CWE-ou-minkata/Sources/Plasma/NucleusLib/pnUtils/Private/pnUtRand.cpp

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*==LICENSE==*/
/*****************************************************************************
*
*   $/Plasma20/Sources/Plasma/NucleusLib/pnUtils/Private/pnUtRand.cpp
*   
***/

#include "../Pch.h"
#pragma hdrstop


/*****************************************************************************
*
*   Private
*
***/

class RandomContext {
    dword m_seed;
    dword m_value;

    void UpdateValue ();

public:
    RandomContext ();

    void     Reset ();
    void     SetSeed (unsigned seed);
    float    GetFloat ();
    float    GetFloat (float minVal, float maxVal);
    unsigned GetUnsigned ();
    unsigned GetUnsigned (unsigned minVal, unsigned maxVal);
};


/*****************************************************************************
*
*   Private data
*
***/

static const dword kDefaultRandomSeed = 0x075bd924;

static RandomContext s_random;


/*****************************************************************************
*
*   RandomContext
*
***/

//============================================================================
RandomContext::RandomContext () 
:   m_seed(kDefaultRandomSeed)
{
    Reset();
}

//============================================================================
void RandomContext::UpdateValue () {
    const dword A = 0xbc8f;
    const dword Q = 0xadc8;
    const dword R = 0x0d47;

    dword div = m_value / Q;
    m_value   = A * (m_value - Q * div) - R * div;
    if (m_value > kRandomMax)
        m_value -= kRandomMax + 1;
    if (!m_value)
        m_value = kDefaultRandomSeed;
}

//============================================================================
void RandomContext::Reset () {
    m_value = m_seed;
}

//============================================================================
void RandomContext::SetSeed (unsigned seed) {
    // Never allow a seed of zero
    m_seed = seed ? seed : kDefaultRandomSeed;
    Reset();
}

//============================================================================
float RandomContext::GetFloat () {
    UpdateValue();
    return m_value * (1.0f / kRandomMax);
}

//============================================================================
float RandomContext::GetFloat (float minVal, float maxVal) {
    float value = GetFloat();
    return minVal + value * (maxVal - minVal);
}

//============================================================================
unsigned RandomContext::GetUnsigned () {
    UpdateValue();
    return (unsigned)m_value;
}

//============================================================================
unsigned RandomContext::GetUnsigned (unsigned minVal, unsigned maxVal) {
    unsigned value = GetUnsigned();
    return minVal + value % (maxVal - minVal + 1);
}


/*****************************************************************************
*
*   Exports
*
***/

//============================================================================
void RandReset () {
    s_random.Reset();
}

//============================================================================
void RandSetSeed (unsigned seed) {
    s_random.SetSeed(seed);
}

//============================================================================
float RandFloat () {
    return s_random.GetFloat();
}

//============================================================================
float RandFloat (float minVal, float maxVal) {
    return s_random.GetFloat(minVal, maxVal);
}

//============================================================================
unsigned RandUnsigned () {
    return s_random.GetUnsigned();
}

//============================================================================
unsigned RandUnsigned (unsigned minVal, unsigned maxVal) {
    return s_random.GetUnsigned(minVal, maxVal);
}