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 `pop_level`.
195 pub fn push_level(&mut self) -> NodeRef<marker::Mut<'_>, K, V, marker::Internal> {
196 let mut new_node = Box::new(unsafe { InternalNode::new() });
197 new_node.edges[0].write(unsafe { BoxedNode::from_ptr(self.node.as_ptr()) });
199 self.node = BoxedNode::from_internal(new_node);
202 let mut ret = NodeRef {
204 node: self.node.as_ptr(),
205 root: self as *mut _,
206 _marker: PhantomData,
210 ret.reborrow_mut().first_edge().correct_parent_link();
216 /// Removes the root node, using its first child as the new root. This cannot be called when
217 /// the tree consists only of a leaf node. As it is intended only to be called when the root
218 /// has only one edge, no cleanup is done on any of the other children of the root.
219 /// This decreases the height by 1 and is the opposite of `push_level`.
220 pub fn pop_level(&mut self) {
221 assert!(self.height > 0);
223 let top = self.node.ptr;
227 self.as_mut().cast_unchecked::<marker::Internal>().first_edge().descend().node,
232 (*self.as_mut().as_leaf_mut()).parent = ptr::null();
236 Global.dealloc(NonNull::from(top).cast(), Layout::new::<InternalNode<K, V>>());
241 // N.B. `NodeRef` is always covariant in `K` and `V`, even when the `BorrowType`
242 // is `Mut`. This is technically wrong, but cannot result in any unsafety due to
243 // internal use of `NodeRef` because we stay completely generic over `K` and `V`.
244 // However, whenever a public type wraps `NodeRef`, make sure that it has the
246 /// A reference to a node.
248 /// This type has a number of parameters that controls how it acts:
249 /// - `BorrowType`: This can be `Immut<'a>` or `Mut<'a>` for some `'a` or `Owned`.
250 /// When this is `Immut<'a>`, the `NodeRef` acts roughly like `&'a Node`,
251 /// when this is `Mut<'a>`, the `NodeRef` acts roughly like `&'a mut Node`,
252 /// and when this is `Owned`, the `NodeRef` acts roughly like `Box<Node>`.
253 /// - `K` and `V`: These control what types of things are stored in the nodes.
254 /// - `Type`: This can be `Leaf`, `Internal`, or `LeafOrInternal`. When this is
255 /// `Leaf`, the `NodeRef` points to a leaf node, when this is `Internal` the
256 /// `NodeRef` points to an internal node, and when this is `LeafOrInternal` the
257 /// `NodeRef` could be pointing to either type of node.
258 pub struct NodeRef<BorrowType, K, V, Type> {
259 /// The number of levels below the node.
261 node: NonNull<LeafNode<K, V>>,
262 // `root` is null unless the borrow type is `Mut`
263 root: *const Root<K, V>,
264 _marker: PhantomData<(BorrowType, Type)>,
267 impl<'a, K: 'a, V: 'a, Type> Copy for NodeRef<marker::Immut<'a>, K, V, Type> {}
268 impl<'a, K: 'a, V: 'a, Type> Clone for NodeRef<marker::Immut<'a>, K, V, Type> {
269 fn clone(&self) -> Self {
274 unsafe impl<BorrowType, K: Sync, V: Sync, Type> Sync for NodeRef<BorrowType, K, V, Type> {}
276 unsafe impl<'a, K: Sync + 'a, V: Sync + 'a, Type> Send for NodeRef<marker::Immut<'a>, K, V, Type> {}
277 unsafe impl<'a, K: Send + 'a, V: Send + 'a, Type> Send for NodeRef<marker::Mut<'a>, K, V, Type> {}
278 unsafe impl<K: Send, V: Send, Type> Send for NodeRef<marker::Owned, K, V, Type> {}
280 impl<BorrowType, K, V> NodeRef<BorrowType, K, V, marker::Internal> {
281 fn as_internal(&self) -> &InternalNode<K, V> {
282 unsafe { &*(self.node.as_ptr() as *mut InternalNode<K, V>) }
286 impl<'a, K, V> NodeRef<marker::Mut<'a>, K, V, marker::Internal> {
287 fn as_internal_mut(&mut self) -> &mut InternalNode<K, V> {
288 unsafe { &mut *(self.node.as_ptr() as *mut InternalNode<K, V>) }
292 impl<BorrowType, K, V, Type> NodeRef<BorrowType, K, V, Type> {
293 /// Finds the length of the node. This is the number of keys or values. In an
294 /// internal node, the number of edges is `len() + 1`.
295 /// For any node, the number of possible edge handles is also `len() + 1`.
296 /// Note that, despite being safe, calling this function can have the side effect
297 /// of invalidating mutable references that unsafe code has created.
298 pub fn len(&self) -> usize {
299 self.as_leaf().len as usize
302 /// Returns the height of this node in the whole tree. Zero height denotes the
304 pub fn height(&self) -> usize {
308 /// Removes any static information about whether this node is a `Leaf` or an
310 pub fn forget_type(self) -> NodeRef<BorrowType, K, V, marker::LeafOrInternal> {
311 NodeRef { height: self.height, node: self.node, root: self.root, _marker: PhantomData }
314 /// Temporarily takes out another, immutable reference to the same node.
315 fn reborrow(&self) -> NodeRef<marker::Immut<'_>, K, V, Type> {
316 NodeRef { height: self.height, node: self.node, root: self.root, _marker: PhantomData }
319 /// Exposes the leaf "portion" of any leaf or internal node.
320 /// If the node is a leaf, this function simply opens up its data.
321 /// If the node is an internal node, so not a leaf, it does have all the data a leaf has
322 /// (header, keys and values), and this function exposes that.
323 fn as_leaf(&self) -> &LeafNode<K, V> {
324 // The node must be valid for at least the LeafNode portion.
