find.hpp

Go to the documentation of this file.

/*
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 <cstddef> // for std::size_t
 
#include <map>     // for std::map
#include <variant> // for std::variant, std::get_if, std::variant_alternative_t, std::visit
 
namespace cbeam::container
{
    template <typename Key, typename Value, typename... VariantTypes>
    bool key_exists(const std::map<std::variant<VariantTypes...>, Value>& t, const Key& key)
    {
        for (const auto& pair : t)
        {
            bool exists = std::visit([&key](auto&& lhs) -> bool
                                     {
                                         if constexpr (std::is_same_v<decltype(lhs), Key>)
                                         {
                                             return lhs == key;
                                         }
                                         return false; },
                                     pair.first);
            if (exists)
            {
                return true;
            }
        }
        return false;
    }

    template <typename T, typename... Types>
    T get_value_or_default(const std::variant<Types...>& value) noexcept
    {
        T* ptr = std::get_if<T>(const_cast<std::variant<Types...>*>(&value));
        if (ptr)
        {
            return *ptr;
        }
        else
        {
            return {};
        }
    }

    template <std::size_t T, typename... Types>
    auto get_value_or_default(const std::variant<Types...>& value) noexcept
    {
        using variant_type = std::variant<Types...>;
        using target_type  = std::variant_alternative_t<T, variant_type>;
 
        const target_type* ptr = std::get_if<T>(&value);
        if (ptr)
        {
            return *ptr;
        }
        else
        {
            return target_type{};
        }
    }
}