I have two time_point objects in my code and I need to use Boost condition variable for the difference:
template<class Clock, class Dur = typename Clock::duration>
class Time {
std::chrono::time_point<Clock, Dur> a;
std::chrono::time_point<Clock, Dur> b;
}
....
boost::condition_variable var;
....
var.wait_for(lock, b - a, [](){ /* something here */}); //<---boost cond var
....
How can I convert b - a
to something usable with boost?
CodePudding user response:
I'd do what I always do: avoid duration_cast
by using arithmetic with UDL values.
You have to select a resolution for this, let's choose microseconds:
#include <boost/thread.hpp>
#include <chrono>
#include <iostream>
using namespace std::chrono_literals;
template <class Clock, class Dur = typename Clock::duration> //
struct Time {
std::chrono::time_point<Clock, Dur> a = Clock::now();
std::chrono::time_point<Clock, Dur> b = a 1s;
boost::mutex mx;
void foo() {
//....
boost::condition_variable var;
//....
boost::unique_lock<boost::mutex> lock(mx);
std::cout << "Waiting " << __PRETTY_FUNCTION__ << "\n";
auto s = var.wait_for(lock, boost::chrono::microseconds((b - a) / 1us),
[] { /* something here */
return false;
}); //<---boost cond var
assert(!s);
//....
}
};
int main() {
Time<std::chrono::system_clock>{}.foo();
Time<std::chrono::steady_clock>{}.foo();
std::cout << "\n";
}
Prints (1 second delay each):
Waiting void Time<Clock, Dur>::foo() [with Clock = std::chrono::_V2::system_clock; Dur = std::chrono::duration<long int, std::ratio<1, 1000000000>
>]
Waiting void Time<Clock, Dur>::foo() [with Clock = std::chrono::_V2::steady_clock; Dur = std::chrono::duration<long int, std::ratio<1, 1000000000>
>]
I must say I can't fathom a scenario where the wait time for a condition would be specified as the difference between absolute time points, but I guess that's more of a "your problem" here :)