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Use dynamically-sized Arcs for Selector.

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MozReview-Commit-ID: hq0jYrx8Sg
This commit is contained in:
Bobby Holley 2017-06-02 17:59:35 -07:00
parent 21448cf266
commit 852efb825f
6 changed files with 29 additions and 340 deletions
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1
Cargo.lock generated
View file

@ -2523,6 +2523,7 @@ dependencies = [
"phf 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
"phf_codegen 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
"precomputed-hash 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
"servo_arc 0.0.1",
"size_of_test 0.0.1",
"smallvec 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
]

1
components/selectors/Cargo.toml
View file

@ -28,6 +28,7 @@ cssparser = "0.13.7"
fnv = "1.0"
phf = "0.7.18"
precomputed-hash = "0.1"
servo_arc = { path = "../servo_arc" }
smallvec = "0.4"
[dev-dependencies]

326
components/selectors/arcslice.rs
View file

@ -1,326 +0,0 @@
/* Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
* http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
* <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
* option. This file may not be copied, modified, or distributed
* except according to those terms.
*
* See the COPYRIGHT file at the top-level directory of this distribution */
//! A thread-safe reference-counted slice type.
//!
//! Forked from https://github.com/huonw/shared_slice , which doesn't work on
//! rust stable.
use std::{cmp, fmt, ops};
use std::hash::{Hash, Hasher};
use std::sync::{Arc, Weak};
/// A reference-counted slice type.
pub struct ArcSlice<T> {
data: *const [T],
counts: Arc<Box<[T]>>,
}
unsafe impl<T: Send + Sync> Send for ArcSlice<T> {}
unsafe impl<T: Send + Sync> Sync for ArcSlice<T> {}
/// A non-owning reference-counted slice type.
///
/// This is to `ArcSlice` as `std::sync::Weak` is to `std::sync::Arc`, and
/// allows one to have cyclic references without stopping memory from
/// being deallocated.
pub struct WeakSlice<T> {
data: *const [T],
counts: Weak<Box<[T]>>,
}
unsafe impl<T: Send + Sync> Send for WeakSlice<T> {}
unsafe impl<T: Send + Sync> Sync for WeakSlice<T> {}
impl<T> ArcSlice<T> {
/// Construct a new `ArcSlice` containing the elements of `slice`.
///
/// This reuses the allocation of `slice`.
pub fn new(slice: Box<[T]>) -> ArcSlice<T> {
ArcSlice {
data: &*slice,
counts: Arc::new(slice),
}
}
/// Downgrade self into a weak slice.
pub fn downgrade(&self) -> WeakSlice<T> {
WeakSlice {
data: self.data,
counts: Arc::downgrade(&self.counts)
}
}
/// Construct a new `ArcSlice` that only points to elements at
/// indices `lo` (inclusive) through `hi` (exclusive).
///
/// This consumes `self` to avoid unnecessary reference-count
/// modifications. Use `.clone()` if it is necessary to refer to
/// `self` after calling this.
///
/// # Panics
///
/// Panics if `lo > hi` or if either are strictly greater than
