71 lines
2.0 KiB
Rust
71 lines
2.0 KiB
Rust
//! An element in a [Tree](super::Tree)
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///
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/// Contains a niche, and as such, [`Option<TreeRef<T>>`] is free :D
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use std::{marker::PhantomData, num::NonZeroUsize};
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/// An element of in a [Tree](super::Tree).
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//? The index of the node is stored as a [NonZeroUsize] for space savings
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//? Making Refs T-specific helps the user keep track of which Refs belong to which trees.
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//? This isn't bulletproof, of course, but it'll keep Ref<Foo> from being used on Tree<Bar>
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pub struct Ref<T: ?Sized>(NonZeroUsize, PhantomData<T>);
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impl<T: ?Sized> Ref<T> {
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/// Constructs a new [Ref] with the given index
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pub fn new_unchecked(index: usize) -> Self {
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// Safety: index cannot be zero because we use saturating addition on unsigned type.
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Self(
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unsafe { NonZeroUsize::new_unchecked(index.saturating_add(1)) },
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PhantomData,
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)
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}
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}
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impl<T: ?Sized> From<Ref<T>> for usize {
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fn from(value: Ref<T>) -> Self {
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usize::from(value.0) - 1
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}
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}
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/* --- implementations of derivable traits, because we don't need bounds here --- */
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impl<T: ?Sized> std::fmt::Debug for Ref<T> {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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f.debug_tuple("TreeRef").field(&self.0).finish()
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}
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}
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impl<T: ?Sized> std::hash::Hash for Ref<T> {
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fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
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self.0.hash(state);
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self.1.hash(state);
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}
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}
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impl<T: ?Sized> PartialEq for Ref<T> {
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fn eq(&self, other: &Self) -> bool {
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self.0 == other.0 && self.1 == other.1
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}
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}
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impl<T: ?Sized> Eq for Ref<T> {}
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impl<T: ?Sized> PartialOrd for Ref<T> {
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fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
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Some(self.cmp(other))
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}
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}
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impl<T: ?Sized> Ord for Ref<T> {
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fn cmp(&self, other: &Self) -> std::cmp::Ordering {
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self.0.cmp(&other.0)
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}
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}
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impl<T: ?Sized> Clone for Ref<T> {
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fn clone(&self) -> Self {
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*self
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}
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}
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impl<T: ?Sized> Copy for Ref<T> {}
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