quick_rng.h

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/* === S Y N F I G ========================================================= */
/* ========================================================================= */

/* === S T A R T =========================================================== */

#ifndef __SYNFIG_QUICK_RNG_H
#define __SYNFIG_QUICK_RNG_H

/* === H E A D E R S ======================================================= */

#include <stdint.h>

/* === M A C R O S ========================================================= */

/* === T Y P E D E F S ===================================================== */

/* === C L A S S E S & S T R U C T S ======================================= */

// A fast 32-bit linear congruential random number generator
class quick_rng
{
    uint32_t next;
public:
    quick_rng(uint32_t seed=0):next(seed) { }

    void set_seed(uint32_t x)
    {
        next=x;
    }

    uint32_t i32()
    {
        static const uint32_t a(1664525);
        static const uint32_t c(1013904223);

        return next=next*a+c;
    }

    uint32_t i16()
    {
        return i32()>>16;
    }

    float f()
    {
        static const float m(int(65535));

        return float(i16())/m;
    }

    uint32_t operator()(const uint32_t& m)
    {
        if(m==65536)
            return i16();
        else
        if(m<=65536)
            return i16()%m;
        else
            return i32()%m;
    }
};

/* === E N D =============================================================== */

#endif