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#include "common.h"
#include "time_convert.h"
void ConvertToAbsolute (const SYSTEMTIME * pstLoc, const SYSTEMTIME * pstDst, SYSTEMTIME * pstDstAbs)
{
static int iDays [12] = { 31, 28, 31, 30, 31, 30,
31, 31, 30, 31, 30, 31 } ;
int iDay ;
// Set up the aboluste date structure except for wDay, which we must find
pstDstAbs->wYear = pstLoc->wYear ; // Notice from local date/time
pstDstAbs->wMonth = pstDst->wMonth ;
pstDstAbs->wDayOfWeek = pstDst->wDayOfWeek ;
pstDstAbs->wHour = pstDst->wHour ;
pstDstAbs->wMinute = pstDst->wMinute ;
pstDstAbs->wSecond = pstDst->wSecond ;
pstDstAbs->wMilliseconds = pstDst->wMilliseconds ;
// Fix the iDays array for leap years
if ((pstLoc->wYear % 4 == 0) && ((pstLoc->wYear % 100 != 0) ||
(pstLoc->wYear % 400 == 0)))
{
iDays[1] = 29 ;
}
// Find a day of the month that falls on the same
// day of the week as the transition.
// Suppose today is the 20th of the month (pstLoc->wDay = 20)
// Suppose today is a Wednesday (pstLoc->wDayOfWeek = 3)
// Suppose the transition occurs on a Friday (pstDst->wDayOfWeek = 5)
// Then iDay = 31, meaning that the 31st falls on a Friday
// (The 7 is this formula avoids negatives.)
iDay = pstLoc->wDay + pstDst->wDayOfWeek + 7 - pstLoc->wDayOfWeek ;
// Now shrink iDay to a value between 1 and 7.
iDay = (iDay - 1) % 7 + 1 ;
// Now iDay is a day of the month ranging from 1 to 7.
// Recall that the wDay field of the structure can range
// from 1 to 5, 1 meaning "first", 2 meaning "second",
// and 5 meaning "last".
// So, increase iDay so it's the proper day of the month.
iDay += 7 * (pstDst->wDay - 1) ;
// Could be that iDay overshot the end of the month, so
// fix it up using the number of days in each month
if (iDay > iDays[pstDst->wMonth - 1])
iDay -= 7 ;
// Assign that day to the structure.
pstDstAbs->wDay = iDay ;
}
BOOL LocalGreaterThanTransition (const SYSTEMTIME * pstLoc, const SYSTEMTIME * pstTran)
{
FILETIME ftLoc, ftTran ;
LARGE_INTEGER liLoc, liTran ;
SYSTEMTIME stTranAbs ;
// Easy case: Just compare the two months
if (pstLoc->wMonth != pstTran->wMonth)
return (pstLoc->wMonth > pstTran->wMonth) ;
// Well, we're in a transition month. That requires a bit more work.
// Check if pstDst is in absolute or day-in-month format.
// (See documentation of TIME_ZONE_INFORMATION, StandardDate field.)
if (pstTran->wYear) // absolute format (haven't seen one yet!)
{
stTranAbs = * pstTran ;
}
else // day-in-month format
{
ConvertToAbsolute (pstLoc, pstTran, &stTranAbs) ;
}
// Now convert both date/time structures to large integers & compare
SystemTimeToFileTime (pstLoc, &ftLoc) ;
liLoc = * (LARGE_INTEGER *) (void *) &ftLoc ;
SystemTimeToFileTime (&stTranAbs, &ftTran) ;
liTran = * (LARGE_INTEGER *) (void *) &ftTran ;
return (liLoc.QuadPart > liTran.QuadPart) ;
}
BOOL MySystemTimeToTzSpecificLocalTime(const TIME_ZONE_INFORMATION *ptzi, const SYSTEMTIME *pstUtc, SYSTEMTIME *pstLoc) {
// st is UTC
FILETIME ft ;
LARGE_INTEGER li ;
SYSTEMTIME stDst ;
// If we're running under NT, just call the real function
if (!(0x80000000 & GetVersion()))
return SystemTimeToTzSpecificLocalTime ((TIME_ZONE_INFORMATION *) ptzi, (SYSTEMTIME *) pstUtc, pstLoc) ;
// Convert time to a LARGE_INTEGER and subtract the bias
SystemTimeToFileTime (pstUtc, &ft) ;
li = * (LARGE_INTEGER *) (void *) &ft;
li.QuadPart -= (LONGLONG) 600000000 * ptzi->Bias ;
// Convert to a local date/time before application of daylight saving time.
