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/).
18 pub use self::Entry::*;
22 use core::borrow::BorrowFrom;
23 use core::cmp::Ordering;
24 use core::default::Default;
26 use core::hash::{Hash, Hasher};
27 use core::iter::{Map, FromIterator};
28 use core::ops::{Index, IndexMut};
29 use core::{iter, fmt, mem};
30 use Bound::{self, Included, Excluded, Unbounded};
32 use ring_buf::RingBuf;
34 use self::Continuation::{Continue, Finished};
36 use super::node::ForceResult::{Leaf, Internal};
37 use super::node::TraversalItem::{self, Elem, Edge};
38 use super::node::{Traversal, MutTraversal, MoveTraversal};
39 use super::node::{self, Node, Found, GoDown};
41 /// A map based on a B-Tree.
43 /// B-Trees represent a fundamental compromise between cache-efficiency and actually minimizing
44 /// the amount of work performed in a search. In theory, a binary search tree (BST) is the optimal
45 /// choice for a sorted map, as a perfectly balanced BST performs the theoretical minimum amount of
46 /// comparisons necessary to find an element (log<sub>2</sub>n). However, in practice the way this
47 /// is done is *very* inefficient for modern computer architectures. In particular, every element
48 /// is stored in its own individually heap-allocated node. This means that every single insertion
49 /// triggers a heap-allocation, and every single comparison should be a cache-miss. Since these
50 /// are both notably expensive things to do in practice, we are forced to at very least reconsider
53 /// A B-Tree instead makes each node contain B-1 to 2B-1 elements in a contiguous array. By doing
54 /// this, we reduce the number of allocations by a factor of B, and improve cache efficiency in
55 /// searches. However, this does mean that searches will have to do *more* comparisons on average.
56 /// The precise number of comparisons depends on the node search strategy used. For optimal cache
57 /// efficiency, one could search the nodes linearly. For optimal comparisons, one could search
58 /// the node using binary search. As a compromise, one could also perform a linear search
59 /// that initially only checks every i<sup>th</sup> element for some choice of i.
61 /// Currently, our implementation simply performs naive linear search. This provides excellent
62 /// performance on *small* nodes of elements which are cheap to compare. However in the future we
63 /// would like to further explore choosing the optimal search strategy based on the choice of B,
64 /// and possibly other factors. Using linear search, searching for a random element is expected
65 /// to take O(B log<sub>B</sub>n) comparisons, which is generally worse than a BST. In practice,
66 /// however, performance is excellent. `BTreeMap` is able to readily outperform `TreeMap` under
67 /// many workloads, and is competitive where it doesn't. BTreeMap also generally *scales* better
68 /// than TreeMap, making it more appropriate for large datasets.
70 /// However, `TreeMap` may still be more appropriate to use in many contexts. If elements are very
71 /// large or expensive to compare, `TreeMap` may be more appropriate. It won't allocate any
72 /// more space than is needed, and will perform the minimal number of comparisons necessary.
73 /// `TreeMap` also provides much better performance stability guarantees. Generally, very few
74 /// changes need to be made to update a BST, and two updates are expected to take about the same
75 /// amount of time on roughly equal sized BSTs. However a B-Tree's performance is much more
76 /// amortized. If a node is overfull, it must be split into two nodes. If a node is underfull, it
77 /// may be merged with another. Both of these operations are relatively expensive to perform, and
78 /// it's possible to force one to occur at every single level of the tree in a single insertion or
79 /// deletion. In fact, a malicious or otherwise unlucky sequence of insertions and deletions can
80 /// force this degenerate behaviour to occur on every operation. While the total amount of work
81 /// done on each operation isn't *catastrophic*, and *is* still bounded by O(B log<sub>B</sub>n),
82 /// it is certainly much slower when it does.
84 #[stable(feature = "rust1", since = "1.0.0")]
85 pub struct BTreeMap<K, V> {
92 /// An abstract base over-which all other BTree iterators are built.
94 traversals: RingBuf<T>,
98 /// An iterator over a BTreeMap's entries.
99 #[stable(feature = "rust1", since = "1.0.0")]
100 pub struct Iter<'a, K: 'a, V: 'a> {
101 inner: AbsIter<Traversal<'a, K, V>>
104 /// A mutable iterator over a BTreeMap's entries.
105 #[stable(feature = "rust1", since = "1.0.0")]
106 pub struct IterMut<'a, K: 'a, V: 'a> {
107 inner: AbsIter<MutTraversal<'a, K, V>>
110 /// An owning iterator over a BTreeMap's entries.
111 #[stable(feature = "rust1", since = "1.0.0")]
112 pub struct IntoIter<K, V> {
113 inner: AbsIter<MoveTraversal<K, V>>
116 /// An iterator over a BTreeMap's keys.
117 #[stable(feature = "rust1", since = "1.0.0")]
118 pub struct Keys<'a, K: 'a, V: 'a> {
119 inner: Map<(&'a K, &'a V), &'a K, Iter<'a, K, V>, fn((&'a K, &'a V)) -> &'a K>
122 /// An iterator over a BTreeMap's values.
123 #[stable(feature = "rust1", since = "1.0.0")]
124 pub struct Values<'a, K: 'a, V: 'a> {
125 inner: Map<(&'a K, &'a V), &'a V, Iter<'a, K, V>, fn((&'a K, &'a V)) -> &'a V>
128 /// An iterator over a sub-range of BTreeMap's entries.
129 pub struct Range<'a, K: 'a, V: 'a> {
130 inner: AbsIter<Traversal<'a, K, V>>
133 /// A mutable iterator over a sub-range of BTreeMap's entries.
134 pub struct RangeMut<'a, K: 'a, V: 'a> {
135 inner: AbsIter<MutTraversal<'a, K, V>>
138 /// A view into a single entry in a map, which may either be vacant or occupied.
139 #[unstable(feature = "collections",
140 reason = "precise API still under development")]
141 pub enum Entry<'a, K:'a, V:'a> {
143 Vacant(VacantEntry<'a, K, V>),
144 /// An occupied Entry
145 Occupied(OccupiedEntry<'a, K, V>),
149 #[unstable(feature = "collections",
150 reason = "precise API still under development")]
151 pub struct VacantEntry<'a, K:'a, V:'a> {
153 stack: stack::SearchStack<'a, K, V, node::handle::Edge, node::handle::Leaf>,
156 /// An occupied Entry.
157 #[unstable(feature = "collections",
158 reason = "precise API still under development")]
159 pub struct OccupiedEntry<'a, K:'a, V:'a> {
160 stack: stack::SearchStack<'a, K, V, node::handle::KV, node::handle::LeafOrInternal>,
163 impl<K: Ord, V> BTreeMap<K, V> {
164 /// Makes a new empty BTreeMap with a reasonable choice for B.
165 #[stable(feature = "rust1", since = "1.0.0")]
166 pub fn new() -> BTreeMap<K, V> {
167 //FIXME(Gankro): Tune this as a function of size_of<K/V>?
171 /// Makes a new empty BTreeMap with the given B.
173 /// B cannot be less than 2.
174 pub fn with_b(b: uint) -> BTreeMap<K, V> {
175 assert!(b > 1, "B must be greater than 1");
179 root: Node::make_leaf_root(b),
184 /// Clears the map, removing all values.
189 /// use std::collections::BTreeMap;
191 /// let mut a = BTreeMap::new();
192 /// a.insert(1u, "a");
194 /// assert!(a.is_empty());
196 #[stable(feature = "rust1", since = "1.0.0")]
197 pub fn clear(&mut self) {
199 // avoid recursive destructors by manually traversing the tree
200 for _ in mem::replace(self, BTreeMap::with_b(b)).into_iter() {};
203 // Searching in a B-Tree is pretty straightforward.
205 // Start at the root. Try to find the key in the current node. If we find it, return it.
206 // If it's not in there, follow the edge *before* the smallest key larger than
207 // the search key. If no such key exists (they're *all* smaller), then just take the last
208 // edge in the node. If we're in a leaf and we don't find our key, then it's not
211 /// Returns a reference to the value corresponding to the key.
