1 use core::borrow::Borrow;
2 use core::cmp::Ordering;
4 use core::hash::{Hash, Hasher};
5 use core::iter::{FromIterator, FusedIterator, Peekable};
6 use core::marker::PhantomData;
7 use core::ops::Bound::{Excluded, Included, Unbounded};
8 use core::ops::{Index, RangeBounds};
9 use core::{fmt, intrinsics, mem, ptr};
11 use super::node::{self, marker, ForceResult::*, Handle, InsertResult::*, NodeRef};
12 use super::search::{self, SearchResult::*};
15 use UnderflowResult::*;
17 /// A map based on a B-Tree.
19 /// B-Trees represent a fundamental compromise between cache-efficiency and actually minimizing
20 /// the amount of work performed in a search. In theory, a binary search tree (BST) is the optimal
21 /// choice for a sorted map, as a perfectly balanced BST performs the theoretical minimum amount of
22 /// comparisons necessary to find an element (log<sub>2</sub>n). However, in practice the way this
23 /// is done is *very* inefficient for modern computer architectures. In particular, every element
24 /// is stored in its own individually heap-allocated node. This means that every single insertion
25 /// triggers a heap-allocation, and every single comparison should be a cache-miss. Since these
26 /// are both notably expensive things to do in practice, we are forced to at very least reconsider
29 /// A B-Tree instead makes each node contain B-1 to 2B-1 elements in a contiguous array. By doing
30 /// this, we reduce the number of allocations by a factor of B, and improve cache efficiency in
31 /// searches. However, this does mean that searches will have to do *more* comparisons on average.
32 /// The precise number of comparisons depends on the node search strategy used. For optimal cache
33 /// efficiency, one could search the nodes linearly. For optimal comparisons, one could search
34 /// the node using binary search. As a compromise, one could also perform a linear search
35 /// that initially only checks every i<sup>th</sup> element for some choice of i.
37 /// Currently, our implementation simply performs naive linear search. This provides excellent
38 /// performance on *small* nodes of elements which are cheap to compare. However in the future we
39 /// would like to further explore choosing the optimal search strategy based on the choice of B,
40 /// and possibly other factors. Using linear search, searching for a random element is expected
41 /// to take O(B log<sub>B</sub>n) comparisons, which is generally worse than a BST. In practice,
42 /// however, performance is excellent.
44 /// It is a logic error for a key to be modified in such a way that the key's ordering relative to
45 /// any other key, as determined by the [`Ord`] trait, changes while it is in the map. This is
46 /// normally only possible through [`Cell`], [`RefCell`], global state, I/O, or unsafe code.
48 /// [`Ord`]: ../../std/cmp/trait.Ord.html
49 /// [`Cell`]: ../../std/cell/struct.Cell.html
50 /// [`RefCell`]: ../../std/cell/struct.RefCell.html
55 /// use std::collections::BTreeMap;
57 /// // type inference lets us omit an explicit type signature (which
58 /// // would be `BTreeMap<&str, &str>` in this example).
59 /// let mut movie_reviews = BTreeMap::new();
61 /// // review some movies.
62 /// movie_reviews.insert("Office Space", "Deals with real issues in the workplace.");
63 /// movie_reviews.insert("Pulp Fiction", "Masterpiece.");
64 /// movie_reviews.insert("The Godfather", "Very enjoyable.");
65 /// movie_reviews.insert("The Blues Brothers", "Eye lyked it a lot.");
67 /// // check for a specific one.
68 /// if !movie_reviews.contains_key("Les Misérables") {
69 /// println!("We've got {} reviews, but Les Misérables ain't one.",
70 /// movie_reviews.len());
73 /// // oops, this review has a lot of spelling mistakes, let's delete it.
74 /// movie_reviews.remove("The Blues Brothers");
76 /// // look up the values associated with some keys.
77 /// let to_find = ["Up!", "Office Space"];
78 /// for movie in &to_find {
79 /// match movie_reviews.get(movie) {
80 /// Some(review) => println!("{}: {}", movie, review),
81 /// None => println!("{} is unreviewed.", movie)
85 /// // Look up the value for a key (will panic if the key is not found).
86 /// println!("Movie review: {}", movie_reviews["Office Space"]);
88 /// // iterate over everything.
89 /// for (movie, review) in &movie_reviews {
90 /// println!("{}: \"{}\"", movie, review);
94 /// `BTreeMap` also implements an [`Entry API`](#method.entry), which allows
95 /// for more complex methods of getting, setting, updating and removing keys and
99 /// use std::collections::BTreeMap;
101 /// // type inference lets us omit an explicit type signature (which
102 /// // would be `BTreeMap<&str, u8>` in this example).
103 /// let mut player_stats = BTreeMap::new();
105 /// fn random_stat_buff() -> u8 {
106 /// // could actually return some random value here - let's just return
107 /// // some fixed value for now
111 /// // insert a key only if it doesn't already exist
112 /// player_stats.entry("health").or_insert(100);
114 /// // insert a key using a function that provides a new value only if it
115 /// // doesn't already exist
116 /// player_stats.entry("defence").or_insert_with(random_stat_buff);
118 /// // update a key, guarding against the key possibly not being set
119 /// let stat = player_stats.entry("attack").or_insert(100);
120 /// *stat += random_stat_buff();
122 #[stable(feature = "rust1", since = "1.0.0")]
123 pub struct BTreeMap<K, V> {
124 root: node::Root<K, V>,
128 #[stable(feature = "btree_drop", since = "1.7.0")]
129 unsafe impl<#[may_dangle] K, #[may_dangle] V> Drop for BTreeMap<K, V> {
132 drop(ptr::read(self).into_iter());
137 #[stable(feature = "rust1", since = "1.0.0")]
138 impl<K: Clone, V: Clone> Clone for BTreeMap<K, V> {
139 fn clone(&self) -> BTreeMap<K, V> {
140 fn clone_subtree<'a, K: Clone, V: Clone>(
141 node: node::NodeRef<marker::Immut<'a>, K, V, marker::LeafOrInternal>,
149 let mut out_tree = BTreeMap { root: node::Root::new_leaf(), length: 0 };
152 let mut out_node = match out_tree.root.as_mut().force() {
154 Internal(_) => unreachable!(),
157 let mut in_edge = leaf.first_edge();
158 while let Ok(kv) = in_edge.right_kv() {
159 let (k, v) = kv.into_kv();
160 in_edge = kv.right_edge();
162 out_node.push(k.clone(), v.clone());
163 out_tree.length += 1;
169 Internal(internal) => {
170 let mut out_tree = clone_subtree(internal.first_edge().descend());
173 let mut out_node = out_tree.root.push_level();
174 let mut in_edge = internal.first_edge();
175 while let Ok(kv) = in_edge.right_kv() {
176 let (k, v) = kv.into_kv();
177 in_edge = kv.right_edge();
179 let k = (*k).clone();
180 let v = (*v).clone();
181 let subtree = clone_subtree(in_edge.descend());
183 // We can't destructure subtree directly
184 // because BTreeMap implements Drop
185 let (subroot, sublength) = unsafe {
186 let root = ptr::read(&subtree.root);
187 let length = subtree.length;
188 mem::forget(subtree);
192 out_node.push(k, v, subroot);
193 out_tree.length += 1 + sublength;
203 // Ideally we'd call `BTreeMap::new` here, but that has the `K:
204 // Ord` constraint, which this method lacks.
205 BTreeMap { root: node::Root::shared_empty_root(), length: 0 }
207 clone_subtree(self.root.as_ref())
211 fn clone_from(&mut self, other: &Self) {
212 BTreeClone::clone_from(self, other);
217 fn clone_from(&mut self, other: &Self);
220 impl<K: Clone, V: Clone> BTreeClone for BTreeMap<K, V> {
221 default fn clone_from(&mut self, other: &Self) {
222 *self = other.clone();
226 impl<K: Clone + Ord, V: Clone> BTreeClone for BTreeMap<K, V> {
227 fn clone_from(&mut self, other: &Self) {
228 // This truncates `self` to `other.len()` by calling `split_off` on
229 // the first key after `other.len()` elements if it exists
231 if self.len() > other.len() {
232 let diff = self.len() - other.len();
233 if diff <= other.len() {
234 self.iter().nth_back(diff - 1).map(|pair| (*pair.0).clone())
236 self.iter().nth(other.len()).map(|pair| (*pair.0).clone())
242 self.split_off(&key);
244 let mut siter = self.range_mut(..);
245 let mut oiter = other.iter();
246 // After truncation, `self` is at most as long as `other` so this loop
247 // replaces every key-value pair in `self`. Since `oiter` is in sorted
248 // order and the structure of the `BTreeMap` stays the same,
249 // the BTree invariants are maintained at the end of the loop
250 while siter.front != siter.back {
251 if let Some((ok, ov)) = oiter.next() {
252 // This is safe because the `siter.front != siter.back` check
253 // ensures that `siter` is nonempty
254 let (sk, sv) = unsafe { siter.next_unchecked() };
261 // If `other` is longer than `self`, the remaining elements are inserted
262 self.extend(oiter.map(|(k, v)| ((*k).clone(), (*v).clone())));
266 impl<K, Q: ?Sized> super::Recover<Q> for BTreeMap<K, ()>
273 fn get(&self, key: &Q) -> Option<&K> {
274 match search::search_tree(self.root.as_ref(), key) {
275 Found(handle) => Some(handle.into_kv().0),
280 fn take(&mut self, key: &Q) -> Option<K> {
281 match search::search_tree(self.root.as_mut(), key) {
282 Found(handle) => Some(
283 OccupiedEntry { handle, length: &mut self.length, _marker: PhantomData }
291 fn replace(&mut self, key: K) -> Option<K> {
292 self.ensure_root_is_owned();
293 match search::search_tree::<marker::Mut<'_>, K, (), K>(self.root.as_mut(), &key) {
294 Found(handle) => Some(mem::replace(handle.into_kv_mut().0, key)),
296 VacantEntry { key, handle, length: &mut self.length, _marker: PhantomData }
304 /// An iterator over the entries of a `BTreeMap`.
