Random.h

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/*
===========================================================================

Doom 3 GPL Source Code
Copyright (C) 1999-2011 id Software LLC, a ZeniMax Media company. 

This file is part of the Doom 3 GPL Source Code (?Doom 3 Source Code?).  

Doom 3 Source Code is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

Doom 3 Source Code is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Doom 3 Source Code.  If not, see <http://www.gnu.org/licenses/>.

In addition, the Doom 3 Source Code is also subject to certain additional terms. You should have received a copy of these additional terms immediately following the terms and conditions of the GNU General Public License which accompanied the Doom 3 Source Code.  If not, please request a copy in writing from id Software at the address below.

If you have questions concerning this license or the applicable additional terms, you may contact in writing id Software LLC, c/o ZeniMax Media Inc., Suite 120, Rockville, Maryland 20850 USA.

===========================================================================
*/

#ifndef __MATH_RANDOM_H__
#define __MATH_RANDOM_H__

/*
===============================================================================

        Random number generator

===============================================================================
*/

class idRandom {
public:
                                                idRandom( int seed = 0 );

        void                            SetSeed( int seed );
        int                                     GetSeed( void ) const;

        int                                     RandomInt( void );                      // random integer in the range [0, MAX_RAND]
        int                                     RandomInt( int max );           // random integer in the range [0, max[
        float                           RandomFloat( void );            // random number in the range [0.0f, 1.0f]
        float                           CRandomFloat( void );           // random number in the range [-1.0f, 1.0f]

        static const int        MAX_RAND = 0x7fff;

private:
        int                                     seed;
};

ID_INLINE idRandom::idRandom( int seed ) {
        this->seed = seed;
}

ID_INLINE void idRandom::SetSeed( int seed ) {
        this->seed = seed;
}

ID_INLINE int idRandom::GetSeed( void ) const {
        return seed;
}

ID_INLINE int idRandom::RandomInt( void ) {
        seed = 69069 * seed + 1;
        return ( seed & idRandom::MAX_RAND );
}

ID_INLINE int idRandom::RandomInt( int max ) {
        if ( max == 0 ) {
                return 0;                       // avoid divide by zero error
        }
        return RandomInt() % max;
}

ID_INLINE float idRandom::RandomFloat( void ) {
        return ( RandomInt() / ( float )( idRandom::MAX_RAND + 1 ) );
}

ID_INLINE float idRandom::CRandomFloat( void ) {
        return ( 2.0f * ( RandomFloat() - 0.5f ) );
}


/*
===============================================================================

        Random number generator

===============================================================================
*/

class idRandom2 {
public:
                                                        idRandom2( unsigned long seed = 0 );

        void                                    SetSeed( unsigned long seed );
        unsigned long                   GetSeed( void ) const;

        int                                             RandomInt( void );                      // random integer in the range [0, MAX_RAND]
        int                                             RandomInt( int max );           // random integer in the range [0, max]
        float                                   RandomFloat( void );            // random number in the range [0.0f, 1.0f]
        float                                   CRandomFloat( void );           // random number in the range [-1.0f, 1.0f]

        static const int                MAX_RAND = 0x7fff;

private:
        unsigned long                   seed;

        static const unsigned long      IEEE_ONE = 0x3f800000;
        static const unsigned long      IEEE_MASK = 0x007fffff;
};

ID_INLINE idRandom2::idRandom2( unsigned long seed ) {
        this->seed = seed;
}

ID_INLINE void idRandom2::SetSeed( unsigned long seed ) {
        this->seed = seed;
}

ID_INLINE unsigned long idRandom2::GetSeed( void ) const {
        return seed;
}

ID_INLINE int idRandom2::RandomInt( void ) {
        seed = 1664525L * seed + 1013904223L;
        return ( (int) seed & idRandom2::MAX_RAND );
}

ID_INLINE int idRandom2::RandomInt( int max ) {
        if ( max == 0 ) {
                return 0;               // avoid divide by zero error
        }
        return ( RandomInt() >> ( 16 - idMath::BitsForInteger( max ) ) ) % max;
}

ID_INLINE float idRandom2::RandomFloat( void ) {
        unsigned long i;
        seed = 1664525L * seed + 1013904223L;
        i = idRandom2::IEEE_ONE | ( seed & idRandom2::IEEE_MASK );
        return ( ( *(float *)&i ) - 1.0f );
}

ID_INLINE float idRandom2::CRandomFloat( void ) {
        unsigned long i;
        seed = 1664525L * seed + 1013904223L;
        i = idRandom2::IEEE_ONE | ( seed & idRandom2::IEEE_MASK );
        return ( 2.0f * ( *(float *)&i ) - 3.0f );
}

#endif /* !__MATH_RANDOM_H__ */