213 /// The key may be any borrowed form of the map's key type, but the ordering
214 /// on the borrowed form *must* match the ordering on the key type.
219 /// use std::collections::BTreeMap;
221 /// let mut map = BTreeMap::new();
222 /// map.insert(1u, "a");
223 /// assert_eq!(map.get(&1), Some(&"a"));
224 /// assert_eq!(map.get(&2), None);
226 #[stable(feature = "rust1", since = "1.0.0")]
227 pub fn get<Q: ?Sized>(&self, key: &Q) -> Option<&V> where Q: BorrowFrom<K> + Ord {
228 let mut cur_node = &self.root;
230 match Node::search(cur_node, key) {
231 Found(handle) => return Some(handle.into_kv().1),
232 GoDown(handle) => match handle.force() {
233 Leaf(_) => return None,
234 Internal(internal_handle) => {
235 cur_node = internal_handle.into_edge();
243 /// Returns true if the map contains a value for the specified key.
245 /// The key may be any borrowed form of the map's key type, but the ordering
246 /// on the borrowed form *must* match the ordering on the key type.
251 /// use std::collections::BTreeMap;
253 /// let mut map = BTreeMap::new();
254 /// map.insert(1u, "a");
255 /// assert_eq!(map.contains_key(&1), true);
256 /// assert_eq!(map.contains_key(&2), false);
258 #[stable(feature = "rust1", since = "1.0.0")]
259 pub fn contains_key<Q: ?Sized>(&self, key: &Q) -> bool where Q: BorrowFrom<K> + Ord {
260 self.get(key).is_some()
263 /// Returns a mutable reference to the value corresponding to the key.
265 /// The key may be any borrowed form of the map's key type, but the ordering
266 /// on the borrowed form *must* match the ordering on the key type.
271 /// use std::collections::BTreeMap;
273 /// let mut map = BTreeMap::new();
274 /// map.insert(1u, "a");
275 /// match map.get_mut(&1) {
276 /// Some(x) => *x = "b",
279 /// assert_eq!(map[1], "b");
281 // See `get` for implementation notes, this is basically a copy-paste with mut's added
282 #[stable(feature = "rust1", since = "1.0.0")]
283 pub fn get_mut<Q: ?Sized>(&mut self, key: &Q) -> Option<&mut V> where Q: BorrowFrom<K> + Ord {
284 // temp_node is a Borrowck hack for having a mutable value outlive a loop iteration
285 let mut temp_node = &mut self.root;
287 let cur_node = temp_node;
288 match Node::search(cur_node, key) {
289 Found(handle) => return Some(handle.into_kv_mut().1),
290 GoDown(handle) => match handle.force() {
291 Leaf(_) => return None,
292 Internal(internal_handle) => {
293 temp_node = internal_handle.into_edge_mut();
301 // Insertion in a B-Tree is a bit complicated.
303 // First we do the same kind of search described in `find`. But we need to maintain a stack of
304 // all the nodes/edges in our search path. If we find a match for the key we're trying to
305 // insert, just swap the vals and return the old ones. However, when we bottom out in a leaf,
306 // we attempt to insert our key-value pair at the same location we would want to follow another
309 // If the node has room, then this is done in the obvious way by shifting elements. However,
310 // if the node itself is full, we split node into two, and give its median key-value
311 // pair to its parent to insert the new node with. Of course, the parent may also be
312 // full, and insertion can propagate until we reach the root. If we reach the root, and
313 // it is *also* full, then we split the root and place the two nodes under a newly made root.
315 // Note that we subtly deviate from Open Data Structures in our implementation of split.
316 // ODS describes inserting into the node *regardless* of its capacity, and then
317 // splitting *afterwards* if it happens to be overfull. However, this is inefficient.
318 // Instead, we split beforehand, and then insert the key-value pair into the appropriate
319 // result node. This has two consequences:
321 // 1) While ODS produces a left node of size B-1, and a right node of size B,
322 // we may potentially reverse this. However, this shouldn't effect the analysis.
324 // 2) While ODS may potentially return the pair we *just* inserted after
325 // the split, we will never do this. Again, this shouldn't effect the analysis.
327 /// Inserts a key-value pair from the map. If the key already had a value
328 /// present in the map, that value is returned. Otherwise, `None` is returned.
333 /// use std::collections::BTreeMap;
335 /// let mut map = BTreeMap::new();
336 /// assert_eq!(map.insert(37u, "a"), None);
337 /// assert_eq!(map.is_empty(), false);
339 /// map.insert(37, "b");
340 /// assert_eq!(map.insert(37, "c"), Some("b"));
341 /// assert_eq!(map[37], "c");
343 #[stable(feature = "rust1", since = "1.0.0")]
344 pub fn insert(&mut self, mut key: K, mut value: V) -> Option<V> {
345 // This is a stack of rawptrs to nodes paired with indices, respectively
346 // representing the nodes and edges of our search path. We have to store rawptrs
347 // because as far as Rust is concerned, we can mutate aliased data with such a
348 // stack. It is of course correct, but what it doesn't know is that we will only
349 // be popping and using these ptrs one at a time in child-to-parent order. The alternative
350 // to doing this is to take the Nodes from their parents. This actually makes
351 // borrowck *really* happy and everything is pretty smooth. However, this creates
352 // *tons* of pointless writes, and requires us to always walk all the way back to
353 // the root after an insertion, even if we only needed to change a leaf. Therefore,
354 // we accept this potential unsafety and complexity in the name of performance.
356 // Regardless, the actual dangerous logic is completely abstracted away from BTreeMap
357 // by the stack module. All it can do is immutably read nodes, and ask the search stack
358 // to proceed down some edge by index. This makes the search logic we'll be reusing in a
359 // few different methods much neater, and of course drastically improves safety.
360 let mut stack = stack::PartialSearchStack::new(self);
363 let result = stack.with(move |pusher, node| {
364 // Same basic logic as found in `find`, but with PartialSearchStack mediating the
365 // actual nodes for us
366 return match Node::search(node, &key) {
367 Found(mut handle) => {
368 // Perfect match, swap the values and return the old one
369 mem::swap(handle.val_mut(), &mut value);
370 Finished(Some(value))
373 // We need to keep searching, try to get the search stack
374 // to go down further
375 match handle.force() {
376 Leaf(leaf_handle) => {
377 // We've reached a leaf, perform the insertion here
378 pusher.seal(leaf_handle).insert(key, value);
381 Internal(internal_handle) => {
382 // We've found the subtree to insert this key/value pair in,
384 Continue((pusher.push(internal_handle), key, value))
391 Finished(ret) => { return ret; },
392 Continue((new_stack, renewed_key, renewed_val)) => {
401 // Deletion is the most complicated operation for a B-Tree.
403 // First we do the same kind of search described in
404 // `find`. But we need to maintain a stack of all the nodes/edges in our search path.
405 // If we don't find the key, then we just return `None` and do nothing. If we do find the
406 // key, we perform two operations: remove the item, and then possibly handle underflow.
408 // # removing the item
409 // If the node is a leaf, we just remove the item, and shift
410 // any items after it back to fill the hole.
412 // If the node is an internal node, we *swap* the item with the smallest item in
413 // in its right subtree (which must reside in a leaf), and then revert to the leaf
416 // # handling underflow
417 // After removing an item, there may be too few items in the node. We want nodes
418 // to be mostly full for efficiency, although we make an exception for the root, which
419 // may have as few as one item. If this is the case, we may first try to steal
420 // an item from our left or right neighbour.
422 // To steal from the left (right) neighbour,
423 // we take the largest (smallest) item and child from it. We then swap the taken item
424 // with the item in their mutual parent that separates them, and then insert the
425 // parent's item and the taken child into the first (last) index of the underflowed node.
427 // However, stealing has the possibility of underflowing our neighbour. If this is the
428 // case, we instead *merge* with our neighbour. This of course reduces the number of
429 // children in the parent. Therefore, we also steal the item that separates the now
430 // merged nodes, and insert it into the merged node.
