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/).
22 use core::borrow::BorrowFrom;
23 use core::cmp::Ordering;
24 use core::default::Default;
26 use core::hash::{Hash, Hasher};
27 use core::iter::{Map, FromIterator, IntoIterator};
28 use core::ops::{Index, IndexMut};
29 use core::{iter, fmt, mem};
30 use Bound::{self, Included, Excluded, Unbounded};
32 use ring_buf::RingBuf;
34 use self::Continuation::{Continue, Finished};
36 use super::node::ForceResult::{Leaf, Internal};
37 use super::node::TraversalItem::{self, Elem, Edge};
38 use super::node::{Traversal, MutTraversal, MoveTraversal};
39 use super::node::{self, Node, Found, GoDown};
41 /// A map based on a B-Tree.
43 /// B-Trees represent a fundamental compromise between cache-efficiency and actually minimizing
44 /// the amount of work performed in a search. In theory, a binary search tree (BST) is the optimal
45 /// choice for a sorted map, as a perfectly balanced BST performs the theoretical minimum amount of
46 /// comparisons necessary to find an element (log<sub>2</sub>n). However, in practice the way this
47 /// is done is *very* inefficient for modern computer architectures. In particular, every element
48 /// is stored in its own individually heap-allocated node. This means that every single insertion
49 /// triggers a heap-allocation, and every single comparison should be a cache-miss. Since these
50 /// are both notably expensive things to do in practice, we are forced to at very least reconsider
53 /// A B-Tree instead makes each node contain B-1 to 2B-1 elements in a contiguous array. By doing
54 /// this, we reduce the number of allocations by a factor of B, and improve cache efficiency in
55 /// searches. However, this does mean that searches will have to do *more* comparisons on average.
56 /// The precise number of comparisons depends on the node search strategy used. For optimal cache
57 /// efficiency, one could search the nodes linearly. For optimal comparisons, one could search
58 /// the node using binary search. As a compromise, one could also perform a linear search
59 /// that initially only checks every i<sup>th</sup> element for some choice of i.
61 /// Currently, our implementation simply performs naive linear search. This provides excellent
62 /// performance on *small* nodes of elements which are cheap to compare. However in the future we
63 /// would like to further explore choosing the optimal search strategy based on the choice of B,
64 /// and possibly other factors. Using linear search, searching for a random element is expected
65 /// to take O(B log<sub>B</sub>n) comparisons, which is generally worse than a BST. In practice,
66 /// however, performance is excellent.
68 #[stable(feature = "rust1", since = "1.0.0")]
69 pub struct BTreeMap<K, V> {
76 /// An abstract base over-which all other BTree iterators are built.
78 traversals: RingBuf<T>,
82 /// An iterator over a BTreeMap's entries.
83 #[stable(feature = "rust1", since = "1.0.0")]
84 pub struct Iter<'a, K: 'a, V: 'a> {
85 inner: AbsIter<Traversal<'a, K, V>>
88 /// A mutable iterator over a BTreeMap's entries.
89 #[stable(feature = "rust1", since = "1.0.0")]
90 pub struct IterMut<'a, K: 'a, V: 'a> {
91 inner: AbsIter<MutTraversal<'a, K, V>>
94 /// An owning iterator over a BTreeMap's entries.
95 #[stable(feature = "rust1", since = "1.0.0")]
96 pub struct IntoIter<K, V> {
97 inner: AbsIter<MoveTraversal<K, V>>
100 /// An iterator over a BTreeMap's keys.
101 #[stable(feature = "rust1", since = "1.0.0")]
102 pub struct Keys<'a, K: 'a, V: 'a> {
103 inner: Map<Iter<'a, K, V>, fn((&'a K, &'a V)) -> &'a K>
106 /// An iterator over a BTreeMap's values.
107 #[stable(feature = "rust1", since = "1.0.0")]
108 pub struct Values<'a, K: 'a, V: 'a> {
109 inner: Map<Iter<'a, K, V>, fn((&'a K, &'a V)) -> &'a V>
112 /// An iterator over a sub-range of BTreeMap's entries.
113 pub struct Range<'a, K: 'a, V: 'a> {
114 inner: AbsIter<Traversal<'a, K, V>>
117 /// A mutable iterator over a sub-range of BTreeMap's entries.
118 pub struct RangeMut<'a, K: 'a, V: 'a> {
119 inner: AbsIter<MutTraversal<'a, K, V>>
122 /// A view into a single entry in a map, which may either be vacant or occupied.
123 #[unstable(feature = "collections",
124 reason = "precise API still under development")]
125 pub enum Entry<'a, K:'a, V:'a> {
127 Vacant(VacantEntry<'a, K, V>),
128 /// An occupied Entry
129 Occupied(OccupiedEntry<'a, K, V>),
133 #[unstable(feature = "collections",
134 reason = "precise API still under development")]
135 pub struct VacantEntry<'a, K:'a, V:'a> {
137 stack: stack::SearchStack<'a, K, V, node::handle::Edge, node::handle::Leaf>,
140 /// An occupied Entry.
141 #[unstable(feature = "collections",
142 reason = "precise API still under development")]
143 pub struct OccupiedEntry<'a, K:'a, V:'a> {
144 stack: stack::SearchStack<'a, K, V, node::handle::KV, node::handle::LeafOrInternal>,
147 impl<K: Ord, V> BTreeMap<K, V> {
148 /// Makes a new empty BTreeMap with a reasonable choice for B.
149 #[stable(feature = "rust1", since = "1.0.0")]
150 pub fn new() -> BTreeMap<K, V> {
151 //FIXME(Gankro): Tune this as a function of size_of<K/V>?
155 /// Makes a new empty BTreeMap with the given B.
157 /// B cannot be less than 2.
158 pub fn with_b(b: usize) -> BTreeMap<K, V> {
159 assert!(b > 1, "B must be greater than 1");
163 root: Node::make_leaf_root(b),
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) {
183 // avoid recursive destructors by manually traversing the tree
184 for _ in mem::replace(self, BTreeMap::with_b(b)) {};
187 // Searching in a B-Tree is pretty straightforward.
189 // Start at the root. Try to find the key in the current node. If we find it, return it.
190 // If it's not in there, follow the edge *before* the smallest key larger than
191 // the search key. If no such key exists (they're *all* smaller), then just take the last
192 // edge in the node. If we're in a leaf and we don't find our key, then it's not
195 /// Returns a reference to the value corresponding to the key.
197 /// The key may be any borrowed form of the map's key type, but the ordering
198 /// on the borrowed form *must* match the ordering on the key type.
203 /// use std::collections::BTreeMap;
205 /// let mut map = BTreeMap::new();
206 /// map.insert(1, "a");
207 /// assert_eq!(map.get(&1), Some(&"a"));
208 /// assert_eq!(map.get(&2), None);
210 #[stable(feature = "rust1", since = "1.0.0")]
211 pub fn get<Q: ?Sized>(&self, key: &Q) -> Option<&V> where Q: BorrowFrom<K> + Ord {
212 let mut cur_node = &self.root;
214 match Node::search(cur_node, key) {
215 Found(handle) => return Some(handle.into_kv().1),
216 GoDown(handle) => match handle.force() {
217 Leaf(_) => return None,
218 Internal(internal_handle) => {
219 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 where Q: BorrowFrom<K> + Ord {
244 self.get(key).is_some()
247 /// Returns a mutable reference to the value corresponding to the key.
249 /// The key may be any borrowed form of the map's key type, but the ordering
250 /// on the borrowed form *must* match the ordering on the key type.
