symport/e32/euser/maths/um_rand.cpp
changeset 1 0a7b44b10206
child 2 806186ab5e14
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/symport/e32/euser/maths/um_rand.cpp	Thu Jun 25 15:59:54 2009 +0100
@@ -0,0 +1,64 @@
+// 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 "Symbian Foundation License v1.0"
+// which accompanies this distribution, and is available
+// at the URL "http://www.symbianfoundation.org/legal/sfl-v10.html".
+//
+// Initial Contributors:
+// Nokia Corporation - initial contribution.
+//
+// Contributors:
+//
+// Description:
+// e32\euser\maths\um_rand.cpp
+// 
+//
+
+#include "um_std.h"
+
+
+
+
+EXPORT_C TInt Math::Rand(TInt64 &aSeed)
+/**
+Generates a stream of uniformly distributed pseudo-random integers
+in the range, 0 to KMaxTInt.
+
+For each stream of pseudo-random numbers you wish to generate, you should
+pass the reference to the same 64-bit seed on each call to this function.
+You should not change the seed between calls.
+
+@param aSeed A reference to a 64-bit seed, which is updated
+             as a result of the call.
+
+@return The next pseudo-random number in the sequence. 
+*/
+	{
+
+	aSeed*=214013;
+    aSeed+=2531011;
+    return(((TInt)(aSeed>>16))&0x7fffffff);
+	}
+
+
+
+
+EXPORT_C TReal Math::FRand(TInt64& aSeed) __SOFTFP
+/**
+Generates a stream of uniformly distributed pseudo-random real numbers
+in the range, 0 to 1.
+
+@param aSeed A reference to a 64-bit seed, which is updated
+             as a result of the call.
+
+@return The next pseudo-random number in the sequence. 
+*/
+	{
+	TUint low = (TUint)Math::Rand(aSeed);
+	TUint high = (TUint)Math::Rand(aSeed)&0x7FFFFFFF;	// make sure TInt64 is positive
+	TRealX f((static_cast<TInt64>(high) << 32) | low);	// construct TRealX 0<=f<2^63
+	if (f.iExp)
+		f.iExp-=63;						// Scale f to range 0<=f<1
+    return(TReal(f));
+	}