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::cmp::Ordering;
23 use core::default::Default;
25 use core::hash::{Hash, Hasher};
26 use core::iter::{Map, FromIterator, IntoIterator};
27 use core::ops::{Index, IndexMut};
28 use core::{iter, fmt, mem};
29 use Bound::{self, Included, Excluded, Unbounded};
32 use vec_deque::VecDeque;
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: VecDeque<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 K: Borrow<Q>, Q: 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 K: Borrow<Q>, Q: 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 K: Borrow<Q>, Q: 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 K: Borrow<Q>, Q: 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 struct InvariantLifetime<'id>(
516 marker::PhantomData<::core::cell::Cell<&'id ()>>);
518 impl<'id> InvariantLifetime<'id> {
519 fn new() -> InvariantLifetime<'id> {
520 InvariantLifetime(marker::PhantomData)
524 /// A generic mutable reference, identical to `&mut` except for the fact that its lifetime
525 /// parameter is invariant. This means that wherever an `IdRef` is expected, only an `IdRef`
526 /// with the exact requested lifetime can be used. This is in contrast to normal references,
527 /// where `&'static` can be used in any function expecting any lifetime reference.
528 pub struct IdRef<'id, T: 'id> {
530 _marker: InvariantLifetime<'id>,
533 impl<'id, T> Deref for IdRef<'id, T> {
536 fn deref(&self) -> &T {
541 impl<'id, T> DerefMut for IdRef<'id, T> {
542 fn deref_mut(&mut self) -> &mut T {
547 type StackItem<K, V> = node::Handle<*mut Node<K, V>, handle::Edge, handle::Internal>;
548 type Stack<K, V> = Vec<StackItem<K, V>>;
550 /// A `PartialSearchStack` handles the construction of a search stack.
551 pub struct PartialSearchStack<'a, K:'a, V:'a> {
552 map: &'a mut BTreeMap<K, V>,
554 next: *mut Node<K, V>,
557 /// A `SearchStack` represents a full path to an element or an edge of interest. It provides
558 /// methods depending on the type of what the path points to for removing an element, inserting
559 /// a new element, and manipulating to element at the top of the stack.
560 pub struct SearchStack<'a, K:'a, V:'a, Type, NodeType> {
561 map: &'a mut BTreeMap<K, V>,
563 top: node::Handle<*mut Node<K, V>, Type, NodeType>,
566 /// A `PartialSearchStack` that doesn't hold a a reference to the next node, and is just
567 /// just waiting for a `Handle` to that next node to be pushed. See `PartialSearchStack::with`
568 /// for more details.
569 pub struct Pusher<'id, 'a, K:'a, V:'a> {
570 map: &'a mut BTreeMap<K, V>,
572 _marker: InvariantLifetime<'id>,
575 impl<'a, K, V> PartialSearchStack<'a, K, V> {
576 /// Creates a new PartialSearchStack from a BTreeMap by initializing the stack with the
577 /// root of the tree.
578 pub fn new(map: &'a mut BTreeMap<K, V>) -> PartialSearchStack<'a, K, V> {
579 let depth = map.depth;
582 next: &mut map.root as *mut _,
584 stack: Vec::with_capacity(depth),
588 /// Breaks up the stack into a `Pusher` and the next `Node`, allowing the given closure
589 /// to interact with, search, and finally push the `Node` onto the stack. The passed in
590 /// closure must be polymorphic on the `'id` lifetime parameter, as this statically
591 /// ensures that only `Handle`s from the correct `Node` can be pushed.
593 /// The reason this works is that the `Pusher` has an `'id` parameter, and will only accept
594 /// handles with the same `'id`. The closure could only get references with that lifetime
595 /// through its arguments or through some other `IdRef` that it has lying around. However,
596 /// no other `IdRef` could possibly work - because the `'id` is held in an invariant
597 /// parameter, it would need to have precisely the correct lifetime, which would mean that
598 /// at least one of the calls to `with` wouldn't be properly polymorphic, wanting a
599 /// specific lifetime instead of the one that `with` chooses to give it.
601 /// See also Haskell's `ST` monad, which uses a similar trick.
602 pub fn with<T, F: for<'id> FnOnce(Pusher<'id, 'a, K, V>,
603 IdRef<'id, Node<K, V>>) -> T>(self, closure: F) -> T {
604 let pusher = Pusher {
607 _marker: InvariantLifetime::new(),
610 inner: unsafe { &mut *self.next },
611 _marker: InvariantLifetime::new(),
614 closure(pusher, node)
618 impl<'id, 'a, K, V> Pusher<'id, 'a, K, V> {
619 /// Pushes the requested child of the stack's current top on top of the stack. If the child
620 /// exists, then a new PartialSearchStack is yielded. Otherwise, a VacantSearchStack is
622 pub fn push(mut self, mut edge: node::Handle<IdRef<'id, Node<K, V>>,
625 -> PartialSearchStack<'a, K, V> {
626 self.stack.push(edge.as_raw());
630 next: edge.edge_mut() as *mut _,
634 /// Converts the PartialSearchStack into a SearchStack.
635 pub fn seal<Type, NodeType>
636 (self, mut handle: node::Handle<IdRef<'id, Node<K, V>>, Type, NodeType>)
637 -> SearchStack<'a, K, V, Type, NodeType> {
641 top: handle.as_raw(),
646 impl<'a, K, V, NodeType> SearchStack<'a, K, V, handle::KV, NodeType> {
647 /// Gets a reference to the value the stack points to.