255 /// use std::collections::BTreeMap;
257 /// let mut map = BTreeMap::new();
258 /// map.insert(1, "a");
259 /// match map.get_mut(&1) {
260 /// Some(x) => *x = "b",
263 /// assert_eq!(map[1], "b");
265 // See `get` for implementation notes, this is basically a copy-paste with mut's added
266 #[stable(feature = "rust1", since = "1.0.0")]
267 pub fn get_mut<Q: ?Sized>(&mut self, key: &Q) -> Option<&mut V> where Q: BorrowFrom<K> + Ord {
268 // temp_node is a Borrowck hack for having a mutable value outlive a loop iteration
269 let mut temp_node = &mut self.root;
271 let cur_node = temp_node;
272 match Node::search(cur_node, key) {
273 Found(handle) => return Some(handle.into_kv_mut().1),
274 GoDown(handle) => match handle.force() {
275 Leaf(_) => return None,
276 Internal(internal_handle) => {
277 temp_node = internal_handle.into_edge_mut();
285 // Insertion in a B-Tree is a bit complicated.
287 // First we do the same kind of search described in `find`. But we need to maintain a stack of
288 // all the nodes/edges in our search path. If we find a match for the key we're trying to
289 // insert, just swap the vals and return the old ones. However, when we bottom out in a leaf,
290 // we attempt to insert our key-value pair at the same location we would want to follow another
293 // If the node has room, then this is done in the obvious way by shifting elements. However,
294 // if the node itself is full, we split node into two, and give its median key-value
295 // pair to its parent to insert the new node with. Of course, the parent may also be
296 // full, and insertion can propagate until we reach the root. If we reach the root, and
297 // it is *also* full, then we split the root and place the two nodes under a newly made root.
299 // Note that we subtly deviate from Open Data Structures in our implementation of split.
300 // ODS describes inserting into the node *regardless* of its capacity, and then
301 // splitting *afterwards* if it happens to be overfull. However, this is inefficient.
302 // Instead, we split beforehand, and then insert the key-value pair into the appropriate
303 // result node. This has two consequences:
305 // 1) While ODS produces a left node of size B-1, and a right node of size B,
306 // we may potentially reverse this. However, this shouldn't effect the analysis.
308 // 2) While ODS may potentially return the pair we *just* inserted after
309 // the split, we will never do this. Again, this shouldn't effect the analysis.
311 /// Inserts a key-value pair from the map. If the key already had a value
312 /// present in the map, that value is returned. Otherwise, `None` is returned.
317 /// use std::collections::BTreeMap;
319 /// let mut map = BTreeMap::new();
320 /// assert_eq!(map.insert(37, "a"), None);
321 /// assert_eq!(map.is_empty(), false);
323 /// map.insert(37, "b");
324 /// assert_eq!(map.insert(37, "c"), Some("b"));
325 /// assert_eq!(map[37], "c");
327 #[stable(feature = "rust1", since = "1.0.0")]
328 pub fn insert(&mut self, mut key: K, mut value: V) -> Option<V> {
329 // This is a stack of rawptrs to nodes paired with indices, respectively
330 // representing the nodes and edges of our search path. We have to store rawptrs
331 // because as far as Rust is concerned, we can mutate aliased data with such a
332 // stack. It is of course correct, but what it doesn't know is that we will only
333 // be popping and using these ptrs one at a time in child-to-parent order. The alternative
334 // to doing this is to take the Nodes from their parents. This actually makes
335 // borrowck *really* happy and everything is pretty smooth. However, this creates
336 // *tons* of pointless writes, and requires us to always walk all the way back to
337 // the root after an insertion, even if we only needed to change a leaf. Therefore,
338 // we accept this potential unsafety and complexity in the name of performance.
340 // Regardless, the actual dangerous logic is completely abstracted away from BTreeMap
341 // by the stack module. All it can do is immutably read nodes, and ask the search stack
342 // to proceed down some edge by index. This makes the search logic we'll be reusing in a
343 // few different methods much neater, and of course drastically improves safety.
344 let mut stack = stack::PartialSearchStack::new(self);
347 let result = stack.with(move |pusher, node| {
348 // Same basic logic as found in `find`, but with PartialSearchStack mediating the
349 // actual nodes for us
350 return match Node::search(node, &key) {
351 Found(mut handle) => {
352 // Perfect match, swap the values and return the old one
353 mem::swap(handle.val_mut(), &mut value);
354 Finished(Some(value))
357 // We need to keep searching, try to get the search stack
358 // to go down further
359 match handle.force() {
360 Leaf(leaf_handle) => {
361 // We've reached a leaf, perform the insertion here
362 pusher.seal(leaf_handle).insert(key, value);
365 Internal(internal_handle) => {
366 // We've found the subtree to insert this key/value pair in,
368 Continue((pusher.push(internal_handle), key, value))
375 Finished(ret) => { return ret; },
376 Continue((new_stack, renewed_key, renewed_val)) => {
385 // Deletion is the most complicated operation for a B-Tree.
387 // First we do the same kind of search described in
388 // `find`. But we need to maintain a stack of all the nodes/edges in our search path.
389 // If we don't find the key, then we just return `None` and do nothing. If we do find the
390 // key, we perform two operations: remove the item, and then possibly handle underflow.
392 // # removing the item
393 // If the node is a leaf, we just remove the item, and shift
394 // any items after it back to fill the hole.
396 // If the node is an internal node, we *swap* the item with the smallest item in
397 // in its right subtree (which must reside in a leaf), and then revert to the leaf
400 // # handling underflow
401 // After removing an item, there may be too few items in the node. We want nodes
402 // to be mostly full for efficiency, although we make an exception for the root, which
403 // may have as few as one item. If this is the case, we may first try to steal
404 // an item from our left or right neighbour.
406 // To steal from the left (right) neighbour,
407 // we take the largest (smallest) item and child from it. We then swap the taken item
408 // with the item in their mutual parent that separates them, and then insert the
409 // parent's item and the taken child into the first (last) index of the underflowed node.
411 // However, stealing has the possibility of underflowing our neighbour. If this is the
412 // case, we instead *merge* with our neighbour. This of course reduces the number of
413 // children in the parent. Therefore, we also steal the item that separates the now
414 // merged nodes, and insert it into the merged node.
416 // Merging may cause the parent to underflow. If this is the case, then we must repeat
417 // the underflow handling process on the parent. If merging merges the last two children
418 // of the root, then we replace the root with the merged node.
420 /// Removes a key from the map, returning the value at the key if the key
421 /// was previously in the map.
423 /// The key may be any borrowed form of the map's key type, but the ordering
424 /// on the borrowed form *must* match the ordering on the key type.
