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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 https://mozilla.org/MPL/2.0/. */
use crate::tree::OpaqueElement;
use fxhash::FxHashMap;
/// A cache to speed up matching of nth-index-like selectors.
///
/// See [1] for some discussion around the design tradeoffs.
///
/// [1] https://bugzilla.mozilla.org/show_bug.cgi?id=1401855#c3
#[derive(Default)]
pub struct NthIndexCache {
nth: NthIndexCacheInner,
nth_last: NthIndexCacheInner,
nth_of_type: NthIndexCacheInner,
nth_last_of_type: NthIndexCacheInner,
}
impl NthIndexCache {
/// Gets the appropriate cache for the given parameters.
pub fn get(&mut self, is_of_type: bool, is_from_end: bool) -> &mut NthIndexCacheInner {
match (is_of_type, is_from_end) {
(false, false) => &mut self.nth,
(false, true) => &mut self.nth_last,
(true, false) => &mut self.nth_of_type,
(true, true) => &mut self.nth_last_of_type,
}
}
}
/// 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()
}
}
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