ADD file via upload

kernel/mktime.c

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+/*
+ *  linux/kernel/mktime.c
+ *
+ *  (C) 1991  Linus Torvalds
+ */
+
+#include <time.h>
+
+/*
+ * This isn't the library routine, it is only used in the kernel.
+ * as such, we don't care about years<1970 etc, but assume everything
+ * is ok. Similarly, TZ etc is happily ignored. We just do everything
+ * as easily as possible. Let's find something public for the library
+ * routines (although I think minix times is public).
+ */
+/*
+ * PS. I hate whoever though up the year 1970 - couldn't they have gotten
+ * a leap-year instead? I also hate Gregorius, pope or no. I'm grumpy.
+ */
+#define MINUTE 60
+#define HOUR (60*MINUTE)
+#define DAY (24*HOUR)
+#define YEAR (365*DAY)
+
+/* interestingly, we assume leap-years */
+static int month[12] = {
+	0,
+	DAY*(31),
+	DAY*(31+29),
+	DAY*(31+29+31),
+	DAY*(31+29+31+30),
+	DAY*(31+29+31+30+31),
+	DAY*(31+29+31+30+31+30),
+	DAY*(31+29+31+30+31+30+31),
+	DAY*(31+29+31+30+31+30+31+31),
+	DAY*(31+29+31+30+31+30+31+31+30),
+	DAY*(31+29+31+30+31+30+31+31+30+31),
+	DAY*(31+29+31+30+31+30+31+31+30+31+30)
+};
+
+long kernel_mktime(struct tm * tm)
+{
+	long res;
+	int year;
+	if (tm->tm_year < 70 ) tm->tm_year += 100;  /* gohigh */
+	year = tm->tm_year - 70;
+/* magic offsets (y+1) needed to get leapyears right.*/
+	res = YEAR*year + DAY*((year+1)/4);
+	res += month[tm->tm_mon];
+/* and (y+2) here. If it wasn't a leap-year, we have to adjust */
+	if (tm->tm_mon>1 && ((year+2)%4))
+		res -= DAY;
+	res += DAY*(tm->tm_mday-1);
+	res += HOUR*tm->tm_hour;
+	res += MINUTE*tm->tm_min;
+	res += tm->tm_sec;
+	return res;
+}