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};
28 use core::{iter, fmt, mem, usize};
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 /// It is a logic error for a key to be modified in such a way that the key's ordering relative to
69 /// any other key, as determined by the `Ord` trait, changes while it is in the map. This is
70 /// normally only possible through `Cell`, `RefCell`, global state, I/O, or unsafe code.
72 #[stable(feature = "rust1", since = "1.0.0")]
73 pub struct BTreeMap<K, V> {
80 /// An abstract base over-which all other BTree iterators are built.
83 traversals: VecDeque<T>,
87 /// An iterator over a BTreeMap's entries.
88 #[stable(feature = "rust1", since = "1.0.0")]
89 pub struct Iter<'a, K: 'a, V: 'a> {
90 inner: AbsIter<Traversal<'a, K, V>>
93 /// A mutable iterator over a BTreeMap's entries.
94 #[stable(feature = "rust1", since = "1.0.0")]
95 pub struct IterMut<'a, K: 'a, V: 'a> {
96 inner: AbsIter<MutTraversal<'a, K, V>>
99 /// An owning iterator over a BTreeMap's entries.
100 #[stable(feature = "rust1", since = "1.0.0")]
101 pub struct IntoIter<K, V> {
102 inner: AbsIter<MoveTraversal<K, V>>
105 /// An iterator over a BTreeMap's keys.
106 #[stable(feature = "rust1", since = "1.0.0")]
107 pub struct Keys<'a, K: 'a, V: 'a> {
108 inner: Map<Iter<'a, K, V>, fn((&'a K, &'a V)) -> &'a K>
111 /// An iterator over a BTreeMap's values.
112 #[stable(feature = "rust1", since = "1.0.0")]
113 pub struct Values<'a, K: 'a, V: 'a> {
114 inner: Map<Iter<'a, K, V>, fn((&'a K, &'a V)) -> &'a V>
117 /// An iterator over a sub-range of BTreeMap's entries.
118 pub struct Range<'a, K: 'a, V: 'a> {
119 inner: AbsIter<Traversal<'a, K, V>>
122 /// A mutable iterator over a sub-range of BTreeMap's entries.
123 pub struct RangeMut<'a, K: 'a, V: 'a> {
124 inner: AbsIter<MutTraversal<'a, K, V>>
127 /// A view into a single entry in a map, which may either be vacant or occupied.
128 #[stable(feature = "rust1", since = "1.0.0")]
129 pub enum Entry<'a, K:'a, V:'a> {
131 #[stable(feature = "rust1", since = "1.0.0")]
132 Vacant(VacantEntry<'a, K, V>),
134 /// An occupied Entry
135 #[stable(feature = "rust1", since = "1.0.0")]
136 Occupied(OccupiedEntry<'a, K, V>),
140 #[stable(feature = "rust1", since = "1.0.0")]
141 pub struct VacantEntry<'a, K:'a, V:'a> {
143 stack: stack::SearchStack<'a, K, V, node::handle::Edge, node::handle::Leaf>,
146 /// An occupied Entry.
147 #[stable(feature = "rust1", since = "1.0.0")]
148 pub struct OccupiedEntry<'a, K:'a, V:'a> {
149 stack: stack::SearchStack<'a, K, V, node::handle::KV, node::handle::LeafOrInternal>,
152 impl<K: Ord, V> BTreeMap<K, V> {
153 /// Makes a new empty BTreeMap with a reasonable choice for B.
154 #[stable(feature = "rust1", since = "1.0.0")]
155 pub fn new() -> BTreeMap<K, V> {
156 //FIXME(Gankro): Tune this as a function of size_of<K/V>?
160 /// Makes a new empty BTreeMap with the given B.
162 /// B cannot be less than 2.
163 pub fn with_b(b: usize) -> BTreeMap<K, V> {
164 assert!(b > 1, "B must be greater than 1");
168 root: Node::make_leaf_root(b),
173 /// Clears the map, removing all values.
178 /// use std::collections::BTreeMap;
180 /// let mut a = BTreeMap::new();
181 /// a.insert(1, "a");
183 /// assert!(a.is_empty());
185 #[stable(feature = "rust1", since = "1.0.0")]
186 pub fn clear(&mut self) {
188 // avoid recursive destructors by manually traversing the tree
189 for _ in mem::replace(self, BTreeMap::with_b(b)) {};
192 // Searching in a B-Tree is pretty straightforward.
194 // Start at the root. Try to find the key in the current node. If we find it, return it.
195 // If it's not in there, follow the edge *before* the smallest key larger than
196 // the search key. If no such key exists (they're *all* smaller), then just take the last
197 // edge in the node. If we're in a leaf and we don't find our key, then it's not
200 /// Returns a reference to the value corresponding to the key.
202 /// The key may be any borrowed form of the map's key type, but the ordering
203 /// on the borrowed form *must* match the ordering on the key type.
208 /// use std::collections::BTreeMap;
210 /// let mut map = BTreeMap::new();
211 /// map.insert(1, "a");
212 /// assert_eq!(map.get(&1), Some(&"a"));
213 /// assert_eq!(map.get(&2), None);
215 #[stable(feature = "rust1", since = "1.0.0")]
216 pub fn get<Q: ?Sized>(&self, key: &Q) -> Option<&V> where K: Borrow<Q>, Q: Ord {
217 let mut cur_node = &self.root;
219 match Node::search(cur_node, key) {
220 Found(handle) => return Some(handle.into_kv().1),
221 GoDown(handle) => match handle.force() {
222 Leaf(_) => return None,
223 Internal(internal_handle) => {
224 cur_node = internal_handle.into_edge();
232 /// Returns true if the map contains a value for the specified key.
234 /// The key may be any borrowed form of the map's key type, but the ordering
235 /// on the borrowed form *must* match the ordering on the key type.
240 /// use std::collections::BTreeMap;
242 /// let mut map = BTreeMap::new();
243 /// map.insert(1, "a");
244 /// assert_eq!(map.contains_key(&1), true);
245 /// assert_eq!(map.contains_key(&2), false);
247 #[stable(feature = "rust1", since = "1.0.0")]
248 pub fn contains_key<Q: ?Sized>(&self, key: &Q) -> bool where K: Borrow<Q>, Q: Ord {
249 self.get(key).is_some()
252 /// Returns a mutable reference to the value corresponding to the key.
254 /// The key may be any borrowed form of the map's key type, but the ordering
255 /// on the borrowed form *must* match the ordering on the key type.