648 pub fn peek(&self) -> &V {
649 unsafe { self.top.from_raw().into_kv().1 }
652 /// Gets a mutable reference to the value the stack points to.
653 pub fn peek_mut(&mut self) -> &mut V {
654 unsafe { self.top.from_raw_mut().into_kv_mut().1 }
657 /// Converts the stack into a mutable reference to the value it points to, with a lifetime
658 /// tied to the original tree.
659 pub fn into_top(mut self) -> &'a mut V {
661 mem::copy_mut_lifetime(
663 self.top.from_raw_mut().val_mut()
669 impl<'a, K, V> SearchStack<'a, K, V, handle::KV, handle::Leaf> {
670 /// Removes the key and value in the top element of the stack, then handles underflows as
671 /// described in BTree's pop function.
672 fn remove_leaf(mut self) -> V {
673 self.map.length -= 1;
675 // Remove the key-value pair from the leaf that this search stack points to.
676 // Then, note if the leaf is underfull, and promptly forget the leaf and its ptr
677 // to avoid ownership issues.
678 let (value, mut underflow) = unsafe {
679 let (_, value) = self.top.from_raw_mut().remove_as_leaf();
680 let underflow = self.top.from_raw().node().is_underfull();
685 match self.stack.pop() {
687 // We've reached the root, so no matter what, we're done. We manually
688 // access the root via the tree itself to avoid creating any dangling
690 if self.map.root.len() == 0 && !self.map.root.is_leaf() {
691 // We've emptied out the root, so make its only child the new root.
692 // If it's a leaf, we just let it become empty.
694 self.map.root.hoist_lone_child();
698 Some(mut handle) => {
700 // Underflow! Handle it!
702 handle.from_raw_mut().handle_underflow();
703 underflow = handle.from_raw().node().is_underfull();
715 impl<'a, K, V> SearchStack<'a, K, V, handle::KV, handle::LeafOrInternal> {
716 /// Removes the key and value in the top element of the stack, then handles underflows as
717 /// described in BTree's pop function.
718 pub fn remove(self) -> V {
719 // Ensure that the search stack goes to a leaf. This is necessary to perform deletion
720 // in a BTree. Note that this may put the tree in an inconsistent state (further
721 // described in into_leaf's comments), but this is immediately fixed by the
722 // removing the value we want to remove
723 self.into_leaf().remove_leaf()
726 /// Subroutine for removal. Takes a search stack for a key that might terminate at an
727 /// internal node, and mutates the tree and search stack to *make* it a search stack
728 /// for that same key that *does* terminates at a leaf. If the mutation occurs, then this
729 /// leaves the tree in an inconsistent state that must be repaired by the caller by
730 /// removing the entry in question. Specifically the key-value pair and its successor will
732 fn into_leaf(mut self) -> SearchStack<'a, K, V, handle::KV, handle::Leaf> {
734 let mut top_raw = self.top;
735 let mut top = top_raw.from_raw_mut();
737 let key_ptr = top.key_mut() as *mut _;
738 let val_ptr = top.val_mut() as *mut _;
740 // Try to go into the right subtree of the found key to find its successor
742 Leaf(mut leaf_handle) => {
743 // We're a proper leaf stack, nothing to do
747 top: leaf_handle.as_raw()
750 Internal(mut internal_handle) => {
751 let mut right_handle = internal_handle.right_edge();
753 //We're not a proper leaf stack, let's get to work.
754 self.stack.push(right_handle.as_raw());
756 let mut temp_node = right_handle.edge_mut();
758 // Walk into the smallest subtree of this node
759 let node = temp_node;
761 match node.kv_handle(0).force() {
762 Leaf(mut handle) => {
763 // This node is a leaf, do the swap and return
764 mem::swap(handle.key_mut(), &mut *key_ptr);
765 mem::swap(handle.val_mut(), &mut *val_ptr);
772 Internal(kv_handle) => {
773 // This node is internal, go deeper
774 let mut handle = kv_handle.into_left_edge();
775 self.stack.push(handle.as_raw());
776 temp_node = handle.into_edge_mut();
786 impl<'a, K, V> SearchStack<'a, K, V, handle::Edge, handle::Leaf> {
787 /// Inserts the key and value into the top element in the stack, and if that node has to
788 /// split recursively inserts the split contents into the next element stack until
791 /// Assumes that the stack represents a search path from the root to a leaf.
793 /// An &mut V is returned to the inserted value, for callers that want a reference to this.
794 pub fn insert(mut self, key: K, val: V) -> &'a mut V {
796 self.map.length += 1;
798 // Insert the key and value into the leaf at the top of the stack
799 let (mut insertion, inserted_ptr) = self.top.from_raw_mut()
800 .insert_as_leaf(key, val);
805 // The last insertion went off without a hitch, no splits! We can stop
807 return &mut *inserted_ptr;
809 Split(key, val, right) => match self.stack.pop() {
810 // The last insertion triggered a split, so get the next element on the
811 // stack to recursively insert the split node into.
813 // The stack was empty; we've split the root, and need to make a
814 // a new one. This is done in-place because we can't move the
815 // root out of a reference to the tree.
