selectors/relative_selector/
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 fxhash::FxHashMap;
6/// Relative selector cache. This is useful for following cases.
7/// First case is non-subject relative selector: Imagine `.anchor:has(<..>) ~ .foo`, with DOM
8/// `.anchor + .foo + .. + .foo`. Each match on `.foo` triggers `:has()` traversal that
9/// yields the same result. This is simple enough, since we just need to store
10/// the exact match on that anchor pass/fail.
11/// Second case is `querySelectorAll`: Imagine `querySelectorAll(':has(.a)')`, with DOM
12/// `div > .. > div > .a`. When the we perform the traversal at the top div,
13/// we basically end up evaluating `:has(.a)` for all anchors, which could be reused.
14/// Also consider the sibling version: `querySelectorAll(':has(~ .a)')` with DOM
15/// `div + .. + div + .a`.
16/// TODO(dshin): Second case is not yet handled. That is tracked in Bug 1845291.
17use std::hash::Hash;
18
19use crate::parser::{RelativeSelector, SelectorKey};
20use crate::{tree::OpaqueElement, SelectorImpl};
21
22/// Match data for a given element and a selector.
23#[derive(Clone, Copy)]
24pub enum RelativeSelectorCachedMatch {
25    /// This selector matches this element.
26    Matched,
27    /// This selector does not match this element.
28    NotMatched,
29}
30
31impl RelativeSelectorCachedMatch {
32    /// Is the cached result a match?
33    pub fn matched(&self) -> bool {
34        matches!(*self, Self::Matched)
35    }
36}
37
38#[derive(Clone, Copy, Hash, Eq, PartialEq)]
39struct Key {
40    element: OpaqueElement,
41    selector: SelectorKey,
42}
43
44impl Key {
45    pub fn new<Impl: SelectorImpl>(
46        element: OpaqueElement,
47        selector: &RelativeSelector<Impl>,
48    ) -> Self {
49        Key {
50            element,
51            selector: SelectorKey::new(&selector.selector),
52        }
53    }
54}
55
56/// Cache to speed up matching of relative selectors.
57#[derive(Default)]
58pub struct RelativeSelectorCache {
59    cache: FxHashMap<Key, RelativeSelectorCachedMatch>,
60}
61
62impl RelativeSelectorCache {
63    /// Add a relative selector match into the cache.
64    pub fn add<Impl: SelectorImpl>(
65        &mut self,
66        anchor: OpaqueElement,
67        selector: &RelativeSelector<Impl>,
68        matched: RelativeSelectorCachedMatch,
69    ) {
70        self.cache.insert(Key::new(anchor, selector), matched);
71    }
72
73    /// Check if we have a cache entry for the element.
74    pub fn lookup<Impl: SelectorImpl>(
75        &mut self,
76        element: OpaqueElement,
77        selector: &RelativeSelector<Impl>,
78    ) -> Option<RelativeSelectorCachedMatch> {
79        self.cache.get(&Key::new(element, selector)).copied()
80    }
81}
selectors/relative_selector/cache.rs

selectors/relative_selector/
cache.rs
