forked from slonk/bingus-blog
51 lines
1.3 KiB
Rust
51 lines
1.3 KiB
Rust
use std::hash::{DefaultHasher, Hash, Hasher};
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use std::marker::PhantomData;
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use std::sync::Arc;
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pub struct HashArcStore<T, Lookup>
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where
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Lookup: Hash,
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{
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inner: Option<Arc<T>>,
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hash: Option<u64>,
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_phantom: PhantomData<Lookup>,
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}
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impl<T, Lookup> HashArcStore<T, Lookup>
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where
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Lookup: Hash,
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{
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pub fn new() -> Self {
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Self {
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inner: None,
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hash: None,
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_phantom: PhantomData,
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}
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}
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/*pub fn get(&self, key: &Lookup) -> Option<Arc<T>> {
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self.hash.and_then(|hash| {
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let mut h = DefaultHasher::new();
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key.hash(&mut h);
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if hash == h.finish() {
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self.inner.clone()
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} else {
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None
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}
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})
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}*/
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pub fn get_or_init(&mut self, key: &Lookup, init: impl Fn(&Lookup) -> Arc<T>) -> Arc<T> {
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let mut h = DefaultHasher::new();
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key.hash(&mut h);
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let hash = h.finish();
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if !self.hash.is_some_and(|inner_hash| inner_hash == hash) {
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let mut h = DefaultHasher::new();
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key.hash(&mut h);
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self.inner = Some(init(key));
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self.hash = Some(h.finish());
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}
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// safety: please.
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unsafe { self.inner.as_ref().unwrap_unchecked().clone() }
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}
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}
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