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")]
130 #[cfg_attr(not(stage0), stable(feature = "rust1", since = "1.0.0"))] VacantEntry<'a, K, V>
133 /// An occupied Entry
134 #[stable(feature = "rust1", since = "1.0.0")]
136 #[cfg_attr(not(stage0), stable(feature = "rust1", since = "1.0.0"))] OccupiedEntry<'a, K, V>
141 #[stable(feature = "rust1", since = "1.0.0")]
142 pub struct VacantEntry<'a, K: 'a, V: 'a> {
144 stack: stack::SearchStack<'a, K, V, node::handle::Edge, node::handle::Leaf>,
147 /// An occupied Entry.
148 #[stable(feature = "rust1", since = "1.0.0")]
149 pub struct OccupiedEntry<'a, K: 'a, V: 'a> {
150 stack: stack::SearchStack<'a, K, V, node::handle::KV, node::handle::LeafOrInternal>,
153 impl<K: Ord, V> BTreeMap<K, V> {
154 /// Makes a new empty BTreeMap with a reasonable choice for B.
155 #[stable(feature = "rust1", since = "1.0.0")]
157 pub fn new() -> BTreeMap<K, V> {
161 root: Node::make_leaf_root(6),
162 // FIXME(Gankro): Tune this as a function of size_of<K/V>?
168 /// Clears the map, removing all values.
173 /// use std::collections::BTreeMap;
175 /// let mut a = BTreeMap::new();
176 /// a.insert(1, "a");
178 /// assert!(a.is_empty());
180 #[stable(feature = "rust1", since = "1.0.0")]
181 pub fn clear(&mut self) {
182 // avoid recursive destructors by manually traversing the tree
183 for _ in mem::replace(self, BTreeMap::new()) {}
186 // Searching in a B-Tree is pretty straightforward.
188 // Start at the root. Try to find the key in the current node. If we find it, return it.
189 // If it's not in there, follow the edge *before* the smallest key larger than
190 // the search key. If no such key exists (they're *all* smaller), then just take the last
191 // edge in the node. If we're in a leaf and we don't find our key, then it's not
194 /// Returns a reference to the value corresponding to the key.
196 /// The key may be any borrowed form of the map's key type, but the ordering
197 /// on the borrowed form *must* match the ordering on the key type.
202 /// use std::collections::BTreeMap;
204 /// let mut map = BTreeMap::new();
205 /// map.insert(1, "a");
206 /// assert_eq!(map.get(&1), Some(&"a"));
207 /// assert_eq!(map.get(&2), None);
209 #[stable(feature = "rust1", since = "1.0.0")]
210 pub fn get<Q: ?Sized>(&self, key: &Q) -> Option<&V>
214 let mut cur_node = &self.root;
216 match Node::search(cur_node, key) {
217 Found(handle) => return Some(handle.into_kv().1),
219 match handle.force() {
220 Leaf(_) => return None,
221 Internal(internal_handle) => {
222 cur_node = internal_handle.into_edge();
231 /// Returns true if the map contains a value for the specified key.
233 /// The key may be any borrowed form of the map's key type, but the ordering
234 /// on the borrowed form *must* match the ordering on the key type.
239 /// use std::collections::BTreeMap;
241 /// let mut map = BTreeMap::new();
242 /// map.insert(1, "a");
243 /// assert_eq!(map.contains_key(&1), true);
244 /// assert_eq!(map.contains_key(&2), false);
246 #[stable(feature = "rust1", since = "1.0.0")]
247 pub fn contains_key<Q: ?Sized>(&self, key: &Q) -> bool
251 self.get(key).is_some()
254 /// Returns a mutable reference to the value corresponding to the key.
256 /// The key may be any borrowed form of the map's key type, but the ordering
257 /// on the borrowed form *must* match the ordering on the key type.
262 /// use std::collections::BTreeMap;
264 /// let mut map = BTreeMap::new();
265 /// map.insert(1, "a");
266 /// if let Some(x) = map.get_mut(&1) {
269 /// assert_eq!(map[&1], "b");
271 // See `get` for implementation notes, this is basically a copy-paste with mut's added
272 #[stable(feature = "rust1", since = "1.0.0")]
273 pub fn get_mut<Q: ?Sized>(&mut self, key: &Q) -> Option<&mut V>
277 // temp_node is a Borrowck hack for having a mutable value outlive a loop iteration
278 let mut temp_node = &mut self.root;
280 let cur_node = temp_node;
281 match Node::search(cur_node, key) {
282 Found(handle) => return Some(handle.into_kv_mut().1),
284 match handle.force() {
285 Leaf(_) => return None,
286 Internal(internal_handle) => {
287 temp_node = internal_handle.into_edge_mut();
296 // Insertion in a B-Tree is a bit complicated.
298 // First we do the same kind of search described in `find`. But we need to maintain a stack of
299 // all the nodes/edges in our search path. If we find a match for the key we're trying to
300 // insert, just swap the vals and return the old ones. However, when we bottom out in a leaf,
301 // we attempt to insert our key-value pair at the same location we would want to follow another
304 // If the node has room, then this is done in the obvious way by shifting elements. However,
305 // if the node itself is full, we split node into two, and give its median key-value
306 // pair to its parent to insert the new node with. Of course, the parent may also be
307 // full, and insertion can propagate until we reach the root. If we reach the root, and
308 // it is *also* full, then we split the root and place the two nodes under a newly made root.
310 // Note that we subtly deviate from Open Data Structures in our implementation of split.
311 // ODS describes inserting into the node *regardless* of its capacity, and then
312 // splitting *afterwards* if it happens to be overfull. However, this is inefficient.
313 // Instead, we split beforehand, and then insert the key-value pair into the appropriate
314 // result node. This has two consequences:
316 // 1) While ODS produces a left node of size B-1, and a right node of size B,
317 // we may potentially reverse this. However, this shouldn't effect the analysis.
319 // 2) While ODS may potentially return the pair we *just* inserted after
320 // the split, we will never do this. Again, this shouldn't effect the analysis.
322 /// Inserts a key-value pair into the map.
324 /// If the map did not have this key present, `None` is returned.
326 /// If the map did have this key present, the key is not updated, the
327 /// value is updated and the old value is returned.
328 /// See the [module-level documentation] for more.
