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/*
* Copyright (C) 2016 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef CLOCK_H_
#define CLOCK_H_
#include <cstdint>
namespace profiler {
// A mockable clock class for getting the current epoch time, in nanoseconds.
// Example:
// SteadyClock clock;
// Log(clock.GetCurrentTime())
//
// Note: If you are more interested in the amount of time an operation took,
// rather than absolute time, use Stopwatch instead.
class Clock {
public:
// Returns a monotonically increasing value. This value is meant for
// comparing two relative times, as the time represented by time=0 is not
// explicitly defined.
virtual uint64_t GetCurrentTime() const = 0;
virtual ~Clock() = default;
};
// A Clock implementation based on clock_gettime(CLOCK_MONOTONIC).
//
// Note: we choose to rely on our own class instead of <chrono> because our most
// important use-case is profiling on Android, and this approach lets us use an
// API which:
// - has satisfactory precision, granularity, and reliability
// - is also accessible from Java via System.nanoTime.
// - is used by the Linux kernel to timestamp events (like in perfs)
class SteadyClock final : public Clock {
public:
virtual uint64_t GetCurrentTime() const override;
};
} // namespace profiler
#endif //CLOCK_H_
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