432 // Merging may cause the parent to underflow. If this is the case, then we must repeat
433 // the underflow handling process on the parent. If merging merges the last two children
434 // of the root, then we replace the root with the merged node.
436 /// Removes a key from the map, returning the value at the key if the key
437 /// was previously in the map.
439 /// The key may be any borrowed form of the map's key type, but the ordering
440 /// on the borrowed form *must* match the ordering on the key type.
445 /// use std::collections::BTreeMap;
447 /// let mut map = BTreeMap::new();
448 /// map.insert(1u, "a");
449 /// assert_eq!(map.remove(&1), Some("a"));
450 /// assert_eq!(map.remove(&1), None);
452 #[stable(feature = "rust1", since = "1.0.0")]
453 pub fn remove<Q: ?Sized>(&mut self, key: &Q) -> Option<V> where Q: BorrowFrom<K> + Ord {
454 // See `swap` for a more thorough description of the stuff going on in here
455 let mut stack = stack::PartialSearchStack::new(self);
457 let result = stack.with(move |pusher, node| {
458 return match Node::search(node, key) {
460 // Perfect match. Terminate the stack here, and remove the entry
461 Finished(Some(pusher.seal(handle).remove()))
464 // We need to keep searching, try to go down the next edge
465 match handle.force() {
466 // We're at a leaf; the key isn't in here
467 Leaf(_) => Finished(None),
468 Internal(internal_handle) => Continue(pusher.push(internal_handle))
474 Finished(ret) => return ret,
475 Continue(new_stack) => stack = new_stack
481 /// A helper enum useful for deciding whether to continue a loop since we can't
482 /// return from a closure
483 enum Continuation<A, B> {
488 /// The stack module provides a safe interface for constructing and manipulating a stack of ptrs
489 /// to nodes. By using this module much better safety guarantees can be made, and more search
490 /// boilerplate gets cut out.
492 use core::prelude::*;
495 use core::ops::{Deref, DerefMut};
497 use super::super::node::{self, Node, Fit, Split, Internal, Leaf};
498 use super::super::node::handle;
501 /// A generic mutable reference, identical to `&mut` except for the fact that its lifetime
502 /// parameter is invariant. This means that wherever an `IdRef` is expected, only an `IdRef`
503 /// with the exact requested lifetime can be used. This is in contrast to normal references,
504 /// where `&'static` can be used in any function expecting any lifetime reference.
505 pub struct IdRef<'id, T: 'id> {
507 marker: marker::InvariantLifetime<'id>
510 impl<'id, T> Deref for IdRef<'id, T> {
513 fn deref(&self) -> &T {
518 impl<'id, T> DerefMut for IdRef<'id, T> {
519 fn deref_mut(&mut self) -> &mut T {
524 type StackItem<K, V> = node::Handle<*mut Node<K, V>, handle::Edge, handle::Internal>;
525 type Stack<K, V> = Vec<StackItem<K, V>>;
527 /// A `PartialSearchStack` handles the construction of a search stack.
528 pub struct PartialSearchStack<'a, K:'a, V:'a> {
529 map: &'a mut BTreeMap<K, V>,
531 next: *mut Node<K, V>,
534 /// A `SearchStack` represents a full path to an element or an edge of interest. It provides
535 /// methods depending on the type of what the path points to for removing an element, inserting
536 /// a new element, and manipulating to element at the top of the stack.
537 pub struct SearchStack<'a, K:'a, V:'a, Type, NodeType> {
538 map: &'a mut BTreeMap<K, V>,
540 top: node::Handle<*mut Node<K, V>, Type, NodeType>,
543 /// A `PartialSearchStack` that doesn't hold a a reference to the next node, and is just
544 /// just waiting for a `Handle` to that next node to be pushed. See `PartialSearchStack::with`
545 /// for more details.
546 pub struct Pusher<'id, 'a, K:'a, V:'a> {
547 map: &'a mut BTreeMap<K, V>,
549 marker: marker::InvariantLifetime<'id>
552 impl<'a, K, V> PartialSearchStack<'a, K, V> {
553 /// Creates a new PartialSearchStack from a BTreeMap by initializing the stack with the
554 /// root of the tree.
555 pub fn new(map: &'a mut BTreeMap<K, V>) -> PartialSearchStack<'a, K, V> {
556 let depth = map.depth;
559 next: &mut map.root as *mut _,
561 stack: Vec::with_capacity(depth),
565 /// Breaks up the stack into a `Pusher` and the next `Node`, allowing the given closure
566 /// to interact with, search, and finally push the `Node` onto the stack. The passed in
567 /// closure must be polymorphic on the `'id` lifetime parameter, as this statically
568 /// ensures that only `Handle`s from the correct `Node` can be pushed.
570 /// The reason this works is that the `Pusher` has an `'id` parameter, and will only accept
571 /// handles with the same `'id`. The closure could only get references with that lifetime
572 /// through its arguments or through some other `IdRef` that it has lying around. However,
573 /// no other `IdRef` could possibly work - because the `'id` is held in an invariant
574 /// parameter, it would need to have precisely the correct lifetime, which would mean that
575 /// at least one of the calls to `with` wouldn't be properly polymorphic, wanting a
576 /// specific lifetime instead of the one that `with` chooses to give it.
578 /// See also Haskell's `ST` monad, which uses a similar trick.
579 pub fn with<T, F: for<'id> FnOnce(Pusher<'id, 'a, K, V>,
580 IdRef<'id, Node<K, V>>) -> T>(self, closure: F) -> T {
581 let pusher = Pusher {
584 marker: marker::InvariantLifetime
587 inner: unsafe { &mut *self.next },
588 marker: marker::InvariantLifetime
591 closure(pusher, node)
595 impl<'id, 'a, K, V> Pusher<'id, 'a, K, V> {
596 /// Pushes the requested child of the stack's current top on top of the stack. If the child
597 /// exists, then a new PartialSearchStack is yielded. Otherwise, a VacantSearchStack is
599 pub fn push(mut self, mut edge: node::Handle<IdRef<'id, Node<K, V>>,
602 -> PartialSearchStack<'a, K, V> {
603 self.stack.push(edge.as_raw());
607 next: edge.edge_mut() as *mut _,
611 /// Converts the PartialSearchStack into a SearchStack.
612 pub fn seal<Type, NodeType>
613 (self, mut handle: node::Handle<IdRef<'id, Node<K, V>>, Type, NodeType>)
614 -> SearchStack<'a, K, V, Type, NodeType> {
618 top: handle.as_raw(),
623 impl<'a, K, V, NodeType> SearchStack<'a, K, V, handle::KV, NodeType> {
624 /// Gets a reference to the value the stack points to.
625 pub fn peek(&self) -> &V {
626 unsafe { self.top.from_raw().into_kv().1 }
629 /// Gets a mutable reference to the value the stack points to.
630 pub fn peek_mut(&mut self) -> &mut V {
631 unsafe { self.top.from_raw_mut().into_kv_mut().1 }
634 /// Converts the stack into a mutable reference to the value it points to, with a lifetime
635 /// tied to the original tree.
636 pub fn into_top(mut self) -> &'a mut V {
638 mem::copy_mut_lifetime(
640 self.top.from_raw_mut().val_mut()
646 impl<'a, K, V> SearchStack<'a, K, V, handle::KV, handle::Leaf> {
647 /// Removes the key and value in the top element of the stack, then handles underflows as
648 /// described in BTree's pop function.
649 fn remove_leaf(mut self) -> V {
650 self.map.length -= 1;
652 // Remove the key-value pair from the leaf that this search stack points to.
653 // Then, note if the leaf is underfull, and promptly forget the leaf and its ptr
654 // to avoid ownership issues.
655 let (value, mut underflow) = unsafe {
656 let (_, value) = self.top.from_raw_mut().remove_as_leaf();
657 let underflow = self.top.from_raw().node().is_underfull();
662 match self.stack.pop() {
664 // We've reached the root, so no matter what, we're done. We manually
665 // access the root via the tree itself to avoid creating any dangling
667 if self.map.root.len() == 0 && !self.map.root.is_leaf() {
668 // We've emptied out the root, so make its only child the new root.
