicit type signature (which
60 /// // would be `BTreeMap<&str, &str>` in this example).
61 /// let mut movie_reviews = BTreeMap::new();
63 /// // review some movies.
64 /// movie_reviews.insert("Office Space", "Deals with real issues in the workplace.");
65 /// movie_reviews.insert("Pulp Fiction", "Masterpiece.");
66 /// movie_reviews.insert("The Godfather", "Very enjoyable.");
67 /// movie_reviews.insert("The Blues Brothers", "Eye lyked it a lot.");
69 /// // check for a specific one.
70 /// if !movie_reviews.contains_key("Les Misérables") {
71 /// println!("We've got {} reviews, but Les Misérables ain't one.",
72 /// movie_reviews.len());
75 /// // oops, this review has a lot of spelling mistakes, let's delete it.
76 /// movie_reviews.remove("The Blues Brothers");
78 /// // look up the values associated with some keys.
79 /// let to_find = ["Up!", "Office Space"];
80 /// for movie in &to_find {
81 /// match movie_reviews.get(movie) {
82 /// Some(review) => println!("{}: {}", movie, review),
83 /// None => println!("{} is unreviewed.", movie)
87 /// // Look up the value for a key (will panic if the key is not found).
88 /// println!("Movie review: {}", movie_reviews["Office Space"]);
90 /// // iterate over everything.
91 /// for (movie, review) in &movie_reviews {
92 /// println!("{}: \"{}\"", movie, review);
96 /// `BTreeMap` also implements an [`Entry API`](#method.entry), which allows
97 /// for more complex methods of getting, setting, updating and removing keys and
101 /// use std::collections::BTreeMap;
103 /// // type inference lets us omit an explicit type signature (which
104 /// // would be `BTreeMap<&str, u8>` in this example).
105 /// let mut player_stats = BTreeMap::new();
107 /// fn random_stat_buff() -> u8 {
108 /// // could actually return some random value here - let's just return
109 /// // some fixed value for now
113 /// // insert a key only if it doesn't already exist
114 /// player_stats.entry("health").or_insert(100);
116 /// // insert a key using a function that provides a new value only if it
117 /// // doesn't already exist
118 /// player_stats.entry("defence").or_insert_with(random_stat_buff);
120 /// // update a key, guarding against the key possibly not being set
121 /// let stat = player_stats.entry("attack").or_insert(100);
122 /// *stat += random_stat_buff();
124 #[stable(feature = "rust1", since = "1.0.0")]
125 pub struct BTreeMap<K, V> {
126 root: Option<node::Root<K, V>>,
130 #[stable(feature = "btree_drop", since = "1.7.0")]
131 unsafe impl<#[may_dangle] K, #[may_dangle] V> Drop for BTreeMap<K, V> {
134 drop(ptr::read(self).into_iter());
139 #[stable(feature = "rust1", since = "1.0.0")]
140 impl<K: Clone, V: Clone> Clone for BTreeMap<K, V> {
141 fn clone(&self) -> BTreeMap<K, V> {
142 fn clone_subtree<'a, K: Clone, V: Clone>(
143 node: node::NodeRef<marker::Immut<'a>, K, V, marker::LeafOrInternal>,
151 let mut out_tree = BTreeMap { root: Some(node::Root::new_leaf()), length: 0 };
154 let root = out_tree.root.as_mut().unwrap();
155 let mut out_node = match root.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());
174 out_tree.ensure_root_is_owned();
177 // Ideally we'd use the return of ensure_root_is_owned
178 // instead of re-unwrapping here but unfortunately that
179 // borrows all of out_tree and we need access to the
181 let mut out_node = out_tree.root.as_mut().unwrap().push_level();
182 let mut in_edge = internal.first_edge();
183 while let Ok(kv) = in_edge.right_kv() {
184 let (k, v) = kv.into_kv();
185 in_edge = kv.right_edge();
187 let k = (*k).clone();
188 let v = (*v).clone();
189 let subtree = clone_subtree(in_edge.descend());
191 // We can't destructure subtree directly
192 // because BTreeMap implements Drop
193 let (subroot, sublength) = unsafe {
194 let subtree = ManuallyDrop::new(subtree);
195 let root = ptr::read(&subtree.root);
196 let length = subtree.length;
200 out_node.push(k, v, subroot.unwrap_or_else(node::Root::new_leaf));
201 out_tree.length += 1 + sublength;
211 // Ideally we'd call `BTreeMap::new` here, but that has the `K:
212 // Ord` constraint, which this method lacks.
213 BTreeMap { root: None, length: 0 }
215 clone_subtree(self.root.as_ref().unwrap().as_ref())
220 impl<K, Q: ?Sized> super::Recover<Q> for BTreeMap<K, ()>
227 fn get(&self, key: &Q) -> Option<&K> {
228 match search::search_tree(self.root.as_ref()?.as_ref(), key) {
229 Found(handle) => Some(handle.into_kv().0),
234 fn take(&mut self, key: &Q) -> Option<K> {
235 match search::search_tree(self.root.as_mut()?.as_mut(), key) {
236 Found(handle) => Some(
237 OccupiedEntry { handle, length: &mut self.length, _marker: PhantomData }
245 fn replace(&mut self, key: K) -> Option<K> {
246 self.ensure_root_is_owned();
247 match search::search_tree::<marker::Mut<'_>, K, (), K>(self.root.as_mut()?.as_mut(), &key) {
248 Found(handle) => Some(mem::replace(handle.into_kv_mut().0, key)),
250 VacantEntry { key, handle, length: &mut self.length, _marker: PhantomData }
258 /// An iterator over the entries of a `BTreeMap`.
260 /// This `struct` is created by the [`iter`] method on [`BTreeMap`]. See its
261 /// documentation for more.
263 /// [`iter`]: struct.BTreeMap.html#method.iter
264 /// [`BTreeMap`]: struct.BTreeMap.html
265 #[stable(feature = "rust1", since = "1.0.0")]
266 pub struct Iter<'a, K: 'a, V: 'a> {
267 range: Range<'a, K, V>,
271 #[stable(feature = "collection_debug", since = "1.17.0")]
272 impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for Iter<'_, K, V> {
273 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
274 f.debug_list().entries(self.clone()).finish()
278 /// A mutable iterator over the entries of a `BTreeMap`.
280 /// This `struct` is created by the [`iter_mut`] method on [`BTreeMap`]. See its
281 /// documentation for more.
283 /// [`iter_mut`]: struct.BTreeMap.html#method.iter_mut
284 /// [`BTreeMap`]: struct.BTreeMap.html
285 #[stable(feature = "rust1", since = "1.0.0")]
287 pub struct IterMut<'a, K: 'a, V: 'a> {
288 range: RangeMut<'a, K, V>,
292 /// An owning iterator over the entries of a `BTreeMap`.
294 /// This `struct` is created by the [`into_iter`] method on [`BTreeMap`]
295 /// (provided by the `IntoIterator` trait). See its documentation for more.
297 /// [`into_iter`]: struct.BTreeMap.html#method.into_iter
298 /// [`BTreeMap`]: struct.BTreeMap.html
299 #[stable(feature = "rust1", since = "1.0.0")]
300 pub struct IntoIter<K, V> {
301 front: Option<Handle<NodeRef<marker::Owned, K, V, marker::Leaf>, marker::Edge>>,
302 back: Option<Handle<NodeRef<marker::Owned, K, V, marker::Leaf>, marker::Edge>>,
306 #[stable(feature = "collection_debug", since = "1.17.0")]
307 impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for IntoIter<K, V> {
308 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
310 front: self.front.as_ref().map(|f| f.reborrow()),
311 back: self.back.as_ref().map(|b| b.reborrow()),
313 f.debug_list().entries(range).finish()
317 /// An iterator over the keys of a `BTreeMap`.
319 /// This `struct` is created by the [`keys`] method on [`BTreeMap`]. See its
320 /// documentation for more.
322 /// [`keys`]: struct.BTreeMap.html#method.keys
323 /// [`BTreeMap`]: struct.BTreeMap.html
324 #[stable(feature = "rust1", since = "1.0.0")]
325 pub struct Keys<'a, K: 'a, V: 'a> {
326 inner: Iter<'a, K, V>,
329 #[stable(feature = "collection_debug", since = "1.17.0")]
330 impl<K: fmt::Debug, V> fmt::Debug for Keys<'_, K, V> {
331 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
332 f.debug_list().entries(self.clone()).finish()
336 /// An iterator over the values of a `BTreeMap`.
338 /// This `struct` is created by the [`values`] method on [`BTreeMap`]. See its
339 /// documentation for more.
341 /// [`values`]: struct.BTreeMap.html#method.values
342 /// [`BTreeMap`]: struct.BTreeMap.html
343 #[stable(feature = "rust1", since = "1.0.0")]
344 pub struct Values<'a, K: 'a, V: 'a> {
345 inner: Iter<'a, K, V>,
348 #[stable(feature = "collection_debug", since = "1.17.0")]
349 impl<K, V: fmt::Debug> fmt::Debug for Values<'_, K, V> {
350 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
351 f.debug_list().entries(self.clone()).finish()
355 /// A mutable iterator over the values of a `BTreeMap`.
357 /// This `struct` is created by the [`values_mut`] method on [`BTreeMap`]. See its
358 /// documentation for more.
360 /// [`values_mut`]: struct.BTreeMap.html#method.values_mut
361 /// [`BTreeMap`]: struct.BTreeMap.html
362 #[stable(feature = "map_values_mut", since = "1.10.0")]
364 pub struct ValuesMut<'a, K: 'a, V: 'a> {
365 inner: IterMut<'a, K, V>,
368 /// An iterator over a sub-range of entries in a `BTreeMap`.
370 /// This `struct` is created by the [`range`] method on [`BTreeMap`]. See its
371 /// documentation for more.
