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_rand.cpp

    15 // 

    16 //

    17 

    18 #include "um_std.h"

    19 

    20 

    21 

    22 

    23 EXPORT_C TInt Math::Rand(TInt64 &aSeed)

    24 /**

    25 Generates a stream of uniformly distributed pseudo-random integers

    26 in the range, 0 to KMaxTInt.

    27 

    28 For each stream of pseudo-random numbers you wish to generate, you should

    29 pass the reference to the same 64-bit seed on each call to this function.

    30 You should not change the seed between calls.

    31 

    32 @param aSeed A reference to a 64-bit seed, which is updated

    33              as a result of the call.

    34 

    35 @return The next pseudo-random number in the sequence. 

    36 */

    37 	{

    38 

    39 	aSeed*=214013;

    40     aSeed+=2531011;

    41     return(((TInt)(aSeed>>16))&0x7fffffff);

    42 	}

    43 

    44 

    45 

    46 

    47 EXPORT_C TReal Math::FRand(TInt64& aSeed) __SOFTFP

    48 /**

    49 Generates a stream of uniformly distributed pseudo-random real numbers

    50 in the range, 0 to 1.

    51 

    52 @param aSeed A reference to a 64-bit seed, which is updated

    53              as a result of the call.

    54 

    55 @return The next pseudo-random number in the sequence. 

    56 */

    57 	{

    58 	TUint low = (TUint)Math::Rand(aSeed);

    59 	TUint high = (TUint)Math::Rand(aSeed)&0x7FFFFFFF;	// make sure TInt64 is positive

    60 	TRealX f((static_cast<TInt64>(high) << 32) | low);	// construct TRealX 0<=f<2^63

    61 	if (f.iExp)

    62 		f.iExp-=63;						// Scale f to range 0<=f<1

    63     return(TReal(f));

    64 	}