669 // If it's a leaf, we just let it become empty.
671 self.map.root.hoist_lone_child();
675 Some(mut handle) => {
677 // Underflow! Handle it!
679 handle.from_raw_mut().handle_underflow();
680 underflow = handle.from_raw().node().is_underfull();
692 impl<'a, K, V> SearchStack<'a, K, V, handle::KV, handle::LeafOrInternal> {
693 /// Removes the key and value in the top element of the stack, then handles underflows as
694 /// described in BTree's pop function.
695 pub fn remove(self) -> V {
696 // Ensure that the search stack goes to a leaf. This is necessary to perform deletion
697 // in a BTree. Note that this may put the tree in an inconsistent state (further
698 // described in into_leaf's comments), but this is immediately fixed by the
699 // removing the value we want to remove
700 self.into_leaf().remove_leaf()
703 /// Subroutine for removal. Takes a search stack for a key that might terminate at an
704 /// internal node, and mutates the tree and search stack to *make* it a search stack
705 /// for that same key that *does* terminates at a leaf. If the mutation occurs, then this
706 /// leaves the tree in an inconsistent state that must be repaired by the caller by
707 /// removing the entry in question. Specifically the key-value pair and its successor will
709 fn into_leaf(mut self) -> SearchStack<'a, K, V, handle::KV, handle::Leaf> {
711 let mut top_raw = self.top;
712 let mut top = top_raw.from_raw_mut();
714 let key_ptr = top.key_mut() as *mut _;
715 let val_ptr = top.val_mut() as *mut _;
717 // Try to go into the right subtree of the found key to find its successor
719 Leaf(mut leaf_handle) => {
720 // We're a proper leaf stack, nothing to do
724 top: leaf_handle.as_raw()
727 Internal(mut internal_handle) => {
728 let mut right_handle = internal_handle.right_edge();
730 //We're not a proper leaf stack, let's get to work.
731 self.stack.push(right_handle.as_raw());
733 let mut temp_node = right_handle.edge_mut();
735 // Walk into the smallest subtree of this node
736 let node = temp_node;
738 match node.kv_handle(0).force() {
739 Leaf(mut handle) => {
740 // This node is a leaf, do the swap and return
741 mem::swap(handle.key_mut(), &mut *key_ptr);
742 mem::swap(handle.val_mut(), &mut *val_ptr);
749 Internal(kv_handle) => {
750 // This node is internal, go deeper
751 let mut handle = kv_handle.into_left_edge();
752 self.stack.push(handle.as_raw());
753 temp_node = handle.into_edge_mut();
763 impl<'a, K, V> SearchStack<'a, K, V, handle::Edge, handle::Leaf> {
764 /// Inserts the key and value into the top element in the stack, and if that node has to
765 /// split recursively inserts the split contents into the next element stack until
768 /// Assumes that the stack represents a search path from the root to a leaf.
770 /// An &mut V is returned to the inserted value, for callers that want a reference to this.
771 pub fn insert(mut self, key: K, val: V) -> &'a mut V {
773 self.map.length += 1;
775 // Insert the key and value into the leaf at the top of the stack
776 let (mut insertion, inserted_ptr) = self.top.from_raw_mut()
777 .insert_as_leaf(key, val);
782 // The last insertion went off without a hitch, no splits! We can stop
784 return &mut *inserted_ptr;
786 Split(key, val, right) => match self.stack.pop() {
787 // The last insertion triggered a split, so get the next element on the
788 // stack to recursively insert the split node into.
790 // The stack was empty; we've split the root, and need to make a
791 // a new one. This is done in-place because we can't move the
792 // root out of a reference to the tree.
793 Node::make_internal_root(&mut self.map.root, self.map.b,
797 return &mut *inserted_ptr;
799 Some(mut handle) => {
800 // The stack wasn't empty, do the insertion and recurse
801 insertion = handle.from_raw_mut()
802 .insert_as_internal(key, val, right);
813 #[stable(feature = "rust1", since = "1.0.0")]
814 impl<K: Ord, V> FromIterator<(K, V)> for BTreeMap<K, V> {
815 fn from_iter<T: Iterator<Item=(K, V)>>(iter: T) -> BTreeMap<K, V> {
816 let mut map = BTreeMap::new();
822 #[stable(feature = "rust1", since = "1.0.0")]
823 impl<K: Ord, V> Extend<(K, V)> for BTreeMap<K, V> {
825 fn extend<T: Iterator<Item=(K, V)>>(&mut self, mut iter: T) {
832 #[stable(feature = "rust1", since = "1.0.0")]
833 impl<S: Hasher, K: Hash<S>, V: Hash<S>> Hash<S> for BTreeMap<K, V> {
834 fn hash(&self, state: &mut S) {
835 for elt in self.iter() {
841 #[stable(feature = "rust1", since = "1.0.0")]
842 impl<K: Ord, V> Default for BTreeMap<K, V> {
843 #[stable(feature = "rust1", since = "1.0.0")]
844 fn default() -> BTreeMap<K, V> {
849 #[stable(feature = "rust1", since = "1.0.0")]
850 impl<K: PartialEq, V: PartialEq> PartialEq for BTreeMap<K, V> {
851 fn eq(&self, other: &BTreeMap<K, V>) -> bool {
852 self.len() == other.len() &&
853 self.iter().zip(other.iter()).all(|(a, b)| a == b)
857 #[stable(feature = "rust1", since = "1.0.0")]
858 impl<K: Eq, V: Eq> Eq for BTreeMap<K, V> {}
860 #[stable(feature = "rust1", since = "1.0.0")]
861 impl<K: PartialOrd, V: PartialOrd> PartialOrd for BTreeMap<K, V> {
863 fn partial_cmp(&self, other: &BTreeMap<K, V>) -> Option<Ordering> {
864 iter::order::partial_cmp(self.iter(), other.iter())
868 #[stable(feature = "rust1", since = "1.0.0")]
869 impl<K: Ord, V: Ord> Ord for BTreeMap<K, V> {
871 fn cmp(&self, other: &BTreeMap<K, V>) -> Ordering {
872 iter::order::cmp(self.iter(), other.iter())
876 #[stable(feature = "rust1", since = "1.0.0")]
877 impl<K: Debug, V: Debug> Debug for BTreeMap<K, V> {
878 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
879 try!(write!(f, "BTreeMap {{"));
881 for (i, (k, v)) in self.iter().enumerate() {
882 if i != 0 { try!(write!(f, ", ")); }
883 try!(write!(f, "{:?}: {:?}", *k, *v));
890 #[stable(feature = "rust1", since = "1.0.0")]
891 impl<K: Ord, Q: ?Sized, V> Index<Q> for BTreeMap<K, V>
892 where Q: BorrowFrom<K> + Ord
896 fn index(&self, key: &Q) -> &V {
897 self.get(key).expect("no entry found for key")
901 #[stable(feature = "rust1", since = "1.0.0")]
902 impl<K: Ord, Q: ?Sized, V> IndexMut<Q> for BTreeMap<K, V>
903 where Q: BorrowFrom<K> + Ord
907 fn index_mut(&mut self, key: &Q) -> &mut V {
908 self.get_mut(key).expect("no entry found for key")
912 /// Genericises over how to get the correct type of iterator from the correct type
913 /// of Node ownership.
915 fn traverse(node: N) -> Self;
918 impl<'a, K, V> Traverse<&'a Node<K, V>> for Traversal<'a, K, V> {
919 fn traverse(node: &'a Node<K, V>) -> Traversal<'a, K, V> {
924 impl<'a, K, V> Traverse<&'a mut Node<K, V>> for MutTraversal<'a, K, V> {
925 fn traverse(node: &'a mut Node<K, V>) -> MutTraversal<'a, K, V> {
930 impl<K, V> Traverse<Node<K, V>> for MoveTraversal<K, V> {
931 fn traverse(node: Node<K, V>) -> MoveTraversal<K, V> {
936 /// Represents an operation to perform inside the following iterator methods.
