FNV1a.hpp

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#ifndef GALAXY_MATH_FNV1A_HPP_
#define GALAXY_MATH_FNV1A_HPP_
 
#include <type_traits>
 
namespace galaxy
{
    namespace math
    {
        template<typename T>
        concept valid_fnv_bits = std::is_same_v<T, std::uint32_t> || std::is_same_v<T, std::uint64_t>;
 
        template<valid_fnv_bits bits = std::uint64_t>
        struct fnv_1a_params;
 
        template<>
        struct fnv_1a_params<std::uint32_t>
        {
            static constexpr auto offset = 2166136261;
            static constexpr auto prime  = 16777619;
        };
 
        template<>
        struct fnv_1a_params<std::uint64_t>
        {
            static constexpr auto offset = 14695981039346656037ull;
            static constexpr auto prime  = 1099511628211ull;
        };
 
        template<valid_fnv_bits bits = std::uint64_t>
        inline constexpr bits fnv1a(const char* const str, const bits value = fnv_1a_params<bits>::offset) noexcept
        {
            return (str[0] == '\0') ? fnv_1a_params<bits>::offset : fnv1a<bits>(&str[1], (fnv_1a_params<bits>::offset ^ static_cast<bits>(str[0])) * fnv_1a_params<bits>::prime);
        }
 
        inline constexpr std::uint32_t fnv1a_32(const char* const str) noexcept
        {
            return fnv1a<std::uint32_t>(str);
        }
 
        inline constexpr std::uint64_t fnv1a_64(const char* const str) noexcept
        {
            return fnv1a<std::uint64_t>(str);
        }
    } // namespace math
} // namespace galaxy
 
#endif