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我想寫一個類,它將能夠使用C++中的QueryPerformanceCounter來計時事件。 這個想法是,你創建一個計時器對象,給一個函數一個雙重格式的時間,並且它計數直到那個時間已經過去,然後做了一些事情。這個類最好用於計算遊戲中的時間(例如,計時器在一秒鐘內計數60次)。當我編譯這段代碼時,它只是將0打印到控制檯,看起來永遠都是。但是我發現了一些我無法理解的bug。如果我點擊控制檯窗口的滾動條並按住它,計時器實際上會正確計數。例如,如果我輸入5.0,然後快速單擊並按住滾動條5秒或更長時間,當我放開時,程序將打印'完成!!!'。那麼爲什麼當我只是讓它將經過的時間打印到控制檯時,它不能正確計數呢?有沒有打印到控制檯的問題,或者我的計時代碼有什麼問題?下面是代碼:C++計時事件控制檯錯誤?
#include <iostream>
#include <iomanip>
#include "windows.h"
using namespace std;
int main()
{
setprecision(10); // i tried to see if precision in the stream was the problem but i don't think it is
cout << "hello! lets time something..." << endl;
bool timing = 0; // a switch to turn the timer on and off
LARGE_INTEGER T1, T2; // the timestamps to count
LARGE_INTEGER freq; // the frequency per seccond for measuring the difference between the stamp values
QueryPerformanceFrequency(&freq); // gets the frequency from the computer
// mil.QuadPart = freq.QuadPart/1000; // not used
double ellapsedtime = 0, desiredtime; // enter a value to count up to in secconds
// if you entered 4.5 for example, then it should wait for 4.5 secconds
cout << "enter the amount of time you would like to wait for in seconds (in double format.)!!" << endl;
cin >> desiredtime;
QueryPerformanceCounter(&T1); // gets the first stamp value
timing = 1; // switches the timer on
while(timing)
{
QueryPerformanceCounter(&T2); // gets another stamp value
ellapsedtime += (T2.QuadPart - T1.QuadPart)/freq.QuadPart; // measures the difference between the two stamp
//values and then divides them by the frequency to get how many secconds has ellapsed
cout << ellapsedtime << endl;
T1.QuadPart = T2.QuadPart; // assigns the value of the second stamp to the first one, so that we can measure the
// difference between them again and again
if(ellapsedtime>=desiredtime) // checks if the elapsed time is bigger than or equal to the desired time,
// and if it is prints done and turns the timer off
{
cout << "done!!!" << endl;
timing = 0; // breaks the loop
}
}
return 0;
}
謝謝您的回答。我已經刪除了打印出當前流逝時間的部分,現在它似乎在正確的時間等待。如果我說等待5.5,它會等待5.5秒,然後打印'完成!'。 – user3023723