937 /// This is necessary to use in `next` because we want to modify `self.traversals` inside
938 /// a match that borrows it. Similarly in `next_back`. Instead, we use this enum to note
939 /// what we want to do, and do it after the match.
944 impl<K, V, E, T> Iterator for AbsIter<T> where
945 T: DoubleEndedIterator<Item=TraversalItem<K, V, E>> + Traverse<E>,
949 // Our iterator represents a queue of all ancestors of elements we have
950 // yet to yield, from smallest to largest. Note that the design of these
951 // iterators permits an *arbitrary* initial pair of min and max, making
952 // these arbitrary sub-range iterators.
953 fn next(&mut self) -> Option<(K, V)> {
955 // We want the smallest element, so try to get the back of the queue
956 let op = match self.traversals.back_mut() {
958 // The queue wasn't empty, so continue along the node in its head
959 Some(iter) => match iter.next() {
960 // The head is empty, so Pop it off and continue the process
962 // The head yielded an edge, so make that the new head
963 Some(Edge(next)) => Push(Traverse::traverse(next)),
964 // The head yielded an entry, so yield that
972 // Handle any operation as necessary, without a conflicting borrow of the queue
974 Push(item) => { self.traversals.push_back(item); },
975 Pop => { self.traversals.pop_back(); },
980 fn size_hint(&self) -> (uint, Option<uint>) {
981 (self.size, Some(self.size))
985 impl<K, V, E, T> DoubleEndedIterator for AbsIter<T> where
986 T: DoubleEndedIterator<Item=TraversalItem<K, V, E>> + Traverse<E>,
988 // next_back is totally symmetric to next
990 fn next_back(&mut self) -> Option<(K, V)> {
992 let op = match self.traversals.front_mut() {
994 Some(iter) => match iter.next_back() {
996 Some(Edge(next)) => Push(Traverse::traverse(next)),
1005 Push(item) => { self.traversals.push_front(item); },
1006 Pop => { self.traversals.pop_front(); }
1012 #[stable(feature = "rust1", since = "1.0.0")]
1013 impl<'a, K, V> Iterator for Iter<'a, K, V> {
1014 type Item = (&'a K, &'a V);
1016 fn next(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next() }
1017 fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
1019 #[stable(feature = "rust1", since = "1.0.0")]
1020 impl<'a, K, V> DoubleEndedIterator for Iter<'a, K, V> {
1021 fn next_back(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next_back() }
1023 #[stable(feature = "rust1", since = "1.0.0")]
1024 impl<'a, K, V> ExactSizeIterator for Iter<'a, K, V> {}
1026 #[stable(feature = "rust1", since = "1.0.0")]
1027 impl<'a, K, V> Iterator for IterMut<'a, K, V> {
1028 type Item = (&'a K, &'a mut V);
1030 fn next(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next() }
1031 fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
1033 #[stable(feature = "rust1", since = "1.0.0")]
1034 impl<'a, K, V> DoubleEndedIterator for IterMut<'a, K, V> {
1035 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next_back() }
1037 #[stable(feature = "rust1", since = "1.0.0")]
1038 impl<'a, K, V> ExactSizeIterator for IterMut<'a, K, V> {}
1040 #[stable(feature = "rust1", since = "1.0.0")]
1041 impl<K, V> Iterator for IntoIter<K, V> {
1044 fn next(&mut self) -> Option<(K, V)> { self.inner.next() }
1045 fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
1047 #[stable(feature = "rust1", since = "1.0.0")]
1048 impl<K, V> DoubleEndedIterator for IntoIter<K, V> {
1049 fn next_back(&mut self) -> Option<(K, V)> { self.inner.next_back() }
1051 #[stable(feature = "rust1", since = "1.0.0")]
1052 impl<K, V> ExactSizeIterator for IntoIter<K, V> {}
1054 #[stable(feature = "rust1", since = "1.0.0")]
1055 impl<'a, K, V> Iterator for Keys<'a, K, V> {
1058 fn next(&mut self) -> Option<(&'a K)> { self.inner.next() }
1059 fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
1061 #[stable(feature = "rust1", since = "1.0.0")]
1062 impl<'a, K, V> DoubleEndedIterator for Keys<'a, K, V> {
1063 fn next_back(&mut self) -> Option<(&'a K)> { self.inner.next_back() }
1065 #[stable(feature = "rust1", since = "1.0.0")]
1066 impl<'a, K, V> ExactSizeIterator for Keys<'a, K, V> {}
1069 #[stable(feature = "rust1", since = "1.0.0")]
1070 impl<'a, K, V> Iterator for Values<'a, K, V> {
1073 fn next(&mut self) -> Option<(&'a V)> { self.inner.next() }
1074 fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
1076 #[stable(feature = "rust1", since = "1.0.0")]
1077 impl<'a, K, V> DoubleEndedIterator for Values<'a, K, V> {
1078 fn next_back(&mut self) -> Option<(&'a V)> { self.inner.next_back() }
1080 #[stable(feature = "rust1", since = "1.0.0")]
1081 impl<'a, K, V> ExactSizeIterator for Values<'a, K, V> {}
1083 impl<'a, K, V> Iterator for Range<'a, K, V> {
1084 type Item = (&'a K, &'a V);
1086 fn next(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next() }
1088 impl<'a, K, V> DoubleEndedIterator for Range<'a, K, V> {
1089 fn next_back(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next_back() }
1092 impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
1093 type Item = (&'a K, &'a mut V);
1095 fn next(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next() }
1097 impl<'a, K, V> DoubleEndedIterator for RangeMut<'a, K, V> {
1098 fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next_back() }
1101 impl<'a, K: Ord, V> Entry<'a, K, V> {
1102 #[unstable(feature = "collections",
1103 reason = "matches collection reform v2 specification, waiting for dust to settle")]
1104 /// Returns a mutable reference to the entry if occupied, or the VacantEntry if vacant
1105 pub fn get(self) -> Result<&'a mut V, VacantEntry<'a, K, V>> {
1107 Occupied(entry) => Ok(entry.into_mut()),
1108 Vacant(entry) => Err(entry),
1113 impl<'a, K: Ord, V> VacantEntry<'a, K, V> {
1114 /// Sets the value of the entry with the VacantEntry's key,
1115 /// and returns a mutable reference to it.
1116 #[unstable(feature = "collections",
1117 reason = "matches collection reform v2 specification, waiting for dust to settle")]
1118 pub fn insert(self, value: V) -> &'a mut V {
1119 self.stack.insert(self.key, value)
1123 impl<'a, K: Ord, V> OccupiedEntry<'a, K, V> {
1124 /// Gets a reference to the value in the entry.
1125 #[unstable(feature = "collections",
1126 reason = "matches collection reform v2 specification, waiting for dust to settle")]
1127 pub fn get(&self) -> &V {
1131 /// Gets a mutable reference to the value in the entry.
1132 #[unstable(feature = "collections",
1133 reason = "matches collection reform v2 specification, waiting for dust to settle")]
1134 pub fn get_mut(&mut self) -> &mut V {
1135 self.stack.peek_mut()
1138 /// Converts the entry into a mutable reference to its value.
1139 #[unstable(feature = "collections",
1140 reason = "matches collection reform v2 specification, waiting for dust to settle")]
1141 pub fn into_mut(self) -> &'a mut V {
1142 self.stack.into_top()
1145 /// Sets the value of the entry with the OccupiedEntry's key,
1146 /// and returns the entry's old value.
1147 #[unstable(feature = "collections",
1148 reason = "matches collection reform v2 specification, waiting for dust to settle")]
1149 pub fn insert(&mut self, mut value: V) -> V {
1150 mem::swap(self.stack.peek_mut(), &mut value);
1154 /// Takes the value of the entry out of the map, and returns it.
