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72 lines
2 KiB
Rust
72 lines
2 KiB
Rust
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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//! A simple LRU cache.
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#![deny(missing_docs)]
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use std::{iter, slice};
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/// A LRU cache used to store a set of at most `n` elements at the same time.
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///
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/// Currently used for the style sharing candidate cache.
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pub struct LRUCache<K> {
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entries: Vec<K>,
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cache_size: usize,
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}
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/// A iterator over the items of the LRU cache.
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pub type LRUCacheIterator<'a, K> = iter::Rev<slice::Iter<'a, K>>;
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/// A iterator over the mutable items of the LRU cache.
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pub type LRUCacheMutIterator<'a, K> = iter::Rev<slice::IterMut<'a, K>>;
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impl<K: PartialEq> LRUCache<K> {
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/// Create a new LRU cache with `size` elements at most.
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pub fn new(size: usize) -> Self {
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LRUCache {
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entries: vec![],
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cache_size: size,
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}
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}
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/// Returns the number of elements in the cache.
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pub fn num_entries(&self) -> usize {
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self.entries.len()
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}
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#[inline]
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/// Touch a given position, and put it in the last item on the list.
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pub fn touch(&mut self, pos: usize) {
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let last_index = self.entries.len() - 1;
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if pos != last_index {
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let entry = self.entries.remove(pos);
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self.entries.push(entry);
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}
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}
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/// Iterate over the contents of this cache, from more to less recently
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/// used.
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pub fn iter(&self) -> LRUCacheIterator<K> {
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self.entries.iter().rev()
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}
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/// Iterate mutably over the contents of this cache.
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pub fn iter_mut(&mut self) -> LRUCacheMutIterator<K> {
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self.entries.iter_mut().rev()
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}
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/// Insert a given key in the cache.
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pub fn insert(&mut self, key: K) {
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if self.entries.len() == self.cache_size {
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self.entries.remove(0);
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}
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self.entries.push(key);
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}
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/// Evict all elements from the cache.
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pub fn evict_all(&mut self) {
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self.entries.clear();
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}
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}
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