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style: Avoid some allocations in selector serialization.

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The allocations in display_to_css_identifier show up in the profiles of
bug 1675628.

Differential Revision: https://phabricator.services.mozilla.com/D97856
This commit is contained in:
Emilio Cobos Álvarez 2020-11-22 01:02:22 +00:00
parent e9c1d490a9
commit 484cf5771b
2 changed files with 51 additions and 53 deletions
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96
components/selectors/parser.rs
View file

@ -10,15 +10,15 @@ use crate::builder::{SelectorBuilder, SelectorFlags, SpecificityAndFlags};
use crate::context::QuirksMode;
use crate::sink::Push;
pub use crate::visitor::SelectorVisitor;
use cssparser::{parse_nth, serialize_identifier};
use cssparser::parse_nth;
use cssparser::{BasicParseError, BasicParseErrorKind, ParseError, ParseErrorKind};
use cssparser::{CowRcStr, Delimiter, SourceLocation};
use cssparser::{CssStringWriter, Parser as CssParser, ToCss, Token};
use cssparser::{Parser as CssParser, ToCss, Token};
use precomputed_hash::PrecomputedHash;
use servo_arc::ThinArc;
use smallvec::SmallVec;
use std::borrow::{Borrow, Cow};
use std::fmt::{self, Debug, Display, Write};
use std::fmt::{self, Debug};
use std::iter::Rev;
use std::slice;
@ -197,8 +197,6 @@ macro_rules! with_all_bounds {
type ExtraMatchingData: Sized + Default + 'static;
type AttrValue: $($InSelector)*;
type Identifier: $($InSelector)*;
type ClassName: $($InSelector)*;
type PartName: $($InSelector)*;
type LocalName: $($InSelector)* + Borrow<Self::BorrowedLocalName>;
type NamespaceUrl: $($CommonBounds)* + Default + Borrow<Self::BorrowedNamespaceUrl>;
type NamespacePrefix: $($InSelector)* + Default;
@ -218,7 +216,7 @@ macro_rules! with_all_bounds {
macro_rules! with_bounds {
( [ $( $CommonBounds: tt )* ] [ $( $FromStr: tt )* ]) => {
with_all_bounds! {
[$($CommonBounds)* + $($FromStr)* + Display]
[$($CommonBounds)* + $($FromStr)* + ToCss]
[$($CommonBounds)*]
[$($FromStr)*]
}
@ -462,7 +460,6 @@ fn collect_ancestor_hashes<Impl: SelectorImpl>(
) -> bool
where
Impl::Identifier: PrecomputedHash,
Impl::ClassName: PrecomputedHash,
Impl::LocalName: PrecomputedHash,
Impl::NamespaceUrl: PrecomputedHash,
{
@ -514,7 +511,6 @@ impl AncestorHashes {
pub fn new<Impl: SelectorImpl>(selector: &Selector<Impl>, quirks_mode: QuirksMode) -> Self
where
Impl::Identifier: PrecomputedHash,
Impl::ClassName: PrecomputedHash,
Impl::LocalName: PrecomputedHash,
Impl::NamespaceUrl: PrecomputedHash,
{
@ -593,7 +589,7 @@ impl<Impl: SelectorImpl> Selector<Impl> {
}
#[inline]
pub fn parts(&self) -> Option<&[Impl::PartName]> {
pub fn parts(&self) -> Option<&[Impl::Identifier]> {
if !self.is_part() {
return None;
}
@ -1012,7 +1008,7 @@ pub enum Component<Impl: SelectorImpl> {
LocalName(LocalName<Impl>),
ID(#[shmem(field_bound)] Impl::Identifier),
Class(#[shmem(field_bound)] Impl::ClassName),
Class(#[shmem(field_bound)] Impl::Identifier),
AttributeInNoNamespaceExists {
#[shmem(field_bound)]
@ -1061,7 +1057,7 @@ pub enum Component<Impl: SelectorImpl> {
Slotted(Selector<Impl>),
/// The `::part` pseudo-element.
