Source code of Windows XP (NT5)
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/***
*gmtime64.c - breaks down a time value into GMT date/time info
*
* Copyright (c) 1998-2001, Microsoft Corporation. All rights reserved.
*
*Purpose:
* defines _gmtime64() - breaks the clock value down into GMT time/date
* information; returns pointer to structure with the data.
*
*Revision History:
* 05-13-98 GJF Created. Adapted from Win64 version of _gmtime64.c.
* 06-12-98 GJF Fixed elapsed years calculation.
*
*******************************************************************************/
#include <cruntime.h>
#include <time.h>
#include <ctime.h>
#include <stddef.h>
#include <internal.h>
#include <mtdll.h>
#ifdef _MT
#include <malloc.h>
#include <stddef.h>
#endif
#include <dbgint.h>
static struct tm tb = { 0 }; /* time block */
/***
*struct tm *_gmtime64(timp) - convert *timp to a structure (UTC)
*
*Purpose:
* Converts the calendar time value, in internal 64-bit format to
* broken-down time (tm structure) with the corresponding UTC time.
*
*Entry:
* const __time64_t *timp - pointer to time_t value to convert
*
*Exit:
* returns pointer to filled-in tm structure.
* returns NULL if *timp < 0
*
*Exceptions:
*
*******************************************************************************/
struct tm * __cdecl _gmtime64 (
const __time64_t *timp
)
{
__time64_t caltim = *timp; /* calendar time to convert */
int islpyr = 0; /* is-current-year-a-leap-year flag */
int tmptim;
int *mdays; /* pointer to days or lpdays */
#ifdef _MT
struct tm *ptb; /* will point to gmtime buffer */
_ptiddata ptd = _getptd();
#else
struct tm *ptb = &tb;
#endif
if ( (caltim < 0) || (caltim > _MAX__TIME64_T) )
return(NULL);
#ifdef _MT
/* Use per thread buffer area (malloc space, if necessary) */
if ( (ptd->_gmtimebuf != NULL) || ((ptd->_gmtimebuf =
_malloc_crt(sizeof(struct tm))) != NULL) )
ptb = ptd->_gmtimebuf;
else
ptb = &tb; /* malloc error: use static buffer */
#endif
/*
* Determine the years since 1900. Start by ignoring leap years.
*/
tmptim = (int)(caltim / _YEAR_SEC) + 70;
caltim -= ((__time64_t)(tmptim - 70) * _YEAR_SEC);
/*
* Correct for elapsed leap years
*/
caltim -= ((__time64_t)_ELAPSED_LEAP_YEARS(tmptim) * _DAY_SEC);
/*
* If we have underflowed the __time64_t range (i.e., if caltim < 0),
* back up one year, adjusting the correction if necessary.
*/
if ( caltim < 0 ) {
caltim += (__time64_t)_YEAR_SEC;
tmptim--;
if ( _IS_LEAP_YEAR(tmptim) ) {
caltim += _DAY_SEC;
islpyr++;
}
}
else
if ( _IS_LEAP_YEAR(tmptim) )
islpyr++;
/*
* tmptim now holds the value for tm_year. caltim now holds the
* number of elapsed seconds since the beginning of that year.
*/
ptb->tm_year = tmptim;
/*
* Determine days since January 1 (0 - 365). This is the tm_yday value.
* Leave caltim with number of elapsed seconds in that day.
*/
ptb->tm_yday = (int)(caltim / _DAY_SEC);
caltim -= (__time64_t)(ptb->tm_yday) * _DAY_SEC;
/*
* Determine months since January (0 - 11) and day of month (1 - 31)
*/
if ( islpyr )
mdays = _lpdays;
else
mdays = _days;
for ( tmptim = 1 ; mdays[tmptim] < ptb->tm_yday ; tmptim++ ) ;
ptb->tm_mon = --tmptim;
ptb->tm_mday = ptb->tm_yday - mdays[tmptim];
/*
* Determine days since Sunday (0 - 6)
*/
ptb->tm_wday = ((int)(*timp / _DAY_SEC) + _BASE_DOW) % 7;
/*
* Determine hours since midnight (0 - 23), minutes after the hour
* (0 - 59), and seconds after the minute (0 - 59).
*/
ptb->tm_hour = (int)(caltim / 3600);
caltim -= (__time64_t)ptb->tm_hour * 3600L;
ptb->tm_min = (int)(caltim / 60);
ptb->tm_sec = (int)(caltim - (ptb->tm_min) * 60);
ptb->tm_isdst = 0;
return( (struct tm *)ptb );
}