text: /*
   * Copyright (c) Facebook, Inc. and its affiliates.
   *
   * 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.
   */
  
  #include <basic/portability/SysTime.h>
  
  #ifdef _WIN32
  
  #include <cstdint>
  
  extern "C" {
  int gettimeofday(timeval* tv, basic_port_struct_timezone*) {
    constexpr auto posixWinFtOffset = 116444736000000000ULL;
  
    if (tv) {
      FILETIME ft;
      ULARGE_INTEGER lft;
      GetSystemTimeAsFileTime(&ft);
      // As per the docs of FILETIME, don't just do an indirect
      // pointer cast, to avoid alignment faults.
      lft.HighPart = ft.dwHighDateTime;
      lft.LowPart = ft.dwLowDateTime;
      uint64_t ns = lft.QuadPart;
      tv->tv_usec = (long)((ns / 10ULL) % 1000000ULL);
      tv->tv_sec = (long)((ns - posixWinFtOffset) / 10000000ULL);
    }
  
    return 0;
  }
  
  void timeradd(timeval* a, timeval* b, timeval* res) {
    res->tv_sec = a->tv_sec + b->tv_sec;
    res->tv_usec = a->tv_usec + b->tv_usec;
    if (res->tv_usec >= 1000000) {
      res->tv_sec++;
      res->tv_usec -= 1000000;
    }
  }
  
  void timersub(timeval* a, timeval* b, timeval* res) {
    res->tv_sec = a->tv_sec - b->tv_sec;
    res->tv_usec = a->tv_usec - b->tv_usec;
    if (res->tv_usec < 0) {
      res->tv_sec--;
      res->tv_usec += 1000000;
    }
  }
  }
  
  #endif
  