429 /// use std::collections::BTreeMap;
431 /// let mut map = BTreeMap::new();
432 /// map.insert(1, "a");
433 /// assert_eq!(map.remove(&1), Some("a"));
434 /// assert_eq!(map.remove(&1), None);
436 #[stable(feature = "rust1", since = "1.0.0")]
437 pub fn remove<Q: ?Sized>(&mut self, key: &Q) -> Option<V> where Q: BorrowFrom<K> + Ord {
438 // See `swap` for a more thorough description of the stuff going on in here
439 let mut stack = stack::PartialSearchStack::new(self);
441 let result = stack.with(move |pusher, node| {
442 return match Node::search(node, key) {
444 // Perfect match. Terminate the stack here, and remove the entry
445 Finished(Some(pusher.seal(handle).remove()))
448 // We need to keep searching, try to go down the next edge
449 match handle.force() {
450 // We're at a leaf; the key isn't in here
451 Leaf(_) => Finished(None),
452 Internal(internal_handle) => Continue(pusher.push(internal_handle))
458 Finished(ret) => return ret,
459 Continue(new_stack) => stack = new_stack
465 #[stable(feature = "rust1", since = "1.0.0")]
466 impl<K, V> IntoIterator for BTreeMap<K, V> {
468 type IntoIter = IntoIter<K, V>;
470 fn into_iter(self) -> IntoIter<K, V> {
475 #[stable(feature = "rust1", since = "1.0.0")]
476 impl<'a, K, V> IntoIterator for &'a BTreeMap<K, V> {
477 type Item = (&'a K, &'a V);
478 type IntoIter = Iter<'a, K, V>;
480 fn into_iter(self) -> Iter<'a, K, V> {
485 #[stable(feature = "rust1", since = "1.0.0")]
486 impl<'a, K, V> IntoIterator for &'a mut BTreeMap<K, V> {
487 type Item = (&'a K, &'a mut V);
488 type IntoIter = IterMut<'a, K, V>;
490 fn into_iter(mut self) -> IterMut<'a, K, V> {
495 /// A helper enum useful for deciding whether to continue a loop since we can't
496 /// return from a closure
497 enum Continuation<A, B> {
502 /// The stack module provides a safe interface for constructing and manipulating a stack of ptrs
503 /// to nodes. By using this module much better safety guarantees can be made, and more search
504 /// boilerplate gets cut out.
506 use core::prelude::*;
509 use core::ops::{Deref, DerefMut};
511 use super::super::node::{self, Node, Fit, Split, Internal, Leaf};
512 use super::super::node::handle;
515 /// A generic mutable reference, identical to `&mut` except for the fact that its lifetime
516 /// parameter is invariant. This means that wherever an `IdRef` is expected, only an `IdRef`
517 /// with the exact requested lifetime can be used. This is in contrast to normal references,
518 /// where `&'static` can be used in any function expecting any lifetime reference.
519 pub struct IdRef<'id, T: 'id> {
521 marker: marker::InvariantLifetime<'id>
524 impl<'id, T> Deref for IdRef<'id, T> {
527 fn deref(&self) -> &T {
532 impl<'id, T> DerefMut for IdRef<'id, T> {
533 fn deref_mut(&mut self) -> &mut T {
538 type StackItem<K, V> = node::Handle<*mut Node<K, V>, handle::Edge, handle::Internal>;
539 type Stack<K, V> = Vec<StackItem<K, V>>;
541 /// A `PartialSearchStack` handles the construction of a search stack.
542 pub struct PartialSearchStack<'a, K:'a, V:'a> {
543 map: &'a mut BTreeMap<K, V>,
545 next: *mut Node<K, V>,
548 /// A `SearchStack` represents a full path to an element or an edge of interest. It provides
549 /// methods depending on the type of what the path points to for removing an element, inserting
550 /// a new element, and manipulating to element at the top of the stack.
551 pub struct SearchStack<'a, K:'a, V:'a, Type, NodeType> {
552 map: &'a mut BTreeMap<K, V>,
554 top: node::Handle<*mut Node<K, V>, Type, NodeType>,
557 /// A `PartialSearchStack` that doesn't hold a a reference to the next node, and is just
558 /// just waiting for a `Handle` to that next node to be pushed. See `PartialSearchStack::with`
559 /// for more details.
560 pub struct Pusher<'id, 'a, K:'a, V:'a> {
561 map: &'a mut BTreeMap<K, V>,
563 marker: marker::InvariantLifetime<'id>
566 impl<'a, K, V> PartialSearchStack<'a, K, V> {
567 /// Creates a new PartialSearchStack from a BTreeMap by initializing the stack with the
568 /// root of the tree.
569 pub fn new(map: &'a mut BTreeMap<K, V>) -> PartialSearchStack<'a, K, V> {
570 let depth = map.depth;
573 next: &mut map.root as *mut _,
575 stack: Vec::with_capacity(depth),
579 /// Breaks up the stack into a `Pusher` and the next `Node`, allowing the given closure
580 /// to interact with, search, and finally push the `Node` onto the stack. The passed in
581 /// closure must be polymorphic on the `'id` lifetime parameter, as this statically
582 /// ensures that only `Handle`s from the correct `Node` can be pushed.
584 /// The reason this works is that the `Pusher` has an `'id` parameter, and will only accept
585 /// handles with the same `'id`. The closure could only get references with that lifetime
586 /// through its arguments or through some other `IdRef` that it has lying around. However,
587 /// no other `IdRef` could possibly work - because the `'id` is held in an invariant
588 /// parameter, it would need to have precisely the correct lifetime, which would mean that
589 /// at least one of the calls to `with` wouldn't be properly polymorphic, wanting a
590 /// specific lifetime instead of the one that `with` chooses to give it.
592 /// See also Haskell's `ST` monad, which uses a similar trick.
593 pub fn with<T, F: for<'id> FnOnce(Pusher<'id, 'a, K, V>,
594 IdRef<'id, Node<K, V>>) -> T>(self, closure: F) -> T {
595 let pusher = Pusher {
598 marker: marker::InvariantLifetime
601 inner: unsafe { &mut *self.next },
602 marker: marker::InvariantLifetime
605 closure(pusher, node)
609 impl<'id, 'a, K, V> Pusher<'id, 'a, K, V> {
610 /// Pushes the requested child of the stack's current top on top of the stack. If the child
611 /// exists, then a new PartialSearchStack is yielded. Otherwise, a VacantSearchStack is
613 pub fn push(mut self, mut edge: node::Handle<IdRef<'id, Node<K, V>>,
616 -> PartialSearchStack<'a, K, V> {
617 self.stack.push(edge.as_raw());
621 next: edge.edge_mut() as *mut _,
625 /// Converts the PartialSearchStack into a SearchStack.
626 pub fn seal<Type, NodeType>
627 (self, mut handle: node::Handle<IdRef<'id, Node<K, V>>, Type, NodeType>)
628 -> SearchStack<'a, K, V, Type, NodeType> {
632 top: handle.as_raw(),
637 impl<'a, K, V, NodeType> SearchStack<'a, K, V, handle::KV, NodeType> {
638 /// Gets a reference to the value the stack points to.
639 pub fn peek(&self) -> &V {
640 unsafe { self.top.from_raw().into_kv().1 }
643 /// Gets a mutable reference to the value the stack points to.
644 pub fn peek_mut(&mut self) -> &mut V {
645 unsafe { self.top.from_raw_mut().into_kv_mut().1 }
648 /// Converts the stack into a mutable reference to the value it points to, with a lifetime
649 /// tied to the original tree.
650 pub fn into_top(mut self) -> &'a mut V {
652 mem::copy_mut_lifetime(
654 self.top.from_raw_mut().val_mut()
660 impl<'a, K, V> SearchStack<'a, K, V, handle::KV, handle::Leaf> {
661 /// Removes the key and value in the top element of the stack, then handles underflows as
662 /// described in BTree's pop function.
663 fn remove_leaf(mut self) -> V {
664 self.map.length -= 1;
666 // Remove the key-value pair from the leaf that this search stack points to.
667 // Then, note if the leaf is underfull, and promptly forget the leaf and its ptr
668 // to avoid ownership issues.
