sl@0: // Copyright (c) 1995-2009 Nokia Corporation and/or its subsidiary(-ies).
sl@0: // All rights reserved.
sl@0: // This component and the accompanying materials are made available
sl@0: // under the terms of the License "Eclipse Public License v1.0"
sl@0: // which accompanies this distribution, and is available
sl@0: // at the URL "http://www.eclipse.org/legal/epl-v10.html".
sl@0: //
sl@0: // Initial Contributors:
sl@0: // Nokia Corporation - initial contribution.
sl@0: //
sl@0: // Contributors:
sl@0: //
sl@0: // Description:
sl@0: // e32\euser\maths\um_asin.cpp
sl@0: // Arc sin.
sl@0: // 
sl@0: //
sl@0: 
sl@0: #include "um_std.h"
sl@0: 
sl@0: #if defined(__USE_VFP_MATH) && !defined(__CPU_HAS_VFP)
sl@0: #error	__USE_VFP_MATH was defined but not __CPU_HAS_VFP - impossible combination, check variant.mmh 
sl@0: #endif
sl@0: 
sl@0: #ifndef __USE_VFP_MATH
sl@0: 
sl@0: LOCAL_D const TUint32 ArcsinCoeffs[] =
sl@0: 	{
sl@0: 	0x00000000,0x80000000,0x7FFF0000,	// polynomial approximation to arcsin(x)
sl@0: 	0xAA893CD8,0xAAAAAAAA,0x7FFC0000,	// for -0.5<=x<=0.5
sl@0: 	0xD07ED410,0x99999999,0x7FFB0000,
sl@0: 	0xB6C64A72,0xB6DB6D94,0x7FFA0000,
sl@0: 	0xF5527DD4,0xF8E3995C,0x7FF90000,
sl@0: 	0xA87499FB,0xB744B969,0x7FF90000,
sl@0: 	0x2E8953AD,0x8E392B24,0x7FF90000,
sl@0: 	0xFEDBB4E4,0xE3481C4A,0x7FF80000,
sl@0: 	0x4A32ED70,0xC89998E1,0x7FF80000,
sl@0: 	0x848A2B53,0xCCAE4AE5,0x7FF70000,
sl@0: 	0x09C1F387,0xA587A043,0x7FF90000,
sl@0: 	0x722B9041,0x8C9BD20B,0x7FF90001,
sl@0: 	0xC88B75CC,0x850CE779,0x7FFA0000
sl@0: 	};
sl@0: 
sl@0: LOCAL_D const TUint32 Onedata[] = {0x00000000,0x80000000,0x7FFF0000};		// 1.0
sl@0: LOCAL_D const TUint32 Halfdata[] = {0x00000000,0x80000000,0x7FFE0000};		// 0.5
sl@0: LOCAL_D const TUint32 Pidata[] = {0x2168C235,0xC90FDAA2,0x80000000};		// pi
sl@0: LOCAL_D const TUint32 PiBy2data[] = {0x2168C235,0xC90FDAA2,0x7FFF0000};		// pi/2
sl@0: 
sl@0: LOCAL_C TInt CalcArcsinArccos(TReal& aTrg, TRealX& x, TBool aCos)
sl@0: 	{
sl@0: 	//	Calculate arcsin (if aCos false) or arccos (if aCos true) of x
sl@0: 	//	and write result to aTrg.
