scc

commit c715d4030343260c37b064df864a91ec1064a13b
parent 999d029a5b062ef4ceb1e7e145eaa1c41e4bfcc5
Author: Roberto E. Vargas Caballero <k0ga@shike2.net>
Date:   Sun, 19 Apr 2026 20:55:58 +0200

libc/time: Support negative time values

Diffstat:
M
src/libc/time/gmtime.c
 | 
50
++++++++++++++++++++++++++++++++++----------------
M
src/libc/time/mktime.c
 | 
12
++++++++++--

2 files changed, 44 insertions(+), 18 deletions(-)
diff --git a/src/libc/time/gmtime.c b/src/libc/time/gmtime.c
@@ -1,3 +1,4 @@
+#include <stdlib.h>
 #include <time.h>
 
 #include "../libc.h"
@@ -7,28 +8,45 @@
 struct tm *
 gmtime(const time_t *tim)
 {
+	div_t d;
+	int month, year;
+	time_t tday, day, t = *tim;
 	static struct tm tm;
-	time_t day;
-	int i;
 
-	tm.tm_sec = *tim % SECDAY;
-	tm.tm_min = tm.tm_sec / 60;
-	tm.tm_sec %= 60;
-	tm.tm_hour = tm.tm_min / 60;
-	tm.tm_min %= 60;
-	day = *tim / SECDAY;
+	day = t / SECDAY;
+	tday = t % SECDAY;
+	if (tday < 0) {
+		tday += SECDAY;
+		day--;
+	}
 
-	tm.tm_wday = (day + THU) % 7; /* 1/1/1970 was Thursday */
+	d = div(tday, 60);
+	tm.tm_sec = d.rem;
 
-	for (i = EPOCH; day >= _daysyear(i); ++i)
-		day -= _daysyear(i);
-	tm.tm_year = i - 1900;
+	d = div(d.quot, 60);
+	tm.tm_min = d.rem;
+
+	tm.tm_hour = d.quot;
+
+	/* 1/1/1970 was Thursday */
+	tm.tm_wday = (day + THU) % 7;
+
+	year = EPOCH;
+	if (day >= 0) {
+		while (day >= _daysyear(year))
+			day -= _daysyear(year++);
+	} else {
+		while (day < 0)
+			day += _daysyear(--year);
+	}
+
+	tm.tm_year = year - 1900;
 	tm.tm_yday = day;
 
-	_daysmon[FEB] = FEBDAYS(i);
-	for (i = JAN; day >= _daysmon[i]; i++)
-		day -= _daysmon[i];
-	tm.tm_mon = i;
+	_daysmon[FEB] = FEBDAYS(year);
+	for (month = JAN; day >= _daysmon[month]; month++)
+		day -= _daysmon[month];
+	tm.tm_mon = month;
 	tm.tm_mday = day + 1;
 
 	tm.tm_isdst = 0;
diff --git a/src/libc/time/mktime.c b/src/libc/time/mktime.c
@@ -110,8 +110,15 @@ mktime(struct tm *tm)
 
 	t = 0;
 	year = tm->tm_year + BASEYEAR;
-	for (i = EPOCH; i < year; ++i)
-		t += _daysyear(i) * SECDAY;
+
+	if (year >= EPOCH) {
+		for (i = EPOCH; i < year; ++i)
+			t += _daysyear(i) * SECDAY;
+	} else {
+		for (i = EPOCH; i > year; --i)
+			t -= _daysyear(i) * SECDAY;
+	}
+
 	for (i = 0; i < tm->tm_mon; ++i)
 		t += _daysmon[i] * SECDAY;
 
@@ -119,6 +126,7 @@ mktime(struct tm *tm)
 	t += tm->tm_min * SECMIN;
 	t += tm->tm_hour * SECHOUR;
 	t += (tm->tm_mday-1) * SECDAY;
+
 	aux = localtime(&t);
 
 	if (tm->tm_isdst == -1)