A `std::chrono::time_point` represents a point in time relative to a clock’s epoch. Its template parameters identify the clock and the duration used to measure time since that epoch. The epoch itself is not directly queryable or specified by the C++ Standard. section 4.3.3
Use time points to represent and compare moments:
- Add a duration to a time point to calculate a future moment, such as a deadline. section 4.3.3
- Subtract time points from the same clock to get the elapsed duration. section 4.3.3
- Use time points with timeout operations such as `wait_until` and `try_lock_until`. section 4.3.4
auto start=std::chrono::high_resolution_clock::now(); do_something(); auto stop=std::chrono::high_resolution_clock::now(); std::cout<<"do_something() took " <<std::chrono::duration<double,std::chrono::seconds>(stop-start).count() <<" seconds"<<std::endl;
Measure elapsed time by subtracting a start time point from a stop time point, then convert the duration to seconds. section 4.3.3
Listing 4.11. Waiting for a condition variable with a timeout
#include <condition_variable>
#include <mutex>
#include <chrono>
std::condition_variable cv;
bool done;
std::mutex m;
bool wait_loop()
{
auto const timeout= std::chrono::steady_clock::now()+
std::chrono::milliseconds(500);
std::unique_lock<std::mutex> lk(m);
while(!done)
{
if(cv.wait_until(lk,timeout)==std::cv_status::timeout)
break;
}
return done;
}
Set a deadline by adding a duration to the current time, then pass it to a condition variable’s `wait_until` operation. section 4.3.3
