c++ - Get a double from boost::chrono::steady_clock::now()

Question

How would I get a double value from boost::chrono::steady_clock::now()? I don't believe there is a .count() parameter for this.

Why do I need this? I have a method that cannot parse the boost return.

Answer 1

• boost::chrono::steady_clock::now()返回一个boost::chrono::time_point。
• boost::chrono::time_point有一个time_since_epoch返回 a 的方法boost::chrono::duration。
• boost::chrono::duration有一种count方法可以给你一个标量。

当我们把它们放在一起时，它归结为：

auto now = boost::chrono::steady_clock::now().time_since_epoch();
auto timeSinceEpoch = boost::chrono::duration_cast<boost::chrono::milliseconds>(now).count();

当然，这还double不够接近：您可以更改duration_cast以获得所需的任何精度和/或根据自己的喜好划分，timeSinceEpoch以double满足您的要求。例如：

// Days since epoch, with millisecond (see duration_cast above) precision
double daysSinceEpoch = double(timeSinceEpoch) / (24. * 3600. * 1000.);

Answer 2

你可以double在里面指定duration：

auto some_time = std::chrono::high_resolution_clock::now();
double duration = std::chrono::duration_cast<std::chrono::duration<double>>(some_time).count();