o3de/Code/Legacy/CryCommon/MTPseudoRandom.h

// mtrand.h
// C++ include file for MT19937, with initialization improved 2002/1/26.
// Coded by Takuji Nishimura and Makoto Matsumoto.
// Ported to C++ by Jasper Bedaux 2003/1/1 (see http://www.bedaux.net/mtrand/).
// The generators returning floating point numbers are based on
// a version by Isaku Wada, 2002/01/09
// Static shared data converted to per-instance, 2008-11-13 by JSP.
//
// Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
//
// 3. The names of its contributors may not be used to endorse or promote
//    products derived from this software without specific prior written
//    permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// Any feedback is very welcome.
// http://www.math.keio.ac.jp/matumoto/emt.html
// email: matumoto@math.keio.ac.jp
//
// Feedback about the C++ port should be sent to Jasper Bedaux,
// see http://www.bedaux.net/mtrand/ for e-mail address and info.

//-------------------------------------------------------------------------
// History:
// - 28:7:2005: File created and minor changes by Marco Corbetta
//
//*************************************************************************/
// Modified from original

#ifndef CRYINCLUDE_CRYCOMMON_MTPSEUDORANDOM_H
#define CRYINCLUDE_CRYCOMMON_MTPSEUDORANDOM_H
#pragma once

#include <CryRandomInternal.h>

//////////////////////////////////////////////////////////////////////////
class CMTRand_int32 
{ 
    // Mersenne Twister random number generator

public:
    // default constructor
    CMTRand_int32() { seed(5489UL); }
    // constructor with 32 bit int as seed
    CMTRand_int32(uint32 seed_value) { seed(seed_value); }
    // constructor with array of 32 bit integers as seed
    CMTRand_int32(const uint32* array, int size) { seed(array, size); }
    // seeds with 32 bit integer
    void seed(uint32 seed_value);
    // seeds with array
    void seed(const uint32*, int size);
    // overloaded operator() to make this a generator (functor)
    //uint32 operator()() { return rand_int32(); }

    ~CMTRand_int32() {}

    // Functions with PascalCase names were added for
    // interchangeability with CRndGen (see LCGRandom.h).

    void Seed(uint32 seed_value)
    {
        seed(seed_value);
    }

    uint32 GenerateUint32()
    {
        return rand_int32();
    }

    uint64 GenerateUint64()
    {
        const uint32 a = GenerateUint32();
        const uint32 b = GenerateUint32();
        return ((uint64)b << 32) | (uint64)a;
    }

    float GenerateFloat()
    {
        return (float)GenerateUint32() * (1.0f / 4294967295.0f);
    }

    // Ranged function returns random value within the *inclusive* range
    // between minValue and maxValue.
    // Any orderings work correctly: minValue <= maxValue and 
    // minValue >= minValue.
    template <class T>
    T GetRandom(const T minValue, const T maxValue)
    {
        return CryRandom_Internal::BoundedRandom<CMTRand_int32, T>::Get(*this, minValue, maxValue);
    }

    // Vector (Vec2, Vec3, Vec4) ranged function returns vector    with 
    // every component within the *inclusive* ranges between minValue.component
    // and maxValue.component.
    // All orderings work correctly: minValue.component <= maxValue.component and
    // minValue.component >= maxValue.component.
    template <class T>
    T GetRandomComponentwise(const T& minValue, const T& maxValue)
    {
        return CryRandom_Internal::BoundedRandomComponentwise<CMTRand_int32, T>::Get(*this, minValue, maxValue);
    }

    // The function returns a random unit vector (Vec2, Vec3, Vec4).
    template <class T>
    T GetRandomUnitVector()
    {
        return CryRandom_Internal::GetRandomUnitVector<CMTRand_int32, T>(*this);
    }

protected: // used by derived classes, otherwise not accessible; use the ()-operator
    // generates 32 bit random int
    uint32 rand_int32() 
    { 
        if (p >= n) gen_state(); // new m_nState vector needed
        // gen_state() is split off to be non-inline, because it is only called once
        // in every 624 calls and otherwise irand() would become too big to get inlined
        uint32 x = m_nState[p++];
        x ^= (x >> 11);
        x ^= (x << 7) & 0x9D2C5680UL;
        x ^= (x << 15) & 0xEFC60000UL;
        return x ^ (x >> 18);
    }

private:
    static const int n = 624, m = 397; // compile time constants

    // the variables below are static (no duplicates can exist)
    uint32 m_nState[n+1]; // m_nState vector array
    int p; // position in m_nState array
    // private functions used to generate the pseudo random numbers
    uint32 twiddle(uint32 u, uint32 v) 
    {
        return (((u & 0x80000000UL) | (v & 0x7FFFFFFFUL)) >> 1)
            ^ ((v & 1UL) ? 0x9908B0DFUL : 0x0UL);
    }
    void gen_state(); // generate new m_nState
    // make copy constructor and assignment operator unavailable, they don't make sense
    CMTRand_int32(const CMTRand_int32&); // copy constructor not defined
    void operator=(const CMTRand_int32&); // assignment operator not defined
};


#endif // CRYINCLUDE_CRYCOMMON_MTPSEUDORANDOM_H