1155 #[unstable(feature = "collections",
1156 reason = "matches collection reform v2 specification, waiting for dust to settle")]
1157 pub fn remove(self) -> V {
1162 impl<K, V> BTreeMap<K, V> {
1163 /// Gets an iterator over the entries of the map.
1168 /// use std::collections::BTreeMap;
1170 /// let mut map = BTreeMap::new();
1171 /// map.insert(1u, "a");
1172 /// map.insert(2u, "b");
1173 /// map.insert(3u, "c");
1175 /// for (key, value) in map.iter() {
1176 /// println!("{}: {}", key, value);
1179 /// let (first_key, first_value) = map.iter().next().unwrap();
1180 /// assert_eq!((*first_key, *first_value), (1u, "a"));
1182 #[stable(feature = "rust1", since = "1.0.0")]
1183 pub fn iter(&self) -> Iter<K, V> {
1184 let len = self.len();
1185 // NB. The initial capacity for ringbuf is large enough to avoid reallocs in many cases.
1186 let mut lca = RingBuf::new();
1187 lca.push_back(Traverse::traverse(&self.root));
1196 /// Gets a mutable iterator over the entries of the map.
1201 /// use std::collections::BTreeMap;
1203 /// let mut map = BTreeMap::new();
1204 /// map.insert("a", 1u);
1205 /// map.insert("b", 2u);
1206 /// map.insert("c", 3u);
1208 /// // add 10 to the value if the key isn't "a"
1209 /// for (key, value) in map.iter_mut() {
1210 /// if key != &"a" {
1215 #[stable(feature = "rust1", since = "1.0.0")]
1216 pub fn iter_mut(&mut self) -> IterMut<K, V> {
1217 let len = self.len();
1218 let mut lca = RingBuf::new();
1219 lca.push_back(Traverse::traverse(&mut self.root));
1228 /// Gets an owning iterator over the entries of the map.
1233 /// use std::collections::BTreeMap;
1235 /// let mut map = BTreeMap::new();
1236 /// map.insert(1u, "a");
1237 /// map.insert(2u, "b");
1238 /// map.insert(3u, "c");
1240 /// for (key, value) in map.into_iter() {
1241 /// println!("{}: {}", key, value);
1244 #[stable(feature = "rust1", since = "1.0.0")]
1245 pub fn into_iter(self) -> IntoIter<K, V> {
1246 let len = self.len();
1247 let mut lca = RingBuf::new();
1248 lca.push_back(Traverse::traverse(self.root));
1257 /// Gets an iterator over the keys of the map.
1262 /// use std::collections::BTreeMap;
1264 /// let mut a = BTreeMap::new();
1265 /// a.insert(1u, "a");
1266 /// a.insert(2u, "b");
1268 /// let keys: Vec<uint> = a.keys().cloned().collect();
1269 /// assert_eq!(keys, vec![1u,2,]);
1271 #[stable(feature = "rust1", since = "1.0.0")]
1272 pub fn keys<'a>(&'a self) -> Keys<'a, K, V> {
1273 fn first<A, B>((a, _): (A, B)) -> A { a }
1274 let first: fn((&'a K, &'a V)) -> &'a K = first; // coerce to fn pointer
1276 Keys { inner: self.iter().map(first) }
1279 /// Gets an iterator over the values of the map.
1284 /// use std::collections::BTreeMap;
1286 /// let mut a = BTreeMap::new();
1287 /// a.insert(1u, "a");
1288 /// a.insert(2u, "b");
1290 /// let values: Vec<&str> = a.values().cloned().collect();
1291 /// assert_eq!(values, vec!["a","b"]);
1293 #[stable(feature = "rust1", since = "1.0.0")]
1294 pub fn values<'a>(&'a self) -> Values<'a, K, V> {
1295 fn second<A, B>((_, b): (A, B)) -> B { b }
1296 let second: fn((&'a K, &'a V)) -> &'a V = second; // coerce to fn pointer
1298 Values { inner: self.iter().map(second) }
1301 /// Return the number of elements in the map.
1306 /// use std::collections::BTreeMap;
1308 /// let mut a = BTreeMap::new();
1309 /// assert_eq!(a.len(), 0);
1310 /// a.insert(1u, "a");
1311 /// assert_eq!(a.len(), 1);
1313 #[stable(feature = "rust1", since = "1.0.0")]
1314 pub fn len(&self) -> uint { self.length }
1316 /// Return true if the map contains no elements.
1321 /// use std::collections::BTreeMap;
1323 /// let mut a = BTreeMap::new();
1324 /// assert!(a.is_empty());
1325 /// a.insert(1u, "a");
1326 /// assert!(!a.is_empty());
1328 #[stable(feature = "rust1", since = "1.0.0")]
1329 pub fn is_empty(&self) -> bool { self.len() == 0 }
1332 macro_rules! range_impl {
1333 ($root:expr, $min:expr, $max:expr, $as_slices_internal:ident, $iter:ident, $Range:ident,
1334 $edges:ident, [$($mutability:ident)*]) => (
1336 // A deque that encodes two search paths containing (left-to-right):
1337 // a series of truncated-from-the-left iterators, the LCA's doubly-truncated iterator,
1338 // and a series of truncated-from-the-right iterators.
1339 let mut traversals = RingBuf::new();
1340 let (root, min, max) = ($root, $min, $max);
1342 let mut leftmost = None;
1343 let mut rightmost = None;
1345 match (&min, &max) {
1346 (&Unbounded, &Unbounded) => {
1347 traversals.push_back(Traverse::traverse(root))
1349 (&Unbounded, &Included(_)) | (&Unbounded, &Excluded(_)) => {
1350 rightmost = Some(root);
1352 (&Included(_), &Unbounded) | (&Excluded(_), &Unbounded) => {
1353 leftmost = Some(root);
1355 (&Included(min_key), &Included(max_key))
1356 | (&Included(min_key), &Excluded(max_key))
1357 | (&Excluded(min_key), &Included(max_key))
1358 | (&Excluded(min_key), &Excluded(max_key)) => {
1359 // lca represents the Lowest Common Ancestor, above which we never
1360 // walk, since everything else is outside the range to iterate.
1361 // ___________________
1362 // |__0_|_80_|_85_|_90_| (root)
1366 // ___________________
1367 // |__5_|_15_|_30_|_73_|
1371 // ___________________
1372 // |_33_|_58_|_63_|_68_| lca for the range [41, 65]
1373 // | |\___|___/| | iterator at traversals[2]
1378 let mut is_leaf = root.is_leaf();
1379 let mut lca = root.$as_slices_internal();
1381 let slice = lca.slice_from(min_key).slice_to(max_key);
1382 if let [ref $($mutability)* edge] = slice.edges {
1383 // Follow the only edge that leads the node that covers the range.
1384 is_leaf = edge.is_leaf();
1385 lca = edge.$as_slices_internal();
1387 let mut iter = slice.$iter();
1392 // Only change the state of nodes with edges.
1393 leftmost = iter.next_edge_item();
1394 rightmost = iter.next_edge_item_back();
1396 traversals.push_back(iter);
1402 // Keep narrowing the range by going down.
1403 // ___________________
1404 // |_38_|_43_|_48_|_53_|
1405 // | |____|____|____/ iterator at traversals[1]
1408 // ___________________
1409 // |_39_|_40_|_41_|_42_| (leaf, the last leftmost)
1410 // \_________| iterator at traversals[0]
1412 Included(key) | Excluded(key) =>
1413 while let Some(left) = leftmost {
1414 let is_leaf = left.is_leaf();
1415 let mut iter = left.$as_slices_internal().slice_from(key).$iter();
1416 leftmost = if is_leaf {
1419 // Only change the state of nodes with edges.
1420 iter.next_edge_item()
1422 traversals.push_back(iter);
1426 // If the leftmost iterator starts with an element, then it was an exact match.
1427 if let (Excluded(_), Some(leftmost_iter)) = (min, traversals.back_mut()) {
1428 // Drop this excluded element. `next_kv_item` has no effect when
1429 // the next item is an edge.
1430 leftmost_iter.next_kv_item();
1433 // The code for the right side is similar.