373 /// [`range`]: struct.BTreeMap.html#method.range
374 /// [`BTreeMap`]: struct.BTreeMap.html
375 #[stable(feature = "btree_range", since = "1.17.0")]
376 pub struct Range<'a, K: 'a, V: 'a> {
377 front: Option<Handle<NodeRef<marker::Immut<'a>, K, V, marker::Leaf>, marker::Edge>>,
378 back: Option<Handle<NodeRef<marker::Immut<'a>, K, V, marker::Leaf>, marker::Edge>>,
381 #[stable(feature = "collection_debug", since = "1.17.0")]
382 impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for Range<'_, K, V> {
383 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
384 f.debug_list().entries(self.clone()).finish()
388 /// A mutable iterator over a sub-range of entries in a `BTreeMap`.
390 /// This `struct` is created by the [`range_mut`] method on [`BTreeMap`]. See its
391 /// documentation for more.
393 /// [`range_mut`]: struct.BTreeMap.html#method.range_mut
394 /// [`BTreeMap`]: struct.BTreeMap.html
395 #[stable(feature = "btree_range", since = "1.17.0")]
396 pub struct RangeMut<'a, K: 'a, V: 'a> {
397 front: Option<Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>>,
398 back: Option<Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>>,
400 // Be invariant in `K` and `V`
401 _marker: PhantomData<&'a mut (K, V)>,
404 #[stable(feature = "collection_debug", since = "1.17.0")]
405 impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for RangeMut<'_, K, V> {
406 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
408 front: self.front.as_ref().map(|f| f.reborrow()),
409 back: self.back.as_ref().map(|b| b.reborrow()),
411 f.debug_list().entries(range).finish()
415 /// A view into a single entry in a map, which may either be vacant or occupied.
417 /// This `enum` is constructed from the [`entry`] method on [`BTreeMap`].
419 /// [`BTreeMap`]: struct.BTreeMap.html
420 /// [`entry`]: struct.BTreeMap.html#method.entry
421 #[stable(feature = "rust1", since = "1.0.0")]
422 pub enum Entry<'a, K: 'a, V: 'a> {
424 #[stable(feature = "rust1", since = "1.0.0")]
425 Vacant(#[stable(feature = "rust1", since = "1.0.0")] VacantEntry<'a, K, V>),
427 /// An occupied entry.
428 #[stable(feature = "rust1", since = "1.0.0")]
429 Occupied(#[stable(feature = "rust1", since = "1.0.0")] OccupiedEntry<'a, K, V>),
432 #[stable(feature = "debug_btree_map", since = "1.12.0")]
433 impl<K: Debug + Ord, V: Debug> Debug for Entry<'_, K, V> {
434 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
436 Vacant(ref v) => f.debug_tuple("Entry").field(v).finish(),
437 Occupied(ref o) => f.debug_tuple("Entry").field(o).finish(),
442 /// A view into a vacant entry in a `BTreeMap`.
443 /// It is part of the [`Entry`] enum.
445 /// [`Entry`]: enum.Entry.html
446 #[stable(feature = "rust1", since = "1.0.0")]
447 pub struct VacantEntry<'a, K: 'a, V: 'a> {
449 handle: Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>,
450 length: &'a mut usize,
452 // Be invariant in `K` and `V`
453 _marker: PhantomData<&'a mut (K, V)>,
456 #[stable(feature = "debug_btree_map", since = "1.12.0")]
457 impl<K: Debug + Ord, V> Debug for VacantEntry<'_, K, V> {
458 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
459 f.debug_tuple("VacantEntry").field(self.key()).finish()
463 /// A view into an occupied entry in a `BTreeMap`.
464 /// It is part of the [`Entry`] enum.
466 /// [`Entry`]: enum.Entry.html
467 #[stable(feature = "rust1", since = "1.0.0")]
468 pub struct OccupiedEntry<'a, K: 'a, V: 'a> {
469 handle: Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, marker::KV>,
471 length: &'a mut usize,
473 // Be invariant in `K` and `V`
474 _marker: PhantomData<&'a mut (K, V)>,
477 #[stable(feature = "debug_btree_map", since = "1.12.0")]
478 impl<K: Debug + Ord, V: Debug> Debug for OccupiedEntry<'_, K, V> {
479 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
480 f.debug_struct("OccupiedEntry").field("key", self.key()).field("value", self.get()).finish()
484 // An iterator for merging two sorted sequences into one
485 struct MergeIter<K, V, I: Iterator<Item = (K, V)>> {
490 impl<K: Ord, V> BTreeMap<K, V> {
491 /// Makes a new empty BTreeMap with a reasonable choice for B.
493 /// Does not allocate anything on its own.
500 /// use std::collections::BTreeMap;
502 /// let mut map = BTreeMap::new();
504 /// // entries can now be inserted into the empty map
505 /// map.insert(1, "a");
507 #[stable(feature = "rust1", since = "1.0.0")]
508 #[rustc_const_unstable(feature = "const_btree_new", issue = "71835")]
509 pub const fn new() -> BTreeMap<K, V> {
510 BTreeMap { root: None, length: 0 }
513 /// Clears the map, removing all elements.
520 /// use std::collections::BTreeMap;
522 /// let mut a = BTreeMap::new();
523 /// a.insert(1, "a");
525 /// assert!(a.is_empty());
527 #[stable(feature = "rust1", since = "1.0.0")]
528 pub fn clear(&mut self) {
529 *self = BTreeMap::new();
532 /// Returns a reference to the value corresponding to the key.
534 /// The key may be any borrowed form of the map's key type, but the ordering
535 /// on the borrowed form *must* match the ordering on the key type.
542 /// use std::collections::BTreeMap;
544 /// let mut map = BTreeMap::new();
545 /// map.insert(1, "a");
546 /// assert_eq!(map.get(&1), Some(&"a"));
547 /// assert_eq!(map.get(&2), None);
549 #[stable(feature = "rust1", since = "1.0.0")]
550 pub fn get<Q: ?Sized>(&self, key: &Q) -> Option<&V>
555 match search::search_tree(self.root.as_ref()?.as_ref(), key) {
556 Found(handle) => Some(handle.into_kv().1),
561 /// Returns the key-value pair corresponding to the supplied key.
563 /// The supplied key may be any borrowed form of the map's key type, but the ordering
564 /// on the borrowed form *must* match the ordering on the key type.
569 /// use std::collections::BTreeMap;
571 /// let mut map = BTreeMap::new();
572 /// map.insert(1, "a");
573 /// assert_eq!(map.get_key_value(&1), Some((&1, &"a")));
574 /// assert_eq!(map.get_key_value(&2), None);
576 #[stable(feature = "map_get_key_value", since = "1.40.0")]
577 pub fn get_key_value<Q: ?Sized>(&self, k: &Q) -> Option<(&K, &V)>
582 match search::search_tree(self.root.as_ref()?.as_ref(), k) {
583 Found(handle) => Some(handle.into_kv()),
588 /// Returns the first key-value pair in the map.
589 /// The key in this pair is the minimum key in the map.
596 /// #![feature(map_first_last)]
597 /// use std::collections::BTreeMap;
599 /// let mut map = BTreeMap::new();
600 /// assert_eq!(map.first_key_value(), None);
601 /// map.insert(1, "b");
602 /// map.insert(2, "a");
603 /// assert_eq!(map.first_key_value(), Some((&1, &"b")));
605 #[unstable(feature = "map_first_last", issue = "62924")]
606 pub fn first_key_value(&self) -> Option<(&K, &V)> {
607 let front = self.root.as_ref()?.as_ref().first_leaf_edge();
608 front.right_kv().ok().map(Handle::into_kv)
611 /// Returns the first entry in the map for in-place manipulation.
612 /// The key of this entry is the minimum key in the map.
617 /// #![feature(map_first_last)]
618 /// use std::collections::BTreeMap;
620 /// let mut map = BTreeMap::new();
621 /// map.insert(1, "a");
622 /// map.insert(2, "b");
623 /// if let Some(mut entry) = map.first_entry() {
624 /// if *entry.key() > 0 {
625 /// entry.insert("first");
628 /// assert_eq!(*map.get(&1).unwrap(), "first");
629 /// assert_eq!(*map.get(&2).unwrap(), "b");
631 #[unstable(feature = "map_first_last", issue = "62924")]
632 pub fn first_entry(&mut self) -> Option<OccupiedEntry<'_, K, V>> {
633 let front = self.root.as_mut()?.as_mut().first_leaf_edge();
634 let kv = front.right_kv().ok()?;
636 handle: kv.forget_node_type(),
637 length: &mut self.length,
638 _marker: PhantomData,
642 /// Removes and returns the first element in the map.
643 /// The key of this element is the minimum key that was in the map.
647 /// Draining elements in ascending order, while keeping a usable map each iteration.
650 /// #![feature(map_first_last)]
651 /// use std::collections::BTreeMap;
653 /// let mut map = BTreeMap::new();
654 /// map.insert(1, "a");
655 /// map.insert(2, "b");
656 /// while let Some((key, _val)) = map.pop_first() {
657 /// assert!(map.iter().all(|(k, _v)| *k > key));
659 /// assert!(map.is_empty());
661 #[unstable(feature = "map_first_last", issue = "62924")]
662 pub fn pop_first(&mut self) -> Option<(K, V)> {
663 self.first_entry().map(|entry| entry.remove_entry())
666 /// Returns the last key-value pair in the map.
667 /// The key in this pair is the maximum key in the map.
674 /// #![feature(map_first_last)]
675 /// use std::collections::BTreeMap;
677 /// let mut map = BTreeMap::new();
678 /// map.insert(1, "b");
679 /// map.insert(2, "a");
680 /// assert_eq!(map.last_key_value(), Some((&2, &"a")));
682 #[unstable(feature = "map_first_last", issue = "62924")]
683 pub fn last_key_value(&self) -> Option<(&K, &V)> {
684 let back = self.root.as_ref()?.as_ref().last_leaf_edge();
685 back.left_kv().ok().map(Handle::into_kv)
688 /// Returns the last entry in the map for in-place manipulation.
689 /// The key of this entry is the maximum key in the map.
