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style: Document and remove dead code from cache.rs

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Emilio Cobos Álvarez 2016-12-31 03:20:03 +01:00
parent fa26e87030
commit b5ba53655f
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1 changed files with 18 additions and 58 deletions
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76
components/style/cache.rs
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@ -2,18 +2,22 @@
* 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/. */
//! Two simple cache data structures.
//! A simple LRU cache.
#![deny(missing_docs)]
use std::collections::hash_map::RandomState;
use std::hash::{Hash, Hasher, BuildHasher};
use std::slice::{Iter, IterMut};
/// A LRU cache used to store a set of at most `n` elements at the same time.
///
/// Currently used for the style sharing candidate cache.
pub struct LRUCache<K, V> {
entries: Vec<(K, V)>,
cache_size: usize,
}
impl<K: PartialEq, V: Clone> LRUCache<K, V> {
/// Create a new LRU cache with `size` elements at most.
pub fn new(size: usize) -> LRUCache<K, V> {
LRUCache {
entries: vec![],
@ -22,6 +26,7 @@ impl<K: PartialEq, V: Clone> LRUCache<K, V> {
}
#[inline]
/// Touch a given position, and put it in the last item on the list.
pub fn touch(&mut self, pos: usize) -> &V {
let last_index = self.entries.len() - 1;
if pos != last_index {
@ -31,14 +36,17 @@ impl<K: PartialEq, V: Clone> LRUCache<K, V> {
&self.entries[last_index].1
}
/// Iterate over the contents of this cache.
pub fn iter(&self) -> Iter<(K, V)> {
self.entries.iter()
}
/// Iterate mutably over the contents of this cache.
pub fn iter_mut(&mut self) -> IterMut<(K, V)> {
self.entries.iter_mut()
}
/// Insert a given key and value in the cache.
pub fn insert(&mut self, key: K, val: V) {
if self.entries.len() == self.cache_size {
self.entries.remove(0);
@ -46,6 +54,7 @@ impl<K: PartialEq, V: Clone> LRUCache<K, V> {
self.entries.push((key, val));
}
/// Try to find a key in the cache.
pub fn find(&mut self, key: &K) -> Option<V> {
match self.entries.iter().position(|&(ref k, _)| key == k) {
Some(pos) => Some(self.touch(pos).clone()),
@ -53,7 +62,11 @@ impl<K: PartialEq, V: Clone> LRUCache<K, V> {
}
}
pub fn find_or_create<F>(&mut self, key: K, mut blk: F) -> V where F: FnMut() -> V {
/// Try to find a given key, or create a given item with that key executing
/// `blk`.
pub fn find_or_create<F>(&mut self, key: K, mut blk: F) -> V
where F: FnMut() -> V,
{
match self.entries.iter().position(|&(ref k, _)| *k == key) {
Some(pos) => self.touch(pos).clone(),
None => {
@ -64,61 +77,8 @@ impl<K: PartialEq, V: Clone> LRUCache<K, V> {
}
}
/// Evict all elements from the cache.
pub fn evict_all(&mut self) {
self.entries.clear();
}
}
pub struct SimpleHashCache<K, V> {
entries: Vec<Option<(K, V)>>,
random: RandomState,
}
impl<K: Clone + Eq + Hash, V: Clone> SimpleHashCache<K, V> {
pub fn new(cache_size: usize) -> SimpleHashCache<K, V> {
SimpleHashCache {
entries: vec![None; cache_size],
random: RandomState::new(),
}
}
#[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 = self.random.build_hasher();
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, mut blk: F) -> V where F: FnMut() -> V {
if let Some(value) = self.find(&key) {
return value;
}
let value = blk();
self.insert(key, value.clone());
value
}
pub fn evict_all(&mut self) {
for slot in &mut self.entries {
*slot = None
}
}
}