使用 C++ 和 Boost 以毫秒为单位获取当前时间

Get current time in milliseconds using C++ and Boost

提问by ghiboz

In my thread (using boost::thread) I need to retrieve the current time in ms or less and to convert into ms:

在我的线程中（使用 boost::thread），我需要以毫秒或更短的时间检索当前时间并转换为毫秒：

Actually, reading here I've found this:

实际上，在这里阅读我发现了这个：

tick = boost::posix_time::second_clock::local_time();
now  = boost::posix_time::second_clock::local_time();

And seems to work, but after I need to have a long value of the milliseconds of the now...

并且似乎有效，但是在我需要现在的毫秒值之后......

How can I do it?

我该怎么做？

回答by mkaes

You can use boost::posix_time::time_durationto get the time range. E.g like this

您可以使用boost::posix_time::time_duration来获取时间范围。比如像这样

boost::posix_time::time_duration diff = tick - now;
diff.total_milliseconds();

And to get a higher resolution you can change the clock you are using. For example to the boost::posix_time::microsec_clock, though this can be OS dependent. On Windows, for example, boost::posix_time::microsecond_clockhas milisecond resolution, not microsecond.

为了获得更高的分辨率，您可以更改正在使用的时钟。例如对于boost::posix_time::microsec_clock，尽管这可能取决于操作系统。例如，在 Windows 上，boost::posix_time::microsecond_clock分辨率为毫秒，而不是微秒。

An example which is a little dependent on the hardware.

一个稍微依赖于硬件的例子。

int main(int argc, char* argv[])
{
    boost::posix_time::ptime t1 = boost::posix_time::second_clock::local_time();
    boost::this_thread::sleep(boost::posix_time::millisec(500));
    boost::posix_time::ptime t2 = boost::posix_time::second_clock::local_time();
    boost::posix_time::time_duration diff = t2 - t1;
    std::cout << diff.total_milliseconds() << std::endl;

    boost::posix_time::ptime mst1 = boost::posix_time::microsec_clock::local_time();
    boost::this_thread::sleep(boost::posix_time::millisec(500));
    boost::posix_time::ptime mst2 = boost::posix_time::microsec_clock::local_time();
    boost::posix_time::time_duration msdiff = mst2 - mst1;
    std::cout << msdiff.total_milliseconds() << std::endl;
    return 0;
}

On my win7 machine. The first out is either 0 or 1000. Second resolution. The second one is nearly always 500, because of the higher resolution of the clock. I hope that help a little.

在我的 win7 机器上。第一个输出是 0 或 1000。第二个分辨率。第二个几乎总是 500，因为时钟的分辨率更高。我希望这有点帮助。

回答by Brian O'Kennedy

If you mean milliseconds since epochyou could do

如果你的意思是自纪元以来的毫秒数，你可以做

ptime time_t_epoch(date(1970,1,1)); 
ptime now = microsec_clock::local_time();
time_duration diff = now - time_t_epoch;
x = diff.total_milliseconds();

However, it's not particularly clear what you're after.

但是，您的目标并不是特别清楚。

Have a look at the example in the documentation for DateTime at Boost Date Time

在Boost Date Time 的DateTime 文档中查看示例

回答by Macbeth's Enigma

// Get current date/time in milliseconds.
#include "boost/date_time/posix_time/posix_time.hpp"
namespace pt = boost::posix_time;

int main()
{
     pt::ptime current_date_microseconds = pt::microsec_clock::local_time();

    long milliseconds = current_date_microseconds.time_of_day().total_milliseconds();

    pt::time_duration current_time_milliseconds = pt::milliseconds(milliseconds);

    pt::ptime current_date_milliseconds(current_date_microseconds.date(), 
                                        current_time_milliseconds);

    std::cout << "Microseconds: " << current_date_microseconds 
              << " Milliseconds: " << current_date_milliseconds << std::endl;

    // Microseconds: 2013-Jul-12 13:37:51.699548 Milliseconds: 2013-Jul-12 13:37:51.699000
}

回答by user1476945

Try this: import headers as mentioned.. gives seconds and milliseconds only. If you need to explain the code read this link.

试试这个： 如上所述的导入标头.. 只给出秒和毫秒。如果您需要解释代码，请阅读此链接。

#include <windows.h>

#include <stdio.h>

void main()
{

    SYSTEMTIME st;
    SYSTEMTIME lt;

    GetSystemTime(&st);
   // GetLocalTime(&lt);

     printf("The system time is: %02d:%03d\n", st.wSecond, st.wMilliseconds);
   //  printf("The local time is: %02d:%03d\n", lt.wSecond, lt.wMilliseconds);

}