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use std::any::Any;
use std::collections::hash_map::{DefaultHasher, HashMap};
use std::hash::{Hash, Hasher};
pub trait Cache {
fn save<K, T>(&mut self, key: K, value: T) where T: Any + 'static, K: CacheKey<Target = T>;
fn get<K, T>(&self, key: &K) -> Option<&T> where T: Any + 'static, K: CacheKey<Target = T>;
fn remove<K, T>(&mut self, key: &K) -> Option<T> where T: Any + 'static, K: CacheKey<Target = T>;
fn clear(&mut self);
}
pub trait CacheKey: Hash {
type Target;
}
pub struct HashCache {
items: HashMap<u64, Box<Any>>
}
impl HashCache {
pub fn new() -> Self {
HashCache {
items: HashMap::new()
}
}
}
impl Default for HashCache {
fn default() -> Self {
Self::new()
}
}
impl Cache for HashCache {
fn save<K, T>(&mut self, key: K, value: T) where T: Any + 'static, K: CacheKey<Target = T> {
let mut hasher = DefaultHasher::new();
key.hash(&mut hasher);
self.items.insert(hasher.finish(), Box::new(value));
}
fn get<K, T>(&self, key: &K) -> Option<&T> where T: Any + 'static, K: CacheKey<Target = T> {
let mut hasher = DefaultHasher::new();
key.hash(&mut hasher);
self.items.get(&hasher.finish()).and_then(|a| { a.downcast_ref::<T>() })
}
fn remove<K, T>(&mut self, key: &K) -> Option<T> where T: Any + 'static, K: CacheKey<Target = T> {
let mut hasher = DefaultHasher::new();
key.hash(&mut hasher);
self.items.remove(&hasher.finish()).and_then(|anybox| anybox.downcast().ok()).map(|b| *b)
}
fn clear(&mut self) {
self.items.clear();
}
}
pub struct DummyCache;
impl DummyCache {
pub fn new() -> Self {
DummyCache
}
}
impl Default for DummyCache {
fn default() -> Self {
DummyCache
}
}
impl Cache for DummyCache {
fn save<K, T>(&mut self, _: K, _: T) where T: Any + 'static, K: CacheKey<Target = T> {
}
fn get<K, T>(&self, _: &K) -> Option<&T> where T: Any + 'static, K: CacheKey<Target = T> {
None
}
fn remove<K, T>(&mut self, _: &K) -> Option<T> where T: Any + 'static, K: CacheKey<Target = T> {
None
}
fn clear(&mut self) {
}
}