/* random.cpp * * Micropolis, Unix Version. This game was released for the Unix platform * in or about 1990 and has been modified for inclusion in the One Laptop * Per Child program. Copyright (C) 1989 - 2007 Electronic Arts Inc. If * you need assistance with this program, you may contact: * http://wiki.laptop.org/go/Micropolis or email micropolis@laptop.org. * * This program 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 3 of the License, or (at * your option) any later version. * * This program 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, see . * * ADDITIONAL TERMS per GNU GPL Section 7 * * No trademark or publicity rights are granted. This license does NOT * give you any right, title or interest in the trademark SimCity or any * other Electronic Arts trademark. You may not distribute any * modification of this program using the trademark SimCity or claim any * affliation or association with Electronic Arts Inc. or its employees. * * Any propagation or conveyance of this program must include this * copyright notice and these terms. * * If you convey this program (or any modifications of it) and assume * contractual liability for the program to recipients of it, you agree * to indemnify Electronic Arts for any liability that those contractual * assumptions impose on Electronic Arts. * * You may not misrepresent the origins of this program; modified * versions of the program must be marked as such and not identified as * the original program. * * This disclaimer supplements the one included in the General Public * License. TO THE FULLEST EXTENT PERMISSIBLE UNDER APPLICABLE LAW, THIS * PROGRAM IS PROVIDED TO YOU "AS IS," WITH ALL FAULTS, WITHOUT WARRANTY * OF ANY KIND, AND YOUR USE IS AT YOUR SOLE RISK. THE ENTIRE RISK OF * SATISFACTORY QUALITY AND PERFORMANCE RESIDES WITH YOU. ELECTRONIC ARTS * DISCLAIMS ANY AND ALL EXPRESS, IMPLIED OR STATUTORY WARRANTIES, * INCLUDING IMPLIED WARRANTIES OF MERCHANTABILITY, SATISFACTORY QUALITY, * FITNESS FOR A PARTICULAR PURPOSE, NONINFRINGEMENT OF THIRD PARTY * RIGHTS, AND WARRANTIES (IF ANY) ARISING FROM A COURSE OF DEALING, * USAGE, OR TRADE PRACTICE. ELECTRONIC ARTS DOES NOT WARRANT AGAINST * INTERFERENCE WITH YOUR ENJOYMENT OF THE PROGRAM; THAT THE PROGRAM WILL * MEET YOUR REQUIREMENTS; THAT OPERATION OF THE PROGRAM WILL BE * UNINTERRUPTED OR ERROR-FREE, OR THAT THE PROGRAM WILL BE COMPATIBLE * WITH THIRD PARTY SOFTWARE OR THAT ANY ERRORS IN THE PROGRAM WILL BE * CORRECTED. NO ORAL OR WRITTEN ADVICE PROVIDED BY ELECTRONIC ARTS OR * ANY AUTHORIZED REPRESENTATIVE SHALL CREATE A WARRANTY. SOME * JURISDICTIONS DO NOT ALLOW THE EXCLUSION OF OR LIMITATIONS ON IMPLIED * WARRANTIES OR THE LIMITATIONS ON THE APPLICABLE STATUTORY RIGHTS OF A * CONSUMER, SO SOME OR ALL OF THE ABOVE EXCLUSIONS AND LIMITATIONS MAY * NOT APPLY TO YOU. */ /** * @file random.cpp * @brief Contains functions for generating random numbers in * Micropolis. * * This file includes functions for generating random numbers used in * various aspects of the Micropolis game. It provides functions for * generating random numbers within specific ranges, signed and * unsigned random numbers, and a method to initialize the random * number generator with a random seed. * * @bug Code seems to assume that \c sizeof(short)==2 and \c * sizeof(int)==4 However, this depends on the compiler. We should * introduce typedefs for them, and check correctness of our * assumptions w.r.t. size of them (eg in * Micropolis::randomlySeedRandom() or in Micropolis::Micropolis()). * * @bug Code stores unsigned 16 bit numbers in \c short which is a * signed type. */ //////////////////////////////////////////////////////////////////////// #include "micropolis.h" //////////////////////////////////////////////////////////////////////// /** * Draw a random number (internal function). * @todo Use Wolfram's fast cellular automata pseudo random number generator. * @return Unsigned 16 bit random number. */ int Micropolis::simRandom() { nextRandom = nextRandom * 1103515245 + 12345; return (nextRandom & 0xffff00) >> 8; } /** * Draw a random number in a given range. * @param range Upper bound of the range (inclusive). * @return Random number between \c 0 and \a range (inclusive). */ short Micropolis::getRandom(short range) { int maxMultiple, rnum; range++; /// @bug Increment may cause range overflow. maxMultiple = 0xffff / range; maxMultiple *= range; do { rnum = getRandom16(); } while (rnum >= maxMultiple); return (rnum % range); } /** * Get random 16 bit number. * @return Unsigned 16 bit random number. */ int Micropolis::getRandom16() { return simRandom() & 0x0000ffff; } /** Get signed 16 bit random number. */ int Micropolis::getRandom16Signed() { int i = getRandom16(); if (i > 0x7fff) { i = 0x7fff - i; } return i; } /** * Get a random number within a given range, with a preference to smaller * values. * @param limit Upper bound of the range (inclusive). * @return Random number between \c 0 and \a limit (inclusive). */ short Micropolis::getERandom(short limit) { short z = getRandom(limit); short x = getRandom(limit); return min(z, x); } /** Initialize the random number generator with a 'random' seed. */ void Micropolis::randomlySeedRandom() { struct timeval time; gettimeofday(&time, NULL); seedRandom(time.tv_usec ^ time.tv_sec); } /** * Set seed of the random number generator. * @param seed New seed. */ void Micropolis::seedRandom(int seed) { nextRandom = seed; } ////////////////////////////////////////////////////////////////////////