udf: Convert udf_disk_stamp_to_time() to use mktime64()

Convert udf_disk_stamp_to_time() to use mktime64() to simplify the code.
As a bonus we get working timestamp conversion for dates before epoch
and after 2038 (both of which are allowed by UDF standard).
Signed-off-by: Jan Kara <jack@suse.cz>

fs/udf/udftime.c

@@ -40,52 +40,9 @@
 #include <linux/kernel.h>
 #include <linux/time.h>
 
-#define EPOCH_YEAR 1970
-
-#ifndef __isleap
-/* Nonzero if YEAR is a leap year (every 4 years,
-   except every 100th isn't, and every 400th is).  */
-#define	__isleap(year)	\
-  ((year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0))
-#endif
-
-/* How many days come before each month (0-12).  */
-static const unsigned short int __mon_yday[2][13] = {
-	/* Normal years.  */
-	{0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365},
-	/* Leap years.  */
-	{0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366}
-};
-
-#define MAX_YEAR_SECONDS	69
-#define SPD			0x15180	/*3600*24 */
-#define SPY(y, l, s)		(SPD * (365 * y + l) + s)
-
-static time_t year_seconds[MAX_YEAR_SECONDS] = {
-/*1970*/ SPY(0,   0, 0), SPY(1,   0, 0), SPY(2,   0, 0), SPY(3,   1, 0),
-/*1974*/ SPY(4,   1, 0), SPY(5,   1, 0), SPY(6,   1, 0), SPY(7,   2, 0),
-/*1978*/ SPY(8,   2, 0), SPY(9,   2, 0), SPY(10,  2, 0), SPY(11,  3, 0),
-/*1982*/ SPY(12,  3, 0), SPY(13,  3, 0), SPY(14,  3, 0), SPY(15,  4, 0),
-/*1986*/ SPY(16,  4, 0), SPY(17,  4, 0), SPY(18,  4, 0), SPY(19,  5, 0),
-/*1990*/ SPY(20,  5, 0), SPY(21,  5, 0), SPY(22,  5, 0), SPY(23,  6, 0),
-/*1994*/ SPY(24,  6, 0), SPY(25,  6, 0), SPY(26,  6, 0), SPY(27,  7, 0),
-/*1998*/ SPY(28,  7, 0), SPY(29,  7, 0), SPY(30,  7, 0), SPY(31,  8, 0),
-/*2002*/ SPY(32,  8, 0), SPY(33,  8, 0), SPY(34,  8, 0), SPY(35,  9, 0),
-/*2006*/ SPY(36,  9, 0), SPY(37,  9, 0), SPY(38,  9, 0), SPY(39, 10, 0),
-/*2010*/ SPY(40, 10, 0), SPY(41, 10, 0), SPY(42, 10, 0), SPY(43, 11, 0),
-/*2014*/ SPY(44, 11, 0), SPY(45, 11, 0), SPY(46, 11, 0), SPY(47, 12, 0),
-/*2018*/ SPY(48, 12, 0), SPY(49, 12, 0), SPY(50, 12, 0), SPY(51, 13, 0),
-/*2022*/ SPY(52, 13, 0), SPY(53, 13, 0), SPY(54, 13, 0), SPY(55, 14, 0),
-/*2026*/ SPY(56, 14, 0), SPY(57, 14, 0), SPY(58, 14, 0), SPY(59, 15, 0),
-/*2030*/ SPY(60, 15, 0), SPY(61, 15, 0), SPY(62, 15, 0), SPY(63, 16, 0),
-/*2034*/ SPY(64, 16, 0), SPY(65, 16, 0), SPY(66, 16, 0), SPY(67, 17, 0),
-/*2038*/ SPY(68, 17, 0)
-};
-
 struct timespec *
 udf_disk_stamp_to_time(struct timespec *dest, struct timestamp src)
 {
-	int yday;
 	u16 typeAndTimezone = le16_to_cpu(src.typeAndTimezone);
 	u16 year = le16_to_cpu(src.year);
 	uint8_t type = typeAndTimezone >> 12;
@@ -100,15 +57,9 @@ udf_disk_stamp_to_time(struct timespec *dest, struct timestamp src)
 	} else
 		offset = 0;
 
-	if ((year < EPOCH_YEAR) ||
-	    (year >= EPOCH_YEAR + MAX_YEAR_SECONDS)) {
-		return NULL;
-	}
-	dest->tv_sec = year_seconds[year - EPOCH_YEAR];
+	dest->tv_sec = mktime64(year, src.month, src.day, src.hour, src.minute,
+			src.second);
 	dest->tv_sec -= offset * 60;
-
-	yday = ((__mon_yday[__isleap(year)][src.month - 1]) + src.day - 1);
-	dest->tv_sec += (((yday * 24) + src.hour) * 60 + src.minute) * 60 + src.second;
 	dest->tv_nsec = 1000 * (src.centiseconds * 10000 +
 			src.hundredsOfMicroseconds * 100 + src.microseconds);
 	return dest;