669 let (value, mut underflow) = unsafe {
670 let (_, value) = self.top.from_raw_mut().remove_as_leaf();
671 let underflow = self.top.from_raw().node().is_underfull();
676 match self.stack.pop() {
678 // We've reached the root, so no matter what, we're done. We manually
679 // access the root via the tree itself to avoid creating any dangling
681 if self.map.root.len() == 0 && !self.map.root.is_leaf() {
682 // We've emptied out the root, so make its only child the new root.
683 // If it's a leaf, we just let it become empty.
685 self.map.root.hoist_lone_child();
689 Some(mut handle) => {
691 // Underflow! Handle it!
693 handle.from_raw_mut().handle_underflow();
694 underflow = handle.from_raw().node().is_underfull();
706 impl<'a, K, V> SearchStack<'a, K, V, handle::KV, handle::LeafOrInternal> {
707 /// Removes the key and value in the top element of the stack, then handles underflows as
708 /// described in BTree's pop function.
709 pub fn remove(self) -> V {
710 // Ensure that the search stack goes to a leaf. This is necessary to perform deletion
711 // in a BTree. Note that this may put the tree in an inconsistent state (further
712 // described in into_leaf's comments), but this is immediately fixed by the
713 // removing the value we want to remove
714 self.into_leaf().remove_leaf()
717 /// Subroutine for removal. Takes a search stack for a key that might terminate at an
718 /// internal node, and mutates the tree and search stack to *make* it a search stack
719 /// for that same key that *does* terminates at a leaf. If the mutation occurs, then this
720 /// leaves the tree in an inconsistent state that must be repaired by the caller by
721 /// removing the entry in question. Specifically the key-value pair and its successor will
723 fn into_leaf(mut self) -> SearchStack<'a, K, V, handle::KV, handle::Leaf> {
725 let mut top_raw = self.top;
726 let mut top = top_raw.from_raw_mut();
728 let key_ptr = top.key_mut() as *mut _;
729 let val_ptr = top.val_mut() as *mut _;
731 // Try to go into the right subtree of the found key to find its successor
733 Leaf(mut leaf_handle) => {
734 // We're a proper leaf stack, nothing to do
738 top: leaf_handle.as_raw()
741 Internal(mut internal_handle) => {
742 let mut right_handle = internal_handle.right_edge();
744 //We're not a proper leaf stack, let's get to work.
745 self.stack.push(right_handle.as_raw());
747 let mut temp_node = right_handle.edge_mut();
749 // Walk into the smallest subtree of this node
750 let node = temp_node;
752 match node.kv_handle(0).force() {
753 Leaf(mut handle) => {
754 // This node is a leaf, do the swap and return
755 mem::swap(handle.key_mut(), &mut *key_ptr);
756 mem::swap(handle.val_mut(), &mut *val_ptr);
763 Internal(kv_handle) => {
764 // This node is internal, go deeper
765 let mut handle = kv_handle.into_left_edge();
766 self.stack.push(handle.as_raw());
767 temp_node = handle.into_edge_mut();
777 impl<'a, K, V> SearchStack<'a, K, V, handle::Edge, handle::Leaf> {
778 /// Inserts the key and value into the top element in the stack, and if that node has to
779 /// split recursively inserts the split contents into the next element stack until
782 /// Assumes that the stack represents a search path from the root to a leaf.
784 /// An &mut V is returned to the inserted value, for callers that want a reference to this.
785 pub fn insert(mut self, key: K, val: V) -> &'a mut V {
787 self.map.length += 1;
789 // Insert the key and value into the leaf at the top of the stack
790 let (mut insertion, inserted_ptr) = self.top.from_raw_mut()
791 .insert_as_leaf(key, val);
796 // The last insertion went off without a hitch, no splits! We can stop
798 return &mut *inserted_ptr;
800 Split(key, val, right) => match self.stack.pop() {
801 // The last insertion triggered a split, so get the next element on the
802 // stack to recursively insert the split node into.
804 // The stack was empty; we've split the root, and need to make a
805 // a new one. This is done in-place because we can't move the
806 // root out of a reference to the tree.
807 Node::make_internal_root(&mut self.map.root, self.map.b,
811 return &mut *inserted_ptr;
813 Some(mut handle) => {
814 // The stack wasn't empty, do the insertion and recurse
815 insertion = handle.from_raw_mut()
816 .insert_as_internal(key, val, right);
827 #[stable(feature = "rust1", since = "1.0.0")]
828 impl<K: Ord, V> FromIterator<(K, V)> for BTreeMap<K, V> {
829 fn from_iter<T: Iterator<Item=(K, V)>>(iter: T) -> BTreeMap<K, V> {
830 let mut map = BTreeMap::new();
836 #[stable(feature = "rust1", since = "1.0.0")]
837 impl<K: Ord, V> Extend<(K, V)> for BTreeMap<K, V> {
839 fn extend<T: Iterator<Item=(K, V)>>(&mut self, iter: T) {
846 #[stable(feature = "rust1", since = "1.0.0")]
847 impl<S: Hasher, K: Hash<S>, V: Hash<S>> Hash<S> for BTreeMap<K, V> {
848 fn hash(&self, state: &mut S) {
855 #[stable(feature = "rust1", since = "1.0.0")]
856 impl<K: Ord, V> Default for BTreeMap<K, V> {
857 #[stable(feature = "rust1", since = "1.0.0")]
858 fn default() -> BTreeMap<K, V> {
863 #[stable(feature = "rust1", since = "1.0.0")]
864 impl<K: PartialEq, V: PartialEq> PartialEq for BTreeMap<K, V> {
865 fn eq(&self, other: &BTreeMap<K, V>) -> bool {
866 self.len() == other.len() &&
867 self.iter().zip(other.iter()).all(|(a, b)| a == b)
871 #[stable(feature = "rust1", since = "1.0.0")]
872 impl<K: Eq, V: Eq> Eq for BTreeMap<K, V> {}
874 #[stable(feature = "rust1", since = "1.0.0")]
875 impl<K: PartialOrd, V: PartialOrd> PartialOrd for BTreeMap<K, V> {
877 fn partial_cmp(&self, other: &BTreeMap<K, V>) -> Option<Ordering> {
878 iter::order::partial_cmp(self.iter(), other.iter())
882 #[stable(feature = "rust1", since = "1.0.0")]
883 impl<K: Ord, V: Ord> Ord for BTreeMap<K, V> {
885 fn cmp(&self, other: &BTreeMap<K, V>) -> Ordering {
886 iter::order::cmp(self.iter(), other.iter())
890 #[stable(feature = "rust1", since = "1.0.0")]
891 impl<K: Debug, V: Debug> Debug for BTreeMap<K, V> {
892 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
893 try!(write!(f, "BTreeMap {{"));
895 for (i, (k, v)) in self.iter().enumerate() {
896 if i != 0 { try!(write!(f, ", ")); }
897 try!(write!(f, "{:?}: {:?}", *k, *v));
904 #[stable(feature = "rust1", since = "1.0.0")]
905 impl<K: Ord, Q: ?Sized, V> Index<Q> for BTreeMap<K, V>
906 where Q: BorrowFrom<K> + Ord
910 fn index(&self, key: &Q) -> &V {
911 self.get(key).expect("no entry found for key")
915 #[stable(feature = "rust1", since = "1.0.0")]
916 impl<K: Ord, Q: ?Sized, V> IndexMut<Q> for BTreeMap<K, V>
917 where Q: BorrowFrom<K> + Ord
919 fn index_mut(&mut self, key: &Q) -> &mut V {
920 self.get_mut(key).expect("no entry found for key")
924 /// Genericises over how to get the correct type of iterator from the correct type
925 /// of Node ownership.
