1 // This is an attempt at an implementation following the ideal
4 // struct BTreeMap<K, V> {
6 // root: Option<Box<Node<K, V, height>>>
9 // struct Node<K, V, height: usize> {
10 // keys: [K; 2 * B - 1],
11 // vals: [V; 2 * B - 1],
12 // edges: if height > 0 {
13 // [Box<Node<K, V, height - 1>>; 2 * B]
15 // parent: *const Node<K, V, height + 1>,
21 // Since Rust doesn't actually have dependent types and polymorphic recursion,
22 // we make do with lots of unsafety.
24 // A major goal of this module is to avoid complexity by treating the tree as a generic (if
25 // weirdly shaped) container and avoiding dealing with most of the B-Tree invariants. As such,
26 // this module doesn't care whether the entries are sorted, which nodes can be underfull, or
27 // even what underfull means. However, we do rely on a few invariants:
29 // - Trees must have uniform depth/height. This means that every path down to a leaf from a
30 // given node has exactly the same length.
31 // - A node of length `n` has `n` keys, `n` values, and (in an internal node) `n + 1` edges.
32 // This implies that even an empty internal node has at least one edge.
34 use core::cmp::Ordering;
35 use core::marker::PhantomData;
36 use core::mem::{self, MaybeUninit};
37 use core::ptr::{self, NonNull, Unique};
40 use crate::alloc::{AllocRef, Global, Layout};
41 use crate::boxed::Box;
44 pub const MIN_LEN: usize = B - 1;
45 pub const CAPACITY: usize = 2 * B - 1;
47 /// The underlying representation of leaf nodes.
49 struct LeafNode<K, V> {
50 /// We use `*const` as opposed to `*mut` so as to be covariant in `K` and `V`.
51 /// This either points to an actual node or is null.
52 parent: *const InternalNode<K, V>,
54 /// This node's index into the parent node's `edges` array.
55 /// `*node.parent.edges[node.parent_idx]` should be the same thing as `node`.
56 /// This is only guaranteed to be initialized when `parent` is non-null.
57 parent_idx: MaybeUninit<u16>,
59 /// The number of keys and values this node stores.
61 /// This next to `parent_idx` to encourage the compiler to join `len` and
62 /// `parent_idx` into the same 32-bit word, reducing space overhead.
65 /// The arrays storing the actual data of the node. Only the first `len` elements of each
66 /// array are initialized and valid.
67 keys: [MaybeUninit<K>; CAPACITY],
68 vals: [MaybeUninit<V>; CAPACITY],
71 impl<K, V> LeafNode<K, V> {
72 /// Creates a new `LeafNode`. Unsafe because all nodes should really be hidden behind
73 /// `BoxedNode`, preventing accidental dropping of uninitialized keys and values.
74 unsafe fn new() -> Self {
76 // As a general policy, we leave fields uninitialized if they can be, as this should
77 // be both slightly faster and easier to track in Valgrind.
78 keys: [MaybeUninit::UNINIT; CAPACITY],
79 vals: [MaybeUninit::UNINIT; CAPACITY],
81 parent_idx: MaybeUninit::uninit(),
87 /// The underlying representation of internal nodes. As with `LeafNode`s, these should be hidden
88 /// behind `BoxedNode`s to prevent dropping uninitialized keys and values. Any pointer to an
89 /// `InternalNode` can be directly casted to a pointer to the underlying `LeafNode` portion of the
90 /// node, allowing code to act on leaf and internal nodes generically without having to even check
91 /// which of the two a pointer is pointing at. This property is enabled by the use of `repr(C)`.
93 struct InternalNode<K, V> {
96 /// The pointers to the children of this node. `len + 1` of these are considered
97 /// initialized and valid. Although during the process of `into_iter` or `drop`,
98 /// some pointers are dangling while others still need to be traversed.
99 edges: [MaybeUninit<BoxedNode<K, V>>; 2 * B],
102 impl<K, V> InternalNode<K, V> {
103 /// Creates a new `InternalNode`.
105 /// This is unsafe for two reasons. First, it returns an `InternalNode` by value, risking
106 /// dropping of uninitialized fields. Second, an invariant of internal nodes is that `len + 1`
107 /// edges are initialized and valid, meaning that even when the node is empty (having a
108 /// `len` of 0), there must be one initialized and valid edge. This function does not set up
110 unsafe fn new() -> Self {
111 InternalNode { data: unsafe { LeafNode::new() }, edges: [MaybeUninit::UNINIT; 2 * B] }
115 /// A managed, non-null pointer to a node. This is either an owned pointer to
116 /// `LeafNode<K, V>` or an owned pointer to `InternalNode<K, V>`.
118 /// However, `BoxedNode` contains no information as to which of the two types
119 /// of nodes it actually contains, and, partially due to this lack of information,
120 /// has no destructor.
121 struct BoxedNode<K, V> {
122 ptr: Unique<LeafNode<K, V>>,
125 impl<K, V> BoxedNode<K, V> {
126 fn from_leaf(node: Box<LeafNode<K, V>>) -> Self {
127 BoxedNode { ptr: Box::into_unique(node) }
130 fn from_internal(node: Box<InternalNode<K, V>>) -> Self {
131 BoxedNode { ptr: Box::into_unique(node).cast() }
134 unsafe fn from_ptr(ptr: NonNull<LeafNode<K, V>>) -> Self {
135 BoxedNode { ptr: unsafe { Unique::new_unchecked(ptr.as_ptr()) } }
138 fn as_ptr(&self) -> NonNull<LeafNode<K, V>> {
139 NonNull::from(self.ptr)
145 /// Note that this does not have a destructor, and must be cleaned up manually.
146 pub struct Root<K, V> {
147 node: BoxedNode<K, V>,
148 /// The number of levels below the root node.
152 unsafe impl<K: Sync, V: Sync> Sync for Root<K, V> {}
153 unsafe impl<K: Send, V: Send> Send for Root<K, V> {}
155 impl<K, V> Root<K, V> {
156 /// Returns the number of levels below the root.
157 pub fn height(&self) -> usize {
161 /// Returns a new owned tree, with its own root node that is initially empty.
162 pub fn new_leaf() -> Self {
163 Root { node: BoxedNode::from_leaf(Box::new(unsafe { LeafNode::new() })), height: 0 }
166 pub fn as_ref(&self) -> NodeRef<marker::Immut<'_>, K, V, marker::LeafOrInternal> {
169 node: self.node.as_ptr(),
171 _marker: PhantomData,
175 pub fn as_mut(&mut self) -> NodeRef<marker::Mut<'_>, K, V, marker::LeafOrInternal> {
178 node: self.node.as_ptr(),
179 root: self as *mut _,
180 _marker: PhantomData,
184 pub fn into_ref(self) -> NodeRef<marker::Owned, K, V, marker::LeafOrInternal> {
187 node: self.node.as_ptr(),
189 _marker: PhantomData,
193 /// Adds a new internal node with a single edge, pointing to the previous root, and make that
194 /// new node the root. This increases the height by 1 and is the opposite of
195 /// `pop_internal_level`.
