c++ - 限制事件的发生

Question

我有一个控制灯泡的函数。灯泡被编程为在按下某个键时闪烁。但是，我想限制闪光之间的最小间隔，以防止灯泡烧坏。灯泡由接在串口上的继电器开关控制，代码如下:

void WINAPI flash (HINSTANCE hThisInstance, HINSTANCE hPrevInstance, LPSTR lpszArgument, int nFunsterStil)
{
    //MATT: Define the serial port procedure
    HANDLE hSerial;

    //MATT: Fire the flash (by initialising and uninitialising the port)
    hSerial = CreateFile("COM1",GENERIC_WRITE, 0, 0, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0); CloseHandle(hSerial);
}

如何限制以毫秒为单位的最小闪烁间隔(毫秒精度非常重要)？

Answer 1

您可以使用一个简单的变量来保持 QueryPerformanceCounter 报告的时间。 QPC 的准确性在大多数系统上都非常非常高。在我的系统上，频率为 280 万次或每十个处理器时钟一个滴答。

class bulb {
    __int64 clocks;
    __int64 frequency;
public:
    static const int max_ms_between_flashes = 1;
    bulb() {
        LARGE_INTEGER li;
        QueryPerformanceFrequency(&li);
        frequency = li.QuadPart;
        clocks = 0;
    }
    void flash(...) {
        LARGE_INTEGER li;
        QueryPerformanceCounter(&li);
        if (clocks == 0) { 
            // We are the first time, so set the clocks var
            // and flash the bulb
            clocks = li.QuadPart;       
        } else {
            __int64 timepassed = clocks - li.QuadPart;
            if (timepassed >= (((double)frequency) / (max_ms_between_flashes * 1000))) {
                // It's been more than 1ms
                clocks = li.QuadPart;
                // flash the bulb
            }
        }
    }
}