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style: Reduce allocations in selector matching.

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This is a 27% improvement in CSS selector matching performance.
This commit is contained in:
Patrick Walton 2013-12-12 12:29:07 -08:00
parent 8c3c547c07
commit a5f16f5bbc
1 changed files with 134 additions and 70 deletions
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204
src/components/style/selector_matching.rs
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@ -21,6 +21,8 @@ pub enum StylesheetOrigin {
UserOrigin,
}
/// The definition of whitespace per CSS Selectors Level 3 § 4.
static SELECTOR_WHITESPACE: &'static [char] = &'static [' ', '\t', '\n', '\r', '\x0C'];
/// Map node attributes to Rules whose last simple selector starts with them.
///
@ -65,67 +67,84 @@ impl SelectorMap {
///
/// Extract matching rules as per node's ID, classes, tag name, etc..
/// Sort the Rules at the end to maintain cascading order.
fn get_all_matching_rules<N: TreeNode<T>, T: TreeNodeRefAsElement<N, E>, E: ElementLike>(
&self, node: &T,
pseudo_element: Option<PseudoElement>,
matching_rules_list: &mut [~[Rule]],
list_index: uint) {
let init_len = matching_rules_list[list_index].len();
static WHITESPACE: &'static [char] = &'static [' ', '\t', '\n', '\r', '\x0C'];
do node.with_imm_element_like |element: &E| {
fn get_all_matching_rules<N:TreeNode<T>,
T:TreeNodeRefAsElement<N,E>,
E:ElementLike>(
&self,
node: &T,
pseudo_element: Option<PseudoElement>,
matching_rules_list: &mut ~[Rule]) {
// 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();
node.with_imm_element_like(|element: &E| {
match element.get_attr(None, "id") {
Some(id) => SelectorMap::get_matching_rules_from_hash(
node, pseudo_element, &self.id_hash, id, &mut matching_rules_list[list_index]),
Some(id) => {
SelectorMap::get_matching_rules_from_hash(node,
pseudo_element,
&self.id_hash,
id,
matching_rules_list)
}
None => {}
}
match element.get_attr(None, "class") {
Some(ref class_attr) => {
for class in class_attr.split_iter(WHITESPACE) {
SelectorMap::get_matching_rules_from_hash(
node, pseudo_element, &self.class_hash, class, &mut matching_rules_list[list_index]);
for class in class_attr.split_iter(SELECTOR_WHITESPACE) {
SelectorMap::get_matching_rules_from_hash(node,
pseudo_element,
&self.class_hash,
class,
matching_rules_list)
}
}
None => {}
}
SelectorMap::get_matching_rules_from_hash(
node, pseudo_element, &self.element_hash,
// HTML elements in HTML documents must be matched case-insensitively
// TODO: case-sensitivity depends on the document type
element.get_local_name().to_ascii_lower(),
&mut matching_rules_list[list_index]);
SelectorMap::get_matching_rules(
node, pseudo_element, self.universal_rules, &mut matching_rules_list[list_index]);
}
// HTML elements in HTML documents must be matched case-insensitively.
// TODO(pradeep): Case-sensitivity depends on the document type.
SelectorMap::get_matching_rules_from_hash(node,
pseudo_element,
&self.element_hash,
element.get_local_name().to_ascii_lower(),
matching_rules_list);
SelectorMap::get_matching_rules(node,
pseudo_element,
self.universal_rules,
matching_rules_list);
});
// Sort only the rules we just added.
tim_sort(matching_rules_list[list_index].mut_slice_from(init_len));
tim_sort(matching_rules_list.mut_slice_from(init_len));
}
fn get_matching_rules_from_hash<N: TreeNode<T>, T: TreeNodeRefAsElement<N, E>, E: ElementLike>(
node: &T,
pseudo_element: Option<PseudoElement>,
hash: &HashMap<~str, ~[Rule]>,
key: &str,
matching_rules: &mut ~[Rule]) {
fn get_matching_rules_from_hash<N:TreeNode<T>,
T:TreeNodeRefAsElement<N,E>,
E:ElementLike>(
node: &T,
pseudo_element: Option<PseudoElement>,
hash: &HashMap<~str,~[Rule]>,
key: &str,
matching_rules: &mut ~[Rule]) {
match hash.find(&key.to_str()) {
Some(rules) => SelectorMap::get_matching_rules(node, pseudo_element, *rules,
matching_rules),
Some(rules) => {
SelectorMap::get_matching_rules(node, pseudo_element, *rules, matching_rules)
}
None => {}
};
}
}
/// Return rules in `rules` that match `node`.
