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Commit | Line | Data |
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29967ef6 | 1 | use super::map::MIN_LEN; |
fc512014 | 2 | use super::node::{marker, ForceResult::*, Handle, LeftOrRight::*, NodeRef}; |
29967ef6 XL |
3 | |
4 | impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, marker::KV> { | |
fc512014 XL |
5 | /// Removes a key-value pair from the tree, and returns that pair, as well as |
6 | /// the leaf edge corresponding to that former pair. It's possible this empties | |
7 | /// a root node that is internal, which the caller should pop from the map | |
8 | /// holding the tree. The caller should also decrement the map's length. | |
29967ef6 XL |
9 | pub fn remove_kv_tracking<F: FnOnce()>( |
10 | self, | |
11 | handle_emptied_internal_root: F, | |
12 | ) -> ((K, V), Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>) { | |
fc512014 XL |
13 | match self.force() { |
14 | Leaf(node) => node.remove_leaf_kv(handle_emptied_internal_root), | |
15 | Internal(node) => node.remove_internal_kv(handle_emptied_internal_root), | |
16 | } | |
17 | } | |
18 | } | |
29967ef6 | 19 | |
fc512014 XL |
20 | impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::KV> { |
21 | fn remove_leaf_kv<F: FnOnce()>( | |
22 | self, | |
23 | handle_emptied_internal_root: F, | |
24 | ) -> ((K, V), Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>) { | |
25 | let (old_kv, mut pos) = self.remove(); | |
26 | let len = pos.reborrow().into_node().len(); | |
27 | if len < MIN_LEN { | |
28 | let idx = pos.idx(); | |
29 | // We have to temporarily forget the child type, because there is no | |
30 | // distinct node type for the immediate parents of a leaf. | |
31 | let new_pos = match pos.into_node().forget_type().choose_parent_kv() { | |
32 | Ok(Left(left_parent_kv)) => { | |
33 | debug_assert!(left_parent_kv.right_child_len() == MIN_LEN - 1); | |
34 | if left_parent_kv.can_merge() { | |
5869c6ff | 35 | left_parent_kv.merge_tracking_child_edge(Right(idx)) |
29967ef6 | 36 | } else { |
fc512014 XL |
37 | debug_assert!(left_parent_kv.left_child_len() > MIN_LEN); |
38 | left_parent_kv.steal_left(idx) | |
29967ef6 XL |
39 | } |
40 | } | |
fc512014 XL |
41 | Ok(Right(right_parent_kv)) => { |
42 | debug_assert!(right_parent_kv.left_child_len() == MIN_LEN - 1); | |
43 | if right_parent_kv.can_merge() { | |
5869c6ff | 44 | right_parent_kv.merge_tracking_child_edge(Left(idx)) |
fc512014 XL |
45 | } else { |
46 | debug_assert!(right_parent_kv.right_child_len() > MIN_LEN); | |
47 | right_parent_kv.steal_right(idx) | |
29967ef6 | 48 | } |
29967ef6 | 49 | } |
fc512014 XL |
50 | Err(pos) => unsafe { Handle::new_edge(pos, idx) }, |
51 | }; | |
52 | // SAFETY: `new_pos` is the leaf we started from or a sibling. | |
53 | pos = unsafe { new_pos.cast_to_leaf_unchecked() }; | |
29967ef6 | 54 | |
fc512014 XL |
55 | // Only if we merged, the parent (if any) has shrunk, but skipping |
56 | // the following step otherwise does not pay off in benchmarks. | |
57 | // | |
58 | // SAFETY: We won't destroy or rearrange the leaf where `pos` is at | |
59 | // by handling its parent recursively; at worst we will destroy or | |
60 | // rearrange the parent through the grandparent, thus change the | |
61 | // link to the parent inside the leaf. | |
62 | if let Ok(parent) = unsafe { pos.reborrow_mut() }.into_node().ascend() { | |
6a06907d XL |
63 | if !parent.into_node().forget_type().fix_node_and_affected_ancestors() { |
64 | handle_emptied_internal_root(); | |
65 | } | |
fc512014 | 66 | } |
29967ef6 | 67 | } |
29967ef6 XL |
68 | (old_kv, pos) |
69 | } | |
70 | } | |
71 | ||
fc512014 XL |
72 | impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::KV> { |
73 | fn remove_internal_kv<F: FnOnce()>( | |
74 | self, | |
75 | handle_emptied_internal_root: F, | |
76 | ) -> ((K, V), Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>) { | |
77 | // Remove an adjacent KV from its leaf and then put it back in place of | |
78 | // the element we were asked to remove. Prefer the left adjacent KV, | |
79 | // for the reasons listed in `choose_parent_kv`. | |
80 | let left_leaf_kv = self.left_edge().descend().last_leaf_edge().left_kv(); | |
6a06907d | 81 | let left_leaf_kv = unsafe { left_leaf_kv.ok().unwrap_unchecked() }; |
fc512014 | 82 | let (left_kv, left_hole) = left_leaf_kv.remove_leaf_kv(handle_emptied_internal_root); |
29967ef6 | 83 | |
fc512014 XL |
84 | // The internal node may have been stolen from or merged. Go back right |
85 | // to find where the original KV ended up. | |
6a06907d | 86 | let mut internal = unsafe { left_hole.next_kv().ok().unwrap_unchecked() }; |
fc512014 XL |
87 | let old_kv = internal.replace_kv(left_kv.0, left_kv.1); |
88 | let pos = internal.next_leaf_edge(); | |
89 | (old_kv, pos) | |
90 | } | |
91 | } |