DiceHashPolicies.hpp

#ifndef DICE_HASH_DICEHASHPOLICIES_HPP
#define DICE_HASH_DICEHASHPOLICIES_HPP
 
#include "martinus_robinhood_hash.hpp"
#include "wyhash.h"
#ifdef __x86_64__
#include "xxhash.hpp"
#endif
#include <type_traits>
 
namespace dice::hash::Policies {
    template<typename T>
    concept HashPolicy =
    std::is_convertible_v<decltype(T::ErrorValue), std::size_t>
    &&std::is_nothrow_invocable_r_v<std::size_t, decltype(T::template hash_fundamental<int>), int>
    &&std::is_nothrow_invocable_r_v<std::size_t, decltype(T::template hash_fundamental<long>), long>
    &&std::is_nothrow_invocable_r_v<std::size_t, decltype(T::template hash_fundamental<std::size_t>), std::size_t>
    &&std::is_nothrow_invocable_r_v<std::size_t, decltype(T::hash_bytes), void const *, std::size_t>
    &&std::is_nothrow_invocable_r_v<std::size_t, decltype(T::hash_combine), std::initializer_list<std::size_t>>
    &&std::is_nothrow_invocable_r_v<std::size_t, decltype(T::hash_invertible_combine), std::initializer_list<std::size_t>>
    &&std::is_nothrow_constructible_v<typename T::HashState, std::size_t>
    &&std::is_nothrow_invocable_r_v<void, decltype(&T::HashState::add), typename T::HashState &, std::size_t>
    &&std::is_nothrow_invocable_r_v<std::size_t, decltype(&T::HashState::digest), typename T::HashState &>;
 
    struct wyhash {
        inline static constexpr uint64_t kSeed = 0xe17a1465UL;
        inline static constexpr uint64_t kWyhashSalt[4] = {
                dice::hash::wyhash::_wyp[0],
                dice::hash::wyhash::_wyp[1],
                dice::hash::wyhash::_wyp[2],
                dice::hash::wyhash::_wyp[3]
        };
        inline static constexpr std::size_t ErrorValue = kSeed;
 
        template<typename T>
        static std::size_t hash_fundamental(T x) noexcept {
            if constexpr (std::is_integral_v<T>) {
                return static_cast<std::size_t>(dice::hash::wyhash::wyhash64(kSeed, x));
            }
            return static_cast<std::size_t>(dice::hash::wyhash::wyhash(&x, sizeof(T), kSeed, kWyhashSalt));
        }
 
        static std::size_t hash_bytes(void const *ptr, std::size_t len) noexcept {
            return static_cast<std::size_t>(dice::hash::wyhash::wyhash(ptr, len, kSeed, kWyhashSalt));
        }
 
        static std::size_t hash_combine(std::initializer_list<size_t> hashes) noexcept {
            uint64_t state = kSeed;
            for (auto hash : hashes) {
                state = dice::hash::wyhash::_wymix(state, hash);
            }
            return static_cast<std::size_t>(state);
        }
 
        static std::size_t hash_invertible_combine(std::initializer_list<size_t> hashes) noexcept {
            std::size_t result = 0;
            for (auto hash : hashes) {
                result = result xor hash;
            }
            return result;
        }
 
        class HashState {
        private:
            uint64_t state = kSeed;
        public:
            explicit HashState(std::size_t) noexcept {}
            void add (std::size_t hash) noexcept {
                state = dice::hash::wyhash::_wymix(state, static_cast<uint64_t>(hash));
            }
            [[nodiscard]] std::size_t digest() noexcept {
                return static_cast<std::size_t>(state);
            }
        };
    };
 
#ifdef __x86_64__
    struct xxh3 {
        inline static constexpr std::size_t size_t_bits = 8 * sizeof(std::size_t);
        inline static constexpr std::size_t seed = std::size_t(0xA24BAED4963EE407UL);
        inline static constexpr std::size_t ErrorValue = seed;
 
        template<typename T>
        static std::size_t hash_fundamental(T x) noexcept {
            return hash_bytes(&x, sizeof(x));
        }
        static std::size_t hash_bytes(void const *ptr, std::size_t len) noexcept {
            return xxh::xxhash3<size_t_bits>(ptr, len, seed);
        }
        static std::size_t hash_combine(std::initializer_list<std::size_t> hashes) noexcept {
            return xxh::xxhash3<size_t_bits>(hashes, seed);
        }
        static std::size_t hash_invertible_combine(std::initializer_list<size_t> hashes) noexcept {
            std::size_t result = 0;
            for (auto hash : hashes) {
                result = result xor hash;
            }
            return result;
        }
        class HashState {
        private:
            xxh::hash3_state64_t hash_state{seed};
 
        public:
            explicit HashState(std::size_t) noexcept {}
 
            void add(std::size_t hash) noexcept {
                hash_state.update(&hash, sizeof(std::size_t));
            }
            [[nodiscard]] std::size_t digest() noexcept {
                return hash_state.digest();
            }
        };
    };
#endif
 
    struct Martinus {
        static constexpr std::size_t ErrorValue = dice::hash::martinus::seed;
        template<typename T>
        static std::size_t hash_fundamental(T x) noexcept {
            if constexpr (sizeof(std::decay_t<T>) == sizeof(size_t)) {
                return dice::hash::martinus::hash_int(*reinterpret_cast<size_t const *>(&x));
            } else if constexpr (sizeof(std::decay_t<T>) > sizeof(size_t) or std::is_floating_point_v<std::decay_t<T>>) {
                return hash_bytes(&x, sizeof(x));
            } else {
                return dice::hash::martinus::hash_int(static_cast<size_t>(x));
            }
        }
        static std::size_t hash_bytes(void const *ptr, std::size_t len) noexcept {
            return dice::hash::martinus::hash_bytes(ptr, len);
        }
        static std::size_t hash_combine(std::initializer_list<size_t> hashes) noexcept {
            return dice::hash::martinus::hash_combine(hashes);
        }
        static std::size_t hash_invertible_combine(std::initializer_list<size_t> hashes) noexcept {
            std::size_t result = 0;
            for (auto hash : hashes) {
                result = result xor hash;
            }
            return result;
        }
        class HashState {
        private:
            dice::hash::martinus::HashState state;
 
        public:
            explicit HashState(std::size_t size) noexcept : state(size) {}
            void add(std::size_t hash) noexcept {
                state.add(hash);
            }
            [[nodiscard]] std::size_t digest() noexcept {
                return state.digest();
            }
        };
    };
}// namespace dice::hash::Policies
#endif//DICE_HASH_DICEHASHPOLICIES_HPP