325 // This is not a reference in the NodeRef type because we don't know if
326 // it should be unique or shared.
327 unsafe { self.node.as_ref() }
330 /// Borrows a view into the keys stored in the node.
331 pub fn keys(&self) -> &[K] {
332 self.reborrow().into_key_slice()
335 /// Borrows a view into the values stored in the node.
336 fn vals(&self) -> &[V] {
337 self.reborrow().into_val_slice()
340 /// Finds the parent of the current node. Returns `Ok(handle)` if the current
341 /// node actually has a parent, where `handle` points to the edge of the parent
342 /// that points to the current node. Returns `Err(self)` if the current node has
343 /// no parent, giving back the original `NodeRef`.
345 /// `edge.descend().ascend().unwrap()` and `node.ascend().unwrap().descend()` should
346 /// both, upon success, do nothing.
349 ) -> Result<Handle<NodeRef<BorrowType, K, V, marker::Internal>, marker::Edge>, Self> {
350 let parent_as_leaf = self.as_leaf().parent as *const LeafNode<K, V>;
351 if let Some(non_zero) = NonNull::new(parent_as_leaf as *mut _) {
354 height: self.height + 1,
357 _marker: PhantomData,
359 idx: unsafe { usize::from(*self.as_leaf().parent_idx.as_ptr()) },
360 _marker: PhantomData,
367 pub fn first_edge(self) -> Handle<Self, marker::Edge> {
368 unsafe { Handle::new_edge(self, 0) }
371 pub fn last_edge(self) -> Handle<Self, marker::Edge> {
372 let len = self.len();
373 unsafe { Handle::new_edge(self, len) }
376 /// Note that `self` must be nonempty.
377 pub fn first_kv(self) -> Handle<Self, marker::KV> {
378 let len = self.len();
380 unsafe { Handle::new_kv(self, 0) }
383 /// Note that `self` must be nonempty.
384 pub fn last_kv(self) -> Handle<Self, marker::KV> {
385 let len = self.len();
387 unsafe { Handle::new_kv(self, len - 1) }
391 impl<K, V> NodeRef<marker::Owned, K, V, marker::LeafOrInternal> {
392 /// Similar to `ascend`, gets a reference to a node's parent node, but also
393 /// deallocate the current node in the process. This is unsafe because the
394 /// current node will still be accessible despite being deallocated.
395 pub unsafe fn deallocate_and_ascend(
397 ) -> Option<Handle<NodeRef<marker::Owned, K, V, marker::Internal>, marker::Edge>> {
398 let height = self.height;
399 let node = self.node;
400 let ret = self.ascend().ok();
405 Layout::new::<InternalNode<K, V>>()
407 Layout::new::<LeafNode<K, V>>()
415 impl<'a, K, V, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
416 /// Unsafely asserts to the compiler some static information about whether this
417 /// node is a `Leaf` or an `Internal`.
418 unsafe fn cast_unchecked<NewType>(&mut self) -> NodeRef<marker::Mut<'_>, K, V, NewType> {
419 NodeRef { height: self.height, node: self.node, root: self.root, _marker: PhantomData }
422 /// Temporarily takes out another, mutable reference to the same node. Beware, as
423 /// this method is very dangerous, doubly so since it may not immediately appear
426 /// Because mutable pointers can roam anywhere around the tree and can even (through
427 /// `into_root_mut`) mess with the root of the tree, the result of `reborrow_mut`
428 /// can easily be used to make the original mutable pointer dangling, or, in the case
429 /// of a reborrowed handle, out of bounds.
430 // FIXME(@gereeter) consider adding yet another type parameter to `NodeRef` that restricts
431 // the use of `ascend` and `into_root_mut` on reborrowed pointers, preventing this unsafety.
432 unsafe fn reborrow_mut(&mut self) -> NodeRef<marker::Mut<'_>, K, V, Type> {
433 NodeRef { height: self.height, node: self.node, root: self.root, _marker: PhantomData }
436 /// Exposes the leaf "portion" of any leaf or internal node for writing.
437 /// If the node is a leaf, this function simply opens up its data.
438 /// If the node is an internal node, so not a leaf, it does have all the data a leaf has
439 /// (header, keys and values), and this function exposes that.
441 /// Returns a raw ptr to avoid asserting exclusive access to the entire node.
442 fn as_leaf_mut(&mut self) -> *mut LeafNode<K, V> {
446 fn keys_mut(&mut self) -> &mut [K] {
447 // SAFETY: the caller will not be able to call further methods on self
448 // until the key slice reference is dropped, as we have unique access
449 // for the lifetime of the borrow.
450 unsafe { self.reborrow_mut().into_key_slice_mut() }
453 fn vals_mut(&mut self) -> &mut [V] {
454 // SAFETY: the caller will not be able to call further methods on self
455 // until the value slice reference is dropped, as we have unique access
456 // for the lifetime of the borrow.
457 unsafe { self.reborrow_mut().into_val_slice_mut() }
461 impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Immut<'a>, K, V, Type> {
462 fn into_key_slice(self) -> &'a [K] {
463 unsafe { slice::from_raw_parts(MaybeUninit::first_ptr(&self.as_leaf().keys), self.len()) }
466 fn into_val_slice(self) -> &'a [V] {
467 unsafe { slice::from_raw_parts(MaybeUninit::first_ptr(&self.as_leaf().vals), self.len()) }
470 fn into_slices(self) -> (&'a [K], &'a [V]) {
471 // SAFETY: equivalent to reborrow() except not requiring Type: 'a
472 let k = unsafe { ptr::read(&self) };
473 (k.into_key_slice(), self.into_val_slice())
477 impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
478 /// Gets a mutable reference to the root itself. This is useful primarily when the
479 /// height of the tree needs to be adjusted. Never call this on a reborrowed pointer.
