RandomNumberGenerator.hpp

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// This file is part of INSTINCT, the INS Toolkit for Integrated
// Navigation Concepts and Training by the Institute of Navigation of
// the University of Stuttgart, Germany.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at https://mozilla.org/MPL/2.0/.
 
 
#pragma once
 
#include <random>
#include <string>
 
#include <nlohmann/json.hpp>
using json = nlohmann::json; 
 
#include "SHA256.hpp"
 
namespace NAV
{
 
class RandomNumberGenerator
{
  public:
    explicit RandomNumberGenerator(bool useSeed = true) : useSeed(useSeed) {} // NOLINT(cert-msc32-c,cert-msc51-cpp)
    RandomNumberGenerator(const RandomNumberGenerator&) = delete;
    RandomNumberGenerator(RandomNumberGenerator&&) = delete;
    RandomNumberGenerator& operator=(const RandomNumberGenerator&) = delete;
    RandomNumberGenerator& operator=(RandomNumberGenerator&&) = delete;
    ~RandomNumberGenerator() = default;
 
    void resetSeed(size_t id = 0)
    {
        uint64_t seed = useSeed ? this->seed : static_cast<uint64_t>(std::chrono::system_clock::now().time_since_epoch().count());
        auto hash = hashSeed(std::to_string(seed) + (useSeed || id == 0 ? "" : " " + std::to_string(id)));
        std::seed_seq seed_seq(hash.begin(), hash.end());
        _generator.seed(seed_seq);
    }
 
    void resetSeedOnce(uint64_t userSeed)
    {
        auto hash = hashSeed(std::to_string(userSeed));
        std::seed_seq seed_seq(hash.begin(), hash.end());
        _generator.seed(seed_seq);
    }
 
    template<typename IntType = int>
    double getRand_uniformIntDist(IntType min = 0, IntType max = std::numeric_limits<IntType>::max())
    {
        return std::uniform_int_distribution<IntType>(min, max)(_generator);
    }
 
    template<typename RealType = double>
    double getRand_uniformRealDist(RealType min = 0.0, RealType max = 1.0)
    {
        return std::uniform_real_distribution<RealType>(min, max)(_generator);
    }
 
    template<typename RealType = double>
    double getRand_normalDist(RealType mean = 0.0, RealType stddev = 1.0)
    {
        return std::normal_distribution<RealType>(mean, stddev)(_generator);
    }
 
    bool useSeed = true; 
    uint64_t seed = 0;   
 
  private:
    static std::string hashSeed(const std::string& seed)
    {
        SHA256 sha;
        sha.update(seed);
        uint8_t* digest = sha.digest();
 
        std::string hashed(digest, digest + 32); // NOLINT //SHA256::ToString method is shady... (manipulates data?). Keep Pointer Arithmetic
        delete[] digest;                         // NOLINT
 
        return hashed;
    }
 
    std::mt19937_64 _generator; 
};
 
void to_json(json& j, const RandomNumberGenerator& rng);
void from_json(const json& j, RandomNumberGenerator& rng);
 
} // namespace NAV