330 /// [module-level documentation]: index.html#insert-and-complex-keys
335 /// use std::collections::BTreeMap;
337 /// let mut map = BTreeMap::new();
338 /// assert_eq!(map.insert(37, "a"), None);
339 /// assert_eq!(map.is_empty(), false);
341 /// map.insert(37, "b");
342 /// assert_eq!(map.insert(37, "c"), Some("b"));
343 /// assert_eq!(map[&37], "c");
345 #[stable(feature = "rust1", since = "1.0.0")]
346 pub fn insert(&mut self, mut key: K, mut value: V) -> Option<V> {
347 // This is a stack of rawptrs to nodes paired with indices, respectively
348 // representing the nodes and edges of our search path. We have to store rawptrs
349 // because as far as Rust is concerned, we can mutate aliased data with such a
350 // stack. It is of course correct, but what it doesn't know is that we will only
351 // be popping and using these ptrs one at a time in child-to-parent order. The alternative
352 // to doing this is to take the Nodes from their parents. This actually makes
353 // borrowck *really* happy and everything is pretty smooth. However, this creates
354 // *tons* of pointless writes, and requires us to always walk all the way back to
355 // the root after an insertion, even if we only needed to change a leaf. Therefore,
356 // we accept this potential unsafety and complexity in the name of performance.
358 // Regardless, the actual dangerous logic is completely abstracted away from BTreeMap
359 // by the stack module. All it can do is immutably read nodes, and ask the search stack
360 // to proceed down some edge by index. This makes the search logic we'll be reusing in a
361 // few different methods much neater, and of course drastically improves safety.
362 let mut stack = stack::PartialSearchStack::new(self);
365 let result = stack.with(move |pusher, node| {
366 // Same basic logic as found in `find`, but with PartialSearchStack mediating the
367 // actual nodes for us
368 match Node::search(node, &key) {
369 Found(mut handle) => {
370 // Perfect match, swap the values and return the old one
371 mem::swap(handle.val_mut(), &mut value);
372 Finished(Some(value))
375 // We need to keep searching, try to get the search stack
376 // to go down further
377 match handle.force() {
378 Leaf(leaf_handle) => {
379 // We've reached a leaf, perform the insertion here
380 pusher.seal(leaf_handle).insert(key, value);
383 Internal(internal_handle) => {
384 // We've found the subtree to insert this key/value pair in,
386 Continue((pusher.push(internal_handle), key, value))
393 Finished(ret) => return ret,
394 Continue((new_stack, renewed_key, renewed_val)) => {
403 // Deletion is the most complicated operation for a B-Tree.
405 // First we do the same kind of search described in
406 // `find`. But we need to maintain a stack of all the nodes/edges in our search path.
407 // If we don't find the key, then we just return `None` and do nothing. If we do find the
408 // key, we perform two operations: remove the item, and then possibly handle underflow.
410 // # removing the item
411 // If the node is a leaf, we just remove the item, and shift
412 // any items after it back to fill the hole.
414 // If the node is an internal node, we *swap* the item with the smallest item in
415 // in its right subtree (which must reside in a leaf), and then revert to the leaf
418 // # handling underflow
419 // After removing an item, there may be too few items in the node. We want nodes
420 // to be mostly full for efficiency, although we make an exception for the root, which
421 // may have as few as one item. If this is the case, we may first try to steal
422 // an item from our left or right neighbour.
424 // To steal from the left (right) neighbour,
425 // we take the largest (smallest) item and child from it. We then swap the taken item
426 // with the item in their mutual parent that separates them, and then insert the
427 // parent's item and the taken child into the first (last) index of the underflowed node.
429 // However, stealing has the possibility of underflowing our neighbour. If this is the
430 // case, we instead *merge* with our neighbour. This of course reduces the number of
431 // children in the parent. Therefore, we also steal the item that separates the now
432 // merged nodes, and insert it into the merged node.
434 // Merging may cause the parent to underflow. If this is the case, then we must repeat
435 // the underflow handling process on the parent. If merging merges the last two children
436 // of the root, then we replace the root with the merged node.
438 /// Removes a key from the map, returning the value at the key if the key
439 /// was previously in the map.
441 /// The key may be any borrowed form of the map's key type, but the ordering
442 /// on the borrowed form *must* match the ordering on the key type.
447 /// use std::collections::BTreeMap;
449 /// let mut map = BTreeMap::new();
450 /// map.insert(1, "a");
451 /// assert_eq!(map.remove(&1), Some("a"));
452 /// assert_eq!(map.remove(&1), None);
454 #[stable(feature = "rust1", since = "1.0.0")]
455 pub fn remove<Q: ?Sized>(&mut self, key: &Q) -> Option<V>
459 // See `swap` for a more thorough description of the stuff going on in here
460 let mut stack = stack::PartialSearchStack::new(self);
462 let result = stack.with(move |pusher, node| {
463 match Node::search(node, key) {
465 // Perfect match. Terminate the stack here, and remove the entry
466 Finished(Some(pusher.seal(handle).remove()))
469 // We need to keep searching, try to go down the next edge
470 match handle.force() {
471 // We're at a leaf; the key isn't in here
472 Leaf(_) => Finished(None),
473 Internal(internal_handle) => Continue(pusher.push(internal_handle)),
479 Finished(ret) => return ret.map(|(_, v)| v),
480 Continue(new_stack) => stack = new_stack,
486 #[stable(feature = "rust1", since = "1.0.0")]
487 impl<K, V> IntoIterator for BTreeMap<K, V> {
489 type IntoIter = IntoIter<K, V>;
491 /// Gets an owning iterator over the entries of the map.
496 /// use std::collections::BTreeMap;
498 /// let mut map = BTreeMap::new();
499 /// map.insert(1, "a");
500 /// map.insert(2, "b");
501 /// map.insert(3, "c");
503 /// for (key, value) in map.into_iter() {
504 /// println!("{}: {}", key, value);
507 fn into_iter(self) -> IntoIter<K, V> {
508 let len = self.len();
509 let mut lca = VecDeque::new();
510 lca.push_back(Traverse::traverse(self.root));
520 #[stable(feature = "rust1", since = "1.0.0")]
521 impl<'a, K, V> IntoIterator for &'a BTreeMap<K, V> {
522 type Item = (&'a K, &'a V);
523 type IntoIter = Iter<'a, K, V>;
525 fn into_iter(self) -> Iter<'a, K, V> {
530 #[stable(feature = "rust1", since = "1.0.0")]
531 impl<'a, K, V> IntoIterator for &'a mut BTreeMap<K, V> {
532 type Item = (&'a K, &'a mut V);
533 type IntoIter = IterMut<'a, K, V>;
535 fn into_iter(mut self) -> IterMut<'a, K, V> {
540 /// A helper enum useful for deciding whether to continue a loop since we can't
541 /// return from a closure
542 enum Continuation<A, B> {
547 /// The stack module provides a safe interface for constructing and manipulating a stack of ptrs
548 /// to nodes. By using this module much better safety guarantees can be made, and more search
549 /// boilerplate gets cut out.
