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.
98 edges: [MaybeUninit<BoxedNode<K, V>>; 2 * B],
101 impl<K, V> InternalNode<K, V> {
102 /// Creates a new `InternalNode`.
104 /// This is unsafe for two reasons. First, it returns an `InternalNode` by value, risking
105 /// dropping of uninitialized fields. Second, an invariant of internal nodes is that `len + 1`
106 /// edges are initialized and valid, meaning that even when the node is empty (having a
107 /// `len` of 0), there must be one initialized and valid edge. This function does not set up
109 unsafe fn new() -> Self {
110 InternalNode { data: unsafe { LeafNode::new() }, edges: [MaybeUninit::UNINIT; 2 * B] }
114 /// A managed, non-null pointer to a node. This is either an owned pointer to
115 /// `LeafNode<K, V>` or an owned pointer to `InternalNode<K, V>`.
117 /// However, `BoxedNode` contains no information as to which of the two types
118 /// of nodes it actually contains, and, partially due to this lack of information,
119 /// has no destructor.
120 struct BoxedNode<K, V> {
121 ptr: Unique<LeafNode<K, V>>,
124 impl<K, V> BoxedNode<K, V> {
125 fn from_leaf(node: Box<LeafNode<K, V>>) -> Self {
126 BoxedNode { ptr: Box::into_unique(node) }
129 fn from_internal(node: Box<InternalNode<K, V>>) -> Self {
130 BoxedNode { ptr: Box::into_unique(node).cast() }
133 unsafe fn from_ptr(ptr: NonNull<LeafNode<K, V>>) -> Self {
134 BoxedNode { ptr: unsafe { Unique::new_unchecked(ptr.as_ptr()) } }
137 fn as_ptr(&self) -> NonNull<LeafNode<K, V>> {
138 NonNull::from(self.ptr)
144 /// Note that this does not have a destructor, and must be cleaned up manually.
145 pub struct Root<K, V> {
146 node: BoxedNode<K, V>,
147 /// The number of levels below the root node.
151 unsafe impl<K: Sync, V: Sync> Sync for Root<K, V> {}
152 unsafe impl<K: Send, V: Send> Send for Root<K, V> {}
154 impl<K, V> Root<K, V> {
155 /// Returns a new owned tree, with its own root node that is initially empty.
156 pub fn new_leaf() -> Self {
157 Root { node: BoxedNode::from_leaf(Box::new(unsafe { LeafNode::new() })), height: 0 }
160 pub fn as_ref(&self) -> NodeRef<marker::Immut<'_>, K, V, marker::LeafOrInternal> {
163 node: self.node.as_ptr(),
165 _marker: PhantomData,
169 pub fn as_mut(&mut self) -> NodeRef<marker::Mut<'_>, K, V, marker::LeafOrInternal> {
172 node: self.node.as_ptr(),
173 root: self as *mut _,
174 _marker: PhantomData,
178 pub fn into_ref(self) -> NodeRef<marker::Owned, K, V, marker::LeafOrInternal> {
181 node: self.node.as_ptr(),
183 _marker: PhantomData,
187 /// Adds a new internal node with a single edge, pointing to the previous root, and make that
188 /// new node the root. This increases the height by 1 and is the opposite of `pop_level`.
189 pub fn push_level(&mut self) -> NodeRef<marker::Mut<'_>, K, V, marker::Internal> {
190 let mut new_node = Box::new(unsafe { InternalNode::new() });
191 new_node.edges[0].write(unsafe { BoxedNode::from_ptr(self.node.as_ptr()) });
193 self.node = BoxedNode::from_internal(new_node);
196 let mut ret = NodeRef {
198 node: self.node.as_ptr(),
199 root: self as *mut _,
200 _marker: PhantomData,
204 ret.reborrow_mut().first_edge().correct_parent_link();
210 /// Removes the root node, using its first child as the new root. This cannot be called when
211 /// the tree consists only of a leaf node. As it is intended only to be called when the root
212 /// has only one edge, no cleanup is done on any of the other children of the root.
213 /// This decreases the height by 1 and is the opposite of `push_level`.
214 pub fn pop_level(&mut self) {
215 assert!(self.height > 0);
217 let top = self.node.ptr;
221 self.as_mut().cast_unchecked::<marker::Internal>().first_edge().descend().node,
226 (*self.as_mut().as_leaf_mut()).parent = ptr::null();
230 Global.dealloc(NonNull::from(top).cast(), Layout::new::<InternalNode<K, V>>());
235 // N.B. `NodeRef` is always covariant in `K` and `V`, even when the `BorrowType`
236 // is `Mut`. This is technically wrong, but cannot result in any unsafety due to
237 // internal use of `NodeRef` because we stay completely generic over `K` and `V`.
238 // However, whenever a public type wraps `NodeRef`, make sure that it has the
240 /// A reference to a node.
242 /// This type has a number of parameters that controls how it acts:
243 /// - `BorrowType`: This can be `Immut<'a>` or `Mut<'a>` for some `'a` or `Owned`.
244 /// When this is `Immut<'a>`, the `NodeRef` acts roughly like `&'a Node`,
245 /// when this is `Mut<'a>`, the `NodeRef` acts roughly like `&'a mut Node`,
246 /// and when this is `Owned`, the `NodeRef` acts roughly like `Box<Node>`.
247 /// - `K` and `V`: These control what types of things are stored in the nodes.
248 /// - `Type`: This can be `Leaf`, `Internal`, or `LeafOrInternal`. When this is
249 /// `Leaf`, the `NodeRef` points to a leaf node, when this is `Internal` the
250 /// `NodeRef` points to an internal node, and when this is `LeafOrInternal` the
251 /// `NodeRef` could be pointing to either type of node.
252 pub struct NodeRef<BorrowType, K, V, Type> {
253 /// The number of levels below the node.
