/* * This routine converts time as follows. * The epoch is 0000 Jan 1 1970 GMT. * The argument time is in seconds since then. * The localtime(t) entry returns a pointer to an array * containing * *	seconds (0-59) *	minutes (0-59) *	hours (0-23) *	day of month (1-31) *	month (0-11) *	year-1970 *	weekday (0-6, Sun is 0) *	day of the year *	daylight savings flag * * The routine gets the daylight savings time from the environment. * * asctime(tvec)) * where tvec is produced by localtime * returns a ptr to a character string * that has the ascii time in the form * *	                            \\ *	Thu Jan 01 00:00:00 GMT 1970n0 *	012345678901234567890123456789 *	0	  1	    2 * * ctime(t) just calls localtime, then asctime. */ #include <u.h>#include <libc.h> static	char	dmsize[12] ={	31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; /* * The following table is used for 1974 and 1975 and * gives the day number of the first day after the Sunday of the * change. */ #define dysize _dysize	/* conflicts on unix */ static intdysize(int y){ 	if(y%4 == 0 && (y%100 != 0 || y%400 == 0))		return 366;	return 365;} Tm*gmtime(long tim){	int d0, d1;	long hms, day;	static Tm xtime; 	/*	 * break initial number into days	 */	hms = tim % 86400L;	day = tim / 86400L;	if(hms < 0) {		hms += 86400L;		day -= 1;	} 	/*	 * generate hours:minutes:seconds	 */	xtime.sec = hms % 60;	d1 = hms / 60;	xtime.min = d1 % 60;	d1 /= 60;	xtime.hour = d1; 	/*	 * day is the day number.	 * generate day of the week.	 * The addend is 4 mod 7 (1/1/1970 was Thursday)	 */ 	xtime.wday = (day + 7340036L) % 7; 	/*	 * year number	 */	if(day >= 0)		for(d1 = 1970; day >= dysize(d1); d1++)			day -= dysize(d1);	else		for (d1 = 1970; day < 0; d1--)			day += dysize(d1-1);	xtime.year = d1-1900;	xtime.yday = d0 = day; 	/*	 * generate month	 */ 	if(dysize(d1) == 366)		dmsize[1] = 29;	for(d1 = 0; d0 >= dmsize[d1]; d1++)		d0 -= dmsize[d1];	dmsize[1] = 28;	xtime.mday = d0 + 1;	xtime.mon = d1;	strcpy(xtime.zone, "GMT");	return &xtime;}