hash.hpp

/*
 * mstd - Maipa's Standard Library
 *
 * Licensed under the BSD 3-Clause License with Attribution Requirement.
 * See the LICENSE file for details: https://github.com/MAIPA01/mstd/blob/main/LICENSE
 *
 * Copyright (c) 2025, Patryk Antosik (MAIPA01)
 */
 
#pragma once
#ifndef _MSTD_HASH_HPP_
    #define _MSTD_HASH_HPP_
 
    #include <mstd/config.hpp>
 
    #if !_MSTD_HAS_CXX17
_MSTD_WARNING("this is only available for c++17 and greater!");
    #else
 
        #include <mstd/types.hpp>
 
namespace mstd {
    template<class T, class... Ts>
    inline void hash_append(size_t& hashValue, const T& value, const Ts&... values) {
        static _MSTD_CONSTEXPR17 const size_t left_shift   = 6;
        static _MSTD_CONSTEXPR17 const size_t right_shift  = 2;
        static _MSTD_CONSTEXPR17 const size_t magic_number = 0x9E37'79B9;
 
        hashValue ^= std::hash<T>()(value) + magic_number + (hashValue << left_shift) + (hashValue >> right_shift);
 
            if _MSTD_CONSTEXPR17 (sizeof...(Ts) != 0) { hash_append(hashValue, values...); }
    }
 
    template<class T0, class T1, class... Ts>
    inline size_t hash_combine(const T0& value0, const T1& value1, const Ts&... values) {
        size_t hashValue = 0;
        hash_append(hashValue, value0, value1, values...);
        return hashValue;
    }
 
    template<class Iter>
    inline void hash_range(size_t& seed, const Iter& begin, const Iter& end) {
            for (Iter i = begin; i != end; ++i) { hash_append(seed, *i); }
    }
} // namespace mstd
 
    #endif
#endif