816 Node::make_internal_root(&mut self.map.root, self.map.b,
820 return &mut *inserted_ptr;
822 Some(mut handle) => {
823 // The stack wasn't empty, do the insertion and recurse
824 insertion = handle.from_raw_mut()
825 .insert_as_internal(key, val, right);
836 #[stable(feature = "rust1", since = "1.0.0")]
837 impl<K: Ord, V> FromIterator<(K, V)> for BTreeMap<K, V> {
838 fn from_iter<T: IntoIterator<Item=(K, V)>>(iter: T) -> BTreeMap<K, V> {
839 let mut map = BTreeMap::new();
845 #[stable(feature = "rust1", since = "1.0.0")]
846 impl<K: Ord, V> Extend<(K, V)> for BTreeMap<K, V> {
848 fn extend<T: IntoIterator<Item=(K, V)>>(&mut self, iter: T) {
855 #[stable(feature = "rust1", since = "1.0.0")]
856 impl<K: Hash, V: Hash> Hash for BTreeMap<K, V> {
857 fn hash<H: Hasher>(&self, state: &mut H) {
864 #[stable(feature = "rust1", since = "1.0.0")]
865 impl<K: Ord, V> Default for BTreeMap<K, V> {
866 #[stable(feature = "rust1", since = "1.0.0")]
867 fn default() -> BTreeMap<K, V> {
872 #[stable(feature = "rust1", since = "1.0.0")]
873 impl<K: PartialEq, V: PartialEq> PartialEq for BTreeMap<K, V> {
874 fn eq(&self, other: &BTreeMap<K, V>) -> bool {
875 self.len() == other.len() &&
876 self.iter().zip(other.iter()).all(|(a, b)| a == b)
880 #[stable(feature = "rust1", since = "1.0.0")]
881 impl<K: Eq, V: Eq> Eq for BTreeMap<K, V> {}
883 #[stable(feature = "rust1", since = "1.0.0")]
884 impl<K: PartialOrd, V: PartialOrd> PartialOrd for BTreeMap<K, V> {
886 fn partial_cmp(&self, other: &BTreeMap<K, V>) -> Option<Ordering> {
887 iter::order::partial_cmp(self.iter(), other.iter())
891 #[stable(feature = "rust1", since = "1.0.0")]
892 impl<K: Ord, V: Ord> Ord for BTreeMap<K, V> {
894 fn cmp(&self, other: &BTreeMap<K, V>) -> Ordering {
895 iter::order::cmp(self.iter(), other.iter())
899 #[stable(feature = "rust1", since = "1.0.0")]
900 impl<K: Debug, V: Debug> Debug for BTreeMap<K, V> {
901 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
902 try!(write!(f, "BTreeMap {{"));
904 for (i, (k, v)) in self.iter().enumerate() {
905 if i != 0 { try!(write!(f, ", ")); }
906 try!(write!(f, "{:?}: {:?}", *k, *v));
913 #[stable(feature = "rust1", since = "1.0.0")]
914 impl<K: Ord, Q: ?Sized, V> Index<Q> for BTreeMap<K, V>
915 where K: Borrow<Q>, Q: Ord
919 fn index(&self, key: &Q) -> &V {
920 self.get(key).expect("no entry found for key")
924 #[stable(feature = "rust1", since = "1.0.0")]
925 impl<K: Ord, Q: ?Sized, V> IndexMut<Q> for BTreeMap<K, V>
926 where K: Borrow<Q>, Q: Ord
928 fn index_mut(&mut self, key: &Q) -> &mut V {
929 self.get_mut(key).expect("no entry found for key")
933 /// Genericises over how to get the correct type of iterator from the correct type
934 /// of Node ownership.
936 fn traverse(node: N) -> Self;
939 impl<'a, K, V> Traverse<&'a Node<K, V>> for Traversal<'a, K, V> {
940 fn traverse(node: &'a Node<K, V>) -> Traversal<'a, K, V> {
945 impl<'a, K, V> Traverse<&'a mut Node<K, V>> for MutTraversal<'a, K, V> {
946 fn traverse(node: &'a mut Node<K, V>) -> MutTraversal<'a, K, V> {
951 impl<K, V> Traverse<Node<K, V>> for MoveTraversal<K, V> {
952 fn traverse(node: Node<K, V>) -> MoveTraversal<K, V> {
957 /// Represents an operation to perform inside the following iterator methods.
958 /// This is necessary to use in `next` because we want to modify `self.traversals` inside
959 /// a match that borrows it. Similarly in `next_back`. Instead, we use this enum to note
960 /// what we want to do, and do it after the match.
965 impl<K, V, E, T> Iterator for AbsIter<T> where
966 T: DoubleEndedIterator<Item=TraversalItem<K, V, E>> + Traverse<E>,
970 // Our iterator represents a queue of all ancestors of elements we have
971 // yet to yield, from smallest to largest. Note that the design of these
972 // iterators permits an *arbitrary* initial pair of min and max, making
973 // these arbitrary sub-range iterators.
