实现高精度定时器

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我是靠谱客的博主满意煎饼，最近开发中收集的这篇文章主要介绍实现高精度定时器，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

#include <windows.h>
#include <stdio.h>

/*
typedef union _LARGE_INTEGER {
	struct {
		DWORD LowPart;
		LONG HighPart;
	};
	struct {
		DWORD LowPart;
		LONG HighPart;
	} u;
	LONGLONG QuadPart;
} LARGE_INTEGER, *PLARGE_INTEGER;
*/

void DelayUs(__int64 Us)
{
    LARGE_INTEGER CurrTicks, TicksCount; 

    QueryPerformanceFrequency(&TicksCount);
    QueryPerformanceCounter(&CurrTicks); 

    TicksCount.QuadPart = TicksCount.QuadPart * Us / 1000000ll;
    TicksCount.QuadPart += CurrTicks.QuadPart; 

    while(CurrTicks.QuadPart<TicksCount.QuadPart)
        QueryPerformanceCounter(&CurrTicks);
}

__int64 __rdtsc()
{
#if 1
    __int64 val;
    __asm__ ("rdtsc" : "=A" (val));
    return val;
#else
    __int32 lo, hi;
    __asm__ __volatile__
    (
     	"rdtsc" : "=a"(lo), "=d"(hi)
    );
    return (__int64)((lo) | (hi) << 32);
#endif
}

int CPU_Frequency(void)      //CPU MHz
{
    LARGE_INTEGER CurrTicks, TicksCount;
    __int64 iStartCounter, iStopCounter;
/*
    DWORD dwOldProcessP = GetPriorityClass(GetCurrentProcess());
    DWORD dwOldThreadP = GetThreadPriority(GetCurrentThread());

    SetPriorityClass(GetCurrentProcess(), REALTIME_PRIORITY_CLASS);
    SetThreadPriority(GetCurrentThread(), THREAD_PRIORITY_TIME_CRITICAL);
*/
    QueryPerformanceFrequency(&TicksCount);
    QueryPerformanceCounter(&CurrTicks);

    TicksCount.QuadPart /= 16;
    TicksCount.QuadPart += CurrTicks.QuadPart;
/*
    __asm__ ("rdtsc");
    __asm__ ("mov DWORD PTR iStartCounter, EAX");
    __asm__ ("mov DWORD PTR (iStartCounter+4), EDX");
*/
    iStartCounter = __rdtsc();

    while(CurrTicks.QuadPart<TicksCount.QuadPart)
        QueryPerformanceCounter(&CurrTicks);
/*
    __asm__ ("rdtsc");
    __asm__ ("mov DWORD PTR iStopCounter, EAX");
    __asm__ ("mov DWORD PTR (iStopCounter + 4), EDX");
*/
    iStopCounter = __rdtsc();
/*
    SetThreadPriority(GetCurrentThread(), dwOldThreadP);
    SetPriorityClass(GetCurrentProcess(), dwOldProcessP);
*/
    return (int)(((double)iStopCounter-(double)iStartCounter)/(double)62500);
}

int main()
{
    DWORD dwOldProcessP = GetPriorityClass(GetCurrentProcess());
    DWORD dwOldThreadP = GetThreadPriority(GetCurrentThread());

    SetPriorityClass(GetCurrentProcess(), REALTIME_PRIORITY_CLASS);
    SetThreadPriority(GetCurrentThread(), THREAD_PRIORITY_TIME_CRITICAL);

    int s = CPU_Frequency();
    printf("cpu: %d Mhzn", s);

    __int64 k = __rdtsc();
    printf("%ldn", (unsigned long long)k);

    __int64 iStartCounter, iStopCounter; 
    int i;
    
    for (i = 0; i < 10; i++) {
        iStartCounter = __rdtsc();
        DelayUs(50);
        //Sleep(10);
        iStopCounter = __rdtsc();
        printf("%dn", (iStopCounter - iStartCounter) / s);
    }

    printf("ok!n");

    SetThreadPriority(GetCurrentThread(), dwOldThreadP);
    SetPriorityClass(GetCurrentProcess(), dwOldProcessP);
    
    return 0;
}