// Copyright (c) 1995-2009 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\euser\maths\um_tan.cpp

// Tangent.

// 

//

#include "um_std.h"

#if defined(__USE_VFP_MATH) && !defined(__CPU_HAS_VFP)

#error	__USE_VFP_MATH was defined but not __CPU_HAS_VFP - impossible combination, check variant.mmh 

#endif

#ifndef __USE_VFP_MATH

LOCAL_D const TUint32 TanCoeffs[] =

	{

	0x2168C235,0xC90FDAA2,0x7FFF0000,	// polynomial approximation to tan((pi/2)*x)

	0x2DF4707D,0xA55DE731,0x7FFF0000,	// for |x|<=0.25

	0xA9A1A71A,0xA335E33B,0x7FFF0000,

	0x0BB9E431,0xA2FFFCDD,0x7FFF0000,

	0x3E523A39,0xA2FA3863,0x7FFF0000,

	0x8A35C401,0xA2F9D38B,0x7FFF0000,

	0x91269411,0xA2F16003,0x7FFF0000,

	0xDA32CC78,0xA3A93B13,0x7FFF0000,

	0x4FB88317,0x9A146197,0x7FFF0000,

	0x0D787ECE,0xE131DEE5,0x7FFF0000

	};

LOCAL_D const TUint32 Onedata[] = {0x00000000,0x80000000,0x7FFF0000};		// 1.0

LOCAL_D const TUint32 Halfdata[] = {0x00000000,0x80000000,0x7FFE0000};		// 0.5

LOCAL_D const TUint32 PiBy2Invdata[] = {0x4E44152A,0xA2F9836E,0x7FFE0000};	// 2/pi

EXPORT_C TInt Math::Tan(TReal& aTrg, const TReal& aSrc)

/**

Calculates the tangent of a number.

@param aTrg A reference containing the result.

@param aSrc The argument of the tan function in radians. 

@return KErrNone if successful, otherwise another of

        the system-wide error codes. 

*/

	{

	// Calculate tan(aSrc) and write result to aTrg.

	// Algorithm:

	//		Let x=aSrc/(pi/2). Throw away integer part, but if integer part odd

	//			then replace final result y with -1/y

	//			( use identities tan(x+n*pi)=tan(x), tan(x+pi/2)=-1/tan(x) )

	//		Replace x with fractional part after division.

	//		If x>=0.5, replace x with 1-x and replace result y with 1/y

	//			( use identity tan(pi/2-x)=1/tan(x) )

	//		If x>=0.25, replace x with 0.5-x and replace result y with (1-y)/(1+y)

	//			( use identity tan(pi/4-x)=(1-tan(x))/(1+tan(x)) )

	//		Use polynomial approximation to calculate tan(pi*x/2) for |x|<=0.25

	const TRealX& One = *(const TRealX*)Onedata;

	const TRealX& Half = *(const TRealX*)Halfdata;

	const TRealX& PiBy2Inv = *(const TRealX*)PiBy2Invdata;

	TRealX x;

	TInt r=x.Set(aSrc);

	if (r==KErrNone)

		{

		TInt8 sign=x.iSign;

		x.iSign=0;

		x*=PiBy2Inv;

		TInt n=(TInt)x;

		if (n<KMaxTInt && n>KMinTInt)

			{

			TInt flags=(n&1)<<1;

			x-=TRealX(n);

			if (x.iExp>=0x7FFE)

				{

				x=One-x;

				flags^=2;

				}

			if (x.iExp>=0x7FFD)

				{

				x=Half-x;

				flags^=1;

				}

			TRealX y;

			PolyX(y,x*x,9,(const TRealX*)TanCoeffs);

			y*=x;

			if (flags==3)

				y=(One+y)/(One-y);

			else if (flags==2)

				y=One/y;

			else if (flags==1)

				y=(One-y)/(One+y);

			y.iSign=TInt8(sign ^ (n&1));

			return y.GetTReal(aTrg);

			}

		}

	SetNaN(aTrg);

	return KErrArgument;

	}

#else // __USE_VFP_MATH

// definitions come from RVCT math library

extern "C" TReal tan(TReal);

EXPORT_C TInt Math::Tan(TReal& aTrg, const TReal& aSrc)

	{

	if (aSrc<KMaxTInt && aSrc>KMinTInt)

		{

		aTrg = tan(aSrc);

		if (Math::IsFinite(aTrg))

			return KErrNone;

		}

	SetNaN(aTrg);

	return KErrArgument;

	}

#endif