306 /// This `struct` is created by the [`iter`] method on [`BTreeMap`]. See its
307 /// documentation for more.
309 /// [`iter`]: struct.BTreeMap.html#method.iter
310 /// [`BTreeMap`]: struct.BTreeMap.html
311 #[stable(feature = "rust1", since = "1.0.0")]
312 pub struct Iter<'a, K: 'a, V: 'a> {
313 range: Range<'a, K, V>,
317 #[stable(feature = "collection_debug", since = "1.17.0")]
318 impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for Iter<'_, K, V> {
319 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
320 f.debug_list().entries(self.clone()).finish()
324 /// A mutable iterator over the entries of a `BTreeMap`.
326 /// This `struct` is created by the [`iter_mut`] method on [`BTreeMap`]. See its
327 /// documentation for more.
329 /// [`iter_mut`]: struct.BTreeMap.html#method.iter_mut
330 /// [`BTreeMap`]: struct.BTreeMap.html
331 #[stable(feature = "rust1", since = "1.0.0")]
333 pub struct IterMut<'a, K: 'a, V: 'a> {
334 range: RangeMut<'a, K, V>,
338 /// An owning iterator over the entries of a `BTreeMap`.
340 /// This `struct` is created by the [`into_iter`] method on [`BTreeMap`][`BTreeMap`]
341 /// (provided by the `IntoIterator` trait). See its documentation for more.
343 /// [`into_iter`]: struct.BTreeMap.html#method.into_iter
344 /// [`BTreeMap`]: struct.BTreeMap.html
345 #[stable(feature = "rust1", since = "1.0.0")]
346 pub struct IntoIter<K, V> {
347 front: Handle<NodeRef<marker::Owned, K, V, marker::Leaf>, marker::Edge>,
348 back: Handle<NodeRef<marker::Owned, K, V, marker::Leaf>, marker::Edge>,
352 #[stable(feature = "collection_debug", since = "1.17.0")]
353 impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for IntoIter<K, V> {
354 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
355 let range = Range { front: self.front.reborrow(), back: self.back.reborrow() };
356 f.debug_list().entries(range).finish()
360 /// An iterator over the keys of a `BTreeMap`.
362 /// This `struct` is created by the [`keys`] method on [`BTreeMap`]. See its
363 /// documentation for more.
365 /// [`keys`]: struct.BTreeMap.html#method.keys
366 /// [`BTreeMap`]: struct.BTreeMap.html
367 #[stable(feature = "rust1", since = "1.0.0")]
368 pub struct Keys<'a, K: 'a, V: 'a> {
369 inner: Iter<'a, K, V>,
372 #[stable(feature = "collection_debug", since = "1.17.0")]
373 impl<K: fmt::Debug, V> fmt::Debug for Keys<'_, K, V> {
374 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
375 f.debug_list().entries(self.clone()).finish()
379 /// An iterator over the values of a `BTreeMap`.
381 /// This `struct` is created by the [`values`] method on [`BTreeMap`]. See its
382 /// documentation for more.
384 /// [`values`]: struct.BTreeMap.html#method.values
385 /// [`BTreeMap`]: struct.BTreeMap.html
386 #[stable(feature = "rust1", since = "1.0.0")]
387 pub struct Values<'a, K: 'a, V: 'a> {
388 inner: Iter<'a, K, V>,
391 #[stable(feature = "collection_debug", since = "1.17.0")]
392 impl<K, V: fmt::Debug> fmt::Debug for Values<'_, K, V> {
393 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
394 f.debug_list().entries(self.clone()).finish()
398 /// A mutable iterator over the values of a `BTreeMap`.
400 /// This `struct` is created by the [`values_mut`] method on [`BTreeMap`]. See its
401 /// documentation for more.
403 /// [`values_mut`]: struct.BTreeMap.html#method.values_mut
404 /// [`BTreeMap`]: struct.BTreeMap.html
405 #[stable(feature = "map_values_mut", since = "1.10.0")]
407 pub struct ValuesMut<'a, K: 'a, V: 'a> {
408 inner: IterMut<'a, K, V>,
411 /// An iterator over a sub-range of entries in a `BTreeMap`.
413 /// This `struct` is created by the [`range`] method on [`BTreeMap`]. See its
414 /// documentation for more.
416 /// [`range`]: struct.BTreeMap.html#method.range
417 /// [`BTreeMap`]: struct.BTreeMap.html
418 #[stable(feature = "btree_range", since = "1.17.0")]
419 pub struct Range<'a, K: 'a, V: 'a> {
420 front: Handle<NodeRef<marker::Immut<'a>, K, V, marker::Leaf>, marker::Edge>,
421 back: Handle<NodeRef<marker::Immut<'a>, K, V, marker::Leaf>, marker::Edge>,
424 #[stable(feature = "collection_debug", since = "1.17.0")]
425 impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for Range<'_, K, V> {
426 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
427 f.debug_list().entries(self.clone()).finish()
431 /// A mutable iterator over a sub-range of entries in a `BTreeMap`.
433 /// This `struct` is created by the [`range_mut`] method on [`BTreeMap`]. See its
434 /// documentation for more.
436 /// [`range_mut`]: struct.BTreeMap.html#method.range_mut
437 /// [`BTreeMap`]: struct.BTreeMap.html
438 #[stable(feature = "btree_range", since = "1.17.0")]
439 pub struct RangeMut<'a, K: 'a, V: 'a> {
440 front: Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>,
441 back: Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>,
443 // Be invariant in `K` and `V`
444 _marker: PhantomData<&'a mut (K, V)>,
447 #[stable(feature = "collection_debug", since = "1.17.0")]
448 impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for RangeMut<'_, K, V> {
449 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
450 let range = Range { front: self.front.reborrow(), back: self.back.reborrow() };
451 f.debug_list().entries(range).finish()
455 /// A view into a single entry in a map, which may either be vacant or occupied.
457 /// This `enum` is constructed from the [`entry`] method on [`BTreeMap`].
459 /// [`BTreeMap`]: struct.BTreeMap.html
460 /// [`entry`]: struct.BTreeMap.html#method.entry
461 #[stable(feature = "rust1", since = "1.0.0")]
462 pub enum Entry<'a, K: 'a, V: 'a> {
464 #[stable(feature = "rust1", since = "1.0.0")]
465 Vacant(#[stable(feature = "rust1", since = "1.0.0")] VacantEntry<'a, K, V>),
467 /// An occupied entry.
468 #[stable(feature = "rust1", since = "1.0.0")]
469 Occupied(#[stable(feature = "rust1", since = "1.0.0")] OccupiedEntry<'a, K, V>),
472 #[stable(feature = "debug_btree_map", since = "1.12.0")]
473 impl<K: Debug + Ord, V: Debug> Debug for Entry<'_, K, V> {
474 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
476 Vacant(ref v) => f.debug_tuple("Entry").field(v).finish(),
477 Occupied(ref o) => f.debug_tuple("Entry").field(o).finish(),
482 /// A view into a vacant entry in a `BTreeMap`.
483 /// It is part of the [`Entry`] enum.
485 /// [`Entry`]: enum.Entry.html
486 #[stable(feature = "rust1", since = "1.0.0")]
487 pub struct VacantEntry<'a, K: 'a, V: 'a> {
489 handle: Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>,
490 length: &'a mut usize,
492 // Be invariant in `K` and `V`
493 _marker: PhantomData<&'a mut (K, V)>,
496 #[stable(feature = "debug_btree_map", since = "1.12.0")]
497 impl<K: Debug + Ord, V> Debug for VacantEntry<'_, K, V> {
498 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
499 f.debug_tuple("VacantEntry").field(self.key()).finish()
503 /// A view into an occupied entry in a `BTreeMap`.
504 /// It is part of the [`Entry`] enum.
506 /// [`Entry`]: enum.Entry.html
507 #[stable(feature = "rust1", since = "1.0.0")]
508 pub struct OccupiedEntry<'a, K: 'a, V: 'a> {
509 handle: Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, marker::KV>,
511 length: &'a mut usize,
513 // Be invariant in `K` and `V`
514 _marker: PhantomData<&'a mut (K, V)>,
517 #[stable(feature = "debug_btree_map", since = "1.12.0")]
518 impl<K: Debug + Ord, V: Debug> Debug for OccupiedEntry<'_, K, V> {
519 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
520 f.debug_struct("OccupiedEntry").field("key", self.key()).field("value", self.get()).finish()
524 // An iterator for merging two sorted sequences into one
525 struct MergeIter<K, V, I: Iterator<Item = (K, V)>> {
530 impl<K: Ord, V> BTreeMap<K, V> {
531 /// Makes a new empty BTreeMap with a reasonable choice for B.
538 /// use std::collections::BTreeMap;
540 /// let mut map = BTreeMap::new();
542 /// // entries can now be inserted into the empty map
543 /// map.insert(1, "a");
545 #[stable(feature = "rust1", since = "1.0.0")]
546 pub fn new() -> BTreeMap<K, V> {
547 BTreeMap { root: node::Root::shared_empty_root(), length: 0 }
550 /// Clears the map, removing all values.
557 /// use std::collections::BTreeMap;
559 /// let mut a = BTreeMap::new();
560 /// a.insert(1, "a");
562 /// assert!(a.is_empty());
564 #[stable(feature = "rust1", since = "1.0.0")]
565 pub fn clear(&mut self) {
566 *self = BTreeMap::new();
569 /// Returns a reference to the value corresponding to the key.
