sl@0: // Copyright (c) 1997-2009 Nokia Corporation and/or its subsidiary(-ies).
sl@0: // All rights reserved.
sl@0: // This component and the accompanying materials are made available
sl@0: // under the terms of "Eclipse Public License v1.0"
sl@0: // which accompanies this distribution, and is available
sl@0: // at the URL "http://www.eclipse.org/legal/epl-v10.html".
sl@0: //
sl@0: // Initial Contributors:
sl@0: // Nokia Corporation - initial contribution.
sl@0: //
sl@0: // Contributors:
sl@0: //
sl@0: // Description:
sl@0: // FUNCTION
sl@0: // <<rand>>, <<srand>>---pseudo-random numbers
sl@0: // INDEX
sl@0: // rand
sl@0: // INDEX
sl@0: // srand
sl@0: // INDEX
sl@0: // _rand_r
sl@0: // INDEX
sl@0: // _srand_r
sl@0: // ANSI_SYNOPSIS
sl@0: //
sl@0: 
sl@0: // #include <stdlib.h>
sl@0: // int rand(void);
sl@0: // void srand(unsigned int <[seed]>);
sl@0: // int _rand_r(void *<[reent]>);
sl@0: // void _srand_r(void *<[reent]>, unsigned int <[seed]>);
sl@0: // TRAD_SYNOPSIS
sl@0: // #include <stdlib.h>
sl@0: // int rand();
sl@0: // void srand(<[seed]>)
sl@0: // unsigned int <[seed]>;
sl@0: // int _rand_r(<[reent]>);
sl@0: // char *<[reent]>
sl@0: // void _srand_r(<[data]>,<[seed]>)
sl@0: // char *<[reent]>;
sl@0: // unsigned int <[seed]>;
sl@0: // <<rand>> returns a different integer each time it is called; each
sl@0: // integer is chosen by an algorithm designed to be unpredictable, so
sl@0: // that you can use <<rand>> when you require a random number.
sl@0: // The algorithm depends on a static variable called the ``random seed'';
sl@0: // starting with a given value of the random seed always produces the
sl@0: // same sequence of numbers in successive calls to <<rand>>.
sl@0: // You can set the random seed using <<srand>>; it does nothing beyond
sl@0: // storing its argument in the static variable used by <<rand>>.  You can
sl@0: // exploit this to make the pseudo-random sequence less predictable, if
sl@0: // you wish, by using some other unpredictable value (often the least
sl@0: // significant parts of a time-varying value) as the random seed before
sl@0: // beginning a sequence of calls to <<rand>>; or, if you wish to ensure
sl@0: // (for example, while debugging) that successive runs of your program
sl@0: // use the same ``random'' numbers, you can use <<srand>> to set the same
sl@0: // random seed at the outset.
sl@0: // <<_rand_r>> and <<_srand_r>> are reentrant versions of <<rand>> and
sl@0: // <<srand>>.  The extra argument <[reent]> is a pointer to a reentrancy
sl@0: // structure.
sl@0: // RETURNS
sl@0: // <<rand>> returns the next pseudo-random integer in sequence; it is a
sl@0: // number between <<0>> and <<RAND_MAX>> (inclusive).
sl@0: // <<srand>> does not return a result.
sl@0: // PORTABILITY
sl@0: // <<rand>> is required by ANSI, but the algorithm for pseudo-random
sl@0: // number generation is not specified; therefore, even if you use
sl@0: // the same random seed, you cannot expect the same sequence of results
sl@0: // on two different systems.
sl@0: // <<rand>> requires no supporting OS subroutines.
sl@0: //
sl@0: 
sl@0: #include <e32math.h>
sl@0: #include <stdlib_r.h>
sl@0: 
sl@0: extern "C" {
sl@0: 
sl@0: /**
sl@0: Reentrant versions of rand()
sl@0: @param ptr
sl@0: */
sl@0: EXPORT_C int _rand_r(struct _reent *ptr)
sl@0: 	{
sl@0: 	return Math::Rand(*(TInt64*)ptr->_next);
sl@0: 	}
sl@0: 
sl@0: /**
sl@0: Reentrant versions of srand()
sl@0: @param ptr
sl@0: @param seed
sl@0: */
sl@0: EXPORT_C void _srand_r (struct _reent *ptr, unsigned int seed)
sl@0: 	{
sl@0: 	ptr->_next[0] = seed;
sl@0: 	ptr->_next[1] = seed;
sl@0: 	}
sl@0: 
sl@0: /**
sl@0: Returns a different integer each time it is called; each
sl@0: integer is chosen by an algorithm designed to be unpredictable, so
sl@0: that you can use <<rand>> when you require a random number.
sl@0: @return the next pseudo-random integer in sequence; it is a
sl@0: number between 0 and RAND_MAX (inclusive).
sl@0: */
sl@0: EXPORT_C int rand (void)
sl@0: 	{
sl@0: 	return _rand_r (_REENT);
sl@0: 	}
sl@0: 
sl@0: /**
sl@0: Sets the random seed.
sl@0: @param seed seed
sl@0: */
sl@0: EXPORT_C void srand (unsigned int seed)
sl@0: 	{
sl@0: 	_srand_r (_REENT, seed);
sl@0: 	}
sl@0: 
sl@0: } // extern "C"