1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 // This implementation is largely based on the high-level description and analysis of B-Trees
12 // found in *Open Data Structures* (ODS). Although our implementation does not use any of
13 // the source found in ODS, if one wishes to review the high-level design of this structure, it
14 // can be freely downloaded at http://opendatastructures.org/. Its contents are as of this
15 // writing (August 2014) freely licensed under the following Creative Commons Attribution
16 // License: [CC BY 2.5 CA](http://creativecommons.org/licenses/by/2.5/ca/).
20 use core::cmp::Ordering;
22 use core::hash::{Hash, Hasher};
23 use core::iter::{Map, FromIterator};
25 use core::{fmt, mem, usize};
26 use Bound::{self, Included, Excluded, Unbounded};
29 use vec_deque::VecDeque;
31 use self::Continuation::{Continue, Finished};
33 use super::node::ForceResult::{Leaf, Internal};
34 use super::node::TraversalItem::{self, Elem, Edge};
35 use super::node::{Traversal, MutTraversal, MoveTraversal};
36 use super::node::{self, Node, Found, GoDown};
38 /// A map based on a B-Tree.
40 /// B-Trees represent a fundamental compromise between cache-efficiency and actually minimizing
41 /// the amount of work performed in a search. In theory, a binary search tree (BST) is the optimal
42 /// choice for a sorted map, as a perfectly balanced BST performs the theoretical minimum amount of
43 /// comparisons necessary to find an element (log<sub>2</sub>n). However, in practice the way this
44 /// is done is *very* inefficient for modern computer architectures. In particular, every element
45 /// is stored in its own individually heap-allocated node. This means that every single insertion
46 /// triggers a heap-allocation, and every single comparison should be a cache-miss. Since these
47 /// are both notably expensive things to do in practice, we are forced to at very least reconsider
50 /// A B-Tree instead makes each node contain B-1 to 2B-1 elements in a contiguous array. By doing
51 /// this, we reduce the number of allocations by a factor of B, and improve cache efficiency in
52 /// searches. However, this does mean that searches will have to do *more* comparisons on average.
53 /// The precise number of comparisons depends on the node search strategy used. For optimal cache
54 /// efficiency, one could search the nodes linearly. For optimal comparisons, one could search
55 /// the node using binary search. As a compromise, one could also perform a linear search
56 /// that initially only checks every i<sup>th</sup> element for some choice of i.
58 /// Currently, our implementation simply performs naive linear search. This provides excellent
59 /// performance on *small* nodes of elements which are cheap to compare. However in the future we
60 /// would like to further explore choosing the optimal search strategy based on the choice of B,
61 /// and possibly other factors. Using linear search, searching for a random element is expected
62 /// to take O(B log<sub>B</sub>n) comparisons, which is generally worse than a BST. In practice,
63 /// however, performance is excellent.
65 /// It is a logic error for a key to be modified in such a way that the key's ordering relative to
66 /// any other key, as determined by the `Ord` trait, changes while it is in the map. This is
67 /// normally only possible through `Cell`, `RefCell`, global state, I/O, or unsafe code.
69 #[stable(feature = "rust1", since = "1.0.0")]
70 pub struct BTreeMap<K, V> {
77 /// An abstract base over-which all other BTree iterators are built.
80 traversals: VecDeque<T>,
84 /// An iterator over a BTreeMap's entries.
85 #[stable(feature = "rust1", since = "1.0.0")]
86 pub struct Iter<'a, K: 'a, V: 'a> {
87 inner: AbsIter<Traversal<'a, K, V>>,
90 /// A mutable iterator over a BTreeMap's entries.
91 #[stable(feature = "rust1", since = "1.0.0")]
92 pub struct IterMut<'a, K: 'a, V: 'a> {
93 inner: AbsIter<MutTraversal<'a, K, V>>,
96 /// An owning iterator over a BTreeMap's entries.
97 #[stable(feature = "rust1", since = "1.0.0")]
98 pub struct IntoIter<K, V> {
99 inner: AbsIter<MoveTraversal<K, V>>,
102 /// An iterator over a BTreeMap's keys.
103 #[stable(feature = "rust1", since = "1.0.0")]
104 pub struct Keys<'a, K: 'a, V: 'a> {
105 inner: Map<Iter<'a, K, V>, fn((&'a K, &'a V)) -> &'a K>,
108 /// An iterator over a BTreeMap's values.
109 #[stable(feature = "rust1", since = "1.0.0")]
110 pub struct Values<'a, K: 'a, V: 'a> {
111 inner: Map<Iter<'a, K, V>, fn((&'a K, &'a V)) -> &'a V>,
114 /// An iterator over a sub-range of BTreeMap's entries.
115 pub struct Range<'a, K: 'a, V: 'a> {
116 inner: AbsIter<Traversal<'a, K, V>>,
119 /// A mutable iterator over a sub-range of BTreeMap's entries.
120 pub struct RangeMut<'a, K: 'a, V: 'a> {
121 inner: AbsIter<MutTraversal<'a, K, V>>,
124 /// A view into a single entry in a map, which may either be vacant or occupied.
125 #[stable(feature = "rust1", since = "1.0.0")]
126 pub enum Entry<'a, K: 'a, V: 'a> {
128 #[stable(feature = "rust1", since = "1.0.0")]
129 Vacant(VacantEntry<'a, K, V>),
131 /// An occupied Entry
132 #[stable(feature = "rust1", since = "1.0.0")]
133 Occupied(OccupiedEntry<'a, K, V>),
137 #[stable(feature = "rust1", since = "1.0.0")]
138 pub struct VacantEntry<'a, K: 'a, V: 'a> {
140 stack: stack::SearchStack<'a, K, V, node::handle::Edge, node::handle::Leaf>,
143 /// An occupied Entry.
144 #[stable(feature = "rust1", since = "1.0.0")]
145 pub struct OccupiedEntry<'a, K: 'a, V: 'a> {
146 stack: stack::SearchStack<'a, K, V, node::handle::KV, node::handle::LeafOrInternal>,
149 impl<K: Ord, V> BTreeMap<K, V> {
150 /// Makes a new empty BTreeMap with a reasonable choice for B.
151 #[stable(feature = "rust1", since = "1.0.0")]
153 pub fn new() -> BTreeMap<K, V> {
157 root: Node::make_leaf_root(6),
158 // FIXME(Gankro): Tune this as a function of size_of<K/V>?
164 /// Clears the map, removing all values.
169 /// use std::collections::BTreeMap;
171 /// let mut a = BTreeMap::new();
172 /// a.insert(1, "a");
174 /// assert!(a.is_empty());
176 #[stable(feature = "rust1", since = "1.0.0")]
177 pub fn clear(&mut self) {
178 // avoid recursive destructors by manually traversing the tree
179 for _ in mem::replace(self, BTreeMap::new()) {}
182 // Searching in a B-Tree is pretty straightforward.
184 // Start at the root. Try to find the key in the current node. If we find it, return it.
