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/* ScummVM - Graphic Adventure Engine
*
* ScummVM is the legal property of its developers, whose names
* are too numerous to list here. Please refer to the COPYRIGHT
* file distributed with this source distribution.
*
* 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 <http://www.gnu.org/licenses/>.
*
*/
#include "common/random.h"
#include "common/system.h"
#include "common/config-manager.h"
#include "gui/EventRecorder.h"
namespace Common {
RandomSource::RandomSource(const String &name) {
// Use system time as RNG seed. Normally not a good idea, if you are using
// a RNG for security purposes, but good enough for our purposes.
assert(g_system);
#ifdef ENABLE_EVENTRECORDER
setSeed(g_eventRec.getRandomSeed(name));
#else
setSeed(generateNewSeed());
#endif
}
uint32 RandomSource::generateNewSeed() {
if (ConfMan.hasKey("random_seed"))
return ConfMan.getInt("random_seed");
TimeDate time;
g_system->getTimeAndDate(time);
uint32 newSeed = time.tm_sec + time.tm_min * 60U + time.tm_hour * 3600U;
newSeed += time.tm_mday * 86400U + time.tm_mon * 86400U * 31U;
newSeed += time.tm_year * 86400U * 366U;
newSeed = newSeed * 1000U + g_system->getMillis();
return newSeed;
}
void RandomSource::setSeed(uint32 seed) {
if (seed == 0)
seed++;
_randSeed = seed;
}
uint RandomSource::getRandomNumber(uint max) {
scrambleSeed();
if (max == UINT_MAX)
return (_randSeed * 0xDEADBF03);
return (_randSeed * 0xDEADBF03) % (max + 1);
}
uint RandomSource::getRandomBit() {
scrambleSeed();
return _randSeed & 1;
}
uint RandomSource::getRandomNumberRng(uint min, uint max) {
return getRandomNumber(max - min) + min;
}
int RandomSource::getRandomNumberRngSigned(int min, int max) {
return getRandomNumber(max - min) + min;
}
inline void RandomSource::scrambleSeed() {
//marsaglia's paper says that any of 81 triplets are feasible
//(11,21,13) was chosen, with (cba) and (>>,<<,>>)
_randSeed ^= _randSeed >> 13;
_randSeed ^= _randSeed << 21;
_randSeed ^= _randSeed >> 11;
}
} // End of namespace Common
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