694 /// #![feature(map_first_last)]
695 /// use std::collections::BTreeMap;
697 /// let mut map = BTreeMap::new();
698 /// map.insert(1, "a");
699 /// map.insert(2, "b");
700 /// if let Some(mut entry) = map.last_entry() {
701 /// if *entry.key() > 0 {
702 /// entry.insert("last");
705 /// assert_eq!(*map.get(&1).unwrap(), "a");
706 /// assert_eq!(*map.get(&2).unwrap(), "last");
708 #[unstable(feature = "map_first_last", issue = "62924")]
709 pub fn last_entry(&mut self) -> Option<OccupiedEntry<'_, K, V>> {
710 let back = self.root.as_mut()?.as_mut().last_leaf_edge();
711 let kv = back.left_kv().ok()?;
713 handle: kv.forget_node_type(),
714 length: &mut self.length,
715 _marker: PhantomData,
719 /// Removes and returns the last element in the map.
720 /// The key of this element is the maximum key that was in the map.
724 /// Draining elements in descending order, while keeping a usable map each iteration.
727 /// #![feature(map_first_last)]
728 /// use std::collections::BTreeMap;
730 /// let mut map = BTreeMap::new();
731 /// map.insert(1, "a");
732 /// map.insert(2, "b");
733 /// while let Some((key, _val)) = map.pop_last() {
734 /// assert!(map.iter().all(|(k, _v)| *k < key));
736 /// assert!(map.is_empty());
738 #[unstable(feature = "map_first_last", issue = "62924")]
739 pub fn pop_last(&mut self) -> Option<(K, V)> {
740 self.last_entry().map(|entry| entry.remove_entry())
743 /// Returns `true` if the map contains a value for the specified key.
745 /// The key may be any borrowed form of the map's key type, but the ordering
746 /// on the borrowed form *must* match the ordering on the key type.
753 /// use std::collections::BTreeMap;
755 /// let mut map = BTreeMap::new();
756 /// map.insert(1, "a");
757 /// assert_eq!(map.contains_key(&1), true);
758 /// assert_eq!(map.contains_key(&2), false);
760 #[stable(feature = "rust1", since = "1.0.0")]
761 pub fn contains_key<Q: ?Sized>(&self, key: &Q) -> bool
766 self.get(key).is_some()
769 /// Returns a mutable reference to the value corresponding to the key.
771 /// The key may be any borrowed form of the map's key type, but the ordering
772 /// on the borrowed form *must* match the ordering on the key type.
779 /// use std::collections::BTreeMap;
781 /// let mut map = BTreeMap::new();
782 /// map.insert(1, "a");
783 /// if let Some(x) = map.get_mut(&1) {
786 /// assert_eq!(map[&1], "b");
788 // See `get` for implementation notes, this is basically a copy-paste with mut's added
789 #[stable(feature = "rust1", since = "1.0.0")]
790 pub fn get_mut<Q: ?Sized>(&mut self, key: &Q) -> Option<&mut V>
795 match search::search_tree(self.root.as_mut()?.as_mut(), key) {
796 Found(handle) => Some(handle.into_kv_mut().1),
801 /// Inserts a key-value pair into the map.
803 /// If the map did not have this key present, `None` is returned.
805 /// If the map did have this key present, the value is updated, and the old
806 /// value is returned. The key is not updated, though; this matters for
807 /// types that can be `==` without being identical. See the [module-level
808 /// documentation] for more.
810 /// [module-level documentation]: index.html#insert-and-complex-keys
817 /// use std::collections::BTreeMap;
819 /// let mut map = BTreeMap::new();
820 /// assert_eq!(map.insert(37, "a"), None);
821 /// assert_eq!(map.is_empty(), false);
823 /// map.insert(37, "b");
824 /// assert_eq!(map.insert(37, "c"), Some("b"));
825 /// assert_eq!(map[&37], "c");
827 #[stable(feature = "rust1", since = "1.0.0")]
828 pub fn insert(&mut self, key: K, value: V) -> Option<V> {
829 match self.entry(key) {
830 Occupied(mut entry) => Some(entry.insert(value)),
838 /// Removes a key from the map, returning the value at the key if the key
839 /// was previously in the map.
841 /// The key may be any borrowed form of the map's key type, but the ordering
842 /// on the borrowed form *must* match the ordering on the key type.
849 /// use std::collections::BTreeMap;
851 /// let mut map = BTreeMap::new();
852 /// map.insert(1, "a");
853 /// assert_eq!(map.remove(&1), Some("a"));
854 /// assert_eq!(map.remove(&1), None);
856 #[stable(feature = "rust1", since = "1.0.0")]
857 pub fn remove<Q: ?Sized>(&mut self, key: &Q) -> Option<V>
862 self.remove_entry(key).map(|(_, v)| v)
865 /// Removes a key from the map, returning the stored key and value if the key
866 /// was previously in the map.
868 /// The key may be any borrowed form of the map's key type, but the ordering
869 /// on the borrowed form *must* match the ordering on the key type.
876 /// use std::collections::BTreeMap;
878 /// let mut map = BTreeMap::new();
879 /// map.insert(1, "a");
880 /// assert_eq!(map.remove_entry(&1), Some((1, "a")));
881 /// assert_eq!(map.remove_entry(&1), None);
883 #[stable(feature = "btreemap_remove_entry", since = "1.45.0")]
884 pub fn remove_entry<Q: ?Sized>(&mut self, key: &Q) -> Option<(K, V)>
889 match search::search_tree(self.root.as_mut()?.as_mut(), key) {
890 Found(handle) => Some(
891 OccupiedEntry { handle, length: &mut self.length, _marker: PhantomData }
898 /// Moves all elements from `other` into `Self`, leaving `other` empty.
903 /// use std::collections::BTreeMap;
905 /// let mut a = BTreeMap::new();
906 /// a.insert(1, "a");
907 /// a.insert(2, "b");
908 /// a.insert(3, "c");
910 /// let mut b = BTreeMap::new();
911 /// b.insert(3, "d");
912 /// b.insert(4, "e");
913 /// b.insert(5, "f");
915 /// a.append(&mut b);
917 /// assert_eq!(a.len(), 5);
918 /// assert_eq!(b.len(), 0);
920 /// assert_eq!(a[&1], "a");
921 /// assert_eq!(a[&2], "b");
922 /// assert_eq!(a[&3], "d");
923 /// assert_eq!(a[&4], "e");
924 /// assert_eq!(a[&5], "f");
926 #[stable(feature = "btree_append", since = "1.11.0")]
927 pub fn append(&mut self, other: &mut Self) {
928 // Do we have to append anything at all?
929 if other.is_empty() {
933 // We can just swap `self` and `other` if `self` is empty.
935 mem::swap(self, other);
939 // First, we merge `self` and `other` into a sorted sequence in linear time.
940 let self_iter = mem::take(self).into_iter();
941 let other_iter = mem::take(other).into_iter();
942 let iter = MergeIter { left: self_iter.peekable(), right: other_iter.peekable() };
944 // Second, we build a tree from the sorted sequence in linear time.
945 self.from_sorted_iter(iter);
946 self.fix_right_edge();
949 /// Constructs a double-ended iterator over a sub-range of elements in the map.
950 /// The simplest way is to use the range syntax `min..max`, thus `range(min..max)` will
951 /// yield elements from min (inclusive) to max (exclusive).
952 /// The range may also be entered as `(Bound<T>, Bound<T>)`, so for example
953 /// `range((Excluded(4), Included(10)))` will yield a left-exclusive, right-inclusive
954 /// range from 4 to 10.
958 /// Panics if range `start > end`.
959 /// Panics if range `start == end` and both bounds are `Excluded`.
966 /// use std::collections::BTreeMap;
967 /// use std::ops::Bound::Included;
969 /// let mut map = BTreeMap::new();
970 /// map.insert(3, "a");
971 /// map.insert(5, "b");
972 /// map.insert(8, "c");
973 /// for (&key, &value) in map.range((Included(&4), Included(&8))) {
974 /// println!("{}: {}", key, value);
976 /// assert_eq!(Some((&5, &"b")), map.range(4..).next());
978 #[stable(feature = "btree_range", since = "1.17.0")]
979 pub fn range<T: ?Sized, R>(&self, range: R) -> Range<'_, K, V>
985 if let Some(root) = &self.root {
986 let (f, b) = range_search(root.as_ref(), range);
988 Range { front: Some(f), back: Some(b) }
990 Range { front: None, back: None }
994 /// Constructs a mutable double-ended iterator over a sub-range of elements in the map.
995 /// The simplest way is to use the range syntax `min..max`, thus `range(min..max)` will
996 /// yield elements from min (inclusive) to max (exclusive).
997 /// The range may also be entered as `(Bound<T>, Bound<T>)`, so for example
998 /// `range((Excluded(4), Included(10)))` will yield a left-exclusive, right-inclusive
999 /// range from 4 to 10.
1003 /// Panics if range `start > end`.
1004 /// Panics if range `start == end` and both bounds are `Excluded`.
1011 /// use std::collections::BTreeMap;
1013 /// let mut map: BTreeMap<&str, i32> = ["Alice", "Bob", "Carol", "Cheryl"]
1015 /// .map(|&s| (s, 0))
1017 /// for (_, balance) in map.range_mut("B".."Cheryl") {
1018 /// *balance += 100;
1020 /// for (name, balance) in &map {
1021 /// println!("{} => {}", name, balance);
1024 #[stable(feature = "btree_range", since = "1.17.0")]
1025 pub fn range_mut<T: ?Sized, R>(&mut self, range: R) -> RangeMut<'_, K, V>
1031 if let Some(root) = &mut self.root {
1032 let (f, b) = range_search(root.as_mut(), range);
1034 RangeMut { front: Some(f), back: Some(b), _marker: PhantomData }
1036 RangeMut { front: None, back: None, _marker: PhantomData }
1040 /// Gets the given key's corresponding entry in the map for in-place manipulation.
