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// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_CSS_SEEKER_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_CSS_SEEKER_H_
#include <iterator>
#include "base/memory/stack_allocated.h"
#include "third_party/blink/renderer/core/css/rule_set.h"
namespace blink {
// Sequentially scans a sorted list of RuleSet::Interval<T> and seeks
// for the value for a rule (given by its position). Seek() must be called
// with non-decreasing rule positions, so that we only need to go
// through the layer list at most once for all Seek() calls.
template <class T>
class Seeker {
STACK_ALLOCATED();
public:
explicit Seeker(const HeapVector<RuleSet::Interval<T>>& intervals)
: intervals_(intervals), iter_(intervals_.begin()) {}
const T* Seek(unsigned rule_position) {
#if DCHECK_IS_ON()
DCHECK_GE(rule_position, last_rule_position_);
last_rule_position_ = rule_position;
#endif
iter_ = std::find_if(iter_, intervals_.end(),
[rule_position](const RuleSet::Interval<T>& interval) {
return interval.start_position > rule_position;
});
if (iter_ == intervals_.begin()) {
return nullptr;
}
return std::prev(iter_)->value.Get();
}
private:
const HeapVector<RuleSet::Interval<T>>& intervals_;
HeapVector<RuleSet::Interval<T>>::const_iterator iter_;
#if DCHECK_IS_ON()
unsigned last_rule_position_ = 0;
#endif
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_CORE_CSS_SEEKER_H_
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