185 // If it's not in there, follow the edge *before* the smallest key larger than
186 // the search key. If no such key exists (they're *all* smaller), then just take the last
187 // edge in the node. If we're in a leaf and we don't find our key, then it's not
190 /// Returns a reference to the value corresponding to the key.
192 /// The key may be any borrowed form of the map's key type, but the ordering
193 /// on the borrowed form *must* match the ordering on the key type.
198 /// use std::collections::BTreeMap;
200 /// let mut map = BTreeMap::new();
201 /// map.insert(1, "a");
202 /// assert_eq!(map.get(&1), Some(&"a"));
203 /// assert_eq!(map.get(&2), None);
205 #[stable(feature = "rust1", since = "1.0.0")]
206 pub fn get<Q: ?Sized>(&self, key: &Q) -> Option<&V>
210 let mut cur_node = &self.root;
212 match Node::search(cur_node, key) {
213 Found(handle) => return Some(handle.into_kv().1),
215 match handle.force() {
216 Leaf(_) => return None,
217 Internal(internal_handle) => {
218 cur_node = internal_handle.into_edge();
227 /// Returns true if the map contains a value for the specified key.
229 /// The key may be any borrowed form of the map's key type, but the ordering
230 /// on the borrowed form *must* match the ordering on the key type.
235 /// use std::collections::BTreeMap;
237 /// let mut map = BTreeMap::new();
238 /// map.insert(1, "a");
239 /// assert_eq!(map.contains_key(&1), true);
240 /// assert_eq!(map.contains_key(&2), false);
242 #[stable(feature = "rust1", since = "1.0.0")]
243 pub fn contains_key<Q: ?Sized>(&self, key: &Q) -> bool
247 self.get(key).is_some()
250 /// Returns a mutable reference to the value corresponding to the key.
252 /// The key may be any borrowed form of the map's key type, but the ordering
253 /// on the borrowed form *must* match the ordering on the key type.
258 /// use std::collections::BTreeMap;
260 /// let mut map = BTreeMap::new();
261 /// map.insert(1, "a");
262 /// if let Some(x) = map.get_mut(&1) {
265 /// assert_eq!(map[&1], "b");
267 // See `get` for implementation notes, this is basically a copy-paste with mut's added
268 #[stable(feature = "rust1", since = "1.0.0")]
269 pub fn get_mut<Q: ?Sized>(&mut self, key: &Q) -> Option<&mut V>
273 // temp_node is a Borrowck hack for having a mutable value outlive a loop iteration
274 let mut temp_node = &mut self.root;
276 let cur_node = temp_node;
277 match Node::search(cur_node, key) {
278 Found(handle) => return Some(handle.into_kv_mut().1),
280 match handle.force() {
281 Leaf(_) => return None,
282 Internal(internal_handle) => {
283 temp_node = internal_handle.into_edge_mut();
292 // Insertion in a B-Tree is a bit complicated.
294 // First we do the same kind of search described in `find`. But we need to maintain a stack of
295 // all the nodes/edges in our search path. If we find a match for the key we're trying to
296 // insert, just swap the vals and return the old ones. However, when we bottom out in a leaf,
297 // we attempt to insert our key-value pair at the same location we would want to follow another
300 // If the node has room, then this is done in the obvious way by shifting elements. However,
301 // if the node itself is full, we split node into two, and give its median key-value
302 // pair to its parent to insert the new node with. Of course, the parent may also be
303 // full, and insertion can propagate until we reach the root. If we reach the root, and
304 // it is *also* full, then we split the root and place the two nodes under a newly made root.
306 // Note that we subtly deviate from Open Data Structures in our implementation of split.
307 // ODS describes inserting into the node *regardless* of its capacity, and then
308 // splitting *afterwards* if it happens to be overfull. However, this is inefficient.
309 // Instead, we split beforehand, and then insert the key-value pair into the appropriate
310 // result node. This has two consequences:
312 // 1) While ODS produces a left node of size B-1, and a right node of size B,
313 // we may potentially reverse this. However, this shouldn't effect the analysis.
315 // 2) While ODS may potentially return the pair we *just* inserted after
316 // the split, we will never do this. Again, this shouldn't effect the analysis.
318 /// Inserts a key-value pair into the map.
320 /// If the map did not have this key present, `None` is returned.
322 /// If the map did have this key present, the key is not updated, the
323 /// value is updated and the old value is returned.
324 /// See the [module-level documentation] for more.
326 /// [module-level documentation]: index.html#insert-and-complex-keys
331 /// use std::collections::BTreeMap;
333 /// let mut map = BTreeMap::new();
334 /// assert_eq!(map.insert(37, "a"), None);
335 /// assert_eq!(map.is_empty(), false);
337 /// map.insert(37, "b");
338 /// assert_eq!(map.insert(37, "c"), Some("b"));
339 /// assert_eq!(map[&37], "c");
341 #[stable(feature = "rust1", since = "1.0.0")]
342 pub fn insert(&mut self, mut key: K, mut value: V) -> Option<V> {
343 // This is a stack of rawptrs to nodes paired with indices, respectively
344 // representing the nodes and edges of our search path. We have to store rawptrs
345 // because as far as Rust is concerned, we can mutate aliased data with such a
346 // stack. It is of course correct, but what it doesn't know is that we will only
347 // be popping and using these ptrs one at a time in child-to-parent order. The alternative
348 // to doing this is to take the Nodes from their parents. This actually makes
349 // borrowck *really* happy and everything is pretty smooth. However, this creates
350 // *tons* of pointless writes, and requires us to always walk all the way back to
351 // the root after an insertion, even if we only needed to change a leaf. Therefore,
352 // we accept this potential unsafety and complexity in the name of performance.
354 // Regardless, the actual dangerous logic is completely abstracted away from BTreeMap
355 // by the stack module. All it can do is immutably read nodes, and ask the search stack
356 // to proceed down some edge by index. This makes the search logic we'll be reusing in a
357 // few different methods much neater, and of course drastically improves safety.
358 let mut stack = stack::PartialSearchStack::new(self);
361 let result = stack.with(move |pusher, node| {
362 // Same basic logic as found in `find`, but with PartialSearchStack mediating the
363 // actual nodes for us
364 match Node::search(node, &key) {
365 Found(mut handle) => {
366 // Perfect match, swap the values and return the old one
367 mem::swap(handle.val_mut(), &mut value);
368 Finished(Some(value))
371 // We need to keep searching, try to get the search stack
372 // to go down further
373 match handle.force() {
374 Leaf(leaf_handle) => {
375 // We've reached a leaf, perform the insertion here
376 pusher.seal(leaf_handle).insert(key, value);
379 Internal(internal_handle) => {
380 // We've found the subtree to insert this key/value pair in,
382 Continue((pusher.push(internal_handle), key, value))
389 Finished(ret) => return ret,
390 Continue((new_stack, renewed_key, renewed_val)) => {
399 // Deletion is the most complicated operation for a B-Tree.