260 /// use std::collections::BTreeMap;
262 /// let mut map = BTreeMap::new();
263 /// map.insert(1, "a");
264 /// match map.get_mut(&1) {
265 /// Some(x) => *x = "b",
268 /// assert_eq!(map[&1], "b");
270 // See `get` for implementation notes, this is basically a copy-paste with mut's added
271 #[stable(feature = "rust1", since = "1.0.0")]
272 pub fn get_mut<Q: ?Sized>(&mut self, key: &Q) -> Option<&mut V> where K: Borrow<Q>, Q: Ord {
273 // temp_node is a Borrowck hack for having a mutable value outlive a loop iteration
274 let mut temp_node = &mut self.root;
276 let cur_node = temp_node;
277 match Node::search(cur_node, key) {
278 Found(handle) => return Some(handle.into_kv_mut().1),
279 GoDown(handle) => match handle.force() {
280 Leaf(_) => return None,
281 Internal(internal_handle) => {
282 temp_node = internal_handle.into_edge_mut();
290 // Insertion in a B-Tree is a bit complicated.
292 // First we do the same kind of search described in `find`. But we need to maintain a stack of
293 // all the nodes/edges in our search path. If we find a match for the key we're trying to
294 // insert, just swap the vals and return the old ones. However, when we bottom out in a leaf,
295 // we attempt to insert our key-value pair at the same location we would want to follow another
298 // If the node has room, then this is done in the obvious way by shifting elements. However,
299 // if the node itself is full, we split node into two, and give its median key-value
300 // pair to its parent to insert the new node with. Of course, the parent may also be
301 // full, and insertion can propagate until we reach the root. If we reach the root, and
302 // it is *also* full, then we split the root and place the two nodes under a newly made root.
304 // Note that we subtly deviate from Open Data Structures in our implementation of split.
305 // ODS describes inserting into the node *regardless* of its capacity, and then
306 // splitting *afterwards* if it happens to be overfull. However, this is inefficient.
307 // Instead, we split beforehand, and then insert the key-value pair into the appropriate
308 // result node. This has two consequences:
310 // 1) While ODS produces a left node of size B-1, and a right node of size B,
311 // we may potentially reverse this. However, this shouldn't effect the analysis.
313 // 2) While ODS may potentially return the pair we *just* inserted after
314 // the split, we will never do this. Again, this shouldn't effect the analysis.
316 /// Inserts a key-value pair from the map. If the key already had a value
317 /// present in the map, that value is returned. Otherwise, `None` is returned.
322 /// use std::collections::BTreeMap;
324 /// let mut map = BTreeMap::new();
325 /// assert_eq!(map.insert(37, "a"), None);
326 /// assert_eq!(map.is_empty(), false);
328 /// map.insert(37, "b");
329 /// assert_eq!(map.insert(37, "c"), Some("b"));
330 /// assert_eq!(map[&37], "c");
332 #[stable(feature = "rust1", since = "1.0.0")]
333 pub fn insert(&mut self, mut key: K, mut value: V) -> Option<V> {
334 // This is a stack of rawptrs to nodes paired with indices, respectively
335 // representing the nodes and edges of our search path. We have to store rawptrs
336 // because as far as Rust is concerned, we can mutate aliased data with such a
337 // stack. It is of course correct, but what it doesn't know is that we will only
338 // be popping and using these ptrs one at a time in child-to-parent order. The alternative
339 // to doing this is to take the Nodes from their parents. This actually makes
340 // borrowck *really* happy and everything is pretty smooth. However, this creates
341 // *tons* of pointless writes, and requires us to always walk all the way back to
342 // the root after an insertion, even if we only needed to change a leaf. Therefore,
343 // we accept this potential unsafety and complexity in the name of performance.
345 // Regardless, the actual dangerous logic is completely abstracted away from BTreeMap
346 // by the stack module. All it can do is immutably read nodes, and ask the search stack
347 // to proceed down some edge by index. This makes the search logic we'll be reusing in a
348 // few different methods much neater, and of course drastically improves safety.
349 let mut stack = stack::PartialSearchStack::new(self);
352 let result = stack.with(move |pusher, node| {
353 // Same basic logic as found in `find`, but with PartialSearchStack mediating the
354 // actual nodes for us
355 match Node::search(node, &key) {
356 Found(mut handle) => {
357 // Perfect match, swap the values and return the old one
358 mem::swap(handle.val_mut(), &mut value);
359 Finished(Some(value))
362 // We need to keep searching, try to get the search stack
363 // to go down further
364 match handle.force() {
365 Leaf(leaf_handle) => {
366 // We've reached a leaf, perform the insertion here
367 pusher.seal(leaf_handle).insert(key, value);
370 Internal(internal_handle) => {
371 // We've found the subtree to insert this key/value pair in,
373 Continue((pusher.push(internal_handle), key, value))
380 Finished(ret) => return ret,
381 Continue((new_stack, renewed_key, renewed_val)) => {
390 // Deletion is the most complicated operation for a B-Tree.
392 // First we do the same kind of search described in
393 // `find`. But we need to maintain a stack of all the nodes/edges in our search path.
394 // If we don't find the key, then we just return `None` and do nothing. If we do find the
395 // key, we perform two operations: remove the item, and then possibly handle underflow.
397 // # removing the item
398 // If the node is a leaf, we just remove the item, and shift
399 // any items after it back to fill the hole.
401 // If the node is an internal node, we *swap* the item with the smallest item in
402 // in its right subtree (which must reside in a leaf), and then revert to the leaf
405 // # handling underflow
406 // After removing an item, there may be too few items in the node. We want nodes
407 // to be mostly full for efficiency, although we make an exception for the root, which
408 // may have as few as one item. If this is the case, we may first try to steal
409 // an item from our left or right neighbour.
411 // To steal from the left (right) neighbour,
412 // we take the largest (smallest) item and child from it. We then swap the taken item
413 // with the item in their mutual parent that separates them, and then insert the
414 // parent's item and the taken child into the first (last) index of the underflowed node.
416 // However, stealing has the possibility of underflowing our neighbour. If this is the
417 // case, we instead *merge* with our neighbour. This of course reduces the number of
418 // children in the parent. Therefore, we also steal the item that separates the now
419 // merged nodes, and insert it into the merged node.
421 // Merging may cause the parent to underflow. If this is the case, then we must repeat
422 // the underflow handling process on the parent. If merging merges the last two children
423 // of the root, then we replace the root with the merged node.
