mt.c

static unsigned long x[624];
static int           n;
void seed(unsigned long s) {
    x[0] = s & 0xFFFFFFFFUL;
    for (n=1;n<624;n++){x[n]=(1812433253UL*(x[n-1]^(x[n-1]>>30))+n);}n=0;
}
unsigned long rand() {
    unsigned long y[2];
    if (n==624) {
        for (n = 0; n < 624 - 1; n++)
        *y=(x[n]  &0x80000000UL)|x[n+1]&0x7FFFFFFFUL,y[1]=(*y&0x1UL)?0x9908B0DFUL:0x0UL,x[n]  =x[(n+397)%624]^(*y>>1)^a;
        *y=(x[623]&0x80000000UL)|x[0]  &0x7FFFFFFFUL,y[1]=(*y&0x1UL)?0x9908B0DFUL:0x0UL,x[623]=x[396]        ^(*y>>1)^y[1],n=0;
    }
    *y=x[n++],*y^=(*y>>11),*y^=(*y<<7)&0x9D2C5680UL,*y^=(*y<<15)&0xEFC60000UL,*y=(*y>>18);
}