win32gettimeofday.c

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/*
 * win32gettimeofday.c
 *    Win32 gettimeofday() replacement
 *
 * src/port/win32gettimeofday.c
 *
 * Copyright (c) 2003 SRA, Inc.
 * Copyright (c) 2003 SKC, Inc.
 *
 * Permission to use, copy, modify, and distribute this software and
 * its documentation for any purpose, without fee, and without a
 * written agreement is hereby granted, provided that the above
 * copyright notice and this paragraph and the following two
 * paragraphs appear in all copies.
 *
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE TO ANY PARTY FOR DIRECT,
 * INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
 * LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
 * DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * THE AUTHOR SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS
 * IS" BASIS, AND THE AUTHOR HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE,
 * SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
 */
 
#include "c.h"
 
#include <sysinfoapi.h>
 
#include <sys/time.h>
 
/* FILETIME of Jan 1 1970 00:00:00, the PostgreSQL epoch */
static const unsigned __int64 epoch = UINT64CONST(116444736000000000);
 
/*
 * FILETIME represents the number of 100-nanosecond intervals since
 * January 1, 1601 (UTC).
 */
#define FILETIME_UNITS_PER_SEC  10000000L
#define FILETIME_UNITS_PER_USEC 10
 
 
/*
 * timezone information is stored outside the kernel so tzp isn't used anymore.
 *
 * Note: this function is not for Win32 high precision timing purposes. See
 * elapsed_time().
 */
int
gettimeofday(struct timeval *tp, void *tzp)
{
    FILETIME    file_time;
    ULARGE_INTEGER ularge;
 
    /*
     * POSIX declines to define what tzp points to, saying "If tzp is not a
     * null pointer, the behavior is unspecified".  Let's take this
     * opportunity to verify that noplace in Postgres tries to use any
     * unportable behavior.
     */
    Assert(tzp == NULL);
 
    GetSystemTimePreciseAsFileTime(&file_time);
    ularge.LowPart = file_time.dwLowDateTime;
    ularge.HighPart = file_time.dwHighDateTime;
 
    tp->tv_sec = (long) ((ularge.QuadPart - epoch) / FILETIME_UNITS_PER_SEC);
    tp->tv_usec = (long) (((ularge.QuadPart - epoch) % FILETIME_UNITS_PER_SEC)
                          / FILETIME_UNITS_PER_USEC);
 
    return 0;
}