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// Copyright © Tavian Barnes <tavianator@tavianator.com>
// SPDX-License-Identifier: 0BSD
#include "xtime.h"
#include "bfstd.h"
#include "config.h"
#include "diag.h"
#include <errno.h>
#include <limits.h>
#include <sys/time.h>
#include <time.h>
#include <unistd.h>
int xmktime(struct tm *tm, time_t *timep) {
*timep = mktime(tm);
if (*timep == -1) {
int error = errno;
struct tm tmp;
if (!localtime_r(timep, &tmp)) {
bfs_bug("localtime_r(-1): %s", xstrerror(errno));
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 a decimal digit. */
static int xgetdigit(char c) {
int ret = c - '0';
if (ret < 0 || ret > 9) {
return -1;
} else {
return ret;
}
}
/** Parse some digits from a timestamp. */
static int xgetpart(const char **str, size_t n, int *result) {
*result = 0;
for (size_t i = 0; i < n; ++i, ++*str) {
int dig = xgetdigit(**str);
if (dig < 0) {
return -1;
}
*result *= 10;
*result += dig;
}
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;
} else if (xgetdigit(*str) < 0) {
goto zone;
}
if (xgetpart(&str, 2, &tm.tm_min) != 0) {
goto invalid;
}
// ss
if (!*str) {
goto end;
} else if (*str == ':') {
++str;
} else if (xgetdigit(*str) < 0) {
goto zone;
}
if (xgetpart(&str, 2, &tm.tm_sec) != 0) {
goto invalid;
}
zone:
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 = (tz_hour * 60 + tz_min) * 60;
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
}
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