480 pub fn into_root_mut(self) -> &'a mut Root<K, V> {
481 unsafe { &mut *(self.root as *mut Root<K, V>) }
484 fn into_key_slice_mut(mut self) -> &'a mut [K] {
485 // SAFETY: The keys 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()).keys),
494 fn into_val_slice_mut(mut self) -> &'a mut [V] {
495 // SAFETY: The values of a node must always be initialized up to length.
497 slice::from_raw_parts_mut(
498 MaybeUninit::first_ptr_mut(&mut (*self.as_leaf_mut()).vals),
504 fn into_slices_mut(mut self) -> (&'a mut [K], &'a mut [V]) {
505 // We cannot use the getters here, because calling the second one
506 // invalidates the reference returned by the first.
507 // More precisely, it is the call to `len` that is the culprit,
508 // because that creates a shared reference to the header, which *can*
509 // overlap with the keys (and even the values, for ZST keys).
510 let len = self.len();
511 let leaf = self.as_leaf_mut();
512 // SAFETY: The keys and values of a node must always be initialized up to length.
514 slice::from_raw_parts_mut(MaybeUninit::first_ptr_mut(&mut (*leaf).keys), len)
517 slice::from_raw_parts_mut(MaybeUninit::first_ptr_mut(&mut (*leaf).vals), len)
523 impl<'a, K, V> NodeRef<marker::Mut<'a>, K, V, marker::Leaf> {
524 /// Adds a key/value pair to the end of the node.
525 pub fn push(&mut self, key: K, val: V) {
526 assert!(self.len() < CAPACITY);
528 let idx = self.len();
531 ptr::write(self.keys_mut().get_unchecked_mut(idx), key);
532 ptr::write(self.vals_mut().get_unchecked_mut(idx), val);
534 (*self.as_leaf_mut()).len += 1;
538 /// Adds a key/value pair to the beginning of the node.
539 pub fn push_front(&mut self, key: K, val: V) {
540 assert!(self.len() < CAPACITY);
543 slice_insert(self.keys_mut(), 0, key);
544 slice_insert(self.vals_mut(), 0, val);
546 (*self.as_leaf_mut()).len += 1;
551 impl<'a, K, V> NodeRef<marker::Mut<'a>, K, V, marker::Internal> {
552 /// Adds a key/value pair and an edge to go to the right of that pair to
553 /// the end of the node.
554 pub fn push(&mut self, key: K, val: V, edge: Root<K, V>) {
555 assert!(edge.height == self.height - 1);
556 assert!(self.len() < CAPACITY);
558 let idx = self.len();
561 ptr::write(self.keys_mut().get_unchecked_mut(idx), key);
562 ptr::write(self.vals_mut().get_unchecked_mut(idx), val);
563 self.as_internal_mut().edges.get_unchecked_mut(idx + 1).write(edge.node);
565 (*self.as_leaf_mut()).len += 1;
567 Handle::new_edge(self.reborrow_mut(), idx + 1).correct_parent_link();
571 // Unsafe because 'first' and 'after_last' must be in range
572 unsafe fn correct_childrens_parent_links(&mut self, first: usize, after_last: usize) {
573 debug_assert!(first <= self.len());
574 debug_assert!(after_last <= self.len() + 1);
575 for i in first..after_last {
576 unsafe { Handle::new_edge(self.reborrow_mut(), i) }.correct_parent_link();
580 fn correct_all_childrens_parent_links(&mut self) {
581 let len = self.len();
582 unsafe { self.correct_childrens_parent_links(0, len + 1) };
585 /// Adds a key/value pair and an edge to go to the left of that pair to
586 /// the beginning of the node.
587 pub fn push_front(&mut self, key: K, val: V, edge: Root<K, V>) {
588 assert!(edge.height == self.height - 1);
589 assert!(self.len() < CAPACITY);
592 slice_insert(self.keys_mut(), 0, key);
593 slice_insert(self.vals_mut(), 0, val);
595 slice::from_raw_parts_mut(
596 MaybeUninit::first_ptr_mut(&mut self.as_internal_mut().edges),
603 (*self.as_leaf_mut()).len += 1;
605 self.correct_all_childrens_parent_links();
610 impl<'a, K, V> NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal> {
611 /// Removes a key/value pair from the end of this node and returns the pair.
612 /// If this is an internal node, also removes the edge that was to the right
613 /// of that pair and returns the orphaned node that this edge owned with its
615 pub fn pop(&mut self) -> (K, V, Option<Root<K, V>>) {
616 assert!(self.len() > 0);
618 let idx = self.len() - 1;
621 let key = ptr::read(self.keys().get_unchecked(idx));
622 let val = ptr::read(self.vals().get_unchecked(idx));
623 let edge = match self.reborrow_mut().force() {
624 ForceResult::Leaf(_) => None,
625 ForceResult::Internal(internal) => {
627 ptr::read(internal.as_internal().edges.get_unchecked(idx + 1).as_ptr());
628 let mut new_root = Root { node: edge, height: internal.height - 1 };
629 (*new_root.as_mut().as_leaf_mut()).parent = ptr::null();
634 (*self.as_leaf_mut()).len -= 1;
639 /// Removes a key/value pair from the beginning of this node. If this is an internal node,
640 /// also removes the edge that was to the left of that pair.