553 use core::ops::{Deref, DerefMut};
555 use super::super::node::{self, Node, Fit, Split, Internal, Leaf};
556 use super::super::node::handle;
559 struct InvariantLifetime<'id>(marker::PhantomData<::core::cell::Cell<&'id ()>>);
561 impl<'id> InvariantLifetime<'id> {
562 fn new() -> InvariantLifetime<'id> {
563 InvariantLifetime(marker::PhantomData)
567 /// A generic mutable reference, identical to `&mut` except for the fact that its lifetime
568 /// parameter is invariant. This means that wherever an `IdRef` is expected, only an `IdRef`
569 /// with the exact requested lifetime can be used. This is in contrast to normal references,
570 /// where `&'static` can be used in any function expecting any lifetime reference.
571 pub struct IdRef<'id, T: 'id> {
573 _marker: InvariantLifetime<'id>,
576 impl<'id, T> Deref for IdRef<'id, T> {
579 fn deref(&self) -> &T {
584 impl<'id, T> DerefMut for IdRef<'id, T> {
585 fn deref_mut(&mut self) -> &mut T {
590 type StackItem<K, V> = node::Handle<*mut Node<K, V>, handle::Edge, handle::Internal>;
591 type Stack<K, V> = Vec<StackItem<K, V>>;
593 /// A `PartialSearchStack` handles the construction of a search stack.
594 pub struct PartialSearchStack<'a, K: 'a, V: 'a> {
595 map: &'a mut BTreeMap<K, V>,
597 next: *mut Node<K, V>,
600 /// A `SearchStack` represents a full path to an element or an edge of interest. It provides
601 /// methods depending on the type of what the path points to for removing an element, inserting
602 /// a new element, and manipulating to element at the top of the stack.
603 pub struct SearchStack<'a, K: 'a, V: 'a, Type, NodeType> {
604 map: &'a mut BTreeMap<K, V>,
606 top: node::Handle<*mut Node<K, V>, Type, NodeType>,
609 /// A `PartialSearchStack` that doesn't hold a reference to the next node, and is just
610 /// just waiting for a `Handle` to that next node to be pushed. See `PartialSearchStack::with`
611 /// for more details.
612 pub struct Pusher<'id, 'a, K: 'a, V: 'a> {
613 map: &'a mut BTreeMap<K, V>,
615 _marker: InvariantLifetime<'id>,
618 impl<'a, K, V> PartialSearchStack<'a, K, V> {
619 /// Creates a new PartialSearchStack from a BTreeMap by initializing the stack with the
620 /// root of the tree.
621 pub fn new(map: &'a mut BTreeMap<K, V>) -> PartialSearchStack<'a, K, V> {
622 let depth = map.depth;
625 next: &mut map.root as *mut _,
627 stack: Vec::with_capacity(depth),
631 /// Breaks up the stack into a `Pusher` and the next `Node`, allowing the given closure
632 /// to interact with, search, and finally push the `Node` onto the stack. The passed in
633 /// closure must be polymorphic on the `'id` lifetime parameter, as this statically
634 /// ensures that only `Handle`s from the correct `Node` can be pushed.
636 /// The reason this works is that the `Pusher` has an `'id` parameter, and will only accept
637 /// handles with the same `'id`. The closure could only get references with that lifetime
638 /// through its arguments or through some other `IdRef` that it has lying around. However,
639 /// no other `IdRef` could possibly work - because the `'id` is held in an invariant
640 /// parameter, it would need to have precisely the correct lifetime, which would mean that
641 /// at least one of the calls to `with` wouldn't be properly polymorphic, wanting a
642 /// specific lifetime instead of the one that `with` chooses to give it.
644 /// See also Haskell's `ST` monad, which uses a similar trick.
645 pub fn with<T, F: for<'id> FnOnce(Pusher<'id, 'a, K, V>,
646 IdRef<'id, Node<K, V>>) -> T>(self, closure: F) -> T {
647 let pusher = Pusher {
650 _marker: InvariantLifetime::new(),
653 inner: unsafe { &mut *self.next },
654 _marker: InvariantLifetime::new(),
657 closure(pusher, node)
661 impl<'id, 'a, K, V> Pusher<'id, 'a, K, V> {
662 /// Pushes the requested child of the stack's current top on top of the stack. If the child
663 /// exists, then a new PartialSearchStack is yielded. Otherwise, a VacantSearchStack is
665 pub fn push(mut self,
666 mut edge: node::Handle<IdRef<'id, Node<K, V>>, handle::Edge, handle::Internal>)
667 -> PartialSearchStack<'a, K, V> {
668 self.stack.push(edge.as_raw());
672 next: edge.edge_mut() as *mut _,
676 /// Converts the PartialSearchStack into a SearchStack.
677 pub fn seal<Type, NodeType>(self,
678 mut handle: node::Handle<IdRef<'id, Node<K, V>>,
681 -> SearchStack<'a, K, V, Type, NodeType> {
685 top: handle.as_raw(),
690 impl<'a, K, V, NodeType> SearchStack<'a, K, V, handle::KV, NodeType> {
691 /// Gets a reference to the value the stack points to.
692 pub fn peek(&self) -> &V {
693 unsafe { self.top.from_raw().into_kv().1 }
696 /// Gets a mutable reference to the value the stack points to.
697 pub fn peek_mut(&mut self) -> &mut V {
698 unsafe { self.top.from_raw_mut().into_kv_mut().1 }
701 /// Converts the stack into a mutable reference to the value it points to, with a lifetime
702 /// tied to the original tree.
