// Copyright © Tavian Barnes <tavianator@tavianator.com> // SPDX-License-Identifier: 0BSD #include "xtime.h" #include "atomic.h" #include "config.h" #include <errno.h> #include <limits.h> #include <stdlib.h> #include <sys/time.h> #include <time.h> #include <unistd.h> /** Call tzset() if necessary. */ static void xtzset(void) { static atomic bool is_set = false; if (!load(&is_set, relaxed)) { tzset(); store(&is_set, true, relaxed); } } int xlocaltime(const time_t *timep, struct tm *result) { // Should be called before localtime_r() according to POSIX.1-2004 xtzset(); 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 xtzset(); 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 xgetpart(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 xgetdate(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 (xgetpart(&str, 4, &tm.tm_year) != 0) { goto invalid; } tm.tm_year -= 1900; // MM if (*str == '-') { ++str; } if (xgetpart(&str, 2, &tm.tm_mon) != 0) { goto invalid; } tm.tm_mon -= 1; // DD if (*str == '-') { ++str; } if (xgetpart(&str, 2, &tm.tm_mday) != 0) { goto invalid; } if (!*str) { goto end; } else if (*str == 'T' || *str == ' ') { ++str; } // hh if (xgetpart(&str, 2, &tm.tm_hour) != 0) { goto invalid; } // mm if (!*str) { goto end; } else if (*str == ':') { ++str; } if (xgetpart(&str, 2, &tm.tm_min) != 0) { goto invalid; } // ss if (!*str) { goto end; } else if (*str == ':') { ++str; } if (xgetpart(&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 (xgetpart(&str, 2, &tz_hour) != 0) { goto invalid; } // mm if (!*str) { goto end; } else if (*str == ':') { ++str; } if (xgetpart(&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; } int xgettime(struct timespec *result) { #if _POSIX_TIMERS > 0 return clock_gettime(CLOCK_REALTIME, result); #else struct timeval tv; int ret = gettimeofday(&tv, NULL); if (ret == 0) { result->tv_sec = tv.tv_sec; result->tv_nsec = tv.tv_usec * 1000L; } return ret; #endif }