Start:=GetTickCount;
...//执行耗时的操作
Stop:=GetTickCount;
TimeUsed:=(Stop-Start)/1000; //使用了xxx秒
void main()
{
DWORD dwLast;
DWORD dwCurrent;
DWORD dwInterval = 1000;
dwLast = GetTickCount();
int i = 0;
while(true)
{
dwCurrent = GetTickCount();
if( dwCurrent - dwLast < dwInterval )
continue;
//your code to be executed when interval is elapsed
printf("dwLast,dwCurrent,diff:%d,%d,%d ",dwLast,dwCurrent,dwCurrent-dwLast);
//your code to determine when to break
if( i > 10 ) break;
i++;
dwLast = dwCurrent;
printf("Time is up!");
break;
}
getchar();
return;
}
对于一般的实时控制,使用GetTickCount()函数就可以满足精度要求,但要进一步提高计时精度,就要采用 QueryPerformanceFrequency()函数和QueryPerformanceCounter()函数。这两个函数是VC提供的仅供 Windows 9X使用的高精度时间函数,并要求计算机从硬件上支持高精度计时器。
QueryPerformanceFrequency()函数和QueryPerformanceCounter()函数的原型为:
BOOL QueryPerformanceFrequency(LARGE—INTEGER *lpFrequency);
BOOL QueryPerformanceCounter(LARGE—INTEGER *lpCount);
数据类型LARGE—INTEGER既可以是一个作为8字节长的整型数,也可以是作为两个4字节长的整型数的联合结构,其具体用法根据编译器是否支持64位而定。该类型的定义如下:
typedef union —LARGE—INTEGER
{
struct
{
DWORD LowPart; // 4字节整型数
LONG HighPart; // 4字节整型数
};
LONGLONG QuadPart;
// 8字节整型数
}LARGE—INTEGER;
LARGE—INTEGER litmp;
LONGLONG QPart1,QPart2;
double dfMinus, dfFreq, dfTim;
QueryPerformanceFrequency(&litmp);
// 获得计数器的时钟频率
dfFreq = (double)litmp.QuadPart;
QueryPerformanceCounter(&litmp);
// 获得初始值
QPart1 = litmp.QuadPart;
Sleep(100) ;
QueryPerformanceCounter(&litmp);
// 获得终止值
QPart2 = litmp.QuadPart;
dfMinus = (double)(QPart2 - QPart1);
dfTim = dfMinus / dfFreq;
// 获得对应的时间值