571 /// The key may be any borrowed form of the map's key type, but the ordering
572 /// on the borrowed form *must* match the ordering on the key type.
579 /// use std::collections::BTreeMap;
581 /// let mut map = BTreeMap::new();
582 /// map.insert(1, "a");
583 /// assert_eq!(map.get(&1), Some(&"a"));
584 /// assert_eq!(map.get(&2), None);
586 #[stable(feature = "rust1", since = "1.0.0")]
587 pub fn get<Q: ?Sized>(&self, key: &Q) -> Option<&V>
592 match search::search_tree(self.root.as_ref(), key) {
593 Found(handle) => Some(handle.into_kv().1),
598 /// Returns the key-value pair corresponding to the supplied key.
600 /// The supplied key may be any borrowed form of the map's key type, but the ordering
601 /// on the borrowed form *must* match the ordering on the key type.
606 /// use std::collections::BTreeMap;
608 /// let mut map = BTreeMap::new();
609 /// map.insert(1, "a");
610 /// assert_eq!(map.get_key_value(&1), Some((&1, &"a")));
611 /// assert_eq!(map.get_key_value(&2), None);
613 #[stable(feature = "map_get_key_value", since = "1.40.0")]
614 pub fn get_key_value<Q: ?Sized>(&self, k: &Q) -> Option<(&K, &V)>
619 match search::search_tree(self.root.as_ref(), k) {
620 Found(handle) => Some(handle.into_kv()),
625 /// Returns the first key-value pair in the map.
626 /// The key in this pair is the minimum key in the map.
633 /// #![feature(map_first_last)]
634 /// use std::collections::BTreeMap;
636 /// let mut map = BTreeMap::new();
637 /// assert_eq!(map.first_key_value(), None);
638 /// map.insert(1, "b");
639 /// map.insert(2, "a");
640 /// assert_eq!(map.first_key_value(), Some((&1, &"b")));
642 #[unstable(feature = "map_first_last", issue = "62924")]
643 pub fn first_key_value<T: ?Sized>(&self) -> Option<(&K, &V)>
648 let front = first_leaf_edge(self.root.as_ref());
649 front.right_kv().ok().map(Handle::into_kv)
652 /// Returns the first entry in the map for in-place manipulation.
653 /// The key of this entry is the minimum key in the map.
657 /// Contrived way to `clear` a map:
660 /// #![feature(map_first_last)]
661 /// use std::collections::BTreeMap;
663 /// let mut map = BTreeMap::new();
664 /// map.insert(1, "a");
665 /// map.insert(2, "b");
666 /// while let Some(entry) = map.first_entry() {
667 /// let (key, val) = entry.remove_entry();
668 /// assert!(!map.contains_key(&key));
671 #[unstable(feature = "map_first_last", issue = "62924")]
672 pub fn first_entry<T: ?Sized>(&mut self) -> Option<OccupiedEntry<'_, K, V>>
679 _ => Some(OccupiedEntry {
680 handle: self.root.as_mut().first_kv(),
681 length: &mut self.length,
682 _marker: PhantomData,
687 /// Returns the last key-value pair in the map.
688 /// The key in this pair is the maximum key in the map.
695 /// #![feature(map_first_last)]
696 /// use std::collections::BTreeMap;
698 /// let mut map = BTreeMap::new();
699 /// map.insert(1, "b");
700 /// map.insert(2, "a");
701 /// assert_eq!(map.last_key_value(), Some((&2, &"a")));
703 #[unstable(feature = "map_first_last", issue = "62924")]
704 pub fn last_key_value<T: ?Sized>(&self) -> Option<(&K, &V)>
709 let back = last_leaf_edge(self.root.as_ref());
710 back.left_kv().ok().map(Handle::into_kv)
713 /// Returns the last entry in the map for in-place manipulation.
714 /// The key of this entry is the maximum key in the map.
718 /// Contrived way to `clear` a map:
721 /// #![feature(map_first_last)]
722 /// use std::collections::BTreeMap;
724 /// let mut map = BTreeMap::new();
725 /// map.insert(1, "a");
726 /// map.insert(2, "b");
727 /// while let Some(entry) = map.last_entry() {
728 /// let (key, val) = entry.remove_entry();
729 /// assert!(!map.contains_key(&key));
732 #[unstable(feature = "map_first_last", issue = "62924")]
733 pub fn last_entry<T: ?Sized>(&mut self) -> Option<OccupiedEntry<'_, K, V>>
740 _ => Some(OccupiedEntry {
741 handle: self.root.as_mut().last_kv(),
742 length: &mut self.length,
743 _marker: PhantomData,
748 /// Returns `true` if the map contains a value for the specified key.
750 /// The key may be any borrowed form of the map's key type, but the ordering
751 /// on the borrowed form *must* match the ordering on the key type.
758 /// use std::collections::BTreeMap;
760 /// let mut map = BTreeMap::new();
761 /// map.insert(1, "a");
762 /// assert_eq!(map.contains_key(&1), true);
763 /// assert_eq!(map.contains_key(&2), false);
765 #[stable(feature = "rust1", since = "1.0.0")]
766 pub fn contains_key<Q: ?Sized>(&self, key: &Q) -> bool
771 self.get(key).is_some()
774 /// Returns a mutable reference to the value corresponding to the key.
776 /// The key may be any borrowed form of the map's key type, but the ordering
777 /// on the borrowed form *must* match the ordering on the key type.
784 /// use std::collections::BTreeMap;
786 /// let mut map = BTreeMap::new();
787 /// map.insert(1, "a");
788 /// if let Some(x) = map.get_mut(&1) {
791 /// assert_eq!(map[&1], "b");
793 // See `get` for implementation notes, this is basically a copy-paste with mut's added
794 #[stable(feature = "rust1", since = "1.0.0")]
795 pub fn get_mut<Q: ?Sized>(&mut self, key: &Q) -> Option<&mut V>
800 match search::search_tree(self.root.as_mut(), key) {
801 Found(handle) => Some(handle.into_kv_mut().1),
806 /// Inserts a key-value pair into the map.
808 /// If the map did not have this key present, `None` is returned.
810 /// If the map did have this key present, the value is updated, and the old
811 /// value is returned. The key is not updated, though; this matters for
812 /// types that can be `==` without being identical. See the [module-level
813 /// documentation] for more.
815 /// [module-level documentation]: index.html#insert-and-complex-keys
822 /// use std::collections::BTreeMap;
824 /// let mut map = BTreeMap::new();
825 /// assert_eq!(map.insert(37, "a"), None);
826 /// assert_eq!(map.is_empty(), false);
828 /// map.insert(37, "b");
829 /// assert_eq!(map.insert(37, "c"), Some("b"));
830 /// assert_eq!(map[&37], "c");
832 #[stable(feature = "rust1", since = "1.0.0")]
833 pub fn insert(&mut self, key: K, value: V) -> Option<V> {
834 match self.entry(key) {
835 Occupied(mut entry) => Some(entry.insert(value)),
843 /// Removes a key from the map, returning the value at the key if the key
844 /// was previously in the map.
846 /// The key may be any borrowed form of the map's key type, but the ordering
847 /// on the borrowed form *must* match the ordering on the key type.
854 /// use std::collections::BTreeMap;
856 /// let mut map = BTreeMap::new();
857 /// map.insert(1, "a");
858 /// assert_eq!(map.remove(&1), Some("a"));
859 /// assert_eq!(map.remove(&1), None);
861 #[stable(feature = "rust1", since = "1.0.0")]
862 pub fn remove<Q: ?Sized>(&mut self, key: &Q) -> Option<V>
867 match search::search_tree(self.root.as_mut(), key) {
868 Found(handle) => Some(
869 OccupiedEntry { handle, length: &mut self.length, _marker: PhantomData }.remove(),
875 /// Moves all elements from `other` into `Self`, leaving `other` empty.
880 /// use std::collections::BTreeMap;
882 /// let mut a = BTreeMap::new();
883 /// a.insert(1, "a");
884 /// a.insert(2, "b");
885 /// a.insert(3, "c");
887 /// let mut b = BTreeMap::new();
888 /// b.insert(3, "d");
889 /// b.insert(4, "e");
890 /// b.insert(5, "f");
892 /// a.append(&mut b);
894 /// assert_eq!(a.len(), 5);
895 /// assert_eq!(b.len(), 0);
897 /// assert_eq!(a[&1], "a");
898 /// assert_eq!(a[&2], "b");
899 /// assert_eq!(a[&3], "d");
900 /// assert_eq!(a[&4], "e");
901 /// assert_eq!(a[&5], "f");
903 #[stable(feature = "btree_append", since = "1.11.0")]
904 pub fn append(&mut self, other: &mut Self) {
905 // Do we have to append anything at all?
906 if other.is_empty() {
910 // We can just swap `self` and `other` if `self` is empty.
912 mem::swap(self, other);
916 // First, we merge `self` and `other` into a sorted sequence in linear time.
917 let self_iter = mem::take(self).into_iter();
918 let other_iter = mem::take(other).into_iter();
919 let iter = MergeIter { left: self_iter.peekable(), right: other_iter.peekable() };
921 // Second, we build a tree from the sorted sequence in linear time.
922 self.from_sorted_iter(iter);
923 self.fix_right_edge();
926 /// Constructs a double-ended iterator over a sub-range of elements in the map.
927 /// The simplest way is to use the range syntax `min..max`, thus `range(min..max)` will
928 /// yield elements from min (inclusive) to max (exclusive).