fn get_matching_rules<N: TreeNode<T>, T: TreeNodeRefAsElement<N, E>, E: ElementLike>(
node: &T,
pseudo_element: Option<PseudoElement>,
rules: &[Rule],
matching_rules: &mut ~[Rule]) {
/// Adds rules in `rules` that match `node` to the `matching_rules` list.
fn get_matching_rules<N:TreeNode<T>,
T:TreeNodeRefAsElement<N,E>,
E:ElementLike>(
node: &T,
pseudo_element: Option<PseudoElement>,
rules: &[Rule],
matching_rules: &mut ~[Rule]) {
for rule in rules.iter() {
if matches_selector(rule.selector.get(), node, pseudo_element) {
// TODO: Is the cloning inefficient?
// TODO(pradeep): Is the cloning inefficient?
matching_rules.push(rule.clone());
}
}
@ -186,7 +205,8 @@ impl SelectorMap {
let simple_selector_sequence = &rule.selector.get().compound_selectors.simple_selectors;
for ss in simple_selector_sequence.iter() {
match *ss {
// TODO: Implement case-sensitivity based on the document type and quirks mode
// TODO(pradeep): Implement case-sensitivity based on the document type and quirks
// mode.
IDSelector(ref id) => return Some(id.clone()),
_ => {}
}
@ -199,7 +219,8 @@ impl SelectorMap {
let simple_selector_sequence = &rule.selector.get().compound_selectors.simple_selectors;
for ss in simple_selector_sequence.iter() {
match *ss {
// TODO: Implement case-sensitivity based on the document type and quirks mode
// TODO(pradeep): Implement case-sensitivity based on the document type and quirks
// mode.
ClassSelector(ref class) => return Some(class.clone()),
_ => {}
}
@ -278,45 +299,84 @@ impl Stylist {
self.stylesheet_index += 1;
}
pub fn get_applicable_declarations<N: TreeNode<T>, T: TreeNodeRefAsElement<N, E>, E: ElementLike>(
&self, element: &T, style_attribute: Option<&PropertyDeclarationBlock>,
pseudo_element: Option<PseudoElement>) -> ~[Arc<~[PropertyDeclaration]>] {
/// Returns the applicable CSS declarations for the given element. This corresponds to
/// `ElementRuleCollector` in WebKit.
pub fn get_applicable_declarations<N:TreeNode<T>,
T:TreeNodeRefAsElement<N,E>,
E:ElementLike>(
&self,
element: &T,
style_attribute: Option<&PropertyDeclarationBlock>,
pseudo_element: Option<PseudoElement>)
-> ~[Arc<~[PropertyDeclaration]>] {
assert!(element.is_element());
assert!(style_attribute.is_none() || pseudo_element.is_none(),
"Style attributes do not apply to pseudo-elements");
// In cascading order
let rule_map_list = [&self.ua_rule_map.normal,
&self.user_rule_map.normal,
&self.author_rule_map.normal,
&self.author_rule_map.important,
&self.user_rule_map.important,
&self.ua_rule_map.important];
// In cascading order:
let rule_map_list = [
&self.ua_rule_map.normal,
&self.user_rule_map.normal,
&self.author_rule_map.normal,
&self.author_rule_map.important,
&self.user_rule_map.important,
&self.ua_rule_map.important
];
// We keep track of the indices of each of the rule maps in the list we're building so that
// we have the indices straight at the end.
let mut rule_map_indices = [ 0, ..6 ];
// TODO(pcwalton): Small vector optimization.
let mut matching_rules_list = ~[];
let mut matching_rules_list: [~[Rule], ..6] = [~[], ~[], ~[], ~[], ~[], ~[]];
for (i, rule_map) in rule_map_list.iter().enumerate() {
rule_map.get_all_matching_rules(element, pseudo_element, matching_rules_list, i);
rule_map_indices[i] = matching_rules_list.len();
rule_map.get_all_matching_rules(element, pseudo_element, &mut matching_rules_list);
}
// Keeping this as a separate step because we will need it for further
// optimizations regarding grouping of Rules having the same Selector.
