1 // Copyright (c) 1995-2009 Nokia Corporation and/or its subsidiary(-ies).

     2 // All rights reserved.

     3 // This component and the accompanying materials are made available

     4 // under the terms of the License "Symbian Foundation License v1.0"

     5 // which accompanies this distribution, and is available

     6 // at the URL "http://www.symbianfoundation.org/legal/sfl-v10.html".

     7 //

     8 // Initial Contributors:

     9 // Nokia Corporation - initial contribution.

    10 //

    11 // Contributors:

    12 //

    13 // Description:

    14 // e32\euser\maths\um_sqrt.cpp

    15 // Square root.

    16 // 

    17 //

    18 

    19 #include "um_std.h"

    20 

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

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

    23 #endif

    24 

    25 

    26 #ifndef __USE_VFP_MATH

    27 

    28 #ifndef __REALS_MACHINE_CODED__

    29 LOCAL_D const TUint32 KConstAdata[] = {0x00000000,0xD5A9A805,0x7FFD0000};

    30 LOCAL_D const TUint32 KConstBdata[] = {0x00000000,0x9714B9CB,0x7FFE0000};

    31 LOCAL_D const TUint32 Sqr2Invdata[] = {0xF9DE6484,0xB504F333,0x7FFE0000};		// 1/sqr2

    32 

    33 

    34 

    35 

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

    37 /**

    38 Calculates the square root of a number.

    39 

    40 @param aTrg A reference containing the result. 

    41 @param aSrc The number whose square-root is required.

    42 

    43 @return KErrNone if successful, otherwise another of

    44         the system-wide error codes. 

    45 */

    46 //

    47 // Fast sqrt routine. See Software manual by W.J.Cody & W.Waite Chapter 4.

    48 //

    49 	{

    50 	const TRealX& KConstA=*(const TRealX*)KConstAdata;

    51 	const TRealX& KConstB=*(const TRealX*)KConstBdata;

    52 	const TRealX& Sqr2Inv=*(const TRealX*)Sqr2Invdata;

    53 

    54 	TRealX x;

    55 	TInt r=x.Set(aSrc);

    56 	if (x.IsZero())

    57 		{

    58 		aTrg=aSrc;

    59 		return(KErrNone);

    60 		}   

    61 	if (r==KErrArgument || x.iSign&1)

    62 		{

    63 		SetNaN(aTrg);

    64 		return(KErrArgument);

    65 		}

    66 	if (r==KErrOverflow)	// positive infinity

    67 		{

    68 		aTrg=aSrc;

    69 		return(r);

    70 		}

    71 	TInt n=x.iExp-0x7FFE;

    72 	x.iExp=0x7FFE;

    73 	TRealX y=KConstB*x+KConstA;

    74 	y=y+(x/y);

    75 	y.iExp--;

    76 	y=y+(x/y);

    77 	y.iExp--;

    78 	y=y+(x/y);

    79 	y.iExp--;

    80 	if (n&1)

    81 		{

    82 		y*=Sqr2Inv;

    83 		n++;

    84 		}

    85 	y.iExp=TUint16(TInt(y.iExp)+(n>>1));

    86 	return y.GetTReal(aTrg);

    87 	}

    88 #endif

    89 

    90 #endif // !__USE_VFP_MATH - VFP version is in assembler