ref: a7de023df75d9812c925ec5655be09ef0c02646e
dir: /src/libc/time/strftime.c/
#include <string.h>
#include <time.h>
#include "../libc.h"
#undef strftime
static char *days[] = {
"Sunday", "Monday", "Tuesday", "Wednesday",
"Thursday", "Friday", "Saturday",
};
static char *months[] = {
"January", "February", "March", "April",
"May", "June", "July", "August",
"September", "October", "November", "December"
};
static char *am_pm[] = {"AM", "PM"};
static int
first(int day, int year)
{
int ny;
ny = _newyear(year);
if (ny == day)
return 0;
if (day - ny < 0)
return 7 - (ny - day);
return day - ny;
}
static int
weeknum(struct tm *tm, int day)
{
int fday, val;
fday = first(day, tm->tm_year);
if (tm->tm_yday < fday) {
val = 0;
} else {
val = tm->tm_yday - fday;
val /= 7;
val++;
}
return val;
}
static int
isoyear(struct tm *tm)
{
int monday;
if (tm->tm_yday < 7) {
monday = first(THU, tm->tm_year) - 3;
if (tm->tm_yday < monday)
return tm->tm_year - 1;
} else if (tm->tm_yday > 357) {
monday = first(THU, tm->tm_year + 1) - 3;
if (tm->tm_mday >= (31 + monday))
return tm->tm_year + 1;
}
return tm->tm_year;
}
static int
isoweek(struct tm *tm)
{
int year, monday, yday, val;
year = isoyear(tm);
monday = first(THU, year) - 3;
yday = tm->tm_yday;
if (year > tm->tm_year)
yday = tm->tm_mday - 31 + monday;
else if (year < tm->tm_year)
yday = _daysyear(year) + yday;
val = yday - monday;
val /= 7;
val++;
return val;
}
static int
isoday(struct tm *tm)
{
if (tm->tm_wday == 0)
return 7;
return tm->tm_wday;
}
static size_t
sval(char *s, size_t siz, char **strs, int abrev, int idx, int max)
{
char *str;
size_t len;
if (idx < 0 && idx >= max)
goto wrong;
str = strs[idx];
len = (!abrev) ? strlen(str) : 3;
if (len > siz)
goto wrong;
memcpy(s, str, len);
return len;
wrong:
*s = '?';
return 1;
}
static size_t
dval(char *s, size_t siz, int prec, int fill, int val)
{
char *t;
int n;
static char digits[] = "0123456789";
if (prec > siz || val < 0) {
*s = '?';
return 1;
}
n = prec;
do {
s[--n] = digits[val % 10];
val /= 10;
} while (n > 0 && val > 0);
while (n > 0)
s[--n] = fill;
return prec;
}
static size_t
timezone(char *s, size_t prec, const struct tm * restrict tm)
{
long off = tm->tm_gmtoff;
if (prec < 5) {
*s = '?';
return 1;
}
if (off >= 0) {
*s++ = '+';
} else {
*s++ = '-';
off = -off;
}
dval(s, 2, 2, '0', off / 3600);
dval(s, 2, 2, '0', (off % 3600) / 60);
return 5;
}
size_t
strftime(char *restrict s, size_t maxsize,
const char *restrict format, const struct tm *restrict timeptr)
{
int ch, abrev, val, fill, width;
size_t n, inc;
char *tfmt;
for (n = --maxsize; (ch = *format++) && n > 0; s += inc, n -= inc) {
if (ch != '%') {
*s = ch;
inc = 1;
continue;
}
abrev = 0;
fill = '0';
width = 2;
if (*format == 'E' || *format == 'O')
format++;
switch (*format++) {
case 'a':
abrev = 1;
case 'A':
inc = sval(s, n, days, abrev, timeptr->tm_wday, 7);
break;
case 'h':
case 'b':
abrev = 1;
case 'B':
inc = sval(s, n, months, abrev, timeptr->tm_mon, 12);
break;
case 'c':
tfmt = "%a %b %e %T %Y";
goto recursive;
case 'C':
val = (timeptr->tm_year + 1900) / 100;
goto number;
case 'd':
val = timeptr->tm_mday;
goto number;
case 'D':
tfmt = "%m/%d/%y";
goto recursive;
case 'e':
fill = ' ';
val = timeptr->tm_mday;
goto number;
case 'F':
tfmt = "%Y-%m-%d";
goto recursive;
case 'g':
val = isoyear(timeptr);
goto number;
case 'G':
val = isoyear(timeptr);
val += 1900;
width = 4;
goto number;
case 'H':
val = timeptr->tm_hour;
goto number;
case 'I':
val = timeptr->tm_hour;
if (val == 0)
val = 12;
if (val > 12)
val -= 12;
goto number;
case 'j':
width = 3;
val = timeptr->tm_yday+1;
goto number;
case 'm':
val = timeptr->tm_mon+1;
goto number;
case 'M':
val = timeptr->tm_min;
goto number;
case 'n':
val = '\n';
goto character;
case 'p':
inc = sval(s, n, am_pm, 0, timeptr->tm_hour > 12, 2);
break;
case 'r':
tfmt = "%I:%M:%S %p";
goto recursive;
case 'R':
tfmt = "%H:%M";
goto recursive;
case 'S':
val = timeptr->tm_sec;
goto number;
case 't':
val = '\t';
goto character;
case 'u':
width = 1;
val = isoday(timeptr);
goto number;
case 'U':
val = weeknum(timeptr, SUN);
goto number;
case 'V':
val = isoweek(timeptr);
goto number;
case 'w':
width = 1;
val = timeptr->tm_wday;
goto number;
case 'W':
val = weeknum(timeptr, MON);
goto number;
case 'X':
case 'T':
tfmt = "%H:%M:%S";
goto recursive;
case 'x':
tfmt = "%m/%d/%y";
goto recursive;
case 'y':
val = timeptr->tm_year%100;
goto number;
case 'Y':
width = 4;
val = 1900 + timeptr->tm_year;
goto number;
case 'z':
inc = timezone(s, n, timeptr);
break;
case 'Z':
memcpy(s, timeptr->tm_zone, 3);
inc = 3;
break;
case '\0':
inc = 0;
--format;
break;
case '%':
val = '%';
character:
*s = val;
inc = 1;
break;
number:
inc = dval(s, n, width, fill, val);
break;
recursive:
inc = strftime(s, n+1, tfmt, timeptr);
break;
}
}
*s = '\0';
return maxsize - n;
}