/* * 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 calls the system to determine the local * timezone and whether Daylight Saving Time is permitted locally. * (DST is then determined by the current US standard rules) * There is a table that accounts for the peculiarities * undergone by daylight time in 1974-1975. * * The routine does not work * in Saudi Arabia which runs on Solar time. * * 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 1970n0\\ *	01234567890123456789012345 *	0	  1	    2 * * ctime(t) just calls localtime, then asctime. */#include <time.h>#include <sys/types.h>#include <sys/timeb.h>static	char	cbuf[26];static	int	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. */static struct {	int	daylb;	int	dayle;} daytab[] = {	5,	333,	/* 1974: Jan 6 - last Sun. in Nov */	58,	303,	/* 1975: Last Sun. in Feb - last Sun in Oct */};struct tm	*gmtime();char		*ct_numb();struct tm	*localtime();char	*ctime();char	*ct_num();char	*asctime();char *ctime(t)long *t;{	return(asctime(localtime(t)));}struct tm *localtime(tim)long *tim;{	register int dayno;	register struct tm *ct;	register daylbegin, daylend;	long copyt;	struct timeb systime;	ftime(&systime);	copyt = *tim - (long)systime.timezone*60;	ct = gmtime(&copyt);	dayno = ct->tm_yday;	daylbegin = 119;	/* last Sun in Apr */	daylend = 303;		/* Last Sun in Oct */	if (ct->tm_year==74 || ct->tm_year==75) {		daylbegin = daytab[ct->tm_year-74].daylb;		daylend = daytab[ct->tm_year-74].dayle;	}	daylbegin = sunday(ct, daylbegin);	daylend = sunday(ct, daylend);	if (systime.dstflag &&	    (dayno>daylbegin || (dayno==daylbegin && ct->tm_hour>=2)) &&	    (dayno<daylend || (dayno==daylend && ct->tm_hour<1))) {		copyt += 1*60*60;		ct = gmtime(&copyt);		ct->tm_isdst++;	}	return(ct);}/* * The argument is a 0-origin day number. * The value is the day number of the first * Sunday on or after the day. */staticsunday(t, d)register struct tm *t;register int d;{	if (d >= 58)		d += dysize(t->tm_year) - 365;	return(d - (d - t->tm_yday + t->tm_wday + 700) % 7);}struct tm *gmtime(tim)long *tim;{	register int d0, d1;	long hms, day;	register int *tp;	static struct tm xtime;	/*	 * break initial number into days	 */	hms = *tim % 86400;	day = *tim / 86400;	if (hms<0) {		hms += 86400;		day -= 1;	}	tp = (int *)&xtime;	/*	 * generate hours:minutes:seconds	 */	*tp++ = hms%60;	d1 = hms/60;	*tp++ = d1%60;	d1 /= 60;	*tp++ = d1;	/*	 * day is the day number.	 * generate day of the week.	 * The addend is 4 mod 7 (1/1/1970 was Thursday)	 */	xtime.tm_wday = (day+7340036)%7;	/*	 * year number	 */	if (day>=0) for(d1=70; day >= dysize(d1); d1++)		day -= dysize(d1);	else for (d1=70; day<0; d1--)		day += dysize(d1-1);	xtime.tm_year = d1;	xtime.tm_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;	*tp++ = d0+1;	*tp++ = d1;	xtime.tm_isdst = 0;	return(&xtime);}char *asctime(t)struct tm *t;{	register char *cp, *ncp;	register int *tp;	cp = cbuf;	for (ncp = "Day Mon 00 00:00:00 1900\n"; *cp++ = *ncp++;);	ncp = &"SunMonTueWedThuFriSat"[3*t->tm_wday];	cp = cbuf;	*cp++ = *ncp++;	*cp++ = *ncp++;	*cp++ = *ncp++;	cp++;	tp = &t->tm_mon;	ncp = &"JanFebMarAprMayJunJulAugSepOctNovDec"[(*tp)*3];	*cp++ = *ncp++;	*cp++ = *ncp++;	*cp++ = *ncp++;	cp = ct_numb(cp, *--tp);	cp = ct_numb(cp, *--tp+100);	cp = ct_numb(cp, *--tp+100);	cp = ct_numb(cp, *--tp+100);	if (t->tm_year>=100) {		cp[1] = '2';		cp[2] = '0';	}	cp += 2;	cp = ct_numb(cp, t->tm_year+100);	return(cbuf);}dysize(y){	if((y%4) == 0)		return(366);	return(365);}static char *ct_numb(cp, n)register char *cp;{	cp++;	if (n>=10)		*cp++ = (n/10)%10 + '0';	else		*cp++ = ' ';	*cp++ = n%10 + '0';	return(cp);}