// Copyright (c) 1998-2009 Nokia Corporation and/or its subsidiary(-ies).

// All rights reserved.

// This component and the accompanying materials are made available

// under the terms of the License "Eclipse Public License v1.0"

// which accompanies this distribution, and is available

// at the URL "http://www.eclipse.org/legal/epl-v10.html".

//

// Initial Contributors:

// Nokia Corporation - initial contribution.

//

// Contributors:

//

// Description:

// e32\nkern\win32\ncutilf.cpp

// 

//

#include "nk_priv.h"

// Win32 fast counter implementation

static TBool FastCounterSupported = FALSE;

static TInt FastCounterShift;

static TInt FastCounterAdjustedFreq;

/** Initialise the fast counter.

    Check whether a high performance counter is available and determine its

    frequency.  Work out a scaling that allows a 32 bit counter value that wraps

    at most every 16 seconds.

*/

void FastCounterInit()

	{

	// Test support by getting count - QueryPerformanceFrequency can succeed

	// even if not supported

	LARGE_INTEGER count;

	count.QuadPart = 0;

	if (!QueryPerformanceCounter(&count) || count.QuadPart == 0)

		return;  // not supported

	LARGE_INTEGER freq;

	freq.QuadPart = 0;

	if (!QueryPerformanceFrequency(&freq) || freq.QuadPart == 0)

		return;  // not supported

	TInt mso = __e32_find_ms1_32(freq.LowPart);

	FastCounterShift = (mso > 27) ? mso - 27 : 0;

	FastCounterSupported = TRUE;

	FastCounterAdjustedFreq = freq.LowPart >> FastCounterShift;	

	}

/** Get the current value of the high performance counter.

    If a high performance counter is not available, this uses the millisecond

    tick count instead.

*/

EXPORT_C TUint32 NKern::FastCounter()

	{

	if (FastCounterSupported)

		{

		LARGE_INTEGER count;

		count.QuadPart = 0;

		QueryPerformanceCounter(&count);

		return (TUint32)(count.QuadPart >> FastCounterShift);

		}

	else

		return NTickCount();

	}

/** Get the frequency of counter queried by NKern::FastCounter().

*/

EXPORT_C TInt NKern::FastCounterFrequency()

	{

	if (FastCounterSupported)

		return FastCounterAdjustedFreq;

	else

		return 1000000 / TickPeriod();

	}