927 fn traverse(node: N) -> Self;
930 impl<'a, K, V> Traverse<&'a Node<K, V>> for Traversal<'a, K, V> {
931 fn traverse(node: &'a Node<K, V>) -> Traversal<'a, K, V> {
936 impl<'a, K, V> Traverse<&'a mut Node<K, V>> for MutTraversal<'a, K, V> {
937 fn traverse(node: &'a mut Node<K, V>) -> MutTraversal<'a, K, V> {
942 impl<K, V> Traverse<Node<K, V>> for MoveTraversal<K, V> {
943 fn traverse(node: Node<K, V>) -> MoveTraversal<K, V> {
948 /// Represents an operation to perform inside the following iterator methods.
949 /// This is necessary to use in `next` because we want to modify `self.traversals` inside
950 /// a match that borrows it. Similarly in `next_back`. Instead, we use this enum to note
951 /// what we want to do, and do it after the match.
956 impl<K, V, E, T> Iterator for AbsIter<T> where
957 T: DoubleEndedIterator<Item=TraversalItem<K, V, E>> + Traverse<E>,
961 // Our iterator represents a queue of all ancestors of elements we have
962 // yet to yield, from smallest to largest. Note that the design of these
963 // iterators permits an *arbitrary* initial pair of min and max, making
964 // these arbitrary sub-range iterators.
965 fn next(&mut self) -> Option<(K, V)> {
967 // We want the smallest element, so try to get the back of the queue
968 let op = match self.traversals.back_mut() {
970 // The queue wasn't empty, so continue along the node in its head
971 Some(iter) => match iter.next() {
972 // The head is empty, so Pop it off and continue the process
974 // The head yielded an edge, so make that the new head
975 Some(Edge(next)) => Push(Traverse::traverse(next)),
976 // The head yielded an entry, so yield that
984 // Handle any operation as necessary, without a conflicting borrow of the queue
986 Push(item) => { self.traversals.push_back(item); },
987 Pop => { self.traversals.pop_back(); },
992 fn size_hint(&self) -> (usize, Option<usize>) {
993 (self.size, Some(self.size))
997 impl<K, V, E, T> DoubleEndedIterator for AbsIter<T> where
998 T: DoubleEndedIterator<Item=TraversalItem<K, V, E>> + Traverse<E>,
1000 // next_back is totally symmetric to next
1002 fn next_back(&mut self) -> Option<(K, V)> {
1004 let op = match self.traversals.front_mut() {
1005 None => return None,
1006 Some(iter) => match iter.next_back() {
1008 Some(Edge(next)) => Push(Traverse::traverse(next)),
1017 Push(item) => { self.traversals.push_front(item); },
1018 Pop => { self.traversals.pop_front(); }
1024 #[stable(feature = "rust1", since = "1.0.0")]
1025 impl<'a, K, V> Iterator for Iter<'a, K, V> {
1026 type Item = (&'a K, &'a V);
1028 fn next(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next() }
1029 fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1031 #[stable(feature = "rust1", since = "1.0.0")]
1032 impl<'a, K, V> DoubleEndedIterator for Iter<'a, K, V> {
1033 fn next_back(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next_back() }
1035 #[stable(feature = "rust1", since = "1.0.0")]
1036 impl<'a, K, V> ExactSizeIterator for Iter<'a, K, V> {}
1038 #[stable(feature = "rust1", since = "1.0.0")]
1039 impl<'a, K, V> Iterator for IterMut<'a, K, V> {
1040 type Item = (&'a K, &'a mut V);
1042 fn next(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next() }
1043 fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1045 #[stable(feature = "rust1", since = "1.0.0")]
1046 impl<'a, K, V> DoubleEndedIterator for IterMut<'a, K, V> {
1047 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next_back() }
1049 #[stable(feature = "rust1", since = "1.0.0")]
1050 impl<'a, K, V> ExactSizeIterator for IterMut<'a, K, V> {}
1052 #[stable(feature = "rust1", since = "1.0.0")]
1053 impl<K, V> Iterator for IntoIter<K, V> {
1056 fn next(&mut self) -> Option<(K, V)> { self.inner.next() }
1057 fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1059 #[stable(feature = "rust1", since = "1.0.0")]
1060 impl<K, V> DoubleEndedIterator for IntoIter<K, V> {
1061 fn next_back(&mut self) -> Option<(K, V)> { self.inner.next_back() }
1063 #[stable(feature = "rust1", since = "1.0.0")]
1064 impl<K, V> ExactSizeIterator for IntoIter<K, V> {}
1066 #[stable(feature = "rust1", since = "1.0.0")]
1067 impl<'a, K, V> Iterator for Keys<'a, K, V> {
1070 fn next(&mut self) -> Option<(&'a K)> { self.inner.next() }
1071 fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1073 #[stable(feature = "rust1", since = "1.0.0")]
1074 impl<'a, K, V> DoubleEndedIterator for Keys<'a, K, V> {
1075 fn next_back(&mut self) -> Option<(&'a K)> { self.inner.next_back() }
1077 #[stable(feature = "rust1", since = "1.0.0")]
1078 impl<'a, K, V> ExactSizeIterator for Keys<'a, K, V> {}
1081 #[stable(feature = "rust1", since = "1.0.0")]
1082 impl<'a, K, V> Iterator for Values<'a, K, V> {
1085 fn next(&mut self) -> Option<(&'a V)> { self.inner.next() }
1086 fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1088 #[stable(feature = "rust1", since = "1.0.0")]
1089 impl<'a, K, V> DoubleEndedIterator for Values<'a, K, V> {
1090 fn next_back(&mut self) -> Option<(&'a V)> { self.inner.next_back() }
1092 #[stable(feature = "rust1", since = "1.0.0")]
1093 impl<'a, K, V> ExactSizeIterator for Values<'a, K, V> {}
1095 impl<'a, K, V> Iterator for Range<'a, K, V> {
1096 type Item = (&'a K, &'a V);
1098 fn next(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next() }
1100 impl<'a, K, V> DoubleEndedIterator for Range<'a, K, V> {
1101 fn next_back(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next_back() }
1104 impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
1105 type Item = (&'a K, &'a mut V);
1107 fn next(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next() }
1109 impl<'a, K, V> DoubleEndedIterator for RangeMut<'a, K, V> {
1110 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next_back() }
1113 impl<'a, K: Ord, V> Entry<'a, K, V> {
1114 #[unstable(feature = "collections",
1115 reason = "matches collection reform v2 specification, waiting for dust to settle")]
1116 /// Returns a mutable reference to the entry if occupied, or the VacantEntry if vacant
1117 pub fn get(self) -> Result<&'a mut V, VacantEntry<'a, K, V>> {
1119 Occupied(entry) => Ok(entry.into_mut()),
1120 Vacant(entry) => Err(entry),
1125 impl<'a, K: Ord, V> VacantEntry<'a, K, V> {
1126 /// Sets the value of the entry with the VacantEntry's key,
1127 /// and returns a mutable reference to it.
1128 #[stable(feature = "rust1", since = "1.0.0")]
1129 pub fn insert(self, value: V) -> &'a mut V {
1130 self.stack.insert(self.key, value)
1134 impl<'a, K: Ord, V> OccupiedEntry<'a, K, V> {
1135 /// Gets a reference to the value in the entry.
1136 #[stable(feature = "rust1", since = "1.0.0")]
1137 pub fn get(&self) -> &V {
1141 /// Gets a mutable reference to the value in the entry.