641 pub fn pop_front(&mut self) -> (K, V, Option<Root<K, V>>) {
642 assert!(self.len() > 0);
644 let old_len = self.len();
647 let key = slice_remove(self.keys_mut(), 0);
648 let val = slice_remove(self.vals_mut(), 0);
649 let edge = match self.reborrow_mut().force() {
650 ForceResult::Leaf(_) => None,
651 ForceResult::Internal(mut internal) => {
652 let edge = slice_remove(
653 slice::from_raw_parts_mut(
654 MaybeUninit::first_ptr_mut(&mut internal.as_internal_mut().edges),
660 let mut new_root = Root { node: edge, height: internal.height - 1 };
661 (*new_root.as_mut().as_leaf_mut()).parent = ptr::null();
663 for i in 0..old_len {
664 Handle::new_edge(internal.reborrow_mut(), i).correct_parent_link();
671 (*self.as_leaf_mut()).len -= 1;
677 fn into_kv_pointers_mut(mut self) -> (*mut K, *mut V) {
678 (self.keys_mut().as_mut_ptr(), self.vals_mut().as_mut_ptr())
682 impl<BorrowType, K, V> NodeRef<BorrowType, K, V, marker::LeafOrInternal> {
683 /// Checks whether a node is an `Internal` node or a `Leaf` node.
687 NodeRef<BorrowType, K, V, marker::Leaf>,
688 NodeRef<BorrowType, K, V, marker::Internal>,
690 if self.height == 0 {
691 ForceResult::Leaf(NodeRef {
695 _marker: PhantomData,
698 ForceResult::Internal(NodeRef {
702 _marker: PhantomData,
708 /// A reference to a specific key/value pair or edge within a node. The `Node` parameter
709 /// must be a `NodeRef`, while the `Type` can either be `KV` (signifying a handle on a key/value
710 /// pair) or `Edge` (signifying a handle on an edge).
712 /// Note that even `Leaf` nodes can have `Edge` handles. Instead of representing a pointer to
713 /// a child node, these represent the spaces where child pointers would go between the key/value
714 /// pairs. For example, in a node with length 2, there would be 3 possible edge locations - one
715 /// to the left of the node, one between the two pairs, and one at the right of the node.
716 pub struct Handle<Node, Type> {
719 _marker: PhantomData<Type>,
722 impl<Node: Copy, Type> Copy for Handle<Node, Type> {}
723 // We don't need the full generality of `#[derive(Clone)]`, as the only time `Node` will be
724 // `Clone`able is when it is an immutable reference and therefore `Copy`.
725 impl<Node: Copy, Type> Clone for Handle<Node, Type> {
726 fn clone(&self) -> Self {
731 impl<Node, Type> Handle<Node, Type> {
732 /// Retrieves the node that contains the edge of key/value pair this handle points to.
733 pub fn into_node(self) -> Node {
737 /// Returns the position of this handle in the node.
738 pub fn idx(&self) -> usize {
743 impl<BorrowType, K, V, NodeType> Handle<NodeRef<BorrowType, K, V, NodeType>, marker::KV> {
744 /// Creates a new handle to a key/value pair in `node`.
745 /// Unsafe because the caller must ensure that `idx < node.len()`.
746 pub unsafe fn new_kv(node: NodeRef<BorrowType, K, V, NodeType>, idx: usize) -> Self {
747 debug_assert!(idx < node.len());
749 Handle { node, idx, _marker: PhantomData }
752 pub fn left_edge(self) -> Handle<NodeRef<BorrowType, K, V, NodeType>, marker::Edge> {
753 unsafe { Handle::new_edge(self.node, self.idx) }
756 pub fn right_edge(self) -> Handle<NodeRef<BorrowType, K, V, NodeType>, marker::Edge> {
757 unsafe { Handle::new_edge(self.node, self.idx + 1) }
761 impl<BorrowType, K, V, NodeType, HandleType> PartialEq
762 for Handle<NodeRef<BorrowType, K, V, NodeType>, HandleType>
764 fn eq(&self, other: &Self) -> bool {
765 self.node.node == other.node.node && self.idx == other.idx
769 impl<BorrowType, K, V, NodeType, HandleType> PartialOrd
770 for Handle<NodeRef<BorrowType, K, V, NodeType>, HandleType>
772 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
773 if self.node.node == other.node.node { Some(self.idx.cmp(&other.idx)) } else { None }
777 impl<BorrowType, K, V, NodeType, HandleType>
778 Handle<NodeRef<BorrowType, K, V, NodeType>, HandleType>
780 /// Temporarily takes out another, immutable handle on the same location.
781 pub fn reborrow(&self) -> Handle<NodeRef<marker::Immut<'_>, K, V, NodeType>, HandleType> {
782 // We can't use Handle::new_kv or Handle::new_edge because we don't know our type
783 Handle { node: self.node.reborrow(), idx: self.idx, _marker: PhantomData }
787 impl<'a, K, V, NodeType, HandleType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>, HandleType> {
788 /// Temporarily takes out another, mutable handle on the same location. Beware, as
789 /// this method is very dangerous, doubly so since it may not immediately appear
792 /// Because mutable pointers can roam anywhere around the tree and can even (through
793 /// `into_root_mut`) mess with the root of the tree, the result of `reborrow_mut`
794 /// can easily be used to make the original mutable pointer dangling, or, in the case
795 /// of a reborrowed handle, out of bounds.
796 // FIXME(@gereeter) consider adding yet another type parameter to `NodeRef` that restricts
797 // the use of `ascend` and `into_root_mut` on reborrowed pointers, preventing this unsafety.
798 pub unsafe fn reborrow_mut(
800 ) -> Handle<NodeRef<marker::Mut<'_>, K, V, NodeType>, HandleType> {
801 // We can't use Handle::new_kv or Handle::new_edge because we don't know our type
802 Handle { node: unsafe { self.node.reborrow_mut() }, idx: self.idx, _marker: PhantomData }
806 impl<BorrowType, K, V, NodeType> Handle<NodeRef<BorrowType, K, V, NodeType>, marker::Edge> {
807 /// Creates a new handle to an edge in `node`.
808 /// Unsafe because the caller must ensure that `idx <= node.len()`.