929 /// The range may also be entered as `(Bound<T>, Bound<T>)`, so for example
930 /// `range((Excluded(4), Included(10)))` will yield a left-exclusive, right-inclusive
931 /// range from 4 to 10.
935 /// Panics if range `start > end`.
936 /// Panics if range `start == end` and both bounds are `Excluded`.
943 /// use std::collections::BTreeMap;
944 /// use std::ops::Bound::Included;
946 /// let mut map = BTreeMap::new();
947 /// map.insert(3, "a");
948 /// map.insert(5, "b");
949 /// map.insert(8, "c");
950 /// for (&key, &value) in map.range((Included(&4), Included(&8))) {
951 /// println!("{}: {}", key, value);
953 /// assert_eq!(Some((&5, &"b")), map.range(4..).next());
955 #[stable(feature = "btree_range", since = "1.17.0")]
956 pub fn range<T: ?Sized, R>(&self, range: R) -> Range<'_, K, V>
962 let root1 = self.root.as_ref();
963 let root2 = self.root.as_ref();
964 let (f, b) = range_search(root1, root2, range);
966 Range { front: f, back: b }
969 /// Constructs a mutable double-ended iterator over a sub-range of elements in the map.
970 /// The simplest way is to use the range syntax `min..max`, thus `range(min..max)` will
971 /// yield elements from min (inclusive) to max (exclusive).
972 /// The range may also be entered as `(Bound<T>, Bound<T>)`, so for example
973 /// `range((Excluded(4), Included(10)))` will yield a left-exclusive, right-inclusive
974 /// range from 4 to 10.
978 /// Panics if range `start > end`.
979 /// Panics if range `start == end` and both bounds are `Excluded`.
986 /// use std::collections::BTreeMap;
988 /// let mut map: BTreeMap<&str, i32> = ["Alice", "Bob", "Carol", "Cheryl"]
990 /// .map(|&s| (s, 0))
992 /// for (_, balance) in map.range_mut("B".."Cheryl") {
995 /// for (name, balance) in &map {
996 /// println!("{} => {}", name, balance);
999 #[stable(feature = "btree_range", since = "1.17.0")]
1000 pub fn range_mut<T: ?Sized, R>(&mut self, range: R) -> RangeMut<'_, K, V>
1006 let root1 = self.root.as_mut();
1007 let root2 = unsafe { ptr::read(&root1) };
1008 let (f, b) = range_search(root1, root2, range);
1010 RangeMut { front: f, back: b, _marker: PhantomData }
1013 /// Gets the given key's corresponding entry in the map for in-place manipulation.
1020 /// use std::collections::BTreeMap;
1022 /// let mut count: BTreeMap<&str, usize> = BTreeMap::new();
1024 /// // count the number of occurrences of letters in the vec
1025 /// for x in vec!["a","b","a","c","a","b"] {
1026 /// *count.entry(x).or_insert(0) += 1;
1029 /// assert_eq!(count["a"], 3);
1031 #[stable(feature = "rust1", since = "1.0.0")]
1032 pub fn entry(&mut self, key: K) -> Entry<'_, K, V> {
1033 // FIXME(@porglezomp) Avoid allocating if we don't insert
1034 self.ensure_root_is_owned();
1035 match search::search_tree(self.root.as_mut(), &key) {
1037 Occupied(OccupiedEntry { handle, length: &mut self.length, _marker: PhantomData })
1040 Vacant(VacantEntry { key, handle, length: &mut self.length, _marker: PhantomData })
1045 fn from_sorted_iter<I: Iterator<Item = (K, V)>>(&mut self, iter: I) {
1046 self.ensure_root_is_owned();
1047 let mut cur_node = last_leaf_edge(self.root.as_mut()).into_node();
1048 // Iterate through all key-value pairs, pushing them into nodes at the right level.
1049 for (key, value) in iter {
1050 // Try to push key-value pair into the current leaf node.
1051 if cur_node.len() < node::CAPACITY {
1052 cur_node.push(key, value);
1054 // No space left, go up and push there.
1056 let mut test_node = cur_node.forget_type();
1058 match test_node.ascend() {
1060 let parent = parent.into_node();
1061 if parent.len() < node::CAPACITY {
1062 // Found a node with space left, push here.
1067 test_node = parent.forget_type();
1071 // We are at the top, create a new root node and push there.
1072 open_node = node.into_root_mut().push_level();
1078 // Push key-value pair and new right subtree.
1079 let tree_height = open_node.height() - 1;
1080 let mut right_tree = node::Root::new_leaf();
1081 for _ in 0..tree_height {
1082 right_tree.push_level();
1084 open_node.push(key, value, right_tree);
1086 // Go down to the right-most leaf again.
1087 cur_node = last_leaf_edge(open_node.forget_type()).into_node();
1094 fn fix_right_edge(&mut self) {
1095 // Handle underfull nodes, start from the top.
1096 let mut cur_node = self.root.as_mut();
1097 while let Internal(internal) = cur_node.force() {
1098 // Check if right-most child is underfull.
1099 let mut last_edge = internal.last_edge();
1100 let right_child_len = last_edge.reborrow().descend().len();
1101 if right_child_len < node::MIN_LEN {
1102 // We need to steal.
1103 let mut last_kv = match last_edge.left_kv() {
1105 Err(_) => unreachable!(),
1107 last_kv.bulk_steal_left(node::MIN_LEN - right_child_len);
1108 last_edge = last_kv.right_edge();
1112 cur_node = last_edge.descend();
1116 /// Splits the collection into two at the given key. Returns everything after the given key,
1117 /// including the key.
1124 /// use std::collections::BTreeMap;
1126 /// let mut a = BTreeMap::new();
1127 /// a.insert(1, "a");
1128 /// a.insert(2, "b");
1129 /// a.insert(3, "c");
1130 /// a.insert(17, "d");
1131 /// a.insert(41, "e");
1133 /// let b = a.split_off(&3);
1135 /// assert_eq!(a.len(), 2);
1136 /// assert_eq!(b.len(), 3);
1138 /// assert_eq!(a[&1], "a");
1139 /// assert_eq!(a[&2], "b");
1141 /// assert_eq!(b[&3], "c");
1142 /// assert_eq!(b[&17], "d");
1143 /// assert_eq!(b[&41], "e");
1145 #[stable(feature = "btree_split_off", since = "1.11.0")]
1146 pub fn split_off<Q: ?Sized + Ord>(&mut self, key: &Q) -> Self
1150 if self.is_empty() {
1154 let total_num = self.len();
1156 let mut right = Self::new();
1157 right.root = node::Root::new_leaf();
1158 for _ in 0..(self.root.as_ref().height()) {
1159 right.root.push_level();
1163 let mut left_node = self.root.as_mut();
1164 let mut right_node = right.root.as_mut();
1167 let mut split_edge = match search::search_node(left_node, key) {
1168 // key is going to the right tree
1169 Found(handle) => handle.left_edge(),
1170 GoDown(handle) => handle,
1173 split_edge.move_suffix(&mut right_node);
1175 match (split_edge.force(), right_node.force()) {
1176 (Internal(edge), Internal(node)) => {
1177 left_node = edge.descend();
1178 right_node = node.first_edge().descend();
1180 (Leaf(_), Leaf(_)) => {
1190 self.fix_right_border();
1191 right.fix_left_border();
1193 if self.root.as_ref().height() < right.root.as_ref().height() {
1194 self.recalc_length();
1195 right.length = total_num - self.len();
1197 right.recalc_length();
1198 self.length = total_num - right.len();
1204 /// Calculates the number of elements if it is incorrect.
1205 fn recalc_length(&mut self) {
1206 fn dfs<'a, K, V>(node: NodeRef<marker::Immut<'a>, K, V, marker::LeafOrInternal>) -> usize
1211 let mut res = node.len();
1213 if let Internal(node) = node.force() {
1214 let mut edge = node.first_edge();
1216 res += dfs(edge.reborrow().descend());
1217 match edge.right_kv() {
1219 edge = right_kv.right_edge();
1231 self.length = dfs(self.root.as_ref());
1234 /// Removes empty levels on the top.
1235 fn fix_top(&mut self) {
1238 let node = self.root.as_ref();
1239 if node.height() == 0 || node.len() > 0 {
1243 self.root.pop_level();
1247 fn fix_right_border(&mut self) {
1251 let mut cur_node = self.root.as_mut();
1253 while let Internal(node) = cur_node.force() {
1254 let mut last_kv = node.last_kv();
1256 if last_kv.can_merge() {
1257 cur_node = last_kv.merge().descend();
1259 let right_len = last_kv.reborrow().right_edge().descend().len();
1260 // `MINLEN + 1` to avoid readjust if merge happens on the next level.
1261 if right_len < node::MIN_LEN + 1 {
1262 last_kv.bulk_steal_left(node::MIN_LEN + 1 - right_len);
1264 cur_node = last_kv.right_edge().descend();
1272 /// The symmetric clone of `fix_right_border`.
1273 fn fix_left_border(&mut self) {
1277 let mut cur_node = self.root.as_mut();
1279 while let Internal(node) = cur_node.force() {
1280 let mut first_kv = node.first_kv();
1282 if first_kv.can_merge() {
1283 cur_node = first_kv.merge().descend();
1285 let left_len = first_kv.reborrow().left_edge().descend().len();
1286 if left_len < node::MIN_LEN + 1 {
1287 first_kv.bulk_steal_right(node::MIN_LEN + 1 - left_len);
1289 cur_node = first_kv.left_edge().descend();
1297 /// If the root node is the shared root node, allocate our own node.