1047 /// use std::collections::BTreeMap;
1049 /// let mut count: BTreeMap<&str, usize> = BTreeMap::new();
1051 /// // count the number of occurrences of letters in the vec
1052 /// for x in vec!["a","b","a","c","a","b"] {
1053 /// *count.entry(x).or_insert(0) += 1;
1056 /// assert_eq!(count["a"], 3);
1058 #[stable(feature = "rust1", since = "1.0.0")]
1059 pub fn entry(&mut self, key: K) -> Entry<'_, K, V> {
1060 // FIXME(@porglezomp) Avoid allocating if we don't insert
1061 self.ensure_root_is_owned();
1062 match search::search_tree(self.root.as_mut().unwrap().as_mut(), &key) {
1064 Occupied(OccupiedEntry { handle, length: &mut self.length, _marker: PhantomData })
1067 Vacant(VacantEntry { key, handle, length: &mut self.length, _marker: PhantomData })
1072 fn from_sorted_iter<I: Iterator<Item = (K, V)>>(&mut self, iter: I) {
1073 self.ensure_root_is_owned();
1074 let mut cur_node = self.root.as_mut().unwrap().as_mut().last_leaf_edge().into_node();
1075 // Iterate through all key-value pairs, pushing them into nodes at the right level.
1076 for (key, value) in iter {
1077 // Try to push key-value pair into the current leaf node.
1078 if cur_node.len() < node::CAPACITY {
1079 cur_node.push(key, value);
1081 // No space left, go up and push there.
1083 let mut test_node = cur_node.forget_type();
1085 match test_node.ascend() {
1087 let parent = parent.into_node();
1088 if parent.len() < node::CAPACITY {
1089 // Found a node with space left, push here.
1094 test_node = parent.forget_type();
1098 // We are at the top, create a new root node and push there.
1099 open_node = node.into_root_mut().push_level();
1105 // Push key-value pair and new right subtree.
1106 let tree_height = open_node.height() - 1;
1107 let mut right_tree = node::Root::new_leaf();
1108 for _ in 0..tree_height {
1109 right_tree.push_level();
1111 open_node.push(key, value, right_tree);
1113 // Go down to the right-most leaf again.
1114 cur_node = open_node.forget_type().last_leaf_edge().into_node();
1121 fn fix_right_edge(&mut self) {
1122 // Handle underfull nodes, start from the top.
1123 let mut cur_node = self.root.as_mut().unwrap().as_mut();
1124 while let Internal(internal) = cur_node.force() {
1125 // Check if right-most child is underfull.
1126 let mut last_edge = internal.last_edge();
1127 let right_child_len = last_edge.reborrow().descend().len();
1128 if right_child_len < node::MIN_LEN {
1129 // We need to steal.
1130 let mut last_kv = match last_edge.left_kv() {
1132 Err(_) => unreachable!(),
1134 last_kv.bulk_steal_left(node::MIN_LEN - right_child_len);
1135 last_edge = last_kv.right_edge();
1139 cur_node = last_edge.descend();
1143 /// Splits the collection into two at the given key. Returns everything after the given key,
1144 /// including the key.
1151 /// use std::collections::BTreeMap;
1153 /// let mut a = BTreeMap::new();
1154 /// a.insert(1, "a");
1155 /// a.insert(2, "b");
1156 /// a.insert(3, "c");
1157 /// a.insert(17, "d");
1158 /// a.insert(41, "e");
1160 /// let b = a.split_off(&3);
1162 /// assert_eq!(a.len(), 2);
1163 /// assert_eq!(b.len(), 3);
1165 /// assert_eq!(a[&1], "a");
1166 /// assert_eq!(a[&2], "b");
1168 /// assert_eq!(b[&3], "c");
1169 /// assert_eq!(b[&17], "d");
1170 /// assert_eq!(b[&41], "e");
1172 #[stable(feature = "btree_split_off", since = "1.11.0")]
1173 pub fn split_off<Q: ?Sized + Ord>(&mut self, key: &Q) -> Self
1177 if self.is_empty() {
1181 let total_num = self.len();
1183 let mut right = Self::new();
1184 let right_root = right.ensure_root_is_owned();
1185 for _ in 0..(self.root.as_ref().unwrap().as_ref().height()) {
1186 right_root.push_level();
1190 let mut left_node = self.root.as_mut().unwrap().as_mut();
1191 let mut right_node = right.root.as_mut().unwrap().as_mut();
1194 let mut split_edge = match search::search_node(left_node, key) {
1195 // key is going to the right tree
1196 Found(handle) => handle.left_edge(),
1197 GoDown(handle) => handle,
1200 split_edge.move_suffix(&mut right_node);
1202 match (split_edge.force(), right_node.force()) {
1203 (Internal(edge), Internal(node)) => {
1204 left_node = edge.descend();
1205 right_node = node.first_edge().descend();
1207 (Leaf(_), Leaf(_)) => {
1217 self.fix_right_border();
1218 right.fix_left_border();
1220 if self.root.as_ref().unwrap().as_ref().height()
1221 < right.root.as_ref().unwrap().as_ref().height()
1223 self.recalc_length();
1224 right.length = total_num - self.len();
1226 right.recalc_length();
1227 self.length = total_num - right.len();
1233 /// Creates an iterator which uses a closure to determine if an element should be removed.
1235 /// If the closure returns true, the element is removed from the map and yielded.
1236 /// If the closure returns false, or panics, the element remains in the map and will not be
1239 /// Note that `drain_filter` lets you mutate every value in the filter closure, regardless of
1240 /// whether you choose to keep or remove it.
1242 /// If the iterator is only partially consumed or not consumed at all, each of the remaining
1243 /// elements will still be subjected to the closure and removed and dropped if it returns true.
1245 /// It is unspecified how many more elements will be subjected to the closure
1246 /// if a panic occurs in the closure, or a panic occurs while dropping an element,
1247 /// or if the `DrainFilter` value is leaked.
1251 /// Splitting a map into even and odd keys, reusing the original map:
1254 /// #![feature(btree_drain_filter)]
1255 /// use std::collections::BTreeMap;
1257 /// let mut map: BTreeMap<i32, i32> = (0..8).map(|x| (x, x)).collect();
1258 /// let evens: BTreeMap<_, _> = map.drain_filter(|k, _v| k % 2 == 0).collect();
1260 /// assert_eq!(evens.keys().copied().collect::<Vec<_>>(), vec![0, 2, 4, 6]);
1261 /// assert_eq!(odds.keys().copied().collect::<Vec<_>>(), vec![1, 3, 5, 7]);
1263 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1264 pub fn drain_filter<F>(&mut self, pred: F) -> DrainFilter<'_, K, V, F>
1266 F: FnMut(&K, &mut V) -> bool,
1268 DrainFilter { pred, inner: self.drain_filter_inner() }
1270 pub(super) fn drain_filter_inner(&mut self) -> DrainFilterInner<'_, K, V> {
1271 let front = self.root.as_mut().map(|r| r.as_mut().first_leaf_edge());
1272 DrainFilterInner { length: &mut self.length, cur_leaf_edge: front }
1275 /// Calculates the number of elements if it is incorrect.
1276 fn recalc_length(&mut self) {
1277 fn dfs<'a, K, V>(node: NodeRef<marker::Immut<'a>, K, V, marker::LeafOrInternal>) -> usize
1282 let mut res = node.len();
1284 if let Internal(node) = node.force() {
1285 let mut edge = node.first_edge();
1287 res += dfs(edge.reborrow().descend());
1288 match edge.right_kv() {
1290 edge = right_kv.right_edge();
1302 self.length = dfs(self.root.as_ref().unwrap().as_ref());
1305 /// Removes empty levels on the top.
1306 fn fix_top(&mut self) {
1309 let node = self.root.as_ref().unwrap().as_ref();
1310 if node.height() == 0 || node.len() > 0 {
1314 self.root.as_mut().unwrap().pop_level();
1318 fn fix_right_border(&mut self) {
1322 let mut cur_node = self.root.as_mut().unwrap().as_mut();
1324 while let Internal(node) = cur_node.force() {
1325 let mut last_kv = node.last_kv();
1327 if last_kv.can_merge() {
1328 cur_node = last_kv.merge().descend();
1330 let right_len = last_kv.reborrow().right_edge().descend().len();
1331 // `MINLEN + 1` to avoid readjust if merge happens on the next level.
1332 if right_len < node::MIN_LEN + 1 {
1333 last_kv.bulk_steal_left(node::MIN_LEN + 1 - right_len);
1335 cur_node = last_kv.right_edge().descend();
1343 /// The symmetric clone of `fix_right_border`.
