lewp_selectors/
nth_index_cache.rs

1/* This Source Code Form is subject to the terms of the Mozilla Public
2 * License, v. 2.0. If a copy of the MPL was not distributed with this
3 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
4
5use crate::tree::OpaqueElement;
6use fxhash::FxHashMap;
7
8/// A cache to speed up matching of nth-index-like selectors.
9///
10/// See [1] for some discussion around the design tradeoffs.
11///
12/// [1] https://bugzilla.mozilla.org/show_bug.cgi?id=1401855#c3
13#[derive(Default)]
14pub struct NthIndexCache {
15    nth: NthIndexCacheInner,
16    nth_last: NthIndexCacheInner,
17    nth_of_type: NthIndexCacheInner,
18    nth_last_of_type: NthIndexCacheInner,
19}
20
21impl NthIndexCache {
22    /// Gets the appropriate cache for the given parameters.
23    pub fn get(&mut self, is_of_type: bool, is_from_end: bool) -> &mut NthIndexCacheInner {
24        match (is_of_type, is_from_end) {
25            (false, false) => &mut self.nth,
26            (false, true) => &mut self.nth_last,
27            (true, false) => &mut self.nth_of_type,
28            (true, true) => &mut self.nth_last_of_type,
29        }
30    }
31}
32
33/// The concrete per-pseudo-class cache.
34#[derive(Default)]
35pub struct NthIndexCacheInner(FxHashMap<OpaqueElement, i32>);
36
37impl NthIndexCacheInner {
38    /// Does a lookup for a given element in the cache.
39    pub fn lookup(&mut self, el: OpaqueElement) -> Option<i32> {
40        self.0.get(&el).copied()
41    }
42
43    /// Inserts an entry into the cache.
44    pub fn insert(&mut self, element: OpaqueElement, index: i32) {
45        self.0.insert(element, index);
46    }
47
48    /// Returns whether the cache is empty.
49    pub fn is_empty(&self) -> bool {
50        self.0.is_empty()
51    }
52}
lewp_selectors/nth_index_cache.rs

lewp_selectors/
nth_index_cache.rs
