---

TimeInfo.h

Go to the documentation of this file.

#ifndef CLASSLIB_TIME_INFO_H
# define CLASSLIB_TIME_INFO_H

//<<<<<< INCLUDES                                                       >>>>>>

# include "classlib/utils/IntBits.h"

namespace lat {
//<<<<<< PUBLIC DEFINES                                                 >>>>>>
//<<<<<< PUBLIC CONSTANTS                                               >>>>>>
//<<<<<< PUBLIC TYPES                                                   >>>>>>
//<<<<<< PUBLIC VARIABLES                                               >>>>>>
//<<<<<< PUBLIC FUNCTIONS                                               >>>>>>
//<<<<<< CLASS DECLARATIONS                                             >>>>>>

class TimeInfo
{
public:
    // FIXME: feature bits for...?
    //  - whether real cycles are exact or derived
    //  - whether real nsecs are exact or derived
    //  - whether real nsecs were derived from cycles and mhz
    //  - whether real cycles were derived from nsecs and mhz
    //  - (the above four for virtual)
    //  - whether virtual nsecs were derived from process times
    //  - real/virtual resolution
    //  - sleep resolution

    static const int FEATURE_EXACT_MHZ          = 1;

    static const int FEATURE_TIME_EPOCH         = 2;

    static const int FEATURE_REAL_COUNT_EPOCH   = 4;

    static const int FEATURE_PROCESS_TIMES      = 16;

    typedef double              NanoSecs;

    typedef IntBits<64>::SLeast NanoTicks;

    static void         init (void);
    static double       mhz (void);
    static double       ghz (void);
    static unsigned     features ();

    static NanoSecs     realNsecs (void);
    static NanoTicks    realCycles (void);
    static NanoSecs     virtualNsecs (void);
    static NanoTicks    virtualCycles (void);

    // FIXME: Wall clock/real time support?  This really is #Time.
    // Would be neat however if we can find out accurate process
    // start-up time.  Do we need more than just processTimes()?
    //
    // POSIX systems with clock_gettime() may provide CLOCK_REALTIME
    // (= wall), CLOCK_MONOTONIC (= real), CLOCK_PROCESS_CPUTIME_ID (=
    // virtual) and CLOCK_THREAD_CPUTIME_ID (= virtual thread-specific)
    // -- check.

    // FIXME: Provide estimate of clock read overhead?

    // high-res monotonic process time consumption
    static void         processTimes (NanoSecs &user, NanoSecs &system,
                                      NanoSecs &real);
    static NanoSecs     processUserTime (void);
    static NanoSecs     processSystemTime (void);
    static NanoSecs     processCpuTime (void);
    static NanoSecs     processIdleTime (void);
    static NanoSecs     processRealTime (void);

    // high-res system timer; not (necessarily) anchored to process
    // time but guaranteed to be monotonic; usually measures system
    // time since boot or something like that.
    static NanoSecs     time (void);
    static NanoSecs     elapsedTime (void);
    static NanoSecs     resolution (void);

    // high-res napping
    static void         sleep (NanoSecs secs);
    static void         msleep (NanoSecs msecs);
    static void         usleep (NanoSecs usecs);
    static void         nanosleep (NanoSecs nanosecs);

private:
    static void         spin (NanoSecs duration, NanoTicks &low, NanoTicks &high);

    static bool         s_initialised;
    static unsigned     s_features;
    static double       s_ghz;
    static double       s_hiResFactor;
    static NanoSecs     s_clockBase;
};

//<<<<<< INLINE PUBLIC FUNCTIONS                                        >>>>>>

} // namespace lat
#endif // CLASSLIB_TIME_INFO_H

---