将日期时间转换为毫秒-C ++-跨平台 [英] Convert Date-Time to Milliseconds - C++ - cross platform

问题描述

我想将格式为"20160907-05:00:54.123"的字符串转换为毫秒. 我知道 strptime 在Windows中不可用，我想在Windows和Linux中都运行我的程序.我也不能使用第三方库. 我可以标记字符串并进行转换.但是，有没有像使用strptime这样更优雅的方式呢?

解决方案

鉴于字符串的格式，按如下方式解析它相当容易(尽管正则表达式或get_time可能更优雅):

tm t;
t.tm_year = stoi(s.substr(0, 4));
t.tm_mon = stoi(s.substr(4, 2));
t.tm_mday = stoi(s.substr(6, 2));
t.tm_hour = stoi(s.substr(9, 2));
t.tm_min = stoi(s.substr(12, 2));
t.tm_sec = 0;
double sec = stod(s.substr(15));

使用 mktime 查找自纪元以来的时间:

mktime(&t) + sec * 1000

请注意，小数秒的处理方式需要不同-不幸的是， tm仅具有整数秒.

(请参见完整代码此处.)

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修改

正如Mine和Panagiotis Kanavos在注释中正确指出的那样，Visual C ++显然支持get_time相当长一段时间，并且它要短得多(请注意，小数秒需要以相同的方式处理). /p>

I want to convert a string in the format of "20160907-05:00:54.123" into milliseconds. I know that strptime is not available in Windows and I want to run my program in both windows and linux. I can't use third party libraries as well. I can tokenize the string and convert it. But is there a more elegant way like using the strptime to do so?

解决方案

Given the format of your string, it is fairly easy to parse it as follows (although a regex or get_time might be more elegant):

tm t;
t.tm_year = stoi(s.substr(0, 4));
t.tm_mon = stoi(s.substr(4, 2));
t.tm_mday = stoi(s.substr(6, 2));
t.tm_hour = stoi(s.substr(9, 2));
t.tm_min = stoi(s.substr(12, 2));
t.tm_sec = 0;
double sec = stod(s.substr(15));

Finding the time since the epoch can be done with mktime:

mktime(&t) + sec * 1000

Note that the fractional seconds need to be handled differently - unfortunately, tm has only integer seconds.

(See the full code here.)

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Edit

As Mine and Panagiotis Kanavos correctly note in the comments, Visual C++ apparently supports get_time for quite a while, and it's much shorter with it (note that the fractional seconds need to be handled the same way, though).

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