703 pub fn into_top(mut self) -> &'a mut V {
704 unsafe { &mut *(self.top.from_raw_mut().val_mut() as *mut V) }
708 impl<'a, K, V> SearchStack<'a, K, V, handle::KV, handle::Leaf> {
709 /// Removes the key and value in the top element of the stack, then handles underflows as
710 /// described in BTree's pop function.
711 fn remove_leaf(mut self) -> (K, V) {
712 self.map.length -= 1;
714 // Remove the key-value pair from the leaf that this search stack points to.
715 // Then, note if the leaf is underfull, and promptly forget the leaf and its ptr
716 // to avoid ownership issues.
717 let (key_val, mut underflow) = unsafe {
718 let key_val = self.top.from_raw_mut().remove_as_leaf();
719 let underflow = self.top.from_raw().node().is_underfull();
724 match self.stack.pop() {
726 // We've reached the root, so no matter what, we're done. We manually
727 // access the root via the tree itself to avoid creating any dangling
729 if self.map.root.is_empty() && !self.map.root.is_leaf() {
730 // We've emptied out the root, so make its only child the new root.
731 // If it's a leaf, we just let it become empty.
733 self.map.root.hoist_lone_child();
737 Some(mut handle) => {
739 // Underflow! Handle it!
741 handle.from_raw_mut().handle_underflow();
742 underflow = handle.from_raw().node().is_underfull();
754 impl<'a, K, V> SearchStack<'a, K, V, handle::KV, handle::LeafOrInternal> {
755 /// Removes the key and value in the top element of the stack, then handles underflows as
756 /// described in BTree's pop function.
757 pub fn remove(self) -> (K, V) {
758 // Ensure that the search stack goes to a leaf. This is necessary to perform deletion
759 // in a BTree. Note that this may put the tree in an inconsistent state (further
760 // described in into_leaf's comments), but this is immediately fixed by the
761 // removing the value we want to remove
762 self.into_leaf().remove_leaf()
765 /// Subroutine for removal. Takes a search stack for a key that might terminate at an
766 /// internal node, and mutates the tree and search stack to *make* it a search stack
767 /// for that same key that *does* terminates at a leaf. If the mutation occurs, then this
768 /// leaves the tree in an inconsistent state that must be repaired by the caller by
769 /// removing the entry in question. Specifically the key-value pair and its successor will
771 fn into_leaf(mut self) -> SearchStack<'a, K, V, handle::KV, handle::Leaf> {
773 let mut top_raw = self.top;
774 let mut top = top_raw.from_raw_mut();
776 let key_ptr = top.key_mut() as *mut _;
777 let val_ptr = top.val_mut() as *mut _;
779 // Try to go into the right subtree of the found key to find its successor
781 Leaf(mut leaf_handle) => {
782 // We're a proper leaf stack, nothing to do
786 top: leaf_handle.as_raw(),
789 Internal(mut internal_handle) => {
790 let mut right_handle = internal_handle.right_edge();
792 // We're not a proper leaf stack, let's get to work.
793 self.stack.push(right_handle.as_raw());
795 let mut temp_node = right_handle.edge_mut();
797 // Walk into the smallest subtree of this node
798 let node = temp_node;
800 match node.kv_handle(0).force() {
801 Leaf(mut handle) => {
802 // This node is a leaf, do the swap and return
803 mem::swap(handle.key_mut(), &mut *key_ptr);
804 mem::swap(handle.val_mut(), &mut *val_ptr);
808 top: handle.as_raw(),
811 Internal(kv_handle) => {
812 // This node is internal, go deeper
813 let mut handle = kv_handle.into_left_edge();
814 self.stack.push(handle.as_raw());
815 temp_node = handle.into_edge_mut();
825 impl<'a, K, V> SearchStack<'a, K, V, handle::Edge, handle::Leaf> {
826 /// Inserts the key and value into the top element in the stack, and if that node has to
827 /// split recursively inserts the split contents into the next element stack until
830 /// Assumes that the stack represents a search path from the root to a leaf.
832 /// An &mut V is returned to the inserted value, for callers that want a reference to this.
833 pub fn insert(mut self, key: K, val: V) -> &'a mut V {
835 self.map.length += 1;
837 // Insert the key and value into the leaf at the top of the stack
838 let (mut insertion, inserted_ptr) = self.top
840 .insert_as_leaf(key, val);
845 // The last insertion went off without a hitch, no splits! We can stop
847 return &mut *inserted_ptr;
849 Split(key, val, right) => {
850 match self.stack.pop() {
851 // The last insertion triggered a split, so get the next element on
852 // the stack to recursively insert the split node into.
854 // The stack was empty; we've split the root, and need to make a
855 // a new one. This is done in-place because we can't move the
856 // root out of a reference to the tree.
857 Node::make_internal_root(&mut self.map.root,
864 return &mut *inserted_ptr;
866 Some(mut handle) => {
867 // The stack wasn't empty, do the insertion and recurse
868 insertion = handle.from_raw_mut()
869 .insert_as_internal(key, val, right);
881 #[stable(feature = "rust1", since = "1.0.0")]
882 impl<K: Ord, V> FromIterator<(K, V)> for BTreeMap<K, V> {
883 fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> BTreeMap<K, V> {
884 let mut map = BTreeMap::new();
890 #[stable(feature = "rust1", since = "1.0.0")]
891 impl<K: Ord, V> Extend<(K, V)> for BTreeMap<K, V> {
893 fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T) {
900 #[stable(feature = "extend_ref", since = "1.2.0")]
901 impl<'a, K: Ord + Copy, V: Copy> Extend<(&'a K, &'a V)> for BTreeMap<K, V> {
902 fn extend<I: IntoIterator<Item = (&'a K, &'a V)>>(&mut self, iter: I) {
903 self.extend(iter.into_iter().map(|(&key, &value)| (key, value)));
907 #[stable(feature = "rust1", since = "1.0.0")]
908 impl<K: Hash, V: Hash> Hash for BTreeMap<K, V> {
909 fn hash<H: Hasher>(&self, state: &mut H) {
916 #[stable(feature = "rust1", since = "1.0.0")]
917 impl<K: Ord, V> Default for BTreeMap<K, V> {
918 fn default() -> BTreeMap<K, V> {
923 #[stable(feature = "rust1", since = "1.0.0")]
924 impl<K: PartialEq, V: PartialEq> PartialEq for BTreeMap<K, V> {
925 fn eq(&self, other: &BTreeMap<K, V>) -> bool {
926 self.len() == other.len() && self.iter().zip(other).all(|(a, b)| a == b)
930 #[stable(feature = "rust1", since = "1.0.0")]
931 impl<K: Eq, V: Eq> Eq for BTreeMap<K, V> {}
933 #[stable(feature = "rust1", since = "1.0.0")]
934 impl<K: PartialOrd, V: PartialOrd> PartialOrd for BTreeMap<K, V> {
936 fn partial_cmp(&self, other: &BTreeMap<K, V>) -> Option<Ordering> {
937 self.iter().partial_cmp(other.iter())
941 #[stable(feature = "rust1", since = "1.0.0")]
942 impl<K: Ord, V: Ord> Ord for BTreeMap<K, V> {
944 fn cmp(&self, other: &BTreeMap<K, V>) -> Ordering {
945 self.iter().cmp(other.iter())
949 #[stable(feature = "rust1", since = "1.0.0")]
950 impl<K: Debug, V: Debug> Debug for BTreeMap<K, V> {
951 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
952 f.debug_map().entries(self.iter()).finish()
956 #[stable(feature = "rust1", since = "1.0.0")]
957 impl<'a, K: Ord, Q: ?Sized, V> Index<&'a Q> for BTreeMap<K, V>
964 fn index(&self, key: &Q) -> &V {
965 self.get(key).expect("no entry found for key")
969 /// Genericizes over how to get the correct type of iterator from the correct type
970 /// of Node ownership.
