generators.hpp

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/*
Copyright (c) 2025 acrion innovations GmbH
Authors: Stefan Zipproth, s.zipproth@acrion.ch
 
This file is part of Cbeam, see https://github.com/acrion/cbeam and https://cbeam.org
 
Cbeam is offered under a commercial and under the AGPL license.
For commercial licensing, contact us at https://acrion.ch/sales. For AGPL licensing, see below.
 
AGPL licensing:
 
Cbeam is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
 
Cbeam 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 Affero General Public License for more details.
 
You should have received a copy of the GNU Affero General Public License
along with Cbeam. If not, see <https://www.gnu.org/licenses/>.
*/
 
#pragma once
 
#include <random> // for std::mt19937, std::random_device, std::uniform_int_distribution
#include <string> // for std::string
 
namespace cbeam::random
{
    inline std::mt19937& default_generator()
    {
        thread_local static std::mt19937 gen{std::random_device{}()};
        return gen;
    }

    inline std::size_t random_number(const std::size_t n, std::mt19937& gen = default_generator())
    {
        std::uniform_int_distribution<std::size_t> dist(0, n - 1);
        return dist(gen);
    }

    inline std::string random_string(std::string::size_type length, std::mt19937& gen = default_generator())
    {
        static auto& chrs = "0123456789"
                            "abcdefghijklmnopqrstuvwxyz"
                            "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
 
        thread_local static std::uniform_int_distribution<std::string::size_type> pick(0, sizeof(chrs) - 2);
 
        std::string s;
 
        s.reserve(length);
 
        while (length--)
        {
            s += chrs[pick(gen)];
        }
 
        return s;
    }
}