/* random.c - Z-machine random number generator * Copyright (c) 1995-1997 Stefan Jokisch * * This file is part of Frotz. * * Frotz is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * Frotz is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA */ #include "frotz.h" static long A = 1; static int interval = 0; static int counter = 0; /* * seed_random * * Set the seed value for the random number generator. * */ void seed_random (int value) { if (value == 0) { /* ask interface for seed value */ A = os_random_seed (); interval = 0; } else if (value < 1000) { /* special seed value */ counter = 0; interval = value; } else { /* standard seed value */ A = value; interval = 0; } }/* seed_random */ /* * z_random, store a random number or set the random number seed. * * zargs[0] = range (positive) or seed value (negative) * */ void z_random () { if ((short) zargs[0] <= 0) { /* set random seed */ seed_random (- (short) zargs[0]); store (0); } else { /* generate random number */ zword result; if (interval != 0) { /* ...in special mode */ result = counter++; if (counter == interval) counter = 0; } else { /* ...in standard mode */ A = 0x015a4e35L * A + 1; result = (A >> 16) & 0x7fff; } store ((zword) (result % zargs[0] + 1)); } }/* z_random */