symport/e32/euser/maths/um_frac.cpp
author jjkang
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// Copyright (c) 1995-2009 Nokia Corporation and/or its subsidiary(-ies).
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// All rights reserved.
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// This component and the accompanying materials are made available
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// under the terms of the License "Eclipse Public License v1.0"
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// which accompanies this distribution, and is available
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// at the URL "http://www.eclipse.org/legal/epl-v10.html".
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//
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// Initial Contributors:
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// Nokia Corporation - initial contribution.
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//
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// Contributors:
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//
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// Description:
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// e32\euser\maths\um_frac.cpp
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// Writes the fractional part of aTrg to aSrc
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// 
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//
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#include "um_std.h"
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#if defined(__USE_VFP_MATH) && !defined(__CPU_HAS_VFP)
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#error	__USE_VFP_MATH was defined but not __CPU_HAS_VFP - impossible combination, check variant.mmh 
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#endif
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#ifndef __USE_VFP_MATH
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#ifndef __REALS_MACHINE_CODED__
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EXPORT_C TInt Math::Frac(TReal &aTrg,const TReal &aSrc)
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/**
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Calculates the fractional part of a number.
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The fractional part is that after a decimal point.
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Truncation is toward zero, so that
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Frac(2.4)=0.4, Frac(2)=0, Frac(-1)=0, Frac(-1.4)=0.4.
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@param aTrg A reference containing the result.
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@param aSrc The number whose fractional part is required. 
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@return KErrNone if successful, otherwise another of
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        the system-wide error codes.
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*/
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	{
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	TRealX f;
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	TInt ret=f.Set(aSrc);
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	if (ret!=KErrNone)
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		{
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		if (ret==KErrArgument)
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			SetNaN(aTrg);
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		if (ret==KErrOverflow)
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			SetZero(aTrg,f.iSign&1);
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		return(ret);
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		}
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	TInt intbits=f.iExp-0x7FFE;
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	if (intbits<=0)	 // aSrc is already a fraction
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		{
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		aTrg=aSrc;
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		return(KErrNone);
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		}
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	if (intbits>KMantissaBits)
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		{
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		SetZero(aTrg,f.iSign&1);
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		return(KErrNone);
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		}
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	// calculate integer part and subtract
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	// this means that the subtraction normalises the result
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	TRealX g=f;
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	TUint64 mask = ~(UI64LIT(0));
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	mask <<= (64 - intbits);
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	g.iMantHi &= static_cast<TUint32>(mask >> 32);
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	g.iMantLo &= static_cast<TUint32>(mask);
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	f-=g;
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	f.GetTReal(aTrg);
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	return(KErrNone);
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	}
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#endif //__REALS_MACHINE_CODED__
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#else // __USE_VFP_MATH
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// definitions come from RVCT math library
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extern "C" TReal modf(TReal,TReal*);
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EXPORT_C TInt Math::Frac(TReal& aTrg, const TReal& aSrc)
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	{
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	if (Math::IsNaN(aSrc))
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		{
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		SetNaN(aTrg);
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		return KErrArgument;
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		}
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	if (Math::IsInfinite(aSrc))
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		{
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		SetZero(aTrg);
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		return KErrOverflow;
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		}
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	TReal temp;
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	aTrg = modf(aSrc,&temp);
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	return KErrNone;
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	}
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#endif