255 node: NonNull<LeafNode<K, V>>,
256 // `root` is null unless the borrow type is `Mut`
257 root: *const Root<K, V>,
258 _marker: PhantomData<(BorrowType, Type)>,
261 impl<'a, K: 'a, V: 'a, Type> Copy for NodeRef<marker::Immut<'a>, K, V, Type> {}
262 impl<'a, K: 'a, V: 'a, Type> Clone for NodeRef<marker::Immut<'a>, K, V, Type> {
263 fn clone(&self) -> Self {
268 unsafe impl<BorrowType, K: Sync, V: Sync, Type> Sync for NodeRef<BorrowType, K, V, Type> {}
270 unsafe impl<'a, K: Sync + 'a, V: Sync + 'a, Type> Send for NodeRef<marker::Immut<'a>, K, V, Type> {}
271 unsafe impl<'a, K: Send + 'a, V: Send + 'a, Type> Send for NodeRef<marker::Mut<'a>, K, V, Type> {}
272 unsafe impl<K: Send, V: Send, Type> Send for NodeRef<marker::Owned, K, V, Type> {}
274 impl<BorrowType, K, V> NodeRef<BorrowType, K, V, marker::Internal> {
275 fn as_internal(&self) -> &InternalNode<K, V> {
276 unsafe { &*(self.node.as_ptr() as *mut InternalNode<K, V>) }
280 impl<'a, K, V> NodeRef<marker::Mut<'a>, K, V, marker::Internal> {
281 fn as_internal_mut(&mut self) -> &mut InternalNode<K, V> {
282 unsafe { &mut *(self.node.as_ptr() as *mut InternalNode<K, V>) }
286 impl<BorrowType, K, V, Type> NodeRef<BorrowType, K, V, Type> {
287 /// Finds the length of the node. This is the number of keys or values. In an
288 /// internal node, the number of edges is `len() + 1`.
289 /// For any node, the number of possible edge handles is also `len() + 1`.
290 /// Note that, despite being safe, calling this function can have the side effect
291 /// of invalidating mutable references that unsafe code has created.
292 pub fn len(&self) -> usize {
293 self.as_leaf().len as usize
296 /// Returns the height of this node in the whole tree. Zero height denotes the
298 pub fn height(&self) -> usize {
302 /// Removes any static information about whether this node is a `Leaf` or an
304 pub fn forget_type(self) -> NodeRef<BorrowType, K, V, marker::LeafOrInternal> {
305 NodeRef { height: self.height, node: self.node, root: self.root, _marker: PhantomData }
308 /// Temporarily takes out another, immutable reference to the same node.
309 fn reborrow(&self) -> NodeRef<marker::Immut<'_>, K, V, Type> {
310 NodeRef { height: self.height, node: self.node, root: self.root, _marker: PhantomData }
313 /// Exposes the leaf "portion" of any leaf or internal node.
314 /// If the node is a leaf, this function simply opens up its data.
315 /// If the node is an internal node, so not a leaf, it does have all the data a leaf has
316 /// (header, keys and values), and this function exposes that.
317 fn as_leaf(&self) -> &LeafNode<K, V> {
318 // The node must be valid for at least the LeafNode portion.
319 // This is not a reference in the NodeRef type because we don't know if
320 // it should be unique or shared.
321 unsafe { self.node.as_ref() }
324 /// Borrows a view into the keys stored in the node.
325 pub fn keys(&self) -> &[K] {
326 self.reborrow().into_key_slice()
329 /// Borrows a view into the values stored in the node.
330 fn vals(&self) -> &[V] {
331 self.reborrow().into_val_slice()
334 /// Finds the parent of the current node. Returns `Ok(handle)` if the current
335 /// node actually has a parent, where `handle` points to the edge of the parent
336 /// that points to the current node. Returns `Err(self)` if the current node has
337 /// no parent, giving back the original `NodeRef`.
339 /// `edge.descend().ascend().unwrap()` and `node.ascend().unwrap().descend()` should
340 /// both, upon success, do nothing.
343 ) -> Result<Handle<NodeRef<BorrowType, K, V, marker::Internal>, marker::Edge>, Self> {
344 let parent_as_leaf = self.as_leaf().parent as *const LeafNode<K, V>;
345 if let Some(non_zero) = NonNull::new(parent_as_leaf as *mut _) {
348 height: self.height + 1,
351 _marker: PhantomData,
353 idx: unsafe { usize::from(*self.as_leaf().parent_idx.as_ptr()) },
354 _marker: PhantomData,
361 pub fn first_edge(self) -> Handle<Self, marker::Edge> {
362 unsafe { Handle::new_edge(self, 0) }
365 pub fn last_edge(self) -> Handle<Self, marker::Edge> {
366 let len = self.len();
367 unsafe { Handle::new_edge(self, len) }
370 /// Note that `self` must be nonempty.
371 pub fn first_kv(self) -> Handle<Self, marker::KV> {
372 let len = self.len();
374 unsafe { Handle::new_kv(self, 0) }
377 /// Note that `self` must be nonempty.
378 pub fn last_kv(self) -> Handle<Self, marker::KV> {
379 let len = self.len();
381 unsafe { Handle::new_kv(self, len - 1) }
385 impl<K, V> NodeRef<marker::Owned, K, V, marker::LeafOrInternal> {
386 /// Similar to `ascend`, gets a reference to a node's parent node, but also
387 /// deallocate the current node in the process. This is unsafe because the
388 /// current node will still be accessible despite being deallocated.
389 pub unsafe fn deallocate_and_ascend(
391 ) -> Option<Handle<NodeRef<marker::Owned, K, V, marker::Internal>, marker::Edge>> {
392 let height = self.height;
393 let node = self.node;
394 let ret = self.ascend().ok();
399 Layout::new::<InternalNode<K, V>>()
401 Layout::new::<LeafNode<K, V>>()
409 impl<'a, K, V, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
410 /// Unsafely asserts to the compiler some static information about whether this
411 /// node is a `Leaf`.
412 unsafe fn cast_unchecked<NewType>(&mut self) -> NodeRef<marker::Mut<'_>, K, V, NewType> {
413 NodeRef { height: self.height, node: self.node, root: self.root, _marker: PhantomData }
416 /// Temporarily takes out another, mutable reference to the same node. Beware, as
417 /// this method is very dangerous, doubly so since it may not immediately appear
420 /// Because mutable pointers can roam anywhere around the tree and can even (through
421 /// `into_root_mut`) mess with the root of the tree, the result of `reborrow_mut`
422 /// can easily be used to make the original mutable pointer dangling, or, in the case
423 /// of a reborrowed handle, out of bounds.
