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/*
* CRandomGenerator.h, part of VCMI engine
*
* Authors: listed in file AUTHORS in main folder
*
* License: GNU General Public License v2.0 or later
* Full text of license available in license.txt file, in main folder
*
*/
#pragma once
#include <vstd/RNG.h>
#include "serializer/Serializeable.h"
VCMI_LIB_NAMESPACE_BEGIN
/// Generator to use for all randomization in game
/// minstd_rand is selected due to following reasons:
/// 1. Its randomization quality is below mt_19937 however this is unlikely to be noticeable in game
/// 2. It has very low state size, leading to low overhead in size of saved games (due to large number of random generator instances in game)
using TGenerator = std::minstd_rand;
using TIntDist = std::uniform_int_distribution<int>;
using TInt64Dist = std::uniform_int_distribution<int64_t>;
using TRealDist = std::uniform_real_distribution<double>;
/// The random generator randomly generates integers and real numbers("doubles") between
/// a given range. This is a header only class and mainly a wrapper for
/// convenient usage of the standard random API. An instance of this RNG is not thread safe.
class DLL_LINKAGE CRandomGenerator final : public vstd::RNG, boost::noncopyable, public Serializeable
{
public:
/// Seeds the generator by default with the product of the current time in milliseconds and the
/// current thread ID.
CRandomGenerator();
/// Seeds the generator with provided initial seed
explicit CRandomGenerator(int seed);
void setSeed(int seed);
/// Resets the seed to the product of the current time in milliseconds and the
/// current thread ID.
void resetSeed();
/// Generates an integer between 0 and upper.
/// requires: 0 <= upper
int nextInt(int upper) override;
int64_t nextInt64(int64_t upper) override;
/// requires: lower <= upper
int nextInt(int lower, int upper) override;
int64_t nextInt64(int64_t lower, int64_t upper) override;
/// Generates an integer between 0 and the maximum value it can hold.
int nextInt() override;
///
int nextBinomialInt(int coinsCount, double coinChance) override;
/// Generates a double between 0 and upper.
/// requires: 0 <= upper
double nextDouble(double upper) override;
/// requires: lower <= upper
double nextDouble(double lower, double upper) override;
/// Gets a globally accessible RNG which will be constructed once per thread. For the
/// seed a combination of the thread ID and current time in milliseconds will be used.
static CRandomGenerator & getDefault();
private:
TGenerator rand;
public:
template <typename Handler>
void serialize(Handler & h)
{
if(h.saving)
{
std::ostringstream stream;
stream << rand;
std::string str = stream.str();
h & str;
}
else
{
std::string str;
h & str;
std::istringstream stream(str);
stream >> rand;
}
}
};
VCMI_LIB_NAMESPACE_END
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