/*****************************************************************************
 * Copyright (c) 1998, 1999, Robert Klapper. All Rights Reserved.
 *----------------------------------------------------------------------------
 *****************************************************************************/

#include "sd_rand.h"

const unsigned long int sd_RandomGenerator::DefaultSeed = 1618033987;

void sd_RandomGenerator::seed(unsigned long int j){
    unsigned long int k;
    unsigned short int i, ii;
    
    rtable_[55] = j;
    k = 1;
    for(i = 1; i <= 54; i++){
        ii = (21*i)%55;
        rtable_[ii] = k;
        k = j - k;
        j = rtable_[ii];
    }
    for(i = 0; i <= 3; i++){
        for(ii = 1; ii <= 55; ii++){
            rtable_[ii] = rtable_[ii] - ((ii < 25) ? rtable_[ii+31] : rtable_[ii-24]);
        }
    }
    idx_ = 0;
}

unsigned long int sd_RandomGenerator::operator()(unsigned long int j){
    if(++idx_ > 55){
        idx_ = 1;
    }
    rtable_[idx_] = rtable_[idx_] - ((idx_ < 25) ? rtable_[idx_+31] : rtable_[idx_-24]);
    return rtable_[idx_]%j;
}