aboutsummaryrefslogtreecommitdiffstats
path: root/components/util/cache.rs
diff options
context:
space:
mode:
Diffstat (limited to 'components/util/cache.rs')
-rw-r--r--components/util/cache.rs279
1 files changed, 279 insertions, 0 deletions
diff --git a/components/util/cache.rs b/components/util/cache.rs
new file mode 100644
index 00000000000..1b159cea8c1
--- /dev/null
+++ b/components/util/cache.rs
@@ -0,0 +1,279 @@
+/* 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)
+}
generated by cgit v1.2.3 (git 2.25.1) at 2025-04-28 04:50:11 +0000