196 pub fn push_internal_level(&mut self) -> NodeRef<marker::Mut<'_>, K, V, marker::Internal> {
197 let mut new_node = Box::new(unsafe { InternalNode::new() });
198 new_node.edges[0].write(unsafe { BoxedNode::from_ptr(self.node.as_ptr()) });
200 self.node = BoxedNode::from_internal(new_node);
203 let mut ret = NodeRef {
205 node: self.node.as_ptr(),
206 root: self as *mut _,
207 _marker: PhantomData,
211 ret.reborrow_mut().first_edge().correct_parent_link();
217 /// Removes the internal root node, using its first child as the new root.
218 /// As it is intended only to be called when the root has only one child,
219 /// no cleanup is done on any of the other children of the root.
220 /// This decreases the height by 1 and is the opposite of `push_internal_level`.
221 /// Panics if there is no internal level, i.e. if the root is a leaf.
222 pub fn pop_internal_level(&mut self) {
223 assert!(self.height > 0);
225 let top = self.node.ptr;
229 self.as_mut().cast_unchecked::<marker::Internal>().first_edge().descend().node,
234 (*self.as_mut().as_leaf_mut()).parent = ptr::null();
238 Global.dealloc(NonNull::from(top).cast(), Layout::new::<InternalNode<K, V>>());
243 // N.B. `NodeRef` is always covariant in `K` and `V`, even when the `BorrowType`
244 // is `Mut`. This is technically wrong, but cannot result in any unsafety due to
245 // internal use of `NodeRef` because we stay completely generic over `K` and `V`.
246 // However, whenever a public type wraps `NodeRef`, make sure that it has the
248 /// A reference to a node.
250 /// This type has a number of parameters that controls how it acts:
251 /// - `BorrowType`: This can be `Immut<'a>` or `Mut<'a>` for some `'a` or `Owned`.
252 /// When this is `Immut<'a>`, the `NodeRef` acts roughly like `&'a Node`,
253 /// when this is `Mut<'a>`, the `NodeRef` acts roughly like `&'a mut Node`,
254 /// and when this is `Owned`, the `NodeRef` acts roughly like `Box<Node>`.
255 /// - `K` and `V`: These control what types of things are stored in the nodes.
256 /// - `Type`: This can be `Leaf`, `Internal`, or `LeafOrInternal`. When this is
257 /// `Leaf`, the `NodeRef` points to a leaf node, when this is `Internal` the
258 /// `NodeRef` points to an internal node, and when this is `LeafOrInternal` the
259 /// `NodeRef` could be pointing to either type of node.
260 pub struct NodeRef<BorrowType, K, V, Type> {
261 /// The number of levels below the node.
263 node: NonNull<LeafNode<K, V>>,
264 // `root` is null unless the borrow type is `Mut`
265 root: *const Root<K, V>,
266 _marker: PhantomData<(BorrowType, Type)>,
269 impl<'a, K: 'a, V: 'a, Type> Copy for NodeRef<marker::Immut<'a>, K, V, Type> {}
270 impl<'a, K: 'a, V: 'a, Type> Clone for NodeRef<marker::Immut<'a>, K, V, Type> {
271 fn clone(&self) -> Self {
276 unsafe impl<BorrowType, K: Sync, V: Sync, Type> Sync for NodeRef<BorrowType, K, V, Type> {}
278 unsafe impl<'a, K: Sync + 'a, V: Sync + 'a, Type> Send for NodeRef<marker::Immut<'a>, K, V, Type> {}
279 unsafe impl<'a, K: Send + 'a, V: Send + 'a, Type> Send for NodeRef<marker::Mut<'a>, K, V, Type> {}
280 unsafe impl<K: Send, V: Send, Type> Send for NodeRef<marker::Owned, K, V, Type> {}
282 impl<BorrowType, K, V> NodeRef<BorrowType, K, V, marker::Internal> {
283 fn as_internal(&self) -> &InternalNode<K, V> {
284 unsafe { &*(self.node.as_ptr() as *mut InternalNode<K, V>) }
288 impl<'a, K, V> NodeRef<marker::Mut<'a>, K, V, marker::Internal> {
289 fn as_internal_mut(&mut self) -> &mut InternalNode<K, V> {
290 unsafe { &mut *(self.node.as_ptr() as *mut InternalNode<K, V>) }
294 impl<BorrowType, K, V, Type> NodeRef<BorrowType, K, V, Type> {
295 /// Finds the length of the node. This is the number of keys or values. In an
296 /// internal node, the number of edges is `len() + 1`.
297 /// For any node, the number of possible edge handles is also `len() + 1`.
298 /// Note that, despite being safe, calling this function can have the side effect
299 /// of invalidating mutable references that unsafe code has created.
300 pub fn len(&self) -> usize {
301 self.as_leaf().len as usize
304 /// Returns the height of this node in the whole tree. Zero height denotes the
306 pub fn height(&self) -> usize {
310 /// Temporarily takes out another, immutable reference to the same node.
311 fn reborrow(&self) -> NodeRef<marker::Immut<'_>, K, V, Type> {
312 NodeRef { height: self.height, node: self.node, root: self.root, _marker: PhantomData }
315 /// Exposes the leaf "portion" of any leaf or internal node.
316 /// If the node is a leaf, this function simply opens up its data.
317 /// If the node is an internal node, so not a leaf, it does have all the data a leaf has
318 /// (header, keys and values), and this function exposes that.
319 fn as_leaf(&self) -> &LeafNode<K, V> {
320 // The node must be valid for at least the LeafNode portion.
321 // This is not a reference in the NodeRef type because we don't know if
322 // it should be unique or shared.
323 unsafe { self.node.as_ref() }
326 /// Borrows a view into the keys stored in the node.
327 pub fn keys(&self) -> &[K] {
328 self.reborrow().into_key_slice()
331 /// Borrows a view into the values stored in the node.
332 fn vals(&self) -> &[V] {
333 self.reborrow().into_val_slice()
336 /// Finds the parent of the current node. Returns `Ok(handle)` if the current
337 /// node actually has a parent, where `handle` points to the edge of the parent
338 /// that points to the current node. Returns `Err(self)` if the current node has
339 /// no parent, giving back the original `NodeRef`.
341 /// `edge.descend().ascend().unwrap()` and `node.ascend().unwrap().descend()` should
342 /// both, upon success, do nothing.
345 ) -> Result<Handle<NodeRef<BorrowType, K, V, marker::Internal>, marker::Edge>, Self> {
346 let parent_as_leaf = self.as_leaf().parent as *const LeafNode<K, V>;
347 if let Some(non_zero) = NonNull::new(parent_as_leaf as *mut _) {
350 height: self.height + 1,
353 _marker: PhantomData,
355 idx: unsafe { usize::from(*self.as_leaf().parent_idx.as_ptr()) },
356 _marker: PhantomData,
363 pub fn first_edge(self) -> Handle<Self, marker::Edge> {
364 unsafe { Handle::new_edge(self, 0) }
367 pub fn last_edge(self) -> Handle<Self, marker::Edge> {
368 let len = self.len();
369 unsafe { Handle::new_edge(self, len) }
372 /// Note that `self` must be nonempty.