425 /// Removes a key from the map, returning the value at the key if the key
426 /// was previously in the map.
428 /// The key may be any borrowed form of the map's key type, but the ordering
429 /// on the borrowed form *must* match the ordering on the key type.
434 /// use std::collections::BTreeMap;
436 /// let mut map = BTreeMap::new();
437 /// map.insert(1, "a");
438 /// assert_eq!(map.remove(&1), Some("a"));
439 /// assert_eq!(map.remove(&1), None);
441 #[stable(feature = "rust1", since = "1.0.0")]
442 pub fn remove<Q: ?Sized>(&mut self, key: &Q) -> Option<V> where K: Borrow<Q>, Q: Ord {
443 // See `swap` for a more thorough description of the stuff going on in here
444 let mut stack = stack::PartialSearchStack::new(self);
446 let result = stack.with(move |pusher, node| {
447 match Node::search(node, key) {
449 // Perfect match. Terminate the stack here, and remove the entry
450 Finished(Some(pusher.seal(handle).remove()))
453 // We need to keep searching, try to go down the next edge
454 match handle.force() {
455 // We're at a leaf; the key isn't in here
456 Leaf(_) => Finished(None),
457 Internal(internal_handle) => Continue(pusher.push(internal_handle))
463 Finished(ret) => return ret,
464 Continue(new_stack) => stack = new_stack
470 #[stable(feature = "rust1", since = "1.0.0")]
471 impl<K, V> IntoIterator for BTreeMap<K, V> {
473 type IntoIter = IntoIter<K, V>;
475 fn into_iter(self) -> IntoIter<K, V> {
480 #[stable(feature = "rust1", since = "1.0.0")]
481 impl<'a, K, V> IntoIterator for &'a BTreeMap<K, V> {
482 type Item = (&'a K, &'a V);
483 type IntoIter = Iter<'a, K, V>;
485 fn into_iter(self) -> Iter<'a, K, V> {
490 #[stable(feature = "rust1", since = "1.0.0")]
491 impl<'a, K, V> IntoIterator for &'a mut BTreeMap<K, V> {
492 type Item = (&'a K, &'a mut V);
493 type IntoIter = IterMut<'a, K, V>;
495 fn into_iter(mut self) -> IterMut<'a, K, V> {
500 /// A helper enum useful for deciding whether to continue a loop since we can't
501 /// return from a closure
502 enum Continuation<A, B> {
507 /// The stack module provides a safe interface for constructing and manipulating a stack of ptrs
508 /// to nodes. By using this module much better safety guarantees can be made, and more search
509 /// boilerplate gets cut out.
511 use core::prelude::*;
514 use core::ops::{Deref, DerefMut};
516 use super::super::node::{self, Node, Fit, Split, Internal, Leaf};
517 use super::super::node::handle;
520 struct InvariantLifetime<'id>(
521 marker::PhantomData<::core::cell::Cell<&'id ()>>);
523 impl<'id> InvariantLifetime<'id> {
524 fn new() -> InvariantLifetime<'id> {
525 InvariantLifetime(marker::PhantomData)
529 /// A generic mutable reference, identical to `&mut` except for the fact that its lifetime
530 /// parameter is invariant. This means that wherever an `IdRef` is expected, only an `IdRef`
531 /// with the exact requested lifetime can be used. This is in contrast to normal references,
532 /// where `&'static` can be used in any function expecting any lifetime reference.
533 pub struct IdRef<'id, T: 'id> {
535 _marker: InvariantLifetime<'id>,
538 impl<'id, T> Deref for IdRef<'id, T> {
541 fn deref(&self) -> &T {
546 impl<'id, T> DerefMut for IdRef<'id, T> {
547 fn deref_mut(&mut self) -> &mut T {
552 type StackItem<K, V> = node::Handle<*mut Node<K, V>, handle::Edge, handle::Internal>;
553 type Stack<K, V> = Vec<StackItem<K, V>>;
555 /// A `PartialSearchStack` handles the construction of a search stack.
556 pub struct PartialSearchStack<'a, K:'a, V:'a> {
557 map: &'a mut BTreeMap<K, V>,
559 next: *mut Node<K, V>,
562 /// A `SearchStack` represents a full path to an element or an edge of interest. It provides
563 /// methods depending on the type of what the path points to for removing an element, inserting
564 /// a new element, and manipulating to element at the top of the stack.
565 pub struct SearchStack<'a, K:'a, V:'a, Type, NodeType> {
566 map: &'a mut BTreeMap<K, V>,
568 top: node::Handle<*mut Node<K, V>, Type, NodeType>,
571 /// A `PartialSearchStack` that doesn't hold a a reference to the next node, and is just
572 /// just waiting for a `Handle` to that next node to be pushed. See `PartialSearchStack::with`
573 /// for more details.
574 pub struct Pusher<'id, 'a, K:'a, V:'a> {
575 map: &'a mut BTreeMap<K, V>,
577 _marker: InvariantLifetime<'id>,
580 impl<'a, K, V> PartialSearchStack<'a, K, V> {
581 /// Creates a new PartialSearchStack from a BTreeMap by initializing the stack with the
582 /// root of the tree.
583 pub fn new(map: &'a mut BTreeMap<K, V>) -> PartialSearchStack<'a, K, V> {
584 let depth = map.depth;
587 next: &mut map.root as *mut _,
589 stack: Vec::with_capacity(depth),
593 /// Breaks up the stack into a `Pusher` and the next `Node`, allowing the given closure
594 /// to interact with, search, and finally push the `Node` onto the stack. The passed in
595 /// closure must be polymorphic on the `'id` lifetime parameter, as this statically
596 /// ensures that only `Handle`s from the correct `Node` can be pushed.
598 /// The reason this works is that the `Pusher` has an `'id` parameter, and will only accept
599 /// handles with the same `'id`. The closure could only get references with that lifetime
600 /// through its arguments or through some other `IdRef` that it has lying around. However,
601 /// no other `IdRef` could possibly work - because the `'id` is held in an invariant
602 /// parameter, it would need to have precisely the correct lifetime, which would mean that
603 /// at least one of the calls to `with` wouldn't be properly polymorphic, wanting a
604 /// specific lifetime instead of the one that `with` chooses to give it.
606 /// See also Haskell's `ST` monad, which uses a similar trick.
