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// Copyright (C) 2019 Google LLC
//
// 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 ICING_UTIL_CLOCK_H_
#define ICING_UTIL_CLOCK_H_
#include <cstdint>
#include <functional>
#include <memory>
namespace icing {
namespace lib {
// Returns the current steady time in nanoseconds. The steady clock is different
// from the system clock. It's monotonic and never returns a lower value than a
// previous call, while a system clock can be occasionally adjusted.
int64_t GetSteadyTimeNanoseconds();
// Returns the current steady time in Milliseconds. The steady clock is
// different from the system clock. It's monotonic and never returns a lower
// value than a previous call, while a system clock can be occasionally
// adjusted.
int64_t GetSteadyTimeMilliseconds();
// Used to calculate the elapsed time.
class Timer {
public:
// Creates and starts the timer.
Timer() : start_timestamp_nanoseconds_(GetSteadyTimeNanoseconds()) {}
virtual ~Timer() = default;
// Returns the elapsed time from when timer started.
virtual int64_t GetElapsedMilliseconds() const {
return GetElapsedNanoseconds() / 1000000;
}
// Returns the elapsed time from when timer started.
virtual int64_t GetElapsedNanoseconds() const {
return GetSteadyTimeNanoseconds() - start_timestamp_nanoseconds_;
}
private:
int64_t start_timestamp_nanoseconds_;
};
// Wrapper around real-time clock functions. This is separated primarily so
// tests can override this clock and inject it into the class under test.
class Clock {
public:
virtual ~Clock() = default;
// Returns the current time in milliseconds, it's guaranteed that the return
// value is non-negative.
virtual int64_t GetSystemTimeMilliseconds() const;
// Returns a timer used to calculate the elapsed time. The timer starts when
// the method returns.
virtual std::unique_ptr<Timer> GetNewTimer() const;
};
// A convenient RAII timer class that receives a callback. Upon destruction, the
// callback will be called with the elapsed milliseconds or nanoseconds passed
// as a parameter, depending on which Unit was passed in the constructor.
class ScopedTimer {
public:
enum class Unit { kMillisecond, kNanosecond };
ScopedTimer(std::unique_ptr<Timer> timer,
std::function<void(int64_t)> callback,
Unit unit = Unit::kMillisecond)
: timer_(std::move(timer)), callback_(std::move(callback)), unit_(unit) {}
~ScopedTimer() {
if (unit_ == Unit::kMillisecond) {
callback_(timer_->GetElapsedMilliseconds());
} else {
callback_(timer_->GetElapsedNanoseconds());
}
}
const Timer& timer() const { return *timer_; }
private:
std::unique_ptr<Timer> timer_;
std::function<void(int64_t)> callback_;
Unit unit_;
};
} // namespace lib
} // namespace icing
#endif // ICING_UTIL_CLOCK_H_
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