// 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