author | Pat Downey <patrick.downey@nokia.com> |
Thu, 25 Jun 2009 15:59:54 +0100 | |
changeset 1 | 0a7b44b10206 |
child 2 | 806186ab5e14 |
permissions | -rw-r--r-- |
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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 "Symbian Foundation License v1.0" |
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// which accompanies this distribution, and is available |
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// at the URL "http://www.symbianfoundation.org/legal/sfl-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_sqrt.cpp |
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// Square root. |
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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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LOCAL_D const TUint32 KConstAdata[] = {0x00000000,0xD5A9A805,0x7FFD0000}; |
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LOCAL_D const TUint32 KConstBdata[] = {0x00000000,0x9714B9CB,0x7FFE0000}; |
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LOCAL_D const TUint32 Sqr2Invdata[] = {0xF9DE6484,0xB504F333,0x7FFE0000}; // 1/sqr2 |
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EXPORT_C TInt Math::Sqrt(TReal& aTrg,const TReal &aSrc) |
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/** |
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Calculates the square root of a number. |
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@param aTrg A reference containing the result. |
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@param aSrc The number whose square-root 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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// Fast sqrt routine. See Software manual by W.J.Cody & W.Waite Chapter 4. |
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// |
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{ |
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const TRealX& KConstA=*(const TRealX*)KConstAdata; |
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const TRealX& KConstB=*(const TRealX*)KConstBdata; |
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const TRealX& Sqr2Inv=*(const TRealX*)Sqr2Invdata; |
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TRealX x; |
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TInt r=x.Set(aSrc); |
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if (x.IsZero()) |
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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 (r==KErrArgument || x.iSign&1) |
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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 (r==KErrOverflow) // positive infinity |
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{ |
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aTrg=aSrc; |
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return(r); |
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} |
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TInt n=x.iExp-0x7FFE; |
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x.iExp=0x7FFE; |
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TRealX y=KConstB*x+KConstA; |
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y=y+(x/y); |
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y.iExp--; |
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y=y+(x/y); |
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y.iExp--; |
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y=y+(x/y); |
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y.iExp--; |
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if (n&1) |
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{ |
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y*=Sqr2Inv; |
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n++; |
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} |
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y.iExp=TUint16(TInt(y.iExp)+(n>>1)); |
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return y.GetTReal(aTrg); |
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} |
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#endif |
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#endif // !__USE_VFP_MATH - VFP version is in assembler |