util.hpp

/*
 * live_cells_cpp
 * Copyright (C) 2024  Alexander Gutev <alex.gutev@gmail.com>
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you
 * may not use this file except in compliance with the License.  You
 * may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied.  See the License for the specific language governing
 * permissions and limitations under the License.
 */
 
#ifndef LIVE_CELLS_UTIL_HPP
#define LIVE_CELLS_UTIL_HPP
 
#include <tuple>
#include <utility>
 
namespace live_cells {
 
    namespace internal {
 
        inline std::size_t hash_combine(std::size_t seed) {
            return seed;
        }
 
        template <typename T, typename... Rest>
        std::size_t hash_combine(std::size_t seed, const T& v, const Rest&... rest)
        {
            seed ^= std::hash<T>{}(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
            return hash_combine(seed, rest...);
        }
 
        template <typename... Ts>
        struct count_args {
        };
 
        template <typename T, typename... Ts>
        struct count_args<T, Ts...> {
            static constexpr size_t size = 1 + count_args<Ts...>::size;
        };
 
        template <>
        struct count_args<> {
            static constexpr size_t size = 0;
        };
 
        template <size_t S, typename... Ts>
        struct is_size {
            static constexpr bool value = S == count_args<Ts...>::size;
        };
 
        template <size_t S, typename... Ts>
        struct is_at_least {
            static constexpr bool value = count_args<Ts...>::size >= S;
        };
 
        template <size_t S, bool enable, typename... As>
        struct packer {
        };
 
        template <size_t S, typename A, typename... As>
        struct packer<S, false, A, As...> {
            template <typename Tuple>
            static auto pack(const Tuple &packed, const A &arg, const As&... args) {
                return packer<S, is_size<S, As...>::value, As...>::pack(std::tuple_cat(packed, std::make_tuple(arg)), args...);
            }
        };
 
        template <size_t S, typename... As>
        struct packer<S, true, As...> {
            template <typename Tuple>
            static auto pack(const Tuple &packed, const As&... args) {
                return std::make_tuple(packed, args...);
            }
        };
 
        template <size_t S, typename... As>
        auto pack(const As&... args) {
            static_assert(is_at_least<S, As...>::value, "Not enough arguments provided to pack()");
 
            return packer<S, is_size<S, As...>::value, As...>::pack(std::make_tuple(), args...);
        }
 
        template <typename F, typename Tuple, std::size_t... I>
        auto unpack(const F &fn, const Tuple &args, std::index_sequence<I...>) {
            return fn(std::get<I>(args)...);
        }
 
        template <typename F, typename Tuple>
        auto unpack(const F &fn, const Tuple &args) {
            constexpr auto size = std::tuple_size<Tuple>::value;
            return unpack(fn, args, std::make_index_sequence<size>());
        }
 
    }  // internal
 
}  // live_cells
 
#endif /* LIVE_CELLS_UTIL_HPP */