MiniUnix/usr/source/s4/ctime.c
#
/*
* 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 corrects for daylight saving
* time and will work in any time zone provided
* "timezone" is adjusted to the difference between
* Greenwich and local standard time (measured in seconds).
* In places like Michigan "daylight" must
* be initialized to 0 to prevent the conversion
* to daylight time.
* There is a table which 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.
*/
char cbuf[26];
int dmsize[12]
{
31,
28,
31,
30,
31,
30,
31,
31,
30,
31,
30,
31
};
int timezone 5*60*60;
int tzname[]
{
"EST",
"EDT",
};
int daylight 1; /* Allow daylight conversion */
/*
* The following table is used for 1974 and 1975 and
* gives the day number of the first day after the Sunday of the
* change.
*/
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 */
};
#define SEC 0
#define MIN 1
#define HOUR 2
#define MDAY 3
#define MON 4
#define YEAR 5
#define WDAY 6
#define YDAY 7
#define ISDAY 8
ctime(at)
int *at;
{
return(asctime(localtime(at)));
}
localtime(tim)
int tim[];
{
register int *t, *ct, dayno;
int daylbegin, daylend;
int copyt[2];
t = copyt;
t[0] = tim[0];
t[1] = tim[1];
dpadd(t, -timezone);
ct = gmtime(t);
dayno = ct[YDAY];
daylbegin = 119; /* last Sun in Apr */
daylend = 303; /* Last Sun in Oct */
if (ct[YEAR]==74 || ct[YEAR]==75) {
daylbegin = daytab[ct[YEAR]-74].daylb;
daylend = daytab[ct[YEAR]-74].dayle;
}
daylbegin = sunday(ct, daylbegin);
daylend = sunday(ct, daylend);
if (daylight &&
(dayno>daylbegin || (dayno==daylbegin && ct[HOUR]>=2)) &&
(dayno<daylend || (dayno==daylend && ct[HOUR]<1))) {
dpadd(t, 1*60*60);
ct = gmtime(t);
ct[ISDAY]++;
}
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.
*/
sunday(at, ad)
int *at;
{
register int *t, d;
t = at;
d = ad;
if (d >= 58)
d =+ dysize(t[YEAR]) - 365;
return(d - (d - t[YDAY] + t[WDAY] + 700) % 7);
}
gmtime(tim)
int tim[];
{
register int d0, d1;
register *tp;
static xtime[9];
extern int ldivr;
/*
* break initial number into
* multiples of 8 hours.
* (28800 = 60*60*8)
*/
d0 = ldiv(tim[0], tim[1], 28800);
d1 = ldivr;
tp = &xtime[0];
/*
* generate hours:minutes:seconds
*/
*tp++ = d1%60;
d1 =/ 60;
*tp++ = d1%60;
d1 =/ 60;
d1 =+ (d0%3)*8;
d0 =/ 3;
*tp++ = d1;
/*
* d0 is the day number.
* generate day of the week.
*/
xtime[WDAY] = (d0+4)%7;
/*
* year number
*/
for(d1=70; d0 >= dysize(d1); d1++)
d0 =- dysize(d1);
xtime[YEAR] = d1;
xtime[YDAY] = d0;
/*
* 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[ISDAY] = 0;
return(xtime);
}
asctime(t)
int *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[6]];
cp = cbuf;
*cp++ = *ncp++;
*cp++ = *ncp++;
*cp++ = *ncp++;
cp++;
tp = &t[4];
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);
cp =+ 2;
cp = ct_numb(cp, t[YEAR]);
return(cbuf);
}
dysize(y)
{
if((y%4) == 0)
return(366);
return(365);
}
ct_numb(acp, n)
{
register char *cp;
cp = acp;
cp++;
if (n>=10)
*cp++ = (n/10)%10 + '0';
else
*cp++ = ' ';
*cp++ = n%10 + '0';
return(cp);
}