809 pub unsafe fn new_edge(node: NodeRef<BorrowType, K, V, NodeType>, idx: usize) -> Self {
810 debug_assert!(idx <= node.len());
812 Handle { node, idx, _marker: PhantomData }
815 pub fn left_kv(self) -> Result<Handle<NodeRef<BorrowType, K, V, NodeType>, marker::KV>, Self> {
817 Ok(unsafe { Handle::new_kv(self.node, self.idx - 1) })
823 pub fn right_kv(self) -> Result<Handle<NodeRef<BorrowType, K, V, NodeType>, marker::KV>, Self> {
824 if self.idx < self.node.len() {
825 Ok(unsafe { Handle::new_kv(self.node, self.idx) })
832 impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge> {
833 /// Inserts a new key/value pair between the key/value pairs to the right and left of
834 /// this edge. This method assumes that there is enough space in the node for the new
837 /// The returned pointer points to the inserted value.
838 fn insert_fit(&mut self, key: K, val: V) -> *mut V {
839 // Necessary for correctness, but in a private module
840 debug_assert!(self.node.len() < CAPACITY);
843 slice_insert(self.node.keys_mut(), self.idx, key);
844 slice_insert(self.node.vals_mut(), self.idx, val);
846 (*self.node.as_leaf_mut()).len += 1;
848 self.node.vals_mut().get_unchecked_mut(self.idx)
852 /// Inserts a new key/value pair between the key/value pairs to the right and left of
853 /// this edge. This method splits the node if there isn't enough room.
855 /// The returned pointer points to the inserted value.
856 pub fn insert(mut self, key: K, val: V) -> (InsertResult<'a, K, V, marker::Leaf>, *mut V) {
857 if self.node.len() < CAPACITY {
858 let ptr = self.insert_fit(key, val);
859 let kv = unsafe { Handle::new_kv(self.node, self.idx) };
860 (InsertResult::Fit(kv), ptr)
862 let middle = unsafe { Handle::new_kv(self.node, B) };
863 let (mut left, k, v, mut right) = middle.split();
864 let ptr = if self.idx <= B {
865 unsafe { Handle::new_edge(left.reborrow_mut(), self.idx).insert_fit(key, val) }
869 right.as_mut().cast_unchecked::<marker::Leaf>(),
872 .insert_fit(key, val)
875 (InsertResult::Split(left, k, v, right), ptr)
880 impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::Edge> {
881 /// Fixes the parent pointer and index in the child node below this edge. This is useful
882 /// when the ordering of edges has been changed, such as in the various `insert` methods.
883 fn correct_parent_link(mut self) {
884 let idx = self.idx as u16;
885 let ptr = self.node.as_internal_mut() as *mut _;
886 let mut child = self.descend();
888 (*child.as_leaf_mut()).parent = ptr;
889 (*child.as_leaf_mut()).parent_idx.write(idx);
893 /// Unsafely asserts to the compiler some static information about whether the underlying
894 /// node of this handle is a `Leaf` or an `Internal`.
895 unsafe fn cast_unchecked<NewType>(
897 ) -> Handle<NodeRef<marker::Mut<'_>, K, V, NewType>, marker::Edge> {
898 unsafe { Handle::new_edge(self.node.cast_unchecked(), self.idx) }
901 /// Inserts a new key/value pair and an edge that will go to the right of that new pair
902 /// between this edge and the key/value pair to the right of this edge. This method assumes
903 /// that there is enough space in the node for the new pair to fit.
904 fn insert_fit(&mut self, key: K, val: V, edge: Root<K, V>) {
905 // Necessary for correctness, but in an internal module
906 debug_assert!(self.node.len() < CAPACITY);
907 debug_assert!(edge.height == self.node.height - 1);
910 // This cast is a lie, but it allows us to reuse the key/value insertion logic.
911 self.cast_unchecked::<marker::Leaf>().insert_fit(key, val);
914 slice::from_raw_parts_mut(
915 MaybeUninit::first_ptr_mut(&mut self.node.as_internal_mut().edges),
922 for i in (self.idx + 1)..(self.node.len() + 1) {
923 Handle::new_edge(self.node.reborrow_mut(), i).correct_parent_link();
928 /// Inserts a new key/value pair and an edge that will go to the right of that new pair
929 /// between this edge and the key/value pair to the right of this edge. This method splits
930 /// the node if there isn't enough room.
936 ) -> InsertResult<'a, K, V, marker::Internal> {
937 assert!(edge.height == self.node.height - 1);
939 if self.node.len() < CAPACITY {
940 self.insert_fit(key, val, edge);
941 let kv = unsafe { Handle::new_kv(self.node, self.idx) };
942 InsertResult::Fit(kv)
944 let middle = unsafe { Handle::new_kv(self.node, B) };
945 let (mut left, k, v, mut right) = middle.split();
948 Handle::new_edge(left.reborrow_mut(), self.idx).insert_fit(key, val, edge);
953 right.as_mut().cast_unchecked::<marker::Internal>(),
956 .insert_fit(key, val, edge);
959 InsertResult::Split(left, k, v, right)
964 impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V, marker::Internal>, marker::Edge> {
965 /// Finds the node pointed to by this edge.
967 /// `edge.descend().ascend().unwrap()` and `node.ascend().unwrap().descend()` should
968 /// both, upon success, do nothing.