401 // First we do the same kind of search described in
402 // `find`. But we need to maintain a stack of all the nodes/edges in our search path.
403 // If we don't find the key, then we just return `None` and do nothing. If we do find the
404 // key, we perform two operations: remove the item, and then possibly handle underflow.
406 // # removing the item
407 // If the node is a leaf, we just remove the item, and shift
408 // any items after it back to fill the hole.
410 // If the node is an internal node, we *swap* the item with the smallest item in
411 // in its right subtree (which must reside in a leaf), and then revert to the leaf
414 // # handling underflow
415 // After removing an item, there may be too few items in the node. We want nodes
416 // to be mostly full for efficiency, although we make an exception for the root, which
417 // may have as few as one item. If this is the case, we may first try to steal
418 // an item from our left or right neighbour.
420 // To steal from the left (right) neighbour,
421 // we take the largest (smallest) item and child from it. We then swap the taken item
422 // with the item in their mutual parent that separates them, and then insert the
423 // parent's item and the taken child into the first (last) index of the underflowed node.
425 // However, stealing has the possibility of underflowing our neighbour. If this is the
426 // case, we instead *merge* with our neighbour. This of course reduces the number of
427 // children in the parent. Therefore, we also steal the item that separates the now
428 // merged nodes, and insert it into the merged node.
430 // Merging may cause the parent to underflow. If this is the case, then we must repeat
431 // the underflow handling process on the parent. If merging merges the last two children
432 // of the root, then we replace the root with the merged node.
434 /// Removes a key from the map, returning the value at the key if the key
435 /// was previously in the map.
437 /// The key may be any borrowed form of the map's key type, but the ordering
438 /// on the borrowed form *must* match the ordering on the key type.
443 /// use std::collections::BTreeMap;
445 /// let mut map = BTreeMap::new();
446 /// map.insert(1, "a");
447 /// assert_eq!(map.remove(&1), Some("a"));
448 /// assert_eq!(map.remove(&1), None);
450 #[stable(feature = "rust1", since = "1.0.0")]
451 pub fn remove<Q: ?Sized>(&mut self, key: &Q) -> Option<V>
455 // See `swap` for a more thorough description of the stuff going on in here
456 let mut stack = stack::PartialSearchStack::new(self);
458 let result = stack.with(move |pusher, node| {
459 match Node::search(node, key) {
461 // Perfect match. Terminate the stack here, and remove the entry
462 Finished(Some(pusher.seal(handle).remove()))
465 // We need to keep searching, try to go down the next edge
466 match handle.force() {
467 // We're at a leaf; the key isn't in here
468 Leaf(_) => Finished(None),
469 Internal(internal_handle) => Continue(pusher.push(internal_handle)),
475 Finished(ret) => return ret.map(|(_, v)| v),
476 Continue(new_stack) => stack = new_stack,
482 #[stable(feature = "rust1", since = "1.0.0")]
483 impl<K, V> IntoIterator for BTreeMap<K, V> {
485 type IntoIter = IntoIter<K, V>;
487 /// Gets an owning iterator over the entries of the map.
492 /// use std::collections::BTreeMap;
494 /// let mut map = BTreeMap::new();
495 /// map.insert(1, "a");
496 /// map.insert(2, "b");
497 /// map.insert(3, "c");
499 /// for (key, value) in map.into_iter() {
500 /// println!("{}: {}", key, value);
503 fn into_iter(self) -> IntoIter<K, V> {
504 let len = self.len();
505 let mut lca = VecDeque::new();
506 lca.push_back(Traverse::traverse(self.root));
516 #[stable(feature = "rust1", since = "1.0.0")]
517 impl<'a, K, V> IntoIterator for &'a BTreeMap<K, V> {
518 type Item = (&'a K, &'a V);
519 type IntoIter = Iter<'a, K, V>;
521 fn into_iter(self) -> Iter<'a, K, V> {
526 #[stable(feature = "rust1", since = "1.0.0")]
527 impl<'a, K, V> IntoIterator for &'a mut BTreeMap<K, V> {
528 type Item = (&'a K, &'a mut V);
529 type IntoIter = IterMut<'a, K, V>;
531 fn into_iter(mut self) -> IterMut<'a, K, V> {
536 /// A helper enum useful for deciding whether to continue a loop since we can't
537 /// return from a closure
538 enum Continuation<A, B> {
543 /// The stack module provides a safe interface for constructing and manipulating a stack of ptrs
544 /// to nodes. By using this module much better safety guarantees can be made, and more search
545 /// boilerplate gets cut out.
549 use core::ops::{Deref, DerefMut};
551 use super::super::node::{self, Node, Fit, Split, Internal, Leaf};
552 use super::super::node::handle;
555 struct InvariantLifetime<'id>(marker::PhantomData<::core::cell::Cell<&'id ()>>);
557 impl<'id> InvariantLifetime<'id> {
558 fn new() -> InvariantLifetime<'id> {
559 InvariantLifetime(marker::PhantomData)
563 /// A generic mutable reference, identical to `&mut` except for the fact that its lifetime
564 /// parameter is invariant. This means that wherever an `IdRef` is expected, only an `IdRef`
565 /// with the exact requested lifetime can be used. This is in contrast to normal references,
566 /// where `&'static` can be used in any function expecting any lifetime reference.
567 pub struct IdRef<'id, T: 'id> {
569 _marker: InvariantLifetime<'id>,
572 impl<'id, T> Deref for IdRef<'id, T> {
575 fn deref(&self) -> &T {
580 impl<'id, T> DerefMut for IdRef<'id, T> {
581 fn deref_mut(&mut self) -> &mut T {
586 type StackItem<K, V> = node::Handle<*mut Node<K, V>, handle::Edge, handle::Internal>;
587 type Stack<K, V> = Vec<StackItem<K, V>>;
589 /// A `PartialSearchStack` handles the construction of a search stack.
590 pub struct PartialSearchStack<'a, K: 'a, V: 'a> {
591 map: &'a mut BTreeMap<K, V>,
593 next: *mut Node<K, V>,
596 /// A `SearchStack` represents a full path to an element or an edge of interest. It provides
597 /// methods depending on the type of what the path points to for removing an element, inserting
598 /// a new element, and manipulating to element at the top of the stack.
599 pub struct SearchStack<'a, K: 'a, V: 'a, Type, NodeType> {
600 map: &'a mut BTreeMap<K, V>,
602 top: node::Handle<*mut Node<K, V>, Type, NodeType>,
605 /// A `PartialSearchStack` that doesn't hold a reference to the next node, and is just
606 /// just waiting for a `Handle` to that next node to be pushed. See `PartialSearchStack::with`
607 /// for more details.
608 pub struct Pusher<'id, 'a, K: 'a, V: 'a> {
609 map: &'a mut BTreeMap<K, V>,
611 _marker: InvariantLifetime<'id>,
614 impl<'a, K, V> PartialSearchStack<'a, K, V> {
615 /// Creates a new PartialSearchStack from a BTreeMap by initializing the stack with the
616 /// root of the tree.
