source: git/src-cryptopp/hrtimer.h

#ifndef CRYPTOPP_HRTIMER_H
#define CRYPTOPP_HRTIMER_H

#include "config.h"

#if !defined(HIGHRES_TIMER_AVAILABLE) || (defined(CRYPTOPP_WIN32_AVAILABLE) && !defined(THREAD_TIMER_AVAILABLE))
#include <time.h>
#endif

NAMESPACE_BEGIN(CryptoPP)

#ifdef HIGHRES_TIMER_AVAILABLE
        typedef word64 TimerWord;
#else
        typedef clock_t TimerWord;
#endif

//! \class TimerBase
//! \brief Base class for timers
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE TimerBase
{
public:
        enum Unit {SECONDS = 0, MILLISECONDS, MICROSECONDS, NANOSECONDS};
        TimerBase(Unit unit, bool stuckAtZero)
                : m_timerUnit(unit), m_stuckAtZero(stuckAtZero), m_started(false)
                , m_start(0), m_last(0) {}

        virtual TimerWord GetCurrentTimerValue() =0;    // GetCurrentTime is a macro in MSVC 6.0
        virtual TimerWord TicksPerSecond() =0;  // this is not the resolution, just a conversion factor into seconds

        void StartTimer();
        double ElapsedTimeAsDouble();
        unsigned long ElapsedTime();

private:
        double ConvertTo(TimerWord t, Unit unit);

        Unit m_timerUnit;       // HPUX workaround: m_unit is a system macro on HPUX
        bool m_stuckAtZero, m_started;
        TimerWord m_start, m_last;
};

//! \class ThreadUserTimer
//! \brief Measure CPU time spent executing instructions of this thread (if supported by OS)
//! \note ThreadUserTimer only works correctly on Windows NT or later desktops and servers.
//! On Unix-based it reports process time. On Windows Phone and Windows Store it reports wall
//! clock time with performance counter precision. On all others it reports wall clock time.
class ThreadUserTimer : public TimerBase
{
public:
        ThreadUserTimer(Unit unit = TimerBase::SECONDS, bool stuckAtZero = false) : TimerBase(unit, stuckAtZero) {}
        TimerWord GetCurrentTimerValue();
        TimerWord TicksPerSecond();
};

//! high resolution timer
class CRYPTOPP_DLL Timer : public TimerBase
{
public:
        Timer(Unit unit = TimerBase::SECONDS, bool stuckAtZero = false) : TimerBase(unit, stuckAtZero) {}
        TimerWord GetCurrentTimerValue();
        TimerWord TicksPerSecond();
};

NAMESPACE_END

#endif