373 pub fn first_kv(self) -> Handle<Self, marker::KV> {
374 let len = self.len();
376 unsafe { Handle::new_kv(self, 0) }
379 /// Note that `self` must be nonempty.
380 pub fn last_kv(self) -> Handle<Self, marker::KV> {
381 let len = self.len();
383 unsafe { Handle::new_kv(self, len - 1) }
387 impl<K, V> NodeRef<marker::Owned, K, V, marker::LeafOrInternal> {
388 /// Similar to `ascend`, gets a reference to a node's parent node, but also
389 /// deallocate the current node in the process. This is unsafe because the
390 /// current node will still be accessible despite being deallocated.
391 pub unsafe fn deallocate_and_ascend(
393 ) -> Option<Handle<NodeRef<marker::Owned, K, V, marker::Internal>, marker::Edge>> {
394 let height = self.height;
395 let node = self.node;
396 let ret = self.ascend().ok();
401 Layout::new::<InternalNode<K, V>>()
403 Layout::new::<LeafNode<K, V>>()
411 impl<'a, K, V, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
412 /// Unsafely asserts to the compiler some static information about whether this
413 /// node is a `Leaf` or an `Internal`.
414 unsafe fn cast_unchecked<NewType>(&mut self) -> NodeRef<marker::Mut<'_>, K, V, NewType> {
415 NodeRef { height: self.height, node: self.node, root: self.root, _marker: PhantomData }
418 /// Temporarily takes out another, mutable reference to the same node. Beware, as
419 /// this method is very dangerous, doubly so since it may not immediately appear
422 /// Because mutable pointers can roam anywhere around the tree and can even (through
423 /// `into_root_mut`) mess with the root of the tree, the result of `reborrow_mut`
424 /// can easily be used to make the original mutable pointer dangling, or, in the case
425 /// of a reborrowed handle, out of bounds.
426 // FIXME(@gereeter) consider adding yet another type parameter to `NodeRef` that restricts
427 // the use of `ascend` and `into_root_mut` on reborrowed pointers, preventing this unsafety.
428 unsafe fn reborrow_mut(&mut self) -> NodeRef<marker::Mut<'_>, K, V, Type> {
429 NodeRef { height: self.height, node: self.node, root: self.root, _marker: PhantomData }
432 /// Exposes the leaf "portion" of any leaf or internal node for writing.
433 /// If the node is a leaf, this function simply opens up its data.
434 /// If the node is an internal node, so not a leaf, it does have all the data a leaf has
435 /// (header, keys and values), and this function exposes that.
437 /// Returns a raw ptr to avoid asserting exclusive access to the entire node.
438 fn as_leaf_mut(&mut self) -> *mut LeafNode<K, V> {
442 fn keys_mut(&mut self) -> &mut [K] {
443 // SAFETY: the caller will not be able to call further methods on self
444 // until the key slice reference is dropped, as we have unique access
445 // for the lifetime of the borrow.
446 unsafe { self.reborrow_mut().into_key_slice_mut() }
449 fn vals_mut(&mut self) -> &mut [V] {
450 // SAFETY: the caller will not be able to call further methods on self
451 // until the value slice reference is dropped, as we have unique access
452 // for the lifetime of the borrow.
453 unsafe { self.reborrow_mut().into_val_slice_mut() }
457 impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Immut<'a>, K, V, Type> {
458 fn into_key_slice(self) -> &'a [K] {
459 unsafe { slice::from_raw_parts(MaybeUninit::first_ptr(&self.as_leaf().keys), self.len()) }
462 fn into_val_slice(self) -> &'a [V] {
463 unsafe { slice::from_raw_parts(MaybeUninit::first_ptr(&self.as_leaf().vals), self.len()) }
467 impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
468 /// Gets a mutable reference to the root itself. This is useful primarily when the
469 /// height of the tree needs to be adjusted. Never call this on a reborrowed pointer.
470 pub fn into_root_mut(self) -> &'a mut Root<K, V> {
471 unsafe { &mut *(self.root as *mut Root<K, V>) }
474 fn into_key_slice_mut(mut self) -> &'a mut [K] {
475 // SAFETY: The keys of a node must always be initialized up to length.
477 slice::from_raw_parts_mut(
478 MaybeUninit::first_ptr_mut(&mut (*self.as_leaf_mut()).keys),
484 fn into_val_slice_mut(mut self) -> &'a mut [V] {
485 // SAFETY: The values of a node must always be initialized up to length.
487 slice::from_raw_parts_mut(
488 MaybeUninit::first_ptr_mut(&mut (*self.as_leaf_mut()).vals),
494 fn into_slices_mut(mut self) -> (&'a mut [K], &'a mut [V]) {
495 // We cannot use the getters here, because calling the second one
496 // invalidates the reference returned by the first.
497 // More precisely, it is the call to `len` that is the culprit,
498 // because that creates a shared reference to the header, which *can*
499 // overlap with the keys (and even the values, for ZST keys).
500 let len = self.len();
501 let leaf = self.as_leaf_mut();
502 // SAFETY: The keys and values of a node must always be initialized up to length.
504 slice::from_raw_parts_mut(MaybeUninit::first_ptr_mut(&mut (*leaf).keys), len)
507 slice::from_raw_parts_mut(MaybeUninit::first_ptr_mut(&mut (*leaf).vals), len)
513 impl<'a, K, V> NodeRef<marker::Mut<'a>, K, V, marker::Leaf> {
514 /// Adds a key/value pair to the end of the node.
515 pub fn push(&mut self, key: K, val: V) {
516 assert!(self.len() < CAPACITY);
518 let idx = self.len();
521 ptr::write(self.keys_mut().get_unchecked_mut(idx), key);
522 ptr::write(self.vals_mut().get_unchecked_mut(idx), val);
524 (*self.as_leaf_mut()).len += 1;
528 /// Adds a key/value pair to the beginning of the node.
529 pub fn push_front(&mut self, key: K, val: V) {
530 assert!(self.len() < CAPACITY);
533 slice_insert(self.keys_mut(), 0, key);
534 slice_insert(self.vals_mut(), 0, val);
536 (*self.as_leaf_mut()).len += 1;
541 impl<'a, K, V> NodeRef<marker::Mut<'a>, K, V, marker::Internal> {
542 /// Adds a key/value pair and an edge to go to the right of that pair to
543 /// the end of the node.
