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use std::borrow::Borrow;
use std::collections::HashMap;
use std::hash::Hash;
use super::{
policy::{EvictionPolicy, InsertionPolicy},
Cache,
};
#[derive(Default)]
pub struct ModularCache<K, V, IP, EP>
where
K: Hash + Eq,
IP: Default + InsertionPolicy<K>,
EP: Default + EvictionPolicy<K>,
{
data: HashMap<K, V>,
insertion_policy: IP,
eviction_policy: EP,
maximum_size: usize,
}
impl<K, V, IP, EP> ModularCache<K, V, IP, EP>
where
K: Hash + Eq + std::fmt::Debug,
IP: Default + InsertionPolicy<K>,
EP: Default + EvictionPolicy<K>,
{
pub fn new(maximum_size: usize) -> Self {
Self {
data: HashMap::new(),
insertion_policy: IP::default(),
eviction_policy: EP::default(),
maximum_size,
}
}
}
impl<K, V, IP, EP> Cache for ModularCache<K, V, IP, EP>
where
K: Hash + Eq + std::fmt::Debug,
IP: Default + InsertionPolicy<K>,
EP: Default + EvictionPolicy<K>,
{
type Key = K;
type Value = V;
fn insert(&mut self, key: K, value: V) -> (bool, Option<V>) {
let is_in_cache = self.data.contains_key(&key);
if is_in_cache {
self.eviction_policy.on_update(&key);
self.data.insert(key, value);
return (true, None);
} else if self.data.len() < self.maximum_size {
if self.insertion_policy.should_add(&key) {
self.eviction_policy.on_insert(&key);
self.data.insert(key, value);
return (true, None);
}
} else {
let victim_key = self.eviction_policy.get_victim().unwrap();
if self.insertion_policy.should_replace(&key, &victim_key) {
self.eviction_policy.on_eviction(&victim_key);
let evicted = self.data.remove(&victim_key).unwrap();
self.eviction_policy.on_insert(&key);
self.data.insert(key, value);
return (true, Some(evicted));
}
}
(false, None)
}
fn get<Q: ?Sized>(&mut self, key: &Q) -> Option<&V>
where
K: Borrow<Q>,
Q: Hash + Eq,
{
match self.data.get(key) {
Some(d) => {
self.eviction_policy.on_cache_hit(key);
self.insertion_policy.on_cache_hit(key);
Some(d)
}
None => {
self.insertion_policy.on_cache_miss(key);
None
}
}
}
fn invalidate<Q: ?Sized>(&mut self, key: &Q)
where
K: Borrow<Q>,
Q: Hash + Eq,
{
self.data.remove(key);
self.insertion_policy.invalidate(key);
self.eviction_policy.invalidate(key);
}
fn clear(&mut self) {
self.data.clear();
}
}