// COTD Entry submitted by Gaz Iqbal [devvoid@home.com]

#ifndef VOID_SYS_TIME
#define VOID_SYS_TIME

/*
====================================================
A Simple Timer class which tries to use the 
Win32 HighPerformance Timer. Will default to 
the Windows Multimedia timer if the High Performance
Timer is not found.

I call the GetCurrent/Frame time functions from a 
pair of globally accessible functions which I define 
in namespace System{} to hide the implementation of 
CTime from all the other game code.
====================================================
*/
class CTime
{
public:

	CTime();
	~CTime();

	void Init();
	void Reset();
	
	//Call this onces per game frame
	void Update();

	//Access funcs
	inline const float & GetCurrentTime() const { return m_fCurrentTime; }
	inline const float & GetFrameTime()   const { return m_fFrameTime;   } 

private:

	typedef float (CTime::* TimeUpdateFunc) ();
	TimeUpdateFunc m_pfnUpdate;

	float	m_fBaseTime;
	float	m_fLastTime;
	float	m_fSecsPerTick;

	float	m_fCurrentTime;
	float	m_fFrameTime;

	//QueryPerformancesCounter related 64bit integers.
	//These are Microsoft specific, and will have to be changed for
	//different compilers.
	_int64	m_dTimerStart;
	_int64  m_dCurTime;

	//One of these gets bound to the TimeUpdateFunc pointer
	float	GetPerformanceCounterTime();
	float	GetMMTime();
};

#endif 

// COTD Entry submitted by Gaz Iqbal [devvoid@home.com]

#include "Sys_hdr.h"
#include <mmsystem.h>
#include "Sys_time.h"

/*
=====================================
Constructor/Destructor
=====================================
*/
CTime::CTime() : 
		m_pfnUpdate(0),
		m_fBaseTime(0.0f),
		m_fLastTime(0.0f),
		m_fSecsPerTick(0.0f),
		m_fCurrentTime(0.0f),
		m_fFrameTime(0.0f),
		m_dTimerStart(0),
		m_dCurTime(0)
{
}

CTime::~CTime()
{	m_pfnUpdate = 0;
}

/*
=====================================
Initialize the timer
=====================================
*/
void CTime::Init()
{
	_int64	dTicksPerSec =0;

	if (QueryPerformanceFrequency(reinterpret_cast<LARGE_INTEGER *>(&dTicksPerSec)))
	{ 
		// performance counter is available, use it instead of multimedia timer
		QueryPerformanceCounter(reinterpret_cast<LARGE_INTEGER *>(&m_dTimerStart));
		m_fSecsPerTick = (1.0f)/(static_cast<float>(dTicksPerSec));
		m_pfnUpdate = &CTime::GetPerformanceCounterTime;
	}
	else
	{ 
		//Use MM timer if unable to use the High Frequency timer
		m_dTimerStart = timeGetTime();
		m_fSecsPerTick = 1.0f/1000.0f;
		m_pfnUpdate = &CTime::GetMMTime;
	}
}

/*
================================================
Update time
================================================
*/
void CTime::Update()
{
	//The ->* operator binds the function pointer to the object pointed to by
	//the right hand pointer. which is THIS below
	m_fCurrentTime =  (this->*m_pfnUpdate)() - m_fBaseTime;
	m_fFrameTime = m_fCurrentTime - m_fLastTime;
	m_fLastTime = m_fCurrentTime;
}

/*
=====================================
Reset the Timer
=====================================
*/
void CTime::Reset()
{
	m_fBaseTime =  (this->*m_pfnUpdate)();
	m_fLastTime = m_fCurrentTime = m_fFrameTime = 0.0;
}

/*
=====================================
Time update funcs
=====================================
*/
float CTime::GetPerformanceCounterTime()
{
	QueryPerformanceCounter(reinterpret_cast<LARGE_INTEGER *>(&m_dCurTime));
	return (m_fSecsPerTick * (m_dCurTime - m_dTimerStart));
}

float CTime::GetMMTime()
{	return (m_fSecsPerTick * (timeGetTime()- m_dTimerStart));
}