1298 fn ensure_root_is_owned(&mut self) {
1299 if self.root.is_shared_root() {
1300 self.root = node::Root::new_leaf();
1305 #[stable(feature = "rust1", since = "1.0.0")]
1306 impl<'a, K: 'a, V: 'a> IntoIterator for &'a BTreeMap<K, V> {
1307 type Item = (&'a K, &'a V);
1308 type IntoIter = Iter<'a, K, V>;
1310 fn into_iter(self) -> Iter<'a, K, V> {
1315 #[stable(feature = "rust1", since = "1.0.0")]
1316 impl<'a, K: 'a, V: 'a> Iterator for Iter<'a, K, V> {
1317 type Item = (&'a K, &'a V);
1319 fn next(&mut self) -> Option<(&'a K, &'a V)> {
1320 if self.length == 0 {
1324 unsafe { Some(self.range.next_unchecked()) }
1328 fn size_hint(&self) -> (usize, Option<usize>) {
1329 (self.length, Some(self.length))
1332 fn last(mut self) -> Option<(&'a K, &'a V)> {
1337 #[stable(feature = "fused", since = "1.26.0")]
1338 impl<K, V> FusedIterator for Iter<'_, K, V> {}
1340 #[stable(feature = "rust1", since = "1.0.0")]
1341 impl<'a, K: 'a, V: 'a> DoubleEndedIterator for Iter<'a, K, V> {
1342 fn next_back(&mut self) -> Option<(&'a K, &'a V)> {
1343 if self.length == 0 {
1347 unsafe { Some(self.range.next_back_unchecked()) }
1352 #[stable(feature = "rust1", since = "1.0.0")]
1353 impl<K, V> ExactSizeIterator for Iter<'_, K, V> {
1354 fn len(&self) -> usize {
1359 #[stable(feature = "rust1", since = "1.0.0")]
1360 impl<K, V> Clone for Iter<'_, K, V> {
1361 fn clone(&self) -> Self {
1362 Iter { range: self.range.clone(), length: self.length }
1366 #[stable(feature = "rust1", since = "1.0.0")]
1367 impl<'a, K: 'a, V: 'a> IntoIterator for &'a mut BTreeMap<K, V> {
1368 type Item = (&'a K, &'a mut V);
1369 type IntoIter = IterMut<'a, K, V>;
1371 fn into_iter(self) -> IterMut<'a, K, V> {
1376 #[stable(feature = "rust1", since = "1.0.0")]
1377 impl<'a, K: 'a, V: 'a> Iterator for IterMut<'a, K, V> {
1378 type Item = (&'a K, &'a mut V);
1380 fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
1381 if self.length == 0 {
1386 let (k, v) = self.range.next_unchecked();
1387 Some((k, v)) // coerce k from `&mut K` to `&K`
1392 fn size_hint(&self) -> (usize, Option<usize>) {
1393 (self.length, Some(self.length))
1396 fn last(mut self) -> Option<(&'a K, &'a mut V)> {
1401 #[stable(feature = "rust1", since = "1.0.0")]
1402 impl<'a, K: 'a, V: 'a> DoubleEndedIterator for IterMut<'a, K, V> {
1403 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> {
1404 if self.length == 0 {
1408 unsafe { Some(self.range.next_back_unchecked()) }
1413 #[stable(feature = "rust1", since = "1.0.0")]
1414 impl<K, V> ExactSizeIterator for IterMut<'_, K, V> {
1415 fn len(&self) -> usize {
1420 #[stable(feature = "fused", since = "1.26.0")]
1421 impl<K, V> FusedIterator for IterMut<'_, K, V> {}
1423 #[stable(feature = "rust1", since = "1.0.0")]
1424 impl<K, V> IntoIterator for BTreeMap<K, V> {
1426 type IntoIter = IntoIter<K, V>;
1428 fn into_iter(self) -> IntoIter<K, V> {
1429 let root1 = unsafe { ptr::read(&self.root).into_ref() };
1430 let root2 = unsafe { ptr::read(&self.root).into_ref() };
1431 let len = self.length;
1434 IntoIter { front: first_leaf_edge(root1), back: last_leaf_edge(root2), length: len }
1438 #[stable(feature = "btree_drop", since = "1.7.0")]
1439 impl<K, V> Drop for IntoIter<K, V> {
1440 fn drop(&mut self) {
1441 self.for_each(drop);
1443 let leaf_node = ptr::read(&self.front).into_node();
1444 if leaf_node.is_shared_root() {
1448 if let Some(first_parent) = leaf_node.deallocate_and_ascend() {
1449 let mut cur_node = first_parent.into_node();
1450 while let Some(parent) = cur_node.deallocate_and_ascend() {
1451 cur_node = parent.into_node()
1458 #[stable(feature = "rust1", since = "1.0.0")]
1459 impl<K, V> Iterator for IntoIter<K, V> {
1462 fn next(&mut self) -> Option<(K, V)> {
1463 if self.length == 0 {
1469 let handle = unsafe { ptr::read(&self.front) };
1471 let mut cur_handle = match handle.right_kv() {
1473 let k = unsafe { ptr::read(kv.reborrow().into_kv().0) };
1474 let v = unsafe { ptr::read(kv.reborrow().into_kv().1) };
1475 self.front = kv.right_edge();
1476 return Some((k, v));
1478 Err(last_edge) => unsafe {
1479 unwrap_unchecked(last_edge.into_node().deallocate_and_ascend())
1484 match cur_handle.right_kv() {
1486 let k = unsafe { ptr::read(kv.reborrow().into_kv().0) };
1487 let v = unsafe { ptr::read(kv.reborrow().into_kv().1) };
1488 self.front = first_leaf_edge(kv.right_edge().descend());
1489 return Some((k, v));
1491 Err(last_edge) => unsafe {
1492 cur_handle = unwrap_unchecked(last_edge.into_node().deallocate_and_ascend());
1498 fn size_hint(&self) -> (usize, Option<usize>) {
1499 (self.length, Some(self.length))
1503 #[stable(feature = "rust1", since = "1.0.0")]
1504 impl<K, V> DoubleEndedIterator for IntoIter<K, V> {
1505 fn next_back(&mut self) -> Option<(K, V)> {
1506 if self.length == 0 {
1512 let handle = unsafe { ptr::read(&self.back) };
1514 let mut cur_handle = match handle.left_kv() {
1516 let k = unsafe { ptr::read(kv.reborrow().into_kv().0) };
1517 let v = unsafe { ptr::read(kv.reborrow().into_kv().1) };
1518 self.back = kv.left_edge();
1519 return Some((k, v));
1521 Err(last_edge) => unsafe {
1522 unwrap_unchecked(last_edge.into_node().deallocate_and_ascend())
1527 match cur_handle.left_kv() {
1529 let k = unsafe { ptr::read(kv.reborrow().into_kv().0) };
1530 let v = unsafe { ptr::read(kv.reborrow().into_kv().1) };
1531 self.back = last_leaf_edge(kv.left_edge().descend());
1532 return Some((k, v));
1534 Err(last_edge) => unsafe {
1535 cur_handle = unwrap_unchecked(last_edge.into_node().deallocate_and_ascend());
1542 #[stable(feature = "rust1", since = "1.0.0")]
1543 impl<K, V> ExactSizeIterator for IntoIter<K, V> {
1544 fn len(&self) -> usize {
1549 #[stable(feature = "fused", since = "1.26.0")]
1550 impl<K, V> FusedIterator for IntoIter<K, V> {}
1552 #[stable(feature = "rust1", since = "1.0.0")]
1553 impl<'a, K, V> Iterator for Keys<'a, K, V> {
1556 fn next(&mut self) -> Option<&'a K> {
1557 self.inner.next().map(|(k, _)| k)
1560 fn size_hint(&self) -> (usize, Option<usize>) {
1561 self.inner.size_hint()
1564 fn last(mut self) -> Option<&'a K> {
1569 #[stable(feature = "rust1", since = "1.0.0")]
1570 impl<'a, K, V> DoubleEndedIterator for Keys<'a, K, V> {
1571 fn next_back(&mut self) -> Option<&'a K> {
1572 self.inner.next_back().map(|(k, _)| k)
1576 #[stable(feature = "rust1", since = "1.0.0")]
1577 impl<K, V> ExactSizeIterator for Keys<'_, K, V> {
1578 fn len(&self) -> usize {
1583 #[stable(feature = "fused", since = "1.26.0")]
1584 impl<K, V> FusedIterator for Keys<'_, K, V> {}
1586 #[stable(feature = "rust1", since = "1.0.0")]
1587 impl<K, V> Clone for Keys<'_, K, V> {
1588 fn clone(&self) -> Self {
1589 Keys { inner: self.inner.clone() }
1593 #[stable(feature = "rust1", since = "1.0.0")]
1594 impl<'a, K, V> Iterator for Values<'a, K, V> {
1597 fn next(&mut self) -> Option<&'a V> {
1598 self.inner.next().map(|(_, v)| v)
1601 fn size_hint(&self) -> (usize, Option<usize>) {
1602 self.inner.size_hint()
1605 fn last(mut self) -> Option<&'a V> {
1610 #[stable(feature = "rust1", since = "1.0.0")]
1611 impl<'a, K, V> DoubleEndedIterator for Values<'a, K, V> {
1612 fn next_back(&mut self) -> Option<&'a V> {
1613 self.inner.next_back().map(|(_, v)| v)
1617 #[stable(feature = "rust1", since = "1.0.0")]
1618 impl<K, V> ExactSizeIterator for Values<'_, K, V> {
1619 fn len(&self) -> usize {
1624 #[stable(feature = "fused", since = "1.26.0")]
1625 impl<K, V> FusedIterator for Values<'_, K, V> {}
1627 #[stable(feature = "rust1", since = "1.0.0")]
1628 impl<K, V> Clone for Values<'_, K, V> {
1629 fn clone(&self) -> Self {
1630 Values { inner: self.inner.clone() }
1634 #[stable(feature = "btree_range", since = "1.17.0")]
1635 impl<'a, K, V> Iterator for Range<'a, K, V> {
