来个屌大的解释一下，我还是搞不懂，那种方式更快。。
本帖最后由 server 于 2025-5-19 00:15 编辑有问题吗？？
<火山程序 类型 = "通常" 版本 = 1 />
方法 取现行时间2 <类型 = 小数 折叠 @禁止流程检查 = 真>
{
@ FILETIME ftUtc, ftLocal;
@ ::GetSystemTimeAsFileTime(&ftUtc);
@ if (!::FileTimeToLocalFileTime(&ftUtc, &ftLocal)) {return 0; }
@ ULARGE_INTEGER uli;
@ uli.LowPart = ftLocal.dwLowDateTime;
@ uli.HighPart = ftLocal.dwHighDateTime;
@ return static_cast<DOUBLE>(uli.QuadPart - 109205ULL * 864000000000ULL) / 864000000000.0;
}
<火山程序 类型 = "通常" 版本 = 1 />
方法 _取本地时间NT <公开 静态 类型 = 小数 折叠2 @视窗.外部头文件 = "winternl.h" @视窗.外部库 = "ntdll.lib" @禁止流程检查 = 真>
{
@ LARGE_INTEGER SystemTime = {0};
@ if(NtQuerySystemTime(&SystemTime) == 0){
@ FILETIME ft_utc, ft_local;
@ ft_utc.dwLowDateTime = SystemTime.LowPart;
@ ft_utc.dwHighDateTime = SystemTime.HighPart;
@ if(FileTimeToLocalFileTime(&ft_utc, &ft_local)) {
@ return static_cast<double>(((((ULONGLONG)ft_local.dwHighDateTime << 32) | ft_local.dwLowDateTime)-109205ULL * 864000000000ULL)) / 864000000000.0;
@ }
@ }
@ return 0;
}
下面是火山官方的写法：
DOUBLE GetCurrentDateTime ()
{
SYSTEMTIME st;
::GetLocalTime (&st);
return ToDate ((INT_P)(UINT_P)st.wYear, (INT_P)(UINT_P)st.wMonth, (INT_P)(UINT_P)st.wDay, (INT_P)(UINT_P)st.wHour, (INT_P)(UINT_P)st.wMinute, (INT_P)(UINT_P)st.wSecond, (INT_P)(UINT_P)st.wMilliseconds, _VOL_MIN_DATE);
}
DOUBLE ToDate (INT_P npYear, INT_P npMonth, INT_P npDay, INT_P npHour, INT_P npMinute, INT_P npSecond, INT_P npMillSecond, const DOUBLE dbDateFailed)
{
npYear = CLIP (npYear, 100, 9999);
npMonth = CLIP (npMonth, 1, 12);
npDay = CLIP (npDay, 1, 31);
npHour = CLIP (npHour, 0, 23);
npMinute = CLIP (npMinute, 0, 59);
npSecond = CLIP (npSecond, 0, 59);
npMillSecond = CLIP (npMillSecond, 0, 999);
const INT_P npDaysOfMonth = GetDaysOfMonth (npYear, npMonth);
npDay = MIN (npDaysOfMonth, npDay);
//---------------------------------------------------------------------------------
SYSTEMTIME st;
ZERO_MEM (&st, sizeof (SYSTEMTIME));
st.wYear = (WORD)npYear;
st.wMonth = (WORD)npMonth;
st.wDay = (WORD)npDay;
st.wHour = (WORD)npHour;
st.wMinute = (WORD)npMinute;
st.wSecond = (WORD)npSecond;
st.wMilliseconds = 0;// SystemTimeToVariantTime没有处理毫秒字段
DOUBLE dbDate;
if (::SystemTimeToVariantTime (&st, &dbDate) == FALSE)
return dbDateFailed;
return dbDate + (DOUBLE)npMillSecond / (1000.0 * 60.0 * 60.0 * 24.0);// 手动将毫秒字段添加进去
/*if (::SystemTimeToVariantTime (&st, &dbDate) == FALSE)
return dbDateFailed;
ZERO_MEM (&st, sizeof (SYSTEMTIME));
if (::VariantTimeToSystemTime (dbDate, &st) == FALSE)
return dbDateFailed;
return (((INT_P)st.wYear == npYear &&
(INT_P)st.wMonth == npMonth &&
(INT_P)st.wDay == npDay &&
(INT_P)st.wHour == npHour &&
(INT_P)st.wMinute == npMinute &&
(INT_P)st.wSecond == npSecond) ? dbDate : dbDateFailed); */
}
你跑一下性能测试不就知道了，前面的当然更快，官方那个写得太复杂。
GetSystemTimeAsFileTime 也比 NtQuerySystemTime 快，这两个的作用是一样的。
FILETIME的精度也更高，可以到100纳秒，官方那个只能到毫秒。
如果是输出时间戳的话，FILETIME可以更快，保留精度也更多。
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