* localtime.c (transtime): Refactor to allow negative years
and years of a different type in future versions. Make the
code a bit clearer and faster with fewer conditional branches.
This does not change current behavior.
---
localtime.c | 68 ++++++++++++++++++-----------------------------------
1 file changed, 23 insertions(+), 45 deletions(-)
diff --git a/localtime.c b/localtime.c
index 8044f1a0..c2d58027 100644
--- a/localtime.c
+++ b/localtime.c
@@ -1536,37 +1536,23 @@ static int_fast32_t
transtime(const int year, register const struct rule *const rulep,
const int_fast32_t offset)
{
+ int d; /* Day of year (zero-origin). */
register bool leapyear;
- register int_fast32_t value;
- register int i;
- int d, m1, yy0, yy1, yy2, dow;
leapyear = isleap(year);
- switch (rulep->r_type) {
- case JULIAN_DAY:
+ if (rulep->r_type <= DAY_OF_YEAR) {
/*
** Jn - Julian day, 1 == January 1, 60 == March 1 even in leap
** years.
** In non-leap years, or if the day number is 59 or less, just
- ** add SECSPERDAY times the day number-1 to the time of
- ** January 1, midnight, to get the day.
- */
- value = (rulep->r_day - 1) * SECSPERDAY;
- if (leapyear && rulep->r_day >= 60)
- value += SECSPERDAY;
- break;
-
- case DAY_OF_YEAR:
- /*
+ ** use the day number - 1.
+ **
** n - day of year.
- ** Just add SECSPERDAY times the day number to the time of
- ** January 1, midnight, to get the day.
*/
- value = rulep->r_day * SECSPERDAY;
- break;
-
- case MONTH_NTH_DAY_OF_WEEK:
+ d = rulep->r_day - ((rulep->r_type < DAY_OF_YEAR)
+ & (!leapyear | (rulep->r_day <= 59)));
+ } else {
/*
** Mm.n.d - nth "dth day" of month m.
*/
@@ -1575,14 +1561,15 @@ transtime(const int year, register const struct rule
*const rulep,
** Use Zeller's Congruence to get day-of-week of first day of
** month.
*/
- m1 = (rulep->r_mon + 9) % 12 + 1;
- yy0 = (rulep->r_mon <= 2) ? (year - 1) : year;
- yy1 = yy0 / 100;
- yy2 = yy0 % 100;
- dow = ((26 * m1 - 2) / 10 +
- 1 + yy2 + yy2 / 4 + yy1 / 4 - 2 * yy1) % 7;
- if (dow < 0)
- dow += DAYSPERWEEK;
+ int i;
+ bool janfeb = rulep->r_mon <= 2;
+ int month = (rulep->r_mon
+ + (janfeb ? MONSPERYEAR : 0)); /* 3..14 */
+ int ay_rem = (year - janfeb) % YEARSPERREPEAT;
+ int y = ay_rem + (ay_rem < 0 ? YEARSPERREPEAT : 0);
+ int dow = (((13 * (month + 1)) / 5
+ + y + y / 4 - y / 100 + y / 400)
+ % DAYSPERWEEK);
/*
** "dow" is the day-of-week of the first day of the month. Get
@@ -1590,33 +1577,24 @@ transtime(const int year, register const struct rule
*const rulep,
** month.
*/
d = rulep->r_day - dow;
- if (d < 0)
- d += DAYSPERWEEK;
- for (i = 1; i < rulep->r_week; ++i) {
- if (d + DAYSPERWEEK >=
- mon_lengths[leapyear][rulep->r_mon - 1])
- break;
- d += DAYSPERWEEK;
- }
+ d += (rulep->r_week - (0 <= d)) * DAYSPERWEEK;
+ if (mon_lengths[leapyear][rulep->r_mon - 1] <= d)
+ d -= DAYSPERWEEK;
/*
** "d" is the day-of-month (zero-origin) of the day we want.
*/
- value = d * SECSPERDAY;
for (i = 0; i < rulep->r_mon - 1; ++i)
- value += mon_lengths[leapyear][i] * SECSPERDAY;
- break;
-
- default: unreachable();
+ d += mon_lengths[leapyear][i];
}
/*
- ** "value" is the year-relative time of 00:00:00 UT on the day in
+ ** d is the origin-0 year-relative day in
** question. To get the year-relative time of the specified local
** time on that day, add the transition time and the current offset
- ** from UT.
+ ** from UT to d * SECSPERDAY.
*/
- return value + rulep->r_time + offset;
+ return d * SECSPERDAY + rulep->r_time + offset;
}
/*
--
2.55.0