974 fn next(&mut self) -> Option<(K, V)> {
976 // We want the smallest element, so try to get the back of the queue
977 let op = match self.traversals.back_mut() {
979 // The queue wasn't empty, so continue along the node in its head
980 Some(iter) => match iter.next() {
981 // The head is empty, so Pop it off and continue the process
983 // The head yielded an edge, so make that the new head
984 Some(Edge(next)) => Push(Traverse::traverse(next)),
985 // The head yielded an entry, so yield that
993 // Handle any operation as necessary, without a conflicting borrow of the queue
995 Push(item) => { self.traversals.push_back(item); },
996 Pop => { self.traversals.pop_back(); },
1001 fn size_hint(&self) -> (usize, Option<usize>) {
1002 (self.size, Some(self.size))
1006 impl<K, V, E, T> DoubleEndedIterator for AbsIter<T> where
1007 T: DoubleEndedIterator<Item=TraversalItem<K, V, E>> + Traverse<E>,
1009 // next_back is totally symmetric to next
1011 fn next_back(&mut self) -> Option<(K, V)> {
1013 let op = match self.traversals.front_mut() {
1014 None => return None,
1015 Some(iter) => match iter.next_back() {
1017 Some(Edge(next)) => Push(Traverse::traverse(next)),
1026 Push(item) => { self.traversals.push_front(item); },
1027 Pop => { self.traversals.pop_front(); }
1033 #[stable(feature = "rust1", since = "1.0.0")]
1034 impl<'a, K, V> Iterator for Iter<'a, K, V> {
1035 type Item = (&'a K, &'a V);
1037 fn next(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next() }
1038 fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1040 #[stable(feature = "rust1", since = "1.0.0")]
1041 impl<'a, K, V> DoubleEndedIterator for Iter<'a, K, V> {
1042 fn next_back(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next_back() }
1044 #[stable(feature = "rust1", since = "1.0.0")]
1045 impl<'a, K, V> ExactSizeIterator for Iter<'a, K, V> {}
1047 #[stable(feature = "rust1", since = "1.0.0")]
1048 impl<'a, K, V> Iterator for IterMut<'a, K, V> {
1049 type Item = (&'a K, &'a mut V);
1051 fn next(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next() }
1052 fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1054 #[stable(feature = "rust1", since = "1.0.0")]
1055 impl<'a, K, V> DoubleEndedIterator for IterMut<'a, K, V> {
1056 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next_back() }
1058 #[stable(feature = "rust1", since = "1.0.0")]
1059 impl<'a, K, V> ExactSizeIterator for IterMut<'a, K, V> {}
1061 #[stable(feature = "rust1", since = "1.0.0")]
1062 impl<K, V> Iterator for IntoIter<K, V> {
1065 fn next(&mut self) -> Option<(K, V)> { self.inner.next() }
1066 fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1068 #[stable(feature = "rust1", since = "1.0.0")]
1069 impl<K, V> DoubleEndedIterator for IntoIter<K, V> {
1070 fn next_back(&mut self) -> Option<(K, V)> { self.inner.next_back() }
1072 #[stable(feature = "rust1", since = "1.0.0")]
1073 impl<K, V> ExactSizeIterator for IntoIter<K, V> {}
1075 #[stable(feature = "rust1", since = "1.0.0")]
1076 impl<'a, K, V> Iterator for Keys<'a, K, V> {
1079 fn next(&mut self) -> Option<(&'a K)> { self.inner.next() }
1080 fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1082 #[stable(feature = "rust1", since = "1.0.0")]
1083 impl<'a, K, V> DoubleEndedIterator for Keys<'a, K, V> {
1084 fn next_back(&mut self) -> Option<(&'a K)> { self.inner.next_back() }
1086 #[stable(feature = "rust1", since = "1.0.0")]
1087 impl<'a, K, V> ExactSizeIterator for Keys<'a, K, V> {}
1090 #[stable(feature = "rust1", since = "1.0.0")]
1091 impl<'a, K, V> Iterator for Values<'a, K, V> {
1094 fn next(&mut self) -> Option<(&'a V)> { self.inner.next() }
1095 fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1097 #[stable(feature = "rust1", since = "1.0.0")]
1098 impl<'a, K, V> DoubleEndedIterator for Values<'a, K, V> {
1099 fn next_back(&mut self) -> Option<(&'a V)> { self.inner.next_back() }
1101 #[stable(feature = "rust1", since = "1.0.0")]
1102 impl<'a, K, V> ExactSizeIterator for Values<'a, K, V> {}
1104 impl<'a, K, V> Iterator for Range<'a, K, V> {
1105 type Item = (&'a K, &'a V);
1107 fn next(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next() }
1109 impl<'a, K, V> DoubleEndedIterator for Range<'a, K, V> {
1110 fn next_back(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next_back() }
1113 impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
1114 type Item = (&'a K, &'a mut V);
1116 fn next(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next() }
1118 impl<'a, K, V> DoubleEndedIterator for RangeMut<'a, K, V> {
1119 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next_back() }
1122 impl<'a, K: Ord, V> Entry<'a, K, V> {
1123 #[unstable(feature = "collections",
1124 reason = "matches collection reform v2 specification, waiting for dust to settle")]
1125 /// Returns a mutable reference to the entry if occupied, or the VacantEntry if vacant
1126 pub fn get(self) -> Result<&'a mut V, VacantEntry<'a, K, V>> {
1128 Occupied(entry) => Ok(entry.into_mut()),
1129 Vacant(entry) => Err(entry),
1134 impl<'a, K: Ord, V> VacantEntry<'a, K, V> {
1135 /// Sets the value of the entry with the VacantEntry's key,
1136 /// and returns a mutable reference to it.
1137 #[stable(feature = "rust1", since = "1.0.0")]
1138 pub fn insert(self, value: V) -> &'a mut V {
1139 self.stack.insert(self.key, value)
1143 impl<'a, K: Ord, V> OccupiedEntry<'a, K, V> {
1144 /// Gets a reference to the value in the entry.
1145 #[stable(feature = "rust1", since = "1.0.0")]
1146 pub fn get(&self) -> &V {
1150 /// Gets a mutable reference to the value in the entry.
1151 #[stable(feature = "rust1", since = "1.0.0")]
1152 pub fn get_mut(&mut self) -> &mut V {
1153 self.stack.peek_mut()
1156 /// Converts the entry into a mutable reference to its value.
1157 #[stable(feature = "rust1", since = "1.0.0")]
1158 pub fn into_mut(self) -> &'a mut V {
1159 self.stack.into_top()
1162 /// Sets the value of the entry with the OccupiedEntry's key,
1163 /// and returns the entry's old value.
