我应该使用在Windows替换的gettimeofday（）？

Question

我正在写支持发送和接收......为了实现这些超时我使用select()超时便携式Socket类....但是，我有时需要知道我被封内select()多久这当然，在Linux上我会通过之前和之后我打电话gettimeofday()打电话select()，然后使用timersub()计算增量实现...

由于在Windows select()接受struct timeval为它的超时，我应该用什么方法在Windows替换的gettimeofday（）？

Answer 1

我最终找到此页：函数gettimeofday（）在Windows [编辑：链接删除，因为它指向一个广告网站。其中有一个方便，花花公子执行函数gettimeofday的（）在Windows上。它使用GetSystemTimeAsFileTime()方法以获得准确的时钟。

更新：这是一个活动链接[编辑：链接删除，因为它指向一个广告网站]指向OP中提到的执行。同时，有一个错字在链接的实现注意：

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

示出丢失在端部的额外的0值（它们假定微秒，100纳秒的时间间隔不数目）。这个错字经此评论上一个谷歌代码项目页面。使用正确的值如下所示：

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

---

<强> PostgreSQL的实施gettimeofday的用于窗口：

/*
 * 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;
}

Answer 2

如何：

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

GetTickCount()不是很精确，但可能会很好地工作。如果看到了大量的0，16或31毫秒的间隔，尽量定时在较长的时间间隔，或使用更精确的功能像timeGetTime。

我最常做的是这样的：

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;  
}

Answer 3

在你的情况我会使用独立于平台的的std ::时钟

Answer 4

您可以检查出QueryPerformanceCounter和QueryPerformanceFrequency的。这些是非常高与分辨率降低到每十个循环一个刻度上的一些硬件定时器。