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random.cpp

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00001 /* ScummVM - Graphic Adventure Engine
00002  *
00003  * ScummVM is the legal property of its developers, whose names
00004  * are too numerous to list here. Please refer to the COPYRIGHT
00005  * file distributed with this source distribution.
00006  *
00007  * This program is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU General Public License
00009  * as published by the Free Software Foundation; either version 2
00010  * of the License, or (at your option) any later version.
00011  *
00012  * This program is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00015  * GNU General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU General Public License
00018  * along with this program; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
00020  *
00021  */
00022 
00023 #include "common/random.h"
00024 #include "common/system.h"
00025 #include "gui/EventRecorder.h"
00026 
00027 
00028 namespace Common {
00029 
00030 RandomSource::RandomSource(const String &name) {
00031     // Use system time as RNG seed. Normally not a good idea, if you are using
00032     // a RNG for security purposes, but good enough for our purposes.
00033     assert(g_system);
00034 
00035 #ifdef ENABLE_EVENTRECORDER
00036     setSeed(g_eventRec.getRandomSeed(name));
00037 #else
00038     setSeed(g_system->getMillis());
00039 #endif
00040 }
00041 
00042 void RandomSource::setSeed(uint32 seed) {
00043     _randSeed = seed;
00044 }
00045 
00046 uint RandomSource::getRandomNumber(uint max) {
00047     _randSeed = 0xDEADBF03 * (_randSeed + 1);
00048     _randSeed = (_randSeed >> 13) | (_randSeed << 19);
00049     return _randSeed % (max + 1);
00050 }
00051 
00052 uint RandomSource::getRandomBit() {
00053     _randSeed = 0xDEADBF03 * (_randSeed + 1);
00054     _randSeed = (_randSeed >> 13) | (_randSeed << 19);
00055     return _randSeed & 1;
00056 }
00057 
00058 uint RandomSource::getRandomNumberRng(uint min, uint max) {
00059     return getRandomNumber(max - min) + min;
00060 }
00061 
00062 } // End of namespace Common


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