/// `self.len()`.
pub fn slice(mut self, lo: usize, hi: usize) -> ArcSlice<T> {
self.data = &self[lo..hi];
self
}
/// Construct a new `ArcSlice` that only points to elements at
/// indices up to `hi` (exclusive).
///
/// This consumes `self` to avoid unnecessary reference-count
/// modifications. Use `.clone()` if it is necessary to refer to
/// `self` after calling this.
///
/// # Panics
///
/// Panics if `hi > self.len()`.
pub fn slice_to(self, hi: usize) -> ArcSlice<T> {
self.slice(0, hi)
}
/// Construct a new `ArcSlice` that only points to elements at
/// indices starting at `lo` (inclusive).
///
/// This consumes `self` to avoid unnecessary reference-count
/// modifications. Use `.clone()` if it is necessary to refer to
/// `self` after calling this.
///
/// # Panics
///
/// Panics if `lo > self.len()`.
pub fn slice_from(self, lo: usize) -> ArcSlice<T> {
let hi = self.len();
self.slice(lo, hi)
}
}
impl<T> Clone for ArcSlice<T> {
fn clone(&self) -> ArcSlice<T> {
ArcSlice {
data: self.data,
counts: self.counts.clone()
}
}
}
impl<T> ops::Deref for ArcSlice<T> {
type Target = [T];
fn deref<'a>(&'a self) -> &'a [T] {
unsafe { &*self.data }
}
}
impl<T> AsRef<[T]> for ArcSlice<T> {
fn as_ref(&self) -> &[T] { &**self }
}
impl<T: PartialEq> PartialEq for ArcSlice<T> {
fn eq(&self, other: &ArcSlice<T>) -> bool { **self == **other }
fn ne(&self, other: &ArcSlice<T>) -> bool { **self != **other }
}
impl<T: Eq> Eq for ArcSlice<T> {}
impl<T: PartialOrd> PartialOrd for ArcSlice<T> {
fn partial_cmp(&self, other: &ArcSlice<T>) -> Option<cmp::Ordering> {
(**self).partial_cmp(&**other)
}
fn lt(&self, other: &ArcSlice<T>) -> bool { **self < **other }
fn le(&self, other: &ArcSlice<T>) -> bool { **self <= **other }
fn gt(&self, other: &ArcSlice<T>) -> bool { **self > **other }
fn ge(&self, other: &ArcSlice<T>) -> bool { **self >= **other }
}
impl<T: Ord> Ord for ArcSlice<T> {
fn cmp(&self, other: &ArcSlice<T>) -> cmp::Ordering { (**self).cmp(&**other) }
}
impl<T: Hash> Hash for ArcSlice<T> {
fn hash<H: Hasher>(&self, state: &mut H) {
Hash::hash(&**self, state)
}
}
impl<T: fmt::Debug> fmt::Debug for ArcSlice<T> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
fmt::Debug::fmt(&**self, f)
}
}
impl<T> WeakSlice<T> {
/// Attempt to upgrade `self` to a strongly-counted `ArcSlice`.
///
/// Returns `None` if this is not possible (the data has already
/// been freed).
pub fn upgrade(&self) -> Option<ArcSlice<T>> {
self.counts.upgrade().map(|counts| {
ArcSlice {
data: self.data,
counts: counts
}
})
}
}
#[cfg(test)]
mod tests {
use std::cell::Cell;
use std::cmp::Ordering;
use std::sync::{Arc, Mutex};
use super::{ArcSlice, WeakSlice};
#[test]
fn clone() {
let x = ArcSlice::new(Box::new([Cell::new(false)]));
let y = x.clone();
assert_eq!(x[0].get(), false);
assert_eq!(y[0].get(), false);
x[0].set(true);
assert_eq!(x[0].get(), true);
assert_eq!(y[0].get(), true);
}
#[test]
fn test_upgrade_downgrade() {
let x = ArcSlice::new(Box::new([1]));