424 // FIXME(@gereeter) consider adding yet another type parameter to `NodeRef` that restricts
425 // the use of `ascend` and `into_root_mut` on reborrowed pointers, preventing this unsafety.
426 unsafe fn reborrow_mut(&mut self) -> NodeRef<marker::Mut<'_>, K, V, Type> {
427 NodeRef { height: self.height, node: self.node, root: self.root, _marker: PhantomData }
430 /// Exposes the leaf "portion" of any leaf or internal node for writing.
431 /// If the node is a leaf, this function simply opens up its data.
432 /// If the node is an internal node, so not a leaf, it does have all the data a leaf has
433 /// (header, keys and values), and this function exposes that.
435 /// Returns a raw ptr to avoid asserting exclusive access to the entire node.
436 fn as_leaf_mut(&mut self) -> *mut LeafNode<K, V> {
440 fn keys_mut(&mut self) -> &mut [K] {
441 // SAFETY: the caller will not be able to call further methods on self
442 // until the key slice reference is dropped, as we have unique access
443 // for the lifetime of the borrow.
444 unsafe { self.reborrow_mut().into_key_slice_mut() }
447 fn vals_mut(&mut self) -> &mut [V] {
448 // SAFETY: the caller will not be able to call further methods on self
449 // until the value slice reference is dropped, as we have unique access
450 // for the lifetime of the borrow.
451 unsafe { self.reborrow_mut().into_val_slice_mut() }
455 impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Immut<'a>, K, V, Type> {
456 fn into_key_slice(self) -> &'a [K] {
457 unsafe { slice::from_raw_parts(MaybeUninit::first_ptr(&self.as_leaf().keys), self.len()) }
460 fn into_val_slice(self) -> &'a [V] {
461 unsafe { slice::from_raw_parts(MaybeUninit::first_ptr(&self.as_leaf().vals), self.len()) }
464 fn into_slices(self) -> (&'a [K], &'a [V]) {
465 // SAFETY: equivalent to reborrow() except not requiring Type: 'a
466 let k = unsafe { ptr::read(&self) };
467 (k.into_key_slice(), self.into_val_slice())
471 impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
472 /// Gets a mutable reference to the root itself. This is useful primarily when the
473 /// height of the tree needs to be adjusted. Never call this on a reborrowed pointer.
474 pub fn into_root_mut(self) -> &'a mut Root<K, V> {
475 unsafe { &mut *(self.root as *mut Root<K, V>) }
478 fn into_key_slice_mut(mut self) -> &'a mut [K] {
479 // SAFETY: The keys of a node must always be initialized up to length.
481 slice::from_raw_parts_mut(
482 MaybeUninit::first_ptr_mut(&mut (*self.as_leaf_mut()).keys),
488 fn into_val_slice_mut(mut self) -> &'a mut [V] {
489 // SAFETY: The values of a node must always be initialized up to length.
491 slice::from_raw_parts_mut(
492 MaybeUninit::first_ptr_mut(&mut (*self.as_leaf_mut()).vals),
498 fn into_slices_mut(mut self) -> (&'a mut [K], &'a mut [V]) {
499 // We cannot use the getters here, because calling the second one
500 // invalidates the reference returned by the first.
501 // More precisely, it is the call to `len` that is the culprit,
502 // because that creates a shared reference to the header, which *can*
503 // overlap with the keys (and even the values, for ZST keys).
504 let len = self.len();
505 let leaf = self.as_leaf_mut();
506 // SAFETY: The keys and values of a node must always be initialized up to length.
508 slice::from_raw_parts_mut(MaybeUninit::first_ptr_mut(&mut (*leaf).keys), len)
511 slice::from_raw_parts_mut(MaybeUninit::first_ptr_mut(&mut (*leaf).vals), len)
517 impl<'a, K, V> NodeRef<marker::Mut<'a>, K, V, marker::Leaf> {
518 /// Adds a key/value pair the end of the node.
519 pub fn push(&mut self, key: K, val: V) {
520 assert!(self.len() < CAPACITY);
522 let idx = self.len();
525 ptr::write(self.keys_mut().get_unchecked_mut(idx), key);
526 ptr::write(self.vals_mut().get_unchecked_mut(idx), val);
528 (*self.as_leaf_mut()).len += 1;
532 /// Adds a key/value pair to the beginning of the node.
533 pub fn push_front(&mut self, key: K, val: V) {
534 assert!(self.len() < CAPACITY);
537 slice_insert(self.keys_mut(), 0, key);
538 slice_insert(self.vals_mut(), 0, val);
540 (*self.as_leaf_mut()).len += 1;
545 impl<'a, K, V> NodeRef<marker::Mut<'a>, K, V, marker::Internal> {
546 /// Adds a key/value pair and an edge to go to the right of that pair to
547 /// the end of the node.
548 pub fn push(&mut self, key: K, val: V, edge: Root<K, V>) {
549 assert!(edge.height == self.height - 1);
550 assert!(self.len() < CAPACITY);
552 let idx = self.len();
555 ptr::write(self.keys_mut().get_unchecked_mut(idx), key);
556 ptr::write(self.vals_mut().get_unchecked_mut(idx), val);
557 self.as_internal_mut().edges.get_unchecked_mut(idx + 1).write(edge.node);
559 (*self.as_leaf_mut()).len += 1;
561 Handle::new_edge(self.reborrow_mut(), idx + 1).correct_parent_link();
565 // Unsafe because 'first' and 'after_last' must be in range
566 unsafe fn correct_childrens_parent_links(&mut self, first: usize, after_last: usize) {
567 debug_assert!(first <= self.len());
568 debug_assert!(after_last <= self.len() + 1);
569 for i in first..after_last {
570 unsafe { Handle::new_edge(self.reborrow_mut(), i) }.correct_parent_link();
574 fn correct_all_childrens_parent_links(&mut self) {
575 let len = self.len();
576 unsafe { self.correct_childrens_parent_links(0, len + 1) };
579 /// Adds a key/value pair and an edge to go to the left of that pair to
580 /// the beginning of the node.
