ClickHouse/libs/libcommon/include/ext/bit_cast.hpp

#pragma once

#include <type_traits>


namespace ext
{
    template <typename To, typename From>
    union bit_cast_helper_t
    {
        using dst = std::decay_t<To>;
        using src = std::decay_t<From>;

        static_assert(std::is_copy_constructible<dst>::value, "destination type must be CopyConstructible");
        static_assert(std::is_copy_constructible<src>::value, "source type must be CopyConstructible");

        /** value-initialize member `to` first in case destination type is larger than source */
        dst to{};
        src from;

        bit_cast_helper_t(const From & from) : from{from} {}

        operator dst() const { return to; }
    };

    /** \brief Returns value `from` converted to type `To` while retaining bit representation.
     *    `To` and `From` must satisfy `CopyConstructible`. */
    template <typename To, typename From>
    std::decay_t<To> bit_cast(const From & from)
    {
        return bit_cast_helper_t<To, From>{from};
    };

    /** \brief Returns value `from` converted to type `To` while retaining bit representation.
     *    `To` and `From` must satisfy `CopyConstructible`. */
    template <typename To, typename From>
    std::decay_t<To> safe_bit_cast(const From & from)
    {
        static_assert(sizeof(To) == sizeof(From), "bit cast on types of different width");
        return bit_cast_helper_t<To, From>{from};
    };
}