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1 // Copyright (c) 1995-2009 Nokia Corporation and/or its subsidiary(-ies). |
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2 // All rights reserved. |
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3 // This component and the accompanying materials are made available |
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4 // under the terms of the License "Eclipse Public License v1.0" |
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5 // which accompanies this distribution, and is available |
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6 // at the URL "http://www.eclipse.org/legal/epl-v10.html". |
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7 // |
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8 // Initial Contributors: |
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9 // Nokia Corporation - initial contribution. |
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10 // |
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11 // Contributors: |
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12 // |
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13 // Description: |
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14 // e32\euser\maths\um_sqrt.cpp |
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15 // Square root. |
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16 // |
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17 // |
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18 |
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19 #include "um_std.h" |
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20 |
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21 #if defined(__USE_VFP_MATH) && !defined(__CPU_HAS_VFP) |
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22 #error __USE_VFP_MATH was defined but not __CPU_HAS_VFP - impossible combination, check variant.mmh |
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23 #endif |
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24 |
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25 |
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26 #ifndef __USE_VFP_MATH |
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27 |
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28 #ifndef __REALS_MACHINE_CODED__ |
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29 LOCAL_D const TUint32 KConstAdata[] = {0x00000000,0xD5A9A805,0x7FFD0000}; |
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30 LOCAL_D const TUint32 KConstBdata[] = {0x00000000,0x9714B9CB,0x7FFE0000}; |
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31 LOCAL_D const TUint32 Sqr2Invdata[] = {0xF9DE6484,0xB504F333,0x7FFE0000}; // 1/sqr2 |
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32 |
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33 |
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34 |
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35 |
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36 EXPORT_C TInt Math::Sqrt(TReal& aTrg,const TReal &aSrc) |
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37 /** |
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38 Calculates the square root of a number. |
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39 |
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40 @param aTrg A reference containing the result. |
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41 @param aSrc The number whose square-root is required. |
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42 |
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43 @return KErrNone if successful, otherwise another of |
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44 the system-wide error codes. |
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45 */ |
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46 // |
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47 // Fast sqrt routine. See Software manual by W.J.Cody & W.Waite Chapter 4. |
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48 // |
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49 { |
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50 const TRealX& KConstA=*(const TRealX*)KConstAdata; |
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51 const TRealX& KConstB=*(const TRealX*)KConstBdata; |
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52 const TRealX& Sqr2Inv=*(const TRealX*)Sqr2Invdata; |
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53 |
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54 TRealX x; |
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55 TInt r=x.Set(aSrc); |
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56 if (x.IsZero()) |
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57 { |
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58 aTrg=aSrc; |
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59 return(KErrNone); |
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60 } |
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61 if (r==KErrArgument || x.iSign&1) |
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62 { |
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63 SetNaN(aTrg); |
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64 return(KErrArgument); |
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65 } |
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66 if (r==KErrOverflow) // positive infinity |
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67 { |
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68 aTrg=aSrc; |
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69 return(r); |
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70 } |
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71 TInt n=x.iExp-0x7FFE; |
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72 x.iExp=0x7FFE; |
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73 TRealX y=KConstB*x+KConstA; |
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74 y=y+(x/y); |
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75 y.iExp--; |
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76 y=y+(x/y); |
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77 y.iExp--; |
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78 y=y+(x/y); |
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79 y.iExp--; |
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80 if (n&1) |
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81 { |
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82 y*=Sqr2Inv; |
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83 n++; |
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84 } |
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85 y.iExp=TUint16(TInt(y.iExp)+(n>>1)); |
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86 return y.GetTReal(aTrg); |
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87 } |
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88 #endif |
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89 |
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90 #endif // !__USE_VFP_MATH - VFP version is in assembler |