/*Copyright (c) 2004 Nils O. Selåsdal <NOS {on} Utel {dot} no> */
/*Straight forward attempt at a Mersenne Twister PRNG */

#include "ucore/mersenne_twister.h"


/*Beware , pollution. But the names are from the spec */
enum {
    N =  MT_RAND_N,
    w =  32,
    M =  387,
    R =  19,
    U =  0x80000000,
    LL=  0x7FFFFFFF,
    a =  0x9908B0DF,
    s =  7,
    t =  15,
    b =  0x9D2C5680,
    c =  0xEFC60000,
    l =  18,
    u =  11,
};


void mtsrand(int seed, MTRand *r)
{
    int j;
    for (j = 0 ; j < N ; j++) {
        r->x[j] = seed * ((j+1)<< 3)|0x1;
    }
    r->i = 0;

}

unsigned int mtrand(MTRand *r)
{
    unsigned int y;
    unsigned int ch[] = {0, a};
    
    y = r->x[r->i] & U;
    y |= r->x[r->i % N];
    y &= LL;
    
    r->x[r->i] = r->x[(r->i + M ) %N];
    r->x[r->i] ^= y >> 1;

    r->x[r->i] ^= ch[y&0x1];
    
    y = r->x[r->i];
    y ^= y >> u;
    y ^= (y << s) & b;
    y ^= (y << t) & c;
    y ^= y >> l;

    r->i = (r->i + 1) % N;

    return y;
}   
#ifdef TEST_MT
#include <stdio.h>
#include <time.h>
int main(int argc,char *argv[])
{
    MTRand r;
    mtsrand(time(NULL),&r);
    for (;;){
        unsigned int _y = mtrand(&r);

        if (_y < 100)
        printf("%u \n",_y);
    }

    return 0;
}

#endif