1164 #[stable(feature = "rust1", since = "1.0.0")]
1165 pub fn insert(&mut self, mut value: V) -> V {
1166 mem::swap(self.stack.peek_mut(), &mut value);
1170 /// Takes the value of the entry out of the map, and returns it.
1171 #[stable(feature = "rust1", since = "1.0.0")]
1172 pub fn remove(self) -> V {
1177 impl<K, V> BTreeMap<K, V> {
1178 /// Gets an iterator over the entries of the map.
1183 /// use std::collections::BTreeMap;
1185 /// let mut map = BTreeMap::new();
1186 /// map.insert(1, "a");
1187 /// map.insert(2, "b");
1188 /// map.insert(3, "c");
1190 /// for (key, value) in map.iter() {
1191 /// println!("{}: {}", key, value);
1194 /// let (first_key, first_value) = map.iter().next().unwrap();
1195 /// assert_eq!((*first_key, *first_value), (1, "a"));
1197 #[stable(feature = "rust1", since = "1.0.0")]
1198 pub fn iter(&self) -> Iter<K, V> {
1199 let len = self.len();
1200 // NB. The initial capacity for ringbuf is large enough to avoid reallocs in many cases.
1201 let mut lca = VecDeque::new();
1202 lca.push_back(Traverse::traverse(&self.root));
1211 /// Gets a mutable iterator over the entries of the map.
1216 /// use std::collections::BTreeMap;
1218 /// let mut map = BTreeMap::new();
1219 /// map.insert("a", 1);
1220 /// map.insert("b", 2);
1221 /// map.insert("c", 3);
1223 /// // add 10 to the value if the key isn't "a"
1224 /// for (key, value) in map.iter_mut() {
1225 /// if key != &"a" {
1230 #[stable(feature = "rust1", since = "1.0.0")]
1231 pub fn iter_mut(&mut self) -> IterMut<K, V> {
1232 let len = self.len();
1233 let mut lca = VecDeque::new();
1234 lca.push_back(Traverse::traverse(&mut self.root));
1243 /// Gets an owning iterator over the entries of the map.
1248 /// use std::collections::BTreeMap;
1250 /// let mut map = BTreeMap::new();
1251 /// map.insert(1, "a");
1252 /// map.insert(2, "b");
1253 /// map.insert(3, "c");
1255 /// for (key, value) in map.into_iter() {
1256 /// println!("{}: {}", key, value);
1259 #[stable(feature = "rust1", since = "1.0.0")]
1260 pub fn into_iter(self) -> IntoIter<K, V> {
1261 let len = self.len();
1262 let mut lca = VecDeque::new();
1263 lca.push_back(Traverse::traverse(self.root));
1272 /// Gets an iterator over the keys of the map.
1277 /// use std::collections::BTreeMap;
1279 /// let mut a = BTreeMap::new();
1280 /// a.insert(1, "a");
1281 /// a.insert(2, "b");
1283 /// let keys: Vec<usize> = a.keys().cloned().collect();
1284 /// assert_eq!(keys, vec![1,2,]);
1286 #[stable(feature = "rust1", since = "1.0.0")]
1287 pub fn keys<'a>(&'a self) -> Keys<'a, K, V> {
1288 fn first<A, B>((a, _): (A, B)) -> A { a }
1289 let first: fn((&'a K, &'a V)) -> &'a K = first; // coerce to fn pointer
1291 Keys { inner: self.iter().map(first) }
1294 /// Gets an iterator over the values of the map.
1299 /// use std::collections::BTreeMap;
1301 /// let mut a = BTreeMap::new();
1302 /// a.insert(1, "a");
1303 /// a.insert(2, "b");
1305 /// let values: Vec<&str> = a.values().cloned().collect();
1306 /// assert_eq!(values, vec!["a","b"]);
1308 #[stable(feature = "rust1", since = "1.0.0")]
1309 pub fn values<'a>(&'a self) -> Values<'a, K, V> {
1310 fn second<A, B>((_, b): (A, B)) -> B { b }
1311 let second: fn((&'a K, &'a V)) -> &'a V = second; // coerce to fn pointer
1313 Values { inner: self.iter().map(second) }
1316 /// Return the number of elements in the map.
1321 /// use std::collections::BTreeMap;
1323 /// let mut a = BTreeMap::new();
1324 /// assert_eq!(a.len(), 0);
1325 /// a.insert(1, "a");
1326 /// assert_eq!(a.len(), 1);
1328 #[stable(feature = "rust1", since = "1.0.0")]
1329 pub fn len(&self) -> usize { self.length }
1331 /// Return true if the map contains no elements.
1336 /// use std::collections::BTreeMap;
1338 /// let mut a = BTreeMap::new();
1339 /// assert!(a.is_empty());
1340 /// a.insert(1, "a");
1341 /// assert!(!a.is_empty());
1343 #[stable(feature = "rust1", since = "1.0.0")]
1344 pub fn is_empty(&self) -> bool { self.len() == 0 }
1347 macro_rules! range_impl {
1348 ($root:expr, $min:expr, $max:expr, $as_slices_internal:ident, $iter:ident, $Range:ident,
1349 $edges:ident, [$($mutability:ident)*]) => (
1351 // A deque that encodes two search paths containing (left-to-right):
1352 // a series of truncated-from-the-left iterators, the LCA's doubly-truncated iterator,
1353 // and a series of truncated-from-the-right iterators.