544 pub fn push(&mut self, key: K, val: V, edge: Root<K, V>) {
545 assert!(edge.height == self.height - 1);
546 assert!(self.len() < CAPACITY);
548 let idx = self.len();
551 ptr::write(self.keys_mut().get_unchecked_mut(idx), key);
552 ptr::write(self.vals_mut().get_unchecked_mut(idx), val);
553 self.as_internal_mut().edges.get_unchecked_mut(idx + 1).write(edge.node);
555 (*self.as_leaf_mut()).len += 1;
557 Handle::new_edge(self.reborrow_mut(), idx + 1).correct_parent_link();
561 // Unsafe because 'first' and 'after_last' must be in range
562 unsafe fn correct_childrens_parent_links(&mut self, first: usize, after_last: usize) {
563 debug_assert!(first <= self.len());
564 debug_assert!(after_last <= self.len() + 1);
565 for i in first..after_last {
566 unsafe { Handle::new_edge(self.reborrow_mut(), i) }.correct_parent_link();
570 fn correct_all_childrens_parent_links(&mut self) {
571 let len = self.len();
572 unsafe { self.correct_childrens_parent_links(0, len + 1) };
575 /// Adds a key/value pair and an edge to go to the left of that pair to
576 /// the beginning of the node.
577 pub fn push_front(&mut self, key: K, val: V, edge: Root<K, V>) {
578 assert!(edge.height == self.height - 1);
579 assert!(self.len() < CAPACITY);
582 slice_insert(self.keys_mut(), 0, key);
583 slice_insert(self.vals_mut(), 0, val);
585 slice::from_raw_parts_mut(
586 MaybeUninit::first_ptr_mut(&mut self.as_internal_mut().edges),
593 (*self.as_leaf_mut()).len += 1;
595 self.correct_all_childrens_parent_links();
600 impl<'a, K, V> NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal> {
601 /// Removes a key/value pair from the end of this node and returns the pair.
602 /// If this is an internal node, also removes the edge that was to the right
603 /// of that pair and returns the orphaned node that this edge owned with its
605 pub fn pop(&mut self) -> (K, V, Option<Root<K, V>>) {
606 assert!(self.len() > 0);
608 let idx = self.len() - 1;
611 let key = ptr::read(self.keys().get_unchecked(idx));
612 let val = ptr::read(self.vals().get_unchecked(idx));
613 let edge = match self.reborrow_mut().force() {
614 ForceResult::Leaf(_) => None,
615 ForceResult::Internal(internal) => {
617 ptr::read(internal.as_internal().edges.get_unchecked(idx + 1).as_ptr());
618 let mut new_root = Root { node: edge, height: internal.height - 1 };
619 (*new_root.as_mut().as_leaf_mut()).parent = ptr::null();
624 (*self.as_leaf_mut()).len -= 1;
629 /// Removes a key/value pair from the beginning of this node. If this is an internal node,
630 /// also removes the edge that was to the left of that pair.
631 pub fn pop_front(&mut self) -> (K, V, Option<Root<K, V>>) {
632 assert!(self.len() > 0);
634 let old_len = self.len();
637 let key = slice_remove(self.keys_mut(), 0);
638 let val = slice_remove(self.vals_mut(), 0);
639 let edge = match self.reborrow_mut().force() {
640 ForceResult::Leaf(_) => None,
641 ForceResult::Internal(mut internal) => {
642 let edge = slice_remove(
643 slice::from_raw_parts_mut(
644 MaybeUninit::first_ptr_mut(&mut internal.as_internal_mut().edges),
650 let mut new_root = Root { node: edge, height: internal.height - 1 };
651 (*new_root.as_mut().as_leaf_mut()).parent = ptr::null();
653 for i in 0..old_len {
654 Handle::new_edge(internal.reborrow_mut(), i).correct_parent_link();
661 (*self.as_leaf_mut()).len -= 1;
667 fn into_kv_pointers_mut(mut self) -> (*mut K, *mut V) {
668 (self.keys_mut().as_mut_ptr(), self.vals_mut().as_mut_ptr())
672 impl<BorrowType, K, V> NodeRef<BorrowType, K, V, marker::LeafOrInternal> {
673 /// Checks whether a node is an `Internal` node or a `Leaf` node.
677 NodeRef<BorrowType, K, V, marker::Leaf>,
678 NodeRef<BorrowType, K, V, marker::Internal>,
680 if self.height == 0 {
681 ForceResult::Leaf(NodeRef {
685 _marker: PhantomData,
688 ForceResult::Internal(NodeRef {
692 _marker: PhantomData,
698 /// A reference to a specific key/value pair or edge within a node. The `Node` parameter
699 /// must be a `NodeRef`, while the `Type` can either be `KV` (signifying a handle on a key/value
700 /// pair) or `Edge` (signifying a handle on an edge).
702 /// Note that even `Leaf` nodes can have `Edge` handles. Instead of representing a pointer to
703 /// a child node, these represent the spaces where child pointers would go between the key/value
704 /// pairs. For example, in a node with length 2, there would be 3 possible edge locations - one
705 /// to the left of the node, one between the two pairs, and one at the right of the node.
706 pub struct Handle<Node, Type> {
709 _marker: PhantomData<Type>,
712 impl<Node: Copy, Type> Copy for Handle<Node, Type> {}
713 // We don't need the full generality of `#[derive(Clone)]`, as the only time `Node` will be
714 // `Clone`able is when it is an immutable reference and therefore `Copy`.
715 impl<Node: Copy, Type> Clone for Handle<Node, Type> {
716 fn clone(&self) -> Self {
721 impl<Node, Type> Handle<Node, Type> {
722 /// Retrieves the node that contains the edge of key/value pair this handle points to.
723 pub fn into_node(self) -> Node {
727 /// Returns the position of this handle in the node.
728 pub fn idx(&self) -> usize {
733 impl<BorrowType, K, V, NodeType> Handle<NodeRef<BorrowType, K, V, NodeType>, marker::KV> {
734 /// Creates a new handle to a key/value pair in `node`.
735 /// Unsafe because the caller must ensure that `idx < node.len()`.
736 pub unsafe fn new_kv(node: NodeRef<BorrowType, K, V, NodeType>, idx: usize) -> Self {
737 debug_assert!(idx < node.len());
739 Handle { node, idx, _marker: PhantomData }
742 pub fn left_edge(self) -> Handle<NodeRef<BorrowType, K, V, NodeType>, marker::Edge> {
743 unsafe { Handle::new_edge(self.node, self.idx) }
746 pub fn right_edge(self) -> Handle<NodeRef<BorrowType, K, V, NodeType>, marker::Edge> {
747 unsafe { Handle::new_edge(self.node, self.idx + 1) }
751 impl<BorrowType, K, V, NodeType, HandleType> PartialEq
752 for Handle<NodeRef<BorrowType, K, V, NodeType>, HandleType>
754 fn eq(&self, other: &Self) -> bool {
755 self.node.node == other.node.node && self.idx == other.idx
759 impl<BorrowType, K, V, NodeType, HandleType> PartialOrd
760 for Handle<NodeRef<BorrowType, K, V, NodeType>, HandleType>
762 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
763 if self.node.node == other.node.node { Some(self.idx.cmp(&other.idx)) } else { None }
767 impl<BorrowType, K, V, NodeType, HandleType>
768 Handle<NodeRef<BorrowType, K, V, NodeType>, HandleType>
770 /// Temporarily takes out another, immutable handle on the same location.