1344 fn fix_left_border(&mut self) {
1348 let mut cur_node = self.root.as_mut().unwrap().as_mut();
1350 while let Internal(node) = cur_node.force() {
1351 let mut first_kv = node.first_kv();
1353 if first_kv.can_merge() {
1354 cur_node = first_kv.merge().descend();
1356 let left_len = first_kv.reborrow().left_edge().descend().len();
1357 if left_len < node::MIN_LEN + 1 {
1358 first_kv.bulk_steal_right(node::MIN_LEN + 1 - left_len);
1360 cur_node = first_kv.left_edge().descend();
1369 #[stable(feature = "rust1", since = "1.0.0")]
1370 impl<'a, K: 'a, V: 'a> IntoIterator for &'a BTreeMap<K, V> {
1371 type Item = (&'a K, &'a V);
1372 type IntoIter = Iter<'a, K, V>;
1374 fn into_iter(self) -> Iter<'a, K, V> {
1379 #[stable(feature = "rust1", since = "1.0.0")]
1380 impl<'a, K: 'a, V: 'a> Iterator for Iter<'a, K, V> {
1381 type Item = (&'a K, &'a V);
1383 fn next(&mut self) -> Option<(&'a K, &'a V)> {
1384 if self.length == 0 {
1388 unsafe { Some(self.range.next_unchecked()) }
1392 fn size_hint(&self) -> (usize, Option<usize>) {
1393 (self.length, Some(self.length))
1396 fn last(mut self) -> Option<(&'a K, &'a V)> {
1401 #[stable(feature = "fused", since = "1.26.0")]
1402 impl<K, V> FusedIterator for Iter<'_, K, V> {}
1404 #[stable(feature = "rust1", since = "1.0.0")]
1405 impl<'a, K: 'a, V: 'a> DoubleEndedIterator for Iter<'a, K, V> {
1406 fn next_back(&mut self) -> Option<(&'a K, &'a V)> {
1407 if self.length == 0 {
1411 unsafe { Some(self.range.next_back_unchecked()) }
1416 #[stable(feature = "rust1", since = "1.0.0")]
1417 impl<K, V> ExactSizeIterator for Iter<'_, K, V> {
1418 fn len(&self) -> usize {
1423 #[stable(feature = "rust1", since = "1.0.0")]
1424 impl<K, V> Clone for Iter<'_, K, V> {
1425 fn clone(&self) -> Self {
1426 Iter { range: self.range.clone(), length: self.length }
1430 #[stable(feature = "rust1", since = "1.0.0")]
1431 impl<'a, K: 'a, V: 'a> IntoIterator for &'a mut BTreeMap<K, V> {
1432 type Item = (&'a K, &'a mut V);
1433 type IntoIter = IterMut<'a, K, V>;
1435 fn into_iter(self) -> IterMut<'a, K, V> {
1440 #[stable(feature = "rust1", since = "1.0.0")]
1441 impl<'a, K: 'a, V: 'a> Iterator for IterMut<'a, K, V> {
1442 type Item = (&'a K, &'a mut V);
1444 fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
1445 if self.length == 0 {
1449 let (k, v) = unsafe { self.range.next_unchecked() };
1450 Some((k, v)) // coerce k from `&mut K` to `&K`
1454 fn size_hint(&self) -> (usize, Option<usize>) {
1455 (self.length, Some(self.length))
1458 fn last(mut self) -> Option<(&'a K, &'a mut V)> {
1463 #[stable(feature = "rust1", since = "1.0.0")]
1464 impl<'a, K: 'a, V: 'a> DoubleEndedIterator for IterMut<'a, K, V> {
1465 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> {
1466 if self.length == 0 {
1470 let (k, v) = unsafe { self.range.next_back_unchecked() };
1471 Some((k, v)) // coerce k from `&mut K` to `&K`
1476 #[stable(feature = "rust1", since = "1.0.0")]
1477 impl<K, V> ExactSizeIterator for IterMut<'_, K, V> {
1478 fn len(&self) -> usize {
1483 #[stable(feature = "fused", since = "1.26.0")]
1484 impl<K, V> FusedIterator for IterMut<'_, K, V> {}
1486 #[stable(feature = "rust1", since = "1.0.0")]
1487 impl<K, V> IntoIterator for BTreeMap<K, V> {
1489 type IntoIter = IntoIter<K, V>;
1491 fn into_iter(self) -> IntoIter<K, V> {
1492 let mut me = ManuallyDrop::new(self);
1493 if let Some(root) = me.root.take() {
1494 let (f, b) = full_range_search(root.into_ref());
1496 IntoIter { front: Some(f), back: Some(b), length: me.length }
1498 IntoIter { front: None, back: None, length: 0 }
1503 #[stable(feature = "btree_drop", since = "1.7.0")]
1504 impl<K, V> Drop for IntoIter<K, V> {
1505 fn drop(&mut self) {
1506 struct DropGuard<'a, K, V>(&'a mut IntoIter<K, V>);
1508 impl<'a, K, V> Drop for DropGuard<'a, K, V> {
1509 fn drop(&mut self) {
1510 // Continue the same loop we perform below. This only runs when unwinding, so we
1511 // don't have to care about panics this time (they'll abort).
1512 while let Some(_) = self.0.next() {}
1516 unwrap_unchecked(ptr::read(&self.0.front)).into_node().forget_type();
1517 while let Some(parent) = node.deallocate_and_ascend() {
1518 node = parent.into_node().forget_type();
1524 while let Some(pair) = self.next() {
1525 let guard = DropGuard(self);
1531 if let Some(front) = ptr::read(&self.front) {
1532 let mut node = front.into_node().forget_type();
1533 // Most of the nodes have been deallocated while traversing
1534 // but one pile from a leaf up to the root is left standing.
1535 while let Some(parent) = node.deallocate_and_ascend() {
1536 node = parent.into_node().forget_type();
1543 #[stable(feature = "rust1", since = "1.0.0")]
1544 impl<K, V> Iterator for IntoIter<K, V> {
1547 fn next(&mut self) -> Option<(K, V)> {
1548 if self.length == 0 {
1552 Some(unsafe { self.front.as_mut().unwrap().next_unchecked() })
1556 fn size_hint(&self) -> (usize, Option<usize>) {
1557 (self.length, Some(self.length))
1561 #[stable(feature = "rust1", since = "1.0.0")]
1562 impl<K, V> DoubleEndedIterator for IntoIter<K, V> {
1563 fn next_back(&mut self) -> Option<(K, V)> {
1564 if self.length == 0 {
1568 Some(unsafe { self.back.as_mut().unwrap().next_back_unchecked() })
1573 #[stable(feature = "rust1", since = "1.0.0")]
1574 impl<K, V> ExactSizeIterator for IntoIter<K, V> {
1575 fn len(&self) -> usize {
1580 #[stable(feature = "fused", since = "1.26.0")]
1581 impl<K, V> FusedIterator for IntoIter<K, V> {}
1583 #[stable(feature = "rust1", since = "1.0.0")]
1584 impl<'a, K, V> Iterator for Keys<'a, K, V> {
1587 fn next(&mut self) -> Option<&'a K> {
1588 self.inner.next().map(|(k, _)| k)
1591 fn size_hint(&self) -> (usize, Option<usize>) {
1592 self.inner.size_hint()
1595 fn last(mut self) -> Option<&'a K> {
1600 #[stable(feature = "rust1", since = "1.0.0")]
1601 impl<'a, K, V> DoubleEndedIterator for Keys<'a, K, V> {
1602 fn next_back(&mut self) -> Option<&'a K> {
1603 self.inner.next_back().map(|(k, _)| k)
1607 #[stable(feature = "rust1", since = "1.0.0")]
1608 impl<K, V> ExactSizeIterator for Keys<'_, K, V> {
1609 fn len(&self) -> usize {
1614 #[stable(feature = "fused", since = "1.26.0")]
1615 impl<K, V> FusedIterator for Keys<'_, K, V> {}
1617 #[stable(feature = "rust1", since = "1.0.0")]
1618 impl<K, V> Clone for Keys<'_, K, V> {
1619 fn clone(&self) -> Self {
1620 Keys { inner: self.inner.clone() }
1624 #[stable(feature = "rust1", since = "1.0.0")]
1625 impl<'a, K, V> Iterator for Values<'a, K, V> {
1628 fn next(&mut self) -> Option<&'a V> {
1629 self.inner.next().map(|(_, v)| v)
1632 fn size_hint(&self) -> (usize, Option<usize>) {
1633 self.inner.size_hint()
1636 fn last(mut self) -> Option<&'a V> {
1641 #[stable(feature = "rust1", since = "1.0.0")]
1642 impl<'a, K, V> DoubleEndedIterator for Values<'a, K, V> {
1643 fn next_back(&mut self) -> Option<&'a V> {
1644 self.inner.next_back().map(|(_, v)| v)
1648 #[stable(feature = "rust1", since = "1.0.0")]
1649 impl<K, V> ExactSizeIterator for Values<'_, K, V> {
1650 fn len(&self) -> usize {
1655 #[stable(feature = "fused", since = "1.26.0")]
1656 impl<K, V> FusedIterator for Values<'_, K, V> {}
1658 #[stable(feature = "rust1", since = "1.0.0")]
1659 impl<K, V> Clone for Values<'_, K, V> {
1660 fn clone(&self) -> Self {
1661 Values { inner: self.inner.clone() }
1665 /// An iterator produced by calling `drain_filter` on BTreeMap.
1666 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1667 pub struct DrainFilter<'a, K, V, F>
1671 F: 'a + FnMut(&K, &mut V) -> bool,
1674 inner: DrainFilterInner<'a, K, V>,
1676 pub(super) struct DrainFilterInner<'a, K: 'a, V: 'a> {
1677 length: &'a mut usize,
1678 cur_leaf_edge: Option<Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>>,
1681 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1682 impl<K, V, F> Drop for DrainFilter<'_, K, V, F>
1684 F: FnMut(&K, &mut V) -> bool,
1686 fn drop(&mut self) {
1687 self.for_each(drop);
1691 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1692 impl<K, V, F> fmt::Debug for DrainFilter<'_, K, V, F>
1696 F: FnMut(&K, &mut V) -> bool,
1698 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1699 f.debug_tuple("DrainFilter").field(&self.inner.peek()).finish()
1703 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1704 impl<K, V, F> Iterator for DrainFilter<'_, K, V, F>
1706 F: FnMut(&K, &mut V) -> bool,
1710 fn next(&mut self) -> Option<(K, V)> {
1711 self.inner.next(&mut self.pred)
1714 fn size_hint(&self) -> (usize, Option<usize>) {
1715 self.inner.size_hint()
1719 impl<'a, K: 'a, V: 'a> DrainFilterInner<'a, K, V> {
1720 /// Allow Debug implementations to predict the next element.
1721 pub(super) fn peek(&self) -> Option<(&K, &V)> {
1722 let edge = self.cur_leaf_edge.as_ref()?;
1723 edge.reborrow().next_kv().ok().map(|kv| kv.into_kv())
1728 ) -> Option<Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, marker::KV>> {
1729 let edge = self.cur_leaf_edge.as_ref()?;
1730 unsafe { ptr::read(edge).next_kv().ok() }
1733 /// Implementation of a typical `DrainFilter::next` method, given the predicate.