/// https://drafts.csswg.org/css-shadow-parts/#part
Part(#[shmem(field_bound)] Box<[Impl::PartName]>),
Part(#[shmem(field_bound)] Box<[Impl::Identifier]>),
/// The `:host` pseudo-class:
///
/// https://drafts.csswg.org/css-scoping/#host-selector
@ -1470,18 +1466,18 @@ impl<Impl: SelectorImpl> ToCss for Component<Impl> {
if i != 0 {
dest.write_char(' ')?;
}
display_to_css_identifier(name, dest)?;
name.to_css(dest)?;
}
dest.write_char(')')
},
PseudoElement(ref p) => p.to_css(dest),
ID(ref s) => {
dest.write_char('#')?;
display_to_css_identifier(s, dest)
s.to_css(dest)
},
Class(ref s) => {
dest.write_char('.')?;
display_to_css_identifier(s, dest)
s.to_css(dest)
},
LocalName(ref s) => s.to_css(dest),
ExplicitUniversalType => dest.write_char('*'),
@ -1490,13 +1486,13 @@ impl<Impl: SelectorImpl> ToCss for Component<Impl> {
ExplicitNoNamespace => dest.write_char('|'),
ExplicitAnyNamespace => dest.write_str("*|"),
Namespace(ref prefix, _) => {
display_to_css_identifier(prefix, dest)?;
prefix.to_css(dest)?;
dest.write_char('|')
},
AttributeInNoNamespaceExists { ref local_name, .. } => {
dest.write_char('[')?;
display_to_css_identifier(local_name, dest)?;
local_name.to_css(dest)?;
dest.write_char(']')
},
AttributeInNoNamespace {
@ -1507,10 +1503,10 @@ impl<Impl: SelectorImpl> ToCss for Component<Impl> {
..
} => {
dest.write_char('[')?;
display_to_css_identifier(local_name, dest)?;
local_name.to_css(dest)?;
operator.to_css(dest)?;
dest.write_char('"')?;
write!(CssStringWriter::new(dest), "{}", value)?;
value.to_css(dest)?;
dest.write_char('"')?;
match case_sensitivity {
ParsedCaseSensitivity::CaseSensitive |
@ -1582,13 +1578,13 @@ impl<Impl: SelectorImpl> ToCss for AttrSelectorWithOptionalNamespace<Impl> {
dest.write_char('[')?;
match self.namespace {
Some(NamespaceConstraint::Specific((ref prefix, _))) => {
display_to_css_identifier(prefix, dest)?;
prefix.to_css(dest)?;
dest.write_char('|')?
},
Some(NamespaceConstraint::Any) => dest.write_str("*|")?,
None => {},
}
display_to_css_identifier(&self.local_name, dest)?;
self.local_name.to_css(dest)?;
match self.operation {
ParsedAttrSelectorOperation::Exists => {},
ParsedAttrSelectorOperation::WithValue {
@ -1598,7 +1594,7 @@ impl<Impl: SelectorImpl> ToCss for AttrSelectorWithOptionalNamespace<Impl> {
} => {
operator.to_css(dest)?;
dest.write_char('"')?;
write!(CssStringWriter::new(dest), "{}", expected_value)?;
expected_value.to_css(dest)?;
dest.write_char('"')?;
match case_sensitivity {
ParsedCaseSensitivity::CaseSensitive |
@ -1617,29 +1613,10 @@ impl<Impl: SelectorImpl> ToCss for LocalName<Impl> {
where
W: fmt::Write,
{
display_to_css_identifier(&self.name, dest)
self.name.to_css(dest)
}
}
/// Serialize the output of Display as a CSS identifier
fn display_to_css_identifier<T: Display, W: fmt::Write>(x: &T, dest: &mut W) -> fmt::Result {
// FIXME(SimonSapin): it is possible to avoid this heap allocation
// by creating a stream adapter like cssparser::CssStringWriter
// that holds and writes to `&mut W` and itself implements `fmt::Write`.
//
// I haven’t done this yet because it would require somewhat complex and fragile state machine