972 fn traverse(node: N) -> Self;
975 impl<'a, K, V> Traverse<&'a Node<K, V>> for Traversal<'a, K, V> {
976 fn traverse(node: &'a Node<K, V>) -> Traversal<'a, K, V> {
981 impl<'a, K, V> Traverse<&'a mut Node<K, V>> for MutTraversal<'a, K, V> {
982 fn traverse(node: &'a mut Node<K, V>) -> MutTraversal<'a, K, V> {
987 impl<K, V> Traverse<Node<K, V>> for MoveTraversal<K, V> {
988 fn traverse(node: Node<K, V>) -> MoveTraversal<K, V> {
993 /// Represents an operation to perform inside the following iterator methods.
994 /// This is necessary to use in `next` because we want to modify `self.traversals` inside
995 /// a match that borrows it. Similarly in `next_back`. Instead, we use this enum to note
996 /// what we want to do, and do it after the match.
1001 impl<K, V, E, T> Iterator for AbsIter<T>
1002 where T: DoubleEndedIterator<Item = TraversalItem<K, V, E>> + Traverse<E>
1006 // Our iterator represents a queue of all ancestors of elements we have
1007 // yet to yield, from smallest to largest. Note that the design of these
1008 // iterators permits an *arbitrary* initial pair of min and max, making
1009 // these arbitrary sub-range iterators.
1010 fn next(&mut self) -> Option<(K, V)> {
1012 // We want the smallest element, so try to get the back of the queue
1013 let op = match self.traversals.back_mut() {
1014 None => return None,
1015 // The queue wasn't empty, so continue along the node in its head
1018 // The head is empty, so Pop it off and continue the process
1020 // The head yielded an edge, so make that the new head
1021 Some(Edge(next)) => Push(Traverse::traverse(next)),
1022 // The head yielded an entry, so yield that
1031 // Handle any operation as necessary, without a conflicting borrow of the queue
1034 self.traversals.push_back(item);
1037 self.traversals.pop_back();
1043 fn size_hint(&self) -> (usize, Option<usize>) {
1044 (self.size, Some(self.size))
1048 impl<K, V, E, T> DoubleEndedIterator for AbsIter<T>
1049 where T: DoubleEndedIterator<Item = TraversalItem<K, V, E>> + Traverse<E>
1051 // next_back is totally symmetric to next
1053 fn next_back(&mut self) -> Option<(K, V)> {
1055 let op = match self.traversals.front_mut() {
1056 None => return None,
1058 match iter.next_back() {
1060 Some(Edge(next)) => Push(Traverse::traverse(next)),
1071 self.traversals.push_front(item);
1074 self.traversals.pop_front();
1081 impl<'a, K, V> Clone for Iter<'a, K, V> {
1082 fn clone(&self) -> Iter<'a, K, V> {
1083 Iter { inner: self.inner.clone() }
1086 #[stable(feature = "rust1", since = "1.0.0")]
1087 impl<'a, K, V> Iterator for Iter<'a, K, V> {
1088 type Item = (&'a K, &'a V);
1090 fn next(&mut self) -> Option<(&'a K, &'a V)> {
1093 fn size_hint(&self) -> (usize, Option<usize>) {
1094 self.inner.size_hint()
1097 #[stable(feature = "rust1", since = "1.0.0")]
1098 impl<'a, K, V> DoubleEndedIterator for Iter<'a, K, V> {
1099 fn next_back(&mut self) -> Option<(&'a K, &'a V)> {
1100 self.inner.next_back()
1103 #[stable(feature = "rust1", since = "1.0.0")]
1104 impl<'a, K, V> ExactSizeIterator for Iter<'a, K, V> {}
1106 #[stable(feature = "rust1", since = "1.0.0")]
1107 impl<'a, K, V> Iterator for IterMut<'a, K, V> {
1108 type Item = (&'a K, &'a mut V);
1110 fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
1113 fn size_hint(&self) -> (usize, Option<usize>) {
1114 self.inner.size_hint()
1117 #[stable(feature = "rust1", since = "1.0.0")]
1118 impl<'a, K, V> DoubleEndedIterator for IterMut<'a, K, V> {
1119 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> {
1120 self.inner.next_back()
1123 #[stable(feature = "rust1", since = "1.0.0")]
1124 impl<'a, K, V> ExactSizeIterator for IterMut<'a, K, V> {}
1126 #[stable(feature = "rust1", since = "1.0.0")]
1127 impl<K, V> Iterator for IntoIter<K, V> {
1130 fn next(&mut self) -> Option<(K, V)> {
1133 fn size_hint(&self) -> (usize, Option<usize>) {
1134 self.inner.size_hint()
1137 #[stable(feature = "rust1", since = "1.0.0")]
1138 impl<K, V> DoubleEndedIterator for IntoIter<K, V> {
1139 fn next_back(&mut self) -> Option<(K, V)> {
1140 self.inner.next_back()
1143 #[stable(feature = "rust1", since = "1.0.0")]
1144 impl<K, V> ExactSizeIterator for IntoIter<K, V> {}
1146 impl<'a, K, V> Clone for Keys<'a, K, V> {
1147 fn clone(&self) -> Keys<'a, K, V> {
1148 Keys { inner: self.inner.clone() }
1151 #[stable(feature = "rust1", since = "1.0.0")]
1152 impl<'a, K, V> Iterator for Keys<'a, K, V> {
1155 fn next(&mut self) -> Option<(&'a K)> {
1158 fn size_hint(&self) -> (usize, Option<usize>) {
1159 self.inner.size_hint()
