tor-browser

The Tor Browser
git clone https://git.dasho.dev/tor-browser.git
Log | Files | Refs | README | LICENSE

cache.rs (2743B)

      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 
      5 use rustc_hash::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.
     17 use std::hash::Hash;
     18 
     19 use crate::parser::{RelativeSelector, SelectorKey};
     20 use crate::{tree::OpaqueElement, SelectorImpl};
     21 
     22 /// Match data for a given element and a selector.
     23 #[derive(Clone, Copy)]
     24 pub enum RelativeSelectorCachedMatch {
     25    /// This selector matches this element.
     26    Matched,
     27    /// This selector does not match this element.
     28    NotMatched,
     29 }
     30 
     31 impl 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)]
     39 struct Key {
     40    element: OpaqueElement,
     41    selector: SelectorKey,
     42 }
     43 
     44 impl 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)]
     58 pub struct RelativeSelectorCache {
     59    cache: FxHashMap<Key, RelativeSelectorCachedMatch>,
     60 }
     61 
     62 impl 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 }