1734 pub(super) fn next<F>(&mut self, pred: &mut F) -> Option<(K, V)>
1736 F: FnMut(&K, &mut V) -> bool,
1738 while let Some(mut kv) = unsafe { self.next_kv() } {
1739 let (k, v) = kv.kv_mut();
1742 let (k, v, leaf_edge_location) = kv.remove_kv_tracking();
1743 self.cur_leaf_edge = Some(leaf_edge_location);
1744 return Some((k, v));
1746 self.cur_leaf_edge = Some(kv.next_leaf_edge());
1751 /// Implementation of a typical `DrainFilter::size_hint` method.
1752 pub(super) fn size_hint(&self) -> (usize, Option<usize>) {
1753 (0, Some(*self.length))
1757 #[unstable(feature = "btree_drain_filter", issue = "70530")]
1758 impl<K, V, F> FusedIterator for DrainFilter<'_, K, V, F> where F: FnMut(&K, &mut V) -> bool {}
1760 #[stable(feature = "btree_range", since = "1.17.0")]
1761 impl<'a, K, V> Iterator for Range<'a, K, V> {
1762 type Item = (&'a K, &'a V);
1764 fn next(&mut self) -> Option<(&'a K, &'a V)> {
1765 if self.is_empty() { None } else { unsafe { Some(self.next_unchecked()) } }
1768 fn last(mut self) -> Option<(&'a K, &'a V)> {
1773 #[stable(feature = "map_values_mut", since = "1.10.0")]
1774 impl<'a, K, V> Iterator for ValuesMut<'a, K, V> {
1775 type Item = &'a mut V;
1777 fn next(&mut self) -> Option<&'a mut V> {
1778 self.inner.next().map(|(_, v)| v)
1781 fn size_hint(&self) -> (usize, Option<usize>) {
1782 self.inner.size_hint()
1785 fn last(mut self) -> Option<&'a mut V> {
1790 #[stable(feature = "map_values_mut", since = "1.10.0")]
1791 impl<'a, K, V> DoubleEndedIterator for ValuesMut<'a, K, V> {
1792 fn next_back(&mut self) -> Option<&'a mut V> {
1793 self.inner.next_back().map(|(_, v)| v)
1797 #[stable(feature = "map_values_mut", since = "1.10.0")]
1798 impl<K, V> ExactSizeIterator for ValuesMut<'_, K, V> {
1799 fn len(&self) -> usize {
1804 #[stable(feature = "fused", since = "1.26.0")]
1805 impl<K, V> FusedIterator for ValuesMut<'_, K, V> {}
1807 impl<'a, K, V> Range<'a, K, V> {
1808 fn is_empty(&self) -> bool {
1809 self.front == self.back
1812 unsafe fn next_unchecked(&mut self) -> (&'a K, &'a V) {
1813 unsafe { unwrap_unchecked(self.front.as_mut()).next_unchecked() }
1817 #[stable(feature = "btree_range", since = "1.17.0")]
1818 impl<'a, K, V> DoubleEndedIterator for Range<'a, K, V> {
1819 fn next_back(&mut self) -> Option<(&'a K, &'a V)> {
1820 if self.is_empty() { None } else { Some(unsafe { self.next_back_unchecked() }) }
1824 impl<'a, K, V> Range<'a, K, V> {
1825 unsafe fn next_back_unchecked(&mut self) -> (&'a K, &'a V) {
1826 unsafe { unwrap_unchecked(self.back.as_mut()).next_back_unchecked() }
1830 #[stable(feature = "fused", since = "1.26.0")]
1831 impl<K, V> FusedIterator for Range<'_, K, V> {}
1833 #[stable(feature = "btree_range", since = "1.17.0")]
1834 impl<K, V> Clone for Range<'_, K, V> {
1835 fn clone(&self) -> Self {
1836 Range { front: self.front, back: self.back }
1840 #[stable(feature = "btree_range", since = "1.17.0")]
1841 impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
1842 type Item = (&'a K, &'a mut V);
1844 fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
1845 if self.is_empty() {
1848 let (k, v) = unsafe { self.next_unchecked() };
1849 Some((k, v)) // coerce k from `&mut K` to `&K`
1853 fn last(mut self) -> Option<(&'a K, &'a mut V)> {
1858 impl<'a, K, V> RangeMut<'a, K, V> {
1859 fn is_empty(&self) -> bool {
1860 self.front == self.back
1863 unsafe fn next_unchecked(&mut self) -> (&'a mut K, &'a mut V) {
1864 unsafe { unwrap_unchecked(self.front.as_mut()).next_unchecked() }
1868 #[stable(feature = "btree_range", since = "1.17.0")]
1869 impl<'a, K, V> DoubleEndedIterator for RangeMut<'a, K, V> {
1870 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> {
1871 if self.is_empty() {
1874 let (k, v) = unsafe { self.next_back_unchecked() };
1875 Some((k, v)) // coerce k from `&mut K` to `&K`
1880 #[stable(feature = "fused", since = "1.26.0")]
1881 impl<K, V> FusedIterator for RangeMut<'_, K, V> {}
1883 impl<'a, K, V> RangeMut<'a, K, V> {
1884 unsafe fn next_back_unchecked(&mut self) -> (&'a mut K, &'a mut V) {
1885 unsafe { unwrap_unchecked(self.back.as_mut()).next_back_unchecked() }
1889 #[stable(feature = "rust1", since = "1.0.0")]
1890 impl<K: Ord, V> FromIterator<(K, V)> for BTreeMap<K, V> {
1891 fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> BTreeMap<K, V> {
1892 let mut map = BTreeMap::new();
1898 #[stable(feature = "rust1", since = "1.0.0")]
1899 impl<K: Ord, V> Extend<(K, V)> for BTreeMap<K, V> {
1901 fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T) {
1902 iter.into_iter().for_each(move |(k, v)| {
1908 fn extend_one(&mut self, (k, v): (K, V)) {
1913 #[stable(feature = "extend_ref", since = "1.2.0")]
1914 impl<'a, K: Ord + Copy, V: Copy> Extend<(&'a K, &'a V)> for BTreeMap<K, V> {
1915 fn extend<I: IntoIterator<Item = (&'a K, &'a V)>>(&mut self, iter: I) {
1916 self.extend(iter.into_iter().map(|(&key, &value)| (key, value)));
1920 fn extend_one(&mut self, (&k, &v): (&'a K, &'a V)) {
1925 #[stable(feature = "rust1", since = "1.0.0")]
1926 impl<K: Hash, V: Hash> Hash for BTreeMap<K, V> {
1927 fn hash<H: Hasher>(&self, state: &mut H) {
1934 #[stable(feature = "rust1", since = "1.0.0")]
1935 impl<K: Ord, V> Default for BTreeMap<K, V> {
1936 /// Creates an empty `BTreeMap<K, V>`.
1937 fn default() -> BTreeMap<K, V> {
1942 #[stable(feature = "rust1", since = "1.0.0")]
1943 impl<K: PartialEq, V: PartialEq> PartialEq for BTreeMap<K, V> {
1944 fn eq(&self, other: &BTreeMap<K, V>) -> bool {
1945 self.len() == other.len() && self.iter().zip(other).all(|(a, b)| a == b)
1949 #[stable(feature = "rust1", since = "1.0.0")]
1950 impl<K: Eq, V: Eq> Eq for BTreeMap<K, V> {}
1952 #[stable(feature = "rust1", since = "1.0.0")]
1953 impl<K: PartialOrd, V: PartialOrd> PartialOrd for BTreeMap<K, V> {
1955 fn partial_cmp(&self, other: &BTreeMap<K, V>) -> Option<Ordering> {
1956 self.iter().partial_cmp(other.iter())
1960 #[stable(feature = "rust1", since = "1.0.0")]
1961 impl<K: Ord, V: Ord> Ord for BTreeMap<K, V> {
1963 fn cmp(&self, other: &BTreeMap<K, V>) -> Ordering {
1964 self.iter().cmp(other.iter())
1968 #[stable(feature = "rust1", since = "1.0.0")]
1969 impl<K: Debug, V: Debug> Debug for BTreeMap<K, V> {
1970 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1971 f.debug_map().entries(self.iter()).finish()
1975 #[stable(feature = "rust1", since = "1.0.0")]
1976 impl<K: Ord, Q: ?Sized, V> Index<&Q> for BTreeMap<K, V>
1983 /// Returns a reference to the value corresponding to the supplied key.
1987 /// Panics if the key is not present in the `BTreeMap`.
1989 fn index(&self, key: &Q) -> &V {
1990 self.get(key).expect("no entry found for key")
1994 /// Finds the leaf edges delimiting a specified range in or underneath a node.
1995 fn range_search<BorrowType, K, V, Q: ?Sized, R: RangeBounds<Q>>(
1996 root: NodeRef<BorrowType, K, V, marker::LeafOrInternal>,
1999 Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge>,
2000 Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge>,
2006 match (range.start_bound(), range.end_bound()) {
2007 (Excluded(s), Excluded(e)) if s == e => {
2008 panic!("range start and end are equal and excluded in BTreeMap")
2010 (Included(s) | Excluded(s), Included(e) | Excluded(e)) if s > e => {
2011 panic!("range start is greater than range end in BTreeMap")
2016 // We duplicate the root NodeRef here -- we will never access it in a way
2017 // that overlaps references obtained from the root.
2018 let mut min_node = unsafe { ptr::read(&root) };
2019 let mut max_node = root;
2020 let mut min_found = false;
2021 let mut max_found = false;
2024 let front = match (min_found, range.start_bound()) {
2025 (false, Included(key)) => match search::search_node(min_node, key) {
2030 GoDown(edge) => edge,
2032 (false, Excluded(key)) => match search::search_node(min_node, key) {
2037 GoDown(edge) => edge,
2039 (true, Included(_)) => min_node.last_edge(),
2040 (true, Excluded(_)) => min_node.first_edge(),
2041 (_, Unbounded) => min_node.first_edge(),
2044 let back = match (max_found, range.end_bound()) {
2045 (false, Included(key)) => match search::search_node(max_node, key) {
2050 GoDown(edge) => edge,
2052 (false, Excluded(key)) => match search::search_node(max_node, key) {
2057 GoDown(edge) => edge,
2059 (true, Included(_)) => max_node.first_edge(),
2060 (true, Excluded(_)) => max_node.last_edge(),
2061 (_, Unbounded) => max_node.last_edge(),
2064 if front.partial_cmp(&back) == Some(Ordering::Greater) {
2065 panic!("Ord is ill-defined in BTreeMap range");
2067 match (front.force(), back.force()) {
2068 (Leaf(f), Leaf(b)) => {
2071 (Internal(min_int), Internal(max_int)) => {
2072 min_node = min_int.descend();
2073 max_node = max_int.descend();
2075 _ => unreachable!("BTreeMap has different depths"),
2080 /// Equivalent to `range_search(k, v, ..)` without the `Ord` bound.
