monotonic_clock.h

Go to the documentation of this file.

// Copyright (C) 2013-2020 iFunFactory Inc. All Rights Reserved.
//
// This work is confidential and proprietary to iFunFactory Inc. and
// must not be used, disclosed, copied, or distributed without the prior
// consent of iFunFactory Inc.

#ifndef INCLUDE_FUNAPI_TIME_MONOTONIC_CLOCK_H_
#define INCLUDE_FUNAPI_TIME_MONOTONIC_CLOCK_H_

#ifndef _WIN32

#include <stdint.h>
#include <time.h>

#include <funapi/types.h>


namespace fun {


class FUNAPI_DLL_VISIBILITY MonotonicClock {
 public:
  typedef int64_t Value;

  typedef int64_t Duration;

  static void ToTimespec(const Value &value, struct timespec *ret) {
    ret->tv_sec = value / (1000 * 1000);
    ret->tv_nsec = value % (1000 * 1000) * 1000;
  }

  static Duration FromSec(int64_t sec) {
    return sec * 1000 * 1000;
  }

  static Duration FromMsec(int64_t msec) {
    return msec * 1000;
  }

  static Duration FromUsec(int64_t usec) {
    return usec;
  }

  static Value Now() {
    struct timespec now;
    clock_gettime(CLOCK_MONOTONIC, &now);
    return now.tv_sec * 1000 * 1000 + now.tv_nsec / 1000;
  }

 private:
  MonotonicClock() { }
};

}  // namespace fun

#else  // _WIN32

#include <funapi/types.h>

#include <cstddef>
#include <cstdint>
#include <ctime>


namespace fun {

class FUNAPI_DLL_VISIBILITY MonotonicClock {
 public:
  typedef LONGLONG Value;

  typedef LONGLONG Duration;

  static void ToTimespec(const Value &value, struct timespec *ret) {
    ret->tv_sec = value / (1000 * 1000);
    ret->tv_nsec = value % (1000 * 1000) * 1000;
  }

  static Duration FromSec(int64_t sec) {
    return sec * 1000 * 1000;
  }

  static Duration FromMsec(int64_t msec) {
    return msec * 1000;
  }

  static Duration FromUsec(int64_t usec) {
    return usec;
  }

  static Value Now() {
    static bool init = false;
    static LARGE_INTEGER frequency;  // frequency.QuadPart 는 ticks per second 를 포함한다.
    static LARGE_INTEGER epoch;

    if (!init) {
      init = true;
      QueryPerformanceFrequency(&frequency);
      QueryPerformanceCounter(&epoch);
    }

    LARGE_INTEGER now;
    QueryPerformanceCounter(&now);

    LARGE_INTEGER diff;
    diff.QuadPart = now.QuadPart - epoch.QuadPart;

    // 아래 작업은 tick 에 곱하는 작업을 먼저하고 tick 을 sec 으로 바꾸는 것을 나중에 한다.
    // 이는 precision 을 잃지 않기 위해서이다.
    diff.QuadPart *= 1000 * 1000;  // usec 으로 바꾸기 위해서 tick 값을 조정한다.
    diff.QuadPart /= frequency.QuadPart;

    return diff.QuadPart;
  }

 private:
  MonotonicClock() { }
};

}  // namespace fun

#endif  // _WIN32

#endif  // INCLUDE_FUNAPI_TIME_MONOTONIC_CLOCK_H_