1142 #[stable(feature = "rust1", since = "1.0.0")]
1143 pub fn get_mut(&mut self) -> &mut V {
1144 self.stack.peek_mut()
1147 /// Converts the entry into a mutable reference to its value.
1148 #[stable(feature = "rust1", since = "1.0.0")]
1149 pub fn into_mut(self) -> &'a mut V {
1150 self.stack.into_top()
1153 /// Sets the value of the entry with the OccupiedEntry's key,
1154 /// and returns the entry's old value.
1155 #[stable(feature = "rust1", since = "1.0.0")]
1156 pub fn insert(&mut self, mut value: V) -> V {
1157 mem::swap(self.stack.peek_mut(), &mut value);
1161 /// Takes the value of the entry out of the map, and returns it.
1162 #[stable(feature = "rust1", since = "1.0.0")]
1163 pub fn remove(self) -> V {
1168 impl<K, V> BTreeMap<K, V> {
1169 /// Gets an iterator over the entries of the map.
1174 /// use std::collections::BTreeMap;
1176 /// let mut map = BTreeMap::new();
1177 /// map.insert(1, "a");
1178 /// map.insert(2, "b");
1179 /// map.insert(3, "c");
1181 /// for (key, value) in map.iter() {
1182 /// println!("{}: {}", key, value);
1185 /// let (first_key, first_value) = map.iter().next().unwrap();
1186 /// assert_eq!((*first_key, *first_value), (1, "a"));
1188 #[stable(feature = "rust1", since = "1.0.0")]
1189 pub fn iter(&self) -> Iter<K, V> {
1190 let len = self.len();
1191 // NB. The initial capacity for ringbuf is large enough to avoid reallocs in many cases.
1192 let mut lca = RingBuf::new();
1193 lca.push_back(Traverse::traverse(&self.root));
1202 /// Gets a mutable iterator over the entries of the map.
1207 /// use std::collections::BTreeMap;
1209 /// let mut map = BTreeMap::new();
1210 /// map.insert("a", 1);
1211 /// map.insert("b", 2);
1212 /// map.insert("c", 3);
1214 /// // add 10 to the value if the key isn't "a"
1215 /// for (key, value) in map.iter_mut() {
1216 /// if key != &"a" {
1221 #[stable(feature = "rust1", since = "1.0.0")]
1222 pub fn iter_mut(&mut self) -> IterMut<K, V> {
1223 let len = self.len();
1224 let mut lca = RingBuf::new();
1225 lca.push_back(Traverse::traverse(&mut self.root));
1234 /// Gets an owning iterator over the entries of the map.
1239 /// use std::collections::BTreeMap;
1241 /// let mut map = BTreeMap::new();
1242 /// map.insert(1, "a");
1243 /// map.insert(2, "b");
1244 /// map.insert(3, "c");
1246 /// for (key, value) in map.into_iter() {
1247 /// println!("{}: {}", key, value);
1250 #[stable(feature = "rust1", since = "1.0.0")]
1251 pub fn into_iter(self) -> IntoIter<K, V> {
1252 let len = self.len();
1253 let mut lca = RingBuf::new();
1254 lca.push_back(Traverse::traverse(self.root));
1263 /// Gets an iterator over the keys of the map.
1268 /// use std::collections::BTreeMap;
1270 /// let mut a = BTreeMap::new();
1271 /// a.insert(1, "a");
1272 /// a.insert(2, "b");
1274 /// let keys: Vec<usize> = a.keys().cloned().collect();
1275 /// assert_eq!(keys, vec![1,2,]);
1277 #[stable(feature = "rust1", since = "1.0.0")]
1278 pub fn keys<'a>(&'a self) -> Keys<'a, K, V> {
1279 fn first<A, B>((a, _): (A, B)) -> A { a }
1280 let first: fn((&'a K, &'a V)) -> &'a K = first; // coerce to fn pointer
1282 Keys { inner: self.iter().map(first) }
1285 /// Gets an iterator over the values of the map.
1290 /// use std::collections::BTreeMap;
1292 /// let mut a = BTreeMap::new();
1293 /// a.insert(1, "a");
1294 /// a.insert(2, "b");
1296 /// let values: Vec<&str> = a.values().cloned().collect();
1297 /// assert_eq!(values, vec!["a","b"]);
1299 #[stable(feature = "rust1", since = "1.0.0")]
1300 pub fn values<'a>(&'a self) -> Values<'a, K, V> {
1301 fn second<A, B>((_, b): (A, B)) -> B { b }
1302 let second: fn((&'a K, &'a V)) -> &'a V = second; // coerce to fn pointer
1304 Values { inner: self.iter().map(second) }
1307 /// Return the number of elements in the map.
1312 /// use std::collections::BTreeMap;
1314 /// let mut a = BTreeMap::new();
1315 /// assert_eq!(a.len(), 0);
1316 /// a.insert(1, "a");
1317 /// assert_eq!(a.len(), 1);
1319 #[stable(feature = "rust1", since = "1.0.0")]
1320 pub fn len(&self) -> usize { self.length }
1322 /// Return true if the map contains no elements.
1327 /// use std::collections::BTreeMap;
1329 /// let mut a = BTreeMap::new();
1330 /// assert!(a.is_empty());
1331 /// a.insert(1, "a");
1332 /// assert!(!a.is_empty());
1334 #[stable(feature = "rust1", since = "1.0.0")]
1335 pub fn is_empty(&self) -> bool { self.len() == 0 }
1338 macro_rules! range_impl {
1339 ($root:expr, $min:expr, $max:expr, $as_slices_internal:ident, $iter:ident, $Range:ident,
1340 $edges:ident, [$($mutability:ident)*]) => (
1342 // A deque that encodes two search paths containing (left-to-right):
1343 // a series of truncated-from-the-left iterators, the LCA's doubly-truncated iterator,
1344 // and a series of truncated-from-the-right iterators.
1345 let mut traversals = RingBuf::new();
1346 let (root, min, max) = ($root, $min, $max);
1348 let mut leftmost = None;
1349 let mut rightmost = None;
1351 match (&min, &max) {
1352 (&Unbounded, &Unbounded) => {
1353 traversals.push_back(Traverse::traverse(root))
1355 (&Unbounded, &Included(_)) | (&Unbounded, &Excluded(_)) => {
1356 rightmost = Some(root);
1358 (&Included(_), &Unbounded) | (&Excluded(_), &Unbounded) => {
1359 leftmost = Some(root);
1361 (&Included(min_key), &Included(max_key))
1362 | (&Included(min_key), &Excluded(max_key))
1363 | (&Excluded(min_key), &Included(max_key))
1364 | (&Excluded(min_key), &Excluded(max_key)) => {
1365 // lca represents the Lowest Common Ancestor, above which we never
1366 // walk, since everything else is outside the range to iterate.
1367 // ___________________
1368 // |__0_|_80_|_85_|_90_| (root)
1372 // ___________________
1373 // |__5_|_15_|_30_|_73_|
1377 // ___________________
1378 // |_33_|_58_|_63_|_68_| lca for the range [41, 65]
1379 // | |\___|___/| | iterator at traversals[2]
1384 let mut is_leaf = root.is_leaf();
1385 let mut lca = root.$as_slices_internal();
1387 let slice = lca.slice_from(min_key).slice_to(max_key);
1388 if let [ref $($mutability)* edge] = slice.edges {
1389 // Follow the only edge that leads the node that covers the range.
