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//==================================================================================================

//  Includes

//==================================================================================================

//  Self Include

#include "ARTimeStampGenerator.h"

//  System Includes

#include <libkern/libkern.h>

#include <kern/clock.h>

//==================================================================================================

//  ARTimeStampGenerator

//==================================================================================================

ARTimeStampGenerator::ARTimeStampGenerator()

:

    mSampleRate(44100),

    mRateScalar(1UL << 28),

    mFramesPerRingBuffer(44100),

    mMaximumJitter(0),

    mStartTime(0),

    mScaledTicksPerRingBuffer(0)

{

}

ARTimeStampGenerator::~ARTimeStampGenerator()

{

}

void    ARTimeStampGenerator::GetNextTimeStamp(UInt32 inLoopCount, AbsoluteTime* outTimeStamp)

{

    UInt64 theTimeStamp = 0;

    //  make sure we have a start time

    if(mStartTime == 0)

    {

        clock_get_uptime((AbsoluteTime*)&mStartTime);

        theTimeStamp = mStartTime;

    }

    else

    {

        //  start at the start

        theTimeStamp = mStartTime;

        //  add in the number of loops through the ring buffer

        theTimeStamp += inLoopCount * mScaledTicksPerRingBuffer;

        //  compute the amount of jitter

        UInt32 theRandomNumber = random();

        UInt64 theJitter = UInt64(theRandomNumber) * UInt64(mMaximumJitter);

        theJitter = theJitter >> 32;

        //  add the jitter to the time stamp

        theTimeStamp += theJitter;

    }

    //  return the time stamp as an AbsoluteTime to make life easy on the driver

    *outTimeStamp = *((AbsoluteTime*)&theTimeStamp);

}

void    ARTimeStampGenerator::Reset()

{

    mStartTime = 0;

}

void    ARTimeStampGenerator::CalculateValues()

{

    //  ge the host time base info

    mach_timebase_info theTimeBaseInfo;

    clock_timebase_info(&theTimeBaseInfo);

    //  compute the unscaled host ticks per ring buffer

    //  computed in steps to make sure we don't overflow

    //  note that we really don't care about fractional host ticks here

    mScaledTicksPerRingBuffer = 1000000000ULL * mFramesPerRingBuffer;

    mScaledTicksPerRingBuffer /= mSampleRate;

    mScaledTicksPerRingBuffer *= theTimeBaseInfo.denom;

    mScaledTicksPerRingBuffer /= theTimeBaseInfo.numer;

    //  scale by the rate scalar

    //  note that the rate scalar is stored as a 4.28 fixed point number which allows for a range of 0 to 8.

    //  note also that we don't care about fractions here.

    mScaledTicksPerRingBuffer *= mRateScalar;

    mScaledTicksPerRingBuffer = mScaledTicksPerRingBuffer >> 28;

}