617 pub fn new(map: &'a mut BTreeMap<K, V>) -> PartialSearchStack<'a, K, V> {
618 let depth = map.depth;
621 next: &mut map.root as *mut _,
623 stack: Vec::with_capacity(depth),
627 /// Breaks up the stack into a `Pusher` and the next `Node`, allowing the given closure
628 /// to interact with, search, and finally push the `Node` onto the stack. The passed in
629 /// closure must be polymorphic on the `'id` lifetime parameter, as this statically
630 /// ensures that only `Handle`s from the correct `Node` can be pushed.
632 /// The reason this works is that the `Pusher` has an `'id` parameter, and will only accept
633 /// handles with the same `'id`. The closure could only get references with that lifetime
634 /// through its arguments or through some other `IdRef` that it has lying around. However,
635 /// no other `IdRef` could possibly work - because the `'id` is held in an invariant
636 /// parameter, it would need to have precisely the correct lifetime, which would mean that
637 /// at least one of the calls to `with` wouldn't be properly polymorphic, wanting a
638 /// specific lifetime instead of the one that `with` chooses to give it.
640 /// See also Haskell's `ST` monad, which uses a similar trick.
641 pub fn with<T, F: for<'id> FnOnce(Pusher<'id, 'a, K, V>,
642 IdRef<'id, Node<K, V>>) -> T>(self, closure: F) -> T {
643 let pusher = Pusher {
646 _marker: InvariantLifetime::new(),
649 inner: unsafe { &mut *self.next },
650 _marker: InvariantLifetime::new(),
653 closure(pusher, node)
657 impl<'id, 'a, K, V> Pusher<'id, 'a, K, V> {
658 /// Pushes the requested child of the stack's current top on top of the stack. If the child
659 /// exists, then a new PartialSearchStack is yielded. Otherwise, a VacantSearchStack is
661 pub fn push(mut self,
662 mut edge: node::Handle<IdRef<'id, Node<K, V>>, handle::Edge, handle::Internal>)
663 -> PartialSearchStack<'a, K, V> {
664 self.stack.push(edge.as_raw());
668 next: edge.edge_mut() as *mut _,
672 /// Converts the PartialSearchStack into a SearchStack.
673 pub fn seal<Type, NodeType>(self,
674 mut handle: node::Handle<IdRef<'id, Node<K, V>>,
677 -> SearchStack<'a, K, V, Type, NodeType> {
681 top: handle.as_raw(),
686 impl<'a, K, V, NodeType> SearchStack<'a, K, V, handle::KV, NodeType> {
687 /// Gets a reference to the value the stack points to.
688 pub fn peek(&self) -> &V {
689 unsafe { self.top.from_raw().into_kv().1 }
692 /// Gets a mutable reference to the value the stack points to.
693 pub fn peek_mut(&mut self) -> &mut V {
694 unsafe { self.top.from_raw_mut().into_kv_mut().1 }
697 /// Converts the stack into a mutable reference to the value it points to, with a lifetime
698 /// tied to the original tree.
699 pub fn into_top(mut self) -> &'a mut V {
700 unsafe { &mut *(self.top.from_raw_mut().val_mut() as *mut V) }
704 impl<'a, K, V> SearchStack<'a, K, V, handle::KV, handle::Leaf> {
705 /// Removes the key and value in the top element of the stack, then handles underflows as
706 /// described in BTree's pop function.
707 fn remove_leaf(mut self) -> (K, V) {
708 self.map.length -= 1;
710 // Remove the key-value pair from the leaf that this search stack points to.
711 // Then, note if the leaf is underfull, and promptly forget the leaf and its ptr
712 // to avoid ownership issues.
713 let (key_val, mut underflow) = unsafe {
714 let key_val = self.top.from_raw_mut().remove_as_leaf();
715 let underflow = self.top.from_raw().node().is_underfull();
720 match self.stack.pop() {
722 // We've reached the root, so no matter what, we're done. We manually
723 // access the root via the tree itself to avoid creating any dangling
725 if self.map.root.is_empty() && !self.map.root.is_leaf() {
726 // We've emptied out the root, so make its only child the new root.
727 // If it's a leaf, we just let it become empty.
729 self.map.root.hoist_lone_child();
733 Some(mut handle) => {
735 // Underflow! Handle it!
737 handle.from_raw_mut().handle_underflow();
738 underflow = handle.from_raw().node().is_underfull();
750 impl<'a, K, V> SearchStack<'a, K, V, handle::KV, handle::LeafOrInternal> {
751 /// Removes the key and value in the top element of the stack, then handles underflows as
752 /// described in BTree's pop function.
753 pub fn remove(self) -> (K, V) {
754 // Ensure that the search stack goes to a leaf. This is necessary to perform deletion
755 // in a BTree. Note that this may put the tree in an inconsistent state (further
756 // described in into_leaf's comments), but this is immediately fixed by the
757 // removing the value we want to remove
758 self.into_leaf().remove_leaf()
761 /// Subroutine for removal. Takes a search stack for a key that might terminate at an
762 /// internal node, and mutates the tree and search stack to *make* it a search stack
763 /// for that same key that *does* terminates at a leaf. If the mutation occurs, then this
764 /// leaves the tree in an inconsistent state that must be repaired by the caller by
765 /// removing the entry in question. Specifically the key-value pair and its successor will
767 fn into_leaf(mut self) -> SearchStack<'a, K, V, handle::KV, handle::Leaf> {
769 let mut top_raw = self.top;
770 let mut top = top_raw.from_raw_mut();
772 let key_ptr = top.key_mut() as *mut _;
773 let val_ptr = top.val_mut() as *mut _;
775 // Try to go into the right subtree of the found key to find its successor
777 Leaf(mut leaf_handle) => {
778 // We're a proper leaf stack, nothing to do
782 top: leaf_handle.as_raw(),
785 Internal(mut internal_handle) => {
786 let mut right_handle = internal_handle.right_edge();
788 // We're not a proper leaf stack, let's get to work.
789 self.stack.push(right_handle.as_raw());
791 let mut temp_node = right_handle.edge_mut();
793 // Walk into the smallest subtree of this node
794 let node = temp_node;
796 match node.kv_handle(0).force() {
797 Leaf(mut handle) => {
798 // This node is a leaf, do the swap and return
799 mem::swap(handle.key_mut(), &mut *key_ptr);
800 mem::swap(handle.val_mut(), &mut *val_ptr);
804 top: handle.as_raw(),
807 Internal(kv_handle) => {
808 // This node is internal, go deeper
809 let mut handle = kv_handle.into_left_edge();
810 self.stack.push(handle.as_raw());
811 temp_node = handle.into_edge_mut();
821 impl<'a, K, V> SearchStack<'a, K, V, handle::Edge, handle::Leaf> {
822 /// Inserts the key and value into the top element in the stack, and if that node has to
823 /// split recursively inserts the split contents into the next element stack until
826 /// Assumes that the stack represents a search path from the root to a leaf.