let y: WeakSlice<_> = x.downgrade();
assert_eq!(y.upgrade(), Some(x.clone()));
drop(x);
assert!(y.upgrade().is_none())
}
#[test]
fn test_total_cmp() {
let x = ArcSlice::new(Box::new([1, 2, 3]));
let y = ArcSlice::new(Box::new([1, 2, 3]));
let z = ArcSlice::new(Box::new([1, 2, 4]));
assert_eq!(x, x);
assert_eq!(x, y);
assert!(x != z);
assert!(y != z);
assert!(x < z);
assert!(x <= z);
assert!(!(x > z));
assert!(!(x >= z));
assert!(!(z < x));
assert!(!(z <= x));
assert!(z > x);
assert!(z >= x);
assert_eq!(x.partial_cmp(&x), Some(Ordering::Equal));
assert_eq!(x.partial_cmp(&y), Some(Ordering::Equal));
assert_eq!(x.partial_cmp(&z), Some(Ordering::Less));
assert_eq!(z.partial_cmp(&y), Some(Ordering::Greater));
assert_eq!(x.cmp(&x), Ordering::Equal);
assert_eq!(x.cmp(&y), Ordering::Equal);
assert_eq!(x.cmp(&z), Ordering::Less);
assert_eq!(z.cmp(&y), Ordering::Greater);
}
#[test]
fn test_partial_cmp() {
use std::f64;
let x = ArcSlice::new(Box::new([1.0, f64::NAN]));
let y = ArcSlice::new(Box::new([1.0, f64::NAN]));
let z = ArcSlice::new(Box::new([2.0, f64::NAN]));
let w = ArcSlice::new(Box::new([f64::NAN, 1.0]));
assert!(!(x == y));
assert!(x != y);
assert!(!(x < y));
assert!(!(x <= y));
assert!(!(x > y));
assert!(!(x >= y));
assert!(x < z);
assert!(x <= z);
assert!(!(x > z));
assert!(!(x >= z));
assert!(!(z < w));
assert!(!(z <= w));
assert!(!(z > w));
assert!(!(z >= w));
assert_eq!(x.partial_cmp(&x), None);
assert_eq!(x.partial_cmp(&y), None);
assert_eq!(x.partial_cmp(&z), Some(Ordering::Less));
assert_eq!(z.partial_cmp(&x), Some(Ordering::Greater));
assert_eq!(x.partial_cmp(&w), None);
assert_eq!(y.partial_cmp(&w), None);
assert_eq!(z.partial_cmp(&w), None);
assert_eq!(w.partial_cmp(&w), None);
}
#[test]
fn test_show() {
let x = ArcSlice::new(Box::new([1, 2]));
assert_eq!(format!("{:?}", x), "[1, 2]");
let y: ArcSlice<i32> = ArcSlice::new(Box::new([]));
assert_eq!(format!("{:?}", y), "[]");
}
#[test]
fn test_slice() {
let x = ArcSlice::new(Box::new([1, 2, 3]));
let real = [1, 2, 3];
for i in 0..3 + 1 {
for j in i..3 + 1 {
let slice: ArcSlice<_> = x.clone().slice(i, j);
assert_eq!(&*slice, &real[i..j]);
}
assert_eq!(&*x.clone().slice_to(i), &real[..i]);
assert_eq!(&*x.clone().slice_from(i), &real[i..]);
}
}
#[test]
fn test_send_sync() {
fn assert_send<T: Send>() {}
fn assert_sync<T: Send>() {}
assert_send::<ArcSlice<u8>>();
assert_sync::<ArcSlice<u8>>();
assert_send::<WeakSlice<u8>>();
assert_sync::<WeakSlice<u8>>();
}
#[test]
fn test_drop() {
let drop_flag = Arc::new(Mutex::new(0));
struct Foo(Arc<Mutex<i32>>);
impl Drop for Foo {
fn drop(&mut self) {
let mut n = self.0.lock().unwrap();
*n += 1;
}
}
let whole = ArcSlice::new(Box::new([Foo(drop_flag.clone()), Foo(drop_flag.clone())]));
drop(whole);
assert_eq!(*drop_flag.lock().unwrap(), 2);
*drop_flag.lock().unwrap() = 0;
let whole = ArcSlice::new(Box::new([Foo(drop_flag.clone()), Foo(drop_flag.clone())]));
let part = whole.slice(1, 2);
drop(part);
assert_eq!(*drop_flag.lock().unwrap(), 2);
}
}