581 pub fn push_front(&mut self, key: K, val: V, edge: Root<K, V>) {
582 assert!(edge.height == self.height - 1);
583 assert!(self.len() < CAPACITY);
586 slice_insert(self.keys_mut(), 0, key);
587 slice_insert(self.vals_mut(), 0, val);
589 slice::from_raw_parts_mut(
590 MaybeUninit::first_ptr_mut(&mut self.as_internal_mut().edges),
597 (*self.as_leaf_mut()).len += 1;
599 self.correct_all_childrens_parent_links();
604 impl<'a, K, V> NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal> {
605 /// Removes a key/value pair from the end of this node. If this is an internal node,
606 /// also removes the edge that was to the right of that pair.
607 pub fn pop(&mut self) -> (K, V, Option<Root<K, V>>) {
608 assert!(self.len() > 0);
610 let idx = self.len() - 1;
613 let key = ptr::read(self.keys().get_unchecked(idx));
614 let val = ptr::read(self.vals().get_unchecked(idx));
615 let edge = match self.reborrow_mut().force() {
616 ForceResult::Leaf(_) => None,
617 ForceResult::Internal(internal) => {
619 ptr::read(internal.as_internal().edges.get_unchecked(idx + 1).as_ptr());
620 let mut new_root = Root { node: edge, height: internal.height - 1 };
621 (*new_root.as_mut().as_leaf_mut()).parent = ptr::null();
626 (*self.as_leaf_mut()).len -= 1;
631 /// Removes a key/value pair from the beginning of this node. If this is an internal node,
632 /// also removes the edge that was to the left of that pair.
633 pub fn pop_front(&mut self) -> (K, V, Option<Root<K, V>>) {
634 assert!(self.len() > 0);
636 let old_len = self.len();
639 let key = slice_remove(self.keys_mut(), 0);
640 let val = slice_remove(self.vals_mut(), 0);
641 let edge = match self.reborrow_mut().force() {
642 ForceResult::Leaf(_) => None,
643 ForceResult::Internal(mut internal) => {
644 let edge = slice_remove(
645 slice::from_raw_parts_mut(
646 MaybeUninit::first_ptr_mut(&mut internal.as_internal_mut().edges),
652 let mut new_root = Root { node: edge, height: internal.height - 1 };
653 (*new_root.as_mut().as_leaf_mut()).parent = ptr::null();
655 for i in 0..old_len {
656 Handle::new_edge(internal.reborrow_mut(), i).correct_parent_link();
663 (*self.as_leaf_mut()).len -= 1;
669 fn into_kv_pointers_mut(mut self) -> (*mut K, *mut V) {
670 (self.keys_mut().as_mut_ptr(), self.vals_mut().as_mut_ptr())
674 impl<BorrowType, K, V> NodeRef<BorrowType, K, V, marker::LeafOrInternal> {
675 /// Checks whether a node is an `Internal` node or a `Leaf` node.
679 NodeRef<BorrowType, K, V, marker::Leaf>,
680 NodeRef<BorrowType, K, V, marker::Internal>,
682 if self.height == 0 {
683 ForceResult::Leaf(NodeRef {
687 _marker: PhantomData,
690 ForceResult::Internal(NodeRef {
694 _marker: PhantomData,
700 /// A reference to a specific key/value pair or edge within a node. The `Node` parameter
701 /// must be a `NodeRef`, while the `Type` can either be `KV` (signifying a handle on a key/value
702 /// pair) or `Edge` (signifying a handle on an edge).
704 /// Note that even `Leaf` nodes can have `Edge` handles. Instead of representing a pointer to
705 /// a child node, these represent the spaces where child pointers would go between the key/value
706 /// pairs. For example, in a node with length 2, there would be 3 possible edge locations - one
707 /// to the left of the node, one between the two pairs, and one at the right of the node.
708 pub struct Handle<Node, Type> {
711 _marker: PhantomData<Type>,
714 impl<Node: Copy, Type> Copy for Handle<Node, Type> {}
715 // We don't need the full generality of `#[derive(Clone)]`, as the only time `Node` will be
716 // `Clone`able is when it is an immutable reference and therefore `Copy`.
717 impl<Node: Copy, Type> Clone for Handle<Node, Type> {
718 fn clone(&self) -> Self {
723 impl<Node, Type> Handle<Node, Type> {
724 /// Retrieves the node that contains the edge of key/value pair this handle points to.
725 pub fn into_node(self) -> Node {
729 /// Returns the position of this handle in the node.
730 pub fn idx(&self) -> usize {
735 impl<BorrowType, K, V, NodeType> Handle<NodeRef<BorrowType, K, V, NodeType>, marker::KV> {
736 /// Creates a new handle to a key/value pair in `node`.
737 /// Unsafe because the caller must ensure that `idx < node.len()`.
738 pub unsafe fn new_kv(node: NodeRef<BorrowType, K, V, NodeType>, idx: usize) -> Self {
739 debug_assert!(idx < node.len());
741 Handle { node, idx, _marker: PhantomData }
744 pub fn left_edge(self) -> Handle<NodeRef<BorrowType, K, V, NodeType>, marker::Edge> {
745 unsafe { Handle::new_edge(self.node, self.idx) }
748 pub fn right_edge(self) -> Handle<NodeRef<BorrowType, K, V, NodeType>, marker::Edge> {
749 unsafe { Handle::new_edge(self.node, self.idx + 1) }
753 impl<BorrowType, K, V, NodeType, HandleType> PartialEq
754 for Handle<NodeRef<BorrowType, K, V, NodeType>, HandleType>
756 fn eq(&self, other: &Self) -> bool {
757 self.node.node == other.node.node && self.idx == other.idx
761 impl<BorrowType, K, V, NodeType, HandleType> PartialOrd
762 for Handle<NodeRef<BorrowType, K, V, NodeType>, HandleType>
764 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
765 if self.node.node == other.node.node { Some(self.idx.cmp(&other.idx)) } else { None }
769 impl<BorrowType, K, V, NodeType, HandleType>
770 Handle<NodeRef<BorrowType, K, V, NodeType>, HandleType>
772 /// Temporarily takes out another, immutable handle on the same location.