1162 #[stable(feature = "rust1", since = "1.0.0")]
1163 impl<'a, K, V> DoubleEndedIterator for Keys<'a, K, V> {
1164 fn next_back(&mut self) -> Option<(&'a K)> {
1165 self.inner.next_back()
1168 #[stable(feature = "rust1", since = "1.0.0")]
1169 impl<'a, K, V> ExactSizeIterator for Keys<'a, K, V> {}
1172 impl<'a, K, V> Clone for Values<'a, K, V> {
1173 fn clone(&self) -> Values<'a, K, V> {
1174 Values { inner: self.inner.clone() }
1177 #[stable(feature = "rust1", since = "1.0.0")]
1178 impl<'a, K, V> Iterator for Values<'a, K, V> {
1181 fn next(&mut self) -> Option<(&'a V)> {
1184 fn size_hint(&self) -> (usize, Option<usize>) {
1185 self.inner.size_hint()
1188 #[stable(feature = "rust1", since = "1.0.0")]
1189 impl<'a, K, V> DoubleEndedIterator for Values<'a, K, V> {
1190 fn next_back(&mut self) -> Option<(&'a V)> {
1191 self.inner.next_back()
1194 #[stable(feature = "rust1", since = "1.0.0")]
1195 impl<'a, K, V> ExactSizeIterator for Values<'a, K, V> {}
1197 impl<'a, K, V> Clone for Range<'a, K, V> {
1198 fn clone(&self) -> Range<'a, K, V> {
1199 Range { inner: self.inner.clone() }
1202 impl<'a, K, V> Iterator for Range<'a, K, V> {
1203 type Item = (&'a K, &'a V);
1205 fn next(&mut self) -> Option<(&'a K, &'a V)> {
1209 impl<'a, K, V> DoubleEndedIterator for Range<'a, K, V> {
1210 fn next_back(&mut self) -> Option<(&'a K, &'a V)> {
1211 self.inner.next_back()
1215 impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
1216 type Item = (&'a K, &'a mut V);
1218 fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
1222 impl<'a, K, V> DoubleEndedIterator for RangeMut<'a, K, V> {
1223 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> {
1224 self.inner.next_back()
1228 impl<'a, K: Ord, V> Entry<'a, K, V> {
1229 #[stable(feature = "rust1", since = "1.0.0")]
1230 /// Ensures a value is in the entry by inserting the default if empty, and returns
1231 /// a mutable reference to the value in the entry.
1232 pub fn or_insert(self, default: V) -> &'a mut V {
1234 Occupied(entry) => entry.into_mut(),
1235 Vacant(entry) => entry.insert(default),
1239 #[stable(feature = "rust1", since = "1.0.0")]
1240 /// Ensures a value is in the entry by inserting the result of the default function if empty,
1241 /// and returns a mutable reference to the value in the entry.
1242 pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V {
1244 Occupied(entry) => entry.into_mut(),
1245 Vacant(entry) => entry.insert(default()),
1250 impl<'a, K: Ord, V> VacantEntry<'a, K, V> {
1251 /// Sets the value of the entry with the VacantEntry's key,
1252 /// and returns a mutable reference to it.
1253 #[stable(feature = "rust1", since = "1.0.0")]
1254 pub fn insert(self, value: V) -> &'a mut V {
1255 self.stack.insert(self.key, value)
1259 impl<'a, K: Ord, V> OccupiedEntry<'a, K, V> {
1260 /// Gets a reference to the value in the entry.
1261 #[stable(feature = "rust1", since = "1.0.0")]
1262 pub fn get(&self) -> &V {
1266 /// Gets a mutable reference to the value in the entry.
1267 #[stable(feature = "rust1", since = "1.0.0")]
1268 pub fn get_mut(&mut self) -> &mut V {
1269 self.stack.peek_mut()
1272 /// Converts the entry into a mutable reference to its value.
1273 #[stable(feature = "rust1", since = "1.0.0")]
1274 pub fn into_mut(self) -> &'a mut V {
1275 self.stack.into_top()
1278 /// Sets the value of the entry with the OccupiedEntry's key,
1279 /// and returns the entry's old value.
1280 #[stable(feature = "rust1", since = "1.0.0")]
1281 pub fn insert(&mut self, mut value: V) -> V {
1282 mem::swap(self.stack.peek_mut(), &mut value);
1286 /// Takes the value of the entry out of the map, and returns it.
1287 #[stable(feature = "rust1", since = "1.0.0")]
1288 pub fn remove(self) -> V {
1289 self.stack.remove().1
1293 impl<K, V> BTreeMap<K, V> {
1294 /// Gets an iterator over the entries of the map.
1299 /// use std::collections::BTreeMap;
1301 /// let mut map = BTreeMap::new();
1302 /// map.insert(1, "a");
1303 /// map.insert(2, "b");
1304 /// map.insert(3, "c");
1306 /// for (key, value) in map.iter() {
1307 /// println!("{}: {}", key, value);
1310 /// let (first_key, first_value) = map.iter().next().unwrap();
1311 /// assert_eq!((*first_key, *first_value), (1, "a"));
1313 #[stable(feature = "rust1", since = "1.0.0")]
1314 pub fn iter(&self) -> Iter<K, V> {
1315 let len = self.len();
1316 // NB. The initial capacity for ringbuf is large enough to avoid reallocs in many cases.
1317 let mut lca = VecDeque::new();
1318 lca.push_back(Traverse::traverse(&self.root));
1327 /// Gets a mutable iterator over the entries of the map.