2
components/selectors/lib.rs
View file

@ -9,9 +9,9 @@ extern crate fnv;
extern crate phf;
extern crate precomputed_hash;
#[cfg(test)] #[macro_use] extern crate size_of_test;
extern crate servo_arc;
extern crate smallvec;
pub mod arcslice;
pub mod attr;
pub mod bloom;
pub mod matching;

37
components/selectors/parser.rs
View file

@ -2,11 +2,11 @@
* 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/. */
use arcslice::ArcSlice;
use attr::{AttrSelectorWithNamespace, ParsedAttrSelectorOperation, AttrSelectorOperator};
use attr::{ParsedCaseSensitivity, SELECTOR_WHITESPACE, NamespaceConstraint};
use cssparser::{Token, Parser as CssParser, parse_nth, ToCss, serialize_identifier, CssStringWriter};
use precomputed_hash::PrecomputedHash;
use servo_arc::{Arc, HeaderSlice};
use smallvec::SmallVec;
use std::ascii::AsciiExt;
use std::borrow::{Borrow, Cow};
@ -302,6 +302,19 @@ pub fn namespace_empty_string<Impl: SelectorImpl>() -> Impl::NamespaceUrl {
Impl::NamespaceUrl::default()
}
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
struct SpecificityAndFlags(u32);
impl SpecificityAndFlags {
fn specificity(&self) -> u32 {
self.0 & !HAS_PSEUDO_BIT
}
fn has_pseudo_element(&self) -> bool {
(self.0 & HAS_PSEUDO_BIT) != 0
}
}
/// A Selector stores a sequence of simple selectors and combinators. The
/// iterator classes allow callers to iterate at either the raw sequence level or
/// at the level of sequences of simple selectors separated by combinators. Most
@ -311,15 +324,15 @@ pub fn namespace_empty_string<Impl: SelectorImpl>() -> Impl::NamespaceUrl {
/// canonical iteration order is right-to-left (selector matching order). The
/// iterators abstract over these details.
#[derive(Clone, Eq, PartialEq)]
pub struct Selector<Impl: SelectorImpl>(ArcSlice<Component<Impl>>, u32);
pub struct Selector<Impl: SelectorImpl>(Arc<HeaderSlice<SpecificityAndFlags, [Component<Impl>]>>);
impl<Impl: SelectorImpl> Selector<Impl> {
pub fn specificity(&self) -> u32 {
self.1 & !HAS_PSEUDO_BIT
self.0.header.specificity()
}
pub fn has_pseudo_element(&self) -> bool {
(self.1 & HAS_PSEUDO_BIT) != 0
self.0.header.has_pseudo_element()
}
pub fn pseudo_element(&self) -> Option<&Impl::PseudoElement> {
@ -362,8 +375,7 @@ impl<Impl: SelectorImpl> Selector<Impl> {
pub fn iter_from(&self, offset: usize) -> SelectorIter<Impl> {
// Note: selectors are stored left-to-right but logical order is right-to-left.
let slice = self.0.as_ref();
let iter = slice[..(slice.len() - offset)].iter().rev();
let iter = self.0.slice[..(self.0.slice.len() - offset)].iter().rev();
SelectorIter {
iter: iter,
next_combinator: None,
@ -379,12 +391,13 @@ impl<Impl: SelectorImpl> Selector<Impl> {
/// Returns an iterator over the entire sequence of simple selectors and combinators,
/// from left to right.
pub fn iter_raw_rev(&self) -> slice::Iter<Component<Impl>> {
self.0.iter()
self.0.slice.iter()
}
/// Creates a Selector from a vec of Components. Used in tests.
pub fn from_vec(vec: Vec<Component<Impl>>, specificity_and_flags: u32) -> Self {
Selector(ArcSlice::new(vec.into_boxed_slice()), specificity_and_flags)
let spec = SpecificityAndFlags(specificity_and_flags);
Selector(Arc::from_header_and_iter(spec, vec.into_iter()))
}
}
@ -985,15 +998,15 @@ fn parse_complex_selector<P, Impl>(
sequence.push(Component::Combinator(combinator));
}
let mut specificity = specificity(SelectorIter {
let mut spec = SpecificityAndFlags(specificity(SelectorIter {
iter: sequence.iter().rev(),
next_combinator: None,
});
}));
if parsed_pseudo_element {
specificity |= HAS_PSEUDO_BIT;
spec.0 |= HAS_PSEUDO_BIT;
}
let complex = Selector(ArcSlice::new(sequence.into_vec().into_boxed_slice()), specificity);
let complex = Selector(Arc::from_header_and_iter(spec, sequence.into_iter()));
Ok(complex)
}

2
tests/unit/stylo/size_of.rs
View file

@ -22,7 +22,7 @@ fn size_of_selectors_dummy_types() {
// The size of this is critical to performance on the bloom-basic microbenchmark.
// When iterating over a large Rule array, we want to be able to fast-reject
// selectors (with the inline hashes) with as few cache misses as possible.
size_of_test!(test_size_of_rule, style::stylist::Rule, 64);
size_of_test!(test_size_of_rule, style::stylist::Rule, 48);
size_of_test!(test_size_of_property_declaration, style::properties::PropertyDeclaration, 32);