607 pub fn with<T, F: for<'id> FnOnce(Pusher<'id, 'a, K, V>,
608 IdRef<'id, Node<K, V>>) -> T>(self, closure: F) -> T {
609 let pusher = Pusher {
612 _marker: InvariantLifetime::new(),
615 inner: unsafe { &mut *self.next },
616 _marker: InvariantLifetime::new(),
619 closure(pusher, node)
623 impl<'id, 'a, K, V> Pusher<'id, 'a, K, V> {
624 /// Pushes the requested child of the stack's current top on top of the stack. If the child
625 /// exists, then a new PartialSearchStack is yielded. Otherwise, a VacantSearchStack is
627 pub fn push(mut self, mut edge: node::Handle<IdRef<'id, Node<K, V>>,
630 -> PartialSearchStack<'a, K, V> {
631 self.stack.push(edge.as_raw());
635 next: edge.edge_mut() as *mut _,
639 /// Converts the PartialSearchStack into a SearchStack.
640 pub fn seal<Type, NodeType>
641 (self, mut handle: node::Handle<IdRef<'id, Node<K, V>>, Type, NodeType>)
642 -> SearchStack<'a, K, V, Type, NodeType> {
646 top: handle.as_raw(),
651 impl<'a, K, V, NodeType> SearchStack<'a, K, V, handle::KV, NodeType> {
652 /// Gets a reference to the value the stack points to.
653 pub fn peek(&self) -> &V {
654 unsafe { self.top.from_raw().into_kv().1 }
657 /// Gets a mutable reference to the value the stack points to.
658 pub fn peek_mut(&mut self) -> &mut V {
659 unsafe { self.top.from_raw_mut().into_kv_mut().1 }
662 /// Converts the stack into a mutable reference to the value it points to, with a lifetime
663 /// tied to the original tree.
664 pub fn into_top(mut self) -> &'a mut V {
666 mem::copy_mut_lifetime(
668 self.top.from_raw_mut().val_mut()
674 impl<'a, K, V> SearchStack<'a, K, V, handle::KV, handle::Leaf> {
675 /// Removes the key and value in the top element of the stack, then handles underflows as
676 /// described in BTree's pop function.
677 fn remove_leaf(mut self) -> V {
678 self.map.length -= 1;
680 // Remove the key-value pair from the leaf that this search stack points to.
681 // Then, note if the leaf is underfull, and promptly forget the leaf and its ptr
682 // to avoid ownership issues.
683 let (value, mut underflow) = unsafe {
684 let (_, value) = self.top.from_raw_mut().remove_as_leaf();
685 let underflow = self.top.from_raw().node().is_underfull();
690 match self.stack.pop() {
692 // We've reached the root, so no matter what, we're done. We manually
693 // access the root via the tree itself to avoid creating any dangling
695 if self.map.root.len() == 0 && !self.map.root.is_leaf() {
696 // We've emptied out the root, so make its only child the new root.
697 // If it's a leaf, we just let it become empty.
699 self.map.root.hoist_lone_child();
703 Some(mut handle) => {
705 // Underflow! Handle it!
707 handle.from_raw_mut().handle_underflow();
708 underflow = handle.from_raw().node().is_underfull();
720 impl<'a, K, V> SearchStack<'a, K, V, handle::KV, handle::LeafOrInternal> {
721 /// Removes the key and value in the top element of the stack, then handles underflows as
722 /// described in BTree's pop function.
723 pub fn remove(self) -> V {
724 // Ensure that the search stack goes to a leaf. This is necessary to perform deletion
725 // in a BTree. Note that this may put the tree in an inconsistent state (further
726 // described in into_leaf's comments), but this is immediately fixed by the
727 // removing the value we want to remove
728 self.into_leaf().remove_leaf()
731 /// Subroutine for removal. Takes a search stack for a key that might terminate at an
732 /// internal node, and mutates the tree and search stack to *make* it a search stack
733 /// for that same key that *does* terminates at a leaf. If the mutation occurs, then this
734 /// leaves the tree in an inconsistent state that must be repaired by the caller by
735 /// removing the entry in question. Specifically the key-value pair and its successor will
737 fn into_leaf(mut self) -> SearchStack<'a, K, V, handle::KV, handle::Leaf> {
739 let mut top_raw = self.top;
740 let mut top = top_raw.from_raw_mut();
742 let key_ptr = top.key_mut() as *mut _;
743 let val_ptr = top.val_mut() as *mut _;
745 // Try to go into the right subtree of the found key to find its successor
747 Leaf(mut leaf_handle) => {
748 // We're a proper leaf stack, nothing to do
752 top: leaf_handle.as_raw()
755 Internal(mut internal_handle) => {
756 let mut right_handle = internal_handle.right_edge();
758 //We're not a proper leaf stack, let's get to work.
759 self.stack.push(right_handle.as_raw());
761 let mut temp_node = right_handle.edge_mut();
763 // Walk into the smallest subtree of this node
764 let node = temp_node;
766 match node.kv_handle(0).force() {
767 Leaf(mut handle) => {
768 // This node is a leaf, do the swap and return
769 mem::swap(handle.key_mut(), &mut *key_ptr);
770 mem::swap(handle.val_mut(), &mut *val_ptr);
777 Internal(kv_handle) => {
778 // This node is internal, go deeper
779 let mut handle = kv_handle.into_left_edge();
780 self.stack.push(handle.as_raw());
781 temp_node = handle.into_edge_mut();
791 impl<'a, K, V> SearchStack<'a, K, V, handle::Edge, handle::Leaf> {
792 /// Inserts the key and value into the top element in the stack, and if that node has to
793 /// split recursively inserts the split contents into the next element stack until
796 /// Assumes that the stack represents a search path from the root to a leaf.
798 /// An &mut V is returned to the inserted value, for callers that want a reference to this.
799 pub fn insert(mut self, key: K, val: V) -> &'a mut V {
801 self.map.length += 1;
803 // Insert the key and value into the leaf at the top of the stack
804 let (mut insertion, inserted_ptr) = self.top.from_raw_mut()
805 .insert_as_leaf(key, val);
810 // The last insertion went off without a hitch, no splits! We can stop
812 return &mut *inserted_ptr;
814 Split(key, val, right) => match self.stack.pop() {
815 // The last insertion triggered a split, so get the next element on the
816 // stack to recursively insert the split node into.
818 // The stack was empty; we've split the root, and need to make a
819 // a new one. This is done in-place because we can't move the
820 // root out of a reference to the tree.
