C++ 获取当前时间的两种方法(精确到毫秒)

1. boost 方法

#include <boost/date_time/posix_time/posix_time.hpp>
std::string now_str1()
{
    // Get current time from the clock, using microseconds resolution
    const boost::posix_time::ptime now = boost::posix_time::microsec_clock::local_time();
    
    // Get the time offset in current day
    const boost::posix_time::time_duration td = now.time_of_day();
    
    //
    // Extract hours, minutes, seconds and milliseconds.
    //
    // Since there is no direct accessor ".milliseconds()",
    // milliseconds are computed _by difference_ between total milliseconds
    // (for which there is an accessor), and the hours/minutes/seconds
    // values previously fetched.
    //
    const long hours  = td.hours();
    const long minutes  = td.minutes();
    const long seconds  = td.seconds();
    const long milliseconds = td.total_milliseconds() - (hours * 3600 + minutes * 60 + seconds) * 1000;
    
    
    char buf[40];
    sprintf(buf, "%02ld:%02ld:%02ld.%03ld",  hours, minutes, seconds, milliseconds);
    return buf;
}

 

2. 标准库方法

#include <sys/time.h>

using namespace std;

std::string now_str2()
{
    struct timeval tpend;
    gettimeofday(&tpend,NULL);

    int secofday = (tpend.tv_sec + 3600 * 8 ) % 86400;
    int hours = secofday / 3600;
    int minutes = (secofday - hours * 3600 ) / 60;
    int seconds = secofday % 60;
    int milliseconds = tpend.tv_usec/1000;

    char buf[40];
    sprintf(buf, "%02ld:%02ld:%02ld.%03ld",  hours, minutes, seconds, milliseconds);
    return buf;
}

 

3.  chrono

 #include <chrono>

using namespace std::chrono;

    time_point<high_resolution_clock> t1 = std::chrono::system_clock::now();
    QThread::usleep(5432);
    time_point<high_resolution_clock> t2 = std::chrono:: system_clock::now();
    cout << "tick count = " << (t2-t1).count() <<endl;

   //微秒
    int64_t elapsed_micro() const
    {
        return duration_cast<chrono::microseconds>(high_resolution_clock::now() - m_begin).count();
    }