--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/kernel/eka/euser/maths/um_ln.cpp	Mon Oct 19 15:55:17 2009 +0100
@@ -0,0 +1,143 @@
+// 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_ln.cpp
+// Natural log.
+// 
+//
+
+#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 ArtanhCoeffs[] =
+	{
+	0x5C17F0BC,0xB8AA3B29,0x80010000,	// polynomial approximation to (4/ln2)artanh(x)
+	0xD02489EE,0xF6384EE1,0x7FFF0000,	// for |x| <= (sqr2-1)/(sqr2+1)
+	0x7008CA5F,0x93BB6287,0x7FFF0000,
+	0xE32D1D6B,0xD30BB16D,0x7FFE0000,
+	0x461D071E,0xA4257CE2,0x7FFE0000,
+	0xC3B0EC87,0x8650D459,0x7FFE0000,
+	0x53BEC0CD,0xE23137E3,0x7FFD0000,
+	0xC523F21B,0xDAF79221,0x7FFD0000
+	};
+
+LOCAL_D const TUint32 Ln2By2data[] = {0xD1CF79AC,0xB17217F7,0x7FFD0000};	// (ln2)/2
+LOCAL_D const TUint32 Sqr2data[] = {0xF9DE6484,0xB504F333,0x7FFF0000};		// sqr2
+LOCAL_D const TUint32 Sqr2Invdata[] = {0xF9DE6484,0xB504F333,0x7FFE0000};	// 1/sqr2
+LOCAL_D const TUint32 Onedata[] = {0x00000000,0x80000000,0x7FFF0000};		// 1.0
+
+
+
+
+EXPORT_C TInt Math::Ln(TReal& aTrg, const TReal& aSrc)
+/**
+Calculates the natural logarithm of a number.
+
+@param aTrg A reference containing the result. 
+@param aSrc The number whose natural logarithm is required.
+
+@return KErrNone if successful, otherwise another of
+        the system-wide error codes. 
+*/
+	{
+	// Calculate ln(aSrc) and write to aTrg
+	// Algorithm:
+	//		Calculate log2(aSrc) and multiply by ln2
+	//		log2(aSrc)=log2(2^e.m) e=exponent of aSrc, m=mantissa 1<=m<2
+	//		log2(aSrc)=e+log2(m)
+	//		If e=-1 (0.5<=aSrc<1), let x=aSrc else let x=mantissa(aSrc)
+	//		If x>Sqr2, replace x with x/Sqr2
+	//		If x<Sqr2/2, replace x with x*Sqr2
+	//		Replace x with (x-1)/(x+1)
+	//		Use polynomial to calculate artanh(x) for |x| <= (sqr2-1)/(sqr2+1)
+	//			( use identity ln(x) = 2artanh((x-1)/(x+1)) )
+
+	TRealX x;
+	const TRealX& Ln2By2=*(const TRealX*)Ln2By2data;
+	const TRealX& Sqr2=*(const TRealX*)Sqr2data;
+	const TRealX& Sqr2Inv=*(const TRealX*)Sqr2Invdata;
+	const TRealX& One=*(const TRealX*)Onedata;
+
+	TInt r=x.Set(aSrc);
+	if (r==KErrNone)
+		{
+		if (x.iExp==0)
+			{
+			SetInfinite(aTrg,1);
+			return KErrOverflow;
+			}
+		if (x.iSign&1)
+			{
+			SetNaN(aTrg);
+			return KErrArgument;
+			}
+		TInt n=(x.iExp-0x7FFF)<<1;
+		x.iExp=0x7FFF;
+		if (n!=-2)
+			{
+			if (x>Sqr2)
+				{
+				x*=Sqr2Inv;
+				n++;
+				}
+			}
+		else 
+			{
+			n=0;
+			x.iExp=0x7FFE;
+			if (x<Sqr2Inv)
+				{
+				x*=Sqr2;
+				n--;
+				}
+			}
+		x=(x-One)/(x+One);	// ln(x)=2artanh((x-1)/(x+1))
+		TRealX y;
+		PolyX(y,x*x,7,(const TRealX*)ArtanhCoeffs);
+		y*=x;
+		y+=TRealX(n);
+		y*=Ln2By2;
+		return y.GetTReal(aTrg);
+		}
+	if (r==KErrArgument || (r==KErrOverflow && (x.iSign&1)))
+		{
+		SetNaN(aTrg);
+		return KErrArgument;
+		}
+	SetInfinite(aTrg,0);
+	return KErrOverflow;
+	}
+
+#else // __USE_VFP_MATH
+
+// definitions come from RVCT math library
+extern "C" TReal log(TReal);
+
+EXPORT_C TInt Math::Ln(TReal& aTrg, const TReal& aSrc)
+	{
+	aTrg = log(aSrc);
+	if (Math::IsFinite(aTrg))
+		return KErrNone;
+	if (Math::IsInfinite(aTrg))
+		return KErrOverflow;
+	SetNaN(aTrg);
+	return KErrArgument;
+	}
+
+#endif