828 /// An &mut V is returned to the inserted value, for callers that want a reference to this.
829 pub fn insert(mut self, key: K, val: V) -> &'a mut V {
831 self.map.length += 1;
833 // Insert the key and value into the leaf at the top of the stack
834 let (mut insertion, inserted_ptr) = self.top
836 .insert_as_leaf(key, val);
841 // The last insertion went off without a hitch, no splits! We can stop
843 return &mut *inserted_ptr;
845 Split(key, val, right) => {
846 match self.stack.pop() {
847 // The last insertion triggered a split, so get the next element on
848 // the stack to recursively insert the split node into.
850 // The stack was empty; we've split the root, and need to make a
851 // a new one. This is done in-place because we can't move the
852 // root out of a reference to the tree.
853 Node::make_internal_root(&mut self.map.root,
860 return &mut *inserted_ptr;
862 Some(mut handle) => {
863 // The stack wasn't empty, do the insertion and recurse
864 insertion = handle.from_raw_mut()
865 .insert_as_internal(key, val, right);
877 #[stable(feature = "rust1", since = "1.0.0")]
878 impl<K: Ord, V> FromIterator<(K, V)> for BTreeMap<K, V> {
879 fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> BTreeMap<K, V> {
880 let mut map = BTreeMap::new();
886 #[stable(feature = "rust1", since = "1.0.0")]
887 impl<K: Ord, V> Extend<(K, V)> for BTreeMap<K, V> {
889 fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T) {
896 #[stable(feature = "extend_ref", since = "1.2.0")]
897 impl<'a, K: Ord + Copy, V: Copy> Extend<(&'a K, &'a V)> for BTreeMap<K, V> {
898 fn extend<I: IntoIterator<Item = (&'a K, &'a V)>>(&mut self, iter: I) {
899 self.extend(iter.into_iter().map(|(&key, &value)| (key, value)));
903 #[stable(feature = "rust1", since = "1.0.0")]
904 impl<K: Hash, V: Hash> Hash for BTreeMap<K, V> {
905 fn hash<H: Hasher>(&self, state: &mut H) {
912 #[stable(feature = "rust1", since = "1.0.0")]
913 impl<K: Ord, V> Default for BTreeMap<K, V> {
914 fn default() -> BTreeMap<K, V> {
919 #[stable(feature = "rust1", since = "1.0.0")]
920 impl<K: PartialEq, V: PartialEq> PartialEq for BTreeMap<K, V> {
921 fn eq(&self, other: &BTreeMap<K, V>) -> bool {
922 self.len() == other.len() && self.iter().zip(other).all(|(a, b)| a == b)
926 #[stable(feature = "rust1", since = "1.0.0")]
927 impl<K: Eq, V: Eq> Eq for BTreeMap<K, V> {}
929 #[stable(feature = "rust1", since = "1.0.0")]
930 impl<K: PartialOrd, V: PartialOrd> PartialOrd for BTreeMap<K, V> {
932 fn partial_cmp(&self, other: &BTreeMap<K, V>) -> Option<Ordering> {
933 self.iter().partial_cmp(other.iter())
937 #[stable(feature = "rust1", since = "1.0.0")]
938 impl<K: Ord, V: Ord> Ord for BTreeMap<K, V> {
940 fn cmp(&self, other: &BTreeMap<K, V>) -> Ordering {
941 self.iter().cmp(other.iter())
945 #[stable(feature = "rust1", since = "1.0.0")]
946 impl<K: Debug, V: Debug> Debug for BTreeMap<K, V> {
947 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
948 f.debug_map().entries(self.iter()).finish()
952 #[stable(feature = "rust1", since = "1.0.0")]
953 impl<'a, K: Ord, Q: ?Sized, V> Index<&'a Q> for BTreeMap<K, V>
960 fn index(&self, key: &Q) -> &V {
961 self.get(key).expect("no entry found for key")
965 /// Genericizes over how to get the correct type of iterator from the correct type
966 /// of Node ownership.
968 fn traverse(node: N) -> Self;
971 impl<'a, K, V> Traverse<&'a Node<K, V>> for Traversal<'a, K, V> {
972 fn traverse(node: &'a Node<K, V>) -> Traversal<'a, K, V> {
977 impl<'a, K, V> Traverse<&'a mut Node<K, V>> for MutTraversal<'a, K, V> {
978 fn traverse(node: &'a mut Node<K, V>) -> MutTraversal<'a, K, V> {
983 impl<K, V> Traverse<Node<K, V>> for MoveTraversal<K, V> {
984 fn traverse(node: Node<K, V>) -> MoveTraversal<K, V> {
989 /// Represents an operation to perform inside the following iterator methods.
990 /// This is necessary to use in `next` because we want to modify `self.traversals` inside
991 /// a match that borrows it. Similarly in `next_back`. Instead, we use this enum to note
992 /// what we want to do, and do it after the match.
997 impl<K, V, E, T> Iterator for AbsIter<T>
998 where T: DoubleEndedIterator<Item = TraversalItem<K, V, E>> + Traverse<E>
1002 // Our iterator represents a queue of all ancestors of elements we have
1003 // yet to yield, from smallest to largest. Note that the design of these
1004 // iterators permits an *arbitrary* initial pair of min and max, making
1005 // these arbitrary sub-range iterators.
