QueryPerformanceCounter与QueryPerformanceFrequency

可以实现毫秒微秒计时器：

在使用QueryPerformanceCounter之前和之后可得到一个高精度计时器值，然后使用QueryPerformanceFrequency得到每秒滴答数，最后将时差除以这个数可转换为秒。

1 LARGE_INTEGER m_liPerformanceFrequency;
2 QueryPerformanceFrequency( &m_liPerformanceFrequency);
3 
4 //...
5 
6 LARGE_INTEGER liPerformanceCount;
7 QueryPerformanceCounter( &liPerformanceCount);
8 double dTime = double(liPerformanceCount.QuadPart)/double(m_liPerformanceFrequency.QuadPart);

对于IARGE_INTEGER union,可参考上一篇博文。

 

QueryPerformanceFrequency的函数原型为BOOL QueryPerformanceFrequency(LARGE_INTEGER *lpFrequency)，返回硬件是否支持高精度计数器。

QueryPerformanceCounter的函数原型为BOOL QueryPerformanceCounter (LARGE_INTEGER *lpCount)。

下面给出具体例子：

 1 #include <windows.h>
 2 
 3 double PCFreq = 0.0;
 4 __int64 CounterStart = 0;
 5 
 6 void StartCounter()
 7 {
 8     LARGE_INTEGER li;
 9     if(!QueryPerformanceFrequency(&li))
10     cout << "QueryPerformanceFrequency failed!\n";
11 
12     PCFreq = double(li.QuadPart)/1000.0;
13 
14     QueryPerformanceCounter(&li);
15     CounterStart = li.QuadPart;
16 }
17 double GetCounter()
18 {
19     LARGE_INTEGER li;
20     QueryPerformanceCounter(&li);
21     return double(li.QuadPart-CounterStart)/PCFreq;
22 }
23 
24 int main()
25 {
26     StartCounter();
27     Sleep(1000);
28     cout << GetCounter() <<"\n";
29     return 0;
30 }

得出结果应该接近windows睡眠了1000s。

如果想要结果以秒为单位输出：

PCFreq = double(li.QuadPart);

或者以微秒为单位输出：

PCFreq = double(li.QuadPart)/1000000.0;

关于QueryPerformanceCounter的细节，msdn给出了文档：在关于时间代码中如何使用QueryPerformanceCounter？

posted @ 2016-04-10 15:20  clairvoyant  阅读(1667)  评论(0)  编辑  收藏  举报