1332 /// use std::collections::BTreeMap;
1334 /// let mut map = BTreeMap::new();
1335 /// map.insert("a", 1);
1336 /// map.insert("b", 2);
1337 /// map.insert("c", 3);
1339 /// // add 10 to the value if the key isn't "a"
1340 /// for (key, value) in map.iter_mut() {
1341 /// if key != &"a" {
1346 #[stable(feature = "rust1", since = "1.0.0")]
1347 pub fn iter_mut(&mut self) -> IterMut<K, V> {
1348 let len = self.len();
1349 let mut lca = VecDeque::new();
1350 lca.push_back(Traverse::traverse(&mut self.root));
1359 /// Gets an iterator over the keys of the map.
1364 /// use std::collections::BTreeMap;
1366 /// let mut a = BTreeMap::new();
1367 /// a.insert(1, "a");
1368 /// a.insert(2, "b");
1370 /// let keys: Vec<_> = a.keys().cloned().collect();
1371 /// assert_eq!(keys, [1, 2]);
1373 #[stable(feature = "rust1", since = "1.0.0")]
1374 pub fn keys<'a>(&'a self) -> Keys<'a, K, V> {
1375 fn first<A, B>((a, _): (A, B)) -> A {
1378 let first: fn((&'a K, &'a V)) -> &'a K = first; // coerce to fn pointer
1380 Keys { inner: self.iter().map(first) }
1383 /// Gets an iterator over the values of the map.
1388 /// use std::collections::BTreeMap;
1390 /// let mut a = BTreeMap::new();
1391 /// a.insert(1, "a");
1392 /// a.insert(2, "b");
1394 /// let values: Vec<&str> = a.values().cloned().collect();
1395 /// assert_eq!(values, ["a", "b"]);
1397 #[stable(feature = "rust1", since = "1.0.0")]
1398 pub fn values<'a>(&'a self) -> Values<'a, K, V> {
1399 fn second<A, B>((_, b): (A, B)) -> B {
1402 let second: fn((&'a K, &'a V)) -> &'a V = second; // coerce to fn pointer
1404 Values { inner: self.iter().map(second) }
1407 /// Returns the number of elements in the map.
1412 /// use std::collections::BTreeMap;
1414 /// let mut a = BTreeMap::new();
1415 /// assert_eq!(a.len(), 0);
1416 /// a.insert(1, "a");
1417 /// assert_eq!(a.len(), 1);
1419 #[stable(feature = "rust1", since = "1.0.0")]
1420 pub fn len(&self) -> usize {
1424 /// Returns true if the map contains no elements.
1429 /// use std::collections::BTreeMap;
1431 /// let mut a = BTreeMap::new();
1432 /// assert!(a.is_empty());
1433 /// a.insert(1, "a");
1434 /// assert!(!a.is_empty());
1436 #[stable(feature = "rust1", since = "1.0.0")]
1437 pub fn is_empty(&self) -> bool {
1442 macro_rules! range_impl {
1443 ($root:expr, $min:expr, $max:expr, $as_slices_internal:ident, $iter:ident, $Range:ident,
1444 $edges:ident, [$($mutability:ident)*]) => (
1446 // A deque that encodes two search paths containing (left-to-right):
1447 // a series of truncated-from-the-left iterators, the LCA's doubly-truncated iterator,
1448 // and a series of truncated-from-the-right iterators.
1449 let mut traversals = VecDeque::new();
1450 let (root, min, max) = ($root, $min, $max);
1452 let mut leftmost = None;
1453 let mut rightmost = None;
1455 match (&min, &max) {
1456 (&Unbounded, &Unbounded) => {
1457 traversals.push_back(Traverse::traverse(root))
1459 (&Unbounded, &Included(_)) | (&Unbounded, &Excluded(_)) => {
1460 rightmost = Some(root);
1462 (&Included(_), &Unbounded) | (&Excluded(_), &Unbounded) => {
1463 leftmost = Some(root);
1465 (&Included(min_key), &Included(max_key))
1466 | (&Included(min_key), &Excluded(max_key))
1467 | (&Excluded(min_key), &Included(max_key))
1468 | (&Excluded(min_key), &Excluded(max_key)) => {
1469 // lca represents the Lowest Common Ancestor, above which we never
1470 // walk, since everything else is outside the range to iterate.
1471 // ___________________
1472 // |__0_|_80_|_85_|_90_| (root)
1476 // ___________________
1477 // |__5_|_15_|_30_|_73_|
1481 // ___________________
1482 // |_33_|_58_|_63_|_68_| lca for the range [41, 65]
1483 // | |\___|___/| | iterator at traversals[2]
1488 let mut is_leaf = root.is_leaf();
1489 let mut lca = root.$as_slices_internal();
1491 let slice = lca.slice_from(min_key).slice_to(max_key);
1492 if let [ref $($mutability)* edge] = slice.edges {
1493 // Follow the only edge that leads the node that covers the range.
1494 is_leaf = edge.is_leaf();
1495 lca = edge.$as_slices_internal();
1497 let mut iter = slice.$iter();
1502 // Only change the state of nodes with edges.
1503 leftmost = iter.next_edge_item();
1504 rightmost = iter.next_edge_item_back();
1506 traversals.push_back(iter);
1512 // Keep narrowing the range by going down.
1513 // ___________________
1514 // |_38_|_43_|_48_|_53_|
1515 // | |____|____|____/ iterator at traversals[1]
1518 // ___________________
1519 // |_39_|_40_|_41_|_42_| (leaf, the last leftmost)
1520 // \_________| iterator at traversals[0]
1522 Included(key) | Excluded(key) =>
1523 while let Some(left) = leftmost {
1524 let is_leaf = left.is_leaf();
1525 let mut iter = left.$as_slices_internal().slice_from(key).$iter();
1526 leftmost = if is_leaf {
1529 // Only change the state of nodes with edges.
1530 iter.next_edge_item()
1532 traversals.push_back(iter);
1536 // If the leftmost iterator starts with an element, then it was an exact match.
1537 if let (Excluded(_), Some(leftmost_iter)) = (min, traversals.back_mut()) {
1538 // Drop this excluded element. `next_kv_item` has no effect when
1539 // the next item is an edge.
1540 leftmost_iter.next_kv_item();
1543 // The code for the right side is similar.
