QT获取UTC时间、windows下获取精确耗时、linux下获取精确耗时

QT获取UTC时间：

QDateTime origin_time = QDateTime::fromString("1970-01-01 08:00:00","yyyy-MM-dd hh:mm:ss");
QDateTime current_time = QDateTime::currentDateTime();//显示时间，格式为：年-月-日 时：分：秒 周几
qint64 nSeconds = origin_time.secsTo(current_time);//获取距离1970-01-01 08:00:00的总秒数
qint64 nMilliseconds = current_time.time().msec();//获取毫秒数

windows下获取精确耗时：
首先写一个计算耗时的类：

   #include <windows.h>
    class chronograph
    {
    public:
    	chronograph()
    	{
    		QueryPerformanceFrequency(&m_freq);
    		QueryPerformanceCounter(&m_bgn);
    	}
    	void start()
    	{
    		QueryPerformanceCounter(&m_bgn);
    	}
    
    	double duration()
    	{
    		QueryPerformanceCounter(&m_end);
    		return (m_end.QuadPart - m_bgn.QuadPart) * 1000.0 / m_freq.QuadPart;
    	}
    	LARGE_INTEGER now()
    	{
    		LARGE_INTEGER now;
    		QueryPerformanceCounter(&now);
    		return now;
    	}
    	double DoubleNow()
    	{
    		LARGE_INTEGER now;
    		QueryPerformanceCounter(&now);
    		return now.QuadPart*1000.0 / m_freq.QuadPart;
    	}
    private:
    	LARGE_INTEGER m_freq;
    	LARGE_INTEGER m_bgn;
    	LARGE_INTEGER m_end;
    };

使用方法：

chronograph calcuTime；
calcuTime.start();
//耗时的操作······
double  nUsetime = calcuTime.duration();//计算出来的耗时

Linux下获取精确耗时的方法：

#include <time.h>

struct timespec time1,time2;
clock_gettime(CLOCK_MONOTONIC,&time1);//开始计时
Sleep(10);//需要计时的操作
clock_gettime(CLOCK_MONOTONIC,&time2);//结束计时
double usetime = (time2.tv_sec-time1.tv_sec)*1000.0+(time2.tv_nsec-time1.tv_nsec)/1000000.0;//计算耗时，单位为ms