1354 let mut traversals = VecDeque::new();
1355 let (root, min, max) = ($root, $min, $max);
1357 let mut leftmost = None;
1358 let mut rightmost = None;
1360 match (&min, &max) {
1361 (&Unbounded, &Unbounded) => {
1362 traversals.push_back(Traverse::traverse(root))
1364 (&Unbounded, &Included(_)) | (&Unbounded, &Excluded(_)) => {
1365 rightmost = Some(root);
1367 (&Included(_), &Unbounded) | (&Excluded(_), &Unbounded) => {
1368 leftmost = Some(root);
1370 (&Included(min_key), &Included(max_key))
1371 | (&Included(min_key), &Excluded(max_key))
1372 | (&Excluded(min_key), &Included(max_key))
1373 | (&Excluded(min_key), &Excluded(max_key)) => {
1374 // lca represents the Lowest Common Ancestor, above which we never
1375 // walk, since everything else is outside the range to iterate.
1376 // ___________________
1377 // |__0_|_80_|_85_|_90_| (root)
1381 // ___________________
1382 // |__5_|_15_|_30_|_73_|
1386 // ___________________
1387 // |_33_|_58_|_63_|_68_| lca for the range [41, 65]
1388 // | |\___|___/| | iterator at traversals[2]
1393 let mut is_leaf = root.is_leaf();
1394 let mut lca = root.$as_slices_internal();
1396 let slice = lca.slice_from(min_key).slice_to(max_key);
1397 if let [ref $($mutability)* edge] = slice.edges {
1398 // Follow the only edge that leads the node that covers the range.
1399 is_leaf = edge.is_leaf();
1400 lca = edge.$as_slices_internal();
1402 let mut iter = slice.$iter();
1407 // Only change the state of nodes with edges.
1408 leftmost = iter.next_edge_item();
1409 rightmost = iter.next_edge_item_back();
1411 traversals.push_back(iter);
1417 // Keep narrowing the range by going down.
1418 // ___________________
1419 // |_38_|_43_|_48_|_53_|
1420 // | |____|____|____/ iterator at traversals[1]
1423 // ___________________
1424 // |_39_|_40_|_41_|_42_| (leaf, the last leftmost)
1425 // \_________| iterator at traversals[0]
1427 Included(key) | Excluded(key) =>
1428 while let Some(left) = leftmost {
1429 let is_leaf = left.is_leaf();
1430 let mut iter = left.$as_slices_internal().slice_from(key).$iter();
1431 leftmost = if is_leaf {
1434 // Only change the state of nodes with edges.
1435 iter.next_edge_item()
1437 traversals.push_back(iter);
1441 // If the leftmost iterator starts with an element, then it was an exact match.
1442 if let (Excluded(_), Some(leftmost_iter)) = (min, traversals.back_mut()) {
1443 // Drop this excluded element. `next_kv_item` has no effect when
1444 // the next item is an edge.
1445 leftmost_iter.next_kv_item();
1448 // The code for the right side is similar.
1450 Included(key) | Excluded(key) =>
1451 while let Some(right) = rightmost {
1452 let is_leaf = right.is_leaf();
1453 let mut iter = right.$as_slices_internal().slice_to(key).$iter();
1454 rightmost = if is_leaf {
1457 iter.next_edge_item_back()
1459 traversals.push_front(iter);
1463 if let (Excluded(_), Some(rightmost_iter)) = (max, traversals.front_mut()) {
1464 rightmost_iter.next_kv_item_back();
1469 traversals: traversals,
1477 impl<K: Ord, V> BTreeMap<K, V> {
1478 /// Constructs a double-ended iterator over a sub-range of elements in the map, starting
1479 /// at min, and ending at max. If min is `Unbounded`, then it will be treated as "negative
1480 /// infinity", and if max is `Unbounded`, then it will be treated as "positive infinity".
1481 /// Thus range(Unbounded, Unbounded) will yield the whole collection.
1486 /// use std::collections::BTreeMap;
1487 /// use std::collections::Bound::{Included, Unbounded};
1489 /// let mut map = BTreeMap::new();
1490 /// map.insert(3, "a");
1491 /// map.insert(5, "b");
1492 /// map.insert(8, "c");
1493 /// for (&key, &value) in map.range(Included(&4), Included(&8)) {
1494 /// println!("{}: {}", key, value);
1496 /// assert_eq!(Some((&5, &"b")), map.range(Included(&4), Unbounded).next());
1498 #[unstable(feature = "collections",
1499 reason = "matches collection reform specification, waiting for dust to settle")]
1500 pub fn range<'a>(&'a self, min: Bound<&K>, max: Bound<&K>) -> Range<'a, K, V> {
1501 range_impl!(&self.root, min, max, as_slices_internal, iter, Range, edges, [])
1504 /// Constructs a mutable double-ended iterator over a sub-range of elements in the map, starting
1505 /// at min, and ending at max. If min is `Unbounded`, then it will be treated as "negative
1506 /// infinity", and if max is `Unbounded`, then it will be treated as "positive infinity".
1507 /// Thus range(Unbounded, Unbounded) will yield the whole collection.
1512 /// use std::collections::BTreeMap;
1513 /// use std::collections::Bound::{Included, Excluded};
1515 /// let mut map: BTreeMap<&str, i32> = ["Alice", "Bob", "Carol", "Cheryl"].iter()
1516 /// .map(|&s| (s, 0))
1518 /// for (_, balance) in map.range_mut(Included(&"B"), Excluded(&"Cheryl")) {
1519 /// *balance += 100;
1521 /// for (name, balance) in map.iter() {
1522 /// println!("{} => {}", name, balance);
1525 #[unstable(feature = "collections",
1526 reason = "matches collection reform specification, waiting for dust to settle")]
1527 pub fn range_mut<'a>(&'a mut self, min: Bound<&K>, max: Bound<&K>) -> RangeMut<'a, K, V> {
1528 range_impl!(&mut self.root, min, max, as_slices_internal_mut, iter_mut, RangeMut,
1532 /// Gets the given key's corresponding entry in the map for in-place manipulation.