1545 Included(key) | Excluded(key) =>
1546 while let Some(right) = rightmost {
1547 let is_leaf = right.is_leaf();
1548 let mut iter = right.$as_slices_internal().slice_to(key).$iter();
1549 rightmost = if is_leaf {
1552 iter.next_edge_item_back()
1554 traversals.push_front(iter);
1558 if let (Excluded(_), Some(rightmost_iter)) = (max, traversals.front_mut()) {
1559 rightmost_iter.next_kv_item_back();
1564 traversals: traversals,
1565 size: usize::MAX, // unused
1572 impl<K: Ord, V> BTreeMap<K, V> {
1573 /// Constructs a double-ended iterator over a sub-range of elements in the map, starting
1574 /// at min, and ending at max. If min is `Unbounded`, then it will be treated as "negative
1575 /// infinity", and if max is `Unbounded`, then it will be treated as "positive infinity".
1576 /// Thus range(Unbounded, Unbounded) will yield the whole collection.
1581 /// #![feature(btree_range, collections_bound)]
1583 /// use std::collections::BTreeMap;
1584 /// use std::collections::Bound::{Included, Unbounded};
1586 /// let mut map = BTreeMap::new();
1587 /// map.insert(3, "a");
1588 /// map.insert(5, "b");
1589 /// map.insert(8, "c");
1590 /// for (&key, &value) in map.range(Included(&4), Included(&8)) {
1591 /// println!("{}: {}", key, value);
1593 /// assert_eq!(Some((&5, &"b")), map.range(Included(&4), Unbounded).next());
1595 #[unstable(feature = "btree_range",
1596 reason = "matches collection reform specification, waiting for dust to settle",
1598 pub fn range<Min: ?Sized + Ord, Max: ?Sized + Ord>(&self,
1602 where K: Borrow<Min> + Borrow<Max>
1604 range_impl!(&self.root,
1614 /// Constructs a mutable double-ended iterator over a sub-range of elements in the map, starting
1615 /// at min, and ending at max. If min is `Unbounded`, then it will be treated as "negative
1616 /// infinity", and if max is `Unbounded`, then it will be treated as "positive infinity".
1617 /// Thus range(Unbounded, Unbounded) will yield the whole collection.
1622 /// #![feature(btree_range, collections_bound)]
1624 /// use std::collections::BTreeMap;
1625 /// use std::collections::Bound::{Included, Excluded};
1627 /// let mut map: BTreeMap<&str, i32> = ["Alice", "Bob", "Carol", "Cheryl"].iter()
1628 /// .map(|&s| (s, 0))
1630 /// for (_, balance) in map.range_mut(Included("B"), Excluded("Cheryl")) {
1631 /// *balance += 100;
1633 /// for (name, balance) in &map {
1634 /// println!("{} => {}", name, balance);
1637 #[unstable(feature = "btree_range",
1638 reason = "matches collection reform specification, waiting for dust to settle",
1640 pub fn range_mut<Min: ?Sized + Ord, Max: ?Sized + Ord>(&mut self,
1644 where K: Borrow<Min> + Borrow<Max>
1646 range_impl!(&mut self.root,
1649 as_slices_internal_mut,
1656 /// Gets the given key's corresponding entry in the map for in-place manipulation.
1661 /// use std::collections::BTreeMap;
1663 /// let mut count: BTreeMap<&str, usize> = BTreeMap::new();
1665 /// // count the number of occurrences of letters in the vec
1666 /// for x in vec!["a","b","a","c","a","b"] {
1667 /// *count.entry(x).or_insert(0) += 1;
1670 /// assert_eq!(count["a"], 3);
1672 #[stable(feature = "rust1", since = "1.0.0")]
1673 pub fn entry(&mut self, mut key: K) -> Entry<K, V> {
1674 // same basic logic of `swap` and `pop`, blended together
1675 let mut stack = stack::PartialSearchStack::new(self);
1677 let result = stack.with(move |pusher, node| {
1678 match Node::search(node, &key) {
1681 Finished(Occupied(OccupiedEntry { stack: pusher.seal(handle) }))
1684 match handle.force() {
1685 Leaf(leaf_handle) => {
1686 Finished(Vacant(VacantEntry {
1687 stack: pusher.seal(leaf_handle),
1691 Internal(internal_handle) => {
1692 Continue((pusher.push(internal_handle), key))
1699 Finished(finished) => return finished,
1700 Continue((new_stack, renewed_key)) => {
1709 impl<K, Q: ?Sized> super::Recover<Q> for BTreeMap<K, ()>
1710 where K: Borrow<Q> + Ord,
1715 fn get(&self, key: &Q) -> Option<&K> {
1716 let mut cur_node = &self.root;
1718 match Node::search(cur_node, key) {
1719 Found(handle) => return Some(handle.into_kv().0),
1721 match handle.force() {
1722 Leaf(_) => return None,
1723 Internal(internal_handle) => {
1724 cur_node = internal_handle.into_edge();
1733 fn take(&mut self, key: &Q) -> Option<K> {
1734 // See `remove` for an explanation of this.
1736 let mut stack = stack::PartialSearchStack::new(self);
1738 let result = stack.with(move |pusher, node| {
1739 match Node::search(node, key) {
1741 // Perfect match. Terminate the stack here, and remove the entry
1742 Finished(Some(pusher.seal(handle).remove()))
1745 // We need to keep searching, try to go down the next edge
1746 match handle.force() {
1747 // We're at a leaf; the key isn't in here
1748 Leaf(_) => Finished(None),
1749 Internal(internal_handle) => Continue(pusher.push(internal_handle)),
1755 Finished(ret) => return ret.map(|(k, _)| k),
1756 Continue(new_stack) => stack = new_stack,
1761 fn replace(&mut self, mut key: K) -> Option<K> {
1762 // See `insert` for an explanation of this.
1764 let mut stack = stack::PartialSearchStack::new(self);
1767 let result = stack.with(move |pusher, node| {
1768 match Node::search::<K, _>(node, &key) {
1769 Found(mut handle) => {
1770 mem::swap(handle.key_mut(), &mut key);
1774 match handle.force() {
1775 Leaf(leaf_handle) => {
1776 pusher.seal(leaf_handle).insert(key, ());
1779 Internal(internal_handle) => {
1780 Continue((pusher.push(internal_handle), key, ()))
1787 Finished(ret) => return ret,
1788 Continue((new_stack, renewed_key, _)) => {