Source code of Windows XP (NT5)
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/***
*time.c - get current system time
*
* Copyright (c) 1989-2001, Microsoft Corporation. All rights reserved.
*
*Purpose:
* defines time() - gets the current system time and converts it to
* internal (time_t) format time.
*
*Revision History:
* 06-07-89 PHG Module created, based on asm version
* 03-20-90 GJF Made calling type _CALLTYPE1, added #include
* <cruntime.h> and fixed the copyright. Also, cleaned
* up the formatting a bit.
* 07-25-90 SBM Removed '32' from API names
* 10-04-90 GJF New-style function declarator.
* 12-04-90 SRW Changed to include <oscalls.h> instead of <doscalls.h>
* 12-06-90 SRW Added _CRUISER_ and _WIN32 conditionals.
* 05-19-92 DJM ifndef for POSIX build.
* 03-30-93 GJF Replaced dtoxtime() reference by __gmtotime_t. Also
* purged Cruiser support.
* 04-06-93 SKS Replace _CRTAPI* with __cdecl
* 07-21-93 GJF Converted from using __gmtotime_t and GetSystemTime,
* to using __loctotime_t and GetLocalTime.
* 02-13-95 GJF Merged in Mac version.
* 09-22-95 GJF Obtain and use Win32's DST flag.
* 10-24-95 GJF GetTimeZoneInformation is *EXPENSIVE* on NT. Use a
* cache to minimize calls to this API.
* 12-13-95 GJF Optimization above wasn't working because I had
* switched gmt and gmt_cache (thanks PhilipLu!)
* 10-11-96 GJF More elaborate test needed to determine if current
* time is a DST time.
* 05-20-98 GJF Get UTC time directly from the system.
* 05-17-99 PML Remove all Macintosh support.
*
*******************************************************************************/
#ifndef _POSIX_
#include <cruntime.h>
#include <time.h>
#include <internal.h>
#include <windows.h>
/*
* Number of 100 nanosecond units from 1/1/1601 to 1/1/1970
*/
#define EPOCH_BIAS 116444736000000000i64
/*
* Union to facilitate converting from FILETIME to unsigned __int64
*/
typedef union {
unsigned __int64 ft_scalar;
FILETIME ft_struct;
} FT;
/***
*time_t time(timeptr) - Get current system time and convert to time_t value.
*
*Purpose:
* Gets the current date and time and stores it in internal (time_t)
* format. The time is returned and stored via the pointer passed in
* timeptr. If timeptr == NULL, the time is only returned, not stored in
* *timeptr. The internal (time_t) format is the number of seconds since
* 00:00:00, Jan 1 1970 (UTC).
*
* Note: We cannot use GetSystemTime since its return is ambiguous. In
* Windows NT, in return UTC. In Win32S, probably also Win32C, it
* returns local time.
*
*Entry:
* time_t *timeptr - pointer to long to store time in.
*
*Exit:
* returns the current time.
*
*Exceptions:
*
*******************************************************************************/
time_t __cdecl time (
time_t *timeptr
)
{
time_t tim;
FT nt_time;
GetSystemTimeAsFileTime( &(nt_time.ft_struct) );
tim = (time_t)((nt_time.ft_scalar - EPOCH_BIAS) / 10000000i64);
if (timeptr)
*timeptr = tim; /* store time if requested */
return tim;
}
#endif /* _POSIX_ */