int SetNonBlocking(int fd) {
#if defined(OS_WIN)
  unsigned long no_block = 1;
  return ioctlsocket(fd, FIONBIO, &no_block);
#elif defined(OS_POSIX)
  int flags = fcntl(fd, F_GETFL, 0);
  if (-1 == flags)
    flags = 0;
  return fcntl(fd, F_SETFL, flags | O_NONBLOCK);
#endif
}

Unknown