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//! A simple id-based arena, similar to https://github.com/fitzgen/id-arena.
//! We use our own version for more compact id's and to allow inherent impls
//! on Ids.
use std::{
fmt,
hash::{Hash, Hasher},
marker::PhantomData,
};
pub(crate) struct Id<T> {
idx: u32,
_ty: PhantomData<fn() -> T>,
}
impl<T> fmt::Debug for Id<T> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.debug_tuple("Id").field(&self.idx).finish()
}
}
impl<T> Copy for Id<T> {}
impl<T> Clone for Id<T> {
fn clone(&self) -> Id<T> {
*self
}
}
impl<T> PartialEq for Id<T> {
fn eq(&self, other: &Id<T>) -> bool {
self.idx == other.idx
}
}
impl<T> Eq for Id<T> {}
impl<T> Hash for Id<T> {
fn hash<H: Hasher>(&self, h: &mut H) {
self.idx.hash(h);
}
}
#[derive(Debug, PartialEq, Eq)]
pub(crate) struct ArenaBehavior<T> {
_ty: PhantomData<T>,
}
impl<T> id_arena::ArenaBehavior for ArenaBehavior<T> {
type Id = Id<T>;
fn new_arena_id() -> usize {
0
}
fn new_id(_arena_id: usize, index: usize) -> Id<T> {
Id {
idx: index as u32,
_ty: PhantomData,
}
}
fn index(id: Id<T>) -> usize {
id.idx as usize
}
fn arena_id(_id: Id<T>) -> usize {
0
}
}
pub(crate) type Arena<T> = id_arena::Arena<T, ArenaBehavior<T>>;
|
