/* 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 http://mozilla.org/MPL/2.0/. */
//! A data structure to efficiently index structs containing selectors by local
//! name, ids and hash.
use {Atom, LocalName, WeakAtom};
use applicable_declarations::ApplicableDeclarationList;
use context::QuirksMode;
use dom::TElement;
use fallible::FallibleVec;
use hash::{HashMap, HashSet};
use hash::map as hash_map;
use hashglobe::FailedAllocationError;
use precomputed_hash::PrecomputedHash;
use rule_tree::CascadeLevel;
use selector_parser::SelectorImpl;
use selectors::matching::{matches_selector, MatchingContext, ElementSelectorFlags};
use selectors::parser::{Component, Combinator, SelectorIter};
use smallvec::SmallVec;
use std::hash::{BuildHasherDefault, Hash, Hasher};
use stylist::Rule;
/// A hasher implementation that doesn't hash anything, because it expects its
/// input to be a suitable u32 hash.
pub struct PrecomputedHasher {
hash: Option<u32>,
}
impl Default for PrecomputedHasher {
fn default() -> Self {
Self { hash: None }
}
}
/// A simple alias for a hashmap using PrecomputedHasher.
pub type PrecomputedHashMap<K, V> = HashMap<K, V, BuildHasherDefault<PrecomputedHasher>>;
/// A simple alias for a hashset using PrecomputedHasher.
pub type PrecomputedHashSet<K> = HashSet<K, BuildHasherDefault<PrecomputedHasher>>;
impl Hasher for PrecomputedHasher {
#[inline]
fn write(&mut self, _: &[u8]) {
unreachable!("Called into PrecomputedHasher with something that isn't \
a u32")
}
#[inline]
fn write_u32(&mut self, i: u32) {
debug_assert!(self.hash.is_none());
self.hash = Some(i);
}
#[inline]
fn finish(&self) -> u64 {
self.hash.expect("PrecomputedHasher wasn't fed?") as u64
}
}
/// A trait to abstract over a given selector map entry.
pub trait SelectorMapEntry : Sized + Clone {
/// Gets the selector we should use to index in the selector map.
fn selector(&self) -> SelectorIter<SelectorImpl>;
}
/// Map element data to selector-providing objects for which the last simple
/// selector starts with them.
///
/// e.g.,
/// "p > img" would go into the set of selectors corresponding to the
/// element "img"
/// "a .foo .bar.baz" would go into the set of selectors corresponding to
/// the class "bar"
///
/// Because we match selectors right-to-left (i.e., moving up the tree
/// from an element), we need to compare the last simple selector in the
/// selector with the element.
///
/// So, if an element has ID "id1" and classes "foo" and "bar", then all
/// the rules it matches will have their last simple selector starting
/// either with "#id1" or with ".foo" or with ".bar".
///
/// Hence, the union of the rules keyed on each of element's classes, ID,
/// element name, etc. will contain the Selectors that actually match that
/// element.
///
/// We use a 1-entry SmallVec to avoid a separate heap allocation in the case
/// where we only have one entry, which is quite common. See measurements in:
/// * https://bugzilla.mozilla.org/show_bug.cgi?id=1363789#c5
/// * https://bugzilla.mozilla.org/show_bug.cgi?id=681755
///
/// TODO: Tune the initial capacity of the HashMap
#[derive(Debug, MallocSizeOf)]
pub struct SelectorMap<T: 'static> {
/// A hash from an ID to rules which contain that ID selector.
pub id_hash: MaybeCaseInsensitiveHashMap<Atom, SmallVec<[T; 1]>>,
/// A hash from a class name to rules which contain that class selector.
pub class_hash: MaybeCaseInsensitiveHashMap<Atom, SmallVec<[T; 1]>>,
/// A hash from local name to rules which contain that local name selector.
pub local_name_hash: PrecomputedHashMap<LocalName, SmallVec<[T; 1]>>,
/// Rules that don't have ID, class, or element selectors.
pub other: SmallVec<[T; 1]>,
/// The number of entries in this map.
pub count: usize,
}
impl<T: 'static> Default for SelectorMap<T> {
#[inline]
fn default() -> Self {
Self::new()
}
}
// FIXME(Manishearth) the 'static bound can be removed when
// our HashMap fork (hashglobe) is able to use NonZero,
// or when stdlib gets fallible collections
impl<T: 'static> SelectorMap<T> {
/// Trivially constructs an empty `SelectorMap`.
pub fn new() -> Self {
SelectorMap {
id_hash: MaybeCaseInsensitiveHashMap::new(),
class_hash: MaybeCaseInsensitiveHashMap::new(),
local_name_hash: HashMap::default(),
other: SmallVec::new(),
count: 0,
}
}
/// Clears the hashmap retaining storage.
pub fn clear(&mut self) {
self.id_hash.clear();
self.class_hash.clear();
self.local_name_hash.clear();
self.other.clear();
self.count = 0;
}
/// Returns whether there are any entries in the map.
pub fn is_empty(&self) -> bool {
self.count == 0
}
/// Returns the number of entries.
pub fn len(&self) -> usize {
self.count
}
}
impl SelectorMap<Rule> {
/// Append to `rule_list` all Rules in `self` that match element.
