:: limine / common / lib / time.c 2.0 KB raw

#include <stddef.h>

#include <stdint.h>

#include <lib/time.h>

#if defined (BIOS)

#  include <lib/real.h>

#elif defined (UEFI)

#  include <efi.h>

#endif

#include <lib/misc.h>

​

// Julian date calculation from https://en.wikipedia.org/wiki/Julian_day

static int get_jdn(int days, int months, int years) {

    return (1461 * (years + 4800 + (months - 14)/12))/4 + (367 *

           (months - 2 - 12 * ((months - 14)/12)))/12 -

           (3 * ((years + 4900 + (months - 14)/12)/100))/4

           + days - 32075;

}

​

static uint64_t get_unix_epoch(uint8_t seconds, uint8_t minutes, uint8_t  hours,

                               uint8_t days,    uint8_t months,  uint16_t years) {

    uint64_t jdn_current = get_jdn(days, months, years);

    uint64_t jdn_1970    = get_jdn(1, 1, 1970);

​

    uint64_t jdn_diff = jdn_current - jdn_1970;

​

    return (jdn_diff * (60 * 60 * 24)) + hours * 3600 + minutes * 60 + seconds;

}

​

#if defined (BIOS)

uint64_t time(void) {

    struct rm_regs r;

​

again:

    r = (struct rm_regs){0};

    r.eax = 0x0400;

    rm_int(0x1a, &r, &r);

​

    uint8_t  day    = bcd_to_int( r.edx & 0x00ff);

    uint8_t  month  = bcd_to_int((r.edx & 0xff00) >> 8);

    uint16_t year   = bcd_to_int( r.ecx & 0x00ff) +

    /* century */     bcd_to_int((r.ecx & 0xff00) >> 8) * 100;

​

    r = (struct rm_regs){0};

    r.eax = 0x0200;

    rm_int(0x1a, &r, &r);

​

    uint8_t second  = bcd_to_int((r.edx & 0xff00) >> 8);

    uint8_t minute  = bcd_to_int( r.ecx & 0x00ff);

    uint8_t hour    = bcd_to_int((r.ecx & 0xff00) >> 8);

​

    // Check RTC day wraparound

    r = (struct rm_regs){0};

    r.eax = 0x0400;

    rm_int(0x1a, &r, &r);

    if (bcd_to_int(r.edx & 0x00ff) != day) {

        goto again;

    }

​

    return get_unix_epoch(second, minute, hour, day, month, year);

}

#endif

​

#if defined (UEFI)

uint64_t time(void) {

    EFI_TIME time;

    EFI_STATUS status = gRT->GetTime(&time, NULL);

​

    if (status != 0) {

        return 0;

    }

​

    return get_unix_epoch(time.Second, time.Minute, time.Hour,

                          time.Day, time.Month, time.Year);

}

#endif