1006 fn next(&mut self) -> Option<(K, V)> {
1008 // We want the smallest element, so try to get the back of the queue
1009 let op = match self.traversals.back_mut() {
1010 None => return None,
1011 // The queue wasn't empty, so continue along the node in its head
1014 // The head is empty, so Pop it off and continue the process
1016 // The head yielded an edge, so make that the new head
1017 Some(Edge(next)) => Push(Traverse::traverse(next)),
1018 // The head yielded an entry, so yield that
1027 // Handle any operation as necessary, without a conflicting borrow of the queue
1030 self.traversals.push_back(item);
1033 self.traversals.pop_back();
1039 fn size_hint(&self) -> (usize, Option<usize>) {
1040 (self.size, Some(self.size))
1044 impl<K, V, E, T> DoubleEndedIterator for AbsIter<T>
1045 where T: DoubleEndedIterator<Item = TraversalItem<K, V, E>> + Traverse<E>
1047 // next_back is totally symmetric to next
1049 fn next_back(&mut self) -> Option<(K, V)> {
1051 let op = match self.traversals.front_mut() {
1052 None => return None,
1054 match iter.next_back() {
1056 Some(Edge(next)) => Push(Traverse::traverse(next)),
1067 self.traversals.push_front(item);
1070 self.traversals.pop_front();
1077 impl<'a, K, V> Clone for Iter<'a, K, V> {
1078 fn clone(&self) -> Iter<'a, K, V> {
1079 Iter { inner: self.inner.clone() }
1082 #[stable(feature = "rust1", since = "1.0.0")]
1083 impl<'a, K, V> Iterator for Iter<'a, K, V> {
1084 type Item = (&'a K, &'a V);
1086 fn next(&mut self) -> Option<(&'a K, &'a V)> {
1089 fn size_hint(&self) -> (usize, Option<usize>) {
1090 self.inner.size_hint()
1093 #[stable(feature = "rust1", since = "1.0.0")]
1094 impl<'a, K, V> DoubleEndedIterator for Iter<'a, K, V> {
1095 fn next_back(&mut self) -> Option<(&'a K, &'a V)> {
1096 self.inner.next_back()
1099 #[stable(feature = "rust1", since = "1.0.0")]
1100 impl<'a, K, V> ExactSizeIterator for Iter<'a, K, V> {}
1102 #[stable(feature = "rust1", since = "1.0.0")]
1103 impl<'a, K, V> Iterator for IterMut<'a, K, V> {
1104 type Item = (&'a K, &'a mut V);
1106 fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
1109 fn size_hint(&self) -> (usize, Option<usize>) {
1110 self.inner.size_hint()
1113 #[stable(feature = "rust1", since = "1.0.0")]
1114 impl<'a, K, V> DoubleEndedIterator for IterMut<'a, K, V> {
1115 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> {
1116 self.inner.next_back()
1119 #[stable(feature = "rust1", since = "1.0.0")]
1120 impl<'a, K, V> ExactSizeIterator for IterMut<'a, K, V> {}
1122 #[stable(feature = "rust1", since = "1.0.0")]
1123 impl<K, V> Iterator for IntoIter<K, V> {
1126 fn next(&mut self) -> Option<(K, V)> {
1129 fn size_hint(&self) -> (usize, Option<usize>) {
1130 self.inner.size_hint()
1133 #[stable(feature = "rust1", since = "1.0.0")]
1134 impl<K, V> DoubleEndedIterator for IntoIter<K, V> {
1135 fn next_back(&mut self) -> Option<(K, V)> {
1136 self.inner.next_back()
1139 #[stable(feature = "rust1", since = "1.0.0")]
1140 impl<K, V> ExactSizeIterator for IntoIter<K, V> {}
1142 impl<'a, K, V> Clone for Keys<'a, K, V> {
1143 fn clone(&self) -> Keys<'a, K, V> {
1144 Keys { inner: self.inner.clone() }
1147 #[stable(feature = "rust1", since = "1.0.0")]
1148 impl<'a, K, V> Iterator for Keys<'a, K, V> {
1151 fn next(&mut self) -> Option<(&'a K)> {
1154 fn size_hint(&self) -> (usize, Option<usize>) {
1155 self.inner.size_hint()
1158 #[stable(feature = "rust1", since = "1.0.0")]
1159 impl<'a, K, V> DoubleEndedIterator for Keys<'a, K, V> {
1160 fn next_back(&mut self) -> Option<(&'a K)> {
1161 self.inner.next_back()
1164 #[stable(feature = "rust1", since = "1.0.0")]
1165 impl<'a, K, V> ExactSizeIterator for Keys<'a, K, V> {}
1168 impl<'a, K, V> Clone for Values<'a, K, V> {
1169 fn clone(&self) -> Values<'a, K, V> {
1170 Values { inner: self.inner.clone() }
1173 #[stable(feature = "rust1", since = "1.0.0")]
1174 impl<'a, K, V> Iterator for Values<'a, K, V> {
1177 fn next(&mut self) -> Option<(&'a V)> {
1180 fn size_hint(&self) -> (usize, Option<usize>) {
1181 self.inner.size_hint()
1184 #[stable(feature = "rust1", since = "1.0.0")]
1185 impl<'a, K, V> DoubleEndedIterator for Values<'a, K, V> {
1186 fn next_back(&mut self) -> Option<(&'a V)> {
1187 self.inner.next_back()
1190 #[stable(feature = "rust1", since = "1.0.0")]
1191 impl<'a, K, V> ExactSizeIterator for Values<'a, K, V> {}
1193 impl<'a, K, V> Clone for Range<'a, K, V> {
1194 fn clone(&self) -> Range<'a, K, V> {
1195 Range { inner: self.inner.clone() }
1198 impl<'a, K, V> Iterator for Range<'a, K, V> {
1199 type Item = (&'a K, &'a V);
1201 fn next(&mut self) -> Option<(&'a K, &'a V)> {
1205 impl<'a, K, V> DoubleEndedIterator for Range<'a, K, V> {
1206 fn next_back(&mut self) -> Option<(&'a K, &'a V)> {
1207 self.inner.next_back()
1211 impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
1212 type Item = (&'a K, &'a mut V);
1214 fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
1218 impl<'a, K, V> DoubleEndedIterator for RangeMut<'a, K, V> {
1219 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> {
1220 self.inner.next_back()
1224 impl<'a, K: Ord, V> Entry<'a, K, V> {
1225 #[stable(feature = "rust1", since = "1.0.0")]
1226 /// Ensures a value is in the entry by inserting the default if empty, and returns
1227 /// a mutable reference to the value in the entry.
1228 pub fn or_insert(self, default: V) -> &'a mut V {
1230 Occupied(entry) => entry.into_mut(),
1231 Vacant(entry) => entry.insert(default),
1235 #[stable(feature = "rust1", since = "1.0.0")]
1236 /// Ensures a value is in the entry by inserting the result of the default function if empty,
1237 /// and returns a mutable reference to the value in the entry.
1238 pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V {
1240 Occupied(entry) => entry.into_mut(),
1241 Vacant(entry) => entry.insert(default()),
1246 impl<'a, K: Ord, V> VacantEntry<'a, K, V> {
1247 /// Sets the value of the entry with the VacantEntry's key,
1248 /// and returns a mutable reference to it.
1249 #[stable(feature = "rust1", since = "1.0.0")]
1250 pub fn insert(self, value: V) -> &'a mut V {
1251 self.stack.insert(self.key, value)
1255 impl<'a, K: Ord, V> OccupiedEntry<'a, K, V> {
1256 /// Gets a reference to the value in the entry.
1257 #[stable(feature = "rust1", since = "1.0.0")]
1258 pub fn get(&self) -> &V {
1262 /// Gets a mutable reference to the value in the entry.
1263 #[stable(feature = "rust1", since = "1.0.0")]
1264 pub fn get_mut(&mut self) -> &mut V {
1265 self.stack.peek_mut()
1268 /// Converts the entry into a mutable reference to its value.
1269 #[stable(feature = "rust1", since = "1.0.0")]
1270 pub fn into_mut(self) -> &'a mut V {
1271 self.stack.into_top()
1274 /// Sets the value of the entry with the OccupiedEntry's key,
1275 /// and returns the entry's old value.
1276 #[stable(feature = "rust1", since = "1.0.0")]
1277 pub fn insert(&mut self, mut value: V) -> V {
1278 mem::swap(self.stack.peek_mut(), &mut value);
1282 /// Takes the value of the entry out of the map, and returns it.
