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construct/include/ircd/util/timer.h

117 lines
2.6 KiB
C++

// Matrix Construct
//
// Copyright (C) Matrix Construct Developers, Authors & Contributors
// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice is present in all copies. The
// full license for this software is available in the LICENSE file.
#pragma once
#define HAVE_IRCD_UTIL_TIMER_H
namespace ircd {
inline namespace util
{
struct timer;
}}
/// Stopwatch w/ accumulation.
///
/// This utility can be used to gauge the duration of something. The clock
/// is started by default upon construction. Users can query the running time
/// using the at(), or using the pretty() convenience.
///
/// This timer features an accumulator state so the clock can be stopped and
/// continued, and each time the accumulator is updated. The accumulator
/// value is always added into results: when the timer is stopped, the result
/// is simply the accumulator value; when the clock is running, the result is
/// the accumulator value added to the difference of the current time and the
/// last start time.
///
/// One can instantiate the timer without starting the clock with the `nostart`
/// overload. Additionally, a lambda constructor will accumulate the time it
/// takes to execute the provided function.
struct ircd::util::timer
{
using clock = std::chrono::steady_clock;
IRCD_OVERLOAD(nostart)
nanoseconds accumulator
{
0ns
};
clock::time_point start
{
clock::now()
};
// Observers
bool stopped() const;
template<class duration = std::chrono::seconds> duration at() const;
// Convenience wrapper for util::pretty()
string_view pretty(const mutable_buffer &out, const int &fmt = 0) const;
std::string pretty(const int &fmt = 0) const;
// Control
void cont();
void stop();
constexpr timer(nostart_t);
constexpr timer(const bool cond);
timer(const std::function<void ()> &);
timer() = default;
};
constexpr
ircd::util::timer::timer(const bool cond)
:start
{
cond?
clock::now():
clock::time_point::min()
}
{}
constexpr
ircd::util::timer::timer(nostart_t)
:start
{
clock::time_point::min()
}
{}
template<class duration>
inline duration
ircd::util::timer::at()
const
{
const auto now
{
!stopped()?
clock::now():
start
};
const auto elapsed
{
duration_cast<decltype(accumulator)>(now - start)
};
const auto accumulator
{
this->accumulator + elapsed
};
return duration_cast<duration>(accumulator);
}
inline bool
ircd::util::timer::stopped()
const
{
return start == clock::time_point::min();
}