1636 type Item = (&'a K, &'a V);
1638 fn next(&mut self) -> Option<(&'a K, &'a V)> {
1639 if self.front == self.back { None } else { unsafe { Some(self.next_unchecked()) } }
1642 fn last(mut self) -> Option<(&'a K, &'a V)> {
1647 #[stable(feature = "map_values_mut", since = "1.10.0")]
1648 impl<'a, K, V> Iterator for ValuesMut<'a, K, V> {
1649 type Item = &'a mut V;
1651 fn next(&mut self) -> Option<&'a mut V> {
1652 self.inner.next().map(|(_, v)| v)
1655 fn size_hint(&self) -> (usize, Option<usize>) {
1656 self.inner.size_hint()
1659 fn last(mut self) -> Option<&'a mut V> {
1664 #[stable(feature = "map_values_mut", since = "1.10.0")]
1665 impl<'a, K, V> DoubleEndedIterator for ValuesMut<'a, K, V> {
1666 fn next_back(&mut self) -> Option<&'a mut V> {
1667 self.inner.next_back().map(|(_, v)| v)
1671 #[stable(feature = "map_values_mut", since = "1.10.0")]
1672 impl<K, V> ExactSizeIterator for ValuesMut<'_, K, V> {
1673 fn len(&self) -> usize {
1678 #[stable(feature = "fused", since = "1.26.0")]
1679 impl<K, V> FusedIterator for ValuesMut<'_, K, V> {}
1681 impl<'a, K, V> Range<'a, K, V> {
1682 unsafe fn next_unchecked(&mut self) -> (&'a K, &'a V) {
1683 let handle = self.front;
1685 let mut cur_handle = match handle.right_kv() {
1687 let ret = kv.into_kv();
1688 self.front = kv.right_edge();
1692 let next_level = last_edge.into_node().ascend().ok();
1693 unwrap_unchecked(next_level)
1698 match cur_handle.right_kv() {
1700 let ret = kv.into_kv();
1701 self.front = first_leaf_edge(kv.right_edge().descend());
1705 let next_level = last_edge.into_node().ascend().ok();
1706 cur_handle = unwrap_unchecked(next_level);
1713 #[stable(feature = "btree_range", since = "1.17.0")]
1714 impl<'a, K, V> DoubleEndedIterator for Range<'a, K, V> {
1715 fn next_back(&mut self) -> Option<(&'a K, &'a V)> {
1716 if self.front == self.back { None } else { unsafe { Some(self.next_back_unchecked()) } }
1720 impl<'a, K, V> Range<'a, K, V> {
1721 unsafe fn next_back_unchecked(&mut self) -> (&'a K, &'a V) {
1722 let handle = self.back;
1724 let mut cur_handle = match handle.left_kv() {
1726 let ret = kv.into_kv();
1727 self.back = kv.left_edge();
1731 let next_level = last_edge.into_node().ascend().ok();
1732 unwrap_unchecked(next_level)
1737 match cur_handle.left_kv() {
1739 let ret = kv.into_kv();
1740 self.back = last_leaf_edge(kv.left_edge().descend());
1744 let next_level = last_edge.into_node().ascend().ok();
1745 cur_handle = unwrap_unchecked(next_level);
1752 #[stable(feature = "fused", since = "1.26.0")]
1753 impl<K, V> FusedIterator for Range<'_, K, V> {}
1755 #[stable(feature = "btree_range", since = "1.17.0")]
1756 impl<K, V> Clone for Range<'_, K, V> {
1757 fn clone(&self) -> Self {
1758 Range { front: self.front, back: self.back }
1762 #[stable(feature = "btree_range", since = "1.17.0")]
1763 impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
1764 type Item = (&'a K, &'a mut V);
1766 fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
1767 if self.front == self.back {
1771 let (k, v) = self.next_unchecked();
1772 Some((k, v)) // coerce k from `&mut K` to `&K`
1777 fn last(mut self) -> Option<(&'a K, &'a mut V)> {
1782 impl<'a, K, V> RangeMut<'a, K, V> {
1783 unsafe fn next_unchecked(&mut self) -> (&'a mut K, &'a mut V) {
1784 let handle = ptr::read(&self.front);
1786 let mut cur_handle = match handle.right_kv() {
1788 self.front = ptr::read(&kv).right_edge();
1789 // Doing the descend invalidates the references returned by `into_kv_mut`,
1790 // so we have to do this last.
1791 return kv.into_kv_mut();
1794 let next_level = last_edge.into_node().ascend().ok();
1795 unwrap_unchecked(next_level)
1800 match cur_handle.right_kv() {
1802 self.front = first_leaf_edge(ptr::read(&kv).right_edge().descend());
1803 // Doing the descend invalidates the references returned by `into_kv_mut`,
1804 // so we have to do this last.
1805 return kv.into_kv_mut();
1808 let next_level = last_edge.into_node().ascend().ok();
1809 cur_handle = unwrap_unchecked(next_level);
1816 #[stable(feature = "btree_range", since = "1.17.0")]
1817 impl<'a, K, V> DoubleEndedIterator for RangeMut<'a, K, V> {
1818 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> {
1819 if self.front == self.back { None } else { unsafe { Some(self.next_back_unchecked()) } }
1823 #[stable(feature = "fused", since = "1.26.0")]
1824 impl<K, V> FusedIterator for RangeMut<'_, K, V> {}
1826 impl<'a, K, V> RangeMut<'a, K, V> {
1827 unsafe fn next_back_unchecked(&mut self) -> (&'a K, &'a mut V) {
1828 let handle = ptr::read(&self.back);
1830 let mut cur_handle = match handle.left_kv() {
1832 self.back = ptr::read(&kv).left_edge();
1833 // Doing the descend invalidates the references returned by `into_kv_mut`,
1834 // so we have to do this last.
1835 let (k, v) = kv.into_kv_mut();
1836 return (k, v); // coerce k from `&mut K` to `&K`
1839 let next_level = last_edge.into_node().ascend().ok();
1840 unwrap_unchecked(next_level)
1845 match cur_handle.left_kv() {
1847 self.back = last_leaf_edge(ptr::read(&kv).left_edge().descend());
1848 // Doing the descend invalidates the references returned by `into_kv_mut`,
1849 // so we have to do this last.
1850 let (k, v) = kv.into_kv_mut();
1851 return (k, v); // coerce k from `&mut K` to `&K`
1854 let next_level = last_edge.into_node().ascend().ok();
1855 cur_handle = unwrap_unchecked(next_level);
1862 #[stable(feature = "rust1", since = "1.0.0")]
1863 impl<K: Ord, V> FromIterator<(K, V)> for BTreeMap<K, V> {
1864 fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> BTreeMap<K, V> {
1865 let mut map = BTreeMap::new();
1871 #[stable(feature = "rust1", since = "1.0.0")]
1872 impl<K: Ord, V> Extend<(K, V)> for BTreeMap<K, V> {
1874 fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T) {
1875 iter.into_iter().for_each(move |(k, v)| {
1881 #[stable(feature = "extend_ref", since = "1.2.0")]
1882 impl<'a, K: Ord + Copy, V: Copy> Extend<(&'a K, &'a V)> for BTreeMap<K, V> {
1883 fn extend<I: IntoIterator<Item = (&'a K, &'a V)>>(&mut self, iter: I) {
1884 self.extend(iter.into_iter().map(|(&key, &value)| (key, value)));
1888 #[stable(feature = "rust1", since = "1.0.0")]
1889 impl<K: Hash, V: Hash> Hash for BTreeMap<K, V> {
1890 fn hash<H: Hasher>(&self, state: &mut H) {
1897 #[stable(feature = "rust1", since = "1.0.0")]
1898 impl<K: Ord, V> Default for BTreeMap<K, V> {
1899 /// Creates an empty `BTreeMap<K, V>`.
1900 fn default() -> BTreeMap<K, V> {
1905 #[stable(feature = "rust1", since = "1.0.0")]
1906 impl<K: PartialEq, V: PartialEq> PartialEq for BTreeMap<K, V> {
1907 fn eq(&self, other: &BTreeMap<K, V>) -> bool {
1908 self.len() == other.len() && self.iter().zip(other).all(|(a, b)| a == b)
1912 #[stable(feature = "rust1", since = "1.0.0")]
1913 impl<K: Eq, V: Eq> Eq for BTreeMap<K, V> {}
1915 #[stable(feature = "rust1", since = "1.0.0")]
1916 impl<K: PartialOrd, V: PartialOrd> PartialOrd for BTreeMap<K, V> {
1918 fn partial_cmp(&self, other: &BTreeMap<K, V>) -> Option<Ordering> {
1919 self.iter().partial_cmp(other.iter())
1923 #[stable(feature = "rust1", since = "1.0.0")]
1924 impl<K: Ord, V: Ord> Ord for BTreeMap<K, V> {
1926 fn cmp(&self, other: &BTreeMap<K, V>) -> Ordering {
1927 self.iter().cmp(other.iter())
1931 #[stable(feature = "rust1", since = "1.0.0")]
1932 impl<K: Debug, V: Debug> Debug for BTreeMap<K, V> {
1933 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1934 f.debug_map().entries(self.iter()).finish()
1938 #[stable(feature = "rust1", since = "1.0.0")]
1939 impl<K: Ord, Q: ?Sized, V> Index<&Q> for BTreeMap<K, V>
1946 /// Returns a reference to the value corresponding to the supplied key.
1950 /// Panics if the key is not present in the `BTreeMap`.