// The local date/time must be used to determine when the conversion occurs.
ft = * (FILETIME *) (void *) &li ;
FileTimeToSystemTime (&ft, pstLoc) ;
// Find the time assuming Daylight Saving Time
li.QuadPart -= (LONGLONG) 600000000 * ptzi->DaylightBias ;
ft = * (FILETIME *) (void *) &li ;
FileTimeToSystemTime (&ft, &stDst) ;
// Now put li back the way it was
li.QuadPart += (LONGLONG) 600000000 * ptzi->DaylightBias ;
if (ptzi->StandardDate.wMonth) // ie, daylight savings time
{
// Northern hemisphere
if ((ptzi->DaylightDate.wMonth < ptzi->StandardDate.wMonth) &&
(stDst.wMonth >= pstLoc->wMonth) && // avoid the end of year problem
LocalGreaterThanTransition (pstLoc, &ptzi->DaylightDate) &&
!LocalGreaterThanTransition (&stDst, &ptzi->StandardDate))
{
li.QuadPart -= (LONGLONG) 600000000 * ptzi->DaylightBias ;
}
// Southern hemisphere
else if ((ptzi->StandardDate.wMonth < ptzi->DaylightDate.wMonth) &&
(!LocalGreaterThanTransition (&stDst, &ptzi->StandardDate) ||
LocalGreaterThanTransition (pstLoc, &ptzi->DaylightDate)))
{
li.QuadPart -= (LONGLONG) 600000000 * ptzi->DaylightBias ;
}
else
{
li.QuadPart -= (LONGLONG) 600000000 * ptzi->StandardBias ;
}
}
ft = * (FILETIME *) (void *) &li ;
FileTimeToSystemTime (&ft, pstLoc) ;
return TRUE ;
}
VOID MyGetSystemTime(LPSYSTEMTIME lpSystemTime) {
//TIME_ZONE_INFORMATION tzi;
//FILETIME ft;
//LARGE_INTEGER li;
GetSystemTime(lpSystemTime);
//GetTimeZoneInformation(&tzi);
/*
// this condition occurs when 'automaticall adjust for daylight savings' is off, but the timezone info
// says it is daylight savings time. The following attempts to correct for this, but assumes that the user
// has corrected for DST by changing their clock time rather than their timezone. This is invalid so
// it has been removed
if(tzi.StandardDate.wMonth != 0 && tzi.DaylightBias == 0 && tzi.StandardBias == 0) {
if ((tzi.DaylightDate.wMonth < tzi.StandardDate.wMonth) &&
LocalGreaterThanTransition (lpSystemTime, &tzi.DaylightDate) &&
!LocalGreaterThanTransition (lpSystemTime, &tzi.StandardDate))
{
// add one hour to the system time
SystemTimeToFileTime(lpSystemTime, &ft);
li = * (LARGE_INTEGER *) (void *) &ft;
li.QuadPart += (LONGLONG) 600000000 * 60;
ft = * (FILETIME *) (void *) &li ;
FileTimeToSystemTime(&ft, lpSystemTime);
}
// Southern hemisphere
else if ((tzi.StandardDate.wMonth < tzi.DaylightDate.wMonth) &&
(!LocalGreaterThanTransition (lpSystemTime, &tzi.StandardDate) ||
LocalGreaterThanTransition (lpSystemTime, &tzi.DaylightDate)))
{
// add one hour to the system time
SystemTimeToFileTime(lpSystemTime, &ft);
li = * (LARGE_INTEGER *) (void *) &ft;
li.QuadPart += (LONGLONG) 600000000 * 60;
ft = * (FILETIME *) (void *) &li ;
FileTimeToSystemTime(&ft, lpSystemTime);
}
}
*/
}
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