我应该用什么来替换 Windows 上的 gettimeofday()？
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What should I use to replace gettimeofday() on Windows?
提问by dicroce
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...
我正在编写一个可移植的 Socket 类，它支持发送和接收的超时......为了实现我正在使用的这些超时select()......但是，我有时需要知道我被阻塞了多长时间select()，当然在 Linux 上我将通过gettimeofday()在我调用之前和之后调用select()然后timersub()用于计算增量来实现...
Given that select()on Windows accepts struct timevalfor it's timeout, what method should I used to replace gettimeofday() on Windows?
鉴于select()在 Windows 上接受struct timeval它的超时，我应该使用什么方法来替换 Windows 上的 gettimeofday()？
回答by dicroce
I ended up finding this page: gettimeofday()function for Windows(now via the Wayback Machine) which has a handy, dandy implementation of gettimeofday()on Windows. It uses the GetSystemTimeAsFileTime()method to get an accurate clock.
我最终找到了这个页面：gettimeofday()Windows 的函数（现在通过 Wayback Machine），它gettimeofday()在 Windows 上有一个方便、漂亮的实现。它使用该GetSystemTimeAsFileTime()方法来获得准确的时钟。
Update: Here's an alternative active link from the 'Unix to Windows Porting Dictionary for HPC' gettimeofday()(now via the Wayback Machine) that points to the implementation the OP referred to. Note also that there's a typo in the linked implementation:
更新：这是“用于 HPC 的 Unix 到 Windows 移植字典” gettimeofday()（现在通过 Wayback 机器）的替代活动链接， 它指向 OP 所指的实现。另请注意，链接实现中有一个错字：
#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 0at the end (they assumed microseconds, not the number of 100-nanosecond intervals). This typo was found via this commenton a Google code project page. The correct values to use are shown below:
显示的值0最后缺少一个额外的值（它们假定为微秒，而不是 100 纳秒间隔的数量）。这个错字是通过谷歌代码项目页面上的这个评论发现的。要使用的正确值如下所示：
#if defined(_MSC_VER) || defined(_MSC_EXTENSIONS)
#define DELTA_EPOCH_IN_MICROSECS 116444736000000000Ui64 // CORRECT
#else
#define DELTA_EPOCH_IN_MICROSECS 116444736000000000ULL // CORRECT
#endif
PostgreSQL's implementation of gettimeofday for Windows:
PostgreSQL 对 Windows 的 gettimeofday 的实现：
/*
* 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;
}
回答by knight666
How about:
怎么样：
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.
GetTickCount()不是很精确，但可能会很好地工作。如果您看到很多 0、16 或 31 毫秒的间隔，请尝试在更长的间隔内计时或使用更精确的函数，例如timeGetTime.
What I usually do is this:
我通常做的是这样的：
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;
}
回答by Shay Erlichmen
In your case I would use the platform independent std::clock
在你的情况下，我会使用平台独立的std::clock
回答by Puppy
You can check out QueryPerformanceCounter and QueryPerformanceFrequency. These are veryhigh resolution- down to one tick per ten cycles on some hardware- timers.
您可以查看 QueryPerformanceCounter 和 QueryPerformanceFrequency。这些分辨率非常高——在某些硬件定时器上低至每十个周期一个滴答。