///
/// Extract matching rules as per element's ID, classes, tag name, etc..
/// Sort the Rules at the end to maintain cascading order.
pub fn get_all_matching_rules<E, F>(
&self,
element: E,
rule_hash_target: E,
matching_rules_list: &mut ApplicableDeclarationList,
context: &mut MatchingContext<E::Impl>,
flags_setter: &mut F,
cascade_level: CascadeLevel,
)
where
E: TElement,
F: FnMut(&E, ElementSelectorFlags),
{
if self.is_empty() {
return
}
let quirks_mode = context.quirks_mode();
// At the end, we're going to sort the rules that we added, so remember
// where we began.
let init_len = matching_rules_list.len();
if let Some(id) = rule_hash_target.id() {
if let Some(rules) = self.id_hash.get(id, quirks_mode) {
SelectorMap::get_matching_rules(
element,
rules,
matching_rules_list,
context,
flags_setter,
cascade_level,
)
}
}
rule_hash_target.each_class(|class| {
if let Some(rules) = self.class_hash.get(&class, quirks_mode) {
SelectorMap::get_matching_rules(
element,
rules,
matching_rules_list,
context,
flags_setter,
cascade_level,
)
}
});
if let Some(rules) = self.local_name_hash.get(rule_hash_target.local_name()) {
SelectorMap::get_matching_rules(
element,
rules,
matching_rules_list,
context,
flags_setter,
cascade_level,
)
}
SelectorMap::get_matching_rules(
element,
&self.other,
matching_rules_list,
context,
flags_setter,
cascade_level,
);
// Sort only the rules we just added.
matching_rules_list[init_len..].sort_unstable_by_key(|block| (block.specificity, block.source_order()));
}
/// Adds rules in `rules` that match `element` to the `matching_rules` list.
fn get_matching_rules<E, F>(
element: E,
rules: &[Rule],
matching_rules: &mut ApplicableDeclarationList,
context: &mut MatchingContext<E::Impl>,
flags_setter: &mut F,
cascade_level: CascadeLevel,
)
where
E: TElement,
F: FnMut(&E, ElementSelectorFlags),
{
for rule in rules {
if matches_selector(&rule.selector,
0,
Some(&rule.hashes),
&element,
context,
flags_setter) {
matching_rules.push(
rule.to_applicable_declaration_block(cascade_level));
}
}
}
}
impl<T: SelectorMapEntry> SelectorMap<T> {
/// Inserts into the correct hash, trying id, class, and localname.
pub fn insert(
&mut self,
entry: T,
quirks_mode: QuirksMode,
) -> Result<(), FailedAllocationError> {
self.count += 1;
let vector = match find_bucket(entry.selector()) {
Bucket::ID(id) => {
self.id_hash.try_entry(id.clone(), quirks_mode)?
.or_insert_with(SmallVec::new)
}
Bucket::Class(class) => {
self.class_hash.try_entry(class.clone(), quirks_mode)?
.or_insert_with(SmallVec::new)
}
Bucket::LocalName { name, lower_name } => {
// If the local name in the selector isn't lowercase, insert it
// into the rule hash twice. This means that, during lookup, we
// can always find the rules based on the local name of the
// element, regardless of whether it's an html element in an
// html document (in which case we match against lower_name) or
// not (in which case we match against name).
//
// In the case of a non-html-element-in-html-document with a
// lowercase localname and a non-lowercase selector, the
// rulehash lookup may produce superfluous selectors, but the
// subsequent selector matching work will filter them out.
if name != lower_name {
self.local_name_hash
.try_entry(lower_name.clone())?
.or_insert_with(SmallVec::new)
.try_push(entry.clone())?;
}
self.local_name_hash.try_entry(name.clone())?
.or_insert_with(SmallVec::new)
}
Bucket::Universal => {
&mut self.other
}
};
vector.try_push(entry)
}
/// Looks up entries by id, class, local name, and other (in order).
///
/// Each entry is passed to the callback, which returns true to continue
/// iterating entries, or false to terminate the lookup.
///
/// Returns false if the callback ever returns false.
///
/// FIXME(bholley) This overlaps with SelectorMap<Rule>::get_all_matching_rules,
/// but that function is extremely hot and I'd rather not rearrange it.
#[inline]
pub fn lookup<'a, E, F>(&'a self, element: E, quirks_mode: QuirksMode, mut f: F) -> bool
where
E: TElement,
F: FnMut(&'a T) -> bool
{
// Id.
if let Some(id) = element.id() {
if let Some(v) = self.id_hash.get(id, quirks_mode) {
for entry in v.iter() {
if !f(&entry) {
return false;
}
}
}
}
// Class.
let mut done = false;
element.each_class(|class| {
if !done {
if let Some(v) = self.class_hash.get(class, quirks_mode) {
for entry in v.iter() {
if !f(&entry) {
done = true;
return;
}
}
}
}
});
if done {
return false;
}
// Local name.
if let Some(v) = self.local_name_hash.get(element.local_name()) {
for entry in v.iter() {
if !f(&entry) {
return false;
}
}
}
// Other.
for entry in self.other.iter() {
if !f(&entry) {
return false;
}
}
true
}
/// Performs a normal lookup, and also looks up entries for the passed-in
/// id and classes.
