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diff --git a/05/time.h b/05/time.h
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+#ifndef _TIME_H
+#define _TIME_H
+
+#include <stdc_common.h>
+#define CLK_TCK 1000000000 // doesnt matter; clock() will always fail.
+
+typedef long clock_t;
+
+clock_t clock(void) {
+ // "If the processor time used is not available or its value cannot be represented, the function returns the value (clock_t)-1." C89 ยง 4.12.2.1
+ return -1;
+}
+
+double difftime(time_t time1, time_t time0) {
+ return (double)(time1 - time0);
+}
+
+time_t time(time_t *timer) {
+ struct timespec ts = {0};
+ if (clock_gettime(CLOCK_REALTIME, &ts) != 0) return -1;
+ if (timer) *timer = ts.tv_sec;
+ return ts.tv_sec;
+}
+
+
+// @NONSTANDARD(except in UTC+0): we don't support local time in timezones other than UTC+0.
+
+struct tm {
+ int tm_sec; /* seconds after the minute --- [0, 60] */
+ int tm_min; /* minutes after the hour --- [0, 59] */
+ int tm_hour; /* hours since midnight --- [0, 23] */
+ int tm_mday; /* day of the month --- [1, 31] */
+ int tm_mon; /* months since January --- [0, 11] */
+ int tm_year; /* years since 1900 */
+ int tm_wday; /* days since Sunday --- [0, 6] */
+ int tm_yday; /* days since January 1 --- [0, 365] */
+ int tm_isdst; /* Daylight Saving Time flag */
+};
+
+
+void _gmtime_r(const time_t *timer, struct tm *tm) {
+ time_t t = *timer;
+ int year = 1970;
+ int days = t / 86400;
+ int leap_year;
+ int month;
+
+ tm->tm_isdst = 0;
+ tm->tm_wday = (4 + days) % 7; // jan 1 1970 was a thursday
+ while (1) {
+ leap_year = year % 4 == 0 && (year % 100 != 0 || year % 400 == 0);
+ int ydays = leap_year ? 366 : 365;
+ if (days < ydays) break;
+ days -= ydays;
+ ++year;
+ }
+ tm->tm_year = year - 1900;
+ tm->tm_yday = days;
+ for (month = 0; month < 12; ++month) {
+ int mdays;
+ switch (month) {
+ case 0: case 2: case 4: case 6: case 7: case 9: case 11:
+ mdays = 31;
+ break;
+ case 3: case 5: case 8: case 10:
+ mdays = 30;
+ break;
+ case 1:
+ mdays = 28 + leap_year;
+ break;
+ }
+ if (days < mdays) break;
+ days -= mdays;
+ }
+ tm->tm_mday = days + 1;
+ tm->tm_mon = month;
+ t %= 86400;
+ tm->tm_hour = t / 3600;
+ t %= 3600;
+ tm->tm_min = t / 60;
+ tm->tm_sec = t % 60;
+}
+
+time_t mktime(struct tm *tm) {
+ // @NONSTANDARD-ish.
+ // not implementing this -- note that the implementation has to support tm_* values
+ // outside of their proper ranges.
+ return (time_t)-1;
+
+}
+
+struct tm *gmtime(const time_t *timer) {
+ static struct tm result;
+ _gmtime_r(timer, &result);
+ return &result;
+}
+
+struct tm *localtime(const time_t *timer) {
+ static struct tm result;
+ _gmtime_r(timer, &result);
+ return &result;
+}
+
+static const char _wday_name[7][4] = {
+ "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
+};
+static const char _weekday_name[7][16] = {
+ "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"
+};
+static const char _mon_name[12][4] = {
+ "Jan", "Feb", "Mar", "Apr", "May", "Jun",
+ "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
+};
+static const char _month_name[12][16] = {
+ "January", "February", "March", "April", "May", "June",
+ "July", "August", "September", "October", "November", "December"
+};
+
+char *asctime(const struct tm *timeptr) {
+ // lifted from the (draft of the) C standard
+ static char result[32];
+ sprintf(result, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n",
+ _wday_name[timeptr->tm_wday],
+ _mon_name[timeptr->tm_mon],