821 Node::make_internal_root(&mut self.map.root, self.map.b,
825 return &mut *inserted_ptr;
827 Some(mut handle) => {
828 // The stack wasn't empty, do the insertion and recurse
829 insertion = handle.from_raw_mut()
830 .insert_as_internal(key, val, right);
841 #[stable(feature = "rust1", since = "1.0.0")]
842 impl<K: Ord, V> FromIterator<(K, V)> for BTreeMap<K, V> {
843 fn from_iter<T: IntoIterator<Item=(K, V)>>(iter: T) -> BTreeMap<K, V> {
844 let mut map = BTreeMap::new();
850 #[stable(feature = "rust1", since = "1.0.0")]
851 impl<K: Ord, V> Extend<(K, V)> for BTreeMap<K, V> {
853 fn extend<T: IntoIterator<Item=(K, V)>>(&mut self, iter: T) {
860 #[stable(feature = "rust1", since = "1.0.0")]
861 impl<K: Hash, V: Hash> Hash for BTreeMap<K, V> {
862 fn hash<H: Hasher>(&self, state: &mut H) {
869 #[stable(feature = "rust1", since = "1.0.0")]
870 impl<K: Ord, V> Default for BTreeMap<K, V> {
871 #[stable(feature = "rust1", since = "1.0.0")]
872 fn default() -> BTreeMap<K, V> {
877 #[stable(feature = "rust1", since = "1.0.0")]
878 impl<K: PartialEq, V: PartialEq> PartialEq for BTreeMap<K, V> {
879 fn eq(&self, other: &BTreeMap<K, V>) -> bool {
880 self.len() == other.len() &&
881 self.iter().zip(other.iter()).all(|(a, b)| a == b)
885 #[stable(feature = "rust1", since = "1.0.0")]
886 impl<K: Eq, V: Eq> Eq for BTreeMap<K, V> {}
888 #[stable(feature = "rust1", since = "1.0.0")]
889 impl<K: PartialOrd, V: PartialOrd> PartialOrd for BTreeMap<K, V> {
891 fn partial_cmp(&self, other: &BTreeMap<K, V>) -> Option<Ordering> {
892 iter::order::partial_cmp(self.iter(), other.iter())
896 #[stable(feature = "rust1", since = "1.0.0")]
897 impl<K: Ord, V: Ord> Ord for BTreeMap<K, V> {
899 fn cmp(&self, other: &BTreeMap<K, V>) -> Ordering {
900 iter::order::cmp(self.iter(), other.iter())
904 #[stable(feature = "rust1", since = "1.0.0")]
905 impl<K: Debug, V: Debug> Debug for BTreeMap<K, V> {
906 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
907 try!(write!(f, "{{"));
909 for (i, (k, v)) in self.iter().enumerate() {
910 if i != 0 { try!(write!(f, ", ")); }
911 try!(write!(f, "{:?}: {:?}", *k, *v));
919 #[stable(feature = "rust1", since = "1.0.0")]
920 impl<K: Ord, Q: ?Sized, V> Index<Q> for BTreeMap<K, V>
921 where K: Borrow<Q>, Q: Ord
926 fn index(&self, key: &Q) -> &V {
927 self.get(key).expect("no entry found for key")
932 #[stable(feature = "rust1", since = "1.0.0")]
933 impl<'a, K: Ord, Q: ?Sized, V> Index<&'a Q> for BTreeMap<K, V>
934 where K: Borrow<Q>, Q: Ord
939 fn index(&self, key: &Q) -> &V {
940 self.get(key).expect("no entry found for key")
944 /// Genericises over how to get the correct type of iterator from the correct type
945 /// of Node ownership.
947 fn traverse(node: N) -> Self;
950 impl<'a, K, V> Traverse<&'a Node<K, V>> for Traversal<'a, K, V> {
951 fn traverse(node: &'a Node<K, V>) -> Traversal<'a, K, V> {
956 impl<'a, K, V> Traverse<&'a mut Node<K, V>> for MutTraversal<'a, K, V> {
957 fn traverse(node: &'a mut Node<K, V>) -> MutTraversal<'a, K, V> {
962 impl<K, V> Traverse<Node<K, V>> for MoveTraversal<K, V> {
963 fn traverse(node: Node<K, V>) -> MoveTraversal<K, V> {
968 /// Represents an operation to perform inside the following iterator methods.
969 /// This is necessary to use in `next` because we want to modify `self.traversals` inside
970 /// a match that borrows it. Similarly in `next_back`. Instead, we use this enum to note
971 /// what we want to do, and do it after the match.
976 impl<K, V, E, T> Iterator for AbsIter<T> where
977 T: DoubleEndedIterator<Item=TraversalItem<K, V, E>> + Traverse<E>,
981 // Our iterator represents a queue of all ancestors of elements we have
982 // yet to yield, from smallest to largest. Note that the design of these
983 // iterators permits an *arbitrary* initial pair of min and max, making
984 // these arbitrary sub-range iterators.