969 pub fn descend(self) -> NodeRef<BorrowType, K, V, marker::LeafOrInternal> {
971 height: self.node.height - 1,
973 (&*self.node.as_internal().edges.get_unchecked(self.idx).as_ptr()).as_ptr()
975 root: self.node.root,
976 _marker: PhantomData,
981 impl<'a, K: 'a, V: 'a, NodeType> Handle<NodeRef<marker::Immut<'a>, K, V, NodeType>, marker::KV> {
982 pub fn into_kv(self) -> (&'a K, &'a V) {
984 let (keys, vals) = self.node.into_slices();
985 (keys.get_unchecked(self.idx), vals.get_unchecked(self.idx))
990 impl<'a, K: 'a, V: 'a, NodeType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>, marker::KV> {
991 pub fn into_kv_mut(self) -> (&'a mut K, &'a mut V) {
993 let (keys, vals) = self.node.into_slices_mut();
994 (keys.get_unchecked_mut(self.idx), vals.get_unchecked_mut(self.idx))
999 impl<'a, K, V, NodeType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>, marker::KV> {
1000 pub fn kv_mut(&mut self) -> (&mut K, &mut V) {
1002 let (keys, vals) = self.node.reborrow_mut().into_slices_mut();
1003 (keys.get_unchecked_mut(self.idx), vals.get_unchecked_mut(self.idx))
1008 impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::KV> {
1009 /// Splits the underlying node into three parts:
1011 /// - The node is truncated to only contain the key/value pairs to the right of
1013 /// - The key and value pointed to by this handle and extracted.
1014 /// - All the key/value pairs to the right of this handle are put into a newly
1016 pub fn split(mut self) -> (NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, K, V, Root<K, V>) {
1018 let mut new_node = Box::new(LeafNode::new());
1020 let k = ptr::read(self.node.keys().get_unchecked(self.idx));
1021 let v = ptr::read(self.node.vals().get_unchecked(self.idx));
1023 let new_len = self.node.len() - self.idx - 1;
1025 ptr::copy_nonoverlapping(
1026 self.node.keys().as_ptr().add(self.idx + 1),
1027 new_node.keys.as_mut_ptr() as *mut K,
1030 ptr::copy_nonoverlapping(
1031 self.node.vals().as_ptr().add(self.idx + 1),
1032 new_node.vals.as_mut_ptr() as *mut V,
1036 (*self.node.as_leaf_mut()).len = self.idx as u16;
1037 new_node.len = new_len as u16;
1039 (self.node, k, v, Root { node: BoxedNode::from_leaf(new_node), height: 0 })
1043 /// Removes the key/value pair pointed to by this handle and returns it, along with the edge
1044 /// between the now adjacent key/value pairs (if any) to the left and right of this handle.
1047 ) -> (Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>, K, V) {
1049 let k = slice_remove(self.node.keys_mut(), self.idx);
1050 let v = slice_remove(self.node.vals_mut(), self.idx);
1051 (*self.node.as_leaf_mut()).len -= 1;
1052 (self.left_edge(), k, v)
1057 impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::KV> {
1058 /// Splits the underlying node into three parts:
1060 /// - The node is truncated to only contain the edges and key/value pairs to the
1061 /// right of this handle.
1062 /// - The key and value pointed to by this handle and extracted.
1063 /// - All the edges and key/value pairs to the right of this handle are put into
1064 /// a newly allocated node.
1065 pub fn split(mut self) -> (NodeRef<marker::Mut<'a>, K, V, marker::Internal>, K, V, Root<K, V>) {
1067 let mut new_node = Box::new(InternalNode::new());
1069 let k = ptr::read(self.node.keys().get_unchecked(self.idx));
1070 let v = ptr::read(self.node.vals().get_unchecked(self.idx));
1072 let height = self.node.height;
1073 let new_len = self.node.len() - self.idx - 1;
1075 ptr::copy_nonoverlapping(
1076 self.node.keys().as_ptr().add(self.idx + 1),
1077 new_node.data.keys.as_mut_ptr() as *mut K,
1080 ptr::copy_nonoverlapping(
1081 self.node.vals().as_ptr().add(self.idx + 1),
1082 new_node.data.vals.as_mut_ptr() as *mut V,
1085 ptr::copy_nonoverlapping(
1086 self.node.as_internal().edges.as_ptr().add(self.idx + 1),
1087 new_node.edges.as_mut_ptr(),
1091 (*self.node.as_leaf_mut()).len = self.idx as u16;
1092 new_node.data.len = new_len as u16;
1094 let mut new_root = Root { node: BoxedNode::from_internal(new_node), height };
1096 for i in 0..(new_len + 1) {
1097 Handle::new_edge(new_root.as_mut().cast_unchecked(), i).correct_parent_link();
1100 (self.node, k, v, new_root)
1104 /// Returns `true` if it is valid to call `.merge()`, i.e., whether there is enough room in
1105 /// a node to hold the combination of the nodes to the left and right of this handle along
1106 /// with the key/value pair at this handle.
1107 pub fn can_merge(&self) -> bool {
1108 (self.reborrow().left_edge().descend().len()
1109 + self.reborrow().right_edge().descend().len()
1114 /// Combines the node immediately to the left of this handle, the key/value pair pointed
1115 /// to by this handle, and the node immediately to the right of this handle into one new
1116 /// child of the underlying node, returning an edge referencing that new child.
1118 /// Assumes that this edge `.can_merge()`.
