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lib/datetime: Support dates outside of 1901..2038 range

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Fixes: https://savannah.gnu.org/bugs/?63894
Fixes: https://savannah.gnu.org/bugs/?66301

Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Signed-off-by: Andrew Hamilton <adhamilt@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Vladimir Serbinenko 2025-08-27 17:32:13 -05:00 committed by Daniel Kiper
parent 02788bfdf9
commit 6837293b87
2 changed files with 76 additions and 23 deletions
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65
grub-core/lib/datetime.c
View File

@ -64,7 +64,10 @@ grub_get_weekday_name (struct grub_datetime *datetime)
#define SECPERDAY (24*SECPERHOUR)
#define DAYSPERYEAR 365
#define DAYSPER4YEARS (4*DAYSPERYEAR+1)
/* 24 leap years in 100 years */
#define DAYSPER100YEARS (100 * DAYSPERYEAR + 24)
/* 97 leap years in 400 years */
#define DAYSPER400YEARS (400 * DAYSPERYEAR + 97)
void
grub_unixtime2datetime (grub_int64_t nix, struct grub_datetime *datetime)
@ -76,10 +79,12 @@ grub_unixtime2datetime (grub_int64_t nix, struct grub_datetime *datetime)
/* Convenience: let's have 3 consecutive non-bissextile years
at the beginning of the counting date. So count from 1901. */
int days_epoch;
/* Number of days since 1st Januar, 1901. */
/* Number of days since 1st January, 1 (proleptic). */
unsigned days;
/* Seconds into current day. */
unsigned secs_in_day;
/* Tracks whether this is a leap year. */
bool bisextile;
/* Transform C divisions and modulos to mathematical ones */
if (nix < 0)
@ -92,27 +97,63 @@ grub_unixtime2datetime (grub_int64_t nix, struct grub_datetime *datetime)
days_epoch = grub_divmod64 (nix, SECPERDAY, NULL);
secs_in_day = nix - days_epoch * SECPERDAY;
days = days_epoch + 69 * DAYSPERYEAR + 17;
/*
* 1970 is Unix Epoch. Adjust to a year 1 epoch:
* Leap year logic:
* - Years evenly divisible by 400 are leap years
* - Otherwise, if divisible by 100 are not leap years
* - Otherwise, if divisible by 4 are leap years
* There are four 400-year periods (1600 years worth of days with leap days)
* There are 369 years in addition to the four 400 year periods
* There are three 100-year periods worth of leap days (3*24)
* There are 17 leap days in 69 years (beyond the three 100 year periods)
*/
days = 4 * DAYSPER400YEARS + 369 * DAYSPERYEAR + 3 * 24 + 17 + days_epoch;
datetime->year = 1901 + 4 * (days / DAYSPER4YEARS);
datetime->year = 1 + 400 * (days / DAYSPER400YEARS);
days %= DAYSPER400YEARS;
/*
* On 31st December of bissextile (leap) years 365 days from the beginning
* of the year elapsed but year isn't finished yet - every 400 years
* 396 is 4 years less than 400 year leap cycle
* 96 is 1 day less than number of leap days in 400 years
*/
if (days / DAYSPER100YEARS == 4)
{
datetime->year += 396;
days -= 396 * DAYSPERYEAR + 96;
}
else
{
datetime->year += 100 * (days / DAYSPER100YEARS);
days %= DAYSPER100YEARS;
}
datetime->year += 4 * (days / DAYSPER4YEARS);
days %= DAYSPER4YEARS;
/* On 31st December of bissextile years 365 days from the beginning
of the year elapsed but year isn't finished yet */
/*
* On 31st December of bissextile (leap) years 365 days from the beginning
* of the year elapsed but year isn't finished yet - every 4 years
*/
if (days / DAYSPERYEAR == 4)
{
datetime->year += 3;
days -= 3*DAYSPERYEAR;
days -= 3 * DAYSPERYEAR;
}
else
{
datetime->year += days / DAYSPERYEAR;
days %= DAYSPERYEAR;
}
for (i = 0; i < 12
&& days >= (i==1 && datetime->year % 4 == 0
? 29 : months[i]); i++)
days -= (i==1 && datetime->year % 4 == 0
? 29 : months[i]);
bisextile = (datetime->year % 4 == 0
&& (datetime->year % 100 != 0
|| datetime->year % 400 == 0)) ? true : false;
for (i = 0;
i < 12 && days >= ((i == 1 && bisextile == true) ? 29 : months[i]);
i++)
days -= ((i == 1 && bisextile == true) ? 29 : months[i]);
datetime->month = i + 1;
datetime->day = 1 + days;
datetime->hour = (secs_in_day / SECPERHOUR);