985 fn next(&mut self) -> Option<(K, V)> {
987 // We want the smallest element, so try to get the back of the queue
988 let op = match self.traversals.back_mut() {
990 // The queue wasn't empty, so continue along the node in its head
991 Some(iter) => match iter.next() {
992 // The head is empty, so Pop it off and continue the process
994 // The head yielded an edge, so make that the new head
995 Some(Edge(next)) => Push(Traverse::traverse(next)),
996 // The head yielded an entry, so yield that
1004 // Handle any operation as necessary, without a conflicting borrow of the queue
1006 Push(item) => { self.traversals.push_back(item); },
1007 Pop => { self.traversals.pop_back(); },
1012 fn size_hint(&self) -> (usize, Option<usize>) {
1013 (self.size, Some(self.size))
1017 impl<K, V, E, T> DoubleEndedIterator for AbsIter<T> where
1018 T: DoubleEndedIterator<Item=TraversalItem<K, V, E>> + Traverse<E>,
1020 // next_back is totally symmetric to next
1022 fn next_back(&mut self) -> Option<(K, V)> {
1024 let op = match self.traversals.front_mut() {
1025 None => return None,
1026 Some(iter) => match iter.next_back() {
1028 Some(Edge(next)) => Push(Traverse::traverse(next)),
1037 Push(item) => { self.traversals.push_front(item); },
1038 Pop => { self.traversals.pop_front(); }
1044 impl<'a, K, V> Clone for Iter<'a, K, V> {
1045 fn clone(&self) -> Iter<'a, K, V> { Iter { inner: self.inner.clone() } }
1047 #[stable(feature = "rust1", since = "1.0.0")]
1048 impl<'a, K, V> Iterator for Iter<'a, K, V> {
1049 type Item = (&'a K, &'a V);
1051 fn next(&mut self) -> Option<(&'a K, &'a 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 Iter<'a, K, V> {
1056 fn next_back(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next_back() }
1058 #[stable(feature = "rust1", since = "1.0.0")]
1059 impl<'a, K, V> ExactSizeIterator for Iter<'a, K, V> {}
1061 #[stable(feature = "rust1", since = "1.0.0")]
1062 impl<'a, K, V> Iterator for IterMut<'a, K, V> {
1063 type Item = (&'a K, &'a mut V);
1065 fn next(&mut self) -> Option<(&'a K, &'a mut 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<'a, K, V> DoubleEndedIterator for IterMut<'a, K, V> {
1070 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next_back() }
1072 #[stable(feature = "rust1", since = "1.0.0")]
1073 impl<'a, K, V> ExactSizeIterator for IterMut<'a, K, V> {}
1075 #[stable(feature = "rust1", since = "1.0.0")]
1076 impl<K, V> Iterator for IntoIter<K, V> {
1079 fn next(&mut self) -> Option<(K, V)> { 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<K, V> DoubleEndedIterator for IntoIter<K, V> {
1084 fn next_back(&mut self) -> Option<(K, V)> { self.inner.next_back() }
1086 #[stable(feature = "rust1", since = "1.0.0")]
1087 impl<K, V> ExactSizeIterator for IntoIter<K, V> {}
1089 impl<'a, K, V> Clone for Keys<'a, K, V> {
1090 fn clone(&self) -> Keys<'a, K, V> { Keys { inner: self.inner.clone() } }
1092 #[stable(feature = "rust1", since = "1.0.0")]
1093 impl<'a, K, V> Iterator for Keys<'a, K, V> {
1096 fn next(&mut self) -> Option<(&'a K)> { self.inner.next() }
1097 fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1099 #[stable(feature = "rust1", since = "1.0.0")]
1100 impl<'a, K, V> DoubleEndedIterator for Keys<'a, K, V> {
1101 fn next_back(&mut self) -> Option<(&'a K)> { self.inner.next_back() }
1103 #[stable(feature = "rust1", since = "1.0.0")]
1104 impl<'a, K, V> ExactSizeIterator for Keys<'a, K, V> {}
1107 impl<'a, K, V> Clone for Values<'a, K, V> {
1108 fn clone(&self) -> Values<'a, K, V> { Values { inner: self.inner.clone() } }
1110 #[stable(feature = "rust1", since = "1.0.0")]
1111 impl<'a, K, V> Iterator for Values<'a, K, V> {
1114 fn next(&mut self) -> Option<(&'a V)> { self.inner.next() }
1115 fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1117 #[stable(feature = "rust1", since = "1.0.0")]
1118 impl<'a, K, V> DoubleEndedIterator for Values<'a, K, V> {
1119 fn next_back(&mut self) -> Option<(&'a V)> { self.inner.next_back() }
1121 #[stable(feature = "rust1", since = "1.0.0")]
1122 impl<'a, K, V> ExactSizeIterator for Values<'a, K, V> {}
1124 impl<'a, K, V> Clone for Range<'a, K, V> {
1125 fn clone(&self) -> Range<'a, K, V> { Range { inner: self.inner.clone() } }
1127 impl<'a, K, V> Iterator for Range<'a, K, V> {
1128 type Item = (&'a K, &'a V);
1130 fn next(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next() }
1132 impl<'a, K, V> DoubleEndedIterator for Range<'a, K, V> {
1133 fn next_back(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next_back() }
1136 impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
1137 type Item = (&'a K, &'a mut V);
1139 fn next(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next() }
1141 impl<'a, K, V> DoubleEndedIterator for RangeMut<'a, K, V> {
1142 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next_back() }
1145 impl<'a, K: Ord, V> Entry<'a, K, V> {
1146 #[unstable(feature = "std_misc",
1147 reason = "will soon be replaced by or_insert")]
1148 #[deprecated(since = "1.0",
1149 reason = "replaced with more ergonomic `or_insert` and `or_insert_with`")]
1150 /// Returns a mutable reference to the entry if occupied, or the VacantEntry if vacant
1151 pub fn get(self) -> Result<&'a mut V, VacantEntry<'a, K, V>> {
1153 Occupied(entry) => Ok(entry.into_mut()),
1154 Vacant(entry) => Err(entry),
1158 #[unstable(feature = "collections",
1159 reason = "matches entry v3 specification, waiting for dust to settle")]
1160 /// Ensures a value is in the entry by inserting the default if empty, and returns
1161 /// a mutable reference to the value in the entry.
1162 pub fn or_insert(self, default: V) -> &'a mut V {
1164 Occupied(entry) => entry.into_mut(),
1165 Vacant(entry) => entry.insert(default),
1169 #[unstable(feature = "collections",
1170 reason = "matches entry v3 specification, waiting for dust to settle")]
1171 /// Ensures a value is in the entry by inserting the result of the default function if empty,
1172 /// and returns a mutable reference to the value in the entry.
1173 pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V {
1175 Occupied(entry) => entry.into_mut(),
1176 Vacant(entry) => entry.insert(default()),
1181 impl<'a, K: Ord, V> VacantEntry<'a, K, V> {
1182 /// Sets the value of the entry with the VacantEntry's key,
1183 /// and returns a mutable reference to it.
1184 #[stable(feature = "rust1", since = "1.0.0")]
1185 pub fn insert(self, value: V) -> &'a mut V {
1186 self.stack.insert(self.key, value)
1190 impl<'a, K: Ord, V> OccupiedEntry<'a, K, V> {
1191 /// Gets a reference to the value in the entry.
1192 #[stable(feature = "rust1", since = "1.0.0")]
1193 pub fn get(&self) -> &V {
1197 /// Gets a mutable reference to the value in the entry.
1198 #[stable(feature = "rust1", since = "1.0.0")]
1199 pub fn get_mut(&mut self) -> &mut V {
1200 self.stack.peek_mut()
1203 /// Converts the entry into a mutable reference to its value.
1204 #[stable(feature = "rust1", since = "1.0.0")]
1205 pub fn into_mut(self) -> &'a mut V {
1206 self.stack.into_top()
1209 /// Sets the value of the entry with the OccupiedEntry's key,
1210 /// and returns the entry's old value.