let declarations_list: ~[~[Arc<~[PropertyDeclaration]>]] = matching_rules_list.iter().map(
|rules| rules.iter().map(|r| r.declarations.clone()).collect()).collect();
let count = matching_rules_list.len();
let mut declaration_iter = matching_rules_list.move_iter().map(|rule| {
let Rule {
declarations,
_
} = rule;
declarations
});
// Gather up all rules.
let mut applicable_declarations = ~[];
applicable_declarations.push_all_move(declarations_list.slice(0, 3).concat_vec());
// Style attributes have author origin but higher specificity than style rules.
// TODO: avoid copying?
let mut i = 0;
// Step 1: Normal rules.
while i < rule_map_indices[3] {
applicable_declarations.push(declaration_iter.next().unwrap());
i += 1
}
// Step 2: Normal style attributes.
style_attribute.map(|sa| applicable_declarations.push(sa.normal.clone()));
applicable_declarations.push_all_move(declarations_list.slice(3, 4).concat_vec());
// Step 3: Author-supplied `!important` rules.
while i < rule_map_indices[4] {
applicable_declarations.push(declaration_iter.next().unwrap());
i += 1
}
// Step 4: `!important` style attributes.
style_attribute.map(|sa| applicable_declarations.push(sa.important.clone()));
applicable_declarations.push_all_move(declarations_list.slice(4, 6).concat_vec());
// Step 5: User and UA `!important` rules.
while i < count {
applicable_declarations.push(declaration_iter.next().unwrap());
i += 1
}
applicable_declarations
}
}
struct PerOriginRules {
normal: ~[Rule],
important: ~[Rule],
@ -325,7 +385,10 @@ struct PerOriginRules {
impl PerOriginRules {
#[inline]
fn new() -> PerOriginRules {
PerOriginRules { normal: ~[], important: ~[] }
PerOriginRules {
normal: ~[],
important: ~[],
}
}
}
@ -337,7 +400,10 @@ struct PerOriginSelectorMap {
impl PerOriginSelectorMap {
#[inline]
fn new() -> PerOriginSelectorMap {
PerOriginSelectorMap { normal: SelectorMap::new(), important:SelectorMap::new() }
PerOriginSelectorMap {
normal: SelectorMap::new(),
important: SelectorMap::new(),
}
}
}
@ -415,8 +481,6 @@ fn matches_compound_selector<N: TreeNode<T>, T: TreeNodeRefAsElement<N, E>, E: E
#[inline]
fn matches_simple_selector<N: TreeNode<T>, T: TreeNodeRefAsElement<N, E>, E: ElementLike>(
selector: &SimpleSelector, element: &T) -> bool {
static WHITESPACE: &'static [char] = &'static [' ', '\t', '\n', '\r', '\x0C'];
match *selector {
// TODO: case-sensitivity depends on the document type
// TODO: intern element names
@ -447,7 +511,7 @@ fn matches_simple_selector<N: TreeNode<T>, T: TreeNodeRefAsElement<N, E>, E: Ele
None => false,
// TODO: case-sensitivity depends on the document type and quirks mode
Some(ref class_attr)
=> class_attr.split_iter(WHITESPACE).any(|c| c == class.as_slice()),
=> class_attr.split_iter(SELECTOR_WHITESPACE).any(|c| c == class.as_slice()),
}
}
}
@ -455,7 +519,7 @@ fn matches_simple_selector<N: TreeNode<T>, T: TreeNodeRefAsElement<N, E>, E: Ele
AttrExists(ref attr) => match_attribute(attr, element, |_| true),
AttrEqual(ref attr, ref value) => match_attribute(attr, element, |v| v == value.as_slice()),
AttrIncludes(ref attr, ref value) => do match_attribute(attr, element) |attr_value| {
attr_value.split_iter(WHITESPACE).any(|v| v == value.as_slice())
attr_value.split_iter(SELECTOR_WHITESPACE).any(|v| v == value.as_slice())
},
AttrDashMatch(ref attr, ref value, ref dashing_value)
=> do match_attribute(attr, element) |attr_value| {