主要用到了win32里面的QueryPerformanceCounter和QueryPerformanceFrequency两个函数
文档链接：https://docs.microsoft.com/zh-cn/windows/win32/api/profileapi/nf-profileapi-queryperformancecounter
class NanoSecondTimer
{
[DllImport("Kernel32.dll")]
private static extern bool QueryPerformanceCounter(out long lpPerformanceCount);
[DllImport("Kernel32.dll")]
private static extern bool QueryPerformanceFrequency(out long lpFrequency);
private long startTime, stopTime;
private long freq;
public NanoSecondTimer()
{
startTime = 0;
stopTime = 0;
if (QueryPerformanceFrequency(out freq) == false)
{
throw new Win32Exception();
}
}
/// <summary>
/// 开始计时
/// </summary>
public void Start()
{
Thread.Sleep(0);
QueryPerformanceCounter(out startTime);
}
/// <summary>
/// 停止计时
/// </summary>
public void Stop()
{
QueryPerformanceCounter(out stopTime);
}
/// <summary>
/// 返回计时器经过时间(单位：秒)
/// </summary>
public double Duration
{
get
{
return (double)(stopTime - startTime) / (double)freq;
}
}
}
QueryPerformanceFrequency这个函数会检索性能计数器的频率。性能计数器的频率在系统启动时是固定的，并且在所有处理器上都是一致的。因此，只需在应用初始化时查询频率，即可缓存结果。在运行 Windows XP 或更高版本的系统上，该函数将始终成功，因此永远不会返回零。
下面是测试代码：
NanoSecondTimer nanoSecondTimer = new NanoSecondTimer();
nanoSecondTimer.Start();
for (int i = 0; i < 100000; i++)
{
i++;
}
nanoSecondTimer.Stop();
double time = nanoSecondTimer.Duration;