771 pub fn reborrow(&self) -> Handle<NodeRef<marker::Immut<'_>, K, V, NodeType>, HandleType> {
772 // We can't use Handle::new_kv or Handle::new_edge because we don't know our type
773 Handle { node: self.node.reborrow(), idx: self.idx, _marker: PhantomData }
777 impl<'a, K, V, NodeType, HandleType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>, HandleType> {
778 /// Temporarily takes out another, mutable handle on the same location. Beware, as
779 /// this method is very dangerous, doubly so since it may not immediately appear
782 /// Because mutable pointers can roam anywhere around the tree and can even (through
783 /// `into_root_mut`) mess with the root of the tree, the result of `reborrow_mut`
784 /// can easily be used to make the original mutable pointer dangling, or, in the case
785 /// of a reborrowed handle, out of bounds.
786 // FIXME(@gereeter) consider adding yet another type parameter to `NodeRef` that restricts
787 // the use of `ascend` and `into_root_mut` on reborrowed pointers, preventing this unsafety.
788 pub unsafe fn reborrow_mut(
790 ) -> Handle<NodeRef<marker::Mut<'_>, K, V, NodeType>, HandleType> {
791 // We can't use Handle::new_kv or Handle::new_edge because we don't know our type
792 Handle { node: unsafe { self.node.reborrow_mut() }, idx: self.idx, _marker: PhantomData }
796 impl<BorrowType, K, V, NodeType> Handle<NodeRef<BorrowType, K, V, NodeType>, marker::Edge> {
797 /// Creates a new handle to an edge in `node`.
798 /// Unsafe because the caller must ensure that `idx <= node.len()`.
799 pub unsafe fn new_edge(node: NodeRef<BorrowType, K, V, NodeType>, idx: usize) -> Self {
800 debug_assert!(idx <= node.len());
802 Handle { node, idx, _marker: PhantomData }
805 pub fn left_kv(self) -> Result<Handle<NodeRef<BorrowType, K, V, NodeType>, marker::KV>, Self> {
807 Ok(unsafe { Handle::new_kv(self.node, self.idx - 1) })
813 pub fn right_kv(self) -> Result<Handle<NodeRef<BorrowType, K, V, NodeType>, marker::KV>, Self> {
814 if self.idx < self.node.len() {
815 Ok(unsafe { Handle::new_kv(self.node, self.idx) })
822 impl<'a, K, V, NodeType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>, marker::Edge> {
823 /// Helps implementations of `insert_fit` for a particular `NodeType`,
824 /// by taking care of leaf data.
825 /// Inserts a new key/value pair between the key/value pairs to the right and left of
826 /// this edge. This method assumes that there is enough space in the node for the new
828 fn leafy_insert_fit(&mut self, key: K, val: V) {
829 // Necessary for correctness, but in a private module
830 debug_assert!(self.node.len() < CAPACITY);
833 slice_insert(self.node.keys_mut(), self.idx, key);
834 slice_insert(self.node.vals_mut(), self.idx, val);
836 (*self.node.as_leaf_mut()).len += 1;
841 impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge> {
842 /// Inserts a new key/value pair between the key/value pairs to the right and left of
843 /// this edge. This method assumes that there is enough space in the node for the new
846 /// The returned pointer points to the inserted value.
847 fn insert_fit(&mut self, key: K, val: V) -> *mut V {
848 self.leafy_insert_fit(key, val);
849 unsafe { self.node.vals_mut().get_unchecked_mut(self.idx) }
853 impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge> {
854 /// Inserts a new key/value pair between the key/value pairs to the right and left of
855 /// this edge. This method splits the node if there isn't enough room.
857 /// The returned pointer points to the inserted value.
858 fn insert(mut self, key: K, val: V) -> (InsertResult<'a, K, V, marker::Leaf>, *mut V) {
859 if self.node.len() < CAPACITY {
860 let ptr = self.insert_fit(key, val);
861 let kv = unsafe { Handle::new_kv(self.node, self.idx) };
862 (InsertResult::Fit(kv), ptr)
864 let middle = unsafe { Handle::new_kv(self.node, B) };
865 let (mut left, k, v, mut right) = middle.split();
866 let ptr = if self.idx <= B {
867 unsafe { Handle::new_edge(left.reborrow_mut(), self.idx).insert_fit(key, val) }
871 right.as_mut().cast_unchecked::<marker::Leaf>(),
874 .insert_fit(key, val)
877 (InsertResult::Split(SplitResult { left: left.forget_type(), k, v, right }), ptr)
882 impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::Edge> {
883 /// Fixes the parent pointer and index in the child node below this edge. This is useful
884 /// when the ordering of edges has been changed, such as in the various `insert` methods.
885 fn correct_parent_link(mut self) {
886 let idx = self.idx as u16;
887 let ptr = self.node.as_internal_mut() as *mut _;
888 let mut child = self.descend();
890 (*child.as_leaf_mut()).parent = ptr;
891 (*child.as_leaf_mut()).parent_idx.write(idx);
895 /// Inserts a new key/value pair and an edge that will go to the right of that new pair
896 /// between this edge and the key/value pair to the right of this edge. This method assumes
897 /// that there is enough space in the node for the new pair to fit.
898 fn insert_fit(&mut self, key: K, val: V, edge: Root<K, V>) {
899 // Necessary for correctness, but in an internal module
900 debug_assert!(self.node.len() < CAPACITY);
901 debug_assert!(edge.height == self.node.height - 1);
904 self.leafy_insert_fit(key, val);
907 slice::from_raw_parts_mut(
908 MaybeUninit::first_ptr_mut(&mut self.node.as_internal_mut().edges),
915 for i in (self.idx + 1)..(self.node.len() + 1) {
916 Handle::new_edge(self.node.reborrow_mut(), i).correct_parent_link();
921 /// Inserts a new key/value pair and an edge that will go to the right of that new pair
922 /// between this edge and the key/value pair to the right of this edge. This method splits
923 /// the node if there isn't enough room.
929 ) -> InsertResult<'a, K, V, marker::Internal> {
930 assert!(edge.height == self.node.height - 1);
932 if self.node.len() < CAPACITY {
933 self.insert_fit(key, val, edge);
934 let kv = unsafe { Handle::new_kv(self.node, self.idx) };
935 InsertResult::Fit(kv)
937 let middle = unsafe { Handle::new_kv(self.node, B) };
938 let (mut left, k, v, mut right) = middle.split();
941 Handle::new_edge(left.reborrow_mut(), self.idx).insert_fit(key, val, edge);
946 right.as_mut().cast_unchecked::<marker::Internal>(),
949 .insert_fit(key, val, edge);
952 InsertResult::Split(SplitResult { left: left.forget_type(), k, v, right })
957 impl<'a, K: 'a, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge> {
958 /// Inserts a new key/value pair between the key/value pairs to the right and left of
959 /// this edge. This method splits the node if there isn't enough room, and tries to
960 /// insert the split off portion into the parent node recursively, until the root is reached.
