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// Copyright 2018 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_TIMING_TIME_CLAMPER_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_TIMING_TIME_CLAMPER_H_
#include "base/time/time.h"
#include "build/build_config.h"
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
#include <stdint.h>
namespace blink {
class CORE_EXPORT TimeClamper {
USING_FAST_MALLOC(TimeClamper);
public:
static constexpr int kCoarseResolutionMicroseconds = 100;
static constexpr int kFineResolutionMicroseconds = 5;
TimeClamper();
TimeClamper(const TimeClamper&) = delete;
TimeClamper& operator=(const TimeClamper&) = delete;
// Deterministically clamp the time value |time_microseconds| to a fixed
// interval to prevent timing attacks. See
// http://www.w3.org/TR/hr-time-2/#privacy-security.
//
// For each clamped time interval, we compute a pseudorandom transition
// threshold. The returned time will either be the start of that interval or
// the next one depending on which side of the threshold |time_microseconds|
// is.
base::TimeDelta ClampTimeResolution(
base::TimeDelta time,
bool cross_origin_isolated_capability) const;
private:
inline double ThresholdFor(int64_t clamped_time, int resolution) const;
static inline double ToDouble(uint64_t value);
static inline uint64_t MurmurHash3(uint64_t value);
uint64_t secret_;
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_CORE_TIMING_TIME_CLAMPER_H_
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