FILETIME 、SYSTEMTIME的转换

 

FILETIME结构体

typedef struct _FILETIME {
    DWORD dwLowDateTime;
    DWORD dwHighDateTime;
} FILETIME, *PFILETIME, *LPFILETIME;

 

typedef struct _SYSTEMTIME {
    WORD wYear;
    WORD wMonth;
    WORD wDayOfWeek;
    WORD wDay;
    WORD wHour;
    WORD wMinute;
    WORD wSecond;
    WORD wMilliseconds;
} SYSTEMTIME, *LPSYSTEMTIME;

FILETIME和SYSTEMTIME都只是记录时间的结构。

GetLocalTime能够得到本地电脑设置时区的时间，得到的类型是SYSTEMTIME的类型。

MSND关于FILETIME的说明：

Contains a 64-bit value representing the number of 100-nanosecond intervals since January 1, 1601 (UTC).

因此，通常的换算情况为：

#define  PER_SECOND    1*10*1000*1000     //1秒

依次类推，1小时就是36000000000；1天就是864000000000

一个使用例子如下：

//获取进程的cpu占用时间,间隔为上次调用该函数到这次调用该函数

//返回单位为微妙

DWORD CpuOccupyTime( HANDLE hCurrProcess )

{

if( NULL == hCurrProcess )

return -1;

DWORD ret;

FILETIME createTime;

FILETIME exitTime;

FILETIME kernelTime;

FILETIME userTime;

static FILETIME lastKernelTime;

static FILETIME lastUserTime;

BOOL timeSucc = GetProcessTimes( hCurrProcess, (LPFILETIME)(&createTime), 

(LPFILETIME)(&exitTime), (LPFILETIME)(&kernelTime), (LPFILETIME)(&userTime) );

if( timeSucc )

{

UINT64 tempKenelTime_ = kernelTime.dwHighDateTime - lastKernelTime.dwHighDateTime;

tempKenelTime_ = (tempKenelTime_ << 32) + kernelTime.dwLowDateTime -  lastKernelTime.dwLowDateTime;

UINT64 tempUserTime_ = userTime.dwHighDateTime - lastUserTime.dwHighDateTime;

tempUserTime_ = (tempUserTime_ << 32) + userTime.dwLowDateTime -  lastUserTime.dwLowDateTime;

lastKernelTime = kernelTime;

lastUserTime = userTime;

//tempKenelTime_,tempUserTime_时间单位为100纳秒

ret = DWORD( (tempKenelTime_ + tempUserTime_)/10 );

return ret>=0 ? ret:-1;

}

return -1;//时间出错

}