1537 /// use std::collections::BTreeMap;
1538 /// use std::collections::btree_map::Entry;
1540 /// let mut count: BTreeMap<&str, usize> = BTreeMap::new();
1542 /// // count the number of occurrences of letters in the vec
1543 /// for x in vec!["a","b","a","c","a","b"].iter() {
1544 /// match count.entry(*x) {
1545 /// Entry::Vacant(view) => {
1548 /// Entry::Occupied(mut view) => {
1549 /// let v = view.get_mut();
1555 /// assert_eq!(count["a"], 3);
1557 #[stable(feature = "rust1", since = "1.0.0")]
1558 pub fn entry(&mut self, mut key: K) -> Entry<K, V> {
1559 // same basic logic of `swap` and `pop`, blended together
1560 let mut stack = stack::PartialSearchStack::new(self);
1562 let result = stack.with(move |pusher, node| {
1563 return match Node::search(node, &key) {
1566 Finished(Occupied(OccupiedEntry {
1567 stack: pusher.seal(handle)
1571 match handle.force() {
1572 Leaf(leaf_handle) => {
1573 Finished(Vacant(VacantEntry {
1574 stack: pusher.seal(leaf_handle),
1578 Internal(internal_handle) => {
1580 pusher.push(internal_handle),
1589 Finished(finished) => return finished,
1590 Continue((new_stack, renewed_key)) => {
1606 use std::iter::range_inclusive;
1608 use super::BTreeMap;
1609 use super::Entry::{Occupied, Vacant};
1610 use Bound::{self, Included, Excluded, Unbounded};
1613 fn test_basic_large() {
1614 let mut map = BTreeMap::new();
1616 assert_eq!(map.len(), 0);
1619 assert_eq!(map.insert(i, 10*i), None);
1620 assert_eq!(map.len(), i + 1);
1624 assert_eq!(map.get(&i).unwrap(), &(i*10));
1627 for i in size..size*2 {
1628 assert_eq!(map.get(&i), None);
1632 assert_eq!(map.insert(i, 100*i), Some(10*i));
1633 assert_eq!(map.len(), size);
1637 assert_eq!(map.get(&i).unwrap(), &(i*100));
1640 for i in 0..size/2 {
1641 assert_eq!(map.remove(&(i*2)), Some(i*200));
1642 assert_eq!(map.len(), size - i - 1);
1645 for i in 0..size/2 {
1646 assert_eq!(map.get(&(2*i)), None);
1647 assert_eq!(map.get(&(2*i+1)).unwrap(), &(i*200 + 100));
1650 for i in 0..size/2 {
1651 assert_eq!(map.remove(&(2*i)), None);
1652 assert_eq!(map.remove(&(2*i+1)), Some(i*200 + 100));
1653 assert_eq!(map.len(), size/2 - i - 1);
1658 fn test_basic_small() {
1659 let mut map = BTreeMap::new();
1660 assert_eq!(map.remove(&1), None);
1661 assert_eq!(map.get(&1), None);
1662 assert_eq!(map.insert(1, 1), None);
1663 assert_eq!(map.get(&1), Some(&1));
1664 assert_eq!(map.insert(1, 2), Some(1));
1665 assert_eq!(map.get(&1), Some(&2));
1666 assert_eq!(map.insert(2, 4), None);
1667 assert_eq!(map.get(&2), Some(&4));
1668 assert_eq!(map.remove(&1), Some(2));
1669 assert_eq!(map.remove(&2), Some(4));
1670 assert_eq!(map.remove(&1), None);
1678 let mut map: BTreeMap<_, _> = (0..size).map(|i| (i, i)).collect();
1680 fn test<T>(size: usize, mut iter: T) where T: Iterator<Item=(usize, usize)> {
1682 assert_eq!(iter.size_hint(), (size - i, Some(size - i)));
1683 assert_eq!(iter.next().unwrap(), (i, i));
1685 assert_eq!(iter.size_hint(), (0, Some(0)));
1686 assert_eq!(iter.next(), None);
1688 test(size, map.iter().map(|(&k, &v)| (k, v)));
1689 test(size, map.iter_mut().map(|(&k, &mut v)| (k, v)));
1690 test(size, map.into_iter());
1694 fn test_iter_rev() {
1698 let mut map: BTreeMap<_, _> = (0..size).map(|i| (i, i)).collect();
1700 fn test<T>(size: usize, mut iter: T) where T: Iterator<Item=(usize, usize)> {
1702 assert_eq!(iter.size_hint(), (size - i, Some(size - i)));
1703 assert_eq!(iter.next().unwrap(), (size - i - 1, size - i - 1));
1705 assert_eq!(iter.size_hint(), (0, Some(0)));
1706 assert_eq!(iter.next(), None);
1708 test(size, map.iter().rev().map(|(&k, &v)| (k, v)));
1709 test(size, map.iter_mut().rev().map(|(&k, &mut v)| (k, v)));
1710 test(size, map.into_iter().rev());
1714 fn test_iter_mixed() {
1718 let mut map: BTreeMap<_, _> = (0..size).map(|i| (i, i)).collect();
1720 fn test<T>(size: usize, mut iter: T)
1721 where T: Iterator<Item=(usize, usize)> + DoubleEndedIterator {