773 pub fn reborrow(&self) -> Handle<NodeRef<marker::Immut<'_>, K, V, NodeType>, HandleType> {
774 // We can't use Handle::new_kv or Handle::new_edge because we don't know our type
775 Handle { node: self.node.reborrow(), idx: self.idx, _marker: PhantomData }
779 impl<'a, K, V, NodeType, HandleType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>, HandleType> {
780 /// Temporarily takes out another, mutable handle on the same location. Beware, as
781 /// this method is very dangerous, doubly so since it may not immediately appear
784 /// Because mutable pointers can roam anywhere around the tree and can even (through
785 /// `into_root_mut`) mess with the root of the tree, the result of `reborrow_mut`
786 /// can easily be used to make the original mutable pointer dangling, or, in the case
787 /// of a reborrowed handle, out of bounds.
788 // FIXME(@gereeter) consider adding yet another type parameter to `NodeRef` that restricts
789 // the use of `ascend` and `into_root_mut` on reborrowed pointers, preventing this unsafety.
790 pub unsafe fn reborrow_mut(
792 ) -> Handle<NodeRef<marker::Mut<'_>, K, V, NodeType>, HandleType> {
793 // We can't use Handle::new_kv or Handle::new_edge because we don't know our type
794 Handle { node: unsafe { self.node.reborrow_mut() }, idx: self.idx, _marker: PhantomData }
798 impl<BorrowType, K, V, NodeType> Handle<NodeRef<BorrowType, K, V, NodeType>, marker::Edge> {
799 /// Creates a new handle to an edge in `node`.
800 /// Unsafe because the caller must ensure that `idx <= node.len()`.
801 pub unsafe fn new_edge(node: NodeRef<BorrowType, K, V, NodeType>, idx: usize) -> Self {
802 debug_assert!(idx <= node.len());
804 Handle { node, idx, _marker: PhantomData }
807 pub fn left_kv(self) -> Result<Handle<NodeRef<BorrowType, K, V, NodeType>, marker::KV>, Self> {
809 Ok(unsafe { Handle::new_kv(self.node, self.idx - 1) })
815 pub fn right_kv(self) -> Result<Handle<NodeRef<BorrowType, K, V, NodeType>, marker::KV>, Self> {
816 if self.idx < self.node.len() {
817 Ok(unsafe { Handle::new_kv(self.node, self.idx) })
824 impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge> {
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
829 /// The returned pointer points to the inserted value.
830 fn insert_fit(&mut self, key: K, val: V) -> *mut V {
831 // Necessary for correctness, but in a private module
832 debug_assert!(self.node.len() < CAPACITY);
835 slice_insert(self.node.keys_mut(), self.idx, key);
836 slice_insert(self.node.vals_mut(), self.idx, val);
838 (*self.node.as_leaf_mut()).len += 1;
840 self.node.vals_mut().get_unchecked_mut(self.idx)
844 /// Inserts a new key/value pair between the key/value pairs to the right and left of
845 /// this edge. This method splits the node if there isn't enough room.
847 /// The returned pointer points to the inserted value.
848 pub fn insert(mut self, key: K, val: V) -> (InsertResult<'a, K, V, marker::Leaf>, *mut V) {
849 if self.node.len() < CAPACITY {
850 let ptr = self.insert_fit(key, val);
851 let kv = unsafe { Handle::new_kv(self.node, self.idx) };
852 (InsertResult::Fit(kv), ptr)
854 let middle = unsafe { Handle::new_kv(self.node, B) };
855 let (mut left, k, v, mut right) = middle.split();
856 let ptr = if self.idx <= B {
857 unsafe { Handle::new_edge(left.reborrow_mut(), self.idx).insert_fit(key, val) }
861 right.as_mut().cast_unchecked::<marker::Leaf>(),
864 .insert_fit(key, val)
867 (InsertResult::Split(left, k, v, right), ptr)
872 impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::Edge> {
873 /// Fixes the parent pointer and index in the child node below this edge. This is useful
874 /// when the ordering of edges has been changed, such as in the various `insert` methods.
875 fn correct_parent_link(mut self) {
876 let idx = self.idx as u16;
877 let ptr = self.node.as_internal_mut() as *mut _;
878 let mut child = self.descend();
880 (*child.as_leaf_mut()).parent = ptr;
881 (*child.as_leaf_mut()).parent_idx.write(idx);
885 /// Unsafely asserts to the compiler some static information about whether the underlying
886 /// node of this handle is a `Leaf`.
887 unsafe fn cast_unchecked<NewType>(
889 ) -> Handle<NodeRef<marker::Mut<'_>, K, V, NewType>, marker::Edge> {
890 unsafe { Handle::new_edge(self.node.cast_unchecked(), self.idx) }
893 /// Inserts a new key/value pair and an edge that will go to the right of that new pair
894 /// between this edge and the key/value pair to the right of this edge. This method assumes
895 /// that there is enough space in the node for the new pair to fit.
896 fn insert_fit(&mut self, key: K, val: V, edge: Root<K, V>) {
897 // Necessary for correctness, but in an internal module
898 debug_assert!(self.node.len() < CAPACITY);
899 debug_assert!(edge.height == self.node.height - 1);
902 // This cast is a lie, but it allows us to reuse the key/value insertion logic.
903 self.cast_unchecked::<marker::Leaf>().insert_fit(key, val);
906 slice::from_raw_parts_mut(
907 MaybeUninit::first_ptr_mut(&mut self.node.as_internal_mut().edges),
914 for i in (self.idx + 1)..(self.node.len() + 1) {
915 Handle::new_edge(self.node.reborrow_mut(), i).correct_parent_link();
920 /// Inserts a new key/value pair and an edge that will go to the right of that new pair
921 /// between this edge and the key/value pair to the right of this edge. This method splits
922 /// the node if there isn't enough room.
