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#include <stdio.h>
#include <stdlib.h>
#include <langinfo.h>
#include <time.h>
#include <limits.h>
#include "__time.h"
// FIXME: integer overflows
const char *__langinfo(nl_item);
static int is_leap(int y)
{
/* Avoid overflow */
if (y>INT_MAX-1900) y -= 2000;
y += 1900;
return !(y%4) && ((y%100) || !(y%400));
}
static int week_num(const struct tm *tm)
{
int val = (tm->tm_yday + 7 - (tm->tm_wday+6)%7) / 7;
/* If 1 Jan is just 1-3 days past Monday,
* the previous week is also in this year. */
if ((tm->tm_wday - tm->tm_yday - 2 + 371) % 7 <= 2)
val++;
if (!val) {
val = 52;
/* If 31 December of prev year a Thursday,
* or Friday of a leap year, then the
* prev year has 53 weeks. */
int dec31 = (tm->tm_wday - tm->tm_yday - 1 + 7) % 7;
if (dec31 == 4 || (dec31 == 5 && is_leap(tm->tm_year%400-1)))
val++;
} else if (val == 53) {
/* If 1 January is not a Thursday, and not
* a Wednesday of a leap year, then this
* year has only 52 weeks. */
int jan1 = (tm->tm_wday - tm->tm_yday + 371) % 7;
if (jan1 != 4 && (jan1 != 3 || !is_leap(tm->tm_year)))
val = 1;
}
return val;
}
size_t strftime(char *restrict s, size_t n, const char *restrict f, const struct tm *restrict tm)
{
nl_item item;
int val;
const char *fmt;
size_t l;
for (l=0; *f && l<n; f++) {
if (*f == '%') {
do_fmt:
switch (*++f) {
case '%':
goto literal;
case 'E':
case 'O':
goto do_fmt;
case 'a':
item = ABDAY_1 + tm->tm_wday;
goto nl_strcat;
case 'A':
item = DAY_1 + tm->tm_wday;
goto nl_strcat;
case 'h':
case 'b':
item = ABMON_1 + tm->tm_mon;
goto nl_strcat;
case 'B':
item = MON_1 + tm->tm_mon;
goto nl_strcat;
case 'c':
item = D_T_FMT;
goto nl_strftime;
case 'C':
val = (1900+tm->tm_year) / 100;
fmt = "%02d";
goto number;
case 'd':
val = tm->tm_mday;
fmt = "%02d";
goto number;
case 'D':
fmt = "%m/%d/%y";
goto recu_strftime;
case 'e':
val = tm->tm_mday;
fmt = "%2d";
goto number;
case 'F':
fmt = "%Y-%m-%d";
goto recu_strftime;
case 'g':
case 'G':
fmt = "%04d";
val = tm->tm_year + 1900;
if (tm->tm_yday < 3 && week_num(tm) != 1) val--;
else if (tm->tm_yday > 360 && week_num(tm) == 1) val++;
if (*f=='g') {
fmt = "%02d";
val %= 100;
}
goto number;
case 'H':
val = tm->tm_hour;
fmt = "%02d";
goto number;
case 'I':
val = tm->tm_hour;
if (!val) val = 12;
else if (val > 12) val -= 12;
fmt = "%02d";
goto number;
case 'j':
val = tm->tm_yday+1;
fmt = "%03d";
goto number;
case 'm':
val = tm->tm_mon+1;
fmt = "%02d";
goto number;
case 'M':
val = tm->tm_min;
fmt = "%02d";
goto number;
case 'n':
s[l++] = '\n';
continue;
case 'p':
item = tm->tm_hour >= 12 ? PM_STR : AM_STR;
goto nl_strcat;
case 'r':
item = T_FMT_AMPM;
goto nl_strftime;
case 'R':
fmt = "%H:%M";
goto recu_strftime;
case 'S':
val = tm->tm_sec;
fmt = "%02d";
goto number;
case 't':
s[l++] = '\t';
continue;
case 'T':
fmt = "%H:%M:%S";
goto recu_strftime;
case 'u':
val = tm->tm_wday ? tm->tm_wday : 7;
fmt = "%d";
goto number;
case 'U':
val = (tm->tm_yday + 7 - tm->tm_wday) / 7;
fmt = "%02d";
goto number;
case 'W':
val = (tm->tm_yday + 7 - (tm->tm_wday+6)%7) / 7;
fmt = "%02d";
goto number;
case 'V':
val = week_num(tm);
fmt = "%02d";
goto number;
case 'w':
val = tm->tm_wday;
fmt = "%d";
goto number;
case 'x':
item = D_FMT;
goto nl_strftime;
case 'X':
item = T_FMT;
goto nl_strftime;
case 'y':
val = tm->tm_year % 100;
fmt = "%02d";
goto number;
case 'Y':
val = tm->tm_year + 1900;
fmt = "%04d";
goto number;
case 'z':
if (tm->tm_isdst < 0) continue;
val = -__timezone - (tm->tm_isdst ? __dst_offset : 0);
l += snprintf(s+l, n-l, "%+.2d%.2d", val/3600, abs(val%3600)/60);
continue;
case 'Z':
if (tm->tm_isdst < 0 || !__tzname[0] || !__tzname[0][0])
continue;
l += snprintf(s+l, n-l, "%s", __tzname[!!tm->tm_isdst]);
continue;
default:
return 0;
}
}
literal:
s[l++] = *f;
continue;
number:
l += snprintf(s+l, n-l, fmt, val);
continue;
nl_strcat:
l += snprintf(s+l, n-l, "%s", __langinfo(item));
continue;
nl_strftime:
fmt = __langinfo(item);
recu_strftime:
l += strftime(s+l, n-l, fmt, tm);
}
if (l >= n) return 0;
s[l] = 0;
return l;
}
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