1722 for i in 0..size / 4 {
1723 assert_eq!(iter.size_hint(), (size - i * 2, Some(size - i * 2)));
1724 assert_eq!(iter.next().unwrap(), (i, i));
1725 assert_eq!(iter.next_back().unwrap(), (size - i - 1, size - i - 1));
1727 for i in size / 4..size * 3 / 4 {
1728 assert_eq!(iter.size_hint(), (size * 3 / 4 - i, Some(size * 3 / 4 - i)));
1729 assert_eq!(iter.next().unwrap(), (i, i));
1731 assert_eq!(iter.size_hint(), (0, Some(0)));
1732 assert_eq!(iter.next(), None);
1734 test(size, map.iter().map(|(&k, &v)| (k, v)));
1735 test(size, map.iter_mut().map(|(&k, &mut v)| (k, v)));
1736 test(size, map.into_iter());
1740 fn test_range_small() {
1744 let map: BTreeMap<_, _> = (0..size).map(|i| (i, i)).collect();
1747 for ((&k, &v), i) in map.range(Included(&2), Unbounded).zip(2..size) {
1752 assert_eq!(j, size - 2);
1756 fn test_range_1000() {
1758 let map: BTreeMap<_, _> = (0..size).map(|i| (i, i)).collect();
1760 fn test(map: &BTreeMap<u32, u32>, size: u32, min: Bound<&u32>, max: Bound<&u32>) {
1761 let mut kvs = map.range(min, max).map(|(&k, &v)| (k, v));
1762 let mut pairs = (0..size).map(|i| (i, i));
1764 for (kv, pair) in kvs.by_ref().zip(pairs.by_ref()) {
1765 assert_eq!(kv, pair);
1767 assert_eq!(kvs.next(), None);
1768 assert_eq!(pairs.next(), None);
1770 test(&map, size, Included(&0), Excluded(&size));
1771 test(&map, size, Unbounded, Excluded(&size));
1772 test(&map, size, Included(&0), Included(&(size - 1)));
1773 test(&map, size, Unbounded, Included(&(size - 1)));
1774 test(&map, size, Included(&0), Unbounded);
1775 test(&map, size, Unbounded, Unbounded);
1781 let map: BTreeMap<_, _> = (0..size).map(|i| (i, i)).collect();
1785 let mut kvs = map.range(Included(&i), Included(&j)).map(|(&k, &v)| (k, v));
1786 let mut pairs = range_inclusive(i, j).map(|i| (i, i));
1788 for (kv, pair) in kvs.by_ref().zip(pairs.by_ref()) {
1789 assert_eq!(kv, pair);
1791 assert_eq!(kvs.next(), None);
1792 assert_eq!(pairs.next(), None);
1799 let xs = [(1, 10), (2, 20), (3, 30), (4, 40), (5, 50), (6, 60)];
1801 let mut map: BTreeMap<_, _> = xs.iter().cloned().collect();
1803 // Existing key (insert)
1804 match map.entry(1) {
1805 Vacant(_) => unreachable!(),
1806 Occupied(mut view) => {
1807 assert_eq!(view.get(), &10);
1808 assert_eq!(view.insert(100), 10);
1811 assert_eq!(map.get(&1).unwrap(), &100);
1812 assert_eq!(map.len(), 6);
1815 // Existing key (update)
1816 match map.entry(2) {
1817 Vacant(_) => unreachable!(),
1818 Occupied(mut view) => {
1819 let v = view.get_mut();
1823 assert_eq!(map.get(&2).unwrap(), &200);
1824 assert_eq!(map.len(), 6);
1826 // Existing key (take)
1827 match map.entry(3) {
1828 Vacant(_) => unreachable!(),
1830 assert_eq!(view.remove(), 30);
1833 assert_eq!(map.get(&3), None);
1834 assert_eq!(map.len(), 5);
1837 // Inexistent key (insert)
1838 match map.entry(10) {
1839 Occupied(_) => unreachable!(),
1841 assert_eq!(*view.insert(1000), 1000);
1844 assert_eq!(map.get(&10).unwrap(), &1000);
1845 assert_eq!(map.len(), 6);
1857 use std::rand::{weak_rng, Rng};
1858 use test::{Bencher, black_box};
1860 use super::BTreeMap;
1862 map_insert_rand_bench!{insert_rand_100, 100, BTreeMap}
1863 map_insert_rand_bench!{insert_rand_10_000, 10_000, BTreeMap}
1865 map_insert_seq_bench!{insert_seq_100, 100, BTreeMap}
1866 map_insert_seq_bench!{insert_seq_10_000, 10_000, BTreeMap}
1868 map_find_rand_bench!{find_rand_100, 100, BTreeMap}
1869 map_find_rand_bench!{find_rand_10_000, 10_000, BTreeMap}
1871 map_find_seq_bench!{find_seq_100, 100, BTreeMap}
1872 map_find_seq_bench!{find_seq_10_000, 10_000, BTreeMap}
1874 fn bench_iter(b: &mut Bencher, size: i32) {
1875 let mut map = BTreeMap::<i32, i32>::new();
1876 let mut rng = weak_rng();
1879 map.insert(rng.gen(), rng.gen());
1890 pub fn iter_20(b: &mut Bencher) {
1895 pub fn iter_1000(b: &mut Bencher) {
1896 bench_iter(b, 1000);
1900 pub fn iter_100000(b: &mut Bencher) {
1901 bench_iter(b, 100000);