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/* 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 */
use fxhash::FxHashMap;
/// Relative selector cache. This is useful for following cases.
/// First case is non-subject relative selector: Imagine `.anchor:has(<..>) ~ .foo`, with DOM
/// `.anchor + .foo + .. + .foo`. Each match on `.foo` triggers `:has()` traversal that
/// yields the same result. This is simple enough, since we just need to store
/// the exact match on that anchor pass/fail.
/// Second case is `querySelectorAll`: Imagine `querySelectorAll(':has(.a)')`, with DOM
/// `div > .. > div > .a`. When the we perform the traversal at the top div,
/// we basically end up evaluating `:has(.a)` for all anchors, which could be reused.
/// Also consider the sibling version: `querySelectorAll(':has(~ .a)')` with DOM
/// `div + .. + div + .a`.
/// TODO(dshin): Second case is not yet handled. That is tracked in Bug 1845291.
use std::hash::Hash;
use crate::parser::{RelativeSelector, SelectorKey};
use crate::{tree::OpaqueElement, SelectorImpl};
/// Match data for a given element and a selector.
#[derive(Clone, Copy)]
pub enum RelativeSelectorCachedMatch {
/// This selector matches this element.
/// This selector does not match this element.
impl RelativeSelectorCachedMatch {
/// Is the cached result a match?
pub fn matched(&self) -> bool {
matches!(*self, Self::Matched)
#[derive(Clone, Copy, Hash, Eq, PartialEq)]
struct Key {
element: OpaqueElement,
selector: SelectorKey,
impl Key {
pub fn new<Impl: SelectorImpl>(
element: OpaqueElement,
selector: &RelativeSelector<Impl>,
) -> Self {
Key {
selector: SelectorKey::new(&selector.selector),
/// Cache to speed up matching of relative selectors.
pub struct RelativeSelectorCache {
cache: FxHashMap<Key, RelativeSelectorCachedMatch>,
impl RelativeSelectorCache {
/// Add a relative selector match into the cache.
pub fn add<Impl: SelectorImpl>(
&mut self,
anchor: OpaqueElement,
selector: &RelativeSelector<Impl>,
matched: RelativeSelectorCachedMatch,
) {
self.cache.insert(Key::new(anchor, selector), matched);
/// Check if we have a cache entry for the element.
pub fn lookup<Impl: SelectorImpl>(
&mut self,
element: OpaqueElement,
selector: &RelativeSelector<Impl>,
) -> Option<RelativeSelectorCachedMatch> {
self.cache.get(&Key::new(element, selector)).copied()