stk::time::Stopwatch Struct Reference

Lightweight elapsed-cycle measurement utility. More...

#include <stk_time_util.h>

Public Member Functions
	Stopwatch ()
	Construct a Stopwatch.
template<typename Func>
void	Start (Func now_func)
	Capture the start time.
template<typename Func>
Cycles	Update (Func now_func)
	Return the number of cycles elapsed since the last Start() or Update().

Protected Attributes
Cycles	m_prev
	Counter value captured at the last Start() or Update() call.

Static Private Attributes
static constexpr Cycles	NOT_STARTED = 0ULL
	Value of m_prev meaning that stopwatch is not started.

Detailed Description

Lightweight elapsed-cycle measurement utility.

Measures the number of CPU cycles (or other monotonic counter units) that have elapsed between successive calls to Update(). The time source is supplied by the caller as a callable (function pointer, lambda, or functor), allowing the stopwatch to remain independent of any particular hardware counter.

Typical usage:

stk::time::Stopwatch sw;
sw.Start([]() { return stk::hw::HiResClock::GetCycles(); });
 
// ... work to be measured ...
 
Cycles elapsed = sw.Update([]() { return stk::hw::HiResClock::GetCycles(); });
// elapsed holds the number of cycles since the last Start() or Update().

Note

Not thread-safe. Intended for use within a single task or ISR context.

If Update() is called before Start(), the first call is treated as a start point and returns 0 cycles elapsed.

Wrap-around of the underlying counter is handled naturally by unsigned subtraction, provided the elapsed time does not exceed one full counter period.

Definition at line 156 of file stk_time_util.h.

Constructor & Destructor Documentation

Stopwatch()

stk::time::Stopwatch::Stopwatch ( )

inline

Construct a Stopwatch.

Note

The stopwatch is initially stopped. Call Start() before the first meaningful Update() call; otherwise the first Update() call will implicitly act as the start point and return 0.

Definition at line 166 of file stk_time_util.h.

                : m_prev(NOT_STARTED)
    {}

References m_prev, and NOT_STARTED.

Member Function Documentation

Start()

template<typename Func>

void stk::time::Stopwatch::Start ( Func now_func )

inline

Capture the start time.

Template Parameters

Func	Callable type returning a Cycles value.

Parameters

[in]

now_func

Callable invoked with no arguments that returns the current time as a Cycles value (e.g. a CPU cycle counter read function or a lambda wrapping one).

Note

Resets the internal reference point to the current counter value. The next Update() call will measure elapsed cycles from this moment.

Definition at line 178 of file stk_time_util.h.

    {
        m_prev = static_cast<Cycles>(now_func());
    }

References m_prev.

Update()

template<typename Func>

Cycles stk::time::Stopwatch::Update ( Func now_func )

inline

Return the number of cycles elapsed since the last Start() or Update().

Template Parameters

Func	Callable type returning a Cycles value.

Parameters

[in]

now_func

Callable invoked with no arguments that returns the current time as a Cycles value. Must be the same counter source used in the preceding Start() call.

Returns

Elapsed Cycles since the previous reference point. Returns 0 on the very first call when Start() was not called beforehand (the call itself becomes the new reference point).

Note

Updates the internal reference point to the current counter value, so each successive call measures the interval since the previous one.

Definition at line 195 of file stk_time_util.h.

    {
        Cycles now = static_cast<Cycles>(now_func());
 
        if (STK_UNLIKELY(m_prev == NOT_STARTED))
        {
            m_prev = now;
        }
 
        Cycles diff = now - m_prev;
        m_prev = now;
 
        return diff;
    }

References m_prev, NOT_STARTED, and STK_UNLIKELY.

Member Data Documentation

m_prev

Cycles stk::time::Stopwatch::m_prev

protected

Counter value captured at the last Start() or Update() call.

Definition at line 211 of file stk_time_util.h.

Referenced by Start(), Stopwatch(), and Update().

NOT_STARTED

Cycles stk::time::Stopwatch::NOT_STARTED = 0ULL

staticconstexprprivate

Value of m_prev meaning that stopwatch is not started.

Definition at line 158 of file stk_time_util.h.

Referenced by Stopwatch(), and Update().

---

The documentation for this struct was generated from the following file:

• stk_time_util.h