1435 Included(key) | Excluded(key) =>
1436 while let Some(right) = rightmost {
1437 let is_leaf = right.is_leaf();
1438 let mut iter = right.$as_slices_internal().slice_to(key).$iter();
1439 rightmost = if is_leaf {
1442 iter.next_edge_item_back()
1444 traversals.push_front(iter);
1448 if let (Excluded(_), Some(rightmost_iter)) = (max, traversals.front_mut()) {
1449 rightmost_iter.next_kv_item_back();
1454 traversals: traversals,
1462 impl<K: Ord, V> BTreeMap<K, V> {
1463 /// Constructs a double-ended iterator over a sub-range of elements in the map, starting
1464 /// at min, and ending at max. If min is `Unbounded`, then it will be treated as "negative
1465 /// infinity", and if max is `Unbounded`, then it will be treated as "positive infinity".
1466 /// Thus range(Unbounded, Unbounded) will yield the whole collection.
1471 /// use std::collections::BTreeMap;
1472 /// use std::collections::Bound::{Included, Unbounded};
1474 /// let mut map = BTreeMap::new();
1475 /// map.insert(3u, "a");
1476 /// map.insert(5u, "b");
1477 /// map.insert(8u, "c");
1478 /// for (&key, &value) in map.range(Included(&4), Included(&8)) {
1479 /// println!("{}: {}", key, value);
1481 /// assert_eq!(Some((&5u, &"b")), map.range(Included(&4), Unbounded).next());
1483 #[unstable(feature = "collections",
1484 reason = "matches collection reform specification, waiting for dust to settle")]
1485 pub fn range<'a>(&'a self, min: Bound<&K>, max: Bound<&K>) -> Range<'a, K, V> {
1486 range_impl!(&self.root, min, max, as_slices_internal, iter, Range, edges, [])
1489 /// Constructs a mutable double-ended iterator over a sub-range of elements in the map, starting
1490 /// at min, and ending at max. If min is `Unbounded`, then it will be treated as "negative
1491 /// infinity", and if max is `Unbounded`, then it will be treated as "positive infinity".
1492 /// Thus range(Unbounded, Unbounded) will yield the whole collection.
1497 /// use std::collections::BTreeMap;
1498 /// use std::collections::Bound::{Included, Excluded};
1500 /// let mut map: BTreeMap<&str, i32> = ["Alice", "Bob", "Carol", "Cheryl"].iter()
1501 /// .map(|&s| (s, 0))
1503 /// for (_, balance) in map.range_mut(Included(&"B"), Excluded(&"Cheryl")) {
1504 /// *balance += 100;
1506 /// for (name, balance) in map.iter() {
1507 /// println!("{} => {}", name, balance);
1510 #[unstable(feature = "collections",
1511 reason = "matches collection reform specification, waiting for dust to settle")]
1512 pub fn range_mut<'a>(&'a mut self, min: Bound<&K>, max: Bound<&K>) -> RangeMut<'a, K, V> {
1513 range_impl!(&mut self.root, min, max, as_slices_internal_mut, iter_mut, RangeMut,
1517 /// Gets the given key's corresponding entry in the map for in-place manipulation.
1522 /// use std::collections::BTreeMap;
1523 /// use std::collections::btree_map::Entry;
1525 /// let mut count: BTreeMap<&str, uint> = BTreeMap::new();
1527 /// // count the number of occurrences of letters in the vec
1528 /// for x in vec!["a","b","a","c","a","b"].iter() {
1529 /// match count.entry(*x) {
1530 /// Entry::Vacant(view) => {
1533 /// Entry::Occupied(mut view) => {
1534 /// let v = view.get_mut();
1540 /// assert_eq!(count["a"], 3u);
1542 /// The key must have the same ordering before or after `.to_owned()` is called.
1543 #[unstable(feature = "collections",
1544 reason = "precise API still under development")]
1545 pub fn entry<'a>(&'a mut self, mut key: K) -> Entry<'a, K, V> {
1546 // same basic logic of `swap` and `pop`, blended together
1547 let mut stack = stack::PartialSearchStack::new(self);
1549 let result = stack.with(move |pusher, node| {
1550 return match Node::search(node, &key) {
1553 Finished(Occupied(OccupiedEntry {
1554 stack: pusher.seal(handle)
1558 match handle.force() {
1559 Leaf(leaf_handle) => {
1560 Finished(Vacant(VacantEntry {
1561 stack: pusher.seal(leaf_handle),
1565 Internal(internal_handle) => {
1567 pusher.push(internal_handle),
1576 Finished(finished) => return finished,
1577 Continue((new_stack, renewed_key)) => {
1593 use std::iter::range_inclusive;
1595 use super::{BTreeMap, Occupied, Vacant};
1596 use Bound::{self, Included, Excluded, Unbounded};
1599 fn test_basic_large() {
1600 let mut map = BTreeMap::new();
1602 assert_eq!(map.len(), 0);
1604 for i in range(0, size) {
1605 assert_eq!(map.insert(i, 10*i), None);
1606 assert_eq!(map.len(), i + 1);
1609 for i in range(0, size) {
1610 assert_eq!(map.get(&i).unwrap(), &(i*10));
1613 for i in range(size, size*2) {
1614 assert_eq!(map.get(&i), None);
1617 for i in range(0, size) {
1618 assert_eq!(map.insert(i, 100*i), Some(10*i));
1619 assert_eq!(map.len(), size);
1622 for i in range(0, size) {
1623 assert_eq!(map.get(&i).unwrap(), &(i*100));
1626 for i in range(0, size/2) {
1627 assert_eq!(map.remove(&(i*2)), Some(i*200));
1628 assert_eq!(map.len(), size - i - 1);
1631 for i in range(0, size/2) {
1632 assert_eq!(map.get(&(2*i)), None);
1633 assert_eq!(map.get(&(2*i+1)).unwrap(), &(i*200 + 100));
1636 for i in range(0, size/2) {
1637 assert_eq!(map.remove(&(2*i)), None);
1638 assert_eq!(map.remove(&(2*i+1)), Some(i*200 + 100));
1639 assert_eq!(map.len(), size/2 - i - 1);
1644 fn test_basic_small() {
1645 let mut map = BTreeMap::new();
1646 assert_eq!(map.remove(&1), None);
1647 assert_eq!(map.get(&1), None);
1648 assert_eq!(map.insert(1u, 1u), None);
1649 assert_eq!(map.get(&1), Some(&1));
1650 assert_eq!(map.insert(1, 2), Some(1));
1651 assert_eq!(map.get(&1), Some(&2));
1652 assert_eq!(map.insert(2, 4), None);
1653 assert_eq!(map.get(&2), Some(&4));
1654 assert_eq!(map.remove(&1), Some(2));
1655 assert_eq!(map.remove(&2), Some(4));
1656 assert_eq!(map.remove(&1), None);
1664 let mut map: BTreeMap<uint, uint> = range(0, size).map(|i| (i, i)).collect();
1666 fn test<T>(size: uint, mut iter: T) where T: Iterator<Item=(uint, uint)> {
1667 for i in range(0, size) {
1668 assert_eq!(iter.size_hint(), (size - i, Some(size - i)));
1669 assert_eq!(iter.next().unwrap(), (i, i));
1671 assert_eq!(iter.size_hint(), (0, Some(0)));
1672 assert_eq!(iter.next(), None);
1674 test(size, map.iter().map(|(&k, &v)| (k, v)));
1675 test(size, map.iter_mut().map(|(&k, &mut v)| (k, v)));