962 /// If the returned result is a `Fit`, its handle's node can be this edge's node or an ancestor.
963 /// If the returned result is a `Split`, the `left` field will be the root node.
964 /// The returned pointer points to the inserted value.
965 pub fn insert_recursing(
969 ) -> (InsertResult<'a, K, V, marker::LeafOrInternal>, *mut V) {
970 let (mut split, val_ptr) = match self.insert(key, value) {
971 (InsertResult::Fit(handle), ptr) => {
972 return (InsertResult::Fit(handle.forget_node_type()), ptr);
974 (InsertResult::Split(split), val_ptr) => (split, val_ptr),
978 split = match split.left.ascend() {
979 Ok(parent) => match parent.insert(split.k, split.v, split.right) {
980 InsertResult::Fit(handle) => {
981 return (InsertResult::Fit(handle.forget_node_type()), val_ptr);
983 InsertResult::Split(split) => split,
986 return (InsertResult::Split(SplitResult { left: root, ..split }), val_ptr);
993 impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V, marker::Internal>, marker::Edge> {
994 /// Finds the node pointed to by this edge.
996 /// `edge.descend().ascend().unwrap()` and `node.ascend().unwrap().descend()` should
997 /// both, upon success, do nothing.
998 pub fn descend(self) -> NodeRef<BorrowType, K, V, marker::LeafOrInternal> {
1000 height: self.node.height - 1,
1002 (&*self.node.as_internal().edges.get_unchecked(self.idx).as_ptr()).as_ptr()
1004 root: self.node.root,
1005 _marker: PhantomData,
1010 impl<'a, K: 'a, V: 'a, NodeType> Handle<NodeRef<marker::Immut<'a>, K, V, NodeType>, marker::KV> {
1011 pub fn into_kv(self) -> (&'a K, &'a V) {
1012 let keys = self.node.into_key_slice();
1013 let vals = self.node.into_val_slice();
1014 unsafe { (keys.get_unchecked(self.idx), vals.get_unchecked(self.idx)) }
1018 impl<'a, K: 'a, V: 'a, NodeType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>, marker::KV> {
1019 pub fn into_kv_mut(self) -> (&'a mut K, &'a mut V) {
1021 let (keys, vals) = self.node.into_slices_mut();
1022 (keys.get_unchecked_mut(self.idx), vals.get_unchecked_mut(self.idx))
1027 impl<'a, K, V, NodeType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>, marker::KV> {
1028 pub fn kv_mut(&mut self) -> (&mut K, &mut V) {
1030 let (keys, vals) = self.node.reborrow_mut().into_slices_mut();
1031 (keys.get_unchecked_mut(self.idx), vals.get_unchecked_mut(self.idx))
1036 impl<'a, K, V, NodeType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>, marker::KV> {
1037 /// Helps implementations of `split` for a particular `NodeType`,
1038 /// by taking care of leaf data.
1039 fn leafy_split(&mut self, new_node: &mut LeafNode<K, V>) -> (K, V, usize) {
1041 let k = ptr::read(self.node.keys().get_unchecked(self.idx));
1042 let v = ptr::read(self.node.vals().get_unchecked(self.idx));
1044 let new_len = self.node.len() - self.idx - 1;
1046 ptr::copy_nonoverlapping(
1047 self.node.keys().as_ptr().add(self.idx + 1),
1048 new_node.keys.as_mut_ptr() as *mut K,
1051 ptr::copy_nonoverlapping(
1052 self.node.vals().as_ptr().add(self.idx + 1),
1053 new_node.vals.as_mut_ptr() as *mut V,
1057 (*self.node.as_leaf_mut()).len = self.idx as u16;
1058 new_node.len = new_len as u16;
1064 impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::KV> {
1065 /// Splits the underlying node into three parts:
1067 /// - The node is truncated to only contain the key/value pairs to the right of
1069 /// - The key and value pointed to by this handle and extracted.
1070 /// - All the key/value pairs to the right of this handle are put into a newly
1072 pub fn split(mut self) -> (NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, K, V, Root<K, V>) {
1074 let mut new_node = Box::new(LeafNode::new());
1076 let (k, v, _) = self.leafy_split(&mut new_node);
1078 (self.node, k, v, Root { node: BoxedNode::from_leaf(new_node), height: 0 })
1082 /// Removes the key/value pair pointed to by this handle and returns it, along with the edge
1083 /// between the now adjacent key/value pairs (if any) to the left and right of this handle.
1086 ) -> ((K, V), Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>) {
1088 let k = slice_remove(self.node.keys_mut(), self.idx);
1089 let v = slice_remove(self.node.vals_mut(), self.idx);
1090 (*self.node.as_leaf_mut()).len -= 1;
1091 ((k, v), self.left_edge())
1096 impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::KV> {
1097 /// Splits the underlying node into three parts:
1099 /// - The node is truncated to only contain the edges and key/value pairs to the
1100 /// right of this handle.
1101 /// - The key and value pointed to by this handle and extracted.
1102 /// - All the edges and key/value pairs to the right of this handle are put into
1103 /// a newly allocated node.
1104 pub fn split(mut self) -> (NodeRef<marker::Mut<'a>, K, V, marker::Internal>, K, V, Root<K, V>) {
1106 let mut new_node = Box::new(InternalNode::new());
1108 let (k, v, new_len) = self.leafy_split(&mut new_node.data);
1109 let height = self.node.height;
1111 ptr::copy_nonoverlapping(
1112 self.node.as_internal().edges.as_ptr().add(self.idx + 1),
1113 new_node.edges.as_mut_ptr(),
1117 let mut new_root = Root { node: BoxedNode::from_internal(new_node), height };
1119 for i in 0..(new_len + 1) {
1120 Handle::new_edge(new_root.as_mut().cast_unchecked(), i).correct_parent_link();
1123 (self.node, k, v, new_root)
1127 /// Returns `true` if it is valid to call `.merge()`, i.e., whether there is enough room in
1128 /// a node to hold the combination of the nodes to the left and right of this handle along
1129 /// with the key/value pair at this handle.
1130 pub fn can_merge(&self) -> bool {
1131 (self.reborrow().left_edge().descend().len()
1132 + self.reborrow().right_edge().descend().len()
1137 /// Combines the node immediately to the left of this handle, the key/value pair pointed
1138 /// to by this handle, and the node immediately to the right of this handle into one new
1139 /// child of the underlying node, returning an edge referencing that new child.
1141 /// Assumes that this edge `.can_merge()`.