// to support in `fmt::Write::write_char` cases that,
// in `serialize_identifier` (which has the full value as a `&str` slice),
// can be expressed as
// `string.starts_with("--")`, `string == "-"`, `string.starts_with("-")`, etc.
//
// And I don’t even know if this would be a performance win: jemalloc is good at what it does
// and the state machine might be slower than `serialize_identifier` as currently written.
let string = x.to_string();
serialize_identifier(&string, dest)
}
/// Build up a Selector.
/// selector : simple_selector_sequence [ combinator simple_selector_sequence ]* ;
///
@ -1810,7 +1787,7 @@ enum SimpleSelectorParseResult<Impl: SelectorImpl> {
SimpleSelector(Component<Impl>),
PseudoElement(Impl::PseudoElement),
SlottedPseudo(Selector<Impl>),
PartPseudo(Box<[Impl::PartName]>),
PartPseudo(Box<[Impl::Identifier]>),
}
#[derive(Debug)]
@ -2605,10 +2582,8 @@ pub mod tests {
impl SelectorImpl for DummySelectorImpl {
type ExtraMatchingData = ();
type AttrValue = DummyAtom;
type AttrValue = DummyAttrValue;
type Identifier = DummyAtom;
type ClassName = DummyAtom;
type PartName = DummyAtom;
type LocalName = DummyAtom;
type NamespaceUrl = DummyAtom;
type NamespacePrefix = DummyAtom;
@ -2618,12 +2593,35 @@ pub mod tests {
type PseudoElement = PseudoElement;
}
#[derive(Clone, Debug, Default, Eq, Hash, PartialEq)]
pub struct DummyAttrValue(String);
impl ToCss for DummyAttrValue {
fn to_css<W>(&self, dest: &mut W) -> fmt::Result
where
W: fmt::Write,
{
use std::fmt::Write;
write!(cssparser::CssStringWriter::new(dest), "{}", &self.0)
}
}
impl<'a> From<&'a str> for DummyAttrValue {
fn from(string: &'a str) -> Self {
Self(string.into())
}
}
#[derive(Clone, Debug, Default, Eq, Hash, PartialEq)]
pub struct DummyAtom(String);
impl fmt::Display for DummyAtom {
fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
<String as fmt::Display>::fmt(&self.0, fmt)
impl ToCss for DummyAtom {
fn to_css<W>(&self, dest: &mut W) -> fmt::Result
where
W: fmt::Write,
{
serialize_identifier(&self.0, dest)
}
}
@ -3108,7 +3106,7 @@ pub mod tests {
vec![Component::AttributeInNoNamespace {
local_name: DummyAtom::from("attr"),
operator: AttrSelectorOperator::DashMatch,
value: DummyAtom::from("foo"),
value: DummyAttrValue::from("foo"),
never_matches: false,
case_sensitivity: ParsedCaseSensitivity::CaseSensitive,
}],

8
components/selectors/tree.rs
View file

@ -113,7 +113,7 @@ pub trait Element: Sized + Clone + Debug {
fn has_class(
&self,
name: &<Self::Impl as SelectorImpl>::ClassName,
name: &<Self::Impl as SelectorImpl>::Identifier,
case_sensitivity: CaseSensitivity,
) -> bool;
@ -121,10 +121,10 @@ pub trait Element: Sized + Clone + Debug {
/// direction, that is, in an outer-tree -> inner-tree direction.
fn imported_part(
&self,
name: &<Self::Impl as SelectorImpl>::PartName,
) -> Option<<Self::Impl as SelectorImpl>::PartName>;
name: &<Self::Impl as SelectorImpl>::Identifier,
) -> Option<<Self::Impl as SelectorImpl>::Identifier>;
fn is_part(&self, name: &<Self::Impl as SelectorImpl>::PartName) -> bool;
fn is_part(&self, name: &<Self::Impl as SelectorImpl>::Identifier) -> bool;
/// Returns whether this element matches `:empty`.
///