常用函数/功能块记录

短命女 2022-08-02 14:49 226阅读 0赞

1. 获取高精度时间戳

主要用于测试一段代码的执行时间。通过CPU的 tick-per-secs 来获取，可以精确到微秒甚至更高。比GetTickCount() API精确到毫秒要更加精确。

代码如下：

LARGE_INTEGER StartingTime, EndingTime, ElapsedMicroseconds;
    	LARGE_INTEGER Frequency;
    
    	QueryPerformanceFrequency(&Frequency); 
    	QueryPerformanceCounter(&StartingTime);
    	for ( int i = 0; i < 1000; i++)
    	{
    		printf("aaa\n");
    	}
    	QueryPerformanceCounter(&EndingTime);
    	ElapsedMicroseconds.QuadPart = EndingTime.QuadPart - StartingTime.QuadPart;
    	ElapsedMicroseconds.QuadPart *= 1000;	// ms
    	ElapsedMicroseconds.QuadPart /= Frequency.QuadPart;
    	printf("Time is %I64d ms\n", ElapsedMicroseconds.QuadPart);

2. Windows获取版本号

在Win8及其以后的版本，使用GetVersionEx() API 获取的版本号信息结构体是有问题的，可以使用如下的方法来兼容到Win10中。

到了Win10下就有微软建议的获取系统版本方法。可以参考MSDN。

OSVERSIONINFOEXW osver;
    	ZeroMemory(&osver, sizeof(osver));
    	osver.dwOSVersionInfoSize = sizeof(osver);
    	GetVersionExW((LPOSVERSIONINFOW)&osver);
    	printf("GetVersionExW -- Major: %d, Minor: %d, Build: %d\n", osver.dwMajorVersion, osver.dwMinorVersion, osver.dwBuildNumber);
    
    	// 尝试用RtlGetVersion获取
    	typedef LONG (NTAPI * PFN_RtlGetVersion)(OUT PRTL_OSVERSIONINFOW);
    	PFN_RtlGetVersion _RtlGetVersion = (PFN_RtlGetVersion)GetProcAddress(GetModuleHandle(_T("ntdll")), "RtlGetVersion");
    	if (_RtlGetVersion) {
    		RTL_OSVERSIONINFOEXW osver1;
    		ex1.dwOSVersionInfoSize = sizeof(osver1);
    		if (_RtlGetVersion((LPOSVERSIONINFOW)&osver1)>=0) {
    			printf("RtlGetVersion -- Major: %d, Minor: %d, Build: %d\n", osver1.dwMajorVersion, osver1.dwMinorVersion, osver1.dwBuildNumber);
    		}
    	}

3. XXX