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//! A utility to store objects by identity, which deduplicates them while avoiding lifetimes.
//!
//! We chose to use hashing/identity over pointers as it's possible that different objects end up in the same memory location,
//! which would create obscure bugs. The same could happen with hash collisions, but they these are designed to be less likely.
use std::collections::btree_map::Entry;
use std::collections::hash_map::DefaultHasher;
use std::collections::BTreeMap;
use std::hash::{Hash, Hasher};
pub(crate) type RefMapKey = u64;
pub(crate) struct RefMap<T>(BTreeMap<RefMapKey, T>);
impl<T> Default for RefMap<T> {
fn default() -> Self {
RefMap(Default::default())
}
}
impl<T> RefMap<T>
where
T: Hash + Clone,
{
pub(crate) fn insert(&mut self, value: &T) -> RefMapKey {
let mut s = DefaultHasher::new();
value.hash(&mut s);
let key = s.finish();
match self.0.entry(key) {
Entry::Vacant(e) => {
e.insert(value.clone());
key
}
Entry::Occupied(_) => key,
}
}
pub(crate) fn insert_owned(&mut self, value: T) -> RefMapKey {
let mut s = DefaultHasher::new();
value.hash(&mut s);
let key = s.finish();
match self.0.entry(key) {
Entry::Vacant(e) => {
e.insert(value);
key
}
Entry::Occupied(_) => key,
}
}
pub(crate) fn resolve(&self, key: RefMapKey) -> Option<&T> {
self.0.get(&key)
}
}
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