928 ) -> InsertResult<'a, K, V, marker::Internal> {
929 assert!(edge.height == self.node.height - 1);
931 if self.node.len() < CAPACITY {
932 self.insert_fit(key, val, edge);
933 let kv = unsafe { Handle::new_kv(self.node, self.idx) };
934 InsertResult::Fit(kv)
936 let middle = unsafe { Handle::new_kv(self.node, B) };
937 let (mut left, k, v, mut right) = middle.split();
940 Handle::new_edge(left.reborrow_mut(), self.idx).insert_fit(key, val, edge);
945 right.as_mut().cast_unchecked::<marker::Internal>(),
948 .insert_fit(key, val, edge);
951 InsertResult::Split(left, k, v, right)
956 impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V, marker::Internal>, marker::Edge> {
957 /// Finds the node pointed to by this edge.
959 /// `edge.descend().ascend().unwrap()` and `node.ascend().unwrap().descend()` should
960 /// both, upon success, do nothing.
961 pub fn descend(self) -> NodeRef<BorrowType, K, V, marker::LeafOrInternal> {
963 height: self.node.height - 1,
965 (&*self.node.as_internal().edges.get_unchecked(self.idx).as_ptr()).as_ptr()
967 root: self.node.root,
968 _marker: PhantomData,
973 impl<'a, K: 'a, V: 'a, NodeType> Handle<NodeRef<marker::Immut<'a>, K, V, NodeType>, marker::KV> {
974 pub fn into_kv(self) -> (&'a K, &'a V) {
976 let (keys, vals) = self.node.into_slices();
977 (keys.get_unchecked(self.idx), vals.get_unchecked(self.idx))
982 impl<'a, K: 'a, V: 'a, NodeType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>, marker::KV> {
983 pub fn into_kv_mut(self) -> (&'a mut K, &'a mut V) {
985 let (keys, vals) = self.node.into_slices_mut();
986 (keys.get_unchecked_mut(self.idx), vals.get_unchecked_mut(self.idx))
991 impl<'a, K, V, NodeType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>, marker::KV> {
992 pub fn kv_mut(&mut self) -> (&mut K, &mut V) {
994 let (keys, vals) = self.node.reborrow_mut().into_slices_mut();
995 (keys.get_unchecked_mut(self.idx), vals.get_unchecked_mut(self.idx))
1000 impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::KV> {
1001 /// Splits the underlying node into three parts:
1003 /// - The node is truncated to only contain the key/value pairs to the right of
1005 /// - The key and value pointed to by this handle and extracted.
1006 /// - All the key/value pairs to the right of this handle are put into a newly
1008 pub fn split(mut self) -> (NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, K, V, Root<K, V>) {
1010 let mut new_node = Box::new(LeafNode::new());
1012 let k = ptr::read(self.node.keys().get_unchecked(self.idx));
1013 let v = ptr::read(self.node.vals().get_unchecked(self.idx));
1015 let new_len = self.node.len() - self.idx - 1;
1017 ptr::copy_nonoverlapping(
1018 self.node.keys().as_ptr().add(self.idx + 1),
1019 new_node.keys.as_mut_ptr() as *mut K,
1022 ptr::copy_nonoverlapping(
1023 self.node.vals().as_ptr().add(self.idx + 1),
1024 new_node.vals.as_mut_ptr() as *mut V,
1028 (*self.node.as_leaf_mut()).len = self.idx as u16;
1029 new_node.len = new_len as u16;
1031 (self.node, k, v, Root { node: BoxedNode::from_leaf(new_node), height: 0 })
1035 /// Removes the key/value pair pointed to by this handle and returns it, along with the edge
1036 /// between the now adjacent key/value pairs (if any) to the left and right of this handle.
1039 ) -> (Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>, K, V) {
1041 let k = slice_remove(self.node.keys_mut(), self.idx);
1042 let v = slice_remove(self.node.vals_mut(), self.idx);
1043 (*self.node.as_leaf_mut()).len -= 1;
1044 (self.left_edge(), k, v)
1049 impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::KV> {
1050 /// Splits the underlying node into three parts:
1052 /// - The node is truncated to only contain the edges and key/value pairs to the
1053 /// right of this handle.
1054 /// - The key and value pointed to by this handle and extracted.
1055 /// - All the edges and key/value pairs to the right of this handle are put into
1056 /// a newly allocated node.
1057 pub fn split(mut self) -> (NodeRef<marker::Mut<'a>, K, V, marker::Internal>, K, V, Root<K, V>) {
1059 let mut new_node = Box::new(InternalNode::new());
1061 let k = ptr::read(self.node.keys().get_unchecked(self.idx));
1062 let v = ptr::read(self.node.vals().get_unchecked(self.idx));
1064 let height = self.node.height;
1065 let new_len = self.node.len() - self.idx - 1;
1067 ptr::copy_nonoverlapping(
1068 self.node.keys().as_ptr().add(self.idx + 1),
1069 new_node.data.keys.as_mut_ptr() as *mut K,
1072 ptr::copy_nonoverlapping(
1073 self.node.vals().as_ptr().add(self.idx + 1),
1074 new_node.data.vals.as_mut_ptr() as *mut V,
1077 ptr::copy_nonoverlapping(
1078 self.node.as_internal().edges.as_ptr().add(self.idx + 1),
1079 new_node.edges.as_mut_ptr(),
1083 (*self.node.as_leaf_mut()).len = self.idx as u16;
1084 new_node.data.len = new_len as u16;
1086 let mut new_root = Root { node: BoxedNode::from_internal(new_node), height };
1088 for i in 0..(new_len + 1) {
1089 Handle::new_edge(new_root.as_mut().cast_unchecked(), i).correct_parent_link();
1092 (self.node, k, v, new_root)
1096 /// Returns `true` if it is valid to call `.merge()`, i.e., whether there is enough room in
1097 /// a node to hold the combination of the nodes to the left and right of this handle along
1098 /// with the key/value pair at this handle.
1099 pub fn can_merge(&self) -> bool {
1100 (self.reborrow().left_edge().descend().len()
1101 + self.reborrow().right_edge().descend().len()
1106 /// Combines the node immediately to the left of this handle, the key/value pair pointed
1107 /// to by this handle, and the node immediately to the right of this handle into one new
1108 /// child of the underlying node, returning an edge referencing that new child.
1110 /// Assumes that this edge `.can_merge()`.