1121 ) -> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::Edge> {
1122 let self1 = unsafe { ptr::read(&self) };
1123 let self2 = unsafe { ptr::read(&self) };
1124 let mut left_node = self1.left_edge().descend();
1125 let left_len = left_node.len();
1126 let mut right_node = self2.right_edge().descend();
1127 let right_len = right_node.len();
1129 // necessary for correctness, but in a private module
1130 assert!(left_len + right_len < CAPACITY);
1134 left_node.keys_mut().get_unchecked_mut(left_len),
1135 slice_remove(self.node.keys_mut(), self.idx),
1137 ptr::copy_nonoverlapping(
1138 right_node.keys().as_ptr(),
1139 left_node.keys_mut().as_mut_ptr().add(left_len + 1),
1143 left_node.vals_mut().get_unchecked_mut(left_len),
1144 slice_remove(self.node.vals_mut(), self.idx),
1146 ptr::copy_nonoverlapping(
1147 right_node.vals().as_ptr(),
1148 left_node.vals_mut().as_mut_ptr().add(left_len + 1),
1152 slice_remove(&mut self.node.as_internal_mut().edges, self.idx + 1);
1153 for i in self.idx + 1..self.node.len() {
1154 Handle::new_edge(self.node.reborrow_mut(), i).correct_parent_link();
1156 (*self.node.as_leaf_mut()).len -= 1;
1158 (*left_node.as_leaf_mut()).len += right_len as u16 + 1;
1160 let layout = if self.node.height > 1 {
1161 ptr::copy_nonoverlapping(
1162 right_node.cast_unchecked().as_internal().edges.as_ptr(),
1172 for i in left_len + 1..left_len + right_len + 2 {
1173 Handle::new_edge(left_node.cast_unchecked().reborrow_mut(), i)
1174 .correct_parent_link();
1177 Layout::new::<InternalNode<K, V>>()
1179 Layout::new::<LeafNode<K, V>>()
1181 Global.dealloc(right_node.node.cast(), layout);
1183 Handle::new_edge(self.node, self.idx)
1187 /// This removes a key/value pair from the left child and places it in the key/value storage
1188 /// pointed to by this handle while pushing the old key/value pair of this handle into the right
1190 pub fn steal_left(&mut self) {
1192 let (k, v, edge) = self.reborrow_mut().left_edge().descend().pop();
1194 let k = mem::replace(self.reborrow_mut().into_kv_mut().0, k);
1195 let v = mem::replace(self.reborrow_mut().into_kv_mut().1, v);
1197 match self.reborrow_mut().right_edge().descend().force() {
1198 ForceResult::Leaf(mut leaf) => leaf.push_front(k, v),
1199 ForceResult::Internal(mut internal) => internal.push_front(k, v, edge.unwrap()),
1204 /// This removes a key/value pair from the right child and places it in the key/value storage
1205 /// pointed to by this handle while pushing the old key/value pair of this handle into the left
1207 pub fn steal_right(&mut self) {
1209 let (k, v, edge) = self.reborrow_mut().right_edge().descend().pop_front();
1211 let k = mem::replace(self.reborrow_mut().into_kv_mut().0, k);
1212 let v = mem::replace(self.reborrow_mut().into_kv_mut().1, v);
1214 match self.reborrow_mut().left_edge().descend().force() {
1215 ForceResult::Leaf(mut leaf) => leaf.push(k, v),
1216 ForceResult::Internal(mut internal) => internal.push(k, v, edge.unwrap()),
1221 /// This does stealing similar to `steal_left` but steals multiple elements at once.
1222 pub fn bulk_steal_left(&mut self, count: usize) {
1224 let mut left_node = ptr::read(self).left_edge().descend();
1225 let left_len = left_node.len();
1226 let mut right_node = ptr::read(self).right_edge().descend();
1227 let right_len = right_node.len();
1229 // Make sure that we may steal safely.
1230 assert!(right_len + count <= CAPACITY);
1231 assert!(left_len >= count);
1233 let new_left_len = left_len - count;
1237 let left_kv = left_node.reborrow_mut().into_kv_pointers_mut();
1238 let right_kv = right_node.reborrow_mut().into_kv_pointers_mut();
1240 let kv = self.reborrow_mut().into_kv_mut();
1241 (kv.0 as *mut K, kv.1 as *mut V)
1244 // Make room for stolen elements in the right child.
1245 ptr::copy(right_kv.0, right_kv.0.add(count), right_len);
1246 ptr::copy(right_kv.1, right_kv.1.add(count), right_len);
1248 // Move elements from the left child to the right one.
1249 move_kv(left_kv, new_left_len + 1, right_kv, 0, count - 1);
1251 // Move parent's key/value pair to the right child.
1252 move_kv(parent_kv, 0, right_kv, count - 1, 1);
1254 // Move the left-most stolen pair to the parent.
1255 move_kv(left_kv, new_left_len, parent_kv, 0, 1);
1258 (*left_node.reborrow_mut().as_leaf_mut()).len -= count as u16;
1259 (*right_node.reborrow_mut().as_leaf_mut()).len += count as u16;
1261 match (left_node.force(), right_node.force()) {
1262 (ForceResult::Internal(left), ForceResult::Internal(mut right)) => {
1263 // Make room for stolen edges.
1264 let right_edges = right.reborrow_mut().as_internal_mut().edges.as_mut_ptr();
1265 ptr::copy(right_edges, right_edges.add(count), right_len + 1);
1266 right.correct_childrens_parent_links(count, count + right_len + 1);
1268 move_edges(left, new_left_len + 1, right, 0, count);
1270 (ForceResult::Leaf(_), ForceResult::Leaf(_)) => {}
1278 /// The symmetric clone of `bulk_steal_left`.
1279 pub fn bulk_steal_right(&mut self, count: usize) {
1281 let mut left_node = ptr::read(self).left_edge().descend();
1282 let left_len = left_node.len();
1283 let mut right_node = ptr::read(self).right_edge().descend();
1284 let right_len = right_node.len();
1286 // Make sure that we may steal safely.
1287 assert!(left_len + count <= CAPACITY);
1288 assert!(right_len >= count);
1290 let new_right_len = right_len - count;
1294 let left_kv = left_node.reborrow_mut().into_kv_pointers_mut();
1295 let right_kv = right_node.reborrow_mut().into_kv_pointers_mut();
1297 let kv = self.reborrow_mut().into_kv_mut();
1298 (kv.0 as *mut K, kv.1 as *mut V)
1301 // Move parent's key/value pair to the left child.
1302 move_kv(parent_kv, 0, left_kv, left_len, 1);
1304 // Move elements from the right child to the left one.
1305 move_kv(right_kv, 0, left_kv, left_len + 1, count - 1);
1307 // Move the right-most stolen pair to the parent.
