Function stringzone

zic.c:3286–3407

Store into RESULT a proleptic TZ string that represent the future predictions for the zone ZPFIRST with ZONECOUNT entries. Return a compatibility indicator (a TZDB release year) if successful, a negative integer if no such TZ string exists. */

		return 1;
	if (a->r_hiyear != b->r_hiyear)
		return a->r_hiyear < b->r_hiyear ? -1 : 1;
	if (a->r_hiyear == ZIC_MAX)
		return 0;
	if (a->r_month - b->r_month != 0)
		return a->r_month - b->r_month;
	return a->r_dayofmonth - b->r_dayofmonth;
}

/* Store into RESULT a proleptic TZ string that represent the future
   predictions for the zone ZPFIRST with ZONECOUNT entries.  Return a
   compatibility indicator (a TZDB release year) if successful, a
   negative integer if no such TZ string exists.  */
static int
stringzone(char *result, struct zone const *zpfirst, ptrdiff_t zonecount)
{
	register const struct zone *	zp;
	register struct rule *		rp;
	register struct rule *		stdrp;
	register struct rule *		dstrp;
	register ptrdiff_t		i;
	register int			compat = 0;
	register int			c;
	int				offsetlen;
	struct rule			stdr, dstr;
	ptrdiff_t len;
	int dstcmp;
	struct rule *lastrp[2] = { NULL, NULL };
	struct zone zstr[2];
	struct zone const *stdzp;
	struct zone const *dstzp;

	result[0] = '\0';

	/* Internet RFC 9636 section 6.1 says to use an empty TZ string if
	   future timestamps are truncated.  */
	if (hi_time < max_time)
	  return -1;

	zp = zpfirst + zonecount - 1;
	for (i = 0; i < zp->z_nrules; ++i) {
		struct rule **last;
		int cmp;
		rp = &zp->z_rules[i];
		last = &lastrp[rp->r_isdst];
		cmp = rule_cmp(*last, rp);
		if (cmp < 0)
		  *last = rp;
		else if (cmp == 0)
		  return -1;
	}
	stdrp = lastrp[false];
	dstrp = lastrp[true];
	dstcmp = zp->z_nrules ? rule_cmp(dstrp, stdrp) : zp->z_isdst ? 1 : -1;
	stdzp = dstzp = zp;

	if (dstcmp < 0) {
	  /* Standard time all year.  */
	  dstrp = NULL;