1952 fn index(&self, key: &Q) -> &V {
1953 self.get(key).expect("no entry found for key")
1957 fn first_leaf_edge<BorrowType, K, V>(
1958 mut node: NodeRef<BorrowType, K, V, marker::LeafOrInternal>,
1959 ) -> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge> {
1961 match node.force() {
1962 Leaf(leaf) => return leaf.first_edge(),
1963 Internal(internal) => {
1964 node = internal.first_edge().descend();
1970 fn last_leaf_edge<BorrowType, K, V>(
1971 mut node: NodeRef<BorrowType, K, V, marker::LeafOrInternal>,
1972 ) -> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge> {
1974 match node.force() {
1975 Leaf(leaf) => return leaf.last_edge(),
1976 Internal(internal) => {
1977 node = internal.last_edge().descend();
1983 fn range_search<BorrowType, K, V, Q: ?Sized, R: RangeBounds<Q>>(
1984 root1: NodeRef<BorrowType, K, V, marker::LeafOrInternal>,
1985 root2: NodeRef<BorrowType, K, V, marker::LeafOrInternal>,
1988 Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge>,
1989 Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge>,
1995 match (range.start_bound(), range.end_bound()) {
1996 (Excluded(s), Excluded(e)) if s == e => {
1997 panic!("range start and end are equal and excluded in BTreeMap")
1999 (Included(s), Included(e))
2000 | (Included(s), Excluded(e))
2001 | (Excluded(s), Included(e))
2002 | (Excluded(s), Excluded(e))
2005 panic!("range start is greater than range end in BTreeMap")
2010 let mut min_node = root1;
2011 let mut max_node = root2;
2012 let mut min_found = false;
2013 let mut max_found = false;
2014 let mut diverged = false;
2017 let min_edge = match (min_found, range.start_bound()) {
2018 (false, Included(key)) => match search::search_linear(&min_node, key) {
2025 (false, Excluded(key)) => match search::search_linear(&min_node, key) {
2032 (_, Unbounded) => 0,
2033 (true, Included(_)) => min_node.keys().len(),
2034 (true, Excluded(_)) => 0,
2037 let max_edge = match (max_found, range.end_bound()) {
2038 (false, Included(key)) => match search::search_linear(&max_node, key) {
2045 (false, Excluded(key)) => match search::search_linear(&max_node, key) {
2052 (_, Unbounded) => max_node.keys().len(),
2053 (true, Included(_)) => 0,
2054 (true, Excluded(_)) => max_node.keys().len(),
2058 if max_edge < min_edge {
2059 panic!("Ord is ill-defined in BTreeMap range")
2061 if min_edge != max_edge {
2066 let front = Handle::new_edge(min_node, min_edge);
2067 let back = Handle::new_edge(max_node, max_edge);
2068 match (front.force(), back.force()) {
2069 (Leaf(f), Leaf(b)) => {
2072 (Internal(min_int), Internal(max_int)) => {
2073 min_node = min_int.descend();
2074 max_node = max_int.descend();
2076 _ => unreachable!("BTreeMap has different depths"),
2082 unsafe fn unwrap_unchecked<T>(val: Option<T>) -> T {
2083 val.unwrap_or_else(|| {
2084 if cfg!(debug_assertions) {
2085 panic!("'unchecked' unwrap on None in BTreeMap");
2087 intrinsics::unreachable();
2092 impl<K, V> BTreeMap<K, V> {
2093 /// Gets an iterator over the entries of the map, sorted by key.
2100 /// use std::collections::BTreeMap;
2102 /// let mut map = BTreeMap::new();
2103 /// map.insert(3, "c");
2104 /// map.insert(2, "b");
2105 /// map.insert(1, "a");
2107 /// for (key, value) in map.iter() {
2108 /// println!("{}: {}", key, value);
2111 /// let (first_key, first_value) = map.iter().next().unwrap();
2112 /// assert_eq!((*first_key, *first_value), (1, "a"));
2114 #[stable(feature = "rust1", since = "1.0.0")]
2115 pub fn iter(&self) -> Iter<'_, K, V> {
2118 front: first_leaf_edge(self.root.as_ref()),
2119 back: last_leaf_edge(self.root.as_ref()),
2121 length: self.length,
2125 /// Gets a mutable iterator over the entries of the map, sorted by key.
2132 /// use std::collections::BTreeMap;
2134 /// let mut map = BTreeMap::new();
2135 /// map.insert("a", 1);
2136 /// map.insert("b", 2);
2137 /// map.insert("c", 3);
2139 /// // add 10 to the value if the key isn't "a"
2140 /// for (key, value) in map.iter_mut() {
2141 /// if key != &"a" {
2146 #[stable(feature = "rust1", since = "1.0.0")]
2147 pub fn iter_mut(&mut self) -> IterMut<'_, K, V> {
2148 let root1 = self.root.as_mut();
2149 let root2 = unsafe { ptr::read(&root1) };
2152 front: first_leaf_edge(root1),
2153 back: last_leaf_edge(root2),
2154 _marker: PhantomData,
2156 length: self.length,
2160 /// Gets an iterator over the keys of the map, in sorted order.
2167 /// use std::collections::BTreeMap;
2169 /// let mut a = BTreeMap::new();
2170 /// a.insert(2, "b");
2171 /// a.insert(1, "a");
2173 /// let keys: Vec<_> = a.keys().cloned().collect();
2174 /// assert_eq!(keys, [1, 2]);
2176 #[stable(feature = "rust1", since = "1.0.0")]
2177 pub fn keys(&self) -> Keys<'_, K, V> {
2178 Keys { inner: self.iter() }
2181 /// Gets an iterator over the values of the map, in order by key.
2188 /// use std::collections::BTreeMap;
2190 /// let mut a = BTreeMap::new();
2191 /// a.insert(1, "hello");
2192 /// a.insert(2, "goodbye");
2194 /// let values: Vec<&str> = a.values().cloned().collect();
2195 /// assert_eq!(values, ["hello", "goodbye"]);
2197 #[stable(feature = "rust1", since = "1.0.0")]
2198 pub fn values(&self) -> Values<'_, K, V> {
2199 Values { inner: self.iter() }
2202 /// Gets a mutable iterator over the values of the map, in order by key.
2209 /// use std::collections::BTreeMap;
2211 /// let mut a = BTreeMap::new();
2212 /// a.insert(1, String::from("hello"));
2213 /// a.insert(2, String::from("goodbye"));
2215 /// for value in a.values_mut() {
2216 /// value.push_str("!");
2219 /// let values: Vec<String> = a.values().cloned().collect();
2220 /// assert_eq!(values, [String::from("hello!"),
2221 /// String::from("goodbye!")]);
2223 #[stable(feature = "map_values_mut", since = "1.10.0")]
2224 pub fn values_mut(&mut self) -> ValuesMut<'_, K, V> {
2225 ValuesMut { inner: self.iter_mut() }
2228 /// Returns the number of elements in the map.
2235 /// use std::collections::BTreeMap;
2237 /// let mut a = BTreeMap::new();
2238 /// assert_eq!(a.len(), 0);
2239 /// a.insert(1, "a");
2240 /// assert_eq!(a.len(), 1);
2242 #[stable(feature = "rust1", since = "1.0.0")]
2243 pub fn len(&self) -> usize {
2247 /// Returns `true` if the map contains no elements.
2254 /// use std::collections::BTreeMap;
2256 /// let mut a = BTreeMap::new();
2257 /// assert!(a.is_empty());
2258 /// a.insert(1, "a");
2259 /// assert!(!a.is_empty());
2261 #[stable(feature = "rust1", since = "1.0.0")]
2262 pub fn is_empty(&self) -> bool {
2267 impl<'a, K: Ord, V> Entry<'a, K, V> {
2268 /// Ensures a value is in the entry by inserting the default if empty, and returns
2269 /// a mutable reference to the value in the entry.
2274 /// use std::collections::BTreeMap;
2276 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2277 /// map.entry("poneyland").or_insert(12);
2279 /// assert_eq!(map["poneyland"], 12);
2281 #[stable(feature = "rust1", since = "1.0.0")]
2282 pub fn or_insert(self, default: V) -> &'a mut V {
2284 Occupied(entry) => entry.into_mut(),
2285 Vacant(entry) => entry.insert(default),
2289 /// Ensures a value is in the entry by inserting the result of the default function if empty,
2290 /// and returns a mutable reference to the value in the entry.
2295 /// use std::collections::BTreeMap;
2297 /// let mut map: BTreeMap<&str, String> = BTreeMap::new();
2298 /// let s = "hoho".to_string();
2300 /// map.entry("poneyland").or_insert_with(|| s);
2302 /// assert_eq!(map["poneyland"], "hoho".to_string());
2304 #[stable(feature = "rust1", since = "1.0.0")]
2305 pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V {
2307 Occupied(entry) => entry.into_mut(),
2308 Vacant(entry) => entry.insert(default()),
2312 /// Returns a reference to this entry's key.
2317 /// use std::collections::BTreeMap;
2319 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2320 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2322 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2323 pub fn key(&self) -> &K {
2325 Occupied(ref entry) => entry.key(),
2326 Vacant(ref entry) => entry.key(),
2330 /// Provides in-place mutable access to an occupied entry before any
2331 /// potential inserts into the map.
2336 /// use std::collections::BTreeMap;
2338 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2340 /// map.entry("poneyland")
2341 /// .and_modify(|e| { *e += 1 })
2343 /// assert_eq!(map["poneyland"], 42);
2345 /// map.entry("poneyland")
2346 /// .and_modify(|e| { *e += 1 })
2348 /// assert_eq!(map["poneyland"], 43);
2350 #[stable(feature = "entry_and_modify", since = "1.26.0")]
2351 pub fn and_modify<F>(self, f: F) -> Self
2356 Occupied(mut entry) => {
2360 Vacant(entry) => Vacant(entry),
2365 impl<'a, K: Ord, V: Default> Entry<'a, K, V> {
2366 #[stable(feature = "entry_or_default", since = "1.28.0")]
2367 /// Ensures a value is in the entry by inserting the default value if empty,
2368 /// and returns a mutable reference to the value in the entry.
