8 // FIXME: integer overflows
10 const char *__langinfo(nl_item);
12 static int is_leap(int y)
15 if (y>INT_MAX-1900) y -= 2000;
17 return !(y%4) && ((y%100) || !(y%400));
20 static int week_num(const struct tm *tm)
22 int val = (tm->tm_yday + 7 - (tm->tm_wday+6)%7) / 7;
23 /* If 1 Jan is just 1-3 days past Monday,
24 * the previous week is also in this year. */
25 if ((tm->tm_wday - tm->tm_yday - 2 + 371) % 7 <= 2)
29 /* If 31 December of prev year a Thursday,
30 * or Friday of a leap year, then the
31 * prev year has 53 weeks. */
32 int dec31 = (tm->tm_wday - tm->tm_yday - 1 + 7) % 7;
33 if (dec31 == 4 || (dec31 == 5 && is_leap(tm->tm_year%400-1)))
35 } else if (val == 53) {
36 /* If 1 January is not a Thursday, and not
37 * a Wednesday of a leap year, then this
38 * year has only 52 weeks. */
39 int jan1 = (tm->tm_wday - tm->tm_yday + 371) % 7;
40 if (jan1 != 4 && (jan1 != 3 || !is_leap(tm->tm_year)))
46 size_t strftime(char *restrict s, size_t n, const char *restrict f, const struct tm *restrict tm)
52 for (l=0; *f && l<n; f++) {
62 item = ABDAY_1 + tm->tm_wday;
65 item = DAY_1 + tm->tm_wday;
69 item = ABMON_1 + tm->tm_mon;
72 item = MON_1 + tm->tm_mon;
78 val = (1900+tm->tm_year) / 100;
98 val = tm->tm_year + 1900;
99 if (tm->tm_yday < 3 && week_num(tm) != 1) val--;
100 else if (tm->tm_yday > 360 && week_num(tm) == 1) val++;
113 else if (val > 12) val -= 12;
132 item = tm->tm_hour >= 12 ? PM_STR : AM_STR;
151 val = tm->tm_wday ? tm->tm_wday : 7;
155 val = (tm->tm_yday + 7 - tm->tm_wday) / 7;
159 val = (tm->tm_yday + 7 - (tm->tm_wday+6)%7) / 7;
177 val = tm->tm_year % 100;
181 val = tm->tm_year + 1900;
185 if (tm->tm_isdst < 0) continue;
186 val = -__timezone - (tm->tm_isdst ? __dst_offset : 0);
187 l += snprintf(s+l, n-l, "%+.2d%.2d", val/3600, abs(val%3600)/60);
190 if (tm->tm_isdst < 0 || !__tzname[0] || !__tzname[0][0])
192 l += snprintf(s+l, n-l, "%s", __tzname[!!tm->tm_isdst]);
202 l += snprintf(s+l, n-l, fmt, val);
205 l += snprintf(s+l, n-l, "%s", __langinfo(item));
208 fmt = __langinfo(item);
210 l += strftime(s+l, n-l, fmt, tm);
212 if (l >= n) return 0;