1113 ) -> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::Edge> {
1114 let self1 = unsafe { ptr::read(&self) };
1115 let self2 = unsafe { ptr::read(&self) };
1116 let mut left_node = self1.left_edge().descend();
1117 let left_len = left_node.len();
1118 let mut right_node = self2.right_edge().descend();
1119 let right_len = right_node.len();
1121 // necessary for correctness, but in a private module
1122 assert!(left_len + right_len < CAPACITY);
1126 left_node.keys_mut().get_unchecked_mut(left_len),
1127 slice_remove(self.node.keys_mut(), self.idx),
1129 ptr::copy_nonoverlapping(
1130 right_node.keys().as_ptr(),
1131 left_node.keys_mut().as_mut_ptr().add(left_len + 1),
1135 left_node.vals_mut().get_unchecked_mut(left_len),
1136 slice_remove(self.node.vals_mut(), self.idx),
1138 ptr::copy_nonoverlapping(
1139 right_node.vals().as_ptr(),
1140 left_node.vals_mut().as_mut_ptr().add(left_len + 1),
1144 slice_remove(&mut self.node.as_internal_mut().edges, self.idx + 1);
1145 for i in self.idx + 1..self.node.len() {
1146 Handle::new_edge(self.node.reborrow_mut(), i).correct_parent_link();
1148 (*self.node.as_leaf_mut()).len -= 1;
1150 (*left_node.as_leaf_mut()).len += right_len as u16 + 1;
1152 let layout = if self.node.height > 1 {
1153 ptr::copy_nonoverlapping(
1154 right_node.cast_unchecked().as_internal().edges.as_ptr(),
1164 for i in left_len + 1..left_len + right_len + 2 {
1165 Handle::new_edge(left_node.cast_unchecked().reborrow_mut(), i)
1166 .correct_parent_link();
1169 Layout::new::<InternalNode<K, V>>()
1171 Layout::new::<LeafNode<K, V>>()
1173 Global.dealloc(right_node.node.cast(), layout);
1175 Handle::new_edge(self.node, self.idx)
1179 /// This removes a key/value pair from the left child and places it in the key/value storage
1180 /// pointed to by this handle while pushing the old key/value pair of this handle into the right
1182 pub fn steal_left(&mut self) {
1184 let (k, v, edge) = self.reborrow_mut().left_edge().descend().pop();
1186 let k = mem::replace(self.reborrow_mut().into_kv_mut().0, k);
1187 let v = mem::replace(self.reborrow_mut().into_kv_mut().1, v);
1189 match self.reborrow_mut().right_edge().descend().force() {
1190 ForceResult::Leaf(mut leaf) => leaf.push_front(k, v),
1191 ForceResult::Internal(mut internal) => internal.push_front(k, v, edge.unwrap()),
1196 /// This removes a key/value pair from the right child and places it in the key/value storage
1197 /// pointed to by this handle while pushing the old key/value pair of this handle into the left
1199 pub fn steal_right(&mut self) {
1201 let (k, v, edge) = self.reborrow_mut().right_edge().descend().pop_front();
1203 let k = mem::replace(self.reborrow_mut().into_kv_mut().0, k);
1204 let v = mem::replace(self.reborrow_mut().into_kv_mut().1, v);
1206 match self.reborrow_mut().left_edge().descend().force() {
1207 ForceResult::Leaf(mut leaf) => leaf.push(k, v),
1208 ForceResult::Internal(mut internal) => internal.push(k, v, edge.unwrap()),
1213 /// This does stealing similar to `steal_left` but steals multiple elements at once.
1214 pub fn bulk_steal_left(&mut self, count: usize) {
1216 let mut left_node = ptr::read(self).left_edge().descend();
1217 let left_len = left_node.len();
1218 let mut right_node = ptr::read(self).right_edge().descend();
1219 let right_len = right_node.len();
1221 // Make sure that we may steal safely.
1222 assert!(right_len + count <= CAPACITY);
1223 assert!(left_len >= count);
1225 let new_left_len = left_len - count;
1229 let left_kv = left_node.reborrow_mut().into_kv_pointers_mut();
1230 let right_kv = right_node.reborrow_mut().into_kv_pointers_mut();
1232 let kv = self.reborrow_mut().into_kv_mut();
1233 (kv.0 as *mut K, kv.1 as *mut V)
1236 // Make room for stolen elements in the right child.
1237 ptr::copy(right_kv.0, right_kv.0.add(count), right_len);
1238 ptr::copy(right_kv.1, right_kv.1.add(count), right_len);
1240 // Move elements from the left child to the right one.
1241 move_kv(left_kv, new_left_len + 1, right_kv, 0, count - 1);
1243 // Move parent's key/value pair to the right child.
1244 move_kv(parent_kv, 0, right_kv, count - 1, 1);
1246 // Move the left-most stolen pair to the parent.
1247 move_kv(left_kv, new_left_len, parent_kv, 0, 1);
1250 (*left_node.reborrow_mut().as_leaf_mut()).len -= count as u16;
1251 (*right_node.reborrow_mut().as_leaf_mut()).len += count as u16;
1253 match (left_node.force(), right_node.force()) {
1254 (ForceResult::Internal(left), ForceResult::Internal(mut right)) => {
1255 // Make room for stolen edges.
1256 let right_edges = right.reborrow_mut().as_internal_mut().edges.as_mut_ptr();
1257 ptr::copy(right_edges, right_edges.add(count), right_len + 1);
1258 right.correct_childrens_parent_links(count, count + right_len + 1);
1260 move_edges(left, new_left_len + 1, right, 0, count);
1262 (ForceResult::Leaf(_), ForceResult::Leaf(_)) => {}
1270 /// The symmetric clone of `bulk_steal_left`.
1271 pub fn bulk_steal_right(&mut self, count: usize) {
1273 let mut left_node = ptr::read(self).left_edge().descend();
1274 let left_len = left_node.len();
1275 let mut right_node = ptr::read(self).right_edge().descend();
1276 let right_len = right_node.len();
1278 // Make sure that we may steal safely.
1279 assert!(left_len + count <= CAPACITY);
1280 assert!(right_len >= count);
1282 let new_right_len = right_len - count;
1286 let left_kv = left_node.reborrow_mut().into_kv_pointers_mut();
1287 let right_kv = right_node.reborrow_mut().into_kv_pointers_mut();
1289 let kv = self.reborrow_mut().into_kv_mut();
1290 (kv.0 as *mut K, kv.1 as *mut V)
1293 // Move parent's key/value pair to the left child.
