ref: fe3430ea998a3a494fa22ed574f97834cff38f7f
dir: /sys/src/ape/lib/ap/plan9/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 1970n0
* 01234567890123456789012345
* 0 1 2
*
* ctime(t) just calls localtime, then asctime.
*/
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <time.h>
#include <unistd.h>
#include <string.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);
static void readtimezone(void);
static int rd_name(char**, char*);
static int rd_long(char**, long*);
#define TZSIZE 150
static
struct
{
char stname[4];
char dlname[4];
long stdiff;
long dldiff;
long dlpairs[TZSIZE];
} tz;
char*
ctime(const time_t *t)
{
return asctime(localtime(t));
}
struct tm*
gmtime_r(const time_t *timp, struct tm *result)
{
int d0, d1;
long hms, day;
time_t tim;
tim = *timp;
/*
* break initial number into days
*/
hms = tim % 86400L;
day = tim / 86400L;
if(hms < 0) {
hms += 86400L;
day -= 1;
}
/*
* generate hours:minutes:seconds
*/
result->tm_sec = hms % 60;
d1 = hms / 60;
result->tm_min = d1 % 60;
d1 /= 60;
result->tm_hour = d1;
/*
* day is the day number.
* generate day of the week.
* The addend is 4 mod 7 (1/1/1970 was Thursday)
*/
result->tm_wday = (day + 7340036L) % 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);
result->tm_year = d1;
result->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;
result->tm_mday = d0 + 1;
result->tm_mon = d1;
result->tm_isdst = 0;
return result;
}
struct tm*
gmtime(const time_t *timp)
{
static struct tm xtime;
return gmtime_r(timp, &xtime);
}
struct tm*
localtime_r(const time_t *timp, struct tm *result)
{
struct tm *ct;
time_t t, tim;
long *p;
int dlflag;
tim = *timp;
if(tz.stname[0] == 0)
readtimezone();
t = tim + tz.stdiff;
dlflag = 0;
for(p = tz.dlpairs; *p; p += 2)
if(t >= p[0])
if(t < p[1]) {
t = tim + tz.dldiff;
dlflag++;
break;
}
ct = gmtime_r(&t, result);
ct->tm_isdst = dlflag;
return ct;
}
struct tm*
localtime(const time_t *timp)
{
static struct tm xtime;
return localtime_r(timp, &xtime);
}
char*
asctime_r(const struct tm *t, char *buf)
{
char *ncp;
strcpy(buf, "Thu Jan 01 00:00:00 1970\n");
ncp = &"SunMonTueWedThuFriSat"[t->tm_wday*3];
buf[0] = *ncp++;
buf[1] = *ncp++;
buf[2] = *ncp;
ncp = &"JanFebMarAprMayJunJulAugSepOctNovDec"[t->tm_mon*3];
buf[4] = *ncp++;
buf[5] = *ncp++;
buf[6] = *ncp;
ct_numb(buf+8, t->tm_mday);
ct_numb(buf+11, t->tm_hour+100);
ct_numb(buf+14, t->tm_min+100);
ct_numb(buf+17, t->tm_sec+100);
if(t->tm_year >= 100) {
buf[20] = '2';
buf[21] = '0';
}
ct_numb(buf+22, t->tm_year+100);
return buf;
}
char*
asctime(const struct tm *t)
{
static char cbuf[30];
return asctime_r(t, cbuf);
}
static
dysize(int y)
{
if((y%4) == 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))
goto error;
close(i);
p = buf;
if(rd_name(&p, tz.stname))
goto error;
if(rd_long(&p, &tz.stdiff))
goto error;
if(rd_name(&p, tz.dlname))
goto error;
if(rd_long(&p, &tz.dldiff))
goto error;
for(i=0; i<TZSIZE; i++) {
if(rd_long(&p, &tz.dlpairs[i]))
goto error;
if(tz.dlpairs[i] == 0)
return;
}
error:
tz.stdiff = 0;
strcpy(tz.stname, "GMT");
tz.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;
}