CWE-ou-minkata/Sources/Plasma/PubUtilLib/plMath/plRandom.h

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*==LICENSE==*/

#ifndef plRandom_inc
#define plRandom_inc

// FAST_Q is basically lifted from Numerical Recipes.
// The RandZeroToOne and RandMinusOneToOne were "enhanced"
// a bit, but tested out nicely to generate sequences with
// appropriate maxs, mins, and means.
// FAST_Q depends on IEEE floating point format. Undefine
// it for any platform which doesn't satisfy this, or
// come up with the appropriate constants for that platform.
#define FAST_Q


class plRandom
{
protected:
    mutable uint32_t      fSeed;
public:
    inline float        RandNorm() const;
    inline int          Rand() const;
    inline int          RandRangeI(int lo, int hi) const;
    inline float        RandRangeF(float lo, float hi) const;
    inline float        RandMinusOneToOne() const;
    inline float        RandZeroToOne() const;

    uint32_t              GetSeed() const { return fSeed; }
    void                SetSeed(int seed) { fSeed = seed; }

    plRandom(int seed = 1) : fSeed(seed) {}
};

inline float plRandom::RandNorm() const
{ 
#ifndef FAST_Q
    return 1.f / 32767.f; 
#else // FAST_Q
    return (1.f / float(~0UL));
#endif // FAST_Q
} 

inline int plRandom::Rand() const
{
#ifndef FAST_Q
    register int temp;
    fSeed = fSeed * 1103515245 + 12345;
    temp = (int)((fSeed/65536)&32767);
    return (temp);
#else // FAST_Q
    return fSeed = 1664525L * fSeed + 1013904223L;
#endif // FAST_Q
}

// RandZeroToOne - take our usual random uint32_t.
// We're going to mask in an exponent to make it
// a float in range [1..2). Then subtract 1.f to
// make it [0..1). We shift our random uint32_t down
// by 9 because the upper bits are the most random.
inline float plRandom::RandZeroToOne() const
{
#ifndef FAST_Q
    return Rand() * RandNorm();
#else // FAST_Q
    const uint32_t kOneExp = 0x3f800000;
    uint32_t temp = kOneExp | (uint32_t(Rand()) >> 9);
    return (*(float*)&temp) - 1.f;
#endif // FAST_Q
}

// RandMinusOneToOne - same as RandZeroToOne, but we
// mask in an exponent putting it in range [2..4), 
// then subtract 3 to give [-1..1).
inline float plRandom::RandMinusOneToOne() const
{
#ifndef FAST_Q
    return RandZeroToOne() * 2.f - 1.f;
#else // FAST_Q
    const uint32_t kTwoExp = 0x40000000;
    uint32_t temp = kTwoExp | (uint32_t(Rand()) >> 9);
    return (*(float*)&temp) - 3.f;
#endif // FAST_Q
}

inline float plRandom::RandRangeF(float lo, float hi) const
{
    return lo + RandZeroToOne() * (hi - lo);
}

inline int plRandom::RandRangeI(int lo, int hi) const
{
    return lo + int(RandZeroToOne() * float(hi + 1 - lo));
}


#endif // plRandom_inc