1283 #[stable(feature = "rust1", since = "1.0.0")]
1284 pub fn remove(self) -> V {
1285 self.stack.remove().1
1289 impl<K, V> BTreeMap<K, V> {
1290 /// Gets an iterator over the entries of the map.
1295 /// use std::collections::BTreeMap;
1297 /// let mut map = BTreeMap::new();
1298 /// map.insert(1, "a");
1299 /// map.insert(2, "b");
1300 /// map.insert(3, "c");
1302 /// for (key, value) in map.iter() {
1303 /// println!("{}: {}", key, value);
1306 /// let (first_key, first_value) = map.iter().next().unwrap();
1307 /// assert_eq!((*first_key, *first_value), (1, "a"));
1309 #[stable(feature = "rust1", since = "1.0.0")]
1310 pub fn iter(&self) -> Iter<K, V> {
1311 let len = self.len();
1312 // NB. The initial capacity for ringbuf is large enough to avoid reallocs in many cases.
1313 let mut lca = VecDeque::new();
1314 lca.push_back(Traverse::traverse(&self.root));
1323 /// Gets a mutable iterator over the entries of the map.
1328 /// use std::collections::BTreeMap;
1330 /// let mut map = BTreeMap::new();
1331 /// map.insert("a", 1);
1332 /// map.insert("b", 2);
1333 /// map.insert("c", 3);
1335 /// // add 10 to the value if the key isn't "a"
1336 /// for (key, value) in map.iter_mut() {
1337 /// if key != &"a" {
1342 #[stable(feature = "rust1", since = "1.0.0")]
1343 pub fn iter_mut(&mut self) -> IterMut<K, V> {
1344 let len = self.len();
1345 let mut lca = VecDeque::new();
1346 lca.push_back(Traverse::traverse(&mut self.root));
1355 /// Gets an iterator over the keys of the map.
1360 /// use std::collections::BTreeMap;
1362 /// let mut a = BTreeMap::new();
1363 /// a.insert(1, "a");
1364 /// a.insert(2, "b");
1366 /// let keys: Vec<_> = a.keys().cloned().collect();
1367 /// assert_eq!(keys, [1, 2]);
1369 #[stable(feature = "rust1", since = "1.0.0")]
1370 pub fn keys<'a>(&'a self) -> Keys<'a, K, V> {
1371 fn first<A, B>((a, _): (A, B)) -> A {
1374 let first: fn((&'a K, &'a V)) -> &'a K = first; // coerce to fn pointer
1376 Keys { inner: self.iter().map(first) }
1379 /// Gets an iterator over the values of the map.
1384 /// use std::collections::BTreeMap;
1386 /// let mut a = BTreeMap::new();
1387 /// a.insert(1, "a");
1388 /// a.insert(2, "b");
1390 /// let values: Vec<&str> = a.values().cloned().collect();
1391 /// assert_eq!(values, ["a", "b"]);
1393 #[stable(feature = "rust1", since = "1.0.0")]
1394 pub fn values<'a>(&'a self) -> Values<'a, K, V> {
1395 fn second<A, B>((_, b): (A, B)) -> B {
1398 let second: fn((&'a K, &'a V)) -> &'a V = second; // coerce to fn pointer
1400 Values { inner: self.iter().map(second) }
1403 /// Returns the number of elements in the map.
1408 /// use std::collections::BTreeMap;
1410 /// let mut a = BTreeMap::new();
1411 /// assert_eq!(a.len(), 0);
1412 /// a.insert(1, "a");
1413 /// assert_eq!(a.len(), 1);
1415 #[stable(feature = "rust1", since = "1.0.0")]
1416 pub fn len(&self) -> usize {
1420 /// Returns true if the map contains no elements.
1425 /// use std::collections::BTreeMap;
1427 /// let mut a = BTreeMap::new();
1428 /// assert!(a.is_empty());
1429 /// a.insert(1, "a");
1430 /// assert!(!a.is_empty());
1432 #[stable(feature = "rust1", since = "1.0.0")]
1433 pub fn is_empty(&self) -> bool {
1438 macro_rules! range_impl {
1439 ($root:expr, $min:expr, $max:expr, $as_slices_internal:ident, $iter:ident, $Range:ident,
1440 $edges:ident, [$($mutability:ident)*]) => (
1442 // A deque that encodes two search paths containing (left-to-right):
1443 // a series of truncated-from-the-left iterators, the LCA's doubly-truncated iterator,
1444 // and a series of truncated-from-the-right iterators.
1445 let mut traversals = VecDeque::new();
1446 let (root, min, max) = ($root, $min, $max);
1448 let mut leftmost = None;
1449 let mut rightmost = None;
1451 match (&min, &max) {
1452 (&Unbounded, &Unbounded) => {
1453 traversals.push_back(Traverse::traverse(root))
1455 (&Unbounded, &Included(_)) | (&Unbounded, &Excluded(_)) => {
1456 rightmost = Some(root);
1458 (&Included(_), &Unbounded) | (&Excluded(_), &Unbounded) => {
1459 leftmost = Some(root);
1461 (&Included(min_key), &Included(max_key))
1462 | (&Included(min_key), &Excluded(max_key))
1463 | (&Excluded(min_key), &Included(max_key))
1464 | (&Excluded(min_key), &Excluded(max_key)) => {
1465 // lca represents the Lowest Common Ancestor, above which we never
1466 // walk, since everything else is outside the range to iterate.
1467 // ___________________
1468 // |__0_|_80_|_85_|_90_| (root)
1472 // ___________________
1473 // |__5_|_15_|_30_|_73_|
1477 // ___________________
1478 // |_33_|_58_|_63_|_68_| lca for the range [41, 65]
1479 // | |\___|___/| | iterator at traversals[2]
1484 let mut is_leaf = root.is_leaf();
1485 let mut lca = root.$as_slices_internal();
1487 let slice = lca.slice_from(min_key).slice_to(max_key);
1488 if let [ref $($mutability)* edge] = slice.edges {
1489 // Follow the only edge that leads the node that covers the range.
1490 is_leaf = edge.is_leaf();
1491 lca = edge.$as_slices_internal();
1493 let mut iter = slice.$iter();
1498 // Only change the state of nodes with edges.
1499 leftmost = iter.next_edge_item();
1500 rightmost = iter.next_edge_item_back();
1502 traversals.push_back(iter);
1508 // Keep narrowing the range by going down.
1509 // ___________________
1510 // |_38_|_43_|_48_|_53_|
1511 // | |____|____|____/ iterator at traversals[1]
1514 // ___________________
1515 // |_39_|_40_|_41_|_42_| (leaf, the last leftmost)
1516 // \_________| iterator at traversals[0]
1518 Included(key) | Excluded(key) =>
1519 while let Some(left) = leftmost {
1520 let is_leaf = left.is_leaf();
1521 let mut iter = left.$as_slices_internal().slice_from(key).$iter();
1522 leftmost = if is_leaf {
1525 // Only change the state of nodes with edges.
