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refactor(arena): use slice::as_ptr_range in Arena::get_node_id #108

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merged 2 commits into from
Jun 25, 2024
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refactor(arena): use slice::as_ptr_range in Arena::get_node_id #108

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e948a18
refactor(arena): use `slice::as_ptr_range` in `Arena::get_node_id`
alexmozaidze Jun 21, 2024
f826828
style(arena): reformat the code
alexmozaidze Jun 24, 2024
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26 changes: 15 additions & 11 deletions src/arena.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@ use alloc::vec::Vec;

#[cfg(not(feature = "std"))]
use core::{
mem,
num::NonZeroUsize,
ops::{Index, IndexMut},
};
Expand All @@ -17,6 +18,7 @@ use serde::{Deserialize, Serialize};

#[cfg(feature = "std")]
use std::{
mem,
num::NonZeroUsize,
ops::{Index, IndexMut},
};
Expand Down Expand Up @@ -79,18 +81,20 @@ impl<T> Arena<T> {
/// assert_eq!(*arena[node_id].get(), "foo");
/// ```
pub fn get_node_id(&self, node: &Node<T>) -> Option<NodeId> {
// self.nodes.as_ptr_range() is not stable until rust 1.48
let start = self.nodes.as_ptr() as usize;
let end = start + self.nodes.len() * core::mem::size_of::<Node<T>>();
let p = node as *const Node<T> as usize;
if (start..end).contains(&p) {
let node_id = (p - start) / core::mem::size_of::<Node<T>>();
NonZeroUsize::new(node_id.wrapping_add(1)).map(|node_id_non_zero| {
NodeId::from_non_zero_usize(node_id_non_zero, self.nodes[node_id].stamp)
})
} else {
None
let nodes_range = self.nodes.as_ptr_range();
let p = node as *const Node<T>;

if !nodes_range.contains(&p) {
return None;
}

let node_index = (p as usize - nodes_range.start as usize) / mem::size_of::<Node<T>>();
let node_id = NonZeroUsize::new(node_index.wrapping_add(1))?;

Some(NodeId::from_non_zero_usize(
node_id,
self.nodes[node_index].stamp,
))
}

/// Retrieves the `NodeId` corresponding to the `Node` at `index` in the `Arena`, if it exists.
Expand Down
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