ref: c172881606bfa194399a0b181b419a34488331d6
dir: /sys/src/libc/9sys/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 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.
*/
static int dysize(int);
static void ct_numb(char*, int);
#define TZSIZE 150
static void readtimezone(void);
static int rd_name(char**, char*);
static int rd_long(char**, long*);
static
struct
{
char stname[4];
char dlname[4];
long stdiff;
long dldiff;
long dlpairs[TZSIZE];
} timezone;
char*
ctime(long t)
{
return asctime(localtime(t));
}
Tm*
localtime(long tim)
{
Tm *ct;
long t, *p;
int dlflag;
if(timezone.stname[0] == 0)
readtimezone();
t = tim + timezone.stdiff;
dlflag = 0;
for(p = timezone.dlpairs; *p; p += 2)
if(t >= p[0])
if(t < p[1]) {
t = tim + timezone.dldiff;
dlflag++;
break;
}
ct = gmtime(t);
if(dlflag){
strcpy(ct->zone, timezone.dlname);
ct->tzoff = timezone.dldiff;
} else {
strcpy(ct->zone, timezone.stname);
ct->tzoff = timezone.stdiff;
}
return ct;
}
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;
}
char*
asctime(Tm *t)
{
char *ncp;
static char cbuf[30];
strcpy(cbuf, "Thu Jan 01 00:00:00 GMT 1970\n");
ncp = &"SunMonTueWedThuFriSat"[t->wday*3];
cbuf[0] = *ncp++;
cbuf[1] = *ncp++;
cbuf[2] = *ncp;
ncp = &"JanFebMarAprMayJunJulAugSepOctNovDec"[t->mon*3];
cbuf[4] = *ncp++;
cbuf[5] = *ncp++;
cbuf[6] = *ncp;
ct_numb(cbuf+8, t->mday);
ct_numb(cbuf+11, t->hour+100);
ct_numb(cbuf+14, t->min+100);
ct_numb(cbuf+17, t->sec+100);
ncp = t->zone;
cbuf[20] = *ncp++;
cbuf[21] = *ncp++;
cbuf[22] = *ncp;
ct_numb(cbuf+24, (t->year+1900) / 100 + 100);
ct_numb(cbuf+26, t->year+100);
return cbuf;
}
static
dysize(int y)
{
if(y%4 == 0 && (y%100 != 0 || y%400 == 0))
return 366;
return 365;
}
static
void
ct_numb(char *cp, int n)
{
cp[0] = ' ';
if(n >= 10)
cp[0] = (n/10)%10 + '0';
cp[1] = n%10 + '0';
}
static
void
readtimezone(void)
{
char buf[TZSIZE*11+30], *p;
int i;
memset(buf, 0, sizeof(buf));
i = open("/env/timezone", 0);
if(i < 0)
goto error;
if(read(i, buf, sizeof(buf)) >= sizeof(buf)){
close(i);
goto error;
}
close(i);
p = buf;
if(rd_name(&p, timezone.stname))
goto error;
if(rd_long(&p, &timezone.stdiff))
goto error;
if(rd_name(&p, timezone.dlname))
goto error;
if(rd_long(&p, &timezone.dldiff))
goto error;
for(i=0; i<TZSIZE; i++) {
if(rd_long(&p, &timezone.dlpairs[i]))
goto error;
if(timezone.dlpairs[i] == 0)
return;
}
error:
timezone.stdiff = 0;
strcpy(timezone.stname, "GMT");
timezone.dlpairs[0] = 0;
}
static
rd_name(char **f, char *p)
{
int c, i;
for(;;) {
c = *(*f)++;
if(c != ' ' && c != '\n')
break;
}
for(i=0; i<3; i++) {
if(c == ' ' || c == '\n')
return 1;
*p++ = c;
c = *(*f)++;
}
if(c != ' ' && c != '\n')
return 1;
*p = 0;
return 0;
}
static
rd_long(char **f, long *p)
{
int c, s;
long l;
s = 0;
for(;;) {
c = *(*f)++;
if(c == '-') {
s++;
continue;
}
if(c != ' ' && c != '\n')
break;
}
if(c == 0) {
*p = 0;
return 0;
}
l = 0;
for(;;) {
if(c == ' ' || c == '\n')
break;
if(c < '0' || c > '9')
return 1;
l = l*10 + c-'0';
c = *(*f)++;
}
if(s)
l = -l;
*p = l;
return 0;
}