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