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Auto merge of #15890 - emilio:bloom, r=heycam

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selectors: Check the bloom filter at most once per complex selector.

Fixes https://github.com/servo/rust-selectors/issues/107

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This commit is contained in:
bors-servo 2017-03-20 06:26:38 -07:00 • committed by GitHub
commit 4fa40c7703
1 changed files with 73 additions and 84 deletions
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157
components/selectors/matching.rs
View file

@ -112,12 +112,56 @@ pub fn matches<E>(selector_list: &[Selector<E::Impl>],
})
}
fn may_match<E>(mut selector: &ComplexSelector<E::Impl>,
bf: &BloomFilter)
-> bool
where E: Element,
{
// See if the bloom filter can exclude any of the descendant selectors, and
// reject if we can.
loop {
match selector.next {
None => break,
Some((ref cs, Combinator::Descendant)) => selector = &**cs,
Some((ref cs, _)) => {
selector = &**cs;
continue;
}
};
for ss in selector.compound_selector.iter() {
match *ss {
SimpleSelector::LocalName(LocalName { ref name, ref lower_name }) => {
if !bf.might_contain(name) &&
!bf.might_contain(lower_name) {
return false
}
},
SimpleSelector::Namespace(ref namespace) => {
if !bf.might_contain(&namespace.url) {
return false
}
},
SimpleSelector::ID(ref id) => {
if !bf.might_contain(id) {
return false
}
},
SimpleSelector::Class(ref class) => {
if !bf.might_contain(class) {
return false
}
},
_ => {},
}
}
}
// If we haven't proven otherwise, it may match.
true
}
/// Determines whether the given element matches the given complex selector.
///
/// NB: If you add support for any new kinds of selectors to this routine, be sure to set
/// `shareable` to false unless you are willing to update the style sharing logic. Otherwise things
/// will almost certainly break as elements will start mistakenly sharing styles. (See
/// `can_share_style_with` in `servo/components/style/matching.rs`.)
pub fn matches_complex_selector<E>(selector: &ComplexSelector<E::Impl>,
element: &E,
parent_bf: Option<&BloomFilter>,
@ -126,7 +170,13 @@ pub fn matches_complex_selector<E>(selector: &ComplexSelector<E::Impl>,
-> bool
where E: Element
{
match matches_complex_selector_internal(selector, element, parent_bf, relations, flags) {
if let Some(filter) = parent_bf {
if !may_match::<E>(selector, filter) {
return false;
}
}
match matches_complex_selector_internal(selector, element, relations, flags) {
SelectorMatchingResult::Matched => {
match selector.next {
Some((_, Combinator::NextSibling)) |
@ -190,81 +240,19 @@ enum SelectorMatchingResult {
NotMatchedGlobally,
}
/// Quickly figures out whether or not the complex selector is worth doing more
/// work on. If the simple selectors don't match, or there's a child selector
/// that does not appear in the bloom parent bloom filter, we can exit early.
fn can_fast_reject<E>(mut selector: &ComplexSelector<E::Impl>,
element: &E,
parent_bf: Option<&BloomFilter>,
relations: &mut StyleRelations,
flags: &mut ElementSelectorFlags)
-> Option<SelectorMatchingResult>
where E: Element
{
if !selector.compound_selector.iter().all(|simple_selector| {
matches_simple_selector(simple_selector, element, parent_bf, relations, flags) }) {
return Some(SelectorMatchingResult::NotMatchedAndRestartFromClosestLaterSibling);
}
let bf: &BloomFilter = match parent_bf {
None => return None,
Some(ref bf) => bf,
};
// See if the bloom filter can exclude any of the descendant selectors, and
// reject if we can.
loop {
match selector.next {
None => break,
Some((ref cs, Combinator::Descendant)) => selector = &**cs,
Some((ref cs, _)) => {
selector = &**cs;
continue;
}
};
for ss in selector.compound_selector.iter() {
match *ss {
SimpleSelector::LocalName(LocalName { ref name, ref lower_name }) => {
if !bf.might_contain(name) &&
!bf.might_contain(lower_name) {
return Some(SelectorMatchingResult::NotMatchedGlobally);
}
},
SimpleSelector::Namespace(ref namespace) => {
if !bf.might_contain(&namespace.url) {
return Some(SelectorMatchingResult::NotMatchedGlobally);
}
},
SimpleSelector::ID(ref id) => {
if !bf.might_contain(id) {
return Some(SelectorMatchingResult::NotMatchedGlobally);
}
},
SimpleSelector::Class(ref class) => {
if !bf.might_contain(class) {
return Some(SelectorMatchingResult::NotMatchedGlobally);
}
},
_ => {},
}
}
}
// Can't fast reject.
None
}
fn matches_complex_selector_internal<E>(selector: &ComplexSelector<E::Impl>,
element: &E,
parent_bf: Option<&BloomFilter>,
relations: &mut StyleRelations,
flags: &mut ElementSelectorFlags)
-> SelectorMatchingResult
element: &E,
relations: &mut StyleRelations,
flags: &mut ElementSelectorFlags)
-> SelectorMatchingResult
where E: Element
{
if let Some(result) = can_fast_reject(selector, element, parent_bf, relations, flags) {
return result;
let matches_all_simple_selectors = selector.compound_selector.iter().all(|simple| {
matches_simple_selector(simple, element, relations, flags)
});
if !matches_all_simple_selectors {
return SelectorMatchingResult::NotMatchedAndRestartFromClosestLaterSibling;
}
match selector.next {
@ -287,10 +275,9 @@ fn matches_complex_selector_internal<E>(selector: &ComplexSelector<E::Impl>,
Some(next_element) => next_element,
};
let result = matches_complex_selector_internal(&**next_selector,
&element,
parent_bf,
relations,
flags);
&element,
relations,
flags);
match (result, combinator) {
// Return the status immediately.
(SelectorMatchingResult::Matched, _) => return result,
@ -332,7 +319,6 @@ fn matches_complex_selector_internal<E>(selector: &ComplexSelector<E::Impl>,
fn matches_simple_selector<E>(
selector: &SimpleSelector<E::Impl>,
element: &E,
parent_bf: Option<&BloomFilter>,
relations: &mut StyleRelations,
flags: &mut ElementSelectorFlags)
-> bool
@ -466,7 +452,10 @@ fn matches_simple_selector<E>(
}
SimpleSelector::Negation(ref negated) => {
!negated.iter().all(|s| {
matches_complex_selector(s, element, parent_bf, relations, flags)
match matches_complex_selector_internal(s, element, relations, flags) {
SelectorMatchingResult::Matched => true,
_ => false,
}
})
}
}