servo/components/util/cache.rs
2014-09-08 20:21:42 -06:00

279 lines
7.6 KiB
Rust

/* 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::HashMap;
use rand::Rng;
use std::hash::{Hash, sip};
use std::rand::task_rng;
use std::slice::Items;
#[cfg(test)]
use std::cell::Cell;
pub trait Cache<K: PartialEq, V: Clone> {
fn insert(&mut self, key: K, value: V);
fn find(&mut self, key: &K) -> Option<V>;
fn find_or_create(&mut self, key: &K, blk: |&K| -> V) -> V;
fn evict_all(&mut self);
}
pub struct MonoCache<K, V> {
entry: Option<(K,V)>,
}
impl<K: Clone + PartialEq, V: Clone> MonoCache<K,V> {
pub fn new(_size: uint) -> MonoCache<K,V> {
MonoCache { entry: None }
}
}
impl<K: Clone + PartialEq, V: Clone> Cache<K,V> for MonoCache<K,V> {
fn insert(&mut self, key: K, value: V) {
self.entry = Some((key, value));
}
fn find(&mut self, key: &K) -> Option<V> {
match self.entry {
None => None,
Some((ref k, ref v)) => if *k == *key { Some(v.clone()) } else { None }
}
}
fn find_or_create(&mut self, key: &K, blk: |&K| -> V) -> V {
match self.find(key) {
Some(value) => value,
None => {
let value = blk(key);
self.entry = Some((key.clone(), value.clone()));
value
}
}
}
fn evict_all(&mut self) {
self.entry = None;
}
}
#[test]
fn test_monocache() {
let mut cache: MonoCache<uint,Cell<&str>> = MonoCache::new(10);
let one = Cell::new("one");
let two = Cell::new("two");
cache.insert(1, one);
assert!(cache.find(&1).is_some());
assert!(cache.find(&2).is_none());
cache.find_or_create(&2, |_v| { two });
assert!(cache.find(&2).is_some());
assert!(cache.find(&1).is_none());
}
pub struct HashCache<K, V> {
entries: HashMap<K, V>,
}
impl<K: Clone + PartialEq + Eq + Hash, V: Clone> HashCache<K,V> {
pub fn new() -> HashCache<K, V> {
HashCache {
entries: HashMap::new(),
}
}
}
impl<K: Clone + PartialEq + Eq + Hash, V: Clone> Cache<K,V> for HashCache<K,V> {
fn insert(&mut self, key: K, value: V) {
self.entries.insert(key, value);
}
fn find(&mut self, key: &K) -> Option<V> {
match self.entries.find(key) {
Some(v) => Some(v.clone()),
None => None,
}
}
fn find_or_create(&mut self, key: &K, blk: |&K| -> V) -> V {
self.entries.find_or_insert_with(key.clone(), blk).clone()
}
fn evict_all(&mut self) {
self.entries.clear();
}
}
#[test]
fn test_hashcache() {
let mut cache: HashCache<uint, Cell<&str>> = HashCache::new();
let one = Cell::new("one");
let two = Cell::new("two");
cache.insert(1, one);
assert!(cache.find(&1).is_some());
assert!(cache.find(&2).is_none());
cache.find_or_create(&2, |_v| { two });
assert!(cache.find(&1).is_some());
assert!(cache.find(&2).is_some());
}
pub struct LRUCache<K, V> {
entries: Vec<(K, V)>,
cache_size: uint,
}
impl<K: Clone + PartialEq, V: Clone> LRUCache<K,V> {
pub fn new(size: uint) -> LRUCache<K, V> {
LRUCache {
entries: vec!(),
cache_size: size,
}
}
#[inline]
pub fn touch(&mut self, pos: uint) -> V {
let last_index = self.entries.len() - 1;
if pos != last_index {
let entry = self.entries.remove(pos);
self.entries.push(entry.unwrap());
}
self.entries[last_index].ref1().clone()
}
pub fn iter<'a>(&'a self) -> Items<'a,(K,V)> {
self.entries.iter()
}
}
impl<K: Clone + PartialEq, V: Clone> Cache<K,V> for LRUCache<K,V> {
fn insert(&mut self, key: K, val: V) {
if self.entries.len() == self.cache_size {
self.entries.remove(0);
}
self.entries.push((key, val));
}
fn find(&mut self, key: &K) -> Option<V> {
match self.entries.iter().position(|&(ref k, _)| *k == *key) {
Some(pos) => Some(self.touch(pos)),
None => None,
}
}
fn find_or_create(&mut self, key: &K, blk: |&K| -> V) -> 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
}
}
}
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+PartialEq+Hash,V:Clone> SimpleHashCache<K,V> {
pub fn new(cache_size: uint) -> SimpleHashCache<K,V> {
let mut r = task_rng();
SimpleHashCache {
entries: Vec::from_elem(cache_size, None),
k0: r.gen(),
k1: r.gen(),
}
}
#[inline]
fn to_bucket(&self, h: uint) -> uint {
h % self.entries.len()
}
#[inline]
fn bucket_for_key<Q:Hash>(&self, key: &Q) -> uint {
self.to_bucket(sip::hash_with_keys(self.k0, self.k1, key) as uint)
}
#[inline]
pub fn find_equiv<'a,Q:Hash+Equiv<K>>(&'a self, key: &Q) -> Option<&'a V> {
let bucket_index = self.bucket_for_key(key);
match self.entries[bucket_index] {
Some((ref existing_key, ref value)) if key.equiv(existing_key) => Some(value),
_ => None,
}
}
}
impl<K:Clone+PartialEq+Hash,V:Clone> Cache<K,V> for SimpleHashCache<K,V> {
fn insert(&mut self, key: K, value: V) {
let bucket_index = self.bucket_for_key(&key);
*self.entries.get_mut(bucket_index) = Some((key, value));
}
fn find(&mut self, key: &K) -> Option<V> {
let bucket_index = self.bucket_for_key(key);
match self.entries[bucket_index] {
Some((ref existing_key, ref value)) if existing_key == key => Some((*value).clone()),
_ => None,
}
}
fn find_or_create(&mut self, key: &K, blk: |&K| -> V) -> V {
match self.find(key) {
Some(value) => return value,
None => {}
}
let value = blk(key);
self.insert((*key).clone(), value.clone());
value
}
fn evict_all(&mut self) {
for slot in self.entries.mut_iter() {
*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<uint,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, |_| { 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)
}