geometry_rtree/
node.rs

1//! Tree nodes: leaves hold values, branches hold child subtrees.
2//!
3//! Mirrors `index/detail/rtree/node/variant.hpp`. Boost dispatches over
4//! its node variant with a runtime visitor; the port uses a plain enum
5//! and lets `match` be the visitor — the same shape, no vtable.
6
7use alloc::vec::Vec;
8
9use crate::bounds::{Bounds, union_all};
10use crate::indexable::Indexable;
11
12/// One node of the tree.
13///
14/// A [`Node::Leaf`] stores the indexed values directly; a
15/// [`Node::Branch`] stores `(child_bounds, child_node)` pairs. Mirrors
16/// the leaf / internal split of Boost's rtree node variant.
17#[derive(Debug)]
18pub enum Node<T> {
19    /// Values at the bottom of the tree.
20    Leaf(Vec<T>),
21    /// Child subtrees, each paired with its bounding box.
22    Branch(Vec<(Bounds, Node<T>)>),
23}
24
25impl<T: Indexable> Node<T> {
26    /// The bounding box covering everything in this node, or `None` for
27    /// an empty node.
28    #[must_use]
29    pub fn bounds(&self) -> Option<Bounds> {
30        match self {
31            Node::Leaf(values) => {
32                if values.is_empty() {
33                    None
34                } else {
35                    let boxes: Vec<Bounds> = values.iter().map(Indexable::bounds).collect();
36                    Some(union_all(&boxes))
37                }
38            }
39            Node::Branch(children) => {
40                if children.is_empty() {
41                    None
42                } else {
43                    let boxes: Vec<Bounds> = children.iter().map(|(b, _)| *b).collect();
44                    Some(union_all(&boxes))
45                }
46            }
47        }
48    }
49
50    /// Number of immediate entries (values in a leaf, children in a
51    /// branch).
52    #[must_use]
53    pub fn entry_count(&self) -> usize {
54        match self {
55            Node::Leaf(values) => values.len(),
56            Node::Branch(children) => children.len(),
57        }
58    }
59
60    /// Total number of leaf values in this subtree.
61    #[must_use]
62    pub fn value_count(&self) -> usize {
63        match self {
64            Node::Leaf(values) => values.len(),
65            Node::Branch(children) => children.iter().map(|(_, child)| child.value_count()).sum(),
66        }
67    }
68
69    /// Height of this subtree: a leaf is height 1.
70    #[must_use]
71    pub fn height(&self) -> usize {
72        match self {
73            Node::Leaf(_) => 1,
74            Node::Branch(children) => {
75                1 + children
76                    .iter()
77                    .map(|(_, child)| child.height())
78                    .max()
79                    .unwrap_or(0)
80            }
81        }
82    }
83}
84
85#[cfg(test)]
86mod tests {
87    use super::Node;
88    use crate::bounds::Bounds;
89
90    #[test]
91    fn leaf_bounds_union_of_values() {
92        let leaf: Node<Bounds> = Node::Leaf(alloc::vec![
93            Bounds::point([0.0, 0.0]),
94            Bounds::point([2.0, 3.0]),
95        ]);
96        assert_eq!(leaf.bounds(), Some(Bounds::new([0.0, 0.0], [2.0, 3.0])));
97        assert_eq!(leaf.entry_count(), 2);
98        assert_eq!(leaf.height(), 1);
99    }
100
101    #[test]
102    fn branch_bounds_and_height() {
103        let leaf_a: Node<Bounds> = Node::Leaf(alloc::vec![Bounds::point([0.0, 0.0])]);
104        let leaf_b: Node<Bounds> = Node::Leaf(alloc::vec![Bounds::point([5.0, 5.0])]);
105        let branch: Node<Bounds> = Node::Branch(alloc::vec![
106            (leaf_a.bounds().unwrap(), leaf_a),
107            (leaf_b.bounds().unwrap(), leaf_b),
108        ]);
109        assert_eq!(branch.bounds(), Some(Bounds::new([0.0, 0.0], [5.0, 5.0])));
110        assert_eq!(branch.height(), 2);
111        assert_eq!(branch.value_count(), 2);
112    }
113
114    #[test]
115    fn empty_leaf_has_no_bounds() {
116        let leaf: Node<Bounds> = Node::Leaf(alloc::vec![]);
117        assert_eq!(leaf.bounds(), None);
118    }
119}
geometry_rtree/node.rs

geometry_rtree/
node.rs
