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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
use std::collections::HashMap;
use std::collections::hash_map::Entry::{Occupied, Vacant};
use std::collections::hash_state::DefaultState;
use rand::Rng;
use std::hash::{Hash, Hasher, SipHasher};
use std::iter::repeat;
use rand;
use std::slice::Iter;
use std::default::Default;
#[cfg(test)]
use std::cell::Cell;
pub struct HashCache<K, V> {
entries: HashMap<K, V, DefaultState<SipHasher>>,
}
impl<K, V> HashCache<K,V>
where K: Clone + PartialEq + Eq + Hash,
V: Clone,
{
pub fn new() -> HashCache<K,V> {
HashCache {
entries: HashMap::with_hash_state(<DefaultState<SipHasher> as Default>::default()),
}
}
pub fn insert(&mut self, key: K, value: V) {
self.entries.insert(key, value);
}
pub fn find(&self, key: &K) -> Option<V> {
match self.entries.get(key) {
Some(v) => Some(v.clone()),
None => None,
}
}
pub fn find_or_create<F>(&mut self, key: &K, blk: F) -> V where F: Fn(&K) -> V {
match self.entries.entry(key.clone()) {
Occupied(occupied) => {
(*occupied.get()).clone()
}
Vacant(vacant) => {
(*vacant.insert(blk(key))).clone()
}
}
}
pub fn evict_all(&mut self) {
self.entries.clear();
}
}
#[test]
fn test_hashcache() {
let mut cache: HashCache<usize, Cell<&str>> = HashCache::new();
cache.insert(1, Cell::new("one"));
assert!(cache.find(&1).is_some());
assert!(cache.find(&2).is_none());
cache.find_or_create(&2, |_v| { Cell::new("two") });
assert!(cache.find(&1).is_some());
assert!(cache.find(&2).is_some());
}
pub struct LRUCache<K, V> {
entries: Vec<(K, V)>,
cache_size: usize,
}
impl<K: Clone + PartialEq, V: Clone> LRUCache<K,V> {
pub fn new(size: usize) -> LRUCache<K, V> {
LRUCache {
entries: vec!(),
cache_size: size,
}
}
#[inline]
pub fn touch(&mut self, pos: usize) -> V {
let last_index = self.entries.len() - 1;
if pos != last_index {
let entry = self.entries.remove(pos);
self.entries.push(entry);
}
self.entries[last_index].1.clone()
}
pub fn iter<'a>(&'a self) -> Iter<'a,(K,V)> {
self.entries.iter()
}
pub fn insert(&mut self, key: K, val: V) {
if self.entries.len() == self.cache_size {
self.entries.remove(0);
}
self.entries.push((key, val));
}
pub fn find(&mut self, key: &K) -> Option<V> {
match self.entries.iter().position(|&(ref k, _)| key == k) {
Some(pos) => Some(self.touch(pos)),
None => None,
}
}
pub fn find_or_create<F>(&mut self, key: &K, blk: F) -> V where F: Fn(&K) -> V {
match self.entries.iter().position(|&(ref k, _)| *k == *key) {
Some(pos) => self.touch(pos),
None => {
let val = blk(key);
self.insert(key.clone(), val.clone());
val
}
}
}
pub fn evict_all(&mut self) {
self.entries.clear();
}
}
pub struct SimpleHashCache<K,V> {
entries: Vec<Option<(K,V)>>,
k0: u64,
k1: u64,
}
impl<K:Clone+Eq+Hash,V:Clone> SimpleHashCache<K,V> {
pub fn new(cache_size: usize) -> SimpleHashCache<K,V> {
let mut r = rand::thread_rng();
SimpleHashCache {
entries: repeat(None).take(cache_size).collect(),
k0: r.gen(),
k1: r.gen(),
}
}
#[inline]
fn to_bucket(&self, h: usize) -> usize {
h % self.entries.len()
}
#[inline]
fn bucket_for_key<Q:Hash>(&self, key: &Q) -> usize {
let mut hasher = SipHasher::new_with_keys(self.k0, self.k1);
key.hash(&mut hasher);
self.to_bucket(hasher.finish() as usize)
}
pub fn insert(&mut self, key: K, value: V) {
let bucket_index = self.bucket_for_key(&key);
self.entries[bucket_index] = Some((key, value));
}
pub fn find<Q>(&self, key: &Q) -> Option<V> where Q: PartialEq<K> + Hash + Eq {
let bucket_index = self.bucket_for_key(key);
match self.entries[bucket_index] {
Some((ref existing_key, ref value)) if key == existing_key => Some((*value).clone()),
_ => None,
}
}
pub fn find_or_create<F>(&mut self, key: &K, blk: F) -> V where F: Fn(&K) -> V {
match self.find(key) {
Some(value) => return value,
None => {}
}
let value = blk(key);
self.insert((*key).clone(), value.clone());
value
}
pub fn evict_all(&mut self) {
for slot in self.entries.iter_mut() {
*slot = None
}
}
}
#[test]
fn test_lru_cache() {
let one = Cell::new("one");
let two = Cell::new("two");
let three = Cell::new("three");
let four = Cell::new("four");
// Test normal insertion.
let mut cache: LRUCache<usize,Cell<&str>> = LRUCache::new(2); // (_, _) (cache is empty)
cache.insert(1, one); // (1, _)
cache.insert(2, two); // (1, 2)
cache.insert(3, three); // (2, 3)
assert!(cache.find(&1).is_none()); // (2, 3) (no change)
assert!(cache.find(&3).is_some()); // (2, 3)
assert!(cache.find(&2).is_some()); // (3, 2)
// Test that LRU works (this insertion should replace 3, not 2).
cache.insert(4, four); // (2, 4)
assert!(cache.find(&1).is_none()); // (2, 4) (no change)
assert!(cache.find(&2).is_some()); // (4, 2)
assert!(cache.find(&3).is_none()); // (4, 2) (no change)
assert!(cache.find(&4).is_some()); // (2, 4) (no change)
// Test find_or_create.
cache.find_or_create(&1, |_| { Cell::new("one") }); // (4, 1)
assert!(cache.find(&1).is_some()); // (4, 1) (no change)
assert!(cache.find(&2).is_none()); // (4, 1) (no change)
assert!(cache.find(&3).is_none()); // (4, 1) (no change)
assert!(cache.find(&4).is_some()); // (1, 4)
}
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