1676 test(size, map.into_iter());
1680 fn test_iter_rev() {
1684 let mut map: BTreeMap<uint, uint> = range(0, size).map(|i| (i, i)).collect();
1686 fn test<T>(size: uint, mut iter: T) where T: Iterator<Item=(uint, uint)> {
1687 for i in range(0, size) {
1688 assert_eq!(iter.size_hint(), (size - i, Some(size - i)));
1689 assert_eq!(iter.next().unwrap(), (size - i - 1, size - i - 1));
1691 assert_eq!(iter.size_hint(), (0, Some(0)));
1692 assert_eq!(iter.next(), None);
1694 test(size, map.iter().rev().map(|(&k, &v)| (k, v)));
1695 test(size, map.iter_mut().rev().map(|(&k, &mut v)| (k, v)));
1696 test(size, map.into_iter().rev());
1700 fn test_iter_mixed() {
1704 let mut map: BTreeMap<uint, uint> = range(0, size).map(|i| (i, i)).collect();
1706 fn test<T>(size: uint, mut iter: T)
1707 where T: Iterator<Item=(uint, uint)> + DoubleEndedIterator {
1708 for i in range(0, size / 4) {
1709 assert_eq!(iter.size_hint(), (size - i * 2, Some(size - i * 2)));
1710 assert_eq!(iter.next().unwrap(), (i, i));
1711 assert_eq!(iter.next_back().unwrap(), (size - i - 1, size - i - 1));
1713 for i in range(size / 4, size * 3 / 4) {
1714 assert_eq!(iter.size_hint(), (size * 3 / 4 - i, Some(size * 3 / 4 - i)));
1715 assert_eq!(iter.next().unwrap(), (i, i));
1717 assert_eq!(iter.size_hint(), (0, Some(0)));
1718 assert_eq!(iter.next(), None);
1720 test(size, map.iter().map(|(&k, &v)| (k, v)));
1721 test(size, map.iter_mut().map(|(&k, &mut v)| (k, v)));
1722 test(size, map.into_iter());
1726 fn test_range_small() {
1730 let map: BTreeMap<uint, uint> = range(0, size).map(|i| (i, i)).collect();
1733 for ((&k, &v), i) in map.range(Included(&2), Unbounded).zip(range(2u, size)) {
1738 assert_eq!(j, size - 2);
1742 fn test_range_1000() {
1744 let map: BTreeMap<uint, uint> = range(0, size).map(|i| (i, i)).collect();
1746 fn test(map: &BTreeMap<uint, uint>, size: uint, min: Bound<&uint>, max: Bound<&uint>) {
1747 let mut kvs = map.range(min, max).map(|(&k, &v)| (k, v));
1748 let mut pairs = range(0, size).map(|i| (i, i));
1750 for (kv, pair) in kvs.by_ref().zip(pairs.by_ref()) {
1751 assert_eq!(kv, pair);
1753 assert_eq!(kvs.next(), None);
1754 assert_eq!(pairs.next(), None);
1756 test(&map, size, Included(&0), Excluded(&size));
1757 test(&map, size, Unbounded, Excluded(&size));
1758 test(&map, size, Included(&0), Included(&(size - 1)));
1759 test(&map, size, Unbounded, Included(&(size - 1)));
1760 test(&map, size, Included(&0), Unbounded);
1761 test(&map, size, Unbounded, Unbounded);
1767 let map: BTreeMap<uint, uint> = range(0, size).map(|i| (i, i)).collect();
1769 for i in range(0, size) {
1770 for j in range(i, size) {
1771 let mut kvs = map.range(Included(&i), Included(&j)).map(|(&k, &v)| (k, v));
1772 let mut pairs = range_inclusive(i, j).map(|i| (i, i));
1774 for (kv, pair) in kvs.by_ref().zip(pairs.by_ref()) {
1775 assert_eq!(kv, pair);
1777 assert_eq!(kvs.next(), None);
1778 assert_eq!(pairs.next(), None);
1785 let xs = [(1i, 10i), (2, 20), (3, 30), (4, 40), (5, 50), (6, 60)];
1787 let mut map: BTreeMap<int, int> = xs.iter().map(|&x| x).collect();
1789 // Existing key (insert)
1790 match map.entry(1) {
1791 Vacant(_) => unreachable!(),
1792 Occupied(mut view) => {
1793 assert_eq!(view.get(), &10);
1794 assert_eq!(view.insert(100), 10);
1797 assert_eq!(map.get(&1).unwrap(), &100);
1798 assert_eq!(map.len(), 6);
1801 // Existing key (update)
1802 match map.entry(2) {
1803 Vacant(_) => unreachable!(),
1804 Occupied(mut view) => {
1805 let v = view.get_mut();
1809 assert_eq!(map.get(&2).unwrap(), &200);
1810 assert_eq!(map.len(), 6);
1812 // Existing key (take)
1813 match map.entry(3) {
1814 Vacant(_) => unreachable!(),
1816 assert_eq!(view.remove(), 30);
1819 assert_eq!(map.get(&3), None);
1820 assert_eq!(map.len(), 5);
1823 // Inexistent key (insert)
1824 match map.entry(10) {
1825 Occupied(_) => unreachable!(),
1827 assert_eq!(*view.insert(1000), 1000);
1830 assert_eq!(map.get(&10).unwrap(), &1000);
1831 assert_eq!(map.len(), 6);
1843 use std::rand::{weak_rng, Rng};
1844 use test::{Bencher, black_box};
1846 use super::BTreeMap;
1847 use bench::{insert_rand_n, insert_seq_n, find_rand_n, find_seq_n};
1850 pub fn insert_rand_100(b: &mut Bencher) {
1851 let mut m : BTreeMap<uint,uint> = BTreeMap::new();
1852 insert_rand_n(100, &mut m, b,
1853 |m, i| { m.insert(i, 1); },
1854 |m, i| { m.remove(&i); });
1858 pub fn insert_rand_10_000(b: &mut Bencher) {
1859 let mut m : BTreeMap<uint,uint> = BTreeMap::new();
1860 insert_rand_n(10_000, &mut m, b,
1861 |m, i| { m.insert(i, 1); },
1862 |m, i| { m.remove(&i); });
1867 pub fn insert_seq_100(b: &mut Bencher) {
1868 let mut m : BTreeMap<uint,uint> = BTreeMap::new();
1869 insert_seq_n(100, &mut m, b,
1870 |m, i| { m.insert(i, 1); },
1871 |m, i| { m.remove(&i); });
1875 pub fn insert_seq_10_000(b: &mut Bencher) {
1876 let mut m : BTreeMap<uint,uint> = BTreeMap::new();
1877 insert_seq_n(10_000, &mut m, b,
1878 |m, i| { m.insert(i, 1); },
1879 |m, i| { m.remove(&i); });
1884 pub fn find_rand_100(b: &mut Bencher) {
1885 let mut m : BTreeMap<uint,uint> = BTreeMap::new();
1886 find_rand_n(100, &mut m, b,
1887 |m, i| { m.insert(i, 1); },
1888 |m, i| { m.get(&i); });
1892 pub fn find_rand_10_000(b: &mut Bencher) {
1893 let mut m : BTreeMap<uint,uint> = BTreeMap::new();
1894 find_rand_n(10_000, &mut m, b,
1895 |m, i| { m.insert(i, 1); },
1896 |m, i| { m.get(&i); });
1901 pub fn find_seq_100(b: &mut Bencher) {
1902 let mut m : BTreeMap<uint,uint> = BTreeMap::new();
1903 find_seq_n(100, &mut m, b,
1904 |m, i| { m.insert(i, 1); },
1905 |m, i| { m.get(&i); });
1909 pub fn find_seq_10_000(b: &mut Bencher) {
1910 let mut m : BTreeMap<uint,uint> = BTreeMap::new();
1911 find_seq_n(10_000, &mut m, b,
1912 |m, i| { m.insert(i, 1); },
1913 |m, i| { m.get(&i); });
1916 fn bench_iter(b: &mut Bencher, size: uint) {
1917 let mut map = BTreeMap::<uint, uint>::new();
1918 let mut rng = weak_rng();
1920 for _ in range(0, size) {
1921 map.insert(rng.gen(), rng.gen());
1925 for entry in map.iter() {
1932 pub fn iter_20(b: &mut Bencher) {
1937 pub fn iter_1000(b: &mut Bencher) {
1938 bench_iter(b, 1000);
1942 pub fn iter_100000(b: &mut Bencher) {
1943 bench_iter(b, 100000);