Add build system scaffolding and libc headers

1 files changed, 42 insertions, 0 deletions

diff --git a/lib/libc/time/gmtime_r.c b/lib/libc/time/gmtime_r.c
new file mode 100644
index 00000000..8d441549
--- /dev/null
+++ b/lib/libc/time/gmtime_r.c
@@ -0,0 +1,42 @@
+#include <time.h>
+
+struct tm *gmtime_r(const time_t *timer, struct tm *result)
+{
+	time_t t = *timer;
+	int days, rem;
+	int year, month;
+
+	rem = t % 86400;
+	days = t / 86400;
+	if (rem < 0) {
+		rem += 86400;
+		days--;
+	}
+
+	result->tm_hour = rem / 3600;
+	rem %= 3600;
+	result->tm_min = rem / 60;
+	result->tm_sec = rem % 60;
+	result->tm_isdst = 0;
+
+	result->tm_wday = (4 + days) % 7;
+	if (result->tm_wday < 0)
+		result->tm_wday += 7;
+
+	long z = days + 719468;
+	long era = (z >= 0 ? z : z - 146096) / 146097;
+	long day_of_era = z - era * 146097;
+	long yoe = (day_of_era - day_of_era / 1460 + day_of_era / 36524 -
+		    day_of_era / 146096) /
+		   365;
+	year = (int)(yoe + era * 400);
+	long doy = day_of_era - (365 * yoe + yoe / 4 - yoe / 100);
+	result->tm_yday = (int)doy;
+
+	int mp = (5 * doy + 2) / 153;
+	result->tm_mday = (int)(doy - (153 * mp + 2) / 5 + 1);
+	result->tm_mon = (mp + 2) % 12;
+	result->tm_year = year - 1900 + (mp / 10);
+
+	return result;
+}