1144 ) -> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::Edge> {
1145 let self1 = unsafe { ptr::read(&self) };
1146 let self2 = unsafe { ptr::read(&self) };
1147 let mut left_node = self1.left_edge().descend();
1148 let left_len = left_node.len();
1149 let mut right_node = self2.right_edge().descend();
1150 let right_len = right_node.len();
1152 // necessary for correctness, but in a private module
1153 assert!(left_len + right_len < CAPACITY);
1157 left_node.keys_mut().get_unchecked_mut(left_len),
1158 slice_remove(self.node.keys_mut(), self.idx),
1160 ptr::copy_nonoverlapping(
1161 right_node.keys().as_ptr(),
1162 left_node.keys_mut().as_mut_ptr().add(left_len + 1),
1166 left_node.vals_mut().get_unchecked_mut(left_len),
1167 slice_remove(self.node.vals_mut(), self.idx),
1169 ptr::copy_nonoverlapping(
1170 right_node.vals().as_ptr(),
1171 left_node.vals_mut().as_mut_ptr().add(left_len + 1),
1175 slice_remove(&mut self.node.as_internal_mut().edges, self.idx + 1);
1176 for i in self.idx + 1..self.node.len() {
1177 Handle::new_edge(self.node.reborrow_mut(), i).correct_parent_link();
1179 (*self.node.as_leaf_mut()).len -= 1;
1181 (*left_node.as_leaf_mut()).len += right_len as u16 + 1;
1183 let layout = if self.node.height > 1 {
1184 ptr::copy_nonoverlapping(
1185 right_node.cast_unchecked().as_internal().edges.as_ptr(),
1195 for i in left_len + 1..left_len + right_len + 2 {
1196 Handle::new_edge(left_node.cast_unchecked().reborrow_mut(), i)
1197 .correct_parent_link();
1200 Layout::new::<InternalNode<K, V>>()
1202 Layout::new::<LeafNode<K, V>>()
1204 Global.dealloc(right_node.node.cast(), layout);
1206 Handle::new_edge(self.node, self.idx)
1210 /// This removes a key/value pair from the left child and places it in the key/value storage
1211 /// pointed to by this handle while pushing the old key/value pair of this handle into the right
1213 pub fn steal_left(&mut self) {
1215 let (k, v, edge) = self.reborrow_mut().left_edge().descend().pop();
1217 let k = mem::replace(self.reborrow_mut().into_kv_mut().0, k);
1218 let v = mem::replace(self.reborrow_mut().into_kv_mut().1, v);
1220 match self.reborrow_mut().right_edge().descend().force() {
1221 ForceResult::Leaf(mut leaf) => leaf.push_front(k, v),
1222 ForceResult::Internal(mut internal) => internal.push_front(k, v, edge.unwrap()),
1227 /// This removes a key/value pair from the right child and places it in the key/value storage
1228 /// pointed to by this handle while pushing the old key/value pair of this handle into the left
1230 pub fn steal_right(&mut self) {
1232 let (k, v, edge) = self.reborrow_mut().right_edge().descend().pop_front();
1234 let k = mem::replace(self.reborrow_mut().into_kv_mut().0, k);
1235 let v = mem::replace(self.reborrow_mut().into_kv_mut().1, v);
1237 match self.reborrow_mut().left_edge().descend().force() {
1238 ForceResult::Leaf(mut leaf) => leaf.push(k, v),
1239 ForceResult::Internal(mut internal) => internal.push(k, v, edge.unwrap()),
1244 /// This does stealing similar to `steal_left` but steals multiple elements at once.
1245 pub fn bulk_steal_left(&mut self, count: usize) {
1247 let mut left_node = ptr::read(self).left_edge().descend();
1248 let left_len = left_node.len();
1249 let mut right_node = ptr::read(self).right_edge().descend();
1250 let right_len = right_node.len();
1252 // Make sure that we may steal safely.
1253 assert!(right_len + count <= CAPACITY);
1254 assert!(left_len >= count);
1256 let new_left_len = left_len - count;
1260 let left_kv = left_node.reborrow_mut().into_kv_pointers_mut();
1261 let right_kv = right_node.reborrow_mut().into_kv_pointers_mut();
1263 let kv = self.reborrow_mut().into_kv_mut();
1264 (kv.0 as *mut K, kv.1 as *mut V)
1267 // Make room for stolen elements in the right child.
1268 ptr::copy(right_kv.0, right_kv.0.add(count), right_len);
1269 ptr::copy(right_kv.1, right_kv.1.add(count), right_len);
1271 // Move elements from the left child to the right one.
1272 move_kv(left_kv, new_left_len + 1, right_kv, 0, count - 1);
1274 // Move parent's key/value pair to the right child.
1275 move_kv(parent_kv, 0, right_kv, count - 1, 1);
1277 // Move the left-most stolen pair to the parent.
1278 move_kv(left_kv, new_left_len, parent_kv, 0, 1);
1281 (*left_node.reborrow_mut().as_leaf_mut()).len -= count as u16;
1282 (*right_node.reborrow_mut().as_leaf_mut()).len += count as u16;
1284 match (left_node.force(), right_node.force()) {
1285 (ForceResult::Internal(left), ForceResult::Internal(mut right)) => {
1286 // Make room for stolen edges.
1287 let right_edges = right.reborrow_mut().as_internal_mut().edges.as_mut_ptr();
1288 ptr::copy(right_edges, right_edges.add(count), right_len + 1);
1289 right.correct_childrens_parent_links(count, count + right_len + 1);
1291 move_edges(left, new_left_len + 1, right, 0, count);
1293 (ForceResult::Leaf(_), ForceResult::Leaf(_)) => {}
1301 /// The symmetric clone of `bulk_steal_left`.
1302 pub fn bulk_steal_right(&mut self, count: usize) {
1304 let mut left_node = ptr::read(self).left_edge().descend();
1305 let left_len = left_node.len();
1306 let mut right_node = ptr::read(self).right_edge().descend();
1307 let right_len = right_node.len();
1309 // Make sure that we may steal safely.
1310 assert!(left_len + count <= CAPACITY);
1311 assert!(right_len >= count);
1313 let new_right_len = right_len - count;
1317 let left_kv = left_node.reborrow_mut().into_kv_pointers_mut();
1318 let right_kv = right_node.reborrow_mut().into_kv_pointers_mut();
1320 let kv = self.reborrow_mut().into_kv_mut();
1321 (kv.0 as *mut K, kv.1 as *mut V)
1324 // Move parent's key/value pair to the left child.
1325 move_kv(parent_kv, 0, left_kv, left_len, 1);
1327 // Move elements from the right child to the left one.
1328 move_kv(right_kv, 0, left_kv, left_len + 1, count - 1);
1330 // Move the right-most stolen pair to the parent.
1331 move_kv(right_kv, count - 1, parent_kv, 0, 1);
1333 // Fix right indexing
1334 ptr::copy(right_kv.0.add(count), right_kv.0, new_right_len);
1335 ptr::copy(right_kv.1.add(count), right_kv.1, new_right_len);
1338 (*left_node.reborrow_mut().as_leaf_mut()).len += count as u16;
1339 (*right_node.reborrow_mut().as_leaf_mut()).len -= count as u16;
1341 match (left_node.force(), right_node.force()) {
1342 (ForceResult::Internal(left), ForceResult::Internal(mut right)) => {
1343 move_edges(right.reborrow_mut(), 0, left, left_len + 1, count);
1345 // Fix right indexing.
