Function LocalDateTimeString

deps/google-benchmark/src/timers.cc:195–268

}

std::string LocalDateTimeString() {
  // Write the local time in RFC3339 format yyyy-mm-ddTHH:MM:SS+/-HH:MM.
  typedef std::chrono::system_clock Clock;
  std::time_t now = Clock::to_time_t(Clock::now());
  const std::size_t kTzOffsetLen = 6;
  const std::size_t kTimestampLen = 19;

  std::size_t tz_len;
  std::size_t timestamp_len;
  long int offset_minutes;
  char tz_offset_sign = '+';
  // tz_offset is set in one of three ways:
  // * strftime with %z - This either returns empty or the ISO 8601 time.  The
  // maximum length an
  //   ISO 8601 string can be is 7 (e.g. -03:30, plus trailing zero).
  // * snprintf with %c%02li:%02li - The maximum length is 41 (one for %c, up to
  // 19 for %02li,
  //   one for :, up to 19 %02li, plus trailing zero).
  // * A fixed string of "-00:00".  The maximum length is 7 (-00:00, plus
  // trailing zero).
  //
  // Thus, the maximum size this needs to be is 41.
  char tz_offset[41];
  // Long enough buffer to avoid format-overflow warnings
  char storage[128];

#if defined(BENCHMARK_OS_WINDOWS)
  std::tm* timeinfo_p = ::localtime(&now);
#else
  std::tm timeinfo;
  std::tm* timeinfo_p = &timeinfo;
  ::localtime_r(&now, &timeinfo);
#endif

  tz_len = std::strftime(tz_offset, sizeof(tz_offset), "%z", timeinfo_p);

  if (tz_len < kTzOffsetLen && tz_len > 1) {
    // Timezone offset was written. strftime writes offset as +HHMM or -HHMM,
    // RFC3339 specifies an offset as +HH:MM or -HH:MM. To convert, we parse
    // the offset as an integer, then reprint it to a string.

    offset_minutes = ::strtol(tz_offset, NULL, 10);
    if (offset_minutes < 0) {
      offset_minutes *= -1;
      tz_offset_sign = '-';
    }

    tz_len =
        ::snprintf(tz_offset, sizeof(tz_offset), "%c%02li:%02li",
                   tz_offset_sign, offset_minutes / 100, offset_minutes % 100);
    BM_CHECK(tz_len == kTzOffsetLen);
    ((void)tz_len);  // Prevent unused variable warning in optimized build.
  } else {
    // Unknown offset. RFC3339 specifies that unknown local offsets should be
    // written as UTC time with -00:00 timezone.
#if defined(BENCHMARK_OS_WINDOWS)
    // Potential race condition if another thread calls localtime or gmtime.
    timeinfo_p = ::gmtime(&now);