Boost C++ Libraries

boost/pfr/detail/functional.hpp

// Copyright (c) 2016-2024 Antony Polukhin
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

#ifndef BOOST_PFR_DETAIL_FUNCTIONAL_HPP
#define BOOST_PFR_DETAIL_FUNCTIONAL_HPP
#pragma once

#include <boost/pfr/detail/config.hpp>

#include <functional>
#include <cstdint>

#include <boost/pfr/detail/sequence_tuple.hpp>

namespace boost { namespace pfr { namespace detail {
    template <std::size_t I, std::size_t N>
    struct equal_impl {
        template <class T, class U>
        constexpr static bool cmp(const T& v1, const U& v2) noexcept {
            return ::boost::pfr::detail::sequence_tuple::get<I>(v1) == ::boost::pfr::detail::sequence_tuple::get<I>(v2)
                && equal_impl<I + 1, N>::cmp(v1, v2);
        }
    };

    template <std::size_t N>
    struct equal_impl<N, N> {
        template <class T, class U>
        constexpr static bool cmp(const T&, const U&) noexcept {
            return T::size_v == U::size_v;
        }
    };

    template <std::size_t I, std::size_t N>
    struct not_equal_impl {
        template <class T, class U>
        constexpr static bool cmp(const T& v1, const U& v2) noexcept {
            return ::boost::pfr::detail::sequence_tuple::get<I>(v1) != ::boost::pfr::detail::sequence_tuple::get<I>(v2)
                || not_equal_impl<I + 1, N>::cmp(v1, v2);
        }
    };

    template <std::size_t N>
    struct not_equal_impl<N, N> {
        template <class T, class U>
        constexpr static bool cmp(const T&, const U&) noexcept {
            return T::size_v != U::size_v;
        }
    };

    template <std::size_t I, std::size_t N>
    struct less_impl {
        template <class T, class U>
        constexpr static bool cmp(const T& v1, const U& v2) noexcept {
            return sequence_tuple::get<I>(v1) < sequence_tuple::get<I>(v2)
                || (sequence_tuple::get<I>(v1) == sequence_tuple::get<I>(v2) && less_impl<I + 1, N>::cmp(v1, v2));
        }
    };

    template <std::size_t N>
    struct less_impl<N, N> {
        template <class T, class U>
        constexpr static bool cmp(const T&, const U&) noexcept {
            return T::size_v < U::size_v;
        }
    };

    template <std::size_t I, std::size_t N>
    struct less_equal_impl {
        template <class T, class U>
        constexpr static bool cmp(const T& v1, const U& v2) noexcept {
            return sequence_tuple::get<I>(v1) < sequence_tuple::get<I>(v2)
                || (sequence_tuple::get<I>(v1) == sequence_tuple::get<I>(v2) && less_equal_impl<I + 1, N>::cmp(v1, v2));
        }
    };

    template <std::size_t N>
    struct less_equal_impl<N, N> {
        template <class T, class U>
        constexpr static bool cmp(const T&, const U&) noexcept {
            return T::size_v <= U::size_v;
        }
    };

    template <std::size_t I, std::size_t N>
    struct greater_impl {
        template <class T, class U>
        constexpr static bool cmp(const T& v1, const U& v2) noexcept {
            return sequence_tuple::get<I>(v1) > sequence_tuple::get<I>(v2)
                || (sequence_tuple::get<I>(v1) == sequence_tuple::get<I>(v2) && greater_impl<I + 1, N>::cmp(v1, v2));
        }
    };

    template <std::size_t N>
    struct greater_impl<N, N> {
        template <class T, class U>
        constexpr static bool cmp(const T&, const U&) noexcept {
            return T::size_v > U::size_v;
        }
    };

    template <std::size_t I, std::size_t N>
    struct greater_equal_impl {
        template <class T, class U>
        constexpr static bool cmp(const T& v1, const U& v2) noexcept {
            return sequence_tuple::get<I>(v1) > sequence_tuple::get<I>(v2)
                || (sequence_tuple::get<I>(v1) == sequence_tuple::get<I>(v2) && greater_equal_impl<I + 1, N>::cmp(v1, v2));
        }
    };

    template <std::size_t N>
    struct greater_equal_impl<N, N> {
        template <class T, class U>
        constexpr static bool cmp(const T&, const U&) noexcept {
            return T::size_v >= U::size_v;
        }
    };