34
include/grub/datetime.h
View File

@ -54,8 +54,9 @@ void grub_unixtime2datetime (grub_int64_t nix,
static inline int
grub_datetime2unixtime (const struct grub_datetime *datetime, grub_int64_t *nix)
{
grub_int32_t ret;
grub_int64_t ret;
int y4, ay;
bool bisextile;
const grub_uint16_t monthssum[12]
= { 0,
31,
@ -75,15 +76,11 @@ grub_datetime2unixtime (const struct grub_datetime *datetime, grub_int64_t *nix)
const int SECPERHOUR = 60 * SECPERMIN;
const int SECPERDAY = 24 * SECPERHOUR;
const int SECPERYEAR = 365 * SECPERDAY;
const int SECPER4YEARS = 4 * SECPERYEAR + SECPERDAY;
const grub_int64_t SECPER4YEARS = 4 * SECPERYEAR + SECPERDAY;
if (datetime->year > 2038 || datetime->year < 1901)
return 0;
if (datetime->month > 12 || datetime->month < 1)
return 0;
/* In the period of validity of unixtime all years divisible by 4
are bissextile*/
/* Convenience: let's have 3 consecutive non-bissextile years
at the beginning of the epoch. So count from 1973 instead of 1970 */
ret = 3 * SECPERYEAR + SECPERDAY;
@ -91,16 +88,31 @@ grub_datetime2unixtime (const struct grub_datetime *datetime, grub_int64_t *nix)
/* Transform C divisions and modulos to mathematical ones */
y4 = ((datetime->year - 1) >> 2) - (1973 / 4);
ay = datetime->year - 1973 - 4 * y4;
ret += y4 * SECPER4YEARS;
ret += ay * SECPERYEAR;
ret += (grub_int64_t) y4 * SECPER4YEARS;
ret += (grub_int64_t) ay * SECPERYEAR;
ret += monthssum[datetime->month - 1] * SECPERDAY;
if (ay == 3 && datetime->month >= 3)
/*
* Correct above calculation (which assumes every 4 years is a leap year)
* to remove those "false leap years" that are divisible by 100 but not 400.
* Since this logic starts with seconds since 1973, 15 is used because:
* - (1973 - 1) / 100 = 19 (floor due to integer math)
* - (1973 - 1) / 400 = 4 (floor due to integer math)
* - 19 - 4 - 15 = 0 (we want to start with no "false leap years" at time
* zero of 1973)
*/
ret -= ((datetime->year - 1) / 100 - (datetime->year - 1) / 400 - 15)
* SECPERDAY;
ret += (grub_int64_t) monthssum[datetime->month - 1] * SECPERDAY;
bisextile = (ay == 3
&& (datetime->year % 100 != 0
|| datetime->year % 400 == 0)) ? true : false;
if (bisextile == true && datetime->month >= 3)
ret += SECPERDAY;
ret += (datetime->day - 1) * SECPERDAY;
if ((datetime->day > months[datetime->month - 1]
&& (!ay || datetime->month != 2 || datetime->day != 29))
&& !(bisextile == true && datetime->month == 2 && datetime->day == 29))
|| datetime->day < 1)
return 0;