///
/// Each entry is passed to the callback, which returns true to continue
/// iterating entries, or false to terminate the lookup.
///
/// Returns false if the callback ever returns false.
#[inline]
pub fn lookup_with_additional<'a, E, F>(
&'a self,
element: E,
quirks_mode: QuirksMode,
additional_id: Option<&WeakAtom>,
additional_classes: &[Atom],
mut f: F,
) -> bool
where
E: TElement,
F: FnMut(&'a T) -> bool
{
// Do the normal lookup.
if !self.lookup(element, quirks_mode, |entry| f(entry)) {
return false;
}
// Check the additional id.
if let Some(id) = additional_id {
if let Some(v) = self.id_hash.get(id, quirks_mode) {
for entry in v.iter() {
if !f(&entry) {
return false;
}
}
}
}
// Check the additional classes.
for class in additional_classes {
if let Some(v) = self.class_hash.get(class, quirks_mode) {
for entry in v.iter() {
if !f(&entry) {
return false;
}
}
}
}
true
}
}
enum Bucket<'a> {
ID(&'a Atom),
Class(&'a Atom),
LocalName { name: &'a LocalName, lower_name: &'a LocalName, },
Universal,
}
fn specific_bucket_for<'a>(
component: &'a Component<SelectorImpl>
) -> Bucket<'a> {
match *component {
Component::ID(ref id) => Bucket::ID(id),
Component::Class(ref class) => Bucket::Class(class),
Component::LocalName(ref selector) => {
Bucket::LocalName {
name: &selector.name,
lower_name: &selector.lower_name,
}
}
// ::slotted(..) isn't a normal pseudo-element, so we can insert it on
// the rule hash normally without much problem. For example, in a
// selector like:
//
// div::slotted(span)::before
//
// It looks like:
//
// [
// LocalName(div),
// Combinator(SlotAssignment),
// Slotted(span),
// Combinator::PseudoElement,
// PseudoElement(::before),
// ]
//
// So inserting `span` in the rule hash makes sense since we want to
// match the slotted <span>.
//
// FIXME(emilio, bug 1426516): The line below causes valgrind failures
// and it's probably a false positive, we should uncomment whenever
// jseward is back to confirm / whitelist it.
//
// Meanwhile taking the code path below is slower, but still correct.
// Component::Slotted(ref selector) => find_bucket(selector.iter()),
_ => Bucket::Universal
}
}
/// Searches a compound selector from left to right, and returns the appropriate
/// bucket for it.
#[inline(always)]
fn find_bucket<'a>(mut iter: SelectorIter<'a, SelectorImpl>) -> Bucket<'a> {
let mut current_bucket = Bucket::Universal;
loop {
// We basically want to find the most specific bucket,
// where:
//
// id > class > local name > universal.
//
for ss in &mut iter {
let new_bucket = specific_bucket_for(ss);
match new_bucket {
Bucket::ID(..) => return new_bucket,
Bucket::Class(..) => {
current_bucket = new_bucket;
}
Bucket::LocalName { .. } => {
if matches!(current_bucket, Bucket::Universal) {
current_bucket = new_bucket;
}
}
Bucket::Universal => {},
}
}
// Effectively, pseudo-elements are ignored, given only state
// pseudo-classes may appear before them.
if iter.next_sequence() != Some(Combinator::PseudoElement) {
break;
}
}
return current_bucket
}
/// Wrapper for PrecomputedHashMap that does ASCII-case-insensitive lookup in quirks mode.
#[derive(Debug, MallocSizeOf)]
pub struct MaybeCaseInsensitiveHashMap<K: PrecomputedHash + Hash + Eq, V: 'static>(PrecomputedHashMap<K, V>);
// FIXME(Manishearth) the 'static bound can be removed when
// our HashMap fork (hashglobe) is able to use NonZero,
// or when stdlib gets fallible collections
impl<V: 'static> MaybeCaseInsensitiveHashMap<Atom, V> {
/// Empty map
pub fn new() -> Self {
MaybeCaseInsensitiveHashMap(PrecomputedHashMap::default())
}
/// HashMap::try_entry
pub fn try_entry(
&mut self,
mut key: Atom,
quirks_mode: QuirksMode,
) -> Result<hash_map::Entry<Atom, V>, FailedAllocationError> {
if quirks_mode == QuirksMode::Quirks {
key = key.to_ascii_lowercase()
}
self.0.try_entry(key)
}
/// HashMap::iter
pub fn iter(&self) -> hash_map::Iter<Atom, V> {
self.0.iter()
}
/// HashMap::clear
pub fn clear(&mut self) {
self.0.clear()
}
/// HashMap::get
pub fn get(&self, key: &WeakAtom, quirks_mode: QuirksMode) -> Option<&V> {
if quirks_mode == QuirksMode::Quirks {
self.0.get(&key.to_ascii_lowercase())
} else {
self.0.get(key)
}
}
}