if (fd < 0) fd = __open (OLD_HOSTIDFILE, O_RDONLY);
gethostid (){  char hostname[MAXHOSTNAMELEN + 1];  size_t buflen;  char *buffer;  struct hostent hostbuf, *hp;  unsigned long int id;  struct in_addr in;  int herr;  int fd;  /* First try to get the ID from a former invocation of sethostid.  */  fd = __open (HOSTIDFILE, O_RDONLY);  if (fd >= 0)    {      ssize_t n = __read (fd, &id, sizeof (id));      __close (fd);      if (n == sizeof (id))	return id;    }  /* Getting from the file was not successful.  An intelligent guess for     a unique number of a host is its IP address.  Return this.  */  if (__gethostname (hostname, MAXHOSTNAMELEN) < 0 || hostname[0] == '\0')    /* This also fails.  Return and arbitrary value.  */    return 0;  buflen = 1024;  buffer = __alloca (buflen);  /* To get the IP address we need to know the host name.  */  while (__gethostbyname_r (hostname, &hostbuf, buffer, buflen, &hp, &herr)	 != 0	 || hp == NULL)    if (herr != NETDB_INTERNAL || errno != ERANGE)      return 0;    else      {	/* Enlarge buffer.  */	buflen *= 2;	buffer = __alloca (buflen);      }  in.s_addr = 0;  memcpy (&in, hp->h_addr,	  (int) sizeof (in) < hp->h_length ? sizeof (in) : hp->h_length);  /* For the return value to be not exactly the IP address we do some     bit fiddling.  */  return in.s_addr << 16 | in.s_addr >> 16;}