在SYSTEMTIME上执行算术 [英] performing Arithmetic on SYSTEMTIME

问题描述

我有一个用SYSTEMTIME表示的时间值，我想从中减去1小时并获得新获得的SYSTEMTIME.我希望转换应考虑加减法的日期更改或月份更改或e1年更改.

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 .

如果有一些可以在SYSTEMTIME上进行算术运算的Windows API，有人可以帮我吗?

Can someone help me with this if there is some windows api which does arithmetic on SYSTEMTIME

推荐答案

如果您使用的是C#(或VB.NET或ASP.NET)，则可以使用

If you're using C# (or VB.NET, or ASP.NET) you can use

DateTime dt = DateTime.Now.AddHours(1);

您可以使用负数减去:

DateTime dt = DateTime.Now.AddHours(-1);

已编辑: 我从这篇文章

他们建议将SYSTEMTIME转换为FILETIME，这是许多 从一个时代开始滴答作响.然后，您可以添加所需数量的滴答声" (即100ns间隔)表示您的时间，然后转换回 系统时间.

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.

ULARGE_INTEGER结构是与QuadPart成员的并集，即 一个64位的数字，可以直接添加到该数字(在最新的硬件上).

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).

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;
 }

如果要增加一个小时，请使用SYSTEMTIME s2 = add(s1, 60*60)

If you want to add an hour use SYSTEMTIME s2 = add(s1, 60*60)

这篇关于在SYSTEMTIME上执行算术的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！