2373 /// use std::collections::BTreeMap;
2375 /// let mut map: BTreeMap<&str, Option<usize>> = BTreeMap::new();
2376 /// map.entry("poneyland").or_default();
2378 /// assert_eq!(map["poneyland"], None);
2380 pub fn or_default(self) -> &'a mut V {
2382 Occupied(entry) => entry.into_mut(),
2383 Vacant(entry) => entry.insert(Default::default()),
2388 impl<'a, K: Ord, V> VacantEntry<'a, K, V> {
2389 /// Gets a reference to the key that would be used when inserting a value
2390 /// through the VacantEntry.
2395 /// use std::collections::BTreeMap;
2397 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2398 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2400 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2401 pub fn key(&self) -> &K {
2405 /// Take ownership of the key.
2410 /// use std::collections::BTreeMap;
2411 /// use std::collections::btree_map::Entry;
2413 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2415 /// if let Entry::Vacant(v) = map.entry("poneyland") {
2419 #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
2420 pub fn into_key(self) -> K {
2424 /// Sets the value of the entry with the `VacantEntry`'s key,
2425 /// and returns a mutable reference to it.
2430 /// use std::collections::BTreeMap;
2432 /// let mut count: BTreeMap<&str, usize> = BTreeMap::new();
2434 /// // count the number of occurrences of letters in the vec
2435 /// for x in vec!["a","b","a","c","a","b"] {
2436 /// *count.entry(x).or_insert(0) += 1;
2439 /// assert_eq!(count["a"], 3);
2441 #[stable(feature = "rust1", since = "1.0.0")]
2442 pub fn insert(self, value: V) -> &'a mut V {
2451 let mut cur_parent = match self.handle.insert(self.key, value) {
2452 (Fit(handle), _) => return handle.into_kv_mut().1,
2453 (Split(left, k, v, right), ptr) => {
2458 left.ascend().map_err(|n| n.into_root_mut())
2464 Ok(parent) => match parent.insert(ins_k, ins_v, ins_edge) {
2465 Fit(_) => return unsafe { &mut *out_ptr },
2466 Split(left, k, v, right) => {
2470 cur_parent = left.ascend().map_err(|n| n.into_root_mut());
2474 root.push_level().push(ins_k, ins_v, ins_edge);
2475 return unsafe { &mut *out_ptr };
2482 impl<'a, K: Ord, V> OccupiedEntry<'a, K, V> {
2483 /// Gets a reference to the key in the entry.
2488 /// use std::collections::BTreeMap;
2490 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2491 /// map.entry("poneyland").or_insert(12);
2492 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2494 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2495 pub fn key(&self) -> &K {
2496 self.handle.reborrow().into_kv().0
2499 /// Take ownership of the key and value from the map.
2504 /// use std::collections::BTreeMap;
2505 /// use std::collections::btree_map::Entry;
2507 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2508 /// map.entry("poneyland").or_insert(12);
2510 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2511 /// // We delete the entry from the map.
2512 /// o.remove_entry();
2515 /// // If now try to get the value, it will panic:
2516 /// // println!("{}", map["poneyland"]);
2518 #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
2519 pub fn remove_entry(self) -> (K, V) {
2523 /// Gets a reference to the value in the entry.
2528 /// use std::collections::BTreeMap;
2529 /// use std::collections::btree_map::Entry;
2531 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2532 /// map.entry("poneyland").or_insert(12);
2534 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2535 /// assert_eq!(o.get(), &12);
2538 #[stable(feature = "rust1", since = "1.0.0")]
2539 pub fn get(&self) -> &V {
2540 self.handle.reborrow().into_kv().1
2543 /// Gets a mutable reference to the value in the entry.
2545 /// If you need a reference to the `OccupiedEntry` that may outlive the
2546 /// destruction of the `Entry` value, see [`into_mut`].
2548 /// [`into_mut`]: #method.into_mut
2553 /// use std::collections::BTreeMap;
2554 /// use std::collections::btree_map::Entry;
2556 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2557 /// map.entry("poneyland").or_insert(12);
2559 /// assert_eq!(map["poneyland"], 12);
2560 /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
2561 /// *o.get_mut() += 10;
2562 /// assert_eq!(*o.get(), 22);
2564 /// // We can use the same Entry multiple times.
2565 /// *o.get_mut() += 2;
2567 /// assert_eq!(map["poneyland"], 24);
2569 #[stable(feature = "rust1", since = "1.0.0")]
2570 pub fn get_mut(&mut self) -> &mut V {
2571 self.handle.kv_mut().1
2574 /// Converts the entry into a mutable reference to its value.
2576 /// If you need multiple references to the `OccupiedEntry`, see [`get_mut`].
2578 /// [`get_mut`]: #method.get_mut
2583 /// use std::collections::BTreeMap;
2584 /// use std::collections::btree_map::Entry;
2586 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2587 /// map.entry("poneyland").or_insert(12);
2589 /// assert_eq!(map["poneyland"], 12);
2590 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2591 /// *o.into_mut() += 10;
2593 /// assert_eq!(map["poneyland"], 22);
2595 #[stable(feature = "rust1", since = "1.0.0")]
2596 pub fn into_mut(self) -> &'a mut V {
2597 self.handle.into_kv_mut().1
2600 /// Sets the value of the entry with the `OccupiedEntry`'s key,
2601 /// and returns the entry's old value.
2606 /// use std::collections::BTreeMap;
2607 /// use std::collections::btree_map::Entry;
2609 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2610 /// map.entry("poneyland").or_insert(12);
2612 /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
2613 /// assert_eq!(o.insert(15), 12);
2615 /// assert_eq!(map["poneyland"], 15);
2617 #[stable(feature = "rust1", since = "1.0.0")]
2618 pub fn insert(&mut self, value: V) -> V {
2619 mem::replace(self.get_mut(), value)
2622 /// Takes the value of the entry out of the map, and returns it.
2627 /// use std::collections::BTreeMap;
2628 /// use std::collections::btree_map::Entry;
2630 /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
2631 /// map.entry("poneyland").or_insert(12);
2633 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2634 /// assert_eq!(o.remove(), 12);
2636 /// // If we try to get "poneyland"'s value, it'll panic:
2637 /// // println!("{}", map["poneyland"]);
2639 #[stable(feature = "rust1", since = "1.0.0")]
2640 pub fn remove(self) -> V {
2644 fn remove_kv(self) -> (K, V) {
2647 let (small_leaf, old_key, old_val) = match self.handle.force() {
2649 let (hole, old_key, old_val) = leaf.remove();
2650 (hole.into_node(), old_key, old_val)
2652 Internal(mut internal) => {
2653 let key_loc = internal.kv_mut().0 as *mut K;
2654 let val_loc = internal.kv_mut().1 as *mut V;
2656 let to_remove = first_leaf_edge(internal.right_edge().descend()).right_kv().ok();
2657 let to_remove = unsafe { unwrap_unchecked(to_remove) };
2659 let (hole, key, val) = to_remove.remove();
2661 let old_key = unsafe { mem::replace(&mut *key_loc, key) };
2662 let old_val = unsafe { mem::replace(&mut *val_loc, val) };
2664 (hole.into_node(), old_key, old_val)
2669 let mut cur_node = small_leaf.forget_type();
2670 while cur_node.len() < node::CAPACITY / 2 {
2671 match handle_underfull_node(cur_node) {
2673 EmptyParent(_) => unreachable!(),
2675 if parent.len() == 0 {
2676 // We must be at the root
2677 parent.into_root_mut().pop_level();
2680 cur_node = parent.forget_type();
2691 enum UnderflowResult<'a, K, V> {
2693 EmptyParent(NodeRef<marker::Mut<'a>, K, V, marker::Internal>),
2694 Merged(NodeRef<marker::Mut<'a>, K, V, marker::Internal>),
2695 Stole(NodeRef<marker::Mut<'a>, K, V, marker::Internal>),
2698 fn handle_underfull_node<K, V>(
2699 node: NodeRef<marker::Mut<'_>, K, V, marker::LeafOrInternal>,
2700 ) -> UnderflowResult<'_, K, V> {
2701 let parent = if let Ok(parent) = node.ascend() {
2707 let (is_left, mut handle) = match parent.left_kv() {
2708 Ok(left) => (true, left),
2709 Err(parent) => match parent.right_kv() {
2710 Ok(right) => (false, right),
2712 return EmptyParent(parent.into_node());
2717 if handle.can_merge() {
2718 Merged(handle.merge().into_node())
2721 handle.steal_left();
2723 handle.steal_right();
2725 Stole(handle.into_node())
2729 impl<K: Ord, V, I: Iterator<Item = (K, V)>> Iterator for MergeIter<K, V, I> {
2732 fn next(&mut self) -> Option<(K, V)> {
2733 let res = match (self.left.peek(), self.right.peek()) {
2734 (Some(&(ref left_key, _)), Some(&(ref right_key, _))) => left_key.cmp(right_key),
2735 (Some(_), None) => Ordering::Less,
2736 (None, Some(_)) => Ordering::Greater,
2737 (None, None) => return None,
2740 // Check which elements comes first and only advance the corresponding iterator.
2741 // If two keys are equal, take the value from `right`.
2743 Ordering::Less => self.left.next(),
2744 Ordering::Greater => self.right.next(),
2745 Ordering::Equal => {