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// Copyright 2023 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_MODULES_COMPUTE_PRESSURE_CHANGE_RATE_MONITOR_H_
#define THIRD_PARTY_BLINK_RENDERER_MODULES_COMPUTE_PRESSURE_CHANGE_RATE_MONITOR_H_
#include <array>
#include "base/timer/timer.h"
#include "third_party/blink/renderer/bindings/modules/v8/v8_pressure_source.h"
#include "third_party/blink/renderer/modules/compute_pressure/pressure_record.h"
#include "third_party/blink/renderer/platform/heap/collection_support/heap_hash_map.h"
namespace blink {
// ChangeRateMonitor is a class encompassing the implementation of
// parameters involved the rate obfuscation mitigation.
// https://w3c.github.io/compute-pressure/#ref-for-dfn-rate-obfuscation-1
class ChangeRateMonitor final {
public:
ChangeRateMonitor();
~ChangeRateMonitor();
// Reset counters and internal data if more time has passed than the
// current observation window's length.
void ResetIfNeeded();
void ResetChangeCount(V8PressureSource::Enum);
void IncreaseChangeCount(V8PressureSource::Enum);
// Check if the amount of state changes is exceeding the limit of changes
// allowed during the observation window's length.
bool ChangeCountExceedsLimit(V8PressureSource::Enum) const;
void set_change_count_threshold_for_testing(uint64_t count) {
change_count_threshold_ = count;
}
void set_penalty_duration_for_testing(base::TimeDelta time) {
penalty_duration_ = time;
}
// Return the penalty duration applied during the observation window's
// duration;
base::TimeDelta penalty_duration() const { return penalty_duration_; }
private:
// Reset all private members.
void Reset();
// Timestamp when the observation window is created.
base::TimeTicks start_time_;
// Duration of the current observation window.
// A randomized number.
base::TimeDelta observation_window_time_;
// Maximum number of state changes during observation window length.
// A randomized number.
uint64_t change_count_threshold_;
// Penalty duration when |change_count_| reaches |change_count_threshold_|.
// A randomized number.
base::TimeDelta penalty_duration_;
// Map to keep the state changes count per source.
std::array<uint64_t, V8PressureSource::kEnumSize> change_count_;
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_MODULES_COMPUTE_PRESSURE_CHANGE_RATE_MONITOR_H_
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