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-rw-r--r--xtime.c323
1 files changed, 323 insertions, 0 deletions
diff --git a/xtime.c b/xtime.c
new file mode 100644
index 0000000..b83bf20
--- /dev/null
+++ b/xtime.c
@@ -0,0 +1,323 @@
+/****************************************************************************
+ * bfs *
+ * Copyright (C) 2020 Tavian Barnes <tavianator@tavianator.com> *
+ * *
+ * Permission to use, copy, modify, and/or distribute this software for any *
+ * purpose with or without fee is hereby granted. *
+ * *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES *
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF *
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR *
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES *
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN *
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF *
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. *
+ ****************************************************************************/
+
+#include "xtime.h"
+#include <errno.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <time.h>
+
+/** Whether tzset() has been called. */
+static bool tz_is_set = false;
+
+int xlocaltime(const time_t *timep, struct tm *result) {
+ // Should be called before localtime_r() according to POSIX.1-2004
+ if (!tz_is_set) {
+ tzset();
+ tz_is_set = true;
+ }
+
+ if (localtime_r(timep, result)) {
+ return 0;
+ } else {
+ return -1;
+ }
+}
+
+int xgmtime(const time_t *timep, struct tm *result) {
+ // Should be called before gmtime_r() according to POSIX.1-2004
+ if (!tz_is_set) {
+ tzset();
+ tz_is_set = true;
+ }
+
+ if (gmtime_r(timep, result)) {
+ return 0;
+ } else {
+ return -1;
+ }
+}
+
+int xmktime(struct tm *tm, time_t *timep) {
+ *timep = mktime(tm);
+
+ if (*timep == -1) {
+ int error = errno;
+
+ struct tm tmp;
+ if (xlocaltime(timep, &tmp) != 0) {
+ return -1;
+ }
+
+ if (tm->tm_year != tmp.tm_year || tm->tm_yday != tmp.tm_yday
+ || tm->tm_hour != tmp.tm_hour || tm->tm_min != tmp.tm_min || tm->tm_sec != tmp.tm_sec) {
+ errno = error;
+ return -1;
+ }
+ }
+
+ return 0;
+}
+
+static int safe_add(int *value, int delta) {
+ if (*value >= 0) {
+ if (delta > INT_MAX - *value) {
+ return -1;
+ }
+ } else {
+ if (delta < INT_MIN - *value) {
+ return -1;
+ }
+ }
+
+ *value += delta;
+ return 0;
+}
+
+static int floor_div(int n, int d) {
+ int a = n < 0;
+ return (n + a)/d - a;
+}
+
+static int wrap(int *value, int max, int *next) {
+ int carry = floor_div(*value, max);
+ *value -= carry * max;
+ return safe_add(next, carry);
+}
+
+static int month_length(int year, int month) {
+ static const int month_lengths[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
+ int ret = month_lengths[month];
+ if (month == 1 && year%4 == 0 && (year%100 != 0 || (year + 300)%400 == 0)) {
+ ++ret;
+ }
+ return ret;
+}
+
+int xtimegm(struct tm *tm, time_t *timep) {
+ tm->tm_isdst = 0;
+
+ if (wrap(&tm->tm_sec, 60, &tm->tm_min) != 0) {
+ goto overflow;
+ }
+ if (wrap(&tm->tm_min, 60, &tm->tm_hour) != 0) {
+ goto overflow;
+ }
+ if (wrap(&tm->tm_hour, 24, &tm->tm_mday) != 0) {
+ goto overflow;
+ }
+
+ // In order to wrap the days of the month, we first need to know what
+ // month it is
+ if (wrap(&tm->tm_mon, 12, &tm->tm_year) != 0) {
+ goto overflow;
+ }
+
+ if (tm->tm_mday < 1) {
+ do {
+ --tm->tm_mon;
+ if (wrap(&tm->tm_mon, 12, &tm->tm_year) != 0) {
+ goto overflow;
+ }
+
+ tm->tm_mday += month_length(tm->tm_year, tm->tm_mon);
+ } while (tm->tm_mday < 1);