1308 move_kv(right_kv, count - 1, parent_kv, 0, 1);
1310 // Fix right indexing
1311 ptr::copy(right_kv.0.add(count), right_kv.0, new_right_len);
1312 ptr::copy(right_kv.1.add(count), right_kv.1, new_right_len);
1315 (*left_node.reborrow_mut().as_leaf_mut()).len += count as u16;
1316 (*right_node.reborrow_mut().as_leaf_mut()).len -= count as u16;
1318 match (left_node.force(), right_node.force()) {
1319 (ForceResult::Internal(left), ForceResult::Internal(mut right)) => {
1320 move_edges(right.reborrow_mut(), 0, left, left_len + 1, count);
1322 // Fix right indexing.
1323 let right_edges = right.reborrow_mut().as_internal_mut().edges.as_mut_ptr();
1324 ptr::copy(right_edges.add(count), right_edges, new_right_len + 1);
1325 right.correct_childrens_parent_links(0, new_right_len + 1);
1327 (ForceResult::Leaf(_), ForceResult::Leaf(_)) => {}
1336 unsafe fn move_kv<K, V>(
1337 source: (*mut K, *mut V),
1338 source_offset: usize,
1339 dest: (*mut K, *mut V),
1344 ptr::copy_nonoverlapping(source.0.add(source_offset), dest.0.add(dest_offset), count);
1345 ptr::copy_nonoverlapping(source.1.add(source_offset), dest.1.add(dest_offset), count);
1349 // Source and destination must have the same height.
1350 unsafe fn move_edges<K, V>(
1351 mut source: NodeRef<marker::Mut<'_>, K, V, marker::Internal>,
1352 source_offset: usize,
1353 mut dest: NodeRef<marker::Mut<'_>, K, V, marker::Internal>,
1357 let source_ptr = source.as_internal_mut().edges.as_mut_ptr();
1358 let dest_ptr = dest.as_internal_mut().edges.as_mut_ptr();
1360 ptr::copy_nonoverlapping(source_ptr.add(source_offset), dest_ptr.add(dest_offset), count);
1361 dest.correct_childrens_parent_links(dest_offset, dest_offset + count);
1365 impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge> {
1366 pub fn forget_node_type(
1368 ) -> Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, marker::Edge> {
1369 unsafe { Handle::new_edge(self.node.forget_type(), self.idx) }
1373 impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V, marker::Internal>, marker::Edge> {
1374 pub fn forget_node_type(
1376 ) -> Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, marker::Edge> {
1377 unsafe { Handle::new_edge(self.node.forget_type(), self.idx) }
1381 impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::KV> {
1382 pub fn forget_node_type(
1384 ) -> Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, marker::KV> {
1385 unsafe { Handle::new_kv(self.node.forget_type(), self.idx) }
1389 impl<BorrowType, K, V, HandleType>
1390 Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, HandleType>
1392 /// Checks whether the underlying node is an `Internal` node or a `Leaf` node.
1396 Handle<NodeRef<BorrowType, K, V, marker::Leaf>, HandleType>,
1397 Handle<NodeRef<BorrowType, K, V, marker::Internal>, HandleType>,
1399 match self.node.force() {
1400 ForceResult::Leaf(node) => {
1401 ForceResult::Leaf(Handle { node, idx: self.idx, _marker: PhantomData })
1403 ForceResult::Internal(node) => {
1404 ForceResult::Internal(Handle { node, idx: self.idx, _marker: PhantomData })
1410 impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, marker::Edge> {
1411 /// Move the suffix after `self` from one node to another one. `right` must be empty.
1412 /// The first edge of `right` remains unchanged.
1415 right: &mut NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>,
1418 let left_new_len = self.idx;
1419 let mut left_node = self.reborrow_mut().into_node();
1421 let right_new_len = left_node.len() - left_new_len;
1422 let mut right_node = right.reborrow_mut();
1424 assert!(right_node.len() == 0);
1425 assert!(left_node.height == right_node.height);
1427 if right_new_len > 0 {
1428 let left_kv = left_node.reborrow_mut().into_kv_pointers_mut();
1429 let right_kv = right_node.reborrow_mut().into_kv_pointers_mut();
1431 move_kv(left_kv, left_new_len, right_kv, 0, right_new_len);
1433 (*left_node.reborrow_mut().as_leaf_mut()).len = left_new_len as u16;
1434 (*right_node.reborrow_mut().as_leaf_mut()).len = right_new_len as u16;
1436 match (left_node.force(), right_node.force()) {
1437 (ForceResult::Internal(left), ForceResult::Internal(right)) => {
1438 move_edges(left, left_new_len + 1, right, 1, right_new_len);
1440 (ForceResult::Leaf(_), ForceResult::Leaf(_)) => {}
1450 pub enum ForceResult<Leaf, Internal> {
1455 pub enum InsertResult<'a, K, V, Type> {
1456 Fit(Handle<NodeRef<marker::Mut<'a>, K, V, Type>, marker::KV>),
1457 Split(NodeRef<marker::Mut<'a>, K, V, Type>, K, V, Root<K, V>),
1461 use core::marker::PhantomData;
1464 pub enum Internal {}
1465 pub enum LeafOrInternal {}
1468 pub struct Immut<'a>(PhantomData<&'a ()>);
1469 pub struct Mut<'a>(PhantomData<&'a mut ()>);
1475 unsafe fn slice_insert<T>(slice: &mut [T], idx: usize, val: T) {
1477 ptr::copy(slice.as_ptr().add(idx), slice.as_mut_ptr().add(idx + 1), slice.len() - idx);
1478 ptr::write(slice.get_unchecked_mut(idx), val);
1482 unsafe fn slice_remove<T>(slice: &mut [T], idx: usize) -> T {
1484 let ret = ptr::read(slice.get_unchecked(idx));
1485 ptr::copy(slice.as_ptr().add(idx + 1), slice.as_mut_ptr().add(idx), slice.len() - idx - 1);