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style: Add a very simple use counter implementation.
As simple as I could make it, for now. We can improve on this. Differential Revision: https://phabricator.services.mozilla.com/D3827
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4 changed files with 105 additions and 45 deletions
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components/style/use_counters/mod.rs
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components/style/use_counters/mod.rs
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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//! Various stuff for CSS property use counters.
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use properties::{NonCustomPropertyId, NON_CUSTOM_PROPERTY_ID_COUNT};
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// FIXME(emilio): We need AtomicU32 on stable ASAP...
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use std::sync::atomic::AtomicUsize;
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use std::sync::atomic::Ordering;
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#[cfg(target_pointer_width = "64")]
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const BITS_PER_ENTRY: usize = 64;
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#[cfg(target_pointer_width = "32")]
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const BITS_PER_ENTRY: usize = 32;
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/// One bit per each non-custom CSS property.
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#[derive(Default)]
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pub struct NonCustomPropertyUseCounters {
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storage: [AtomicUsize; (NON_CUSTOM_PROPERTY_ID_COUNT - 1 + BITS_PER_ENTRY) / BITS_PER_ENTRY],
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}
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impl NonCustomPropertyUseCounters {
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/// Record that a given non-custom property ID has been parsed.
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#[inline]
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pub fn record(&self, id: NonCustomPropertyId) {
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let bit = id.bit();
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let bucket = bit / BITS_PER_ENTRY;
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let bit_in_bucket = bit % BITS_PER_ENTRY;
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self.storage[bucket].fetch_or(1 << bit_in_bucket, Ordering::Relaxed);
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}
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}
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/// The use-counter data related to a given document we want to store.
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pub struct UseCounters {
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/// The counters for non-custom properties that have been parsed in the
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/// document's stylesheets.
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pub non_custom_properties: NonCustomPropertyUseCounters,
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}
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