+ timeptr->tm_mday, timeptr->tm_hour,
+ timeptr->tm_min, timeptr->tm_sec,
+ 1900 + timeptr->tm_year);
+ return result;
+}
+
+char *ctime(const time_t *timer) {
+ return asctime(localtime(timer));
+}
+
+size_t strftime(char *s, size_t maxsize, const char *format, const struct tm *tm) {
+ size_t n = 0, l;
+ char *name;
+
+ while (*format) {
+ if (*format == '%') {
+ ++format;
+ int c = *format++;
+ switch (c) {
+ case 'a':
+ if (n+4 >= maxsize) return 0;
+ strcpy(s, _wday_name[tm->tm_wday]);
+ s += 3;
+ n += 3;
+ break;
+ case 'A':
+ name = _weekday_name[tm->tm_wday];
+ l = strlen(name);
+ if (n+l+1 >= maxsize) return 0;
+ strcpy(s, name);
+ s += l;
+ n += l;
+ break;
+ case 'b':
+ if (n+4 >= maxsize) return 0;
+ strcpy(s, _mon_name[tm->tm_mon]);
+ s += 3;
+ n += 3;
+ break;
+ case 'B':
+ name = _month_name[tm->tm_mon];
+ l = strlen(name);
+ if (n+l+1 >= maxsize) return 0;
+ strcpy(s, name);
+ s += l;
+ n += l;
+ break;
+ case 'c':
+ if (n+32 >= maxsize) return 0;
+ sprintf(s, "%s %02d %s %d %02d:%02d:%02d %s UTC",
+ _wday_name[tm->tm_wday], tm->tm_mday, _mon_name[tm->tm_mon],
+ 1900+tm->tm_year, (tm->tm_hour + 11) % 12 + 1, tm->tm_min, tm->tm_sec,
+ tm->tm_hour >= 12 ? "PM" : "AM");
+ s += 31;
+ n += 31;
+ break;
+ case 'd':
+ if (n+3 >= maxsize) return 0;
+ sprintf(s, "%02d", tm->tm_mday);
+ s += 2;
+ n += 2;
+ break;
+ case 'H':
+ if (n+3 >= maxsize) return 0;
+ sprintf(s, "%02d", tm->tm_hour);
+ s += 2;
+ n += 2;
+ break;
+ case 'I':
+ if (n+3 >= maxsize) return 0;
+ sprintf(s, "%02d", (tm->tm_hour + 11) % 12 + 1);
+ s += 2;
+ n += 2;
+ break;
+ case 'j':
+ if (n+4 >= maxsize) return 0;
+ sprintf(s, "%03d", tm->tm_yday + 1);
+ s += 3;
+ n += 3;
+ break;
+ case 'm':
+ if (n+3 >= maxsize) return 0;
+ sprintf(s, "%02d", tm->tm_mon + 1);
+ s += 2;
+ n += 2;
+ break;
+ case 'M':
+ if (n+3 >= maxsize) return 0;
+ sprintf(s, "%02d", tm->tm_min);
+ s += 2;
+ n += 2;
+ break;
+ case 'p':
+ if (n+3 >= maxsize) return 0;
+ sprintf(s, "%s", tm->tm_hour >= 12 ? "PM" : "AM");
+ s += 2;
+ n += 2;
+ break;
+ case 'S':
+ if (n+3 >= maxsize) return 0;
+ sprintf(s, "%02d", tm->tm_sec);
+ s += 2;
+ n += 2;
+ break;
+ case 'w':
+ if (n+2 >= maxsize) return 0;
+ sprintf(s, "%d", tm->tm_wday);
+ s += 1;
+ n += 1;
+ break;
+ case 'x':
+ if (n+16 >= maxsize) return 0;
+ sprintf(s, "%s %02d %s %d",
+ _wday_name[tm->tm_wday], tm->tm_mday, _mon_name[tm->tm_mon],
+ 1900+tm->tm_year);
+ s += 15;
+ n += 15;
+ break;
+ case 'X':
+ if (n+16 >= maxsize) return 0;
+ sprintf(s, "%02d:%02d:%02d %s UTC",
+ (tm->tm_hour + 11) % 12 + 1, tm->tm_min, tm->tm_sec,
+ tm->tm_hour >= 12 ? "PM" : "AM");
+ s += 15;
+ n += 15;
+ break;
+ case 'y':
+ if (n+3 >= maxsize) return 0;
+ sprintf(s, "%02d", tm->tm_year % 100);
+ s += 2;
+ n += 2;
+ break;
+ case 'Y':
+ if (n+5 >= maxsize) return 0;
+ sprintf(s, "%d", tm->tm_year + 1900);
+ s += 4;
+ n += 4;
+ break;
+ case 'Z':
+ if (n+4 >= maxsize) return 0;
+ strcpy(s, "UTC");
+ s += 3;
+ n += 3;
+ break;
+ case '%':
+ if (n >= maxsize) return 0;
+ *s++ = '%';
+ n += 1;
+ break;
+ case 'U': // WEEK NUMBER OF THE YEAR? WHO GIVES A SHIT?
+ case 'W': // WEEK NUMBER OF THE YEAR MONDAY-BASED EDITION. IF YOU DIDNT ALREADY GET ENOUGH WEEK NUMBERS. FUCK YOU
+ default:
+ fprintf(stderr, "Bad strftime format.\n");
+ abort();
+
+ }
+ } else {
+ if (n >= maxsize) return 0;
+ *s++ = *format++;
+ n += 1;
+ }
+ }
+ if (n >= maxsize) return 0;
+ *s = 0;
+ #undef _Push_str
+ return n;
+}
+
+#endif // _TIME_H
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