2081 fn full_range_search<BorrowType, K, V>(
2082 root: NodeRef<BorrowType, K, V, marker::LeafOrInternal>,
2084 Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge>,
2085 Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge>,
2087 // We duplicate the root NodeRef here -- we will never access it in a way
2088 // that overlaps references obtained from the root.
2089 let mut min_node = unsafe { ptr::read(&root) };
2090 let mut max_node = root;
2092 let front = min_node.first_edge();
2093 let back = max_node.last_edge();
2094 match (front.force(), back.force()) {
2095 (Leaf(f), Leaf(b)) => {
2098 (Internal(min_int), Internal(max_int)) => {
2099 min_node = min_int.descend();
2100 max_node = max_int.descend();
2102 _ => unreachable!("BTreeMap has different depths"),
2107 impl<K, V> BTreeMap<K, V> {
2108 /// Gets an iterator over the entries of the map, sorted by key.
2115 /// use std::collections::BTreeMap;
2117 /// let mut map = BTreeMap::new();
2118 /// map.insert(3, "c");
2119 /// map.insert(2, "b");
2120 /// map.insert(1, "a");
2122 /// for (key, value) in map.iter() {
2123 /// println!("{}: {}", key, value);
2126 /// let (first_key, first_value) = map.iter().next().unwrap();
2127 /// assert_eq!((*first_key, *first_value), (1, "a"));
2129 #[stable(feature = "rust1", since = "1.0.0")]
2130 pub fn iter(&self) -> Iter<'_, K, V> {
2131 if let Some(root) = &self.root {
2132 let (f, b) = full_range_search(root.as_ref());
2134 Iter { range: Range { front: Some(f), back: Some(b) }, length: self.length }
2136 Iter { range: Range { front: None, back: None }, length: 0 }
2140 /// Gets a mutable iterator over the entries of the map, sorted by key.
2147 /// use std::collections::BTreeMap;
2149 /// let mut map = BTreeMap::new();
2150 /// map.insert("a", 1);
2151 /// map.insert("b", 2);
2152 /// map.insert("c", 3);
2154 /// // add 10 to the value if the key isn't "a"
2155 /// for (key, value) in map.iter_mut() {
2156 /// if key != &"a" {
2161 #[stable(feature = "rust1", since = "1.0.0")]
2162 pub fn iter_mut(&mut self) -> IterMut<'_, K, V> {
2163 if let Some(root) = &mut self.root {
2164 let (f, b) = full_range_search(root.as_mut());
2167 range: RangeMut { front: Some(f), back: Some(b), _marker: PhantomData },
2168 length: self.length,
2171 IterMut { range: RangeMut { front: None, back: None, _marker: PhantomData }, length: 0 }
2175 /// Gets an iterator over the keys of the map, in sorted order.
2182 /// use std::collections::BTreeMap;
2184 /// let mut a = BTreeMap::new();
2185 /// a.insert(2, "b");
2186 /// a.insert(1, "a");
2188 /// let keys: Vec<_> = a.keys().cloned().collect();
2189 /// assert_eq!(keys, [1, 2]);
2191 #[stable(feature = "rust1", since = "1.0.0")]
2192 pub fn keys(&self) -> Keys<'_, K, V> {
2193 Keys { inner: self.iter() }
2196 /// Gets an iterator over the values of the map, in order by key.
2203 /// use std::collections::BTreeMap;
2205 /// let mut a = BTreeMap::new();
2206 /// a.insert(1, "hello");
2207 /// a.insert(2, "goodbye");
2209 /// let values: Vec<&str> = a.values().cloned().collect();
2210 /// assert_eq!(values, ["hello", "goodbye"]);
2212 #[stable(feature = "rust1", since = "1.0.0")]
2213 pub fn values(&self) -> Values<'_, K, V> {
2214 Values { inner: self.iter() }
2217 /// Gets a mutable iterator over the values of the map, in order by key.
2224 /// use std::collections::BTreeMap;
2226 /// let mut a = BTreeMap::new();
2227 /// a.insert(1, String::from("hello"));
2228 /// a.insert(2, String::from("goodbye"));
2230 /// for value in a.values_mut() {
2231 /// value.push_str("!");
2234 /// let values: Vec<String> = a.values().cloned().collect();
2235 /// assert_eq!(values, [String::from("hello!"),
2236 /// String::from("goodbye!")]);
2238 #[stable(feature = "map_values_mut", since = "1.10.0")]
2239 pub fn values_mut(&mut self) -> ValuesMut<'_, K, V> {
2240 ValuesMut { inner: self.iter_mut() }
2243 /// Returns the number of elements in the map.
2250 /// use std::collections::BTreeMap;
2252 /// let mut a = BTreeMap::new();
2253 /// assert_eq!(a.len(), 0);
2254 /// a.insert(1, "a");
2255 /// assert_eq!(a.len(), 1);
2257 #[stable(feature = "rust1", since = "1.0.0")]
2258 pub fn len(&self) -> usize {
2262 /// Returns `true` if the map contains no elements.
2269 /// use std::collections::BTreeMap;
2271 /// let mut a = BTreeMap::new();
2272 /// assert!(a.is_empty());
2273 /// a.insert(1, "a");
2274 /// assert!(!a.is_empty());
2276 #[stable(feature = "rust1", since = "1.0.0")]
2277 pub fn is_empty(&self) -> bool {
2281 /// If the root node is the empty (non-allocated) root node, allocate our
2283 fn ensure_root_is_owned(&mut self) -> &mut node::Root<K, V> {
2284 self.root.get_or_insert_with(node::Root::new_leaf)
2288 impl<'a, K: Ord, V> Entry<'a, K, V> {
2289 /// Ensures a value is in the entry by inserting the default if empty, and returns
2290 /// a mutable reference to the value in the entry.
2295 /// use std::collections::BTreeMap;
2297 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2298 /// map.entry("poneyland").or_insert(12);
2300 /// assert_eq!(map["poneyland"], 12);
2302 #[stable(feature = "rust1", since = "1.0.0")]
2303 pub fn or_insert(self, default: V) -> &'a mut V {
2305 Occupied(entry) => entry.into_mut(),
2306 Vacant(entry) => entry.insert(default),
2310 /// Ensures a value is in the entry by inserting the result of the default function if empty,
2311 /// and returns a mutable reference to the value in the entry.
2316 /// use std::collections::BTreeMap;
2318 /// let mut map: BTreeMap<&str, String> = BTreeMap::new();
2319 /// let s = "hoho".to_string();
2321 /// map.entry("poneyland").or_insert_with(|| s);
2323 /// assert_eq!(map["poneyland"], "hoho".to_string());
2325 #[stable(feature = "rust1", since = "1.0.0")]
2326 pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V {
2328 Occupied(entry) => entry.into_mut(),
2329 Vacant(entry) => entry.insert(default()),
2333 #[unstable(feature = "or_insert_with_key", issue = "71024")]
2334 /// Ensures a value is in the entry by inserting, if empty, the result of the default function,
2335 /// which takes the key as its argument, and returns a mutable reference to the value in the
2341 /// #![feature(or_insert_with_key)]
2342 /// use std::collections::BTreeMap;
2344 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2346 /// map.entry("poneyland").or_insert_with_key(|key| key.chars().count());
2348 /// assert_eq!(map["poneyland"], 9);
2351 pub fn or_insert_with_key<F: FnOnce(&K) -> V>(self, default: F) -> &'a mut V {
2353 Occupied(entry) => entry.into_mut(),
2355 let value = default(entry.key());
2361 /// Returns a reference to this entry's key.
2366 /// use std::collections::BTreeMap;
2368 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2369 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2371 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2372 pub fn key(&self) -> &K {
2374 Occupied(ref entry) => entry.key(),
2375 Vacant(ref entry) => entry.key(),
2379 /// Provides in-place mutable access to an occupied entry before any
2380 /// potential inserts into the map.
2385 /// use std::collections::BTreeMap;
2387 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2389 /// map.entry("poneyland")
2390 /// .and_modify(|e| { *e += 1 })
2392 /// assert_eq!(map["poneyland"], 42);
2394 /// map.entry("poneyland")
2395 /// .and_modify(|e| { *e += 1 })
2397 /// assert_eq!(map["poneyland"], 43);
2399 #[stable(feature = "entry_and_modify", since = "1.26.0")]
2400 pub fn and_modify<F>(self, f: F) -> Self
2405 Occupied(mut entry) => {
2409 Vacant(entry) => Vacant(entry),
2414 impl<'a, K: Ord, V: Default> Entry<'a, K, V> {
2415 #[stable(feature = "entry_or_default", since = "1.28.0")]
2416 /// Ensures a value is in the entry by inserting the default value if empty,
2417 /// and returns a mutable reference to the value in the entry.
2422 /// use std::collections::BTreeMap;
2424 /// let mut map: BTreeMap<&str, Option<usize>> = BTreeMap::new();
2425 /// map.entry("poneyland").or_default();
2427 /// assert_eq!(map["poneyland"], None);
2429 pub fn or_default(self) -> &'a mut V {
2431 Occupied(entry) => entry.into_mut(),
2432 Vacant(entry) => entry.insert(Default::default()),
2437 impl<'a, K: Ord, V> VacantEntry<'a, K, V> {
2438 /// Gets a reference to the key that would be used when inserting a value
2439 /// through the VacantEntry.
