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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include <chrono>
namespace vespalib {
/**
* Simple utility for time boxing your activity
*
* <pre>
* Example:
*
* TimeBox timebox(5.0);
* while (timebox.hasTimeLeft()) {
* ... do stuff
* ... do stuff with timeout(timebox.timeLeft())
* }
* </pre>
**/
class TimeBox
{
private:
using clock = std::conditional<std::chrono::high_resolution_clock::is_steady,
std::chrono::high_resolution_clock,
std::chrono::steady_clock>::type;
using seconds = std::chrono::duration<double, std::ratio<1,1>>;
static inline clock::duration to_internal(double x) {
return std::chrono::duration_cast<clock::duration>(seconds(x));
}
static inline double to_external(clock::duration x) {
return std::chrono::duration_cast<seconds>(x).count();
}
clock::time_point _end_time;
clock::duration _min_time;
public:
/**
* Construct a TimeBox with a given budget from now
* @param budget amount of time in seconds
**/
explicit TimeBox(double budget)
: _end_time(clock::now() + to_internal(budget)),
_min_time(to_internal(0))
{
}
/**
* Construct a TimeBox with a given budget from now
* @param budget amount of time in seconds
* @param min_time a minimum to be returned from timeLeft()
**/
TimeBox(double budget, double min_time)
: _end_time(clock::now() + to_internal(budget)),
_min_time(to_internal(min_time))
{
}
/**
* @return true if there is time left in the budget
**/
bool hasTimeLeft() {
return clock::now() < _end_time;
}
/**
* Note: Never returns less than min_time even if budget is expired.
* @return the seconds left before the budget expires
**/
double timeLeft() {
clock::time_point now = clock::now();
if (now + _min_time < _end_time) {
return to_external(_end_time - now);
}
return to_external(_min_time);
}
};
} // namespace vespalib
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