本代码来自ReactOS-0.4.0lib tl ime.c中的函数RtlTimeToTimeFields(IN PLARGE_INTEGER Time, OUT PTIME_FIELDS TimeFields);
源代码如下:
#define TICKSPERMIN 600000000 #define TICKSPERSEC 10000000 #define TICKSPERMSEC 10000 #define SECSPERDAY 86400 #define SECSPERHOUR 3600 #define SECSPERMIN 60 #define MINSPERHOUR 60 #define HOURSPERDAY 24 #define EPOCHWEEKDAY 1 #define DAYSPERWEEK 7 #define EPOCHYEAR 1601 #define DAYSPERNORMALYEAR 365 #define DAYSPERLEAPYEAR 366 #define MONSPERYEAR 12 static const unsigned int YearLengths[2] = { DAYSPERNORMALYEAR, DAYSPERLEAPYEAR }; static const UCHAR MonthLengths[2][MONSPERYEAR] = { { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }, { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 } }; static __inline int IsLeapYear(int Year) { return Year % 4 == 0 && (Year % 100 != 0 || Year % 400 == 0) ? 1 : 0; } static int DaysSinceEpoch(int Year) { int Days; Year--; /* Don't include a leap day from the current year */ Days = Year * DAYSPERNORMALYEAR + Year / 4 - Year / 100 + Year / 400; Days -= (EPOCHYEAR - 1) * DAYSPERNORMALYEAR + (EPOCHYEAR - 1) / 4 - (EPOCHYEAR - 1) / 100 + (EPOCHYEAR - 1) / 400; return Days; } VOID RtlTimeToTimeFields(IN PLARGE_INTEGER Time, OUT LPSYSTEMTIME TimeFields) { const UCHAR *Months; ULONG SecondsInDay, CurYear; ULONG LeapYear, CurMonth; ULONG Days; ULONGLONG IntTime = Time->QuadPart; /* Extract millisecond from time and convert time into seconds */ TimeFields->wMilliseconds = (WORD) ((IntTime % TICKSPERSEC) / TICKSPERMSEC); IntTime = IntTime / TICKSPERSEC; /* Split the time into days and seconds within the day */ Days = (ULONG)(IntTime / SECSPERDAY); SecondsInDay = IntTime % SECSPERDAY; /* compute time of day */ TimeFields->wHour = (WORD) (SecondsInDay / SECSPERHOUR); SecondsInDay = SecondsInDay % SECSPERHOUR; TimeFields->wMinute = (WORD) (SecondsInDay / SECSPERMIN); TimeFields->wSecond = (WORD) (SecondsInDay % SECSPERMIN); /* compute day of week */ TimeFields->wDayOfWeek = (WORD) ((EPOCHWEEKDAY + Days) % DAYSPERWEEK); /* compute year */ CurYear = EPOCHYEAR; CurYear += Days / DAYSPERLEAPYEAR; Days -= DaysSinceEpoch(CurYear); while (1) { LeapYear = IsLeapYear(CurYear); if (Days < YearLengths[LeapYear]) { break; } CurYear++; Days = Days - YearLengths[LeapYear]; } TimeFields->wYear = (WORD) CurYear; /* Compute month of year */ LeapYear = IsLeapYear(CurYear); Months = MonthLengths[LeapYear]; for (CurMonth = 0; Days >= Months[CurMonth]; CurMonth++) Days = Days - Months[CurMonth]; TimeFields->wMonth = (WORD) (CurMonth + 1); TimeFields->wDay = (WORD) (Days + 1); }