1390 is_leaf = edge.is_leaf();
1391 lca = edge.$as_slices_internal();
1393 let mut iter = slice.$iter();
1398 // Only change the state of nodes with edges.
1399 leftmost = iter.next_edge_item();
1400 rightmost = iter.next_edge_item_back();
1402 traversals.push_back(iter);
1408 // Keep narrowing the range by going down.
1409 // ___________________
1410 // |_38_|_43_|_48_|_53_|
1411 // | |____|____|____/ iterator at traversals[1]
1414 // ___________________
1415 // |_39_|_40_|_41_|_42_| (leaf, the last leftmost)
1416 // \_________| iterator at traversals[0]
1418 Included(key) | Excluded(key) =>
1419 while let Some(left) = leftmost {
1420 let is_leaf = left.is_leaf();
1421 let mut iter = left.$as_slices_internal().slice_from(key).$iter();
1422 leftmost = if is_leaf {
1425 // Only change the state of nodes with edges.
1426 iter.next_edge_item()
1428 traversals.push_back(iter);
1432 // If the leftmost iterator starts with an element, then it was an exact match.
1433 if let (Excluded(_), Some(leftmost_iter)) = (min, traversals.back_mut()) {
1434 // Drop this excluded element. `next_kv_item` has no effect when
1435 // the next item is an edge.
1436 leftmost_iter.next_kv_item();
1439 // The code for the right side is similar.
1441 Included(key) | Excluded(key) =>
1442 while let Some(right) = rightmost {
1443 let is_leaf = right.is_leaf();
1444 let mut iter = right.$as_slices_internal().slice_to(key).$iter();
1445 rightmost = if is_leaf {
1448 iter.next_edge_item_back()
1450 traversals.push_front(iter);
1454 if let (Excluded(_), Some(rightmost_iter)) = (max, traversals.front_mut()) {
1455 rightmost_iter.next_kv_item_back();
1460 traversals: traversals,
1468 impl<K: Ord, V> BTreeMap<K, V> {
1469 /// Constructs a double-ended iterator over a sub-range of elements in the map, starting
1470 /// at min, and ending at max. If min is `Unbounded`, then it will be treated as "negative
1471 /// infinity", and if max is `Unbounded`, then it will be treated as "positive infinity".
1472 /// Thus range(Unbounded, Unbounded) will yield the whole collection.
1477 /// use std::collections::BTreeMap;
1478 /// use std::collections::Bound::{Included, Unbounded};
1480 /// let mut map = BTreeMap::new();
1481 /// map.insert(3, "a");
1482 /// map.insert(5, "b");
1483 /// map.insert(8, "c");
1484 /// for (&key, &value) in map.range(Included(&4), Included(&8)) {
1485 /// println!("{}: {}", key, value);
1487 /// assert_eq!(Some((&5, &"b")), map.range(Included(&4), Unbounded).next());
1489 #[unstable(feature = "collections",
1490 reason = "matches collection reform specification, waiting for dust to settle")]
1491 pub fn range<'a>(&'a self, min: Bound<&K>, max: Bound<&K>) -> Range<'a, K, V> {
1492 range_impl!(&self.root, min, max, as_slices_internal, iter, Range, edges, [])
1495 /// Constructs a mutable double-ended iterator over a sub-range of elements in the map, starting
1496 /// at min, and ending at max. If min is `Unbounded`, then it will be treated as "negative
1497 /// infinity", and if max is `Unbounded`, then it will be treated as "positive infinity".
1498 /// Thus range(Unbounded, Unbounded) will yield the whole collection.
1503 /// use std::collections::BTreeMap;
1504 /// use std::collections::Bound::{Included, Excluded};
1506 /// let mut map: BTreeMap<&str, i32> = ["Alice", "Bob", "Carol", "Cheryl"].iter()
1507 /// .map(|&s| (s, 0))
1509 /// for (_, balance) in map.range_mut(Included(&"B"), Excluded(&"Cheryl")) {
1510 /// *balance += 100;
1512 /// for (name, balance) in map.iter() {
1513 /// println!("{} => {}", name, balance);
1516 #[unstable(feature = "collections",
1517 reason = "matches collection reform specification, waiting for dust to settle")]
1518 pub fn range_mut<'a>(&'a mut self, min: Bound<&K>, max: Bound<&K>) -> RangeMut<'a, K, V> {
1519 range_impl!(&mut self.root, min, max, as_slices_internal_mut, iter_mut, RangeMut,
1523 /// Gets the given key's corresponding entry in the map for in-place manipulation.
1528 /// use std::collections::BTreeMap;
1529 /// use std::collections::btree_map::Entry;
1531 /// let mut count: BTreeMap<&str, usize> = BTreeMap::new();
1533 /// // count the number of occurrences of letters in the vec
1534 /// for x in vec!["a","b","a","c","a","b"].iter() {
1535 /// match count.entry(*x) {
1536 /// Entry::Vacant(view) => {
1539 /// Entry::Occupied(mut view) => {
1540 /// let v = view.get_mut();
1546 /// assert_eq!(count["a"], 3);
1548 #[stable(feature = "rust1", since = "1.0.0")]
1549 pub fn entry(&mut self, mut key: K) -> Entry<K, V> {
1550 // same basic logic of `swap` and `pop`, blended together
1551 let mut stack = stack::PartialSearchStack::new(self);
1553 let result = stack.with(move |pusher, node| {
1554 return match Node::search(node, &key) {
1557 Finished(Occupied(OccupiedEntry {
1558 stack: pusher.seal(handle)
1562 match handle.force() {
1563 Leaf(leaf_handle) => {
1564 Finished(Vacant(VacantEntry {
1565 stack: pusher.seal(leaf_handle),
1569 Internal(internal_handle) => {
1571 pusher.push(internal_handle),
1580 Finished(finished) => return finished,
1581 Continue((new_stack, renewed_key)) => {
1597 use std::iter::range_inclusive;
1599 use super::BTreeMap;
1600 use super::Entry::{Occupied, Vacant};
1601 use Bound::{self, Included, Excluded, Unbounded};
1604 fn test_basic_large() {
1605 let mut map = BTreeMap::new();
1607 assert_eq!(map.len(), 0);
1610 assert_eq!(map.insert(i, 10*i), None);
1611 assert_eq!(map.len(), i + 1);
1615 assert_eq!(map.get(&i).unwrap(), &(i*10));
1618 for i in size..size*2 {
1619 assert_eq!(map.get(&i), None);
1623 assert_eq!(map.insert(i, 100*i), Some(10*i));
1624 assert_eq!(map.len(), size);
1628 assert_eq!(map.get(&i).unwrap(), &(i*100));
1631 for i in 0..size/2 {
1632 assert_eq!(map.remove(&(i*2)), Some(i*200));
1633 assert_eq!(map.len(), size - i - 1);
1636 for i in 0..size/2 {
1637 assert_eq!(map.get(&(2*i)), None);
