windows 在 SYSTEMTIME 上执行算术
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performing Arithmetic on SYSTEMTIME
提问by Peter
I have a time value represented in SYSTEMTIME, i want to add/subtract 1 hour from it and get the newly obtained SYSTEMTIME. I want the conversion should take care of the date change on addition/subtraction or month change or e1 year change .
我有一个以 SYSTEMTIME 表示的时间值，我想从中加/减 1 小时并获得新获得的 SYSTEMTIME。我希望转换应该处理加法/减法或月份更改或 e1 年更改的日期更改。
Can someone help me with this if there is some windows api which does arithmetic on SYSTEMTIME
如果有一些 Windows api 在 SYSTEMTIME 上进行算术运算，有人可以帮我解决这个问题吗
回答by Marco
If you're using C# (or VB.NET, or ASP.NET) you can use
如果您使用 C#（或 VB.NET，或 ASP.NET），您可以使用
DateTime dt = DateTime.Now.AddHours(1);
You can use negative numbers to subtract:
您可以使用负数来减去：
DateTime dt = DateTime.Now.AddHours(-1);
EDITED:I extract an asnwer from this post
编辑：我从这篇文章中提取了一个答案
They suggest converting SYSTEMTIME to FILETIME, which is a number of ticks since an epoch. You can then add the required number of 'ticks' (i.e. 100ns intervals) to indicate your time, and convert back to SYSTEMTIME.
The ULARGE_INTEGER struct is a union with a QuadPart member, which is a 64bit number, that can be directly added to (on recent hardware).
他们建议将 SYSTEMTIME 转换为 FILETIME，这是自一个纪元以来的刻度数。然后，您可以添加所需数量的“滴答”（即 100ns 间隔）以指示您的时间，并转换回 SYSTEMTIME。
ULARGE_INTEGER 结构是与 QuadPart 成员的联合，它是一个 64 位数字，可以直接添加到（在最近的硬件上）。
SYSTEMTIME add( SYSTEMTIME s, double seconds ) {
FILETIME f;
SystemTimeToFileTime( &s, &f );
ULARGE_INTEGER u ;
memcpy( &u , &f , sizeof( u ) );
const double c_dSecondsPer100nsInterval = 100. * 1.E-9;
u.QuadPart += seconds / c_dSecondsPer100nsInterval;
memcpy( &f, &u, sizeof( f ) );
FileTimeToSystemTime( &f, &s );
return s;
}
If you want to add an hour use SYSTEMTIME s2 = add(s1, 60*60)
如果你想增加一个小时使用 SYSTEMTIME s2 = add(s1, 60*60)
回答by Rick C. Hodgin
To add signed seconds (forward or backward in time) in C++:
在 C++ 中添加有符号秒数（时间向前或向后）：
const double clfSecondsPer100ns = 100. * 1.E-9;
void iAddSecondsToSystemTime(SYSTEMTIME* timeIn, SYSTEMTIME* timeOut, double tfSeconds)
{
union {
ULARGE_INTEGER li;
FILETIME ft;
};
// Convert timeIn to filetime
SystemTimeToFileTime(timeIn, &ft);
// Add in the seconds
li.QuadPart += tfSeconds / clfSecondsPer100ns;
// Convert back to systemtime
FileTimeToSystemTime(&ft, timeOut);
}
回答by puccipucci
#include <stdio.h>
#include <windows.h>
#define NSEC 60*60
main()
{
SYSTEMTIME st;
FILETIME ft;
// Get local time from system
GetLocalTime(&st);
printf("%02d/%02d/%04d %02d:%02d:%02d\n",
st.wDay,st.wMonth,st.wYear,st.wHour,st.wMinute,st.wSecond);
// Convert to filetime
SystemTimeToFileTime(&st,&ft);
// Add NSEC seconds
((ULARGE_INTEGER *)&ft)->QuadPart +=(NSEC*10000000LLU);
// Convert back to systemtime
FileTimeToSystemTime(&ft,&st);
printf("%02d/%02d/%04d %02d:%02d:%02d\n",
st.wDay,st.wMonth,st.wYear,st.wHour,st.wMinute,st.wSecond);
}
