zvault/src/util/lru_cache.rs

54 lines
1.3 KiB
Rust
Raw Normal View History

2017-03-10 11:43:32 +00:00
use std::hash::Hash;
use std::collections::HashMap;
pub struct LruCache<K, V> {
items: HashMap<K, (V, u64)>,
min_size: usize,
max_size: usize,
next: u64
}
impl<K: Eq+Hash, V> LruCache<K, V> {
#[inline]
pub fn new(min_size: usize, max_size: usize) -> Self {
LruCache {
items: HashMap::default(),
min_size: min_size,
max_size: max_size,
next: 0
}
}
#[inline]
pub fn put(&mut self, key: K, value: V) {
self.items.insert(key, (value, self.next));
self.next += 1;
if self.items.len() > self.max_size {
self.shrink()
}
}
#[inline]
pub fn get(&mut self, key: &K) -> Option<&V> {
if let Some(&mut (ref item, ref mut n)) = self.items.get_mut(key) {
*n = self.next;
self.next += 1;
Some(item)
} else {
None
}
}
#[inline]
fn shrink(&mut self) {
let mut tags: Vec<u64> = self.items.values().map(|&(_, n)| n).collect();
tags.sort();
2017-03-15 20:53:05 +00:00
let min = tags[tags.len()-self.min_size];
2017-03-10 11:43:32 +00:00
let mut new = HashMap::with_capacity(self.min_size);
2017-03-15 20:53:05 +00:00
new.extend(self.items.drain().filter(|&(_,(_, n))| n>=min));
2017-03-10 11:43:32 +00:00
self.items = new;
}
}