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https://github.com/libretro/scummvm.git
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91 lines
2.5 KiB
C++
91 lines
2.5 KiB
C++
/* ScummVM - Graphic Adventure Engine
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*
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* ScummVM is the legal property of its developers, whose names
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* are too numerous to list here. Please refer to the COPYRIGHT
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* file distributed with this source distribution.
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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*/
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#include "common/random.h"
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#include "common/system.h"
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#include "common/config-manager.h"
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#include "gui/EventRecorder.h"
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namespace Common {
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RandomSource::RandomSource(const String &name) {
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// Use system time as RNG seed. Normally not a good idea, if you are using
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// a RNG for security purposes, but good enough for our purposes.
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assert(g_system);
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#ifdef ENABLE_EVENTRECORDER
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setSeed(g_eventRec.getRandomSeed(name));
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#else
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setSeed(generateNewSeed());
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#endif
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}
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uint32 RandomSource::generateNewSeed() {
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if (ConfMan.hasKey("random_seed"))
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return ConfMan.getInt("random_seed");
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TimeDate time;
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g_system->getTimeAndDate(time);
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uint32 newSeed = time.tm_sec + time.tm_min * 60U + time.tm_hour * 3600U;
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newSeed += time.tm_mday * 86400U + time.tm_mon * 86400U * 31U;
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newSeed += time.tm_year * 86400U * 366U;
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newSeed = newSeed * 1000U + g_system->getMillis();
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return newSeed;
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}
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void RandomSource::setSeed(uint32 seed) {
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if (seed == 0)
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seed++;
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_randSeed = seed;
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}
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uint RandomSource::getRandomNumber(uint max) {
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scrambleSeed();
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if (max == UINT_MAX)
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return (_randSeed * 0xDEADBF03);
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return (_randSeed * 0xDEADBF03) % (max + 1);
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}
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uint RandomSource::getRandomBit() {
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scrambleSeed();
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return _randSeed & 1;
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}
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uint RandomSource::getRandomNumberRng(uint min, uint max) {
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return getRandomNumber(max - min) + min;
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}
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int RandomSource::getRandomNumberRngSigned(int min, int max) {
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return getRandomNumber(max - min) + min;
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}
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inline void RandomSource::scrambleSeed() {
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//marsaglia's paper says that any of 81 triplets are feasible
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//(11,21,13) was chosen, with (cba) and (>>,<<,>>)
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_randSeed ^= _randSeed >> 13;
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_randSeed ^= _randSeed << 21;
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_randSeed ^= _randSeed >> 11;
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}
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} // End of namespace Common
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