2444 /// use std::collections::BTreeMap;
2446 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2447 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2449 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2450 pub fn key(&self) -> &K {
2454 /// Take ownership of the key.
2459 /// use std::collections::BTreeMap;
2460 /// use std::collections::btree_map::Entry;
2462 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2464 /// if let Entry::Vacant(v) = map.entry("poneyland") {
2468 #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
2469 pub fn into_key(self) -> K {
2473 /// Sets the value of the entry with the `VacantEntry`'s key,
2474 /// and returns a mutable reference to it.
2479 /// use std::collections::BTreeMap;
2480 /// use std::collections::btree_map::Entry;
2482 /// let mut map: BTreeMap<&str, u32> = BTreeMap::new();
2484 /// if let Entry::Vacant(o) = map.entry("poneyland") {
2487 /// assert_eq!(map["poneyland"], 37);
2489 #[stable(feature = "rust1", since = "1.0.0")]
2490 pub fn insert(self, value: V) -> &'a mut V {
2499 let mut cur_parent = match self.handle.insert(self.key, value) {
2500 (Fit(handle), _) => return handle.into_kv_mut().1,
2501 (Split(left, k, v, right), ptr) => {
2506 left.ascend().map_err(|n| n.into_root_mut())
2512 Ok(parent) => match parent.insert(ins_k, ins_v, ins_edge) {
2513 Fit(_) => return unsafe { &mut *out_ptr },
2514 Split(left, k, v, right) => {
2518 cur_parent = left.ascend().map_err(|n| n.into_root_mut());
2522 root.push_level().push(ins_k, ins_v, ins_edge);
2523 return unsafe { &mut *out_ptr };
2530 impl<'a, K: Ord, V> OccupiedEntry<'a, K, V> {
2531 /// Gets a reference to the key in the entry.
2536 /// use std::collections::BTreeMap;
2538 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2539 /// map.entry("poneyland").or_insert(12);
2540 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2542 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2543 pub fn key(&self) -> &K {
2544 self.handle.reborrow().into_kv().0
2547 /// Take ownership of the key and value from the map.
2552 /// use std::collections::BTreeMap;
2553 /// use std::collections::btree_map::Entry;
2555 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2556 /// map.entry("poneyland").or_insert(12);
2558 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2559 /// // We delete the entry from the map.
2560 /// o.remove_entry();
2563 /// // If now try to get the value, it will panic:
2564 /// // println!("{}", map["poneyland"]);
2566 #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
2567 pub fn remove_entry(self) -> (K, V) {
2571 /// Gets a reference to the value in the entry.
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 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2583 /// assert_eq!(o.get(), &12);
2586 #[stable(feature = "rust1", since = "1.0.0")]
2587 pub fn get(&self) -> &V {
2588 self.handle.reborrow().into_kv().1
2591 /// Gets a mutable reference to the value in the entry.
2593 /// If you need a reference to the `OccupiedEntry` that may outlive the
2594 /// destruction of the `Entry` value, see [`into_mut`].
2596 /// [`into_mut`]: #method.into_mut
2601 /// use std::collections::BTreeMap;
2602 /// use std::collections::btree_map::Entry;
2604 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2605 /// map.entry("poneyland").or_insert(12);
2607 /// assert_eq!(map["poneyland"], 12);
2608 /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
2609 /// *o.get_mut() += 10;
2610 /// assert_eq!(*o.get(), 22);
2612 /// // We can use the same Entry multiple times.
2613 /// *o.get_mut() += 2;
2615 /// assert_eq!(map["poneyland"], 24);
2617 #[stable(feature = "rust1", since = "1.0.0")]
2618 pub fn get_mut(&mut self) -> &mut V {
2619 self.handle.kv_mut().1
2622 /// Converts the entry into a mutable reference to its value.
2624 /// If you need multiple references to the `OccupiedEntry`, see [`get_mut`].
2626 /// [`get_mut`]: #method.get_mut
2631 /// use std::collections::BTreeMap;
2632 /// use std::collections::btree_map::Entry;
2634 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2635 /// map.entry("poneyland").or_insert(12);
2637 /// assert_eq!(map["poneyland"], 12);
2638 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2639 /// *o.into_mut() += 10;
2641 /// assert_eq!(map["poneyland"], 22);
2643 #[stable(feature = "rust1", since = "1.0.0")]
2644 pub fn into_mut(self) -> &'a mut V {
2645 self.handle.into_kv_mut().1
2648 /// Sets the value of the entry with the `OccupiedEntry`'s key,
2649 /// and returns the entry's old value.
2654 /// use std::collections::BTreeMap;
2655 /// use std::collections::btree_map::Entry;
2657 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2658 /// map.entry("poneyland").or_insert(12);
2660 /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
2661 /// assert_eq!(o.insert(15), 12);
2663 /// assert_eq!(map["poneyland"], 15);
2665 #[stable(feature = "rust1", since = "1.0.0")]
2666 pub fn insert(&mut self, value: V) -> V {
2667 mem::replace(self.get_mut(), value)
2670 /// Takes the value of the entry out of the map, and returns it.
2675 /// use std::collections::BTreeMap;
2676 /// use std::collections::btree_map::Entry;
2678 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2679 /// map.entry("poneyland").or_insert(12);
2681 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2682 /// assert_eq!(o.remove(), 12);
2684 /// // If we try to get "poneyland"'s value, it'll panic:
2685 /// // println!("{}", map["poneyland"]);
2687 #[stable(feature = "rust1", since = "1.0.0")]
2688 pub fn remove(self) -> V {
2692 fn remove_kv(self) -> (K, V) {
2695 let (old_key, old_val, _) = self.handle.remove_kv_tracking();
2700 impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, marker::KV> {
2701 /// Removes a key/value-pair from the map, and returns that pair, as well as
2702 /// the leaf edge corresponding to that former pair.
2703 fn remove_kv_tracking(
2705 ) -> (K, V, Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>) {
2706 let (mut pos, old_key, old_val, was_internal) = match self.force() {
2708 let (hole, old_key, old_val) = leaf.remove();
2709 (hole, old_key, old_val, false)
2711 Internal(mut internal) => {
2712 // Replace the location freed in the internal node with the next KV,
2713 // and remove that next KV from its leaf.
2715 let key_loc = internal.kv_mut().0 as *mut K;
2716 let val_loc = internal.kv_mut().1 as *mut V;
2718 // Deleting from the left side is typically faster since we can
2719 // just pop an element from the end of the KV array without
2720 // needing to shift the other values.
2721 let to_remove = internal.left_edge().descend().last_leaf_edge().left_kv().ok();
2722 let to_remove = unsafe { unwrap_unchecked(to_remove) };
2724 let (hole, key, val) = to_remove.remove();
2726 let old_key = unsafe { mem::replace(&mut *key_loc, key) };
2727 let old_val = unsafe { mem::replace(&mut *val_loc, val) };
2729 (hole, old_key, old_val, true)
2734 let mut cur_node = unsafe { ptr::read(&pos).into_node().forget_type() };
2735 let mut at_leaf = true;
2736 while cur_node.len() < node::MIN_LEN {
2737 match handle_underfull_node(cur_node) {
2739 Merged(edge, merged_with_left, offset) => {
2740 // If we merged with our right sibling then our tracked
2741 // position has not changed. However if we merged with our
2742 // left sibling then our tracked position is now dangling.
2743 if at_leaf && merged_with_left {
2744 let idx = pos.idx() + offset;
2745 let node = match unsafe { ptr::read(&edge).descend().force() } {
2747 Internal(_) => unreachable!(),
2749 pos = unsafe { Handle::new_edge(node, idx) };
2752 let parent = edge.into_node();
2753 if parent.len() == 0 {
2754 // We must be at the root
2755 parent.into_root_mut().pop_level();
2758 cur_node = parent.forget_type();
2762 Stole(stole_from_left) => {
2763 // Adjust the tracked position if we stole from a left sibling
2764 if stole_from_left && at_leaf {
2765 // SAFETY: This is safe since we just added an element to our node.
2767 pos.next_unchecked();
2775 // If we deleted from an internal node then we need to compensate for
2776 // the earlier swap and adjust the tracked position to point to the
2779 pos = unsafe { unwrap_unchecked(pos.next_kv().ok()).next_leaf_edge() };
2782 (old_key, old_val, pos)
2786 enum UnderflowResult<'a, K, V> {
2788 Merged(Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::Edge>, bool, usize),
2792 fn handle_underfull_node<K, V>(
2793 node: NodeRef<marker::Mut<'_>, K, V, marker::LeafOrInternal>,
2794 ) -> UnderflowResult<'_, K, V> {
2795 let parent = match node.ascend() {
2796 Ok(parent) => parent,
2797 Err(_) => return AtRoot,
2800 let (is_left, mut handle) = match parent.left_kv() {
2801 Ok(left) => (true, left),
2803 let right = unsafe { unwrap_unchecked(parent.right_kv().ok()) };
2808 if handle.can_merge() {
2809 let offset = if is_left { handle.reborrow().left_edge().descend().len() + 1 } else { 0 };
2810 Merged(handle.merge(), is_left, offset)
2813 handle.steal_left();
2815 handle.steal_right();
2821 impl<K: Ord, V, I: Iterator<Item = (K, V)>> Iterator for MergeIter<K, V, I> {
2824 fn next(&mut self) -> Option<(K, V)> {
2825 let res = match (self.left.peek(), self.right.peek()) {
2826 (Some(&(ref left_key, _)), Some(&(ref right_key, _))) => left_key.cmp(right_key),
2827 (Some(_), None) => Ordering::Less,
2828 (None, Some(_)) => Ordering::Greater,
2829 (None, None) => return None,
2832 // Check which elements comes first and only advance the corresponding iterator.
2833 // If two keys are equal, take the value from `right`.
2835 Ordering::Less => self.left.next(),
2836 Ordering::Greater => self.right.next(),
2837 Ordering::Equal => {