1526 iter.next_edge_item()
1528 traversals.push_back(iter);
1532 // If the leftmost iterator starts with an element, then it was an exact match.
1533 if let (Excluded(_), Some(leftmost_iter)) = (min, traversals.back_mut()) {
1534 // Drop this excluded element. `next_kv_item` has no effect when
1535 // the next item is an edge.
1536 leftmost_iter.next_kv_item();
1539 // The code for the right side is similar.
1541 Included(key) | Excluded(key) =>
1542 while let Some(right) = rightmost {
1543 let is_leaf = right.is_leaf();
1544 let mut iter = right.$as_slices_internal().slice_to(key).$iter();
1545 rightmost = if is_leaf {
1548 iter.next_edge_item_back()
1550 traversals.push_front(iter);
1554 if let (Excluded(_), Some(rightmost_iter)) = (max, traversals.front_mut()) {
1555 rightmost_iter.next_kv_item_back();
1560 traversals: traversals,
1561 size: usize::MAX, // unused
1568 impl<K: Ord, V> BTreeMap<K, V> {
1569 /// Constructs a double-ended iterator over a sub-range of elements in the map, starting
1570 /// at min, and ending at max. If min is `Unbounded`, then it will be treated as "negative
1571 /// infinity", and if max is `Unbounded`, then it will be treated as "positive infinity".
1572 /// Thus range(Unbounded, Unbounded) will yield the whole collection.
1577 /// #![feature(btree_range, collections_bound)]
1579 /// use std::collections::BTreeMap;
1580 /// use std::collections::Bound::{Included, Unbounded};
1582 /// let mut map = BTreeMap::new();
1583 /// map.insert(3, "a");
1584 /// map.insert(5, "b");
1585 /// map.insert(8, "c");
1586 /// for (&key, &value) in map.range(Included(&4), Included(&8)) {
1587 /// println!("{}: {}", key, value);
1589 /// assert_eq!(Some((&5, &"b")), map.range(Included(&4), Unbounded).next());
1591 #[unstable(feature = "btree_range",
1592 reason = "matches collection reform specification, waiting for dust to settle",
1594 pub fn range<Min: ?Sized + Ord, Max: ?Sized + Ord>(&self,
1598 where K: Borrow<Min> + Borrow<Max>
1600 range_impl!(&self.root,
1610 /// Constructs a mutable double-ended iterator over a sub-range of elements in the map, starting
1611 /// at min, and ending at max. If min is `Unbounded`, then it will be treated as "negative
1612 /// infinity", and if max is `Unbounded`, then it will be treated as "positive infinity".
1613 /// Thus range(Unbounded, Unbounded) will yield the whole collection.
1618 /// #![feature(btree_range, collections_bound)]
1620 /// use std::collections::BTreeMap;
1621 /// use std::collections::Bound::{Included, Excluded};
1623 /// let mut map: BTreeMap<&str, i32> = ["Alice", "Bob", "Carol", "Cheryl"].iter()
1624 /// .map(|&s| (s, 0))
1626 /// for (_, balance) in map.range_mut(Included("B"), Excluded("Cheryl")) {
1627 /// *balance += 100;
1629 /// for (name, balance) in &map {
1630 /// println!("{} => {}", name, balance);
1633 #[unstable(feature = "btree_range",
1634 reason = "matches collection reform specification, waiting for dust to settle",
1636 pub fn range_mut<Min: ?Sized + Ord, Max: ?Sized + Ord>(&mut self,
1640 where K: Borrow<Min> + Borrow<Max>
1642 range_impl!(&mut self.root,
1645 as_slices_internal_mut,
1652 /// Gets the given key's corresponding entry in the map for in-place manipulation.
1657 /// use std::collections::BTreeMap;
1659 /// let mut count: BTreeMap<&str, usize> = BTreeMap::new();
1661 /// // count the number of occurrences of letters in the vec
1662 /// for x in vec!["a","b","a","c","a","b"] {
1663 /// *count.entry(x).or_insert(0) += 1;
1666 /// assert_eq!(count["a"], 3);
1668 #[stable(feature = "rust1", since = "1.0.0")]
1669 pub fn entry(&mut self, mut key: K) -> Entry<K, V> {
1670 // same basic logic of `swap` and `pop`, blended together
1671 let mut stack = stack::PartialSearchStack::new(self);
1673 let result = stack.with(move |pusher, node| {
1674 match Node::search(node, &key) {
1677 Finished(Occupied(OccupiedEntry { stack: pusher.seal(handle) }))
1680 match handle.force() {
1681 Leaf(leaf_handle) => {
1682 Finished(Vacant(VacantEntry {
1683 stack: pusher.seal(leaf_handle),
1687 Internal(internal_handle) => {
1688 Continue((pusher.push(internal_handle), key))
1695 Finished(finished) => return finished,
1696 Continue((new_stack, renewed_key)) => {
1705 impl<K, Q: ?Sized> super::Recover<Q> for BTreeMap<K, ()>
1706 where K: Borrow<Q> + Ord,
1711 fn get(&self, key: &Q) -> Option<&K> {
1712 let mut cur_node = &self.root;
1714 match Node::search(cur_node, key) {
1715 Found(handle) => return Some(handle.into_kv().0),
1717 match handle.force() {
1718 Leaf(_) => return None,
1719 Internal(internal_handle) => {
1720 cur_node = internal_handle.into_edge();
1729 fn take(&mut self, key: &Q) -> Option<K> {
1730 // See `remove` for an explanation of this.
1732 let mut stack = stack::PartialSearchStack::new(self);
1734 let result = stack.with(move |pusher, node| {
1735 match Node::search(node, key) {
1737 // Perfect match. Terminate the stack here, and remove the entry
1738 Finished(Some(pusher.seal(handle).remove()))
1741 // We need to keep searching, try to go down the next edge
1742 match handle.force() {
1743 // We're at a leaf; the key isn't in here
1744 Leaf(_) => Finished(None),
1745 Internal(internal_handle) => Continue(pusher.push(internal_handle)),
1751 Finished(ret) => return ret.map(|(k, _)| k),
1752 Continue(new_stack) => stack = new_stack,
1757 fn replace(&mut self, mut key: K) -> Option<K> {
1758 // See `insert` for an explanation of this.
1760 let mut stack = stack::PartialSearchStack::new(self);
1763 let result = stack.with(move |pusher, node| {
1764 match Node::search::<K, _>(node, &key) {
1765 Found(mut handle) => {
1766 mem::swap(handle.key_mut(), &mut key);
1770 match handle.force() {
1771 Leaf(leaf_handle) => {
1772 pusher.seal(leaf_handle).insert(key, ());
1775 Internal(internal_handle) => {
1776 Continue((pusher.push(internal_handle), key, ()))
1783 Finished(ret) => return ret,
1784 Continue((new_stack, renewed_key, _)) => {