sl@0: 	//	Algorithm (arcsin):
sl@0: 	//		If x>0.5, replace x with Sqrt((1-x)/2)
sl@0: 	//			( use identity cos(x)=2(cos(x/2))^2-1 )
sl@0: 	//		Use polynomial approximation for arcsin(x), 0<=x<=0.5
sl@0: 	//		If original x>0.5, replace result y with pi/2-2y
sl@0: 
sl@0: 	const TRealX One = *(const TRealX*)Onedata;
sl@0: 	const TRealX Half = *(const TRealX*)Halfdata;
sl@0: 	const TRealX Pi = *(const TRealX*)Pidata;
sl@0: 	const TRealX PiBy2 = *(const TRealX*)PiBy2data;
sl@0: 
sl@0: 	TInt sign=x.iSign&1;
sl@0: 	x.iSign=0;
sl@0: 	if (x<=One)
sl@0: 		{
sl@0: 		TBool big=(x>Half);
sl@0: 		if (big)
sl@0: 			{
sl@0: 			x=One-x;
sl@0: 			if (x.iExp>1)
sl@0: 				x.iExp--;
sl@0: 			TReal temp;
sl@0: 			Math::Sqrt(temp, (TReal)x);
sl@0: 			x=temp;
sl@0: 			}
sl@0: 		TRealX y;
sl@0: 		Math::PolyX(y,x*x,12,(const TRealX*)ArcsinCoeffs);
sl@0: 		y*=x;
sl@0: 		if (big)
sl@0: 			{
sl@0: 			if (y.iExp)
sl@0: 				y.iExp++;
sl@0: 			if (aCos)
sl@0: 				{
sl@0: 				if (sign)
sl@0: 					y=Pi-y;
sl@0: 				}
sl@0: 			else
sl@0: 				{
sl@0: 				y=PiBy2-y;
sl@0: 				y.iSign=TInt8(sign);
sl@0: 				}
sl@0: 			}
sl@0: 		else
sl@0: 			{
sl@0: 			y.iSign=TInt8(sign);
sl@0: 			if (aCos)
sl@0: 				y=PiBy2-y;
sl@0: 			}
sl@0: 		return y.GetTReal(aTrg);
sl@0: 		}
sl@0: 	return KErrArgument;
sl@0: 	}
sl@0: 
sl@0: 
sl@0: 
sl@0: 
sl@0: EXPORT_C TInt Math::ASin(TReal& aTrg, const TReal& aSrc)
sl@0: /**
sl@0: Calculates the principal value of the inverse sine of a number.
sl@0: 
sl@0: @param aTrg A reference containing the result in radians,
sl@0:             a value between -pi/2 and +pi/2. 
sl@0: @param aSrc The argument of the arcsin function, a value
sl@0:             between -1 and +1 inclusive.
sl@0: 
sl@0: @return KErrNone if successful, otherwise another of the system-wide
sl@0:         error codes.
sl@0: */
sl@0: 	{
sl@0: 	TRealX x;
sl@0: 	TInt r=x.Set(aSrc);
sl@0: 	if (r==KErrNone)
sl@0: 		r=CalcArcsinArccos(aTrg,x,EFalse);
sl@0: 	if (r==KErrNone)
sl@0: 		return r;
sl@0: 	SetNaN(aTrg);
sl@0: 	return KErrArgument;
sl@0: 	}
sl@0: 
sl@0: 
sl@0: 
sl@0: 
sl@0: EXPORT_C TInt Math::ACos(TReal& aTrg, const TReal& aSrc)
sl@0: /**
sl@0: Calculates the principal value of the inverse cosine of a number.
sl@0: 
sl@0: @param aTrg A reference containing the result in radians,
sl@0:             a value between 0 and pi. 
sl@0: @param aSrc The argument of the arccos function, a value
sl@0:             between -1 and +1 inclusive. 
sl@0: 
sl@0: @return KErrNone if successful, otherwise another of the system-wide
sl@0:         error codes.
sl@0: */
sl@0: 	{
sl@0: 	TRealX x;
sl@0: 	TInt r=x.Set(aSrc);
sl@0: 	if (r==KErrNone)
sl@0: 		r=CalcArcsinArccos(aTrg,x,ETrue);
sl@0: 	if (r==KErrNone)
sl@0: 		return r;
sl@0: 	SetNaN(aTrg);
sl@0: 	return KErrArgument;
sl@0: 	}
sl@0: 
sl@0: #else // __USE_VFP_MATH
sl@0: 
sl@0: // definitions come from RVCT math library
sl@0: extern "C" TReal asin(TReal);
sl@0: extern "C" TReal acos(TReal);
sl@0: 
sl@0: EXPORT_C TInt Math::ASin(TReal& aTrg, const TReal& aSrc)
sl@0: 	{
sl@0: 	aTrg = asin(aSrc);
sl@0: 	if (Math::IsFinite(aTrg))
sl@0: 		return KErrNone;
sl@0: 	SetNaN(aTrg);
sl@0: 	return KErrArgument;
sl@0: 	}
sl@0: 
sl@0: EXPORT_C TInt Math::ACos(TReal& aTrg, const TReal& aSrc)
sl@0: 	{
sl@0: 	aTrg = acos(aSrc);
sl@0: 	if (Math::IsFinite(aTrg))
sl@0: 		return KErrNone;
sl@0: 	SetNaN(aTrg);
sl@0: 	return KErrArgument;
sl@0: 	}
sl@0: 
sl@0: #endif