常用函数/功能块 记录

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