1294 move_kv(parent_kv, 0, left_kv, left_len, 1);
1296 // Move elements from the right child to the left one.
1297 move_kv(right_kv, 0, left_kv, left_len + 1, count - 1);
1299 // Move the right-most stolen pair to the parent.
1300 move_kv(right_kv, count - 1, parent_kv, 0, 1);
1302 // Fix right indexing
1303 ptr::copy(right_kv.0.add(count), right_kv.0, new_right_len);
1304 ptr::copy(right_kv.1.add(count), right_kv.1, new_right_len);
1307 (*left_node.reborrow_mut().as_leaf_mut()).len += count as u16;
1308 (*right_node.reborrow_mut().as_leaf_mut()).len -= count as u16;
1310 match (left_node.force(), right_node.force()) {
1311 (ForceResult::Internal(left), ForceResult::Internal(mut right)) => {
1312 move_edges(right.reborrow_mut(), 0, left, left_len + 1, count);
1314 // Fix right indexing.
1315 let right_edges = right.reborrow_mut().as_internal_mut().edges.as_mut_ptr();
1316 ptr::copy(right_edges.add(count), right_edges, new_right_len + 1);
1317 right.correct_childrens_parent_links(0, new_right_len + 1);
1319 (ForceResult::Leaf(_), ForceResult::Leaf(_)) => {}
1328 unsafe fn move_kv<K, V>(
1329 source: (*mut K, *mut V),
1330 source_offset: usize,
1331 dest: (*mut K, *mut V),
1336 ptr::copy_nonoverlapping(source.0.add(source_offset), dest.0.add(dest_offset), count);
1337 ptr::copy_nonoverlapping(source.1.add(source_offset), dest.1.add(dest_offset), count);
1341 // Source and destination must have the same height.
1342 unsafe fn move_edges<K, V>(
1343 mut source: NodeRef<marker::Mut<'_>, K, V, marker::Internal>,
1344 source_offset: usize,
1345 mut dest: NodeRef<marker::Mut<'_>, K, V, marker::Internal>,
1349 let source_ptr = source.as_internal_mut().edges.as_mut_ptr();
1350 let dest_ptr = dest.as_internal_mut().edges.as_mut_ptr();
1352 ptr::copy_nonoverlapping(source_ptr.add(source_offset), dest_ptr.add(dest_offset), count);
1353 dest.correct_childrens_parent_links(dest_offset, dest_offset + count);
1357 impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge> {
1358 pub fn forget_node_type(
1360 ) -> Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, marker::Edge> {
1361 unsafe { Handle::new_edge(self.node.forget_type(), self.idx) }
1365 impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V, marker::Internal>, 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::Leaf>, marker::KV> {
1374 pub fn forget_node_type(
1376 ) -> Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, marker::KV> {
1377 unsafe { Handle::new_kv(self.node.forget_type(), self.idx) }
1381 impl<BorrowType, K, V, HandleType>
1382 Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, HandleType>
1384 /// Checks whether the underlying node is an `Internal` node or a `Leaf` node.
1388 Handle<NodeRef<BorrowType, K, V, marker::Leaf>, HandleType>,
1389 Handle<NodeRef<BorrowType, K, V, marker::Internal>, HandleType>,
1391 match self.node.force() {
1392 ForceResult::Leaf(node) => {
1393 ForceResult::Leaf(Handle { node, idx: self.idx, _marker: PhantomData })
1395 ForceResult::Internal(node) => {
1396 ForceResult::Internal(Handle { node, idx: self.idx, _marker: PhantomData })
1402 impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, marker::Edge> {
1403 /// Move the suffix after `self` from one node to another one. `right` must be empty.
1404 /// The first edge of `right` remains unchanged.
1407 right: &mut NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>,
1410 let left_new_len = self.idx;
1411 let mut left_node = self.reborrow_mut().into_node();
1413 let right_new_len = left_node.len() - left_new_len;
1414 let mut right_node = right.reborrow_mut();
1416 assert!(right_node.len() == 0);
1417 assert!(left_node.height == right_node.height);
1419 if right_new_len > 0 {
1420 let left_kv = left_node.reborrow_mut().into_kv_pointers_mut();
1421 let right_kv = right_node.reborrow_mut().into_kv_pointers_mut();
1423 move_kv(left_kv, left_new_len, right_kv, 0, right_new_len);
1425 (*left_node.reborrow_mut().as_leaf_mut()).len = left_new_len as u16;
1426 (*right_node.reborrow_mut().as_leaf_mut()).len = right_new_len as u16;
1428 match (left_node.force(), right_node.force()) {
1429 (ForceResult::Internal(left), ForceResult::Internal(right)) => {
1430 move_edges(left, left_new_len + 1, right, 1, right_new_len);
1432 (ForceResult::Leaf(_), ForceResult::Leaf(_)) => {}
1442 pub enum ForceResult<Leaf, Internal> {
1447 pub enum InsertResult<'a, K, V, Type> {
1448 Fit(Handle<NodeRef<marker::Mut<'a>, K, V, Type>, marker::KV>),
1449 Split(NodeRef<marker::Mut<'a>, K, V, Type>, K, V, Root<K, V>),
1453 use core::marker::PhantomData;
1456 pub enum Internal {}
1457 pub enum LeafOrInternal {}
1460 pub struct Immut<'a>(PhantomData<&'a ()>);
1461 pub struct Mut<'a>(PhantomData<&'a mut ()>);
1467 unsafe fn slice_insert<T>(slice: &mut [T], idx: usize, val: T) {
1469 ptr::copy(slice.as_ptr().add(idx), slice.as_mut_ptr().add(idx + 1), slice.len() - idx);
1470 ptr::write(slice.get_unchecked_mut(idx), val);
1474 unsafe fn slice_remove<T>(slice: &mut [T], idx: usize) -> T {
1476 let ret = ptr::read(slice.get_unchecked(idx));
1477 ptr::copy(slice.as_ptr().add(idx + 1), slice.as_mut_ptr().add(idx), slice.len() - idx - 1);