在windows上使用gettimeofday()等效项
在windows上使用gettimeofday()等效项
提问于 2016-01-17 03:25:20
我正在尝试使用Visual Studio 2013在Windows上为UNIX的gettimeofday()函数使用两个不同的等价物。
我从here那里拿到了第一个。作为第二个函数，我使用了here所解释的_ftime64_s函数。
它们起作用了，但并不像我预期的那样。我希望在打印秒数时获得不同的值，或者至少是毫秒数，但使用gettimeofday() (mytime1 & mytime2)和_ftime64_s (mytime3 & mytime4)打印时得到的值是相同的。
然而，值得一提的是，这两个函数的毫秒值确实不同(即mytime1/mytime2的毫秒值与mytime3/mytime4的毫秒值不同)。
下面是我的代码：
#include <stdio.h>
#include <Windows.h>
#include <stdint.h>
#include <sys/timeb.h>
#include <time.h>
#define WIN32_LEAN_AND_MEAN
int gettimeofday(struct timeval * tp, struct timezone * tzp)
{
// Note: some broken versions only have 8 trailing zero's, the correct epoch has 9 trailing zero's
static const uint64_t EPOCH = ((uint64_t)116444736000000000ULL);
SYSTEMTIME system_time;
FILETIME file_time;
uint64_t time;
GetSystemTime(&system_time);
SystemTimeToFileTime(&system_time, &file_time);
time = ((uint64_t)file_time.dwLowDateTime);
time += ((uint64_t)file_time.dwHighDateTime) << 32;
tp->tv_sec = (long)((time - EPOCH) / 10000000L);
tp->tv_usec = (long)(system_time.wMilliseconds * 1000);
return 0;
}
int main()
{
/* working with struct timeval and gettimeofday equivalent */
struct timeval mytime1;
struct timeval mytime2;
gettimeofday(&(mytime1), NULL);
gettimeofday(&(mytime2), NULL);
printf("Seconds: %d\n", (int)(mytime1.tv_sec));
printf("Milliseconds: %d\n", (int)(mytime1.tv_usec));
printf("Seconds: %d\n", (int)(mytime2.tv_sec));
printf("Milliseconds: %d\n", (int)(mytime2.tv_usec));
/* working with _ftime64_s */
struct _timeb mytime3;
struct _timeb mytime4;
_ftime64_s(&mytime3);
_ftime64_s(&mytime4);
printf("Seconds: %d\n", mytime3.time);
printf("Milliseconds: %d\n", mytime3.millitm);
printf("Seconds: %d\n", mytime4.time);
printf("Milliseconds: %d\n", mytime4.millitm);
return (0);
}我尝试过其他格式说明符(%f，%lu)和类型转换((float)，(double)，(long)，(size_t))，但都无关紧要。欢迎提出建议。
回答 1
Stack Overflow用户
发布于 2016-01-17 07:06:52
QueryPerformanceCounter用于windows上的精确计时。用法如下：
uint64_t microseconds()
{
LARGE_INTEGER fq, t;
QueryPerformanceFrequency(&fq);
QueryPerformanceCounter(&t);
return (1000000 * t.QuadPart) / fq.QuadPart;
}据我所知，这不适用于任何EPOCH。为此，你需要GetSystemTimePreciseAsFileTime，它只在Windows8和更高版本上可用。
uint64_t MyGetSystemTimePreciseAsFileTime()
{
HMODULE lib = LoadLibraryW(L"kernel32.dll");
if (!lib) return 0;
FARPROC fp = GetProcAddress(lib, "GetSystemTimePreciseAsFileTime");
ULARGE_INTEGER largeInt;
largeInt.QuadPart = 0;
if (fp)
{
T_GetSystemTimePreciseAsFileTime* pfn = (T_GetSystemTimePreciseAsFileTime*)fp;
FILETIME fileTime = { 0 };
pfn(&fileTime);
largeInt.HighPart = fileTime.dwHighDateTime;
largeInt.LowPart = fileTime.dwLowDateTime;
}
FreeLibrary(lib);
return largeInt.QuadPart;
}
int main()
{
uint64_t t1 = microseconds();
uint64_t t2 = microseconds();
printf("t1: %llu\n", t1);
printf("t2: %llu\n", t2);
return (0);
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/34831145
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