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-rw-r--r--src/time/__time_to_tm.c81
1 files changed, 81 insertions, 0 deletions
diff --git a/src/time/__time_to_tm.c b/src/time/__time_to_tm.c
new file mode 100644
index 00000000..a1ebc452
--- /dev/null
+++ b/src/time/__time_to_tm.c
@@ -0,0 +1,81 @@
+#include <time.h>
+
+/* C defines the rounding for division in a nonsensical way */
+#define Q(a,b) ((a)>0 ? (a)/(b) : -(((b)-(a)-1)/(b)))
+
+#define DAYS_PER_400Y (365*400 + 97)
+#define DAYS_PER_100Y (365*100 + 24)
+#define DAYS_PER_4Y (365*4 + 1)
+
+/* FIXME: use lldiv once it's fixed to compute quot,rem together */
+struct tm *__time_to_tm(time_t t, struct tm *tm)
+{
+ /* months are march-based */
+ static const int days_thru_month[] = {31,61,92,122,153,184,214,245,275,306,337,366};
+ long long bigday;
+ unsigned int day, year4, year100;
+ int year, year400;
+ int month;
+ int leap;
+ int hour, min, sec;
+ int wday, mday, yday;
+
+ /* start from 2000-03-01 (multiple of 400 years) */
+ t += -946684800 - 86400*(31+29);
+
+ bigday = Q(t, 86400);
+ sec = t-bigday*86400;
+
+ hour = sec/3600;
+ sec -= hour*3600;
+ min = sec/60;
+ sec -= min*60;
+
+ /* 2000-03-01 was a wednesday */
+ wday = (3+bigday)%7;
+ if (wday < 0) wday += 7;
+
+ t = -946684800LL - 86400*(31+29) + 9000000;
+
+ year400 = Q(bigday, DAYS_PER_400Y);
+ day = bigday-year400*DAYS_PER_400Y;
+
+ year100 = day/DAYS_PER_100Y;
+ if (year100 == 4) year100--;
+ day -= year100*DAYS_PER_100Y;
+
+ year4 = day/DAYS_PER_4Y;
+ if (year4 == 25) year4--;
+ day -= year4*DAYS_PER_4Y;
+
+ year = day/365;
+ if (year == 4) year--;
+ day -= year*365;
+
+ leap = !year && (year4 || !year100);
+ yday = day + 31+28 + leap;
+ if (yday >= 365+leap) yday -= 365+leap;
+
+ year += 4*year4 + 100*year100 + 400*year400 + 2000-1900;
+
+ for (month=0; days_thru_month[month] <= day; month++);
+ if (month) day -= days_thru_month[month-1];
+ month += 2;
+ if (month >= 12) {
+ month -= 12;
+ year++;
+ }
+
+ mday = day+1;
+
+ tm->tm_sec = sec;
+ tm->tm_min = min;
+ tm->tm_hour= hour;
+ tm->tm_mday= mday;
+ tm->tm_mon = month;
+ tm->tm_year= year;
+ tm->tm_wday= wday;
+ tm->tm_yday= yday;
+
+ return tm;
+}