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Replace lookup-based time logic with direct epoch calculation formulas
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This commit is contained in:
Aiken Harris
2026-04-24 23:27:25 +02:00
parent 8ab3ddb8eb
commit 439ea891ca
3 changed files with 60 additions and 34 deletions
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87
xtoskrnl/rtl/time.cc
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@@ -45,23 +45,49 @@ XTSTATUS
RTL::Time::TimeFieldsToUnixEpoch(IN PTIME_FIELDS TimeFields,
OUT PLONGLONG UnixTime)
{
LONGLONG TotalSeconds;
LARGE_INTEGER XtTime;
XTSTATUS Status;
LONGLONG ElapsedDays, TotalSeconds;
LONG Month, Year;
ULONG Leap;
/* Convert to XT Epoch */
Status = TimeFieldsToXtEpoch(TimeFields, &XtTime);
if(Status != STATUS_SUCCESS)
/* Check leap year */
Leap = LeapYear(TimeFields->Year) ? 1 : 0;
/* 2. Validate input data */
if(TimeFields->Hour < 0 || TimeFields->Hour > 23 ||
TimeFields->Minute < 0 || TimeFields->Minute > 59 ||
TimeFields->Second < 0 || TimeFields->Second > 59 ||
TimeFields->Year < 0 || TimeFields->Year > 30827 ||
TimeFields->Month < 1 || TimeFields->Month > 12 ||
TimeFields->Day < 1 || TimeFields->Day > DaysInMonth[Leap][TimeFields->Month - 1])
{
/* Failed to convert to XT Epoch, return error code */
return Status;
/* Invalid input data, return error code */
return STATUS_INVALID_PARAMETER;
}
/* Convert 100-nanosecond intervals (TICKS) to whole seconds */
TotalSeconds = XtTime.QuadPart / TIME_TICKS_PER_SECOND;
/* Copy year and month */
Year = (LONG)TimeFields->Year;
Month = (LONG)TimeFields->Month;
/* Subtract the number of seconds between January 1, 1601 and January 1, 1970 */
*UnixTime = TotalSeconds - 11644473600LL;
/* Put February at the end of the calculation cycle, making leap day handling implicit in the year division */
if(0 >= (LONG)(Month -= 2))
{
/* Adjust month and year */
Month += 12;
Year -= 1;
}
/* Calculate absolute elapsed days */
ElapsedDays = (LONGLONG)(Year/4 - Year/100 + Year/400 + 367*Month/12 + TimeFields->Day) +
(LONGLONG)Year*365 - 719499LL;
/* Calculate total seconds */
TotalSeconds = (ElapsedDays * TIME_SECONDS_PER_DAY) +
((LONGLONG)TimeFields->Hour * TIME_SECONDS_PER_HOUR) +
((LONGLONG)TimeFields->Minute * TIME_SECONDS_PER_MINUTE) +
(LONGLONG)TimeFields->Second;
/* Output the final Unix timestamp */
*UnixTime = TotalSeconds;
/* Return success */
return STATUS_SUCCESS;
@@ -86,8 +112,9 @@ XTSTATUS
RTL::Time::TimeFieldsToXtEpoch(IN PTIME_FIELDS TimeFields,
OUT PLARGE_INTEGER XtTime)
{
ULONG Leap, ElapsedYears, ElapsedDays;
ULONGLONG TotalSeconds;
LONGLONG ElapsedDays, TotalSeconds;
LONG Month, Year;
ULONG Leap;
/* Check leap year */
Leap = LeapYear(TimeFields->Year) ? 1 : 0;
@@ -105,25 +132,31 @@ RTL::Time::TimeFieldsToXtEpoch(IN PTIME_FIELDS TimeFields,
return STATUS_INVALID_PARAMETER;
}
/* Calculate days elapsed in previous years */
ElapsedYears = (ULONG)(TimeFields->Year - 1601);
ElapsedDays = (ElapsedYears * 365) + (ElapsedYears / 4) - (ElapsedYears / 100) + (ElapsedYears / 400);
/* Copy year and month */
Year = (LONG)TimeFields->Year;
Month = (LONG)TimeFields->Month;
/* Add days elapsed in previous months of the current year */
ElapsedDays += DaysPrecedingMonth[Leap][TimeFields->Month - 1];
/* Put February at the end of the calculation cycle, making leap day handling implicit in the year division */
if(0 >= (LONG)(Month -= 2))
{
/* Adjust month and year */
Month += 12;
Year -= 1;
}
/* Add days elapsed in the current month */
ElapsedDays += (TimeFields->Day - 1);
/* Calculate absolute elapsed days */
ElapsedDays = (LONGLONG)(Year/4 - Year/100 + Year/400 + 367*Month/12 + TimeFields->Day) +
(LONGLONG)Year*365 - 584725LL;
/* Calculate a total number of seconds */
TotalSeconds = ((ULONGLONG)ElapsedDays * TIME_SECONDS_PER_DAY) +
((ULONGLONG)TimeFields->Hour * TIME_SECONDS_PER_HOUR) +
((ULONGLONG)TimeFields->Minute * TIME_SECONDS_PER_MINUTE) +
(ULONGLONG)TimeFields->Second;
/* Calculate total seconds */
TotalSeconds = (ElapsedDays * TIME_SECONDS_PER_DAY) +
((LONGLONG)TimeFields->Hour * TIME_SECONDS_PER_HOUR) +
((LONGLONG)TimeFields->Minute * TIME_SECONDS_PER_MINUTE) +
(LONGLONG)TimeFields->Second;
/* Convert to 100-ns intervals and slap milliseconds on top */
XtTime->QuadPart = (TotalSeconds * TIME_TICKS_PER_SECOND) +
((ULONGLONG)TimeFields->Milliseconds * TIME_TICKS_PER_MILLISECOND);
((LONGLONG)TimeFields->Milliseconds * TIME_TICKS_PER_MILLISECOND);
/* Return success */
return STATUS_SUCCESS;