Source code of Windows XP (NT5)
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/***
*dtoxtm64.c - convert OS local time to __time64_t
*
* Copyright (c) 1998-2001, Microsoft Corporation. All rights reserved.
*
*Purpose:
* defines __loctotime64_t() - convert OS local time to internal format
* (__time64_t).
*
*Revision History:
* 05-21-98 GJF Created.
* 10-19-98 GJF Fill in tm_min and tm_sec before calling _isindst
*
*******************************************************************************/
#include <cruntime.h>
#include <time.h>
#include <ctime.h>
#include <internal.h>
/***
*__time64_t __loctotime64_t(yr, mo, dy, hr, mn, sc, dstflag) - converts OS
* local time to internal time format (i.e., a __time64_t value)
*
*Purpose:
* Converts a local time value, obtained in a broken down format from
* the host OS, to __time64_t format (i.e., the number elapsed seconds
* since 01-01-70, 00:00:00, UTC).
*
*Entry:
* int yr, mo, dy - date
* int hr, mn, sc - time
* int dstflag - 1 if Daylight Time, 0 if Standard Time, -1 if
* not specified.
*
*Exit:
* Returns calendar time value.
*
*Exceptions:
*
*******************************************************************************/
__time64_t __cdecl __loctotime64_t (
int yr, /* 0 based */
int mo, /* 1 based */
int dy, /* 1 based */
int hr,
int mn,
int sc,
int dstflag )
{
int tmpdays;
__time64_t tmptim;
struct tm tb;
/*
* Do a quick range check on the year and convert it to a delta
* off of 1900.
*/
if ( ((long)(yr -= 1900) < _BASE_YEAR) || ((long)yr > _MAX_YEAR64) )
return (__time64_t)(-1);
/*
* Compute the number of elapsed days in the current year.
*/
tmpdays = dy + _days[mo - 1];
if ( _IS_LEAP_YEAR(yr) && (mo > 2) )
tmpdays++;
/*
* Compute the number of elapsed seconds since the Epoch. Note the
* computation of elapsed leap years would break down after 2100
* if such values were in range (fortunately, they aren't).
*/
tmptim = /* 365 days for each year */
(((__time64_t)yr - _BASE_YEAR) * 365
/* one day for each elapsed leap year */
+ (__time64_t)_ELAPSED_LEAP_YEARS(yr)
/* number of elapsed days in yr */
+ tmpdays)
/* convert to hours and add in hr */
* 24 + hr;
tmptim = /* convert to minutes and add in mn */
(tmptim * 60 + mn)
/* convert to seconds and add in sec */
* 60 + sc;
/*
* Account for time zone.
*/
__tzset();
tmptim += _timezone;
/*
* Fill in enough fields of tb for _isindst(), then call it to
* determine DST.
*/
tb.tm_yday = tmpdays;
tb.tm_year = yr;
tb.tm_mon = mo - 1;
tb.tm_hour = hr;
tb.tm_min = mn;
tb.tm_sec = sc;
if ( (dstflag == 1) || ((dstflag == -1) && _daylight &&
_isindst(&tb)) )
tmptim += _dstbias;
return(tmptim);
}