cl_structures/tree/
tree_ref.rs

1//! An element in a [Tree](super::Tree)
2///
3/// Contains a niche, and as such, [`Option<TreeRef<T>>`] is free :D
4use std::{marker::PhantomData, num::NonZeroUsize};
5
6/// An element of in a [Tree](super::Tree).
7//? The index of the node is stored as a [NonZeroUsize] for space savings
8//? Making Refs T-specific helps the user keep track of which Refs belong to which trees.
9//? This isn't bulletproof, of course, but it'll keep Ref<Foo> from being used on Tree<Bar>
10pub struct Ref<T: ?Sized>(NonZeroUsize, PhantomData<T>);
11
12impl<T: ?Sized> Ref<T> {
13    /// Constructs a new [Ref] with the given index
14    pub fn new_unchecked(index: usize) -> Self {
15        // Safety: index cannot be zero because we use saturating addition on unsigned type.
16        Self(
17            unsafe { NonZeroUsize::new_unchecked(index.saturating_add(1)) },
18            PhantomData,
19        )
20    }
21}
22
23impl<T: ?Sized> From<Ref<T>> for usize {
24    fn from(value: Ref<T>) -> Self {
25        usize::from(value.0) - 1
26    }
27}
28
29/* --- implementations of derivable traits, because we don't need bounds here --- */
30
31impl<T: ?Sized> std::fmt::Debug for Ref<T> {
32    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
33        f.debug_tuple("TreeRef").field(&self.0).finish()
34    }
35}
36
37impl<T: ?Sized> std::hash::Hash for Ref<T> {
38    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
39        self.0.hash(state);
40        self.1.hash(state);
41    }
42}
43
44impl<T: ?Sized> PartialEq for Ref<T> {
45    fn eq(&self, other: &Self) -> bool {
46        self.0 == other.0 && self.1 == other.1
47    }
48}
49
50impl<T: ?Sized> Eq for Ref<T> {}
51
52impl<T: ?Sized> PartialOrd for Ref<T> {
53    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
54        Some(self.cmp(other))
55    }
56}
57
58impl<T: ?Sized> Ord for Ref<T> {
59    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
60        self.0.cmp(&other.0)
61    }
62}
63
64impl<T: ?Sized> Clone for Ref<T> {
65    fn clone(&self) -> Self {
66        *self
67    }
68}
69
70impl<T: ?Sized> Copy for Ref<T> {}
cl_structures/tree/tree_ref.rs

cl_structures/tree/
tree_ref.rs