+ } else {
+ while (true) {
+ int days = month_length(tm->tm_year, tm->tm_mon);
+ if (tm->tm_mday <= days) {
+ break;
+ }
+
+ tm->tm_mday -= days;
+ ++tm->tm_mon;
+ if (wrap(&tm->tm_mon, 12, &tm->tm_year) != 0) {
+ goto overflow;
+ }
+ }
+ }
+
+ tm->tm_yday = 0;
+ for (int i = 0; i < tm->tm_mon; ++i) {
+ tm->tm_yday += month_length(tm->tm_year, i);
+ }
+ tm->tm_yday += tm->tm_mday - 1;
+
+ int leap_days;
+ // Compute floor((year - 69)/4) - floor((year - 1)/100) + floor((year + 299)/400) without overflows
+ if (tm->tm_year >= 0) {
+ leap_days = floor_div(tm->tm_year - 69, 4) - floor_div(tm->tm_year - 1, 100) + floor_div(tm->tm_year - 101, 400) + 1;
+ } else {
+ leap_days = floor_div(tm->tm_year + 3, 4) - floor_div(tm->tm_year + 99, 100) + floor_div(tm->tm_year + 299, 400) - 17;
+ }
+
+ long long epoch_days = 365LL*(tm->tm_year - 70) + leap_days + tm->tm_yday;
+ tm->tm_wday = (epoch_days + 4)%7;
+ if (tm->tm_wday < 0) {
+ tm->tm_wday += 7;
+ }
+
+ long long epoch_time = tm->tm_sec + 60*(tm->tm_min + 60*(tm->tm_hour + 24*epoch_days));
+ *timep = (time_t)epoch_time;
+ if ((long long)*timep != epoch_time) {
+ goto overflow;
+ }
+ return 0;
+
+overflow:
+ errno = EOVERFLOW;
+ return -1;
+}
+
+/** Parse some digits from a timestamp. */
+static int parse_timestamp_part(const char **str, size_t n, int *result) {
+ char buf[n + 1];
+ for (size_t i = 0; i < n; ++i, ++*str) {
+ char c = **str;
+ if (c < '0' || c > '9') {
+ return -1;
+ }
+ buf[i] = c;
+ }
+ buf[n] = '\0';
+
+ *result = atoi(buf);
+ return 0;
+}
+
+int parse_timestamp(const char *str, struct timespec *result) {
+ struct tm tm = {
+ .tm_isdst = -1,
+ };
+
+ int tz_hour = 0;
+ int tz_min = 0;
+ bool tz_negative = false;
+ bool local = true;
+
+ // YYYY
+ if (parse_timestamp_part(&str, 4, &tm.tm_year) != 0) {
+ goto invalid;
+ }
+ tm.tm_year -= 1900;
+
+ // MM
+ if (*str == '-') {
+ ++str;
+ }
+ if (parse_timestamp_part(&str, 2, &tm.tm_mon) != 0) {
+ goto invalid;
+ }
+ tm.tm_mon -= 1;
+
+ // DD
+ if (*str == '-') {
+ ++str;
+ }
+ if (parse_timestamp_part(&str, 2, &tm.tm_mday) != 0) {
+ goto invalid;
+ }
+
+ if (!*str) {
+ goto end;
+ } else if (*str == 'T') {
+ ++str;
+ }
+
+ // hh
+ if (parse_timestamp_part(&str, 2, &tm.tm_hour) != 0) {
+ goto invalid;
+ }
+
+ // mm
+ if (!*str) {
+ goto end;
+ } else if (*str == ':') {
+ ++str;
+ }
+ if (parse_timestamp_part(&str, 2, &tm.tm_min) != 0) {
+ goto invalid;
+ }
+
+ // ss
+ if (!*str) {
+ goto end;
+ } else if (*str == ':') {
+ ++str;
+ }
+ if (parse_timestamp_part(&str, 2, &tm.tm_sec) != 0) {
+ goto invalid;
+ }
+
+ if (!*str) {
+ goto end;
+ } else if (*str == 'Z') {
+ local = false;
+ ++str;
+ } else if (*str == '+' || *str == '-') {
+ local = false;
+ tz_negative = *str == '-';
+ ++str;
+
+ // hh
+ if (parse_timestamp_part(&str, 2, &tz_hour) != 0) {
+ goto invalid;
+ }
+
+ // mm
+ if (!*str) {
+ goto end;
+ } else if (*str == ':') {
+ ++str;
+ }
+ if (parse_timestamp_part(&str, 2, &tz_min) != 0) {
+ goto invalid;
+ }
+ } else {
+ goto invalid;
+ }
+
+ if (*str) {
+ goto invalid;
+ }
+
+end:
+ if (local) {
+ if (xmktime(&tm, &result->tv_sec) != 0) {
+ goto error;
+ }
+ } else {
+ if (xtimegm(&tm, &result->tv_sec) != 0) {
+ goto error;
+ }
+
+ int offset = 60*tz_hour + tz_min;
+ if (tz_negative) {
+ result->tv_sec -= offset;
+ } else {
+ result->tv_sec += offset;
+ }
+ }
+
+ result->tv_nsec = 0;
+ return 0;
+
+invalid:
+ errno = EINVAL;
+error:
+ return -1;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-10 22:42:44 +0000