What should I use to replace gettimeofday() on Windows?

I'm writing a portable Socket class that supports timeouts for both sending and receiving... To implement these timeouts I'm using select().... But, I sometimes need to know how long I was blocked inside select() which of course on Linux I would implement by calling gettimeofday() before and after I call select() and then using timersub() to calculate the delta...

Given that select() on Windows accepts struct timeval for it's timeout, what method should I used to replace gettimeofday() on Windows?

dicroce

I ended up finding this page: gettimeofday() on windows [edit: link removed because it now points to an advertising site]. Which has a handy, dandy implementation of gettimeofday() on Windows. It uses the GetSystemTimeAsFileTime() method to get an accurate clock.

Update: Here's an active link [edit: link removed because it now points to an advertising site] that points to the implementation the OP referred to. Note also that there's a typo in the linked implementation:

#if defined(_MSC_VER) || defined(_MSC_EXTENSIONS)
  #define DELTA_EPOCH_IN_MICROSECS  11644473600000000Ui64 // WRONG
#else
  #define DELTA_EPOCH_IN_MICROSECS  11644473600000000ULL // WRONG
#endif

The values shown are missing an extra 0 at the end (they assumed microseconds, not the number of 100-nanosecond intervals). This typo was found via this comment on a Google code project page. The correct values to use are shown below:

#if defined(_MSC_VER) || defined(_MSC_EXTENSIONS)
  #define DELTA_EPOCH_IN_MICROSECS  116444736000000000Ui64 // CORRECT
#else
  #define DELTA_EPOCH_IN_MICROSECS  116444736000000000ULL // CORRECT
#endif

PostgreSQL's implementation of gettimeofday for windows:

/*
 * gettimeofday.c
 *    Win32 gettimeofday() replacement
 *
 * src/port/gettimeofday.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 <sys/time.h>


/* FILETIME of Jan 1 1970 00:00:00. */
static const unsigned __int64 epoch = ((unsigned __int64) 116444736000000000ULL);

/*
 * timezone information is stored outside the kernel so tzp isn't used anymore.
 *
 * Note: this function is not for Win32 high precision timing purpose. See
 * elapsed_time().
 */
int
gettimeofday(struct timeval * tp, struct timezone * tzp)
{
    FILETIME    file_time;
    SYSTEMTIME  system_time;
    ULARGE_INTEGER ularge;

    GetSystemTime(&system_time);
    SystemTimeToFileTime(&system_time, &file_time);
    ularge.LowPart = file_time.dwLowDateTime;
    ularge.HighPart = file_time.dwHighDateTime;

    tp->tv_sec = (long) ((ularge.QuadPart - epoch) / 10000000L);
    tp->tv_usec = (long) (system_time.wMilliseconds * 1000);

    return 0;
}

How about:

unsigned long start = GetTickCount();
// stuff that needs to be timed
unsigned long delta = GetTickCount() - start;

GetTickCount() is not very precise, but will probably work well. If you see a lot of 0, 16 or 31 millisecond intervals, try timing over longer intervals or use a more precise function like timeGetTime.

What I usually do is this:

unsigned long deltastack;
int samples = 0;
float average;

unsigned long start = GetTickCount();
// stuff that needs to be timed
unsigned long delta = GetTickCount() - start;

deltastack += delta;
if (samples++ == 10)
{
   // total time divided by amount of samples
   average = (float)deltastack / 10.f;
   deltastack = 0;
   samples = 0;  
}

In your case I would use the platform independent std::clock

You can check out QueryPerformanceCounter and QueryPerformanceFrequency. These are very high resolution- down to one tick per ten cycles on some hardware- timers.

来源：https://stackoverflow.com/questions/1676036/what-should-i-use-to-replace-gettimeofday-on-windows

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