78 lines
1.7 KiB
C++
78 lines
1.7 KiB
C++
#include <sys/syscall.h>
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#include <time.h>
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#include <unistd.h>
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int clock_gettime(clockid_t clock_id, struct timespec* tp)
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{
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return syscall(SYS_CLOCK_GETTIME, clock_id, tp);
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}
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int nanosleep(const struct timespec* rqtp, struct timespec* rmtp)
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{
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return syscall(SYS_NANOSLEEP, rqtp, rmtp);
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}
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time_t time(time_t* tloc)
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{
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timespec tp;
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if (clock_gettime(CLOCK_REALTIME, &tp) == -1)
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return -1;
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if (tloc)
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*tloc = tp.tv_sec;
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return tp.tv_sec;
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}
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struct tm* gmtime(const time_t* timer)
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{
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static struct tm tm;
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constexpr auto is_leap_year =
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[](time_t year) -> bool
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{
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if (year % 400 == 0)
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return true;
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if (year % 100 == 0)
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return false;
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if (year % 4 == 0)
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return true;
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return false;
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};
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constexpr uint64_t month_days[] { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 };
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time_t time = *timer;
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tm.tm_sec = time % 60; time /= 60;
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tm.tm_min = time % 60; time /= 60;
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tm.tm_hour = time % 24; time /= 24;
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time_t total_days = time;
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tm.tm_wday = (total_days + 4) % 7;
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tm.tm_year = 1970;
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while (total_days >= 365U + is_leap_year(tm.tm_year))
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{
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total_days -= 365U + is_leap_year(tm.tm_year);
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tm.tm_year++;
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}
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bool is_leap_day = is_leap_year(tm.tm_year) && total_days == month_days[2];
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bool had_leap_day = is_leap_year(tm.tm_year) && total_days > month_days[2];
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for (tm.tm_mon = 0; tm.tm_mon < 12; tm.tm_mon++)
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if (total_days < month_days[tm.tm_mon + 1] + (is_leap_day || had_leap_day))
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break;
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tm.tm_mday = total_days - month_days[tm.tm_mon] + !had_leap_day;
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tm.tm_yday = total_days;
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tm.tm_year -= 1900;
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tm.tm_isdst = 0;
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return &tm;
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}
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struct tm* localtime(const time_t* timer)
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{
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// FIXME: support timezones
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return gmtime(timer);
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}
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