    // Hash combine functions copied from Boost.ContainerHash
    // https://github.com/boostorg/container_hash/blob/171c012d4723c5e93cc7cffe42919afdf8b27dfa/include/boost/container_hash/hash.hpp#L311
    // that is based on Peter Dimov's proposal
    // http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2005/n1756.pdf
    // issue 6.18.
    //
    // This also contains public domain code from MurmurHash. From the
    // MurmurHash header:
    //
    // MurmurHash3 was written by Austin Appleby, and is placed in the public
    // domain. The author hereby disclaims copyright to this source code.
    template <typename SizeT>
    constexpr void hash_combine(SizeT& seed, SizeT value) noexcept {
        seed ^= value + 0x9e3779b9 + (seed<<6) + (seed>>2);
    }

    constexpr auto rotl(std::uint32_t x, std::uint32_t r) noexcept {
        return (x << r) | (x >> (32 - r));
    }

    constexpr void hash_combine(std::uint32_t& h1, std::uint32_t k1) noexcept {
          const std::uint32_t c1 = 0xcc9e2d51;
          const std::uint32_t c2 = 0x1b873593;

          k1 *= c1;
          k1 = detail::rotl(k1,15);
          k1 *= c2;

          h1 ^= k1;
          h1 = detail::rotl(h1,13);
          h1 = h1*5+0xe6546b64;
    }

#if defined(INT64_MIN) && defined(UINT64_MAX)
    constexpr void hash_combine(std::uint64_t& h, std::uint64_t k) noexcept {
        const std::uint64_t m = 0xc6a4a7935bd1e995ULL;
        const int r = 47;

        k *= m;
        k ^= k >> r;
        k *= m;

        h ^= k;
        h *= m;

        // Completely arbitrary number, to prevent 0's
        // from hashing to 0.
        h += 0xe6546b64;
    }
#endif

    template <typename T>
    auto compute_hash(const T& value, long /*priority*/)
        -> decltype(std::hash<T>()(value))
    {
        return std::hash<T>()(value);
    }

    template <typename T>
    std::size_t compute_hash(const T& /*value*/, int /*priority*/) {
        static_assert(sizeof(T) && false, "====================> Boost.PFR: std::hash not specialized for type T");
        return 0;
    }

    template <std::size_t I, std::size_t N>
    struct hash_impl {
        template <class T>
        constexpr static std::size_t compute(const T& val) noexcept {
            std::size_t h = detail::compute_hash( ::boost::pfr::detail::sequence_tuple::get<I>(val), 1L );
            detail::hash_combine(h, hash_impl<I + 1, N>::compute(val) );
            return h;
        }
    };

    template <std::size_t N>
    struct hash_impl<N, N> {
        template <class T>
        constexpr static std::size_t compute(const T&) noexcept {
            return 0;
        }
    };

///////////////////// Define min_element and to avoid inclusion of <algorithm>
    constexpr std::size_t min_size(std::size_t x, std::size_t y) noexcept {
        return x < y ? x : y;
    }

    template <template <std::size_t, std::size_t> class Visitor, class T, class U>
    constexpr bool binary_visit(const T& x, const U& y) {
        constexpr std::size_t fields_count_lhs = detail::fields_count<std::remove_reference_t<T>>();
        constexpr std::size_t fields_count_rhs = detail::fields_count<std::remove_reference_t<U>>();
        constexpr std::size_t fields_count_min = detail::min_size(fields_count_lhs, fields_count_rhs);
        typedef Visitor<0, fields_count_min> visitor_t;

#if BOOST_PFR_USE_CPP17 || BOOST_PFR_USE_LOOPHOLE
        return visitor_t::cmp(detail::tie_as_tuple(x), detail::tie_as_tuple(y));
#else
        bool result = true;
        ::boost::pfr::detail::for_each_field_dispatcher(
            x,
            [&result, &y](const auto& lhs) {
                constexpr std::size_t fields_count_rhs_ = detail::fields_count<std::remove_reference_t<U>>();
                ::boost::pfr::detail::for_each_field_dispatcher(
                    y,
                    [&result, &lhs](const auto& rhs) {
                        result = visitor_t::cmp(lhs, rhs);
                    },
                    detail::make_index_sequence<fields_count_rhs_>{}
                );
            },
            detail::make_index_sequence<fields_count_lhs>{}
        );

        return result;
#endif
    }

}}} // namespace boost::pfr::detail

#endif // BOOST_PFR_DETAIL_FUNCTIONAL_HPP