1211 #[stable(feature = "rust1", since = "1.0.0")]
1212 pub fn insert(&mut self, mut value: V) -> V {
1213 mem::swap(self.stack.peek_mut(), &mut value);
1217 /// Takes the value of the entry out of the map, and returns it.
1218 #[stable(feature = "rust1", since = "1.0.0")]
1219 pub fn remove(self) -> V {
1224 impl<K, V> BTreeMap<K, V> {
1225 /// Gets an iterator over the entries of the map.
1230 /// use std::collections::BTreeMap;
1232 /// let mut map = BTreeMap::new();
1233 /// map.insert(1, "a");
1234 /// map.insert(2, "b");
1235 /// map.insert(3, "c");
1237 /// for (key, value) in map.iter() {
1238 /// println!("{}: {}", key, value);
1241 /// let (first_key, first_value) = map.iter().next().unwrap();
1242 /// assert_eq!((*first_key, *first_value), (1, "a"));
1244 #[stable(feature = "rust1", since = "1.0.0")]
1245 pub fn iter(&self) -> Iter<K, V> {
1246 let len = self.len();
1247 // NB. The initial capacity for ringbuf is large enough to avoid reallocs in many cases.
1248 let mut lca = VecDeque::new();
1249 lca.push_back(Traverse::traverse(&self.root));
1258 /// Gets a mutable iterator over the entries of the map.
1263 /// use std::collections::BTreeMap;
1265 /// let mut map = BTreeMap::new();
1266 /// map.insert("a", 1);
1267 /// map.insert("b", 2);
1268 /// map.insert("c", 3);
1270 /// // add 10 to the value if the key isn't "a"
1271 /// for (key, value) in map.iter_mut() {
1272 /// if key != &"a" {
1277 #[stable(feature = "rust1", since = "1.0.0")]
1278 pub fn iter_mut(&mut self) -> IterMut<K, V> {
1279 let len = self.len();
1280 let mut lca = VecDeque::new();
1281 lca.push_back(Traverse::traverse(&mut self.root));
1290 /// Gets an owning iterator over the entries of the map.
1295 /// use std::collections::BTreeMap;
1297 /// let mut map = BTreeMap::new();
1298 /// map.insert(1, "a");
1299 /// map.insert(2, "b");
1300 /// map.insert(3, "c");
1302 /// for (key, value) in map.into_iter() {
1303 /// println!("{}: {}", key, value);
1306 #[stable(feature = "rust1", since = "1.0.0")]
1307 pub fn into_iter(self) -> IntoIter<K, V> {
1308 let len = self.len();
1309 let mut lca = VecDeque::new();
1310 lca.push_back(Traverse::traverse(self.root));
1319 /// Gets an iterator over the keys of the map.
1324 /// # #![feature(core)]
1325 /// use std::collections::BTreeMap;
1327 /// let mut a = BTreeMap::new();
1328 /// a.insert(1, "a");
1329 /// a.insert(2, "b");
1331 /// let keys: Vec<usize> = a.keys().cloned().collect();
1332 /// assert_eq!(keys, [1, 2]);
1334 #[stable(feature = "rust1", since = "1.0.0")]
1335 pub fn keys<'a>(&'a self) -> Keys<'a, K, V> {
1336 fn first<A, B>((a, _): (A, B)) -> A { a }
1337 let first: fn((&'a K, &'a V)) -> &'a K = first; // coerce to fn pointer
1339 Keys { inner: self.iter().map(first) }
1342 /// Gets an iterator over the values of the map.
1347 /// # #![feature(core)]
1348 /// use std::collections::BTreeMap;
1350 /// let mut a = BTreeMap::new();
1351 /// a.insert(1, "a");
1352 /// a.insert(2, "b");
1354 /// let values: Vec<&str> = a.values().cloned().collect();
1355 /// assert_eq!(values, ["a", "b"]);
1357 #[stable(feature = "rust1", since = "1.0.0")]
1358 pub fn values<'a>(&'a self) -> Values<'a, K, V> {
1359 fn second<A, B>((_, b): (A, B)) -> B { b }
1360 let second: fn((&'a K, &'a V)) -> &'a V = second; // coerce to fn pointer
1362 Values { inner: self.iter().map(second) }
1365 /// Return the number of elements in the map.
1370 /// use std::collections::BTreeMap;
1372 /// let mut a = BTreeMap::new();
1373 /// assert_eq!(a.len(), 0);
1374 /// a.insert(1, "a");
1375 /// assert_eq!(a.len(), 1);
1377 #[stable(feature = "rust1", since = "1.0.0")]
1378 pub fn len(&self) -> usize { self.length }
1380 /// Return true if the map contains no elements.
1385 /// use std::collections::BTreeMap;
1387 /// let mut a = BTreeMap::new();
1388 /// assert!(a.is_empty());
1389 /// a.insert(1, "a");
1390 /// assert!(!a.is_empty());
1392 #[stable(feature = "rust1", since = "1.0.0")]
1393 pub fn is_empty(&self) -> bool { self.len() == 0 }
1396 macro_rules! range_impl {
1397 ($root:expr, $min:expr, $max:expr, $as_slices_internal:ident, $iter:ident, $Range:ident,
1398 $edges:ident, [$($mutability:ident)*]) => (
1400 // A deque that encodes two search paths containing (left-to-right):
1401 // a series of truncated-from-the-left iterators, the LCA's doubly-truncated iterator,
1402 // and a series of truncated-from-the-right iterators.
1403 let mut traversals = VecDeque::new();
1404 let (root, min, max) = ($root, $min, $max);
1406 let mut leftmost = None;
1407 let mut rightmost = None;
1409 match (&min, &max) {
1410 (&Unbounded, &Unbounded) => {
1411 traversals.push_back(Traverse::traverse(root))
1413 (&Unbounded, &Included(_)) | (&Unbounded, &Excluded(_)) => {
1414 rightmost = Some(root);
1416 (&Included(_), &Unbounded) | (&Excluded(_), &Unbounded) => {
1417 leftmost = Some(root);
1419 (&Included(min_key), &Included(max_key))
1420 | (&Included(min_key), &Excluded(max_key))
1421 | (&Excluded(min_key), &Included(max_key))
1422 | (&Excluded(min_key), &Excluded(max_key)) => {
1423 // lca represents the Lowest Common Ancestor, above which we never
1424 // walk, since everything else is outside the range to iterate.