1638 assert_eq!(map.get(&(2*i+1)).unwrap(), &(i*200 + 100));
1641 for i in 0..size/2 {
1642 assert_eq!(map.remove(&(2*i)), None);
1643 assert_eq!(map.remove(&(2*i+1)), Some(i*200 + 100));
1644 assert_eq!(map.len(), size/2 - i - 1);
1649 fn test_basic_small() {
1650 let mut map = BTreeMap::new();
1651 assert_eq!(map.remove(&1), None);
1652 assert_eq!(map.get(&1), None);
1653 assert_eq!(map.insert(1, 1), None);
1654 assert_eq!(map.get(&1), Some(&1));
1655 assert_eq!(map.insert(1, 2), Some(1));
1656 assert_eq!(map.get(&1), Some(&2));
1657 assert_eq!(map.insert(2, 4), None);
1658 assert_eq!(map.get(&2), Some(&4));
1659 assert_eq!(map.remove(&1), Some(2));
1660 assert_eq!(map.remove(&2), Some(4));
1661 assert_eq!(map.remove(&1), None);
1669 let mut map: BTreeMap<_, _> = (0..size).map(|i| (i, i)).collect();
1671 fn test<T>(size: usize, mut iter: T) where T: Iterator<Item=(usize, usize)> {
1673 assert_eq!(iter.size_hint(), (size - i, Some(size - i)));
1674 assert_eq!(iter.next().unwrap(), (i, i));
1676 assert_eq!(iter.size_hint(), (0, Some(0)));
1677 assert_eq!(iter.next(), None);
1679 test(size, map.iter().map(|(&k, &v)| (k, v)));
1680 test(size, map.iter_mut().map(|(&k, &mut v)| (k, v)));
1681 test(size, map.into_iter());
1685 fn test_iter_rev() {
1689 let mut map: BTreeMap<_, _> = (0..size).map(|i| (i, i)).collect();
1691 fn test<T>(size: usize, mut iter: T) where T: Iterator<Item=(usize, usize)> {
1693 assert_eq!(iter.size_hint(), (size - i, Some(size - i)));
1694 assert_eq!(iter.next().unwrap(), (size - i - 1, size - i - 1));
1696 assert_eq!(iter.size_hint(), (0, Some(0)));
1697 assert_eq!(iter.next(), None);
1699 test(size, map.iter().rev().map(|(&k, &v)| (k, v)));
1700 test(size, map.iter_mut().rev().map(|(&k, &mut v)| (k, v)));
1701 test(size, map.into_iter().rev());
1705 fn test_iter_mixed() {
1709 let mut map: BTreeMap<_, _> = (0..size).map(|i| (i, i)).collect();
1711 fn test<T>(size: usize, mut iter: T)
1712 where T: Iterator<Item=(usize, usize)> + DoubleEndedIterator {
1713 for i in 0..size / 4 {
1714 assert_eq!(iter.size_hint(), (size - i * 2, Some(size - i * 2)));
1715 assert_eq!(iter.next().unwrap(), (i, i));
1716 assert_eq!(iter.next_back().unwrap(), (size - i - 1, size - i - 1));
1718 for i in size / 4..size * 3 / 4 {
1719 assert_eq!(iter.size_hint(), (size * 3 / 4 - i, Some(size * 3 / 4 - i)));
1720 assert_eq!(iter.next().unwrap(), (i, i));
1722 assert_eq!(iter.size_hint(), (0, Some(0)));
1723 assert_eq!(iter.next(), None);
1725 test(size, map.iter().map(|(&k, &v)| (k, v)));
1726 test(size, map.iter_mut().map(|(&k, &mut v)| (k, v)));
1727 test(size, map.into_iter());
1731 fn test_range_small() {
1735 let map: BTreeMap<_, _> = (0..size).map(|i| (i, i)).collect();
1738 for ((&k, &v), i) in map.range(Included(&2), Unbounded).zip(2..size) {
1743 assert_eq!(j, size - 2);
1747 fn test_range_1000() {
1749 let map: BTreeMap<_, _> = (0..size).map(|i| (i, i)).collect();
1751 fn test(map: &BTreeMap<u32, u32>, size: u32, min: Bound<&u32>, max: Bound<&u32>) {
1752 let mut kvs = map.range(min, max).map(|(&k, &v)| (k, v));
1753 let mut pairs = (0..size).map(|i| (i, i));
1755 for (kv, pair) in kvs.by_ref().zip(pairs.by_ref()) {
1756 assert_eq!(kv, pair);
1758 assert_eq!(kvs.next(), None);
1759 assert_eq!(pairs.next(), None);
1761 test(&map, size, Included(&0), Excluded(&size));
1762 test(&map, size, Unbounded, Excluded(&size));
1763 test(&map, size, Included(&0), Included(&(size - 1)));
1764 test(&map, size, Unbounded, Included(&(size - 1)));
1765 test(&map, size, Included(&0), Unbounded);
1766 test(&map, size, Unbounded, Unbounded);
1772 let map: BTreeMap<_, _> = (0..size).map(|i| (i, i)).collect();
1776 let mut kvs = map.range(Included(&i), Included(&j)).map(|(&k, &v)| (k, v));
1777 let mut pairs = range_inclusive(i, j).map(|i| (i, i));
1779 for (kv, pair) in kvs.by_ref().zip(pairs.by_ref()) {
1780 assert_eq!(kv, pair);
1782 assert_eq!(kvs.next(), None);
1783 assert_eq!(pairs.next(), None);
1790 let xs = [(1, 10), (2, 20), (3, 30), (4, 40), (5, 50), (6, 60)];
1792 let mut map: BTreeMap<_, _> = xs.iter().cloned().collect();
1794 // Existing key (insert)
1795 match map.entry(1) {
1796 Vacant(_) => unreachable!(),
1797 Occupied(mut view) => {
1798 assert_eq!(view.get(), &10);
1799 assert_eq!(view.insert(100), 10);
1802 assert_eq!(map.get(&1).unwrap(), &100);
1803 assert_eq!(map.len(), 6);
1806 // Existing key (update)
1807 match map.entry(2) {
1808 Vacant(_) => unreachable!(),
1809 Occupied(mut view) => {
1810 let v = view.get_mut();
1814 assert_eq!(map.get(&2).unwrap(), &200);
1815 assert_eq!(map.len(), 6);
1817 // Existing key (take)
1818 match map.entry(3) {
1819 Vacant(_) => unreachable!(),
1821 assert_eq!(view.remove(), 30);
1824 assert_eq!(map.get(&3), None);
1825 assert_eq!(map.len(), 5);
1828 // Inexistent key (insert)
1829 match map.entry(10) {
1830 Occupied(_) => unreachable!(),
1832 assert_eq!(*view.insert(1000), 1000);
1835 assert_eq!(map.get(&10).unwrap(), &1000);
1836 assert_eq!(map.len(), 6);
1848 use std::rand::{weak_rng, Rng};
1849 use test::{Bencher, black_box};
1851 use super::BTreeMap;
1853 map_insert_rand_bench!{insert_rand_100, 100, BTreeMap}
1854 map_insert_rand_bench!{insert_rand_10_000, 10_000, BTreeMap}
1856 map_insert_seq_bench!{insert_seq_100, 100, BTreeMap}
1857 map_insert_seq_bench!{insert_seq_10_000, 10_000, BTreeMap}
1859 map_find_rand_bench!{find_rand_100, 100, BTreeMap}
1860 map_find_rand_bench!{find_rand_10_000, 10_000, BTreeMap}
1862 map_find_seq_bench!{find_seq_100, 100, BTreeMap}
1863 map_find_seq_bench!{find_seq_10_000, 10_000, BTreeMap}
1865 fn bench_iter(b: &mut Bencher, size: i32) {
1866 let mut map = BTreeMap::<i32, i32>::new();
1867 let mut rng = weak_rng();
1870 map.insert(rng.gen(), rng.gen());
1881 pub fn iter_20(b: &mut Bencher) {
1886 pub fn iter_1000(b: &mut Bencher) {
1887 bench_iter(b, 1000);
1891 pub fn iter_100000(b: &mut Bencher) {
1892 bench_iter(b, 100000);