C/C++ in Embedded Chronographs

Listing 2: clock.cpp.

// clock.cpp Begin 
#include <clock.hpp>

#ifdef __PALMOS
  inline clock_t clock();
#elif defined ( __WINDOWS )
  inline clock_t clock();
#endif

clock_t cClock::_mClockStart = 0;
clock_t cClock::_mNumClockCalls = 0;
clock_t cClock::_mDesClockRes = 0;
clock_t cClock::_mDesClocksPerSec = 0;
clock_t cClock::_mNatClockRes = 0;
clock_t cClock::_mCalPeriod = 0;
clock_t cClock::_mCalCorrection = 0;

cClock::cClock( clock_t ClocksPerSec )
  {
  if ( !_mNumClockCalls )
     { // First time through so initialize
     InitClock();
     SetClockRes( ClocksPerSec );
     }
  }
cClock::cClock( clock_t CalPeriod, clock_t CalCorrection,
     clock_t ClocksPerSec )
  {
  this->cClock::cClock( ClocksPerSec );
  _mCalPeriod = CalPeriod;
  _mCalCorrection = CalCorrection;
  }
clock_t cClock::StartClock()
  {
  _mClockStart = 0;
  _mClockStart = GetClock();
  return ( _mClockStart );
  }
clock_t cClock::GetClock()
  {
  clock_t Clock1, Clock2 = 0, NumCalls = 0;
  Clock1 = clock();
  if ( _mDesClockRes < _mNatClockRes )
     { // Use number of clock calls to get finer resolution
     Clock2 = LoopClock( Clock1, &NumCalls );
     if ( NumCalls < _mNumClockCalls )
        { // Get fraction of clock tick res that had transpired
        Clock2 = _mNumClockCalls - NumCalls;
        Clock2 *= _mNatClockRes;
        if ( _mDesClocksPerSec > CLOCKS_PER_SEC )
           { // Covnert clock value to designated units
           Clock2 *= _mDesClocksPerSec / CLOCKS_PER_SEC;
           }
        Clock2 /= _mNumClockCalls;
        }
     else
        { // clock had just ticked
        Clock2 = 0;
        }
     }
  if ( _mDesClocksPerSec > CLOCKS_PER_SEC )
     { // Covnert clock value to designated units
     Clock1 *= _mDesClocksPerSec / CLOCKS_PER_SEC;
     }
  Clock2 += Clock1;
  if ( _mDesClocksPerSec < CLOCKS_PER_SEC )
     { // Covnert clock value to designated units
     Clock2 = RoundToRes( Clock2 );
     }
  Clock2 -= _mClockStart; // Get time from start
  return ( Clock2 );
  }
clock_t cClock::GetCalClock()
  {
  clock_t Clock = GetClock();
  if ( _mCalPeriod && _mClockStart )
     { // Adjust time by the calibration correction
     Clock += ( ( _mCalCorrection * Clock ) / _mCalPeriod );
     }
  return ( Clock );
  }
clock_t cClock::GetClocksPerSec()
  {
  return ( _mDesClocksPerSec );
  }
void cClock::SetCalibration( clock_t CalPeriod,
     clock_t CalCorrection )
  {
  _mCalPeriod = CalPeriod;
  _mCalCorrection = CalCorrection;
  }
void cClock::CalcCalibration( clock_t ActualTime,
     clock_t MeasuredTime, clock_t Correction )
  {
  clock_t Error = ActualTime - MeasuredTime;
  clock_t Periods = Error / Correction;
  _mCalPeriod = 0;
  if ( Periods != 0 )
     {
     _mCalPeriod = MeasuredTime / Periods;
     _mCalCorrection = Correction;
     }
  }
void cClock::InitClock()
  {
  clock_t Clock1, Clock2, Clock3;
  clock_t Dummy = 0, NumCalls1 = 0, NumCalls2 = 0;
  Clock1 = clock();
  Clock2 = LoopClock( Clock1, &Dummy ); // Make clock tick
  Clock3 = LoopClock( Clock2, &NumCalls1 );
  Clock1 = LoopClock( Clock3, &NumCalls2 );
  // Average two clock ticks
  _mNumClockCalls = ( NumCalls1 + NumCalls2 ) / 2;
  _mNatClockRes = ( Clock1 - Clock2 ) / 2;
  }
clock_t cClock::LoopClock( clock_t Clock1, clock_t *NumCalls )
  {
  clock_t Clock2;
  do
     { // Call the clock function till it updates (or ticks)
     (*NumCalls)++; // Count the number of times called
     Clock2 = clock();
     }
  while ( Clock2 == Clock1 );
  return ( Clock2 );
  }
void cClock::SetClockRes( clock_t ClocksPerSec )
  {
  if ( !ClocksPerSec )
     { // Set the designated units to the native value
     _mDesClocksPerSec = CLOCKS_PER_SEC;
     }
  else
     {
     _mDesClocksPerSec = ClocksPerSec;
     }
  // Calculate the designated resolution
  // A 0 value means the designated units are finer then the native units
  _mDesClockRes = CLOCKS_PER_SEC / _mDesClocksPerSec;
  }
clock_t cClock::RoundToRes( clock_t Clock )
  {
  clock_t Remainder =
        Clock % ( CLOCKS_PER_SEC / _mDesClocksPerSec );
  Clock = ( Clock * _mDesClocksPerSec ) / CLOCKS_PER_SEC;
  if ( Remainder >= 5 )
     { // Round the time up by one
     Clock++;
     }
  return ( Clock );
  }
#ifdef __PALMOS
inline clock_t clock()
  {
  return ( (clock_t)TimGetTicks() );
  }
#elif defined( __WINDOWS )
inline clock_t clock()
  {
  return ( (clock_t)GetTickCount() );
  }
#endif

// clock.cpp End