1425 // ___________________
1426 // |__0_|_80_|_85_|_90_| (root)
1430 // ___________________
1431 // |__5_|_15_|_30_|_73_|
1435 // ___________________
1436 // |_33_|_58_|_63_|_68_| lca for the range [41, 65]
1437 // | |\___|___/| | iterator at traversals[2]
1442 let mut is_leaf = root.is_leaf();
1443 let mut lca = root.$as_slices_internal();
1445 let slice = lca.slice_from(min_key).slice_to(max_key);
1446 if let [ref $($mutability)* edge] = slice.edges {
1447 // Follow the only edge that leads the node that covers the range.
1448 is_leaf = edge.is_leaf();
1449 lca = edge.$as_slices_internal();
1451 let mut iter = slice.$iter();
1456 // Only change the state of nodes with edges.
1457 leftmost = iter.next_edge_item();
1458 rightmost = iter.next_edge_item_back();
1460 traversals.push_back(iter);
1466 // Keep narrowing the range by going down.
1467 // ___________________
1468 // |_38_|_43_|_48_|_53_|
1469 // | |____|____|____/ iterator at traversals[1]
1472 // ___________________
1473 // |_39_|_40_|_41_|_42_| (leaf, the last leftmost)
1474 // \_________| iterator at traversals[0]
1476 Included(key) | Excluded(key) =>
1477 while let Some(left) = leftmost {
1478 let is_leaf = left.is_leaf();
1479 let mut iter = left.$as_slices_internal().slice_from(key).$iter();
1480 leftmost = if is_leaf {
1483 // Only change the state of nodes with edges.
1484 iter.next_edge_item()
1486 traversals.push_back(iter);
1490 // If the leftmost iterator starts with an element, then it was an exact match.
1491 if let (Excluded(_), Some(leftmost_iter)) = (min, traversals.back_mut()) {
1492 // Drop this excluded element. `next_kv_item` has no effect when
1493 // the next item is an edge.
1494 leftmost_iter.next_kv_item();
1497 // The code for the right side is similar.
1499 Included(key) | Excluded(key) =>
1500 while let Some(right) = rightmost {
1501 let is_leaf = right.is_leaf();
1502 let mut iter = right.$as_slices_internal().slice_to(key).$iter();
1503 rightmost = if is_leaf {
1506 iter.next_edge_item_back()
1508 traversals.push_front(iter);
1512 if let (Excluded(_), Some(rightmost_iter)) = (max, traversals.front_mut()) {
1513 rightmost_iter.next_kv_item_back();
1518 traversals: traversals,
1519 size: usize::MAX, // unused
1526 impl<K: Ord, V> BTreeMap<K, V> {
1527 /// Constructs a double-ended iterator over a sub-range of elements in the map, starting
1528 /// at min, and ending at max. If min is `Unbounded`, then it will be treated as "negative
1529 /// infinity", and if max is `Unbounded`, then it will be treated as "positive infinity".
1530 /// Thus range(Unbounded, Unbounded) will yield the whole collection.
1535 /// # #![feature(collections)]
1536 /// use std::collections::BTreeMap;
1537 /// use std::collections::Bound::{Included, Unbounded};
1539 /// let mut map = BTreeMap::new();
1540 /// map.insert(3, "a");
1541 /// map.insert(5, "b");
1542 /// map.insert(8, "c");
1543 /// for (&key, &value) in map.range(Included(&4), Included(&8)) {
1544 /// println!("{}: {}", key, value);
1546 /// assert_eq!(Some((&5, &"b")), map.range(Included(&4), Unbounded).next());
1548 #[unstable(feature = "collections",
1549 reason = "matches collection reform specification, waiting for dust to settle")]
1550 pub fn range<'a>(&'a self, min: Bound<&K>, max: Bound<&K>) -> Range<'a, K, V> {
1551 range_impl!(&self.root, min, max, as_slices_internal, iter, Range, edges, [])
1554 /// Constructs a mutable double-ended iterator over a sub-range of elements in the map, starting
1555 /// at min, and ending at max. If min is `Unbounded`, then it will be treated as "negative
1556 /// infinity", and if max is `Unbounded`, then it will be treated as "positive infinity".
1557 /// Thus range(Unbounded, Unbounded) will yield the whole collection.
1562 /// # #![feature(collections)]
1563 /// use std::collections::BTreeMap;
1564 /// use std::collections::Bound::{Included, Excluded};
1566 /// let mut map: BTreeMap<&str, i32> = ["Alice", "Bob", "Carol", "Cheryl"].iter()
1567 /// .map(|&s| (s, 0))
1569 /// for (_, balance) in map.range_mut(Included(&"B"), Excluded(&"Cheryl")) {
1570 /// *balance += 100;
1572 /// for (name, balance) in map.iter() {
1573 /// println!("{} => {}", name, balance);
1576 #[unstable(feature = "collections",
1577 reason = "matches collection reform specification, waiting for dust to settle")]
1578 pub fn range_mut<'a>(&'a mut self, min: Bound<&K>, max: Bound<&K>) -> RangeMut<'a, K, V> {
1579 range_impl!(&mut self.root, min, max, as_slices_internal_mut, iter_mut, RangeMut,
1583 /// Gets the given key's corresponding entry in the map for in-place manipulation.
1588 /// # #![feature(collections)]
1589 /// use std::collections::BTreeMap;
1591 /// let mut count: BTreeMap<&str, usize> = BTreeMap::new();
1593 /// // count the number of occurrences of letters in the vec
1594 /// for x in vec!["a","b","a","c","a","b"] {
1595 /// *count.entry(x).or_insert(0) += 1;
1598 /// assert_eq!(count["a"], 3);
1600 #[stable(feature = "rust1", since = "1.0.0")]
1601 pub fn entry(&mut self, mut key: K) -> Entry<K, V> {
1602 // same basic logic of `swap` and `pop`, blended together
1603 let mut stack = stack::PartialSearchStack::new(self);
1605 let result = stack.with(move |pusher, node| {
1606 match Node::search(node, &key) {
1609 Finished(Occupied(OccupiedEntry {
1610 stack: pusher.seal(handle)
1614 match handle.force() {
1615 Leaf(leaf_handle) => {
1616 Finished(Vacant(VacantEntry {
1617 stack: pusher.seal(leaf_handle),
1621 Internal(internal_handle) => {
1623 pusher.push(internal_handle),
1632 Finished(finished) => return finished,
1633 Continue((new_stack, renewed_key)) => {