зеркало из https://github.com/mozilla/gecko-dev.git
103 строки
3.1 KiB
Rust
103 строки
3.1 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 https://mozilla.org/MPL/2.0/. */
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use std::hash::Hash;
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use crate::{parser::Selector, tree::OpaqueElement, SelectorImpl};
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use fxhash::FxHashMap;
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/// A cache to speed up matching of nth-index-like selectors.
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///
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/// See [1] for some discussion around the design tradeoffs.
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///
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/// [1] https://bugzilla.mozilla.org/show_bug.cgi?id=1401855#c3
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#[derive(Default)]
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pub struct NthIndexCache {
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nth: NthIndexCacheInner,
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nth_of_selectors: NthIndexOfSelectorsCaches,
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nth_last: NthIndexCacheInner,
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nth_last_of_selectors: NthIndexOfSelectorsCaches,
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nth_of_type: NthIndexCacheInner,
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nth_last_of_type: NthIndexCacheInner,
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}
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impl NthIndexCache {
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/// Gets the appropriate cache for the given parameters.
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pub fn get<Impl: SelectorImpl>(
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&mut self,
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is_of_type: bool,
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is_from_end: bool,
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selectors: &[Selector<Impl>],
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) -> &mut NthIndexCacheInner {
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if is_of_type {
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return if is_from_end {
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&mut self.nth_last_of_type
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} else {
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&mut self.nth_of_type
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};
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}
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if !selectors.is_empty() {
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return if is_from_end {
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self.nth_last_of_selectors.lookup(selectors)
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} else {
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self.nth_of_selectors.lookup(selectors)
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};
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}
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if is_from_end {
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&mut self.nth_last
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} else {
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&mut self.nth
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}
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}
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}
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#[derive(Hash, Eq, PartialEq)]
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struct SelectorListCacheKey(usize);
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/// Use the selector list's pointer as the cache key
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impl SelectorListCacheKey {
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// :nth-child of selectors are reference-counted with `ThinArc`, so we know their pointers are stable.
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fn new<Impl: SelectorImpl>(selectors: &[Selector<Impl>]) -> Self {
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Self(selectors.as_ptr() as usize)
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}
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}
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/// Use a different map of cached indices per :nth-child's or :nth-last-child's selector list
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#[derive(Default)]
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pub struct NthIndexOfSelectorsCaches(FxHashMap<SelectorListCacheKey, NthIndexCacheInner>);
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/// Get or insert a map of cached incides for the selector list of this
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/// particular :nth-child or :nth-last-child pseudoclass
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impl NthIndexOfSelectorsCaches {
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pub fn lookup<Impl: SelectorImpl>(
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&mut self,
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selectors: &[Selector<Impl>],
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) -> &mut NthIndexCacheInner {
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self.0
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.entry(SelectorListCacheKey::new(selectors))
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.or_default()
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}
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}
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/// The concrete per-pseudo-class cache.
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#[derive(Default)]
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pub struct NthIndexCacheInner(FxHashMap<OpaqueElement, i32>);
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impl NthIndexCacheInner {
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/// Does a lookup for a given element in the cache.
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pub fn lookup(&mut self, el: OpaqueElement) -> Option<i32> {
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self.0.get(&el).copied()
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}
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/// Inserts an entry into the cache.
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pub fn insert(&mut self, element: OpaqueElement, index: i32) {
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self.0.insert(element, index);
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}
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/// Returns whether the cache is empty.
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pub fn is_empty(&self) -> bool {
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self.0.is_empty()
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}
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}
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