chromium/third_party/webrtc/rtc_base/time_utils.cc

/*
 *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#include <stdint.h>

#if defined(WEBRTC_POSIX)
#include <sys/time.h>
#endif

#include "rtc_base/checks.h"
#include "rtc_base/numerics/safe_conversions.h"
#include "rtc_base/system_time.h"
#include "rtc_base/time_utils.h"
#if defined(WEBRTC_WIN)
#include "rtc_base/win32.h"
#endif
#if defined(WEBRTC_WIN)
#include <minwinbase.h>
#endif

namespace rtc {

#if defined(WEBRTC_WIN) || defined(WINUWP)
// FileTime (January 1st 1601) to Unix time (January 1st 1970)
// offset in units of 100ns.
static constexpr uint64_t kFileTimeToUnixTimeEpochOffset =
    116444736000000000ULL;
static constexpr uint64_t kFileTimeToMicroSeconds = 10LL;
#endif

ClockInterface* g_clock = …;

ClockInterface* SetClockForTesting(ClockInterface* clock) { … }

ClockInterface* GetClockForTesting() { … }

#if defined(WINUWP)

namespace {

class TimeHelper final {
 public:
  TimeHelper(const TimeHelper&) = delete;

  // Resets the clock based upon an NTP server. This routine must be called
  // prior to the main system start-up to ensure all clocks are based upon
  // an NTP server time if NTP synchronization is required. No critical
  // section is used thus this method must be called prior to any clock
  // routines being used.
  static void SyncWithNtp(int64_t ntp_server_time_ms) {
    auto& singleton = Singleton();
    TIME_ZONE_INFORMATION time_zone;
    GetTimeZoneInformation(&time_zone);
    int64_t time_zone_bias_ns =
        rtc::dchecked_cast<int64_t>(time_zone.Bias) * 60 * 1000 * 1000 * 1000;
    singleton.app_start_time_ns_ =
        (ntp_server_time_ms - kNTPTimeToUnixTimeEpochOffset) * 1000000 -
        time_zone_bias_ns;
    singleton.UpdateReferenceTime();
  }

  // Returns the number of nanoseconds that have passed since unix epoch.
  static int64_t TicksNs() {
    auto& singleton = Singleton();
    int64_t result = 0;
    LARGE_INTEGER qpcnt;
    QueryPerformanceCounter(&qpcnt);
    result = rtc::dchecked_cast<int64_t>(
        (rtc::dchecked_cast<uint64_t>(qpcnt.QuadPart) * 100000 /
         rtc::dchecked_cast<uint64_t>(singleton.os_ticks_per_second_)) *
        10000);
    result = singleton.app_start_time_ns_ + result -
             singleton.time_since_os_start_ns_;
    return result;
  }

 private:
  TimeHelper() {
    TIME_ZONE_INFORMATION time_zone;
    GetTimeZoneInformation(&time_zone);
    int64_t time_zone_bias_ns =
        rtc::dchecked_cast<int64_t>(time_zone.Bias) * 60 * 1000 * 1000 * 1000;
    FILETIME ft;
    // This will give us system file in UTC format.
    GetSystemTimeAsFileTime(&ft);
    LARGE_INTEGER li;
    li.HighPart = ft.dwHighDateTime;
    li.LowPart = ft.dwLowDateTime;

    app_start_time_ns_ = (li.QuadPart - kFileTimeToUnixTimeEpochOffset) * 100 -
                         time_zone_bias_ns;

    UpdateReferenceTime();
  }

  static TimeHelper& Singleton() {
    static TimeHelper singleton;
    return singleton;
  }

  void UpdateReferenceTime() {
    LARGE_INTEGER qpfreq;
    QueryPerformanceFrequency(&qpfreq);
    os_ticks_per_second_ = rtc::dchecked_cast<int64_t>(qpfreq.QuadPart);

    LARGE_INTEGER qpcnt;
    QueryPerformanceCounter(&qpcnt);
    time_since_os_start_ns_ = rtc::dchecked_cast<int64_t>(
        (rtc::dchecked_cast<uint64_t>(qpcnt.QuadPart) * 100000 /
         rtc::dchecked_cast<uint64_t>(os_ticks_per_second_)) *
        10000);
  }

 private:
  static constexpr uint64_t kNTPTimeToUnixTimeEpochOffset = 2208988800000L;

  // The number of nanoseconds since unix system epoch
  int64_t app_start_time_ns_;
  // The number of nanoseconds since the OS started
  int64_t time_since_os_start_ns_;
  // The OS calculated ticks per second
  int64_t os_ticks_per_second_;
};

}  // namespace

void SyncWithNtp(int64_t time_from_ntp_server_ms) {
  TimeHelper::SyncWithNtp(time_from_ntp_server_ms);
}

int64_t WinUwpSystemTimeNanos() {
  return TimeHelper::TicksNs();
}

#endif  // defined(WINUWP)

int64_t SystemTimeMillis() { … }

int64_t TimeNanos() { … }

uint32_t Time32() { … }

int64_t TimeMillis() { … }

int64_t TimeMicros() { … }

int64_t TimeAfter(int64_t elapsed) { … }

int32_t TimeDiff32(uint32_t later, uint32_t earlier) { … }

int64_t TimeDiff(int64_t later, int64_t earlier) { … }

int64_t TmToSeconds(const tm& tm) { … }

int64_t TimeUTCMicros() { … }

int64_t TimeUTCMillis() { … }

}  // namespace rtc