NULL;
;
res_hnok(dn)	const char *dn;{	int ppch = '\0', pch = PERIOD, ch = *dn++;	while (ch != '\0') {		int nch = *dn++;		if (periodchar(ch)) {			NULL;		} else if (periodchar(pch)) {			if (!borderchar(ch))				return (0);		} else if (periodchar(nch) || nch == '\0') {			if (!borderchar(ch))				return (0);		} else {			if (!middlechar(ch))				return (0);		}		ppch = pch, pch = ch, ch = nch;	}	return (1);}