1346 let right_edges = right.reborrow_mut().as_internal_mut().edges.as_mut_ptr();
1347 ptr::copy(right_edges.add(count), right_edges, new_right_len + 1);
1348 right.correct_childrens_parent_links(0, new_right_len + 1);
1350 (ForceResult::Leaf(_), ForceResult::Leaf(_)) => {}
1359 unsafe fn move_kv<K, V>(
1360 source: (*mut K, *mut V),
1361 source_offset: usize,
1362 dest: (*mut K, *mut V),
1367 ptr::copy_nonoverlapping(source.0.add(source_offset), dest.0.add(dest_offset), count);
1368 ptr::copy_nonoverlapping(source.1.add(source_offset), dest.1.add(dest_offset), count);
1372 // Source and destination must have the same height.
1373 unsafe fn move_edges<K, V>(
1374 mut source: NodeRef<marker::Mut<'_>, K, V, marker::Internal>,
1375 source_offset: usize,
1376 mut dest: NodeRef<marker::Mut<'_>, K, V, marker::Internal>,
1380 let source_ptr = source.as_internal_mut().edges.as_mut_ptr();
1381 let dest_ptr = dest.as_internal_mut().edges.as_mut_ptr();
1383 ptr::copy_nonoverlapping(source_ptr.add(source_offset), dest_ptr.add(dest_offset), count);
1384 dest.correct_childrens_parent_links(dest_offset, dest_offset + count);
1388 impl<BorrowType, K, V> NodeRef<BorrowType, K, V, marker::Leaf> {
1389 /// Removes any static information asserting that this node is a `Leaf` node.
1390 pub fn forget_type(self) -> NodeRef<BorrowType, K, V, marker::LeafOrInternal> {
1391 NodeRef { height: self.height, node: self.node, root: self.root, _marker: PhantomData }
1395 impl<BorrowType, K, V> NodeRef<BorrowType, K, V, marker::Internal> {
1396 /// Removes any static information asserting that this node is an `Internal` node.
1397 pub fn forget_type(self) -> NodeRef<BorrowType, K, V, marker::LeafOrInternal> {
1398 NodeRef { height: self.height, node: self.node, root: self.root, _marker: PhantomData }
1402 impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge> {
1403 pub fn forget_node_type(
1405 ) -> Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, marker::Edge> {
1406 unsafe { Handle::new_edge(self.node.forget_type(), self.idx) }
1410 impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V, marker::Internal>, marker::Edge> {
1411 pub fn forget_node_type(
1413 ) -> Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, marker::Edge> {
1414 unsafe { Handle::new_edge(self.node.forget_type(), self.idx) }
1418 impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::KV> {
1419 pub fn forget_node_type(
1421 ) -> Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, marker::KV> {
1422 unsafe { Handle::new_kv(self.node.forget_type(), self.idx) }
1426 impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V, marker::Internal>, marker::KV> {
1427 pub fn forget_node_type(
1429 ) -> Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, marker::KV> {
1430 unsafe { Handle::new_kv(self.node.forget_type(), self.idx) }
1434 impl<BorrowType, K, V, HandleType>
1435 Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, HandleType>
1437 /// Checks whether the underlying node is an `Internal` node or a `Leaf` node.
1441 Handle<NodeRef<BorrowType, K, V, marker::Leaf>, HandleType>,
1442 Handle<NodeRef<BorrowType, K, V, marker::Internal>, HandleType>,
1444 match self.node.force() {
1445 ForceResult::Leaf(node) => {
1446 ForceResult::Leaf(Handle { node, idx: self.idx, _marker: PhantomData })
1448 ForceResult::Internal(node) => {
1449 ForceResult::Internal(Handle { node, idx: self.idx, _marker: PhantomData })
1455 impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, marker::Edge> {
1456 /// Move the suffix after `self` from one node to another one. `right` must be empty.
1457 /// The first edge of `right` remains unchanged.
1460 right: &mut NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>,
1463 let left_new_len = self.idx;
1464 let mut left_node = self.reborrow_mut().into_node();
1466 let right_new_len = left_node.len() - left_new_len;
1467 let mut right_node = right.reborrow_mut();
1469 assert!(right_node.len() == 0);
1470 assert!(left_node.height == right_node.height);
1472 if right_new_len > 0 {
1473 let left_kv = left_node.reborrow_mut().into_kv_pointers_mut();
1474 let right_kv = right_node.reborrow_mut().into_kv_pointers_mut();
1476 move_kv(left_kv, left_new_len, right_kv, 0, right_new_len);
1478 (*left_node.reborrow_mut().as_leaf_mut()).len = left_new_len as u16;
1479 (*right_node.reborrow_mut().as_leaf_mut()).len = right_new_len as u16;
1481 match (left_node.force(), right_node.force()) {
1482 (ForceResult::Internal(left), ForceResult::Internal(right)) => {
1483 move_edges(left, left_new_len + 1, right, 1, right_new_len);
1485 (ForceResult::Leaf(_), ForceResult::Leaf(_)) => {}
1495 pub enum ForceResult<Leaf, Internal> {
1500 /// Result of insertion, when a node needed to expand beyond its capacity.
1501 /// Does not distinguish between `Leaf` and `Internal` because `Root` doesn't.
1502 pub struct SplitResult<'a, K, V> {
1503 // Altered node in existing tree with elements and edges that belong to the left of `k`.
1504 pub left: NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>,
1505 // Some key and value split off, to be inserted elsewhere.
1508 // Owned, unattached, new node with elements and edges that belong to the right of `k`.
1509 pub right: Root<K, V>,
1512 pub enum InsertResult<'a, K, V, Type> {
1513 Fit(Handle<NodeRef<marker::Mut<'a>, K, V, Type>, marker::KV>),
1514 Split(SplitResult<'a, K, V>),
1518 use core::marker::PhantomData;
1521 pub enum Internal {}
1522 pub enum LeafOrInternal {}
1525 pub struct Immut<'a>(PhantomData<&'a ()>);
1526 pub struct Mut<'a>(PhantomData<&'a mut ()>);
1532 unsafe fn slice_insert<T>(slice: &mut [T], idx: usize, val: T) {
1534 ptr::copy(slice.as_ptr().add(idx), slice.as_mut_ptr().add(idx + 1), slice.len() - idx);
1535 ptr::write(slice.get_unchecked_mut(idx), val);
1539 unsafe fn slice_remove<T>(slice: &mut [T], idx: usize) -> T {
1541 let ret = ptr::read(slice.get_unchecked(idx));
1542 ptr::copy(slice.as_ptr().add(idx + 1), slice.as_mut_ptr().add(idx), slice.len() - idx - 1);